Eldorado Community:
http://hdl.handle.net/2003/27022
2024-03-29T06:01:44ZMagnetic Pulse Welding of Sheets – Process Modelling
http://hdl.handle.net/2003/40672
Title: Magnetic Pulse Welding of Sheets – Process Modelling
Authors: Shotri, R.; Racineux, G.; De, A.
Abstract: Magnetic pulse welding involves the application of a controlled electromagnetic impulse
and consequent high velocity impact between two overlapped parts, which leads to plastic
deformation and consolidation between the parts along the interface without melting. The
key variables in magnetic pulse welding include a high magnitude discharge energy of
damped sinusoidal nature, the coil type and geometry and the materials, thicknesses and
geometry of the overlapped metallic sheets. A computer-based coupled electromagnetic
and dynamic mechanical analysis of magnetic pulse welding of sheets is presented in this
work to provide an insightful understanding of the evolution of joints, which is otherwise
intractable for monitoring due to the high speed of the process and the presence of a high
electromagnetic field. The computed results show that such a computational process model
can serve as a robust design tool for a fundamental understanding as well as for the
identification of suitable conditions for achieving a defect-free, reliable joint.2021-10-14T00:00:00ZDevelopment phases of 2 high volume industrial products using high strain rates forming processes
http://hdl.handle.net/2003/40671
Title: Development phases of 2 high volume industrial products using high strain rates forming processes
Authors: Avrillaud, Gilles2021-10-14T00:00:00ZDetermination of material and fracture parameters for high strain rate processes, especially considering the local adiabatic heating in the fracture zone of the sample
http://hdl.handle.net/2003/40670
Title: Determination of material and fracture parameters for high strain rate processes, especially considering the local adiabatic heating in the fracture zone of the sample
Authors: Galiev, E.; Tulke, M.; Psyk, V.; Brosius, A.; Kräusel, V.2021-10-15T00:00:00ZA micro-mechanical and microstructural analysis at the joint interface between dissimilar materials in magnetic pulse welding (MPW)
http://hdl.handle.net/2003/40669
Title: A micro-mechanical and microstructural analysis at the joint interface between dissimilar materials in magnetic pulse welding (MPW)
Authors: Zielinski, Benjamin; Sadat, Tarik; Jouaffre, Denis; Dubois, Rudy; Kossman, Stephania; Dubar, Laurent; Markiewicz, Eric2021-10-15T00:00:00ZPrediction of adiabatic blanking process properties with temperature dependent fracture criterion
http://hdl.handle.net/2003/40668
Title: Prediction of adiabatic blanking process properties with temperature dependent fracture criterion
Authors: Schmitz, Fabian; Rakshit, Tanmoy; Hahn, Marlon; Clausmeyer, Till; Tekkaya, A. Erman2021-10-15T00:00:00ZA novel Hopkinson-based technique for high-speed biaxial testing of sheet metals
http://hdl.handle.net/2003/40667
Title: A novel Hopkinson-based technique for high-speed biaxial testing of sheet metals
Authors: Corallo, L.; Verleysen, P.
Abstract: Forming processes of sheet metals require knowledge of the material behaviour up to
large levels of plastic deformation. To this purpose, biaxial bulge tests are often used. In
present paper, a dynamic bulge test is presented. The testing principle relies on
conventional split Hopkinson bar testing. Though, as opposed to existing setups, a different
positioning of the bars leaves the sample fully accessible for optical measurements. The
pressure imposed to a circular sample, together with the sample strain fields, allow to
obtain reliable stress-strain data till significantly larger strains compared to tensile tests.
The technique is illustrated by tests on an Al2024-T3 sheet. High speed camera imaging of
the deforming sample combined with digital image processing is used to obtain full-field
strain data. To quantitatively assess the added value of full-field strain measurements,
stress-strain curves obtained with and without the strain data are compared.2021-10-15T00:00:00ZEffects of temperature on quality of Al/Fe tube joints manufactured by magnetic pulse welding
http://hdl.handle.net/2003/40666
Title: Effects of temperature on quality of Al/Fe tube joints manufactured by magnetic pulse welding
Authors: Dang, Haiqing; Yu, Haiping2021-10-15T00:00:00ZParticle Ejection by Jetting and Related Effects in Impact Welding Processes & Interface Formation during Collision Welding of Aluminum
http://hdl.handle.net/2003/40665
Title: Particle Ejection by Jetting and Related Effects in Impact Welding Processes & Interface Formation during Collision Welding of Aluminum
Authors: Bellmann, Jörg; Schumacher, Eugen2021-10-15T00:00:00Z3D Simulation of the Magnetic Pulse Welding Process
http://hdl.handle.net/2003/40664
Title: 3D Simulation of the Magnetic Pulse Welding Process
Authors: Lashkari, Mohammadjavad; Goyal, Siddhant; Hahn, Marlon; Beraudo, Christine; Tekkaya, A. Erman; Alves, José2021-10-14T00:00:00ZProcess Parameter Sensitivity in Magnetic Pulse Welding: An Artificial Neural Network approach
http://hdl.handle.net/2003/40663
Title: Process Parameter Sensitivity in Magnetic Pulse Welding: An Artificial Neural Network approach
Authors: Kapil, A.; Mastanaiah, P.; Sharma, A.
Abstract: Magnetic pulse welding (MPW), a solid-state impact welding technique provides the ability
to join a wide array of material combinations, whilst introducing little to no heat to the
system and preserving the base metal microstructure. Impact velocity is one of the key
criteria which determines the weldability of the joint during MPW. Experimental
measurement of impact velocity in MPW across wide-ranging parameters is expensive and
time-consuming. Therefore, guidelines for process selection and knowledge of relative
influence of parameters on impact velocity is limited. This study presents the applicability
of coupling finite element method (FEM) and artificial neural network (ANN) modelling to
perform sensitivity analysis of MPW. The welding process was simulated using FEM, and
multilayer modular feedforward networks based on the results from finite element
simulations were developed. The results of the present study revealed that the coil cross sectional area and turns primarily governed the process, followed by the voltage. The
relative sensitivity of the parameters remained independent of the material combination.
Inclusion of shop floor applicable process parameters suggests that the developed ANN
models can substantially narrow down experimental runs and simultaneously act as a
decision support tool for end users.2021-10-14T00:00:00ZSeparating the roles of speed, strain-rate and shock in interpreting dynamic hardness
http://hdl.handle.net/2003/40662
Title: Separating the roles of speed, strain-rate and shock in interpreting dynamic hardness
Authors: Mao, Yu; Barnett, Blake; Prasad, K. Sajun; Vivek, Anupam; Daehn, Glenn2021-10-14T00:00:00ZAdvances in electrical high current connections for electrical propulsion systems
http://hdl.handle.net/2003/40661
Title: Advances in electrical high current connections for electrical propulsion systems
Authors: Marschner, O.; Pabst, C.; Pasquale, P.
Abstract: Many countries strongly support electric propulsion for various fields of transportation, be
it people or goods on land, at sea or in the air. Although electric drive systems appear much
simpler than (internal) combustion systems, they exhibit their own challenging development
tasks. This becomes obvious when an ever-increasing efficiency, performance or production
rate is required, just to name a few.
The new challenges can be tackled with the help of new electromagnetic manufacturing
processes. High speed processes with their well-known unique capabilities offer promising
approaches. However, development is required in order to deliver the required performance.
High-speed forming with electromagnetic tools allows the production of sharp-edged battery
housings. For body panels, sharp edges are mainly a design feature. For batteries, however,
sharp edges allow for an almost ideally rectangular housing, enabling a higher energy
density. Increases in the range of up to 10 % are achievable.
When it comes to packaging, the liquid cooling and heating of battery packs is of equally
large importance. The channels for the medium must not consume too much space. The
integration of channels inside the aluminium or steel frame of the battery pack is a promising
approach. Due to the high welding speeds of up to 500 mm per second at optimum conditions
and at the same time the ability to weld aluminium to aluminium or even steel without any
loss in strength, electromagnetic pulse welding offers a promising solution.
The conduction of high electrical currents with for example the strong demand to save
weight and thus use as little material as possible also requires new processes.
Electromagnetic pulse welding of aluminium to aluminium and aluminium to copper is well
known, investigated and already used in mass production. However, this is suitable for bus
bars only. The connection of terminals to cables is mostly done by crimping. Using a pulsed
force for crimping improves the compaction and thus the resistance of the joint, especially
of cables with large cross sections. This allows for smaller connectors and reduced cable
cross sections.2021-10-14T00:00:00ZNumerical Identification of Design Parameters for Electromagnetic Forming
http://hdl.handle.net/2003/40660
Title: Numerical Identification of Design Parameters for Electromagnetic Forming
Authors: Stiemer, M.; Nezhi, Z.; Rathjen, K.; Zazai, F.; Hagel, M.; Rozgic, M.
Abstract: In this work, approaches to the identification of high speed forming processes, whose simu lation requires models from different parts of physics are discussed. Particularly emphasis
is laid on situations in which it is possible to break off the coupling and to profit from partial
solutions for the design of the whole process. Such situations arise if it is possible to select
relevant features that allow for a stable transfer of information between the different models.
Creating situations in which a sequential approach to a coupled problem is favourably pos sible requires a profound process understanding. As an example, an electromagnetic form ing process is considered here. Approaches at identifying a coil geometry for electromag netic forming are discussed in case of an exemplary case involving the definition of a suitable
feature-list and the study of several methods to tackle the electromagnetic subproblem, in cluding Nelder Mead Simplex Search, a combination of it with a neural network as surrogate
model, and optimization via a neural network. These approaches are compared to each
other, and quantitative results are given.2021-10-14T00:00:00ZInvestigation of Collision Welding by High-Speed Imaging
http://hdl.handle.net/2003/40659
Title: Investigation of Collision Welding by High-Speed Imaging
Authors: Niessen, B.; Groche, P.
Abstract: Collision welding bases on the oblique collision of two joining partners at high relative
velocities. Until today, the mechanisms of collision welding are not yet fully understood
due to the variety of phenomena occurring during the collision. One of these phenomena is
the cloud of particles whose influence on bond formation has been neglected concerning
its stored thermal energy. For the investigation of this influence, a collision welding model
test rig was used which allowed the precise adjustment of the process parameters. The
process observation was implemented by an image intensifier camera to visualize the
ongoing collision and the occurring process phenomena. In this manuscript the developed
methodology and the results of high-speed process observation are presented. The findings
confirmed previous research regarding the shape formation of the cloud of particles and
the influence on bond formation. It was found that the temperature of the cloud of particles
depends strongly on the collision angle. Furthermore, an accumulation of the cloud of
particles during the collision process was recorded which might influence the steadiness of
the welding process.2021-10-14T00:00:00ZSuitable Design for Electromagnetic Pulse Processes
http://hdl.handle.net/2003/40658
Title: Suitable Design for Electromagnetic Pulse Processes
Authors: Marschner, O.; Pabst, C.; Schäfer, R.; Pasquale, P.
Abstract: Basic conventional production processes, such as arc welding or forming, are more or less
thoroughly investigated, reliable process guidelines have been developed and trained
engineers are available. This allows them to be put into use usually fast, thus facilitating a
wide application.
The usage of electromagnetic pulse processes, on the contrary, still lacks a broad
propagation. Despite having a history reaching back several decades, these processes are
mostly limited to niche applications. Admittedly, theoretical considerations have been made
and various experiments have been carried out. However, when a given joining or forming
task needs to be realized with electro-magnetic force, a huge invest is necessary even before
the first part is made. This involves the design of the machine, especially of the tool coil, as
well as the design of the workpieces to be processed.
In industrial environmentsthis challenge is tackled step by step: After the theoretical product
concept in close collaboration with the customer, numerical and experimental trials are
carried out. In many cases, iterations are necessary and both geometry and process are
optimized. The experimental trials can be conducted with universal sheet welding tool coils
or tube compression tool coils with custom field shapers. This procedure allows keeping the
prototyping costs low, but at the same time provides valid information on the feasibility in
general, the requirements to the workpieces, the design of the tool coil and the properties of
the pulse generator. Subsequently, the tool coil is designed and manufactured according to
the prior findings. The pulse generator as modular component is assembled and adapted to
the customer’s requirements.
The iterative product and process design is the most important phase of the whole procedure,
which is in accordance with good project management. It significantly lowers the risk of an
expensive project cancellation during the late steps.2021-10-14T00:00:00ZSingle-turn Coils for Magnetic Pulse Welding of High-strength Steel Parts
http://hdl.handle.net/2003/40657
Title: Single-turn Coils for Magnetic Pulse Welding of High-strength Steel Parts
Authors: Krutikov, V. I.; Paranin, S. N.; Spirin, A. V.; Zaytsev, E. Yu.
Abstract: Magnetic pulse welding provides high quality joining of fuel pin cladding for fast nuclear
reactors. The tool coil there operates under the most stressful conditions: 40 T magnetic
fields with tens of microseconds duration. This requires minimal coil inductance and
affects the capabilities and lifetime of the coils. Two approaches are being practiced to
enhance the coil durability: material research and construction optimization. The first
approach considers the use of high strength steels or composite materials for the coil
working area. The present work is aimed to realize the second approach – the use of multi position coils in order to maximize the number of parts welded in one coil.
Experiments and finite element modeling were carried out for two designs of two- and
four-position single-turn coils, which were made to process several workpieces in one
current pulse. The main parameters measured and calculated were the magnetic field
between the coil and the workpiece, and the ratio of its amplitude to the discharge current,
Bm/Im. The currents flowing through the coils were about 700 kA, which correspond to the
magnetic fields of 40–45 T. The FEM modeling revealed a 17–19% drop of the magnetic
induction near the insulated slit, which, however, did not prevent the helium-tight joining
of the tubes to the end plugs.2021-10-13T00:00:00ZElectrohydraulic Crimping of 316L Tube in a 316L Thick Ring
http://hdl.handle.net/2003/40656
Title: Electrohydraulic Crimping of 316L Tube in a 316L Thick Ring
Authors: Le Mentec, R.; Sow, C.; Heuzé, T.; Racineux, G.
Abstract: During the electrohydraulic forming process a high current, up to one hundred of kilo amperes, is discharged between two electrodes immersed in a water tank. This creates
plasma that generates a primary shock wave and secondary pressure waves. If these
pressures are applied in a tube, it is then possible to deform dynamically this tube against
a ring, leading to crimping. This process presents several advantages: it is possible to
deform internally tubes of diameters ranging from a few millimetres to several centimetres,
no lubrication is needed and because the process is dynamic, the spring back is limited and
some materials can present an improved behaviour compared to quasi-static forming.
In this paper, we present an original electrohydraulic crimping device. We successively
present the operating principle of our system, the time evolution of the crimping pressure
and the strain rate in the tube for two kinds of pulse shaper. Finally crimping tests are
done to evaluate the efficiency of the process.2021-10-13T00:00:00ZImpact-activated fluid-solid tool: towards more flexible high speed forming
http://hdl.handle.net/2003/40655
Title: Impact-activated fluid-solid tool: towards more flexible high speed forming
Authors: Hahn, Marlon; Kumar, V.; Tekkaya, A. Erman2021-10-13T00:00:00ZElectrohydraulic full-forward extrusion of small parts through high aspect ratio forming channels
http://hdl.handle.net/2003/40654
Title: Electrohydraulic full-forward extrusion of small parts through high aspect ratio forming channels
Authors: Langstädtler, L.; Herrmann, M.; Schenck, C.; Kuhfuss, B.
Abstract: Electrohydraulic incremental bulk forming was introduced as a novel micro part forming
technology. Forming of parts from different materials and different initial diameter values was
investigated in single-stage full-forward extrusion in recent work. In this paper, multi-stage
extrusion in high aspect ratio forming channels is presented. Thereby, the aspect ratio of
forming channel is high, when the channel length is much higher than the channel diameter
and formed part length. Analytical and experimental investigations are carried out to correlate
the supplied and required energy for extrusion. Experiments were made using an optical access
made of sapphire as part of the extrusion channel to measure the position during forming
increments. The influence of channel depth and curvature as well as of fluctuations in the
transmitting media on the energy transmission to the formed EN AW-6061 aluminum alloy parts
were found to be low.2021-10-13T00:00:00ZAnalytical-based modeling for electromagnetic sheet metal forming with multi-turn coils
http://hdl.handle.net/2003/40653
Title: Analytical-based modeling for electromagnetic sheet metal forming with multi-turn coils
Authors: Goyal, Siddhant; Lashkari, Mohammadjavad; Hahn, Marlon; Tekkaya, A. Erman2021-10-13T00:00:00ZDevelopment and Experiment of Electromagnetic Pulse Crimping System for Terminal-Wire of Electric Vehicles
http://hdl.handle.net/2003/40651
Title: Development and Experiment of Electromagnetic Pulse Crimping System for Terminal-Wire of Electric Vehicles
Authors: Zhou, Y.; Li, C.; Shen, T.; Zhang, B.; Wu, H.; Dai, M.; Wang, X.
Abstract: The safety and reliability of the energy transmission system of electric vehicles (EVs) are
decided by the connection reliability of the high-voltage (HV) wire harness and terminals.
When the terminal and the HV wire harness are connected by the usual mechanical
crimping methods such as hydraulic pressure, there are the edges and corners on the
terminal, and gaps between the wire harness and terminal, which are prone to fretting
corrosion and threaten the power system. In this work, an electromagnetic pulse crimping
(EMPC) system has been designed and developed for joining the Cu wire harness and the
Cu terminal of the EV. When the discharge voltage is 13 kV, it can deliver the discharge
current of 70 kA peak value, causing the joint of the Cu terminal and the Cu HV wire
harness. Scanning electron microscope (SEM) and energy dispersive spectrometer (EDS)
were used to analyze the microstructure and element distribution of the joint interface. A
good and strong metallurgical bond was obtained at the surface of the Cu HV wire harness,
the Cu terminal, and each strand of the Cu HV wire harness. There were a flat interface
and a wavy interface between the Cu HV wire harness and the Cu terminal because of the
gap on the field shaper.2021-10-13T00:00:00ZInvestigation of Turn Number of the Coil on Tube Forming Performance in Electromagnetic Pulse Forming
http://hdl.handle.net/2003/40650
Title: Investigation of Turn Number of the Coil on Tube Forming Performance in Electromagnetic Pulse Forming
Authors: Wang, Xianmin; Li, Chengxiang; Zhou, Yan; Du, Jian; Liao, Zhingang
Abstract: Electromagnetic pulse forming (EMPF) is an environmentally friendly and high-speed
forming method without pollution generating. As the key component for energy conversion,
the coil has a significant influence on the forming performance. Consequently, this paper
aims to study the effect of the turn number of the coil on the performance of the tube forming
through the theoretical analysis model and experiments. Based on the connection among the
electrical parameters of the coil, the current parameters of the discharge pulse, and
electromagnetic force, a theoretical model is built to analyze the qualitative connection
between the number of turns of the coil and the amount of forming. Then, the EMPF
experiments with the same discharge energy of 3.4kJ are carried out to verify the established
model through the established EMPF equipment. The experimental results are consistent
with the theoretical analysis. The results show that the peak value of the current amplitude
and rise time of the pulse decrease respectively with the increase of the number of turns of
the coil because the increments of the number of turns lead to the rising coil inductance. But
the forming amount of the tube increases first and then decreases. So there is an optimal
value of the turn number for the coil to generate the maximum Lorentz force to deform the
workpiece. Therefore, it is worthwhile to choose the proper number of coil turn to improve
the effect of EMPF.2021-10-13T00:00:00ZHigh Strength Impact Welding of HSLA 340 to Al 5754 and Application Prototype
http://hdl.handle.net/2003/40649
Title: High Strength Impact Welding of HSLA 340 to Al 5754 and Application Prototype
Authors: Mao, Yu; Thurson, Brian; Li, Jianxiong; Vivek, Anupam; Daehn, Glenn
Abstract: Vaporizing Foil Actuator Welding (VFAW) technique was applied to join 4 mm thick aluminium alloy 5754 to 2.5 mm thick High Strength Low Alloy (HSLA) steel 340 with a 1 mm thick aluminium alloy 3003-H14 interlayer. Welds with consistent peak loads of 17.6 kN were achieved with input energy less than 5 kJ. Tension-tension fatigue testing yielded high cycle around 1000k cycles under the peak load of 40% tensile strength from static testing. Microscopic characterization revealed no continuous melting zones in the welding interfaces. Coupled with lightweight designs, the approach was utilized on prototype production of an aluminium-steel vehicle subframe. Issues related to arcing arose and were tackled during the development of prototype production.2021-10-13T00:00:00ZPrediction of Achievable Energy Deposition for Vaporizing Foil Actuators
http://hdl.handle.net/2003/37136
Title: Prediction of Achievable Energy Deposition for Vaporizing Foil Actuators
Authors: Hahn, M.; Hansen, S. R.; Gies, S.; Vivek, A.; Daehn, G. S.; Tekkaya, A. E.
Abstract: A novel iterative analytic approach allowing for the prediction of energy deposition into Vaporizing Foil Actuators (VFA) is presented. Besides the process parameters of actuator geometry and pulse generator configuration, it takes into account the energy dependence of the resistivity as well as the rate dependence of the achievable energy deposition. This rate dependency is found experimentally for aluminum foils and subsequently used in the modeling. With an average deviation of less than 15% the predicted energy depositions are in acceptable accordance with the experiments, but only as long as homogeneous Joule heating can be assumed. The proposed model has thus the potential to ease the future VFA process design, e.g. for manufacturing applications.2018-05-15T00:00:00Z5083 Al/1060 Al/AZ31 Composite Plates Fabricated by Explosive Welding
http://hdl.handle.net/2003/37066
Title: 5083 Al/1060 Al/AZ31 Composite Plates Fabricated by Explosive Welding
Authors: Suyuan, Yang; Jiawei, Bao2018-05-15T00:00:00ZWelding of 2024 and 7075 Aluminum Alloys by Vaporizing Foil Actuator
http://hdl.handle.net/2003/37064
Title: Welding of 2024 and 7075 Aluminum Alloys by Vaporizing Foil Actuator
Authors: Meng, Z.; Mao, Y.; Huang, S. Y.; Hua, L.; Vivek, A.; Daehn, G. S.2018-05-15T00:00:00ZApplication of Smoothed Particle Hydrodynamics Method in Simulation of Highvelocity Impact Welding
http://hdl.handle.net/2003/37062
Title: Application of Smoothed Particle Hydrodynamics Method in Simulation of Highvelocity Impact Welding
Authors: Nassiri, Ali; Abke, Tim; Vivek, Anupam; Daehn, Glenn2018-05-15T00:00:00ZNumerical and Experimental Study of Electromagnetic Crimping
http://hdl.handle.net/2003/37061
Title: Numerical and Experimental Study of Electromagnetic Crimping
Authors: Kumar, R.; Rajak, A. K.; Kore, S. D.
Abstract: Electromagnetic pulse crimping is a solid state, high speed, and high strain rate joining process. In this process, the flyer is deformed over the base plastically to produce the joint. In this work, copper tube was crimped over the aluminium rod by using single step field-shaper. Finite element analysis, as well as experimental study, was carried out on the single step field-shaper to crimp the copper tube on the aluminium rod. The finite element model was validated based on the measured temperature and outer diameter of the crimped rod. The validated model was used to study the effect of the working length position on the electromagnetic crimping. The variation in the working length position of the field-shaper was analysed to increase the concentration of the electromagnetic pressure at the desired location to produce an effective joint with better mechanical strength. It was found that with the change in the position of the working length of the field-shaper the impact velocity, temperature gen-eration, magnetic field density, and uniformity in crimping of the tube also changes.2018-05-14T00:00:00ZLaser Impulse Generation - Parameter Effects and Applications
http://hdl.handle.net/2003/37060
Title: Laser Impulse Generation - Parameter Effects and Applications
Authors: Bovid, Stan2018-05-14T00:00:00ZState of the Art in Explosion Welding
http://hdl.handle.net/2003/37047
Title: State of the Art in Explosion Welding
Authors: Blakely, Mike2018-05-15T00:00:00ZSupersonic Impact of Metallic Microparticles
http://hdl.handle.net/2003/37046
Title: Supersonic Impact of Metallic Microparticles
Authors: Hassani-Gangaraj, Mostafa; Veysset, David; Nelson, Keith A.; Schuh, Christopher A.2018-05-15T00:00:00ZAtomic Scale Characterization of an Al-Steel Weld Interface
http://hdl.handle.net/2003/37044
Title: Atomic Scale Characterization of an Al-Steel Weld Interface
Authors: Sridharan, Niyanth; Vivek, Anupam; Poplowsky, Jonathan; Lee, T.; Daehn, Glenn2018-05-15T00:00:00ZEffect of coil to tubular workpiece magnetic coupling on electromagnetic expansion process
http://hdl.handle.net/2003/36987
Title: Effect of coil to tubular workpiece magnetic coupling on electromagnetic expansion process
Authors: Dond, S. K.; Kolge, Tanmay; Choudhary, Hitesh; Sharma, Archana
Abstract: Efficiency of the electromagnetic forming process is very less. Leakage flux contributes to a fraction of total energy loss in the forming process, and it is related to the coupling between the coil and workpiece. The workpiece experiencing Lorentz force should be as close as possible to the tool coil in order to achieve higher utilization of discharge energy. In this paper, experimental and numerical simulation study is performed to observe the coil-tube magnetic coupling effect on tube expansion and thereby on process efficiency. Aluminum tube of 100 mm length and 1.5 mm thickness is electromagnetically expanded using a 7 turn helical coil. Trials are taken for the different gaps between the coil and tube whereas discharge energy kept constant. 2D sequentially coupled numerical simulation carried out using COMSOL software. The tube displacement and the coupling factor obtained in the simulation showed good agreement with experimental observations. The coupling factor decreases with increase in the coil-tube gap. The Process efficiency and tube displacement are found to be improved exponentially with increasing in coupling factor. Considering various design aspects, coil and workpiece should be tightly coupled to achieve higher process efficiency.2018-05-14T00:00:00ZInfluence of the Ambient Pressure on the Weld Quality for Magnetic Pulse Welded Sheet Joints
http://hdl.handle.net/2003/36986
Title: Influence of the Ambient Pressure on the Weld Quality for Magnetic Pulse Welded Sheet Joints
Authors: Kümper, S.; Schumacher, E.; Böhm, S.
Abstract: This paper examines the effect of reduced ambient pressure during the welding process on the quality of magnetic pulse weld seams. For this purpose, a specifically developed vacuum chamber was applied, which enables a reproducible implementation. This, in turn, prepared the ground for a systematic examination of this promising process parameter. The tests focused on comparison of the weld seams realized with different currents and acceleration distances under atmospheric pressure and in the vacuum chamber. Here, both similar (EN AW-1050-H14) and dissimilar material combinations were considered (EN AW-1050A-H14 + S235JR; EN-AW 6016-T6 + DC04). The evaluation criteria for the quality of the welds were the tensile strength of the joint and the size of the weld seam.2018-05-15T00:00:00ZApplication of Electromagnetic Forming as a Light-Weight Manufacturing Method for Large-Scale Sheet Metal Parts
http://hdl.handle.net/2003/36985
Title: Application of Electromagnetic Forming as a Light-Weight Manufacturing Method for Large-Scale Sheet Metal Parts
Authors: Lai, Zhipeng; Cao, Quanliang; Han, Xiaotao; Liu, Ning; Chen, Meng; Li, Xiaoxiang; Huang, Yujie; Chen, Qi; Li, Liang
Abstract: Electromagnetic forming (EMF), due to its advantages of light-equipment, single-side die, improved formability, reduced wrinkling, lower spring-back, and so on, is high potential for shaping large sheet metal parts in aviation and aerospace industries, which are generally relative expensive and difficult to be formed with conventional process. By exploiting the potential benefits of EMF, the required forming cost can be reduced, and the forming quality can be improved. Until now, however, the EMF of large sheet metal is still under-developed, which is highly attributed to the limited forming capability of the present equipment and the lack of a systematic design methodology for the process.
In recently, we developed an EMF process that capable of shaping large sheet metal parts with light-weight equipment, and has successfully applied this process for manufacturing ellipsoid shaped aluminium alloy parts with 1378 mm diameter. To realize the light-weight of the proposed process, two newly–developed devices are highlighted. In this paper, the forming performance of the process are experimentally evaluated for AA5083 and AA2219 sheet workpieces, in terms of die fittability, thickness distribution, and radial material flow distribution. Furthermore, the comparisons of the proposed process with several other related forming processes are conducted to identify the advantages of the proposed process.2018-05-14T00:00:00ZApplications of Electromagnetic Forming Technology at the Wuhan National High Magnetic Field Center
http://hdl.handle.net/2003/36984
Title: Applications of Electromagnetic Forming Technology at the Wuhan National High Magnetic Field Center
Authors: Li, Liang; Han, Xiaotao; Cao, Quangliang; Lai, Zhipeng; Deng, Fangxiong; Huang, Yuje; Liu, Ning; Chen, Meng; Li, Xiaoxiang; Chen, Qi
Abstract: The research of the electromagnetic forming (EMF) technology at the Wuhan National High Magnetic Field Center (WHMFC) has focused on designing electromagnetic system for generating a more flex-ible and strong Lorentz forces acting on workpieces, and then expanding the applications of EMF technology to solve current problems in forming large-scale and complex components. In this paper, we will sum up the latest progress of EMF technology at the WHMFC in detail according to recently reported works.2018-05-14T00:00:00ZA computational model for magnetic pulse forming processes – Application to a test case and sensitivity to dynamic material behaviour
http://hdl.handle.net/2003/36983
Title: A computational model for magnetic pulse forming processes – Application to a test case and sensitivity to dynamic material behaviour
Authors: Bay, F.; Alves, J.
Abstract: This paper aims at presenting an efficient computational tool for magnetic pulse forming processes. This too - based on the coupling between the FORGE® thermomechanical solver and an electromagnetic module - is then applied to investigating a test case provided by the I2FG Group for benchmarking purposes. Comparisons carried out between the results obtained using a quasi-static constitutive law with one taking into account the dynamic behaviour of the material emphasize the sensitivity to dynamic material behaviour – and thus the need for carrying out material behaviour identification for strain rates close to the ones experiences by the material in such processes.2018-05-14T00:00:00ZEffect of Eccentric Field-shaper on Electromagnetic Crimping of Terminal Wire Interconnections
http://hdl.handle.net/2003/36982
Title: Effect of Eccentric Field-shaper on Electromagnetic Crimping of Terminal Wire Interconnections
Authors: Rajak, Ashish K.; Kumar, Ramesh; Kore, Sachin D.
Abstract: With the increase in losses in electric power transmission in crimped terminal-wire interconnections, due to improper crimping using conventional crimping process, it is essential to find a more efficient crimping technique. Some crucial challenges in conventional terminal-wire crimping process are spring back of terminal on tool relaxation, non-uniform terminal deformation due to tool-terminal contact process, flash out of material, voids between the wire strands etc. To overcome these problems Electromagnetic crimping process is found to be a most suitable technique. In this work, an eccentric geometry field-shaper is used for electromagnetic crimping of aluminium terminal over the aluminium wires which hasn’t been used yet in this field. Numerical simulations were carried out using LSDYNATM Electromagnetic module software. Results like current density, magnetic field, Lorentz force, and terminal deformation were discussed. The results from the numerical simulations were used for carrying out experiments. The validation was carried out using terminal deformation and terminal-wire contact length. The result of the work will be useful for electromagnetic crimping, welding and cladding process for similar applications.2018-05-15T00:00:00ZConsideration of the Magnetic Field Penetration through the Blank Wall in the Processes of Pulse-Magnetic Forming
http://hdl.handle.net/2003/36981
Title: Consideration of the Magnetic Field Penetration through the Blank Wall in the Processes of Pulse-Magnetic Forming
Authors: Karpukhin, V. F.; Chernikov, D.
Abstract: The results of the investigation of the effect of the magnetic field penetration through a blank wall on the necessary parameters of the pulse-magnetic forming are presented in this paper. The purpose of the work is to determine the permissible scope of engineering techniques for calculating the processes of pulse-magnetic forming of thin-walled parts. Process studies include conducting experiments, calculating by engineering methods and computer simulation of the process using LS-DYNA. As a result of the research it has been established that the engineering technique allows calculating the processes with sufficient accuracy at a blank thickness exceeding the value of the penetration depth of the pulse magnetic field into the blank material.2018-05-14T00:00:00ZOn Process, Structure, Property Relationships in Impact Welding of Aluminum 6061 and Steel 4130
http://hdl.handle.net/2003/36980
Title: On Process, Structure, Property Relationships in Impact Welding of Aluminum 6061 and Steel 4130
Authors: Mao, Y.; Gupta, V.; Ufferman, B.; Vivek, A.; Choi, K. S.; Sun, X.; Daehn, G. S.
Abstract: Vaporizing Foil Actuator Welding process was used to weld 1mm thick aluminum alloy 6061 sheet to 3.2 mm thick 4130 grade steel plate. Temporal evolution of the flyer sheet velocity was recorded at four locations on the flyer sheet using photonic Doppler velocimetry. The welded samples were subjected to mechanical and microstructural characterization. Although the welded interface did not show a very wavy characteristic, the welds had substantial strength. Welds made with a softer temper, T4 alloy were found to be stronger than the one created with a harder, T6 temper alloy. A coupled Lagrangian-Eulerian numerical framework was also utilized to predict the structure of the interface based on the measured velocity profile. The model also depicted absence of large waves although the jetting phenomenon was observed, thereby providing insight into necessary conditions for impact welding.2018-05-15T00:00:00ZNumerical Simulation of Electrohydraulic Forming of Aluminium Alloy Tubes
http://hdl.handle.net/2003/36979
Title: Numerical Simulation of Electrohydraulic Forming of Aluminium Alloy Tubes
Authors: Zheng, Q. L.; Yu, H. P.
Abstract: Electrohydraulic forming has the advantages in improving formability and deformation precision of the workpiece, so it is concerned and applied in the plastic deformation for high precision parts, which are made of sheet or tube and difficult to form by traditional methods. However, electrohydraulic forming is based on a coupled effect of gaseous, liquid, and solid media and materials, and its states cannot be identified by experiments alone. Therefore, this paper takes the local bulging deformation behaviour of 5052 aluminium alloy tubes as the research object, used FEM software ANSYS/LS-DYNA to establish the numerical simulation model, and studied the plastic deformation behaviour of tubes under the action of shockwave load during electrohydraulic forming.2018-05-14T00:00:00ZMolecular Dynamics Modeling of Atomic Diffusion Across Fe-Al Magnetic-pulse-welding Interface
http://hdl.handle.net/2003/36978
Title: Molecular Dynamics Modeling of Atomic Diffusion Across Fe-Al Magnetic-pulse-welding Interface
Authors: Fan, Zhisong; Yu, Haiping; Deng, Jianghua; Li, Chunfeng
Abstract: In the present study, a molecular dynamic model has been developed for simulating of atomic diffusion behaviour in the Al-Fe system during the magnetic pulse welding process. Our simulations predict the structural evolution of the interfacial region. And the thickness of diffusion layer was studied. The atomic diffusion features at the bonding interface were investigated in detail. Furthermore, the concentration distribution of the elements across the diffusion layer was also presented in this paper. To verify the simulation results, relevant verification experiments were also carried out. The simulation results show a good correspondence with the experiments.2018-05-15T00:00:00ZDevelopment of Numerical Simulation Model and Formability Evaluation for Electrohydraulic Forming Process
http://hdl.handle.net/2003/36977
Title: Development of Numerical Simulation Model and Formability Evaluation for Electrohydraulic Forming Process
Authors: Woo, M. A.; Song, W. J.; Kang, B. S.; Kim, J.
Abstract: In the automotive industry, the consumption of advanced high strength steels and aluminium alloys is increased to reduce the weight of automotive parts. However, because these materials have lower formability, it is not easy to deform these in the general forming process. Therefore, high speed forming processes are introduced such as electrohydraulic forming, electromagnetic forming and explosive forming. High speed forming is a process that deforms a material at a speed of more than 100 m/s. This paper describes the electrohydraulic forming (EHF) process. EHF is high strain rate forming process based on the electric discharge in the fluid. This process can improve the formability of the material due to the high strain rate of 103 ~ 104 s-1 and it can reduce the experimental cost by using only one-sided rigid tool. In this study, numerical model of EHF was developed in LS-DYNA commercial program and it showed that the material could be deformed by electric energy input inside the fluid. In addition, forming limit diagram (FLD) at high strain rate condition was obtained from M-K theory as criteria of formability evaluation and it was applied to the results of numerical simulation. As a result, it was predicted that the material has no cracks or wrinkles at a given energy input.2018-05-14T00:00:00ZMagnetic pulse forming of smalls aeronautic pieces
http://hdl.handle.net/2003/36976
Title: Magnetic pulse forming of smalls aeronautic pieces
Authors: Sow, C.; Bazin, G.; Daniel, D.; Bon, E.; Priem, D.; Racineux, G.
Abstract: Stelia Aerospace is specialized in the forming of small (Lmax < 200 mm), medium
(200 mm < Lmax < 1000 mm) and large (Lmin > 1000 mm) sheets for the aerospace
industry. In order to diversify the production facilities of Stelia Aerospace we evaluated the
capacity of the magnetic pulse forming to produce small parts. The material used is the
aluminum alloy 2024-T4. The sheets used have a thickness of 1 mm, 2 mm and 1.6 mm.
There are more than 100 references of small parts but they are all made up of a limited set
of elementary geometries. These elementary geometries include: straight and interrupted
straight fallen edges, convex and concave fallen edges, fallen edges holes and joggling.
For each of these geometries we designed a specific inductor and die, we measured the
geometric dispersions and checked the material health of the parts. At the same time, in
order to facilitate tool design, we developed a numerical model in the LS DYNA computing
environment. The dynamic behavior of the material was measured by dynamic
compression tests on Hopkinson bar. The model was validated from the tests.2018-05-14T00:00:00ZFully coupled semi-analytical model for an electromagnetic-mechanical-thermal problem of a ring expansion test
http://hdl.handle.net/2003/36975
Title: Fully coupled semi-analytical model for an electromagnetic-mechanical-thermal problem of a ring expansion test
Authors: Yang, K.; Sapanathan, T.; Raoelison, R. N.; Buiron, N.; Rachik, M.
Abstract: A fully coupled semi-analytical model is proposed for a ring expansion test. In this model, we consider the electromagnetic, mechanical and thermal effects. During the development, an ideal case of electromagnetic ring expansion test is modelled using both semi-analytical and finite element methods. The analytical model also includes the changes in electrical resistance, mutual inductance and self-inductance as a function of radius during the ring expansion. The development procedure is divided into four separate calculation parts. Each individual part is validated before making the independent validation of the semi-analytical method to obtain a model with high accuracy and a robust calculation speed. The final prediction using this model closely resemble with the coupled finite element predictions, and it can be further extended to exploit for an inverse identification problem.2018-05-14T00:00:00ZAnalysis of the Weld Seam Area of Magnetic Pulse Welded Aluminium-Steel-Sheet-Connections on its Suitability as a Sign of Quality
http://hdl.handle.net/2003/36974
Title: Analysis of the Weld Seam Area of Magnetic Pulse Welded Aluminium-Steel-Sheet-Connections on its Suitability as a Sign of Quality
Authors: Schumacher, E.; Kümper, S.; Kryukov, I.; Böhm, S.
Abstract: This paper deals with the characterisation of the weld seam area of magnetic pulse welded aluminium-steel-sheet-connections for different material combinations and its suitability as a sign of quality. The goal of this work is to suggest a relationship between the weld seam area and the strength of the generated joint. Based on the results of this work, the weld seam area could be established as a basis of design and for dimensioning the magnetic pulse welded hybrid joints. To identify the correlation of the generated weld seam area with the maximum tensile force of the welded samples, several aluminium-steel-joints were welded and tested using tensile shear test. Thereafter, the weld seam area was measured and correlated to the maximum bearable tensile force of the joint. The tested material combinations were EN AW-1050A-H14 / S235JR and EN AW-6016-T6 / HCT780X. The results illustrate a positive linear correlation between the weld seam area of the joint and the maximum tensile force. At the same time further weld seam irregularities were identified which have to be considered for evaluating the suitability of the weld seam area as a sign of quality. Additionally, in order to prevent such irregularities or to ensure a good weld seam, the non-destructive testing method of active thermography is presented.2018-05-15T00:00:00ZInvestigations on Shock Waves during Collision Welding
http://hdl.handle.net/2003/36973
Title: Investigations on Shock Waves during Collision Welding
Authors: Niessen, B.; Siegel, M.; Groche, P.
Abstract: Collision welding is a joining process that bases on the high speed impact between two joining partners. Caused by the dynamic behaviour (welding time < 10 μs), the investigation of the actual process is associated with a high technical effort. Therefore, the basic mechanisms of the process and a possible interaction have not yet been conclusively clarified.
In previous experiments on a model test rig for collision welding, indications have occurred on some high-speed images that could be characterized as shock waves. This paper describes the set-up of a Background-Oriented-Schlieren system (BOS) and its integration in the existing test rig for a closer examination of the occurring phenomena. The first aim was to increase the visibility of the occurrences in the medium surrounding the collision. As a result of the commissioning, it can be stated that shock waves were detected and propagate at supersonic speed. However, these do not only originate from the closing gap, but there is also an interaction between the colliding samples and the set-up environment.2018-05-15T00:00:00ZForming limit curves for quasi-static and dynamic working-media-based forming processes
http://hdl.handle.net/2003/36972
Title: Forming limit curves for quasi-static and dynamic working-media-based forming processes
Authors: Djakow, E.; Homberg, W.; Springer, R.
Abstract: The production of complex, multi-functional, high-strength components is becoming increasingly important in the sheet metal industry. Especially with small batch sizes, quasi-static working-media-based forming processes (WMF), such as hydromechanical deep drawing (HMD) or high-pressure sheet metal forming (HPF), can be advantageous. If shorter process times or higher forming speeds are necessary, working-media-based high-speed forming processes (WMHSF) are best used. These permit the production of sharp edged parts with less tooling than for quasi-static WMF. The successful use of WMB processes requires knowledge of the significant process parameters and the material characteristics under process-specific conditions. This paper describes the new approach of a modified hydraulic bulge test, which permits the flexible determination of forming limit curves (FLC) under true quasi-static and dynamic WMF process conditions. Results for the formability of steel DC04 and aluminium (A5754, A1050) alloys in the WMF process are shown. Here, the dynamic conditions are analysed through the use of pneumo-mechanical (PMF) testing equipment. The application of quasi-static forming conditions is analysed in high-pressure sheet metal forming (HPF) processes. A comparison of the maximum strains of parts formed by HPF and PMF shows that quasi-static and dynamic working-media-based forming processes lead to different forming limits.2018-05-14T00:00:00ZEffects of Reactive Interlayers in Magnetic Pulse Welding
http://hdl.handle.net/2003/36971
Title: Effects of Reactive Interlayers in Magnetic Pulse Welding
Authors: Bellmann, J.; Lueg-Althoff, J.; Schulze, S.; Gies, S.; Beyer, E.; Tekkaya, A. E.
Abstract: Surface coatings affect the joint formation in magnetic pulse welding processes (MPW).
Two types of coatings were identified in former studies. Anodized layers, for instance, are
detrimental for the weld formation if they are not removed before or during welding.
Contrastingly, a nickel layer on a steel parent part was found to be advantageous since it
increased the weld seam length when it was impacted by an aluminum flyer. This paper
gives insights into the welding mechanism with nickel coatings during MPW and explains
one reason for the improved weld formation.
Metallographic analyses showed that the coating is evidently not fractured, but an
interlayer between aluminum and nickel is formed. Scanning electron microscopy and
energy dispersive X-ray spectroscopy revealed that nickel and aluminum have interacted.
The energy release rate of the exothermic reaction is higher than the reaction of aluminum
with steel in direct contact. Since all other parameters were kept constant, it is assumed
that the additional heat of the nickel-aluminum reaction promotes the welding effect,
especially at positions with lower impact pressures. This effect, for instance, enables a
significant reduction of the required impact energy for MPW. The formation of the
interaction zone was studied for different well defined collision conditions. A newly
developed process measurement system was utilized, which records the characteristic
process light emission and enables insights into the prevalent collision conditions.2018-05-15T00:00:00ZFirst Results of Superconducting RF (SRF) Cavity Fabrication by Electrohydraulic Forming
http://hdl.handle.net/2003/36970
Title: First Results of Superconducting RF (SRF) Cavity Fabrication by Electrohydraulic Forming
Authors: Cantergiani, E.; Avrillaud, G.; Abajo Clemente, C.; Atieh, S.; Favre, G.; Deroy, J.; Raveleau, F.
Abstract: In the framework of many accelerator projects relying on RF superconducting technology, shape conformity and processing time are key aspects for the optimization of copper and niobium cavities fabrication. An alternative technique to traditional shaping methods, such as deep-drawing and spinning is electrohydraulic forming (EHF). In EHF, half-cells are obtained through ultrahigh-speed deformation of blank sheets by using shockwaves induced in water by a pulsed electrical discharge. Compared to traditional shaping methods, EHF can bring valuable results in terms of final shape precision, reduced springback and high repeatability. In this paper, the first results of EHF on copper and niobium prototypes are discussed. The simulations performed to reproduce the embedded multi-physics phenomena and to optimize process parameters are also presented.2018-05-14T00:00:00ZIdentification of additional process parameters for impact welding and their influence on the process window
http://hdl.handle.net/2003/36969
Title: Identification of additional process parameters for impact welding and their influence on the process window
Authors: Pabst, C.; Pasquale, P.
Abstract: Impact welding in general facilitates the metallurgical bond even between dissimilar metals due to the lack of extensive heat input. It thus offers superior joint properties such as a good mechanical strength. However, in contrast to fusion welding, the fundamentals are not fully understood. As a direct consequence, not all influencing process parameters are known or quantified yet. However, this is crucial in order to further comprehend, develop and optimize the process. The objective of this study is to investigate the influence of the surrounding gaseous medium on the weld strength as additional parameter. This issue has been discussed in earlier publications of other researchers already, though without any consistent conclusion yet. The results of this study show that a lower gas density results in higher weld strength, whereas higher densities may even inhibit the joint completely at identical impact velocities. High speed images of the electromagnetic pulse welding process indicate that this might be caused by the jet which is obstructed by the ambient gas atmosphere on its way out of the impact area. The higher the density, the slower the visible jet is. Thus, superficial material of the workpieces and contaminants cannot leave the welding area and hinder its formation instead.2018-05-15T00:00:00ZNew Methods to Speed-up the Boundary Element Method in LS-DYNA
http://hdl.handle.net/2003/36968
Title: New Methods to Speed-up the Boundary Element Method in LS-DYNA
Authors: L‘Eplattenier, Pierre; Ashcraft, Cleve; Rouet, François-Henry; Weisbecker, Clement; Bateau-Meyer, Sarah
Abstract: LS-DYNA is a general purpose explicit and implicit finite element program used to analyse the non linear dynamic response of three-dimensional solids and fluids. It is developed by Livermore Software Technology Corporation (LSTC). An electromagnetism (EM) module has been added to LS-DYNA for coupled mechanical/thermal/electromagnetic simulations, which have been extensively performed and benchmarked against experimental results for Magnetic Metal Forming (MMF) and Welding (MMW) applications. These simulations are done using a Finite Element Method (FEM) for the conductors coupled with a Boundary Element Method (BEM) for the surrounding air.
The BEM has the advantage that it does not require an air mesh, which can be difficult to build when the gaps between conductors are very small, and to adapt when the conductors are moving, with contact possibly arising. Besides, the BEM does not require the introduction of infinite boundary conditions which are somehow artificial and can create discrepancies. On another hand, it generates dense matrices which take time to assemble and solve, and require a lot of memory. In LS-DYNA, the memory issue is handled by using low rank approximations on the off diagonal sub-blocks of the BEM matrices, creating a so-called Block Low Rank (BLR) matrix structure.
The issue of the assembly and solve time is now being studied, and we present the so called “Multi-Center” (MC) method where the computation of the far-field submatrices is greatly reduced and the solve time somehow reduced.
We will present the method as well as some first results.2018-05-14T00:00:00ZCrash and Durability of Aluminum and Mixed Steel Aluminum Joints Made by Electromagnetic Pulse Welding
http://hdl.handle.net/2003/36962
Title: Crash and Durability of Aluminum and Mixed Steel Aluminum Joints Made by Electromagnetic Pulse Welding
Authors: Huberth, F.; Klitschke, S.; Gall, M.; Sommer, S.; Schnabel, K.; Baumgartner, J.
Abstract: In this paper, results of the research project “Failure behavior of mixed weld joints under multi-axial crash-like and cyclic loads on the example of EMPT sheet metal joints” funded by the German Federal Ministry for Economic Affairs and Energy are presented and discussed. Aluminum and mixed aluminum-steel joints were prepared using electromagnetic pulse technology (EMPT) at PSTproducts GmbH (PST). Investigations on coupon samples were performed under oscillating and monotone (crash) loadings until failure. Based on the coupon tests, parameters for modelling the crash performance were derived, using both a detailed continuum model and an application driven simplified FE-model. The derived FE-modelling concept for crash behavior was validated by comparison of component tests and simulations Durability analysis of the joint specimens was performed combined with FEM analysis, applying the notch stress concept. For the notch stress concept a notch model with a reference radius of rref=0.05 mm was used for the FE-simulations. The endurable notch stresses were compared to reference S-N curves derived for conventional welded samples. The EMPT-results fit well in the scatter band of the conventional laser-welded joints. This is the verification that the notch stress concept can be successfully applied also for EMPT joints.2018-05-15T00:00:00ZCharacterization of High-Speed Flyer Evolution by Multi-Probe Photon Doppler Velocimetry
http://hdl.handle.net/2003/36961
Title: Characterization of High-Speed Flyer Evolution by Multi-Probe Photon Doppler Velocimetry
Authors: Lee, T.; Taber, G.; Vivek, A.; Daehn, G. S.
Abstract: In this paper, the shape evolution of an aluminium flyer is characterized by a 16-probe Photonic Doppler Velocimeter while being impulsed by a Vaporizing Foil Actuator. For high-speed manufacturing, understanding the shape evolution of a flyer can advance the understanding of the characteristics of the applied pressure as well as the dynamics of the material; however, shock-driven process conditions often make it difficult to perform an in-situ study due to its rapidity and high non-equilibrium nature. Characterization of flyer evolution is also essential for comprehending the mechanism of impact welding, as it can enable measuring the process parameters at the time of collision, thus allowing for the prediction of the weld interface structure. An example is provided with an Al-Mg weld interface, showing the process-microstructure relationship of an impact welding process.2018-05-14T00:00:00ZInfluence of the Free Compression Stage on Magnetic Pulse Welding of Tubes
http://hdl.handle.net/2003/36960
Title: Influence of the Free Compression Stage on Magnetic Pulse Welding of Tubes
Authors: Lueg-Althoff, J.; Schilling, B.; Bellmann, J.; Gies, S.; Schulze, S.; Tekkaya, A. E.; Beyer, E.
Abstract: In magnetic pulse welding (MPW) of tubular parts, the acceleration of the ‘flyer’ part typically
corresponds to a free electromagnetic compression (EMC) process over the distance
of the initial standoff between the outer and inner tube. During this process stage, already
significant plastic strains occur. In addition, wrinkling is a phenomenon frequently observed
during EMC. In this manuscript, influencing factors on the wrinkling effect are
identified, taking the initial geometry of the flyer tube and its manufacturing process into
account. Moreover, a link between the strains and wrinkles caused by the tube compression
and the MPW process is made.
An experimental study is performed aiming for the quantification of the plastic deformation
during EMC. The effect of this deformation on the stability and adhesion of brittle
surface layers is analyzed. Accompanying numerical simulations help to understand the
wrinkle formation and its influencing factors. Based on the results, hints for an improved
process design of MPW are given.2018-05-15T00:00:00ZPlasma Induced On Indenter Balls
http://hdl.handle.net/2003/36959
Title: Plasma Induced On Indenter Balls
Authors: Czotscher, T.; Vollertsen, F.
Abstract: There is an increasing demand to enable high throughput experimentation to characterize and develop new materials in a very short time. The investigated hardness measurement method differs from conventional hardness measurements in how the force is applied. The new method is based on laser-induced shockwaves. A shockwave is created with a nanosecond pulsed TEA CO2 laser on top of an indenter. The pressure of the shockwave is used to push an indenter inside a workpiece. A quadratic laser focus area of 4 mm², having a diagonal larger than the indenter diameter, leads to interactions of the laser beam with the surrounding material, which affects the plasma formation and results in heating of the material underneath. Material heating decreases the yield point and accordingly the hardness. Therefore, influence of pulse energy and plasma formation on heating of material are investigated to understand the interaction between the high intensity laser beam, the indenter and the material underneath. It is shown that a 3 mm indenter diameter reduces the maximum estimated temperature of the workpiece (X5CrNi18-10) underneath down to 64°C. With an additional positioning unit in combination with indenter diameter of 3 mm or larger no significant heat input was obtained anymore in the workpiece underneath.2018-05-14T00:00:00ZApplication of Electrohydraulic Forming for low volume and prototype parts
http://hdl.handle.net/2003/36958
Title: Application of Electrohydraulic Forming for low volume and prototype parts
Authors: Golovashchenko, S. F.; Mamutov, A. V.; Mamutov, V. S.
Abstract: Electrohydraulic forming process enables forming of panels from Dual Phase steels in case the strain level required to fill the shape exceeds formability limit. Filling of the die cavity was conducted in nine discharges to allow for smoother materials flow from the flanges. Additional formability benefit was obtained by preforming operation which was based on bulging the areas of low strain adjacent to heavily stretched areas of the blank. Filling of all the radii was achieved during final higher energy discharges.2018-05-14T00:00:00ZNumerical Simulation and Experiments for Dynamic Material Properties of Aluminium Alloy in SHPB Experiment using Pulse Shaping Method
http://hdl.handle.net/2003/36957
Title: Numerical Simulation and Experiments for Dynamic Material Properties of Aluminium Alloy in SHPB Experiment using Pulse Shaping Method
Authors: Kim, J.; Kim, Y. H.; Kang, B. S.; Woo, M. A.; Koo, T. W.
Abstract: For the analysis of high speed forming such as electromagnetic forming and electrohydraulic forming, dynamic material properties are required. The split Hopkinson pressure bar (Kolsky bar) was suggested for measuring dynamic material properties from 100 to 10000 /sec strain rate. In the SHPB experiments, the assumption is needed that specimen between incident bar and transmitted bar reaches the dynamic stress equilibrium. For the derivation of average engineering strain and average engineering stress in SHPB experiments, the stress wave at the front and the back of specimen should match each other.
A pulse shaping method helps to improve the stress equilibrium of specimen. As one of the various pulse shaping methods, a method of attaching a pulse shaper in front of incident bar was carried out.
Numerical simulation and SHPB experiments was performed for verification about pulse shaper effect. The result of experiments and numerical analysis show that the pulse shaper contributes to the dynamic stress equilibrium. The dynamic material properties of Al6061-T6 were obtained, and the simulation was implemented by inputting that properties. As a result of comparing the experiments with new simulation, it was confirmed that the error of specimen length was within 5%.2018-05-14T00:00:00ZUtilizing a Meso Scale Limited Dome Test to Study the Effect of Strain Rate on the Formability of Commercial Pure Titanium Grade Two Foil
http://hdl.handle.net/2003/36956
Title: Utilizing a Meso Scale Limited Dome Test to Study the Effect of Strain Rate on the Formability of Commercial Pure Titanium Grade Two Foil
Authors: Gau, J.-T.; Zhang, K.; Wang, Z.
Abstract: Due to its hexagonal close-packed (HCP) crystal structures and limited slipping systems, commercial pure titanium (CP Ti) has a relatively low ductility at room temperature. In order to understand the effect of strain rate on formability of the as-received tempered CP Ti grade 2 foils with thickness of 38µm, a series of meso-limited dome height (meso-LDH) tests were designed and conducted at three punch speeds (0.01mm/sec, 12m/sec and 17m/sec) without lubricant at room temperature. The forming limit curves of the foil at three different punch speeds were obtained, and can be used right away for product design, process design and development, die design, and simulations etc. As discovered in this experimental study, the reasons why increasing strain rate can improve the formability are: n value increases with increasing strain rate, the temperature of part increases rapidly due to adiabatic effect, and the negative influence of friction can be reduced.2018-05-14T00:00:00ZInterfacial Morphology Prediction of Impact Welding by Eulerian Method
http://hdl.handle.net/2003/36955
Title: Interfacial Morphology Prediction of Impact Welding by Eulerian Method
Authors: Zhang, Shunyi; Kinsey, Brad
Abstract: In this paper, results from LS-DYNA numerical simulations are presented with respect to the interfacial morphology of an impact weld of dissimilar sheet materials, i.e., Cu110 (flyer) and CP-Ti (base), both 1 mm thick. These materials were selected as the workpieces since vortices are known to occur at the interface during experimental welding of this material combination. But a conventional Lagrangian numerical method is not capable of capturing this phenomenon due to large element distortions at the interface. Thus, a numerical simulation with the Eulerian method was used to investigate this local, large plastic deformation of materials at high strain rate. Unlike the Lagrangian method, the surrounding air is modelled in the Eulerian method, with a 5 by 5-micron element size in this research, to capture the vortices at the interface. A Johnson-Cook material model, which is widely used for deformation processes at high strain rates, was used for both flyer and base workpieces. Also, a Mie-Grueneisen’s equation of state (EOS) was defined to describe the variation in pressure based on the dynamic condition of materials.2018-05-15T00:00:00ZElectrohydraulic extrusion of spherical bronze (CuSn6) micro samples
http://hdl.handle.net/2003/36954
Title: Electrohydraulic extrusion of spherical bronze (CuSn6) micro samples
Authors: Langstädtler, L.; Pegel, H.; Herrmann, M.; Schenck, C.; Stöbener, D.; Westerkamp, J. F.; Fischer, A.; Kuhfuss, B.
Abstract: Conventional material testing strategies are time and cost intensive. In this paper, a new method for contactless high-speed testing of spherical micro samples by an electrohydraulic punch is introduced. The punch transfers the punching force incrementally to extrude the samples stepwise in dies with high aspect ratios. The sample’s material behavior is characterized by analyzing the deformation behavior between the extrusion steps and at different forming stages.2018-05-14T00:00:00ZAnalysis of electromagnetic field generated by a magnetic pulse joining machine
http://hdl.handle.net/2003/36953
Title: Analysis of electromagnetic field generated by a magnetic pulse joining machine
Authors: Sofi, K.; Hamzaoui, M.; El Idrissi, H.; Nait Sidi Moh, A.; Hamzaoui, A.
Abstract: In magnetic pulse joining process, the principal components are the massive coil and the workpieces. In the coil-workpiece region, the magnetic field is generated by a pulsed and intense current. The welding is produced by the eddy current in the workpieces. An equivalent electrical scheme is proposed to specify the characteristics of the magnetic pulse generator. The main purpose of this article is to study the propagation of the electromagnetic fields in the coil and its propagation around the coil. The generator is modelled by an RLC circuit. The current pulse is based on experimental measurements using a Rogowski coil and integrated in the numerical simulation as an RLC circuit. Then using magnetic field theory, we measured the magnetic field around the coil using a flux loop and by introducing an analytical model of a massive one turn coil transformed into a multi-turn one. The analytical model is based on mutual inductance between two coaxial circular coils. A 3D numerical simulation using the finite element method and electromagnetic solver in ls-dyna software is developed to calculate the current distribution in the coil. The current density given by numerical analysis shows how the current is insignificant in the outer corners of the massive coil. This approximation is related to the analytical model design by neglecting these corners. Finally, we proposed an experimental setup to estimate electromagnetic fields around the coil. To validate the analytical method and using a massive one turn coil, we performed experimental measurements of magnetic flux density using an external one-turn coil.2018-05-14T00:00:00ZUltrasonic Assessment of Permanent Joints of Powder Metallurgy Parts Obtained by Pulsed Electromagnetic Field
http://hdl.handle.net/2003/36952
Title: Ultrasonic Assessment of Permanent Joints of Powder Metallurgy Parts Obtained by Pulsed Electromagnetic Field
Authors: Tatarinov, A.; Mironov, V.; Kolbe, M.
Abstract: Radial pressing by a pulsed electromagnetic field (PEMF) is a fast and effective way of rigid connection of thin-walled powder parts. The quality of joining depends on well-chosen intensity and uniformity of the applied PEMF. The difficulty of non-destructive tests of joints by standard ultrasonic flaw detectors is often caused by a curved shape and a small radius of parts. The coarse-grained structure and porosity of powder parts cause a strong attenuation of ultrasound at frequencies above 3 MHz. Two ultrasonic methods were compared for sensitivity to weak and tight connections of “bush-on-bush” and “bush-on-rod” joints – pulse-echo and time-of-flight (TOF). Bushes were made of powder bronze graphite. The pulse-echo method was implemented using a commercial flaw detector with a 3MHz dual-element probe. A custom setup with quasi-point transducers at 2MHz was used in the TOF method. Weak joining between parts resulted in increased reflection of ultrasound from the bonded zones between the parts and the corresponding changes in the ultrasonic patterns. Both methods are potentially applicable to quality assurance in PEMF joining, where TOF is preferable for testing small curved parts.2018-05-14T00:00:00ZDesign of Hybrid Conductors for Electromagnetic Forming Coils
http://hdl.handle.net/2003/36950
Title: Design of Hybrid Conductors for Electromagnetic Forming Coils
Authors: Gies, S.; Tekkaya, A. E.
Abstract: The use of hybrid coil turns made of steel (St) and copper (Cu) is originally motivated by the
increased mechanical strength compared to monolithic copper conductors. Due to the
differing electrical conductivities of the two materials, the hybrid design also changes the
current density distribution in the conductor cross section. This affects crucial process
parameters such as the magnetic pressure and the Joule heat losses.
The effect of the hybrid conductor design on the process efficiency is investigated. An
electromagnetic sheet metal forming operation using a one-turn coil with rectangular cross
section is used as reference case. The copper layer (CuCr1Zr) was deposited on a tool steel
substrate (X40CrMoV5-1) using a selective laser melting process. The copper layer
thickness is varied ranging from a monolithic steel conductor to a monolithic copper
conductor. The workpiece (EN AW-5083, t_w = 1 mm) is formed through a drawing ring so
that the final forming height is a qualitative measure for the process efficiency. The
experimental results prove that the efficiency in case of a properly designed hybrid
conductor can exceed the efficiency of a monolithic copper coil. The current density
distribution in the hybrid cross section is investigated by means of numerical simulations.
This way a deeper insight into the physical effects of a varying copper layer thickness is
gained. The results reveal that the optimum layer thickness is not just a function of the coil
cross section and the current frequency. It is also affected by the coil length and the
resistance of the pulse generator.2018-05-14T00:00:00ZA Study on the Critical Thickness of the Inner Tube for Magnetic Pulse Welding Using FEM and BEM
http://hdl.handle.net/2003/34950
Title: A Study on the Critical Thickness of the Inner Tube for Magnetic Pulse Welding Using FEM and BEM
Authors: Geng, H.; Cui, J.; Sun, G.; Li, G.
Abstract: Due to high efficiency and quality in welding dissimilar metals, Magnetic Pulse Welding
(MPW) has attracted much attention. In this study, 3A21 aluminium alloy used as outer
tube was welded to 20Fe tube by MPW. In order to investigate the critical thickness of the
inner tube (20Fe) which is subjected to huge impact pressure from the outer tube (3A21),
both numerical simulations and experiments were carried out.
For the purpose of investigating the critical thickness of the inner tube under various
impact velocities, four discharge voltages (9 kV, 11 kV, 13 kV and 14 kV) were employed
in the MPW experiment. The diameters of inner tube at different locations were measured
to obtain its plastic deformation at various discharge voltages. The simulations
considering the coupled effects of the mechanical, thermal and electromagnetic process
were performed to research the impact velocity and deformation of tubular fittings in the
electromagnetic module (EM) in LS-DYNA. An inverse method was proposed to find the
dynamic yield stress of inner tube, and the predicted yield stress was then employed in
models with critical thickness. Both of the impact velocity and deformation were verified
experimentally.2016-04-27T00:00:00ZThe Influence of Thermal and Mechanical Effects on the Bond Formation During Impact Welding
http://hdl.handle.net/2003/34949
Title: The Influence of Thermal and Mechanical Effects on the Bond Formation During Impact Welding
Authors: Pabst, C.; Groche, P.
Abstract: Impact welding, usually applied as explosion welding or electromagnetic pulse welding, is
a highly transient joining process. Strain rates in orders of magnitude far above 104 1/s and
resultant thermal effects occur and influence the formation of the joint significantly.
Experimental and microscopic investigations as well as analytical estimations are carried
out and presented in this paper in order to gain a more comprehensive understanding of the
effective mechanisms and their relevance. In addition to electromagnetic pulse welding, a
specially built test rig is used to identify the process window and its change due to modified
parameters. The test rig allows to change both impact parameters, angle β and velocity v_c ,
independently.
It will be shown that the actual formation of the joint and its characteristics are greatly
affected by the surrounding gaseous media. Strength and size of the joint can be influenced
as well as the location of the process window. Theories will be developed to explain these
results and to make them usable for the practical application. Furthermore, experimental
results indicate that the compression of the ambient atmosphere in the closing gap between
the two specimens evokes highly elevated temperature, which is in good accordance with
earlier findings.2016-04-27T00:00:00ZElectromagnetic Pulse Welded Aluminium to Copper Sheet Joints: Morphological and Mechanical Characterization
http://hdl.handle.net/2003/34948
Title: Electromagnetic Pulse Welded Aluminium to Copper Sheet Joints: Morphological and Mechanical Characterization
Authors: Faes, K.; Kwee, I.
Abstract: This study investigated joining of Al to Cu sheets by electromagnetic pulse welding, which
is a solid-state welding process that uses electromagnetic forces to join materials. The
interfacial morphology and mechanical properties of the Al/Cu joints were analysed and
related to the welding process parameters. The centre section of the Al/Cu joints evolved
from a non-welded to a welded zone. The welded zone started with a wavy interface,
consisting of thick interfacial layers with defects and evolved to a relatively flat interface
without an interfacial layer. Interfacial phases resulted from solid-state mechanical mixing
and/or very localised interfacial heating. The interfacial layers had a thickness ranging
from 2-39 μm, an interface waviness amplitude up to 11 μm and contained 31-75 wt% Cu.
The interfacial layer thickness and the weld length are determined by both the discharge
energy and the stand-off distance. A trade-off existed between a homogeneous interface
and the maximum weld length when the stand-off distance is changed. The interfacial layer
exhibited an increased hardness compared to Al and Cu. A higher tensile force, up to
4,9 kN, was achieved at a higher energy and a lower stand-off distance. One of the factors
determining the tensile force was the width of the welded area.2016-04-27T00:00:00ZBenchmarking and Refining the Vaporizing Foil Actuator Spot Welding Process
http://hdl.handle.net/2003/34947
Title: Benchmarking and Refining the Vaporizing Foil Actuator Spot Welding Process
Authors: Vivek, A.; Wright, S. M.; Liu, B. C.; Hansen, S. R.; Brune, R. C.; Thurston, B. P.; Taber, G. A.; Lee, T.; Mao, Y.; Dittrich, T. J.; Daehn, G. S.
Abstract: Impact spot welding implemented by the vaporizing foil actuator welding method has been
studied. With significantly lower input energy levels as compared to resistance spot
welding, similar and dissimilar lap welding of aluminium alloys (AA) of types 5052 and
7075 was implemented. The dissimilar welds between 2 mm thick AA5052 and 2.3 mm
thick AA7075 were created with 4 kilojoules input energy, whereas the similar welds
between 1 mm thick AA5052 sheets required only 0.6 kilojoules. Flyer sheet velocities of
approximately 750 m/s were measured with a PDV system. Microhardness measurements,
performed across the dissimilar weld interfaces, showed no softening of the base materials
due to the welding process. A few distinct welding configurations were investigated for
improving process feasibility and obtaining the highest possible weld strength. Lap shear
tests and pry tests revealed that the configuration of the starting weld geometry greatly
affected weld quality.2016-04-27T00:00:00ZEffects of Surface Coatings on the Joint Formation During Magnetic Pulse Welding in Tube-to-Cylinder Configuration
http://hdl.handle.net/2003/34946
Title: Effects of Surface Coatings on the Joint Formation During Magnetic Pulse Welding in Tube-to-Cylinder Configuration
Authors: Bellmann, J.; Lueg-Althoff, J.; Goebel, G.; Gies, S.; Beyer, E.; Tekkaya, A. E.
Abstract: Magnetic Pulse Welding (MPW) is a joining technique favorable for the generation of
strong atomic bonded areas between different metals, e.g. aluminum and steel. Brittle
intermetallic phases can be avoided due to the high-speed collision and the absence of
external heat. The demand for the use of this technique in industries like automotive and
plant engineering rises. However, workpieces used in these fields are often coated, e.g. in
order to improve the corrosion resistance. Since the weld quality depends on the material’s
behavior at the collision zone, surface layers in that region have to be taken into account
as well.
This work investigates the influences of different coating types. Aluminum to steel
welding is used as an example system. On the inner steel part (C45) coatings like zinc,
nickel and chrome are applied, while the aluminum flyer tubes (EN AW-6060) are
anodized, chromated and passivated. Welding tests are performed using two different
welding systems with varying discharging frequencies and four geometrical part setups.
For all combinations, the flyer velocity during the process is measured by Photon Doppler
Velocimetry (PDV). By using the uncoated material combination as a reference, the
removal of surface layers due to jetting is analyzed. Finally, the weld quality is
characterized in peel tests, shear-push tests and by the help of metallographic analysis. It
is found that certain coatings improve the joint formation, while others are obstructive for
the performance of MPW. Some coatings have no influence on the joining process at all.2016-04-27T00:00:00ZImpact Welding Structural Aluminium Alloys to High Strength Steels Using Vaporizing Foil Actuator
http://hdl.handle.net/2003/34945
Title: Impact Welding Structural Aluminium Alloys to High Strength Steels Using Vaporizing Foil Actuator
Authors: Liu, B.; Vivek, A.; Daehn, G. S.
Abstract: Dissimilar Al/Fe joining was achieved using vaporizing foil actuator welding. Flyer
velocities up to 727 m/s were reached using 10 kJ input energy. Four Al/Fe combinations
involving AA5052, AA6111-T4, JAC980, and JSC1500 were examined. Weld samples were
mechanically tested in lap-shear in three conditions: as-welded, corrosion-tested with ecoating,
and corrosion-tested without coating. In all three conditions, the majority of the
samples failed in the base aluminium instead of the weld. This shows that the weld was
stronger than at least one of the base materials, both before and after corrosion testing.
Galvanic corrosion was not significant since the differences in open cell potential, which
represent the driving forces for galvanic corrosion, were small among these materials—no
more than 60 mV in all cases. Nonetheless, through corrosion testing, the base materials
suffered general corrosion, which accounted for the weakening of the base materials.2016-04-27T00:00:00ZInfluence of the Wall Thicknesses on the Joint Quality During Magnetic Pulse Welding in Tube-to-Tube Configuration
http://hdl.handle.net/2003/34944
Title: Influence of the Wall Thicknesses on the Joint Quality During Magnetic Pulse Welding in Tube-to-Tube Configuration
Authors: Lueg-Althoff, J.; Schilling, B.; Bellmann, J.; Gies, S.; Schulze, S.; Tekkaya, A. E.; Beyer, E.
Abstract: The implementation of multi-material concepts, for example, in automotive engineering or
aerospace technologies, requires adequate joining techniques. The Magnetic Pulse Welding
(MPW) process allows for joining both similar and dissimilar materials without additional
mechanical elements, chemical binders, or adverse influences of heat on the joining partners.
In this process, an electro-conductive at (‘flyer’) part is accelerated by Lorentz forces
and impacts the inner (‘parent’) part under high velocity and high pressure, leading to the
formation of a metallurgical joint. Besides joining of sheets and tubes to solid cylinders, the
connection of two tubes is of particular interest due to the increased lightweight potential.
The present paper focuses on the MPW of aluminum (EN AW-6060) to steel (C45) tubes. An
experimental study was performed, in which the wall thickness of the parent part was reduced
successively. The deformation behavior of both the flyer and parent parts was recorded
during the experiments by a two-probe Photon Doppler Velocimeter (PDV). The final
shape of the joined specimens was analyzed by a 3D digitizer. An instrumented peel test was
used for the determination of the weld quality. It was found that defect-free MPW of aluminum
tubes on steel tubes without supporting mandrel is possible.2016-04-27T00:00:00ZInfluence of Different Strain Rates on the Flow Curve and the Formability of Thin Aluminium and Tinplate Sheets
http://hdl.handle.net/2003/34943
Title: Influence of Different Strain Rates on the Flow Curve and the Formability of Thin Aluminium and Tinplate Sheets
Authors: Linnemann, M.; Lieber, T.; Scheffler, C.; Psyk, V.; Müller, R.; Landgrebe, D.
Abstract: Due to this high number of produced units and the very thin sheet metals used for beverage
cans, precise production processes with high production volumes are necessary. To save
expenses, while optimising these processes, numerical simulation methods are exploited.
Considering this, it is indispensable to identify the material behaviour as exactly as possible.
In practise, often results of quasi static tensile tests are used, although these are insufficient
for the precise modelling of the material behaviour during can production, since strain rates
of up to 10³ s-1 can occur, here. Therefore, quasi static and high speed tensile test have been
done on specimens featuring the typical materials and thicknesses of semi-finished parts
used for beverage can production. The results were compared with similar materials at
higher sheet metal thicknesses and authenticated by numerical simulation. It was shown that
there is an influence of the strain rate on the material behaviour and it is necessary to
determine material characteristics at strain rates, which are close to the process speed.
Furthermore, the results were classified in their signification for beverage can production
and forming technologies in general.2016-04-27T00:00:00ZExperimental and Numerical Prediction of the Static and Dynamic Forming Properties of Ti6Al4V
http://hdl.handle.net/2003/34942
Title: Experimental and Numerical Prediction of the Static and Dynamic Forming Properties of Ti6Al4V
Authors: Verleysen, P.; Galan-Lopez, J.
Abstract: The strain rate dependence of the plastic yield and failure properties displayed by most
metals affects energies, forces and forming limits involved in high speed forming processes.
In this contribution a technique is presented to assess the influence of the strain rate on the
forming properties of Ti6Al4V sheet. In a first step, static and dynamic tensile experiments
are carried out using a classical tensile test device and a split Hopkinson tensile bar facility
respectively. Next to uniaxial tensile, also purpose-developed plain strain and shear stress
samples are tested. The experimental results clearly show that the mechanical behaviour of
Ti6Al4V is strain rate dependent. Indeed, with increasing strain rate, plastic stress levels
increase, however, this occurs at the expense of the deformation capacity. Subsequently, to
allow simulation of forming processes, Johnson-Cook, Swift and Voce material model
parameters are determined. Finally, the influence of the strain rate on the forming limits is
assessed using the uni-axial tensile test results. Prediction of the initiation of necking in the
Ti6Al4V sheets subjected to multi-axial strain states is based on the Marciniak-Kuczynski
model. The thus obtained forming limit diagrams (FLDs) show a non-negligible effect of the
strain rate. The reduced ductility at higher strain rates is reflected into an unfavourable
downward shift of the FLD. Compared with the experimental data, the static FLD is clearly
conservative.2016-04-27T00:00:00ZDevelopment of Vibration During the Electromagnetic Ring Expansion Test
http://hdl.handle.net/2003/34941
Title: Development of Vibration During the Electromagnetic Ring Expansion Test
Authors: Yang, K.; Taber, G.; Sapanathan, T.; Vivek, A.; Daehn, G. S.; Raoelison, R. N.; Buiron, N.; Rachik, M.
Abstract: Magnetic pulse forming (MPF) techniques work on the principle of Lorentz force induced
by eddy current which can cause plastic deformation in a metal workpiece. Lorentz force
depends on parameters such as frequency and amplitude of input current, electromagnetic
properties of materials and distance between the work piece and coil. The development of
vibration as a consequence of elastic strain recovery in a ring expansion process using a
MPF technique has been identified and presented in this paper. Coupled mechanicalelectromagnetic
3D simulations were carried out to investigate the effect of various
magnetic pulse currents in the development of reversal of motion during the MPF process
using LS-DYNA package. Ring expansion using a multi-turn helix coil with an applied
pulse current, with the rings made of aluminum alloy AA6061 –T6 is investigated for the
effect of vibration during the process. The numerical results show good agreement with
the experimental work for various currents. The underlying principle of vibration and
formability has respectively been studied using force analysis and stress analysis. The
results also show that the 5.6kJ energy already increased the formability by ~66 percent in
comparison with the quasi-static formability value from the literature.2016-04-27T00:00:00ZDevelopment of an Interrupted Pulse Expanding Ring Test
http://hdl.handle.net/2003/34940
Title: Development of an Interrupted Pulse Expanding Ring Test
Authors: Imbert, J.; Worswick, M.
Abstract: An interrupted pulse electromagnetic (EM) expanding ring test is being developed at the
University of Waterloo to study the high rate behaviour of sheet metals. In a classic EM
expanding ring test, a ring is expanded radially using the forces induced on the ring by a
high frequency high intensity current flowing in a nearby coil. If the driving force and the
acceleration of the ring are known, then the stress-strain history of the ring can be
determined. Coil currents are typically generated by large capacitor banks that produce a
current discharge in the shape of a damped sinusoid. To properly determine the stress of the
ring, the forces induced on the ring by the current pulse must be known, which is difficult to
do in practice. The approach taken in this work is to interrupt the current by means of an
exploding wire switch to eliminate the Lorentz forces and achieve a free flight condition,
where the stress can be determined using only the measured velocity and density of the ring.
The velocity of the rings was measured using a photon Doppler velocimeter (PDV). With
this technique significant periods of free-flight were obtained, with the corresponding stressstrain
data. Results for 1.5 mm sheet of AA 5182-O are presented.2016-04-27T00:00:00ZA New Experimental Technique for Applying Impulse Tension Loading
http://hdl.handle.net/2003/34939
Title: A New Experimental Technique for Applying Impulse Tension Loading
Authors: Fan, Z. S.; Yu, H. P.; Su, H.; Zhang, X.; Li, C. F.
Abstract: This paper deals with a new experimental technique for applying impulse tension loads.
Briefly, the technique is based on the use of pulsed-magnetic-driven tension loading.
Electromagnetic forming (EMF) can be quite effective in increasing the forming limits of
metal sheets, such as aluminium and magnesium alloys. Yet, why the forming limit is
increased is still an open question. One reason for this is the difficulty to let forming
proceed on a certain influence monotonically: the main phenomena causing this increase
in formability are considered to due to “body force” effect, inertia effect, changes in strain
rate sensitivity. In this study, an impulse tension loading setup is presented. “Body force”
effect and strain rate, which are known to be the two key factors leading to higher
formability, can now be separated freely by our designed device. Reproducible and
adjustable loading rate (80s-1~3267s-1) can be achieved by adjusting the discharge
voltage and capacitance. The relation between the discharge voltage and strain rate was
obtained with the help of finite element calculations and high-camera measurement results.
The results of an exploratory experiment carried out on the designed device are presented
for aluminum alloy AA5052 sheet. It shows that this technique could be used to study the
dynamic response of sheets.2016-04-27T00:00:00ZA Study to Improve the Crash Performance of Plastic Materials Considering the Strain Rate and Fracture Characteristic
http://hdl.handle.net/2003/34938
Title: A Study to Improve the Crash Performance of Plastic Materials Considering the Strain Rate and Fracture Characteristic
Authors: Kim, H. Y.; Lee, C. A.; Bamg, J. H.; Cho, B. C.; Kim, D. Y.; Ha, D. Y.
Abstract: The numerical simulation of structural parts made from plastics is becoming increasingly
important nowadays. The fact that almost any structural requirement can be combined in a
lightweight, durable and cost effective structure is the driving force behind its widespread
application. More and more structural relevant parts are being constructed and
manufactured from plastics. It is difficult accurately to predict the reliability according to
finite element analysis, because plastics materials show the complex material behaviour.
Thus, it is demanded for reliable and obvious methods to design these parts and to predict
their material behaviour. For the finite element simulations of polymeric materials
mathematical models are needed which cover all the phenomena of the material.
In this paper, it is possible to describe accurately the mechanical behaviour of
thermoplastic materials using a new constitutive model termed as SAMP-1(Semi-
Analytical Model for Polymers) in LS-dyna. We performed the high speed tension tests
(strain rate: 0.001/s, 0.1/s, 1/s, 50/s, 100/s) for the characterisation of the plastics
material. Also, the parameters of the SAMP-1 model were identified by using multidirectional
mechanical tests such as uniaxial tension, simple shear, and compression tests.
As validation purpose, the SMAP-1 model was compared to the existing models for
predicting the stress-strain behaviour in the test specimens and the dynatup impact test.2016-04-27T00:00:00ZMaterial Constitutive Behavior Identification at High Strain Rates Using a Direct-Impact Hopkinson Device
http://hdl.handle.net/2003/34937
Title: Material Constitutive Behavior Identification at High Strain Rates Using a Direct-Impact Hopkinson Device
Authors: Guo, X.; Sow, C.; Khalil, C.; Heuzé, T.; Racineux, G.
Abstract: Modern numerical simulation techniques allow nowadays obtaining accurate solutions of
magnetic pulse and electrohydraulic forming/welding processes. However, one major
difficulty persists: the identification of material constitutive equations behavior at levels of
high strain rates reached by these processes, and which varies between 103 and 105 s-1.
To address this challenge, a direct-impact Hopkinson system was developed at ECN.
It permits to perform dynamic tests at very high strain rates exceeding the range of the
traditional Split Hopkinson Pressure Bars and hence enable us to identify constitutive
models for a wide range of strain rates. The alloy used to test this device was Ti-6Al-4V.
Strain rates up to 2.5×103 s-1 were attained.2016-04-27T00:00:00ZQualification of CuCr1Zr for the SLM Process
http://hdl.handle.net/2003/34936
Title: Qualification of CuCr1Zr for the SLM Process
Authors: Uhlmann, E.; Tekkaya, A. E.; Kashevko, V.; Gies, S.; Reimann, R.; John, P.
Abstract: Working coils for electromagnetic forming processes need to comply with a wide list of
requirements such as durability, efficiency and a tailored pressure distribution. Due to its
unique combination of high strength and high electrical conductivity CuCr1Zr meets these
requirements and is a common material for coil turns. In combination with conventional coil
production processes like winding or waterjet cutting the use of this material is state of the
art. A promising approach for coil production is the use of additive manufacturing (AM)
processes. In comparison to conventional manufacturing processes, AM offers tremendous
advantages such as feature-integration e.g. undercuts or lattice structures. However, this
increased design freedom only leads to improved working coils if copper alloys with high
strength and high electrical conductivity such as CuCr1Zr can be processed. Due to the high
thermal conductivity and reflectivity the use of suchlike materials in additive manufacturing
processes is challenging. Considering the effects of the required pre- and post-processing
treatments for additive manufactured parts the need for research is further increased. The
objective of this paper is to develop a method for the qualification of CuCr1Zr for the
selective laser melting (SLM) process. This comprises the powder characterization, the
process parameter identification and the microstructure investigation of the generated test
geometries.2016-04-27T00:00:00ZElectrodynamics of Magnetic Pulse Welding Machines: Global and Local Electrical Analogues
http://hdl.handle.net/2003/34935
Title: Electrodynamics of Magnetic Pulse Welding Machines: Global and Local Electrical Analogues
Authors: Bouzerar, R.; Bougrioua, F.; Tekaya, I.; Foy, N.; Hamzaoui, M.; Bourny, V.; Durand-Drouhin, O.; Jouaffre, D.; Haye, D.
Abstract: In this paper, a theoretical, experimental and numerical study of MPW machines is carried
out. While it is known that such machines are very complex by nature because of the coupling
between different parts, we used simple electrical analogues to describe its dynamics. A RLC
circuit modeling the whole machine is depicted and experimental results are shown. A
further study including numerical simulations allows to compute the current distribution and
estimate the magnetic field within the coil but also the magnetic pressure generated in the
process, all using a 2D model and reasonable assumptions. A late theoretical study opens
the way for innovative experimental measurements regarding the kinetics of the
deformations of metallic tubes, but also their mechanical behavior before the welding
process, making use of their capacitive properties.2016-04-27T00:00:00ZEfficient Coil Design by Electromagnetic Topology Optimization for Electromagnetic Sharp Edge Forming of DP980 Steel Sheet
http://hdl.handle.net/2003/34934
Title: Efficient Coil Design by Electromagnetic Topology Optimization for Electromagnetic Sharp Edge Forming of DP980 Steel Sheet
Authors: Choi, M. K.; Huh, H.; Seo, M. H.; Kang, Y.
Abstract: This paper proposes a design method of the tool coil by topology optimization for the
electromagnetic sharp edge forming process. Topology optimization is an approach that
optimizes material configuration in a given domain to meet the design requirements. The
design problem for the tool coil is defined as enhancing efficiency of the forming process
and optimization problem is set to be maximization of the Lorentz force induced on the tool
coil. A new topology optimization formulation based on the numerical methods for
electromagnetism using FEM and BEM is developed for maximization of the Lorentz force.
Optimum design of the tool coil is obtained by the topology optimization using the element
density approach. The optimized result is compared with other coils which have different
configurations to show the effectiveness of the proposed method. The idea of applying
topology optimization to the design of the tool coil is successful and this formulation deals
effectively for the optimization problems.2016-04-27T00:00:00ZEffect of Conductivity of the Inner Rod on the Collision Conditions During a Magnetic Pulse Welding Process
http://hdl.handle.net/2003/34933
Title: Effect of Conductivity of the Inner Rod on the Collision Conditions During a Magnetic Pulse Welding Process
Authors: Sapanathan, T.; Yang, K.; Raoelison, R. N.; Buiron, N.; Jouaffre, D.; Rachik, M.
Abstract: The Magnetic Pulse Welding (MPW) process involves a high speed collision between the
flyer and inner rod. Conductivity of the inner rod may play a significant role in the collision
speed and collision angle. The collision conditions were investigated with varying
conductivity of the inner rod in this study. Coupled mechanical-electromagnetic 3D
simulations were carried out using LS-DYNA package to investigate the effect of
conductivity of the inner rod on the collision patterns during the MPW process. The
simulation involves a welding process with a tube and a rod using a one turn coil with a
separate field shaper. The electrical conductivity was varied to a wide range to investigate
the influence on the collision condition. Moreover, in order to verify the independency of the
collision condition with the mechanical properties of the inner rod, two cases including
aluminum alloy AA2024-T351 and copper with appropriate Johnson-Cook parameters were
used for the rod. In the entire simulations aluminum alloy was used as the tube material. It
was identified that the impact velocity is almost consistent for each case and the impact
angles vary between negative and positive values according to the angular measurement
convention used in this study. Although, influence of the conductivity of the inner rod is not
significant for the investigated current flow while it may sometime delay the incidence of
collision at lower frequencies than the critical frequency (FCrit). Optimizing the collision
conditions in the MPW process can help to identify the suitable materials for prescribed
welding conditions.2016-04-27T00:00:00ZA Coupled 3D/2D Axisymmetric Method for Simulating Magnetic Metal Forming Processes in LS-DYNA
http://hdl.handle.net/2003/34932
Title: A Coupled 3D/2D Axisymmetric Method for Simulating Magnetic Metal Forming Processes in LS-DYNA
Authors: L‘Eplattenier, P.; Çaldichoury, I.
Abstract: LS-DYNA is a general purpose explicit and implicit finite element program used to analyse
the non-linear dynamic response of three-dimensional solids and fluids. It is developed by
Livermore Software Technology Corporation (LSTC). An electromagnetism (EM) module
has been added to LS-DYNA for coupled mechanical/thermal/electromagnetic simulations,
which have been extensively performed and benchmarked against experimental results for
Magnetic Metal Forming (MMF) and Welding (MMW) applications. These simulations are
done using a Finite Element Method (FEM) for the conductors coupled with a Boundary
Element Method (BEM) for the surrounding air, hence avoiding the need of an air mesh.
More recently, a 2D axisymmetric version of the electromagnetic solver was
introduced for much faster simulations when the rotational invariance can be assumed.
In many MMF and MMW applications though, the rotational invariance exists only
for part of the geometry (typically the coil), but other parts (typically the workpiece or the
die) may not have this symmetry, or at least not for the whole simulation time.
In order to take advantage of the partial symmetry without limiting the geometry to
fully symmetric cases, a coupling between 2D and 3D was introduced in the EM. The user
can define the parts that can be solved in 2D and the ones which need to be solved in 3D
and the solver will assume the rotational invariance only on the 2D parts, thus keeping the
results accurate while significantly reducing the computation time.
In this paper, the coupling method will be presented along with benchmarks with fully
3D and fully 2D simulations, comparing the accuracy of the results and the simulation times.2016-04-27T00:00:00ZIncrease of the Reproducibility of Joints Welded with Magnetic Pulse Technology Using Graded Surface Topographies
http://hdl.handle.net/2003/34931
Title: Increase of the Reproducibility of Joints Welded with Magnetic Pulse Technology Using Graded Surface Topographies
Authors: Rebensdorf, A.; Boehm, S.
Abstract: The reproducibility of individual welding methods depends to large extents on the material
properties. This is especially the case for impact welding as tests have shown that the surface
properties influence the joint formation. With the aim to influence the formation and position
of the lower curve of the welding process window, this paper focuses on how the surface
topography influences an asymmetrical impact. Additionally, relevant process parameters
(e.g. collision speed, collision angle, jet formation) will be included and disturbance
contours that are placed transversely to the collision vector will be examined. A high-speed
camera was used to measure the collision speed as well as the collision angle. The specific
surface topographies were created using belt grinding (cutting with geometrically undefined
edges) and laser ablation (non-cutting process, local vaporization of materials through
pulsed laser beams). The tests exemplarily show a strong correlation between the surface
geometries and the joint. The disturbance contours that were introduced transversely to the
collision vector shift the lower weld seam boundary, whereas a reduction of the discharge
energy leads to a relative strength of the joint of 1.0.
In sum, this paper offers fundamental insights into the mechanisms of the joint
formation when using magnetic pulse welding and shows the influence of the surface
topographies on the conflict between relevant procedural parameters and the possibility to
shift the lower procedural window.2016-04-27T00:00:00ZElectrohydraulic Forming of Light Weight Automotive Panels
http://hdl.handle.net/2003/34930
Title: Electrohydraulic Forming of Light Weight Automotive Panels
Authors: Mamutov, A. V.; Golovashchenko, S. F.; Bonnen, J. J.; Gillard, A. J.; Dawson, S. A.; Maison, L.
Abstract: This paper describes the results of development of the electrohydraulic forming (EHF)
process as a near-net shape automotive panel manufacturing technology. EHF is an
electro-dynamic process based upon high-voltage discharge of capacitors between two
electrodes positioned in a fluid-filled chamber. This process is extremely fast, uses lowercost
single-sided tooling, and potentially derives significantly increased formability from
many sheet metal materials due to the elevated strain rate. Major results obtained during
this study include: developing numerical model of the EHF; demonstrating increased
formability for high-strength materials and other technical benefits of using EHF;
developing the electrode design suitable for high volume production conditions;
understanding the limitations on loads on the die in pulsed forming conditions; developing
an automated fully computer controlled and robust EHF cell; demonstration of
electrohydraulic springback calibration and electrohydraulic trimming of stamped panels;
full scale demonstration of a hybrid conventional and EHF forming process for automotive
dash panel.2016-04-27T00:00:00ZDetermination of Forming Speed at a Laser Shock Stretch Drawing Process
http://hdl.handle.net/2003/34929
Title: Determination of Forming Speed at a Laser Shock Stretch Drawing Process
Authors: Veenaas, S.; Vollertsen, F.; Krüger, M.; Meyer, F.; Hartmann, M.
Abstract: Laser shock forming is a new high speed forming process based on TEA-CO2-laser induced
shock waves. In former publications laser shock forming was already presented as a process
which can be used for deep drawing, stretch drawing and cutting of thin copper and
aluminum sheets. The process utilizes an initiated plasma shock wave on the target surface,
which leads to the sheets forming. Several pulses can be applied at one point in order to
achieve a high forming degree without increasing the energy density beyond the ablation
limit. During the process, pressure peaks in the range of some MPa can be achieved. In
order to classify the process in the framework of high speed forming processes, the temporal
varying deformation velocity due to different materials have been identified based on a
stretch drawing process by using different pulse energies. Therefore a new high speed
measurement system based on the shadowing effects is designed and its suitability is shown.
The determined strain rate of 520 s-1 meets one of the criteria for the classification of laser
shock stretch drawing as a high-speed forming process.2016-04-27T00:00:00ZAnalytical and Numerical Investigation of Tube Compression with a Multi-Turn, Axisymmetric Coil
http://hdl.handle.net/2003/34928
Title: Analytical and Numerical Investigation of Tube Compression with a Multi-Turn, Axisymmetric Coil
Authors: Nassiri, A.; Zhang, S.; Reisert, K.; Kinsey, B.
Abstract: While some Finite Element software packages exist that are capable of modelling the
electromagnetic forming process and estimating the corresponding process parameters
(e.g., magnetic pressure and workpiece velocity), there is a lack of simplified and accuracy
analytical modelling tools for this purpose. In this study, a coupled analytical model was
created to predict the magnetic pressure generated by a multi-turn, axisymmetric coil and
the corresponding tube radial displacement and velocity. In the proposed model, at each
time increment, the magnetic field geometry is updated in response to the tube deformation.
To assess the proposed analytical model, numerical simulations were conducted where the
pressure distribution from the analytical model was applied. The results show good
agreement between analytical and numerical results.2016-04-27T00:00:00ZAnalytical 1D-calculation of a 1-turn Coil Parameters for the Magneto-Forming Technology
http://hdl.handle.net/2003/34927
Title: Analytical 1D-calculation of a 1-turn Coil Parameters for the Magneto-Forming Technology
Authors: Mansouri, O.; Maloberti, O.; Jouaffre, D.; Hamzaoui, M.; Derosiere, J.; Haye, D.; Leonard, J. P.; Pelca, P.
Abstract: In this paper, we will present an analytical modelling of a one-turn coil dedicated to
magnetic-pulse technologies. The goal is to be able to determine the main useful parameters
of an inductor by calculating the magnetic vector potential “A” diffusion. The concerned
parameters are electromagnetic (electromagnetic fields, magnetic flux and electric current
densities), electrical (resistance and inductance, maximum field coefficient) and
electromechanical (Lorentz force density and maximum force coefficient). The results
obtained will then be compared to numerical computations performed onto some test cases.
In order to get an approximate but robust analytical solution, it is proposed to assume an
axial symmetry and to solve the problem in the harmonic working condition before studying
the transient state.2016-04-27T00:00:00ZDetachment of Conductive Coatings by Pulsed Electromagnetic Field
http://hdl.handle.net/2003/34926
Title: Detachment of Conductive Coatings by Pulsed Electromagnetic Field
Authors: Mironov, V.; Tatarinov, A.; Kolbe, M.; Gluschenkov, V.
Abstract: The paper presents results of studies on the detachment of conductive coatings from the
metal substrate by pulsed electromagnetic field (PEMF). It is known that at the boundary of
a metal substrate and an electrically conductive coating having different electrical
conductivities sharp changes of PEMF strength arise. This effect has been used to remove a
copper layer from a steel substrate. Experimental studies were carried out in the Riga
Technical University (Latvia), West Saxony University of Applied Science Zwickau,
(Germany) and the Samara Aerospace University (Russia). Generators of pulsed current
with power capacity from 1 to 60 kJ with discharge rates from 10 to 100 kHz were used.
Treatment of coatings was performed using both flat and cylindrical inductors. The influence
of a number of factors on the efficiency of the separation of conductive coating (Cu, Al),
such as the thickness and material properties of the coating and substrate, the strength of
adhesion of the coating to the substrate, the electrical parameters of the equipment and the
inductor system, are shown. Examples demonstrating the main application potential of the
method include: deleting of a thin conductive coating induced on metallic and non-metallic
products by spraying; separation of layers of metal sheets after their joint rolling or
punching; removal of conductive membranes used in the magnetic pulse compression of
powders.2016-04-27T00:00:00ZNumerical and Experimental Investigation of Joining Aluminium and Carbon Fiber Reinforced Composites by Electromagnetic Forming Process
http://hdl.handle.net/2003/34925
Title: Numerical and Experimental Investigation of Joining Aluminium and Carbon Fiber Reinforced Composites by Electromagnetic Forming Process
Authors: Zajkani, A.; Salamati, M.
Abstract: Carbon fiber reinforced composites became so popular in automotive, aerospace, marine
and military industries in past years, because of their high strength, low weight and
subsequently high specific strength. The basic challenges of producing the CFRP
components are their forming and joining techniques. In this study, a finite element analysis
is carried out by the purpose that the optimum geometries to be selected for manufacturing
an electromagnetically assisted joining by forming system of two aluminium and CFRP
sheets. Electromagnetic forming is one of the high speed forming technologies that uses the
Lorentz force as a forming pressure. High speed and usually one-step forming process are
some of its advantages while, the necessity of high electrical conductivity of the work-piece
is an important restriction. Aluminium deformed in this study, so that its behaviour is
assumed to be dependent on the strain rate. Also, the hardening behaviour of aluminium is
described by the Johnson-Cook material model. The joining by forming system is modelled
in the finite element code by means of the ABAQUS 6.13 FEM software. The magnetic
pressure pulse of the coil is described by the VDLOAD subroutine to apply it to the lower
surface of the aluminium field shaper. Under influence of this force, the punch bulges the
aluminium sheet into the hole on the CFRP sheet and a cavity on die helps the bulged region
to form a mechanical interlock. In the experimental investigations, predrilled CFRP sheets
with different diameter holes and locations are used. The effect of geometrical parameters
such as metal thickness are studied on the quality of joints. The most important parameter
to be considered here, is the tensile strength of the joints. Therefore, the joint samples had
been applied under tensile test in order to consider failure modes, experimentally.2016-04-27T00:00:00ZProcess Design for Electromagnetic Forming of Magnesium Alloy AZ31 Using FE Simulation
http://hdl.handle.net/2003/34924
Title: Process Design for Electromagnetic Forming of Magnesium Alloy AZ31 Using FE Simulation
Authors: Uhlmann, E.; Prasol, L.; Roehrs, H.
Abstract: Magnesium wrought alloys are outstanding lightweight materials due to their low density
and high specific strength. The low formability of magnesium wrought alloy AZ31 at room
temperature is increased by electromagnetic forming in comparison to quasi-static
forming. For a detailed study of electro-magnetic process a coupled FE simulation must be
performed. In this paper the process design for electromagnetic forming of magnesium
wrought alloy AZ1 using FE simulation is presented.
The complexity of an electromagnetic forming process requires the illustration of
magnetic, thermal and structural dynamic domains. Moreover, it is also necessary to
illustrate the electromagnetic resonant circuit RLC. Short processing time and the strong
dependence of the physical domains to each other requires a coupled FE simulation.
The illustration of resonant circuit and the resulting formation of magnetic field is
carried out in two-dimensional rotationally symmetric model in ANSYS MAPDL using a
suitable material model. As a result time-dependent and location-dependent eddy currents
and Lorentz forces are estimated.
Subsequently, the transmission of the estimated Lorentz forces and joule heat
generation rates to ANSYS LS-DYNA is done. Due to the rotational symmetry of 2D ANSYS
MAPDL model a transformation of the loads on 3D structures can be realized. The
formation of an optimum deformation of a work piece in dependence of a defined die has
been carried out. Here, the influence of different coil designs, die materials and geometries
and RLC parameters was investigated.2016-04-27T00:00:00ZCombined Working Media-Based Forming on a Pneumo-Mechanical High Speed Forming Machine
http://hdl.handle.net/2003/34923
Title: Combined Working Media-Based Forming on a Pneumo-Mechanical High Speed Forming Machine
Authors: Djakow, E.; Homberg, W.; Tabakajew, D.
Abstract: Quasi-static working media-based forming processes (WMF) permit the production of
complex sheet metal parts with relatively little expense. The associated need for very high
pressures and hence complex tools and machines for the production of fine geometrical
details is often problematic. The use of high speed forming processes (HSF) can offer many
benefits, including a reduced financial outlay on equipment and better part properties in this
case. But these processes also have disadvantages, of course, such as if they are used for the
production of complex large-surface parts. Consequently, a combination of both approaches
would be ideal. This paper describes a new approach to combining high pressure sheet metal
forming (HPF) and pneumo-mechanical HSF for the production of complex sheet metal
parts.2016-04-27T00:00:00ZMathematical Optimization for the Virtual Design of Process Chains with Electromagnetic Forming
http://hdl.handle.net/2003/34922
Title: Mathematical Optimization for the Virtual Design of Process Chains with Electromagnetic Forming
Authors: Rozgic, M.; Stiemer, M.
Abstract: In this work, a framework for virtual process design for coupled processes including
electromagnetic impulse forming is presented. Virtual process design is here understood as
the computer based identification of suitable geometry and process parameters to reach a
predefined forming result via physically feasible process paths. Implementation of this
concept relies on three pillars: a physical process model, its implementation within a
numerical simulation, and a mathematical optimization algorithm. This methodology is
particularly applied to a combination of deep drawing and subsequent electromagnetic
forming (EMF). In this case, the model is given by an anisotropic elasto-viscoplastic
material model augmented by damage evolution and coupled with the magneto-quasistatic
approximation to Maxwell's equations. For constrained mathematical optimization, an inner
point algorithm is applied. With this method for virtual process design at hand, several
technological problems are addressed including tool coil design and the identification of
ideal electrical parameters of the tool coil circuit. Employing this framework requires the
identification of the material model described above. It turns out that a high precision
identification of material parameters can be achieved with basically the same mathematical
algorithm as derived for process identification.2016-04-27T00:00:00Z3D Impacts Modeling of the Magnetic Pulse Welding Process and Comparison to Experimental Data
http://hdl.handle.net/2003/34921
Title: 3D Impacts Modeling of the Magnetic Pulse Welding Process and Comparison to Experimental Data
Authors: Cuq-Lelandais, J.-P.; Avrillaud, G.; Ferreira, S.; Mazars, G.; Nottebaert, A.; Teilla, G.; Shribman, V.
Abstract: Magnetic Pulse Welding (MPW) is a solid state (cold) welding process known to present
several advantages. When properly designed, such an assembly is stronger than the
weakest base material even for multi-material joining. These high quality welds are due to
an almost inexistent Heat Affected Zone which is not the case with fusion welding
solutions. Another advantage is a welding time that is under a millisecond. In order to
define the MPW parameters (mainly geometry, current and frequency), recent
developments have made it possible to adapt welding windows from the Explosive Welding
(EXW) for use in MPW. Until now, these welding windows have been simulated only in 2D
geometries showing how the impact angle and the radial velocities progress in a welding
window. The aim of this paper is to present our most recent development, which builds on
this analysis to develop a 3D model in order to deal for example with local planar MPW.
Simulation results will be presented and then compared to experimental data for a multimaterial
join case.2016-04-27T00:00:00ZHigh Speed Forming 2016 - Proceedings of the 7th International Conference
http://hdl.handle.net/2003/34920
Title: High Speed Forming 2016 - Proceedings of the 7th International Conference
Editors: Tekkaya, A. E.; Kleiner, M.
Abstract: The “International Conference on High Speed Forming” has developed into a major event for
impulse forming, its processes, and its applications. Since the first ICHSF in Dortmund in 2004, the
latest developments in the analysis of high speed forming and joining processes, tools and machines
as well as material characterization have been introduced at the biannual conferences with growing
interest and impact. I am especially proud to recognize that the last ICHSF 2014 in Daejeon/Korea
has strengthened the ties between the European, American, and Asian impulse forming communities. The objectives of the 7th ICHSF are to offer a platform for innovative presentations from international
universities, research institutes, and companies and to support discussions and the informal exchange
of experiences and knowledge between scientists, practicing engineers, manufacturers, and industrial
operators.2016-04-27T00:00:00ZA Numerical Investigation on Magnetic Pulse Cladding of Bi-Metal Tubes
http://hdl.handle.net/2003/33518
Title: A Numerical Investigation on Magnetic Pulse Cladding of Bi-Metal Tubes
Authors: Fan, Zhisong; Yu, Haiping; Li, Chunfeng
Editors: Huh, H.; Tekkaya, A. E.
Abstract: Bimetal tubes are widely applicable in refrigerating industry, liquid conduit systems and
other similar installations. Magnetic pulse cladding (MPC), based on a sequential
joining/welding of lapping portions of long tubes, is a novel approach to fabricate bimetal
tubes. This work presents an efficient numerical simulation of the MPC process to analyze
the dynamic deformation and its effect on cladding result from a numerical view. A 2D
axisymmetric model was established and a multi-steps cladding by forming was simulated
based on the models similar to an actual MPC process. Between two subsequent steps,
the stresses and strains were transferred from previous step to next one. The model
predictions and experimental results were compared by the contour of the clad tube and
showed an acceptable agreement. The advantages of a new field shaper with tile angle
α1 of 3° and angle α2 of 13° were presented, and the magnitude of the magnetic pressure,
the stress-strain field and velocity of collision were investigated. The numerical simulation
benefits the process knowledge and assists the design of the field shaper.2014-01-01T00:00:00ZStrain-rate effect on the dynamic behaviours of a rectangular conducting plate
http://hdl.handle.net/2003/33511
Title: Strain-rate effect on the dynamic behaviours of a rectangular conducting plate
Authors: Gao, Y.; Huh, H.
Editors: Huh, H.; Tekkaya, A. E.
Abstract: This paper is concerned with thermo-elasto-plastic dynamic response of a conductive
plate in a magnetic pulse field. The influence of the strain rate effect and the temperature
effect are taken into account for the electromagnetic elasto-plastic dynamic transient
response and deformation of the conductive plate which made of strain-rate sensitive
materials. The Johnson-Cook model is employed to study the strain rate effect and the
temperature effect on the deformation of the plate. Basic governing equations are derived
for electro-magnetic field considering the eddy current. The analysis includes the elastoplastic
transient dynamic response and the heat transfer of a conductive rectangular plate,
and then an appropriate numerical code based on the finite element method to
quantitatively simulate the electro-magneto-elasto-plastic mechanical behaviors of the
conductive rectangular plate. The numerical results indicate that the strain rate effect has
to be considered for the conductive plates, especially for those with high strain rate
sensitivity. Comparison of the influence of the temperature effect on the deformation of the
plate with that of the strain rate effect shows that the influence of the temperature effect
on the deformation of a plate is not significant.2014-01-01T00:00:00ZPulsed Electromagnetic Attraction Processes for Sheet Metal Components
http://hdl.handle.net/2003/33510
Title: Pulsed Electromagnetic Attraction Processes for Sheet Metal Components
Authors: Batygin, Yuri V.; Golovashchenko, Sergey F.; Gnatov, Andrey V.; Chaplygin, Evgeniy A.
Editors: Huh, H.; Tekkaya, A. E.
Abstract: The work is dedicated to EMF attraction processes which can deform both ferromagnetic
and non-ferromagnetic sheet metal materials (low carbon steels, stainless steels and
aluminum alloys) using low frequency discharges. The analytical models of both tooling
configurations are based upon the solution of Maxwell equations in axially symmetrical
formulation. For ferromagnetic materials, the attraction effect is based upon magnetic
forces prevailing over the Lorentz forces for low frequency discharges. For nonferromagnetic
materials, the attraction forces are created by employing the auxiliary
screen which attracts the sheet metal blank. The concept of attraction in this inductor
system is based upon inducing currents flowing in the same directions in the screen and
in the sheet metal blank. In addition to the analytical models, the described concepts are
illustrated by the experimental results on attraction of sheet metal blanks employing a
single turn inductor.2014-01-01T00:00:00ZResearch on homogeneous deformation of electromagnetic incremental tube bulging
http://hdl.handle.net/2003/33509
Title: Research on homogeneous deformation of electromagnetic incremental tube bulging
Authors: Cui, Xiaohui; Mo, Jianhua; Li, Jianjun
Editors: Huh, H.; Tekkaya, A. E.
Abstract: The electromagnetic incremental forming (EMIF) method is used for tube forming process.
Suitable 2D FE models are designed to predict the forming process with a moving coil. In
comparison with experimental values, simulation method can obtain accurate results. Then,
effect factors named overlapping ration of adjacent discharge positions, discharge voltage,
forming sequence and die dimension on tube homogeneous deformation are discussed. The
result demonstrates that it is feasible to produce long-straight wall tubes using a small coil by
electromagnetic incremental tube bulging.2014-01-01T00:00:00ZAn experiment and simulation study of the rebound effect in electromagnetic forming process
http://hdl.handle.net/2003/33508
Title: An experiment and simulation study of the rebound effect in electromagnetic forming process
Authors: Liu, Xianlong; Huang, Liang; Li, Jianjun
Editors: Huh, H.; Tekkaya, A. E.
Abstract: Electromagnetic forming (EMF) has been proved to be a useful method to form the
aluminium alloy sheet as it has so many advantages. As a high-speed forming process, it
can suppress crack, reduce springback, and improve the formability of material at room
temperature. But in the process of EMF, the rebound effect caused by high velocity impact
has an important effect on the flatness of the formed part. Then a spring damper system
has been added under the female stop block to eliminate this effect. The results of formed
shape, thickness distribution and stress and strain state are investigated by comparing with
free-forming process. On the other hand, the influence of spring stiffness and damping
coefficient is analysed by using of ANSYS loose-coupled method. The results shows that it
helps to improve the flatness of formed parts with a spring damper system used. Beside of
the changing of formed shape, the difference of stress strain state results in difference of
thickness distribution. And crack happened at the bottom is supressed, and this does
favour for further processing. Furthermore, the results also shows that low spring stiffness
and right damping coefficient are benefit for reducing the rebound effect.2014-01-01T00:00:00Z