ICHSF 2012

Permanent URI for this collection

http://hdl.handle.net/2003/29260

About ICHSF

Prof. Matthias Kleiner initiated the Conference on High Speed Forming (ICHSF) in 2002. Since the first ICHSF, which was held in Dortmund, this biannual conference has become one of the major events for high speed forming technologies and its applications. Like its four predecessors, the ICHSF 2012 shall provide scientists, manufacturers, industrial operators as well as other interested persons an international forum for the exchange of experience and knowledge. The topics covered by the conference will reach from new developments in impulse forming to current industrial applications of these processes to future aims of high speed forming.

Organizers

The 5th International Conference on High Speed Forming (ICHSF 2012) is organized in cooperation of the Institute of Forming Technology and Lightweight Construction (IUL) of TU Dortmund University and the Department of Materials Science and Engineering of the Ohio State University.

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Now showing 1 - 20 of 34

Online measurement of the radial workpiece displacement in electromagnetic forming subsequent to hot aluminum extrusion
(2012-07-18) Jäger, Andreas; Tekkaya, A. Erman
Electromagnetic compression was integrated into the process chain of hot metal extrusion in order to reduce the cross section of the workpiece locally. To integrate both processes, a tool coil for electro-magnetic compression is positioned behind the die exit and coaxially to the extrudate. Additionally, a counter die in the shape of a mandrel can be mounted to the mandrel of a porthole extrusion die, which extends into the working area of the tool coil. Experiments were conducted on hollow profiles which were compressed by electromagnetic forming subsequent to extrusion. Due to an extremely short processing time of the high speed forming process, a compensation of the relative speed between the workpiece and the tooling can be ignored. For determine the workpiece displacement during the electromagnetic forming process, a new measuring strategy based on the Photon Doppler Velocimetry was developed.
Pressure Fields Repeatability at Electrohydraulic Pulse Loading in Discharge Chamber with Single Electrode Pair
(2012-07-18) Knyazyev, M.; Perez, I.; San José, J.; Zhovnovatyuk, Ya.
The paper is devoted to improvements in technology of electrohydraulic impact forming (EHF) via investigation of stability of high-voltage underwater discharges and pressure fields they generate along surface of a sheet blank. The experimental research is held with use of conical discharge chamber equipped with one pair of electrodes. Measurements of pressure fields along round flat area are based on application of multi-point membrane pressure gauge (MPG). The tests conditions include wide range of spark gaps with four levels of charge voltage and energy. The investigation results showed strong influence of geometric parameters of discharge work volume and electric parameters of discharge circuit on repeatability of pressure fields. The spark gap value should be in severe correlation with distance to a sheet blank and dimensions of a loaded area. Parameter “normalised spark gap” is proposed for determination of geometric characteristics of discharge volume. The results confirm the validity of charge voltage-to-spark gap ratio of 1 kV/mm recommended for approximate setting the gap in order to ensure high pressure generation. This ratio is also good for repeatability of pressure fields and can be also expended. The factors that influence the stability of discharge parameters, shock wave generation and pressure fields are analysed.
Compression Testing Using a CAM-Driven Electromagnetic Machine
(2012-07-18) Martins, Paulo; Rosa, Pedro; Silva, Carlos
This paper presents new equipment for the compression testing of materials under high rates of loading. The equipment consists of an electromagnetic actuator, a fixed housing containing two flat compression platens, a translating cam and a follower. The electromagnetic actuator makes possible reaching high strain rates with a very precise control of the impact velocity and of the energy transmitted to the translating cam. The cam profile enables compression testing to be performed under the strain-rate vs. strain loading paths that are commonly found in manufacturing in order to meet the machine-tool and process combined specifications. The equipment was designed, fabricated and instrumented by the authors and, besides giving constructive details for those readers that may be interested in developing a low-cost equipment for compression testing at high rates of loading, the paper also puts emphasis on the flexibility and adequacy of its operative conditions for determining the mechanical behaviour of Aluminium AA1050-O under different testing conditions.
Electromagnetic pulse crimping of axial form fit joints
(2012-07-18) De Waele, W.; Faes, Koen; Zaitov, O.
Electromagnetic pulse crimping of form fit joints was investigated using tubes in the aluminium alloy EN AW-6060, with a diameter of 50 mm and a wall thickness of 1,5 mm. First the influence of the charging voltage and the geometrical groove parameters on the deformation behaviour and localised thickness reduction of the tube wall was investigated. The experimental results provided data for optimising the groove design. The Design of Experiments method was used to optimise the shape and dimensions of the internal workpieces with a double groove design. Results of tensile tests on the crimp joints allowed determining the most important parameters for the groove design. Based on these observations an optimal double groove joint design was proposed. The deformation and failure behaviour of the crimp joints during tensile testing were experimentally studied using the digital image correlation technique. This technique was used to measure the local and global deformation of the joint. Failure mechanisms include pull-out, local shearing and fracture of the tube. Three main failure modes were observed.
Robot automated EMPT sheet welding
(2012-07-18) Pasquale, Pablo; Schäfer, Ralph
Many industrial applications require sheet to sheet or sheet to tube joints. The electromagnetic pulse technology is capable to produce these kinds of joints. In literature many examples of sheet to sheet solid state welding between similar and dissimilar metals are presented and analyzed in detail. However, the most of the presented welding applications, which are very focussed on the academic level, are simple specimens for example for tensile test. These specimens are usually very small in their dimensions and therewith capable to be welded with the help of stationary EMPT coils. In contrast to this approach the majority of typical industrial applications demand the ability of manufacturing several welds in different positions on the same assembly application comparable to the spot welding process of an automotive car body. Here several spot welds are realised in a variety of positions by a robot mounted spot welding gun. The use of a stationary coil is no option here. A first step in manufacturing complex assemblies by EMPT was done by PSTproducts by welding a car- shaped space frame. Within this project substantial knowledge has been generated with respect to non stationary EMPT coils and the flexibility of the cables connecting the coil with the pulse generator. The results were transferred into the next step, the development of an EMPT robotic welding head. This report details requirements and possibilities of robot automated EMPT sheet welding with respect to complex structures.
Space-Time-Controlled Multi-Stage Pulsed Magnetic Field Forming
(2012-07-18) Ding, Hongfa; Han, Xiaotao; Huang, Liang; Li, Jianjun; Li, Liang; Liu, Lin; Mo, Jianhua; Peng, Tao; Qiu, Li; Zhou, Zhongyu
Electromagnetic forming (EMF) is a high strain-rate forming method where a pulsed electromagnetic force is applied to a conductive metallic workpiece. To improve the performance of the EMF system, the current problems which restrict its extensive application have been analyzed. To this end, a space-time-controlled EMF technology with multi-stage and multi-direction coils system has been developed. In our new EMF system, the magnetic field generated by driving coils is much higher than in conventional EMF due to introducing design methods developed for non-destructive pulsed high field magnets. This technology enables the forming of complex, large-scale sheets and tubes that may be difficult to deform by conventional methods, as well as controlling particular properties of the work pieces.
Effect of Workpiece Motion on Forming Velocity in Electromagnetic Forming
(2012-07-18) Han, Xiaotao; Li, Liang; Qiu, Li; Xiong, Qi; Zhou, Zhongyu
The effect of workpiece motion on the forming velocity is analysed by the finite element method. To study the two factors of workpiece displacement and motional electromotive force, a static model, an incomplete motional model and a complete motional model are created. The incomplete motional model is simulated by the finite element software COMSOL, while the complete motional model is simulated by another finite element software Flux. To ensure the correctness of the model, the static model is created by both softwares. For the specific system treated in this paper, the results show that when the workpiece velocity is below 100 m/s, the workpiece displacement has only a small effect on the forming velocity. But when the workpiece velocity is above 200 m/s, the effect of the workpiece displacement on the forming velocity must be taken into account in the finite element model of the electromagnetic forming process.
Laser Impact Welding
(2012-07-18) Daehn, Glenn S.; Lippold, John; Liu, Deijan; Taber, Geoff; Wang, Huimin
Laser impact welding is a solid-state, collision-based welding process. In this process, laser-generated optical energy is converted to kinetic energy through the ablation at the surface and confinement of the gas generated between a flyer and backing plate. The launch of the flyer can be affected by many factors, for example, backing material, ablative layer, and flyer thickness. In this paper, the effect of three backing materials: glass, polycarbonate and cellophane tape, were studied with different laser spot size and commercially pure aluminum alloy 1100 was used as the flyer. The results show that glass can provide the most efficient launches, but is damaged. Polycarbonate is a good compromise between efficiency and robustness. Welding is possible between many similar and dissimilar material pairs. In this study, commercially pure nickel was joined to commercially pure nickel. There are several possible geometric arrangements of the target relative to the flyer. With flat targets, metallurgical bonding takes place along the edges of the spot, and jet was observed in the center of the spot. Corrugated targets provide more surface area for metallurgical bonding. In this paper, the flyer launch velocity-time profile is also demonstrated using a photon Doppler velocimetry technique.
An electromagnetically driven metalworking press
(2012-07-18) Boos, K.N.; Daehn, G.S.; Kabert, B.A.; Slone, C.E.; Taber, G.A.; Washburn, A.T.; Windholtz, T.N.
A small press operated by electromagnetic repulsion and driven by a pulse power supply was constructed at The Ohio State University. This design that applies kinetic energy rather than static force to do work on materials is much lighter and potentially much less expensive than traditional hydraulic, mechanical or servo presses. Performance of the kinetic press is compared to traditional presses in the applications of powder compaction and forming. The results tend to indicate that modest impact speeds of 3 to 18 m/s can improve performance in these manufacturing operations as compared to traditional low-speed machines.
Produce a large aluminium alloy sheet metal using electromagnetic-incremental forming (EM-IF) method
(2012-07-18) Cui, Xiaohui; Li, Jianjun; Mo, Jianhua; Xiao, Shijie; Zhao, Jian
The conventional electromagnetic forming processing can’t shape large parts due to limitation of the strength of working coil and the capacity of capacitor bank. In this paper, a novel technology named electromagnetic-incremental forming (EMIF) has been proposed. A small working coil moves along the special motion trail and many small electromagnetic pulses energy are used to form a larger aluminum alloy sheet. The effect of vent holes, discharge voltage on sheet final profiles are analyzed. In addition, two discharge times with varying value of discharge voltage is used to obtain better final sheet profiles. The effect of the previous discharge on the second one is also analyzed. Then, a 3D sequential coupling method is used to calculate the magnetic force on the sheet and analyze the forming process. In the latter deformation, the deformation information is also considered from the former one, such as the deflection, velocity, stress, strain, et al. The simulation values are in better agreement with the experimental ones. This work demonstrates that the new technology offers an ability to form large and complex components with a small working coil and small discharging energy of the electromagnetic machine. Moreover, the simulation method can be used for more complex forming system.
Coining of micro Structures with an electromagnetically driven Tool
(2012-07-18) König, Christoph; Prasol, Lukas; Uhlmann, Eckart; Ziefle, Alexander
For coining micro structures into high-grade steel 1.4301 a highly dynamic tool system based on a pulsed magnetic field inside a cylindrical coil was developed. Two kinds of structures were coined at different tool velocities. The coining results were evaluated regarding geometrical accuracy, material flow behaviour and energy input. In addition the high velocity process was compared to a quasi-static process. By increasing the coining velocity to 30 m/s the accuracy of the quasi-static process can be reached. The energy that is needed for reaching a similar result is less for coining at high velocities. The tool velocity also influences the flow behaviour of the workpiece material.
Pulsed magnetic forming of the magnesium alloy AZ31 – Comparison to quasi-static forming
(2012-07-18) König, Christoph; Prasol, Lukas; Uhlmann, Eckart; Ziefle, Alexander
Magnesium alloy AZ31 metal sheets were formed at room temperature with a pulsed magnetic field induced by a flat coil. For this a die with variable die radius and inside diameter was used. The forming results were evaluated regarding to deformation, die radius, inside diameter, micro hardness, texture examination of forming area and energy input. In addition high velocity forming process was compared to a quasi-static forming process at room temperature. Therefore an experimental setup with an adapted punch was constructed. Punch geometry was defined in dependence of the high velocity forming structure of a sample at well-defined energy input. By comparing texture and micro hardness at forming area a distinction of high-speed forming process and quasi-static process is determined.
Coupled FEM-Simulation of Magnetic Pulse Welding for Nonsymmetric Applications
(2012-07-18) König, Christoph; Prasol, Lukas; Uhlmann, Eckart; Ziefle, Alexander
Pulse magnetic welding can be seen as a well developed manufacturing process. However, the realization of this technology implies a high degree of knowledge concerning the intrinsic mechanisms of current transmission and force generation and accordingly a high potential of optimization can be expected. Modelling pulse magnetic forming processes requires a transient electromagnetic calculation in order to obtain the generated currents and forces. The prediction of the deforming result requires an explicit structural simulation, as the forming process is conducted in timescales of a few 100 μs. A close investigation of the relevant physical entities is carried out with ANSYS Workbench and ANSYS Emag. Furthermore, the results of the Emag calculations are used as boundary conditions for explicit structural simulations with ANSYS AUTODYN in order to predict the needed charging energy for a joining process. For validation, a comparison between simulated and measured results with respect to magnetic flux density and discharge current is shown.
Study on the Formability & Shape Confirmity of Mg & Al-alloy sheets in Warm condition by Electromagnetic Forming
(2012-07-18) Date, P.P.; Singhal, M.
Electromagnetic forming is a high strain rate process used for shaping metals. Mg-alloys are of interest by virtue of the light weight and potential for application in automotive industries. These alloys have poor formability at room temperature and have to be formed under warm working conditions. Simulations using COMSOL Multiphysics software were carried out to predict the forming behavior of Mg-alloy sheets deformed at high speeds and different temperatures into a die with a corrugated shape. Conformance of the sheet to the die shape is the objective of this study. These sheets are assumed to be externally heated to different temperatures prior to forming. Possible changes in the mechanical and electrical properties of the material with temperature have been incorporated to show their individual and combined effects. A virtual circuit was built to excite the coil, fully coupled with the Solid Mechanics & Magnetic Fields, through related physics in the software. Optimal parameters that ensure good conformance to die shape are sought as the outcome of the simulation of warm electromagnetic forming of magnesium & aluminium alloy sheets. The quality of strain distribution under different clamping constraints was assessed using the strain non-uniformity index (SNI).
Comparison of Dynamic Hardening Equations for Metallic Materials with three types of Crystalline Structures
(2012-07-18) Ahn, K.; Huh, Hoon; Park, L.
This paper is concerned with dynamic hardening equations of metallic materials with various crystalline structures. The dynamic response of metallic materials is indispensable for analysis of high speed metal forming process. There is, however, no unique equation which can represent the dynamic hardening characteristics of all kinds of materials although various dynamic hardening equations have been suggested by many researchers. Dynamic hardening equations reported have been investigated using the dynamic hardening characteristics of three kinds of materials: 4340Steel (BCC); OFHC (FCC); and Ti6Al4V (HCP). Dynamic hardening characteristics of each material have been obtained by uniaxial tensile tests and SHPB tests. Uniaxial tensile tests have been performed with the variation of the strain rate from 0.001/sec to 100/sec and SHPB tests have been conducted at the strain rate ranged up to 4000/sec. Several existing models have been constructed and evaluated for Johnson-Cook model, Zerilli-Armstrong model, Preston-Tonks-Wallace model, modified Johnson-Cook model, and modified Khan-Huang model using test results of three materials. Strain rate hardening and thermal softening effect during the deformation process were investigated for accurate application of hardening equations. The most applicable equation for each material has been suggested by comparison of constructed results.
Some aspects regarding the use of a pneumomechanical high speed forming process
(2012-07-18) Akst, O.; Djakow, E.; Homberg, W.
A promising approach to the production of thin-walled workpieces in high strength materials is the use of a special pneumomechanical high-speed-forming process. This process uses a pneumatically accelerated plunger that dives into a pressure chamber filled with the working media in order to generate a short pressure pulse. Ways in which the pressure pulse can be influenced include e.g. varying the type of working media, the density of the working media, the accelerating pressure distance and the plunger geometry. The influence of these parameters on the process formed the subject of intense technological research at the Chair of Forming and Machining Technology (LUF) at Paderborn University. The results of these investigations were used to achieve an appropriate process and tool design for the pneumomechanical high-speed forming process. It thus proved possible to manufacture complex workpieces and geometrical details from thin-walled, high strength stainless steel or aluminium alloys that cannot be produced by conventional stamping processes. Because of the high uniformity of the pressure distribution in the radial direction, it is possible to achieve just small dimensional or geometrical deviations in respect of the desired shape of the workpiece. The planned paper will present results of the basic research conducted into pneumomechanical high-speed-forming as well as a comparison with electrohydraulic forming.
Numerical Identification of Optimum Process Parameters for Combined Deep Drawing and Electromagnetic Forming
(2012-07-18) Appel, R.; Rozgic, M.; Stiemer, M.; Taebi, F.
In this paper, a method is presented for the virtual process design of combinations of deep drawing and electromagnetic forming. With suitably chosen parameters, such process combinations of a quasi-static and an impulse forming process extend forming limits of classical, purely quasi-static forming. To determine parameters leading to the desired forming result, a numerical optimization algorithm is employed. The parameters to be adjusted comprise parameters of the triggering current, such as frequency, amplitude, damping, etc., geometric parameters of the tool coil and parameters of the deep drawing process, as, e.g., drawing radii or tribological parameters. To reduce the required number of evaluations of the target function, a gradient based numerical optimization scheme is employed following directions of decent in the parameter space. The quality of a given parameter set is determined by computing the distance of the simulated forming result to the prescribed ideal shape via a finite element simulation. Forming limits are incorporated by so called forming limit surfaces as constraints to the optimization process, considering rate dependence and prestrain in the second impulse forming step.
Coil Development for Electromagnetic Corner Fill of AA 5754 Sheet
(2012-07-18) Imbert, José; Worswick, Michael
Electromagnetic (EM) forming is a high-speed forming process that uses the forces induced on a conductive workpiece by a transient high frequency magnetic field to form the workpiece into a desired shape. It has been reported by several researchers that EM forming (EMF) increases the formability of hard-to-form aluminum alloy sheet under certain circumstances. EMF can be combined with conventional forming (e.g. stamping) operations to create a hybrid forming operation that exploits the strengths of each process. One such operation is the “corner fill” operation, which consists in pre-forming sheet using conventional forming and then using EMF to reduce the radii of different features on the part to values that could not be obtained with conventional forming. This paper describes the development of a coil used for a hybrid operation that consisted on pre-forming AA 5754 1 mm into a v-shape with a 20 mm outer radius and then reducing or “sharpening” the radius to 5 mm using EMF. The coil is one of the most important components of an EMF operation, since it is the means of delivering the energy to the workpiece. Coils are subjected to very high stresses and are typically the element of an EMF operation that will fail first. One successful and four unsuccessful coils designs are presented. The successful coil was a single loop design, with the section closest to the part narrowed to increase the current density. The simplicity of the shape was chosen for its current flow characteristics and for its structural strength.
Experimental Study and Numerical Simulation of Electromagnetic Tube Expansion
(2012-07-17) Hatkevich, Steve; Shang, Jianhui; Wilkerson, Larry
Material constitutive models are important to predict deformation behaviour of materials. To identify parameters of constitutive models for high-strain-rate forming, appropriate methods are needed to investigate the dynamic behaviour of materials. Electromagnetic forming is a high-velocity and high-strain-rate forming process in which velocities of up to 300 m/s and strain rates of more than 103 s−1 can be achieved. Recently, the development of Photon Doppler Velocimetry (PDV) enables the accurate measurement of high velocity, and the electromagnetism module of LS-DYNA allows the reliable simulation of electromagnetic forming. In this study, PDV and LS-DYNA were applied to investigate the electromagnetic tube expansion of Al 6061-T6. The experimental and simulation results are presented and discussed to study the dynamic behaviour of Al 6061-T6 and to verify constitutive model parameters for it.
Investigation of Magnetic Pulse Deformation of Powder Parts
(2012-07-17) Kolbe, M.; Mironov, V.; Shishkin, A.; Zemchenkov, V.
Current article covers basics of powder compaction by electromagnetic impulse field and research results of sintered Fe powder part deformation process. This work is a joint research carried out by Riga Technical University (Latvia) and the Westsächsische Hochschule Zwickau (Germany).

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