ICHSF 2021
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Item Magnetic Pulse Welding of Sheets – Process Modelling(2021-10-14) Shotri, R.; Racineux, G.; De, A.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.Item Development phases of 2 high volume industrial products using high strain rates forming processes(2021-10-14) Avrillaud, GillesItem Determination of material and fracture parameters for high strain rate processes, especially considering the local adiabatic heating in the fracture zone of the sample(2021-10-15) Galiev, E.; Tulke, M.; Psyk, V.; Brosius, A.; Kräusel, V.Item A micro-mechanical and microstructural analysis at the joint interface between dissimilar materials in magnetic pulse welding (MPW)(2021-10-15) Zielinski, Benjamin; Sadat, Tarik; Jouaffre, Denis; Dubois, Rudy; Kossman, Stephania; Dubar, Laurent; Markiewicz, EricItem Prediction of adiabatic blanking process properties with temperature dependent fracture criterion(2021-10-15) Schmitz, Fabian; Rakshit, Tanmoy; Hahn, Marlon; Clausmeyer, Till; Tekkaya, A. ErmanItem A novel Hopkinson-based technique for high-speed biaxial testing of sheet metals(2021-10-15) Corallo, L.; Verleysen, P.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.Item Effects of temperature on quality of Al/Fe tube joints manufactured by magnetic pulse welding(2021-10-15) Dang, Haiqing; Yu, HaipingItem Particle Ejection by Jetting and Related Effects in Impact Welding Processes & Interface Formation during Collision Welding of Aluminum(2021-10-15) Bellmann, Jörg; Schumacher, EugenItem 3D Simulation of the Magnetic Pulse Welding Process(2021-10-14) Lashkari, Mohammadjavad; Goyal, Siddhant; Hahn, Marlon; Beraudo, Christine; Tekkaya, A. Erman; Alves, JoséItem Process Parameter Sensitivity in Magnetic Pulse Welding: An Artificial Neural Network approach(2021-10-14) Kapil, A.; Mastanaiah, P.; Sharma, A.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.Item Separating the roles of speed, strain-rate and shock in interpreting dynamic hardness(2021-10-14) Mao, Yu; Barnett, Blake; Prasad, K. Sajun; Vivek, Anupam; Daehn, GlennItem Advances in electrical high current connections for electrical propulsion systems(2021-10-14) Marschner, O.; Pabst, C.; Pasquale, P.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.Item Numerical Identification of Design Parameters for Electromagnetic Forming(2021-10-14) Stiemer, M.; Nezhi, Z.; Rathjen, K.; Zazai, F.; Hagel, M.; Rozgic, M.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.Item Investigation of Collision Welding by High-Speed Imaging(2021-10-14) Niessen, B.; Groche, P.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.Item Suitable Design for Electromagnetic Pulse Processes(2021-10-14) Marschner, O.; Pabst, C.; Schäfer, R.; Pasquale, P.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.Item Single-turn Coils for Magnetic Pulse Welding of High-strength Steel Parts(2021-10-13) Krutikov, V. I.; Paranin, S. N.; Spirin, A. V.; Zaytsev, E. Yu.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.Item Electrohydraulic Crimping of 316L Tube in a 316L Thick Ring(2021-10-13) Le Mentec, R.; Sow, C.; Heuzé, T.; Racineux, G.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.Item Impact-activated fluid-solid tool: towards more flexible high speed forming(2021-10-13) Hahn, Marlon; Kumar, V.; Tekkaya, A. ErmanItem Electrohydraulic full-forward extrusion of small parts through high aspect ratio forming channels(2021-10-13) Langstädtler, L.; Herrmann, M.; Schenck, C.; Kuhfuss, B.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.Item Analytical-based modeling for electromagnetic sheet metal forming with multi-turn coils(2021-10-13) Goyal, Siddhant; Lashkari, Mohammadjavad; Hahn, Marlon; Tekkaya, A. Erman