ICHSF 2025

Permanent URI for this collection

http://hdl.handle.net/2003/43908

Browse

Now showing 1 - 20 of 30

Determination of GISSMO Damage Parameters for High-Speed Blanking of 22MnB5 and EN AW-5754
(2025-08-26) Galiev, E.; Linnemann, M.; Winter, S.; Psyk, V.; Dix, M.
High-speed blanking (HSB) of high-strength materials, such as the steel 22MnB5, is an established method that delivers high-quality cut surfaces. Due to high shear rates, this process is associated with the formation of adiabatic shear bands (ASB) in the blanking zone. For an in-depth analysis of the effects arising in this process and to support the prototyping of blanking tools, a numerical simulation is required. For this purpose, material parameters, which are valid at elevated strain rates are necessary. In this study, the parameter identification for the GISSMO damage model is presented. For the parameter identification, a series of coupled experimental and numerical investigations were carried out on 22MnB5 and EN AW-5754 with a sheet thickness of 2 mm. The main objective was to determine the damage and failure behaviour of the investigated materials under different loading modes (or triaxialities). The resulting data was used as input for the subsequent optimisation of the parameters in LS-DYNA and LS-OPT.
Electromagnetic incremental assembly for large thin-walled ring shells and microscopic mechanisms of dynamic deformation overlap regions
(2025-08) Cheng, X.; Yu, H. P.; Guo, J. P.; Wang, H.; Yu, T. S.
This paper introduced an electromagnetic incremental assembly (EMIA) method which employed large thin-walled aluminum alloy ring shells as the processing object and a weak rigidity assembled structure with an irregular cross-section as the support object. By experiments, the effects of discharge frequency, discharge voltage, and coil position parameters on the assembly outcome were investigated. The results show that this method successfully achieved a tight fit between the skin and the assembled structure, as well as effective support. During the EMIA, there were many two-step dynamic deformation overlap regions. This paper also conducted an in-depth study on the microstructure evolution of these deformation overlap regions, revealing that dynamic pre-forming enhanced the strength and plasticity of the material. The enhanced strength was attributed to the higher dislocation density within grain boundaries. The plasticity enhancement was mainly due to two factors: firstly, the more uniform dislocation distributions which promoted homogeneous deformation; secondly, the shear stress on the second-phase particles became more concentrated, and the shear action was enhanced. As a result, a large number of original particles were sheared into multiple segments, and large-scaled particles were also fractured, leading to the accumulation of dislocations that eventually cut through the particles, releasing local shear stress.
Strain rates in electrohydraulic forming of thin stainless-steel sheet metals
(2025-08-26) Langstädtler, L.; Schenck, C.
Impulse forming technologies can be used for shaping thin sheet metal parts, e.g. bipolar plates for hydrogen production. Thereby, the energy transmission behaviour to the sheet metals depends on actual process characteristics. In electrohydraulic forming with exploding wire, shockwaves are expected to cause transient pressure fields onto the forming area. This transient force or pressure action realises the punch while the die is a rigid part of the tool. Hence, one part of the forming tool does not feature a defined geometry. To understand the impact of such kind of punches the resulting strain field was mapped during electrohydraulic forming experiments. Different explosion wire materials were used to form 100 µm thin EN 1.4404 / AISI 316L stainless-steel sheet metals. The displacement was measured in-process with two laser triangulation sensors at different positions. This time and space resolving data was taken to represent the initial pressure and resulting strain distribution. The in-process measurements enable further optimisation of the process settings.
Design criteria for a High Power Pulsed generator for the delamination of laminate structures
(2025-08-26) Lagain, B.; Heuzé, T.; Racineux, G.; Arrigoni, M.
Material assemblies combining composites, metals, and ceramics are increasingly used in structural applications due to their high strength-to-weight ratios and durability. However, disassembling such multilayered systems without damaging the constituent materials remains a challenge, particularly for recycling or repair purposes. Magnetic pulse technology offers a promising solution by generating transient mechanical loads through Lorentz forces induced in conductive layers. This paper aims to define the operating conditions of a high-power pulsed (HPP) generator capable of inducing controlled delamination in laminate structures. A simplified model of the current delivered by an HPP generator is introduced, and its temporal evolution is related to the mechanical load applied to the laminate. Previously established delamination criteria, derived from a one dimensional wave propagation analysis using the method of characteristics, are reinterpreted to guide the design of an HPP generator. The required frequency and magnetic field amplitude are then expressed as functions of the laminate's acoustic and geometric properties. The results provide a set of design criteria for HPP generators in magnetic pulse disassembly applications, enabling effective and selective separation of bonded layers in multi-material systems.
Determination of the High Strain Rate Behaviour of a CuCrZr Alloy Using an Electromagnetic Forming Bench Test
(2025-08-26) Mrozowski, N.; Ferreira, S.; Fau, A.; Cuq-Lelandais, J. P.; Mazars, G.; Jeanson, A. C.; Pecquois, R.; Daulhac, G.; Robin, X.
A novel electromagnetic forming (EMF) bench test has been developed to characterize the dynamic behaviour of metallic materials. This paper presents the specific case of a CuCrZr wrought alloy, detailing both the experimental approach and the inverse numerical methodology. The primary advantage of the proposed method lies in its ability to calibrate a dynamic material model, which is particularly relevant for forming applications involving thin specimens, with thicknesses as low as 0.6 mm. The well-known Johnson-Cook model is used without consideration of the thermal softening term. The calibration is validated within the strain rate range of [1-4000]s-1 . It is indeed shown that this method generates a broad variation of strain rates during the 300 µs test duration. The benefits from using a strain rate sensitive law as opposed to a quasi-static one are also demonstrated. Analysis of plastic strains and peak stresses further indicates that the EMF test is particularly well-suited for ductile materials, whereas brittle materials may fracture prematurely or fail to deform sufficiently. Limitations regarding the non-uniqueness of the calibrated model and the incorporation of thermal effects are briefly discussed.
Investigations on the temperature-deformation behaviour of advanced high-strength steel sheets (AHSS) under shear loading from nearly isothermal to the adiabatic state
(2025-08-26) Klitschke, S.; Liewald, M.
Steel sheet materials tend to form adiabatic shear bands at high strain rates, leading to material separation. This phenomenon is used in adiabatic blanking processes, but it should be avoided in crash safety applications. This paper deals with investigations on the main influence parameters on adiabatic heating of advanced high strength steel sheets (AHSS) under shear loading. Focussing on the effect of applied strain rate, experimental investigations were carried out from quasi-static loading up to crash-relevant strain rates. Strain and temperature fields were recorded using a high-speed video camera and a high speed infrared camera, thus enabling a detailed analysis of the generated heat and the heat transport mechanisms in the deformed zones. The examination showed that the isothermal adiabatic transition under shear loading ranges between strain rates of 0,01 s-1 up to 50 s-1 for the investigated materials and thus at higher strain rates compared to tensile loading. This indicates an extreme strain localization in shear bands compared to necking zones at comparable strain rates. Consequently, larger temperature gradients occur in the shear zone, which significantly affect the heat transfer mechanisms. Furthermore, with increasing strain hardening, the isothermal-adiabatic transition region is also shifted to higher strain rates due to a slowdown of the strain and temperature localization process. Based on these results, local heating and the occurrence of adiabatic shear bands can be estimated without costly thermomechanical coupling finite element simulations (FE-Simulations).
Feasibility Study on Joining Aluminum Tube with Alumina Ceramic Rod Using Magnetic Pulse Crimping Process
(2025-08-26) Singh, U.; Rajak, A.
Ceramic-metal joints play a vital role in structural applications, offering benefits such as strength, lightweight, high strength-to-weight ratio, corrosion resistance, and high temperature performance. These joints are widely used in fields ranging from electronics and biomedical devices to aerospace and automotive industries. However, joining ceramics and metals is challenging due to differences in atomic bonding and thermal expansion properties. Traditional methods, such as brazing, friction welding, and fusion welding, often induce thermal stresses and residual strain, leading to defects like cracks and intermetallic formation at the joint interface. Magnetic Pulse Crimping (MPC) is an environmentally friendly, quick, and cold solid-state material joining process that does not create heat affected zones and mitigates these issues. This study uses the MPC process to investigate the feasibility of joining an AA 1050 aluminum alloy tube with an alumina ceramic rod. The experiments were performed at various discharge energies using an Archimedean spiral coil and a step taper field shaper to evaluate the joint's strength and metal-ceramic interface behavior. Non-sinusoidal waviness patterns have been observed at the metal-ceramic joint interface. The numerical analysis used the LS DYNA EM module to measure the current density, magnetic field, Von Mises stresses, and impact velocity on the flyer tube. The manuscript contributes to the understanding of ceramic-metal joining under electromagnetic forming conditions.
Finite element modelling and simulation of the multiscale crystalline structure of aluminium deposit produced by helium cold spray additive manufacturing
(2025-08-26) Qi, J.; Raoelison, R. N.; Li, J.; Rachik, M.
This study addresses an experimental analysis with a multiscale modelling of a pure Aluminium deposit produced by helium cold spraying. The grain morphology and the crystallographic texture of the deposit revealed a significant grain refinement along with a formation of strong metallurgical bonding. Complementing the experiments, a two-part multiscale modelling framework is developed, integrating a simulation of the particle upon impact and a crystal plasticity finite element model for analysing the consolidation and deformation mechanisms across multiple scales. Using Johnson-Cook equations and coupled Eulerian-Lagrangian approach, the particle impact model effectively captures high velocity impact behaviour, deformation mechanisms, and thermal interactions at the particle-substrate interface. The influence of intergranular interactions and phase heterogeneities on the overall mechanical response, at the mesoscale level, is investigated. The crystal plasticity-based approach can simulate the behaviour of individual grains within a representative volume element (RVE), with a prediction of the anisotropic mechanical properties and stress-strain relationships between various grains. The results pave the way for a better understanding of the microstructural evolution and mechanical behaviour of Aluminium deposits produced by helium cold spraying.
Magnetic Pulse Crimping of Power Cables: Process Simulation & Performance Characterization
(2025-08-26) Cuq-Lelandais, J. P.; Innocenti, N.; Gage, W.; Huteau, C:; Daulhac, G.; Mrozowski, N.
Magnetic Pulse Crimping (MPC) represents an interesting alternative to mechanical crimping. This solution is a contactless process using dynamic Lorentz forces induced by high pulse power electrical discharge through a coil. MPC has proven to be effective for cables terminals with both high electrical and mechanical performances. This solution differs from conventional methods for cables with large cross-sections for high voltages especially those manufactured for electric vehicles. The challenge lies in the high thickness of the terminal and the cable to be crimped together while maintaining the performance of the connection during use and ageing, that can be hard to hold with traditional processes. The aim of this work is to characterize the electrical resistance of 120 mm² power cables terminals that are assembled by MPC, with the goal of reducing the process width and potentially reduce the lug mass. First, a numerical study of the process is performed in order to design and characterize the crimping level depending on main process parameters, in particular through the compaction level of the assembly. Then, an experimental study has been carried out by testing assemblies with different crimping widths and generator energies, in order to reduce the crimped length without degrading the performance and repeatability. For each case, the electrical resistance of the cable/lug interface is measured, before and after exposure to thermal and humidity cycling representative of real-life conditions. The results are compared with samples produced using mechanical crimping to compare the performances and repeatability of each process respectively.
A Novel Coil Structure for Metal Sheet Magnetic Pulse Welding
(2025-08-26) Jiang, X.; Yu, H.; Li, H.; Deng, J.
Magnetic pulse welding (MPW) of metal sheets is an efficient and environment-friendly room temperature solid-state welding technology. However, the process involves significant energy dissipation. Limited by the current coil structure, high energy is required to achieve metallurgical welding of metal sheets. To address this issue, novel coil principle and structure has been proposed. The current is simultaneously concentrated into a section of conductor by a unique circuit design, achieving current summation and amplification, thereby enhancing energy efficiency. Numerical simulations were performed to explore the effects of coil parameters on current density, Lorentz force, and flyer sheet motion, revealing that the coil structure can amplify current by 1.5 to 5.3 times as coil turns increase from 2 to 7. The flyer sheet velocity exceeded the critical welding velocity. Experimental results show successful welding of 1060 (1.0 mm) / DP450 (1.0 mm) at 6.05 kJ and 5754 (1.0 mm) / DP600 (1.0 mm) at 9.8 kJ, with all interfaces displaying metallurgical characteristics. These findings confirm the excellent welding capability of the novel coil at low energy, which results from a significant current amplification effect. This reduces the stringent requirements for magnetic pulse discharge equipment, thereby facilitating the further industrial application of MPW technology.
Grain Boundary Motion in Magnetic-Pulse-Welded Al-Fe Bimetal Systems: An Atomistic Simulation Study
(2025-08-26) Fan, Z.; Wang, X.; Xie, M.; Ning, H.; Deng, J.
Magnetic pulse welding (MPW) is an ef ective solid-state welding method of joining dissimilar metals such as Al/Steel, Al/Ti, Al/Cu et al. In order to understand fully such important phenomena as atomic dif usion, grain boundary motion, interfacial non- equilibrium-phase nucleation and growth in MPW, a detailed microscopic description of the MPW interface is necessary. This study is an extension of our previous work. In the present work, we extend the simulation investigation to polycrystal aluminium and iron systems using Molecular dynamic (MD) method. The polycrystal systems allow for the study of interfacial segregation. Our simulations present structural information on the GBs in nanocrystalline microstructures. Flat GBs can move when subjected dynamic load resulting from the high-velocity impact. Plots of the ratio of GB atoms versus time show a distinctly dif erent GB migration behaviors between loading and unloading conditions. By contrast with our earlier simulations, it was observed that crystal order and stability are highly preserved in the loading stage. The transformation of grain boundary structural change is due to stress-driven GB migration and temperature dependent as well. Grain rotation mechanism was identified. This work could provide atomistic insights into the grain refinement during MPW process.
Investigation and Improvement of dissimilar Aluminum-Copper Joining using Magnetic Pulse Welding combined with local Inert Gas Application
(2025-08-26) Graß, M.; Jüngst, J.; Böhm, S.
Well-performing electrical conductors and contacting processes are crucial for a variety of industries and applications, including flat conductors such as busbars. The challenge is to manufacture relevant systems with excellent properties in a cost-efficient and ecological way. From a materials science perspective, one approach could be the utilization of aluminum in electrical systems. This is because aluminum is a better conductor than copper with regard to its weight. However, the exclusive use of aluminum is limited by the constraints of electrical systems that require the partial use of copper. This can be due to space limitations or connections to the power electronics, which are predominantly copper components. Hybrid systems consisting of aluminum, copper and dissimilar joints between both materials have been identified as a viable solution. However, the fabrication of these joints is challenging for conventional fusion welding processes due to chemical and thermophysical incompatibilities. Magnetic Pulse Welding (MPW) is a solid-state welding process which, due to its characteristic low energy input, allows a resource efficient fabrication of dissimilar joints. However, the limitations of MPW and their expandability, its potential for future applications, and the interactions of the process parameters with observed joint properties have not been sufficiently researched. Consequently, this study addresses MPW in the field of joining flat conductors by investigating the correlations between process parameters and mechanical, microstructural, and electrical joint properties. Furthermore, an inert gas supply during joining is investigated in order to determine the potential for improvement of the weldability and the resulting joint properties.
Shear Cutting of Aluminum, Zinc, and Tin at Increased Speeds
(2025-08-26) Holzer, K.; Volk, W.
The temperature and temperature evaluation during shear cutting, particularly at increased speeds, is crucial for understanding the material behavior during cutting, validating thermo mechanical material models used in the finite element method, and predicting the tool wear. In this study, we measured the punch force and temperature for EN AW 6082, zinc, and tin for punch speeds 0.12, 0.2, 0.4, and 0.6 m/s using a cutting clearance of 0.075 mm. The temperature is evaluated based on the thermoelectric voltages arising from the sheet metal and tool material based on the Seebeck effect. The results demonstrate that the sheet metal strongly influences the thermal response during shear cutting. Higher temperature maxima were generally observed to occur later than the force maximum, likely due to additional frictional heating beyond plastic deformation.
Analysis of Shear Localization in High-Speed Blanking of Press-Hardened 22MnB5 Steel
(2025-08-26) Schrage, O.; Dardaei Joghan, H.; Hahn, M.; Tekkaya, A. E.; Korkolis, Y. P.
High-speed blanking induces a shear localization in high-strength steels, improving the quality of the blanked edge in terms of geometrical shape, separation surface roughness, and shear-influenced zone close to the cut edge. High-speed blanking experiments with a 20 mm punch diameter and 8 m/s velocity of 2 mm thick 22MnB5-sheets (ultimate tensile strength of 1550 MPa) utilizing a relative clearance of 2.5 % are carried out. Two types of shear bands are observed in the post-process: A 'deformation shear band,' characterized by elongated grains in shear direction, is distinguished from a ‘transformation shear band’ with a change in microstructure appearing as a white layer in optical microscopy. Previous investigations by transmission electron microscopy showed that this white layer consists of nanosized grains in 22MnB5 material. Light microscopic images show that the transfor mation shear band width varies over the sheet thickness. Independent of the occurrence of a transformation shear band, a localization with a width of less than 20 µm is observed along the blanked edge. Fractographic analysis by scanning electron microscopy shows no evi dence of brittle fracture. Characteristic areas of the separation surfaces coincide with the observed two types of shear bands at the blanked edge
Calibration of Aluminum Sheets by High-Speed Hydroforming
(2025-08-26) Hermes, M.; Weiß-Borkowski, N.; Wieseler, T.; Holstein, V.; Köster, E.
A new, robust production system for tubular and sheet-based workpieces is presented. It combines the methodologies of high-speed forming with conventional hydroforming and is based on components and drive technology that can be easy controlled by the use of standard industrial technology. In the article the new system and its function is explained and potentials are shown. Moreover, the focus is on the experimental results of production and calibration of high quality, thin-walled sheet metal and cast components for aircraft and power electronics industry. Thin-walled metal parts are difficult to machine due to their low stiffness and potentially high residual stresses. The paper shows an application example of the new forming device to calibrate these parts by high-speed forming. Moreover, the technological properties of the parts are analysed and an outlook on further work is shown.
Characterization of thermo-mechanical behavior and adiabatic shear band formation in a press- hardened 22MnB5 steel at different strain rates
(2025-08-26) Schottstedt, L.; Scholze, M.; Wagner, M. F.-X.
Adiabatic Shear Band formation is observed in high-speed shear deformation of metallic materials, particularly in technologically relevant processes. It is characterized by the formation of increasingly localized areas of high shear strains. Depending on the selected process parameters, high-speed or adiabatic blanking can lead to the formation of an adiabatic shear band in the newly generated surface. These blanked surfaces have outstanding properties (e.g. high hardness, low rollover, low roughness, almost no burr) and can be used directly as functional surfaces. This reduces the need for complex and expensive, additional mechanical surface processing, significantly shortening the process chain and thus saving energy. In this contribution, we investigate the thermo-mechanical behavior and shear band formation of a press-hardened martensitic steel 22MnB5 under different strain rates. Tensile and compression tests are performed at different temperatures (in the range from 293 to 673 K) and in a wide range of nominal strain rates between 10-3 and 4∙10 3 s-1. In addition, we use S-shaped samples to introduce a simple shear stress state to generate (adiabatic) shear bands, again while applying quasi-static and dynamic (nominal) strain rates, respectively. The plane surface of this sample geometry enables an in-situ observation of local strain fields by digital image correlation. We show the mechanical similarities and differences of dynamic versus quasi-static shear experiments using digital image correlation. Our experimental approach contributes to a deeper understanding of the rate and stress-state dependent formation of shear bands in press-hardened steels.
Determination of Weld Interface Properties and their Effect on the Strength of Multi-Material Aluminium-Steel Joints
(2025-08-26) Kraus, S. O.; Bruder, J.; Groche, P.
Collision welding is a promising manufacturing approach for joining similar and dissimilar metals without thermally influenced strength loss. This capability unlocks new potential for lightweight construction. Among other things, components and welded joints can be made more filigree and load-optimised. Widespread industrial use of this technology is still limited by insufficient knowledge of the underlying joining mechanisms. In this paper, collision welding is applied to an aluminium-steel material combination of steel (DC04) and aluminium (AA6016). First, the welding process window for the material combination is determined on a special model test rig by varying the collision speed and the collision angle, the two main process parameters in collision welding. Shear tensile tests are then conducted to refine the weld process window, focusing on the region exhibiting the highest shear tensile strength values. Scanning Electron Microscope (SEM) images are used to analyse the weld zone, revealing the formation of four different metallographic structures in the joint zone of the welded samples. The area fractions of these structures are quantified and correlated with collision angles and corresponding shear tensile strength values.
Investigation of Electromagnetic Pulse Welding for the Automated Production of Resource-Efficient Multi-Material Joints
(2025-08-26) Kraus, S. O.; Graß, M.; Bruder, J.; Pabst, C.; Holz, J.; Wiedemann, J.; Frodl, S.; Heckmann, M.; Frint, P.; Böhm, S.; Groche , P.
Electromagnetic pulse welding (EMPW) is a promising technology for the automated production of multi-material joints made of high-strength aluminium alloys and steels and is therefore capable of realising light-weight design by exploiting the potential of both materials. The ongoing Design2Collide research project is investigating the potential applications of EMPW in an industrial environment with the aim of reducing the limitations associated with the use of the process. Its automation capability is demonstrated by converting a state-of-the-art robotic production cell to join a demonstration assembly made of steel (DC04) and aluminium (AA6016). Welding studies to derive process windows with the best joint strengths are carried out using an EMPW system and a special model test rig for collision welding. Reproducible attainment of ample joint strength is indicated by failure of the base material AA6016 due to shearing, while the joint itself remains intact. To ensure excellent joint properties, an in-line quality control method based on active thermography is developed and integrated into the automated process. Initial stand-alone tests of the developed method with the EMPW system show promising results for feasibility and industrial qualification. The examination of the EMPW value chain is currently being completed by the investigation of corrosion prevention and passivation systems for the pre and post-treatment of materials and their impact on weldability, and by the improvement of process simulation. For the latter, adapted material models are essential. Respective flow curves have already been determined for the materials used at high strain rates of up to 104 1/s.
An Experimental Study: Improved Electrohydraulic Forming Efficiency through Wire-Free Discharge
(2025-08-26) Jang, Y. H.; Kim, J.
This experimental research proposes improved electrohydraulic forming (EHF) methods to overcome the limitations of traditional high-speed forming and deep-drawing processes. EHF uses a working fluid to generate forming force, which lasts longer than in electromagnetic or explosive forming, allowing precise shape control. However, conventional EHF requires fastening wires and draining/refilling the working fluid for each experiment, resulting in long preparation times and inconsistent forming due to variation in wire position. To address these issues, two new methods ‘wire-cross EHF’ and ‘wire-free EHF’ were introduced and tested using a free-bulging die and 0.5 t STS430 specimens. Forming distribution was analysed by comparing forming force, forming height, and preparation time. The wire-free EHF showed lower initial forming force but achieved comparable forming height through consecutive experiments. It also demonstrated high consistency and reduced total experiment time by 4.72 times compared to the conventional EHF, which suffered from increased wire length during twisting, leading to variations in forming height and forming distribution. Overall, the wire-free EHF proved most effective in achieving consistent forming results with significantly reduced preparation time, making it a promising approach for efficient EHF process.
Magnetic pulse welding of dissimilar aluminum- copper joints: Impact of downscaling on weldability
(2025-08-26) Jüngst, J.; Graß, M.; Böhm, S.
Due to the higher specific electrical conductivity (conductivity/weight) of aluminum compared to copper and the associated lightweight potential, the electrical industry is moving towards current-conducting components made of aluminum. However, the use of aluminum is associated with a necessity for hybrid aluminum-copper joints, due to space limitations as well as purchased components are often made of copper. Furthermore, it can be observed that numerous flat conductors, such as those used in DC and asynchronous motors, are only a few millimeters wide. Due to the rapidly growing market for electric vehicles, an increasing demand for aluminum-copper dissimilar joints with small dimensions is consequently to be expected. In contrast to conventional fusion welding processes, magnetic pulse welding (MPW) is suitable for joining aluminum-copper dissimilar joints, due to the minimization of brittle intermetallic phases. This is attributed to the low energy input, which is applied as the movement of mass to fabricate a material continuous joint. It is known that MPW reaches its process limits when the dimensions of the joining partners decreases due to the minimization of effective eddy currents. However, these limits are still insufficiently researched. Consequently, this investigation is intended to reveal the process limitations of MPW with regard to the joining partner dimensions. For this purpose, various geometries are evaluated with regard to their weldability and the resulting microstructural, mechanical and electrical properties.

Browse

Recent Submissions