ICHSF 2014

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http://hdl.handle.net/2003/33405

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 five predecessors, the ICHSF 2014 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.

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Now showing 1 - 20 of 27

A Numerical Investigation on Magnetic Pulse Cladding of Bi-Metal Tubes
(2014) Fan, Zhisong; Yu, Haiping; Li, Chunfeng; Huh, H.; Tekkaya, A. E.
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.
Strain-rate effect on the dynamic behaviours of a rectangular conducting plate
(2014) Gao, Y.; Huh, H.; Huh, H.; Tekkaya, A. E.
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.
Pulsed Electromagnetic Attraction Processes for Sheet Metal Components
(2014) Batygin, Yuri V.; Golovashchenko, Sergey F.; Gnatov, Andrey V.; Chaplygin, Evgeniy A.; Huh, H.; Tekkaya, A. E.
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.
Research on homogeneous deformation of electromagnetic incremental tube bulging
(2014) Cui, Xiaohui; Mo, Jianhua; Li, Jianjun; Huh, H.; Tekkaya, A. E.
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.
An experiment and simulation study of the rebound effect in electromagnetic forming process
(2014) Liu, Xianlong; Huang, Liang; Li, Jianjun; Huh, H.; Tekkaya, A. E.
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.
Applications of Pulsed Electromagnetic Fields in Powder Materials High Speed Forming
(2014) Mironovs, V.; Lapkovskis, V.; Kolbe, M.; Zemcenkovs, V.; Shishkin, A.; Huh, H.; Tekkaya, A. E.
In current article, applications of electromagnetic pulsed fields for processing of powder materials are presented. The main attention is paid to the following applications of pulse electromagnetic fields in powder metallurgy and allied industries: pressing of powders, manufacturing of powder coatings, and conveying of ferromagnetic powders by means of pulsed electromagnetic field.
Influence of the Boundary Layer in Magnetic Pulse Sheet Welds of Aluminium to Steel
(2014) Geyer, M.; Rebensdorf, A.; Böhm, S.; Huh, H.; Tekkaya, A. E.
In this paper, influential factors on the bonding strength of magnetic pulse welds between Aluminium (A1050) and Steel (S235JR) sheets are shown. First, a process window defined by varying charging energy and standoff distance for the welds. These welds will be characterised by the means of weld length and shear strength. Sound parameters are worked out at a standoff of 1.5 mm and a charging energy of 9 kJ. Nevertheless, no direct correlation between archived weld length and weld strength can be seen for the specific parameter set with a glass blasted, nearly polished surface. The achievable shear strength for this parameter set varies in the magnitude of 30 %. The chosen parameters are used to investigate the effect of surface preparation on the weld. Surface preparation has an acceptable impact on the achievable weld length in the interface and on the maximum shear strength. Furthermore, a controlled surface appearance reduces the statistic deviation of the weld length. It is shown that machining, which cuts grooves perpendicular to the collision direction, enhances the joint performance as well as the achievable weld characteristics. Furthermore, an acceptable impact of the rolling direction of the steel on the appearance of the joint interface will be shown. A rolling direction which lies perpendicular to the collision direction enhances the bulging of the steel into the aluminium.
Development of Space-Time-Controlled Multi-Stage Pulsed Magnetic Field Forming and Manufacturing Technology at the WHMFC*
(2014) Li, Liang; Han, Xiaotao; Cao, Quanliang; Chen, Qi; Lai, Zhipeng; Zhou, Zhongyu; Xiong, Qi; Zhang, Xiao; Li, Xin; Fu, Jiekai; Liu, Yuanhang; Huh, H.; Tekkaya, A. E.
In November 2011, the Project of Basic Research of Forming by Space-Time-Controlled Multi-Stage Pulsed Magnetic Field (Stic-Must-PMF) was supported by the National Basic Research Program of China (973 Project, 2011.11-2016.08). It is aimed at achieving breakthroughs in manufacturing technology to solve current problems in forming largescale and complex sheet and tube parts and components, imposed by the limitations of existing equipment and materials forming properties. The objective of our research group focuses on the design principles and structural layout optimization of Stic-Must-PMF facility. And this paper will report the development of Stic-Must-PMF forming and manufacturing technology at the Wuhan National High Magnetic Field Center (WHMFC) including numerical modeling, experimental setup and experimental studies.
Design of Electromagnetic Pulse Crimp Torque Joints
(2014) Faes, K.; De Waele, W.; Müller, M.; Cramer, H.; Huh, H.; Tekkaya, A. E.
Electromagnetic pulse crimping of form fit joints was investigated using tubes with a diameter of 50 mm and a wall thickness of 1,5 mm, in the aluminium alloy EN AW-6060. The tubes were crimped onto steel internal parts, which were designed to bear torsional loads. Grooved, knurl rolled and knurl cut internal workpieces were used. To assess the torque strength of the connections, a torque test set-up was designed and built. In a first test series, grooved internal parts were used. The influence of the internal workpiece design and the energy level on the torque resistance was investigated. Related to the geometry of the internal workpiece, the following parameters were varied: the groove depth, the groove width, the edge radius and the number of grooves. In a second test series, knurl rolled and knurl cut internal workpieces were used. For the joints with a knurl rolled internal part, the influence of the knurl pattern, defined by the pitch, was investigated. For the connections with a knurl cut internal part, the influence of the energy level was studied. The different joint failure mechanisms were determined.
Experimental Study on Electromagnetic Forming of High Strength Steel Sheets with Different Dimensions of Aluminum Driver Plate
(2014) Park, Hyeon Il; Kim, Daeyong; Lee, Jinwoo; Kim, Ji Hoon; Lee, Myoung-Gyu; Lee, Youngseon; Song, Jung Han; Huh, H.; Tekkaya, A. E.
Recently, the potential of the electromagnetic forming process has been introduced to form the shallow longitudinal reinforcement ribs in the lateral walls of roll formed parts, made of high strength steel sheets of 340MPa tensile stress grade [1]. However, it seems that the application may not be easy for high strength steel sheet because of its high tensile strength and low electric conductivity. In order to overcome this difficulty, aluminum driver plate could be considered to enhance the formability of high strength steel sheets in the electromagnetic forming process. In this paper, in order to investigate the effect of aluminum driver plate on forming height of high strength steel sheet in electromagnetic forming process, DP780 workpiece sheets were formed into a hemi elliptical protrusion shape with Al1050 driver plate of various thicknesses and sizes. Experiments were performed with a flat spiral coil actuator connected to an electromagnetic forming system. The results, the aluminum driver plate helps to increase the forming height of high strength steel sheets. In addition, the forming height of high strength steel sheet increases as the thickness and size of a driver plate increases.
Extension of formability of the magnesium wrought alloy AZ31B-O at room temperature by pulse magnetic forming
(2014) Uhlmann, E.; Prasol, L.; Kawalla, R.; Schmidt, C.; Becker, T.; Huh, H.; Tekkaya, A. E.
For having the lowest density of all metal construction materials of 1.75 kg/dm3, magnesium wrought alloys are outstanding lightweight materials. The low formability at room temperature limits the industrial use of magnesium AZ31B-O. In this paper the influence of high strain rates was investigated with the aim to improve the formability of the alloy AZ31B-O at room temperature. The negative strain rate sensitivity of quasi-static strain rates causes an early loss of material stability due to formation of local deformation zones on the work piece surface. This leads to a low formability in the forming state of plane strain, in which the forming limit (FLC) of magnesium alloy AZ31B-O has a critical minimum. For process illustration of multi-axial stress states - which appear in conventional forming processes - the pulse magnetic forming process is used. To create plane strain formability a flat coil is used. The applied die is used to control the free formability. Hereby, a change of the maximum loads on the power transfer zone to areas of plane strain formability occurs. The results that have been achieved show that high strain rates at room temperature increase the permitted loads of the material with plane strain formability significantly. High speed forming is linked to a rising strain rate sensitivity which increases the flow resistance in critical forming areas, in favor of a rising material stability. This fact is represented by equally reduction of the sheet thickness on the power transfer area. The homogeneous work piece stress clearly increases the formability of AZ31B-O at room temperature compared to quasi-static forming process.
Ball Pad Mold Electromagnetic Forming Process for Aluminium Alloy Sheet
(2014) Wang, Wen-Ping; Wu, Xiang-Dong; Wan, Min; Chen, Xiao-Wei; Xiong, Wei-Ren; Huh, H.; Tekkaya, A. E.
In order to meet requirements of lightweight technology in the field of aerospace, the new forming technology for aluminium alloy skin parts and integral panel are brought to more attention. Based on the principle of electromagnetic forming (EMF) and energy distribution, a new electromagnetic forming process using ball as pad mold for aluminium alloy sheet forming was suggested and test apparatus was designed. The new method was verified by the finite element simulation and experimental technology, and all studies were carried out on 2024-T3 aluminium alloy sheet. The results show that the new process of ball pad mold electromagnetic forming is feasible to aluminium alloy sheet parts forming. Rubber cushion thickness and electromagnetic pulse voltage are significant contributors to the curvature radius of the test sample. Based on these observations, application advantages and prospects of this new process were pointed out, and the subsequent research was put forward.
Electromagnetic Pulse Welding: Process Insights by High Speed Imaging and Numerical Simulation
(2014) Pabst, C.; Groche, P.; Huh, H.; Tekkaya, A. E.
Most researches on the mechanisms of impact welding in general base their results on the investigation of the joint area after the process, primarily by destructive testing. A detailed analysis of the joining process itself, especially concerning electromagnetic pulse welding, has not been performed yet and thus leads to a lack of understanding. As a consequence of this, the design of the joint area and the process parameters are almost exclusively found empirically. With the help of a special image intensifier camera and a laser, which illuminates the joint area, a new attempt is made to visualize the impact in electromagnetic pulse welding. The results suggest that at least some mechanisms are currently not fully understood. Explanations are developed, mainly concerning jet formation (surface cleaning during the impact) and material behavior of the workpieces under the high strain rates of the process. Areas of large strain rates (liquid-like behavior of the metal) and areas of comparably small strain rates can be found within one workpiece. The question will be discussed whether process parameters can be gained with the help of a simulation that is sufficiently accurate at least in the macroscopic scale.
Effect of the Duration of Electromagnetic Pulse Force on the Rebound Suppression in V-Bending Experiment
(2014) Xiong, WeiRen; Wang, WenPing; Wan, MIn; Pan, Long; Huh, H.; Tekkaya, A. E.
Electromagnetic Forming (EMF) is one of the high speed forming technologies. The spatial distribution and temporal evolution of electromagnetic body force and the constraint imposed by the die on the sheet metal, are key factors which influence the dynamic deformation behaviour of sheet metal. The great force induced by the collision at high speed of the sheet and the die causes the rebound of the sheet off the die. The rebound has a significant influence on the final shape of the part. On the basis of the comparison of time relationship between the displacement of the sheet metal and the amplitude of electromagnetic force, the study about the rebound phenomenon in an electromagnetic V-bending experiment and its numerical simulation model is carried out in this paper. Collision promotes deformation process, resulting in a drastic change of sheet geometry in which a new distribution of electromagnetic force helps the part to fit the die. The attenuation of force caused by distance increase is comparatively weak when forming into a shallow die, so that the electromagnetic force maintains enough intensity which can effectively suppress the rebound and help to calibrate the V-Shape of the part. Increasing the duration of coil current pulse helps to suppress rebound effect of sheet metal when forming into a shallow die.
Process reliability and reproducibility of pneumomechanical and electrohydraulic forming processes
(2014) Homberg, W.; Djakow, E.; Damerow, O.; Huh, H.; Tekkaya, A. E.
A sufficiently high process reliability and reproducibility is mandatory if a high-speed forming process is to be used in industrial production. A great deal of basic research work into pneumo-mechanical and electrohydraulic forming has been successfully performed in different institutions in the past. There, the focus has been more on process related correlations, such as the influence and interaction of different parameters on the course and result of those processes. The aspects of reliability and reproducibility have not been examined to a sufficient extent. Hence, in the case of pneumo-mechanical forming, insufficient investigations have been conducted into the effect that key parameters like the kinetic energy level, the filling height of the working media or the conditions inside the acceleration tube have on the reproducibility and course of the process. For electrohydraulic forming, the repeatability has worsened on occasions up to now. To improve the forming results and, in particular, the reputability of the process, it is necessary to examine the tool parameters associated with the electrodes and the working media. That is why research of this type is currently ongoing at the LUF. One important issue here is examining the options that exist for visualising the way the spark takes hold in the discharge chamber.
Magnetic Pulse Welding of the “Tube – Plug” Pair of STS410 Steel
(2014) Krutikov, V.; Paranin, S.; Ivanov, V.; Spirin, A.; Koleukh, D.; Lee, J.-G.; Lee, M.-K.; Rhee, C.-K.; Huh, H.; Tekkaya, A. E.
The research was focused on the magnetic pulse welding (MPW) of 12.5% Cr steel STS410. The experiments were performed in the tube-plug geometry (both details were made of the same steel). Magnetic pulse unit consisted of pulsed current generator (PCG) loaded to a single-turn coil. Magnetic field amplitude of 40 T was generated in the coil during experiments. The amplitude of pulsed current reached 750 kA. The effects of energy storage capacity, charging voltage, and end plug shape were studied. The welded samples were investigated by optical microscopy. The optimal velocities of impact and contact front motion were evaluated as 300 m/s and 3-3.5 km/s, respectively. The paper includes the leakage test results as well. To date, the joints with a helium leak rate of 10-9 mbar·l·s-1 have been produced.
High Speed Forming Press Using Electromagnetic Pulse Force
(2014) Park, C. G.; Choi, Y.; Shim, J. Y.; Kang, B. Y.; Huh, H.; Tekkaya, A. E.
In this paper, the finite element analysis for the design of a high speed forming press using electromagnetic pulse force has been performed. The punch of the press has been fixed on a aluminium plate, which is driven by the electromagnetic pulse force. The force is the repulsive force between aluminium plate and the coil. The coil has been supplied with a high voltage AC current impulse from the capacitors and then the magnetized aluminium plate has been forced to move upward with high speed. For the analysis of the pressing, the coupled analysis of electromagnetic field and rigid-body dynamic of the aluminium plate has been performed with a commercial FE-software, ANSYS and the rigid-body dynamics theory.
High speed joining process by laser shock forming for the micro range
(2014) Veenaas, S.; Vollersten, F.; Huh, H.; Tekkaya, A. E.
The importance to implement more functionality on the same space pushes miniaturization and makes hybrid joints under various conditions, also in the micro range, necessary. Conventional joining processes, which are used in macro range, cannot be easily transferred to micro range dimensions. In this work a new high speed joining method for the micro range is presented, which is realized by a plastic forming process based on TEA-CO2-Laser induced shockwaves. In a first step it is shown how sheet-sheet joints can be realized with this method. The experimental results illustrate the possibilities as well as the limits of the joining process by laser shock forming. Also the possible defects which can occur during the joining process are presented. Especially fracture of material at the edge. This is explained by the sharp edges in the joining area, which are caused by the production process of the specimen.
Collision Welding of Tungsten Alloy 17D and Copper Using Vaporizing Foil Actuator Welding
(2014) Vivek, A.; Liu, B. C.; Daehn, G. S.; Huh, H.; Tekkaya, A. E.
The objective of this study was to implement collision welding of tungsten alloy 17D (6.5% Ni, 3.3% Fe) and copper at a laboratory scale and subsequently investigate the relationship between interfacial structure and mechanical properties. Vaporizing Foil Actuator (VFA) has recently been demonstrated as a versatile tool for metalworking applications, such as impact welding of dissimilar materials. Its implementation for welding is termed as VFA welding or VFAW. With 8 kJ input energy into an aluminum foil actuator, a 0.5 mm thick Cu110 alloy sheet was launched toward a tungsten alloy target resulting in a collision at a velocity of 580 m/s. The two sheets were found to be welded in the region where the collision velocity and angle were optimal. This range, termed as the welding window was found to be narrow for this combination of target and flyer materials. Scanning electron microscopy of sectioned samples showed regions of wavy interface with significant plastic deformation on both sides. Microhardness tests revealed significant increase in hardness near the interface. Instrumented peel tests showed that the welds were quite strong with peel strength of 60 N/mm.
Control of Velocity, Driving Pressure, and Planarity During Flyer Launch with Vaporizing Foil Actuator
(2014) Hansen, S. R.; Vivek, A.; Daehn, G. S.; Huh, H.; Tekkaya, A. E.
Electrically-driven rapid vaporization of thin conductors produces a high-pressure pulse which can be used to accelerate thin metal sheets to high velocities. Recently, vaporizing foil actuators (VFA) have been applied toward a variety of impulse-based metalworking operations such as collision welding, closed-die forming, embossing, and shearing. To better apply VFA to different purposes, it is necessary to develop an understanding of how variations on the characteristics of the foil actuator affect its mechanical impulse generation. In this work, actuators made out of 0.0508, 0.0762, and 0.127 mm thick full hard temper AA1145 foil were used to launch 0.508 mm thick AA2024-T3 sheets toward a photonic Doppler velocimeter (PDV) probe. Launch velocities ranging between 300 and 1000 m/s were observed over a distance of less than 3 mm, and repeated trials demonstrated repeatable results. Velocity, current and voltage traces were used to examine the effect of deposited energy on average pressure and resulting velocity for foil actuators of various thicknesses. The planarity of the flyer sheets’ launch and flight was demonstrated with 0.0762 mm foil actuators by experiments that employed multiple PDV probes simultaneously recording the velocity evolution at different locations across the surface of the flyer.

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