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LS-DYNA is a general purpose explicit and implicit finite element program used to analyse the non-linear dynamic response of three-dimensional solids and fluids. It is developed by Livermore Software Technology Corporation (LSTC). An electromagnetism (EM) module has been added to LS-DYNA for coupled mechanical/thermal/electromagnetic simulations, which have been extensively performed and benchmarked against experimental results for Magnetic Metal Forming (MMF) and Welding (MMW) applications. These simulations are done using a Finite Element Method (FEM) for the conductors coupled with a Boundary Element Method (BEM) for the surrounding air, hence avoiding the need of an air mesh. More recently, a 2D axisymmetric version of the electromagnetic solver was introduced for much faster simulations when the rotational invariance can be assumed. In many MMF and MMW applications though, the rotational invariance exists only for part of the geometry (typically the coil), but other parts (typically the workpiece or the die) may not have this symmetry, or at least not for the whole simulation time. In order to take advantage of the partial symmetry without limiting the geometry to fully symmetric cases, a coupling between 2D and 3D was introduced in the EM. The user can define the parts that can be solved in 2D and the ones which need to be solved in 3D and the solver will assume the rotational invariance only on the 2D parts, thus keeping the results accurate while significantly reducing the computation time. In this paper, the coupling method will be presented along with benchmarks with fully 3D and fully 2D simulations, comparing the accuracy of the results and the simulation times.

Electromagnetic forming (EMF) is a high speed forming process that has been shown to increase the formability of aluminum alloys under certain conditions. Many authors have reported significant increases in formability; however, there is as of yet no complete understanding of the process. Obtaining a gain in formability is not the only factor that must be considered when studying EMF. The process rapidly generates significant forces which lead to the deformation of the material at very high rates. The applied forces depend on the shape of the electromagnetic coil used, which leads to force distributions that may not be ideal for forming a particular part. Once the sheet is accelerated it will travel at high speeds until it impacts the die. This high speed impact results in the sheet rebounding from the die. Both the force distribution and the rebound affect the final shape of the part. This paper presents the results of experimental and numerical study carried out to determine the effect of the force distribution and the rebound on samples of conical and "v-channel" geometry. It was found that both sample geometries are affected by the force distribution and the rebound, with the v-channel samples being considerably more affected. The results indicate that these effects must be carefully considered when EMF processes are designed.

LS-DYNA is a general multi-purpose explicit and implicit finite element program used to analyse the non-linear dynamic response of three-dimensional solids and fluids. It is developed by Livermore Software Technology Corporation (LSTC). A new electromagnetism module is being developed in LS-DYNA for coupled mechanical/thermal/electromagnetic simulations. One of the main applications of this module is Electromagnetic Metal Forming (EMF). The electromagnetic fields are solved using a Finite Element Method (FEM) for the conductors coupled with a Boundary Element Method (BEM) for the surrounding air/insulators. Both methods use elements based on discrete differential forms for improved accuracy. Recently, a Massively Parallel Processing (MPP) version of the EM module was developed allowing sharing the CPU and memory between different processors and thus faster computations on larger problems. The implementation of the FEM and BEM in MPP will be presented. Finally, the EM module will be illustrated on an actual EMF case. Experimental and numerical results will be compared and the speed-up of the MPP version will be studied.

Modeling electromagnetic forming processes is in many ways simpler than modeling traditional metal forming processes. In electromagnetic forming the problem is often dominated by inertial acceleration by a magnetic field. This is a much better posed problem than the more traditional ones that are often dominated by complex three dimensional constitutive behavior and frictional effects. However, important aspects of the problem are dominated by the constitutive properties of the material, and often electromagnetic forming is performed in a regime where there is little reliable material strength data. Strain rates are often high (102 to 104 s-1 is the typical range for electromagnetic forming). Also, heat is generated both by ohmic heating as well as by plastic deformation, and peak temperatures can be quite high. Also, while hightemperature, high-strain-rate data is scarce, there is little or no data in cases where temperature rises significantly over very short times (tens of micro-seconds) as happens in electromagnetic metal forming. This rapid temperature rise is very important to the material response because the short time scales largely preclude the material from recovery and recrystallization processes and precipitates cannot dissolve as they normally would in an age-hardening alloy in these time scales. This presentation will show how advanced instrumentation, particularly the Photon Doppler Velocimeter (PDV) can be coupled with electromagnetic forming and provide both avenues to characterize material as well as to provide very critical tests of numerical models of the process.

A new electromagnetism module is being developed in LS-DYNA for coupled mechanical/thermal/electromagnetic simulations. One of the main applications of this module is Electromagnetic Metal Forming. The electromagnetic fields are solved using a Finite Element Method for the conductors coupled with a Boundary Element Method for the surrounding air/insulators. Both methods use elements based on discrete differential forms for improved accuracy. The physics, numerical methods and capabilities of this new module are presented in detail as well as its coupling with the mechanical and thermal solvers of LS-DYNA. This module is then illustrated on an Electromagnetic Metal Forming case.