A Coupled 3D/2D Axisymmetric Method for Simulating Magnetic Metal Forming Processes in LS-DYNA
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Date
2016-04-27
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Abstract
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.
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Keywords
simulation, electroforming, finite element method (FEM)