Numerical Simulation of Nonlinear Mechanical Problems using Metafor
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The document discusses the metafor finite element code developed for simulating nonlinear mechanical problems, including applications in metal forming, biomechanics, and crash testing. Key features include an implicit algorithm, thermomechanical time integration, and Python interfaces for user subroutines. Future work involves improving shared memory processing with TBB and exploring distributed memory processing with MPI.
{
e->getForces();
});
int nbelm = els.size();
#pragma omp parallel for
for(int i=0; i<nbelm; ++i)
{
Element *e = els[i];
e->getForces();
}
• C++ iterators are forbidden
• size_t cannot be used as a loop counter
• Calling a function in a for statement is not allowed
• Possibly bad load balancing
• Nested parallelism difficult to handle. Back to 1992!
Example of a loop over the set of Finite Elements…
ORIGINAL C++ LOOP OPENMP LOOP](https://image.slidesharecdn.com/ceci-140527101051-phpapp01/85/Numerical-Simulation-of-Nonlinear-Mechanical-Problems-using-Metafor-9-320.jpg)
{
e->getForces();
});
tbb::parallel_do(els.begin(), els.end(),
[&](Element *e)
{
e->getForces();
});
ORIGINAL C++ LOOP TBB LOOP
Same syntax as modern C++](https://image.slidesharecdn.com/ceci-140527101051-phpapp01/85/Numerical-Simulation-of-Nonlinear-Mechanical-Problems-using-Metafor-10-320.jpg)
Numerical Simulation of Nonlinear Mechanical Problems using Metafor
- 1. Numerical Simulation of Nonlinear Mechanical Problems using Metafor Romain BOMAN Senior Assistant University of Liège Department of Aerospace and Mechanical Engineering CECI Meeting - 16th May 2014
- 2. Outline 2 1. Our in-house FE code : Metafor 2. Libraries and tools 3. Numerical examples 4. Future works
- 3. Outline 3 1. Our in-house FE code : Metafor 2. Libraries and tools 3. Numerical examples 4. Future works
- 4. Metafor 4 Implicit Finite Element code for the simulation of solids submitted to large deformations Metal Forming Applications Biomechanics Crash / Impact •ALE formalism, remeshing, •thermomechanical time integration schemes •fracture modelling, •crack propagation, •contact algorithms •Nonlinear constitutive laws, •Mesh generation from medical images •Enhanced finite elements Fluid Structure Interaction •Fluid elements •Monolothic scheme
- 5. Metafor 5 Version history • 1992 : Version 1 (Fortran): J.-P. Ponthot’s PhD thesis • 1999 : As many versions as researchers • 2000 : Rewritten as an Oofelie solver (C++) • Today : Still one single version for 11 developers How big is it? • ~1500 C++ classes • ~300k lines of code • 52 libraries (.dll/.so) • ~2200 FE models in the test suite Operating Systems Windows, Linux, MacOS Users • Researchers (PhD, FYP), students (FE course) • Companies (ArcelorMittal, Techspace Aero, GDTech, …)
- 6. Outline 6 1. Our in-house FE code : Metafor 2. Libraries and tools 3. Numerical examples 4. Future works
- 7. Libraries and tools 7 Version management Makefiles/project generator 3D display of meshes Widgets, threads (GUI) Interpreter & user subroutines Python interface generator Compiler, BLAS Parallelism (shared memory) Threading Building Blocks Parallel linear solver PARDISO
- 8. Libraries and tools 8 Version management Makefiles/project generator 3D display of meshes Widgets, threads (GUI) Interpreter & user subroutines Python interface generator Compiler, BLAS Parallelism (shared memory) Threading Building Blocks Parallel linear solver PARDISO
- 9. Why TBB? 9 Shared Memory Parallel Programming with OpenMP class Element; // a Finite Element std::vector<Element*> els; // a set of Finite Elements std::for_each(els.begin(), els.end(), [&](Element *e) { e->getForces(); }); int nbelm = els.size(); #pragma omp parallel for for(int i=0; i<nbelm; ++i) { Element *e = els[i]; e->getForces(); } • C++ iterators are forbidden • size_t cannot be used as a loop counter • Calling a function in a for statement is not allowed • Possibly bad load balancing • Nested parallelism difficult to handle. Back to 1992! Example of a loop over the set of Finite Elements… ORIGINAL C++ LOOP OPENMP LOOP
- 10. Why TBB? 10 Intel Threading Building Blocks • High Level Parallel programming library (SMP) • Open Source! • Highly portable (msvc, gcc, even old versions) • Object oriented – similar to STL – tbb namespace ) • Task-oriented (instead of threads) • Thread-safe C++ containers • Efficient overloaded memory allocators (new, delete) • Takes into account OpenMP libraries (Pardiso solver) std::for_each(els.begin(), els.end(), [&](Element *e) { e->getForces(); }); tbb::parallel_do(els.begin(), els.end(), [&](Element *e) { e->getForces(); }); ORIGINAL C++ LOOP TBB LOOP Same syntax as modern C++
- 11. Why TBB? 11 … and it is more efficient and reliable than OpenMP Example: Matrix-vector product : a = B c (size = n) • n=10000 size(B)=763 Mb • multiplication performed 100x Windows Intel Core i7 960 3.2GHz (4 cores) Hyper threading
- 12. Libraries and tools 12 Version management Makefiles/project generator 3D display of meshes Widgets, threads (GUI) Interpreter & user subroutines Python interface generator Compiler, BLAS Parallelism (shared memory) Threading Building Blocks Parallel linear solver PARDISO
- 13. Python interface 13 The main objects of Metafor are available through a python interface for 2 main reasons • Input files are written in python • Less code: no complicated home-made parser required • Full language: use of loops, conditional statements, objects in input files • Extensibility: calls to external libraries (Qt, wxWidgets, numpy, …) • Glue language: calls to external codes (gmsh, SAMCEF, Abaqus, matlab, etc.) • Safety: errors are correctly handled (even C++ exceptions!) • Extension of the code (“user subroutines”) • A lot of C++ classes (boundary conditions, postprocessing commands, geometrical entities, materials, meshers, etc.) can be derived by the user in Python in the input file.
- 14. Python interface 14 Python scripts as input files One Python class is automatically created by SWIG for each C++ class materials.i %module materials %{ %include "ElasticMat.h" %} #include "ElasticMat.h" materials.py materials.pyd from materials import * mat = ElasticMat(E, nu) model.setMaterial(mat) model.run() INPUT SCRIPT (Compiled Python module) (Shadow classes) Adding one new material class requires to add only two lines in the input file of SWIG (material.i) to make it available in Python!
- 15. Python interface 15 Python inheritance of C++ classes : “user subroutines” SWIG can generate the (huge and complex) code required to derive a C++ class in Python! class ElasticMat { public: virtual T computeStress(T &strain); }; C++ ELASTIC MATERIAL from materials import * class ElasticPlasticMat(ElasticMat): def computeStress(self, strain): # compute the stresses # from the strains # using python cmds here… return stress PYTHON ELASTICPLASTIC MATERIAL This python code will be called from the compiled C++ code! Very useful for students (Final Year Projects) A new material law is available without any compiler!
- 16. Outline 16 1. Our in-house FE code : Metafor 2. Libraries and tools 3. Numerical examples 4. Future works
- 17. Fan Blade containment test 17 • Numerical simulation of an engine validation test (FBO : Fan Blade Out) • Implicit algorithm (Chung Hulbert) • Fixed bearing & moving shaft connected by springs • Frictional contact interactions between blades and casing
- 18. Buckling of a blade in LP compressor 18 • Thermo elasto visco plastic model with damage / EAS finite elements • We expect a lower buckling force compared to a purely elastic model the total weight of the engine can be safely decreased. CPU time : • 1 day 16 hours (1 core) • 5h35’ (12 cores)
- 19. Roll forming simulation 19 Sheet Metal Forming : Simulation of a 15-stand forming mill
- 20. Outline 20 1. Our in-house FE code : Metafor 2. Libraries and tools 3. Numerical examples 4. Future works
- 21. Future? 21 Shared Memory Processing (TBB) Go on with TBB parallelisation of loops… • The contact algorithms are still sequential. • Some materials are not thread safe. Distributed Memory Processing (MPI?) Nothing done until today… • Domain decomposition should be implemented. • How to manage contact efficiently?
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