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WeldFormFEM

Updated Lagrangian Explicit Finite Element Method (FEM) CPU/GPU based solver.
WeldFormFEM is aimed to solve solid mechanics large strain problems, such as metal forming.
The idea is to work via 2 different solvers: 1 - Pure lagrangian with rezoning (adaptive mesh refinement or AMR), Work In Progress as first option
2 - Coupled Eulerian (fixed mesh or Arbitrarian Eulerian Lagrangian) Lagrangian solver based on Benson works.
WeldFormFEM works both on Ubuntu and Windows. you can select to build it to CPU and GPU only by changing a single CMAKE var.

Features

  • Structure Of Arrays (SOA) data arrangement which allows fast CUDA accesing
  • Explicit time integration
  • C++/CUDA CPU/GPU(WIP) Architectures
  • Constant Stress Tetra/Triangle Element with Average Nodal Pressure (ANP) for volumetric locking fixing
  • Reduced Integration Hexaheadra with viscous hourglass control
  • OpenMP (WIP) CPU parallelization
  • Contact algorithm (WIP)
  • Automatic Remeshing (rezoning) (WIP)
  • 2D Plain Strain/Axisymm & 3D
  • Thermal-Mechanical coupling (WIP)

Locking (left) and fixing (right) tetra
Compression cylinder

Compression cylinder HEXA w/reduced integration - TETRA

Bending

Hexa/Quad Hourglass

Build instructions

CUDACXX=/usr/local/cuda-12.3/bin/nvcc cmake ../WeldFormFEM -DBUILD_GPU=ON

To update libraries (LSDynaReader and Math)

git submodule update --init --recursive

Link here #https://arnon.dk/matching-sm-architectures-arch-and-gencode-for-various-nvidia-cards/ to see different architectures.

Cuurrently working axisymmetric with hourglass for area weight in F90 version

reduced_int = .True. call AddBoxLength(0, V, Lx, Ly, 1.0d0, r, rho, h,reduced_int)

!! AFTER ADD BOXLEN axisymm_vol_weight = .false. bind_dom_type = 3 !!!AXISYMM, AFTER CREATING BOX!

elem%sigma_y(:,:) = 300.0e6

do i=1,node_count print *, "NODE ELEMENTS " print *,"i count ", i , nod%elxnod(i),nod%nodel(i,:) end do

nod%is_fix(:,3) = .true.

Then in calc elem forces:

''' if Area weight #-------------

          fa = 0.25d0/elem%radius(e,gp) * elem%detJ(e,gp) !!! THEN IS WEIGHTED BY 4 in case of gauss point =1
          !!! AREA WEIGHTED, BENSON EQN 2.4.3.2
          !!! 2.4.3.2 remains sig * Area/(4 r0), which is (4detJ)/(4r0) = detJ /r0
          !!! LATER IS MULTIPLIED BY WEIGHT WICH GIVES THE AREA

          elem%f_int(e,n,1) = elem%f_int(e,n,1) + elem%dHxy_detJ(e,gp,2,n) * elem%sigma (e,gp, 1,2) - &
                                                 (elem%sigma (e,gp, 1,1) - elem%sigma (e,gp, 3,3) ) * fa
                                                 
          elem%f_int(e,n,2) = elem%f_int(e,n,2) + elem%dHxy_detJ(e,gp,1,n) * elem%sigma (e,gp, 1,2) - &
                                                 elem%sigma (e,gp, 1,2) * fa          
          ! print *, "fa ", elem%dHxy_detJ(e,gp,1,n) * elem%sigma (e,gp, 1,2)
          ! print *, "term 2 ", elem%sigma (e,gp, 1,2) * fa

'''

Feature Density Pointwise
Purpose Controls the global mesh density, used for element size adjustment across the entire mesh. Defines a more localized mesh refinement, typically used for adapting based on certain criteria (e.g., features or user-defined conditions).
Usage Typically used to control mesh coarseness or refinement globally, usually through tags like "density" to apply a global criterion for mesh density. Used for more detailed control, typically in localized regions or based on features in the mesh, allowing for finer resolution in specific areas.
Method A global parameter that can influence the entire mesh structure based on a density tag. Localized refinements applied to the mesh based on specific criteria (e.g., pointwise data).
Application Mesh refinement across the entire mesh; can be used to prevent overly large elements and ensure smoother transitions. Localized refinement; commonly used to refine areas of interest such as regions with high gradients, features, or areas requiring higher accuracy.
Example "mesh.add_tag(VERT, 'density', 1, Reals(mesh.nelems(), 1.0));" "mesh.add_tag(VERT, 'pointwise', 1, Reals(mesh.nverts(), some_local_condition));"
Effect Affects mesh element size globally (entire mesh can get finer or coarser depending on density values). Affects only specified points or elements based on conditions, like features, threshold values, or other user-defined criteria.