Defining a reference mesh

This problem contains basic test cases for one or more Abaqus elements and features.

This page discusses:

Elements tested
Problem description
Results and discussion
Input files
Figures

Elements tested

C3D5

C3D6

C3D8

C3D8I

C3D8R

Problem description

If a reference mesh is specified for an element, Abaqus/Explicit computes the initial stresses based on the deformation gradient that maps the reference configuration to the initial configuration. This capability is tested for different element types and materials.

Some tests consist of a two-analysis sequence. In the first analysis, a regular Abaqus/Explicit simulation is performed to compute the element stresses resulting from applied loads and boundary conditions. In the second analysis, the initial mesh of the first analysis is used as the reference mesh and the final configuration of the first analysis is used as the initial mesh. This is accomplished by adjusting the user-specified nodal coordinates (see Adjusting Nodal Coordinates) using the displacement field data from the first analysis (Using an external field to define distributions and initial conditions).

Results and discussion

In all cases, the initial stresses reported at the zero increment match the expected results. This verifies that the definition of a reference mesh leads to the correct initial stress conditions in each case.

Several test cases use the two-analysis sequence with different element types (C3D8 and C3D8R, C3D5 and C3D6). As shown in Figure 1 (an indentation test using C3D8R elements with elastic material), the initial stresses of the second analysis (right image) computed based on the reference mesh method are very close to the the stresses in the final configuration of the first analysis (left image). Additional test cases include a test with three brick elements of different element types (C3D8, C3D8I, and C3D8R) using the same hyperelastic material and reference mesh and two tests consisting of four C3D8 or C3D8R elements each with a reference mesh of different spatial rotations. In each case, it is verified that the initial stresses computed based on the reference mesh method are correct.

Input files

inimetric-indent-ela-c3d8r-0.inp: Indentation test for C3D8R elements using elastic material. First analysis of two-analysis sequence. Displacement results from SIM output used to compute initial mesh for second analysis, inimetric-indent-ela-c3d8r-1.inp.

inimetric-indent-ela-c3d8r-1.inp: Second analysis of two-analysis sequence. Reference mesh defined as initial mesh of first analysis, inimetric-indent-ela-c3d8r-0.inp.

inimetric-indent-hyper-c3d8r-0.inp: Indentation test for C3D8R elements using hyperelastic material. First analysis of two-analysis sequence. Displacement results from SIM output used to compute initial mesh for second analysis, inimetric-indent-hyper-c3d8r-1.inp.

inimetric-indent-hyper-c3d8r-1.inp: Second analysis of two-analysis sequence. Reference mesh defined as initial mesh of first analysis, inimetric-indent-hyper-c3d8r-0.inp
.

inimetric-indent-hyper-c3d8-0.inp: Indentation test for C3D8 elements using hyperelastic material. First analysis of two-analysis sequence. Displacement results from SIM output used to compute initial mesh for second analysis, inimetric-indent-hyper-c3d8-1.inp.

inimetric-indent-hyper-c3d8-1.inp: Second analysis of two-analysis sequence. Reference mesh defined as initial mesh of first analysis, inimetric-indent-hyper-c3d8-0.inp.

inimetric-c3d5-0.inp: Reference mesh test for C3D5 elements using hyperelastic material. First analysis of two-analysis sequence.

inimetric-c3d5-1.inp: Second analysis of two-analysis sequence. Reference mesh defined as initial mesh of first analysis, inimetric-c3d5-0.inp.

inimetric-c3d6-0.inp: Reference mesh test for C3D6 elements using hyperelastic material. First analysis of two-analysis sequence.

inimetric-c3d6-1.inp: Second analysis of two-analysis sequence. Reference mesh defined as initial mesh of first analysis, inimetric-c3d6-0.inp.

inimetric-brick-hyper.inp: Test with three different types of brick elements (C3D8, C3D8I, and C3D8R) using the same hyperelastic material and reference mesh.

inimetric-c3d8r-ela.inp: Test with four C3D8R elements, each with a reference mesh of different spatial rotations.

inimetric-c3d8-ela.inp: Test with four C3D8 elements, each with a reference mesh of different spatial rotations.

inimetric-c3d8i-ela.inp: Test with four C3D8I elements, each with a reference mesh of different spatial rotations.

Figures