CHAPTER 5 Model Generation Procedure and Presentation of Results
5.1 Model Generation
5.1.5 ANSYS
The model generation procedure for the test cases simulated within the ANSYS platform is presented here. The version used, ANSYS 16.1, is licensed to the University of KwaZulu- Natal. The two ANSYS environments used in this research are the ANSYS Static Structural Mechanical environment and the ANSYS Mechanical APDL (ANSYS Parametric Design Language) environment.
74 Test Case 1: Grid Point Load on an Articulated Truss
This test case was generated in the suggested approach. Through prior experience with ANSYS Static Structural Mechanical environment it was noted that this environment was restrictive in the creation of 1D truss structures. It was decided to use the Mechanical APDL environment to generate this model. The Mechanical APDL environment differs from the ANSYS Mechanical environment in that the APDL environment requires more text based input as opposed to the ‘point and click’ method seen amongst contemporary FEA packages.
The process of creating the model geometry can be seen in Figure B.82 through to Figure B.84. The required material properties were applied to the structure as seen in Figure B.85.
The application of the required nodal fixture and force can be seen in Figure B.86 and Figure B.87 respectively. After the model was generated, the simulation was run and the relevant solutions were obtained in a post processing window within the same environment.
Test Case 2: Thin Shell Wall in Pure Bending
This test case was generated in the suggested approach. Suitable 2-D geometry was imported into ANSYS Static Structural Mechanical. The geometrical properties were applied to the surface geometry as shown in Figure B.88. The given material properties were added to the material library. The ANSYS meshing parameters were mostly set to its automatic programme controlled option, an example of which can be seen in Figure B.89. It was assumed that by doing this, a near-optimal mesh would be created. The edge fixture and load were applied as shown in Figure B.90 and B.91 respectively. The relevant solutions were obtained through graphical plots generated by the internal post-processor. The model was rerun varying the mesh sizes accordingly. The recorded result sets consisted of second-order quadrilateral meshes with a maximum element size of 1.0 in, 0.5 in, 0.3 in and 0.15 in.
Test Case 3: Axisymmetric Pressure Vessel
This test case was generated in the suggested approach. The 2-D geometry was imported into ANSYS Static Structural Mechanical within an axisymmetric analysis environment, as shown in Figure B.92. The required material properties were entered into the material library. The meshing parameters, an example of which can be seen in Figure B.93, were mostly set to the programme-controlled settings. This resulted in a second order quadrilateral mesh. The application of the frictionless supports and internal pressure load can be seen in Figure B.94 and Figure B.95. The relevant solutions were obtained through graphical plots generated by the internal post-processor. The model was rerun using the mesh sizes as per previous packages.
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Test Case 4: Internal Pressure on Thick-Walled Spherical Container
This test case was generated in the suggested approach. Appropriate 3-D geometry was used.
The required material data was entered into the material library. The meshing parameters were set to the automatic programme controlled settings. The application of the frictionless supports and pressure load can be seen in Figure B.96 and Figure B.97. The simulation was run and the relevant solutions were obtained through graphical plots generated by the internal post-processor. The model was rerun using the mesh sizes used in the previous benchmarking processes.
Test Case 5: Flat Bar with Stress Concentration
This test case was generated in the suggested approach. The 3-D geometry for this test case was imported into ANSYS. The material data was added into the material library. Meshing parameters were set mostly to programme-controlled options, resulting in a second order hexahedral mesh. The fixture and force were applied to the relevant faces, seen in Figure B.98 and Figure B.99. The relevant solutions were obtained through graphical plots generated by the internal post-processor. The model was rerun using the mesh sizes from previous benchmarking processes.
Test Case 6: Large deflection of a Z-Shaped Cantilever Beam under End Load
This test case was generated using the suggested approach. The 2-D geometry was imported into ANSYS. The ‘Geometry Definition’ tab was used to specify the thickness of the surface.
The given material data was added into the material library. The mesh settings were set to programme-controlled. The required fixture was created using a fixed boundary constraint on the relevant edge. The incremental force values given in the test case data were specified through tabulated data. The time step and load information entered can be seen in Figure B.100. Most of the analysis settings were left as programme-controlled. The number of simulation time steps were set to match the load steps from the test case data. The solution was set to allow large deflection. The model was run using an iterative solver. The relevant solutions were obtained through graphical plots by the post-processor. Incremental solutions were also output in tabular form.
Test Case 7: Plastic Deformation of Tensile Test Specimen
This test case was generated using the suggested approach. The 3-D geometry was imported into ANSY. The material for this test case was created in the material library. In order to model the elasto-plastic behaviour effects, it was required that a plasticity model be used.
The multilinear isotropic hardening model was used as it offers greater accuracy as compared to the bilinear isotropic hardening model also available. This plasticity model
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allowed for the input of the flow curve in terms of true stress and plastic strain. The meshing parameters were mostly set to programme-controlled. The sizing was based on previous benchmarking tests. The fixed edge was imposed using a fully-fixed constraint. The displacement load was applied linearly over 100 increments. The analysis settings were left to programme-controlled. The solver was set to allow for large deformations, which is required when modelling material non-linearity. The model was run and the incremental solutions were output by ANSYS in tabular form.