Week 8-Challenge

CREATING TETRAHEDRAL ELEMENTS USING HYPERMESH

1. Tetramesh for housing and hub assembly: -

Tetrahedral elements are solid elements which have been extracted from 2-D tria elements. HyperMesh builds 4 and 10-noded tetras. HyperMesh provides two methods of generating a tetrahedral element mesh. The volume tetra mesher works directly with surface or solid geometry to automatically generate a tetrahedral mesh. The standard tetra mesher requires a surface mesh of tria or quad elements as input, then provides us with a number of options to control the resulting tetrahedral mesh.

OBJECTIVE -

1. Use standard tetramesh technique to mesh the components.
2. Generate 2-d tria elements mesh on the hub and cover.
3. Check the quality of the tetra elements.

PROCEDURE -

• Import the "housing.stp" file using the import tool option.
• Using the Geometry menu in the menu bar, use the geometry cleanup tools to ensure a fully enclosed volume. Check the topology and verify if we still have free edges.

fig: TOPOLOGY CLEANUP FOR HOUSING COMPONENT

fig: HUB COMPONENT AFTER TOPOLOGY CLEANUP

• Click on automesh panel from the 2-d elements page. Select the surfaces and put element type as trias. We will set the target element length as 5 units.
• After meshing the surfaces and ensuring that no elements are failing for minimum and maximum element length, we can proceed to convert the 2-d tria elements to 3-d tetra elements.

fig: HUB MESHED WITH 2-D TRIA ELEMENTS

• Access the Tetramesh panel from 3D page, and then click on tetramesh subpanel.
• Select the elements selector under Fixed trias/quads to tetra mesh. Click mesh to generate the tetrahedral elements.

fig: TETRAMESH ON THE HUB COMPONENT

• Use Check Elements panel and go to the 3-d subpanel. Identify elements having a tet collapse value smaller than 0.15.
• Remesh the hub’s displayed tetra elements to improve their tetra collapse. Under tetramesh parameters check the minimum tetra and maximum tetra element length box. Also, check the fill voids, fill midnodes and smoothing box. Set the tet collapse value as 0.15.
• Another method to improve the tet collapse is by using distance option. The elements that failed the tetra collapse check is saved in the user mark by clicking on save failed, and can be retrieved in mask panel using the extended selection menu.
• We can increase the distance to improve the tet collapse value.

CONCLUSION -

1. Performed tetrahedral mesh generation by converting the 2D elements into 3D.
2. Achieved a better mesh by clearing the 3D mesh quality errors.

LEARNING OUTCOME -

1. Various techniques for creating the tetrahedral mesh.
2. Understanding the 3D mesh quality error and Clearing that.

II. Creating tetramesh for Crank Housing: -

OBJECTIVE -

1. Use the quick tetra mesh to mesh the geometry.
2. Review the quality of the tetra mesh to validate its integrity.

PROCEDURE -

• Import the ''Crankhousing.hm'' file using the import tool option.
• Observe the topology of the geometry by using the visualisation option. Make sure that there are no free edges.

fig: MODEL AFTER GEOMETRY CLEANUP

• We can access the Quick tetra menu under View >Browsers >Hypermesh > utility. Go to Geom/Mesh and select quick tetraMesh under Mesh tools.
• Select the component and put trias only as mesh type. Fill mesh size as 6 units. Click the mesh button to mesh the component.

fig: TETRAMESH FOR CRANK HOUSING

• Use Check Elements panel and go to the 3-d subpanel. Identify elements having a tet collapse value smaller than 0.15.
• Remesh the crank housing displayed tetra elements to improve their tetra collapse. Under tetramesh parameters check the minimum tetra and maximum tetra element length box. Also, check the fill voids, fill midnodes and smoothing box. Set the tet collapse value as 0.15.
• Another method to improve the tet collapse is by using distance option. The element that failed the tetra collapse check is saved in the user mark by clicking on save failed, and can be retrieved in mask panel using the extended selection menu.
• We can increase the distance to improve the tet collapse value.

CONCLUSION -

1. 3-D mesh generated using the quick tetra method.
2. Performed 3-D quality check and removed all the elements failing for tet collapse.

LEARNING OUTCOME -

1. Understanding about Quick tetra meshing method.
2. Clearing up the tetrahedral quality errors.

III. Creating tetramesh for chassis components: -

OBJECTIVE -

1. Mesh the components using volume tetra meshing technique.
2. Perform elements quality check on each of the components.

PROCEDURE -

• Import the "chassis assy.hm" file from the import model tool.
• Take a moment to inspect the geometry. For the hub component we will convert the trias elements into tetras elements.
• In order to mesh the hub with tria's we need to perform topology cleanup. Remove the surfaces where elements will fail for minimum length. Defeature all of the small surface fillets. Use toggling and replacing points options to clean the geometry.

fig: TOPOLOGY CLEANUP FOR THE HUB

• Mesh the components with trias and then generate the tetrahedral elements using tetra mesh panel.

fig: TETRAMESH ON THE HUB

• For rest of the components use volume tetra meshing method.Access the Tetramesh panel from 3D page.
• Go to the Volume tetra subpanel. Set the entity selector to surfs and select the surfaces in the model. Verify that 2D type is set to trias and 3D type is set to tetras. Specify '6' as the element size. Click mesh to generate the mesh.

• Access the Check Elements panel to eliminate the failing elements. Identify elements having a tet collapse value smaller than 0.15.
• We can rectify the failing elements by remeshing with tetramesh parameters. Increasing the distance between nodes using distance tool can also fix the failing elements.
• Reflect the elements to the other four components by creating a node in between.

CONCLUSION -

1. Tetrahedral mesh generated using the volume tetra meshing technique.
2. Remeshed with tetra parameters to achiev a better element quality.