MODELLING THE REAR SUSPENSION ASSEMBLY FOR STRUCTURAL ANALYSIS USING ANSA

MODELLING THE REAR SUSPENSION ASSEMBLY FOR STRUCTURAL ANALYSIS USING ANSA

OBJECTIVE:

• To clean up the geometrical errors in the rear suspension assembly model.
• To extract mid-surface of the components having a thickness less than 5mm.
• To assign thickness to the mid surfaces.
• To mesh the model using 2D shell elements and to define volume mesh for components having a thickness (non-uniform) greater than 5mm. 
• To ensure connectivity of the components in the assembly.

GIVEN MODEL OF THE REAR SUSPENSION ASSEMBLY:

QUALITY CRITERIA:

Quality Criteria for Tria Elements (Tyre and Rim): 

S.No	Quality Criteria	Value
1	Target/Average length	7.5
2	Minimum Length	5
3	Maximum Length	10
4	Skewness	45

Quality criteria for Mixed elements (For Midsurface only):

S.No	Quality Criteria	Value
1	Target/Average length	4
2	Minimum Length	2
3	Maximum Length	6
4	Aspect	3
5	Warpage	15
6	Skewness	45
7	Jacobian	0.7
8	Minimum Quad Angle	45
9	Maximum Quad Angle	135
10	Minimum  Tria Angle	30
11	Maximum Tria Angle	120

Quality criteria for Tria (For other components):

S.No	Quality Criteria	Value
1	Target/Average length	4
2	Minimum Length	2
3	Maximum Length	6
4	Skewness	45

Common Quality Criteria for Tetra elements are:

S.No	Quality Criteria	Value
1	Tet-collapse	0.2

PROCEDURE:

1.Geometry Clean-up:

• The rear suspension assembly model is imported to the ansa software.
• Use the length option in the mesh tab to define the perimeter and macro length.
• Now use the topo option in the Topo tab to remove connectivity errors of the cons.
• Use the checks option and identify the geometrical errors and fix the errors using the auto-fixing and manual methods.
• Now the geometry is cleaned up for mid-surface extraction and meshing generation.

2. Mid-surface Extraction:

• Create property cards for the components in the assembly. 
• Extract the mid-surface of the components having a uniform thickness of 5mm or less.
• Assign thickness value in the property cards created for the mid-surfaces.

2. 2D Mesh Generation on the Mid-Surfaces 

• Use the spotmesh option to generate the mesh on the mid surfaces extracted.
• Use the cbar option in the nastran tab to capture the spring elements.

3. 3D Mesh Generation

• Use ortho-tria shell elements to model the rim and tire geometry.
• Use the batch mesh option to clean up and mesh the geometry automatically.
• Tire and rim components are meshed for a target element size of 7.5mm  
• After modelling the components using shell elements, define volumes and mesh the volume using the tetra rapid or tetra FE method.
• Other components are modelled at a target element size of 4mm.

4. Connections

• Connections in this assembly model include spot welds, bolts and other rigid body connections.

 5. Mirroring the Components:

Link to the model: https://drive.google.com/file/d/1AxqO2kGmErUVe46Yw6qTHNruvHf1_Iqj/view?usp=sharing

CONCLUSION:

The geometry has been cleaned up successfully for meshing.

For surfaces with uniform thickness(<=5mm ), mid-surface meshing is used to model the components. 

All the components are meshed satisfying the given quality criteria.

Requisite connections are deployed wherever necessary.