Project - 2 - Meshing on the suspension Assembly

Project-2 Meshing on the suspension Assembly

Aim-

• To perform shell and solid meshing on suspension assembly.
• To deploy connection at the required region in that assembly.

Objective-

• To do geometry cleanup for the component.
• Extract mid surface for the component having a thickness less than 5 mm.
• To perform shell mesh (mixed type element) on extracted mid surface according to given quality criteria.
• Perform shell mesh of tria element on the surface and then create volume mesh for the component more than 5 mm thickness.
• Clearing all the failing elements of shell mesh as well as solid mesh.
• Deploying Bolt and seam weld connections at a required region in the assembly.
• Model coil spring as CBAR 1D element.
• To perform the symmetric operation for creating a full visual of the suspension assembly.

Theory

Suspension system-

• Suspension is the system of tires, tire air, springs, shock absorbers, and linkages that connects a vehicle to its wheels and allow relative motion between the two.
• Suspension systems must support both road holding/handling and ride quality which is at odds with each other. The tuning of suspensions involves finding the right compromise.
• It is important for the suspension to keep the road wheel in contact with the road surface as much as possible because all the road or ground forces acting on the vehicle do so through the contact patches of the tires.
• The suspension also protects the vehicle itself and any cargo or luggage from damage and wear. The design of the front and rear suspension of a car may be different.

Rear suspension-

• The rear suspension of a vehicle performs the same general function as front suspension, but the specific construction is typically quite different.
• The most basic purposes of a suspension system are to prevent the body of a vehicle from hitting the ground and to keep the tires in contact with the road.

There are various components in the Suspension system-

Procedure-

Stage- 1

Importing the Model-

• Here we will be importing the CAD file into ANSA.
• Here are many types of file formats supported by ANSA for CAD models like IGES, STEP and sometimes Parasolid also depending upon the requirement of industries.

For importing the model

we will go on pull-down tab >> File >> open >> select the all format >> select the model from folder

Imported model-

• Hence the model is imported on ANSA GUI by following this procedure.

[Note-There are single/free edges on the model which need to get fixed]

Stage-2

Topological cleanup

• Now on this model, we will perform geometrical cleanups to eliminate all kinds of geometrical errors.
• First, we will do topo on the model,

For that, Go to topo module > faces > topo > select the component

After topological cleanup, we can see that model is now free from free edges.

Stage-3

Initial check and Geometry cleanup-

• Now after topological cleanup will do a geometric check on this component.

Go to utilities > check > geometry

Click on geometry a new window will popup

• check this as a table as shown in the figure,

Assigning different PID's to the parts-

• As we can see there are many components in suspension assembly.
• So we need to create different-2 PID's for ease.
• For creating PID's Go to topo module >> Faces >> set PID.

• Now we will do this for all components available in suspension assembly.

Complete assembly-

Stage-4

Midsurface Extraction-

• Before mid-surface extraction, we will change the perimeter and macros length to 1mm.
• We are doing it just because to get a proper and finished surface while extracting mid surface.
• For giving the perimeter and macros length.
• Go to mesh module >> Length >> perimeter >> select region by box drag >> middle click >> put 1mm

• Similarly, we will do for macro length also, as 1 mm.

After giving mesh length as 1 mm,

• As we know in this project we only extract mid surface for the components which have a thickness less than 5 mm.

1. Spring lower insulator-

2. Bracket-

Stage-5

2D and 3D Meshing-

2D Meshing-

Once geometry cleanup and mid-surface extraction are completed it means there should not be any unstitched surfaces, unwanted free edges, etc. Meshing is the next step

Mesh module >> Mesh generation >> Best >> select component and mesh

1. In 2D meshing with ANSA preprocessor easiest way of meshing is by Best mesh option.
2. After giving mesh to the surface usually, we will be using Reconstruction (Recon.) from shell mesh for better mesh flow.
3. Uses of some other tools also like smooth, split, swap, cut, join, project, etc. For better mesh flow

Given Quality criteria for this model for shell meshing:

Target Element Length = 4 Unit

• Now we will set the mesh parameter for this 3D mesh as well.

Start meshing,

Some thumb rule while meshing for better mesh flow-

1. Feature capturing is a must while meshing it means all shared edges should have better nodes connectivity.
2. Try to keep less number of trias.
3. Avoid trias on feature line and edges should swap it.
4. Avoid opposite trias, use the split options and combine them.
5. Try to keep less number of trias on fillets, use split or swap tool.
6. Avoid rotational quads, Recons. or split into trias and move them.
7. Using a mixed type of elements on complex geometry means trais and quads for this 2D meshing.

3D Solid Meshing-

• A 3D mesh consists of finite elements with each element define with specific physical properties.
• This 3D mesh is used for analysis, in various domains such as static structural analysis, dynamic model analysis, thermodynamic analysis, etc.
• Any 3D modeled object with specific volume and dimension can mesh with the finite no of elements that helps in solving for accuracy in pinpointing regions of strain at a higher resolution.
• We will do 3D mesh for the components, thickness more than 8mm.
• Before generating the mesh give the quality criteria and mesh parameters.

Types of the grid in 3D Meshing

1. Structured grid

Structured are identified by regular connectivity. The possible element choices are quadrilateral in 2D and hexahedra in 3D. This model is highly space-efficient since the neighborhood relationships are defined by storage arrangement. Some other advantages of structured grid over unstructured are better convergence and higher resolution.

Advantage-

• Memory Efficient
• Fast to solve

Disadvantage-

• Angled or curved geometries are approximated (Leads to stair-stepping)

2. Unstructured grids

An unstructured is identified by irregular connectivity. It cannot easily be expressed as a two-dimensional or three-dimensional array in computer memory. This allows for any possible element that a solver might be able to use. Compared to structured meshes, this model can be highly space inefficient since it calls for explicit storage of neighborhood relationships. These grids typically employ triangles in 2D and tetrahedral in 3D.

Advantage-

• Complex geometry easy to mesh
• Arbitrary positions

Disadvantage-

• Greater memory requirement
• Slower to solve

Quality Criteria for Surface Meshing of Tyre and Rim (Element type: Tria) :

Before meshing we will set all the quality criteria and mesh parameters. For this particular component, we will set only the maximum and minimum length for the 2D mesh.

S.No Quality Criteria Value

1. Target/Average length 6.5

2. Minimum Length 5

3. Maximum Length 10

4. Skewness 45

3D Meshing of Tire and Rim-

Set Perimeter and Macros length-

• Before meshing we should provide perimeter and macros length for better element capturing.
• Will set the perimeter and macros length according to average element length.

Go to mesh panel > Perimeter > Length > Perimeter(1) ,macros(1)

• Similarly, we will do for macro length also.

Start meshing(surface meshing)

For meshing this component we will go to,

Mesh module > Mesh generation > Spot mesh (ortho mesh) > select component

As we can see here maximum surface portion of this spherical bearing is curved so for the curved surface we will provide ortho trias

And on the flat region, we will use normal trias, which we can switch from here,

• Here element is failing due to the average element length size being 6.5 mm.
• So now we will try to reconstruct it as tria element.

Go to mesh module>> shell mesh >> reconstruct >> element type as tria

• Now after 2D mesh on the surface we will convert it into volume mesh.
• Go to volume mesh module > Define > Manual > Window selection > Create new PSolid

• Now similarly we will do for rim as well.

Checking for Tet collapse-

Tet collapse is one of the quality parameters, which will be checked while generating Tetrahedral elements. It can be calculated by measuring the distance of a node from the opposite face, then each of the four values will be divided by the Square root of the opposite face's area.

Tetra elements whose collapse value falls below the value specified are highlighted when the tetra collapse function is selected these elements remain highlighted until the check elements panel exists.

• In 2D tria mesh, we generally check for failure of max and minimum length of the element.
• In 3D tetra mesh, we generally check for tet collapse in the tetra element.

Set the quality criteria for tet collapse,

Now apply this quality over tetra mesh,

• After applying the quality if we found any failure then will go for cleanup.
• In cleanup, we mostly use MVFree from Grids.
• Using MvFree we can fix the issue by adjusting the edges of elements.

Quality criteria for Surface Meshing of Non-Uniform thickness components other than Tyre and Rim (Element type: Tria)

S.No Quality Criteria Value

1. Target/Average length 4

2. Minimum Length 2

3. Maximum Length 6

4. Skewness 45

• There are new quality criteria for components except for tire and rim.

Before meshing we will give the perimeter and macro length as 4 mm because the average element length is 4 mm for these components.

So now we will start meshing those components.

start with Tie Rod,

• Now we will follow the same procedure for defining volume and creating volume mesh as did earlier.

Solid Mesh of all components-

Modeling coil spring-

Representing coil spring as 1D Bar element-

After integrating all the components of suspension assembly-

Stage 6-

Deploying connections-

• As in this project 2, we will majorly use the RBE2 connection.
• It will be of bolt type, cluster type, and RBE2 Rigid at pin locations.

• We will also use a seam weld connection at the location of the bracket connection to the spring lower insulator.

1. Create curve using cons to curve and then convert those curves to seam line convert tool.
2. Then open task manager and click to the seam line and the enter a window will popup where fill all the details required for seam connection like search distance and width and surfaces which need to connect etc.
3. Then apply and realize the connection.

Stage-7

Now Go for symmetry of the model-

• For creating symmetry we will go for the transform > copy option in the module tab.

Now click on FINISH,

The final model :

Result-

• Geometry cleaned and PIDs assigned.
• Hence no surface deformation and glitch is found in the assembly.
• Performed 2D mesh and assign thickness to bracket and spring insulator.
• Performed 2D mesh and convert it into 3D tetra mesh by defining volume.
• Archived proper mesh flow.
• All required connection has been deployed.

Learning Outcome-

• 2D tria shell meshing on surfaces and then creating 3D Solid tetra mesh for the volume.
• How to create proper mesh flow without kink, raises, and dents.
• How to clear elements failing for tet collapse.
• Deploying connection of RBE2 and seam weld.

Model Link- https://drive.google.com/file/d/1JQpLj9LmL6GcqOa_g1mDLkPGfy5WQitq/view?usp=sharing