ANSA Project - Rear Suspension Assembly & Connections

ABSTRACT:

• By using CAE Pre-Processing Tool ANSA & to develop 2D meshing & 3D volume meshing for an Automobile Rear Suspension.
• Giving out different connections in order to define the surfaces for NVH analysis

METHODOLOGY:

1. Importing the CAD geometry and Assigning Property ID (PID) for each part
2. Checking out the errors.
3. Extracting Mid-Surface (3D to 2D interpretation)
4. Assigning Quality Criteria
5. Meshing and Improving Mesh Quality & Generating Volume Mesh
6. Connections

INTRODUCTION:

• Keeping safety, strength, and many design aspects, Rear Suspension has to undergo many conditions, and final CAD outcome is considered for pre-processing in ANSA.
• The Rear suspension should handle the engine torque while resisting the rotational force of the driveshaft.
• The Rear Suspension usually have more number of components that the front suspension.
• The rear suspension has a profound effect on a vehicle's behaviour, especially while cornering or travelling over bumpy roads. Many specific types of suspension are currently available.
• Here We used Macpherson Strut Suspension.
• The MacPherson strut combines a shock absorber and a coil spring into a single unit.
• The MacPherson strut is commonly used in light vehicles.
• Tyre, Rim, ROTOR, Suspension assembly need to be isolated separately.

PROCEDURE:

1.Importing CAD Geometry of Instrument Panel in ANSA and Assigning Property ID (PID) for each part:

• For any component, we need to assign Property ID(PID) for each and every part so as to differentiate individual checks in our process in later stages.

• This helps in switching to different parts specified upon user requirements.
• Give the Target Length for each part individually as part of Quality to refine the given CAD.

2.Checking Out for Errors:

• After successfully importing the CAD geometry we need to perform the geometry check under CHECKS Manager in order to see any geometrical problems of the model such as Unmeshed Macros, Unchecked Faces, Needle Faces, Collapsed Cons, Triple Cons, Overlaps and Cracks.

• ANSA detects some errors and we need to ensure that these need to fixed manually or by just running the automatic fix command and confirm that there are no geometry errors there in the model.
• Make sure that the CAD is always Gray which indicates Positive in ANSA where yellow stands as Negative.
• Use the Orient option under Faces in Topo Mode to change the colour of the model to Gray if it’s so. (Orient<Visible)

3.Extracting Mid-Surface:

• In order to Mesh the component, it needs to undergo mid-surfacing for all the components/parts as the component becomes a 2D object after extracting Mid-Surface and it will be ideally good for Meshing.
• There are different methods a CAE engineer can use for Mid-Surfacing the component and the best would be Mid-SurfaceModules Buttons in Topo Mode.
• Here I used Offset Mid-surfacing as its easy and much efficient.
• Always enable Cross Hatch while extracting Mid-surface as it helps to select a particular region and space so as to avoid unnecessary errors.
• Create separate PID for all the Mid-Surfaces Extracted in the Property ID Manager in order to obtain the results at the end.
• Make sure that all the PID’s are created and remove any Hot Points if any.

4.Assigning Quality Criteria:

For Mid Surface

For Tyre & Rim (Volume Mesh – Tria Elements)

For Other Components (Volume Mesh – Tria Elements)

• Give Average/Target length to all the individual Mid-Surfaces using the Perimeters<Length.
• The average length alters the shell element length of the component.
• Remaining values are assigned in the Quality Manager or just tapping the F11 key.
• Each element in the Mesh should qualify the Quality Criteria given.
• After assigning the values given for the quality check, we need to perform the topological clean up before meshing.

Topological Clean-Up:

• So as to acquire the smooth flow of mesh a CAE engineer should do topological clean up for each and every corner of the model and examine, remove unwanted CONS by using different options available under Module Buttons, mostly used keys are cut, release, insert & delete.

5. Meshing and Improving Mesh Quality.

Meshing:

• After Topological Clean up, consider meshing each and every part separately
• One can use different methods in order the Mesh the surfaces, I used the Batch Mesh and spot Meshing options under Mesh Generation in Mesh Modules Buttons.
• Batch Mesh ensures the user a good Mesh flow across the part and ANSA provides a decent outcome.
• Once the Meshing is done, try to reconstruct the Mesh generated and Smooth it for enhancing the Mesh.

Improving Mesh Quality:

• Once the Meshing is done with the desired quality criteria, we need to ensure there should be no unnecessary rotating Trias or Quad elements in the model.
• No Tria elements on the edges
• And OFF elements should be zero in order to achieve quality.
• Trias and Quad elements can be adjusted using the Split & Swap options under Element Option, smooth the elements again and again till the flow is fine and accurate.
• In some cases, use the Paste option under the Grids bar to clean the Tria and Quad elements from the Edges.

Generating Volume Mesh:

• After generating the Mesh, we need to define the Shell object to solid and then Mesh it.
• Tetra Rapid & Tetra FEM are mostly used in order to define the mesh under volume.
• Volume Property ID is defined separately with respect to the P-SHELL ID.
• Switch on the Bounce & Volume option and OFF the Geometry & FE-Model in order to view the Volume Mesh generated on the Rear-View Mirror surfaces.

Batch Mesh For RIM part:

Tyre & RIM:

Suspension Assembly:

The Suspension Assembly is isolated to a number of components so as to ease the Meshing process.

All the different parts are assigned with different PID's under PID Manager.

Volume mesh and Midsurfaces are generated and meshed for all the components.

6. Connections:

Some of the connections which are used widely in ANSA are:

• Bolt, Seam Weld – Over Lap shell & Y – Joint Shell, Adessive, Spot Weld, etc
• For seam weld connections users can define the connections according to the orientation of weld by CAD engineer.
• In ANSA we generally use Over Lap Shell Joint for parallel weld connections and Y – Joint shell for Perpendicular weld connections by choosing the right parts P1 & P2 and defining it in the connection manager.
• Here in this model, we are more concerned with Bolt, Rigid, Spot Weld connections mainly and are explained along with proper screenshots.

Cluster RBE 2 definition:

• In order to join some of the rigid parts that tend to join we generally use cluster RBE 2 for connection to define it.

Individual Connections:

• Individual holes are given Many Node RBE2 connections under Mesh Deck then making it rigid in order to gain the extra strength at the particular region/hole

Bolt Connections:

• Bolted holes are given Many Node RBE2 on either end and joined by 2 Node RBE2 connections making or stem connection.

SpotWeld Connections:

• Some parts where the bolt or rigid connections are not possible those need to be welded and defined.
• In order to do so, I created a Weld Spot and by using convert tool changed it to spot weld point.
• Now by selecting the spot weld point and defining it into connection manager, was able to create a spot weld region across 2 components with the help of RBE3-HEXA-RBE3 connections.
• Create a Spot Weld PID of solid which determine the material of weld

Solving the OFF elements:

RESULT:

• A 3D Instrument Panel is Meshed successfully converting into the 2D surface by extracting its Mid-Surface giving the quality criteria and performed the Meshing, Improving Mesh Quality using different tools with the help of ANSA.
• All the parts are defined and captured properly with proper connections.
• No Off elements are present across the model and desired quality criteria is achieved.

Final Outcome:

Google Drive Link: https://drive.google.com/file/d/1bD-xwNLr7pIfYiZRZHK-4O5ysb5_REPH/view?usp=sharing