Project - 2 - Meshing on the suspension Assembly

VOLUME MESH GENERATION AND DEPLOYING CONNECTIONS FOR CAR REAR SUSPENSION

• OBJECTIVE:

• Importing rear car suspension geometry into ANSA.
• Clean up the geometry until no topological error is found
• Generate mid surface for required parts.
• Generate volume mesh for hollow parts.
• Improve the mesh flow and solve off elements according to given quality criteria.
• Give connections for rear suspension for NVH analysis.

link for the componeet:

• https://drive.google.com/file/d/1t2_KspjcA6e0lzKCNMrtk3ylUbiBS-Os/view?usp=sharing

ABSRTACT:

In this Project-2, ANSA pre-processor is used to generate mid surface, volume mesh. The
quality criteria for some parts are different. Therefore, one should carefully apply them
while meshing. Clear all off elements on surface mesh and then proceed to volume mesh.
Understand about various connections used in rear suspension and deploy them
accordingly

INTRODUCTION:

Suspension has been an essential component of automobiles. The rear suspension of a
vehicle performs the same general function as front suspension, but the specific
construction is typically quite different. The ideal suspension for a vehicle depends a lot on
the vehicle's body style and performance requirements. 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.

Cadillac suspension image:

suspension parts:

Suspension systems are generally classified into dependent and independent systems. Th
wheels in a dependent system are perpendicular to the axle and parallel with each other.
The most common suspension of this type is leaf-spring rear suspension, which consists of
multiple metal bars, or leaves, bound together. It is an older design but is still most
common on trucks and other heavy vehicles

QUALITY CRITERIA USED

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

S.No	Quality Criteria	Value
1	Target/Average length	6.5
2	Minimum Length	5
3	Maximum Length	10
4	Skewness	45

Quality Criteria for 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

Quality criteria for Mid surfacing (Element type: Mixed elements) :

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

PROCEDURE:

Step 1:

Import the geometry into ANSA and do topo to stitch the surfaces. Isolate each part
and set PID’s for the rear suspension geometry.

Step 2:

Clean the geometry using checks manager. Enable unchecked faces, collapsed
cons, triple cons, needle faces, overlapped faces, cracks, single cons. Clear all these issues
until no error is found. One can use fix option in ANSA to clear all the errors automatically.
However, sometimes manual intervention is required for fixing some errors. Manually we
can use options like cut, release and delete for topo clean up.

Step 3:

Surface Mesh Generation for Tyre and Rim

One can do mesh generation for tyre and rim either by meshing them manually using spot
mesh or by batch mesh.
The advantage of batch mesh is that ANSA will do topological clean up automatically
which is a time saving process. Even though sometimes we must clear some errors
manually after batch meshing also.
Mesh generation using Batch mesh option.

The 1 step is to create a new part in the model
browser and assign the mid surface to that new part. Then open the batch mesh and
create a new meshing scenario.
Update the content i.e. the mid surface and the required mesh parameters and quality
criteria. Then click on RUN to generate batch mesh.

mesh fro the Rim :

batch mesh is completed for the rim and tyre

now to get the volume mesh for the rim and tyre

volume mesh> define > diagnostic check>ok(click)>

Volume Mesh Generation for Tyre and Rim:

colume mesh> unstructure mesh >tetra rapid >volum(required component)>

middle click on mouse or entre

After clearing all the off elements on the surface mesh one can proceed further to volume
mesh generation.
Volume mesh can be created in ANSA only if it recognizes the geometry as a closed
volume. Therefore, we must manually update our model to closed volume.
To convert our model to closed volume one must define volume.
ANSA might crash if you generate volume mesh for the whole geometry. So, define
individual closed volumes for different PID’s.
Defined volumes can be checked under list option under volume dialog box.
One can give either Tetra Rapid or Tetra FEM under unstructured mesh dialog box for close
volume.

result for the Rim volum mesh as shown in below figure :

same for tyre volumw is generated :

result for the tyre volume mesh:

Step 6:

Connections for rear suspension
After completion of mid surface and volume mesh we must connect them by using
connections like bolt connection, spot weld connection, seam weld connection etc.
Bolt connection can be generated using RB2 option in the Nastran deck.
Cluster or Spider RB2: This connection is used when a manual bolt connection must be
deployed between two or more surfaces.
For automatic bolt connection one must follow these steps, Create COG for the hole à COG
is basically a 3D point, convert this 3D point to bolt à Now open connections manager and
select the bolt symbol which has created in earlier step à Then assign P1,P2,P3 à Select FE
type as Bolt and give the required values and constraints à apply and then realize the
connection.
I have simply given bolt connections by connecting two cluster RB2’s with two node RB2 as
shown in the below figure

CBAR CONNECTION:

Take mid curve and COG and for this create CBAR connection :

mid curve> COG> CABAR> radius(5mm)>ok(click)

to see CBAR element solid mesh

also apply area parameter as shown beleow:

Result for 1D element:

Spot Weld
Spot weld is generally a solid connection deployed between 2 surfaces.
For generating spot weld connection first create a COG point on the FE.
Now, convert this 3D COG point into spot weld using convert option.
Then select the generated spot weld point using connections manager. In the connection’s
manager assign P1 and P2 for 2 mid surfaces which are to be connected using spot weld.

Create COG

Convert COG to spot welding point à Use connections manager to generate
RBE3-HEXA-R

Step 7:

Transform

After completing surface mesh, volume mesh, mid surfacing and connections we have to
use transform option in order to create exact mirror of the model on the other side.
Use transform and select all the entities including connections to generate exact replica of
the model on the other side

Learning Outcomes:

Able to do topological clean-up with no errors.
Assigned separate PIDs for different surfaces and volumes.
Able to generate mid surface and volume mesh.
Aware of all the quality criterias and mesh parameters during mesh generation.Learned
how to improve mesh flow and remove trias to achieve better mesh flow.
Understood concets regarding connections. Deployed different types of connections.
Understood all the concepts regarding mid surface generation,volume mesh generation

Conclusion:

In this project, I have generated mid surfaces and volume mesh using different options
available in ANSA. Did topological clean up. Able to achieve better mesh flow using
smooth,reconstruct,swap,paste,move options. Eliminated kinks and raised edges.
Successfully applied different quality criterias and mesh parameters for different parts and
cleared off elements during mesh generation. Successfully deployed connections for the
rear suspension. Overall I have done pre processing for rear suspension using ANSA.

link for the component :

https://drive.google.com/file/d/1t2_KspjcA6e0lzKCNMrtk3ylUbiBS-Os/view?usp=sharing