PRE-PROCESSING OF IP SUBSTRATES BY MID-SURFACE EXTRACTION METHOD USING ANSAÂ
INTRODUCTION:
The instrument panel in a car is one of the critical parts in a car assembly. This is due to it's complex geometry and the varying thickness throughout the part. Now,five regions which are more complex are isolated ,mid skinned,appropriate thickness is assigned and meshed suitable for the structural analysis.
GENERAL PROCEDURE:
The following procedure will be followed for all the five models and is made ready for analysis.
1.Geometry cleanup:
The imported model is checked for the geometry errors using the checks manager. If there is any problem, it should be corrected and the geometry is made clean.
2.Extracting the mid-surface:
Then the mid-surface should be extracted. It can be extracted either manually or automatically using appropriate methods or a combination of both can be explained. It is based on the thickness variation and time constraints. In manual method, the faces are selected, and the offset value is given. In automatic method, the mid-surface is extracted in a form FE model straight. For this, the whole part is selected, maximum thickness value, target element size are given in prior.
3.Assigning PID and thickness:
Now, the regions with different thickness are assigned with different PID's and the thickness values are assigned accordingly.
4.Mesh generation:
Then,if the mid surface is a CAD geometry, then the model is meshed with the target element size defined.
5.Meeting the quality criteria:
Now, the mesh elements are corrected to meet the quality criteria specified below.
Quality criteria to be followed
| S.N | Quality Criteria | Value |
| 1 | Aspect Ratio | 3 |
| 2 | Skewness | 45 |
| 3 | Warping | 30 |
| 4 | Taper | 0.5 |
| 5 | Min. Length | 2mm |
| 6 | Max. Length | 7mm |
| 7 | Min angle Quad | 45 |
| 8 | Max angle Quad | 135 |
| 9 | Min angle Tria | 30 |
| 10 | Max angle Tria | 110 |
| 11 | Tria % | 15 |
TARGET ELEMENT SIZE FOR ALL THE MODELS: 5 MM
ELEMENT TYPE : MIXED
IP SUBSTRATE MODEL-1:
The following model is cleaned up and the middle surface is extracted using the following options.
For the flat faces with less complex geometry,
TOPO ----> FACES ----> OFFSET
For complex faces,
TOPO ----> FACES ----> MIDDLE ----> MULTI
Then the ribs are mid extracted, and they are extended to meet the original mid surface.
Then they are assigned with different PID's and according thickness.
After assigning thickness, the model is meshed using the following option.
MESH ----> MESH GENERATION ----> MIXED
And the mesh elements are now corrected to meetup the mentioned quality criteria.
IP SUBSTRATE MODEL-2:
The following model is cleaned up and the middle surface is extracted using the following options.
TOPO ----> FACES ----> MID-SURFACE ----> CASTING
There the target element size is given as 5 mm. So the middle surface is extracted automatically in the form of FE model as shown below.
Now, the middle surface can be checked using the following algorithm,
TOPO ----> FACES ----> MID-SURFACE ----> CHECK MIDDLE SURFACE
To automatically assign PID and appropriate thickness,
TOPO ----> FACES ----> MID-SURFACE ----> CALCULATE THICKNESS
Now the FE middle surface is assigned with the PID's and the thickness values. But it should be cross-checked by the user and should be refined for better results.
As the surface is already in the form of FE model, now it should be corrected to meet the quality criteria mentioned. After correction,
IP SUBSTRATE MODEL-3:
The CAD geometry is imported into ANSA,
The following model is cleaned up and the middle surface is extracted using the following options.
TOPO ----> FACES ----> MID-SURFACE ----> CASTING
There the target element size is given as 5 mm. So the middle surface is extracted automatically in the form of FE model as shown below.
Now, the middle surface can be checked using the following algorithm,
TOPO ----> FACES ----> MID-SURFACE ----> CHECK MIDDLE SURFACE
To automatically assign PID and appropriate thickness,
TOPO ----> FACES ----> MID-SURFACE ----> CALCULATE THICKNESS
Now the FE middle surface is assigned with the PID's and the thickness values. But it should be cross-checked by the user and should be refined for better results.
As the surface is already in the form of FE model, now it should be corrected to meet the quality criteria mentioned. After correction,
IP SUBSTRATE MODEL-4:
The CAD geometry is imported into ANSA,
The following model is cleaned up and the middle surface is extracted using the following options.
TOPO ----> FACES ----> MID-SURFACE ----> CASTING
There the target element size is given as 5 mm. So the middle surface is extracted automatically in the form of FE model as shown below.
Now, the middle surface can be checked using the following algorithm,
TOPO ----> FACES ----> MID-SURFACE ----> CHECK MIDDLE SURFACE
To automatically assign PID and appropriate thickness,
TOPO ----> FACES ----> MID-SURFACE ----> CALCULATE THICKNESS
Now the FE middle surface is assigned with the PID's and the thickness values. But it should be cross-checked by the user and should be refined for better results.
As the surface is already in the form of FE model, now it should be corrected to meet the quality criteria mentioned.
IP SUBSTRATE MODEL-5:
The CAD geometry is imported into ANSA,
The following model is cleaned up and the middle surface is extracted using the following options.
TOPO ----> FACES ----> MID-SURFACE ----> CASTING
There the target element size is given as 5 mm. So the middle surface is extracted automatically in the form of FE model as shown below.
Now, the middle surface can be checked using the following algorithm,
TOPO ----> FACES ----> MID-SURFACE ----> CHECK MIDDLE SURFACE
To automatically assign PID and appropriate thickness,
TOPO ----> FACES ----> MID-SURFACE ----> CALCULATE THICKNESS
Now the FE middle surface is assigned with the PID's and the thickness values. But it should be cross-checked by the user and should be refined for better results.
As the surface is already in the form of FE model, now it should be corrected to meet the quality criteria mentioned.
No elements are OFF since all the elements met with the quality criteria mentioned.
CONCLUSION:
Extraction of mid-surface using the automatic method saves a lot of time, but it is the duty of the user to refine it again and check the thickness values. It should be made sure that geometry is captured properly. The mid surface can be viewed as a solid and it is now can be structurally analyzed.