2-D Meshing on Dashboard Model (Instrument Panel) using ANSA

Aim:

To perform the geometry cleanup and create a 2-D mesh in the Dashboard/IP substrate model with the given element quality criteria. After meshing the component has to be assigned with a thickness.

Theory:

Dashboard

The dashboard is a control panel that is located in front of the driver in the car which controls the vehicle and its operation and indicates the features and it's working.

It indicates speed, fuel, control steering wheel, air conditioning, and now modern days it also indicates about oil pressure, weather, lights and in dashboard LED screen are given where we see the operation of parking and front camera, music system, and GPS control system are also attached. So we can see the whole working and movement of the vehicle and it's parts to control them.

Objective:

• Geometry clean up
• Mid Surface extraction, Shell property, and Quality assigning
• Create mid-surface depending on the type of geometry.
• Use of Boolean operations and lock view for better visuality of the geometry.
• 2-D Meshing and assigning thickness to it

Procedure:

1. Import the Dashboard component to ansa environment

File > Open

Figure 1: File opened in Ansa

2. Assign a refinement to the component to see all the faces clearly and set a value of 1mm under the perimeter in Mesh module

Mesh module > Perimeter > Length

3. After refinement, we need to give a topo to get cons correctly share between the faces and to get the correct face view.

Topo module > Faces > Topo

Red represents a single CON, Yellow represents Double CON and Blue represents Triple CONs.

Figure 2: Provided a Topo

4. The basic procedure follows with cleaning up the geometry by identifying the geometrical errors listed under the check manager such as single cons, triple cons, unchecked faces, Collapsed cons, Needle faces, Overlap faces, Cracks errors which should be avoided to proceed further if we clean up the geometry, there will be a least possible error while taking out the mid surface of the component.

We have to check for the error which is in the model and it is done by Checks Manager > Geometry.

Figure 3: Geometry Check under checks manager

Here most of the Errors can be fixed by using Auto Fix option in the check manager menu others can be fixed manually.

From Faces module used - Delete, New, Topo

From Cons module used - Release, Paste

More options supported to clean up geometry error are Focus, Drawing styles, and Faces draw.

So with the above tool, we have done the geometry clean up

Now, again we run check manager and look for any error when there is no error then we can proceed onto the further steps.

Figure 4: Conforming the geometry cleanup.

5. Orientation is given by Faces > Orient > Visible.

By this, we can see only one color on the whole surface rather than the mixed color on the surface when viewed in Entity mode. Here when the orient option is selected such that color which is large in number will be applied to the whole surface. This orientation is very helpful in taking a mid surface for the shell meshing.

6. Measuring the thickness of all the parts like the base frame of the dashboard, ribs, etc in the geometry for Mid-surfacing and thickness assignment and stored these values for future reference.

Utilities > Measure

Figure 5: Measurements

7. Mid-surface is extracted using the offset method. Mid-surfacing depends on the type of geometry, if the thickness is varying across the geometry then a manual mid-surface extraction method should be deployed. For example, the area of the component shown below is having a thickness of 0.6mm, now using the offset method for mid surface extraction we can use feature angle option by defining an angle, so by which it can select the faces up to a given angle.

Topo module > Faces > Offset.

After this, select the surfaces by the offset value, since we need a middle surface so we took in the mid of the thickness value which is -0.6/2mm and negative sign because the direction of the arrow sign is in the opposite direction to that of the surface.

Figure 6: Mid-surface extracted using the offset method

8. For some faces especially in the ribs area, we can use the middle option instead of the offset option for the convenience. We need not measure the thickness of a particular part, by just selecting the opposite faces we can extract the mid surface. This option is only useful when the two surfaces are of the same shape or identical surface on each side.

Topo module > Faces > Middle.

Figure 7&8: Mid-surface extracted using the middle method

9. Now the faces which are been taken out as middle surfaces are lifted from the base will have a single con need to be pasted to the base by using the Extend tool under the 'Faces' option in the 'TOPO' module. Since we need to achieve a proper mid surface from the whole geometry. First selecting the cons followed by middle-click mouse and select the face on to which it is to be deployed.

Topo module > Faces > Extend>Target

Figure 9 &10: Deployed the Extend option

If the Extend option made for intersecting the two faces penetrates without making an intersection, then we can use an Intersection option for making a triple con at the mating of the two faces properly.

Topo module > Faces > Intersect

A view of rib capture

Figure 11: Rib capture from parent geometry

Figure 12: Comparing the extracted mid surface with Geometry in transparency mode

10. After Mid surfacing all the parts in the geometry, the mid-plane geometry is to be checked for any errors such as single cons, triple cons, unchecked faces, Collapsed cons, Needle faces, Overlap faces, Cracks errors which should be avoided to proceed further in the check manager, as shown below:

Figure 13: Geometry checkup after extracting mid-surface

Figure 14: A view of the mid surface extracted from geometry

11. After extracting the mid surface for each part, we have to assign thickness and materials in the Property id (PID) menu.

Figure 15: Assigning of thickness and materials in PIDs

12. The meshing of the geometry done by using the 'Batch' mesh option under 'Mesh Generation' will give a meshed component output with a lot of de-featuring so that here we are going with the manual meshing option rather than the auto-meshing / Batch meshing.

13. Quality Criteria and Mesh Property to be assigned: Before Meshing, the model has to be assigned with the element Quality criteria and also the Mesh properties.

Figure 16: Quality criteria

Figure 17: Mesh parameters

There are two types of two-dimensional cell shapes that are commonly used. These are the triangle(tria) and quadrilateral (quad).

Aspect Ratio:

The aspect ratio is the ratio of maximum edge length to the minimum edge length of an element. The ideal value of the aspect ratio is 1. That means all the sides of an element are of equal length. If the aspect ratio is greater than 5, it means that the max length is 5 times greater than min. length of the element and the element is said to be failed in aspect ratio criteria. However, an aspect ratio of less than 5 is generally accepted.

Fig 18: Aspect ratio of a tria and quad element

Skewness:

Skew in trias is calculated by finding the minimum angle between the vector from each node to the opposing mid-side and the vector between the two adjacent mid-sides at each node of the element. Ninety degrees minus the minimum angle found is reported.

Fig 19: Tria element; tria skew = 90- `alpha`

Skew in quads is calculated by finding the minimum angle between two lines joining opposite mid-sides of the element. Ninety degrees minus the minimum angle found is reported.

Fig 20: Quad element; quad skew = 90- `alpha`

Warping:

It is defined as the angle between the normals to two planes formed by splitting the quad element along the diagonals. The maximum angle of the two possible angles is reported as the warp angle.

Fig 21: Warp angle mentioned

Jacobian:

The Jacobian is a scale factor arising because of the transformation of the coordinate system. Elements are transformed from the global coordinates to local coordinates (defined at the centroid of every element).

Minimum and Maximum length:

Here the average element length is taken as 5mm and minimum length has 3mm and maximum length as 7mm

Minimum and Maximum angle of quad and trias:

Similarly to the length of the element angle between the edge of the quad and tria is also taken under the quality criteria

Triangles %:

Since it is mixed elements considered for the meshing so we taking a percentage of trias to be present in the meshing.

14. For a good mesh flow and to eliminate the Quality criteria errors :

• When the meshing is done on the complex area like features, we need to do some reconstruction and smooth function to properly align the element and to get the best quality meshing which should be rid of the quality issues. For de-featuring the small fillets we can use Dach option in order to get rid of off-elements. Topo module > Faces > Dach > Divide face
• In the Grids module, we can find the MV Free which helps in moving the nodes in order to overcome the quality issues. Mesh module > Grids > MV Free
• If the area is too big we can be able to divide it into small areas lets say the macro area and can be able to do the best meshing out of it.
• Moreover, the options from the module like paste, split, swap, cut, join are used in order to do the meshing properly.

Mesh module > Macros > Cut / Join

Mesh module > Grids > Paste

Mesh module > Elements > Split

• For a good mesh flow, we need to check there should not be two trias pointing at each other. To remove these trias we can use swap, split command and pasting the nodes

Fig 22: Meshed component

Still, a few numbers of off-elements can be seen in the model is due to the connection between ribs and the base of the dashboard where it is failing mainly for the minimum length of elements.

15. After getting rid of all OFF elements, 'Draw shell as solid elements' in the Presentation parameter enables us to view the thickness which we assigned for the whole geometry.

Fig 23 & 24: Elements are visualized in solid representation

Learning outcomes:

• Fixed the geometrical errors in Ansa by manually.
• Learned to extract the mid surface for the component.
• Got the idea to assign the property and material specification to the component.
• Studied to do meshing according to the quality criteria.
• Learned to use options from the module like paste, split, swap, cut, join in order to do the meshing properly
• Learned to use the Dach option to de-featuring the small fillets in order to get rid of off-elements.

Conclusion:

The dashboard component has meshed successfully and the mid-surfacing of critical parts in the component is taken carefully. Here the elements are visualized in solid representation using the 'shell as solid' option in the Quality -Presentation part and covered the Quality criteria using ANSA.

Link for viewing the meshed component is provided below:

https://drive.google.com/drive/folders/15dy5LB3LZpniixC2VMZ3SWGxOJzbwzmV?usp=sharing