Pre-processor for Structural Analysis on Molding & Sheet-metal Component using ANSA

Objective:

• For the Molding & Sheet-metal parts, geometrical cleanup to be done & rectify the issues faced during meshing. Mesh will be done under given element Quality criteria. After meshing the component its thickness will be assigned. Below are the two models used in this case setup.

Molding Part (Switch Panel):

Sheetmetal Part (Bracket):

Element Quality Criteria:

S.No	Quality Criteria	Value
1	Target/Average length	4
2	Minimum Length	2
3	Maximum Length	6
4	Aspect ratio	3
5	Warpage	15
6	Skewness	45
7	Jacobian	0.7
8	Minimum Quad Angle	45
9	Maximum Quad Angle	135
10	Minimum Triangle Angle	30
11	Maximum Triangle Angle	120
10	Triangle Percentage	15

1: Casting Part (Switch Panel):-

Geometry clean up Processing:

These CAD models were now to be checked against any geometrical errors such us normal orientation, Needle faces, etc. This can be done with the ANSA's checks manager which helps us to find the surface errors on the CAD geometry. In the checks manager, some options can be checked ON / OFF depending on the parameters required to be checked.

In the checks manager by clicking the Execute button ANSA will check for the surface errors on the visible geometry.

The above image shows us the surface errors found on the geometry. There were 2 unchecked surface errors found by the checks manager.

Using several surface repairing tools provided by the ANSA these errors should be rectified. some errors can be automatically rectified using the AutoFix option in the checks manager.

After fixing the surface geometry the status icon on the checks managers shows a Green Trick Marks which resembles that the Geometry is error-free. The above images show that the part geometry is passed according to the checks manager criteria.

Mid-Surface Extraction:

After clearing all the geometry errors we can generate the mid surface for the geometry. This is to be done using the Mid Surface option which creates a new surface between the upper & lower sheet surface. This is to be done to make the meshing process easier. Here the CAD geometry is a casting part that has non-uniform thickness all over the cross-section. So Auto Mid Surface Extract tool cannot be used. Instead Offsetting individual faces that help to extract the mid-surface.

Since this part contains non-uniform thickness its thickness value for the individual surfaces to be stored as shown in the above picture.

After offsetting the surfaces, some surfaces will retain some unwanted holes since its a casting part, the triple cons surfaces are not captured. So these holes must be filled with the 'Fill Hole' option as shown in the below picture.

Setting up Quality Criteria:

In quality, criteria wizard the given parameters are entered so that the ANSA could check the mesh generated is under these criteria.

Mesh Preparation:

Before the meshing process some of the features to be checked manually in order to generate mesh under defined quality criteria.

The length between two nodes is maintained between 2 to 6mm if not it will fail as per quality criteria since the range must be controlled. In this case, we can join the two any two surfaces which increases the length between two nodes without defeaturing the geometry.

Removal of Unnecessary perimeters:

Some of the unnecessary perimeter lines & hot points can be removed which makes the meshing to be done under defined quality criteria. Here in this model, the average length of an element is set to 4mm with tolerance the range can be within 2-6mm. So the parametric lines lesser or greater than the provided tolerance then those lines must be removed or altered without defeaturing the geometry.

Before Removing:

After Removing:

Meshing Process:

Before meshing the length of a single element is provided as 4mm so that all the nodes are rearranged with an average distance of 4mm.

After meshing some elements in this component fails upon the defined quality criteria. This can be solved with the Mesh Repair Tools available in ANSA to eliminate all the errors. Make sure that the triangle element is not present at the border perimeter in order to get accurate FEA calculation. There are a total of 740number of elements that had failed under this quality criterion.

The above picture the inner hood model with only a single error thus passing the quality criteria.

2: Sheet Metal Part (Bracket):-

Geometry clean up Processing:

These CAD models were now to be checked against any geometrical errors such us normal orientation, Needle faces, etc. This can be done with the ANSA's checks manager which helps us to find the surface errors on the CAD geometry. In the checks manager, some options can be checked ON / OFF depending on the parameters required to be checked.

In the checks manager by clicking the Execute button ANSA will check for the surface errors on the visible geometry.

The above image shows us the surface errors found on the geometry. There were 28 unchecked surface errors found by the checks manager.

Using several surface repairing tools provided by the ANSA these errors should be rectified. some errors can be automatically rectified using the AutoFix option in the checks manager.

After fixing the surface geometry the status icon on the checks managers shows a Green Trick Marks which resembles that the Geometry is error-free. The above images show that the part geometry is passed according to the checks manager criteria.

Mid-Surface Extraction:

After clearing all the geometry errors we can generate the mid surface for the geometry. This is to be done using the Mid Surface option which creates a new surface between the upper & lower sheet surface. This is to be done to make the meshing process easier. Here the CAD geometry is a Sheet metal part that has uniform thickness all over the cross-section. So Auto Mid Surface Extract tool can be used. The thickness of the sheet metal is found to be 2mm.

In Auto Mid-Surface Wizard we need to check for the correct color representative of the respective surfaces as top face to be Green, Bottom face as Red & Side faces to be Blue. This allows the software to generate the Mid-Surface without any issues.

After offsetting the surfaces, some surfaces will retain some unwanted holes since its a casting part, the triple cons surfaces are not captured. So these holes must be filled with the 'Fill Hole' option .

Setting up Quality Criteria:

In quality, criteria wizard the given parameters are entered so that the ANSA could check the mesh generated is under these criteria.

Mesh Preparation:

Before the meshing process some of the features to be checked manually in order to generate mesh under defined quality criteria.

The length between two nodes is maintained between 2 to 6mm if not it will fail as per quality criteria since the range must be controlled. In this case, we can join the two any two surfaces which increases the length between two nodes without defeaturing the geometry.

The part we are using, in this case, is symmetrical in most of the regions so we can cut one half of the symmetrical portion leaving the asymmetric portion as shown below.

Removal of Unnecessary perimeters:

Some of the unnecessary perimeter lines & hot points can be removed which makes the meshing to be done under defined quality criteria. Here in this model, the average length of an element is set to 4mm with tolerance the range can be within 2-6mm. So the parametric lines lesser or greater than the provided tolerance then those lines must be removed or altered without defeaturing the geometry.

Before Removing:

After Removing:

After removing the unwanted parameters & points we can now mirror the repaired face as shown below.

Meshing Process:

Before meshing the length of a single element is provided as 4mm so that all the nodes are rearranged with an average distance of 4mm.

After meshing some elements in this component fails upon the defined quality criteria. This can be solved with the Mesh Repair Tools available in ANSA to eliminate all the errors. Make sure that the triangle element is not present at the border perimeter in order to get accurate FEA calculation. There are a total of 9216 number of elements that had failed under this quality criterion.

The above picture the model with zero error thus passing the quality criteria.

3: Mesh Element Details:-

The element parameters for all other parts can be found from the below After Mesh Elements table.

These values are measured only in the Mid Surface Region not considering the thickness.

Mid-Surface to Solid Conversion:

The model is not ready yet for FEA calculations since the meshing is done only over the surfaces, not on solid geometry. These surfaces along with the mesh elements can be converted into solids by assigning the thickness of the generated mid surfaces.

From the property dialog box the thickness to be assigned for the mid surfaces as shown in the above picture.

After assigning the thickness for the respective surfaces the solid sheet has not appeared on the graphical window. In order to view the Solid Mesh of the parts Check the Draw Shell as solid option in quality criteria under the presentation parameters tab as shown above.

The above image represents the pre-processed Hood with the solid meshing. The Total elements found in the solid mesh is 9607 Nos. In which 2558 Nos are Quad elements contributing 93.32% & 183 Nos of Triangle elements contributing 6.68% of the entire switch panel component.