Challenge

Week 12:Project 2-Meshing of Rear Wheel Holder challenge

AIM

PROCEDURE

Generating the Midsurface

Since the given component is that of a sheet metal and also doesn't consist of complex features, we can easily extract the midsurface of the component using the 'Auto Midsurface' tool present in the 'Geom' panel.
Within the 'Auto Midsurface' tool, the extraction option is set to 'Offset', since this option helps in generating a midsurface with the utmost accuracy.Finally the component is selected and then the 'Extract' command is initiated.
This process can be visualised through the image below.

Manual Geometry Cleanup

The midsurface generated previously is examined for geometric irregularities.There were discontinuities present at certain regions on the midsurface.
In the case below the discontinuity was fixed by making use of the 'Ruled' option present within the 'Surfaces' tool.

For another case shown below, the midsurface of the particular region had to be extracted using the 'Offset' option present within the 'Surface Edit' tool, since the 'Ruled' option within the 'Surfaces' tool wouldn't help in generating the desired surface.

From the above image, it can be seen that the newly offseted surface of that particular region is not connected to the original midsurface.Hence in order to establish connectivity between the two surfaces, the free edges are toggled using the 'Quick Edit' tool.

Manual Defeaturing

The midsurface is subjected to manual defeaturing in order to remove certain features which are bound to fail for minimum element size during the meshing phase.
The features shown below are very minute and hence have to defeatured.The surfcaces of this particular feature are deleted and then the gap created on the midsurface is closed using the 'Ruled' option present in the 'Surfaces' tool.

Meshing

Before proceeding with the meshing process, we have to define the quality criteria as shown in the image below.

Now, using the 'Automesh' tool under the '2D' panel, the various surfaces of the component are meshed one at a time.The element size is set to 5 units and the mesh type is set to 'mixed' as shown in the image below.

In cases where the mesh obtained using the 'Automesh' tool is not satisfactory, the 'Rebuild Mesh' tool is used, which aids in providing a refined mesh most of the times.

A few elements which are failing for quality criteria can be rectified manually using the 'Translate' tool.In the images below, an element failing for warpage has been rectified accordingly using the 'Translate' tool.

Since we are preparing this model for crash and safety analysis, we have to avoid rotating quads at any cost.The tria elements are acceptable but should not conflict with each other ie. adjacent trias and trias facing opposite to each other should be avoided.Also it is not desirable to have trias in the fillet regions.
The mesh should also be validated using the quality criteria defined previously, the elements which are failing should be rectified as far as possible.At certain intricate parts it is hard to avoid elements failing for minimum size.Most of the quality issues can be rectified using the 'Quality Index' tool present in the '2D' panel.
After meshing the whole component, it is necessary to check the mesh created for free edges and equivalence, which if present have to be rectified accordingly.The nodes being displayed for equivalence in the image below, are due to the fact that the geometry in that particular portion is very intricate.They are not actually failing for equivalence.

We also have to do the normal and dependency check.While doing the normal check we have to make sure that the normals of all the elements are facing in the same direction.In the images below it can be seen that one element has its normal in the opposite direction.

The element having its normal in the opposite direction is selected and then the direction is reversed, hence obtaining the desired orientation.

Assigning thickness to the mesh

After completion of the meshing process, it is necessary to assign the appropriate thickness to the mesh, based on the thickness of the parent geometry.The parent geometry being a sheet metal component has a uniform thickness of 0.75 mm throughout.
A new material collector is created having the characteristics of steel.
A new property collector is also created in order to assign the thickness to the mesh generated.The card image is set to 'PSHELL' , the thickness is set to 0.75 and the newly created material collector 'Steel' is assigned to this property.
Finally this property is assigned to the meshed midsurface and then we have to switch to '2D Detailed Element Representation' to visualize the thickness assigned.

FINAL MODEL IMAGE

Ship work like this
in your own course.