Finite Element Meshing on the Automotive Component Rear Wheel Holder with 2D Shell Element in Hypermesh

Objective of Project - To perform the necessary geometry cleanup and meshing car rear wheel holder using the FEA tool HYPER-MESH.

Why do we carry out Meshing?

The basic idea of FEA is to make calculations at only a limited (finite) number of points and then interpolate the results for the entire domain (surface or volume). Any continuous object has infinite degrees of freedom and it's just not possible to solve the problem in this format. The finite Element Method reduces the degree of freedom from infinite to finite with the help of discretization or meshing (nodes and elements).

Meshing is an integral part of the engineering simulation process where complex geometries are divided into simple elements that can be used as discrete local approximations of the larger domain. The mesh influences the accuracy, convergence, and speed of the simulation. Furthermore, since meshing typically consumes a significant portion of the time it takes to get simulation results, the better and more automated the meshing tools, the faster and more accurate the solution.

2D meshing is carried out on a mid-surface of the spare wheel holder panel parts. By creating 2D elements, the software knows 2 out of the 3 required dimensions, The third dimension, thickness, is been provided by the user as additional input data.

Why is 2D Meshing carried out on a Mid Surface?

Mathematically, the element thickness specified by the user is assigned half on the element top and half on the bottom side. Hence, in order to represent the geometry appropriately, it is necessary to extract the mid surface and the mesh surface.

In the same manner below is the procedure explaining one by one how the mid surface is extracted on each component and how it meshed with the gives quality criteria. After performing the meshing the thickness is assigned by the user to represent the geometry as in a real scenario.

Procedure -

Step I - Import the geometry i.e, the .hm file (extension)using the file tab in the HYPER-MESH window.

fig - Importing the model

Step II - After importing the geometry, switching to the topo module. After this one by one, the component is identified as below

fig - Imported Geometry fig - Topo Mode

The user takes out the mid-surface one by one for all the important features. The use observes the geometry to determine the common features in the geometry so that only the half section of the geometry will mesh and the rest will be reflected based on the symmetrical regions. This will save the time of user.

Bottom View

Top View

Side View

4. Door Handle Outer

Iso View

Step III - Select components one by one of the similar groups and check for the geometrical error and rectify them if any.

As we see in this model the are a lot of geometrical errors in the parent geometry so we go for the next step that is mid-surface extraction by the manual offset of every component.

Step IV - Extracts mid surfaces of the components using the surface edit tool offset option.

Select any one original side of the panel surface with measuring the thickness of the component across various sections as 0.75 mm mid-surface is extracted using offset option of extraction.

In this, we select the base surface either on any side of the two surfaces and offset to extract the mid-surface. Manual offset help generating a proper mid surface among all the option which fit in between the original thickness of the component and gives us the mid-surface accordingly.

Fig - Mid Surface extraction

After Extracting the mid-surface mid-surface is saved as a new component with appropriate thickness identification to make it safe and confusions free from the parent geometry as shown below,

fig -Single Component Creation

Differeent Views of Mid Surface

fig - Extracted Midsurface using Manual Offset

Step V - Deleting the symmetrical Region

fig - Mid surface of the symmetrical region

Step VI - Meshing the geometry (Shift + F12)

Meshing is done using the auto mesh option with the target length of 5mm and quality criteria are set as below to make sure that there is no element failure at the end of meshing.

Fig - Mesh Parameters

Fig - Quality Criteria

After assigning the quality criteria parameter user defeature the geometry wherever necessary keeping the important edges as it is and makes the cuts.

After making the defeaturing the components are meshed using auto mesh component in the 2D panel and with the help of various other commands like edit elements, rebuild, smooth, etc and mesh is obtained as shown below,

Fig - Meshed Wheel Holder

Step VII - Quality Check

Rear Wheel Holder

fig - Element Quality Check

There is no element failing for the set quality criteria after cleaning up all the failed elements using the manual cleanup method and auto cleanup tool.

The percentage of Tria's in the geometry after all cleanup process is observed to be 2.8 % which is within the acceptable range.

Step VIII - Free Edge Check (Shift +F3)

After checking the element quality the user check for the free edge and the equivalence of the element to ensure that that there is no gap present in the component and between the set of elements. If so that are equivalenced using the equivalence option.

fig - Free Edge Check

Note - The color orientation is a change to identify the free edge clearly in the door panel geometry.

Step X - Assign Property Card (Thickness) & Material to the components.

fig - Assign Property Card & Material Card

After obtaining the mesh for all the components we draw the shell as solid using the 2D element representation option which can be seen in the below screenshots,

To draw the shells to solid under the visualization panel there is an option 2D detailed element representation to make the shells as solid as shown,

Fig - 2D Detailed Element Representation

Conclusion -

Here user can conclude that the rear wheel holder is successfully meshed after the geometry topo clean up and performing all the necessary steps with the provided quality criteria. Learning outcomes are tools used to perform meshing in HYPER-MESH. There is a lot of experience gained while working on this model.