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

Objectives:

• To geometrically clean the model for any error on it.
• To extract a mid-surface of the component.
• To clean and defeature the Midsurface so as to avoid any minimum length errors while meshing.
• To mesh the mid surface while trying to minimize the number of tria and their concentration.
• Clear all elements that are failing any Quality criteria that were set.
• To assign thickness to the mesh according to the component.
• Checking for free edges

1. To begin with the meshing process on the model, the very first step is to geometrically clean the model after we import it. There might be the presence of some errors during the importing process. An added step during the geometric clean-up is the process of defeaturing all the fillets that will fail for the minimum length criteria when we mesh on it. So we can either remove these kinds of fillets from the parent surface or we can remove them separately in the mid-surface. Through this process, we can make the extraction of the mid surface much easier and improve the mesh flow overall. After the Defeature command is done, we then need to switch to the surface view to "By Topo" to view for any free edges and then thus resolve them if necessary.

2. After the Geometry clean-up is performed, then we go on to extract the mid surface of the component. Since the component is more or less of a uniform thickness, we can use the Midsurface command available in the Geometry tab. In the mid-surface command, we need to change the extraction option to "Skin offset" to get a much better mid-surface. After the mid-surface is extracted, then we need to proceed to clean the mid surface for anywhere we might get a minimum length error. To do this, we first need to measure the distance between two points on the surface where we might get an element that might fail for a minimum length. To measure the distance, we need to use the Distance command under the Geometry tab (shortcutF4). Then we select the two points and view the distance between them. If the distance is below the minimum element length then we either toggle the line or take a mid-line of the feature so that the feature is also captured. To take the midline, we need to use the Lines command under the Geometry tab. In the lines command, we will see the mid-line option. After this option is selected, we then select the two lines between which we need to extract the mid-line. To toggle any specific line, we need to use the Quick edit tab (shortcut- F11) and use the Toggle edges command.

• Midsurface modeling is a technique for creating a simplified shell representation of a solid model.
• Midsurface modeling can reduce the computational expense of analyzing a complete solid model when a shell model with a defined thickness and fewer details is suitable for the required analysis.
• Midsurface generation by the Geometry toolbar provided in the hypermesh.

3. Before we can start meshing, we need to set the Quality criteria for the meshing process. To do this, we need to use the Preferences tab and use the option of Criteria File Setting. In this option, we need to fill in all the necessary Quality criteria values such as the value of the minimum and maximum length or even the value for warpage, etc.

• 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. We have generated a 2D mesh, for meshing

4. After the Quality criteria are set, we then need to proceed to mesh the midface. To perform meshing on the component, we need to use the command of Automesh (Shortcut-F12) under the 2D Tab. In this command, we need to change the element type to "Mixed" and change the average element length to 5mm (as given in the Quality criteria). Always keep the flow Align and size option ticked as it will give a much better mesh flow on the component. The basic rules while meshing are to be followed here, such as that there should be no tria element on a feature line and even avoid the rotational Quad elements in the mesh. We also need to keep the tria count as low as possible because Tria elements are much stiffer than Quad Elements, but Tria elements are to be given preference over the presence of Rotational Quad Elements. If we get any Fixed/Pattern Tria we simply need to remesh these regions. Or we can simply resolve the Rotational Quad elements into two separate tria elements in two different directions or even resolve the Fixed/pattern tria elements into three different directions as well.

• These elements need to be cleaned to get the requirement mesh criteria.
• The failed elements can be fixed using the element fixing tools in the quality criteria menu.
• While using the quality criteria menu the failed elements are highlighted in yellow and red colors.
• Yellow errors indicate that the errors can be fixed easily, whereas the red color indicates critical errors.

5. Now that the model has cleared all the Quality criteria, the next step is to assign thickness to the model. The first step when assigning thickness is to measure the thickness at various spots in the model.

6. Now that the property is assigned, we can view the 3D elements with the thickness assigned by changing the view from "2D Traditional Element Representation" to "2D Traditional and Element Representation". The final Thickened mesh will look something like the following.

7. The final Step in the meshing process is to check for free edges on the component. To check for free edges on the component we need to use the shortcut of Shift+F3 and select the option of free edges. We then need to select all the elements and then search for Free edges on the component. If there are Free edges present in the middle of the model (except in the cases of holes), then we need to check the connectivity between the nodes and fix them by using the Equivalence command or by using the node connectivity command (shortcut-F3). This connectivity is important as it shows how the energy will flow when the model is being put under certain loads and Boundary conditions.