Assignment 1

Objective:

To conduct geometry cleanup for the given parts and then carry out 2D meshing operation on it ensuring that a desired element size of 5mm is obtained, the element size should be 3.5mm minimum and 7 mm maximum.

Case setup and Execution :

> Download the .hm file models and open them on hypermesh.

> Now the first step is to extract the midsurface of the model. To do that we follow the following step, Geometry > midsurface > ensure it is closed surface > click on extract mid-surface.

> The next step is the geometry cleanup. This can be done by using filler surfaces, washer surfaces, toggle edge, add/remove point, replace point, trim intersect. These options are found under Geometry>quick edit.

• Firstly, we start with the toggle edge, if there are any edges in between the surfaces or a surface which removed will not affect the model and simulation in an extreme manner then those edges can be toggled. This can be done for small edges too.
• hen we start with adding filler surfaces to the small holes (<5mm diameter). We toggle the edge of these filler surfaces created.
• After this, we use the replace point, click on the point that is to be replaced and then click on the point with which it is supposed to be replaced. This is done to points which are very close to each other and sometimes cannot be seen in the model if not zoomed.
• If the are small fillets in the corners of the midsurface that are to be removed then we use trim intersect. Here we first click on a node and then click on another node to create an edge from the intersection.
• We use the washer surface to create an extra edge around the holes that are to be included in the meshing process and simulation.

> After this is done we begin the meshing process. For this, we go to 2d>Automesh.

• First, we need to select the surface that is will be meshed. then the element size is specified, which is 5mm. After that, we click mesh when the desired edge node values are obtained.
• This is done to all the edges that are attached to this surface. Repeat the process until the entire midsurface has meshed.
• Now we need to ensure that our mesh is of the desired size. i.e. 3.5mm (min) and 7mm(max). To do this we go to Tool > check elements > set the parameter for min. size and max. size > then click on min size or max. size to view which elements are not satisfying the condition. The elements which do not satisfy the condition are highlighted.
• To correct this we can use various mesh edit options like, edit elements (Create, combine, split), translate, align node and smooth which are seen under 2D option. After this, we can also use, but this is the last resort, that is element cleanup, which will display the failed elements, click on these elements and hypermesh will try and adjust the elements to satisfy the conditions provided.
• Now we need to check if there are any free edges, to do that we go to Tools > edges > select the component/ edges > find edges. If there are any free edges then select the elements around the edge> preview equivalence (set appropriate tolerance) > equivalence. This will ensure that all the free edges are mended with each other on the basis of their nodes.

The parts after being meshed are given below,

> Now we have to add a generic property to this meshed surface.

• First, we view the entire model. Then we click on F4 to reach the distance option and select the distance between two points. Then we click on two such points on the bottom and the upper surface of the model ensuring we cover the thickness of the model. The distance is displayed and we copy that value.
• Now we click on the property card and assign the card image PSHELL to it. Then we paste this distance value in the thickness input section of the property card.
• Then we assign this property to the midsurface by, right-click on midsurface> the assign> property1.
• Now go to 2D element representation and click on 2D Detailed element representation.

The result obtained is as follows :

Result and Conclusion:

The result of the mesh is checked using the check elements (press F10). And after adding property thickness to the midsurface we see that check the thickness by distance to confirm if the appropriate thickness is applied to the model. Using the above-given steps we obtain a mesh of 5mm target element size (7mm < element size < 3.5 mm) along with the assigned generic property (thickness) of each model.

Google Drive Link: https://drive.google.com/open?id=1-_6X4DIqpOY-lxAuxldduZc3Q9FbYyXY