Week 12 - Project-1

Objective:

• To mesh the given Door component using given Quality criteria and assign thickness

Target Element Length = 4mm

S.N	Quality Criteria	Value
1	Aspect Ratio	5
2	Skewness	45
3	Warping	15
4	Taper	0.5
5	Min. Length	2mm
6	Max. Length	6mm
7	Min angle Quad	45
8	Max angle Quad	135
9	Min angle Tria	20
10	Max angle Tria	120
10	Tria %	10

Case setup and execution:

• Geometry cleanup

The given Door panel component 3D CAD model is imported into Hypermesh. It is checked for CAD errors using visualization tool. Change visualization to “By Topo” and switch to wireframe mode to view the status of each edge.

We also see some edges on the model which are very close to each other and would create problems while meshing (elements would fail because of minimum element length requirement). Toggle unnecessary edges using

Geometry -> Quick Edit -> Toggle edge

We can also use Auto Cleanup option to clean the geometry

Geometry-> Auto Cleanup

• Mid surface creation

Midsurface is generated for the plastic part using

Geometry -> Midsurface -> Auto Midsurfacing

It is better to use Offset planes in the Auto Midsurface options

The midsurface generated using this approach didn’t create enough quality. So we will proceed by offsetting the bottom surface by a distance equal to Thickness/2

Geometry -> Surface Edit -> Offset

• Meshing

We will divide the midsurface into 4 quadrants surfaces for simplicity.

Geometry -> Surface Edit -> trim using points

There are now 4 components in the Door model, and we will mesh them individually using the quality criteria provided

Target Element Length = 4mm

S.N	Quality Criteria	Value
1	Aspect Ratio	5
2	Skewness	45
3	Warping	15
4	Taper	0.5
5	Min. Length	2mm
6	Max. Length	6mm
7	Min angle Quad	45
8	Max angle Quad	135
9	Min angle Tria	20
10	Max angle Tria	120
10	Tria %	10

First, a washer split is created on holes and outer edges to have only quads on edges. Then the other surfaces are automeshed using 5mm as target length and in the automesh option, flow – align and size are checked

It is better to split the surface into smaller rectangles as much as possible to have smooth quads on the surface.

Geometry -> Quick edit -> Split surface (Node to Node or Node to Line)

On fillets/hem regions, it is advisable to capture the high points on the fillet. In order to capture the high points, create a Mid line between the boundary lines of the fillet.

Lines -> Midline

Create nodes/points on the Mid Line

Geometry -> Quick Edit -> Add points on Line (Qty:3 – if given 3, two points will be on the endpoints and one will be created on the midpoints of the line)

Geometry -> Nodes -> Interpolate nodes on line (Qty:3)

Now we can split the fillet/hem region using

Geometry -> Surface edit -> Trim with free lines and N1,N2,N3 and toggle the boundary lines of the fillet so that mesh quality error due to minimum size criteria can be avoided.

2D -> Automesh

Symmetric components are split into two along the symmetric line. Only one surface is meshed and the other surface is meshed by duplicating and reflecting the elements on the meshed surface.

Some of the commonly used commands

Geometry -> Node edit -> Align

2D -> Smooth

2D -> mesh edit -> Split

2D -> mesh edit -> Create

2D -> mesh edit -> combine

Tools -> Reflect

Tools -> Project

Commands under 2D -> Quality Index

Node optimize

Element Optimize

Place Node

Split quad into trias

Combine trias to quads

Drag Tria

Swap Edge – used to swap edges of tria elements on surface edges

These tools are used to make sure the following criteria are satisfied

1. No rotational quads
2. No trias pointing opposite to each other or touching each other
3. Mesh flow is smooth
4. No trias on edges of the midsurface
5. Elements pass the quality criteria provided

Checks

Tools -> normal

To ensure all the element normals from one side of the surface point in one direction

Tools -> Penetrations

To ensure there is no penetration of elements

Tools -> Dependency

To ensure there is no element dependency

Tools -> Edges

To check connectivity of elements. If there are disconnections, equivalence it

Menu bar -> Mesh -> Checks -> Comparison – to check how well the meshes match with the surface. If there are not matching, we can use Project command to project elements/nodes onto the surface/edge.

Finally, after performing the above mentioned procedure for all the 4 components in the Door panel model, the quality of the mesh is checked using

2D -> check elements

Then common material Steel is created and properties are created for each component individually with the respective thickness