Meshing an automobile side door using hypermesh

Objective:

• Extract the mid surface of the given component as per the given quality criteria

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
	Max angle Tria	120

• Generate the 2D mesh
• Generate property file of different thickness and assign it individually

Procedure:

Step 1 – Preparing Geometry

• Import the geometry Side door in Hypermesh
• Separate two components as shown below

Component 1

Component 2

• Since both the component has a variable thickness, we need to extract mid surface manually
• To extract mid surface manually follow the below procedure

• Measure distance between two surfaces
• Go to Surface Edit -> offset -> select surface -> check direction normal -> give the mid-distance -> offset.

• Repeat this step for all the surface and generate a uniform mid surface of the whole model
• There are ribs in the model which need to connect to the base surface. For that follow one of the following steps
• Surface edit -> extend -> select surface to be extended -> select base surface -> extend
• Surface -> Drag along vector -> select the baseline along ribs -> give distance -> MMB. No surface edit -> trim surface with surface -> select both the surface -> trim. Delete additional surfaces
• The Yellow line should appear at the interjection of ribs and base surface.

• Once all the mid surface are extracted, perform geometry cleanup using one of the following options
• Quick edit -> toggle line -> to suppress unwanted edges.
• Quick edit -> Split surface with nodes (to divide the surface into smaller ones)
• Quick edit -> Split surface with node and line ( to divide the surface into smaller ones)
• Quick edit -> replace point (to stick gaps between surfaces and remove red lines)

• Manually check whole geometry to confirm geometry cleanup is successful
• Divide the whole model using different component and name them on the basis of it thickness. Allocate each surface to corresponding thickness component

Step 2 – Generate Mesh

• Since there are different surface along different planes, extra care needs to be taken while meshing
• To generate mesh

2D -> auto mesh -> select surface -> element size = 4 -> element type = mixed -> mesh

• First of all mesh the ribs properly
• Now start selecting adjoining surface one by one
• Check for quality using

Tools -> check elems -> check quality parameters as per given quality criteria

• Repair failed element using one of the following methods
• 2D -> quality index -> cleanup tools -> element optimize
• 2D -> quality index -> cleanup tools -> place nodes
• 2D -> edit elements -> combine / split/ create
• Repeat these steps for all surfaces of the model and generate a uniform 2D mesh satisfying given quality criteria.
• Make sure there is proper mesh connectivity between different parts and no of trias are as low as possible.

Step 3 – Assign thickness to the individual component

• Create different property file with different thickness and color code is similar to its component color for simplification
• Assign these properties to the respective component
• Check using display 2D mesh option to check for the thickness in mesh

Results:

Below images show the mesh of the whole model

No of Nodes: 38756

No of Elements: 38364

No of quads: 37329 (97.302 %)

No of trias: 1035 (2.698 %)

S.N	Quality Criteria	Value	No of failed elements	% of failed elements
1	Aspect Ratio	5	0	0
2	Skewness	45	2	0
3	Warping	15	1	0
4	Taper	0.5	1	0
5	Min. Length	2mm	3	0
6	Max. Length	6mm	0	0
7	Min angle Quad	45	2	0
8	Max angle Quad	135	2	0
9	Min angle Tria	20	0	0
	Max angle Tria	120	0	0

Note: all the failed elements are in component 2, due to a very high difference in thickness for the smaller cross-section.

onclusion:

This activity helped us understand the basic procedure to mesh the component with variable thickness using manual midsurfacing and manual meshing and controlling the mesh quality for such complicated geometry.