Sidedoor Plastic Meshing

Objective:

• To mesh the 'SIDE DOOR' plastic part of a vehicle for the below given quality criterias.
• Target Element Length: 5mm

1. Aspect Ratio : 5
2. Skewness : 45
3. Warping : 15
4. Taper : 0.5
5. Length : 2
6. Length : 6
7. Min Angle Quad : 45
8. Max Angle Quad : 135
9. Min Angle Quad : 20
10. Max Angle Quad : 120
11. % of Tria : 10

Introduction:

• In this challenge the component had to be meshed after creating its midsurface. Manual midsurfacing had to be done for this model as ‘auto midsurfacing’ was not suitable due to varying thicknesses.
• The meshing of the component had to be according to the quality criteria mentioned above. For this purpose there are various tools in HyperMesh to check the quality of the mesh.
• Tools that were used in this challenge were, ‘node edit’, ‘replace node’, edit elements’, ‘align nodes’, ‘check elements’, ‘replace element’, ‘offset surfaces’, ‘trim surfaces’, etc.
• In order to increase the quality of the mesh as per the criteria, the meshed component can be re-meshed. Upon re-iterating it, a good mesh can be achieved.
• Also, a good quality mesh should not consist of rotational quads, elements of abrupt shapes and sizes, and also large number of trias should be avoided.

Procedure:

• The model was provided in the ‘.hm’ format and hence it was directly imported into the HyperMesh ‘RADIOSS’ profile using ‘import model’ option from the toolbar. The image below shows the model as it is, provided in the challenge.
  
  
  
  
• The model was divided into 4 part for the ease of operations with the ‘trim with surfs/planes’ option from ‘surface edit’. The vector selection was changed to axis and a base node and axis was selected and the model was trimmed perpendicular to that axis and node.
• All the four divisions of the model were moved into separate component collector.
• The first division (lower right) was selected and its manual midsurface was extracted. This was done with the help of ‘offset’ option from the ‘Geometry’ tab. The surfaces on one of the sides were offset by exactly half of its thickness at all the areas. All the surfaces of different thicknesses were moved into their respective collectors.
• The image below shows the manual midsurfaces extracted for the first part of the model.
  
  
  
  
• The surface which were not connected were extended using the ‘extend’ option from the ‘surface edit’ panel and then trimmed by ‘trim with surf’ as seen below.
  
  
  
  
  
• After the midsurface was extracted, the topology of the same was cleaned up manually using various tools like ‘add/remove point’, ‘replace point’, ‘toggle edge’, etc. from the quick edit panel.
  
  
  

• Later the part was ‘auto meshed’ by keeping the ‘elem size’ as 4mm and ‘elem type’ as ‘mixed’. The number of nodes was then tweaked to achieve a good quality mesh in the initial stage itself.
• The elements from the parts like the ribs and other surfaces which were not projected exactly onto the bottom surface were projected from ‘tools>project>to surface’.
• But the mesh flow was not proper and the elements of different surfaces were not connected to each other. The mesh flow was thus corrected using ‘replace node’ option from the ‘2D’ panel. Later the nodes were also aligned to match the flow as seen below.
  
  

• After ensuring proper connectivity and mesh flow, the elements were re-meshed and smoothened using the ‘smooth’ option to reduce the tria elements and make the mesh more proper.
• Later the elements were checked for the quality criteria using the ‘check elem’ and ‘quality index’ option, and all the failing elements were optimized.
• The 1^st part was then hidden and the 2^nd part (lower left) was meshed. For this, the midsurface was extracted manually using the ‘offset’ option similar to the previous part.
• All the surfaces with their thicknesses were assigned into their respective component collectors and the topology of the part was cleaned up. The snap below shows the manual midsurfaces extracted for the ribs.
  
  
• The ribs were also midsurfaced separately and their surfaces were extended/dragged to the target bottom surface.
• It was then meshed using the ‘automesh’ from the ‘2D’ panel and the number of nodes was tweaked to achieve good quality mesh.
• Those elements of the ribs which could not get extended were projected manually onto the bottom surface using the ‘project>to surface’ option from the ‘tools’ tab.
• The tria concentration in the part was reduced and the elements failing for the given quality criteria were optimized. The image below shows the mesh of the part.
  
  
  
  
• Similarly the third part i.e. the top left part of the model had to be meshed. The midsurface of that part was also extracted manually following the same procedure as before using the ‘offset’ option and the respective distance for the offset (half of the thickness).
• The image below shows the manual midsurfacing operation.
  
  

• As seen in the image below, all the ribs and the mounting parts of the plastic body were midsurfaced and extended till the bottom surface in order to achieve proper mesh flow in the initial stage itself.
• For this the ‘lines to be extended’ were selected as the edges of the ribs and the ‘surfaces to extend’ was selected as the target surface for extension. The topology was cleaned up using the tools from the ‘quick edit’ panel.
• All the surfaces of this part were then ‘automeshed’ by following the same configurations as before (elem size-4mm, elem type-mixed).
• To ensure the mesh flow in the component, all the elements which were not connected, were joined using the ‘replace’ option from the ‘2D’ panel. This replaced the nodes of the elements with those of the target elements.
  
  
  
  
• The elements were then checked for failure pertaining to the given quality criteria, and all the failing elements were optimized using ‘QI tools’ and ‘elem cleanup’. After ensuring proper mesh flow, and no failing elements, the mesh was finalized as seen below.
  
  
  
  
  

• Later, the midsurface remaining part of the model was extracted manually and the topology was cleaned up. All the voids were filled using the ‘filler surf’ from the ‘quick edit’ panel. The midsurfaces were moved to their respective component collector based on their thickness.
• The midsurfaces for the ribs and the mounting clip were also extracted and extended to their target surfaces as seen in the image.
  
  

• All the surfaces were ‘automeshed’ and their number of nodes was set according to the mesh quality. The mesh was smoothened using the ‘smooth’ command and the elements failing for the quality criteria were optimized.
• Later, the connectivity of this part with the others was checked, and all the elements which were not connected were joined using the ‘replace’ element option as before. Finally the elements from all the parts were checked for quality criteria.
  
  
  
  
• Thus upon ensuring proper mesh flow, 0 failing elements, and connectivity of all the parts with each other, the mesh was finalized. The image below shows the final mesh for all the parts of the model of the sidedoor.
  
  

• After this, the thickness for the each of the component collector had to be assigned according to their parent geometry.
• This was done by creating a separate property for each of the collector. Properties were created by right clicking in the collector area and selecting the ‘property’ command.
• Thickness was assigned to each of the property accordingly and these properties were assigned to the respective components using the ‘assign’ command by right clicking on the component.
• 13 such properties for 13 different thicknesses, were created as shown in the image below.
  
  

Result and Conclusion:

• In this project, the plastic model of the sidedoor of a vehicle was meshed successfully pertaining to the specified quality criteria.
• This project helped in better understanding of 2d meshing for plastic components.
• This model being complex in nature took longer time than usual but many concepts about meshing became crystal clear.

Additional GDrive link for model: Sidedoor plastic model