2D meshing of components with varying thickness using the new direct Midmesh tool in HyperMesh and HyperWorks
2D meshing of components with varying thicknesses such as castings, injection moldings and extrusions have always been a challenge due to their complicated features and varying thicknesses.
The mid-surface extraction tool in HyperMesh does a great job for components with uniform thickness, but for those with varying thicknesses there are lots of challenges. The traditional approach of meshing these parts in HyperMesh is, we start by extracting the mid-surface which is good to an extent of 60-70% and rest other we do mesh either on the inner surface or the outer surface and further offset/project the mesh to the mid-surface using manual tools, which are quite tedious and time consuming, further thickness assignment is also a challenge as we need to measure it manually and then input, whereas for the mesh created on the mid-surface we can automatically assign the thickness, as the mid-surface does have the thickness information saved.
To address these challenges, we have come up with a new tool called direct Midmesh in HyperMesh and HyperWorks (New HyperMesh interface) which generates mesh directly on the mid of the component. We are showcasing this workflow on a Shock tower bracket (Image 1). There is not much of a manual effort and the workflow comprises of 5 steps which are mentioned below (Image 2).
- Automatic Midmesh extraction: we do automatic mesh generation using a criteria file, we are using a mesh size of 5mm and below are more details of all the parameters which can be controlled.
- Clearing mesh intersections and topology corrections: in this step we are looking to correct the mesh intersections i.e. connectivity issues and any geometry deviation using the below highlighted tools.
- Repair/Fill tool can be used to fix topological problems like holes, gaps, cracks, intersections, slivers, overlaps etc. in the mesh, to further remesh the face or create a mesh within a closed topology loop, further attempting to keep tangency
- Midedge tool helps to create a midedge, by selecting node list and two lines as guides, this further helps in repairing the mesh, where mesh is not generated
- Edit Topology tool helps edit Midmesh topology using the below 3 options:
- Delete Edge: This option helps deleting the feature edges which are not necessary
- Imprint Lines onto Elements: This option helps adding a feature using the geometry lines, which are missed during the automatic Midmesh extraction
- Create New Edge: Using this option we can split topology and create a new edge. This option helps correcting the mesh flow, by manually creating the new edges
- Align mesh tool aligns the Midmesh, this helps fixing the locations which are not properly aligned to the geometry
- Global rebuild: We use this tool to remesh the existing meshes to generate a new mesh with good quality and flow. The rebuild mesh functionality utilizes the parameter and criteria files, which are used to define the quality criteria and relevant mesh parameters. In the parameter file we can specify parameters i.e. the node movement allowed to clear the quality, dimensions to capture holes, quality etc.
- Local corrections if necessary (local rebuild and manual corrections): some areas which are not fixed with global rebuild, we try fixing those with local rebuild by just selecting the relevant faces to remesh and further do manual corrections using the edit elements tools to fix those regions, we also do a model tour to review the regions and fix them.
- Thickness assignment: The thickness can be assigned on the Midmesh as properties on elements/ components and nodal thickness on elements, depending on the solver interface we are using. In our case we are applying it as properties on elements. The final part with all the mesh corrections and thicknesses assignment can be seen below.
Please refer to the video link which showcases the complete process:
Prashant Hiremath(Guest Blogger)