2D Meshing of Bottle cap using ANSA
AIM
*To mesh a bottle cap after cleaning up geometry and generating midsurface.
STEPS FOLLOWED
*The CAD model has to be pre-processed before solving and ANSA software is used here to mesh the model.
*Model dimension, Geometry editing and complexity reduction is done in ANSA.
1.GEOMETRY CLEANUP
*Import the model using file_open.
*The given model should be analysed properly.
*The model seems complex as it includes ribs, fins and threads.
*To reduce the complexity and for better visualisation of curves and fillets, select 'length' from Perimeters and change perimeters and macros to 1.
*Apply topo on the selected view and check up the geometry.
*Unchecked faces or triple cons is eliminated as a part of clean up.
*Correct all triple cons using release in CONS and apply TOPO from faces to convert it to double cons.
*Unchecked faces and needle faces should be removed.
2.MIDSURFACING
*Midsurface can be obtained manually and automatically by using Midsurf command.
*Here, midsurface is generated for each and every component of the model using offset.
*Midsurfacing of bottom ring and the mid ring is generated using offset.
*When it comes to features either middle from faces or middle from curves is used as shown below.
*Midsurface for ribs are generated using middle and for fins curves middle is used.
*On coming to teeth, the length is measured and half of its length is offset from the side surface of the teeth.
*Inorder to connect the bottom and mid ring, a new face is created as shown below.
*As in the above picture, the midsurface for the side surface is generated using curves middle and the curve produced is projected to the surface followed by creating a face.
*The top surface shown below consists of rectangular structures and midsurface is done by taking faces middle. But it wont be connected to the surface so the hotpoints are projected to the surface and created a new face connecting coons.
*The curves middle is also used to take the midsurface of the threads present in the inner area of the cap
MIDSURFACE GENERATED
3.MESHING
*A mesh is a network that is formed of cells and points. It can have almost any shape in any size and is used to solve Partial differential equation.Each cell of the mesh represents an individual soultion of equation which, when combined for whole network,results in a solution of entire mesh.
*On meshing the model element size must be consistent and so set element length in perimeters. Here as per the given details, it is 1 and here it is followed initially before geometry cleanup.
*Quality criteria and meshing parameters should be entered according to the given values.
*In quality criteria aspect, skewness, angle, minimum length, maximum length and jacobian is considered here as shown below.
*In presentation parameters of Quality criteria, tick the elements % and all details.
*If diamond structure or any other feature is available in the model, run the number in perimeters and select the structure.
*Check all the fillets before meshing to make sure it is under the minimum length given for meshing.
*In this model most of the features are of curve type and the midsurface should be extracted properly before meshing.
*Quality criteria and mesh parameters are assigned before meshing. Cut or proj cut is used in some areas inorder to get a better mesh.
*In the above image it is diplayed that quality of mesh is failing near to the rib region. It is because the thread inside is of non uniform and it is aligned to the connecting surface in such a way that the area is too narrow and will be failing for quality.
ERRORS AND CORRECTIONS
*After midsuracing meshing was done to each component trying to satisfy quality criteria. On meshing the base surface of teeth the area between the teeth and the con of the base surface was failing for minimum length as shown below.
* So inorder to create a better mesh, the teeth midsurface is extended to the coon of the base surface.
*The same method is followed in the case of fins attached to the bottom ring as shown below.
CONCLUSION
*In preprocessing meshing is significant as it helps in the flow of stress evenly throughout the model.
*A smooth mesh is better in weight distribution analysis.
*Meshing is done in the midplane of the model and not in the parent geometry.
*Initially mesh the features available in the model to reduce the complexity.
*The below link is to check out the model
https://drive.google.com/file/d/1jW1vELq1blkMWX-n98GhMa6t29v9pmNr/view?usp=sharing