METHODOLOGY: 1. Import model to ANSA 2. Check for geometrical error cleanup and topology 3. Extraction of Midsurface 4. Quality criteria setup 5. Assigning property id (PID) 6. Defeaturing 7. Meshing
INTRODUCTION:
A car hood is a hinged cover that rests over the engine of a front-engine vehicle. Its purpose is to provide access to the engine for repair and maintenance. It consists of two parts where the inner part is providing strength and outer part is designed for aerodynamic optimization. The inner structure is capable of pushing the surface of the hood away from the vehicle's hard motor components during the crash of the vehicle. so we have to design a car hood to optimize aerodynamic and provide better safety aspects and crash behavior.
GEOMETRY CLEANUP: After importing of cad model into ANSA, there will be many geometry errors present in the model. we have to check and clean them before meshing.
B Checks Manager (C:/Users/VOSTRO/AppData/Local/Apps/BETA_CAE_Systems/ansa_v19.1.5/config/Checks/ANSA_Templat... X
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Geometry
C Rerun
Yes
Type Message Code Entity ID Description Auto Fix Error E4068
44 Unchecked Faces Yes Error E4071 FACE 431 Needle Face Yes Error E4071 FACE 432 Needle Face Yes Error E4071 FACE 434 Needle Face Error E4071 FACE 435 Needle Face Yes Error E4071 FACE 436 Needle Face Error E4071 FACE 443 Needle Face Error E4071 FACE 444 Needle Face Yes Error E4071 FACE 446 Needle Face Error E4071 FACE 461 Needle Face Yes
Yes
Yes
total 51 selected 0
Value
Geometry
Name
Unchecked Faces Collapsed Cons Triple Cons Needle Faces Overlap Faces Cracks
Locates geometrical problems of the model such as Unmeshed Macros, Unchecked Faces, Needle Faces, Collapsed Cons, Triple Cons, Overlaps and Cracks
The checks manager will check the geometry and show the errors which are in the cad model. The required feature such as unchecked faces, triple cons, needle faces, cracks, collapsed cons has to be kept on so that checks manager will show the errors based on the feature as selected. There are two options for cleaning these geometry errors. These errors can be cleaned one by one approaching the error area and fixing the error by deleting cons and
After measuring the model it has been concluded that hinges and latch has a thickness of 1.20mm, inner part and outer part has a thickness of 0.75mm.
A midsurface can be extracted by two methods:
1. MANUAL MIDSURFACE METHOD
2. AUTO MIDSURFACE METHOD
MANUAL MIDSURACE METHOD:
This method can be done by manually clicking the offset option and selecting the surface, the offset value has to be given when creating a midsurface. The orientation of the surface should be kept uniform, the grey color represents positive and yellow color represents negative. the grey color is always preferred while working on the model.
MESHING:
Meshing is an integral part of the engineering simulation process where complex geometries are divided into simple elements that can be used as discrete local approximations of the larger domain. It is a network that is formed of cells and points. Now we can finally mesh the component after defeaturing the complex areas. there must be better mesh flow in the component. Before starting meshing we have to set perimeter elemental value as 5mm so that perimeter points will be arranged within the limit in the surface edges.
HANDLING OF TRIA ELEMENTS:
Tria elements are formed with 3 nodes, they need to handle carefully while meshing. because when we apply the loads near to fillets or holes where the trias appear, the results will not be accurate. Depending upon the geometry, even when we mesh with all quad elements sometimes we end up having rotating Quad elements. To avoid these rotating quad elements we need to smartly introduce the Tria elements. When it comes to Tria elements, there are a few thumb rules to be followed
• The Tria elements should never be opposite to each other • No Tria elements should be connected back to back • No Tria elements should be on the edge of the geometry • No Tria elements should be near the holes • No Tria elements should be on the feature and the fillets.
• There should be less Tria concentration, i.e., there should be a considerable distance between Tria elements.
REFERENCE: TRIA ELEMENTS CONCLUSION: From the above challenge, the CAD model has been created with 2D mesh with given quality criteria and better mesh flow is created using mesh tools. some areas are compromised because of manufacturing constraints and arranged them with the proper construction lines.
