Week 3

Aim: To check for the geometrical errors and mesh with the given element Quality criteria using ANSA tool. Also thickness to the component is to be assigned after meshing

Objective: To clean up the given automotive hood assembly and perform structural mesh with a target element length of 5mm, by following the below mentioned quality criteria values.

Quality Criteria	Value
Target/Average length	5
Minimum Length	3
Maximum Length	7
Aspect	3
Warpage	15
Skewness	45
Jacobian	0.7
Minimum Quad Angle	45
Maximum Quad Angle	135
Minimum  Tria Angle	30
Maximum Tria Angle	120
Tria Percentage	15

About the given CAD model (Hood assembly):

• The given CAD file format is of .stp and is in readable format for ANSA. 
• The hood assembly comprised of outer panel, inner panel, one latch reinforcement and two hinge reinforcements.
• The inner hood panel is inserted into outer hood panel by hemming connection.
• The inner and outer panels are of 0.75mm thickness while the latch and hinge reinforcements are of 1.2mm thickness.
• Link: https://drive.google.com/file/d/1XQXQkpiaKn_w1aB3OQasH0bpsIRYsKT6/view?usp=sharing

Procedure:

• While opening ANSA, adjust drawing performance and memory usage by using command argument -performance_mode <0/1/2/3>.
• -performance_mode 3 has slower drawing but better quality.
• The given model is then opened in ANSA and is now checked for geometrical errors by using geometry template in checks manager under tools button.
• The various errors like single cons, triple cons and needle faces which have popped up can be fixed using auto fix option and the errors which ANSA could not auto fix have to done manually.
• Once the errors are fixed, the mid surface skin is to be extracted.
• The mid skin is to be taken for outer panel, inner panel, and latch and hinge reinforcements separately.
• Using offset command under faces in Topo module, and with proper orientation, by specifying the offset distance, mid surface is extracted.
• These mid skin surfaces are assigned property ID’s separately by using Set PID option and thickness values are also assigned accordingly.
• Both Outer panel and inner panel look symmetric and are checked for symmetry using the Rm Dbl option. By default it checks for 90% similarity and if it is found similar ANSA takes it into consideration. It's better to take 100% similarity to get the actual result.
• Since the model is symmetric, we can mesh one half of the model and reflect it on the other side using transform option in utilities.
• Half portion of both outer and inner panels are deleted and for left over portions, apply node distance of 5mm for both perimeters and macros
• Quality criteria values are assigned in the quality criteria dialog box and also values of target length, minimum length and maximum length should be given in mesh parameters in utilities.
• Mesh is now generated using best mesh option in mesh generation option.
• This mesh is now refined to avoid tria elements and also to avoid quality criteria errors which are visible under hidden mode
• Reconstruct and smooth options are used to have good quality mesh and when ANSA could not give proper mesh, we do some changes in mesh using split and swap options
• Finally we get mesh for inner, outer and latch and hinge reinforcements
• Link: https://drive.google.com/file/d/1BUqklsQWcL4EumMNVJDrgx7a4BPuD9J9/view?usp=sharing

Conclusion:

• All the errors were eliminated.
• The final finite element model can now be used for finite element analysis as it satisfies all the required quality criteria.