Project 1 - 2D meshing on the instrumental Panel
AIM: Pre-processing of the car instrument panel using ANSA
KEYWORDS: Mid-surface Extraction, Shell Meshing.
OBJECTIVE:
- Introduction to shell meshing i.e. 2D meshing
- Geometry check & Topological error clean up
- Mid surface generation
- Meshing the geometry
METHODOLOGY:
- Import geometry
- Topological error cleanup
- Mid-surface extraction
- Quality criterion setup
- Meshing and Mesh improvement
PROCEDURE:
1. Import model. Firstly, we need to import the model and study geometry.
2.There are two way to extract mid surface
1) The manual mid surface method
2) The Auto mid surface method
Manual mid surface generation
This can be done by manually selecting the surface and giving an offset option in the direction opposite to the grey surface
Note:
1) While giving the offset make sure you do not press YES or else you can delete the parent geometry
2) use Fine option under the auxiliary section in TOPO mode to get a better resolution. (select fine and click on the curved and circular areas)
Auto mid surface generation
If the geometry is closed then we can go for auto mid surface generation option but it will auto-delete the parent geometry.
steps 1) press the mid surface tab under face 2) select the full geometry 3) confirm the mid location
Here I have used the manual offset method extract mid surface as the surface thickness varies and ANSA is unable to segregate separated surfaces for auto mid surface generation.
Quality Criterion Setup
We can say that result quality is directly proportional to the element quality. The parameters like skew, included angle, Jacobian, warpage, etc. are the measure of how far a given element deviates from the ideal shape. If we talk about a square which means 90 degrees and equal side similarly equilateral triangle 60 degrees and each side equal. so we will discuss the quality criterion and try to understand them before assigning them into ANSA environment.
1) Warp Angle: it is defined as the angle between the normal of the two planes by splitting the quad element along the diagonal. so the maximum angle allowed between the two possibilities is called wrap angle. wrap angle is not applicable in the triangular element. the ideal value is 0 degree but less than 10 degree is acceptable as good practices.
2) Aspect Ratio: It is defined as the ratio of max element edge length to the minimum element edge length. the ideal value is 1 but less than 5 is acceptable.
3) Skewness: If the quad element is not square and has deformation then the skewness defined for as the 90 minus the minimum angle between the two lines joining the opposite mid sides of the element and similarly for the triangular element it is 90 minus the between the line from each node to the opposing mid-side. The ideal value is 0 but less than 45 degree is acceptable.
4) Jacobian: it is the scale factor used in the transformation of the co-ordinated system.(global to a local coordinate system). This is used for a faster analysis point of view. The ideal value is 1 but greater than 0.6 is acceptable.
5)Minimum element length: It is very important to check for crash analysis(time step calculation). it is also done to avoid the presence of any zero-length element.
6) Target element length: It is the size of the element by which we can get the most nearer approximate value of the result compared to the experimental result.
7) Remove the redundant and excess construction line to get uniform mesh flow.
8) Divide the surface near the feature into to get better mesh flow pattern
9) Defeature the areas which are going to fail the quality criteria.
10) Mesh density near the critical areas ( features) is preferred.
CONCLUSION:
The panel had been captured quite a well-using shell mesh. The total element 242575 out of which 19045 are Tria element and 223530 are Quads which makes 4.10% which is a decent percentage of Tria element. Also, the 86 no. of elements are failing as shown above report.The mesh flow is smooth nearer to target length as 4 mm and within the quality parameter.
Google link: https://drive.google.com/drive/folders/1_4i48-_snbPKr06HQIuxOTyDeimp-1Wp?usp=sharing