2-D Meshing (Manual Method, Casting Method and Batch Method) of a Component using ANSA

Aim:

1) To check and correct the geometrical errors of the given model.

2) To take Mid Surface of by the Skin Method and Casting method.

3) To mesh using the manual, batch and casting methods given in the question. Also using the following quality criteria.

S.No	Quality Criteria	Value
1	Target/Average length	3
2	Minimum Length	1
3	Maximum Length	5
4	Aspect	3
5	Warpage	15
6	Skewness	45
7	Jacobian	0.7
8	Minimum Quad Angle	45
9	Maximum Quad Angle	135
10	Minimum Tria Angle	30
11	Maximum Tria Angle	120
12	Tria Percentage	15

Theory:

The CAD model to us is a sheet metal model. We deploy mesh using manual, casting and batch meshing methods.

Procedure:

1. Importing the Model:

1) We first the import the CAD model into the ANSA database.

2) We set the perimeters of the CAD model to 1 for better visualization of the CAD model for that we go to the length option under the perimeters tab of the mesh module.

3) After, we go the TOPO module for giving topology to the whole model using the TOPO option present in the faces tab.

2. Geometry Cleanup:

1) We check for the geometric errors using the check geometry option present in the tools option as shown in the image given below.

2) We clear all the geometric errors obtain a clean geometry of the CAD model as shown in the image given below.

3. Mid Surfacing and Meshing:

In the 2-D meshing we will be considering only the above mid surfaced parts and we will be meshing it with mixed elements that include both quad and tria elements according the quality criteria given in the aim. There are some important quality parameters required for the meshing the component namely:

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 possiblities is called the warp angle. Warp is not applicable in the triangular element. The ideal value is 0 degree but less than 10 degree is acceptable for 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.

1) Manual Meshing:

1) In this method, we take the mid surface of the CAD model using the mid-surface-skin option present under the faces tab of the TOPO module and the property gets generated automatically as shown in the images given below.

2)After that, we type in all the mesh parameters, quality criteria in the mesh parameters and quality criteria options present in the utilities tab as shown in the images given below.

3) We mesh the component region by region and clear all the off elements using the best, split, reconstruct, smooth and swap commands in the mesh module.Finally, we obtain a good quality mesh as shown in the image given below.

4) We finally provide the thickness to the model ticking the check box draw shell as solid under presentation parameters of the quality criteria option on the tools tab.

2) Casting Method Meshing:

1) We again reopen the CAD model and perform the process clearing the geometric errors.

2) After that, we proceed to take mid surface using the Mid Surface-Casting option present under the faces tab of the TOPO module were we provide the element thickness and target mesh element length having the same quality criteria and mesh parameters as mentioned above. The casting method mid surfacing is shown in image given below.

3) It also creates the mid surface and deploys the mesh on it as a result the FE gets isolated from the geometry. There are certain elements failing for the given quality criteria and the feature capturing is also not good as shown in the image given below.

4) We provide neccesary cuts using the cut option present under the macros tab of the mesh module for better feature capturing and clear all off elements using the split, reconstruct, smooth and swap commands in the mesh module as shown in the image given below.

5) We finally provide the thickness to the model ticking the check box draw shell as solid under presentation parameters of the quality criteria option on the tools tab.

3) Batch Meshing Method:

1) We again reopen the CAD model and perform the process clearing the geometric errors.

2) We take the mid surface of the CAD model using the mid-surface-skin option present under the faces tab of the TOPO module and the property gets generated automatically as shown in the images given below.

3) We then, use the batch mesh option present in the tools tab and we perform the new meshing senario with the same quality criteria and mesh parameters as shown in the image given below.

4) We then, set the model to be meshed by using edit option in the batch mesh manager as shown in the image given below.

5) We run the meshing senario and we obtain the mesh in which certain elements failing for the given quality criteria and the feature capturing is also not good as shown in the image given below.

6) We provide neccesary cuts using the cut option present under the macros tab of the mesh module for better feature capturing and clear all off elements using the split, reconstruct, smooth and swap commands in the mesh module to get a better mesh flow as shown in the image given below.

7) We finally provide the thickness to the model ticking the check box draw shell as solid under presentation parameters of the quality criteria option on the tools tab.

Comparison Between all meshed models:

In all three meshed models, we find that

1) The manual meshing can be done on any components by manually defeaturing the unessecary construction lines and also unessecary hot points as well. Manual meshing can also be done when we don't have any time constraint.

2) The casting method the FE is removed from the geometry which is not a good practice and the feature capturing is also poor because of heavy defeaturing occuring automatically during the meshing process.

3) The batch mesh deploys mesh with heavy defeaturing which leads improper capturing of the features.

For batch meshing and casting methods we perform these when we have a time constraint. Finally, manual method of meshing is always considered good because we can get good mesh flow without defeaturing some essential features. If there is a time constraint provided to us the best way is to go with the batch mesh or casting method as it saves the a lot of time that goes into meshing the whole model provided we sacrifice of some features.

Conclusion:

We have the checked the given geometry for errors and cleared them then, we have meshed the component 3 times using the all methods mentoined in the question according to the given quality criteria and mesh parameters.

Learning Outcomes:

1) Learnt about Meshing a component using casting method.

2) Learnt about Meshing a component using the Batch meshing method.

3) Comparing Manual, Casting and Batch meshed components in detail.

Model Link:

https://drive.google.com/drive/folders/1a9LFl2wsPpUiXvJxVPuQosFeJn58RoX_?usp=sharing