Project - 2 - Meshing on the suspension Assembly

AIM :

To Perform Preprocessing Operation on a given Rear Supension Assembly model, all should be done by ANSA.

OBJECTIVES :

1) Geometry Cleanuping on a given Rear Suspension system.

2) Extracting the middle surface, if thickness is less than 5mm at which throughout the component.

3) Providing the appropriated Mesh Quality and Element Quality Parameters based on meshing approach and size the component.

4) Performing an shell meshing with mixed type element on a extracted middle surface and Quality Checking.

5) If thickness is more than 5mm, to Performing an shell meshing with tria elements alone on the component surface and Quality checking.

6) Defining the Volumes for which performing the 3d meshing.

7) Performing a tetrahedral 3d meshing on which defined volume and quality Checking.

8) To Represents the coil spring with CBAR 1D Element.

9) Deploying the connections by using RBE2 and Seam weld.

GIVEN CAD MODEL :

Open the ANSA software, import the appropriate file which is Automotive Rear Suspension by using open graphical user interface option. Once file has opened, it will looks like as shown in the below image.

It have consists of several parts like Trye, Rim, Open Coil Spring, Sub Frame, Tie Rod, Metal Brake Disc, Wheel Caliper, Bracket, Wish bone control Arm etc..

In a given model, all sub parts are assigned into the single property card except tyre and rim parts. So, We have to manually creating the new property for each & every component and assigning on it.

After done the property card assigning to all parts and changed into PID mode instead of Entity Mode, it will looks like as shown in below image.

PROCEDURE FOR ATTAINING THE OBJECTIVES :

I) Geometry Checking and Cleanuping :

Before going to discritization process, make sure we have to checking the entire geometry for which knowing us whether if there's any geometrical error are presented or not.

ANSA have by default template which had prebuilded some few important parameters except "Sharped Edge" and "Unmeshed Macros". Because, those parameters are not needed for this case.

Make Sure Keep "Visible On" option from the "Execute On" Option and then click Execute to which finding the geometrical errors from the visible geometry by ANSA itself.

ANSA finded out few error from the visible component like "Crack between Cons" and "single cons" as shown in above image.

Here we can see from the below image, there's few crack between the Cons, by results few single Cons issue also be presented.

Inorder to fix those errors, we have two option in our hand. One is Manual fix and another one automatic fix. In this case, We surely going to with automatic fix for Cranks between the cons issue, because as we notice from the check tab which is "Yes" for "Auto fix". Which means ANSA can able to fix those issues by itself.

Inorder to do fix those thing in automatically, we have to select all errors which are shown up and right click & followingly select fix option. Afterthat, ANSA have fix those issue in proper manner.

After fixing the issues by ANSA itself, it will looks like as shown in the below image.

Again we have to cross check the geometry by using same template. Now, there's no issues are pop uped from the check manager tab.

Once, we fix the "Crank between the cons", it will automatically fix the single cons issues as well.

II) Extracting the Middle Surface :

Generally, a middle surface are generated between at neutral position of the part. It will helps us to reduce the computational calculate time and also reduce the storage space.

Before going to extracting the middle surface from the parent geometry, make sure we have to check the parent component whether it's have proper orientation or not. From here below image, we can able to see which surface has proper orientation.

Yellow means Negative direction, Grey colour means Positive direction.

In the given rear suspension model, there's only two parts are less than 5mm thickness on it. Hereby, we should have generate the middle surface for this parts which shown in above image.

Since, our given parent components are simple with same cross section. So, we can able to generate the middle surface from the parent component by using manual or automatic algorithms.

Here, we can use Offset option under which "Faces" sub modules & " Topology" module to which extract the middle surface from the parent component.

Once, we extracted the middle surface for sleeve & Bracket, it will looks like as shown in the below image.

Apart from this parts, remaining all are more than 5 mm. So, we perform different manner.

III) Setting the Quality Parameters and Mesh Parameters :

i) Mesh Parameters :

Before going to performing the meshing operation, make sure we have to setting the mesh parameters like as shown in the below images.

When we perform meshing operation, initially a mesh algorithm has trys to generating the mesh elements as per macros or perimeter node distances.

If we trys to improve the mesh qualities by using reconstruct or reshape or Improve option, that time those algorithms are try to capturing the elements as per given parameters even if the macros or perimeters node distance is different.

Mesh Parameter for 2D Shell elements on Mid Surface :

We have to generate the 2d shell elements on a extracted middle surface with Mixing of Quad and Trias as per given element length size.

Mesh Parameter for 2D Shell elements on trye and Rim Surface :

We have to generate the 2d shell elements on a surface with only tria elements as per given element length size.

We have to use this mesh parameters only on Trye and Rim component.

Mesh Parameters for 2D Shell elements on non uniform surfaces :

We have to generate the 2d shell elements on a surface with only tria elements as per given element length size.

We have to use this mesh parameters only on non uniform thickness component other than trye and Rim.

ii) Quality Criterias :

Make sure we have to enabling all important quality parameters & provide the appropriate values in numerically. It's helps us to checking the failure of the elements when we will performing an meshing operation.

Element Quality Parameters for Mixed Shell Elements :

If we performing an 2d shell elements on a middle surface, we have to take care of all those element qualities which are checked in the below image.

All elements should be passing these checked qualities.

Element Quality Parameters for Tria Elements on trye and Rim component :

Whenever we create a 2d shell element with only tria for which generating the 3d tetrahedral element. We have only consider Skewness, minimum & Maximum element length criterias.

For generating the 2d tria elements on the trye and Rim component surface, we have to maintain a quality as per given element criterias as shown below image.

Element Quality Parameters for Tria Element on Non Uniform thickness component :

Whenever we create a 2d shell element with only tria for which generating the 3d tetrahedral element. We have only consider Skewness, minimum & Maximum element length criterias.

For generating the 2d tria elements on the Non Uniform thickness component surface, we have to maintain a quality as per given element criterias as shown below image.

Element Quality Parameters for Tetrahedral Meshing :

Whenever we generating the tetrahedral mesh, we have to only concern on tet collapse.

IV) Discritization on a model :

Basically, To divide the entire model into infinitesimal control volume, that framework is called meshing. This process is called discritization.

First of all, Make sure keep the resolution of components to which distance between the two nodes is equal to the target element length by using "Length" option under the "Perimeter" sub module & "Mesh" module.

By using Best or Spot algorithms with appropriate element type based on type meshing approach to which performing the meshing operation on surface by surface along with checking the quality of each & every elements is necessary.

If generated elements are not got proper orientation flow or any elements has been failed due to any of the given element quality criterias. We have to use reconstruct option or Improve option to which remesh on it, by results we get proper mesh flow orientation of elements and also avoid the element failing.

If any of the feature lateral distance is less than the minimum element length criterias. Then, We have manually defeaturing out little bit for which avoiding the elements faling due to minimum element length parameters.

i) Performing an shell meshing on a middle surface

By using Best or Spot algorithms with mixed element type to which performing an meshing on the middle surface.

As we see from the below image, all elements are passed in our given element qualities criterias.

ii) Performing an Shell meshing on a surface :

Inorder to generating the Tetrahedral elements, make sure we have to creating the shell element with tria type.

By using Best or Spot algorthims option with tria element type to which performing an meshing operation on a surface of the solid component.

Shell elements should be created as per mesh parameters & element quality parameters.

Tyre & Rim Component :

As clearly noticed from the below image. Some elements are failing due minimum element length criteria. Because, those few features are very important while analysis on the model. That's why we can allow those failing element in the FE model.

All elements are created based on given element length parameters.

Other Solid Components :

Here also some elements are failing due the minimum element length criteria. Because, those areas are neccessary when we performing an analysis on the model.

All elements are created based on given element length parameters.

V) Defining the control Volume :

Before going to create a volume meshing, make sure we have to defining the volume region for which generating the 3d elements on interior of the shell elements..

Make sure, we had to done the 2d shell element properly without any opening. Then only, we has to define the volume.

After defining the volume to all parts, it will listed out as shown in below image.

We can choose the type of algorithm for which generating the tetrahedral elements on their by either Tetra Rapid or Tetra FEM

In each type have different algorithms & different growth rate as well for which generate the tetrahedral element at interior of the volume.

VI) Perform Tetrahedral meshing :

Inoder to generate the tetrahedral element mesh, make sure we have defined the volume for which generating the volumetric mesh.

Select type of algorithm either Tetra Rapid or Tetra FEM and then Click to generating the volumetric mesh.

Once done the Volumetric meshing on all components, it will looks like as shown in below image.

Also, we have to check the Tet collapse error from the Volumetric elements. Here, there's no elements are failing due to tet collapse.

After done the volumetric mesh on all defined volume, it has changed to Meshed from Unmeshed.

VII) 1D Element to represent the coil Spring :

We have to represents the compressive coil spring by using CBAR 1D Element. Coil Spring image as shown in below.

Inorder to represents the CBAR element, we have to create a middle curve for a coil spring at where neutral axis by using " Middle Curve" option under where " Curves" Sub module and "Topology" module.

After creating the middle curve, it will looks like as below image.

Followingly creating the COG point has been created by using "COG" Points under "Points" sub module and "Topo" module.

Select the "CBAR" Option, followingly check "Orientation with nodes" & keep Curves.

Subsequently, select the Curve COG point and provide the element size which is 3 for this case. Create a New Property card and then provide the appropriate radius of the coil spring cross section.

Once we provided the radius, it will automatically calculated the cross sectional area, minimum & maximum moment of inertia and then Polar moment of inertia by uisng diameter which we given.

Once, we created the 1D CBAR Element, it will looks like as shown in the below image.

Inorder to see like a element, we have to keep "As Solids" under "Line Element Cross Section" at presentation Parameters. After done, it will looks like as shown in the below image.

This is How we represents the Coil spring while we modelling.

VIII) Connections :

i) Deploying the RBE2 1D Element :

A RBE 2 is stands for Rigid Body Element type 2, basically it have infinite stiffness. To defines a rigid body whose indepenedent node degrees of freedom are specifiied at single point and dependent nodes degrees of freedom are specified at an arbitary number of points.

In this case, we use RBE2 1D Element for which represents the bolt holes & Rivet holes at whereever it's required.

Inorder to create the RBE2 Elements, we have select the RBE2 option under which Nastran deck module & Element sub modules.

Here, we create a cluster type RBE 2 elements on each hole like rim and trye part. And then, By using Two node RBE2 Element to which made a connectivity between rim cluster master node to Tyre cluster master node hole.

Once, we done this, it will looks like as shon in below image.

Similarly, we made a RBE2 element by cluster method between the coil spring and Botton struct plate.

ii) Seam Welding :

First of all, Extract the curves from the FE model at where edge by using "Feature 2 Curve " option under which mesh module & perimeter sub module.

Followingly, converting from curves to seam line by using convert gui option. Once converted, it will looks like as shown in below image.

Click the connector manager, immediately one tab has pop up which is "Connection Selection Assistant" and then followingly select the seam line which we going to perform and press middle mouse buttom to get open a new connection manager tab.

Select the parts properly and then Our connection areas has been parallel to each other, so select the OVER LAP SHELL option at where FE Representation. Followingly, we have to provide the search distance and setting like as shown in below and click to realize.

Once We created the Seam weld between the bracket and sleeve, it will looks like as shown in below image.

CONCLUSION :

Successfully done the Preprocessing on a given Rear Suspension model like Geometry Cleanuping, Middle surface extraction, Shell meshing with mixed & tria types, Volume defining for volumetric mesh, Tetrahedral meshing, represent the spring by CBAR and then Deploying the proper connections.