Week 6

Objective:

      The goal is to clean the surface geometry to avoid errors and carry on the solid meshing (3-D) process and provide connections using connection managers that accurately captures the input domain geometry(side door) with high-quality cells so as to make subsequent calculations intractable.

      The above-said goal is achieved by using the most widely used Pre-processing software named ANSA.

What is ANSA?

      ANSA is an advanced multidisciplinary CAE pre-processing tool that provides all the necessary functionality for full-model build up, from CAD data to ready-to-run solver input file, in a single integrated environment.

      ANSA is the user's preference due to its wide range of features and tools that meet their needs. The list of productive and versatile features is long and the alternative tasks and processes to be completed using them are countless.

Mesh generation:

        Mesh generation is the practice of creating a mesh, a subdivision of a continuous geometric space into discrete geometric and topological cells. Often these cells form a simplicial complex. Usually the cells partition the geometric input domain. Mesh cells are used as discrete local approximations of the larger domain.

Purpose of meshing:

        Meshes are used for rendering to a computer screen and for physical simulation such as finite element analysis or Computational fluid dynamics.

        Finite element calculations cannot be done directly on solid parts. We know to perform those calculations only on points created by the mesh generation process. Thus generating mesh is a must and most important step for any CFD or FEA calculations to be performed.

Steps involved in geometry clean-up by ANSA:

1. The solid part made using any cad modeling software is imported into ANSA. The Procedure is File>Open and select the required solid part.

2.The solid part is initially imported as unconnected surfaces as shown above.This may be due to ANSA's translation  issues. TOPO option in faces tab is used to connect the faces of the geometry as shown below. 

3.The geometry is checked using the checks button and selecting the geometry checks option as shown

4. The geometry check dialog box displays various errors in the geometry.

5.You can highlight any of the problematic areas by left-clicking on it, or isolate it on the screen by right-clicking on it and selecting “Show only”. Depending on the type of problem ANSA also offers the option to automatically fix it.

6.Close the Checks Manager window. Click “All” from the focus toolbar to make all the faces visible again.

7.De-activate “Shadow” mode and the visibility flag button for “Double” CONS. You will now isolate a region of your part to work on. Activate the “Or” function located in the Focus Toolbar. Make a box selection of the area shown on the left using the left mouse button. The “Or” function leaves visible only the selected Faces. (If you accidentally select wrong Faces, press the All function of the same Group to bring all the entities back to visible).

8. Activate the “Lock” flag button in the Focus Toolbar to lock the currently visible entities. Now when you press the “All” button, only the selected and locked entities will become visible.

9. To view the complete Faces that you have left visible, activate again the “Double” CONS visibility flag. Activate also the “Cross Hatches” visibility flag. This allows the visualization of two green dashed lines along the center isoparametric of the Faces. Apart from visualization purposes, the crosshatches are also used for selecting Faces.

10. After visualizing the surface to be cleaned using various topo corection tools provided in topo mode. Some of the visualized errors are shown below

11. The topo mode provides following menus to perform geometry cleanup

TOPO menu

In this menu, the user can create, modify and clean up the geometry. The menu is divided in groups of functions according to the entities that they refer to.

Hot Points

These functions are used to create or delete Hot Points or Weld Spots.

CONS

Functions that are applied to CONS (Curves ON Surfaces).

Faces

Functions to create or modify Faces.

Surfaces

Functions that create Faces and modify Surfaces.

Curves

Functions to create 3D Curves.

Points

Functions to create 3D Points.

Auxiliaries

Functions to create Working Planes in order to draw in 2D mode.

12. After performing clean up the geometry is again checked for error using geometry checks.

connection process is explained below:

 1. Assign the given model small component in to different PID.

 2. Now check the given model for  which connection is required like bolt for RBE2, Weld spot "RBE3 HEXA RBE3" and CBUSH for glass . 

4.Go to nastran module then select " RBE2" for all bolt connection , other method is also used for the bolt connection in topo module on COG is used to define centre of gravity of the given bolt connection after middle click choose the bolt option the go to connection manager and efine the bolt pid.

5. For door hinge connection , in nastran module choose RBE2 and select the point after point selection restrict the 5 degree of freedom one degree of freedom is free for the swim .

6. To make the connection between glass and the door first create the curve of the given FE  model using Feat2Curve   from perimeter in Mesh module, then convert the curve line in to connection entities after converting the connection enteties open the connection manager then select the curve where connection is needed select the p1, p2 value there after choose "RBE3 CBUSH RBE3" in connection manager then select the part where connection is needed , enter the value of S then click apply and releaise.   

7.  rear door model door handle is a solid component, enter the mass of the given solid component into tonnes first and create the connection for door handle using RBE2 then enter the mass of the handle using  " CONM2" .

Learning Outcome:

• Was able to understand different types of connections and deploying it with a particular part/region
• Spot-weld, CBUSH, Bolt, Seam Weld, Rigid, Cluster are some of those connections.
• Importance of Zone cut for individual connections.
• Door Handle connection determining the Mass of it.
• Latch & Hinge regions.
• Fixed and movable glass windows

Google Drive Link: https://drive.google.com/file/d/1QpJnHTk8lxN1S-jGjpSzhniVY-_svVg3/view?usp=sharing