Week 3 - 2D meshing for sheet metal

Aim :

For the given Hood model, Take the mid surface for all the components after checking the geometrical errors and mesh the mid surface with the given element Quality criteria.

element Quality criteria.

S.No	Quality Criteria	Value
1	Target/Average length	5
2	Minimum Length	2
3	Maximum Length	7
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
10	Tria Percentage	15

PROCEDURE: -
Open the hood model.stp file. Go to File>Open.

We can now view the faces in gray and yellow. Gray color represents the positive side of th
faces while Yellow the negative one. The orientation is currently random. Activate the

Faces>Orient>Visible function.

• Check the geometry to identify the problematic areas. Click on the “Checks” button,
  located in the “Tools” toolbar on the top of the screen and select “Geometry”. Keep the
  default options and click Execute.
• 
  We will get different type of errors such as needle face, crack between cons, tripple cons
  and missing surface. In order to solve the tripple con release the triple con using the
  "Release" tool in cons. Then select the tripple con and do middle click. Use the Faces>Topo
  tool to combine the surfaces.
• 
  Depending on the type of the problem ansa also offers the option to automatically fix it.
  Select the problems from the check manager window and click right mouse button and
  choose fix from the list

after fixing the geometry cleanup

Now midsurface

• Now midsurface is extracted using the Skin option under Topo>Faces>Midsurface tool. As
  the thickness of the sheet metal component is constant throughout, Skin option will save u
  a lot of time.
• 
  The Macros>SET PID function can be used to assign multiple different PIDs to selected
  macro areas. Assign thickness of 0.75 to the INNER and OUTER Extract. Also, the thickness fo
  latch reinforcement and hinge reinforcement is 1.2.
• 
  Activate the Auxiliaries>Fine function found in the TOPO Menu. Left click a couple of times o
  the crosshatches of the faces in order to reduce the resolution length.
• 
  To eliminate the red cons between surfaces the Faces>Topo function can be used, select
  with a box selection the area and confirm with the middle mouse button.

1. Delete the hot points by Hot Points>Delete function and select with the left mouse button.
   Activating the “Slide” flag allows us to select nodes of a perimeter and slide them along it.
   This is useful in order to change the orientation of a hole.
2. 
   We will assign a uniform distance between perimeter Nodes or element length. Click the
   Perimeters>Length function. Select all the Macro Areas with the left mouse button making a
   box selection. Confirm with the middle mouse button. Type in a value of "5" in the length
   field and press Enter.
3. 
   Perimeter segment that is too short to have even one perimeter node. Activate the
   Mesh>Perimeters>Num+/- function. Use the left mouse button to increase the number of
   nodes and right mouse button to decrease the number.
4. 
   ANSA provides shell mesh quality check of the generated Geometry Mesh elements. Select
   the threshold value of each quality criterion and the criteria has to be active for each
   quality check. Similarly we have to set the meshing parameters. Set the target length as
   5mm, minimum element length as 2mm and maximum element length as 7mm.

S.No	Quality Criteria	Value
1	Target/Average length	5
2	Minimum Length	2
3	Maximum Length	7
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
10	Tria Percentage	15

Click the Mesh>Mesh Generation>Best function. Select with the left mouse button the
macros of the component and confirm with the middle mouse button.The Reconstruct
option means erase and mesh from new with the current algorithm and settings.

• Mesh improvement can be carried out using various tools. Split option can be found in
  Elements in Mesh deck. It can be used to eliminate the rotating quads and trias elements.
  Also, join option can be used to remove the edge and convert two side by side tria into
  quad element.
• 
  The function Elements>Swap can be used in order to swap a common edge of two
  elements. After that apply Mesh>Shell mesh>Smooth command to make the small
  adjustment needed to get the curvature for the entire mesh.
• 
  Also paste tool can be used to eliminate two opposite trias and coarser the mesh pattern.
  PASTE option can be found in GRIDS in the MESH deck

CONCLUSION: -
1. Performed the manual topology cleanup, midsurface extraction and 2-D meshing for all
the components of the hood, also asign thickness as per component.

2. Achieved the mentioned quality criteria for all the components of the hood.