Week 3 - 2D meshing for sheet metal

HOOD MODEL [ANSA]

AIM / OBJECTIVE:

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.

STEPS TO FOLLOW / PROCEDURES:

(Steps to follow in Short : Import Cad Geometry-->Geometry clean -up-->Skin/mid surface generation-->Shell meshing-->Element Quality checks)

In TOPO

1] Geometry checking

After downloading the drawing Geometry, go for a geometry check. Normally if cons are generated select all then clear it by Right click and fix. If not clearing tough fix manually. In this case after selecting all, go for right click and fix. All errors are cleaned and geometry is perfect. If not go for invidual checks and cleaning.

Single Cons(represented by red colour lines) - Edges which are shared with only one surface should be single cons.Single cons denote there is no connectivity between the surfaces in the model.

Double Cons(represented by yellow colour lines) -If any edge shared with two surfaces the that line is called Double Cons.

Triple Cons(represented by cyan colour lines) – if any edge is shared with three or more than three surfaces then that line is called triple cons.

Topology describes how elements are bounded and connected and Geometry describes the shape of each element.

2] Locking

The next part is locking the parent parts in order to take parent part alone.

3] Save

Save the settings from tools- settings and save the file

4] Orient

Apply orient on every mid surfaces, grey on top and yellow on bottom.

Go to module buttons-Faces-Orient-Select

5] Offset / mid surface skin method

Go to- Topo-Faces-Offset- then on the feature area- and make offset

Then separate it from parent part by i-not function.

Try not to delete parent part.

In this case i have choosed mid surface skin method to create offset.

Mid=surface- Skin- select the entire phase by window and give a middle click.

6] Measurements

Apply measurements on every surface and store.

[Cleanup the mid surface for the meshing. Edit the cons and faces using cut, project cut, release, paste, orient and topo options to clean up the geometry for meshing]

In Mesh- Classic Mesh

7] Applying Perimeters

Go to- classic mesh- perimeters- select all-apply perimeters as 5.

Perimeters are the dots b/w two points on mesh.

(Defeaturing- Is used to remove unnecessary surfaces radius, pin holes, edges. In short To neglect one criteria and doing adjustments in another.)

8] Measurement checkup

Check the measurements whether the surfaces are coming under our quality criteria, if not arrange the by using cut in macros.

9] Counting the numbers

Go to perimeter- number to count the numbers and make it into even.

10] Slide

To rotate the circles to an extend, or aligning the side of circle parrallel to the line of the perimeter.

11] Mark and unmarking hotpoint

Points around circles are Marked after checking numbers else if after reconstrution shape or numbers may vary

12] Quality Criteria

Apply the quality criteria given by 'F11 tool'

Si.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

12 Tria Percentage 15

Go to- presentation prameters- put tick in elements

Enable range- apply - okay

Then save the settings.

13] Mesh parameters

Go to-tools-utilities-mesh parameters

Type of mesh- general

Element Type- Mixed( Its amix of quad and tria)

Order of element- First order

Save the setting for future reference

14] Part ID

Create new properties and apply thickness

For using mesh we use 3 tabs mainly-1]Mesh Generation

-2]Shell Mesh

-3] Elements

15] Best mesh

Apply Best mesh to mesh the surfaces. Mesh the components individually. Instead of bestmesh we can also use free mesh.

[In the hemming region(in the Outer panel’s bend region), Elements will fail for the Min length error due to the very small surface to capture the curved surface. In order to solve this Min length error, go for ‘defeaturing’ the midsurface. ]

16] Regeneration

Map-regeneration to get split and straight lines

17] Symmetry

If the part is symmetry then delete the half faces part and do meshing and clean up in rest of the part and go for tranform copy - select region- symmetry.

18] Deleting hotpoints

By hotpoints- delete, for deleting unwanted nodes

19] Copy

Use transform copy – symmetry to copy the surfaces symmetry after meshing the half part

20] Split in elements

Used to delete unwanted trias and to generate a straight line by splitting the lines.

21] Swap

Used to delete unwanted trias and to generate a straight line or it is used to move the end line from one point to the other.

22] Reconstruct

If the mesh flow is not perfect go for reconstructing the mesh and rerunning them will make perfect.

23] Smooth

If the mesh flow is not perfect and after split usage and lines are not keeping uniform distance go for smooth function in the mesh to make perfect line mesh.

24] Improve

Uses both smooth and reconstruction at same time.

25] Property ID

Create property id to assign thickness to the elements.

26] Join

Macros - Join to keep lines in mesh what we have drawn

27] Draw shell as solid

To find the mesh into solids by assigning thickness. Founds in Quality criteria - Presentation parameters

28] Release

Elements- Release to release all the drawings from geometry.

29] Save the file

LEARNING OUTCOMES

• The mesh should always look regular and proper.
• No two opposite trias came back to back, if came go for smooth option.
• For long distance splitting, map- regenerate function can be used.
• By swap, tria's side can be moved or removed if unnecessary.

• The edges in ANSA are called cons and single cons are highlighted in red color, double in yellow color and triple in blue color. Double edge is shared by two surfaces and triple by three. Single cons are open edges.

• Aspect ratio is the ratio of maximum length to the minimum length
• What are Jacobian elements? Ans: In a FEW software jacobian is a measure of deviation of a given element from an ideally shaped elements.
• Skewness is the Angular Measure of Element quality with respect to the Angles of Ideal Element Types.
• Maximum Angle out of the two possibilities is reported as "Warp Angle".

• If the part is symmetry then delete the half faces part and do meshing and clean up in rest of the part and go for tranform copy - select region- symmetry.

CONCLUSION

The mesh was created on all the mid surfaces created from parent geometry.

The quality criteria was satisfied for the given quality parameters.

Thickness is assigned on the mesh as per the thickness of the given geometry..