Week 3 - 2D meshing for sheet metal
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 fixing. If not clearing tough fix manually. In this case after selecting all, go for right-click and fix. All errors are cleaned and the geometry is perfect. If not go for individual checks and cleaning.
Single Cons(represented by red color lines) - Edges that 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 color lines) -If any edge is shared with two surfaces that line is called Double Cons.
Triple Cons(represented by cyan color 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 the parent part alone.
3] Save
Save the settings from tools- settings and save the file
4] Orient
Apply orient on every mid surface, 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 an offset
Then separate it from the parent part by the i-not function.
Try not to delete the parent part.
In this case, I have choose mid surface skin method to create an offset.
Mid=surface- Skin- select the entire phrase by the 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 Hotpoint- delete, for deleting unwanted nodes
19] Copy
Use transform copy–symmetry to copy the symmetry of the surface 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 it perfect.
23] Smooth
If the mesh flow is not perfect and after split usage and lines are not keeping a uniform distance go for smooth function in the mesh to make perfect line mesh.
24] Improve
Uses both smooth and reconstruction at the same time.
25] Property ID
Create a property id to assign thickness to the elements.
26] Join
Macros - Join to keep lines in mesh with what we have drawn
27] Draw the 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…