Week 3 - 2D meshing for sheet metal

                                        2D MESHING FOR SHEET METAL COMPONENT

AIM :-   Preparation of car hood model for finite element analysis which include geometry cleanup and mid surface generation and meshing under quality criteria

S.No   Quality Criteria                Value 

1        Target/Average length      5

2        Minimum Length              2

3        Maximum Length             7

4        Aspect  ratio                    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

PREPROCESSOR :-     ANSA

PROCEDURE : - 

Generally In automotive industry there are many components which have thickness upto or less than 5 mm Such type of component can be treated as planer(2D) component.These type of planar component  can be specified in two ways one having Uniform thickness and other having varying thickness.

Uniform thickness component called as sheet metal component and varying thickness component called as plastic component. 2D simulation is preferred to reduce the lead time and cost instead of 3D simulation.

To perform 2D simulation there are number of stages which are defined below

1. geometry cleanup
2. Mid surface generation
3. Midsurface cleanup
4. Shell meshing

         FIG:- HOOD INNER VIEW

         FIG:- HOOD FRONT VIEW

GEOMETRY CLEANUP

Geometry cleanup is a process in which irregularities In the form of needle shaped crack missing surfaces present in the geometry are fixed. After importing the model in ansa  geometry Command inside the check manager is used to check geometry if there is any irregularity in geometry then we can fix it using auto fix or manually.

MIDSURFACE GENERATION

Mid surface generation is the most important step after geometry cleanup. Mid surface generation is the process in which the middle surface is extracted from the parent geometry to perform structural analysis. In ANSA there are multiple ways to generate mid surface In the Hood model offset command is used to generate mid surface Red line shown here in the image is the midsurface of the model in wireframe mode

            FIG :- model after mid surface generation

MID SURFACE CLEANUP

After mid surface generation there are preparations required to generate proper mesh elements as per quality requirement. This step consists of unwanted cuts removal and  cuts to the geometry for getting better mesh flow

                                                FIG:- cut on geometry to achieve better mesh flow

MESHING

Meshing is a method In which geometry is discretized to generate finite elements Which capture Geometric feature.All elements are connected together with the help of nodes.Structural analysis element should be Quad but in complicated features it is impossible so tria element is allowed. Generally the percentage of tria elements should be less than 15%.In ANSA there are different algorithms to mesh but fastest way to generate mesh is appy the best command first then reconstruct and smooth and if required then use split and paste command to reduce or remove tria concentration.

    FIG:- complete meshing of hood with stisfying quality criteria

CONCLUSION :- 

i successfully acheived the mesh uder defined quality criteria. during the completion of this challenge i understood how to start with new model and steps of preprocessing and how to simplify the geometry whenever some feature is not neccessary to analysis and i learned different meshing techniques like spot mesh map mesh to generate better mesh flow