Tool Test 1
Tool Test 1 Challenge: SHELL (2D) MESHING OF tool test 1 Model USING ANSA PREPROCESSOR TOOL
Course: Preprocessor for Structural Analysis using ANSA
NOVEMBER 9, 2020
Submitted by: Amanpreet Singh Whan
Supervisor: David Nirmal Paul
Abstract
The switch panels are attached to the internal door panel of a motor vehicle. The Switch Panel geometry comprises one or more pushbuttons that can control the operations of other corresponding components in the vehicle being operated by electrical devices. The report presents a strategy that was adopted to mesh the Switch Panel Model and Sheet Metal Component using the ANSA Pre-Processor tool for the fulfillment of the Tool Test 1 Challenge task. The shell meshing is a three-step process that includes geometry clean-up, mid surface extraction and finally performing meshing using setting quality and mesh parameters. The max quads percentage for switch panel model and sheet metal component was found to be 95.19% and 93.83% respectively while the max trias percentage was found to be 4.81% and 6.17% respectively. Lastly, a total of 156 (5.07%) and 294 (2.78%) Off elements in switch panel model and sheet metal component respectively were also found in the regions where triple cons either intersect each other or are present very close to geometry construction lines.
Table of Contents
3.1 Import CAD Model and do Geometry Clean-Up.
List of Figures
Figure 1-Workflow overview of ANSA Pre Processor.
Figure 2- Imported Switch Panel CAD Model.
Figure 3- Topo performed the Switch Panel model.
Figure 4- Geometry check-up executed and its resulted errors.
Figure 5-Eliminating errors using the auto-fix option.
Figure 6-Error free given Switch Panel CAD model.
Figure 7- Imported given Sheet Metal Component.
Figure 8- Topo performed and oriented sheet metal component.
Figure 9-Geometry checkup executed and its resulted errors.
Figure 10-Eliminating errors using the auto-fix option.
Figure 11-Error free Sheet Metal Component.
Figure 12- Mid Surface extracted for the entire Switch Panel Model.
Figure 13-Rib features mid surfaces extracted using Middle commands.
Figure 14-Extracted Mid Surface versus Parent Geometry.
Figure 15- Assigned PIDs to Extracted Mid surface of Switch Panel.
Figure 16- Reduced Sheet Metal Component.
Figure 17- Extracted Mid Surface for Reduced Sheet Metal Component.
Figure 18- Extracted Mid surface versus Parent Sheet metal component.
Figure 19- Assigned PID to the extracted component's Mid Surface.
Figure 20-Mesh Parameters and Quality set as per challenge requirements.
Figure 21- Meshed Switch Panel extracted mid surface.
Figure 22- Meshed Switch panel Model PID view.
Figure 23- Regions where quality has failed in Switch Panel meshed mid surface.
Figure 24- Meshed mid surface of Sheet Metal Component.
Figure 25- Meshed Sheet Metal Component PID View.
Figure 26-Regions where quality has failed in Sheet Metal Component meshed mid surface.
Figure 27- Sheet Metal Meshed Component after fixing warpage errors.
Figure 28- Manipulated construction lines for the Switch Panel Mid surface.
Figure 29-Manipulated construction lines for Sheet metal Component Mid surface.
Figure 30- Switch Panel meshed model view before and after selecting “Draw shell as a solid”.
Figure 32- order of PIDs assigned to locators.
1 Introduction
The motor vehicle door constructions typically feature a metal door frame with inner and outer sheet metal panels (skins) being secured firmly to the door frame. The different components such as audio speakers, latches, and windows rails are fastened into the openings of the inner door panel. Likewise, the switch panels are attached to the internal panel of a motor vehicle door. The switch panel geometry comprises one or more pushbuttons that can control the operations of other corresponding components in the vehicle being operated by electrical devices. The aforesaid pushbuttons generally control the operations of those components of vehicles that are most frequently used by the driver, such as the raising and lowering of the glass door windows.
2 Aims
- Check and fix all the geometry errors of the given Model for Geometry Clean-up purposes.
- Extract/ Generate Middle Surface for all the components of the given model.
- Perform 2D or Shell Meshing of the components of the model as per given Mesh Quality Criterion to generate an overall good mesh flow for the entire model.
- Investigate and Improve the mesh quality wherever required.
3 Methodology and Results
The section describes the different stages that were performed using an engineering tool, ANSA Pre-Processor for the successful generation of an overall good mesh of the given models for the completion of the Tool Test 1 Challenge. These stages can be further broadly sub-categorised into three key steps, starting from importing of cad model to geometry clean-up for mid surface generation and finally carry out meshing of the extracted mid surface as per quality requirements.
ANSA Pre Processor is an advanced computer-aided engineering tool extensively used for FEA (Finite Element Analysis) and CFD (Computational Fluid Dynamics) analysis in the automotive and aerospace industry. ANSA pre-processor is a CAE software developed by BETA CAE Systems and follows a strict workflow when numerically solving a given problem. Figure 1 represents the workflow overview implemented in the software.
3.1 Import CAD Model and do Geometry Clean-Up
After opening the ANSA Pre-processor software, the first and the foremost step is to import the CAD geometry and perform topology using the topo command in the faces section of Topo Module Buttons for the entire model.
In the next step, go to the Checks Manager and select geometry from the options list. The main function of the Checks geometry is to locate geometrical issues such as unmeshed macros, unchecked faces, needle faces, collapsed cons, triple cons, and cracks. Even though most of these errors can be easily eliminated using the Auto-Fix command but issues concerning triple cons must be fixed manually by releasing Cons or Hot-points (nodes) and joining cons/ nodes back again using the topo command. Before executing the Checks geometry operation, make sure to turn on the most essential above stated geometry issues.
What follows hereafter is the set of images showing different results obtained before and after the completion of geometry clean-up for both the given models using ANSA Pre-Processor software.
Model 1- Switch Panel Geometry Clean-up Results
Model 2- Sheet Metal Component Geometry Clean-up Results
3.2 Mid Surface Extraction
The mid surface can be generated both manually and automatically. A manual mid surface can be obtained using Faces->Offset command in the Faces section of Topo module buttons. Moreover, the mid-surface generated using manual operation must be assigned a new PID which can be easily done using the Set PID command in the faces section. However, ANSA directly assigns a new PID to a Mid Surface that is extracted automatically, and it is usually accomplished using Mid Surface->Skin command in the faces section.
The results of the mid surfaces obtained manually (using the commands, Faces->offset, Faces->Middle and Curves-> Middle) for the different regions of the given CAD models are presented in the following pictures.
Model 1- Switch Panel Mid Surface Extraction Results
Model 2- Sheet Metal Component Mid Surface Extraction Results
3.3 Meshing
Meshing is a phase where the CAD geometry is discretised to represent the computational domain in which the solver will discover a solution. A refined mesh helps to achieve better results.
The meshing conducted for the given models is explained in the following steps:
- After the extraction of mid surfaces, the Perimeters length was set to 4 mm in the perimeters section of the Mesh module buttons. This will help to generate a mesh of constant element size.
- In the next step, the values of Quality Criteria and Mesh Parameters were entered as per challenge requirements to get a good flow of the mesh over the model. The values used for the quality criteria and mesh parameters are presented in the following tables.
Table 1-Quality criteria and its respective assigned values
|
Quality Criteria |
|
|
Criteria |
Value |
|
Aspect Ratio |
3 |
|
Skewness |
45 |
|
Warping |
15 |
|
Jacobian |
0.7 |
|
Min length |
2 |
|
Max length |
6 |
|
Min angle quads |
45 |
|
Max angle quads |
135 |
|
Min angle trias |
30 |
|
Max angle trias |
120 |
|
Tria Percentage |
15 |
Table 2- Mesh Parameters and its assigned values
|
Mesh Parameters |
|
|
Parameters |
Value |
|
Target length |
4 |
|
Minimum target length |
2 |
|
Maximum target length |
6 |
|
Distortion distance |
20% |
|
Distortion angle |
0 |
- A combination of the ‘Best’ and ‘Spot Mesh’ Mesh Generation algorithms was used to produce mesh for the models.
- Quality failing elements were eliminated using multiple approaches which include Reconstruction of mesh, smoothing of mesh, Moving & Pasting Grids, and Splitting, Swapping & Joining of elements.
The results of the meshed Switch Panel and Sheet Metal Component are presented in the following pictures.
Model 1- Switch Panel Mid Surface Meshing Results
Model 2- Sheet Metal Component Mid Surface Meshing Results
4 Discussion
ANSA Pre-Processor was used to mesh the Switch Panel and Sheet Metal Component as per asked Quality Criteria and Mesh Parameters to generate a good overall mesh flow for the successful completion of the Tool Test 1 Challenge. To fulfill the requirements of the challenge, Geometry clean-up along with Mid Surface extraction and Meshing was performed and the obtained results are presented in the figures shown above.
In figures 5 and 9, it can be seen that the provided CAD models had multiple errors such as needle faces, cracks, unchecked faces, and triple cons which were fixed using the automated fix option.
The given Switch Panel has multiple ribs with varying thicknesses and the mid extraction was not possible by simply using the Offset-> Faces command. Therefore, Curves-> Middle command was used to extract mid surfaces in the regions of varying thicknesses. In figures 13, the specific regions are designated where this command has been applied to extract the mid surface. However, the given Sheet Metal component has constant thickness throughout, and therefore mid was extracted using Faces-> offset command.
In figures 14 and 18, after switching from Entity to PID mode and by selecting the extracted mid surfaces and the parent bodies while keeping parent bodies in transparency mode and it was found that the mid surfaces extracted falls exactly in the middle of the parent components of geometry, concluding mid extractions performed for both the models were accurate and precise.
The construction lines were manipulated by a certain amount in some critical areas of the geometry where quality could possibly fall to generate an overall good flow of the mesh for the entire model. The following are the figures that represent the areas of both the given models where manipulation of the construction lines has been completed to generate a good mesh flow.
Figures 21 and 27 instruct a total of 156 and 264 quality failed elements are present in the meshed switch panel model and sheet metal component respectively. Moreover, 152 out of 156 elements have failed for minimum length quality for switch panel model while 255 out of 264 elements have failed for minimum length quality for sheet metal component. Figures 23 and 26 indicate that the quality has failed in the locations where triple cons intersect each other or are present very close to the construction lines. However, these errors cannot be eliminated and can be neglected.
5 Conclusion
In conclusion, the main aim of the challenge was to do a geometry clean-up of the Switch Panel and Sheet Metal Component, generate their mid surfaces, and perform 2D meshing. The max quads percentage for the switch panel model was found to be 95.19% while the max trias percentage was found to be 4.81%. The max quads percentage for sheet metal component was found to be 93.83% while the max trias percentage was found to be 6.17%. Moreover, 156 and 264 quality failed elements for the switch panel and sheet metal component respectively were found in the areas either where triple cons are very close to construction lines or in the areas where triple cons intersect each other. Lastly, the meshed model was assigned a thickness by enabling the ‘Draw shell as a solid’ command in the Quality Criteria- Presentation Parameters tab.
6 Learning Outcomes
Throughout this challenge, I have gained knowledge about different commands that are used to fix geometry errors and are used to generate the mid surface of any CAD Model with both auto and manual options. I have also learned that the Mesh Quality can be fixed using several operations like ‘mesh reconstruction’, ‘mesh smoothing,’ ‘grids move or paste’, and ‘elements split and join’.
- It took me approximately 9 hours to finish the Switch Panel CAD Model task.
- It took me approximately 4 hours to complete the Sheet metal Component task.
Appendix
- Here's the link to access the completed Tool Test 1 Challenge:
https://drive.google.com/file/d/1dyToJQIUCv_2KY1OEiM44ZsjmL3gLqrH/view?usp=sharing