Week 3

Week:3 PRE-PROCESSING OF CAR HOOD GEOMETRY ON ANSA

AIM: To perform pre-processing structural analysis on a car hood by obtaining mid surface and 2D mesh with specified quality criteria on ANSA

ABSTRACT: A car hood or a car bonnet is the part that covers the engine of the automobile. It is derived from the old English word 'hod' which means head. Its function is to protect and access the main engine, battery, and other crucial parts for repair and maintenance. The hood gives a luxury look to the car model. so it is very important to optimize the aerodynamic design as well as stiffness to minimize the air drag and flow over the bonnet. So in this challenge, we are going to perform the first in CAE i.e, Pre-processing of car hod geometry on ANSA

SPECIFIED QUALITY CRITERIA:

S.No	Quality Criteria	Value
1	Target/Average length	5
2	Minimum Length	3
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

METHODOLOGY:

• Import the geometry
• Topological error clean up
• Setting up PID
• Mid surface extraction
• Quality criteria setup
• Meshing and Mesh improvement

INTRODUCTION:

CAR HOOD: The hood or the bonnet is the hinged cover over the engine of the motor vehicle that allows access to the engine compartment or trunk on rear-engine and some mid-engine vehicles for maintenance and repair. The car bonnet consists of usually two major parts i.e, an inner bonnet and outer bonnet. The inner bonnet is critical for providing the structural strength, while the outer bonnet is for providing a homogenous style and maintain aerodynamic for the vehicle body. the outer body is not as important for strength as the inner body but it has a vital function in the case of pedestrian safety, being the first surface of contact with pedestrians.

THE GEOMETRY PARTS

• Outer panel
• Inner panel
• Latch reinforcement
• Right hinge
• Left hinge

PROCEDURE:

STEP:1 IMPORT GEOMETRY

• FIRST OPEN ANSA IN THE COMPUTER
• The CAD or CFD design is imported to ANSA for the pre-processing for structural analysis
• The imported design will have some errors which are needed to be checked

Image 1: Import Geometry

STEP:2 GEOMETRY CLEANUP

• With the help of the tool called 'CHECKS', the Topological errors spotted in the imported Model can be fixed.

Image 2: Errors in the model

Image 3: Errors fixed

STEP 3: SETTING UP PROPERTIES FOR THE MODEL

Before setting up the PID we have to change the Orientation in the ENT MODE

• GREY represents Positive Orientation and YELLOW represents Negative Orientation
• NOW, set up PROPERTIES for the model in LIST>PROPERTIES
• After going to PROPERTIES,click the right button on the mouse and select NEw tocreate a nwe PID and Apply the model to the PID

Image 4: Setting PID for the car hood

STEP 4: MID SURFACE EXTRACTION

Before we discuss the mid surface extraction we should know about 2D ELEMENTS

2D ELEMENTS: When two of the dimensions are very large in composition to the third one. 2 dimensions out of 3 are known by creating a 2D element and 3-dimensional data is provided by the user as the additional input data

There are two way to extract the mid surface

1. The manual mid surface method
2. The auto mid surface method

Manual MID SURFACING extraction:

This can be manually done by selecting the surface and giving OFFSET command

1. Measure the thickness(0.75)and give half as the thickness(0.75/2) for offset in the opposite direction of the arrow (-o.75/2)

Image 5: Midsurfacing of hood by OFFSET command

Image 6: Measure the thickness of upper and lower hood

Image 7: Offset of upper and lower hood by the direction of the arrow

• Repeat the same procedure of the lower hood
• Therefore, the mid suraceis genarated for both the surface

Image 8:Midsurface of upper hood

Image 9:Midsurface of lower hood

• Be sure in checking the mid surface is correct or not
• now set up new PID for both the mid surface generated

Image 11: Setting PID for upper and lower hood midsurfaces

STEP 5: GEOMETRY CLEANUP

• Geometry cleanu is the process where the unwanted cons and hot points are removied from the model
• By using the CUT button in the FACES option remove the unwanted geometry and add the required geometry for achieving good result during meshing

" Geometry clean up on UPPER HOOD and LOWER HOOD"

Image 12: Geometry clean up on upper hood and lower hood

STEP 6: QUALITY CRITERIA SETUP

• The quality criteria are given by the user according to the requirements to achieve a good result while meshing

shortcut key for quality criteria window is F11

Image 13: Setting up the quality criteria

MESH PARAMETERS

After the Quality criteria are assigned the MESH PARAMETERS are Assigned

• Target length
• minimum and maximum length, etc

Image 14: setting up the mesh parameters

STEP 7: MESHING AND MESH IMPROVEMENT

MESHING AND MESH IMPROVEMENT

Change the mode from TOPO to MESH

• Before starting meshing we need to set the element length, to do so we have to click the LENGTH button under the PARAMETERS section. after clicking a window is popped up with two options parameters and macros set the targeted length for both by selecting the model.

• After this, by using the BEST button start meshing the model and by PASTE, SPLIT, SWAP, SMOOTH AND RECONSTRUCT improve the mesh quality

Image15(a),15(b): Meshing of upper hood and lowe hood by using BEST command

• After the mesh is genarated by using the best option, we need to improve the mesh bu using commants like PASTE, SPLIT,SWAP ,RECONSTRUCT ans SMOOTH.
• And finally the final mesh result is obtained

FINAL MESHING RESULT:

• Final mesh result of the upper hood and lower hood are obtaine as follows

Image16 : Final mesh result of both the hoods

• All the parts have been meshed as per the quality criteria requirements and are having good mesh flow
• after the meshing we need to assigne the thickness for the model

Image 17: Assigning thicking to the model

RESULT:

Image 16: Final model after meshing and assigning the thickness

LEARNING OUTCOMES:

1. Able to fix topological errors
2. Able to generate mid surface for any complex geometry
3. Quads and Tria importance
4. Basic knowledge of 2D elements and shell meshing
5. Aware of the quality parameters and there meaning during mesh generation
6. Able to understand and execute good practices of meshing any complex geometry
7. Capable in 2D meshing even for complex geometry by achieving better mesh flow

CONCLUSION:

From this challenge, we have achieved the knowledge of meshing any complex geometry models or component in ANSA by following a sequence of operations and methodology. First importing the geometry and checking and fixing the geometry errors, then setting up the PID for the model, Achieving the mid surface of the model, and then doing the geometry clean up. After this, by using the required quality criteria the model is fixed with certain targeted length and then meshed. The component is then meshed and improved by meshing tools. Finally, the model is meshed with a smooth flow of mesh.

GOOGLE DRIVE LINK:

https://drive.google.com/file/d/1IBXML55MJhH_TmSEwNkIZzFGUWhsrBYs/view?usp=sharing