Week 6-Meshing of Hood Challenge
Introduction:
The hood (North American English) or bonnet (Commonwealth English) is the hinged cover over the engine of motor vehicles. Hoods can open to allow access to the engine compartment, or trunk (boot in Commonwealth English) on rear-engine and some mid-engine vehicles) for maintenance and repair.
In recent years, the work has been done on the bumper and hood design of the vehicle front end to reduce the injuries to the pedestrians in the event of a pedestrian vehicle collision. The front portion of the vehicle gets damaged including bonnet when met with an accident. So there is need to change the existing design of bonnet or by changing the material. The bonnet is the hinged cover over the engine of motor vehicles that allows access to the engine compartment for maintenance and repair. Bonnet usually do not directly open onto the passenger cell which greatly reduces the importance (weighting) of certain of the functional requirements normally associated with closures such as air tightness, passenger safety, low cycle fatigue strength etc. The objective of these measures is to reduce the number of road accident fatalities and the severity of injuries sustained by pedestrians involved in a collision with a vehicle in urban traffic. Impact frequency and seriousness of injury has been studied for many years, resulting in rating systems and improved design. The bonnet system is an access panel to the engine compartment to enable maintenance of power train, drive belts, battery, fluid levels and lamp units. It is fundamentally a reinforced skin panel with many Safety and quality requirements.
Engine Hood:
The hood which is also known as ENCON, serves as an access panel to engine compartment of an Automobile. It is an assembly made of Outer and Inner panels to meet various safety and design requirements.
The followings are the design considerations involved in the design of Engine Hood.
- Pedestrian Safety
- Vehicle quality
- Occupant Safety
- Styling
- Manufacturability
Types of Hoods:
- Invalid Hood or Built IN
- Wrap Around Hood
- Hood With Fenders
- Hood with Border Diagonal Frames
- Hood with Brace Frames
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Meshing of Hood:
Here we will see the Meshing of different parts of Hood.
Hood consists four different components as below:
- Inner Extract
- Outer Extract
- Hinge Reinforcement Extract
- Latch Reinforcement Extract
As shown in above image, there are four different components.
In this paper, meshing of these four components is described one by one.
Quality Criteria:
Quality Criteria for the Meshing of all the components are given as below:
- Target Element Length : 5 Units
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Procedure:
Now we will see all the components one by one.
Inner Extract:
- There are four different components in the file when we import it.
- First of all make sure that only “Inner Extract” component is active.
- Delete all solids from the component.
- Create Mid surface for only Inner Extract by selecting particular surfaces.
- Since this component is axis symmetric, we can cut it in to half and mesh it.
- As shown in above image, only the marked portion is not symmetric.
- So we can mesh that at the last.
- As shown in above image, split the midsurface and keep half of that for meshing.
- Start the Meshing with the closed area with less free edges.
- And avoid washer surfaces if possible.
- Keep the Mesh flow as per geometry and create mesh with less tria elements.
- Complete the mesh of the hald portion of the Inner Extract as shown in above image.
- Now we can reflect the elements on the other side and complete the total mesh on the component.
- As shown in above image, elements are reflected on the other side.
- Make sure that elements are in proper connectivity.
- So, create equivalence between the elements which are in symmetric line and make them connected as shown in above image.
- Thus we can complete the Meshing process for “Inner Extract” component.
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Outer Extract:
- Here we can see the component is axis symmetric, so we can cut it into half.
- As shown in above image, the component is divided in to half.
- Create Midsurface after deleting solids from Outer Extract as shown in below image:
- As shown in above image, the hemming portion of the component is very thin.
- So, after creating midsurface, we can toggle the extra edges and split the component from the curvature area as shown in above image and easily create mesh without minimum length element.
- For easy and structured mesh, create rectangular portions by splitting the geometry with lines as shown in above image.
- Start with the curved or radius portion to avoid minimum length elements and step by step create mesh as shown in above image.
- We can further divide the curved portion marked in above image and create better quality elements in that region.
- Reflect the Mesh and create equivalence in the symmetry region.
- Thus we can complete the Mesh of “Outer Extract” component with better mesh flow.
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Latch Reinforcement Extract:
- Delete solids and create Mid surface for Latch Reinforcement Extract component.
- Do necessary cleanup and toggle extra edges.
- Remove edge fillets from marked portion for better mesh quality.
- As shown in above image, create washer surface with 5 mm distance and split the surface for better mesh structure.
- Keep the mesh flow as per geometry.
- Avoid tria elements at the free edges.
- As shown in above image, create mesh at the centre first and then proceed further for good mesh and complete the entire mesh for Latch Reinforcement extract.
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Hinge Reinforcement Extract:
- Here there are two components in Hinge Reinforcement Extract.
- If we create mesh only for one, we can reflect it on other.
- So, delete solids and create midsurface for only one part.
- As shown in above image, avoid creating washer surface for the holes for better mesh arrangement.
- Toggle the edges where minimum length element can occur.
- As shown in above image, mesh is created at the inner most area where less free edges are there.
- Then followed by them, rest of the part is meshed.
- As shown in above image, after creation of mesh on one part, with reflect option, mesh is reflected on the other part as well.
- Thus we can apply mesh on both the parts of Hinge Reinforcement Extract.
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Thickness:
- After meshing all the components, apply 2 units thickness to all.
- After applying thickness, complete Meshed Hood will look as shown in above image.
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Mesh Results:
Inner Extract:
- Tria % = 1.5
Outer Extract:
- Tria % = 0.07
Latch Reinforcement Extract:
- Tria % = 1.1
Hinge Reinforcement Extract:
- Tria % = 1.2
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Inference:
- First thing to do with any given model is geometry cleanup and removing or toggling extra edges or lines.
- For good meshing, we should always take care of necessary lines and edges by which we can create easy and structured mesh.
- If there is small gap between two fillets, we can toggle one of the edges and simplified the meshing area to avoid minimum or maximum length elements.
- Important thing in meshing is mesh flow, which should be followed by the given geometry.
- We should avoid as much tria elements as possible.
- There should not be any rotational quads, which can disorient the analysis process and we can get poor results.
- We cannot avoid tria elements at the rounded or curved portions, so the elements at that area should be taken care with different splitting the surface.
- Where the elements are of poor quality, we can mask them any separately work on them to be corrected.
- Make sure that tria elements do not break the flow of the mesh.
- Thus, we can create good mesh with good arrangements of tria and quad elements and with proper flow and remeshing techniques.
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Thanks & Regards,
Dharmesh Joshi