Week 12:Project 2-Meshing of Rear Wheel Holder challenge

- Aim: Automobile rear wheel holder meshing.

- Objective:

- To extract the mid surface of sheet metal component.

- To mesh the mid surface and obtain proper mesh flow.

- Method:

- Rear-wheel holder is the part that is mostly situated in the trunk or boot space of the vehicle and is used to keep the extra wheel in case of any emergency or failure.

- For the given model the mid has been extracted and the mesh has been done as per the requirement.

- The mesh parameters are given in the challenge and the theory to understand these is mentioned below.

- Meshing:

- In order to mesh the component the criteria are given and it is necessary to mesh as per those criteria.

- A mesh is a network that is formed of cells and points. It can have almost any shape in any size and is used to solve Partial Differential Equations. Each cell of the mesh represents an individual solution of the equation which, when combined for the whole network, results in a solution for the entire mesh.

- Solving the entire object without dividing it into smaller pieces can be impossible because of the complexity that is within the object. Holes, corners and angles can make it extremely difficult for solvers to obtain a solution. Small cells, on the other hand, are comparably easy to solve and therefore the preferred strategy.

- The first step for numerically solving a set of partial differential equations (PDEs) is the discretization of the equations and the discretization of the problem domain. As mentioned earlier, solving the entire problem domain at once is impossible whereas solving multiple small pieces of the problem domain is perfectly fine. The equations discretization process is related to methods such as the Finite Difference Method, Finite Volume Method (FVM) and Finite Element Method, whose purpose is to make equations in continuous form and generate a system of algebraic difference equations. The domain discretization process generates a set of discrete cells and therefore points or nodes that cover the continuous problem domain.

- Meshing is an integral part of the engineering simulation process where complex geometries are divided into simple elements that can be used as discrete local approximations of the larger domain. The mesh influences the accuracy, convergence and speed of the simulation. Furthermore, since meshing typically consumes a significant portion of the time it takes to get simulation results, the better and more automated the meshing tools, the faster and more accurate the solution.

- Most physical phenomena can be solved using Partial Differential Equations (PDEs) but this is very difficult for most real-world problems. Any continuous object has infinite degrees of freedom (DOF) which makes it impossible to solve using hand calculations. So in FEM, we create a mesh that splits the domain into a discrete number of elements for which the solution can be calculated. The data is then interpolated across the whole domain.

- Mesh generation is the practice of creating a mesh, a subdivision of a continuous geometric space into discrete geometric and topological cells.

1. Aspect ratio:

- This computes the ratio of the longest edge of an element (single element) to the shortest edge of the same element.

- In most cases, it is preferable to have an aspect ratio of 3 or 5. Meaning a ratio of 5:1 such that the longest side of an element doesn't cross more than 5x times that of the smallest side of the same element. An aspect ratio of 1 seems to be the most ideal. However, it cannot be achieved at each and every element. 

2. Warpage:

- It is the amount by which a mesh element or the element face deviates from being planar.

- For example, in the case of a quad, it can be calculated by splitting up it into two tria by constructing a diagonal between two opposite sides and finding the angle between these two tria planes. This quality criterion pertains to only quad elements with an element of warpage of 0 indicates it being perfectly planar.

3. Skewness

- Skewness measures the angular deviation of the element from, as usual, being ideal. This parameter can be used to measure both tria and quad shell elements.

- For example, in a tria, it is calculated by finding the minimum angle between the vector from each node to the opposite mid-side AND another vector lying between two adjacent mid sides at each node of the element as shown below. Similarly, skew in quads are calculated by the angle formed between 2 lines joining the opposite mid-sides of a single element

4. Jacobian:

- This is a scale factor arising due to the transformation of the coordinate system i.e from the global coordinate to the local coordinate. It checks for deviation of the element from being perfect or ideal. It is calculated by mapping the element from its parametric coordinate onto its global coordinate.

- Steps and errors that occurred:

Original part to mesh.
As the part is sheet metal with uniform thickness auto mid can be performed however, there are still some errors that need to be removed.	Errors to be removed.
	As per the requirement, the mesh criteria are mentioned and uploaded.
part by part mesh has to be done. It is recommended to mesh from the inside as there are less free edges and it is a more complicated area.	Auto mesh was performed to see how the software captures it, however, for this model manual mesh has been performed.
Features are not getting captured properly by auto-mesh and mesh flow is also not proper.	Manual mesh has been done and step by step is done.
Free edges need to be removed which obstructs the flow of force.
	Complete mesh has been performed.
Smooth mesh flow has to be maintained.	Features must be properly captured and mesh flow must be proper.

- Learning outcomes:

- Manual meshing and how to maintain proper mesh flow.

- Errors removing and capture the features more properly.