Week 12 - Project-1

AIM:

1. To check for the geometrical errors for the given component.
2. To extract all the mid surfaces of the given component with a suitable method.
3. To mesh all components in the model with the given element Quality criteria.

OBJECTIVE:

• To write a detailed report on the meshing process and also mention which method we used to extract the mid-surface.

QUALITY CRITERIA:

Target Element Length = 4mm

S.N	Quality Criteria	Value
1	Aspect Ratio	5
2	Skewness	45
3	Warping	15
4	Taper	0.5
5	Min. Length	2mm
6	Max. Length	6mm
7	Min angle Quad	45
8	Max angle Quad	135
9	Min angle Tria	20
10	Max angle Tria	120
10	Tria %	10

1. Target element length:

It is the size of the element by which we can get the most nearer approximate value of the result compared to the experimental result.

2. Minimum element length:

The minimum element length is given by the instructor for the reason of quality criteria to avoid the presence of any zero-length element. It is very important to check for crash analysis.

3. Aspect ratio:

The aspect ratio is defined as the ratio of max element edge length to the minimum element edge length. The ideal value for aspect ratio is 1 but less than 5 is acceptable.

4. Wrap angle:

Wrap angle is defined as the angle between normal of the two planes by splitting the quad elements along the diagonal. Therefore the maximum angle allowed between the two possibilities is called the wrap angle. The ideal value is 0 degree but less than 10 degree is acceptable for good practices.

The wrap is not applicable in the triangular element.

5. Skewness:

If the quad element is not square and has deformation then the skewness defined as the minimum angle between the two lines joining the opposite mid sides of the element similarly for the triangular element it is 90 minus between the line from each node to the opposing mid-side. The ideal value is 0 but less than 45 degree is acceptable

PROCEDURE:

IMPORTING THE MODEL:

• First, we want to import the model by selecting open>model>select the file Side door edited. hm and click the open option to get the model in the graphical area the selection process is shown below,

Fig: Import selection

Fig: Import model

• After importing the file, an open model will appear in the graphical area and its components are shown in the model view. The open model of a side door is shown as below,

Fig: Open model

• Then delete the solid surface in that model by selecting Delete>select the surface and click delete entity this will delete the solids in that component but here there are no solids present in this model so we directly proceed with the component for the mid surface. The open model by topo mode is shown below,

Fig: Side Door model

• Now create a mid surface for this model by selecting the Geom>mid surface and select the extraction option as skin offset. Here we using the skin offset in the extraction option because the skin offset will give a better mid surface in the region of a fillet, hence the selection process is shown below,

Fig: Extraction option

• After selecting the extraction options click the auto extraction and select the model with surface and click extract to obtain the mid surface for that model. The mid surface selection process is shown below,

Fig: Midsurface option

• In this model, we get only the mid surface for outer body of side door through auto mid surface method so want to take mid surface for other parts in the side door by a manual method using offset option. Here the outer body mid surface for side door model is obtained by auto mid option is shown as below,

Fig: Extracted sruface

• Now take mid surface for ribs individually because each ribs having varying thickness so we want to measure the thickness of rib by using Geom>distance option or press F4 to open distance option then select the two points and measure the rib. For example, we are taking one rib and measuring the distance as 2mm that is shown as below,

Fig: Distance option

• After measuring the distance of that rib take the mid surface for that rib by a manual method using Offset option. By selecting surface edit>offset> and enter the offset value as 1mm because the total distance of rib is 2mm and there is no distance variation along the rib so we consider the distance of rib as 2mm and to take mid surface we taking the offset value as 1mm. That is stated below,

Fig: Offset option

• To obtain the mid surface separately from the parent geometry we selecting offset>right click surfs tab and click duplicate option. After selecting the duplicate option it will show a tab with the options of the original component, and current component selects the current compo portion to get the duplicate surface of that selected component. This will helps to get the mid surface of the rib separately and the selection process is shown as below,

Fig: Offset option

• Finally, select the direction of the mid surface by using vector normal and reverse normal options and click offset to obtain the mid surface of a rib. The mid surface of the rib is shown as below,

Fig: Rib mid surface

Fig: Connected rib

Fig: Mid surface

• Hence by using different methods like auto mid and manual mid methods we obtain the mid surface for the total body of the side door including ribs. The mid surface of the ribs are taken by manual method because of various thickness are occurred in the parent geometry. The mid surface for the side door model is shown as below,

Fig: Side door mid suface

GEOMETRY CLEAN UP:

• Now we want to clean up the geometry in the mid-surface component because of the meshing process. While we doing the meshing operation the quality criteria may be affected due to the unwanted lines in the mid surface that line may below the value of minimum element size so that we are toggling that line to obtain a good mesh flow. The quality will be cleared when we toggling the line.
• Splitting is the method to get the good mesh flow in the non-planner region and other shape regions like a circle, hexagonal and oval, etc. here we splitting the region into two surfaces to get the good mesh flow by selecting the spilt surf node option and select the node or line to split in that region.

Fig: Geometry cleanup

• A toggle option is also used to toggle the line while the clean up in geometry. The lines can arrange with the own ideology that may not affect any mesh and geometry in that model. Toggle the irregular shaped line and create the new lines in the regular shape and that will keep the mesh as good flow.

Fig: Toggle option

Fig: Before geometry cleanup

Fig: After geometry cleanup

Fig: After geometry cleanup

Meshing:

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.

• Now create the mesh for a Side_door model of different components one by one by selecting 2D>automesh>enter element size as 4mm and select the surface to create mesh on that surface. Before that we want to initiate the quality criteria values in the criteria file setting that value will appear in the quality index and shows the element below or above the quality value.
• By selecting the preference >file criteria setting> and enter the quality criteria values that are given by an instructor. The quality criteria values are shown below,

Fig: Criteria editor

• To create the mesh for a side door component by selecting 2D>automesh>enter element size as 4mm and select the surface to create mesh on that mid surface of the component.

Fig: Mesh option

• To move the opposite trias by using drag option in cleanup tools, opposite trias is not allowed during the meshing process, split and swap option also used to move the trias forward and backward direction.
• The trias should be removed by drag option in cleanup tools the rebuild option is used to rearrange the mesh that may be used only for a certain area to get a good flow of mesh. The smooth option in 2D is also used to smooth the mesh and arrange it in a proper manner.

Fig: Meshed model

• Check the connectivity of the mesh by selecting tool>edges>select the entire component to verify the connectivity of that mesh and click the find edges option now the free edges and non-connected areas should be shown we can rectify that by giving the tolerance of connectivity as 1mm and select the component again to connect the mesh flow click preview equivalence>equivalence now the mesh will be connected.
• The connectivity also may be done manually using the replace option.

Fig: Replace option

• The connectivity of edges are checked and that is shown as below,

Fig: Find edges option

• The trias will be eliminated by clean up tools in the quality index. The tools are place node, smooth, drag trias, node optimizes, element optimize, split quad element, and combine trias element, etc. These options are used to remove, drag, combine the trais, and also used to clear the quality criteria.
• A trias can be reduced by different options mentioned above here the tria percentage can be reduced from 1.9% to 1.1% by using the tools of cleanup tools. They are shown as below,

Fig: Actual trias percentage

Fig: Reduced tria percentage

• Therefore the mid surface is created for the side door component and mesh also generated for that component hence their properties are shown below,

Fig: Components table

• The meshing process for the side door component has done and finally, the thickness is assigned as per the parent geometry.

Fig: Properties

• If we want to view it in the 2D representation then we have to provide the thickness value in the section card that is shown below,

Fig: Thickness Assigned

• The number of element failed for the quality criteria is 0 this shows that there is no element failure has occurred under the quality criteria and 0% element failure is obtained through our mesh they are shown below,

Fig: Element Quality

CONCLUSION:

Therefore we meshed all the components in the side door model with individual mid-surface and the quality obtained with failure of elements. The trias percentage we obtained in the overall model is 1.1% and it is below the quality criteria value.