Project 2-Meshing of Rear Wheel Holder [Stepney Spare Wheel Floor Panel]

[Note: Only free edges (red) are valid, and they convert to shared edges (green) after creating the filler surface.]

 

Figure 26-Quick Edit Panel [Filler Surface].

 

 

Figure 27-Bigger Gap.

 

Figure 28-No Free Edges in the parent component.

 

• Switch to tha visualization tab and uncheck all the boxes except free edge one and check whether the free edges exsist in the parent component or not.

 

Figure 29-No free edges.

 

 Phase 4 - Extracting Mid Surface

• The midsurface has been extracted to the components which have less than 6mm thickness.
• We will be extracting midsurface for the sheetmetal and plastic components.

4:1 Why to Extract Mid Surface ?

• Before extracting the mid surface for every component,We should measure the thickness of the component and then we have to proceed to extract the mid surface.If the component thickness is less than 6mm then we will come to know it is a sheet metal component or plastic Component.
• For sheet metal and plastic components,Mid Surface extraction is must.

 

4:2 Midsurfacing: Process & Strategy-

1.Obtain a closed volume of surfaces or solids

• Midsurface : Auto midsurface requires an enclosed volume.
• Use topology repair techniques if needed.
  

2. For complex parts, try defeaturing the surface defining the volume

• This simplifies the part and may give better results with create solid.
  

3. Generate the midsurface using midsurface : auto midsurface

• Use surface pair for areas that need more control.
• Use midsurface : editing tools for midsurfaces that need fine tuning.
  

4. View the midsurface and correct errors using the midsurface editing functionalities

• Can generally use quick edit.

 

4:3 Extract the Mid Surface

• For this component,I'm using auto mid surface extraction.
• Auto Midsurface is used to to extract the midsurface of a more complicated group of surfaces that represent a solid part in one step.
• I'm extracting midsurface by Offset + Planes + Sweeps,Because this component has many features and sweeps.
• Offset + planes + sweeps-It is used to identify the places where a piece of plane or a piece of a sweep surface can be used as a middle surface. A middle surface is constructed at the remaining places in the model, for example the places where planar or sweep surface pieces cannot be used as a middle surface, by the same algorithm as in offset via the offset of the model's sides.
• Geom >> Mid surface >> Auto Midsurface >> Extraction process (Offset + Planes + Sweeps) >> Auto Extraction (Closed Volume) >> Surfaces (Displayed) >> Extract.

 

Figure 30-Mid Surface Panel.

 

 

Figure 31-Extraction Options.

 

• The mid surface created will be assigned to a new collector called Middle Surface.

 

Figure 31-Extracted Mid Surface.

 

4:4 Check for the Duplicate Surfaces

• Sometimes,The duplicates surfaces may occur while extracting the mid surface.
• So check for the duplicates,Give a Clean UP Tolerance value as 0.1 and check.
• Geom >> defeature >> Duplicates >> Surfaces (Displayed) >> Cleanup Tol = 0.1 >> Find >> Delete.

 

Figure 32-Defeature Sub-Panel.

 

[Note:Give the Clean Up Tolerance value based on the thickness of the component.The thickness of stepney floor panel is 0.75.The tolerance value should be less than half of the thickness of the component.]

 

Figure 33-No Duplicated Surfaces Were Found.

 

Phase 5-Geometric Clean Up on the Mid Surface

• Do a geometric clean up on the mid surface extracted.
• Check for the free edges in the middle region of mid surface.
• If there are any free edges,Toggle them and eliminate that free edges.

 

5:1 Filling Gaps on the Surfaces which or not filled

 

• We need to fill the gaps (Free Edges) to get a connectivity while meshing.
• If we won't fill the gaps,There will be no connectivity while meshing.
• If we do analysis without filling that gaps,Forces won't be distributed in that regions,So fill the gaps and equivalence them.
• We can fill the surfaces by using following tools called

1. Filler Surface
2. Ruled Surface
3. Spline
4. Skin

i) Filler Surface -

• This tool is used to fill the gaps which are bigger.
• Use the line(s) selector to select a closed-loop line (a hole) in your model to create a surface that fills the hole.

 iii) Spline

• We can use the Spline/Filler tool  to create surfaces by filling in gaps, such as a hole in an existing surface.
• Select the lines, node list, or points that define the spline/filler area.
• Lines-Select two or more lines. The lines do not have to form a closed loop, as disconnected lines are first connected with straight lines. Both free lines and surface edges can be selected.
• Go to Geometry >> Surfaces >> Spline/Filler >> Select Lines.

 

Figure 40-Spline Sub-Panel.

 

Figure 41-Unfilled Gap.

 

Figure 42-Gap Filled With Spline Tool.

 

iv) Skin

• The skin tool is used to create a surface by skinning across lines.
• At least two input lines are required. Three or more input lines will fit a surface across all of the input lines, with the first and the last input lines defining the surface ends.
• Line List-Select the lines to use as input. The lines used to create the skin surface are automatically smoothed before the surface is created. As a result, the surface is created with a single face.
• Go to Geometry >> Surfaces >> Skin >> Line List >> Select Lines (Skinning across lines) >> Create.

 

Figure 43-Skin Sub-Panel.

 

Figure 44-Lines selected to fill gap.

 

Figure 45-Gap filled using skin tool.

 

5:2 Fixing Deformed Surfaces

• Due to complexity of the features,The software was unable to extract a good mid surface.
• There are some surfaces overlapping and there is no connectivity ,So fix this manually.Do a manual geometric clean up.

 

Figure 46-Delete the deformed surface.

 

Figure 47-Offset the surface.

 

• Now switch on the parent component and take offset manually for the slot region.Select the surfaces and offset it.
• While making offsett,make the mid surface as current component and then offset.
• The manual offset can accessed by the surface edit panel.

 

Figure 48-Surface Edit Panel.

 

• Before making offset check for the Vector normal.
• The arrows will be pointing towards the direction of the offset.
• If the arrow points are facing outward,give for reverse normal to make the arrows point inward.
• Vector Normal [If outward] >> Reverse Normal
• Another option to check for direction is to check for Color Normal:
• Blue indicates towards the screen or inward.
• Red indicates away from the screen or outward.
• If it shows Red, give for reverse normal and it should show blue.
• Color Normal [If Red] >> Reverse Normal
• Color Normal [If Blue] >> Offset
• Once everything is ok,Give offset.

 

 

 

 

 

 

 

 

 

Figure 49-Points projected to the bottom free edge.

 

• Here projrcted the points to the bottom free edge to split the surface.
• Go to Geometry >> Quick Edit [F11] >> Project Points >> Select Point >> Select line to project.
• Project Points is used to control to move free points to existing surfaces or lines. Choose whether this happens singly or as a chain of actions.
• Move the selected point(s) to the selected line.
• Perform additional projections by selecting a new set of points and a new line.

 

Figure 50-Quick Edit Panel.

 

• Now replace the edges to get equivalence.
• Use Replace tool to replace.

Replace Tool -

• Go to Geometry >> Edge Edit >> Replace >> Select Moved Edge which we want to move >> Select Retaned Edge which we want to be reatined >> Clean Up tolerance as 1 or 2 >> Replace.
• It is used to move one edge line to the same edge as another, effectively combining the two edges into a shared edge at the location of one of the original edges.
• This functionality provides additional control over the toggle function. Individual selections are made for the line to move and the line to retain. The resulting shared edge will be at the location of the line selected as retained.
• The cleanup tolerance setting in this panel defines the maximum distance between the selected lines.
• Select the edge line to move the other lines to.

 

Figure 51-Replace Sub-Panel.

 

Figure 52-Replaced Edge.

 

Figure 53-Slot region has been given offset properly without any errors.

 

Figure 54-Free Edges in the Pin Holes.

 

• Clear the free edges shown in the above fig 54,using filler surface,delete surface,toggling. 
• Use these three tools to clear that free edges.

 

Figure 55-Free Edges have been Cleared.

 

 5:3 Delete Small Holes

• Delete the small pin holes because we can't capture the feature there.
• So delete that samll pin holes,After deleting that fill that holes with the filler surface.
• Delete tool is  used to delete data from a model database, preview and delete empty collectors, and preview and delete unused property collectors, material collectors, or curves.
• You can also delete an entire model database, if you wish to start with a clean database.
• Go to Tool >> Delete [F2] >> Surfaces >> Delete Entity.

 

Figure 56-Delete Panel.

 

 

Figure 57-Small Pin Holes.

 

 

Figure 58-Pin Hole Surfaces have been Deleted.

 

• Now fill that holes with filler surface tool from quick edit panel.

 

 

Figure 59-Holes Filled with Filler Surface Tool.

 

 5:4 Toggle the edges which are failing for minimum length

• Toggle the edges which are failing for minimum length.

 

Figure 60-Toggled the line which was failing for min length.

 

Figure 61-Toggled unnecessary edges on the pin holes.

 

 

Figure 62-Detailed Representation View 1.

 

 

Figure 63-Detailed Representation View 2.

 

 

Figure 64-No Free Edges in Mid Region View 1.

 

 

Figure 65-No Free Edges in Mid Region View 2.

 

 Phase 6 - Perform Mesh on the Surfaces

 

• Once geometry cleanup is completed (e.g. surfaces are stitched together — no unwanted free surface edges inside the geometry), meshing is next.

Some rules of thumb when meshing:

• The mesh should look rather smooth and regular (keep in mind that the analysis is based on your mesh and the mesh quality is key.
• Use the simplest element type suited for the problem.
• Start with a coarse mesh and understand the modeling results; then use a finer mesh if needed.
• Try to keep mesh related uncertainties to a minimum if possible. Keep it simple as it can get more complicated on its own.

 

 

Figure 66-2D Element Shapes.

 

• Different Element Type Options for Shell Meshing:

 

 

Figure 67-Element Types.

 

6:1 Enter the quality criteria what they given for the component

• Tool bar → preferences → criteria file settings → checks for the element criteria →Enter values → apply → ok.
• Before generating a mesh on the surfaces.Enter the quality criteria given tou us in the question.
• You can go and enter quality criteria in Tool bar → preferences → criteria file settings → checks for the element criteria →Enter values → apply → ok.

 

Figure 68-Tool Bar Panel.

 

 

Figure 69-Criteria File Settings.

 

[Note : Save the criteria file settings for that component and save it any other drives,Cause whenever we open that component,we can open the element criteria file and criteria will be applied habitually instead of entering again.]

 

Target Element Size - 5 Units

Sl. No.	Quality Criteria	Function / Definition	Value
1	Aspect Ratio Ratio	Ratio of Max. Length by Min. Length	5
2	Skewness	Deviation from the ideal shape	45
3	Warping	Angle between the 2 planes of the same element(Quad)	15
4	Taper	Convergence of a Quad element	0.5
5	Min. Length	Shortest length of any given element	2
6	Max. Length	Longest length of any given element	8
7	Min angle Quad	Minimum angle in any given Quad element	45
8	Max angle Quad	Maximum angle in any given Quad element	135
9	Min angle Tria	Minimum angle in any given Tria element	20
10	Max angle Tria	Maximum angle in any given Tria element	120
11	Tria %	Percentage of Tria on any meshed surface	10

 

1) Aspect Ratio

• This is the ratio of the longest edge of an element to either its shortest edge or the shortest distance from a corner node to the
  opposing edge ("height to closest node").

 

Figure 70-Aspect Ratio Calculation.

 

2) Skewness

• Skew of triangular elements is calculated by finding the minimum angle between the vector from each node to the opposing
  mid-side, and the vector between the two adjacent mid-sides at each node of the element. 
• For Skewness: Ideal=0,But < 45 is acceptable.

 

 

Figure 71-Skew Angle.

 

3) Warping

• This is the amount by which an element (or in the case of solid elements, an element face) deviates from being planar. Since
  three points define a plane, this check only applies to quads. The quad is divided into two trias along its diagonal, and the angle
  between the trias’ normals is measured.

Figure 72-Warp Angle.

 

4) Taper

• Taper ratio for the quadrilateral element is defined by first finding the area of the triangle formed at each corner grid point.These
  areas are then compared to one half of the area of the quadrilateral.                                          

 

 

Figure 73-Taper Angle.

 

5) Minimum and Maximum Length

• The shortest distance from a corner node to its opposing edge (or face, in the case of tetra elements) referred to as height to
  closest node. 

 

6:2 Conditions to be followed while meshing

• Feature Capturing
  

• Feature capturing is must while meshing.All the nodes must be connected to the shared edges.

• Tria Management
  

• Avoig higher number of trias.
  
  

• Important Parameter's in tria management
  

1. No trias in corner's or edge's.
2. No opposite trias.
3. No back to back trias.
4. No trias in fillets or hemmings(We can have minimum but anyhow try to avoid).
5. No rotational quads.
6. No trias should share a boundary with feature line.
7. Connectivity between elements.
8. Split and perform the mesh.
9. Use mixed type mesh for irregular shaped surfaces and quads only for rectangular/square surfaces(Opposite sides should be parallel and equal).

6:3 Begin meshing the surfaces

• Start meshing from the centre regions or from least free edges.You will get proper mesh density and proper mesh flow.

Why Meshing is Needed ?

• Finite Element Method reduces the degrees of freedom from infinite to finite with the help of discretization or meshing (nodes and elements). One of the purposes of meshing is to actually make the problem solvable using Finite Element. By meshing, you break up the domain into pieces, each piece representing an element.

How to Begin Mesh ?

• Start meshing form the least free edges,Like start meshing from the center.
• It will be easy to get proper mesh flow and we will get uniform mesh density.
• Don't mesh form the edges,It will be difficult and you will get many error,So start meshing from the center.
• Choose the element type while meshing.
• For this component we will be using mixed element type and working on it.
• We can also quads element type.This type can be used when we have rectangular surface.
• We can use Tria Element type.This type can be used for 3d tetra meshing.

Start Meshing

• Now start meshing on the surfaces,Go to 2D >> Automesh Panel >> Surfaces >> Element size = 5mm > Mesh Type : Mixed >> Check for align and size >> Mesh.

 

Figure 74-Meshing on Surface.

 

Figure 75-Automesh Panel.

 

• Select the appropriate mesh type based on the shape of the surface.
• Once we give for mesh, we can edit the mesh density by changing the number of nodes.
  

 

Figure 76-Mesh on the Rectangular Surface.

 

• Here i have splitted the surface to rectangular surface and meshed to get proper mesh flow.
• Make sure to check the Link Opposite Edges with AR.
• This option is to be checked when your are meshing on the rectangular surface.
• Link Opposite Edges with AR-[Eg:If we have 29 nodes on left side edge,It will project the same 29 nodes on right side edge.]

• Now if we mesh on the curved surfaces,Choose the mesh type as mixed and mesh.
• If we choose quad mesh type,The mesh will fail,It won't occur on the surfaces.

 

Figure 77-Mesh on the Curved Surface.

 

6:4 Remesh and Rebuild Mesh

 

Remesh-

• Remesh is used to generate a mesh of plate elements using surface geometry or existing shell elements to define the mesh area.
• Elements are remeshed with the use of the HyperMesh inferred surface algorithm, if geometry for theselected elements needs to exist in the model. 
• The inferred surface algorithm interpolates geometry datafrom the selected elements in order to create new mesh.
• When elements are selected to be remeshed, there is the break connectivity option and the vertex angle parameter. The break connectivity option detaches the node connectivity between adjacentselected and unselected elements. This allows you to adjust the node densities along the boundary ofthe selected elements. 
• The vertex angle parameter defines the placement of vertices along theboundary of the selected elements. If the angle between two adjacent element edges along the boundaryis less the specified angle, a vertex is placed at the meeting point of the two edges. 
• Anchor nodes create the effect of a fixed point on the inferred surface (which is derived from the existing mesh) and keep the location of the anchor nodes intact.

Rebuild Mesh-

•  It is the process of remeshing existing meshes to generate a new mesh with good quality and flow.
• The rebuild mesh functionality utilizes the same parameter and criteria files used by BatchMesher to define the quality criteria and relevant mesh parameters.
• This algorithm saves significant time over the traditional automesh and quality correction approach.
• Rebuild is currently supported for first-order 2D meshes that are not attached to 3D element faces. 
• The rebuild algorithm is useful for many different applications like

 

6:7 How to get Proper Mesh Flow ?

• After fixing the quality in mesh.Do the smooth operation on the meshed regions.
• You will get a proper mesh flow,While smoothening some elements may fail like 1 or 2,So try to clear them with distance tool.
• To use smooth tool,Go to 2D >> Smooth >> Elements >> Size Corrected >> Smooth.
• Smooth tool will improve element quality in a surface-based mesh or a mesh of solid elements using one or more algorithms that adjust node positions to moderate sharp variations in size or quality in adjacent elements.
• Iterations specifies the number of passes you wish the smoothing algorithm to run.

 

Figure 79-Smooth Panel.

 

[Note: Smooth every region after meshing every region,Then only you will get good mesh flow.]

 

Figure 80-Before Smoothening.

 

 

Figure 81-After Smoothening.

 

6:8 Aligning the nodes across edges and align nodes to get proper mesh flow

 

• After smoothening the elements,Some elements may not be aligned.
• To make them align we can use align nodes tool to align them.
• Go to Geometry >> Node Edit >> Align >> 1st Node >> 2nd Node >> Align.

 

Figure 82-Alignining Nodes.

 

Figure 83-Aligned Nodes.

 

• Align Nodes across edges - If the nodes are not projected to the edges,then you can use project tool to project or align them cross edges.
• To Project go to Tools >> Project >> To Line >> Select Nodes >> Normal Lines.
• It is used to project nodes or points to a line along a user-defined direction or the normal to the line selected.

 

Figure 84-Project Panel.

 

Figure 85-Element nodes are not projected to the feature lines.

 

• Here this happens due to dragging trias from the feature lines.

[Note:Don't drag the trias away from the feature lines,If you drag,there will be no feature capturing.]

 

Figure 86-Projected to the shared edges using project tool.

 

6:9 Manual Clean Up Using Distance[F4] and Translate[Shift +F4].

• We can use the Distance tool to determine the distance between two nodes/points or the angle between three nodes/points, or to change distances or angles.
• We can also fix the elements failing for the quality like

i) Minimum and Maximum Length

ii) Minimum and Maximum Quad

iii) Minimum and Maximum Tria

iv) Aspect Ratio

• Sometimes we can also fix warpage using distance tool.

Figure 87-Elements Failing for Min and Max Length.

 

Figure 88-Elements failing for min and max length have been solved using distance tool.

 

• Similarly we can fix elements failing for min and max quad,min and maax tria ,aspect ratio using distance tool,Sometimes we can also fix warpage.
• But better to use translate tool to fix warpage.
• We will be translating the some warpage angle to the neighbour element,by using translate tool we can easily fix the warpage.

 

6:10 Fix Warpage

• We can fix warpage by using translate tool.
• We will be translating the some warpage angle to the neighbour element.

 

Figure 89-Warpage.

 

 

Figure 90-Warpage.

 

 

Figure 91-Warpage Fixed.

 

• We can check the warpage angle using check elements [F4].
• Check warpage angle for neighbouring elements also.
• If the neighbouring elements have less warpage angle,we can translate some angle to that element.And then we can clear warpage.
• Go to Tools >> Check Elements >> Warpage.

 

Figure 92-Check Elements Panel.

 

Figure 93-Warpage Angle.

 

• If you click on the element failing for warpage,It will show the warpage angle.Here i clicked on the element which is not failing for the warpage angle.So the value is too less and it not failing.

•  Now after meshing the entire component,Check for 

i) Connectivity [Free Edges]

ii) Duplicates

iii) Normals

 

i) Check for Connectivity [Free Edges]

• Edge Tool will help us to find this error.
• Go to Too >> Edge >> Elements >> Find Edges.

Figure 94-Edges Panel.

 

• If we get the the edges with connectivity,there is no problem,If you get edges without connectivity,then you have to manually connect them with using replace tool.

 

Figure 95-Edges.

 

[Note:While checking free edges,Give the tolerance value as .01.If it is an assembly component,Give tolerance value as .01.It should not exceed more than .01 for assembly check.

If you give high tolerance and click preview equivalence,the software willl show you,many nodes are connected.So go give lower tolerance for the assembly components.Dpn't go betond normalized minimum height.The minimum normaalized height for this component is 2.0.]

 

 

Figure 96-0 nodes were found with tolerance value 2.

 

 

Figure 97-67 nodes were found with tolerance value 5.

 

[Note:Give the tolerance value-0.01 for the assembly check.Don't give higher tolerance,If you give higher,it will result as shown in fig 97.] 

 

ii) Check for Duplicates

• Now check for the duplicate elements
• To check duplicates,Go to Tool >> Check Elements >> Duplicates.

 

Figure 98-0 duplicates were found.

 

 

Figure 99-Shrink Elements.

 

 

Figure 100-Proper Representation of Shrink Element Mode.

 

 

iii) Check for Normals

 

• We can Use the Normals to display and reverse the normals of elements or surfaces. The orientation of element normals can also be adjusted. The normal of an element is determined by following the order of nodes of the element using the right-hand rule.
• Normals can be reviewed showing a vector or by colors. A vector shows in positive normal direction, while the color mode shows the positive side of a shell or surface in red and the negative side in blue.
• To check normals go to Toolbar >> Mesh >> Check >> Elements >> Normals.

 

Figure 101-Check for Normals.

 

Figure 102-Normals Panel.

 

 

Figure 103-Checking for Normals View 1.

 

Figure 104-Checking for Normals View 2.

 

 Final Mesh Model -

 

 

Figure 105-Final Mesh Model.

 

Phase 7 - Assigning Thickness to the Elements

 

7:1 Check thickness in geometry

• First check the thickness in every region and then assign a thickness by creating a collectors and organize it to that newly created collectors.
• Check thickness by distance tool or by dimensioning tool.
• Geometry >> Distance >> Two Points >> Point1,2.
• Geometry >> Dimensioning >> Point1 >> Point 2.

7:2 Create a Collector 

• After measuring thickness,Create a component and rename it as Middle Surface_1 2.8mm [Base Surface].
• Don't organize elements in the base surface,Just rename it as Middle Surface_1 2.8mm.
• Organize the elements in ribs and cylindrical ribs to the newly created collectors.

 

Figure 106-Browser Panel.

 

7:3 Assign Property to the Components 

 

• First Create a property on the browser.
• To create a property,Right click on browser >> Create >> Property.
• After Creating a property rename it and start assigning thickness to the components.

 

Figure 107-Browser Panel.

 

• Now check the complete model,Whether the property has been assigned to the collectors.
• To Check Go to Menu Bar >> Tools >> Component Table.

 

Figure 108-Menu Bar.

 

 

Figure 109-Component Table.

 

• Now Switch to the 2D Detailed Element Representation,The thickness have been applied to the every region.

 

Figure 110-Thickness Assigned to the Component.

 

Figure 111-Detailed Representation.

 

 Final CAD Model Image -

 

Figure 112-Final Meshed FE Model.

 

Figure 113-Final Image.

 

 

Result -

• Hence the mid surface has been extracted from the parent geometry.
• Hence there are no surface deformations in the geometry.
• A well connectivity has been established between the surfaces.
• The features have been captured properly.
• A good mesh flow have been achieved with the zero elements failing for quality
• Hence tria percentage with 2.7 % have been achieved.

 

Learning Outcome and Conclusion -

• In this project,I came to know
• How to mesh a complex sheetmetal component.
• How to extract the mid surface manually for the complex sheetmetal components.
• How to clean complex geometry .
• How to generate a proper mesh flow with low tria percentage.
• How to assign thickness to the components.