Project 1-Meshing of Rear Wheel Holder challenge

Meshing of Rear Wheel Holder [Spare Wheel Floor Panel]

Aim -

To perform preprocessing on the given Rear Wheel Holder [Spare Wheel Floor Panel] Sheet Metal component using hypermesh preprocessing software.

Objective -

To generate the mid surface manually and do a geometry clean up on the component.

To generate a mesh and to get a proper mesh flow on the given component with low tria concentration.

To check the elements quality according to the given quality criteria.

To assign a thickness for the component.

Theoretical Framework -

Stepney Spare Wheel Floor Panel :

The Stepney Spare Wheel was invented by Thomas Morris Davies in Llanelli in 1904. At that time, early motor cars were made without spare wheels, so a puncture was an event dreaded by all drivers. Mr. Davies's brilliant idea was to make a spokeless wheel rim fitted with an inflated tyre.

Pretty soon T. Morris Davies and his brother Walter were in business, turning out spare wheels in their Llanelli works. They became very wealthy men as their business grew and they set up agencies across the world.

Their 1909 catalogue proudly claimed that Stepney Spare Wheels were fitted to all London taxis. In 1922 the company became Stepney Tyres Ltd and their operations moved from Llanelli to Walthamstow.

The days of the patent spare wheel had drawn to a close, as car manufacturers began to provide spare wheels with all new cars. However, the name lived on, long after the last spare wheel was made.

A "stepney" is still today the everyday name for a spare wheel in India, Bangladesh, Malta and Brazil, where it is called an "estepe".

A further twist to the tale is that in Dehli an easy going member of staff, who is not much help, can also be called a "stepney".

Figure 1-Stepney Floor Panel.

A spare tire (or stepney) is an additional (tire or tyre) carried in a motor vehicle as a replacement for one that goes flat, has a blowout, or has another emergency.

Spare tire is generally a misnomer as almost all vehicles actually carry an entire wheel with a tire mounted on it as a spare rather than just a tire, as fitting a tire to a wheel would require a motorist to carry additional, specialized equipment. However, some spare tires ("space-saver" and "donut" types) are not meant to be driven long distances.Space-savers have a maximum speed of around 50 mph (80 km/h).

When replacing a damaged tire, placing the compact spare on a non-drive axle will prevent damage to the drivetrain. If placed on a drivetrain axle, the smaller-diameter tire can put stress on the differential causing damage and reducing handling.

Figure 1:1-Stepney Floor Panel.

A structural shear panel for forming a floor panel for support by a vehicle frame is formed by a composite of top and bottom sheets and a core with a vacuum infused resin.

The core is formed of top and bottom layers each formed from a honeycomb panel defining an array of hexagonal tubular cells with walls which extend in the thickness direction filled with a foam material.

A third layer is located between the first and second layers and is formed of a material such as foam, rubber or cork which is free from tubular cells in the thickness direction and free from rigid structural members in the thickness direction to reduce communication of sound through the panel.

Figure 1:2-Stepney Floor Panel.

Introduction :

The component given to us is car stepney spare wheel floor panel.

This component is a sheet metal component.

For the plastic and sheetmetal component with the thickness less than 6mm,We have to take a mid surface adn then we have to mesh.

Sheet metal is metal formed by an industrial process into thin, flat pieces. Sheet metal is one of the fundamental forms used in metal working, and it can be cut and bent into a variety of shapes.

Countless everyday objects are fabricated from sheet metal.

Thicknesses can vary significantly; extremely thin sheets are considered foil or leaf, and pieces thicker than 6 mm (0.25 in) are considered plate steel or "structural steel".

Procedure -

Phase 1-Importing

Hence we are importing a given CAD geometry into hypermesh.

There are file formates like IGES,STEP,Parasolid where we can import these file formats into any CAD,CAE Softwares.

But in hypermesh we can only import three file formates like

IGES [Initial Graphics Exchange Specification].

STEP [Standard for the Exchange of Product Model Data].

Solidworks.

IGES,STEP,These two are standard file formats which are used most in industries.But now a days in industries,they are aslo using parasolid file format.

While importing the file into the graphical user interface,Be sure whether the file is .step or .iges file.

File > Import > Import Model > File type > Open File > Import File.

Figure 2-Importing Model into GUI.

Figure 3-Imported Model into GUI.

Switch to the topo mode and examine whether the solid exsist in the component or not,If solids exsist,Delete the solids cause we are doing 2d meshing on the component.

You can find topo mode in the tool bar panel.

Delete [F2] >> Solids >> Select by box selection >> Delete Entity.

If solids exsist,It will be highlighted in the green colour.

Example -

[Note:This Model is for only Example]

Figure 4-Before Deleting the Solids

Figure 5-After Deleting the solids

Phase 2- Examining

Before working on the model.We have to check the geometry if there are any errors like

Damaged Geometry.

Free edges in unnecessary areas.

Unnecessary points on the lines.

Unnecessary Connections and connectivity error.

There are some free edges in the model,So clear that free edges in the parent component,Then only you can extract mid surface properly without any glitches in the mid surface geometry.

Figure 6-Free edges in the parent component.

2:1 Inspecting

While inspecting the model,It is a spare wheel floor panel which is used to keep the spare wheel in the car.

While observing the model,There are 17 [Seventeen] components in the model.

Organize them to a single component or delete the unnecessary components.

Figure 7-Unnecessary Components.

Figure 8-All the components organized into one.

2:2 Organizing

We use organize tool to (re)organize your database by copying or moving data (entities) among collectors, includes, or parts.

Select an entity type to copy/move, then use the selector to select specific entities to copy/move. The current collector serves as the default destination.

Elements can be copied/moved into component collectors or groups.Lines, surfaces, solids, points, and connectors can be copied/moved into component collectors.

Here we are selecting the collectors and we are organizing it to one collector.

Tool >> Organize >> Collector SubPanel >> Switch to Surfaces >> Select by Collector >> Move.

Figure 9-Organize Panel.

Figure 10-Switch to the surfaces and select by collector.

Figure 11-Check the components to organize.

2:3 Check for the Thickness

Now go and measure the distance in every region.

We are ensuring whether some regions of this component having uniform thickness or not.

The component given to us is sheet metal component.

The thickness of this stepney floor panel is 0.75 mm.

You can measure the thickness by two methods.

i) Geometry > Dimensioning > Select the Point1 and Point2.

Figure 12-Dimensioning Panel.

Figure 13-The Component has Uniform Thickness.

ii) Tool [F4] > Distance > Points > Select the Point1 and Point2.

Figure 14-Distance Panel.

2:4 Check for Symmetry

This tool is to find symmetrical surfaces or compare selected surface sets for symmetry. You can reorganize found symmetric surfaces into separate components or delete one subset of a pair of symmetric surface sets.

This can be helpful with highly symmetrical components, because you can then perform geometry cleanup on only one half, mesh it, and then mirror the mesh instead of having to clean up the entire component prior to meshing.

Geom >> Surface Edit [Shift + F9] >> Symmetry >> Axis >> Base Point.

Find symmetry-Locate surfaces within a single component that are mirror images of one another across a plane of symmetry that you specify.

Delete Positive-Delete the symmetric surfaces on the positive side of the symmetry axis. Used when finding symmetry.

Delete Negative-Delete the symmetric surfaces on the negative side of the symmetry axis. Used when finding symmetry.

Figure 15-Symmetry Sub Panel.

Figure 16-Surfaces which are symmetric.

[Note: This Symmetric Tool dosen't give a proper result,Don't go with this tool,There are some other surfaces which are symmetric,But it didn't predict that surfaces,So try to avoid this tool.]

Phase 3 - Geometric Clean Up on the Parent Component

If we want we can do geometry clean up on the parent component or after extracting the midsurface also, we can do geometry clean up on mid surface.

[Note:No need to work on the parent geometry,After Extracting the mid surface,We can do a geometry clean up on the mid surface,If we work on parent geometry,It will take lot of time,So try to skip]

3:1 Check for Geometric Deformations

We should also check for any geometric deformations like

Damaged Geometry in some regions.

Overlapped Surfaces.

Free edges.

Unnecessary Connections (Extra points and lines).

Connectivity error.

Figure 17-Damaged Surfaces.

Here i'm doing geometric clean up on the parent component,There is no need to work on parent geometry,If you want you can work on parent geometry or it's fine.

Now fix this damaged surface by deleting the surface.

Geometry >> Quick edit [F11] >> Delete Surface >> Surface (Select).

Figure 18-Quick Edit Panel.

Figure 19-Surface has been deleted.

Now fill this gap with ruled surface,

Use the first selector to define the first edge of the surface to create. Use the second selector to define the second edge of the surface to create.

Figure 20-Ruled Surface Sub-Panel.

Figure 21-Gap Filled with Ruled Surface.

3:2 Fixing Damaged Geometry in surfaces.

Deformed surfaces occur due to the following reasons like

Overlapping surfaces

Connectivity issues

Sometimes this issue occurs due to replacing the points multiple times

These issues can be rectified by using the tools called

[Note:Try to avoid replacing points.Instead of that split the surface and connect.]

We can fix the geometry by quick edit tools.

There some sub tools in the quick edit panel,I have described every tool below,Have a look.

i) Geometry >> Quickedit >> split surface node.

Select two locations of the nodes to split the surface and then select an additional node to continue to split the surface.

ii) Geometry >> Quickedit >> Split surf-line

In this,select a node and select a line to split the surface,here the split will be perpendicular to the line chosen.

iii) Geometry >> Quick edit >> Adjust/set density.

After meshing a particular surface.We can adjust the mesh density by using this tool.While meshing we will increase the

nodes to get a proper mesh flow.We can also increase nodes after meshing by using this tool.

iv) Geometry >> Quick edit >> Release points.

Drag and select the surface,where you want release the points.After releasing the points.The free edges will exsists.

v) Geometry >> Quick edit >> Replace points.

Move points from their current locations to the locations of other points,where we want them to replace it.

vi) Geometry >> Quick edit >> Add/Remove points.

Use window selection (with the left mouse button and right mouse button ) to add and remove any points within the

selection box.

vii) Geometry >> Quick edit >> Add points on line.

Specify the number of points that we wish to add to that line, and then select the desired line in our model.

viii)Geometry >> Quick edit >> Delete surface.

Select the surface which we need to eliminate and delete it.

3:3 Filling Gaps on the Parent Geometry

As we are doing auto mid surface extraction for this component,So try to fill the gaps in the parent geometry.

You can also extract auto mid surface without filling gaps.

We have to close the gaps,where there are free edges in the geometry.

It will be very difficult to find the small free edges.

So go to the Visualization tab .

Figure 22-Visualization Tab.

Figure 23-Free Edges on the Parent Geometry.

The gaps which are narrow,We can toggle them using Quick Edit Panel.

Geom >> Quick Edit [F11] >> Toggle Edges >> Lines (Select).

Toggle Edge -

Use the lines selector to select line(s).

Left-click a free edge (red) to make it shared (green), or a shared edge to make it suppressed (blue).

Right-click a suppressed edge to make it shared, or a shared edge to make it free.

Figure 24-Quick Edit Panel [Toggle Edge].

Figure 25-Narrow Edge.

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.

[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

Filler Surface

Ruled Surface

Spline

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.

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

Figure 34-Quick Edit Panel [Filler Surface].

Figure 35-Unfilled Gap.

Figure 36-Gap filled with filler surface tool.

ii) Ruled Surface

We can also fill the gaps using ruled surface.

Ruled Surface is used to create surfaces by interpolating linearly between lines or nodes.

Line List-Use the first selector to define the first edge of the surface to create. Use the second selector to define the second edge of the surface to create.

If a node list is selected, a line will first be fit through the specified nodes.

Go to Geometry >> Surfaces >> Ruled Surface >> Select Line List 1,2 >> Create.

Figure 37-Ruled Surface Sub-Panel.

Figure 38-Unfilled Gap.

Figure 39-Gap filled with ruled surface.

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 % Percen

tage of Tria on any meshed surface 10

1) Aspect Ratio