Assembling, Connecting and Debugging of Rail Components using Hypermesh

Objective

• To assemble the components with the respective connectors.
• All the connectors should get realized.
• Perform debugging if required.
• After connecting, the mesh flow should be free of distortions.

Procedure

Step 1: Importing

Since we are importing a CAD geometry, the format will be either of the 2 industrial accepted standards:

• STEP (Standard for the Exchange of Product data).
• IGES (Initial Graphics exchange specification).
• When selecting the file for import, be sure to check if it is .stp or .igs.
• File > Import > Import Model > File type > Open File > Import File
• We only have to work on the geometry, so before inspection check for solids and delete if there are any.
• Delete [F2] > Solids > Displayed > Delete Entity

Step 2: Inspection

2.1. Check for the number of components

Upon initial inspection, we can see that there are 9 geometries :

• Front Truss 1
• Front Truss 2
• Right Rail 1
• Right Rail 2
• Left Rail 1
• Left Rail 2
• Rear Truss 1
• Rear Truss 2
• Reinforcement plate

2.2. Organize the components

• It is not possible to learn which component is which in the short time that we have to create connections.
• Also, it is not efficient to look for the desired component by checking the surfaces on/off in the tab bar for all the components one by one.
• There are 2 ways to isolate a model and work on it:
  
  • Isolate shown
  • Selector

2.2.1. Isolate shown

• Why we use Isolate shown?
  • When we want to directly access the component from the tab bar without selecting and deselecting all the components.
  • When we know the name of the component to work on but not the geometry.
• The option is present in the Tab bar right below the search Menu.
  • Isolate shown > Click on the Component ID > Component is displayed on the GUI
• Upon following the above step, only the selected component will be shown and the rest will be hidden.

2.2.2. Selector

• We use Selector for:
  • When we want to directly access the component from the GUI.
  • When we know the geometry to work on but not the component ID.
• The option is present in the Tab bar right below the search Menu:
  • Selector > Click on the Component in the GUI > Component is displayed on the GUI
• Upon following the above step. only the selected component will be shown and the rest will be hidden.

2.2. Check for Geometric Errors

• We just have to check for surface deformations if any.

Step 3: Create Assemblies

[Note: This step is optional]

• As we are working on different connections with different combinations of components, it is time-consuming to go back and forth and select the components individually.
• We can create assemblies based on the connectors used between the components.
• For example, in the challenge, the first connector is Seam-Quad(angled+capped+L) between Right Rail 2 & Front Truss 1.
• We create an assembly and assign the above components to it.
• Steps to be followed to create an assembly:
  • Tool > Assemblies > Create > Assem name = ______ > Card Image = 1 > Comps (Select) > Create
• In future, it will be easier to access the components and the respective connector by just clicking at the assembly.

Step4: Manual Cleanup

• Not much manual cleaning up is actually required for this model.
• But some of the components have holes, in order to get a good mesh flow we have to create washer splits around them.
• Washer split allows us to create a shared edge (green line) around the hole (a free edge - red line) by a certain offset value.
• We create washer split to avoid any trias at free edges and to maintain a good mesh flow around the holes.
• Step to follow to create washer splits is mentioned below:
  • Geom > Quick edit [F11] > Washer split > Give Offset value > Middle Click
• From inspection, we can observe that washer splits are already present. Hence, we don't skip to the next step.

Step 5: Meshing

• Mesh size = 6 mm
• We are not worried about any element quality so we can directly mesh the component.
• 2D > Automesh > Surfs > Elem size = 6mm > Mesh Type : Mixed
• Check the tick boxes for Flow and size to get a good flow.
• Upon giving for mesh, we have an option to alter the mesh density if needed.

Step 6: Establishing Connections

6.1. Right_Rail_2 & Front_truss_1:- Seam-Quad(angled+capped+L)

• We can select the components using either of the 3 steps:
  
  • Isolate shown (refer 2.2.1)
  • Selector (refer 2.2.2)
  • Select Assembly_1 from tab bar (refer step 3)
• Steps to perfrom Seam weld:
  • 2D > Connectors > Seam > Location : NodeList (Select by Node path) > Connect what : Comps (select) > Tolerance = 10mm Type: "Seam-Quad(angled+capped+L)" > Quad Transition > Imprint > Create
  • Loaction spefies the nodes at which the seam welding is done.
  • Connect what specifies the components that we have to seam weld.
  • When we give a Tolerance value, Hypermesh will search for any neighbouring nodes within the circular radius of that tolerance limit.
  • Quad transition depicts the type of mesh flow we wish to follow, in our case quads.
  • Imprint is used for simple components

6.2. Left_Rail_2 & Front_truss_1:- Quad elements

• The steps are very similar to seam welding:

2D > Connectors > Seam > Location : NodeList (Select by Node path) > Connect what : Comps (select) > Tolerance = 10mm Type: "Quads" > Quad Transition > Imprint > Create

6.3. Front_truss_2, Front_truss_1 & Right_Rail_1:- Spot weld with 3 Layers and 5 mm Diameter

2D > Connectors > Spot > Location : NodeList (Select by Node path) > Connect what : Comps (select) > Tolerance > 10 > Type: Weld > Number of layers = 3 > Diameter =5mm

> Create

• Number of Layers depicts the number of surfaces to be spot weld, in our case it is 3.
• No Property means that a flat element (2D) will be used. There won't be any load transfer.

6.4. Front_truss_2, Front_truss_1 & Left_Rail_1:- Hexa (Adhesive)

• Hexa (Adhesive) is available under seam panel.
• 2D > Connectors > Seam > Location : NodeList (Select by Node path) > Connect what : Comps (select) > Tolerance = 10mm > Type: Hexa (Adhesive) > Strips = 1 > Coats = 1 > Width =1 > Create
• Adhesive uses RBE3 elements as RBE2 is infinitely stiff.
• Strips depict the Thickness.
• Coats depict the Width.

6.5. Rear_truss_2 & Right_Rail_2:- Bolt Connector

• 2D > Connectors > Bolt > Location : NodeList (Select by Node path) > Connect what : Comps (select) > Tolerance = 10mm > Create
• Before creating bolt, enter the following parameters from within the spot weld module:
• • Tolerance = 10mm
  • Type: Bolt (general)
  • Create hole, if none > Create
    
  • Since there are no holes to make a bolt connection we have to create a hole using "Create Hole, if none option"

6.6. Rear_truss_2 & Left_Rail_2:- Bolt Connector

The procedure is the same as the previous step (6.5).

6.7. Right_Rail_1 & Right_Rail_2:- Spot-weld with Rigid Elements

• 2D > Connectors > Spot > Location : NodeList (Select by Node path) > Connect what : Comps (select) > Type: Weld > Create
• Before creating weld, enter the following parameters from within the spot weld module.
  • Tolerance = 10mm
  • Number of layers = 2

6.8. Left_Rail_1 & Left_Rail_2:- Spot-weld with Spring Elements

• 2D > Connectors > Spot > Location : NodeList (Select by Node path) > Connect what : Comps (select) > Type: Spring > Create
• Before creating spring, enter the following parameters from within the spot weld module.:
• Tolerance = 10mm
• Number of layers = 2

Result

The Components are joined using the respective connectors:

1. Right_Rail_2 & Front_truss_1: Seam-Quad(angled+capped+L)

2. Left_Rail_2 & Front_truss_1: Quad elements

3. Front_truss_2, Front_truss_1 & Right_Rail_1: Spot weld with 3 Layers and 5 mm Diameter

4. Front_truss_2, Front_truss_1 & Left_Rail_1: Hexa (Adhesive)

5. Rear_truss_2 & Right_Rail_2: Bolt Connector

6. Rear_truss_2 & Left_Rail_2: Bolt Connector

7. Right_Rail_1 & Right_Rail_2: Spot-weld with Rigid Elements

8. Left_Rail_1 & Left_Rail_2: Spot-weld with Spring Elements

9. Remaining components are joined with suitable connectors.

• The Mesh flow remains free of any distortions after connecting.
• The Railed connectors (Red) were fixed.
• All the connectors are Realized (Green). We can view them in the Tab bar.

Conclusion with Learning Outcome

I learnt :

• The significance of using connectors in Pre-processing.
• How to join components using Connectors.
• How to debug Connectors.
• How to choose the appropriate connector for different geometries and conditions.
• To work on different types of connectors, such as:
  • Welds
  • Bolts
  • Adhesives, etc.
• Physical characteristics for seam welding, such as:
  • Weld angle
  • Height
  • Cap Angle
  • Runoff angle