Connectors and Debugging Connectors

Objective:

• The main objective of this challenge was to learn about the use and application of different types of connectors, and connect various parts of the model.

The specific connectors to be used to connect different parts as per the given data are as follows:

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. Connect remaining components with suitable connectors.

Introduction:

• Connectors are different types of 1D, 2D, or 3D elements (bars, rods, springs, links, welds, etc.) used to connect two or more components.
• Use of connectors plays a very essential role during analysis of a certain component as it transfers load from one part to the other.
• There are different types of connectors available in HyperMesh like Spot weld, Bolts, Seam Welds, Adhesives, masses, etc.
• A property and a material can be assigned to connectors to give exact results as per requirement during analysis. Properties for certain connectors are automatically created by HyperMesh itself.
• Applying connectors in a certain area may manipulate or partially destroy the mesh of that part locally.
• The location where the connectors are to be applied can be specified by a point, node, nodelist, or elements.
• The Finite Element representation of a connector is called ‘realization’. A connector should always be in a realized state.
• The model (Frame Assembly) provided in the challenge to which different connectors had to be applied is as shown.
  
  
  
  
  

Procedure:

• The model already had the midsurfaces extracted beforehand, so it was meshed directly using ‘automesh’ option with an element size of 5mm and the element type set on ‘mixed. The nodes in the mesh were tweaked to achieve a good quality of elements as seen below.
  
  

• A material ‘Steel’ and a property ‘frame assembly’ with thickness of 2mm were created. The material was assigned to the property and later the property was assigned to all the components.
• After meshing, all the connectors were applied one by one as follows:
  
  

1. ‘Right_Rail_2’ & ‘Front_truss_1’:

• The two components, Front Truss 1 and Right Rail 2 had to be connected using a ‘Seam Quad (angled+capped+L)’ connector. This connector is also called as ‘Volvo Seam Quads’ as it is developed by Volvo, and is used in many industries.
• To apply this, the ‘seam’ option from the ‘1D>connectors’ tab was used. In the seam option, the ‘type’ was selected as ‘seam-quad (angled+capped+L)’, the location was set on ‘nodelist’ and a line of nodes was selected at the joint of the two components. The spacing was set as 5.00 (equal to the element size), the components to be connected were selected in the ‘connect what’ menu, and tolerance was kept as 10. Weld angle was set as 45, cap angle 60, and the runoff angle as 10. In the ‘property’ tab, the ‘frame assembly’ property was selected and the connector was created.
• The connector was not realized due to some error and hence was displayed in red color. Therefore, a ‘connectors’ tab was opened from ‘view>browser>HyperMesh>connector’. The created connector was selected and by right clicking on it, ‘rerealize’ button was hit. This realized the connector and was then turned green. The image below shows the seam-quad.
  
  
  

2. 'Left_Rail_2 & Front_Truss_1':

• Quad connectors had to be created for these parts. To create the quads, ‘1D>connectors>seam’ was used.
• The type of connector was set as ‘quads’ with a spacing of 5mm, and tolerance of 10mm. the node list on the edge of the edge of the Front Truss 1 was selected where it was joining the other part. Both the components were selected in the ‘connect what’ tab. The property of ‘frame assembly’ was assigned and the connectors were created.
• The following image shows the connectors.
  
  
  
  
  

3.'Front_Truss_2', 'Front_Truss_1', & 'Right_Rail_1':

• Spot weld had to be used for these three above mentioned components of the model. The diameter of the weld was specified as 5mm with number of layers equal to 2.
• This spot weld was applied by using ‘1D>connectors>spot’ with the weld type as ‘plot’, property as ‘frame assembly’, and diameter as 5mm. the node path where the weld had to be applied was selected and the components were specified.
• As three components on top of each other had to be joined, the ‘num layers’ was set as ‘total 3’. This created a spot weld with the links passing through all the three components. After ensuring the connector was realized, the spot weld was finalized as seen below.
  
  
  
  

4. 'Front_Truss_2', 'Front_Truss_1', & 'Left_Rail_1':

• These components were joined using the ‘hexa (adhesive)’ seam welding.
• Hexa (adhesive) connectors are used where the components are joined by using industrial adhesives. It creates a 3D (hexa) element representing the adhesive joint.
• The number of layers and the number of coats of the connector can be changed according to the requirement. This connector creates a separate property and a separate component collector.
• To apply the hexa (adhesive) the ‘seam’ option was selected from the ‘connectors’ tab of ‘1D’. The type of the seam welding was set on ‘hexa (adhesive) from the list with a single layer and a single coat of adhesive.
• Similar to previous cases, the spacing was set as 5, tolerance as 10, and the node list and the components to be connected were selected. This created ‘RBE3’ links for the connector as seen in the following image.
  
  
  
  

5. 'Rear_Truss_2' & 'Right_Rail_2':

• Rear Truss 2 and Right Rail 2 were joined using a bolt connector at two nodes.
• A ‘bolt (general)’ was created at two nodes by using the ‘bolt’ option from the ‘connectors’ tab of 1D. Here the type was selected as ‘bolt (general)’ which was set by default, and the property was selected.
• The ‘consider existing hole only’ option on the right side was changed to ‘create hole, if none’, and the components and the nodes where the bolts had to be created were selected.
• This created two holes around the two selected nodes. But along with this, the local mesh of those components was distorted.
• The mesh was thus optimized by remeshing and using the optimization tools from ‘2D>qualityindex’ option, and the connector was finalized.
  
  
  
  

6. ‘Rear_truss_2’ & ‘Left_Rail_2’:

• These components again had to be joined by bolt connectors. For this, similar procedure as above was followed.
• But for this, the type of the bolt was changed to ‘bolt (CBAR)’ though it was specified in the challenge.
• Similarly two nodes and both the components were selected, the ‘consider existing hole only’ option on the right side was changed to ‘create hole, if none’ and the connector was created as seen in the image below.
  
  

7. ‘Right_Rail_1’ & ‘Right_Rail_2’:

• Spot Weld with rigid elements had to be used as a connector to join these two components. This connector created RBE2 links to join the components.
• To create this spot weld, the ‘spot’ option was selected from the ‘connectors’ tab and the type of weld was set as ‘rigid’.
• The spacing was kept as 5mm, tolerance as 10, and diameter of the weld as 5, and the property was selected as ‘frame assembly’.
• The nodelist was selected on one side of the component and the connector was created. Similarly, by following this procedure, spot weld was created on the other side of the component too. The image below shows both the connectors.
  
  

8.‘Left_Rail_1’ & ‘Left_Rail_2’:

• For both the Left rails, spot weld with spring elements had to be used. Similar procedure like the one above was followed.
• But instead of the ‘rigid’, the type was changed to ‘spring’. This created CELAS (elastic) elements as seen below.
  
  
  
  
• The other side of the two components was also joined by the spring elements of the spot weld.
  
  

9. Other Connections:

• There were some more areas and components which were supposed to be connected using suitable links.
• Two such components were the Left Rail 1 and the Rear Truss 2. These components were connected using the bolts of the spider type.
• To connect these ‘1D>connectors>bolts’ was followed. The type of the bolts was changed to ‘bolt (spider)’ and the all the other options were kept same as before. This connection created RBE2 elements between the two components as seen below.
  
  

• After this, the opposite side of the same components (Left Rail 1 and Rear Truss 2) was connected using the hexa (adhesive) joints.
• ‘Seam’ option was selected from the ‘connectors’ tab and the type of the seam weld was set as ‘hexa (adhesive)’, keeping all the other aspects as the same from the previous instances except the strips and coats
• The ‘strips’ was set as 3, and the ‘coats’ was set as 2. This created 3 strips of the adhesive, one after the other, and 2 coats, one connected on top of the second as seen in the image.
  
  

• Later, the Rear Truss 1 and the Rear Truss 2 were connected. Top side of the components was connected using the spot weld of the ‘rbe3 (load transfer)’ type.
• The RBE3 elements distribute the loads from one end to the other but do not induce the stiffness. To create these connectors, the ‘rbe3 (load transfer)’ was selected as the type for the ‘spot’ weld, and the nodes and components were specified.
• Seam weld was used as connectors for the bottom part of the two components.
• ‘1D>connectors>seam’ was followed and the type of the seam was set as ‘weld’. The spacing of the weld elements was set as 5mm, tolerance as 10, and the property as ‘frame assembly’ and the connector was created.
• The image below shows both the top and the bottom connectors.
  
  

• Another connector used in the challenge was for the Reinforcement Plate between the Front Truss 1 and Front Truss 2.
• Both the sides of the plate were connected using ‘seam-quads (angled+capped+L)’ connectors from the ‘seam’ option.
• But, on the left side of the plate, the ‘weld angle’ was kept as 60^o, the ‘cap angle’ as 45^o, the ‘runoff angle’ as 10^o. While on the right side, the weld angle was kept as 45^o, cap angle as 75^o, and the runoff angle as 10^o.
• These connections distorted the mesh of the plate and thus had be remeshed and optimized again.
  
  
  
  
• After applying suitable connectors at all the component joints, the final connectors of the model was as seen below.
  
  

Result and Conclusion:

• In this challenge, the connectors mentioned, and other different suitable connectors were used and all the components of the model were joined successfully.
• Use of connectors plays a very essential role during analysis of a certain component as it transfers load from one part to the other.
• Apart from these, additional things about the connectors were understood from the support book PDF, of the Altair University.
• For practice purposes, different types of seam welds, spot welds, bolt connectors, area connectors, and other industry specific connectors were used in this challenge.
• This challenge gave an insight about the sheet metal analysis in the HyperMesh.

Additional Gdrive link for the model: Frame Assembly Welding Model