Implementing Connection on the Rear Door FE Model using ANSA
Aim:
To perform the connection of the rear door FE model and explain the different types of connection techniques along with different 1D elements.
Theory:
Figure a: Left side Rear door of SKODA OCTAVIA I
A car door is a type of door, typically hinged, but sometimes attached by other mechanisms such as tracks, in front of an opening which is used for entering and exiting a vehicle. A vehicle door can be opened to provide access to the opening, or closed to secure it. These doors can be opened manually, or powered electronically.
1D Elements and Connectors
- Weld
- Adhesive
- Bolt
- Area contact
- Replace parts
1D Elements are simple connections between nodes. Standard 1D Elements are
RBE2 - Rigid link to transfer motion from the independent node to the dependant nodes
Figure: RBE2 Rigid connection
RBE3 - Rigid link to distribute loads and will not induce stiffness
Figure: RBE3 Rigid connection
Difference between RBE2 and RBE3
RBE2: An Implicit MPC (Multipoint constraint) with one independent node and several dependent nodes. Irrespective of the locations at which the dependent or slave nodes are located from the independent or master node, RBE2 restricts relative displacement between slave nodes.
General Usage:
- When RBE2 is used as a spider connection at a bolt hole, slave nodes on the hole edge will not have relative displacement and as which one cannot observe any ovalizing effect of a hole
- Consider there is a hybrid joint where components are assembled with two sub-components which are made of two different materials and those two sub-components behave integrally as in real scenarios.
RBE3: An Implicit MPC (Multipoint constraint) with one dependent node and several independent nodes. Irrespective of the locations at which the independent or slave nodes are located from the master node, RBE3 distributes the force using a weighted average method using centroid.
Procedure:
Connections performed:
Two Nodes RBE2 - Used to represent the stem of a bolt.
Many Node RBE2 - Represents the Rigid connections
RBE3-HEXA-RBE3 - Standard representation of spot weld
CONMi- CONM2 - For assigning the mass(in Tons)
RBE3- CBUSH-RBE3 - Represents the spring element which will be having damping co-efficient or stiffness values in 3 different directions.
1. Firstly open the given the .nas file using the following steps,
FILE > INPUT > NASTRAN > OPEN
FIGURE 1: File opening
2. The given single PID meshed model is separated into the following PIDs.
FIGURE 2: Meshed Rear door
FIGURE 3: Property IDs
3. The connection starts with the latch & hinge mechanism attaching the door with the body frame.
FIGURE 4: Hinge bolt connection
The provided meshed rear seat model is having a lot of several inconsistencies and parts that were missing for connection. So by the available data as the figure above we selected the hole which is connected by bolt and nut.
Topo module >Points > On COG> Points
With the Loop selection option, we can create a COG point for the hole selected
By using the Convert option from the Assembly module convert this COG point to the 3D point and select the Bolt option for this 3D point.
After converting the COG point to bolt, we need to select the connection manager and to select the bolt connection and assign P1, P2 and P3 and selecting the In/Out Zones. Automatically it will show the stem of the bolt using the yellow color element notation.
FIGURE 5: Bolt and nut connection
Create a 2 node RBE 2 with the required degrees of freedom for the latch connection with the body. Since the door is to be opened and closed in the z-direction
FIGURE 6: Degree of freedom mentioned on door hinge for opening and closing
Create a cluster RBE2 by selecting many node options from RBE2 for the rigid connections.
4. For spot weld, we study the area and make a COG by the following process
Topo module >Points > On COG> Edge.
Then we go to the Convert option from the Assembly module and convert this COG point to spot weld point. For the spot weld, we use RBE3-HEXA-RBE3 elements.
FIGURE 7: Spot weld defining
FIGURE 8: Spot weld connection
5. Normally Door handle will be modeled as a mass element and for that, we need to rigidize the holes by giving a rigid connection.
FIGURE 9: Defining Mass Element for the door handle
After a rigid connection connect the master nodes of the two holes with a many node RBE2 so that at the center of it mass can be deployed.
For assigning the mass, we need to go to CONMi> CONM2> Nodes, define the mass in elements. We apply 0.0001 tonnes of mass (100 gram) for the door handle.
6. There will be black beading which will run across the channel of the glass on both sides of the door (ie, the inner and the outer part of the door).
FIGURE 10: Glass-Door Connection
For deploying a door glass connection we need to create a damping line using the Feat2Curve from Mesh module and select the boundary line of the glass.
After getting the curves, go to the Convert option from the Assembly module and convert this curve to the Spot line.
FIGURE 11: Defining CBUSH Element for the Glass-Door connections
In the Connection Manager select this Spot line and select the part P1 and P2, in the FE Representation type select the RBE3- CBUSH-RBE3 which represents the spring element which will be having damping co-efficient or stiffness values in 3 different directions.
Align the orientation of the CBUSH element: For aligning the CBUSH element we need to select all the CBUSH element's local co-ordinate and selecting them in a single shot and by right click on it and select the modify option and change the Orient > With Cord and CID > 0 of the CBUSH. So that the local co-ordinate will be modified to the global co-ordinate for all the CBUSH elements in a single shot
Here CID means the Co-ordinate ID
Final view of the model after the connections:
FIGURE 12: Final view of connections
Learning Outcomes:
Studied different types of connections and respective steps to do it in the Connection Manager option.
Two Nodes RBE2 - Represents the stem of a bolt.
Many Node RBE2 - Represents the Rigid connections
RBE3-HEXA-RBE3 - Standard representation of spot weld
CONMi- CONM2 - Assigns the mass to a node (in Tons)
RBE3- CBUSH-RBE3 - Represents the spring element which will be having damping co-efficient or stiffness values in 3 different directions.
Learned from the practice models
Seam Weld: Overlap Shell - Parallel surface weld and Y joint Shell - Perpendicular surface weld
Terms like Weld thickness and the Weld parameters like Offset Row and Primary Row
Conclusion:
For the given Rear door FE model, the different types of connection techniques along with different 1D elements are created.
Linked for the Model is provided below:
https://drive.google.com/drive/folders/17YfgdFZNtGVoKqj4UCMpF3o8_fqFDIGT?usp=sharing