Providing Connections to an Automobile Rear Door using ANSA
Aim:
1) To provide connections for the rear door model.
2) Explain about the different connections given for the model.
Theory:
The model given to us is the rear door model. The model also has the glass window which is in closed position for obtaining better results after running a simulation for the model in NASTRAN solver. Here we provide connections to the model for NASTRAN solver which is used in NVH(Noise, Vibration and Harness) simulation of the Pre-processed CAE model.
Procedure:
1. Importing the File:
We first import the model using the NASTRAN option present in Input option of the File menu, since the model is in .nas format which NASTRAN solver format. On opening the model we find that the model is in single PID.
2. Connections:
RBE2 Connections:
1) RBE2 Single Cluster Connections:
In this type of RBE2, we provide connection to two or more holes on two or more surfaces which nearer to each other and lock their in all axes and all degree of freedom so that they can't move in any direction which makes them as rigid during the noise, vibration and harness simulation in NASTRAN. We should go to NASTRAN module and under elements tab we select the RBE2 option. We provide these type of connections wherever the two or more holes near to each other in rear door model as shown in figure given below.
2) RBE2 Spider Connections:
In this type of RBE2, we provide connection to one hole which is present on the model to make it rigid in all the axes which avoids movement of it during the noise, vibration and harness simulation in NASTRAN. We should go to NASTRAN module and under elements tab we select the RBE2 option. We provide these types of connections were there are independent holes present as shown in figure given below.
3) RBE2 Two Node Connections:
In this type of RBE2, we provide connection in places like were the door hinges are present in this model. We should go to NASTRAN module and under elements tab we select the RBE2 option and under RBE2 we select the Two Node option then we select the two required nodes to create a connection as shown in the figure given below.
After that we go to the elements tab and select the Info option. On selecting the info option, we select the two node connection created and we get the information of the connection, in that we lock the degree of freedom i.e. CM to only 5 axes so the movement of the door can only occur in the 6 th axes i.e. the global Z axes during the simulation in NASTRAN solver. The information tab is shown in the figure given below.
4) RBE2 Connections for Door Handle:
In this type of RBE2, we provide connection in the door handle by providing the spider connections of two holes of the door handle and then connecting the two master nodes of the two spider connections to form a centroid or COG as shown in the figure given below.
Then we provide the Con mass for the COG point using the Nodes option present in the CONM2 in CONMi option in the elements tab of NASTRAN module. Then in that tab we provide the COG mass as 100gm, we the values of mass in tonnes i.e. 100gm= 1e-4 tonnes in that tab as shown in the figures given below.
Bolt Connections:
In this type of connections, we provide connections to wherever the bolts are going to be fitted in the rear door model i.e. near to attaching hinges in this case. We first create a 3D point near the holes of the bolt connection using the On COG option present in the Points tab of TOPO module. Then we convert the 3D points into bolt washer point using Convert option present in the Assembly tab as shown in the figure given below.
After that, we go to the Connection Manager option present in the Assembly tab and select on the all washer points and then we press middle mouse button to get the connection manager tab. We have 3 tabs in the connection manager menu namely connectivity list, connection list and FE representation settings. We go to the connection list and we proceed to give connection for which all parts we want using F1 tab we go to the model and we select each and every part and press enter to confirm since this model has a single PID we don't need to go every time and select the parts, after confirming the connectivity list tab is also updated based on the connections given. Finally, we go to the FE representation tab and under it we provide the FE representation type as Bolt and then we provide the zones to be attached as In/Out so that all the zones inside the bolt connections get rigidly fixed. We apply all the settings and click on Realize option. The connection manager tab is shown in the figure given below.
We, finally obtain the bolt connection in which all the nodes nearing to the boundry of the bolt connections are connected using RBE2 and there vertical connection between these connections as shown in the figure given below.
Spot Weld Connections:
In this type of connections, we provide connections to wherever the spot weldings are going to be done in the rear door model. We first create a 3D point near the weldings areas using the On COG option present in the Points tab of TOPO module. Then we convert the 3D points into spotweld points using Convert option present in the Assembly tab as shown in the figure given below.
After that, we go to the Connection Manager option present in the Assembly tab and select on the all spotweld points and then we press middle mouse button to get the connection manager tab. We have 3 tabs in the connection manager menu namely connectivity list, connection list and FE representation settings. We go to the connection list and we proceed to give connection for which all parts we want using F1 tab we go to the model and we select each and every part and press enter to confirm since this model has a single PID we don't need to go every time and select the parts, after confirming the connectivity list tab is also updated based on the connections given. Finally, we go to the FE representation tab and under it we provide the FE representation type as RBE3-HEXA-RBE3 and we then provide the value of the search distance, after that we lock the spotweld in all axes i.e. 123456 using the RBE3 Pinflags option and finally we create a Solid ID to represent the spotweld. We apply all the settings and click on Realize option. The connection manager tab is shown in the figure given below.
We, finally obtain the spotweld connection in which all the nodes nearing to the boundry are connected and the solid hexa elements are formed to represent the spotweld as shown in the figure given below.
Window Bushing Connections:
In this type of connections, we provide connections to the window with the help of bushes so that the window doesn't break during the NASTRAN simulation of the rear door. First, we take the curves from the windows which include the fixed one near the C pillar and the sliding window or main window using the Feat2Curve option present in the Perimeters tab of the Mesh Module. Then, we convert the formed curves into spotlines using the Convert option present in the Assembly tab as shown in the figures given below.
We, then go to the connection manager to provide connect data. We have 3 tabs in the connection manager menu namely connectivity list, connection list and FE representation settings. We go to the connection list and we proceed to give connection for which all parts we want using F1 tab we go to the model and we select each and every part and press enter to confirm since this model has a single PID we don't need to go every time and select the parts, after confirming the connectivity list tab is also updated based on the connections given. We go to the FE Representation type and provide it as RBE3-CBUSH-RBE3. In that, we provide the search distance, we also tick in the check box of the Keep all branches so that we can visualize spotline even after realizing it. We, then provide the Bush ID in which we provide the 6 different stiffness constant to the bush. Finally, we click on apply and realize. The figures of Bush ID and Connection Manager as given below.
After that, we go to the cbush elements and see that all the cbush elements are oriented with respect to the vector direction. Therefore, we change it with respect to the local coordinate system by right click on all the cbush elements and then give modify after it a new tab opens and we go for new modification using modification rules where we provide orient as the modification and align it with respect to the coordinate, then give the coordinate point as 0 and then give ok. We obtain all cbush elements aligned in the same coordinate system according to the local coordinate system. The figures are given below.
Finally, we obtain the cbush connections as shown in the figure given below.
Conclusion:
We obtain connections for the whole rear door model which include RBE2 connections, Bolt connections, Spotweld connections and Window bush connecions. These connections would make the model perform well in the NASTRAN NVH solver simulations. The final connected finished model are shown in figures given below.
Learning Outcomes:
1) Ability to work with complex models like seat, door etc.
2) Giving connections which include RBE2 connections, Bolt connections, Spotweld connections, Seamweld connections and Window bush connecions using the NASTRAN Module.
Model Link:
https://drive.google.com/drive/folders/1RacR-xmJHT7Mdo5bMBFPlxOB7-rSL9e4?usp=sharing