Week 6 - Creating connection for Rear door

Week – 6 Creating connection for Rear door

Objective – To perform suitable connections between various parts in the rear door in the FE model given in the challenge.

Step -1 – Import the CAD model in ANSA as shown in the image below;

Step -2 – In order to setup the connections for the challenge, it is important to differentiate components as the connections require different PIDs. The entire model is separated into different PID. This requires creating said PIDs and that can be done via, Faces> Set PID in the topo deck.

Here, the new property IDs are created for different parts of the model, process is repeated until PIDs have been assigned for every component in the model. As shown in the figure below;

Step -3 We can start with the RBE2 connections in the NASTRAN Deck. The RBE2 tool can be accessed via Elements> RBE2. It has primarily two options ‘many nodes’ and ‘two nodes’ options. In the following example, We deployed the many notes option to connect 2 holes with a single master node. This is also known as a cluster node RBE2. As shown in the figure below;

However in case of hinge of the door panel as shown in the figure below, care must be taken in assigining the DOFs. A hinge joint only has one degree of freedom. During two node RBE2 process, care must be taken to ensure that the value of ‘CM’ is 12345 to allow only one DOF.

There is another way to assign Bolt connections, which becomes especially useful in cases where there are more than 2 layers that require connecting. This will involve using the connections manager. Before that we need to create a COG point in one of the holes from a layer in the middle (using points> on COG tool from the topo deck).

Connections for door handle. In this region, we need to create a connection that applies a mask to represent the handle. For this we need to create RBE2 nodes in either handle holes separately. Using Element> RBE2> Many nodes).

Again, using the same tool, the two master nodes for either handle hole is selected and another connection is created with the algorithm assigning a new master node at the centre of this connection. Now, we make use of con mass tool, accessible through Elements> CONMi>CONM2>Nodes. Then previously mentioned master node is selected, This is where the mass of the handle will be concentrated, as shown in the figure below.

Next, we shall focus on weld connections. We shall be looking at the seam and spot weld connections. In the case of seam welds, the basis is creating the weld locations from curves derived from the feature. Therefore, we shall use the perimeter>Feat2Curve option from mesh deck. This will let us select the edge and derive a curve from it as shown.

Again, as before we make use of connections manager. The seam line is selected and on prceeding, we get the same set of options where we need to tell ANSA what kind of connection we intend on creating. As before, P1 and P2 are selected. The FE Rep type here would be overlap shell since both layers are parallel to each other.

Spot-weld technique is also used for connections wherever required in the model, firstly we need to create a COG point then give connection as spot-weld and then suing connection manager connect the two faces using spot-weld using RBE3-HEXA-RBE3 type. A shown in the figure below.

The last type of connection involved in this challenge would be that of CBUSH RBE 3 elements, which will be used wherever window weather strips (seals used to keep interior air in and external elements out for proper air conditioning) are involved.

To begin, the perimeter of the glass components is used to create curves. For this perimeters> feat2curve tool is used to select and create them, These created curves are then used to create a single set of offset copies, This is considering connection requires setting up on either side of the glass. We can make use of Transform copy options for this. A distance of 10 mm should me adequate.

After converting them, we avail the help of the connections manager again to create these CBUSH connections. This process will be specified (10mm). the FE Rep type would be RBE3-CBUSH-RBE3. After this process is repeated fort each spot line created, we need to reorient them since they use local coordinate system which is different from the global coordinate system.

Final connections for the model is done and as shown in the figure below.

Learning Outcomes –

Learned about various connections available in Nastran deck.

Learned how to connect window with door panel, using CBUSH element.

Learned to convert girls and points into connection lines/points.

Learned to assign properties to connections and edit said connections as per requirement.

Learned about the concept of weather stripping and its importance. Along with the concept of Tailor welds.

Conclusion –

Suitable connections were deployed between various components in the rear door model after PIDs were assigned to each component.