Week 9 - Creating connection for Rear door

1.

AIM : 
To perform suitable connections between various parts/components in the rear door FE model provided, after creating and applying different PIDs to the aforementioned components that are part of the model.

CAD MODEL IMAGE

 PROCEDURE
1. Firstly, in order to set up the more complex connections for the challenge, it is important
to differentiate components as the connections may require different PIDs. This entails the
first step. The entire model will be separated into different PIDs.

This requires creating said
PIDs and that can be done via Faces > Set PID in the topo deck. The region is then selected

 

 after creating the PID for the each region for the part :

 2. We can start off with RBE2 connections. The RBE2 tool can be accessed via Elements >
RBE2 in the NASTRAN deck. It primarily has the 'many nodes' and 'two nodes' options. In the
following example, we deploy the 'many nodes' option to connect two holes with a single
master node. This is merely done by selecting the two sets of nodes surrounding the holes
and letting the algorithm create a master node and form connections by running through
the straightforward process. This is also known as a cluster node RBE2

 Image  is before the connection apply on the part 

 Then there is the two-node RBE2 process. This involves connecting two sets of RBE2 spiders
using a double con. The RBE2 component is created separately for each hole using the
Elements > RBE2 > Many Nodes option discussed before. Through this process, we'll have
two master nodes (which are to be connected). To connect them, we shall be using the
Elements > RBE2 > Two Nodes tool. Then it is just a matter of selecting the two master node
to form the connection. This is typically used in cases where assigning properties for the
bolt stem might be a requirement.

 Image after the connection :

 

 However, in this case (which is a hinge), care must be taken to assign the D.O.F.s
accordingly. A hinge joint requires yaw movement and as such will have 5 D.O.F.s fixed.
Meaning, when defining it during the Two Node RBE process, care must be taken to ensure
the value of 'CM' is 12345 (instead of the standard 123456) to allow the aforementioned.

image fro the around the z- axis roation will be free:

 2. 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 the Points > on COG tool from the topo deck).

 image for the ON COG :

 

FOR BOLT CONNECTION :

 

IMAGE FRO CONNECTION MANAGER CONVERSION :

 In the set of options, the sections P1, P2 & P3 need to be assigned (since there are three
layers). The part on the same plane as that of the bolt point would be P1 and the others can
be assigned interchangeably. To select the PIDs for each, right-click on the option (P1, P2 or
P3). A box pops up. There, we need to press F1. This will let us select the particular PID.
The FE Rep Type needs to be 'BOLT'. The search distance can be assigned according to the
distance from the bolt point (such that the algorithm would detect the other holes in the
search distance). I assigned 30mm in this case. And finally, the Zones option would be
'inner'.

3. Now onto the door handle. In this region, we need to create a connection that applies a
mass (to represent the handle). For this, we need to create RBE2 nodes in either handle
holes separately (using Elements > 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 the Con Mass tool, accessible through Elements > CONMi > CONM2 >
Nodes. Then the previously mentioned master node is selected. This is where the mass of
the handle will be concentrated. After proceeding, the algorithm lets us assign the mass
('M' in tonnes) as shown below:

In this case, the mass of the handle is 150 grams (or 0.00015 tonnes). Hitting 'OK' forms the
Con mass connection

 

4. Next, we shall focus on weld connections. We shall be looking at seam and spot weld
connections. In the case of seam welds, the basis is creating the weld locations from
curves derived from the particular feature. Therefore, we shall be using the Perimeters >
Feat2Curve option from the Mesh deck. This will let us select the edge and derive a curve
from it as shown (after creation, the original component can be hidden to avoid confusion

Image for the seam weld :

For spot welds, we shall be making use of the COG tool again to create 3D points. These 3D
points are then converted into 'spot welds' as shown

After conversion, it's the same process of accessing the connections manager and
assigning properties. This time, since it's a spot weld, the FE Rep Type would be RBE3-HEXA
RBE3. A suitable search distance is assigned. P1 would be the same component on which
the spotweld point is situated and P2 would be the layer

RBE3 pinflags should be constrained in all D.O.F.s. Furthermore, a PSOLID will need to be
created and assigned. The following are the resulting spot weld connections:

5. The last type of connection involved in this challenge would be that of CBUSH RBE3
elements, which will be used wherever window weather strips (seals used to keep interior
air in and external elements out) 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 the Transform > Copy tool for
this. A distance of 5 mm should be adequate

Selecting the curves, they can be converted into Spot Lines using the Convert > Curves
tool. Each curve needs to be selected separately and converted. This is to ensure they
aren't grouped together when establishing the connections

After converting them, we avail the help of the connections manager again to create these
CBUSH connections (FE Model will need to be turned back on if it isn't). The process will be
repeated for each curve.
For the options, we will need to select the P1, P2 (& P3 if needed) as usual. But here, spacing
(S) needs to be specified (10mm). The FE Rep type would be RBE3-CBUSH-RBE3

FINAL MODEL IMAGES

With all connections

LEARNING OUTCOMES
1. Learned about various connections available in the NASTRAN deck.
2. Learned to convert curves and points into connection lines/points.
3. Learned to assign properties to connections and edit said connections as per
requirements.
4. 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.