Week 6

Aim :-

Connections of rear door of car using ANSA Nastran deck

Objective :-

To perform the connections on rear door of the car using the appropriate type of connections

Introduction :-

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. Powered doors are usually found on minivans, high-end cars, or modified cars. Car door parts include

• Door card
• Door handle
• Door switch
• Glass window
• Pillar
• Power door locks, which can work on a remote system
• Interior storage compartment

Fig . all the necesary connectio used in the rear door of the car

fig. connection for the window glass

Methodology :-

1. Import the model into the ANSA Nastran deck.
2. Setting the PID for the model.
3. Perform the connections.

Step1- Importing the file in ANSA Nastran deck :-

NASTRAN is primarily a solver for finite element analysis. It is commonly used for performing the structural analysis. It commonly used in the aerospace and automotive industry for computational stress and strain analysis of components. Moreover it also most commonly used as an NVH ANALYSIS ( noise , vibration and harshness ) .

The model extension .nas is opened as input in NASTRAN as the normal ANSA won’t recognize .nas extension .

Fig 1. Rear door model in NASTRAN deck

Step 2 - Setting the PID for the model parts :-

Since the rear door is not a single component, it is made up of small other sheet metal components joined together. Another reason for assigning the PID so that while performing the connections only specific region or parts can selected for deploying the connections.

Fig 2. PID for the rear door model

Fig 3. Rear door after setting PID

Step 3. Perform the connections :-

Why do we connections ?

Rigid body elements are used creating connections such as representing a bolted connection. Modeling a bolt is complicated, and in many cases it is known from experience that the bolt never fails under conditions we are simulating it for. Therefore a web of rigid elements are connected to the bolt holes. These elements infact will not deform as they are considered to be infinitely rigid (diamond under atmospheric pressure for example even though it's not infinitely rigid) and the sole purpose of these elements is to transfer the loads between the grid points or nodes.

The rear door of the car is made up of sheet metal works and the most connections are temporary connections i.e nut and bolts , screw and nut because for the overhauling purpose in case needed. But the there are certain region where permanent connections are used for ex. Spot weld. So the type of the connections we are going to used here are

1. RBE 2 many and 2 nodes
2. RBE3-CBUSH-RBE3
3. RBE3- HEXA-RBE3
4. Bolt

1. RBE2 MANY and RBE2 TWO NODES

RBE2 transfers the loads in such a way that all the slave (dependent) nodes have zero relative deformation after the load application. Moreover RBE2 elements induce stiffness to the region as compared to the RBE3 element.

Here there 2 hinges one that connected to the door and the other that will be connected to the car and the earlier hinge.

Fig 4. Two hinges of the rear door

For connecting the we are going to use the RBE2 many nodes to constrain the any relative motion between them. Go Nastran > RBE2> MANY NODES.

So all the nodes on both holes are connected with only one master node.

Fig 5. The hinges are connected with RBE2 many nodes

Now in between these 2 hinges one rod must that is responsible for the rotation for the door in one direction. For that we will use the RBE2 two nodes to connect the hinges that will represent the rod for rotation.

Fig6. Using RBE2 two nodes

Here we releasing the one DOF along the Z axis that will be rotation of the door.

Fig7. Releasing the DOF in z direction

Fig 7. RBE2 connection is deployed in hinges

Like we are going to use the RBE2 connection in model as suited in the required region.

2.RBE3-HEXA-RBE3

With one dependent node(master node) and several independent nodes(slave nodes). Irrespective of the locations at which the independent or slave nodes are located from the master node, RBE3 distributes the force using weighted average method using centroid of slave (independent) nodes.

These RBE3 HEXA is used to represent the connection of the spot weld between two parts.

For that first we have to create a COG point then the point is converted to the spot weld.

fig 8. Converting the point to Spot weld point

To realize these point into connection go to CONNECTION > SELECT the spot weld point> RBE3-HEXA-RBE3

Input the search distance ( search distance is distance between two parts ) as per requirement.

Constrain all DOF

Select the part for the connection

Create the PID for the spot weld

Fig9. Creating the PID for spot weld

Fig10. data for connection are assigned

After inputting the requires data the connection is applied and then realized for final representation.

Fig 11. RBE3-HEXA -RBE3 connection representation .

3.RBE3-CBUSH-RBE3

The CBUSH connection are used to represent the weather strip that are installed in the windows between the glass and the window frame. The weather strip allows to make the inner compartment preventing any leakage to outside when the AC is switched on.

So why RBE3 ?

In simple and easy terms RBE3 are a bit softer connection as compared to the RBE2 that are much stiffer. Since here it is the weather strip which actually made up of rubber so the connection dose not need to stiffer.

For deploying the CBUSH connection the outside line of the windows is converted to the CURVE then this CURVE is converted to SPOTLINE.

Fig12. Window glass edges is used to make curve

Fig 13. Curve is converted to the SPOTLINE

For deploying the CBUSH connection go to CONNECTION> select the spotline curve ( select only one part of the curve at a time to deploy)> select RBE3-CBUSH-RBE3

Now unlike spot weld here also we have to create the PBUSH PID

FIG 14. CREATING SPOTLINE (PBUSH) PID

These K is the damping coefficient value of the strip along the 6 direction. These value are provided by the design requirement.

fig 15. Data for the CBUSH are fitted.

Fig 16. RBE3-CBUSH-RBE3 is deployed

Now there are numbers of the CBUSH present and all of them had there own property id and there co-ordinate axis. Like here all bush element are aligned according to the local co -ordinate axis and they need to be aligned with the global axis.

Fig 17. All the bush are aligned according to vector

To align all bush element one by one will take much time. In order to save time

Select all the bush element>modify >modify rules

Creating to ORIENT>CORD ( global co-ordinate)

Cordinate >0>ok

Fig18. Changing the orientation axis of bushes

Fig19. All the bush are aligned with the global axis

1. BOLT

Bolt connection are the temporary connection as they can be removed easily anytime without any damage to the component.

To deploy the bolt connection first the COG point is created and it is then realized to BOLT

Fig20. Realizing the COG point to BOLT

FIG21.inputting all the data for the bolt connection

Now the for the positioning of the bolt there are 4 ways

• Inner
• In/out
• In/out x
• Outer

Any of these can used of positioning , here we are using in/out

Fig22. Bolt connection is deployed using IN/OUT

Connection for the handle of the door :-

The handle of the car has two holes on the door for attachment but the component is the single entity as per the simulation purpose. It can be connected by the RBE2 many nodes .

Fig 23. Handle is connected with RBE2

But the for simulation purpose there is some mass to the handle that needs to assigned. To do that

Nastran>CONMI>CONMI2>NODES > select the node connecting two regions

Fig 24. Assigning the mass to the node(CG) in C0NMI 2

All the mass assigned in the ANSA are used in TONNES. So the 100g mass of handle is inputted as 0.0001

Washer connections :-

Washer connection are used in the nut and bolt to increase the area under stress and to tight the nut and bolt.

To deploy the washer connection first the ZONE CUT options is used to create the zone around the holes

MESH > ZONE CUT > select the holes

Fig 25. Creating the zone cut around the hinge hole

After creating the zones , the RBE2 Many connection is used for the representation but the the ENTITY mode is used for selecting the nodes.

fig 26. Using entity mode for selecting the nodes

Fig 27. RBE2 connection for washer is deployed

Like these using all the above connection type , all the connection are deployed on the rear door as suited.

Fig 28. All the connection are deployed on the rear door

Results :-

• All the RBE2 and RBE3 connection are deployed
• CBUSH connection is deployed
• Washer connection is also deployed

Learning outcomes :-

• Learnt about the RBE2 Many and two node connections
• Learnt about the BOLT and WASHER connection
• Learnt about the RBE3 CBUSH connection
• Learnt about the spot weld connection
• Learnt about the assigning the mass to the nodes

Conclusion:-

All the connection on the rear door are deployed successfully using various type of connections. Some region does not have any holes to do connection but it is necessary to join them otherwise it will have problem in the simulation.

link for the model : https://drive.google.com/drive/folders/1XVxzIrjiSAOXxTYJAi88ctDbGmXvJxeB?usp=sharing