Week 6

WEEK 6 CHALLENGE

REAR DOOR CONNECTIONS FOR CAR USING ANSA

OBJECTIVE:

• To give different types of connections for rear door model of car.
• These connections are given to the model using ANSA in NASTRAN deck which will be used later for NVH simulation.

ABSTRACT

Door assembly is very important model in the car as it consists of different types of connection representations. Different mechanisms are also present in the door assembly model like door lock mechanism, hinge mechanism, glass slider mechanism and latch mechanism. In this challenge I have used RB2, RB3 and seam lines, spot welds etc. These connections are for NVH simulation.

METHODOLOGY

1. Import the meshed model
2. Assign the property ID (PID) for different regions
3. Identify different mechanisms and assign various connections for rear door model.

INTRODUCTION:

Nowadays, automobiles are made using two strategies. One is using lighter materials for cost reduction and other is by improving the designing. Usually tailored cut is used while manufacturing the door model. In this tailored cut the door panel consists of two different thicknesses. Thickness to the side of the hinges is more than the thickness on the other side. This is because the whole weight of the door will act on the side which has more thickness. These two thicknesses are joined using laser welding. Laser welding is used as it has no filler material, ensures that the original chemical composition is maintained due to extreme focus of the beam, even the heat affected zone is reduced to a minimum. It also consists of atmospheric strip (usually made of rubber). which acts as a seal and does not allow outer air to flow inside the cabin.

Dismantled door with panel

rear door without panel Atmospheric strip

PROCEDURE:

Step 1: Import the model. Before assigning connections for the model once observe the real car model as it gives idea for the different types of connections used for various mechanisms.

Imported rear door model

Step 2: Assign different PID’s for Glass and the parts which are needed to be welded.

PID’s assigned for the model

Step 3: In this challenge we use different kinds of connections. The various connections are as follows:

• RB2 Rigid is simply used to rigidize the hole. This type of connection is used where there are no bolts or washer elements. Use Elements --> RB2 --> Many nodes for connection, we can select all the nodes using loop selection. After selecting all the slave nodes a master node will be formed which connects all the slave nodes.

Selecting slave nodes using loop

Master node is created for the selected slave nodes Rigid RB2 connection

• Zone cut: It is used when an area must be rigidized at a particular region. This region acts as a washer element during simulation. Therefore, this type of connection is used where bolts exist. One must click on the edge of the circle using loop selection then the whole circle will be selected. Then specify the offset value. Now some area will be reconstructed using the existing mesh parameters in order to form zone cut.

Specifying offset value for zone cut

Reconstruction selected automatically in order to form zone cut Zone cut formed for the selected hole

• Now use Elements RB2 many nodes, select the region using poly line selection in order to select all the slave nodes easily. Then RB2 connection is deployed along with Zone cut.

Many nodes RB2 with zone cut

• Cluster or Spider RB2: This connection is used when a manual bolt connection must be deployed between two or more surfaces.
• For automatic bolt connection one must follow these steps, Create COG for the hole --> COG is basically a 3D point, convert this 3D point to bolt --> Now open connections manager and select the bolt symbol which has created in earlier step --> Then assign P1,P2,P3 --> Select FE type as Bolt and give the required values and constraints --> apply and then realize the connection.

Deployed bolt connection without body Deployed bolt connection with body

• Hinge connection must be constrained to only five degrees of freedom as this allows the door to open.

Info of RB2 two node for hinge

• Spot welds are also parts of connections. In ANSA spot weld can be deployed between different surfaces. Create curve --> convert the curve to spot weld --> Then open connections manager and select the spot weld curve and then assign P1, P2, P3.
• Mostly overlap shell is used when the surfaces are parallel and y joint shell is used in perpendicular surfaces.

Converting curve to spot weld

Realized spot weld using overlap shell

• Spot weld using RBE3-HEXA-RBE3: Create COG --> Convert COG to spot welding point -->Use connections manager to generate RBE3-HEXA-RBE3.

Realized Spot weld using RBE3-HEXA-RBE3

Generated RBE3-HEXA-RBE3

• CONMi: It is referred to as con mass. It is basically a concentrated mass connection where a point is created for representing the weight of it. We must give the mass in tonnes. Here we gave the handle mass as 100 grams which is 0.0001 ton.

Con-mass for handle

• CBUSH Connection: This connection for the glass is always given in closed. 1^st create curves using Perimeter --> FEAt2Curve option which is available in mesh mode. Then convert those curves to Seam Lines. Now using connections manager assign ‘P’, ‘S’ values and select RBE3-CBUSH-RBE3 as FE type for generating CBUSH connection.

Curves which are converted to seam lines

Connections manager for deploying CBUSH

Generated RBE3-CBUSH-RBE3 Connection

• Generated RBE3-CBUSH-RBE3 Connection has its own Local coordinates which are different from each other. This could create some disturbances during simulation. So, we need to convert all the CBUSH coordinates to Global coordinates. This can be done by changing the CID value to 0 in CBUSH properties.
• We can change all the CID values in a single shot using Modify option.

Local coordinates before modifying

Modifying CID values of CBUSH

Local coordinates after modifying them according to global coordinate

• Atmospheric strip (or simply rubber strip) can be assigned in ANSA. Create curves using Perimeter --> FEAt2Curve option. Then convert those curves to seam line. This acts as a rubber strip during simulation. White line in the below picture indicate rubber strip.

Assigning rubber strip to rear door model

LEARNING OUTCOME:

1. Assigned various connections according to the required mechanism.
2. Learned and implemented all the connections in ANSA.
3. Studied different real-life concepts about connections used in car.

CONCLUSION:

In this challenge I have deployed connections with RB2 and RB3 elements successfully. Constrained the hinges to five degrees of freedom. Learned different concepts regarding tailored cut. Learned all types of connections used in ANSA.

Model of ANSA file link :

https://drive.google.com/file/d/1UPdOJ0sjIw2A_nGh96iX3ZYYMD6n6RoV/view?usp=sharing