PROVIDING CONNECTIONS FOR REAR DOOR MODEL USING ANSA

PROVIDING CONNECTIONS FOR THE REAR DOOR USING ANSA

AIM:

• To give appropriate connections for the given model using ANSA.

OBJECTIVES:

• To set PID’s for various components.
• Getting to know appropriate connections for various parts.
• Providing connections using Assembly Deck.

PROCEDURE:

1.PID SETTING:

We have to define the properties for various components available in the rear door model. So that we can be able to connect the components with appropriate connections.

Step 1: Open the Properties list dialog box from the Lists Deck or by pressing Ctrl+P Shortcut Key. Right click on the properties dialog box then from the list of options select New->PSHELL->PSHELL.

Step 2: PSHELL dialog box opens where you can enter the Thickness property, then click OK. Now new shell property is created. (In this model thickness of all the Shell property were assumed as 1mm).

Step 3: Right click on the property and select Apply from the list of options.

Step 4: Now select the entities to which the property needs to be applied.

Step 5: Now middle click. The selected property will be applied to the selected entities. It can be seen by switching to PID mode from the Drawing Styles Deck. The Entities will change into same colour as PID’s colour as shown below. (The Hinges were turned into Pink colour which is the PID’s colour for hinge)

All the entities should be applied with different PID’s as said above.

The model below shows PID’s applied to all the parts.

2.PROVIDING CONNECTIONS:

In this model we have various types of connections which are listed below,

1. Bolt Connection (RBE2 Connection)
2. Spot Weld Connection.

• CBUSH Connection with RBE3 element.

1. Bolt Connection (RBE2 Connection):

This type of connection is used in places where the bolt and nut are used to join the parts rigidly or to connect the parts allowing any degrees of freedom to get constrained movement. For example, Door Hinges, Folding seats etc. In ANSA we can apply bolt connection either by using Nastran Deck or by using Assembly Module.

1. Bolt connection using Nastran Deck:

In Nastran deck RBE2 connection is given by using the element nodes.

Step 1: In NASTRAN Deck select Elements->RBE2->Many Nodes.

Step 2: Select the nodes to form RBE2 element.

Step 3: On clicking Middle click various options as shown below open. You can apply the DOF of the RBE2 Element and its part.

Step 4: On clicking Finish, RBE2 element is created as shown below. In this kind of pair of elements, one represents bolt and one represents the nut.

Step 5: To create a stem of the bolt Select Elements->RBE2->Two Node. Select the master nodes of two RBE2 elements.

Step 6: On middle click RBE2 properties dialog box opens up as shown below

Step 7: On clicking ok bolt stem is created represented by a double con and it is free to rotate about z axis.

The bolt connection can also be given at one click without the two node RBE2 element by selecting all 8 nodes and once in Step 2 shown above. It will form a cluster RBE2 connection with one master node. The bolt connection will be represented as shown below.

2. Bolt connection using Assembly deck:

In this method the bolt connection is made by using Points as a reference and connection is given using the assembly deck.

Step 1: Create a Points at the centre of the geometry. Select Points->On COG->Edges from Topo module and select the edges of the hole on which you need to create a point. If you have more the two holes try to select the middle one.

Step 2: On middle click the point is generated on COG as shown below.

Step 3: Now the Point is transformed into Bolt connection by using Transform->3D Points Option in Assembly deck.

Step 4: Select the Points that needs to be changed into Bolt Connection and Middle Click. Now ANSA displays list of connection types.

Step 5: Select Bolt from the list and click Ok. The 3D point is converted into a Hexagon shaped point representing the Bolt connection.

Step 6: Now select the Connection manager from the Assembly Deck.

Step 7: Select the Bolt and click Ok. Connection Manager dialog box appears as shown below. Here we have 3 parts to connect. Double Click on P1 and press F1. Select the any of the three part and Give enter. P1 is applied similarly apply P2 and P3. As you select the parts it will be listed in the dialog box with the PID.

Step 8: The parts that needs to be bolted were selected. The above window shows the FE Rep type as none which means the bolt connection is not given. Now click on the FE rep type and ANSA will show the list of connections in ANSA, from the list select Bolt

Now ANSA will show the options in Bolt connection as shown below.

Step 9: When you click Apply and Realize ANSA will show the bolt connection as shown below.

 ii.SPOT WELD CONNECTION:

In Automobile body assembly Spots welds were used at all possible places to reduce the weight as they don’t use any additional material like Bolt Connection.

Spot weld connection is used to weld the parallel Sheet metal parts. In the areas shown below the supporting beams were in parallel with the supporting members attached with the door panel. In this kind of areas generally welding is used.

In ANSA Spot weld connection is given by using Assembly deck as shown below.

Step 1: Create the points where the spot welds needs to be applied using Points->On COG in Topo Module.

Step 2:  Transform the Points into Weld Spots using Transform option in Assembly deck. In the image below you can see that the 3D points have converted into Weld Spots.

Step 3: Select Connection Manager from the Assembly deck and Select the Weld spots and click Ok. Connection manager dialog box appears as shown above.

Step 4: To Assign P1 and P2, Double Click on P1 Data Box press F1 ANSA Shows the PID’s which we’ve created. Select the PID’s to be assigned for P1. Similarly select P2. The PID will be listed in the connection manager.

Step 5: To assign click on FE Rep Type List. ANSA will show the list of connections available Select RBE3-HEXA-RBE3. (In ANSA Spot weld is represented by RBE3-HEXA-RBE3).

Step 6: ANSA will show the list of options to create a spot weld.

Step 7: Once all the details were entered as shown above Click on Apply and Realize. ANSA will Create the spot weld on the places where the points were created as shown below.

Similarly, spot weld is applied in all the places where ever necessary.

iii. CBUSH Connection using RBE3 elements:

CBUSH elements were created at the places where the Damping factor is required. In this model we have the glass on the window on which one is rigid and another one will be sliding up and down between the door panels. Fixed glass should be given with rigid connection it can be done by establishing the RBE3-CBUSH-RBE3 connection on the both sides of the glass. For the sliding window the rigid connection should be given only where the glass slides into the door panel areas, on the remaining three sides the connection is established only one side of the glass.

The steps below show how to establish RBE3-CBUSH-RBE3 connection.

Step 1: Create a curve using the FE of the glass. Select Perimeters->Feat2Curve from the Mesh module. Select the edges that needs to be converted into curves as shown below.

Step 2: On Middle click the model browser opens up, you can create a new part for the curve or use existing part after selecting when the middle click is given curve is generated as shown below.

Step 3: Copy the curves where the rigid connection needs to be given. Select Transform->Copy from Utilities Deck And select the entities that needs to be copied. In below image the curves selected at the places only where the Rigid connection will be given.

Step 4: On Middle click Copy Entities Dialog box opens up. In that Enter dy value as 1 as we need to copy the curve in Y direction. Distance as 10 mm and on middle click Transformation dialog box opens up parallelly after selecting the options and on middle click curves will be offset for 10mm in the direction of y.

In below image you can see the curves offset

Step 5: Covert these lines into Spot Lines using Convert->Curves from the Assembly Deck.

Step 6: Now select the Connection manager in Assembly Deck. Now Connection Selection assistant opens up and select the spot line that needs to be converted into RBE3-CBUSH-RBE3 Element. In the image shown below the spot line which is selected is shown in white colour.

Step 7: On Middle Click the connection manager window opens up in that Double click on the P1 then press F1 ANSA Shows the list of PID’s created, from that list select the Glass PID similarly select P2 as the Inner trim component.

Step 8: After selection of the above said components make a middle click. ASNA will shows the options for creating the RBE3-CBUSH-RBE3 element.

Step 9: After making the selections click Apply and Realize. The CBUSH elements were created.

The RBE3-CBUSH-RBE3 elements in the model is represented as shown below.

The CBUSH elements were created successfully. The Coordinates of the bush elements created doesn’t match the orientation of the Vehicle coordinates. CBUSH Coordinates 1,2,3 represents the X,Y,Z coordinates of the vehicle respectively.

To orient the bush elements, Select Database->Elements->CBUSH. ANSA will list the CBUSH elements in the CBUSH dialog box. Now select all the CBUSH elements from the CBUSH Dialog box. Right Click->Modify in the CBUSH dialog Box. A modify window will pop up in modify rules from the dropdown list select Orient then Click on ‘+’ to add the modify rules Dropdown box from the 2^nd box select CID.

Now from the orient Select “with Coord” and enter 0 in the CID value. Click Ok will orient all the CBUSH elements with the local coordinates.

Click Ok will orient the coordinates of all the CBUSH elements with the vehicle coordinates as shown below.

3.DEFINING MASS:

The parts such as Door handle, Rear View mirrors on the door were not modelled for NVH. Instead of that the mass of the part is assigned in the COG of that part. In this model for door handle we need to define the mass. In ANSA the unit of mass is in tonnes by default. So, whenever the mass value is entered it should be in tonnes.

Below steps shows how the door handle is represented.

Step 1: Define RBE2 connection on the holes provided for mounting the handle by using RBE2-> Many Nodes from the Nastran Deck.

Step 2: Create a RBE2 element using the master nodes of the two RBE2 Elements using RBE2->Many Nodes from the Nastran Deck. The Master node of the RBE2 element will be the COG of the Part.

Step 3: To apply mass. Select CONMi->CONM2->Nodes from the Nastran deck, Select the Master Node and Middle Click. ANSA will show the CONM2 dialog box. In that enter the mass value. Mass of handle assumed to be 150Gms.

(1gram= 1x 10^-6 Tonnes=> 150Grams= 0.000150 Tonnes.)

Step 4: On clicking ok the mass is defined at the Node which is selected and represented as DOT at the selected Node as shown below.

LEARNING OUTCOMES:

• Gained good knowledge on connections and their DOF’s.
• Learned how to give connections on brittle parts.
• Learned to give appropriate connections where the connection data isn’t available.
• Applying mass on the on the COG of elements which weren’t captured in the model.