Connecting the Rear door of a car using connectors in ANSA

AIM

Make the necessary connections for the Backdoor automobile door given

OBJECTIVE

Once we are done with the meshing of the relevant components ,our ultimate aim is make it for the analysis and find out the results we want to check from it such as whether it is durable,weather it is producing a large amount of penetration and stress and strain while the crash happens etc... Such results we need to find out using our FE model.But the backdoor model of the automobile cars itself having some sheet metal parts and inaddition to it. It also have the trim component which is the plastic part for the providing the power window switches and lock switches etc..And obviously it will be having the main window glass and some cases it will be having a non retractable small fixed glass.This is usually seen with the rear door and some cases even front doors also have the same.Here the model we are given is also having the non retractable glass attached with the mian window glass.Now before moving on to the analysis we always make sure that the componenet is perfectly connected well to each other with the exact connections we use while manufacturing the doors. Every preprocessor have the ability to simulate the real life connections in FE .ANSA have the every connections available in it to help us for making the relevant connections for our FE.This we must make sure because the unconnectivity between any parts which are not suppossed to be unconnected will definitely gives us the incorrect results and if we trust those results and then move on with the physical experimentation for the verification of the results we will end up with big loss and we can see the results from both are not same and have drastic differance in between.Even before running the analysis some solvers have the provison to warn us about the unconnectivity so CAE engineers will ensure that,But it is the duty of the integration engineer to ensure this connections .

PROCEDURE

Here we are given with a FE model of a rear door, But the CAD model of the door is not available with us,So the exact connections are not avilable it to us , but we can make the connections by the inspecting the areas one by one.Fisrt open the Nastran file in ANSA by using File >OPEN > Select the file > Open.

Fig 1 Full Rear Door FE Model

We can see in the inner panel there is two differant PID set for the same meshed part.This is made because when the door is in open postion, the entire load of the door will be acting on the door hinges.This door hinges need to be supported inorder to prevent it from failure.So we need to give a little much more thickness to the inner panel area which is near to the hinge.This can be done in FE by only put the area in a different PID and asssign thickness to it.In real life this will be two sheet metal parts having differant thickness whic are welded together .This weld is called TAylor Blank . At the same time why we can't make the entire area with the same thickness is because if we do like that then the weight of the door will get increased a lot due to the addition of more material.SoWe just made those only little bit more strengthed.Nowadays the automobiles OEM's are looking to make more and more light doors.

Fig 2 Taylor Blank in Real Life

Fig 3 Taylor Blank in Fe

When we look into the model we can see the hole in some areas where it may be connected to some other parts.But we are not aware the part.So inorder to make the connection possible with the other part we need to make a RBE2 connection at such places we specifically use a cluster RBE 2 rigid connection at those places.To make up this connection we need to move to the NASTRAN or any other deck module > Select the RBE2 > Many nodes >select the nodes on the hole on which we need to make our cluster RBE2 > Middle click.This can be done on the areas we need to make cluster RBE2.

Fig 4 Cluster RBE2

The hinge part of the car door is avilable in the FE .Hinge is used for the proper opening and closing of the door and check arm portion on sheet metal part is also provided.So in the hinge portion, is connected to the structural part of the door using ths cluster RBE2 and there is a new bolt connection is done on the hinge hole provided,because any way the hinge part must be fixed to the door and the matching holes also available in the door itself.So a bolt connection is deployed there.Here the automatic bolt connection is used to made connection we can also make the bolt connection using the cluster RBE2 and Two node RBE2.We define a 3 D point on the holes using the poioint option in the Topo module and Convert > 3D points >spotweld line> Ok.For realizing a connection we need a weld line.Now the weld line is created using the 3 D point.So using connection manager we can realize thhe joint.For this Connection manger> Select the weld line formed >choose part and part 2 Carefully > Set FE type as BOLT > Give search distance >Give the zones as In/Out > Aplly >Realize .This will realise the bolt connection.

Fig 5 Bolt Connection at the Hinge Joint

Then in the areas where the cross beams are present on the door we need to connect it to it support using the spot weld.The crossbeams are incorporated in the side door inorder to give structural rigidy incase of the side crash happens ,This is a component of structural rigidity and we should provide seam welds for those componenets but here the component is not so large components so a spot weld will be fine here.Similar to what we done in making the bolt here also we need to make the 3D point using the points panel.Then convert that point to the spotweld line.Then the connection Manager > Select the converted spot line >Carefully choose the parts > Give the FE respresentation Type as RBE3 - HEXA - RBE3 > Give the proper search distance > Give RBE3 Pinflags as 123456 in both the pinflags > Set a PID for the spotweld >Applly >Realize.

Fig 6 Spot Weld Connection at Cross beam

The sliding arm is there in the door to slides the window glass up and down.This has to be attached to the glass using the rigid connections.Because unless it is not rigid it cannot be opened and closed perfectly.The up and down movement will be smooth in real life condition .In order to simulate that in CAE we need to provide the RBE2 cluster between them.

Fig 6 Rigid connection deployed between Sliding arm and glass

Also we can see the black strips which are placed at the periphery of the glass all around its circumferance ,it is technically called weather strips .This is what seperates the interior of car from its outside environment,this is what makes us possible to switch On AC while we are in car.The connection we need to deploy is a special connection,The material which is used to make the weather strips are very soft so that it ensures that is the glass is not getting scratched while it moves up and down.This can simulated in ANSA using the RBE3 - CBUSH- RBE3. First we need to create a curve around the glass regions.This can be done suing Fe2Curve tool in perimeters panel in mesh module. And obviously we need to convert this curve to the spotweld line.Then go to connection manager >select the curves one at a time > give search distance a little big value as the distance between parts is little higher > set the differant parts P1 and P2 > Set the FE Rep Type as RB3 _ HEXA - RBE3 > set a new PID > Check keep all branches option > Apply > Realize.This will realise the connection.We set the keep all branches option checked because since it is going to produce RBE3 rigids they can have 3 or more branches ,so if all the branches not formed in the model.This can significantly affect our simulation results.

Fig 7 Weather strips in door area

Fig 8 CBHUSH elements in window glass area

The very same connection need to be employed at the outer surface of the door where the door will get attached to BIW of full vehicle when it is in closed,because at that region also weather strips are provided.Similar strategy of realizing connection one by one is used to realize connection there also.

Fig 9 CBUSH elements near area which will in contavct with the BIW when in closed portion

THen an area which we need to do a similar RBE3 connection is at the door handle area.Here we are provided with the holes where the handle will comes in place.So instead of modelling the handle with some sort of 3D elements and increasing the computational time we can go for the rigid connection between the holes and in the holes seperately as well and assign a mass equal to the mass of the handle at the master node of the handle.

Fig 10 Connection at the door handle

With that we are done with the connections in the backdoor model.

RESULTS

Fig 11 Complete connection of the meshed FE backdoor model

LEARNING OUTCOME

Through this practice ,I get to know about the connections in the automotive real life componenets and how we can simulate that in our FE model.Even the weather strips connections can be exactly implemented in our FE model using the relevant options supported in the ANSA.If we have the exact CAD data we can implement every exact connections in our FE model as well.In some cases we may not be provided with enough CAD data so that time we need to figure out what will be the best connection we can use there.

Link for the Files

https://drive.google.com/file/d/1UJ7Yeey-tZR9H_f0M-mM9N1XjE0xv2K1/view?usp=sharing