Week 6 - Creating connection for Rear door

AIM: To perform different types of 1D connections to the Rear door FE model in order to set it right for further solving.

The procedure is described below for the same.

Note: All the connections are to be done in NASTRAN Deck as the solving will occur for Noise, vibration, and harshness (NVH) calculations

STEP 1: Setting PID

FIG: Sub-part assembly before PID set for all the different parts

FIG: PID set for all the different parts of the sub-assembly.

STEP 2: Deploying Connections

Note: Individual connection types are explained below which are used at various positions in Side door assembly.

A) MANY NODES AND TWO-NODE RBE2's ELEMENTS

They are the building blocks of connections that are used to rigidize parts. These elements can be optimized on the levels of nodes, physical connections, degree of freedom arrested, etc. These elements connect slave nodes with one master node. An example of a basic many-node RBE2 is shown below.

FIG: Slave nodes are selected.

FIG: Many Node cluster RBE2 element connection is created. In entity details "CM with 123456" explains that all the degrees of freedom (3 translations and 3 rotations along XYZ Direction) are arrested to rigidize the parts. It can be later modified if we allow motion in any direction or directions

Similarly, Two-Node RBE2 can also be deployed. Majorly it is used when parts are too big so two-node RBE2s can be deployed in all corners to rigidize two components or when the connection is to be performed where entities are large. Both the cases are elaborated in the figures below.

FIG: To connect the outer door panel with another long part, two-node RBE2s are used on all four corners.

FIG: 3 Number of RBE2s are created by joining four master nodes of the many node RBE2s.

B) Bolt

Major steps include point realization, entity conversion to bolt, connection realization. Steps are elaborated along with the figure below

FIG: Point is realized on a common part to be connected by a bolt.

FIG: Point is converted to Bolt.

FIG: 3 PID's are connected (Instrument panel, hinge, connection 2) using Bolt connection. While making bolt connection maximum of 4 parts can be connected with options use like search distance and zones etc. A cluster or spider representation can be seen as a Bolt connection. The connection can also be confirmed by seeing FE Rep type as "BOLT" and Body as RBE 2

Bolt connection can also be represented

FIG: IN/OUT Zone type representation is used for Bolt connection here Yellow strand represent bolt shank.

C) SPOT WELD

Spot weld is realized where parts are close to each other, points are converted to spot weld connections with allowing parts to connect, FE REP is used as RBE3-HEXA-RBE3 and PSOLID ID is used for SPOT weld body.

FIG: Point is converted to SPOT Weld point.

FIG: In the figure above, structure element 2 and Sliding Glass guide are connected using Spot weld and FE rep type as RBE3-HEXA-RBE3. Later solid Id will be made for the Hexa element which will complete the Spot weld connection.

FIG: Spot weld is realized between Structure element 2 and Sliding glass guide.

D) CONCENTRATED MASS ELEMENTS

In many places in an automobile door assembly, for accessories like side mirrors, handlebars, etc. slots are provided for assembly. In such known cases, slots are connected with many Nodes RBE2s and a concentrated point mass is allocated on the COG of the elements replacing the original unavailable components.

FIG: Concentration mass of .0001 or 100 gm is given to Concentration handle mass.

E) CBUSH CONNECTIONS

In an automobile door assembly, connections with respect to Glass are crucial. In practical application glass in a door assembly moves downward but while doing connections for NVH solving they need to be rigidized. So glasses are connected using CBUSH elements as they hold the property like stiffness and damping coefficient, etc. They are connected with weatherproofing strips.

Typical steps include conversion of glass periphery into curves, curves conversion to spot lines, realizing connections between parts with FE Rep style as RBE3-CBUSH-RBE3, and PBUSH ID is also created.

FIG: Perimeter of the mirror is converted to a curve using "FEAT2CURVE"

FIG: Individual curves are converted to Spot Line.

FIG: Individual sliding glass and outside door panel is connected using RBE3-CBUSH-RBE3 as FE Rep style and a new PBUSH ID is created with stiffness value input.

FIG: Stiffness value input

FIG: CBUSH is realized between Sliding glass and outside door panel.

NOTE: After the glasses are fixed, the orientation of RBE3s is changed to global coordinates.

FIG: Coordinate ID is set to zero.

Using the connections discussed above rest of the Automotive door assembly is connected to each other. Making the model complete for further NVH solving.

CONCLUSION:

1. While preparing any assembly for FEA analysis, physical connections must be provided to represent the actual conditions.

2. Connection types include seam welds, spot welds using elements like ConMass, RBE2s, RBE3s, CBUSH, etc.

3. ANSA offers various connections depending upon the deck types.

4. ANSA provides easy access to review and access all the element types.