Assignment 7

Assignment 7

Neon side crash -BIW

• Check unit system and either follow [Mg mm s] or [Kg mm ms].
• Create appropriate interface, friction 0.2 and recommended parameters.
• Make sure of no penetration and intersections.
• Create rigid wall with friction 0.1 as per reference model.
• Compare the model weight with the reference model and use added masses to reach target weight 700kg while getting CG about the required range.
• Initial velocity as shown in picture.
• Use model checker to ensure good quality.
• Timestep :0.5 to 0.1 microseconds.
• Run 80ms.

Output requests:

• Sectional force in the cross member.
• Intrusion at B pillar, hinge pillar and fuel tank region. Provide recommendation on what can help to reduce Fuel tank intrusion.
• Peak velocity of inner node of the door.

Note:

1. Submit your simulation files including time and h3d files.
2. Plot energies and notice any difference.
3. Explain your errors and how to rectify?

Objective

To perform a side crash test for the given BIW (body in white) model and analyse the deformation and various types of forces produced during the crash. In this project, the velocity of car is set as 35 mph (standard car speeds for frontal crash as per FMVSS norms). The obtained outputs from the analysis are:

1. Sectional forces in the cross member
2. Intrusions at B-pillar, hinge pillar, and fuel tank region
3. Peak velocity at the inner node of the door

Introduction

The crash test is usually done in order to design the vehicle for crash energy management with the objective to reduce the occupant injuries. There are various types of crash test (frontal crash, roof crash, side crash) that are performed on a vehicle. In post processing, the data obtained from the crash testing is usually in terms of forces, stresses, displacements etc. that can analyse. The completion of the simulation is performed in hypermesh using radioss solver. The case setup is done in hypermesh and for post-processing, hyperview andhypergraph 2D is used. Different types of energies, Von-Misses stresses, plastic strains, acceleration curves and forces graphs are computed. Initially the vehicle has been set to crash on a planar rigid wall. As the name suggests, the rigid wall is non-deformable and fixed. Different sections are created on parts of the vehicle body in order to analyse the forces. Along with this, accelerometer is created at the bottom of the B-pillar on the rocker, on the both sides. The mass balancing has been done on the body to get the COG just at the bottom of driver seat or on the rail.

Case setup:

The given model is in. rad format. Due to the restriction of node in Hypermesh student edition, only partial model (up to B-pillar is taken for consideration).

In hypermesh, under model -> groups, all the type 7 interface cards were present in the model were deleted and only one type 7 cards are created for all components. In the slave node and master node segments, all the nodes of the model were selected.

Penetration check

The given model is checked for any penetrations. It is the necessary way to remove the initial penetrations that is present in the model.

Tools -> Penetration check ->

Rigid wall creation

After completion of penetration check, the rigid wall is cretaed in front of the vehicle body. The rigid wall is basically non-deformable (non-yielding) retaining wall defined by user master node and a group of slave nodes.

View-> Browser-> hypermesh->solver

There are four types of rigid wall – out of four, the infinite plane rigid wall is created.The Dsearch( i.e., the search distance between for the slave nodes is kept as 1000mm). The type of rigid wall is set on Type 2: sliding with friction with a friction value of 0.1. A small virtual gap is kept in between the rigid wall and the bumper for illustration purposes.

Mass Balancing:

The initial mass of partial model provided with 166 kg, while the target mass is around 700kg. The remaining mass is added manually on the body by trial and error. After trial and error, the COG came exactly on the rail, under the driver’s seat. The new mass after the addition became 687.31 kg.

Initial velocity

In this project, the velocity of car is set as 35 mph (standard car speeds for frontal crash as per FMVSS norms). This velocity is applied along y-axis direction.

Sections

Sections are used to identify the value of the forces passing through the portion of the component. By the use of the sections, the distribution of forces and stresses can be determined.As per the output requests, the sections had to be made in both the cross-rails under the driver seat.

Intrusions

The diplacement of the specific node can be identified by opting for the intrusions parameter. In this node, for which the diplacement has to be claculated is specified. In this project, the displacement of following node had to be computed.

• B-pillar
• Hinge-pillar
• Fuel tank region

Total number of cycles = 80001

Energy error = - 6 %

Mass error = 0.01077

Displacement:

The maximum amount of displacement in the model is 1350mm at 190233 nodes

Von-misses stress

The maximum amount of stress in the model is found to be 0.3382 kN/mm^2

Plastic strain

The maximum amount of plastic strain found in the model is 1.273

In hypergraph 2D, various energies and forces are analysed.

Rigid wall forces

Peak velocity

Intrusion nodes

Result and conclusion

The side crash or pole impact test analysis is one of the standad crash analysis test performed by the testing agency. In this side crash, there is no crumple zone or any other components to absorb the energy before reaching the driver point. Here, most of the forces are transmitted to the driver and occupant present inside the vehicle.The sectional forces are plotted for cross rails along with the instrusions for the analysis.