Assignment 6-Frontal Crash Simulation Challenge

AIM :-

Necessary Requirements for the frontal crash simulation:

• 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 penetrations and intersection.
• Correct rigid bodies if any issues.
• Create rigid wall with friction 0.1.
• Compare the model weight with the full scale 300k nodes model and use added masses to reach target weight 700kg while getting CG about the required range.
• Initial velocity 35 mph.
• Use model checker to ensure good quality.
• Time-step :0.5 to 0.1 microseconds.
• Run 80 ms.

Output requests:

• Sectional force in the rails at location of indicated node 174247.
• Axial force received on the rails from bumper.
• Shotgun cross sectional forces.
• A pillar cross section.
• Acceleration curve received on the accelerometer at base of B pillar (on B pillar rocker).
• Intrusions on the dash wall 66695,66244.

CASE SETUP :-

• Import neon BIW model into hypermesh using import solver deck option.
• To open in hypercrash just Drag and place the starter file.

unit system :-

contact interface :-

• TYPE 7 contact interface is used to define self-contact for the whole model. the nodes are assigned as slaves and elements are assigned as master.
• Recommended parameters

penetrations and intersections check :-

• there is no penetrations and intersections in the model.

Rigid wall :-

• an infinite plane is created as rigid wall

center of gravity(cg) :-

• Location of CG is very imp for crash simulations, rolling of car depends on CG location. The distributed mass of 700kg is aded to floors using added mass in hypercrash. these aded mass are assigned to move the CG to the below driver seat.

initial velocity :-

Given velocity 15.65 mm/ms in X- axix direction for entire model

Time step :-

The constant nodel time step DT/NODA/CST of 0.0005ms and Runtime of 80ms , animation freequncy is 5ms so it generate animation file as output for every 5ms.

Cross sections and accelerometer :-

• Sectional force in the rails at location of indicated node 174247.
• Axial force received on the rails from bumper.
• Shotgun cross sectional forces.
• A pillar cross section.

• the cross section is created at above locations in both sides to analyse the force passes through that section.

• an accelerometer is created on the rocker at th base of b-pillor. it is used to analyse the rate of change of velocity on the rocker during crash.

instrusions :-

• Intrusions on the dash wall 66695,66244
• created 1-d spring at mentioned location with K=0.0001 , M= 0.0001 property, it is used to measure the shrinkage while crash simulation.

Time history :-

The TH card is created in such a way that we can request outputs in hypergraph.

• now case setup is completed , then go for simulation

RESULTS :-

• LHS of shortgun experiences max force 9.13388KN at 31-32ms.
• RHS of shortgun experiences max force 6.62027KN at 45-46ms.

• Max force at node 174247 (RHS) is 24.0223KN at 25ms.
• Max force at node 174247 (LHS) is 31.107KN at 25ms.

• LHS of Rail near bumper experiences max force 5.58306KN at 44-45ms.
• RHS of Rail near bumper experiences max force 8.25674KN at 25-26ms.

• LHS of A -pillor experiences max force 2.6481KN at 31-33ms.
• RHS of A -pillor experiences max force 2.59763KN at 56-58ms.

compare all sections in single graph

Intrusions on the dash wall

Acceleration curve

Review of output file

• Energy error = -1.5%

If the energy error is neghative it means some energy is dissipated ,may be cause of hourglass energy. the acceptable range of energy error is 10-15% so this model (1.5%) is acceptable.

• mass error = 0.1269E-02 =0.001269=0.12%

acceptable range of mass error is <2% but in this model it is 0.12% so this model is acceptable.

• no.of cycles = 159900
• Time step is constant (0.0005) throughout the simulation.