Week - 4 - crash box simulation

Challenge 4

Crash box Simulation

Introduction-

Crash box is important component in determining the crashworthiness of vehicle. It is used to absorb kinetic energy during Testing of crashworthiness of vehicle or during structural analysis.

• In this simulation a rectangular box is considered as Crash box, which can be considered as most simple model of crash box.

Given K file

• Given k file consists of rectangular crash box meshed with shell elements
• It is meshed with 9656 Shell elements and 9792 Nodes

• Procedure-

  • A rigid wall is not given in K file for crashing, a rigid wall is created by Create entity RIGIDWALL_PLANAR from offset of 15mm from Crash box

• Section for crash box is defined as SECTION_SHELL with I’d of 1 with 1.2 mm of thickness and I’d 2 with 1.5 mm thickness
• Material Properties in PIECEWISEPLASTICITY card by steel properties
• Velocity is given as 13.88mm/ms (50kmph) for crash box by INITIAL_VELOCITY in x direction

• -Contact definition is given as CONTACT_AUTOMATIC_SINGLE_SURFACE for crash box because it will bounce back and deform itself after crashing. Master Id is not given, slave id given as 1.

• Defined Termination of simulation by CONTROL_TERMINATION with termination step at 1.5 ms. CONTROL_ENERGY is given to calculate Hourglass energy

• -For output DATABASE is defined for Binaryd3plot and ASCII(glstat,rcforce,sleout,secforce) with the timestep of 0.05ms, for SecForce sets of elements and nodes are made by create entity

  - Define them in DATABASE_CROSSSECTION

• - finally title is changed to Crash box simulation

Output-

Energies given by Glstat(1.2MM AND 1.5 MM)

Glstat for thickness of 1.2mm

Glstat for thickness of 1.5mm

From above energy plots we can say that crash box of 1.5 mm have more energy than thickness of 1.2. sliding energy, hourglass energy is zero

Crossectional forces(1.2 mm and 1.5 mm)

Cross-sectional forces for thickness of 1.5mm

Cross-sectional forces for thickness of 1.2mm

Acceleration

Nodal Acceleration for 1.5 mm

Nodal Acceleration for 1.2 mm

Von-Mises Stress

Von-mises stress for 1.5mm thickness

Von-mises stress for 1.2mm thickness

For above cases we can say that max stress have surpassed yield stress (310Mpa), crash box undergoes plastic deformation

Effective plastic strain

Effective plastic strain for 1.5mm thickness

effective plastic strain for 1.2mm thickness

• Considering crash box with bothboth thickness of 1.5 mm and 1.2 mm, from above simulation images it is evident that given body undergoes plastic deformation(Permanently) which will not revert or come back into elastic region after bouncing back
• for better understanding of pictures in Challenge Word document is uploaded
• -END.