Week - 4 - crash box simulation

OBJECTIVE:

To simulate the crash test of a crash box for different values of thickness.

• CASE 1 : Thickness=1.2mm
• CASE 2 : Thickness=1.5mm

CRASH BOX MODEL:

BOUNDARY CONDITIONS:

1. The crash box should crash into a rigid wall.
2. Material for the crash box is steel.
3. Thickness of the crash box is 1.2mm for case 1 and 1.5mm for case 2.
4. Initial velocity for the crash box should be around 50 kmph

1. A rigid wall has been created 20mm away from the crash box.
2. Create a material card for steel.
3. Create a section with thickness of 1.2mm for case 1 and 1.5mm for case 2.
4. Assign the material id and section id to the part.
5. Define initial velocity of 50kmph to the crash box by creating a INITIAL_VELOCITY card.
6. Set the termination time as 5ms.
7. Define automatic single surface contact and set the nodes of the crash box as the slave nodes.
8. Now create a SET_SHELL set using the elements at the center of the box and define a cross section set.
9. Now create ASCII_option and BINARY_D3PLOT for the outputs.

RESULTS AND PLOTS:

The crash box 20mm away from the wall and it hits the wall at a an initial velocity of 50kmph. The impact causes it to bounce back. The changes in energies, stress, strain and acceleration are captured during the analysis.

1. Case 1: Thickness=1.2mm

• Effective Stress
• Plot of Energies
• Cross-sectional force generated in the middle of the crashbox
• Acceleration plot of a node in the middle of the crashbox
• Maximum stress in X direction.
• Maximum stress in Y direction.
• Maximum strain in X direction.
• Maximum strain in Y direction.

2. Case: 2 Thickness-1.5mm

• Effective stress
• Cross-sectional force generated in the middle of the crashbox
• Acceleration plot of a node in the middle of the crashbox
• Maximum stress in X direction.
• Maximum stress in y direction.
• Maximum strain in X direction.
• Maximum strain in y direction.
• Plot of all energies

COMPARISON BETWEEN CASE 1 AND CASE 1

• The stress and strain developed in case 2 is less than case 1. This is because of the increased thickness of the elements in case 2.
• Increased thickness also reduces the acceleration of the body.

CONCLUSION:

• The crash box bounces back after the impact.
• The acceleration of the crash box after the impact decreases with the increase in the thickness.
• The deformations in the body are under 1mm and are not noticeable..
• As the thickness increases, the directional stress and strain reduces.
• The maximum value of kinetic energy, internal energy and sliding energy decreases with increase in thickness.
• However, there is a slight increase in the hourglass energy for case 2 than in case 1.