Week - 4 - crash box simulation
OBJECTIVE :
To simulate a crash test for a crash box for which mesh is given. Compare the accelerations and stress/strain plots of 1.2/1.5mm crashboxes.
GIVEN PARAMETERS :
1. Material for the crashbox is steel. 2. Thickness of the crashbox is 1.2mm. 3. Initial velocity for the crashbox should be around 50 kmph = 13.889mm/ms . 4. The units system to be used is gm-mm-ms.
PROCEDURE:
Steps:
1. Material Creation
2. Section Creation
3. Assigning material & section to part
4. Rigid wall creation
5. Assigning intial velocity
6. Creating contact
7. Defining Termination point
8. Database Creation
1. Material Creation:
path : model and part->keyword manager->all->mat
A MAT_PIECEWISE_LINEAR_PLASTICITY 24 has been taken and following parameter values are assigned since given material is STEEL.
|
SNo |
Parameter |
Value |
Units |
|
1 |
Density |
7.85e-3 |
g/mm3 |
|
2 |
Young's Modulus |
2.1e+5 |
g/(mm*ms2) |
|
3 |
Poisson's Ration |
0.3 |
Constant |
|
4 |
Yield Strength |
350 |
MPa |
2. Section Creation:
path: model and part->keyword manager->all->section
Section with thickness 1.2mm is created.
3. Assigning material & section to part:
path: model and part->keyword manager->model->part->select part
4. Rigid wall creation :
Rigid wall planar is created 15mm away from the crash box.
5. Assigning intial velocity:
Intial velocity for the entire crash box is assigned.
6. Creating contact:
Automatic single surface contact is created.
7. Defining Termination point:
8. Database Creation:
To generate Cross-sectional force in the middle of the crashbox a database cross section is created.
The acceleration at the middle node has to be plotted, for this DATABASE_HISTORY_NODE has be created and the DATABASE_D3PLOT with 0.1ms DT for the time interval between output.
ASCII_option: ELOUT,GLSTAT,MATSUM,NODOUT,RCFORC,RWFORC,SECFORC and SLEOUT have been created.
Simulation is performed for both 1.2 and 1.5 thickness.
RESULTS:
I. Output files:
link : https://drive.google.com/file/d/1w24pDJD3yLLkiQePlpIiv6nl2rGupLIv/view?usp=sharing
Animation:
1.2 thickness:
1.5 thickness:
III. CROSS SECTIONAL FORCE:
1.2 thickness:
At point of impact force = 92.4KN and at termination point force = 1.76 KN
1.5 thickness:
At point of impact force = 113KN and at termination point force = 57.1 KN
IV. Acceleration plot of a node in the middle of the crashbox:
1.2 thickness: for node id 6000
1.5 thickness: for node id 6000
V. Maximum directional stress and strain along the length of the crashbox :
1.2 thickness:
1.5 thickness:
VI. Plot of all energies (total, internal, kinetic, hourglass, sliding):
1.2 thickness:
1.5 thickness:
| Thickness | Instant | Total Energy | Internal Energy | Kinetic Energy | Hour glass Energy |
| 1.5mm | Point of Contact | 1.35 e+5 J | 1.1 e+5 J | 2.38 e+4 J | 239 J |
| 1.5mm | Point of termination | 1.35 e+5 J | 1.09 e+5 J | 2.18 e+4 J | 3.45 e+3 J |
| 1.2mm | Point of Contact | 1.08 e+5 J | 0.879 e+4 J | 1.94 e+4 J | 183 J |
| 1.2mm | Point of termination | 1.08 e+5 J | 0.867 e+4 J | 1.74 e+4 J | 3.37 e+3 J |
VII. Compare the accelerations and stress/strain plots of 1.2/1.5mm crashboxes:
| Thickness(mm) | Acceleration (mm/sec2) | Stress (Mpa) | Strain (mm) |
| 1.2 | 2.67 e+3 | 4.098 e+2 | 5.733 e-3 |
| 1.5 | 2.73 e+3 | 4.099 e+2 | 5.712 e-3 |