Explicit Dynamics Analysis of Bullet Penetrating a Bucket
Challenge: Explicit Dynamics Analysis of Bullet Penetrating a Bucket
Objective: Use 3 different non linear materials for the bucket and analyse their behaviour for a velocity of 130m/sec.
Materials used for analyses:
- Bucket- Aluminium Alloy NL, Copper Alloy NL, Structural Steel NL
2. Bullet- Tantalum
After opening Explicit Dynamics Module on Ansys Workbench, the imported model is inspected on SpaceClaim and later loaded on ANSYS Mechanical APDL for analysis.
Since our concerned area for analysis is the bucket, the bullet is assigned a RIGID body behavior, which means, only the forces acting on the bucket are taken into account for analysis. TANTALUM is assigned as the material for bullet while the bucket is assigned three different non-linear materials on a case to case basis to study the results.
Meshing:
While meshing, I had to stick within the constraints of ANSYS academic version and also be cautious of my Computer’s processing capacity. After getting repeated errors saying ‘Time Step Value Too Small’ while generating the solution, I finally arrived at a combination for which results were obtained:
Patch Conforming Method: Tetrahedron
Element Size: 20mm
Adaptive Sizing: YES
Span Angle Center: COARSE
The obtained mesh is of average quality, as evident from the Element Quality graph attached below.
Boundary Conditions:
For the Analysis Settings, an End-Time of 0.001 sec is defined. MAx Energy Error is increased to a value of 5.
For the boundary conditions, the bucket needs to be fixed and the bullet has to pierce through the bucket. This is done by defining a FIXED SUPPORT for the bottom face of the bucket and imparting a VELOCITY of 130 m/sec (130000 mm/sec) to the bullet along the X direction.
Solution:
The parameters to be studied are selected and the solution is run.
Results:
EQUIVALENT STRESS:
Case 1: Aluminium Alloy NL
Case 2: Copper Alloy NL
Case 3: Structural Steel NL
TOTAL DEFORMATION
Case 1: Aluminium Alloy NL
Case 2: Copper Alloy NL
Case 3: Structural Steel NL
Comparing the results:
|
Aluminium Alloy NL |
Copper Alloy NL |
Structural Steel NL |
|
|
Equivalent stress Max (MPa) |
1166.8 | 1953.3 |
4035 |
|
Total Deformation Max (MPa) |
1390 | 1390 | 1390 |
Inference:
- Maximum resistance to the bullet is offered by Structural Steel NL as it experiences the highest equivalent stress among the three materials. Similarly, Aluminium Alloy NL is the least stressed material and is also least deformed as evident from the animations.
- The stress experienced by the bucket drops after hitting the maximum value, which is the point when the bullet pierces the bucket. Copper Alloy NL shows two peak stress points when the bullet enters and leaves the bucket.
- The total deformation is the same in all cases.
THE OVERALL RESULTS MAY NOT BE ACCURATE AS THE MESH IS OF AVERAGE QUALITY.
Animations:
Attaching animations of Al Alloy NL
Equivalent Stress: https://youtu.be/isy1WlLB__c
Total Deformation: https://youtu.be/obHM7z25McQ