Explicit Dynamic Analysis of a Bullet Penetrating a Bucket

TITLE: Explicit Dynamic Analysis of a Bullet Penetrating a Bucket.

SUMMARY: In this project, using Ansys Workbench Explicit Dynamics we have carried out an Analysis of a Bullet Penetrating a Bucket. A bucket is fixed at a particular area of space and the bullet is provided with a certian amount of veleocity and is allow to passed through bucket to observe the penetration. The bullet passes with shearing certain amount of material from bucket. The Analysis we performed here, is followed in three different cases with change in material while keeping the boundary conditions same. Meanwhile, desired parameters such as Total Deformation and Equivalent Stress are carried out.

INTRODUCTION: In order to execute Explicit Dynamic Analysis of a Bullet Penetrating a Bucket, it is necessary to assigned all those required boundary conditions which do requires. Firstly, let's consider a geometric model of Bullet-Bucket assembly. We begins with assigning desired material, for Bucket we uses three different Non-Linear materials they are NL Aluminium alloy, NL Copper alloy, NL Stainless steel alloy. However, the Bullet itself needs a strong and Rigid material hence it is assigned with Explicit material as Tantalum. Since, we don't need any contacts the body body interactions here are completely frictionless.

CAD Model of Bullet-Bucket system

We proceed with meshing the geometric model. The meshing to be used here is set as default by Mechanical solver itself however, the region through which the bullet starts to penetrate is supposed to meshed with lower edge sizing. The bullet obivously will enters and exits at same way for both two surfaces of bucket. Hence, we assigned a Seperate edge sizing of an elemental size 6mm for both edge contacts surfaces.

An elemental edge sizing of 6mm for both edges

Once the sizing is provided, the entire cad model is ready for creating Mesh. We creates a mesh for entire model, which can be seen below. Mesh model tells a lot about itself. As discussed above about the edge surface for penetrate region, the mesh is even fine there.

Final Meshed geometry

Now, we proceed with assigning various boundary conditions requires for executions of analysis. We begin with assigning Analysis setting. The end time plays an important factor for the explicit dynamic analysis to set up. Hence we assigned an end time of 0.01 sec. while, keeping the value of Maximum Energy Error higher for about 5.

Later, we specifies boundary conditions requires for analysis. A fixed support is assigned at bottom of the bucket so that, it won't moves during impact. Meanwhile the bullet is suppose to pentrate through the bucket, in order to do so we assigned velocity of about 139m/s for entire bullet such that its impact causes to pass ot through out bucket in -ve X-Direction.

Boundary Conditions

Once, we assigned all required boundary conditions we insert parameters which are to be carried out which here are Equivalent Stress & Total Deformation. The simulation is ready to went through.

• CASE 1:

For case 1, we begin with assigning materials as Non-Linear Aluminium Alloy for Bucket followed by Tantalum for Bullet.

Non-Linear Aluminium Alloy for Bucket followed by Tantalum for Bullet

Equivalent Stress:

It seems that, a Max. of 511.22MPa of stress is generated with shearing of material

Total Deformation:

Here, the Bullet undergoes a maximum deformation of about 1398mm

For above analysis, a Energy Conversion Graph is being ploted as below,

Energy Conversion Graph

• CASE 2:

Similarly, For case 2 we begin with assigning materials as Non-Linear Copper Alloy for Bucket followed by Tantalum for Bullet.

Non-Linear Copper Alloy for Bucket followed by Tantalum for Bullet

Equivalent Stress:

Here, a Max. of 1256.4MPa of stress is generated along with shearing of material.

Total Deformation:

Here, the Bullet undergoes a maximum deformation of about 1399.3mm

Similarly, For above analysis, a Energy Conversion Graph is being ploted as below,

Energy Conversion Graph

• CASE 3:

For case 3 as well, we begin with assigning materials as Non-Linear Stainless steel for Bucket followed by Tantalum for Bullet.

Non-Linear Stainless Steel for Bucket followed by Tantalum for Bullet

Equivalent Stress:

Here, a Max. of 3486MPa of stress is generated along with shearing of material.

Total Deformation:

Here, the Bullet undergoes a maximum deformation of about 1399.2mm

Similarly, For above analysis, a Energy Conversion Graph is being ploted as below,

Energy Conversion Graph

RESULT:

Based on parameter values obtain, they are compared as follows,

CONCLUSION:

1. So far the equivalent Stress are concerned, the bucket assigned with Non-Linear Stainless Steel undergoes Maximum stress.
2. As a result of maximum stress, a high amount of resistance is offered by the Non-Linear Stainless Steel as well amoung all material in buckets.
3. The Total Deformation is same for all cases.