HESH SHELL -Tank Ammunition 

The project was aimed at designing a HIGH EXPLOSIVE SQUASH HEAD-TANK SHELL . The project was undertaken as a part of undergraduate minor thesis in the third year of the degree.  These have benefit in the defence industry because it doesn't rely on the use of high precision electronics and also penetrates the targeted tank body by creating a highly effective blast shockwave which damages the enemy armour from the inside. 

The Minor thesis project was a preparation for better management of the Major Thesis Project.

Role and Team Structure 

I served as CAD designer ad ANSYS Pre-processor  for the HESH Shell design . My main responsibilities included:

1. Designing the shell body and the infills for the ANSYS Simulation 

2. Executing the Pre-processing part of the ANSYS Simulation 

 In order to successfully complete the project, I collaborated on a regular basis with the following : 

Minor Thesis Supervisor:  Dr P. K.  Soni 

Team members : 

1.  Sanjay Rana - Literature review , CAD and Documentation , 

2. Abhishek Kumar- ANSYS Solver and Optimization 

The outcome of the project was achieved as we had run ANSYS simulation to study the deformation and stress distribution of the HESH Shell on impact using Static structural simulation.  Through my efforts, I was able to enhance my skills in the CAD designing and ANSYS model creation. I would consider this a success because , it gave me an understanding of the ways in which ANSYS models could be created , as I was just a beginner back then. . Overall, my role in the project allowed me to enhance my  CAE and CAD skills  and I feel that I made a valuable contribution to the team.

In addition to working with my direct team members, I also had to coordinate with my thesis supervisor  to ensure that all aspects of the project were aligned and that we were able to meet our goals and deadlines. Through close collaboration and effective communication, we were able to achieve the aim of gaining skills in the ANSYS domain 

Outcome and Accomplishments 

Methodology

For the design of the HESH shell , the project was divided in to three major portions : Research , CAD creation and  Validation . The  inspiration of the project came from the internship that my team mate had done for the Defence research development organization, india. He had learnt about the design of the HESH shell and its importance as a anti tank weapon and got us involved in the project to further optimize it. The project started off with the research on the design methods for a HESH shell which would be a base for the simulation plan and material selection. Also , the boundary condtions of the HESH shell would depend on it. 

Findings

The findings of the project had met the intended goals. Our findings were well within the scope of the project. The results verified HESH Shell performance in the following ways as described below : 

1. Verification of the effectiveness of the HESH Shell 

a. Deformation 

 The project helped us validate the deformation which the HESH shell would experience on sudden impact ( Details in findings section).  One of the key criteria for the HESH Shell to perform its function  is its ability to deform, the deformation of the HESH Shell enables the increase in the area of impact and hence the larges the shock wave which hits the other side of the Tank Armour. 

b . Stress Distribution 

The stress distribution is a critical design parameter in determination of performance of the HESH shell, as the stress strain- curve which determines material's strength can be plotted using the data. The stress distribution was the aim of the optimization process because with better improved stress distribution the impact area on the Tank body would be more. 

 Working Principle 

This is a type of anti-tank ammunition in which the explosive is contained in a thin-walled projectile which deforms on contact with the target, allowing the explosive to spread. A base fuse then detonates the explosive which sends shock waves through the armour chemical energy to achieve its effect. 

The shock waves are reflected from the internal face of the armour and when they meet the next incoming wave, the resulting wave front causes the armour to fracture. This type of ammunition is not velocity dependent as it relies on chemical effect to achieve its energy. 

HESH SHELL Geometry 

The CAD model of the Shell was created using SOLIDWORKS and the three different views are shown in the diagram.  The created design was focussed on the replication of the existing designs of the HESH shell and preparing it for the simulation in the ANSYS Workbench. The Geometry was simplified as much as possible for simplifying the model , considering the computational time required. 

 ANSYS Model 

The ANSYS model was imported into the ANSYS workbench. The assumptions made in the model are: 

1. The contact between the Fuse, Filling and Shell is assumed to be without interference. 

2. Material of the shell is brass. 

3. Symmetry is applied on the angular planes . 

4. Static analysis was carried out in different cases( maximum spin and acceleration case)

Connections 

• Shell to Base 

• Shell to Filling

• Base to Filling 

 Operational Boundary conditions 

• Maximum acceleration case 

Max Chamber Pressure - 145.5 MPa

Velocity – 252.5 m/sec

Acceleration - 1.02 x 105 m/sec2

(Rpm) n1 = (60 v)/(ncx d) put nc =18, d = 0.12 and v = 252.5

So ‘n1 = 7005.5 rpm ‘

For n1(rad/s) = (2 x 3.14 x7005.5) / 60 = 733.24 rad/s

So n1 = 733.24 rad/s

 To generate axisymmetric shell condition, the face of shell perpendicular to y-axis isconstrained to move in x-z plane and the face perpendicular to z-axis is constrained to move in x-y plane only. The shell outer surface is restrained to move in radial direction to simulate axial motion along barrel. Shown in figure

Then, pressure ,acceleration and rotational velocity are applied on the assembly,shown in figure 

 Pressure applied by copper ring P2=30 MPa (D)

 Pressure on the base of Shell due to charge burning P1=87 MPa

Acceleration a= 1.02x 105m/sec^2 (A)

 Rotational velocity n1 = 733.24 rad / sec (B)

 Displacement (1) 

 Displacement (2) 

 Displacement (3) 

• Maximum Spin Case 

Chamber Pressure – 40.13 MPa

Velocity – 744.5 m/sec

Acceleration - 2.863 x 104 m/sec2

(Rpm) n2 = (60 v)/(ncx d) put nc =18, d = 0.12 and v = 744.5

So ‘n2= 20680.55 rpm ‘

For n2 (rad/s) = (2 x 3.14 x20680.55) / 60 = 2164.56 rad/s

So n2= 2164.56 rad/s

 To generate axisymmetric shell condition, the face of shell perpendicular to y-axis is constrained to move in x-z plane and the face perpendicular to z-axis is constrained to move in x-y plane only. The shell outer surface is restrained to move in radial direction to simulate axial motion along barrel. 

Then, pressure ,acceleration and rotational velocity also apply on the final assembly part, shown in figure 

 Pressure applied by copper ring P2=30 MPa 

 Pressure on the base of shell due to charge burning P1=24 MPa 

 Acceleration a= 2.863 x 104 m/sec^2 

 Rotational velocity n2=2164.56rad / sec

 Displacement (1) 

 Displacement (2) 

 Displacement (3)

Deformation 

Total deformation in shell can be seen in the below figure. Red colour shows maximum deformation region and blue colour shows minimum total deformation value region.

Maximum value - 0.46817 mm

Minimum value - 0 mm

Equivalent Stress 

Equivalent stress generated in the shell is expressed in figure.

Maximum value - 1244.2 MPa

Minimum value – 4.9902 MPa

Different view angles are also put in figure 31 for maximum and minimum region.

Deformation

Total deformation in shell can be seen in the below figure 42. Red colour shows maximum deformation region and blue colour shows minimum total deformation value region.

Maximum value - 0.089746 mm

Minimum value - 0 mm

Equivalent Stress 

Equivalent stress generated in the shell is shown in the Figure

Maximum value – 290.62 MPa

Minimum value – 0.14951 MPa

Different view angleare also put in figure 46 for maximum and minimum