Week 10 Bullet penetrating a Bucket Challenge

Stress Concentration on Bullet Penetrating a Bucket

OBJECTIVES:

To carry out an Explicit Dynamic Analysis of the Bullet penetrating a bucket for the given three materials of the bucket and determine the stress, deformation, and strain.

MATERIAL:

The Explicit Dynamic Analysis was carried out on the given specimen. The material used for this analysis was Stainless Steel NL, Cupper Alloy NL, Aluminum Alloy NL, and Tantalum and the study was carried out using ANSYS Mechanical Enterprise. The model for Tension Test was imported to ANSYS Workbench software and is shown in the figure below. The Bullet has been provided with RIGID Stiffness Behavior.

Fig.1 Bullet and the Bucket

Later the material was assigned and its properties used for this analysis are specified below.

• Bucket: Stainless Steel NL, Cupper Alloy NL, Aluminum Alloy NL,
• Bullet: Tantalum

Cases	Case-1	Case-2	Case-3	All Cases
Material	Stainless Steel	Copper Alloy NL	AluminumAlloy NL	Tantalum
Density	7.75e-6 kg/mm3	8.3e-6 kg/mm3	2.77e-6 kg/mm3	1.66e-6 kg/mm3
Young’s Modulus	1.93e+5 MPa	1.1e+5 MPa	71000 MPa
Poisson Ratio	0.31	0.34	0.33
Bulk Modulus	1.693e+5 MPa	1.1458e+5 MPa	69608 MPa
Shear Modulus	73664 MPa	41045 MPa	26692 MPa	65600 MPa
Components	Bucket	Bucket	Bucket	Bullet

CONNECTIONS:

Body Interactions with FRICTIONLESS Type was provided by default to both the Bucket and the Bullet.

Fig.2 Body Interactions

MESHING:

• Edge Sizing: To the 2 edges of the Bucket
  • Element Size: 6mm

Fig.3 Edge Sizing

Fig.4 Meshed Model

A mesh metric that identifies elements according to their quality was employed and it can be seen that the elements of the lowest quality are minimal. Most of the elements have very high quality in the range of 0.5 to 0.9. Hence, the mesh is of acceptable quality. The meshed model is shown below.

Fig.5 Element Quality

ANALYSIS SETTING (All Cases):

• of Steps: 1
• Load Step Type: Explicit Time Integration
• End Time: 0.01s
• No. of Cycles: 1e+7
• Energy Error: 5

Fig.6 Analysis Setting (all cases)

BOUNDARY CONDITIONS AND LOAD (All Cases):

• Fixed Support: Bottom Face of the Bucket
• Velocity: The Bullet
  • X Component: -139000mm/s
  • Y and Z Component: Constant – 0mm/s

Fig.7 Fixed Support

Fig.8 Velocity Load -139000mm/s

Fig.9 Case Setup

RESULTS – Stainless Steel NL:

The Total Deformation obtained from the analysis is shown below.

Fig.10 Total Deformation Contour Plot

The Equivalent (Von-Mises) Stress obtained from the analysis is shown below.

Fig.11 Equivalent Stress Contour Plot

The Equivalent Strain of the Model obtained from the analysis is shown below

Fig.12 Equivalent Strain Contour Plot

RESULTS – Copper Alloy NL:

The Total Deformation obtained from the analysis is shown below.

Fig.13 Total Deformation Contour Plot

The Equivalent (Von-Mises) Stress obtained from the analysis is shown below.

Fig.14 Equivalent Stress Contour Plot

The Equivalent Strain of the Model obtained from the analysis is shown below

Fig.15 Equivalent Strain Contour Plot

RESULTS – Aluminum Alloy NL:

The Total Deformation obtained from the analysis is shown below.

Fig.16 Total Deformation Contour Plot

The Equivalent (Von-Mises) Stress obtained from the analysis is shown below.

Fig.17 Equivalent Stress Contour Plot

The Equivalent Strain of the Model obtained from the analysis is shown below

Fig.18 Equivalent Strain Contour Plot

The simulation was run and the results are tabulated below.

Output	Case-1 Stainless Steel NL	Case-2 Copper Alloy NL	Case-3 Aluminum Alloy NL
Total Deformation Max. [mm]	1390	1390	1390
Equivalent Stress Max. [MPa]	4320.2	2755	1032.7
Equivalent Strain Max. [mm/mm]	2.2385e-2	2.5046e-2	1.6482e-2

CONCLUSION:

The analysis was run successfully and results were obtained and tabulated.

• The Maximum Deformation was identical in all three cases
• The Maximum Stress was 4320.2 obtained for the Stainless Steel NL

The stress generated by the bullet on the bucket is more in the material Stainless Steel NL, than any other material provided above, this is due to the stiffness of the material, as the stiffness of the material increases the stress generated also increases accordingly.