Design and analysis of a gun barrel chamber

3rd National Conference on Advancements in Simulation & Experimental Techniques in Mechanical Engineering (NCASEme-2016)

Design and analysis of a gun barrel chamber Vishvesh Dixit*

Ishbir Singh*

Research scholar [email protected] [email protected]

Vijender Rajora*

Associate professor [email protected]

Assistant professor [email protected]

Department of Mechanical Engineering School of Engineering & Emerging Technologies Baddi University of Emerging Sciences and Technology Baddi, H.P. Abstract- A gun barrel is the backbone for any type of firearm most important parts of the firearm. It may be consider the which is capable of firing any type of material with the help of back bone of the firearm. Barrel chamber works under a very stored energy either by compressing the gas and explosion of the high pressure condition more the 360mpa and it is the most propellants or by any other mean. During the process of firing a common part or component to fail. For that reason the design bullet or projectile the barrel undergoes many types of loads of the barrel must be designed so that the failures do not occur. which produce stresses in it. So that the design of the barrel must be strong enough to withstand the heavy pressure loads. Due to the absence of the design data a simple design of the gun barrel was made using cad software. The chamber of the gun barrel was designed for the 14.5 x 114 mm bullet also known as 0.57 caliber bullet. In most of the developing countries homemade fire arm is a major problem faced by the criminologist not only because it was dangerous for the society but it is also dangerous for the holder itself. Most of the home made fire arms are made up of cheap steel and are weak in there fabrication. Keeping this thing in mind the gun barrel was to be of structural steel, to perform static analysis using ANSYS. Using a finite element analysis package a model was generated for the analysis purpose. This paper deals with the analysis of the gun barrel for the given boundary conditions.

In this particular study the barrel chamber was designed on the basis of the 14.5 x 114mm which is heavy machine gun cartridge and anti-material cartridge which is originally design for the PRTS and PTRD anti-tank rifles by the Soviet Union in 1939. In this document a static structural analysis research was conducted on the gun barrel model, this research deals with the finite element analysis of the 3D model. The 3D model of the barrel is first designed using solid works 2013 and the analysis part was performed using ANSYS software package. As per the earlier studies represents the data related to the fabrication and manufacturing of the homemade firearm throughout the world of various types of improvised firearm like revolver, gun, pipe gun and shotgun, which is very big issue related to the criminology. The data provides the basic knowledge of different designs and special feature like tool marks and mechanism used in there design(4-6).

Keywords- firearm; barrel chamber; 0.57 caliber bullet; finite element analysis.

I.

INTRODUCTION

A barrel chamber is part of the gun barrel which holds the bullet shell during breach loading. It is the most important part of the gun and very common to fail during the firing process of the bullet. On the basis of the barrel chamber drawing the firearm has been classified for their categories like small arms and heavy machine gun etc. A firearm may be defined as the portable gun heaving a barreled weapon that launches one or more projectile often driven by the action of an explosive or by compressed gas. A gun is a normal tubular weapon or other design to discharge projectile or other material. The projectile may be gas, liquid, solid or energy and may be free as with bullet and artillery shell or captive as with the Taser probe and whaling harpoon(1-3). It means the design of the projectile may varies according to the design of the firearm but it usually affected by the action of gas pressure, either by the help of compressed and stored gas by mechanical means or by rapid combustion of propelled material which is more commonly used method for the propulsion of the projectile.

II.

MATERIAL AND METHOD

A. Material Before the fabrication of the geometry of barrel we have to select the material for the fabrication and analysis of the barrel design. Normally there are two materials which are mainly use for the fabrication of the barrel. These two material are used by the U.S. military for the fabrication of the barrel i.e. AISI 4140, UNS S41600. UNS S41600 is mostly used for the fabrication of the aircraft components because of their mechanical properties. The material is very expensive in its cost as well as the machining cost is also very high. This particular material is only used for the weapon designing and fabrication only when specially designed weapon are ordered. Because of that the production plants of the firearm facility mostly use the AISI 4140 material for the mass production. This material is used because of its ability to withstand the (360 MPa to 560 MPa) pressure ranges of the explosive used and because of its low cost compared to the UNS S41600 material.

The destruction of the target always depends on the design of the projectile and energy hold by the projectile. During the rapid expansion or explosion of the propellant the barrel experience different kinds of stresses. The barrel is one of the

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But while generating homemade firearm people generally use cheap steel tubes, water pipes and discarded steel material of automobile, which are very weak in their fabrication as well as in their mechanical properties. Due to the weak design the weapon, the firearm itself, becomes more dangerous to the weapon holder. This paper deals with the behavior exhibited by the material when specified load and boundary conditions have been applied. 1) Material properties Before conducting this study it is important to find out what are the chemical components used to create these particular materials for the fabrication of the gun barrel. The table I provide the chemical composition of the material in percentage to compare with each other. In this particular study there are three different grades of steel. All the three materials are steel alloys contain iron, sulfur, molybdenum, carbon, chromium, manganese, silicon, phosphorus in their composition. The amounts of the chemical component are shown in percentage value in the table. As the earlier studies indicate that the chemical composition plays an important role in the material selection process. Physical properties are also considered as the important part of the material selection process. During the working condition, the material experience different kinds of load on it which leads to its failure. There are many other properties which are generally considered while selecting a material for the fabrication purpose. Some of the properties are shown in the table (II). TABLE I. Material name Component (%) C Mn S Si P Cr

TABLE II. Material Name Property Density Elastic modulus Yield strength Elongation Tensile strength Hardness

UNS S41600 7800 200 795 13 1000 321

B. Method The whole fabrication of the firearm is always based on its internal barrel chamber drawings and the length of the barrel. Some of the firearms are capable of using different size and shape of ammunition as per their requirement in the field. The barrel chamber drawings may differ on the basis of the bullet shell used in the firearms like shotgun shells and the regular rounds or the training ammunitions. The selected 14.5x 114 mm (0.57 caliber) bullet design is used for the fabrication of the barrel chamber of the gun. The particular bullet was chosen because it was used in the long range shooting rifles. Fig. 1. 14.5 x 114 mm bullet dimension

COMPOSITION

UNS S41600 0.15 1.25 0.15 1.0 0.06 12-14

behavior of the 3D model is described in section III analysis and results.

AISI 4140 0.40 0.85 0.020 0.35 0.015 1.0

Structural Steel 0.15 1.25 0.15 1.0 0.060 12-14

As per the official guidelines of the bullet the shoulder angle is approximately equal to 44.500. And its rifling twist is given as 455mm (1 in 17.91 in). The maximum pressure that can be handled by the shell of the bullet is given as 360 MPa and the case capacity of the shell is given as 42.53cm3 (656.3 grains H2O). The case length is 114 mm and the maximum diameter of the shell is 26.96 mm as per the diagram shown in fig 1.

MATERIAL PROPERTIES AISI 4140 7850 190-210 770 17 930 275

Structural Steel 7850 200 255 22 410 262

Units

1) Design The 3D model of the barrel was created using the Solidworks (2013). This software package was selected because of its easy interface and availability . All the dimension of the model was given in in millimetres. Due to the non-arability of the exact dimension of the barrel coincides in this study a simple model of a gun barrel has been designed. The dimensions of the model are given in the fig. (2)[7], [8]. The length of the barrel was taken 1120 mm as per the specification given by the “Vidhwansak” model. Vidhwansak model was originally designed by Ordnance Factory Tiruchirappalli in 2005 [31].The internal radius of the barrel is 9.24 mm. The inner and outer shoulder angles which are commonly defined as alpha are 44.50o and 78.44o respectively. The barrel wall thickness was taken 20.32 mm. The reduction in barrel thickness was not considered along the length.

Kg/m3 GPa MPa % MPa Hb

As shown in the table II we clearly identify that the most suitable material for the fabrication purpose is UNS S41600. But the homemade firearms are generally made up of cheap steal.so this research was performed by selecting the structural steel for the fabrication purpose of the solid model. The main reason of this research work is to find out the effects produced on the barrel design which is made up of structural steel. The

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view. Where as in the fig. (4). an isometric view of the of the gun barrel model was shown.

Fig. 2. Design dimensions

2) Meshing It is important to transfer the geometry to the different software for the simulation of the problem given to it. For this study ANSYS software package was used to simulate the results of the given problem. ANSYS is a finite element analysis package that can be used for the optimization of the problem in real time as well as problem solving for the future work. The geometry file are then converted to the standard (.igs) IGES file and imparted to ANSYS geometry .after importing the files to the geometry file we have to provide the material to the engineering file as well. As we are using the structural steel, it is a default material present in the software package. After providing data to the software the geometry will exhibits the same characteristics as the structural steel itself. Mathematically, mesh can be defined as the procedure of analyzing the structure or model by subdividing the model into very fine and finite number of elements of simple shape. The shapes can be tetrahedral, conical, cubical etc. Hear default mesh generation settings are selected for the research work. The main purpose of the meshing is to simplify the problem by dividing the model into small element of simple shape and size[9]. These simple shapes experience the same effect as the whole model is going to experience. By using small size elements it is easy to calculate the values on these types of shapes as compare to the whole geometry. The values obtain are then arranged in the specific array formation which are further calculated by the mathematical formula to obtain the result for the whole model[10], [11].

Fig. 3. Top and side view of 3D model

Top view

Fig. 5. Mesh generation Front view

Fig. 4. Isometric view of gun barrel model

The side view and the top view of a gun barrel model is shown in fig. (3).as the pictures clearly show a slot was provided for the breach loading mechanism to work properly in the top

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A mesh model generated by the ANSYS work bench was shown in fig. (5). the mesh generation setting has been selected as default. Few of the setting are show in the table III.

provided to the model. The movement was fixed at 0 mm in xaxis and free in both y-axis and z-axis.

Fig. 6. Magnifing image of mesh generated Fig. 7. Boundary condition

Displacement boundary condition

A magnifying image of the section of the gun barrel has been shown in the fig. 6. As it clearly shows the mesh was automatically generated to each and every part of the model. TABLE III. Setting detail Use advance size function

MESH SETTINGS Setting status

Revalance center

Coarse

Span angle center

Coarse

Minimum edge length Maximum layer Growth rate

Pressure boundary condition

Off

Whereas for the secondary boundary condition, we select pressure command which is normal to the plane. The pressure limit provided was 360 MPa because of the bullet condition as mention earlier. A chamber pressure versus time graph was represented in fig .

8.6689e-002 mm 5 1.2

Nodes

9684

Elements

5277

Fig. 8. Chamber pressure versus Time

The Table III was used to provide the mesh setting used during the mesh generation and problem solving. The program creates 9684 nodes and 5277 elements. Whereas the growth rate was considered to be 1.2. 3)

Boundry condition

Boundary conditions are the commands provided by the user to replicate the external environment around the model. And to provide the basic information for the software to implement the loading condition to the 3D model generated. In this study two boundary conditions are used. First is a support condition which provides a support to the 3D model and the other is load condition which provides the different types of loads and forces to the solid model[12]. In the study sis two boundary conditions are used. First of all displacement support was

A sectional view of the gun barrel is represented with the pressure boundary condition in the fig 7.

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III.

ANALYSIS AND RESULTS

The analysis was performed using the ANSYS software package. It is a FEA software package used to analyze different types of models and mechanical component. It is used to find out what behavior they exhibit under different kinds of loads and boundary conditions. The study have consider the Total Deformation, equivalent (von-misses) stress, and maximum principal stress developed in the gun barrel, with the help of the FE analysis tool the result are shown in fig. 8, 9 and 10 respectively. The total deformation has been shown in the fig 8. It is clear from the image that the maximum total deformatiomof the model was obtain at the two edge of the tube , where as minimum deformation was obtain at the centtoid of the gun barrel model.the bending of the model was started from the cavity part created for the breach loading mechanism. In other words the deformation starts because there is not enough material present to provide strength to the model. The maximum deformation was shown by red colour and and is 3.94 mm as its maximum value where as minimum the minimum of the total deformation is 0.08mm and is represented in blue colour.

Fig. 11. Maximum principal elastic strain

Fig. 9. Total deformation

In case of the maximum principal elastic strain .it is clear from the image that the maximum strain was found at the neck of the gun barrel chamber. The maximum calculated strain was 3.47e-003 and is represented by the red color. The strain reduces from the inner wall to outer wall the minimum strain calculated was 2.66e-006 and represented by blue color in fig. 10. While calculating equivalent stress (von misses) it was found that the outer surface of the model was at lower stress, but the inner wall of the tube reaches above 800.68 MPa but still below the maximum value of the equivalent stress 936.66 MPa and is represented by the red color. The minimum equivalent stress is 1.74 MPa and represented by the blue color. By comparing the von messis value with the yielding strength it is clear that the design has f. The analysis is shown in fig. 9.

IV.

CONCLUSION

In this paper solid model of a gun barrel has been generated using Solidworks 2013 software package and ANSYS 15.0 has been used for finite element analysis of the gun barrel. For the current paper analysis, structural steel was used. The loading conditions are mentioned in literature. The result obtained clearly indicates the failure of the model. The results have been compared with the values available in the literature.

Fig. 10. Equivalent (von- misses) stress

V.

SCOPE OF FUTURE WORK

Gun barrel design may be improved to avoid failure by either altering the design geometry or by using different material. While using metal for the fabrication of a firearm component the assembly becomes heavy instead of using

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metal composite material can also be used to fabricate the component Because of their ability to withstand high temperature and heavy loads

[10]

E. Madenci, I. Guven, and SpringerLink (Online service), “The finite element method and applications in engineering using ANSYS,” p. xv, 686 p., 2006.

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Design and analysis of a gun barrel chamber

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