TITLE OF THE INVENTION “BULLET CONTAINMENT TRAP WITH A MODULAR BACKSTOP” Technical Field of the Invention [001] The invention relates to a bullet containment trap that is used for securing used bullets while dry firing practice. Specifically, the invention relates to a bullet containment trap used in conjunction with a Containerized Tubular Shooting Range (CTSR) that is used for training purposes. Background of the Invention [002] Bullet containment traps per se are well known devices which are used for many years in firing ranges. These devices are usually devised at a relatively short distance from the shooter to catch the waste lead, brass and jacket material of the bullet being fired and prevent either the ricochet of a whole bullet or a large fragment thereof. A further object of the device is to provide protection against back splattering of numerous small metal particles, which could return with enough energy to cause injury to the shooter or an innocent bystander. [003] EP0683375A1 discloses a bullet containment trap with an element insertable within a container. All walls apart from the wall facing shooters are constituted of ballistic plates. The surface of the bullet arresting element facing shooters is constituted of a rubber cover. It also discloses a layer that allows the passage of a non-deformed bullet. It is claimed that the said layer does not break or permanently deform after the passage of the bullet. [004] US385546A discloses another bullet containment trap with a plate projecting from the wall of a chamber and inclined at an acute angle to the path of the bullet. The plate is placed in such position in relation to the target that bullet which have passed through the target strike the plate and are thereby deflected and slide along its surface and into the chamber, and continue to circulate around the chamber until their energy of motion is expended, when they drop into a receptacle suitably placed.

[005] US4126311 A discloses another bullet containment trap with an entry funnel with a throat of gradually reduced dimension, the funnel being tangentially secured to a tubular tank. A mouth at an exit end of the funnel throat is aligned with an opening in the tank to direct bullet from the throat into the tank. The tank is closed at its top, and its open bottom is connected to a cone, the cone being of reduced diameter from its point of connection at the tank to its exit aperture. The cone interior may be corrugated to aid in disintegration of the bullet as the bullet expends its travel energy in rotation therein.

[006] US5121671A discloses another bullet containment trap that includes a passageway bounded by upper and lower flat plates. The passageway has an entrance opening and a shallow exit opening or throat, and a generally spiral-walled spent bullet energy-dissipating chamber having a horizontal axis communicates substantially tangentially with the passageway through the throat.

[007] US5259291 discloses another bullet containment trap for receiving a bullet travelling along a substantially horizontal axis of travel at high velocity includes a pair of side walls, a primary, secondary and tertiary deflecting plates. A second primary plate affords a trap of significantly less depth than the trap without such a plate for traps having substantially the same size rectangular mouth. In either embodiment, a tray along the back of the trap collects the trapped bullet or particles thereof.

[008] US5400692 discloses another bullet containment trap for stopping the forward momentum of bullet traveling in a generally horizontal zone of bullet travel. There are side plates on the chamber which combine with the other structure to confine bullet, fragments and particulate matter to the chamber until inertial momentum is arrested and the bullet drops out of an egress.

[009] US5456155 discloses another bullet containment trap in an indoor range having a first end and a second end by use of a bullet trap. The bullet trap is formed from an upper plate and a lower plate and a liquid-filled trough. The bullet trap is positioned near the second end of the indoor range. The upper plate preferably curves downwardly between the slot and the second end of the range and ends in a generally vertically downward orientation pointed toward the liquid filled trough. Bullets fired into the bullet trap from the first end of the range pass through the slot and are trapped in the liquid filled trough.

[010] US5535662 discloses another bullet trap that utilizes angled impact plates to decelerate bullet. Once the bullet had slowed sufficiently, they would fall into a canister mounted below the containment chamber.

[Oi l] JP3806878B2 discloses another bullet trap that is arranged behind a target of actual shooting of a firearm and captures a bullet fired toward the target by a granular member. In this case, the stopping device may be continuously provided so as to surround the archer and bend in a plane.

[012] US2006/0131813 discloses another bullet trap for installation at shooting ranges. The device has a housing, which housing has an L-shaped concrete plate, a resilient top layer and a flexible bottom layer. The inclined bottom surface is inclined at an angle in relation to a horizontal plane. The angle is less than an angle of repose of the granular material.

[013] US20140346734A1 discloses another bullet trap for decelerating bullet including a housing and bullet deceleration material disposed within the housing. The bullet deceleration material may include a plurality of layers of rubber material and metal for safely decelerating a bullet. The bullet trap may also include vent holes for dissipation of the force generated from discharging a firearm in the housing and diverters which channel vented gasses away from a shooter.

[014] US20150184985A1 discloses another bullet trap with tapered shooting lanes or zones. The shooting lanes are wider at the position of the shooter than they are at the end of the range, thereby resulting in a design that is cheaper to build and easier to maintain. The tapering of the lanes can be in the horizontal or vertical directions (or both). This design can be used in indoor or outdoor ranges, with firearms, bows, crossbows, air rifles, air softs, and other types of bullet that are fired, shot, or launched.

[015] US9733050B2 discloses another bullet trap comprising a foundation constituting a floor and a rear wall of the bullet arresting device. It further comprises partition walls extending in a direction substantially perpendicular to the rear wall, wherein the partition walls comprise a rear edge connected to the foundation, and a front edge. In it, the spent bullet penetrates a hollow section expand through the stopping material so that the bullet will be captured between the row of hollow sections and the rear wall.

[016] US7194944 discloses another bullet trap formed without intervening sidewalls to enable cross-shooting and the like with reduced risk or ricochet or damage to the bullet trap. Furthermore, the bullet trap can be configured in a variety of ways to eliminate the need for facing plates while providing a removable attachment mechanism, to enable repair on the trap, to reduce bullet adhesion to the trap and to provide improved containment of lead and improved access to the trap.

[017] All of the above bullet containment traps suffer from the same common problem. Specifically, the side walls limit the ability of the bullet to travel laterally straight ahead; and damages the backstop and the side plates. [018] In addition to the above, many of the prior art bullet containment traps have problems with bullet sticking to the deceleration plates. Though US7194944 discloses reduced bullet adhesion to the trap and claims to provide improved containment of lead and improved access to the trap. The chamber becomes damaged or needs maintenance or repair work, and it is still difficult to access the interior of the trap.

[019] Prior art bullet containment traps are all proposed for short range dry firing practice. The back plates of these containment traps are all designed and can withstand only subsonic projectiles and not supersonic. Inventors felt a dire need for an improved bullet containment trap for short range dry firing practice wherein it withstands both subsonic and supersonic projectiles.

Brief Summary of the Invention

[020] It is an object of the present invention to provide an improved bullet containment trap.

[021] It is another object of the present invention to provide a bullet containment trap with a very strong backstop structure that lasts long and provides better access to the interior of the trap.

[022] Another object of the present invention is that the backstop has a modular structure wherein the damaged plates can be easily changed.

[023] Other key objectives of the present invention is to withstand more than 1 million shots with negligible deformation or damage to the backstop and its armored plates. It is primarily desired that the improved bullet containment trap consists a very strong backstop structure that lasts long and provides better access to the interior of the trap. It is also desired that the backstop has a modular structure wherein the damaged plates can be easily changed and the whole of the bullet containment trap combined with the modular backstop and/or the modular backstop alone is easily movable and adaptable for indoor and outdoor use.

[024] According to a first aspect of the present invention, a bullet containment trap device with a modular backstop is disclosed. The device comprises of at least one open ended bullet receiving chamber, at least one electronic target assembly configured to project at least one target placed at a rear end of the open-ended bullet receiving chamber.

[025] In accordance with the first aspect of the present invention, the device also comprises of a boundary wall means for resisting penetration of bullet and to inhibit rebounding of bullet there from.

[026] In accordance with the first aspect of the present invention, the device further comprises of a plurality of supporting frames for holding the bullet receiving chamber and the said boundary wall means.

[027] In accordance with the first aspect of the present invention, the said boundary wall means is backed with a bullet's deceleration chamber in a horizontal axis, wherein the bullet fired compasses the bullet receiving chamber while in contact with said boundary wall and enters a terminal part of said boundary wall over a throat of a passageway and moves through said throat to dissipate on hitting a modular backstop of the said deceleration chamber.

[028] In accordance with the first aspect of the present invention, the said modular backstop comprises a first impact zone circumferentially oriented at a first angle from the horizontal zone of bullet travel and extends to at least one successive impact zone. [029] In accordance with the first aspect of the present invention, the said modular backstops with at least two impact zones are made by stacking multiple individual armored plates vertically and/or horizontally in to a plurality of cassettes.

[030] In accordance with the first aspect of the present invention, the said cassettes formed by stacking multiple individual armored plates are held vertically and/or horizontally to form the said modular backstop, wherein the said cassettes are held with long bolts making the impinging loads of the bullet hitting the said backstop distributed to multiple individual plates of the said cassettes closely stacked.

[031] In accordance with the first aspect of the present invention, the said cassettes have configurable armored plates and each plate has a configurable size, the said armored plates are screwed with two bolts to engaged and remove the cassette after damage.

[032] In accordance with the first aspect of the present invention, the said cassettes and/or the individual armored plates within each of the said cassettes are all replaceable for deformation.

[033] In accordance with the first aspect of the present invention, the said device is used for de-energizing and collecting the bullet fired along a substantially horizontal path of flight.

[034] In accordance with the first aspect of the present invention, the said bullet that enters the said deceleration chamber, even at a relatively low angle will move along the chamber without being shattered or damaging the walls or the modular backstop.

[035] In accordance with the first aspect of the present invention, the spent bullet ultimately falls off the modular backstop, and are flushed into a passageway and then into a collecting vessel. [036] In accordance with the first aspect of the present invention, the said modular backstop comprises very high flexural bending strength compared to multilayered backstops.

[037] In accordance with the first aspect of the present invention, the said cassettes vertically held with support of long bolts increases the compressive force making all the stacked plates behave like a single lumped block.

[038] In accordance with the first aspect of the present invention, the deformation point is not constrained to single location on the modular backstop of the device, but is distributed to locations which are at considerable distance.

[039] According to a second aspect of the present invention, a method of replacing cassettes and/or the individual armored plates for deformation of the modular backstop of the said bullet containment trap device is disclosed.

[040] In accordance with the second aspect of the present invention, the method comprises a first step of removing a plurality of long bolts that locks a plurality of cassettes formed of stacking multiple individual armored plates vertically and/or horizontally. The said method comprises a second step of removing a back plate and a plurality of side plates to get access to the said cassettes. The said method comprises a third step of identifying a damaged cassette from the lumped block to repair and replace the damaged cassette and/or the individual armored plates.

[041] In accordance with the second aspect of the present invention, the method comprises a fourth step of removing a plurality of cassette locking bolts to remove damaged armored plates of the said cassettes.

[042] In accordance with the second aspect of the present invention, the modular backstop of the said bullet containment trap device (allows cassettes and/or the individual armored plates within each of the said cassettes to be easily replaced and/or repaired for deformation.

[043] In accordance with the second aspect of the present invention, the device is devised at a relatively short distance from the shooter to catch the waste lead, brass and jacket material of the bullet being fired and prevent either the ricochet of a whole bullet or a large fragment thereof.

[044] Considerable concern is the lead contained in a bullet. A considerable amount of lead could be released into the environment, thereby injuring wildlife and contaminating groundwater supplies. The present invention contemplates reuse of the lead and makes the device environmental friendly.

[045] Conventionally rubber layer is used along with the back plates. The modular backstop of the present invention completely avoids usage of rubber.

[046] Consumables like the rubber sheets that are usually used and are to be changed frequently is avoided; back plates that are to be replaced for deformation and damage are minimized.

[047] Material (steel) used is less due to the shape and size of the modular backstop designed on finding an accurate velocity degradation curve of the projectile being dissipated.

[048] The bullet containment trap with the modular backstop is adapted to be used in indoor ranges, outdoor ranges, along with containerized tubular shooting ranges, in containerized modular ranges, and as a portable dry firing shooting range.

[049] Expandable and extendable to multiuser, multiple training ranges with a trainer console. [050] Economic significance to users as it withstands more than 1 million subsonic and supersonic shots used along with different dry practice shooting ranges. Brief Description of the Drawings

[051] The above and other objects, features and advantages of the invention will become apparent from a consideration of the following detailed description presented in connection with the accompanying drawings in which:

FIG. 1 illustrates a perspective of a bullet containment trap with a modular backstop, according to an exemplary embodiment of the present invention;

\ FIG. 2a illustrates a top sectional view of the deceleration chamber that comprises of the said modular backstop according to the exemplary embodiment of the present invention;

FIG. 2b illustrates a half sectional view of the deceleration chamber according to the exemplary embodiment of the present invention;

FIG. 2c illustrates a front view of a cassette, according to the exemplary embodiment of the present invention;

FIG. 3a illustrates a material characteristic of a bullet for steel core, according to the exemplary embodiment of the present invention;

FIG. 3b illustrates a material characteristic of the bullet for steel jacket, according to the exemplary embodiment of the present invention. FIG. 3c illustrates a moderate strain rate compression test results for steel core and steel jacket, according to the exemplary embodiment of the present invention; FIG. 3d illustrates a strain comparison for steel core and steel jacket, according to the exemplary embodiment of the present invention;

FIG. 4a-4b illustrates a velocity degradation of bullets, according to the exemplary embodiment of the present invention;

FIG. 5 illustrates a exploded side view of the said modular backstop according to the exemplary embodiment of the present invention;

It is appreciated that not all aspects and structures of the present invention are visible in a single drawing, and as such multiple views of the invention are presented so as to clearly show the structures of the invention.

Detailed Description of the Invention

[052] The present invention relates to a bullet containment trap for securing used bullets. Specifically, the invention relates to bullet containment traps, be used in conjunction with Containerized Tubular Shooting Range (CTSR) that is used for training purposes.

[053] According to an exemplary embodiment of the present invention, a bullet containment trap with a modular backstop system for securing used bullets is disclosed. The said modular backstop system comprises of at least one electronic target assembly (not shown) configured to project at least one target placed at a rear end of an open-ended bullet receiving chamber. The said bullet receiving chamber is supported by a plurality of supporting frames. The said bullet receiving chamber is backed with a bullet's deceleration chamber in a horizontal axis wherein the bullet that is fired compasses the bullet receiving chamber while in contact with a plurality of boundary walls and enters a terminal part of said boundary wall over a throat of a passageway and moves through said throat to dissipate on hitting a modular backstop of the said deceleration chamber.

[054] In accordance with the exemplary embodiment of the present invention, the said modular backstop with at least two impact zones is made by stacking multiple individual armored plates vertically and/or horizontally in to a plurality of cassettes.

[055] In accordance with the exemplary embodiment of the present invention, the said modular backstop comprises a first impact zone circumferentially oriented at a first angle from the horizontal zone of bullet travel and extends to at least one successive impact zone.

[056] In accordance with the exemplary embodiment of the present invention, the said cassettes formed by stacking multiple individual armored plates are held vertically and/or horizontally to form the said modular backstop, wherein the said cassettes are joined with long bolts making the impinging loads of the bullet hitting the said backstop distributed to multiple individual plates of the said cassettes closely stacked. The said cassettes and/or the individual armored plates within each of the said cassettes are all replaceable for deformation.

[057] In accordance with the exemplary embodiment of the present invention, the said device is used for de-energizing and collecting the bullet fired along a substantially horizontal path of flight. The said bullet that enters the said deceleration chamber, even at a relatively low angle will move along the chamber without being shattered or damaging the walls or the modular backstop.

[058] In accordance with the exemplary embodiment of the present invention, the device can also be rotated to be used in horizontal position by joining number of devices to form a larger device which can be used in both inside and outside ranges. [059] In accordance with the exemplary embodiment of the present invention, the spent bullet ultimately falls off the modular backstop, and are flushed into a passageway and then into a collecting vessel, the modular backstop comprises very high flexural bending strength compared to multilayered backstops.

[060] In accordance with the exemplary embodiment of the present invention, the said cassettes vertically held with support of long bolts increases the compressive force making all the stacked plates behave like a single lumped block. The deformation point is not constrained to single location on the modular backstop of the device, but is distributed to locations which are at considerable distance. The said cassettes have configurable armored plates and each plate has a configurable size.

[061] According to the exemplary embodiment of the present invention, a method of replacing cassettes and/or the individual armored plates for deformation of the modular backstop of the said bullet containment trap device is disclosed.

[062] In accordance with the exemplary embodiment of the present invention, the method comprises a first step of removing a plurality of long bolts that locks a plurality of cassettes formed of stacking multiple individual armored plates vertically and/or horizontally. The said method comprises a second step of removing a back plate and a plurality of side plates to get access to the said cassettes. The said method comprises a third step of identifying a damaged cassette from the lumped block to repair and replace the damaged cassette and/or the individual armored plates.

[063] In accordance with the exemplary embodiment of the present invention, the method comprises a fourth step of removing a plurality of cassette locking bolts to remove damaged armored plates of the said cassettes. [064] In accordance with the exemplary embodiment of the present invention, the modular backstop of the said bullet containment trap device (allows cassettes and/or the individual armored plates within each of the said cassettes to be easily replaced and/or repaired for deformation.

[065] Reference will now be made to the drawings in which the various elements of the present invention will be given numeral designations and in which the invention will be discussed so as to enable one skilled in the art to make and use the invention. It is to be understood that the following description is only exemplary of the principles of the present invention, and should not be viewed as narrowing the pending claims. Additionally, it should be appreciated that the components of the individual embodiments discussed may be selectively combined in accordance with the teachings of the present disclosure. Furthermore, it should be appreciated that various embodiments will accomplish different objects of the invention, and that some embodiments falling within the scope of the invention may not accomplish all of the advantages or objects which other embodiments may achieve.

[066] Referring to FIG 1 , the device ( 1 ) with a modular backstop (7) in accordance with an exemplary embodiment of the present invention is disclosed. The device (1) comprises of a bullet receiving chamber (4) for resisting penetration of bullet and to inhibit rebounding of bullet. The device (1) comprises of a top plate, bottom plate, and left and right plate placed in a rectangular shape to form an open-ended bullet receiving chamber (4), and a deceleration chamber (5), placed at a rear end of the open-ended bullet receiving chamber (4).

[067] The said bullet receiving chamber (4) and deceleration chamber (5) is mounted in between supporting frames top (2) and bottom frame (3) with a wheel

(4) and a collecting vessel (not shown) is placed below the deceleration chamber

(5). The said bullet receiving chamber (4) means is backed with a bullet's deceleration chamber (5) in a horizontal axis. [068] Referring to FIG. 2a-2b the deceleration chamber (5) in accordance with the exemplary embodiment of the present invention is disclosed. The deceleration chamber (5) comprises of modular backstop (7), a plurality of cassettes (11) placed vertically and locked both sides with a nut (8) along with a back top fixing plate (9). A left and right impact plates are placed beside the modular backstop (7) to compass the bullet in its axis. Wherein the said back top fixing plate (10) also comprises of long vertical impact plates (15) are fixed at an angle in at least as great as the secondary angle which is placed on the top and bottom of the cassettes (11).

[069] The bullet fired compasses the bullet receiving chamber (4) while in contact with boundary wall and enters a terminal part of said boundary wall over a throat (6) of a passageway and moves through said throat to dissipate on hitting a modular backstop (7) of the said deceleration chamber (5).

[070] Referring to FIG. 2c the cassettes (11) in accordance with the exemplary embodiment of the present invention is disclosed. The cassette (11) comprises of individual armored plates (12) held vertically and/or horizontally to form the said modular backstop (7). Wherein, the said cassettes (11) are formed by stacking multiple individual armored plates (12) vertically and/or horizontally to form the said modular backstop (7). The said cassettes (11) are joined with long bolts (8) making the impinging loads of the bullet hitting the said backstop (7) distributed to multiple individual plates of the said cassettes (11) closely stacked.

[071] Wherein the said cassette has configurable armored plates (12) and each plate has a configurable size, and is screwed with two bolts to engaged and remove cassette after damage. The said cassettes (11) and/or the individual armored plates (12) within each of the said cassettes (11) are all replaceable for deformation.

[072] Referring to FIG. 3a, the material characteristics of bullet in accordance with the exemplary embodiment of the present invention is disclosed. The yield stress of the material is specified as a function of the equivalent plastic strain at different equivalent plastic strain rates. The material definition also includes failure models with progressive damage, which causes analysis software to remove elements from the mesh as they fail. Both the ductile and shear initiation criteria are used: the ductile criterion is specified in terms of the plastic strain at the onset of damage as a tabular function of the stress tri-axiality. The shear criterion is specified in terms of the plastic strain at the onset of damage as a tabular function of the shear stress ratio. The damage evolution energy is assumed to be 500 N/m. The armored plate of 10 mm thickness, a bullet of 33mm in length and 7.82mm diameter has an initial speed of 850m/sec.

[073] A 3D model of the device (1) is analyzed to understand the structural behavior for different bullet impacts in which 3 case studies were done. The armor plate and associated parts of device were assigned with AR500 material and bullet material properties were assigned with three core material like copper coated steel jacket, lead-antimony and steel.

[074] A bullet fired from the center of the throat (Bulls Eye) in accordance with the exemplary embodiment of the present invention is shown. During the analysis elements from both bodies fail, which calls for the use of element-based surfaces that can adapt to the exposed surfaces of the current non-failed elements. The general contact algorithm supports element-based surfaces that evolve in this manner (whereas the contact pair algorithm does not). To model eroding contact, we must include in the contact domain all surface faces that may become exposed during the analysis, including faces that are originally in the interior of bodies. Only the interior faces that are expected to participate in contact are included in the contact domain in this analysis to minimize the memory use (including interior faces for all elements in the model would more than double the memory use).

[075] By default, the general contact algorithm does not include nodal erosion, so contact nodes will still take part in the contact calculations even after all of the surrounding elements have failed. These nodes act as free-floating point masses that can experience contact with the active contact faces. The analysis is conducted including nodal erosion, which causes the nodes to be removed from the contact calculations once all surrounding elements have failed.

[076] Material Characteristics of Bullet: a compression test of steel being used in accordance with the exemplary embodiment of the present invention is shown. Three different regimes of material’s response to compression can be distinguished. After first, elastic response, with the modulus of elasticity of E1=31.72GPa, and yield point of oy=362 MPa, there are two strain hardening zones with stiffness of E2=1.24GPa and E3=3.45GPa, respectively, ending by load increase due to platen- to-platen compression.

[077] Material Characteristics of Bullet: Referring Fig. 3b, compression test results of a copper plated steel jacket in accordance with the exemplary embodiment of the present invention is shown. Jacket showed to be stiffer, having Young’s modulus ofE=42.5GPa as well as higher yield strength of δy=603.3 MPa, then steel core. During compression, cylindrical test sample, after reaching the yield point, gets crushed including two buckling modes, indicated by two peaks on the graph.

[078] Referring Fig. 3c to 3d, test results for stress and strain of a copper plated steel jacket and steel core, Compared, quasi- static and moderate strain rate compression results, for both bullet core and jacket (Figure 3d-3e show initially stiffer response (marked on graphs) of both core and jacket at higher strain rate. However, it has to be noted that even moderate strain rate of 100 s ^-1 is still much lower than strain rates that bullet materials experience during ballistic event, which are in order of 10,000 s ^-1 .

[079] These above material characteristics were used for Bullet in our device simulation to know the strength of the armored plate. Material characteristics were evaluated by doing above physical tests with high strain rates in dynamic condition.

Damage Evolution type displacement = 0.0001

Mie-gruneise equation of state (used on all the materials)

C _o = 4.596E6 mm/s s = 1.4 r _o = 1.93

Linear elastic shear modulus G = 9.446E3 MPa

Armor Plate Material Properties

Density = 7800Kg/m ³

Elastic Modulus = 210GPa

Poisson’s Ratio = 0.28

Yield Strength = 776 Mpa

Ultimate Tensile Strength = 1810MPa

ASSUMPTIONS FOR THE ANALYSIS:

· AR-500 Material properties are assigned for DEVICE.

· Copper coated steel jacket and Lead- Antimony material properties were applied to the bullet. A non-linear dynamic analysis was performed to account for nonlinearity in the geometry and material. As it is a transient non-linear dynamic analysis inertial effects and whole kinetic energy of the bullet load will be applied and response will be calculated for every micro second.

Steel coated copper jacket lead material are modeled in such a way that they have proper nodal connectivity between them.

Bullet mass of 11.5g and velocity of 850m/s was considered Stresses are presented after removing spurious areas.

Coefficient of friction was assumed as 0.2 between bullet and the device.

[080] Analysis is performed by assuming an ideal condition in which no air gaps will be there and strength of the armor plate is analyzed for ideal conditions. But in field conditions there will be air traps or distorted crystal lattice structure at some locations of the components which will degrade the stiffness of the part causing fatigue failure while in operating conditions.

Mathematical Material Model

Material constitutive Model

In general, the response of material under High-speed impact involves consideration of the effect of strain. Strain rate and temperature.

The Johnson-Cook material model with strain rate dependence was used in the simulation to define the inelastic behavior of die bullet materials.

The static yield stress δ° is assumed to be of the form Where _έ - ^pl is the equivalent plastic strain and A, B, n and m are material parameters measured at or below the transition temperature 0 transition non-dimensional temperature defined as

Where 9 is the current temperature, 0 _meit is the melt temperature and θ transition is the transition temperature defined as the one at or below which there is no temperature dependence on the expression of the yield stress.

The Johnson-Cook strain rate dependence assumes that

Where, δ : yield stress at nonzero strain rate έ~ ^pl : equivalent plastic strain rate έ ₀ : Reference strain rare

C : Material parameters measured at or below the transition temperature δ ⁰ ( _έ - ^pl , θ) : is the static yield stress

R ( _έ - ^pl) : is the ratio of the yield stress at nonzero strain rate 10 the static yield stress (so that R(έ ₀ ) = 1-0)

The elastic behavior of the material was defined with a hydrodynamic material model, in which the pressure is defined as a function of the density and the internal energy.

Dynamic Failure Model for Lead Material The Johnson-Cook dynamic failure model which is suitable for high- strain rate deformation of metals was used to define the lead failure in the high-speed ballistic impact simulation.

The model assumes that the equivalent plastic strain at the onset of damage, is a function of stress triaxiality and strain rate. The failure is assumed to occur when the damage parameter exceeds 1. The damage parameter co is defined as

Where Aε ^-pl an increment of the equivalent plastic strain is , is the strain at failure, and the summation is performed over all increments in the analysis. The strain at failure, is assumed to be dependent on a non dimensional plastic strain rate, a dimensionless pressure deviatoric stress ratio, p/q where p is the pressure and q is the mises stress; and the non dimensional temperature 0. The dependencies are from

[081] The stress on armored plate is illustrated, the results shows when a bullet gets fired from center of trough (6), the stress on armed plate is less than the stress on modular back stop, the said first impact zone (13) circumferentially oriented at a first angle from the horizontal zone has more stress and compared to one successive impact zone (14).

[082] As the plates are stacked to form a rectangular block. This block will have very high flexural bending strength compared to old design causing negligible deflection. As the plates are stacked to form a rectangular block. This block will have very high flexural bending strength compared to old design causing negligible deflection. Irrespective of the bullet hitting direction the deformation point is not constrained to single location on the armor plate. It is distributed to two locations which are at considerable distance. Final Bullet impinging load will be distributed to minimum three to four plates.

[083] If the plates wear further and make a cavity, the bullet goes inside the cavity and retards the speed of the bullet and stops. However, if cavity becomes big removing the distorted bullet can be done by removing the top plate.

[084] The volume of the device has decreased nearly to 1/4th compared to the previous volume and the weight got decreased. Thickness of the armor plate can be increased to our convenience. As the plates are stacked, the self- weight of the plates and the long bolts which hold the plates in stacked manner will increase the compressive force making all the stacked plates behave like a single lumped block.

[085] As the system is designed in modular cassettes, after the plates wear to considerable thickness, each module can be replaced with new cassette without disturbing the whole device.

[086] All the possibilities of the bullet reverse travel were tested using dynamic analysis simulation and is observed that the bullet cannot travel in reverse direction after hitting the target. This system was tested with SLR bullet of weight 11.5g with speed of 850m/s. Kinetic Energy of the bullet is 4.15kJ. When the bullet hits at bulls’ eye (Case-1) the results show that the deflection on armor plate is 0.16mm and could see elastic strains 0.00824 with stress of 633MPa.

[087] As the kinetic energy is 4154J the total reaction force acting on the block is 415.4kN which is equal to 42.34tonnes acting for 0.0117sec as a impulse shock. As the front nose cone of the SLR bullet is 0.5mm thick with lead-antimony (Yield 15MPa) content which is very soft in strength compared to steel (650MPa) is smashed due to 0.5mm thick copper coated steel jacket which causes the surface area of the bullet to increase causing the impact to spread to larger area of the plate.

[088] Analysis results suggest that the device (01) with modular backstop (7) can withstand a greater number of bullet shots before its failure due to more thickness and high flexural bending strength. Its modular cassette (11) design will help us in replacing the distorted and deformed plates (12) easily.

[089] Referring Fig. 4a-4b, Continuous firing of bullets within short time generates high temperatures and causes consequential material property changes of the back plates and leads to deformation in shape of the plates and finally allows penetration of bullets in to the back plates. Whereas in the present invention, the stacked armored plates each act as heat sink fin increases the surface area for heat dissipation. ; the thermal conductivity of the armored plates used in cassette type configuration will increase due to increase in surface area of the armored plates. The heat is dissipated due to conduction, and the modular backstop of the present invention will not deform due to heat accumulation as we see in the prior art bullet/ projectile containment traps. Flexural bending strength of the modular backstop of the present invention is also managed due to high momentum of inertia in the bending direction.

[091] Non linear impact dynamic analysis is performed to calculate velocity degradation of bullets being dissipated with respect to guide plates (6). Many iterations are been performed for smooth velocity degradation and accordingly a profile of the modular backstop is evaluated as shown in Fig. 4a - 4b.

[092] Referring to Fig. 5, a method of replacing cassettes (11) and/or the individual armored plates (12) for deformation of the modular backstop (7) of the said bullet containment trap device (1) is disclosed. [093] In accordance with the exemplary embodiment of the present invention, the method comprises a first step of removing a plurality of long bolts (8) that locks a plurality of cassettes (11) formed of stacking multiple individual armored plates (12) vertically and/or horizontally. The method comprises a second step of removing a back plate (18) and a plurality of side plates to get access to the said cassettes (11). The method comprises a third step of identifying a damaged cassette (11) from the lumped block to repair and replace the damaged cassette (11) and/or the individual armored plates.

[094] In accordance with the exemplary embodiment of the present invention, the method comprises a fourth step of removing a plurality of cassette locking bolts (8a) to remove damaged armored plates (12) of the said cassettes (11).

[095] In accordance with the exemplary embodiment of the present invention, the modular backstop (7) of the said bullet containment trap device (1) allows cassettes (11) and/or the individual armored plates (12) within each of the said cassettes (11) to be easily replaced and/or repaired for deformation.

[096] Thus, there is disclosed an improved bullet containment trap with a modular backstop. Those skilled in the art will appreciate numerous modifications which can be made without departing from the scope and spirit of the present invention. The appended claims are intended to cover such modifications.