ENHANCED RADIAL DAMAGING PROJECTILE AND METHOD OF USE

Description

CROSS REFERENCE TO RELATED APPLICATION

The present application claims the benefit of U.S. Provisional Application No. 63/600,267, filed Nov. 17, 2023, the contents of which are expressly incorporated herein by reference in its entirety.

BACKGROUND OF THE DISCLOSURE

1. Field of the Disclosure

The present disclosure relates to projectiles that use their kinetic energy to inflict damage in targets. More specifically, the present disclosure relates to a method and apparatus operable to leverage the high-rate fracture physics of a multiple radial cracking phenomenon in target-projectile interactions to increase and enhance damage to the target.

2. Description of the Related Art

Small, medium, and large caliber weapons use kinetic energy projectiles to penetrate and damage targets that range from soft materials, for instance personnel and animals, to hard materials, for instance structures and equipment. During terminal ballistic interactions between projectiles and targets multiple cracks may develop in a radial direction along the projectile path.

Projectiles used in weapons are generally designed as deforming or non-deforming respectively trading off penetration or radial damage. Deforming bullets, such as hollow points, expand when entering a target, slowing down over a short distance, to maximize transfer of the projectile's kinetic energy to the target [U.S. Pat. Nos. 8,413,587 B2; 6,805,057-B2; 10,563,964-B2, 9,513,092-B2; 9,003,974-B2; 8,511,233-B2; 6,732,657-B2; 9,702,677-B2; 10,663,271-B2]. Several limitations can prevent these projectiles from performing as designed. Hollow point bullets expand best at higher velocities where greater drag forces can force the projectile to mushroom; however, at low velocities they may not reliably expand. An expanded bullet has a reduced penetration depth as a result of the larger surface area and greater drag. These projectiles are typically not barrier blind. When these projectiles encounter material in front of a target they may expand too early or clog, preventing expansion; both scenarios reduce the bullet's terminal effectiveness on the target. Deforming projectiles are claimed to be more effective because they transfer their kinetic energy to the target; however, just because energy is transferred does not mean that that energy is converted into damage. Some types of materials, especially some biological tissues, can undergo large degrees of elastic stretch and can fully recover after large deformations.

In contrast, non-deforming projectiles can penetrate further into a target than deforming bullets with the reduction of radial damaging effects. Various efforts have been pursued to change non-deforming projectile design to achieve some different effects [U.S. Pat. No. 9,541,362 B2; US-20160265887-A1; U.S. Pat. Nos. 6,973,879-B1; 10,036,619-B2; 8,881,654-B2; 10,436,557-B2; 10,126,105-B2; US-20200141706-A1; U.S. Pat. Nos. 9,829,293-B2; 11,346,641 B2]. These two bullet design principles (deforming and non-deforming) demonstrate a tradeoff between either increasing radial damage or increasing penetration and the tradeoff spans from small to large caliber projectiles.

It is readily observable that projectile impacts fracture targets differently as a result of differences in mechanical properties of the targets. For instance, compare paper and glass. A projectile impact with paper would likely cause a single hole with tears around the circumference, whereas some types of glass could shatter. Just as differences in mechanical properties can influence impact fracture morphology, so too can factors like loading rate (projectile velocity) and initial characteristic length (projectile size). Grady postulated that during a high rate expansion that causes dynamic fragmentation, a correlation horizon exists between growing cracks that limits the distance that stresses can redistribute. The stress around cracks redistributes by influencing other potential cracks within the correlation horizon. This region of influence is governed by the material's elastic wave speed and the time to fracture, the product of which sets the correlation horizon during high rates of deformation [Grady, D. E., 2010. Length scales and size distributions in dynamic fragmentation. Int. J. Fract. 163 (1-2), 85-99]. This concept is repeatable, in that it predicts that the same number of radial cracks will form for a given loading rate, initial cavity size, target material (with a set elastic wave speed and fracture energy). Grady's theories applied to materials like metals and rocks that were explosively loaded.

To date, no projectile designs have identified nor leveraged the multiple radial fracturing. As such, there is a need in the art for projectiles that can enhance damage to a target.

SUMMARY OF THE EMBODIMENTS OF THE DISCLOSURE

This disclosure leverages the multiple radially fracturing phenomenon, arising from the correlation horizon, by designing a projectile having protrusions informed by the correlation horizon. In accordance with aspects of the disclosure, the protrusions, acting as stress concentrators, induce radial cracks where energetically preferred to enhance crack formation and generate greater damage in the target compared to an unmodified projectile.

Furthering Grady's work, the present inventor and coauthor showed that a similar correlation horizon exists in soft materials, similar to tissue [Milner, M. P., and Hutchens, S. B., 2021, “Multi-Crack Formation in Soft Solids During High Rate Cavity Expansion,” Mech. Mater., 154, p. 103741]. The fracture correlation horizon phenomenon indicates that several cracks will appear and grow independently of each other when a material experiences a radial expansion at a high enough rate. A projectile interacting with a target can induce a sufficient expansion rate to produce multiple radial cracks and the theory predicts that the same number of radial cracks will form in a repeatable projectile-target interaction.

Aspects of the present disclosure are directed to a projectile design that uses radial stress concentrating protrusions to induce an energetically preferred crack configuration which maximizes radial damage during projectile impacts. In high-rate cylindrical expansions, like those generated by projectile impacts, multiple radial fractures occur. In a given projectile-target interaction the same number of cracks are generated, based on a crack correlation horizon. The design of protrusion-modified-projectiles is informed by the number of radial cracks naturally formed from unmodified projectile impacts into targets. This effectively designs a projectile to the requirements of the correlation horizon. The protrusions on this projectile function as stress concentrators to initiate and drive crack growth in the required configuration, which causes longer radial cracks and more damage.

This present disclosure poses a solution for increasing damage in targets during a projectile's terminal interaction with the target. This disclosure uses a specific projectile design, with stress concentrating protrusions, to maximize the natural radial fracture behavior to drive radial cracks further into the target. Embodiments of the disclosure utilize circumferentially arrayed stress concentrating protrusions based on the natural radial cracking in any desired soft or hard target.

Embodiments of the disclosure leverage the correlation horizon that determines how many radial fractures will naturally occur during a projectile-target interaction and using a projectile with protrusions corresponding to radial fractures in the correlation horizon to initiate and enhance cracks that correspond to the correlation horizon. In sufficiently high loading rates, such as during projectile impacts, multiple cracks can form around an initial geometry completely independent of each other. In accordance with aspects of the disclosure, this ensures that the same number of cracks will form during the same projectile-target interaction. The cracks grow independently because the stress and strain around an initiated crack can only influence an area within its correlation horizon. This horizon is governed by the material's wave speed and the time to fracture, the product of which sets the correlation horizon during high rates of deformation.

Grady and Kipp derived an expression to predict the number of cracks that will initiate from an explosively loaded wellbore:

N = π ⁢ D ⁢ ( p . 6 ⁢ c l ⁢ K IC ) 2 / 3 .

Where N is the number of cracks, D is the diameter of the wellbore, {dot over (p)} is the loading rate, c_l is the wave speed of the material, and K_IC is the target material's fracture toughness. It is readily observable from the equation that independently increasing the wellbore diameter or the loading rate, while keeping other variables constant, will tend to increase the number of radial cracks that form. Additionally, material that has a higher wave speed or fracture toughness results in a lower number of radial cracks, while holding all else equal [Grady, D. E. and M. E. Kipp, 1985. Mechanisms of Dynamic Fragmentation: Factors Governing Fragment Size. Mechanics of Materials 4, 311-320]. Grady and Kipp made predictions for multiple cracks in materials like rock and metal, the present author and Hutchens examined multiple radial crack formation in soft materials, like tissue simulants. They derived the expression:

N = π ⁢ λ . ⁢ A 0 μ / ρ ⁢ ( Γ 2 ⁢ μ ⁢ A 0 ) - 1 .

Where N is the number of cracks, A₀ is the initial radius of the expansion, {dot over (λ)} is the expansion rate, μ is the material's shear modulus, √{square root over (μ/ρ)} is the wave speed of the material, and Γ is the effective fracture energy. The same relations hold, as described above. Independently increasing the initial radius or the loading rate will increase the number of radial cracks that form, and a higher wave speed or fracture energy decreases the number of radial cracks formed. As is evident from these equations, if the same caliber projectile, with the same geometry, fired at the same velocity, strikes the same target, then the same number of cracks will form.

This disclosure proposes methods to determine the radial fracture characteristics and correlation horizon from an unmodified projectile's ballistic impact and the resulting modified projectile design with circumferentially arrayed stress concentrating protrusions to maximize radial cracking. The protrusions arranged at (or near) the nose of the bullet concentrate the stress at specific points around the projectile that are in the energetically preferred radial configuration for the given target, and which is equivalently at the correlation horizon distance. In accordance with aspects of the disclosure, these protrusions act as stress concentrators to drive cracks further in the energetically preferred configuration because they can form the cracks earlier in the expansion process. That is, as these protrusions create additional wedges around the circumference of the projectile that impact the target material at an earlier point in time than the main surface of the projectile, the protrusions can form the cracks earlier in the expansion process. In accordance with aspects of the disclosure, this maximizes the final radial crack length around the channel as the projectile forces the cavity to expand.

A proposed method to determining the protrusion geometry, which is further discussed in FIG. 2, begins with firing an unmodified projectile into a desired target of interest and then observing the radial damage. Radial damage from a ballistic impact can vary based on the non-exhaustive list of a target material's mechanical wave speed, fracture toughness, and dimensions; additionally, radial damages depends on the non-exhaustive list of a projectile's impact velocity, material, and geometry. A priori predictions of radial crack distribution would require experimental determination of multiple target-dependent parameters that are difficult or impossible to experimentally obtain given current techniques. However, examination after a ballistic impact enables insight into the design of a protrusion modified projectile to enhance the radial cracks present. Those radial cracks present indicate the energetically preferred configuration, or equivalently the correlation horizon, given a particular combination of projectile and target. Designing a projectile with circumferentially spaced protrusions that enhance the naturally occurring radial cracking enables the projectile to generate damage in the energetically preferred configuration to generate greater damage along the projectile path.

The aims and advantages of the projectile design described in the present disclosure can be achieved by modifying the particular design, geometry, spacing, location, method of manufacture, and other parameters that are apparent to those skilled in the art. As such, not all iterations of embodiments are depicted in this disclosure and additional or alternative embodiments can incorporate the broader scope and spirit of the present disclosure. Therefore, the embodiments described herein are intended to be exemplary and not limiting.

The present projectile disclosure represents exemplary embodiments which can be used in a range of calibers with different protrusion geometries and configurations matched to the desired target. In accordance with aspects of the disclosure, protrusion geometry and/or configuration may be altered depending on the caliber of projectile used in dependence upon the mechanical properties of a given target (e.g., how the natural radial fractures occur). For instance, in exemplary embodiments larger caliber weapons used by military forces, like 30 mm projectiles to larger bombs and missile warheads, may be required to penetrate structural material like concrete or steel. However, relatively smaller weapons, like solider carried rifles with 5.56 mm projectiles, could face similar targets (e.g., concrete or steel) or different targets such as enemy soldiers. In accordance with aspects of the disclosure, this span of caliber sizes may necessitate that protrusion geometry is altered relative to the respective projectile caliber to achieve the necessary stress concentrating factor to drive crack formation. Additionally, the same principles of the present disclosure apply in exemplary embodiments across, for example, spans of hunting rifle or handgun projectiles that target soft materials like game.

In further exemplary embodiments the shape of the protrusions can also be varied in dependence upon the nature of stress concentrations in fracture mechanics. For example, varying the sharpness, the longitudinal length, the radial extent, and/or the height of the stress concentrating protrusions may alter the degree to which the magnitude of stress is concentrated. In accordance with aspects of the present disclosure, however, there exist different solutions to generating those stress concentrations. The shape of these protrusions can be influenced by the ease of which they can be built into to the projectile and the method of manufacture for the particular projectile as one skilled in the art would implement. For example, the protrusions can be formed by adding material to the projectile or by removing material from the projectile. (Some exemplary embodiments of protrusion (and edge) shapes can be observed in FIGS. 10A-10L, which are discussed below).

In exemplary embodiments, the protrusions may begin in the front of the projectile, but not necessarily at the tip of the projectile. The protrusions may be placed at any location required for the desired terminal effect against the target (which may be experimentally-determined). The protrusions may extend the entire length of the projectile, but do not have to extend the entire projectile length. The aim of the projectile protrusion configuration is for any projectile to induce the preferred arrangement of cracks in the target material, and that the projections are small enough that they fit on the tapered nose of the projectile and within the barrel of the gun. In accordance with aspects of the disclosure, this can be accomplished by providing protrusions that begin at or near the front end of the projectile, extend along the surface profile of the projectile; and terminate before extending to the largest diameter of the projectile, such that they remain at or within largest diameter of the projectile.

In additional contemplated embodiments, the protrusion may terminate at any point along the projectile surface (which may include protrusions that extend past the to the largest diameter of the projectile). In this scenario, the projectile could be designed such that it is a sub-caliber projectile and encased within another device, such as a sabot, to allowing firing in a barrel. In exemplary embodiments the protrusion can be oriented parallel to the longitudinal axis or at an angle to the longitudinal axis to vary forces on the projectile during flight or during terminal interaction with the target.

In embodiments of the present disclosure, a projectile includes a body having a longitudinal axis, a front end and a rear end at respective ends along the longitudinal axis, and a surface profile extending from the front end to the rear end. The surface profile is radially symmetrical about the longitudinal axis, the body having a caliber size defining a largest diameter of the body along the longitudinal axis. The projectile also includes two or more radially-protruding stress-concentrating protrusions arranged proximate the front end of the body.

In embodiments of the present disclosure, the protrusions are symmetrically spaced about the longitudinal axis.

In embodiments of the present disclosure, the protrusions extend along the surface profile of the body such that the protrusions each have a fore end and an aft end.

In embodiments of the present disclosure, the fore end of each protrusion is arranged at or near the front end of the body.

In embodiments of the present disclosure, the aft end of each protrusion is arranged along the surface profile spaced from the front end at a position such that each protrusion is entirely radially within the largest diameter of the body.

In embodiments of the present disclosure, the protrusions are parallel to the longitudinal axis of the body.

In embodiments of the present disclosure, the protrusions are canted at an angle to the longitudinal axis of the body.

In embodiments of the present disclosure, the protrusions each have a tapering width.

In embodiments of the present disclosure, the tapering width includes a narrow fore end width, a narrow aft end width, and a middle region having a width larger than the fore end width and larger than the aft end width.

In embodiments of the present disclosure, the tapering width includes a narrower fore end width, and a wider aft end width.

In embodiments of the present disclosure, the protrusions each have a tapering radial height along the longitudinal axis.

In embodiments of the present disclosure, the tapering radial height includes a shorter fore end radial height, a shorter aft end radial height, and a middle region having a radial height larger than the fore end radial height and larger than the aft end radial height.

In embodiments of the present disclosure, the fore end of each protrusion is arranged a spaced distance from the front end of the body.

In embodiments of the present disclosure, the protrusions comprise a first group of protrusions and a second group of protrusions, wherein a fore end of each protrusion of the first group of protrusions is arranged a first distance from the front end of the body, and the fore end of each protrusion of the second group of protrusions is arranged a second distance from the front end of the body.

In embodiments of the present disclosure, the first group of protrusions are radially offset from the second group of protrusions.

In embodiments of the present disclosure, the first group of protrusions are radially aligned with the second group of protrusions.

In embodiments of the present disclosure, the fore end tapers to a point.

In embodiments of the present disclosure, the aft end of each protrusion is arranged along the surface profile spaced from the front end at a position, such that at least a portion of each protrusion is radially beyond the largest diameter of the body.

In additional embodiments of the present disclosure, a projectile includes a body having a longitudinal axis, a front end and a rear end at respective ends along the longitudinal axis, and a surface profile extending from the front end to the rear end, wherein the surface profile is radially symmetrical about the longitudinal axis, the body having a caliber size defining a largest diameter of the body along the longitudinal axis. Two or more stress concentrating petals are arranged proximate the front end of the body, wherein the petals are symmetrically spaced about the longitudinal axis and extend along the surface profile of the body such that the petals each have a fore end and an aft end. The fore end of each petal is arranged at or near the front end of the body and the aft end of each petal is arranged along the surface profile spaced from the front end at a position such that each petal is entirely radially within the largest diameter of the body.

In further embodiments of the present disclosure, a projectile includes a body having a longitudinal axis, a front end and a rear end at respective ends along the longitudinal axis, and a surface profile extending from the front end to the rear end, wherein the surface profile is radially symmetric about the longitudinal axis, the body having a caliber size defining a largest diameter of the body along the longitudinal axis. Two or more radially-recessed regions form stress-concentrating edges arranged proximate the front end of the body.

Additional embodiments of the disclosure are directed to a method of determining a projectile protrusion configuration for a projectile for a target material. The method comprises impacting the target material with an un-modified projectile at an impact bore quantifying radial crack damage in the target material to determine a number of radial cracks in the target material circumferentially-spaced around the impact bore; and determining the projectile protrusion configuration as a number of protrusions circumferentially-spaced on the projectile, the number of protrusions informed by the number radial cracks.

One skilled in the art will recognize there are multiple methods of projectile manufacture and the varied approaches for introducing the desired protrusions into the projectile design. For example, protrusions can be incorporated on projectiles by additive or subtractive methods into the projectile during the manufacturing process, which may include traditional projectile manufacturing techniques such as machining, casting, swaging, turning and milling from larger stock, sintering, or other manufacture techniques known or created in the future by those skilled in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings are illustrative of particular embodiments of the present disclosure and therefore do not limit the scope of the present disclosure. All possible embodiments of the concept cannot be shown because they are scale and application dependent. The drawings are not necessarily to scale.

The novel features which are characteristic of the disclosure, both as to structure and method of operation thereof, together with further aims and advantages thereof, will be understood from the following description, considered in connection with the accompanying drawings, in which embodiments of the disclosure are illustrated by way of example. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only, and they are not intended as a definition of the limits of the disclosure. For a more complete understanding of the disclosure, as well as other aims and further features thereof, reference may be had to the following detailed description of the embodiments of the disclosure in conjunction with the following exemplary and non-limiting drawings wherein:

FIG. 1A is a schematic depiction of an expanding cavity, earlier in time, when potential cracks may form, based on the correlation horizon;

FIG. 1B is a schematic depiction of an expanding cavity, later in time, when cracks have formed, based on the correlation horizon;

FIG. 2A is an exemplary flowchart description of a process for designing protrusion-modified projectiles in accordance with aspects of the disclosure;

FIG. 2B is an exemplary flowchart description of a process for testing protrusion-modified projectiles in accordance with aspects of the disclosure;

FIG. 3A is a side perspective view of an exemplary low aspect ratio projectile containing three stress concentrating protrusions near the front end in accordance with aspects of the disclosure;

FIG. 3B is a longitudinal view from the front of the projectile in FIG. 3A in accordance with aspects of the disclosure;

FIG. 4A is a side perspective view of an exemplary low aspect ratio projectile containing five stress concentrating protrusions near the front end in accordance with aspects of the disclosure;

FIG. 4B is a longitudinal view from the front of the projectile in FIG. 4A in accordance with aspects of the disclosure;

FIG. 5A is a side perspective view of an exemplary low aspect ratio projectile containing eight stress concentrating protrusions near the front end in accordance with aspects of the disclosure;

FIG. 5B is a front end view of FIG. 5A in accordance with aspects of the disclosure;

FIG. 5C is a zoomed in view of the stress concentrating protrusions in FIG. 5A in accordance with aspects of the disclosure;

FIG. 6A is a side perspective view of an exemplary high aspect ratio projectile containing four stress concentrating protrusions near the front end in accordance with aspects of the disclosure;

FIG. 6B is a front end view of FIG. 6A in accordance with aspects of the disclosure;

FIG. 7A is a side perspective view of an exemplary high aspect ratio projectile containing five stress concentrating protrusions near the front end in accordance with aspects of the disclosure;

FIG. 7B is a front end view of FIG. 7A in accordance with aspects of the disclosure;

FIG. 7C is a side perspective view of the projectile in FIG. 7A with an aerodynamic cap arranged over the protrusions in accordance with aspects of the disclosure;

FIG. 8A is a side perspective view of an exemplary high aspect ratio projectile containing nine stress concentrating protrusions near the front end in accordance with aspects of the disclosure;

FIG. 8B is a front end view of FIG. 8A in accordance with aspects of the disclosure;

FIG. 8C is a closer view of the stress concentrating protrusions in FIG. 8A in accordance with aspects of the disclosure;

FIG. 9A is a side perspective view of an exemplary high aspect ratio, pre-impact and pre-deformation projectile containing five stress concentrating petals near the front end in accordance with aspects of the disclosure;

FIG. 9B is a side perspective view depicting a post-impact and deformed projectile in accordance with aspects of the disclosure;

FIGS. 10A-10L schematically depict various examples of stress concentrating protrusion arrangements from front end views, front perspective views, and side views in accordance with aspects of the disclosure;

FIG. 11A is a schematically depicted side view of a projectile without stress concentrating protrusions generating damage;

FIG. 11B is a schematically depicted cross-section view of the damage from a projectile without stress concentrating protrusions;

FIG. 12A is a schematically depicted side view of the exemplary projectile with stress concentrating protrusions generating damage in accordance with aspects of the disclosure;

FIG. 12B is a schematically depicted cross-section view of the damage from an exemplary projectile with stress concentrating protrusions in accordance with aspects of the disclosure;

FIG. 13A is a perspective view of damage to an exemplary plate from an impact of a projectile without stress concentrating protrusions; and

FIG. 13B is a perspective view of damage to an exemplary plate from an impact of a projectile with protrusions in accordance with aspects of the disclosure.

Reference numbers refer to the same or equivalent parts of the present disclosure throughout the various figures of the drawings.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE DISCLOSURE

In the following description, the various embodiments of the present disclosure will be described with respect to the enclosed drawings. As required, detailed description of the embodiments of the present disclosure are discussed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the embodiments of the disclosure that may be embodied in various and alternative forms. The figures are not necessarily to scale and some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the embodiments of the present disclosure.

The particulars shown herein are by way of example and for purposes of illustrative discussion of the embodiments of the present disclosure only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the present disclosure. In this regard, no attempt is made to show structural details of the present disclosure in more detail than is necessary for the fundamental understanding of the present disclosure, such that the description, taken with the drawings, making apparent to those skilled in the art how the forms of the present disclosure may be embodied in practice.

As used herein, the singular forms “a,” “an,” and “the” include the plural reference unless the context clearly dictates otherwise. For example, reference to “a magnetic material” would also mean that mixtures of one or more magnetic materials can be present unless specifically excluded.

Except where otherwise indicated, all numbers expressing quantities used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the specification and claims are approximations that may vary depending upon the desired properties sought to be obtained by embodiments of the present disclosure. At the very least, and not to be considered as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should be construed in light of the number of significant digits and ordinary rounding conventions.

Additionally, the recitation of numerical ranges within this specification is considered to be a disclosure of all numerical values and ranges within that range (unless otherwise explicitly indicated). For example, if a range is from about 1 to about 50, it is deemed to include, for example, 1, 7, 34, 46.1, 23.7, or any other value or range within the range.

As used herein, the indefinite article “a” indicates one as well as more than one and does not necessarily limit its referent noun to the singular.

As used herein, the terms “about” and “approximately” indicate that the amount or value in question may be the specific value designated or some other value in its neighborhood. Generally, the terms “about” and “approximately” denoting a certain value is intended to denote a range within ±5% of the value. As one example, the phrase “about 100” denotes a range of 100±5, i.e. the range from 95 to 105. Generally, when the terms “about” and “approximately” are used, it can be expected that similar results or effects according to the disclosure can be obtained within a range of ±5% of the indicated value.

As used herein, the term “and/or” indicates that either all or only one of the elements of said group may be present. For example, “A and/or B” shall mean “only A, or only B, or both A and B”. In the case of “only A”, the term also covers the possibility that B is absent, i.e. “only A, but not B”

The term “substantially parallel” refers to deviating less than 20° from parallel alignment and the term “substantially perpendicular” refers to deviating less than 20° from perpendicular alignment. The term “parallel” refers to deviating less than 5° from mathematically exact parallel alignment. Similarly, “perpendicular” refers to deviating less than 5° from mathematically exact perpendicular alignment.

The term “at least partially” is intended to denote that the following property is fulfilled to a certain extent or completely. The terms “substantially” and “essentially” are used to denote that the following feature, property or parameter is either completely (entirely) realized or satisfied or to a major degree that does not adversely affect the intended result.

The term “comprising” as used herein is intended to be non-exclusive and open-ended. Thus, for instance a composition comprising a compound A may include other compounds besides A. However, the term “comprising” also covers the more restrictive meanings of “consisting essentially of” and “consisting of”, so that for instance “a composition comprising a compound A” may also (essentially) consist of the compound A.

The various embodiments disclosed herein can be used separately and in various combinations unless specifically stated to the contrary.

This disclosure describes a projectile design that leverages the phenomenon of radial crack growth to increase the damage delivered to a desired target. The following descriptions will use exemplary embodiments to explain the embodiments of this disclosure, but one skilled in the art will understand that modifications may be required for the desired terminal effect against a given target, which are not excluded by this disclosure. Aspects of the present disclosure may be applied to small, medium, and large caliber projectiles and other munitions. These may non-restrictively be fired, launched, dropped, or otherwise projected from weapons such as guns, rockets, missiles, bombs. Methods of launching projectiles with stress concentrating protrusions are not discussed in the instant disclosure, which is directed to projectiles with stress concentrating protrusions (and methods of configuring projectiles with stress concentrating protrusions) and on enhancing the terminal effects against targets from stress concentrating protrusions, no matter how the projectiles with stress concentrating protrusions have reached the target. As not all potential uses or embodiments of projectiles with stress concentrating protrusions can be described herein, exemplary descriptions of the design and representative effects will be described.

Projectiles with protrusions described in this disclosure are used to generate stress concentrating regions in a target, during the projectile's interaction with the target. In accordance with aspects of the disclosure, these protrusions lower the threshold for crack initiation and the energy necessary for crack growth in a manner that is consistent with and enhances the radial fracture in terminal ballistic impacts. Although the configuration and geometry of stress concentrating protrusions may depend on various parameters (for instance between different weapons, projectiles, and targets), protrusions in each of the projectiles of the present disclosure into the target can cause an enhanced radial crack pattern.

FIG. 1A is a schematic depiction of an expanding cavity, earlier in time, when potential cracks may form, based on the correlation horizon and FIG. 1B is a schematic depiction of an expanding cavity, later in time, when cracks have formed, based on the correlation horizon. FIGS. 1A and 1B show the formation of multiple radial cracks based on the wave speed dependent correlation horizon. As shown in FIG. 1A, the target material 50 undergoes a rapid radial expansion in which the material in a radially expanding region 30 moves radially outward around a central area or hole 10, such as that generated from a projectile impact. Around the radially expanding region 30 are potential nucleation sites 20 where future cracks could form. The nucleation sites 20 could be small imperfections around the central hole 10. Any of these potential crack nucleation sites 20 could form future larger cracks as radial expansion continues. In small sections around the growing hole, one nucleation site will be energetically preferred and stress in the surrounding material will begin to redistribute. The size of this redistribution region is the correlation horizon 40. The correlation horizon 40 is defined as the wave speed of the material multiplied by the duration of time that has passed since the dynamic event began, having dimensions of length. Stresses around the growing cracks redistribute within the correlation horizon 40, which prevents other nucleation sites within the horizon from growing a crack.

The above described phenomenon of correlation horizon dependent radial fracturing depends on various experimental parameters which with current experimental techniques may not be able to determine. This is especially true in high-rate deformations, where the required experimental parameters may vary with deformation rates. In embodiments, the arrangement of the stress concentrating protrusions necessary to minimize wasted energy and maximize damage can be based on the fracture pattern generated by an unmodified bullet.

FIGS. 2A and 2B show exemplary methods to determine the optimal design for modifying projectiles with protrusions. FIG. 2A is an exemplary flowchart description of a process for designing protrusion-modified projectiles in accordance with aspects of the disclosure. First an unmodified projectile base design and desired target are chosen. Impacts of these projectiles and targets can then be studied experimentally or with computer modeling software known to those skilled in the art. The damage from these impacts is examined to characterize the damage, for instance by counting the naturally occurring radial cracks, measuring the crack lengths, and measuring the damaged area. This information may be used to create a target profile based on the measured and/or characterized damage. The target profile may include a correspondence between a target material and a protrusion layout or pattern based on the measured and/or characterized damage.

FIG. 2B is an exemplary flowchart description of a process for testing protrusion-modified projectiles in accordance with aspects of the disclosure. Upon understanding the unmodified projectile's damage to the target, aspects of the present disclosure are directed to a method for testing (e.g., verifying) a protrusion-modified projectile. In accordance with aspects of the disclosure, the aim is to provide a projectile having protrusions that match the number of radial cracks. Once designed (for example, for a particular material based on measured fracture patterns), protrusion-modified projectiles may be manufactured. The projectiles may be experimentally tested or modeled with appropriate computer simulations. Examination of the damage caused by the protrusion-modified projectiles will suggest the extent of whether an effective design has been achieved (e.g., for that particular material). If the resulting damage (for example, the crack lengths) is not greater than that of the un-modified projectile, then the protrusions may be adjusted (e.g., made larger, longer, and/or of a different shape, and/or other iterations identified in the instant disclosure and then reevaluated by experiment or model. Ultimately, the protrusion design will enhance the desired damage to the target. Finally, selected designs can enter mass production.

FIGS. 3A-5C depict low aspect ratio (length to diameter) projectiles which may be representative of typically manufactured handgun projectiles with varying numbers of protrusions 100. More specifically, FIG. 3A is a side perspective view of an exemplary low aspect ratio projectile 300 containing three stress concentrating protrusions 100 near the front end and FIG. 3B is a longitudinal view from the front of the projectile 300 in FIG. 3A in accordance with aspects of the disclosure. FIGS. 3A and 3B respectively depict a perspective view and a longitudinal view (from the front) of a projectile 300 with three protrusions 100.

FIG. 4A is a side perspective view of an exemplary low aspect ratio projectile 400 containing five stress concentrating protrusions near the front end and FIG. 4B is a longitudinal view from the front of the projectile 400 in FIG. 4A in accordance with aspects of the disclosure. FIGS. 4A and 4B respectively depict a perspective view and a longitudinal view from the front, of a projectile with five protrusions 100.

FIG. 5A is a side perspective view of an exemplary low aspect ratio projectile 500 containing eight stress concentrating protrusions near the front end in accordance with aspects of the disclosure, FIG. 5B is a front end view of FIG. 5A in accordance with aspects of the disclosure, and FIG. 5C is a closer view of the stress concentrating protrusions in FIG. 5A in accordance with aspects of the disclosure. FIGS. 5A and 5B respectively depict a perspective view and a longitudinal view from the front of a projectile 500 with eight protrusions 100. FIG. 5C shows a detailed perspective view of the projectile as indicated from FIG. 5A. Features of FIGS. 3-5 are described simultaneously, with more details on protrusion characteristics emphasized in FIG. 5A.

With these exemplary embodiment, the protrusions 100 are arranged within the front-end 102 of the projectile, where the diameter of the region is less than the nominal caliber 104 of the projectile. In accordance with aspects of the disclosure, the protrusions 100 are provided in the front-end 102 of the projectile as to not interfere with the travel of the projectile in the barrel of the weapon firing the projectile. In accordance with aspects of the disclosure, the number of protrusions 100 may be varied based on: (1) the properties of the projectile (which may include the nominal caliber 104 and the velocity of the projectile); and (2) the properties of the intended target. The number of protrusions may be selected based on the configuration which causes the most damage to the target.

In the exemplary embodiments of FIGS. 3A-5C (for example, with reference to FIG. 5C), the height 106 of the protrusions is designed as to remain within the nominal caliber 104 of the projectile. Just as the number of protrusions may be varied based on projectile and target properties, in accordance with additional aspects of the disclosure, the height 106, and the width 110 of the protrusions, as well as the spacing 108 between protrusions 100, may be varied based on the required dynamic fracture properties encountered as the projectile forces radial expansion within the target and the target cracks. In embodiments, the height 106 of the protrusion 100 in this exemplary embodiment is nonzero and maximally remains within the outer diameter of the projectile. The spacing 108 between protrusions may at a minimum be zero, such that all protrusions 100 may contact adjacent protrusions at some point along the longitudinal axis of the projectile. Maximum spacing 108 between protrusions 100 is dependent on the width 110 of the required protrusion so as to produce the required stress concentration. In order to leverage the radial fracturing, in embodiments all protrusions 100 should be symmetrically arrayed around the front-end 102 of the projectile. Additionally, in this exemplary embodiment, on a particular projectile all protrusions 100 should be of identical height 106, spacing 108, and width 110 at the same position along the longitudinal axis of the projectile. In accordance with aspects of the disclosure, this symmetry ensures that the naturally occurring radial fracture phenomenon, which also is a symmetric phenomenon, is maximized to enable crack growth into the target. Additionally, the symmetry retains projectile balance.

Height 106, spacing 108, and width 110 do not necessarily need to remain constant along the longitudinal axis of the projectile and, in embodiments, may be required to independently vary, for instance, to generate the required stress concentration. For example, in this exemplary embodiment, the protrusion's 100 height 106 and width 110 taper from a commencing point and increase in width and height to a wider and taller middle region and then decrease in width and height from the wider and taller middle region back to a point. Additionally, the spacing 108 between protrusions 100 increases towards the back of the projectile such that protrusion tapers into the front-end 102 of the projectile.

In accordance with additional aspects of the disclosure, the distance 112 from the front of the protrusions 100 to the front of the projectile is an additional design parameter that can be altered to generate enhanced radial cracks. In some contemplated embodiments, minimally the distance 112 may be zero, such that all protrusions begin at the tip of the projectile. Maximally the distance 112 may be at a point along the projectile where the corresponding hoop strain generated in the target is large enough to energetically allow for fractures to occur.

Given the nature of stress concentrators in fracture mechanics, there is an optimal solution of protrusion 100 geometry generated, for instance, by height 106, spacing 108, width 110, and distance 112 from the projectile tip that will allow cracks to form at minimum hoop strain. Various combinations of these geometric parameters can produce optimal solutions for generating damage. For example, variations of two parameters of the distance 112 and the height 106 between two protrusion designs, these two parameters could be varied independently such that the final stress intensity is the same between two exemplary embodiments. In practice, for example, two exemplary embodiments could have protrusions that start at different distances from the front of the projectile and be of different heights such that the stress concentration factor and therefore the terminal radial crack damage could be the same. Furthermore, as one skilled in the art understands, current manufacturing techniques may be limit the ability to construct one particular protrusion geometry. In accordance with aspects of the disclosure, an identical end result may be achieved; however, by varying geometric parameters such that the projectile is able to be manufactured. Finally, as is evident in the preceding description, not all geometric parameters for a given projectile-target interaction can be shown, and this disclosure seeks to describe the methodology for employing these protrusions 100 and related parameters to allow one skilled in the art to construct this design.

FIGS. 6A-8C depict high aspect ratio (length to diameter) projectiles, which may be representative of typically manufactured rifle projectiles or larger caliber bombs or missile warheads, with varying numbers of protrusions 200. FIGS. 6A and 6B respectively depict a perspective view and a longitudinal view from the front of a projectile 600 with four protrusions 200. More specifically, FIG. 6A is a side perspective view of an exemplary high aspect ratio projectile 600 containing four stress concentrating protrusions near the front end and FIG. 6B is a front end view of FIG. 6A in accordance with aspects of the disclosure.

FIG. 7A is a side perspective view of an exemplary high aspect ratio projectile containing five stress concentrating protrusions near the front end, FIG. 7B is a front end view of FIG. 7A, and FIG. 7C is a side perspective view of the projectile in FIG. 7A with an aerodynamic cap arranged over the protrusions in accordance with aspects of the disclosure. FIGS. 7A and 7B respectively depict a perspective view and a longitudinal view from the front of a projectile 700 with five protrusions 200. In accordance with additional aspects of the disclosure, FIG. 7C depicts the projectile 750 in FIGS. 7A and 7B but including an aerodynamic cap 220 over the protrusions 200. This cap 220 can be made from a material, such as a plastic that aids the projectile 750 during flight and be torn away on impact to allow protrusion interaction with the target.

FIG. 8A is a side perspective view of an exemplary high aspect ratio projectile containing nine stress concentrating protrusions near the front end, FIG. 8B is a front end view of FIG. 8A, and FIG. 8C is a closer view of the stress concentrating protrusions in FIG. 8A in accordance with aspects of the disclosure. FIGS. 8A and 8B depict a perspective view and a longitudinal view from the front of a projectile, respectively, of a projectile with nine protrusions 200. FIG. 8C shows a detailed perspective view of the projectile as indicated from FIG. 8A. Features of FIGS. 6A-8C are described simultaneously, with more details on protrusion characteristics emphasized in FIGS. 8A-8C. The features of the projectiles described in FIGS. 6A-8C follow the same pattern as those described in FIGS. 3A-5C, and, as such, not all features are re-described in the description that follows. The pattern of the descriptive features that follow are similar to those previously described. In FIGS. 6A-8C features are described as “2XX” which correspond to similar features described in FIGS. 3A-5C as “1XX” wherein the “XX” corresponds to similar features.

In accordance with aspects of the disclosure, all of the protrusions 200 are arranged within the front-end 202 of the projectile, in a region of the projectile where the diameter is less than the nominal caliber 204 of the projectile. In accordance with aspects of the disclosure, the protrusions 200 are arranged in the front-end 202 of the projectile as to not interfere with the travel of the projectile in the barrel of the weapon firing the projectile. The number of protrusions 200 may be varied based on the properties of the projectile and/or the intended target. The number of protrusions may be selected to enhance the radial damage to the target, whether that is based on the natural radial fragmentation or the end user's desired effect. In these exemplary embodiments, the height 206 of the protrusions is designed as to remain within the nominal caliber 204 of the projectile. As described above, the height 206, the spacing 208, and/or the width 210 may be varied based on the required dynamic fracture properties encountered as the projectile forces radial expansion within the target and the target cracks. These parameters, 2XX, follow the same limitations or restrictions as described by 1XX above.

Naturally, given the nature of stress concentrators in fracture mechanics, there is an optimal solution of protrusion 200 geometry generated by height 206, spacing 208, width 210, and distance 212 from the projectile tip that will allow cracks to form at minimum hoop strain. However, various combinations of these geometric parameters can produce optimal solutions, as described previously. Furthermore, as one skilled in the art understands, limitations may exist in current manufacturing techniques to produce specific geometry. Additionally, as in the aforementioned description, not all geometric parameters for a given projectile-target interaction can be shown, and this disclosure seeks to describe the concept for employing these protrusions 200 and related parameters to allow one skilled in the art to construct this design.

FIG. 9A is a side perspective view of an exemplary high aspect ratio, pre-impact and pre-deformation projectile containing five stress concentrating petals near the front end and FIG. 9B is a side perspective view depicting a post-impact and deformed projectile in accordance with aspects of the disclosure. FIGS. 9A and 9B depict a high aspect ratio (length to diameter) projectile 900 which incorporates stress concentrating petals in the projectile that are designed to deform. In some projectile-target interactions, it may be desirable to have a projectile 900 that deforms or expands to limit penetration into the target. In accordance with additional aspects of the disclosure, the exemplary embodiment of FIGS. 9A and 9B demonstrates that the correlation horizon phenomenon can be applied in deforming projectiles as well as the aforementioned non-deforming projectile. This exemplary embodiment depicts a scenario in which (e.g., based on experimental determination) five stress concentrators are arranged to produce enhanced radial damage in a desired target. Therefore a projectile is designed with 5 petals. FIG. 9A shows the projectile before deformation and FIG. 9B shows the projectile after deformation. All petals 230 are arranged within the front-end 222 of the projectile 900, where the diameter of the region is less than the nominal caliber 224 of the projectile 900.

As shown in FIG. 9A and between the petals 230 are weak points or cracks 220 in the projectile to allow the petals to form on impact. In accordance with aspects of the disclosure, as the petals deform and peel back towards the back of the projectile, the deformed petals function as stress concentrators, in a similar manner to the protrusions, to maximize or enhance radial damage.

FIGS. 10A-10L schematically depict various examples of stress concentrating protrusion arrangements from front end views, front perspective views, and side views in accordance with aspects of the disclosure. The exemplary embodiments of FIGS. 10A-10L are depict various, non-restrictive protrusions to convey some extent of the breadth that the ordinarily-skilled artisan may employ in providing protrusions of the present disclosure. These depictions are meant to demonstrate that protrusions as indicated in all other figures may, in practice, be designed to various end-states. These protrusions may be designed with variations of, for example, geometry, dimensions, spacing, or orientation to in accordance with embodiments of the disclosure. In accordance with aspects of the disclosure, the protrusions are used as stress concentrators to more efficiently initiate and grow radial cracks in a target material, which can be based on the naturally and energetically preferred configuration for a given projectile-target interaction. For example, the ordinarily-skilled artisan will understand that stress concentrators need not require one particular set of physical characteristics to promote enhanced crack growth. The number of protrusions shown Figures in 10A-10L are not meant to be restrictive but as an exemplary number, which can be altered as described herein for the desired projectile-target interaction.

FIGS. 10A and 10B are exemplary embodiments to demonstrate differences in contemplated protrusion size, for instance length 320 and width 310. FIG. 10C is another exemplary embodiment with protrusions of length 320 and width 310, in which the axis of symmetry 330 of the protrusion intersects the longitudinal axis 340 of the projectile. In contrast, the exemplary embodiment of FIG. 10D has protrusions with a length 320 and width 310 with a protrusion axis of symmetry that does not intersect the longitudinal axis 340 of the projectile. That is, in some contemplated embodiments, the protrusions may be offset by an angle 332. In accordance with aspects of the disclosure, the protrusion offset feature may be utilized in projectiles that rotate about the longitudinal axis 340 during flight.

FIG. 10E depicts an exemplary embodiment in which there are plural circumferential arrays of protrusions (e.g., inner/frontward array 310 and outer/rearward array 320) in the nose of the projectile. The plural circumferential arrays 310 and 320 need not necessarily be identical between arrays. Some projectile-target interactions may benefit from additional symmetric arrays of protrusions because, in accordance with aspects of the disclosure, in the dynamic process of projectile impact and radial growth of the damage, the growing cavity may energetically support additional crack growth in the given expansion scenario. Multiple arrays may also be utilized by the ordinarily-skilled artisan in the art of projectile manufacture to compensate for machining restrictions and to balance any restrictions in constructing the minimum feature size and the required number of protrusions for the given projectile-target interaction.

FIG. 10F depicts an exemplary embodiment of a different protrusion shape, with length 320 and width 310, than previously described protrusions to demonstrate the versatility of applying the concepts applied in this disclosure. As shown, in FIG. 10F, the protrusion may have a tapered shape with flat ends. FIG. 10F, thus, demonstrates the disclosure contemplates a multitude of ways to design the protrusions so that enhanced radial fracturing can still be generated in a target material.

FIGS. 10G and 10H show perspective views of cross-sections of protrusions from FIGS. 10E and 10F, respectively. As shown in FIGS. 10G and 10H, the protrusions have a height 306 and a width 310. In FIG. 10G, the cross-section of the exemplary protrusion is round, whereas in FIG. 10H, the cross-section of the exemplary protrusion is trapezoidal. A multitude of other geometries may be utilized by the ordinarily-skilled artisan and the versatility of different geometries is demonstrated by these two contrasting features.

FIGS. 10I and 10J depict front-end views of projectiles where relative protrusions (or edges) are formed by subtractive manufacturing techniques, such as by grinding or cutting flat surfaces onto the nose (instead of additive techniques which have been discussed above). The embodiments of FIGS. 10I and 10J include six relative protrusions 336 (or edges). With the embodiment of FIG. 10I, the protrusions 336 reach the tip of the projectile. With the embodiment of FIG. 10L, the protrusions 336 stop before the tip of the projectile. In embodiments, the protrusions 336 may be formed or manufactured by removing material from a larger projectile shape during the course of manufacture. These removed faces 334 may be flat, concave, or otherwise, so as to produce a stress concentrating protrusion 336 (or edges) between the faces 334. The faces 334 have length 320 and width 310, which dictate the dimensions of the relative protrusions 336 (or edges).

FIGS. 10K and 10L are side views of the projectiles in FIGS. 10I and 10J, respectively. As shown in FIGS. 10K and 10L, the faces 334 have a length 320 and a width 310 formed to produce the stress concentrating protrusions 336 (or edges).

Combinations of features depicted within the exemplary embodiments of FIGS. 10A-10L may be used as necessary to generate the desired stress concentration. There may be a requirement that the protrusion's stress concentrating factor generates a geometry such that the height of the protrusion is larger than the nominal diameter of the projectile. In this scenario a subcaliber projectile with protrusions could be used in a sabot configuration to allow the required projectile design to be fired or launched from a given system. Additionally, materials such as plastic could be fit over top of the protrusions to allow for aerodynamic modifications to the final projectile. The plastic sleeve or cap could break away at impact to expose the protrusions to the target.

FIGS. 11A-13B describe the advantages of using the embodiments of the present disclosure to enhance damage to notional targets. These figures schematically depict damage to a material from an unmodified projectile and damage to a material from a projectile with the protrusions in accordance with the embodiments of the present disclosure to exemplify the utility, advantages, and benefits of using a protrusion-modified projectile in accordance with the present disclosure. FIG. 11A is a schematically depicted side view of a projectile without stress concentrating protrusions generating damage and FIG. 11B is a schematically depicted cross-section view of the damage from a projectile without stress concentrating protrusions.

In FIGS. 11A and 11B an unmodified projectile impacts a target several times thicker than the length of the projectile. While this representative target material could be any material these to-be-explained terminal ballistic phenomena occur, FIGS. 11A and 11B will be described in the context of a soft material like tissue or a tissue simulant. Those of ordinary skill in the art will recognize features of a typical test set up to test bullets against a tissue simulant, such as ballistic gelatin.

In FIG. 11A, a bullet 402 penetrates a target 408, such as ballistic gelatin. As the bullet 402 penetrates the target a permanent channel 404 is created as the bullet 402 crushes and destroys the target material directly in its path. A radial expansion, known as the temporary cavity 406 forms behind the bullet as a result of the radial momentum transferred from the bullet 402 to the target 408. This radial expansion may stretch and crack the target 408 when the failure hoop strain is reached. Most of the extent of the temporary cavity 406 may not be observable unless captured experimentally with a high speed camera. The temporary cavity 406 eventually collapses back inwards towards the permanent channel 404 due to the remaining elasticity in the surrounding target 408. In FIG. 11B, a cross-section of the target 408 damage after the test is shown, with the permanent channel 404 and the extent of the temporary cavity 406. Radial cracks 410 may be present as a result of the large hoop strain generated in the target 408. In this exemplary embodiment (with this material) there are five radial cracks 410 formed. These five radial cracks 410, however, may not reach to the full extent of the maximum stretch of the temporary cavity 406.

FIG. 12A is a schematically depicted side view of the exemplary projectile with stress concentrating protrusions generating damage in accordance with aspects of the disclosure and FIG. 12B is a schematically depicted cross-section view of the damage from an exemplary projectile with stress concentrating protrusions in accordance with aspects of the disclosure. In FIGS. 12A and 12B, a projectile modified with protrusions 400 impacts a similar target 408 described in FIGS. 11A and 11B. In accordance with embodiments of the present disclosure, a projectile with protrusions or petals can be created with five protrusions (as exemplary embodiments described in FIG. 4, 7, or 9) as the exemplary test described in FIGS. 11A and 11B reveals that five cracks naturally form from an unmodified projectile. These five protrusions or petals amplify the natural fracture behavior of the target material and can be leveraged to create more (or enhanced) damage.

For example, in FIG. 12A, a bullet 402′ with protrusions 400 penetrates a target 408, such as ballistic gelatin. The bullet 402′ penetrates the target forming a permanent channel 404. In contrast to FIGS. 11A and 11B, with this example, the projectile (the bullet 402′) includes protrusions 400 to concentrate stress and enable radial crack growth to form earlier in the impact duration and more efficiently. As the temporary cavity 406 forms behind the bullet 402′ the material 408 has undergone additional stress concentrations as a result of the protrusions 400. As a result, the protrusions 400 generate a larger temporary cavity 412 and longer cracks 414 because a lower amount of hoop strain is required to initiate the cracks, so they form earlier in the impact duration. The radial momentum in the temporary cavity 412 continues to drive crack growth as it expands. As a result, in accordance with aspects of the present disclosure, there is a larger temporary cavity 412 from a bullet 402′ with protrusions 400 as compared to the temporary cavity 406 from a bullet without protrusions.

In FIG. 12B a cross-section of the target 408 damage after the test is shown, with the permanent channel 404 and the extent of the temporary cavity 412. The benefit of using protrusions is demonstrated in comparing FIGS. 11B and 12B. The temporary cavity 412 of FIG. 12B is larger and the radial cracks 410 are extended 414 showing more (or enhanced) damage and a more effective projectile. In accordance with aspects of the disclosure, by generating cracks earlier in the temporary cavity, the elastic recovery of the temporary cavity is diminished, increasing the amount of permanent damage to the material. As one skilled in the art will recognize, an additional feature of this protrusion-modified-projectile is that it is barrier blind and maximizes the natural radial crack formation to cause more damage. As it is barrier blind, the bullet can penetrate deeper into targets.

FIG. 13A is a perspective view of damage to an exemplary plate from an impact of a projectile without stress concentrating protrusions and FIG. 13B is a perspective view of damage to an exemplary plate from an impact of a projectile with protrusions in accordance with aspects of the disclosure. FIGS. 13A and 13B respectively show perspective views of damage from an unmodified projectile and damage from a projectile with protrusions to an exemplary target like a plate, e.g., constructed from a hard metallic material. In FIG. 13A, an unmodified projectile has perforated and damaged a metallic plate 508. The projectile has removed material in the center of plate, leaving a hole 506. Additionally, in this exemplary impact scenario, there are four petals 512 that have formed with four cracks 504 between them. In accordance with aspects of the disclosure, to increase the damage in this exemplary projectile-target interaction a projectile with four protrusions can be used, such as the exemplary embodiment in FIG. 6.

FIG. 13B depicts the exemplary damage to the same target as in FIG. 13A, using a projectile with protrusions. The same damage features are present in the plate 508: a hole 506, four petals 512, and four cracks 504. As shown in FIG. 13B, however, by utilizing the protrusion in accordance with the embodiments of the present disclosure, the damage to the material is greater and the hole 506, four petals 512, and four cracks 504 are larger than in FIG. 13A. In accordance with aspects of the disclosure, the protrusions are utilized to leverage the natural crack formation and to drive the cracks a greater distance 510 by concentrating the stress (with this exemplary embodiment) in the four areas. In practice, the embodiments of the present disclosure cause greater damage behind the plate and reduce the integrity of the overall structure, such as a vehicle or aircraft, enabling more efficient defeat by using less projectiles.

One or more embodiments of the disclosure may be referred to herein, individually and/or collectively, by the term “invention” merely for convenience and without intending to voluntarily limit the scope of this application to any particular invention or inventive concept. Moreover, although specific embodiments have been illustrated and described herein, it should be appreciated that any subsequent arrangement designed to achieve the same or similar purpose may be substituted for the specific embodiments shown. This disclosure is intended to cover any and all subsequent adaptations or variations of various embodiments. Combinations of the above embodiments, and other embodiments not specifically described herein, will be apparent to those of skill in the art upon reviewing the description.

The Abstract of the Disclosure is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In addition, in the foregoing Detailed Description of the Embodiments of the Disclosure, various features may be grouped together or described in a single embodiment for the purpose of streamlining the disclosure. This disclosure is not to be interpreted as reflecting an intention that the claimed embodiments require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter may be directed to less than all of the features of any of the disclosed embodiments. Thus, the following claims are incorporated into the Detailed Description, with each claim standing on its own as defining separately claimed subject matter.

The above disclosed subject matter is to be considered illustrative, and not restrictive, and the appended claims are intended to cover all such modifications, enhancements, and other embodiments which fall within the true spirit and scope of the present disclosure. Thus, to the maximum extent allowed by law, the scope of the present disclosure is to be determined by the broadest permissible interpretation of the following claims and their equivalents, and shall not be restricted or limited by the foregoing detailed description.

Accordingly, the novel configuration is intended to embrace all such alterations, modifications and variations that fall within the spirit and scope of the appended claims. Furthermore, to the extent that the term “includes” is used in either the detailed description or the claims, such term is intended to be inclusive in a manner similar to the term “comprising” as “comprising” is interpreted when employed as a transitional word in a claim.

While the disclosure refers to specific embodiments, those skilled in the art will understand that various changes may be made and equivalents may be substituted for elements thereof without departing from the true spirit and scope of the embodiments of the disclosure. While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the disclosure. In addition, modifications may be made without departing from the essential teachings of the disclosure. Furthermore, the features of various implementing embodiments may be combined to form further embodiments of the disclosure.