A rapid design method for aramid body armor against bullet and fragment impact

Abstract

The present invention discloses a rapid design method for aramid bullet-proof vests against impacts of bullets and fragments, comprising: designing a fitting formula for aramid ballistic performance, acquiring several groups of aramid ballistic experimental data to fit the aramid ballistic performance fitting formula; constructing a back depression calculation formula, acquiring back depression data to fit the back depression calculation formula; acquiring protection requirement information, and realizing rapid design of aramid bullet-proof vests based on the fitted aramid ballistic performance fitting formula, back depression calculation formula, and protection requirement information. The present invention establishes a method for designing the number of layers of aramid bullet-proof vests against impacts of bullets and fragments. By carrying out a small amount of ballistic experiments, the ballistic limit of any number of aramid layers and the back depression under the ballistic limit can be obtained, and the optimal design can be performed according to the required protection requirements. The calculation speed is fast and the accuracy is high, which can overcome the shortcomings of high cost and difficulty in implementation of ballistic experiments and finite element simulations of multi-layer bulletproof vests.

Description

Technical Field

[0001] The invention belongs to the field of bulletproof vest protection technology assessment, and in particular relates to a rapid design method for aramid bulletproof vests against bullet and fragment impacts. Background Art

[0002] Bulletproof vests are personal protective equipment that can protect the human body from bullets. According to the national standard GA 141-2010, bulletproof vests need to meet two requirements: one is to prevent projectile penetration; the other is that the back concavity is generally less than 25mm to prevent blunt bullet damage. The standard involves two types of projectiles, bullets and fragments, and has different protection requirements. At present, the evaluation methods for bulletproof vests are mostly carried out through ballistic experiments and finite element simulation. Among them, the ballistic experiment of multi-layer bulletproof vests is costly, the finite element simulation is difficult, and the calculation time is long, which limits the rapid design of bulletproof vests. At present, the main material of bulletproof vests is soft and light high-performance fiber. Aramid is widely used in bulletproof vests due to its high modulus, low density and high strength. It has good application prospects. It is crucial to establish a design method that can quickly and accurately predict the number of layers of aramid bulletproof vests according to bulletproof requirements. Summary of the invention

[0003] In order to solve the above technical problems, the present invention proposes a rapid design method for aramid bulletproof vests against bullet and fragment impacts to solve the above problems in the prior art.

[0004] To achieve the above object, the present invention provides a rapid design method for aramid bulletproof vests against bullet and fragment impact, comprising:

[0005] Designing a fitting formula for aramid ballistic performance, acquiring several groups of aramid ballistic experimental data to fit the fitting formula for aramid ballistic performance;

[0006] Constructing a back concavity calculation formula, acquiring back concavity data and fitting the back concavity calculation formula;

[0007] The protection requirement information is obtained, and the rapid design of aramid bulletproof vests is realized based on the fitted aramid ballistic performance fitting formula, back depression calculation formula, and protection requirement information.

[0008] Optionally, the aramid ballistic performance fitting formula is:

[0009]

[0010] Among them, V C represents the ballistic limit of the bulletproof vest, X1, X2, X3 are fitting parameters, and n is the number of aramid layers.

[0011] Optionally, the number of groups of the aramid ballistic experimental data is determined according to the number of fitting parameters.

[0012] Optionally, a protection index is determined based on the protection type of the aramid bulletproof vest, the correlation between the protection index and the deformation form of the aramid material is analyzed, the deformation process is analyzed based on the correlation to obtain back concavity related parameters, and a back concavity calculation formula under the ballistic limit is constructed.

[0013] Optionally, the back concavity calculation formula is:

[0014] h C ≈ψV C

[0015] Among them, h C is the back concavity at the ballistic limit, and ψ is the limit concavity factor.

[0016] Optionally, according to the protection requirement information, the number of layers of the aramid bulletproof vest input into the fitting formula is determined. If the output ballistic limit is higher than the ballistic limit requirement value, the back is determined to be concave, otherwise the number of layers is increased. If the back concave is lower than the back concave requirement value, the protection requirement is met, otherwise the number of layers is increased until the minimum number of layers that meet the protection requirement is reached.

[0017] Compared with the prior art, the present invention has the following advantages and technical effects:

[0018] The present invention establishes a method for designing the number of layers of aramid bulletproof vests to resist bullet and fragment impact. By carrying out a small amount of ballistic experiments, the ballistic limit of any number of aramid layers and the back concavity under the ballistic limit can be obtained, and the optimal design can be performed according to the required protection requirements. The calculation speed is fast and the accuracy is high, which can overcome the shortcomings of high cost and difficulty in implementation of ballistic experiments and finite element simulations of multi-layer bulletproof vests. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0020] Figure 1 This is a schematic diagram of the deformation of aramid fiber in the stretching stage according to an embodiment of the present invention;

[0021] Figure 2 The figure is a flow chart of a method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0022] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0023] It should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and that, although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0024] Embodiment 1

[0025] like Figure 1-2 As shown, in this embodiment, a rapid design method for aramid bulletproof vests against bullet and fragment impact is provided, which involves the number of aramid bulletproof vest layers that meet the impact of bullets and fragments, and proposes a design model that takes into account both ballistic limit and back concavity. By giving the ballistic limit of different layers of aramid under the impact of bullets and fragments and the fitting formula of back concavity at the limit speed, the minimum number of layers of bulletproof vests can be designed according to the target requirements. The bulletproof vest needs to protect against two types of projectiles at the same time, including fragments and bullets, where one indicator is satisfied for fragments: high ballistic limit; and two indicators are required to be satisfied for bullets at the same time: high ballistic limit and low back concavity.

[0026] First, three sets of aramid layer number-ballistic limit data are obtained through a small number of ballistic experiments or finite element simulations, and the fitting parameters are obtained by fitting formula (1). Then, a set of ballistic limit and back concavity data of aramid bulletproof vests with any number of layers are obtained, and the concavity factor is obtained by fitting formula (2). Formulas (1) and (2) are the ballistic performance fitting formulas of aramid bulletproof vests. According to the ballistic limit and back concavity requirements, the number of layers of aramid bulletproof vests input into the fitting formula is judged. If the output ballistic limit is higher than the target ballistic limit, the back concavity is judged, otherwise the number of layers is increased. If the back concavity is lower than the target back concavity, the protection requirement is met, otherwise the number of layers is increased. Finally, the minimum number of layers that meet the design requirements can be obtained according to the protection requirements.

[0027] The calculation of the ballistic limit of aramid bulletproof vests is carried out through the aramid ballistic performance fitting formula, which is in the form of:

[0028]

[0029] Where V C is the ballistic limit of the bulletproof vest, X1, X2, and X3 are fitting parameters, which can be obtained by fitting a small number of ballistic test results, and n is the number of aramid layers. There are three parameters that need to be fitted, so input three sets of aramid layers and the ballistic limits of fragments or bullets corresponding to the number of layers into formula (1), and the X parameter can be fitted. The ballistic limit of aramid with any number of layers can be obtained through the fitting formula. In the case of fragment impact, there is usually no requirement for back concavity. Only formula (1) can be used to obtain the minimum number of layers that meet the fragment requirements;

[0030] For the back concavity requirement after bullet impact, the following fitting formula can be used:

[0031] h C ≈ψV C (2)

[0032] Among them, h C is the back concavity under ballistic limit, ψ is the limit concavity factor, and the fitting can be performed through a set of ballistic limit and back concavity data under ballistic limit impact of a set of bulletproof vests with any number of layers. The fitting formula is derived below. This scheme establishes a theoretical model to analyze the evolution process of aramid under impact.

[0033] During the bullet impact process, aramid materials usually exhibit two deformation forms: shear punching and tensile bulge deformation, and these two deformation stages are independently decoupled. The energy loss experienced by the projectile in the shear stage is often negligible, and the deformation of the target plate is very small at this time, so it has no significant effect on the back concavity. Our consideration focuses on the tensile bulge stage, such as Figure 1 As shown:

[0034] The initial velocity of the bullet is V b In the stretching stage, the fabric deforms symmetrically with the impact direction as the axis. L The shear wave propagates along the fiber direction toward the boundary at a slower speed C T Propagation. Longitudinal waves stretch the fiber in the plane, while transverse waves cause the fiber to deform transversely, resulting in a prominent deformation cone. During the stretching process, the transverse wavefront is denoted by βr P , where β is the radius of the convex deformation, r P is the radius of the projectile. In addition, γ represents the angle of the convex cone and h is the back concavity. The yarn before and after impact and the back deformation can form a right triangle. Therefore, the back concavity h can be calculated as

[0035] h=βr P (1+ε)sinγ (3)

[0036] Where ε represents the strain of the bulge. Studies have shown that the deformation angle γ during the impact process is a constant, which is determined by the initial velocity V b and the longitudinal wave velocity C L Sure:

[0037] sinγ≈2(V b / C L ) 1 / 3 (4)

[0038] Transverse wave front βr P Equal to the shear wave velocity C T and the projectile motion time t b After the collision, βrP It can be calculated as

[0039] βr P =C T t b (5)

[0040] Studies have shown that C T It tends to a constant value during the projectile impact process and can be expressed as

[0041]

[0042] And for a projectile and a target material, the motion time t of the projectile under the limit velocity impact b is almost constant. Substituting equation (6) into equation (5) yields

[0043]

[0044] Therefore, the deformation area under the limit velocity impact is only determined by the initial velocity of the projectile. Substituting equations (7) and (4) into equation (3), h can be expressed as

[0045]

[0046] When the projectile hits the target at the critical velocity, the final strain ε of the target is constant and equal to the fracture strain ε f Therefore, under extreme speed impact, the back concavity can be expressed as:

[0047]

[0048] For a system consisting of a projectile and a target, ε f and t b It remains constant at the critical speed. Therefore, the value of the back concavity under the critical speed impact can be considered to be proportional to the critical speed of the projectile, and the corresponding coefficient is defined as the critical concavity factor ψ. The relationship between the back concavity and the critical speed is shown in the above formula (2):

[0049] After fitting formulas (1) and (2), the ballistic limit of the projectile corresponding to the number of layers of the aramid bulletproof vest and the back concavity under the ballistic limit can be obtained. According to the two fitting formulas, the number of layers of the bulletproof vest can be optimized according to the bulletproof requirements, thereby meeting the requirements of anti-penetration and anti-blunt injury concavity at the same time. Figure 1 shown.

[0050] Example 1: Designing an aramid body armor for a 1.1g simulated fragment impact

[0051] The protection requirements are shown in Table 1 below:

[0052] Table 1

[0053] Projectile Type Ballistic limit requirements Back concave requirements 1.1g simulated fragments Not less than 661m / s none

[0054] Since there is no requirement for back concavity of fragments, one set of data can be reduced. Through ballistic experiments and finite element simulation, three sets of impact data of aramid bulletproof vests are obtained as shown in Table 2 below:

[0055] Table 2

[0056]

[0057] Substituting into the fitting formula (1), the ballistic limit fitting formula is:

[0058] V C =132.5e^(0.11n 0.77 )

[0059] The fitting parameters are X1 = 132.5, X2 = 0.11, and X3 = 0.77. Substitute the target speed 661 m / s into V C It can be obtained that when n=32, the ballistic limit is higher than 661m / s, and when n=31, the ballistic limit is lower than 661m / s. Therefore, 32 layers of aramid are the minimum number of layers that meet the fragment protection requirements.

[0060] Example 2: Designing an aramid bulletproof vest for 9mm Full Metal Jacket bullet impact conditions

[0061] The protection requirements are shown in Table 3 below:

[0062] Table 3

[0063]

[0064] Since the bullet has a back concavity requirement, it is necessary to obtain four sets of impact data of aramid bulletproof vests through ballistic experiments and finite element simulation, as shown in Table 4:

[0065] Table 4

[0066]

[0067] Substituting into the fitting formulas (1) and (2), the fitting formulas for the back concavity at the ballistic limit and the limit speed are:

[0068]

[0069] The fitting parameters are X1=47.5, X2=0.14, X3=0.77, ψ=8.8×10 -5 Substitute the target speed 464m / s into V CIt can be obtained that when n=38, the ballistic limit is higher than 464m / s, and when n=37, the ballistic limit is lower than 661m / s, so 38 layers of aramid can meet the requirements of the bullet's ballistic limit. For the back concavity, substituting n=38 into the back concavity formula, the back concavity is obtained to be 40.5mm, which is less than the target requirement of 44mm, so 38 layers is the minimum number of layers to meet the protection requirements of 9mm full metal jacket bullets.

[0070] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A rapid design method for aramid bulletproof vests against bullet and fragment impact, characterized in that: The following steps are involved: Designing a fitting formula for aramid ballistic performance, acquiring several groups of aramid ballistic experimental data to fit the fitting formula for aramid ballistic performance; The aramid ballistic performance fitting formula is: Among them, V C represents the ballistic limit of the bulletproof vest, X1, X2, X3 are fitting parameters, n is the number of aramid layers, and e is a natural constant; Constructing a back concavity calculation formula, acquiring back concavity data and fitting the back concavity calculation formula; The back depression calculation formula is: Among them, h C is the back concavity at the ballistic limit, ψ is the limit concavity factor; Obtain protection requirement information, and realize rapid design of aramid bulletproof vests based on the fitted aramid ballistic performance fitting formula, back concave calculation formula, and protection requirement information; According to the protection requirement information, the number of layers of the aramid bulletproof vest input into the fitting formula is determined. If the output ballistic limit is higher than the ballistic limit requirement value, the back is determined to be concave, otherwise the number of layers is increased; if the back concave is lower than the back concave requirement value, the protection requirement is met, otherwise the number of layers is increased until the minimum number of layers that meets the protection requirements is reached.

2. The rapid design method of aramid bulletproof vest against bullet and fragment impact according to claim 1, characterized in that: The number of groups of the aramid ballistic experimental data is determined according to the number of the fitting parameters.

3. The rapid design method of aramid bulletproof vest against bullet and fragment impact according to claim 1, characterized in that: The protection index is determined based on the protection type of the aramid bulletproof vest, the correlation between the protection index and the deformation form of the aramid material is analyzed, the deformation process is analyzed based on the correlation to obtain back concavity related parameters, and a back concavity calculation formula under the ballistic limit is constructed.

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