A kind of cushion board protection evaluation method based on the velocity of projectile impact post-matter scattering

Abstract

The present application relates to a kind of based on the velocity of matter scattering after projectile impact buffer plate protection evaluation method, belong to impact protection evaluation technical field, solve the problem that existing buffer plate evaluation method does not consider the space distribution of shock wave cannot accurately evaluate the protection effect of buffer plate.The method comprises: according to the collision velocity of projectile superhigh speed normal impact buffer plate, projectile radius and material initial sound speed, the initial shock wave wave speed of the shock wave formed by any collision contact point on the projectile is obtained;Based on the initial shock wave wave speed, projectile diameter, buffer plate thickness and material initial sound speed, the shock wave Mach number and shock wave wave speed when shock wave attenuates are obtained;Based on the shock wave Mach number and shock wave wave speed when shock wave attenuates, the velocity of matter scattering of projectile edge is obtained, and then the protection effect of buffer plate is evaluated.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of impact protection evaluation, in particular to a buffer plate protection evaluation method based on the velocity of material scattering after projectile impact. BACKGROUND

[0002] With the continuous exploration of human beings to the space, the space debris generated by human beings in the universe is more and more, which makes the space environment increasingly deteriorating. Compared with micro-meteoroids, orbital debris seriously threatens the normal operation of on-orbit spacecraft. At present, most protection structures are improved based on the Whipple structure, and the basic idea is to place a thin plate as a buffer plate at a certain distance in front of the outer cabin wall of the spacecraft. When the space debris impacts the buffer plate at a high speed, the debris cloud is formed by breaking the buffer plate together. The debris cloud is fully expanded in the space behind the buffer plate, so that the debris cloud collides with the cabin wall is a large area of distributed load, which significantly reduces the damage to the spacecraft. When the buffer plate protection structure is applied to the actual situation, it is necessary to evaluate the protection effect of the buffer plate, so as to determine whether the buffer plate meets the protection requirements.

[0003] At present, when evaluating the protection effect of the buffer plate, it is usually through multiple ball projectile high-speed normal impact test of the buffer plate, which has high test cost and is greatly disturbed by external factors. In theoretical research, based on the analysis of the shock wave propagation and interaction in the formation process of the debris cloud by the high-speed normal impact of the ball projectile on the buffer plate, the motion law of the debris cloud is obtained, and then the protection effect of the buffer plate is obtained according to the motion law characteristics of the debris cloud. However, the current analysis of the formation process of the debris cloud is mainly based on the one-dimensional shock wave generated by the shock wave, without considering the spatial distribution of the shock wave, which cannot accurately describe the complete propagation process of the shock wave and the influence on the debris cloud, and thus cannot accurately evaluate the protection effect of the buffer plate. SUMMARY

[0004] In view of the above analysis, the embodiments of the present application aim to provide a buffer plate protection evaluation method based on the velocity of material scattering after projectile impact, to solve the problem that the existing buffer plate evaluation method does not consider the spatial distribution of the shock wave and cannot accurately evaluate the protection effect of the buffer plate.

[0005] In one aspect, the embodiments of the present application provide a buffer plate protection evaluation method based on the velocity of material scattering after projectile impact, which comprises:

[0006] According to the collision velocity of the projectile high-speed normal impact on the buffer plate, the projectile radius and the initial sound speed of the material, the initial shock wave speed of the shock wave formed by any collision contact point on the projectile is obtained;

[0007] Based on the initial shock wave velocity, the projectile diameter, the buffer plate thickness and the initial sound velocity of the material, the shock wave Mach number and the shock wave velocity when the shock wave attenuates are obtained;

[0008] Based on the shock wave Mach number and the shock wave velocity when the shock wave attenuates, the projectile edge material ejection velocity is obtained, and the protection effect of the buffer plate is evaluated.

[0009] Further, the initial collision point on the projectile is taken as the origin, the direction of the initial collision point pointing to the projectile sphere center is taken as the direction of the z-axis, and the direction perpendicular to the z-axis is taken as the r-axis direction, a coordinate system moving with the projectile is established, and the initial shock wave velocity s0(τ) formed by any collision contact point (z e , r e ) in the projectile is obtained through the following steps:

[0010] The post-shock wave velocity increment U(τ) formed by any collision contact point is obtained according to the following equation group:

[0011]

[0012] In the formula,

[0013]

[0014] Wherein, V0 is the collision speed of the projectile when the projectile hits the buffer plate at a high speed, R is the radius of the projectile, c0 is the initial sound velocity of the material, α is the included angle between the tangent of the projectile at the position of the collision contact point and the interface of the buffer plate, τ is the time interval from the initial collision point to the collision contact point; θ P and θ T are the rotation angles of the projectile and the buffer plate after the shock wave, respectively; λ is the linear relationship coefficient of the shock wave velocity and the micro-cluster velocity of the material;

[0015] When the two solutions of the above equation group are not equal, the solution with the smaller value is taken as the post-shock wave velocity increment U(τ);

[0016] When the two solutions of the above equation group are equal, one solution is taken as the post-shock wave velocity increment U(τ), and at the same time, the shock wave generation is completed, and the time interval τ is taken as the end time t1;

[0017] Based on the post-shock wave velocity increment U(τ), the initial shock wave velocity s0(τ) formed by any collision contact point in the projectile is calculated through the following formula:

[0018] s0(τ)=c0+λU(τ).

[0019] Further, based on the initial shock wave velocity, the projectile diameter, the buffer plate thickness and the initial sound velocity of the material, the shock wave Mach number and the shock wave velocity when the shock wave attenuates are obtained, specifically including:

[0020] a critical ratio is calculated based on an initial shock wave speed at the initial impact point and an initial sound speed of the material;

[0021] When the ratio of the thickness of the buffer plate to the diameter of the projectile is greater than or equal to the critical ratio, the shock wave Mach number at the time when the shock wave attenuation occurs is obtained according to the shock wave Mach number and the position on the shock wave at the time when the shock wave generation ends, and then the shock wave speed at the time when the shock wave attenuation occurs is obtained.

[0022] When the ratio of the thickness of the buffer plate to the diameter of the projectile is less than the critical ratio, the shock wave speed at the time when the shock wave attenuation occurs is obtained according to the time when the shock wave propagates to the back surface of the buffer plate, the position and time when the rarefaction wave front catches up with the shock wave, and then the shock wave Mach number at the time when the shock wave attenuation occurs is obtained; wherein the rarefaction wave is obtained by reflecting the shock wave by the buffer plate.

[0023] Further, the critical ratio ξ c is expressed as:

[0024]

[0025] In the formula,

[0026]

[0027]

[0028] Wherein, c represents the shock wave speed, and γ represents the state parameter.

[0029] Further, when the ratio of the thickness of the buffer plate h to the diameter of the projectile D is greater than or equal to the critical ratio ξ c , the shock wave Mach number M s at any point (z, r) on the shock wave front at the time when the shock wave attenuates is expressed as:

[0030]

[0031] In the formula, M s1 represents the shock wave Mach number of the corresponding point on the shock wave front at t1, r1(τ, t1) represents the r-axis coordinate of the corresponding point on the shock wave at t1; l represents the distance between the corresponding point (z1, r1) on the shock wave front at t1 and the current point (z, r); A1 represents the shock wave area at t1; K represents a correlation coefficient.

[0032] The shock wave speed at the time when the shock wave attenuates is expressed as:

[0033] s=c0M s .

[0034] Further, the correlation coefficient K is determined according to the following formula: K, I and A1:

[0035]

[0036]

[0037]

[0038]

[0039] wherein,

[0040]

[0041]

[0042]

[0043] wherein, s1(τ, t1) represents the shock wave velocity at the corresponding point on the shock wave front at t1, I wl (τ, t1) represents the subwave trajectory at the corresponding point on the shock wave front at t1; k a represents the linear attenuation coefficient of the shock wave in the material.

[0044] Further, when the ratio of the thickness h of the buffer plate to the diameter D of the projectile is less than the critical ratio ξ c , the shock wave velocity at any point (z, r) on the shock wave front during the shock wave attenuation is represented as:

[0045]

[0046] wherein,

[0047]

[0048]

[0049] wherein, t h is the time when the shock wave propagates to the back surface of the buffer plate; z r and t r respectively represent the z-axis position and time when the head of the rarefaction wave catches up with the shock wave;

[0050] The Mach number of the shock wave during the shock wave attenuation is represented as:

[0051]

[0052] Further, a wave coordinate system is established with the shock wave moving to the edge point P(z, r) of the projectile as the origin, the x-axis being tangent to the projectile and pointing to the direction of the shock wave movement, and the y-axis being directed to the center of the sphere, and the material ejection velocity is expressed as:

[0053]

[0054] wherein, is a translation velocity vector of the coordinate system in which the projectile edge point P(z, r) is located, is a material ejection velocity vector of the projectile edge point P(z, r).

[0055] Further, is expressed according to the following formula:

[0056]

[0057] wherein q0 represents a translation velocity value of the coordinate system in which the projectile edge point P(z, r) is located; and β represents an acute angle between the translation velocity direction of the coordinate system in which the projectile edge point P(z, r) is located and the r axis.

[0058] Further, is determined according to the following formula:

[0059]

[0060]

[0061] wherein,

[0062]

[0063]

[0064]

[0065] wherein c f represents a sound speed of the ejection material, q f represents a material ejection velocity value of the projectile edge point P(z, r), ω represents an acute angle between the material ejection velocity direction of the projectile edge point P(z, r) and the z axis, q and θ represent a post-wave material micro-cluster velocity and a post-wave material rotation angle in a wave-following coordinate system when the shock wave moves to the projectile edge point P(z, r); p represents a post-wave pressure, and ρ represents a post-wave density

[0066] Compared with the prior art, the present application can achieve at least one of the following beneficial effects:

[0067] The application provides a buffer plate protection evaluation method based on the material scattering speed after projectile impact, the initial shock wave wave speed of the shock wave formed at any collision contact point on the projectile is based, the shock wave Mach number and the shock wave wave speed during shock wave attenuation are calculated according to the shock wave attenuation conditions, and then the projectile edge material scattering speed is obtained, the influence factors of the shock wave change with time and space distribution are fully considered, and the complete propagation process of the shock wave and the motion law of the projectile edge material are more accurately described. Meanwhile, the protection effect of the buffer plate is evaluated according to the obtained projectile edge scattering speed, and the accuracy of the evaluation effect is improved.

[0068] In the application, the above technical solutions can be combined with each other to realize more preferred combination solutions. Other features and advantages of the application will be described in the subsequent description, and some advantages will become apparent from the description or can be understood by implementing the application. The purposes and other advantages of the application can be realized and obtained from the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0069] The accompanying drawings are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and serve to explain the principles of the application.

[0070] Figure 1 A flow chart of the buffer plate protection evaluation method based on the material scattering speed after projectile impact in the embodiment of the application is shown in the figure.

[0071] Figure 2 A schematic diagram of the shock wave formed by the projectile impacting the buffer plate in the embodiment of the application is shown in the figure.

[0072] Figure 3 A schematic diagram of the shock wave ray in the projectile in the embodiment of the application is shown in the figure.

[0073] Figure 4 A shock wave wave system diagram of the rarefaction wave chasing and unloading the shock wave in the projectile in the embodiment of the application is shown in the figure.

[0074] Figure 5 A schematic diagram of the projectile edge material scattering speed in the embodiment of the application is shown in the figure. DETAILED DESCRIPTION

[0075] The preferred embodiments of the application are specifically described below in combination with the drawings, wherein the drawings constitute a part of this application and are used to illustrate the principles of the embodiments of the application and are not used to limit the scope of the application.

[0076] One specific embodiment of the application discloses a buffer plate protection evaluation method based on the material scattering speed after projectile impact, a flow chart is shown in the figure, the method comprises: Figure 1 ​

[0077] S1, obtaining initial shock wave velocity of shock wave formed by any collision contact point on the projectile based on collision velocity of the projectile super-high-speed normal impact on the buffer plate, projectile radius and initial sound velocity of the material; specifically, the materials of the projectile and the buffer plate are both aluminum alloy materials.

[0078] S2, obtaining shock wave Mach number and shock wave velocity during shock wave attenuation based on the initial shock wave velocity, projectile diameter, buffer plate thickness and initial sound velocity of the material.

[0079] S3, obtaining projectile edge material scattering velocity based on the shock wave Mach number and shock wave velocity during shock wave attenuation, and further evaluating the protection effect of the buffer plate.

[0080] The following will be combined with the process of projectile super-high-speed normal impact on the buffer plate to make the following detailed description of the projectile edge material scattering velocity obtained in this embodiment after the projectile impact:

[0081] First stage: projectile super-high-speed normal impact on the buffer plate to form a shock wave

[0082] The calculation of step S1 is performed in this stage to obtain the initial shock wave velocity of the shock wave formed by any collision contact point on the projectile.

[0083] The super-high-speed normal impact of the spherical projectile on the buffer plate will produce two-dimensional curved shock waves propagating in the projectile and the buffer plate medium respectively, and the motion and intensity of the two-dimensional shock wave have non-uniform spatial distribution, so that the motion state of the shock wave changes and is no longer uniform constant motion. The shock wave in this embodiment refers to the two-dimensional shock wave considering the spatial distribution, and the schematic diagram of the shock wave formation stage is shown in Figure 2 The shock wave wave surface in the projectile and the buffer plate is the envelope line of the circular wavelet family generated by the collision contact point, as shown in S P and S T , and the specific construction process is as follows:

[0084] Taking the initial collision point on the projectile as the origin and the direction of the initial collision point pointing to the center of the projectile as the direction of z-axis and the direction perpendicular to z-axis as the direction of r-axis, a coordinate system moving with the projectile is established, and the wavelet family at time t is represented by a plane curve family S wl .

[0085]

[0086] Wherein, (z e , r e ) represents the coordinates of the collision contact point; l wl (τ,t) represents the wavelet trajectory, which is a function of time t and the time interval τ of the initial collision point moving to the collision contact point (z e , r e ).

[0087] Collision contact point (z) e r e The coordinate expression for ) is as follows:

[0088]

[0089] In the formula, V0 is the collision velocity of the projectile's hypersonic impact with the buffer plate, and R is the radius of the projectile.

[0090] From the collision contact point (z) e r e The expression for the shock wave velocity s1(τ,t) is as follows:

[0091]

[0092] In the formula, s0(τ) represents the point of impact (z) in the projectile. e r e The initial shock wave velocity of the shock wave is c0, where c0 is the initial sound velocity of the material; k is the initial shock wave velocity of the shock wave. a This represents the linear attenuation coefficient of the shock wave in the material; specifically, k a The variation law of shock wave velocity can be obtained through simulation software AUTODYN. In this embodiment, aluminum alloy material is used, k a Take 0.344.

[0093] The wavelet trajectory is the integral of the corresponding shock wave velocity, obtained according to the following formula:

[0094]

[0095] Specifically, the collision contact point (z) in the projectile is determined through the following steps. e r e The initial shock wave velocity s0(τ) of the shock wave formation is:

[0096] Based on the conservation relations and the material state equations on the shock wave front, the relationship between the rotation angle of the micro-particles of material after the shock wave and the velocity increment U(τ) after the wave is obtained in the projectile and the buffer plate. U(τ) is then calculated using the following set of equations:

[0097]

[0098] In the formula, α is the angle between the tangent of the projectile at the point of impact and the interface of the buffer plate; θ P and θ T λ represents the rotation angle of the material particles after the shock wave from the projectile and the buffer plate, respectively; λ is the linear relationship coefficient between the shock wave velocity and the velocity of the material particles. Specifically, in this embodiment, the material is aluminum alloy, and λ is taken as 1.33.

[0099] When the two solutions of the above equation group (4) are equal, take one solution as the wave speed increment U(τ) after the wave, at the same time, the shock wave generation ends, and take the time interval τ as the end time t1, that is, take the time interval τ from the initial collision contact point to the collision contact point at this time as the end time t1 of the first stage, τ is in the range of 0≤τ≤t1.

[0100] When the two solutions of the above equation group (4) are not equal, take the solution with smaller value as the wave speed increment U(τ) after the wave.

[0101] It should be noted that the equation group (4) is solved for any determined τ value, and each time the solution is taken, the solution with smaller value is compared and taken out, and the numerical solution is obtained according to the specific problem.

[0102] Then, according to the equal velocity on the collision interface and the wave speed increment U(τ) after the wave, the initial shock wave speed s0(τ) of any collision contact point (z e , r e ) in the projectile is calculated by the following formula:

[0103] s0(τ)=c0+λU(τ) (5)

[0104] Thus, the sub-wave family formed by different time intervals τ corresponding to different collision positions is obtained, and the envelope of the sub-wave family is the shock wave front.

[0105] The expression of the shock wave front in the projectile is as follows:

[0106]

[0107] In the formula,

[0108] The expression of the shock wave front in the buffer plate is as follows:

[0109]

[0110] Thus, the shock wave waveform formed by the super-high-speed normal impact of the projectile on the buffer plate is obtained, wherein different time interval τ values correspond to positions (z, r) on the shock wave front at t time.

[0111] The shock wave speed s1(τ, t) of any point (z, r) on the shock wave front is obtained from formula (2), and thus the shock wave pressure, i.e. the shock wave intensity, at this position is obtained:

[0112]

[0113] In the formula, γ represents the state parameter, and the expression is as follows:

[0114]

[0115] Second stage: Shock wave intensity attenuation in the projectile

[0116] In this second stage, the above step S2 is performed to obtain the shock wave Mach number and the shock wave speed at the time of shock wave attenuation.

[0117] During the propagation of the shock wave in the projectile, one case is that the shock wave front expands due to the increase in the cross-sectional area of the projectile, thereby causing the shock wave intensity to attenuate; another case is that the rarefaction wave reflected by the buffer plate chases and unloads the shock wave in the projectile, thereby causing the shock wave intensity to attenuate. According to the attenuation mechanism of the shock wave under different conditions, the shock wave Mach number and the shock wave speed at the time of shock wave attenuation are obtained, which are as follows:

[0118] Based on the initial shock wave speed at the initial impact point and the initial sound speed of the material, a critical ratio is calculated.

[0119] When the ratio of the buffer plate thickness to the projectile diameter is greater than or equal to the critical ratio, the shock wave front expands due to the increase in the cross-sectional area of the projectile, thereby causing the shock wave intensity to attenuate. At this time, according to the shock wave Mach number and the position on the shock wave at the time when the generation of the shock wave ends, the shock wave Mach number at the time of shock wave attenuation is obtained, and then the shock wave speed at the time of shock wave attenuation is obtained.

[0120] When the ratio of the buffer plate thickness to the projectile diameter is less than the critical ratio, the rarefaction wave reflected by the buffer plate chases and unloads the shock wave in the projectile, thereby causing the shock wave intensity to attenuate. At this time, according to the time when the shock wave propagates to the back surface of the buffer plate, the position and time when the wave front of the rarefaction wave chases the shock wave, the shock wave speed at the time of shock wave attenuation is obtained, and then the shock wave Mach number at the time of shock wave attenuation is obtained; wherein the rarefaction wave is obtained due to the reflection of the shock wave by the buffer plate.

[0121] Specifically, it is assumed that the shock wave moves at a uniform speed s0(0) during the process of the projectile colliding with the buffer plate, and the wave front of the rarefaction wave chases at the sound speed c behind the shock wave. The minimum ratio at which the rarefaction wave cannot catch up with the shock wave is taken as the critical ratio ξ c , which is expressed as follows:

[0122]

[0123] In the formula, c represents the sound speed behind the shock wave, and the expression is as follows:

[0124]

[0125] In the formula, s0(0) represents the initial shock wave speed of the shock wave formed at the initial impact point.

[0126] Specifically, when the ratio of the buffer plate thickness h to the projectile diameter D is greater than or equal to the critical ratio ξ cAt that time, according to existing shock wave dynamics, a point (z, r) on the shock wave front moves along the shock wave ray, and the shock wave ray is the integral curve of the shock wave velocity, as shown in the figure. Figure 3 As shown in the figure, directed line segments P1A, P1B, and P1C represent the shock wave rays in the projectile. Setting the curvature of the shock wave rays to 0, based on the shock wave dynamics equations, we obtain the relationship between the shock wave Mach number M and the curves. s The equation is as follows:

[0127]

[0128] From formula (12), the shock wave Mach number M at any point (z, r) on the shock wave front surface during shock wave attenuation can be obtained. s The expression is as follows:

[0129]

[0130] In the formula, Let r1(τ,t1) represent the shock wave Mach number at the corresponding point on the shock wave front at time t1, r1(τ,t1) represent the r-axis coordinate of the corresponding point on the shock wave front at time t1, l represent the distance between the corresponding point (z1, r1) on the shock wave front at time t1 and the current point (z, r), A1 represent the shock wave area at time t1, and K represent the correlation coefficient. It should be noted that the corresponding point on the shock wave front refers to the point on the shock wave front at time t1 corresponding to any point (z, r) during shock wave attenuation.

[0131] Based on formula (13), the shock wave velocity at any point (z, r) on the shock wave front surface during shock wave attenuation is expressed as:

[0132] s = c0M s (14)

[0133] More specifically, the expression for K is as follows:

[0134]

[0135] More specifically, based on formula (2), the shock wave velocity s1(τ,t1) at the corresponding point on the shock wave front at time t1 is obtained, and the expression is as follows:

[0136]

[0137] Furthermore, the shock wave Mach number at the corresponding point on the shock wave front at time t1 is obtained. The expression is as follows:

[0138]

[0139] More specifically, the subwave locus l of the corresponding point on the shock wave front at time t1 is obtained based on formula (3) wl (τ, t1), and the expression is as follows:

[0140]

[0141] Further, the coordinates of the corresponding point (z1, r1) on the shock wave front at time t1 are obtained based on formula (6), and the expression is as follows:

[0142]

[0143] Further, the distance l between the corresponding point (z1, r1) on the shock wave front at time t1 and the current point (z, r) is obtained according to formula (19), and the expression is as follows:

[0144]

[0145] More specifically, based on formula (19), the shock wave area A1 at time t1 is obtained by rotary area integration, and the expression is as follows:

[0146]

[0147] Specifically, when the ratio of the thickness h of the buffer plate to the diameter D of the projectile is less than the critical ratio ξ c , as shown in Figure 4 , the time t h at which the shock wave propagates to the back surface of the buffer plate is:

[0148]

[0149] The z-axis position z r and the time t r at which the rarefaction wave front catches up with the shock wave are:

[0150]

[0151] Based on (22) and (23), the shock wave speed of any point (z, r) on the shock wave front during the shock wave attenuation is represented as:

[0152]

[0153] Based on formula (24), the shock wave Mach number M s of any point (z, r) on the shock wave front during the shock wave attenuation is represented as:

[0154]

[0155] Third stage: Ejection of projectile edge material

[0156] The step S3 is performed in this stage to obtain the projectile edge material scattering velocity, and then the protective effect of the buffer plate is evaluated.

[0157] When the point on the shock wave front moves to the projectile edge, as Figure 3 point A, B, and C, the position of the shock wave interacts with the free surface, and the reflected sparse wave is formed. The projectile edge material is first compressed by the shock wave to obtain a certain speed, and then the reflection of the sparse wave makes the material group scattered. The projectile edge material scattering velocity is calculated, and the specific process is as follows:

[0158] The wave coordinate system is established with the point P(z, r) where the shock wave moves to the projectile edge as the origin, the x-axis is tangent to the projectile and points to the direction of the shock wave movement, and the y-axis points to the center of the sphere. The schematic diagram is shown in Figure 5 The projectile edge material scattering velocity is expressed as:

[0159]

[0160] wherein, is the translation velocity vector of the wave coordinate system in which the projectile edge point P(z, r) is located, is the material scattering velocity vector of the projectile edge point P(z, r).

[0161] Specifically, the translation velocity vector of the coordinate system in which the projectile edge point P(z, r) is located is expressed as:

[0162]

[0163] wherein, q0 represents the translation velocity value of the wave coordinate system in which the projectile edge point P(z, r) is located; β represents the acute angle between the translation velocity direction of the wave coordinate system in which the projectile edge point P(z, r) is located and the r-axis.

[0164] Based on the formula (14) or (24), the shock wave velocity s when the shock wave moves to the projectile edge position P(z, r) is obtained, and then the wave-after material group velocity and the wave-after material turning angle q and θ in the wave coordinate system when the shock wave moves to the projectile edge point P(z, r) are obtained, and the expressions are as follows:

[0165]

[0166] Based on the formula (13) or (25), the shock wave Mach number M s when the shock wave moves to the projectile edge position P(z, r) is obtained, and then the wave-after pressure p and the wave-after density ρ are obtained, and the expressions are as follows:

[0167]

[0168] Further, the material scattering speed c of the projectile is obtained f The expression is as follows:

[0169]

[0170] The material scattering speed q of the projectile edge point P(z, r) in the wave coordinate system is obtained from the Bernoulli equation f The expression is as follows:

[0171]

[0172] The acute angle ω between the material scattering speed direction of the projectile edge point P(z, r) and the z-axis is obtained based on the formulas (27) and (28), and the expression is as follows:

[0173]

[0174] In implementation, the protection effect of the buffer plate is evaluated based on the obtained material scattering speed of the projectile edge. It should be noted that the material scattering speed value of the projectile edge after the projectile hits the buffer plate can reflect the motion law of the debris cloud, the greater the material scattering speed value of the projectile edge after the projectile hits the buffer plate, the greater the speed of the debris cloud, the more sufficient the material fragmentation after the projectile collides with the buffer plate, and the better the protection effect of the buffer plate.

[0175] Specifically, a scattering speed threshold and a proportion threshold are set, when the proportion of the material scattering speed value of the projectile edge that is greater than the scattering speed threshold is greater than the proportion threshold, the speed of the debris cloud formed is greater, the material fragmentation after the projectile collides with the buffer plate is sufficient, the protection effect of the buffer plate is better, and the protection requirement is met; wherein the scattering speed threshold and the proportion threshold are set according to actual requirements.

[0176] Compared with the prior art, the buffer plate protection evaluation method based on the material scattering speed after the projectile hits provided by the present application is based on the initial shock wave speed of the shock wave formed by any collision contact point on the projectile, and the shock wave Mach number and the shock wave speed during shock wave attenuation are calculated according to the attenuation of the two shock waves, and then the material scattering speed of the projectile edge is obtained, which fully considers the influencing factors of the change of the shock wave with time and the spatial distribution, and more accurately describes the complete propagation process of the shock wave and the motion law of the material of the projectile edge. At the same time, the protection effect of the buffer plate is evaluated according to the obtained material scattering speed of the projectile edge, which improves the accuracy of the evaluation effect, provides a reference for engineering design, and has obvious practical value.

[0177] Those skilled in the art can understand that all or part of the processes of the above-mentioned embodiment methods can be completed by instructing the relevant hardware by a computer program, and the program can be stored in a computer readable storage medium. The computer readable storage medium is a disk, an optical disk, a read-only memory, a random access memory, etc.

[0178] The above description is merely preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical scope disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A method for evaluating the protection of a buffer plate based on the velocity of material dispersion after projectile impact, characterized in that, The method includes: Based on the collision velocity of the projectile's hypersonic impact with the buffer plate, the projectile's radius, and the material's initial sound velocity, the initial shock wave velocity of the shock wave formed at any point of impact on the projectile is obtained. Based on the initial shock wave velocity, projectile diameter, buffer plate thickness, and initial sound velocity of the material, the shock wave Mach number and shock wave velocity during shock wave attenuation are obtained. Based on the shock wave Mach number and shock wave velocity during shock wave attenuation, the velocity of material scattering at the edge of the projectile is obtained, thereby evaluating the protective effect of the buffer plate. Using the initial collision point on the projectile as the origin, the direction pointing from the initial collision point to the center of the projectile as the z-axis, and the direction perpendicular to the z-axis as the r-axis, a coordinate system is established that translates with the projectile. The following steps are used to obtain the coordinates of any collision point (z) on the projectile. e r e The initial shock wave velocity s0(τ) that forms the shock wave: The velocity increment U(τ) behind the shock wave formed at any collision contact point can be obtained using the following system of equations: In the formula, Where V0 is the impact velocity of the projectile's hypersonic direct impact with the buffer plate, R is the projectile radius, c0 is the initial sound velocity of the material, α is the interface angle between the projectile tangent and the buffer plate at the impact contact point, and τ is the time interval from the initial impact point to the impact contact point; θ P and θ T λ represents the rotation angle of the material particle after the shock wave from the projectile and the buffer plate, respectively; λ is the linear relationship coefficient between the shock wave velocity and the velocity of the material particle. When the two solutions to the above system of equations are not equal, the solution with the smaller value is taken as the wave back velocity increment U(τ); When the two solutions of the above system of equations are equal, one solution is taken as the wave back velocity increment U(τ). At the same time, the generation of the shock wave ends, and the time interval τ is taken as the end time t1. Based on the waveback velocity increment U(τ), the initial shock wave velocity s0(τ) of the shock wave formed at any collision contact point in the projectile is calculated using the following formula: s0(τ)=c0+λU(τ); Based on the initial shock wave velocity, projectile diameter, buffer plate thickness, and initial sound velocity of the material, the shock wave Mach number and shock wave velocity during shock wave attenuation are obtained, specifically including: The critical ratio is calculated based on the initial shock wave velocity and the initial sound velocity of the material at the initial collision point. When the ratio of the thickness of the buffer plate to the diameter of the projectile is greater than or equal to the critical ratio, the shock wave Mach number at the time of shock wave attenuation is obtained based on the shock wave Mach number and position on the shock wave at the end of the shock wave generation, and then the shock wave velocity at the time of shock wave attenuation is obtained. When the ratio of the thickness of the buffer plate to the diameter of the projectile is less than the critical ratio, the shock wave velocity at the time of shock wave attenuation is obtained based on the time when the shock wave propagates to the back surface of the buffer plate and the position and time when the rarefaction wave front catches up with the shock wave, and then the shock wave Mach number at the time of shock wave attenuation is obtained; wherein, the rarefaction wave is obtained by the buffer plate reflecting the shock wave. The critical ratio ξ c Represented as: In the formula, Where c represents the sound velocity behind the shock wave, and γ represents the state parameter; A wave-following coordinate system is established with the point P(z,r) at the edge of the projectile as the origin. The x-axis is tangent to the projectile and points in the direction of the shock wave, and the y-axis points towards the center of the projectile. The velocity of the material scattering at the edge of the projectile is... Represented as: in, Let P(z,r) represent the translational velocity vector of the coordinate system containing the edge point P(z,r) of the projectile. Let P(z,r) be the velocity vector of the material scattered at the edge point P(z,r) of the projectile; According to the following formula Where q0 represents the translational velocity of the coordinate system containing the projectile edge point P(z,r); β represents the acute angle between the direction of the translational velocity of the coordinate system containing the projectile edge point P(z,r) and the r-axis; and s represents the shock wave velocity during shock wave attenuation. Determined according to the following formula In the formula, Among them, c f q represents the speed of sound of the scattered material. f Let ω represent the velocity of the material dispersion at point P(z,r) on the projectile's edge; let ω represent the acute angle between the direction of the material dispersion velocity at point P(z,r) and the z-axis; let q and θ represent the velocity and rotation angle of the material cluster behind the wave in the wave-following coordinate system when the shock wave reaches point P(z,r) on the projectile's edge; let p represent the pressure behind the wave; let ρ represent the density behind the wave; and let M represent the velocity and rotation angle of the material cluster behind the wave. s The Mach number of the shock wave at the edge point P(z,r) of the projectile is represented.

2. The buffer plate protection assessment method based on the dispersion velocity of material after projectile impact as described in claim 1, characterized in that, When the ratio of the buffer plate thickness h to the projectile diameter D is greater than or equal to the critical ratio ξ c When the shock wave decays, the shock wave Mach number M at any point (z, r) on the shock wave front surface is... s Represented as: In the formula, The value represents the shock wave Mach number at the corresponding point on the shock wave front at time t1; r1(τ,t1) represents the r-axis coordinate of the corresponding point on the shock wave at time t1; l represents the distance between the corresponding point (z1, r1) on the shock wave front at time t1 and the current point (z, r); A1 represents the shock wave area at time t1; and K represents the correlation coefficient. The shock wave velocity during shock wave attenuation is expressed as follows: s=c0M s 。 3. The buffer plate protection assessment method based on the dispersion velocity of material after projectile impact as described in claim 2, characterized in that, Determined according to the following formula K, l, and A1: In the formula, Where s1(τ,t1) represents the shock wave velocity at the corresponding point on the shock wave front at time t1, l wl (τ,t1) represents the wavelet trajectory at the corresponding point on the shock wave front at time t1; k a This represents the linear attenuation coefficient of the shock wave in the material.

4. The buffer plate protection assessment method based on the dispersion velocity of material after projectile impact as described in claim 1, characterized in that, When the ratio of the buffer plate thickness h to the projectile diameter D is less than the critical ratio ξ c When the shock wave attenuates, the shock wave velocity at any point (z, r) on the shock wave front is expressed as: In the formula, Among them, t h The moment when the shock wave reaches the back surface of the buffer plate; z r and t r These represent the z-axis position and time at which the rarefaction wavefront catches up with the shock wave, respectively. The shock wave Mach number during attenuation is expressed as:

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