A numerical evaluation method for the safety of near-field sympathetic detonation of anti-explosive ammunition

Abstract

This invention provides a numerical assessment method for the safety of near-field sympathetic detonation of anti-explosive ammunition, including: S1, constructing a numerical model for the sympathetic detonation of anti-explosive ammunition; S2, accurately characterizing the coupled power field of the near-field explosion shock wave and fragment cluster; and S3, assessing the sympathetic detonation response characteristics and ammunition safety. This method accurately characterizes the pressure impulse attenuation pattern of the explosion shock wave and the velocity and mass distribution characteristics of the fragment cluster within the near-field sympathetic detonation range. Using the charge reaction intensity, it can quantitatively assess the ammunition safety level under the influence of typical sympathetic detonation stimuli.

Description

Technical Field

[0001] The invention belongs to the field of ammunition safety assessment, and in particular relates to a numerical assessment method for the near-field sympathetic detonation safety of anti-explosive ammunition. Background Art

[0002] Throughout their lifecycles, weapons and ammunition—including storage, transportation, and service—may be exposed to unexpected stimuli, such as drops, bullet and fragment impacts, fire, and jet penetration, potentially triggering explosions. The resulting high-pressure detonation products, high-temperature flames, and high-velocity fragment swarms can easily cause adjacent ammunition to detonate, triggering chain detonations and posing a serious threat to weapon platform safety. Due to the high risk and cost of near-field detonation experiments, limited data, such as pressure histories at typical locations, witness targets, and damage to the shell, are available. This makes it difficult to quantitatively and accurately assess the safety of near-field detonation of ammunition. Numerical calculation methods, based on modeling real detonation experiments, can capture information such as the global explosion shock wave attenuation, shell fracture and fragment swarm dispersion characteristics, and the reaction evolution of the propellant. These methods are crucial for analyzing and assessing the safety of ammunition detonation.

[0003] Currently, Kim, Milers, and others have used numerical analysis methods to characterize the near-field sympathetic detonation process of anti-explosive munitions. By recovering fragments and measuring pressure data from sympathetic detonation experiments to calibrate numerical models, they concluded that the sympathetic detonation of the explosive charge is caused by the impact of a cluster of fragments and detonation products. A domestic invention patent, CN112380739A, proposes a simulation and evaluation method for the impact detonation of a solid rocket motor using an externally applied shock pressure load. This method applies equivalent load treatment to the fragments and the blast shock wave pressure, and determines the influence of load pressure and action time on the impact detonation of the explosive charge. This numerical evaluation method can determine the reaction characteristics and detonation patterns of the explosive charge in sympathetic detonation experiments, but it has not yet accurately characterized the coupled power field of the sympathetic detonation stimulus, making it difficult to quantitatively assess the safety level of the munition.

[0004] During the near-field sympathetic detonation of anti-explosive ammunition, the pressure of the explosion shock wave of the main ammunition can reach the GPa level. The shell is driven by the explosion to form a high-speed dense fragment group, and the shell speed can reach 1 to 2 km / s. Due to the coupling effect of the near-field explosion shock wave and the fragment group, the fired ammunition is prone to sympathetic detonation reaction.

[0005] Publication No. CN108733925A proposes a numerical simulation-based method for evaluating the destructive power of natural fragmentation grenades. While this method can be used to describe the characteristics of mid- and long-range detonation power fields, the semi-empirical formula employed makes it difficult to accurately describe the attenuation of near-field explosion shock waves, and the velocity and mass distribution of the fragment cluster are not further discussed. Patent No. CN112380739A proposes a simulation method for evaluating the impact detonation of a solid motor with an externally applied shock pressure load. This method can be used to rapidly predict the critical detonation pressure of the charge, but it does not quantitatively assess the munition's reaction intensity or the stimulus-element response characteristics. Summary of the Invention

[0006] To address the shortcomings of existing ammunition near-field detonation power field characterization and sympathetic detonation safety assessment technologies, this paper proposes a numerical assessment method for the near-field sympathetic detonation safety of anti-explosive ammunition. This method can be used to accurately characterize the near-field coupled power field of anti-explosive ammunition and quantitatively assess the sympathetic detonation safety level of ammunition at different spacings.

[0007] The specific technical solutions are:

[0008] A numerical evaluation method for the safety of near-field sympathetic detonation of anti-explosive ammunition can accurately characterize the attenuation law of the explosion shock wave pressure impulse and the velocity and mass distribution characteristics of the fragment group within the near-field sympathetic detonation range, thereby quantitatively evaluating the safety level of the ammunition under the influence of sympathetic detonation stimuli.

[0009] include:

[0010] S1. Construction of numerical model for secondary explosion of explosive-killing ammunition;

[0011] S2. Accurate characterization of the coupling power field between the near-field explosion shock wave and the fragment group;

[0012] S3. Sympathetic detonation response characteristics and ammunition safety assessment.

[0013] The numerical model of the secondary detonation of the killing ammunition described in S1 includes three parts: the main ammunition, the passive ammunition and the witness target.

[0014] The Johnson-Cook constitutive model and Grüneisen equation of state are used to describe the dynamic response mechanism of metal under high pressure for ammunition casing and witness target materials. The cumulative plastic damage model that takes into account flow stress softening and the random weakening model of failure strain that considers the microscopic defects of the material itself are jointly used to describe the fracture and fragmentation behavior of the casing.

[0015] The main ammunition uses the JWL-Milers state equation to describe the non-ideal explosive detonation process, and the passive ammunition uses the Lee-Tarver reaction rate model combined with the JWL state equation of reacted / unreacted explosives to describe the explosive ignition reaction evolution behavior under impact load.

[0016] The main ammunition detonation method is simplified to point source detonation with reference to the detonator layout position in the actual sympathetic explosion experiment.

[0017] The precise characterization method for the coupled power field of near-field explosion shock wave and fragment group described in S2 includes two parts: the characterization of the power field of explosion shock wave and the characterization of the power field of fragment group.

[0018] The method for characterizing the explosive shock wave force field is to obtain the pressure and impulse history at a typical location by numerical calculation, and then obtain the near-field overpressure and impulse attenuation law based on the Kingery-Bulmash formula. The expression is:

[0019] lg(p)=Ag(z) 3 +Bg(z) 2 +Cg(z)+D

[0020]

[0021] In the formula, A, B, C, D are the coefficients to be fitted, and the comparison distance TNT equivalent Q vi and Q vTNT The units of the main explosive and TNT detonation heat, the blast wave overpressure and relative impulse are kPa and kPa·ms·kg respectively. 1 / 3 .

[0022] The force field characteristics of the fragment group include two parts: fragment velocity and mass distribution.

[0023] The average fragment velocity adopts the theoretical formula considering the end cap effect, which is expressed as:

[0024]

[0025] Where V c is the average shell velocity, m c , m e and C are the masses of the shell, end cap and charge respectively, k is the ratio of the end cap thickness to the shell thickness, For Gurney can.

[0026] The axial velocity of fragments adopts a semi-empirical formula that takes into account the cumulative correction of the detonation and non-detonation ends. The expression is:

[0027]

[0028] Where A = (0.869k + 2.770) -1 , C=(4.001k+5.208) -1 , k is the ratio of the end cap thickness to the shell thickness, L is the total length of the ammunition, d is the diameter of the ammunition, V Gurney Gurney speed.

[0029] The expression of the axial dispersion angle of the fragment group is:

[0030] or

[0031]

[0032] Where, Ω is the fragment scattering angle, is the static dispersion range angle, δ is the shell deflection angle, ζ is the detonation wave incident angle, D e is the detonation velocity of the explosive, and F(x) is the product of the correction terms of the detonation end and non-detonation end of the shell axial velocity.

[0033] The expression of axial mass distribution of fragment group is:

[0034]

[0035] Where, is the average axial mass of the shell, ρ is the shell density, a x , b x and δ are the axial fragment width, length, and thickness, respectively, and F(x) is the product of the correction term for the shell axial velocity at the detonation end and the non-detonation end. The typical fragment size and mass are extracted through numerical calculations, and the cumulative mass and number distribution of the fragments are further statistically obtained. The Weibull distribution is used for fitting and calibration, and the expression is:

[0036]

[0037] Where, P M and N M is the cumulative mass and number probability of fragments with a mass greater than m, is the average mass of the shell, N0 is the total number of fragments, and λ and α are the coefficients to be fitted.

[0038] The method for evaluating the sympathetic detonation response characteristics and ammunition safety described in S3 is to carry out numerical calculations of ammunition sympathetic detonation at different distances, obtain the evolution law of the peak value of the reactivity of the fired explosives and the characteristic distance (ammunition spacing / charge diameter) under the action of the sympathetic detonation stimulus, and then quantitatively evaluate the safety of ammunition sympathetic detonation based on the charge reaction level, thereby constructing a numerical evaluation model for ammunition near-field sympathetic detonation.

[0039] With reference to the ammunition safety assessment standards, the ammunition safety assessment level is obtained according to the charge reactivity and reaction intensity, as shown in Table 1.

[0040] Table 1 Ammunition safety assessment levels

[0041]

[0042]

[0043] The present invention provides a numerical evaluation method for the safety of near-field sympathetic detonation of explosive-killing ammunition, which has the following technical effects:

[0044] 1. Existing numerical assessment methods for the destructive power of explosive munitions have difficulty accurately characterizing the near-field blast shock wave attenuation characteristics and the distribution of fragment clusters. The numerical assessment method for sympathetic detonation proposed in this application can accurately characterize the near-field blast shock wave pressure impulse and the velocity and mass distribution of the fragment clusters, and the numerical calculation results are in good agreement with theoretical analysis.

[0045] 2. Existing numerical evaluation methods for sympathetic detonation of ammunition are difficult to quantitatively describe the influence of the intensity of charge reaction and the range of action of sympathetic detonation stimuli. The numerical evaluation method for near-field sympathetic detonation of anti-explosive ammunition proposed in this application can quantitatively analyze the evolution of charge reaction intensity and range under the action of different stimuli. 3. Existing experimental evaluation methods for the safety of sympathetic detonation of ammunition have the disadvantages of high cost, high risk, and small amount of measurement data. The numerical evaluation model for the safety of near-field sympathetic detonation of anti-explosive ammunition proposed in this application can accurately capture the distribution law of global explosion shock waves and fragment groups and the evolution characteristics of the reaction of the explosive, thus supplementing the shortcomings of the sympathetic detonation experimental method. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is a flow chart of the numerical evaluation method for ammunition sympathetic detonation safety of the present invention;

[0047] Figure 2 This is a numerical model of near-field sympathetic detonation of an explosive ammunition in an embodiment;

[0048] Among them: 1-detonator, 2-detonator seat, 3-priming charge, 4-boosting charge, 5-upper end cover, 6-charge, 7-shell

[0049] Figure 3 The attenuation law of the shock wave of the near-field explosion of the killing bomb is shown in the embodiment;

[0050] Figure 4 The evolution law of the near-field fragmentation group velocity of the embodiment of the explosive bomb is shown in FIG.

[0051] Figure 5 The spatial distribution of the near-field fragmentation group of the explosive bomb in the embodiment;

[0052] Figure 6 It is the intensity of charge reaction under the action of sympathetic detonation stimulus in the embodiment. DETAILED DESCRIPTION

[0053] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0054] This embodiment relates to a numerical evaluation method for the safety of near-field sympathetic detonation of anti-explosive ammunition, including the construction of a near-field sympathetic detonation numerical model, the precise characterization of the near-field coupled power field, and the sympathetic detonation response characteristics and safety evaluation. The specific analysis and evaluation process is shown in Figure 1 .

[0055] This embodiment establishes a numerical calculation model for the near-field detonation of explosive ammunition. Figure 2The ammunition case and upper end cap of the test sample are made of 30CrMnSiNi2A high-strength low-carbon steel, the charge is PBX9501, the primary explosive is Poly Black-14, the booster is C4 plastic explosive, the upper end cap and case are fixed with threads, and the detonation method is the upper center detonation of the No. 8 electric detonator.

[0056] This example is based on a real explosion experiment. Figure 2 The numerical calculation model shown in the figure is as follows. The JWL-Milers equation of state is used to describe the non-ideal explosive detonation driving process of the main charge; the JC constitutive model and the Grüneisen equation of state are used to describe the dynamic response characteristics of the material under high pressure for the shell and witness target. The plastic damage model taking into account flow stress softening and the stochastic weakening model are used to jointly describe the shell fracture and fragmentation behavior; the Lee-Tarver three-term reaction rate model and the JWL equation of state are used to describe the evolution of the ignition reaction of the propellant.

[0057] This embodiment establishes a near-explosion coupled power field model that includes two types of sympathetic detonation stimulus elements: explosion shock wave and fragment cluster. First, numerical calculation is used to obtain the pressure impulse history of the explosion shock wave at a typical location. Then, Kingery-Bulmash fitting is used to obtain the spatial attenuation law of the near-field pressure and cumulative impulse, as shown in the following example: Figure 3 As shown, the fitting expression is:

[0058] log(p)=-2log(z) 3 -10log(z) 2 -16log(z)-4

[0059]

[0060] Where, the comparison distance RHBL-1 equivalent TNT equivalent ω e =ω i Q vi / Q vTNT The units of overpressure and relative impulse of detonation products are kPa and kPa·ms·kg 1 / 3 .

[0061] The average fragment velocity expression in this embodiment is:

[0062]

[0063] Where V c is the average shell velocity, m c , m e and C are the masses of the shell, end cap and charge respectively, k is the ratio of the end cap thickness to the shell thickness, For Gurney can.

[0064] The expression of the fragment axial velocity obtained by fitting is:

[0065]

[0066] Where A = (0.869k + 2.770) -1 , C=(4.001k+5.208) -1 In this embodiment, k=1, L is the total length of the ammunition, d is the diameter of the ammunition, V Gurney Gurney speed.

[0067] In this embodiment, the expression of the axial dispersion angle of the fragment group is:

[0068] or

[0069]

[0070] Where, Ω is the fragment scattering angle, is the static dispersion range angle, δ is the shell deflection angle, ζ is the detonation wave incident angle, D e is the detonation velocity of the explosive, and F(x) is the product of the correction terms of the shell axial velocity at the detonation end and the non-detonation end. Figure 4 As shown, the error between the average velocity value and the theoretical value is about 1.7, and the fragment group scattering angle is about 16°.

[0071] In this embodiment, the axial mass distribution characteristic expression of the fragment group is:

[0072]

[0073] Where, is the average axial mass of the shell, ρ is the shell density, a x , b x and δ are the axial fragment width, length and thickness respectively, and F(x) is the product of the shell axial velocity correction term at the detonation end and the non-detonation end. The typical fragment size and mass are extracted by numerical calculation, as shown in the following example: Figure 5 Further statistics were obtained to obtain the distribution law of the cumulative mass and quantity of fragments, and the expression was obtained by fitting the Weibull distribution as follows:

[0074]

[0075] Where, P M and N M is the cumulative mass and number probability of fragments with a mass greater than m, is the average mass of the shell, and N0 is the total number of fragments. Numerical calculations yield an average fragment mass of 1.91 g, which is approximately 17% less than the theoretical calculation. The total number of fragments is 426.

[0076] Based on the calculation results of the near-explosion coupling power field, this embodiment further carries out numerical calculations to obtain the evolution law of charge reactivity at different characteristic distances (ammunition spacing / charge diameter) under the action of the sympathetic detonation stimulus, as shown in the following example: Figure 6 shown.

[0077] In this embodiment, when the test sample detonates within a distance of twice the bullet diameter, the fragment cluster stimulus acts, and the charge reactivity reaches 1, resulting in a reaction severity of Level I, indicating a complete detonation of the charge. When the detonation products act, when the characteristic distance is no greater than 0.3, the charge reactivity is between 0.5 and 0.1, with a reaction severity less than Level III, indicating an explosion or detonation. When the characteristic distance is between 0.3 and 0.5, the charge reactivity is between 0.1 and 0.5, with a reaction severity of Level IV, indicating deflagration or rapid combustion. When the characteristic distance is greater than 0.5, the charge reactivity is less than 0.1, with a reaction severity of Level V, indicating only ignition or localized low-speed combustion.

[0078] Table 2 Safety assessment results of sympathetic detonation of anti-explosive ammunition

[0079]

[0080] With reference to the ammunition sympathetic detonation reaction test standard proposed by the Ammunition Information Security Center (ammunition safety level is greater than level III), the ammunition sympathetic detonation safety assessment results in this embodiment are shown in Table 2.

Claims

1. A numerical evaluation method for the safety of near-field sympathetic detonation of explosive-killing ammunition, characterized in that: The following steps are involved: S1. Construction of numerical model for secondary explosion of explosive-killing ammunition; S2. Accurate characterization of the coupling power field between the near-field explosion shock wave and the fragment group; It includes two parts: characterization of the power field of explosion shock wave and characterization of the power field of fragment group; The method for characterizing the explosive shock wave force field uses numerical calculations to obtain the pressure and impulse history at typical locations. Then, based on the Kingery-Bulmash formula, the near-field overpressure and impulse attenuation law is obtained by fitting. The expression is: lg(p)=Ag(z) 3 +Bg(z) 2 +Cg(z)+D In the formula, A, B, C, D are the coefficients to be fitted, and the comparison distance TNT equivalent Q vi and Q vTNT The units of the main explosive and TNT detonation heat, the blast wave overpressure and relative impulse are kPa and kPa·ms·kg respectively. 1 / 3 ; The fragment group force field characteristics include: The average fragment velocity adopts the theoretical formula considering the end cap effect, which is expressed as: Where V c is the average shell velocity, m c , m e and C are the masses of the shell, end cap and charge respectively, k is the ratio of the end cap thickness to the shell thickness, For Gurney can; The axial velocity of fragments adopts a semi-empirical formula that takes into account the cumulative correction of the detonation and non-detonation ends. The expression is: Where A = (0.869k + 2.770) -1 , C=(4.001k+5.208) -1 , k is the ratio of the end cap thickness to the shell thickness, L is the total length of the ammunition, d is the diameter of the ammunition, V Gurney is Gurney speed; The expression of the axial dispersion angle of the fragment group is: or Where Ω is the fragment scattering angle, is the static dispersion range angle, δ is the shell deflection angle, ζ is the detonation wave incident angle, D e is the detonation velocity of the explosive, F(x) is the product of the correction terms of the shell axial velocity at the detonation end and the non-detonation end; The expression of axial mass distribution of fragment group is: Where, is the average axial mass of the shell, ρ is the shell density, a x , b x and δ are the axial fragment width, length and thickness, respectively; F(x) is the product of the correction terms of the shell axial velocity at the detonation end and the non-detonation end; the typical fragment size and mass are extracted by numerical calculation, and the cumulative mass and number distribution of the fragments are further obtained by statistics. The Weibull distribution is used for fitting and calibration, and the expression is: Where, P M and N M is the cumulative mass and number probability of fragments with a mass greater than m, is the average mass of the shell, N0 is the total number of fragments, λ and α are the coefficients to be fitted; S3. Sympathetic detonation response characteristics and ammunition safety assessment.

2. The numerical evaluation method for the near-field sympathetic detonation safety of explosive-killing ammunition according to claim 1 is characterized in that: The numerical model of the secondary explosion of the killing and explosive ammunition described in S1 includes three parts: the main ammunition, the passive ammunition and the witness target; The Johnson-Cook constitutive model and Grüneisen equation of state are used to describe the dynamic response mechanism of metals under high pressure for the ammunition casing and witness target materials. The cumulative plastic damage model that takes into account flow stress softening and the random weakening model of failure strain that considers the microscopic defects of the material itself are used to describe the fracture and fragmentation behavior of the casing. The main ammunition uses the JWL-Milers state equation to describe the non-ideal explosive detonation process, and the passive ammunition uses the Lee-Tarver reaction rate model combined with the JWL state equation of reacted / unreacted explosives to describe the explosive ignition reaction evolution behavior under impact load.

3. The numerical evaluation method for the near-field sympathetic detonation safety of explosive-killing ammunition according to claim 1 is characterized in that: The S3 method is to carry out numerical calculations of ammunition sympathetic detonation at different distances, obtain the peak value of the reactivity of the fired explosive and the evolution law of the characteristic distance under the action of the sympathetic detonation stimulus, and then quantitatively evaluate the safety of ammunition sympathetic detonation based on the charge reaction level, thereby constructing a numerical evaluation model for ammunition near-field sympathetic detonation.

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