Safety evaluation method of slow cook-off of explosive charge based on equivalent model test

Abstract

The application provides a slow cook-off safety evaluation method of explosive charge based on equivalent model test, comprising the following steps: S1, obtaining the thermodynamic parameters of the explosive charge; S2, determining the equivalent model test method and numerical simulation analysis; S3, slow cook-off numerical simulation analysis of the full-size warhead; S4, reaction grade estimation of the slow cook-off safety of the full-size warhead. The evaluation method of the application designs the model test under the slow cook-off condition of the warhead, combines the numerical simulation to obtain the equivalent wall thickness of the rear end cover of the explosive charge / shell wall thickness, the ignition point temperature and the reaction grade of the explosive charge obtained by the model test, can estimate the reaction grade of the full-size warhead under the slow cook-off condition, and judge the safety. All tests of the evaluation method of the application can be carried out under the laboratory conditions, compared with the full-size live ammunition test research method, has the advantages of low research cost, short cycle, high safety and the like.

Description

Technical Field

[0001] This invention belongs to the field of explosive charge safety technology, and relates to slow-burn safety, specifically to a method for evaluating the slow-burn safety of explosive charges based on equivalent model tests. Background Technology

[0002] Since the last century, with the development of military technology, the modern battlefield environment has become increasingly complex, placing higher demands on the survivability of weapons and ammunition. During the manufacturing, transportation, storage, and use of ammunition, heat stimulation is one of the common threats to warheads, with slow-burn conditions being particularly demanding. After long-term development, slow-burn tests have become an indispensable assessment item in the US MIL-STD-2105D "Non-nuclear Munitions Hazard Assessment Tests," STANAG 4439 "Introduction, Evaluation, and Testing Policy for Insensitive Munitions (MURAT)," and AOP-3 "Guidelines for the Development, Evaluation, and Testing of Insensitive Munitions."

[0003] Currently, the main methods for evaluating the slow-burn safety of explosive charges include live-fire tests, model tests, and numerical simulations. Slow-burn tests typically use a heating rate of 3.3 K / h to test the combustion of scaled-down prototypes or full-size warheads. This method is relatively simple and intuitive, but it is costly, time-consuming, and carries high safety risks. Numerical simulation is an important means of reducing testing costs and can obtain the changes in process parameters such as ignition location and ignition temperature that cannot be observed during testing. However, its results are closely related to thermal decomposition parameters, shell structure parameters, and boundary conditions. Currently, numerical simulation methods struggle to calculate the actual reaction level of the charge. Model tests, on the other hand, use scaled-down equivalent simulation tests to obtain the combustion reaction characteristics of explosives under slow-burn conditions. This allows for the evaluation of the slow-burn stability of explosive charges. This method offers high safety, low research costs, and is suitable for all stages of project demonstration, engineering development, and finalization.

[0004] The shortcomings and defects of existing research techniques are manifested in the following two aspects: (A) Existing methods cannot obtain the relationship between the reaction level and internal response parameters of explosive charges under slow combustion, and cannot accurately evaluate their safety performance; (B) Full-scale live-fire test research methods have high research costs, long cycles, and high safety risks. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a method for evaluating the safety of slow-burning explosive charges based on equivalent model tests, thereby solving the technical problem that existing evaluation methods cannot accurately evaluate the safety of slow-burning explosive charges.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A method for evaluating the safety of slow-burning explosive charges based on equivalent model tests, the method comprising the following steps:

[0008] Step S1: Obtain the thermodynamic parameters of the explosive charge.

[0009] Step S2: Determine the equivalent model test method and numerical simulation analysis:

[0010] Step S201: Based on the actual shell structure, the connection method of the rear end cover and the length-to-diameter ratio of the charge, the explosive charge is designed as a cylindrical shell and charge using the equivalent scaling method, and a simplified equivalent model is established using finite element software.

[0011] Step S202: Conduct equivalent model tests to obtain the range of ratios of the equivalent wall thickness of the rear cover to the shell wall thickness corresponding to different reaction levels.

[0012] Step S203: Based on the thermodynamic parameters of the explosive charge obtained in step S1 and the equivalent model established in step S201, establish a reaction model for the explosive charge.

[0013] The reaction model for the explosive charge is as follows:

[0014]

[0015]

[0016] In the formula:

[0017] ρ is the density of the explosive;

[0018] C is the specific heat capacity of the explosive;

[0019] T is the temperature of the explosive;

[0020] t represents time;

[0021] x, y, and z are the spatial coordinates;

[0022] S represents the self-heating reaction source term of the explosive;

[0023] Q represents the amount of heat released;

[0024] Z is the pre-exponential factor;

[0025] f(α) is the reaction mechanism function;

[0026] α represents the degree of reaction of the explosive;

[0027] E is the activation energy;

[0028] R is the universal gas constant.

[0029] Step S204: The reaction model program established in step S203 is embedded into the finite element software to carry out numerical simulation analysis of equivalent model tests under different shell thicknesses, and the ignition point temperature of the charge under different shell thicknesses and connection lengths is obtained.

[0030] Step S205: Combining the results of the equivalent model test obtained in step S202 and the results of the numerical simulation obtained in step S204, obtain the ratio of the equivalent wall thickness of the rear end cap to the wall thickness of the shell and the ignition temperature corresponding to different reaction levels of the explosive charge, which is used to verify the rationality of the range of the ratio of the equivalent wall thickness of the rear end cap to the wall thickness of the shell corresponding to different reaction levels obtained in step S202.

[0031] Step S3, numerical simulation analysis of slow combustion of full-size warhead:

[0032] A numerical geometric model of slow combustion of a full-size warhead was established using finite element software. The slow combustion numerical geometric model was then incorporated into the thermodynamic parameters of the explosive charge determined in step S1 and the reaction model of the explosive charge established in step S203. Numerical simulation analysis of slow combustion of the full-size warhead was carried out to obtain the ratio of the equivalent wall thickness of the rear end cap to the wall thickness of the shell and the ignition point temperature.

[0033] Step S4, Response level prediction for slow-burn safety of full-size warhead:

[0034] Based on the ratio of the equivalent wall thickness of the rear end cap to the wall thickness of the shell and the ignition temperature of the explosive charge under slow combustion conditions of the full-size warhead obtained in step S3, based on the range of the ratio of the equivalent wall thickness of the rear end cap to the wall thickness of the shell corresponding to different reaction levels obtained in step S202, and based on the ignition temperature obtained in step S205, the reaction level of the safety of the slow combustion of the full-size warhead is estimated.

[0035] The present invention also has the following technical features:

[0036] In step S1, the thermodynamic parameters include thermal decomposition parameters, coefficient of linear expansion, thermal conductivity, and specific heat capacity.

[0037] In step S1, the thermal decomposition parameters are obtained through DSC testing; the heating process of the thermal decomposition parameters of the explosive tested by DSC satisfies the Fourier heat conduction equation.

[0038] In step S202, the process of obtaining the equivalent wall thickness of the rear end cover is as follows: based on the fact that during the burning process, when the internal pressure corresponding to the thread shear failure is the same as the pressure corresponding to the shell tear failure, the thread connection length of the rear end cover is equivalent to the shell wall thickness to obtain the equivalent wall thickness of the rear end cover.

[0039] The equivalent relationship between the shell wall thickness and the threaded connection length is as follows:

[0040]

[0041] In the formula:

[0042] δ is the shell thickness;

[0043] s is the pitch;

[0044] n is the number of thread turns.

[0045] In step S202, the reaction levels are classified as combustion, deflagration, and explosion.

[0046] In step S202, an equivalent model test device is used to conduct an equivalent model test. The equivalent model test device includes a sample shell, which contains multiple sections of propellant charges. The front end of the first section of the propellant charge is pressed against the inner end face of the front end of the sample shell by a gasket, and the rear end of the last section of the propellant charge is pressed against the rear end cover by a gasket. The rear end cover is detachably installed at the rear end of the sample shell.

[0047] The front end of the sample cartridge casing is installed in the middle of the inner end face of the front end of the sample cartridge casing. The rear end of the pressure sensor passes through the middle of the gasket and contacts the propellant column. The front end of the sample cartridge casing has an axial through hole that runs through the inside and outside of the sample cartridge casing. The through hole is coaxially arranged with the pressure sensor.

[0048] The sample shell has a temperature measuring hole on its side wall, which is used to install a temperature sensor.

[0049] It also includes a heating sleeve, which is installed on the outer surface of the sample shell and is tightened by a screw.

[0050] The heating sleeve is connected to the temperature controller.

[0051] The heating sleeve is placed inside the insulation sleeve.

[0052] The rear end cover and the sample shell are connected by a threaded connection to achieve detachable installation.

[0053] Compared with the prior art, the present invention has the following technical effects:

[0054] (I) The evaluation method of the present invention designs a model test under the slow burning condition of the warhead, and combines numerical simulation to obtain the equivalent wall thickness of the rear end cap of the explosive charge / shell wall thickness, the ignition point temperature and the explosive charge reaction level obtained from the model test. It can predict the reaction level of the full-size warhead under the slow burning condition and judge its safety.

[0055] (II) The evaluation method of the present invention can be carried out under laboratory conditions. Compared with the full-scale live-fire test research method, it has the advantages of low research cost, short cycle and high safety.

[0056] (III) The equivalent test device used in the evaluation method of the present invention can more closely approximate the response characteristics of the explosive charge under the shell constraint under slow heating and combustion conditions. Furthermore, the test device can measure the real-time temperature and pressure values ​​at the middle position of the explosive charge while the sample is heated at a uniform rate.

[0057] (IV) The device of the present invention effectively improves the accuracy of equivalent test results and improves the accuracy of safety level assessment. Attached Figure Description

[0058] Figure 1 This is a schematic diagram of the equivalent model test device.

[0059] Figure 2 This is a schematic diagram of the heating sleeve.

[0060] Figure 3 This is a schematic diagram of the insulation jacket.

[0061] Figure 4 This is a schematic diagram of the temperature sensor.

[0062] The meanings of the labels in the diagram are as follows: 1-Sample shell, 2-Gasket, 3-Propellant charge, 4-Temperature measuring hole, 5-Pressure sensor, 6-Through hole, 7-Washer, 8-Temperature controller, 9-Tightening bolt, 10-Heating sleeve, 11-Rear end cap, 12-Temperature sensor, 13-Insulation sleeve.

[0063] The specific content of the present invention will be further explained in detail below with reference to the embodiments. Detailed Implementation

[0064] It should be noted that, unless otherwise specified, all devices and software in this invention are based on existing technologies. For example, the temperature controller and insulation jacket utilize commonly known and existing technologies; the finite element software uses commonly known and existing technologies.

[0065] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0066] Example:

[0067] This embodiment provides a method for evaluating the safety of slow-burning explosive charges based on equivalent model tests. The method includes the following steps:

[0068] Step S1: Obtain the thermodynamic parameters of the explosive charge:

[0069] In step S1, the thermodynamic parameters include thermal decomposition parameters, linear expansion coefficient, thermal conductivity, and specific heat capacity.

[0070] In step S1, the thermal decomposition parameters are obtained by DSC testing. DSC can test the thermal decomposition parameters at different heating rates. The heating process of DSC testing the thermal decomposition parameters of explosives satisfies the Fourier heat conduction equation, that is, the heating heat flux difference is proportional to the temperature signal. Therefore, the temperature difference signal can be converted into a heat flux difference signal.

[0071] In this embodiment, the warhead is a typical invasive warhead with a slow-burning HMX (Octogen)-based compressed charge.

[0072] In this embodiment, an explosive thermal decomposition test experiment was conducted to obtain the thermal decomposition characteristics of the explosive charge. The thermal decomposition parameters at different heating rates were measured using DSC, and the pre-exponential factor was calculated to be approximately 1.1 × 10⁻⁶. 30 s -1 The activation energy is approximately 4.2 × 10⁻⁶. 5 J / mol, other thermodynamic parameters are shown in Table 1.

[0073] Table 1 Thermodynamic parameters of HMX explosive

[0074]

[0075] Step S2: Determine the equivalent model test method and numerical simulation analysis:

[0076] Step S201: Based on the actual shell structure, the connection method of the rear end cover and the length-to-diameter ratio of the charge, the explosive charge is designed as a cylindrical shell and charge using the equivalent scaling method, and a simplified equivalent model is established using finite element software.

[0077] Step S202: Conduct equivalent model tests to obtain the range of ratios of the equivalent wall thickness of the rear cover to the shell wall thickness corresponding to different reaction levels.

[0078] In step S202, the reaction levels are classified as combustion, deflagration, and explosion.

[0079] In this embodiment, model tests were conducted with shell wall thicknesses of 4mm, 10mm, and 20mm, and the equivalent wall thickness of the rear end cover was within the range of 1mm-20mm. The strength range corresponding to different reaction levels of the explosive charge was determined through the experimental results.

[0080] The range of the ratio of the equivalent wall thickness of the rear cover to the wall thickness of the casing is used to determine the damage mode of the incendiary bomb. Specifically:

[0081] Explosive charges with an end cap equivalent wall thickness / shell wall thickness ratio of 0 to 0.6 have intact shells, with the end cap detached, and the reaction level is combustion.

[0082] Explosive charges with an end cap equivalent wall thickness / shell wall thickness ratio of 0.6 to 0.96 have intact shells, with the rear end cap detached, and the reaction level is deflagration.

[0083] When the ratio of the equivalent wall thickness of the end cap to the wall thickness of the explosive charge is 0.96 to 1.06, the explosive charge casing is destroyed, the rear end cap detaches, and the reaction level is explosion.

[0084] When the explosive charge casing ruptures with an end cap equivalent wall thickness / shell wall thickness ratio of 1.06 to 2.1 and the rear end cap does not detach, the reaction level is deflagration.

[0085] If the ratio of the equivalent wall thickness of the end cap to the wall thickness of the explosive charge is 2.1 or higher, the explosive charge casing will rupture, the rear end cap will not detach, and the reaction level will be combustion.

[0086] Preferably, in step S202, the process of obtaining the equivalent wall thickness of the rear end cover is as follows: based on the fact that during the burning process, when the internal pressure corresponding to the thread shear failure is the same as the pressure corresponding to the shell tear failure, the thread connection length of the rear end cover is equivalent to the shell wall thickness to obtain the equivalent wall thickness of the rear end cover.

[0087] The equivalent relationship between the shell wall thickness and the threaded connection length is as follows:

[0088]

[0089] In the formula:

[0090] δ is the shell thickness;

[0091] s is the pitch;

[0092] n is the number of thread turns.

[0093] Preferably, in step S202, an equivalent model test device is used to conduct an equivalent model test, such as... Figure 1 As shown, the equivalent model test device includes a projectile casing 1, which contains multiple propellant charges 3. The front end of the first propellant charge 3 is pressed against the inner end face of the front end of the projectile casing 1 by a gasket 7, and the rear end of the last propellant charge 3 is pressed against the rear end cover 11 by a gasket 2. The rear end cover 11 is detachably installed at the rear end of the projectile casing 1.

[0094] The front end of the pressure sensor 5 is installed in the middle of the inner end face of the front end of the sample shell 1. The rear end of the pressure sensor 5 passes through the middle of the gasket 7 and contacts the charge column 3. The front end of the sample shell 1 has an axial through hole 6 that runs through the inside and outside. The through hole 6 is coaxially arranged with the pressure sensor 5.

[0095] A temperature measuring hole 4 is provided on the side wall of the sample shell 1, and the temperature measuring hole 4 is used to install the temperature sensor 12.

[0096] like Figure 1 As shown, the pressure sensor 5 is located below the sample shell 1 and collects the internal pressure value in real time. Its wiring position is located in the through hole 6. The wiring of the pressure sensor 5 is matched with the through hole 6. The pressure sensor 5 is matched with the sample shell 1, which can ensure the accuracy of the pressure value inside the sample shell during the combustion process and further improve the accuracy of the test of the device in this embodiment.

[0097] like Figure 4 As shown, the temperature sensor 12 collects the temperature of the explosive at the monitoring point through the temperature measuring hole 4. The temperature measuring hole 4 is matched with the temperature sensor 12, which can ensure the accuracy of the pressure value inside the sample shell during the heating process and further improve the accuracy of the test of the device in this embodiment.

[0098] In this embodiment, preferably, the diameter of the temperature measuring hole 4 is 1 mm, and the diameter of the through hole 6 is 2 mm.

[0099] Gasket 2 and washer 7 are used to ensure the uniformity of the density of the propellant column and to prevent gaps in the middle of the propellant column 3, which would affect the accuracy of the test device.

[0100] In this embodiment, preferably, the gasket 2 has a thickness of 1 mm and is made of polyethylene.

[0101] In this embodiment, preferably, the thickness of the washer 7 is usually about 1 mm, and the material must be a non-metallic material.

[0102] As a preferred embodiment of this invention, such as Figure 2 As shown, it also includes a heating sleeve 10, which is installed on the outer surface of the sample shell 1. The heating sleeve 10 is tightened by a tightening bolt 9. The tightening bolt 9 is used to ensure that the outer wall of the sample shell and the inner wall of the sleeve are in close contact during the heating process, so as to avoid the shell and the accuracy of temperature acquisition being reduced during the heating process.

[0103] Further preferred, such as Figure 2 As shown, the heating sleeve 10 is connected to the temperature controller 8. The temperature sensor 12 and the temperature controller 8 are used to accurately control the heating rate of the heating sleeve 10, further improving the accuracy of the test in this embodiment.

[0104] Further preferred, such as Figure 3 As shown, the heating sleeve 10 is placed inside the insulation sleeve 13. The insulation sleeve 13 is used to reduce heat loss during the heating process, ensuring that the outer wall of the sample shell 1 is heated at the target heating rate, and further improving the test efficiency of this embodiment.

[0105] In this embodiment, preferably, the insulation sleeve 13 has a thickness of 5mm and is made of asbestos.

[0106] In a preferred embodiment, the rear end cover 11 and the sample shell 1 are connected by a threaded connection to achieve detachable installation. The threaded connection at the rear end cover 11 and the sample shell 1 is used to ensure the constraint effect on the explosive charge 3 throughout the heating process, which is closer to the response characteristics of the explosive charge under constraint conditions in a real heating and combustion state.

[0107] To further improve the testing efficiency of this embodiment, it is preferred in this embodiment that the material of the sample shell 1 and the rear end cover 11 is 30-CrMnSi.

[0108] Step S203: Based on the thermodynamic parameters of the explosive charge obtained in step S1 and the equivalent model established in step S201, establish a reaction model for the explosive charge.

[0109] In this embodiment, the pre-exponential factor and apparent activation energy of the explosive charge are calculated based on the thermodynamic parameters of the explosive charge obtained in step S1; and a reaction model of the explosive charge is established based on the pre-exponential factor and apparent activation energy of the explosive charge.

[0110] In this embodiment, the reaction model can describe the reaction state of explosives during heating using parameters such as explosive density, specific heat capacity, heat of reaction, thermal conductivity, pre-exponential factor, and activation energy, and is widely used in numerical simulation analysis of materials such as explosives and propellants.

[0111] The reaction model for the explosive charge is as follows:

[0112]

[0113]

[0114] In the formula:

[0115] ρ is the density of the explosive;

[0116] C is the specific heat capacity of the explosive;

[0117] T is the temperature of the explosive;

[0118] t represents time;

[0119] x, y, and z are the spatial coordinates;

[0120] S represents the source term of the explosive's self-heating reaction;

[0121] Q represents the amount of heat released;

[0122] Z is the pre-exponential factor;

[0123] f(α) is the reaction mechanism function;

[0124] α represents the degree of reaction of the explosive;

[0125] E is the activation energy;

[0126] R is the universal gas constant.

[0127] Step S204: The reaction model program established in step S203 is embedded into the finite element software to carry out numerical simulation analysis of equivalent model tests under different shell thicknesses, and the ignition point temperature of the charge under different shell thicknesses and connection lengths is obtained.

[0128] In this embodiment:

[0129] With a shell wall thickness of 4 mm and a connection length of 2 mm, the ratio of the equivalent wall thickness of the rear end cover to the shell wall thickness is 0.35, the reaction level is combustion, and the ignition point temperature is 474.4 K.

[0130] With a shell wall thickness of 4mm and a connection length of 4mm, the ratio of the equivalent wall thickness of the rear end cover to the shell wall thickness is 0.7, the reaction level is deflagration, and the ignition point temperature is 486.9K.

[0131] When the shell wall thickness is 4mm and the connection length is 6mm, the ratio of the equivalent wall thickness of the rear cover to the shell wall thickness is 1.05, the reaction level is explosive, and the ignition temperature is 492.88K.

[0132] Step S205: Combining the results of the equivalent model test obtained in step S202 and the results of the numerical simulation obtained in step S204, obtain the ratio of the equivalent wall thickness of the rear end cap to the wall thickness of the shell and the ignition temperature corresponding to different reaction levels of the explosive charge, which is used to verify the rationality of the range of the ratio of the equivalent wall thickness of the rear end cap to the wall thickness of the shell corresponding to different reaction levels obtained in step S202.

[0133] Step S3, numerical simulation analysis of slow combustion of full-size warhead:

[0134] A numerical geometric model of slow combustion of a full-size warhead was established using finite element software. The slow combustion numerical geometric model was then incorporated into the thermodynamic parameters of the explosive charge determined in step S1 and the reaction model of the explosive charge established in step S203. Numerical simulation analysis of slow combustion of the full-size warhead was carried out to obtain the ratio of the equivalent wall thickness of the rear end cap to the wall thickness of the shell and the ignition point temperature.

[0135] In this embodiment, a numerical simulation analysis of the slow combustion of the full-size warhead at a heating rate of 3.3 K / h was conducted, and the ratio of the equivalent wall thickness of the rear cover to the shell wall thickness was obtained as 0.4125, with a response temperature of 481.1 K.

[0136] Step S4, Response level prediction for slow-burn safety of full-size warhead:

[0137] Based on the ratio of the equivalent wall thickness of the rear end cap to the wall thickness of the shell and the ignition temperature of the explosive charge under slow combustion conditions of the full-size warhead obtained in step S3, based on the range of the ratio of the equivalent wall thickness of the rear end cap to the wall thickness of the shell corresponding to different reaction levels obtained in step S202, and based on the ignition temperature obtained in step S205, the reaction level of the safety of the slow combustion of the full-size warhead is estimated.

[0138] In this embodiment, the reaction level of the estimated full-size warhead slow-burn safety is combustion.

Claims

1. A method for evaluating the safety of slow-burning explosive charges based on equivalent model tests, characterized in that, The method includes the following steps: Step S1: Obtain the thermodynamic parameters of the explosive charge; Step S2: Determine the equivalent model test method and numerical simulation analysis: Step S201: Based on the actual shell structure, the connection method of the rear end cover and the length-to-diameter ratio of the charge, the explosive charge is designed as a cylindrical shell and charge using the equivalent scaling method, and a simplified equivalent model is established using finite element software. Step S202: Conduct equivalent model tests to obtain the range of ratios of the equivalent wall thickness of the rear cover to the shell wall thickness corresponding to different reaction levels; Step S203: Based on the thermodynamic parameters of the explosive charge obtained in step S1 and the equivalent model established in step S201, establish a reaction model for the explosive charge. The reaction model for the explosive charge is as follows: In the formula: ρ is the density of the explosive; C is the specific heat capacity of the explosive; T is the temperature of the explosive; t represents time; x, y, and z are the spatial coordinates; S represents the source term of the explosive's self-heating reaction; Q represents the amount of heat released; Z is the pre-exponential factor; f(α) is the reaction mechanism function; α represents the degree of reaction of the explosive; E is the activation energy; R is the universal gas constant; Step S204: Embed the reaction model program established in step S203 into the finite element software, and conduct numerical simulation analysis of equivalent model tests under different shell thicknesses to obtain the ignition point temperature of the charge under different shell thicknesses and connection lengths. Step S205: Combining the results of the equivalent model test obtained in step S202 and the results of the numerical simulation obtained in step S204, obtain the ratio of the equivalent wall thickness of the rear end cap to the wall thickness of the shell and the ignition temperature corresponding to different reaction levels of the explosive charge, which is used to verify the rationality of the range of the ratio of the equivalent wall thickness of the rear end cap to the wall thickness of the shell corresponding to different reaction levels obtained in step S202. Step S3, numerical simulation analysis of slow combustion of full-size warhead: A numerical geometric model of slow combustion of a full-size warhead was established using finite element software. The slow combustion numerical geometric model was then incorporated into the thermodynamic parameters of the explosive charge determined in step S1 and the reaction model of the explosive charge established in step S203. Numerical simulation analysis of slow combustion of the full-size warhead was carried out to obtain the ratio of the equivalent wall thickness of the rear end cap to the wall thickness of the shell and the ignition point temperature. Step S4, Response level prediction for slow-burn safety of full-size warhead: Based on the ratio of the equivalent wall thickness of the rear end cap to the wall thickness of the shell and the ignition temperature of the explosive charge under slow combustion conditions of the full-size warhead obtained in step S3, based on the range of the ratio of the equivalent wall thickness of the rear end cap to the wall thickness of the shell corresponding to different reaction levels obtained in step S202, and based on the ignition temperature obtained in step 205, the reaction level of the safety of the slow combustion of the full-size warhead is estimated.

2. The method for evaluating the safety of slow-burning explosive charges based on equivalent model tests as described in claim 1, characterized in that, In step S1, the thermodynamic parameters include thermal decomposition parameters, coefficient of linear expansion, thermal conductivity, and specific heat capacity.

3. The method for evaluating the safety of slow combustion of explosive charges based on equivalent model tests as described in claim 1, characterized in that, In step S1, the thermal decomposition parameters are obtained through DSC testing; the heating process of the thermal decomposition parameters of the explosive tested by DSC satisfies the Fourier heat conduction equation.

4. The method for evaluating the safety of slow-burning explosive charges based on equivalent model tests as described in claim 1, characterized in that, In step S202, the process of obtaining the equivalent wall thickness of the rear end cover is as follows: based on the fact that during the burning process, when the internal pressure corresponding to the thread shear failure is the same as the pressure corresponding to the shell tear failure, the thread connection length of the rear end cover is equivalent to the shell wall thickness to obtain the equivalent wall thickness of the rear end cover. The equivalent relationship between the shell wall thickness and the threaded connection length is as follows: In the formula: δ is the shell thickness; s is the pitch; n is the number of thread turns.

5. The method for evaluating the safety of slow-burning explosive charges based on equivalent model tests as described in claim 1, characterized in that, In step S202, the reaction levels are classified as combustion, deflagration, and explosion.

6. The method for evaluating the safety of slow-burning explosive charges based on equivalent model tests as described in claim 1, characterized in that, In step S202, an equivalent model test device is used to carry out an equivalent model test. The equivalent model test device includes a sample shell (1). The sample shell (1) contains multiple sections of propellant columns (3). The front end of the first section of propellant column (3) is pressed against the inner end face of the front end of the sample shell (1) by a gasket (7). The rear end of the last section of propellant column (3) is pressed against the rear end cover (11) by a gasket (2). The rear end cover (11) is detachably installed at the rear end of the sample shell (1). The front end of the sample shell (1) is installed in the middle of the inner end face of the front end of the sample shell (1). The rear end of the pressure sensor (5) passes through the middle of the gasket (7) and contacts the charge column (3). The front end of the sample shell (1) is provided with an axial through hole (6) that runs through the inside and outside. The through hole (6) is coaxially arranged with the pressure sensor (5). A temperature measuring hole (4) is provided on the side wall of the sample shell (1), and the temperature measuring hole (4) is used to install a temperature sensor (12).

7. The method for evaluating the safety of slow-burning explosive charges based on equivalent model tests as described in claim 6, characterized in that, It also includes a heating sleeve (10), which is installed on the outer surface of the sample shell (1). The heating sleeve (10) is tightened by a tightening bolt (9).

8. The method for evaluating the safety of slow-burning explosive charges based on equivalent model tests as described in claim 7, characterized in that, The heating sleeve (10) is connected to the temperature controller (8).

9. The method for evaluating the safety of slow-burning explosive charges based on equivalent model tests as described in claim 7, characterized in that, The heating sleeve (10) is placed in the heat insulation sleeve (13).

10. The method for evaluating the safety of slow combustion of explosive charges based on equivalent model tests as described in claim 6, characterized in that, The rear end cover (11) and the sample shell (1) are connected by a thread to achieve detachable installation.

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