A simulation method for integrated penetration and dynamic explosion based on the volume filling method

Abstract

A penetration and dynamic explosion integrated simulation method based on volume filling method, which relates to the field of blasting technology. The simulation method based on volume filling in the present invention no longer needs to use restart, realizes the integrated simulation of penetration and explosion, and at the same time solves problems such as the initial mesh penetration of explosive materials and the inability to cooperate with the projectile in deformation. It has high simulation accuracy. The present invention can set the performance of the projectile shell material according to the actual situation, without setting the projectile shell as a rigid body during the penetration stage, and realizes the analysis of the secondary damage of fragments to the structure during the dynamic explosion process, and the simulation is more in line with the actual working conditions. The present invention can also analyze the coupling effect between the penetration field and the explosion field, study the influence of the projectile shell, penetration field, and explosion field on the damage response in penetration and dynamic explosion, and solve the problems of difficult measurement, recording, and analysis of damage data in each process of penetration and explosion, and difficult quantification of the damage weight of each part, etc., and is suitable for wide promotion and application.

Description

Technical Field

[0001] The present invention relates to the technical field of blasting, and particularly relates to a simulation method for integrated penetration and dynamic explosion based on the volume filling method. Background Art

[0002] It is known that the damage effect of an armor-piercing explosive projectile on a target is the combined action of multiple damage elements such as projectile penetration, explosive shock, and high-speed flying of fragments. After years of development, the initiation control technology of the warhead in an armor-piercing explosive projectile can meet various damage requirements such as instantaneous and delayed initiation, initiation at a specified speed, acceleration, and penetration depth. Due to the relatively complex combined action mechanism of damage elements, current research on the damage effect of armor-piercing explosive projectiles mainly focuses on the single damage of inert projectile penetration or explosive shock. Based on a large number of theoretical analyses, experimental verifications, and numerical simulation studies, the research results on the single damage effect of penetration and explosion on targets are becoming increasingly perfect. Researchers have proposed a series of theoretical / empirical formulas, engineering algorithms, or numerical simulation methods with high accuracy for calculating the single damage effect of penetration and explosion, which are in good agreement with the experimental data of models or prototypes.

[0003] With the continuous development of ammunition technology and experimental measurement technology, researchers have found that studying the two damage elements of penetration and explosion shock separately can no longer fully reflect the damage ability of weapons and equipment, especially the damage effect of large-equivalent and deep-drilling weapons on underground targets. The most representative is Sun S, Lu H, Yue S, et al. The composite damage effects of explosion after penetration in plain concrete targets [J]. International Journal of Impact Engineering, 2021, 153: 103862. It studied the damage differences between post-penetration static explosion and prefabricated hole charge explosion (ignoring the projectile penetration effect) on concrete targets through experimental and numerical simulation means, and confirmed that the cratering process during penetration has an unignorable impact on the subsequent explosion effect. Based on this understanding, at present, a small number of scholars have also carried out research on the damage effects of ammunition penetration and explosion coupling, or the combined action of explosion and fragments. However, due to the complexity of its theory and the difficulty of experiments, the current relevant results still need to be further improved.

[0004] The research on the combined action of penetration and explosion can be summarized into two types: static explosion of the charge after penetration and integrated penetration and explosion. Static explosion of the charge after penetration means that after the projectile penetration process is completely over, without destroying the structure of the penetration crater, the residual projectile is taken out, and the charge is filled at the final penetration position to conduct a static explosion.

[0005] Among them, the research method of post-penetration charge static detonation has three advantages:

[0006] 1. It can fully consider the influence of the crater formed by the projectile penetration on the explosion effect;

[0007] 2. It can clearly define the boundaries between the penetration and explosion processes, which is convenient for analyzing the damage weights of the two types of damage elements to the target;

[0008] 3. The test technology or numerical simulation method of this scheme is relatively mature, and it has good implementation conditions.

[0009] The deficiencies of post-penetration charge static detonation mainly include the following three points:

[0010] 1. After the projectile penetration is completely over, the stress wave field formed during the penetration process cannot be superimposed with the explosion wave field, and it is impossible to study the cumulative explosion effect when the penetration damage evolution is not over;

[0011] 2. It is impossible to simulate the situation where the explosion occurs before the penetration is over. At this time, the kinetic energy effect of the projectile will affect the explosion damage ability;

[0012] 3. The influence of the projectile shell (fragment) on the explosion effect is not considered, etc.

[0013] The integrated penetration and explosion of ammunition means that the projectile penetration and explosion are a complete continuous process without an obvious time interval. According to the state of the ammunition explosion, it is divided into integrated penetration and static detonation and integrated penetration and dynamic detonation. Integrated penetration and static detonation means that at the moment when the penetration process just ends, the ammunition explodes immediately in a static state; integrated penetration and dynamic detonation means that when the penetration is not completely over, the ammunition explodes when it has kinetic energy. At present, for the research on integrated penetration and explosion, whether it is test technology or numerical simulation method, there are few studies. The main reason is not that the damage effect of integrated penetration and explosion is not much different from that of post-penetration charge static detonation, but because both its test design and numerical simulation are very difficult. There are mainly the following three difficulties in experimental research:

[0014] 1. It is difficult to accurately control the initiation time of the ammunition. If the initiation time is advanced, it becomes integrated penetration and dynamic detonation. If the initiation time is delayed, it becomes post-penetration charge static detonation with a shell. It is very difficult to achieve integrated penetration and static detonation without a sensitive fuse.

[0015] 2. It is difficult to measure, record and analyze the damage data of each process of penetration and explosion. The damage to the target by the integrated penetration and explosion of ammunition is composed of the crater formed by penetration, explosion shock and high-speed flying of fragments. Even if the sensor records various data, the penetration signal, explosion signal and fragment signal after explosion are superimposed together, which is difficult to distinguish and impossible to quantify the damage weights of each part.

[0016] 3. The cost of the penetration and explosion integrated test is high and the risk is great. It is very difficult to meet the requirements with ordinary test guarantee conditions, etc.

[0017] The currently available test research results are as follows: the front section of a short-delay instantaneous fuse is used for initiating detonation, and a horizontal dynamic explosion loading is carried out on a certain artillery shell sample. Through the test, it is proved that the shock wave overpressure along the positive direction of the ammunition movement is greater than that of the static explosion shock wave, while the shock wave overpressure in the negative direction of the movement speed is less than that of the static explosion shock wave, etc. Therefore, how to provide a penetration and dynamic explosion integrated simulation method based on the volume filling method has become a long-term technical requirement of those skilled in the art. Summary of the Invention

[0018] To overcome the deficiencies in the background technology, the present invention provides a penetration and dynamic explosion integrated simulation method based on the volume filling method. The simulation method based on volume filling in the present invention no longer needs to use restart, and truly realizes the integrated simulation of penetration and explosion. At the same time, it solves problems such as the initial mesh penetration of explosive materials and the inability to deform synergistically with the projectile body, and has high simulation accuracy, etc.

[0019] To achieve the above-mentioned invention purpose, the present invention adopts the following technical solutions:

[0020] A penetration and dynamic explosion integrated simulation method based on the volume filling method. The method is to set ALE meshes of air material in the entire model background area. At the initial position of the projectile penetration, the explosive material is filled into the projectile cavity area by using the volume filling method, and at the same time, it is given the same initial penetration speed as the projectile shell. During the penetration process of the projectile, a fluid-structure interaction algorithm is set to constrain the explosive material and the projectile shell meshes, so that the explosive material not only maintains the same change in penetration speed as the projectile shell, but also deforms synergistically with the projectile shell without leakage from the inside to the outside. When the projectile reaches the preset speed, penetration depth and acceleration states during the penetration process, the time points corresponding to each state can be obtained through the pre-calculation of a single penetration process, and finally, the dynamic explosion or static explosion in the medium is caused by controlling the detonation time.

[0021] In the penetration and dynamic explosion integrated simulation method based on the volume filling method, the volume filling method is to use the keyword INITIAL_VOLUME_FRACTION_GEOMETRY to assign the filling material and material speed to the ALE meshes, divide the ALE meshes of the explosive material according to the projectile cavity size, and fill the projectile cavity with the explosive material. The specific operation steps are as follows:

[0022] (1). Establish an ALE air domain covering the entire penetration trajectory and explosion area to provide a sufficient range of fluid medium for the fluid-structure interaction calculation in both the penetration and explosion stages;

[0023] (2) Divide the area filled with explosive in the air domain according to the size of the projectile cavity. In this process, the model grid should be accurately divided to prevent the explosive from overlapping with the projectile shell, which may affect the propagation of energy during explosion.

[0024] (3) Fill the divided area with explosive material and simultaneously assign the same motion speed to the explosive and the projectile shell.

[0025] (4) Establish Lagrange grids for the projectile shell outside the explosive area. Set the fluid-structure interaction algorithm for the penetration process through the CONSTRAINED_LAGRANGE_IN_SOLID keyword. The main media are the explosive and air, and the secondary medium is the projectile shell. Establish Lagrange grids for the target medium below the projectile body. Similarly, set the fluid-structure interaction algorithm for the explosion process through CONSTRAINED_LAGRANGE_IN_SOLID. The main media are the explosive and air, and the secondary media are the projectile shell and the target medium.

[0026] For the penetration and dynamic explosion integrated simulation method based on the volume filling method, the projectile shell is made of metal material 30CrMnSiNi2A.

[0027] Adopting the above technical solution, the present invention has the following advantages:

[0028] The simulation method based on volume filling of the present invention no longer needs to use restart, realizes the integrated simulation of penetration and explosion, and simultaneously solves problems such as the initial grid penetration of explosive materials and the inability to deform synergistically with the projectile body. It has high simulation accuracy. The present invention can set the material properties of the projectile shell according to actual conditions, without setting the projectile shell as a rigid body during the penetration stage, realizes the analysis of the secondary damage of fragments to the structure during the dynamic explosion process, and the simulation is more in line with the actual working conditions. The present invention can also analyze the coupling effect between the penetration field and the explosion field, study the influence of the projectile shell, penetration field, and explosion field on the damage response during penetration and dynamic explosion, solve the problems of difficult measurement, recording, and analysis of damage data in each process of penetration and explosion, and difficult quantification of the damage weight of each part, etc., and is suitable for wide promotion and application. Description of the Drawings

[0029] Figure 1 It is a schematic diagram of the operation steps of the volume filling method in the embodiment of the present invention;

[0030] Figure 2 It is a schematic diagram of the numerical model size and measuring point positions in the embodiment of the present invention;

[0031] Figure 3 It is a schematic diagram of the penetration and explosion damage weights in the embodiment of the present invention;

[0032] Figure 4are the damage cloud maps of C30 concrete and the failure states of the projectile under different penetration velocities in the embodiments of the present invention;

[0033] Figure 5 are the displacement and velocity time history curves of the projectile during the penetration process in the embodiments of the present invention;

[0034] Figure 6 is the comparison of the penetration depths between the numerical calculation and the empirical formula in the embodiments of the present invention;

[0035] Figure 7 are the pressure time history curves of the measurement point S2 under different velocity conditions with delayed initiation in the embodiments of the present invention;

[0036] Figure 8 are the macroscopic damage cloud maps of concrete at different initiation times when the penetration velocity is 650 m / s in the embodiments of the present invention;

[0037] Figure 9 is the pressure in the y direction of the measurement point at different explosion times when the penetration velocity is 650 m / s in the embodiments of the present invention;

[0038] Figure 10 are the concrete damage weights at different initiation times when the penetration velocity is 650 m / s in the embodiments of the present invention;

[0039] Figure 11 are the concrete damage cloud maps under different penetration velocity conditions in the embodiments of the present invention;

[0040] Figure 12 are the pressure time history curves of the measurement point S1 under different penetration velocity conditions in the embodiments of the present invention;

[0041] Figure 13 are the concrete damage weights under different penetration velocity conditions in the embodiments of the present invention. Detailed implementation manners

[0042] The present invention can be more specifically explained by the following embodiments, and the present invention is not limited to the following embodiments;

[0043] The basic principle of the volume filling method is that the detonation products generated after the explosion of the explosive have the properties of a fluid. Generally, the ALE algorithm (Arbitrary Lagrange and Euler algorithm) is required to simulate the explosive and the area where the detonation products are released around it. The ALE algorithm is similar to the Euler algorithm. If the explosive moves in the grid, essentially the explosive material in the grid is moving, while the grid itself does not move. For the existing numerical simulation studies on post-penetration charge static detonation, since the explosive is detonated in a static state, the restart method can be used to achieve it. Specifically, when calculating penetration, the projectile shell, explosive, and penetrated medium are all set as Lagrange grids. After penetration, restart. On the basis of retaining the original damage, the Lagrange grid of the explosive is deleted and replaced with an ALE grid, and then the fluid-structure interaction method is used to calculate the explosion effect. When using the ALE grid to replace the Lagrange grid, if the projectile shell and the explosive are deformed, it is difficult to establish an accurate ALE grid to fit the deformed projectile cavity, which is likely to cause initial grid penetration and have a greater impact on the calculation accuracy. Therefore, in this method, both the projectile shell and the explosive are set as rigid bodies during the penetration stage.

[0044] When using the post-penetration charge static detonation method to simulate the integrated penetration and dynamic detonation, at the detonation moment, the projectile (projectile shell and explosive) has a certain velocity. Even if the restart can use the ALE grid to replace the original explosive Lagrange grid, it is very difficult to endow the explosive ALE material with the same velocity as the projectile shell; on the other hand, using rigid bodies to simulate the projectile shell and the explosive ignores the deformation of the projectile during the actual penetration process, which has a certain impact on the calculation accuracy of the dynamic detonation effect.

[0045] To solve this problem, the present invention provides an integrated penetration and dynamic detonation simulation method based on the volume filling method. The method is to set the ALE grid of air material in the entire model background area. At the initial position of the projectile penetration, the explosive material is filled into the projectile cavity area by using the volume filling method, and at the same time, it is given the same initial penetration velocity as the projectile shell. During the penetration process of the projectile, the fluid-structure interaction algorithm is set to constrain the explosive material and the projectile shell grid, so that the explosive material not only maintains the same change in penetration velocity as the projectile shell, but also coordinates with the deformation of the projectile shell and does not leak from the inside to the outside. When the projectile reaches the preset velocity, penetration depth, and acceleration states during the penetration process, the time points corresponding to each state can be obtained through the pre-calculation of a single penetration process. Finally, the detonation time is controlled to make it undergo dynamic detonation or static detonation in the medium.

[0046] During implementation, the volume filling method is to endow the ALE grid with the filling material and material velocity by using the keyword INITIAL_VOLUME_FRACTION_GEOMETRY, divide the ALE grid of the explosive material according to the projectile cavity size, and fill the projectile cavity with the explosive material. The specific operation steps are as follows:

[0047] (1) Establish an ALE air domain covering the entire penetration trajectory and explosion area to provide a fluid medium with sufficient scope for the fluid-structure interaction calculations in both the penetration and explosion stages;

[0048] (2) According to the size of the projectile cavity, divide the area filled with explosive in the air domain. In this process, the model grid should be precisely divided to prevent the explosive from overlapping with the projectile shell, which may affect the energy propagation during the explosion;

[0049] (3) Fill the divided area with explosive material and simultaneously assign the same motion speed to the explosive and the projectile shell;

[0050] (4) Establish Lagrange grids for the projectile shell around the explosive area. Set the fluid-structure interaction algorithm for the penetration process through the CONSTRAINED_LAGRANGE_IN_SOLID keyword. The main media are the explosive and air, and the secondary medium is the projectile shell. Establish Lagrange grids for the target medium below the projectile body. Similarly, set the fluid-structure interaction algorithm for the explosion process through CONSTRAINED_LAGRANGE_IN_SOLID. The main media are the explosive and air, and the secondary media are the projectile shell and the target medium.

[0051] During implementation, the volume filling method is used to simulate the integrated process of penetration and dynamic explosion. First, it is necessary to obtain the time points corresponding to the states of the projectile body at specified velocities, penetration depths, etc. By controlling the detonation time, the dynamic or static explosion of the explosive can be achieved. Therefore, this method is required to perform budget calculations on the penetration process of inert projectiles (although filled with explosive but not detonated). The penetration velocity and penetration depth changes obtained through pre-calculation can also provide data references for subsequent analysis of the damage effects of the integrated penetration and explosion. This invention uses empirical formulas to verify the reliability of the budget model and related parameters for the penetration of inert projectiles into concrete based on the volume filling method.

[0052] Material models and parameters:

[0053] According to Figure 1The operation steps of the given volume filling method are used to establish a two-dimensional model of a projectile penetrating concrete. The inert projectile takes the center of the upper surface of the concrete as the incident point, and the penetration velocities are 450 m / s, 500 m / s, 550 m / s, 600 m / s, and 650 m / s respectively. The concrete medium is 1000 mm wide, 500 mm thick, and has a compressive strength of 30 MPa; the projectile is 86.45 mm long, the projectile shell is 2.5 mm thick, and the ratio of the curvature radius of the projectile head to the diameter is 2 for the CRH value. The projectile shell is made of the test projectile material 30CrMnSiNi2A, the internal charge is TNT, the mass of the projectile shell is 22.35 g, and the charge amount is 84.65 g. A rectangular coordinate system is established with the incident point as the origin. Points S1 and S2 are pressure measurement points, and the coordinates are: (25, -238) mm and (25, -425) mm respectively. The geometric model is discretized using quadrilateral solid elements, and the mesh sizes are as follows: the air domain and the explosive (ALE) are 1.25 mm, the projectile shell is 0.625 mm, and the concrete is 1.25 mm. The boundary of the air domain is set to non-reflective, the bottom and both sides of the concrete are fixed, and the surface is free. The surface-to-surface erosive contact between the projectile shell and the concrete is defined using the keyword CONTACT_ERODING_SURFACE_TO_SURFACE. The specific model and dimensions are as Figure 2 shown.

[0054] Figure 3 The damage schematic diagram of the target medium during the integrated penetration and explosion is given. Define L pc as the diameter of the crater formed on the surface of the medium, L p as the diameter of the penetration hole, and h p as the depth of the crater. The shaded area represents the damage caused by the explosion to the medium. Define L ec as the diameter of the crater formed on the surface after the explosion, and h e as the depth of the crater after the explosion. Defining the above parameters lays the foundation for the subsequent quantitative analysis of the damage weight of the integrated penetration and explosion.

[0055] The RHT model is selected to simulate C30 concrete. This constitutive model is commonly used to analyze concrete structures under impact loads. This model introduces the elastic limit surface, failure surface, and residual strength surface to describe the changes in the initial yield strength, failure strength, and residual strength of concrete. Table 1 gives the RHT model parameters adopted in the present invention.

[0056] Table 1 RHT model parameters of C30 concrete

[0057] Table 1 RHT model parameters of C30 concrete

[0058]

[0059]

[0060] The cartridge case is made of the metal material 30CrMnSiNi2A. The Johnson-Cook model and the GRUNEISEN equation of state are selected. The JC model is generally used to describe the deformation and failure process of metal materials under large strain, high strain rate and high temperature environments. Equation (1) is the GRUNEISEN equation of state, and the values of related parameters are shown in Table 2.

[0061]

[0062] Table 2 Material model and equation of state parameters of 30CrMnSiNi2A cartridge case

[0063] Table 2 Material model and equation of state parameters of 30CrMnSiNi2A cartridge case

[0064]

[0065] The HIGH_EXPLOSIVE_BURN material model for simulating detonation and the JWL equation of state are selected for the TNT charge. Its equation of state is as follows:

[0066]

[0067] The TNT material parameters and the equation of state parameters are shown in Table 3.

[0068] Table 3 Material model and equation of state parameters of TNT charge

[26]

[0069] Table 3 Material model and equation of state parameters of TNT

[0070]

[0071] The LINEAR_POLYNOMIAL linear polynomial equation of state is selected for air:

[0072] p = C0 + C1μ + C2μ 2 + C3μ 3 +(C4 + C5μ + C6μ 2 )E (3)

[0073] Regarding air as an ideal gas, its material parameters and equation of state parameters are shown in Table 4.

[0074] Table 4 Air material model and LINEAR_POLYNOMIAL state equation parameters

[27]

[0075] Table 4 Material model and state equation parameters of air

[0076]

[0077] Figure 4 The concrete medium damage cloud map is given. From the results, it can be seen that after the projectile squeezes and destroys the concrete, the penetrating stress wave is reflected at the bottom to form a tensile wave and produce a collapse effect. When the projectile penetration speed is 450m / s, the bottom is basically intact. When the penetration speed increases to 600m / s, the bottom begins to be damaged. When the penetration speed is 650m / s, a slight collapse effect occurs at the bottom. Figure 5 The penetration depth and velocity time history curves of five working conditions are given. Table 5 gives the concrete damage data and the projectile negative acceleration peak value under different penetration velocities.

[0078] Table 5 Concrete damage data and projectile acceleration peak values ​​under different penetration speed conditions

[0079] Table 5 Target damage and bullet acceleration peak at different penetration speeds

[0080]

[0081] In order to verify the reliability of the volume filling method for calculating the penetration process of inert projectiles, the penetration depth calculation formula proposed by Wang Anbao et al. in 2021 was used to verify the numerical simulation results (Wang Anbao, Deng Guoqiang, Yang Xiumin, et al. A new universal penetration depth calculation formula [J]. China Civil Engineering Journal, 2021, 54 (10): 36-46. doi:10.15951 / j.tmgcxb.2021.10.004

[0082] WANG A B, DENG G Q, YANG X M, et al. A new general penetration depth calculation formula[J]. Chinese Journal of Civil Engineering, 2021, 54 (10): 36 - 46. doi:10.15951 / j.tmgcxb.2021.10.004). Based on the dimensional analysis of concrete penetration by Teland et al., this formula fits the eigenfunction according to 99 groups of large - scale direct concrete penetration test data and verifies the formula with 213 groups of test data. The calculation results of this formula are in good agreement with the test values, and the overall level, reliability rate, and rationality rate are better than empirical formulas such as the Young formula. The specific form is as follows:

[0083] h q / d = K p [0.9823 + 0.4248Z + 0.0604Z 2 (4)

[0084]

[0085]

[0086] Figure 6 The comparison results of the penetration depths calculated by numerical simulation and empirical formula are given. The agreement between the two is good, and the error in the case of different penetration velocities is less than 10%. The numerical calculation results are on the small side, and the error increases with the increase of the penetration velocity. The main reasons for the analysis are as follows: When the penetration velocity is relatively large, obvious deformation failure occurs at the tip of the projectile in the numerical simulation calculation (see Figure 4 (f)), and the penetration ability decreases compared with the test.

[0087] Through the numerical simulation analysis of penetration - static explosion integration, it is found that at the moment when the penetration process ends, the intensity of the penetration stress wave field at measuring point S2 has decreased from the peak value, and the peak value of the superimposed explosion stress wave field at this moment is not significantly increased compared with the explosion wave field after the penetration is completely over (only increased by 4.2% and 4.5%). To better study the explosion superposition effect at the peak moment of the penetration wave field, the explosion moment can be set at the peak moment of the penetration wave field or near it. At this time, the projectile is in the middle of penetration, and the explosive explodes when it has a certain kinetic energy, that is, penetration - dynamic explosion integration. The present invention first conducts numerical simulation analysis of penetration - dynamic explosion integration for the working conditions of initiating detonation at different moments during the penetration process of projectiles with the same velocity, and then conducts comparative analysis for the working conditions of initiating detonation at the same penetration depth moment for projectiles with different velocities, in order to clearly and intuitively give the changes in the stress wave field and the differences in damage effects in the medium during the penetration - dynamic explosion integration process.

[0088] Taking the working condition of penetration velocity of 650 m / s as the research object, according to Figure 7 the given pressure-time curve, the pressure peak of the penetration field is reached at the measuring point S2 at 0.76 ms, and the initiation times of the penetration dynamic explosion are set to 0.5 ms, 0.76 ms and 1.32 ms (when the penetration velocity just drops to zero). Figure 8 The macroscopic damage cloud maps of the concrete medium at different explosion times are given. The damage differences caused by the three initiation times are relatively obvious. When the explosion occurs at 0.50 ms, the crater diameter on the surface is the largest and the penetration depth is the smallest; when the explosion occurs at 1.32 ms, the crater diameter on the surface is the smallest and the penetration depth is the largest.

[0089] Figure 9 The pressure-time curves of the measuring point S2 at different initiation times are given. When the initiation occurs at 0.5, 0.76 and 1.32 ms, the peak pressures are 14.4, 15.7 and 16.4 MPa respectively. Although the explosive detonates at the peak moment of the penetration pressure field (0.76 ms), the peak value of the measuring point S2 does not reach the highest. The main reasons are as follows: 1. At the peak moment of the penetration field pressure, the projectile does not reach the maximum penetration depth, and the explosion energy coupled into the concrete medium downward at this time is less than the case of explosion at the maximum penetration depth. 2. Although the dynamic explosion effect will increase the explosion pressure field in the velocity direction, the explosion distance between the projectile and the measuring point S2 is still relatively far compared with that at the maximum penetration depth at this time, and the pressure field enhanced by the dynamic explosion is weaker than the influence of the explosion distance.

[0090] Figure 10The concrete damage weights at different detonation times are given. Table 6 specifically gives the concrete damage data and peak pressure of the measuring point at different detonation times when the penetration speed is 650m / s. In terms of surface pitting, the diameter of the surface penetration pit under the 0.5ms working condition is 4.07cm, and the pit increases to 10.3cm after the explosion; the diameter of the surface penetration pit under the 0.76ms working condition is 7.33cm, and the pit increases to 9.8cm after the explosion; the diameter of the surface penetration pit under the 1.32ms working condition is 9.12cm, and the pit increases to 9.4cm after the explosion. The later the detonation time, the longer the evolution time of the penetration effect, and the larger the diameter of the penetration pit. However, due to the increase in penetration depth, the contribution of the explosion effect to the surface pitting is smaller. On the whole, the later the detonation time, the smaller the surface pitting. In terms of pit depth, the penetration depth of the 0.5ms condition is 18.9cm, and the depth increases to 20.8cm after the explosion; the penetration depth of the 0.76ms condition is 22.0cm, and the depth increases to 23.8cm after the explosion; the penetration depth of the 1.32ms condition is 23.2cm, and the depth increases to 24.7cm after the explosion. The later the detonation time, the greater the penetration depth. At the same time, the smaller the contribution of the explosion effect to the pit depth. On the whole, the later the detonation time, the greater the pit depth. The above research results show that for target damage such as airport runways that focuses on the size of the surface pit, the detonation time should not be too late. For target damage such as underground structures that focuses on the intensity of ground stress waves or the depth of the pit, the detonation time should be set to the moment when the projectile velocity just drops to zero.

[0091] Table 6 Concrete damage data and peak pressure at measuring points at different detonation times

[0092] Table 6 Surface crater diameter and pressure peak under different explosion time at penetration speed of 650m / s

[0093]

[0094] To further illustrate the dynamic explosion effect in concrete media, this paper conducts a comparative analysis of the conditions where projectiles with different speeds detonate at the same penetration depth. Five initial penetration velocities of 450, 500, 550, 600, and 650 m / s are used, and the explosion occurs when the projectile penetration depth is 0.155 m (the final penetration depth of the 450 m / s condition). The numerical model is the same as that in Section 4, and the S1 measuring point is selected to observe the pressure changes during the explosion process.

[0095] Figure 11The damage cloud maps of concrete medium under 5 working conditions when detonating at the same position are given. It can be directly seen from the figures that when the penetration velocity is relatively small, transverse cracks are generated on the concrete surface, and the diameter of the surface crater is relatively large. After the velocity increases, the diameter of the surface crater gradually decreases, and the explosion damage area gradually develops downward. The reason for the analysis is that the dynamic explosion effect in the concrete medium has the same nature as that in the air, that is, the explosion shock wave field presents an irregular spherical distribution, and the intensity of the explosion wave field in the velocity direction is positively correlated with the velocity magnitude, and the wave field intensity in the opposite direction is negatively correlated with the velocity.

[0096] Figure 12 The time history curves of the pressure at measuring point S1 under 5 penetration velocity working conditions are given. The higher the penetration velocity, the earlier the projectile reaches the specified penetration depth, the earlier the explosion occurs, and the stronger the dynamic explosion effect of the projectile. Therefore, the peak pressure of the penetration-explosion composite wave field under the 650 m / s working condition is the largest, which is 30.63 MPa. The peak pressures under the 600, 550, 500, and 450 m / s working conditions decrease in turn, which are 27.96, 27.54, 25.64, and 24.61 MPa respectively. The peak pressure under the 650 m / s working condition increases by 24.5% compared with that at 450 m / s, further indicating that the dynamic explosion effect has a non-negligible impact on the explosion shock wave field.

[0097] Figure 13 The concrete damage weights under 5 different penetration velocity working conditions are given. Table 7 specifically gives the corresponding detonation time and the remaining velocity of the projectile, as well as data such as the penetration crater diameter of the concrete medium, the crater diameter after explosion, the penetration depth, and the crater depth after explosion. In terms of surface cratering, although the penetration crater diameter under the 5 working conditions is positively correlated with the initial penetration velocity, the increment of the surface crater after explosion is negatively correlated with the initial penetration velocity. Considering the two surface cratering effects of penetration and explosion comprehensively, the greater the penetration velocity, the smaller the surface crater diameter. In terms of crater depth, the penetration crater depth under the 5 working conditions is 15.5 cm, and the increment of the depth after explosion is positively correlated with the penetration velocity. It can be seen from Figure 13 (b) that although the explosive equivalent is the same, the dynamic explosion effect can significantly increase the crater depth after explosion. Considering the two crater depth effects of penetration and explosion comprehensively, the greater the penetration velocity, the greater the crater depth. The weight analysis of the two damage effects of penetration and explosion shows that if the penetration-explosion projectile is set to explode at a fixed penetration depth (programmable intelligent multi-purpose fuse PIMPF), for the damage of targets that pay attention to the size of the surface crater such as airport runways, the impact velocity should not be too large. For the damage of targets that pay attention to the intensity of ground stress waves or crater depth such as underground bunkers, the impact velocity is the greater the better, so as to make full use of the dynamic explosion effect to enhance the explosion effect field in the velocity direction.

[0098] Table 7 Projectile detonation time, remaining velocity and concrete damage data under different penetration velocities

[0099] Table 7 Explosion time, residual velocity and target damage of projectile under different penetration speeds

[0100]

[0101] Based on the model verification of inert projectile penetration, the numerical simulation of the whole process of penetration, dynamic and explosive integration was completed, the changing rules of the internal pressure field of the medium, surface pit formation and penetration depth were given, and the damage weights of the two damage elements of penetration and explosion in the process of penetration and explosion integration were quantitatively analyzed. The specific conclusions are as follows:

[0102] 1. The calculation results of the volume filling method for simulating the penetration of inert bullets into concrete media are in good agreement with the empirical formula and test results. This method can be used to simulate the entire process of static and dynamic explosions of explosive bombs penetrating concrete media.

[0103] 2. When the penetration and dynamic explosion are combined, the explosion shock wave field inside the medium presents an irregular spherical distribution. The explosion wave field intensity in the velocity direction is positively correlated with the velocity, and the wave field intensity in the opposite direction is negatively correlated with the velocity. Under the influence of the dynamic explosion effect, the contribution weights of penetration and explosion to the surface crater diameter and crater depth show more complex changes and connections. On the whole, under the condition of fixed target impact speed, the later the detonation time, the smaller the surface crater and the greater the crater depth; under the condition of fixed detonation depth, the greater the target impact speed, the smaller the surface crater and the greater the crater depth.

[0104] The advantages of the present invention are as follows:

[0105] 1. The volume filling-based simulation method of the present invention does not need to use restarting, and truly achieves integrated penetration and explosion simulation. It also solves the problems of initial mesh penetration of explosive materials and inability to coordinate deformation with the projectile, and has high simulation accuracy.

[0106] 2. The present invention can set the shell material properties according to actual conditions, without setting the shell as a rigid body in the penetration stage, so as to analyze the secondary damage of the fragments to the structure during the dynamic explosion process, and simulate more closely the actual working conditions.

[0107] 3. The present invention can analyze the coupling effect between the penetration field and the explosion field, study the influence of the shell, penetration field and explosion field on the damage response in the penetration dynamic explosion, and solve the problems of difficulty in experimental measurement, recording and analysis of the damage data of each process of penetration and explosion and difficulty in quantifying the damage weight of each part.

[0108] 4. The present invention can be used to study the damage of most structures such as airports, underground structures, and underwater facilities under dynamic explosion, which is suitable for wide promotion and application. Compared with the dynamic explosion tests with high difficulty and high cost, the present invention plays a certain role in promoting the current status of dynamic explosion research.

[0109] The parts not detailed in the present invention are prior arts.

[0110] The embodiments selected herein for disclosing the invention object of the present invention are considered to be suitable at present. However, it should be understood that the present invention is intended to include all variations and improvements of all embodiments falling within the scope of this concept and invention.

Claims

1. A penetration and dynamic explosion integrated simulation method based on the volume filling method, characterized in that: The method is to set up ALE grids of air material in the entire background area of the model. At the initial position of the projectile penetration, the explosive material is filled into the projectile cavity area by using the volume filling method, and at the same time, it is given the same initial penetration velocity as the projectile shell. During the penetration process of the projectile, the fluid-structure interaction algorithm is set to constrain the grids of the explosive material and the projectile shell, so that the explosive material not only maintains the same change in penetration velocity as the projectile shell, but also coordinates with the deformation of the projectile shell without leakage from the inside to the outside. When the projectile reaches the preset velocity, penetration depth, and acceleration states during the penetration process, the time points corresponding to each state can be obtained through the pre-calculation of a single penetration process. Finally, by controlling the detonation time, the dynamic or static detonation in the medium is caused.

2. The penetration and dynamic explosion integrated simulation method based on the volume filling method according to claim 1, characterized in that: The volume filling method is to assign the filling material and material velocity to the ALE grid by using the keyword INITIAL_VOLUME_FRACTION_GEOMETRY, divide the ALE grid of the explosive material according to the size of the projectile cavity, and fill the projectile cavity with the explosive material. The specific operation steps are as follows: (1) Establish an ALE air domain covering the entire penetration trajectory and explosion area to provide a sufficient range of fluid medium for the fluid-structure interaction calculations in both the penetration and explosion stages; (2) According to the size of the projectile cavity, divide the area filled with explosives in the air domain. In this process, the model grid should be accurately divided to prevent the explosive from overlapping with the projectile shell, which may affect the energy propagation during the explosion; (3) Fill the divided area with explosive material and at the same time give the explosive the same motion velocity as the projectile shell; (4) Establish Lagrange grids of the projectile shell on the periphery of the explosive area, and set the fluid-structure interaction algorithm for the penetration process through the keyword CONSTRAINED_LAGRANGE_IN_SOLID. The main media are the explosive and air, and the secondary medium is the projectile shell. Establish Lagrange grids of the target medium under the projectile, and also set the fluid-structure interaction algorithm for the explosion process through CONSTRAINED_LAGRANGE_IN_SOLID. The main media are the explosive and air, and the secondary media are the projectile shell and the target medium.

3. The penetration and dynamic explosion integrated simulation method based on the volume filling method according to claim 1, characterized in that: The projectile shell is made of the metal material 30CrMnSiNi2A.

Images