Microscale projectile-bore impact behavior modeling method

Abstract

This invention belongs to the field of barrel life research, specifically disclosing a microscale projectile-barrel impact behavior modeling method. This method includes identifying the atomic composition and atomic mass fraction of the projectile-barrel material; determining the potential energy trap depth and zero-potential-energy interatomic spacing of each component atom; determining the two-body potential energy function between atoms in the projectile-barrel material; establishing the polycrystalline structure of the projectile-barrel material; establishing a crystal model of the projectile-barrel material; and solving the microscale projectile-barrel impact behavior using the momentum mirror method. Compared with existing technologies, this invention establishes a model of the projectile-barrel impact behavior of the barrel material from a microscale modeling perspective, improves the two-body potential energy function between atoms in the projectile-barrel material, and links molecular dynamics and impact dynamics, laying the foundation for the study of the mechanism of plastic damage in the barrel bore.

Description

Technical Field

[0001] This invention belongs to the field of cyclic impact fatigue life research of the barrel, and specifically relates to a microscale projectile-barrel impact behavior modeling method. Background Technology

[0002] Improving the service life of weapon barrels has always been an important direction in weapons research. Although current mainstream methods such as hydraulic self-tightening and gradient chrome plating have shown some effectiveness, the lack of research on the impact plastic damage mechanism of the barrel bore has resulted in far from ideal improvements in barrel service life. Due to the specialized nature of weapon barrels, interdisciplinary integration is often more difficult, leading to research on the impact plastic damage behavior of the barrel bore remaining largely based on empirical summaries of experimental data. This empirical approach has become the fundamental reason limiting the improvement of weapon barrel service life.

[0003] Currently, there are two main methods for modeling projectile-barrel impact behavior: macroscopic surface-to-surface impact behavior modeling based on Herzt and Lankarani-Nikravesh contact theory, and mesoscopic crystal plastic finite element impact behavior modeling based on experimental data. The former is applicable to the macroscopic scale, while the latter is applicable to both macroscopic and mesoscopic scales. Both are essentially phenomenological models and cannot accurately describe the mechanistic aspects of impact behavior. Summary of the Invention

[0004] The purpose of this invention is to provide a microscale projectile-barrel impact behavior modeling method to combine molecular dynamics and impact dynamics, lay the foundation for the study of plastic damage mechanism in barrel bore, and promote interdisciplinary integration, injecting new vitality into the field of artillery.

[0005] The technical solution for achieving this invention is: a microscale projectile-barrel impact behavior modeling method, the specific steps of which are as follows:

[0006] Step 1: Identify the atomic composition and atomic mass fraction of the projectile-tube material;

[0007] Step 2: Determine the interatomic potential energy trap depth and zero potential energy interatomic spacing for each component;

[0008] Step 3: Determine the interatomic two-body potential energy function of the projectile-barrel material;

[0009] Step 4: Establish the polycrystalline structure of the projectile-tube material using polycrystalline modeling software;

[0010] Step 5: Establish a crystal model of the projectile-tube material based on the polycrystalline structure model and the two-body potential energy function;

[0011] Step 6: Solve the microscale projectile-barrel impact behavior using the momentum mirror method.

[0012] The significant advantages of this invention compared to existing technologies are:

[0013] (1) The microscale projectile-barrel impact behavior modeling method established in this invention focuses on projectile-barrel impact behavior from the perspective of microscale modeling, laying the foundation for the study of the mechanism of projectile impact on barrel.

[0014] (2) The microscale projectile-barrel impact behavior modeling method established in this invention improves the interatomic two-body potential energy function of the projectile-barrel material (PCrNi3MoVA) based on DFT (density functional theory) calculation, thereby ensuring the correctness of the microscale projectile-barrel impact behavior model.

[0015] (3) The microscale projectile-barrel impact behavior modeling method established in this invention links molecular dynamics and impact dynamics, laying the foundation for the study of the mechanism of plastic damage in the barrel bore and has broad engineering application prospects. Attached Figure Description

[0016] Figure 1 A strategy for modeling the polycrystalline structure of projectile-tube materials;

[0017] Figure 2 It is a polycrystalline structure of projectile-barrel material. Figure 2 (a) shows the atomic composition in the polycrystalline structure. Figure 2 (b) represents grain boundaries in a polycrystalline structure;

[0018] Figure 3 A modeling strategy for crystal models of projectile-tube materials based on polycrystalline structure and potential energy function;

[0019] Figure 4 This is a crystal model in a relaxed state. Figure 4 (a) is the crystal model in the relaxed state after the initial modeling. Figure 4 (b) is the crystal model in the relaxed state after adjusting the potential function;

[0020] Figure 5 The tensile stress-strain law of the microscale crystal model of the projectile-tube material.

[0021] Figure 6 The "momentum mirror" method is used to solve the microscopic projectile-barrel impact behavior. Detailed Implementation

[0022] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0023] The specific steps for determining the potential energy functions of each atom in the microscale projectile-tube material are as follows:

[0024] Step 1: Identification of atomic composition and atomic mass fraction of projectile-barrel materials;

[0025] The identification of atomic composition and atomic mass fraction of projectile-tube materials refers to the process of using inductively coupled plasma atomic emission spectrometry (ICP) to detect the atomic composition of projectile-tube materials for a specified type of tooling, and using energy dispersive X-ray spectroscopy (EDS) in conjunction with scanning electron microscopy to calibrate the atomic mass fraction of the projectile-tube materials. The atomic composition of the projectile and tube materials is related to the calculation of the potential energy trap depth of the atomic interactions of each component and the zero-potential interatomic spacing (i.e., two-body potential), while the atomic composition and atomic mass fraction are related to the establishment of the microscopic crystal model. The specific atomic composition and atomic mass fraction of the projectile-tube materials are shown in Table 1.

[0026] Table 1. Atomic components and mass fractions of projectile-tube materials

[0027] element Fe Cr Ni Mo V mass fraction / % 94.5 2.8 0.9 1.4 0.4

[0028] Step 2: Determine the interatomic potential energy trap depth and zero potential energy interatomic spacing for each component;

[0029] In practical applications, by fitting the potential energy functions of existing elements using density functional theory (DFT), the zero-potential interatomic spacing σ and the potential well depth ξ of each component can be obtained. The approximate fitting formula is as follows:

[0030]

[0031] In the formula σ A , σ B ξ represents the zero-potential interatomic distance between two different atoms A and B, which can be obtained by consulting the literature; A ξ B These represent the potential energy trap depths of two different atoms, A and B, respectively. These values ​​can be obtained by consulting the literature.

[0032] The interatomic potential well depths and zero-potential-energy interatomic spacings are shown in Table 2:

[0033] Table 2. Depth of interatomic potential energy traps and zero-potential-energy interatomic spacing.

[0034]

[0035] Step 3: Determine the interatomic two-body potential energy function of the projectile-barrel material;

[0036] The potential energy function of the two-body potential between atoms in the projectile-tube material directly affects the accuracy of the microcrystalline modeling of the projectile-tube. The relevant parameters of the two-body potential include the atomic potential well depth and the zero-potential two-body distance. Molecular dynamics (MD) simulations use Newtonian mechanics to describe the motion of a group of particles (usually atoms), and the forces acting on the particles are obtained by differentiating the total potential energy of the system with respect to its coordinate variables. Right now

[0037]

[0038] In the formula, U is the total potential energy of the entire system; Let i,j ∈ Ω & i ≠ j, and Ω be the set of all particles.

[0039] The formula for total potential energy is as follows:

[0040]

[0041] In the formula Let i,j,k∈Ω&i≠j≠k. For the potential energy of a single entity, The potential energy is the potential energy of the two bodies. This refers to the three-body potential energy. The two-body and three-body potential energies originate from the interactions between particles, determining the properties of the entire system and serving as a prerequisite for the accuracy of molecular dynamics (MD). In practice, these potentials are usually expressed as an analytical function, with parameters obtained by fitting experimental results and first-principles calculations. The two-body potential energy E between two neutral atoms at a distance l is described by the Lennard-Jones potential:

[0042]

[0043] In the formula, ξ is the depth of the potential energy trap, σ is the distance between two neutral atoms when the interaction potential energy is exactly zero, and l is the distance between neutral atoms. c Let be the interatomic cutoff radius. Combining the approximate fitting formulas for the zero-potential interatomic spacing σ and the potential well depth ξ of each component in step 2, the two-body potential energy E between two neutral atoms at a distance l is:

[0044]

[0045] This allows us to determine the two-body potential energy function of each atom in the tube material.

[0046] Step 4: Establishment of the polycrystalline structure of the projectile-tube material based on the polycrystalline modeling software Atomsk: The basic path for establishing the polycrystalline structure of the projectile-tube material in this embodiment is as follows: Figure 2 As shown, the detailed steps are as follows:

[0047] Step 4.1: Set the compute box size and number of grains, tentatively set to 100nm×100nm×100nm, with a grain count of 32;

[0048] Step 4.2: Establish the unit cell of iron to obtain iron grains; select Fe, the element with the highest atomic mass fraction in the projectile-tube material, and establish the Fe unit cell based on Automsk. Extend the unit cell structure to the grains based on random crystal orientation and Voronoi polygons. At this point, the unit cells within the grain structure have the same crystal orientation.

[0049] Step 4.3: Randomly place grains at locations within the computation box. Consider the "collisions" between grains with different crystal orientations to define grain boundaries. The new structure formed by combining multiple grains with different orientations and the grain boundaries formed by grain "collisions" is the crystal. Furthermore, boundary settings are needed to prevent the filled crystal structure from exceeding the computation box space.

[0050] Step 4.4: Replace some of the Fe atoms in the Fe polycrystalline model based on the atomic composition and atomic composition mass fraction to obtain the complete composite projectile-tube polycrystalline model.

[0051] Step 5: Establish a crystal model of the projectile-tube material based on the polycrystalline structure model and potential energy function; combined with... Figure 3 As shown, based on the polycrystalline structure of the projectile-tube material established in step 4, and combined with the two-body potential energy function of the projectile-tube material determined in step 3, a crystal model of the projectile-tube material is established. The specific steps are as follows:

[0052] Step 5.1: Set the boundary conditions, atom type, time step, and unit system of the calculation box, import the projectile-tube polycrystalline model, and calibrate and verify the relative atomic mass of each element.

[0053] Step 5.2: Divide the established polycrystalline model into regions as needed. The regions must not overlap and the region names must be unique.

[0054] Step 5.3: Based on the two-body potential energy function, set the zero potential energy interatomic spacing and potential energy trap depth of all regions; then set the higher-order volume potential energy function, and then establish the preliminary crystal model of the projectile-tube material;

[0055] The higher-order volume potential energy function can be found in Interatomic Potentials.

[0056] Step 5.4: Perform energy minimization on the initially established projectile-tube material crystal model and conduct relaxation analysis.

[0057] Relaxation refers to the process of gradually returning from a given state to an equilibrium state in a gradual physical process. Relaxation analysis is performed using the open-source molecular dynamics software Lammps. Figure 4 (a) shows the spatial distribution of the crystal structure in the relaxed state after the initial modeling. It can be seen that there are obvious gaps in regions A1 and A2. In particular, in region A1, the crystal model has severe fractures, which is obviously not as expected.

[0058] Step 5.5: Refit the two-body potential energy function, repeating steps 1-4 until a projectile-tube material crystal model that meets expectations is established; the relaxation analysis results after adjusting the potential energy function can be observed as follows: Figure 4 As shown in (b), the cracks in region A1 of the adjusted crystal structure are significantly reduced, and the voids in region A2 are almost completely eliminated. Only when the relaxed crystal model has a balanced spatial distribution and no large-area voids can the established microscale projectile-tube crystal model be usable.

[0059] Combination Figure 5 This study demonstrates the accuracy of the microscale crystal structure of the projectile-tube material. Using the molecular dynamics software Lammps, a 10% strain tensile test was performed on the polycrystalline structure of the projectile-tube material to ensure that the tensile stress-strain curve of the established projectile-tube crystal model starts from 0 MPa, and that the yield strength and its trend are basically consistent with the macroscopic stress-strain law of the tooling material. Figure 5 It can be seen that the stress starting point is basically from 0 MPa, the yield strength is 1100 MPa, and the corresponding strain is 0.3%, which is basically consistent with the yield strength of the projectile-tube material (PCrNi3MoVA). Moreover, the stress also shows a decreasing trend as the strain increases.

[0060] Step 6: Solve the microscale projectile-barrel impact behavior based on the momentum mirror method;

[0061] Combination Figure 6 This section explains the "momentum mirror" method for solving the projectile-barrel impact behavior. For example... Figure 6The upper part shows the established projectile-tube material crystal model, including the projectile material crystal structure on the left and the tube material crystal structure on the right. The two crystal structures are constrained by the external black frame, which is the "computation box". The lower part of Figure (6) is the simplified model of the "momentum mirror" method corresponding to the projectile and tube material crystal models. The impactor corresponds to the projectile material crystal structure, the carrier corresponds to the tube material crystal structure, and the black frame corresponds to the "computation box". The simplified model of the "momentum mirror" method uses the periodic boundary condition PBC on the side of the "computation box" and the non-periodic boundary condition Non-PBC in the impact direction. The simplified model of the "momentum mirror" method regards the impact-compressible continuous material as a material block placed continuously along the impact direction, in which the leftmost projectile material crystal structure is driven by the impact velocity v1. In this case, the projectile material crystal structure moves at a constant velocity v1, and the tube material crystal structure that is first impacted will move at the same velocity as the projectile material crystal structure. However, as the crystal structure of the projectile material moves, the material in front of the crystal structure of the barrel material is "aggregated," that is, the density of the material in front increases. The increase in density will dissipate some of the impact kinetic energy, thereby causing the crystal structure of the barrel material to move forward at a speed of v2.

[0062] In summary, the microscale crystal modeling method for projectile tube materials proposed in this invention is based on the atomic composition of the projectile tube material. It calculates the zero-potential interatomic spacing σ and potential well depth ξ between atoms of each component using DFT (Density Functional Theory), thereby determining the two-body potential energy function between each atom. A polycrystalline model of the projectile tube material is constructed using the polycrystalline modeling software Atomsk along the cell-to-grain-to-crystal (including grain boundaries) route. Based on the polycrystalline structure model and potential energy function, a projectile-tube material crystal model is established. Tensile tests under relaxed conditions are conducted on the polycrystalline model using the molecular dynamics software Lammps to verify the correctness of the established model. Finally, the momentum mirror method is used to solve the microscale projectile-tube impact behavior.

Claims

1. A method for modeling the impact behavior of a projectile-barrel at the microscale, characterized in that, The specific steps are as follows: Step 1: Identify the atomic composition and atomic mass fraction of the projectile-tube material; Step 2: Determine the interatomic potential energy trap depth and zero potential energy interatomic spacing for each component; Step 3: Determine the interatomic two-body potential energy function of the projectile-barrel material; Step 4: Establish a polycrystalline structure model of the projectile-tube material using polycrystalline modeling software; The specific steps are as follows: Step 4.1: Set the compute box size and number of grains; Step 4.2: Fe, the element with the highest atomic mass fraction in the projectile-tube material, is used to establish the unit cell of iron element, thereby obtaining the grains of iron element; Step 4.3: Arrange grains at random positions in the computing box, consider the "collision" between grains with different crystal orientations to divide grain boundaries, and combine multiple grains with different orientations and the grain boundaries formed by grain "collisions" to form a new structure, which is a crystal. Step 4.4: Based on the atomic composition and atomic composition mass fraction, replace some atoms in the polycrystalline model of iron element in Step 4.2 with other atoms in the original projectile-tube material to obtain a complete composite material projectile-tube polycrystalline model; Step 5: Establish a crystal model of the projectile-tube material based on the polycrystalline structure model and potential energy function; The specific steps are as follows: Step 5.1: Set the boundary conditions, atom type, time step, and unit system of the calculation box, import the projectile-tube polycrystalline model, and calibrate and verify the relative atomic mass of each element. Step 5.2: Divide the established polycrystalline model into regions as needed. The regions must not overlap and the region names must be unique. Step 5.3: Based on the two-body potential energy function, set the zero potential energy interatomic spacing and potential energy trap depth for all regions; and then establish a preliminary crystal model of the projectile-tube material. Step 5.4: Perform energy minimization on the initially established projectile-tube material crystal model and conduct relaxation analysis; Step 5.5: Refit the two-body potential energy function and repeat steps 1-4 until a projectile-tube material crystal model that meets expectations is established; Step 6: Solve the microscale projectile-barrel impact behavior using the momentum mirror method.

2. The microscale projectile-barrel impact behavior modeling method according to claim 1, characterized in that, The method for determining the potential energy trap depth and zero-potential-energy interatomic spacing of each component atom in step 2 is as follows: The zero-potential-energy interatomic spacing is obtained by fitting the potential energy functions of the existing elements. and potential energy trap depth The approximate fitting formula is: ； In the formula , The zero-potential interatomic distances for two different atoms A and B were obtained by consulting the literature. , These represent the potential energy trap depths of two different atoms, A and B.

3. The microscale projectile-barrel impact behavior modeling method according to claim 2, characterized in that, In step 3, the two distances are The two-body potential energy E function between neutral atoms is: ； In the formula, l is the neutral atomic spacing, l c This is the interatomic cutoff radius.

4. The microscale projectile-barrel impact behavior modeling method according to claim 1, characterized in that, In step 6, the simplified model of the projectile and barrel material crystal model established by the "momentum mirror" method is the crystal structure of the projectile material corresponding to the impactor, the crystal structure of the barrel material corresponding to the carrier, and the black frame corresponding to the "calculation box".

5. The microscale projectile-barrel impact behavior modeling method according to claim 4, characterized in that, The projectile barrel material is PCrNi3MoVA.

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