Calculation method of environmental damage elastic modulus of surface coatings on cross-scale and cross-domain vehicles

Abstract

The present invention relates to the technical field of aircraft surface coatings, and specifically discloses a cross-scale and cross-domain aircraft surface coating environmental damage elastic modulus calculation method, comprising the following steps: constructing an initial model of a cubic single crystal of a surface coating alloy, simulating the damage process of the coating material in an actual environment, establishing a finite element model of a polycrystalline alloy coating material, simulating the mechanical behavior at the microscale through molecular dynamics, utilizing mesoscopic mechanics verification and macroscopic finite element simulation, and comprehensively considering the influence of different environmental damages on the elastic modulus of the coating material, providing a theoretical basis and technical support for the performance evaluation, design optimization and reliability analysis of the cross-domain aircraft surface coating during long-term service, thereby helping to extend the service life of the coating material and improve the overall performance and safety of the aircraft.

Description

Technical Field

[0001] The present invention belongs to the technical field of aircraft surface coatings, and in particular relates to a method for calculating the environmental damage elastic modulus of a cross-scale and cross-domain aircraft surface coating. Background Art

[0002] With the continuous advancement of aerospace technology, cross-domain vehicles often face increasingly harsh environmental conditions when performing complex missions. In diverse environments such as high altitude, the atmosphere, the deep sea, and even outer space, vehicle surface coatings, as key protective materials, not only withstand external physical and chemical stresses but are also exposed to a variety of environmental factors, including temperature changes, pressure fluctuations, seawater corrosion, and mechanical shock.

[0003] These factors may cause defects such as micropores and microcracks in the coating, thereby affecting the mechanical properties and service life of the aircraft.

[0004] Therefore, studying and evaluating the changes in the elastic modulus of coating materials under complex environmental damage is of great strategic significance for the design optimization of spacecraft and the reliability assurance in long-term service.

[0005] In recent years, molecular dynamics (MD) simulation methods have become an indispensable tool in materials research, with significant advantages at the microscopic scale. By accurately tracking the motion trajectories of atoms or molecules under external forces, molecular dynamics methods can simulate the micromechanical behavior of materials under environmental damage. In particular, they can provide in-depth mechanistic analysis of atomic-level damage (such as point defects, micropores, and microcracks). Through molecular dynamics simulations, the stress state of materials under environments such as radiation, pressure changes, or corrosion can be obtained, providing an important reference for understanding the degradation of material properties.

[0006] However, coating material damage isn't limited to the microscopic level; in actual service, materials are also subject to complex multi-physics coupling. For example, when a vehicle's surface coating is subjected to environmental factors such as external pressure, heat flow, corrosion, and radiation, its macroscopic mechanical properties can also undergo significant changes. Therefore, relying solely on molecular dynamics methods or traditional macroscopic mechanical analysis methods to analyze changes in the elastic modulus of coating materials is insufficient.

[0007] To this end, finite element simulation (FEM), as an effective numerical calculation tool, can analyze the coupling effects of multiple physical fields at a macroscale and study the influence of external environmental factors (such as pressure and temperature) on the mechanical properties of coating materials. By establishing complex geometric and material models, the finite element method can simulate the deformation and damage behavior of materials under different environmental loads, thus compensating for the shortcomings of molecular dynamics simulation at the macroscale.

[0008] Most existing studies focus on analyzing the impact of a single environmental factor on material properties, and lack a comprehensive evaluation of the changes in the elastic modulus of coating materials under various environmental damages. Summary of the Invention

[0009] The purpose of the present invention is to provide a cross-scale and cross-domain method for calculating the environmental damage elastic modulus of the surface coating of an aircraft to solve the problems raised in the above background technology.

[0010] To achieve the above object, the present invention provides the following technical solutions:

[0011] A cross-scale and cross-domain calculation method for the environmental damage elastic modulus of a surface coating of a vehicle includes the following steps:

[0012] S1. Construct an initial model of a cubic single crystal of surface-coated alloy and optimize the structure through Nose-Hoover temperature control to obtain a structurally stable base alloy model.

[0013] S2. Simulate the damage process of coating materials in the application environment. Set a pressure gradient and simulate the generation and evolution of micropores and pre-crack defects using molecular dynamics methods. For each particle in the coating material, establish an interaction list of neighboring particles within a certain range, and calculate the particle's motion trajectory under the influence of environmental damage. By analyzing the displacement evolution of each particle at different motion trajectories, identify the development trend of micropores and microcracks within the coating, and then determine their damage density in the entire coating.

[0014] S3. Based on existing defects and targeting different degrees of environmental damage, the concentration of microscopic defects is adjusted to further simulate the defect evolution of the coating material under long-term service. Experimental parameters are used to rationally design the location of lost atoms and establish dislocations, creating more micropores and pre-cracks, and forming high-concentration defects. Molecular dynamics methods are used to test the elastic modulus of the coating material under variable pressure.

[0015] S4. Establish a finite element model of the polycrystalline alloy coating material; using the basic mechanical parameters of the coating material at different damage levels obtained in S3 as input, perform a finite element uniaxial tensile test on the polycrystalline alloy coating material to obtain a stress-strain curve under elastic deformation, and obtain a macroscopic elastic modulus by curve fitting;

[0016] S5. Based on the multi-scale simulation results, a calculation model of the elastic modulus of the coating material under the coupling of multiple physical fields (such as pressure changes and seawater corrosion) is constructed to realize the prediction of the elastic modulus of the coating material under complex environmental damage.

[0017] Preferably, an isothermal and isobaric ensemble is used for relaxation in S1 to simulate the effect of actual environmental pressure changes on the coating material.

[0018] Preferably, the actual environment simulated in S2 includes but is not limited to pressure changes, seawater corrosion, and mechanical collision environment. When simulating the defect evolution process in the seawater corrosion environment, the microcanonical ensemble is used to maintain the conservation of system energy.

[0019] Preferably, in S2, when simulating the generation of defects in the coating material under environmental damage, the total simulation time and total number of steps are set; when the set total simulation time or total number of steps is reached, the simulation is stopped, and the defect distribution of the coating material is identified based on the atomic state parameters at this time.

[0020] Preferably, in S1, more than 500,000 atoms are used to construct a cubic single crystal initial model of the coating material to improve calculation accuracy and simulation effect.

[0021] Preferably, the Wigner-Seitz cell method is used to identify microscopic defects, including microvoids, microcracks and dislocations.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] Not only does it consider the influence of single environmental factors (such as pressure changes, seawater corrosion, and mechanical collisions) on the performance of coating materials, but it also comprehensively considers the changes in elastic modulus under the coupling of multiple environmental factors, providing an evaluation result that is closer to the actual service environment, and providing a more accurate basis for the design and optimization of coating materials. At the same time, by using more than 500,000 atoms to construct a cubic single crystal initial model of the coating material, and using an isothermal and isobaric ensemble to simulate the actual environmental pressure changes during the relaxation process, the calculation accuracy and simulation effect are improved.

[0024] This invention combines the microscopic accuracy of molecular dynamics simulation with the macroscopic effectiveness of finite element simulation, enabling cross-scale analysis from the microscopic to the macroscopic. This facilitates a more comprehensive understanding of the damage mechanisms and mechanical property variations of coating materials at different scales, providing innovative solutions for the design optimization of surface coatings for cross-domain vehicles and for reliability analysis during long-term service. This helps extend the service life of coating materials and improve the overall performance and safety of vehicles. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of the cross-scale calculation flow chart of the material modulus under harsh environments of the present invention;

[0026] Figure 2 This is a flow chart of the cascade collision molecular dynamics simulation of environmental damage in an embodiment of the present invention;

[0027] Figure 3 Schematic diagram of the finite element geometric model of the two-dimensional polygonal grain of the alloy in an embodiment of the present invention. DETAILED DESCRIPTION

[0028] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0029] Example:

[0030] See also Figures 1 to 2 As shown in the figure, the calculation method of environmental damage elastic modulus of cross-scale and cross-domain vehicle surface coating is as follows:

[0031] (1) First, construct the initial model of the single crystal alloy atomic system, a cubic model composed of a large number of atoms, select the crystal orientation, force field, and give the initial position, initial velocity, and neighboring atoms of the atoms;

[0032] Set the initial temperature and initial pressure, and set the isothermal and isobaric ensemble;

[0033] The structure is optimized to the equilibrium state. Within the integration time t0, τ0 is adjusted to ensure that the moving distance of any particle within the time step is less than the initial setting requirement.

[0034] (2) Calculate the optimal solution for the displacement of particles with different initial displacements in the stable structure. The specific steps are as follows:

[0035] (2.1) Select the central atom as the primary delocalized particle, give the rebound velocity, and fix the direction of movement of the primary delocalized particle;

[0036] (2.2) Set up the ensemble in the damage simulation and give the total simulation time t A , total number of steps N A ;

[0037] (2.3) Determine when simulation time t1≤t A And the simulation step size N1≤N A If yes, go to step (2.4), otherwise go to step (2.6).

[0038] (2.4) The motion state is obtained by constructing an interaction list of neighboring particles within a certain range;

[0039] (2.5) Calculate and update the position and velocity of each particle in the system, assign t1 = t1 + τ, N1 = N1 + 1, update the interaction list, and return to step (2.2);

[0040] (2.6) Record the particle state parameters of the system, and then set different initial delocalized atomic energies E kIf k>M, stop the simulation, otherwise simulate time t1, the number of steps N1 is reset to zero and return to step (2.1);

[0041] (3) By designing particle micropores, vacancies are introduced into the system, microcracks are established, and the elastic modulus of micropores and microcracks under different concentrations and external loads is studied.

[0042] The present invention introduces vacancies into the obtained cascade collision particle system file by constructing a uniform defect distribution method, thereby ensuring local concentration while increasing the overall defect concentration of the system, and solving the problem of microstructural defect simulation of materials under environmental damage.

[0043] Mechanical properties of damaged samples were tested under external loads, with a set strain rate. Stress-strain curves were fitted to obtain the tensile and compressive moduli of the samples. The relationship between the fitted tensile and compressive moduli and damage concentration was compared with the effective modulus of damaged materials from the self-consistent theory of damage based on micromechanics to verify the reliability of the molecular dynamics simulation results.

[0044] (4) A polycrystalline finite element analysis model was established, and the mechanical parameters of the single crystal alloy environmental damage were assigned through random material properties. A uniaxial tensile test was performed to obtain the polycrystalline stress-strain curve under elastic deformation, and the macroscopic mechanical elastic modulus of the material under environmental damage was obtained through curve fitting.

[0045] By setting up scripts to establish a finite element polycrystalline geometric model, the matrix is ​​established and the matrix is ​​cut through library functions to achieve random polygonal grain geometric modeling.

[0046] Assign material properties to the polycrystalline geometry model and use the micromechanical parameters of the single crystal alloy at different damage concentrations from the molecular dynamics simulation results as input. The specific steps are as follows:

[0047] (4.1) Assign random orientation;

[0048] (4.2) Establish sect ion;

[0049] (4.3) Assign the sect i on to a grain;

[0050] (4.4) Repeat (4.1), (4.2), and (4.3) until all grains have material properties.

[0051] A uniaxial stress tensile state is applied to the polycrystal finite element model to obtain the stress-strain curve of the polycrystal under elastic deformation. The macroscopic mechanical elastic modulus of the material under different environmental damage is obtained by curve fitting.

[0052] This study uses molecular dynamics to simulate the changes in mechanical properties of coating materials after environmental damage, deriving the relationship between elastic constants and defects such as microvoids and microcracks. A comparative analysis based on micromechanical damage theory verifies the reliability of the method.

[0053] Gaussian is a powerful, comprehensive software package widely used in quantum chemistry calculations. It performs semi-empirical and ab initio calculations, addressing numerous topics in chemistry, such as molecular orbital calculations, structure optimization, transition state searches, thermodynamic property analysis, dipole and multipole moment calculations, electron density and potential analysis, polarizability and hyperpolarizability calculations, infrared and Raman spectral predictions, NMR calculations, vertical ionization energy and electron affinity calculations, chemical reaction mechanism studies, potential energy surface and excitation energy calculations, and QM / MM calculations. Temperature-controlled relaxation is a common method in molecular dynamics simulations, used to simulate the thermal equilibrium state of a system at a specific temperature.

[0054] Molecular dynamics simulation is a computer simulation technology that can simulate the movement of atoms and molecules to predict the macroscopic properties of materials. Through molecular dynamics simulation, the movement trajectories of atoms in coating materials can be tracked and the generation and evolution of defects such as micropores and pre-cracks can be observed.

[0055] In order to simulate and analyze the mechanical behavior of polycrystalline alloy coating materials on a computer, it is first necessary to establish a finite element model that can reflect its microstructure and macroscopic properties.

[0056] Using the finite element method, the polycrystalline alloy coating material is divided into many small, interconnected units (i.e., finite elements), each of which represents a small part of the material. By defining the geometry of these units, their material properties (such as elastic modulus, Poisson's ratio, etc.), and the way they are connected, a finite element model that can simulate the behavior of the entire coating material can be constructed.

[0057] Environmental damage to coatings involves multi-physics and multi-scale processes. For polycrystalline constitutive problems involving small microvoid strains, a polycrystalline geometric model is constructed, the microstructure mesh of the polycrystalline structure is parameterized, and randomly oriented material properties are assigned to each grain. A tensile model of the polycrystalline alloy coating is then established, and the stress-strain relationship is calculated. Using cloud-based macroscopic visualization and unit-level statistical analysis, the impact of environmental damage on the macroscopic mechanical constitutive relationship is studied.

[0058] In summary, the present invention significantly improves the accuracy and reliability of the calculation of the environmental damage elastic modulus of the surface coating of cross-domain vehicles by comprehensively considering multiple environmental damage factors, improving calculation accuracy and simulation effects, realizing cross-scale analysis, introducing accurate defect identification methods, and providing innovative solutions for design optimization and reliability analysis. It has broad application prospects and important practical value.

[0059] It will be appreciated that in the development of any actual embodiment, as in any engineering or design project, numerous implementation-specific decisions may be made. Such a development effort may be complex and time-consuming, but will, for those of ordinary skill having the benefit of this disclosure, be a routine undertaking of design, fabrication, and production without undue experimentation.

[0060] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A cross-scale and cross-domain method for calculating the environmental damage elastic modulus of surface coatings on aircraft, characterized by: The following steps are involved: S1. Construct an initial model of a cubic single crystal of surface-coated alloy and optimize the structure through Nose-Hoover temperature control to obtain a structurally stable base alloy model. S2. Simulate the damage process of coating materials in the application environment. Set a pressure gradient and simulate the generation and evolution of micropores and pre-crack defects using molecular dynamics methods. For each particle in the coating material, establish an interaction list of neighboring particles within a certain range, and calculate the particle's motion trajectory under the influence of environmental damage. By analyzing the displacement evolution of each particle at different motion trajectories, identify the development trend of micropores and microcracks within the coating, and then determine their damage density in the entire coating. S3. Based on existing defects and targeting different degrees of environmental damage, the concentration of microscopic defects is adjusted to further simulate the defect evolution of the coating material under long-term service. Experimental parameters are used to rationally design the location of lost atoms and establish dislocations, creating more micropores and pre-cracks, and forming high-concentration defects. Molecular dynamics methods are used to test the elastic modulus of the coating material under variable pressure. S4. Establish a finite element model of the polycrystalline alloy coating material; using the basic mechanical parameters of the coating material at different damage levels obtained in S3 as input, perform a finite element uniaxial tensile test on the polycrystalline alloy coating material to obtain a stress-strain curve under elastic deformation, and obtain a macroscopic elastic modulus by curve fitting; S5. Based on the multi-scale simulation results, a calculation model of the elastic modulus of the coating material under multi-physical field coupling is constructed to predict the elastic modulus of the coating material under complex environmental damage. The physical fields include but are not limited to pressure changes and seawater corrosion.

2. The cross-scale and cross-domain calculation method for environmental damage elastic modulus of surface coatings of a cross-domain vehicle according to claim 1 is characterized by: In the S1, an isothermal and isobaric ensemble is used for relaxation to simulate the effect of actual environmental pressure changes on the coating material.

3. The cross-scale and cross-domain calculation method for environmental damage elastic modulus of surface coatings of a cross-domain vehicle according to claim 1 is characterized by: The actual environment simulated in S2 includes but is not limited to pressure change, seawater corrosion, and mechanical collision environment. When simulating the defect evolution process under the seawater corrosion environment, the microcanonical ensemble is used to maintain the conservation of system energy.

4. The cross-scale and cross-domain calculation method for environmental damage elastic modulus of surface coatings of a cross-domain vehicle according to claim 1 is characterized by: In the S2, when simulating the generation of defects in the coating material under environmental damage, the total simulation time and the total number of steps are set; when the set total simulation time or total number of steps is reached, the simulation is stopped, and the defect distribution of the coating material is identified based on the atomic state parameters at this time.

5. The cross-scale and cross-domain calculation method for environmental damage elastic modulus of surface coatings of a cross-domain vehicle according to claim 1 is characterized by: In the S1, more than 500,000 atoms are used to construct a cubic single crystal initial model of the coating material to improve calculation accuracy and simulation effect.

6. The cross-scale and cross-domain calculation method for environmental damage elastic modulus of surface coatings of a cross-domain vehicle according to claim 1 is characterized by: The Wigner-Seitz cell method is used to identify micro defects including microvoids, microcracks and dislocations.

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