Method for calculating friction coefficient of rotary friction alloy by molecular dynamics simulation method

Abstract

The invention discloses a method for calculating the friction coefficient of a rotary friction alloy through a molecular dynamics simulation method. The method comprises the steps that a diamond grinding ball and TiC / Ni composite material matrix model is established; performing structure optimization on the model structure by using conjugate gradient energy minimization to obtain an initial model with stable energy, and performing relaxation under an isothermal isobaric (NVT) ensemble to obtain an energy stable model; a fixed load is applied to the diamond grinding ball under a micro-regularization (NVE) ensemble, and periodic rotating friction is conducted with the Z axis as the axis; the counter-acting force of the base body on the diamond grinding balls is calculated, and the acting force in the X direction, the Y direction and the Z direction is output; combining the acting forces in the X and Y directions to obtain a friction force, and calculating a friction coefficient by combining a Z-axis normal force. According to the method, a diamond grinding ball repeated rotating friction nickel-based composite material model is constructed, friction and wear of the material under the real working condition are better met, and the calculated friction coefficient is more accurate.

Description

Technical Field

[0001] The invention relates to the field of molecular dynamics calculation, and relates to, but is not limited to, a method for calculating the friction coefficient of a rotating friction alloy using a molecular dynamics simulation method. Background Art

[0002] Nickel-based composite materials have good high-temperature strength, thermal fatigue resistance, oxidation resistance and thermal corrosion resistance. They are new composite materials used to manufacture important heat-bearing parts in aviation, ships and industrial gas turbine engines. In particular, nickel-based composite materials doped with carbide phases combine many excellent properties of ceramic materials and nickel-based materials. Among them, nickel-based titanium carbide composite materials are mainly used in high-temperature components with high processing performance and mechanical properties. While not damaging the good performance of nickel-based materials, they have the characteristics of small weight, high temperature resistance, high hardness and corrosion resistance of ceramic materials, which is of great significance to the development of industrial materials. However, nickel-based titanium carbide composite materials often fail due to wear under actual service conditions, and the strengthening mechanism of carbides on nickel-based metal materials is unclear. Therefore, in-depth research on the friction and wear behavior of nickel-based composite materials has very important scientific value.

[0003] Therefore, molecular dynamics simulation has become a powerful tool to reveal various friction and wear behaviors in nickel-based composites at the atomic scale, and has laid a broad foundation for microscopic research on the effects of particle reinforcement on the matrix. Summary of the invention

[0004] In view of this, an embodiment of the present invention provides a method for calculating the friction coefficient of a rotating friction alloy using a molecular dynamics simulation method.

[0005] The technical solution of the embodiment of the present invention is as follows:

[0006] An embodiment of the present invention provides a method for calculating the friction coefficient of a rotating friction alloy using a molecular dynamics simulation method, the method comprising:

[0007] A model of diamond grinding balls and TiC / Ni composite matrix was established. The model structure was optimized using conjugate gradient energy minimization to obtain an energy-stable initial model, which was then relaxed under the NVT ensemble to obtain an energy-stable model. A fixed load was applied to the diamond grinding balls under the NVE ensemble, and periodic rotational friction was performed around the Z axis. The reaction force of the matrix on the diamond grinding balls was calculated, and the forces in the X, Y and Z directions were output. The friction force was obtained by combining the forces in the X and Y directions, and the friction coefficient was calculated in combination with the normal force on the Z axis.

[0008] Furthermore, the establishment of the diamond grinding ball and TiC / Ni composite material matrix model includes: using Lammps software to establish a single crystal matrix, the single crystal matrix structure is a face-centered cubic structure, and the lattice constant of Ni is The substrate size is It includes 2184288 atoms, and then the TiC / Ni composite material model is established by replacing Ni atoms; the radius of the diamond grinding ball is Contains 20112 atoms.

[0009] Furthermore, the structure of the model is optimized by using conjugate gradient energy minimization to obtain an energy-stable initial model, and relaxation is performed under the NVT ensemble to obtain an energy-stable model, including: setting the substrate to be a Newtonian layer, a constant temperature layer and a fixed layer from top to bottom, and the thickness of the constant temperature layer and the fixed layer is A variety of parameters are set for the matrix model, including setting the X and Y directions as periodic boundary conditions, the Z direction as free boundary conditions, setting the time step to 1 femtosecond (fs), setting the simulation temperature to 300K, using MEAM / c, EAM, and Morse potential functions to describe the forces between atoms, setting the fixed layer atoms to remain stationary, and setting the isothermal layer atoms to always remain at 300K; the matrix model is structurally optimized by conjugate gradient energy minimization to obtain an energy-stable initial model; the optimized initial model is used to heat the alloy to 300K through the NVT ensemble, and keep this temperature for a period of time, and the energy-stable model is obtained when the total energy is stable.

[0010] Furthermore, the method of applying a fixed load to the diamond grinding ball in the NVE ensemble and performing periodic rotational friction with the Z axis as the axis includes: using the displace_atom command to make the diamond grinding ball move rapidly along the Z direction. The diamond grinding ball is moved to the surface of the substrate; the diamond grinding ball is tempered using the fix nve / noforce command, and a fixed load of 60nN is applied to the diamond grinding ball in the Z direction using the fix aveforce command; the initial coordinate information of the diamond grinding ball in the X and Y directions is extracted using the fix store / state command, the friction radius and initial angle are calculated using the variable command, and the linear speed is set using the variable command; the displacement in the X and Y directions is calculated based on the initial parameters using the variable command; and the diamond grinding ball is subjected to periodic rotational motion using the fix move variable command.

[0011] Furthermore, the calculation of the reaction force of the substrate on the diamond grinding ball and the output of the forces in the X, Y and Z directions include: using the computer command to calculate the X, Y and Z forces between the diamond grinding ball and the substrate atoms during the friction process, using the thermo command to control the output frequency, outputting once every 500 steps, using the thermo_style custom output method to output the simulation steps, system temperature and force, and saving them in a log file; using the dump command to output a .lammpstrj file every 500 steps to obtain the position parameters of the diamond grinding ball during the friction process.

[0012] Furthermore, the method also includes: exporting the atomic coordinate information of the diamond grinding ball in each time period into a single data file through Ovito software, calculating the center coordinates of the atoms in each data file through Python, determining the motion trajectory of the diamond grinding ball, and drawing a diamond grinding ball motion trajectory diagram.

[0013] The beneficial effects brought by the technical solution provided by the embodiment of the present application include at least:

[0014] In the embodiment of the present invention, a model of diamond grinding balls repeatedly rotating and rubbing nickel-based composite materials is constructed, which is more consistent with the friction and wear of materials under actual working conditions, and the calculated friction coefficient is more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work, among which:

[0016] Figure 1 A schematic flow chart of a method for calculating the friction coefficient of a rotating friction alloy using a molecular dynamics simulation method provided in an embodiment of the present invention;

[0017] Figure 2 A schematic diagram of a friction model of a TiC / Ni-based composite material provided in an embodiment of the present invention;

[0018] Figure 3 A total energy change curve diagram based on molecular dynamics simulation provided by an embodiment of the present invention;

[0019] Figure 4 A flow chart of a friction coefficient calculation method based on molecular dynamics simulation provided by an embodiment of the present invention;

[0020] Figure 5 A friction force component curve diagram based on molecular dynamics simulation provided by an embodiment of the present invention;

[0021] Figure 6 A friction force curve diagram based on molecular dynamics simulation provided by an embodiment of the present invention;

[0022] Figure 7 A friction coefficient curve based on molecular dynamics simulation provided by an embodiment of the present invention;

[0023] Figure 8 A schematic diagram of the position change of a diamond grinding ball in the X and Y directions based on molecular dynamics simulation provided by an embodiment of the present invention;

[0024] Fig. 9 A schematic diagram of the motion trajectory of a diamond grinding ball based on molecular dynamics simulation provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0026] In the following description, reference is made to “some embodiments”, which describe a subset of all possible embodiments, but it will be understood that “some embodiments” may be the same subset or different subsets of all possible embodiments and may be combined with each other without conflict.

[0027] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as those generally understood by those skilled in the art in the field to which the embodiments of the present invention belong. It should also be understood that terms such as those defined in general dictionaries should be understood to have meanings consistent with those in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless specifically defined as here.

[0028] The full name of NVE ensemble is Microcanonical ensemble, which is an ensemble concept in statistical mechanics, used to describe a closed system that has no energy exchange with the outside world, but can exchange volume and particles. In the NVE ensemble, the total energy (E), volume (V) and number of particles (N) of the system are all conserved, that is, they remain unchanged throughout the process. N stands for the number of particles, V stands for volume, and E stands for energy.

[0029] In molecular dynamics simulations, the NVE ensemble is often used to simulate a system under adiabatic conditions, that is, the system does not exchange heat with the outside world, but can expand or contract freely. This ensemble is particularly suitable for studying the dynamic behavior of the system under constant energy, for example, studying the dynamic process of chemical reactions or the thermodynamic properties of materials. In the NVE ensemble, temperature is not a control parameter, but a result of the system.

[0030] Figure 1 A schematic flow chart of a method for calculating the friction coefficient of a rotating friction alloy by a molecular dynamics simulation method provided in an embodiment of the present invention is shown in FIG. Figure 1 As shown, the method comprises at least the following steps:

[0031] Step S110, establishing a diamond grinding ball and TiC / Ni composite material matrix model.

[0032] Here, the molecular dynamics model includes diamond grinding balls and TiC / Ni composite matrix models. The model uses Lammps to establish a single crystal matrix. The single crystal matrix structure is a face-centered cubic structure with a lattice constant of (Ni), the matrix size is Then, by replacing Ni atoms, a TiC / Ni composite material model is established, such as Figure 2 As shown. Create a diamond grinding ball with a radius of The matrix has 2184288 atoms and the diamond grinding ball has 20112 atoms.

[0033] Step S120, using conjugate gradient energy minimization to perform structural optimization on the matrix model to obtain an energy-stable initial model, and performing relaxation under the NVT ensemble to obtain an energy-stable model.

[0034] Here, in this embodiment, the alloy model structure optimization conjugate gradient energy minimization is first performed for structural optimization. The optimized alloy model is heated to 300K by the NVT ensemble, and accurately regulated by the Nosé-Hoover thermostat, and the temperature is maintained for a period of time, and the isothermal layer atoms are always maintained at 300K. When the total energy is stable, a stable model is obtained, such as Figure 3 Make sure the model is energy stable before performing friction simulation to ensure the accuracy of the simulation results.

[0035] Step S130, applying a fixed load to the diamond grinding ball under the NVE ensemble, and performing periodic rotational friction around the Z axis.

[0036] Here, the diamond grinding ball is first moved to the surface of the substrate to reduce the downward pressure process and improve the calculation efficiency. The diamond grinding ball is tempered and a fixed load is applied to the diamond grinding ball under the NVE ensemble. The axes of the diamond grinding ball and the substrate are parallel to the Z axis. Sine and cosine motions are applied to the diamond grinding ball to make it rotate at a uniform speed along the Z axis, thereby realizing the diamond grinding ball rubbing the TiC / Ni substrate.

[0037] By simulating the periodic rotational motion of diamond grinding balls, the friction and wear conditions under actual working conditions are closer.

[0038] Step S140, calculating the reaction force of the substrate on the diamond grinding ball, and outputting the forces in the X, Y and Z directions.

[0039] Here, during the friction process, the forces between the diamond ball and the substrate atoms in the X, Y, and Z directions are calculated using the LAMMPS computer command, and the dynamic parameters are output in the log file using the thermo_style custom output method.

[0040] Step S150, combining the forces in the X and Y directions to obtain the friction force, and calculating the friction coefficient in combination with the Z-axis normal force.

[0041] Here, the friction coefficient is an important parameter that describes the friction behavior between material surfaces, which is crucial for material design and application. Accurately calculating the forces in each direction is the key to obtaining the friction coefficient. The embodiment of the present invention calculates the friction force and the friction coefficient, and analyzes their relationship with the friction time. The force data is extracted from the log file, and a dynamic curve diagram of the friction time and the force is drawn. In implementation, the force changes in each direction are first analyzed, that is, the relationship between the friction component force and the friction time. The relationship between the friction force and the friction time is obtained through the relationship between the friction component force and the friction force. The relationship between the friction coefficient and the friction time is obtained through the relationship between the friction force and the normal force.

[0042] Friction force F f The calculation formulas for the friction coefficient μ are as follows:

[0043]

[0044] μ=F f / F z Formula (2);

[0045] In the formula, F f is the friction force, F x is the force in the X direction, F y is the force in the Y direction, F z It is the force in the Z direction, that is, the normal force along the Z axis.

[0046] like Figure 4 The flowchart of the friction coefficient calculation method based on molecular dynamics simulation provided by an embodiment of the present invention is shown. In the implementation, the size, shape, ensemble and other parameters are first determined, Lammps is used to establish a basic model of the alloy, the potential function used to describe the force between atoms is determined, and the initial conditions such as the time step and the simulation temperature are set to establish an initial molecular dynamics model, and then NVT ensemble relaxation is performed, and NVE ensemble repeated rotation friction is performed under energy stability, and dynamic parameters and atomic coordinate information are obtained, and finally the friction coefficient is calculated. The present invention can provide more accurate friction coefficient data by simulating a friction process close to actual working conditions, which is of great significance to the fields of materials science and engineering applications.

[0047] The embodiments of the present invention provide the actual trajectory of the interaction between atoms through molecular dynamics simulation, which can provide a scientific explanation for the dynamic phenomena of the material. It can systematically explain a series of micro-nanoscale friction and wear mechanisms such as friction coefficient, wear rate and microstructure evolution during the dynamic friction process of metal materials, analyze the movement of atoms at the nanoscale, and predict the structure and performance of the material.

[0048] In some possible embodiments, the above step S110 "establishing a diamond grinding ball and TiC / Ni composite material matrix model" is further implemented by the following process: using Lammps software to establish a single crystal matrix, the single crystal matrix structure is a face-centered cubic structure, and the lattice constant of Ni is The substrate size is It includes 2184288 atoms, and then the TiC / Ni composite material model is established by replacing Ni atoms; the radius of the diamond grinding ball is Contains 20112 atoms.

[0049] In some possible embodiments, the above step S120 of "using conjugate gradient energy minimization to perform structural optimization on the matrix model to obtain an energy-stable initial model, and performing relaxation under the NVT ensemble to obtain an energy-stable model" includes the following steps:

[0050] Step S201, set the substrate to have a Newtonian layer, a constant temperature layer and a fixed layer from top to bottom, and the thickness of the constant temperature layer and the fixed layer is

[0051] Step S202, setting various parameters of the matrix model, including setting the X and Y directions as periodic boundary conditions, the Z direction as free boundary conditions, setting the time step to 1fs, setting the simulation temperature to 300K, using MEAM / c, EAM, and Morse potential functions to describe the forces between atoms, setting the fixed layer atoms to remain stationary, and setting the isothermal layer atoms to always remain at 300K.

[0052] Here, in the embodiment of the present invention, the matrix is ​​TiC and Ni, and TiC is used as a strengthening phase as a whole. The MEAM / c potential function is used to describe the interaction between the ceramic phase (such as TiC) and the metal phase (such as Ni), the EAM describes the interaction between metal atoms, the Morse potential function describes the interaction force between metal atoms and non-metal atoms, the Morse is used to describe the force between atoms, and the Tersoff potential function is used to describe the force of the diamond grinding ball atoms themselves.

[0053] It is worth noting that the choice of potential function is crucial to the accuracy of the simulation, and different potential functions are suitable for different types of interatomic interactions. Periodic boundary conditions are helpful for simulating matrices of infinite size, while free boundary conditions can simulate open systems.

[0054] Step S203, performing conjugate gradient energy minimization on the matrix model to perform structural optimization, and obtaining an energy-stable initial model.

[0055] Step S204, using the optimized initial model to heat the alloy to 300K through the NVT ensemble, and keeping the temperature for a period of time, and obtaining the energy stable model when the total energy is stable.

[0056] Here, the Nosé-Hoover thermostat is used for accurate regulation to keep the isothermal layer atoms of the optimized initial model at 300K. When the total energy is stable, a stable model is obtained, such as Figure 3 Shown is a total energy change curve based on molecular dynamics simulation provided by an embodiment of the present invention.

[0057] It should be noted that the NVT and NVE ensembles are used to control the simulation under the conditions of constant temperature and volume, and constant volume and energy, respectively.

[0058] In some possible embodiments, the above step S130 of "applying a fixed load to the diamond grinding ball under the NVE ensemble and performing periodic rotational friction about the Z axis" includes the following steps:

[0059] Step S301: Use the displace_atom command to quickly move the diamond grinding ball along the Z direction. Move the diamond grinding ball to the substrate surface.

[0060] Step S302, using the fix nve / noforce command to temper the diamond grinding ball, and using the fix aveforce command to apply a fixed load of 60 nN to the diamond grinding ball in the Z direction.

[0061] Step S303, using the fix store / state command to extract the initial coordinate information of the diamond grinding ball in the X and Y directions, using the sqrt and acos in the variable command to calculate the friction radius and the initial angle, and using the variable command to set the linear speed.

[0062] Here, for example, the initial coordinates of the diamond grinding ball are (95,95) and the friction radius is Initial angle 45°.

[0063] Step S304, combining the initial parameters, using cosine and sin in the variable command to calculate the displacement in the X and Y directions.

[0064] Step S305, using the fix move variable command to make the diamond grinding ball rotate periodically.

[0065] In some possible embodiments, the above step S140 of "calculating the reaction force of the substrate on the diamond grinding ball and outputting the forces in the X, Y and Z directions" can be implemented by the following steps:

[0066] Step S401, during the friction process, the computer command is used to calculate the X, Y and Z forces between the diamond grinding ball and the substrate atoms, the thermo command is used to control the output frequency, and the output is output every 500 steps. The thermo_style custom output method is used to output the simulation steps, system temperature and force, and save them in the log file.

[0067] Here, the X-direction force F between the diamond grinding ball and the matrix atoms calculated by the computer is extracted from the log file. x , Y-direction force F y , and the Z-direction force F z , where the X-direction force F x , Y-direction force F y are friction components, such as Figure 5 The friction force component curve diagram based on molecular dynamics simulation provided by the embodiment of the present invention is shown. The friction force (equivalent to the friction force) is calculated by formula (1), and a dynamic curve diagram of the friction force and the friction time is drawn, as shown in FIG. Figure 6 As shown; the friction coefficient is calculated by formula (2), and the relationship between the friction coefficient and the friction time is plotted as shown Figure 7 shown.

[0068] Step S402, using the dump command to output the .lammpstrj file every 500 steps to obtain the position parameters of the diamond grinding ball during the friction process.

[0069] In some possible embodiments, the method further includes: exporting the atomic coordinate information of the diamond grinding ball for each time period into a single data file through Ovito software, calculating the center coordinates of the atoms in each data file through Python, determining the motion trajectory of the diamond grinding ball, and drawing a diamond grinding ball motion trajectory diagram.

[0070] Here, the relationship between the displacement in the X and Y directions and the simulation time is determined by calculating the coordinate information of the diamond atoms. Specifically, the X and Y coordinate information of each atom in each step is output through the Scatterplot module in the Ovito visualization software and exported as a single independent data file. The X and Y coordinates of the atoms in each data file are calculated by Python, and the relationship between the displacement in the X and Y directions of the diamond grinding ball and the friction time is determined and plotted, as shown in the following figure: Figure 8 As shown. Through the Generate particle trajectories module in the Ovito visualization software, the motion trajectory of the diamond grinding ball can be obtained, as shown Fig. 9 shown.

[0071] The method for calculating the friction coefficient of a rotating friction alloy provided in the embodiment of the present invention provides the actual trajectory of the interaction between atoms through molecular dynamics simulation, and can provide a scientific explanation for the dynamic phenomena occurring in the material. It can provide a systematic explanation for a series of micro-nanoscale friction and wear mechanisms such as the friction coefficient, wear rate, and microstructure evolution during the dynamic friction process of metal materials, and can analyze the motion of atoms at the nanoscale to predict the structure and performance of the material.

[0072] 1. Experimental and feasibility: A molecular dynamics simulation model of the ceramic phase and the metal phase is established to realize the repeated rotation friction of the tool at the microscopic level. The influence of the interface between the metal phase and the ceramic phase and the existence of the reinforcement phase on the friction coefficient can be studied at the same time, which is of great significance to the design, preparation and application of materials.

[0073] 2. Scalability: Lammps simulation can adjust the simulation environment arbitrarily, for example, simulation materials, force field parameters, simulation conditions, etc., which significantly improves work efficiency, enables experiments on extremely difficult systems, and reduces experimental costs and research cycles.

[0074] 3. Flexibility: Lammps modeling and simulation can arbitrarily control the shape of the friction pair, for example, the shape, size and position of the diamond grinding balls, making the simulation more in line with the actual friction process.

[0075] It should be understood that "one embodiment" or "an embodiment" mentioned throughout the specification means that specific features, structures or characteristics related to the embodiment are included in at least one embodiment of the present invention. Therefore, "in one embodiment" or "in an embodiment" appearing throughout the specification does not necessarily refer to the same embodiment. In addition, these specific features, structures or characteristics can be combined in one or more embodiments in any suitable manner. It should be understood that in various embodiments of the present invention, the size of the serial number of the above-mentioned processes does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present invention. The serial numbers of the above-mentioned embodiments of the present invention are only for description and do not represent the advantages and disadvantages of the embodiments.

[0076] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0077] In the several embodiments provided by the present invention, it should be understood that the disclosed methods can be implemented in other ways. The methods disclosed in the several method embodiments provided by the present invention can be arbitrarily combined without conflict to obtain new method embodiments. The features disclosed in the several method embodiments provided by the present invention can be arbitrarily combined without conflict to obtain new method embodiments.

[0078] The above is only an embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for calculating the friction coefficient of a rotating friction alloy by molecular dynamics simulation, characterized in that: include: Establish the matrix model of diamond grinding balls and TiC / Ni composite materials; The model structure is optimized using conjugate gradient energy minimization to obtain an energy-stable initial model, which is then relaxed under the NVT ensemble to obtain an energy-stable model. A fixed load is applied to the diamond grinding ball in the NVE ensemble, and periodic rotational friction is performed around the Z axis. Calculate the reaction force of the substrate on the diamond grinding ball and output the forces in the X, Y and Z directions; The friction force is obtained by combining the forces in the X and Y directions, and the friction coefficient is calculated by combining the normal force in the Z axis.

2. The method according to claim 1, characterized in that The method of establishing a diamond grinding ball and TiC / Ni composite material matrix model comprises: Lammps software was used to establish a single crystal matrix. The single crystal matrix structure is a face-centered cubic structure, and the lattice constant of Ni is The substrate size is It includes 2184288 atoms, and then the TiC / Ni composite material model is established by replacing Ni atoms; the radius of the diamond grinding ball is Contains 20112 atoms.

3. The method according to claim 1, characterized in that The structure of the model is optimized by using conjugate gradient energy minimization to obtain an energy-stable initial model, and relaxation is performed under the NVT ensemble to obtain an energy-stable model, including: The substrate is set to consist of a Newtonian layer, a constant temperature layer, and a fixed layer from top to bottom. The thickness of the constant temperature layer and the fixed layer is A variety of parameters were set for the matrix model, including setting the X and Y directions as periodic boundary conditions, the Z direction as free boundary conditions, setting the time step to 1 femtosecond, setting the simulation temperature to 300K, using MEAM / c, EAM, and Morse potential functions to describe the forces between atoms, setting the fixed layer atoms to remain stationary, and setting the isothermal layer atoms to always remain at 300K; The matrix model is subjected to structural optimization by conjugate gradient energy minimization to obtain an energy-stable initial model; The optimized initial model is used to heat the alloy to 300K through the NVT ensemble and keep it at this temperature for a period of time, and the energy stable model is obtained when the total energy is stable.

4. The method according to claim 1, characterized in that: The method of applying a fixed load to the diamond grinding ball under the NVE ensemble and performing periodic rotational friction with the Z axis as the axis includes: Use the displace_atom command to quickly move the diamond grinding ball along the Z direction Moving the diamond grinding ball to the substrate surface; Use the fix nve / noforce command to temper the diamond grinding ball, and the fix aveforce command to apply a fixed load of 60nN to the diamond grinding ball in the Z direction; The fix store / state command is used to extract the initial coordinate information of the diamond grinding ball in the X and Y directions, and the variable command is used to calculate the friction radius and initial angle. The variable command sets the linear speed. Combined with the initial parameters, the variable command is used to calculate the X and Y displacements; Use the fix move variable command to make the diamond grinding ball rotate periodically.

5. The method according to claim 1, characterized in that The calculation of the reaction force of the substrate on the diamond grinding ball and the output of the forces in the X, Y and Z directions include: During the friction process, the computer command is used to calculate the X, Y and Z forces between the diamond grinding ball and the substrate atoms. The thermo command is used to control the output frequency, which is output every 500 steps. The thermo_style custom output method is used to output the simulation steps, system temperature and force, and save them in the log file. The dump command is used to output the .lammpstrj file every 500 steps to obtain the position parameters of the diamond grinding ball during the friction process.

6. The method according to claim 5, characterized in that The method further comprises: The atomic coordinate information of the diamond grinding ball in each time period is exported as a single data file through Ovito software. The center coordinates of the atoms in each data file are calculated by Python, the motion trajectory of the diamond grinding ball is determined, and the motion trajectory diagram of the diamond grinding ball is drawn.

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