Simulation method for strengthening nickel metal through cooperation of magnetic field and laser shock wave

Abstract

The invention relates to the field of metal material strengthening simulation, in particular to a simulation method for strengthening nickel metal through cooperation of a magnetic field and laser shock waves. The method comprises the following steps: S1, generating a polycrystalline nickel model; s2, performing preliminary relaxation to obtain an energy minimization system; s3, setting a model boundary, a constant magnetic field condition and parameters, applying a Langevin method to magnetic spinning, controlling a model temperature and a magnetic damping parameter, performing symmetric integration on particle spinning, and relaxing an energy minimization system to an equilibrium state in cooperation with a potential function; s4, the magnetic field cooperatively utilizes a piston method to generate laser shock waves to induce plastic deformation; step S5, performing relaxation for the first time; step S6, performing relaxation for the second time; step S7, performing visualization; and S8, obtaining the tensile property and the specific damping property. According to the method, the evolution process of the microstructure of the polycrystalline nickel strengthened by the magnetic field and the laser shock wave can be intuitively analyzed, the strengthening mechanism of the magnetic field and the laser shock wave is disclosed from the atomic microscopic level, and the tensile property and the specific damping property are obtained.

Description

Technical Field

[0001] The invention relates to the field of metal material strengthening simulation, and in particular to a simulation method for strengthening nickel metal by using a magnetic field in coordination with a laser shock wave. Background Art

[0002] Nickel and its alloys are often used to manufacture aircraft engine blades because of their excellent high temperature performance, oxidation resistance and good castability. They can withstand high-intensity complex loads and maintain normal operation in high temperature environments of thousands of degrees Celsius. As a key part of aircraft engines, blades are subjected to the combined effects of high temperature, aerodynamic and centrifugal loads during their service life, which can easily lead to vibration fatigue failure of the engine structure and cause aviation accidents.

[0003] Laser shock peening technology, as a new type of surface strengthening technology, uses the mechanical effect of shock waves to induce high-density microscopic defects and high-amplitude residual compressive stresses on the surface of metal materials, which can significantly improve the fatigue limit and life of key components. However, the mismatch of the comprehensive mechanical properties of the strengthened components is a technical bottleneck that limits the application of laser shock peening engineering. At the same time, the extreme non-equilibrium process based on the magnetic field to regulate the microstructure and mechanical properties of metal materials has outstanding technical advantages.

[0004] Based on this, the comprehensive use of the superposition effect of laser shock strengthening and magnetic field is a direction worthy of research and exploration. The microstructure of metal materials evolves very quickly under the action of magnetic field and laser shock wave, which is difficult to observe intuitively in real time through experimental methods. Therefore, it is urgent to design a simulation method for strengthening nickel metal by magnetic field and laser shock wave. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide a simulation method for strengthening nickel metal by magnetic field synergistic laser shock wave, which can intuitively analyze the evolution process of the microstructure of polycrystalline nickel strengthened by magnetic field synergistic laser shock wave, reveal the strengthening mechanism of magnetic field synergistic laser shock wave from the atomic microscopic level, and obtain tensile properties and specific damping properties.

[0006] In order to solve the above technical problems, the technical solution of the present invention is: a simulation method for strengthening nickel metal by magnetic field synergistic with laser shock wave, comprising:

[0007] Step S1, generating a polycrystalline nickel model using molecular dynamics software;

[0008] Step S2, performing preliminary relaxation on the polycrystalline nickel model by using the cg conjugate gradient method to obtain an energy minimized system;

[0009] Step S3, setting the model boundary, constant magnetic field conditions and parameters, applying the Langevin method to the magnetic spin, controlling the model temperature and magnetic damping parameters, performing symmetric integration on the particle spin, and relaxing the energy-minimizing system to an equilibrium state in conjunction with the potential function;

[0010] Step S4, using the piston method to generate laser shock waves to induce plastic deformation, the impact direction is changed to a contraction boundary condition, the ensemble is set to the NVE ensemble, and the piston is set to impact the polycrystalline nickel model at a constant speed;

[0011] Step S5, changing the model ensemble that has completed the stress wave loading stage to the NPT ensemble, removing the influence of the magnetic field, and performing temperature and pressure control simulation on the model until the shock wave is completely unloaded and the first relaxation is completed;

[0012] Step S6, removing the center of mass velocity of the model that has completed the first relaxation or adjusting all atomic velocities to 0, performing temperature and pressure control simulation under the NPT ensemble, simulating until the system energy reaches stability and the global stress is 0, and completing the second relaxation;

[0013] Step S7, visualizing the microstructure of the polycrystalline nickel model during the simulation process;

[0014] Step S8, performing a tensile test and a specific damping performance test simulation on the model that has completed the second relaxation, respectively, to obtain the tensile performance and the specific damping performance.

[0015] Further, step S1 specifically includes:

[0016] Step S11, generating a data file of a nickel element unit cell using molecular dynamics modeling software according to the lattice constant;

[0017] Step S12, establishing a parameter file, setting the dimensions of the nickel polycrystalline model in the x, y, and z directions and the number of grains, and randomly assigning the center position and grain orientation of the grains;

[0018] Step S13, the data file of the nickel element unit cell is converted into a polycrystalline nickel model according to the parameter file to realize the periodicity of polycrystalline nickel.

[0019] Further, in step S3, the model boundary, constant magnetic field conditions and parameters are set; specifically:

[0020] Set the model boundary to a periodic boundary, set the polycrystalline nickel magnetic spin vector, potential function, magnetic field cutoff radius, magnetic field strength and direction, change the energy calculation method, control the system temperature, damping, and integrate spin and atomic movement.

[0021] Furthermore, in step S5, during the temperature and pressure control simulation, non-coupled pressure control is adopted, and pressure control is not performed in the impact direction, and pressure control is performed only in the other two directions, and the impact direction is still a contraction boundary condition.

[0022] Furthermore, in step S6, coupled pressure control is adopted during the temperature and pressure control simulation process.

[0023] Further, in step S8, the tensile test is simulated using the deform method; the specific damping test uses the deform method to apply tensile and compressive cyclic loads to the model to obtain a tensile-compressive stress-strain curve, and the specific damping performance is calculated based on the ratio of lost energy to maximum stored energy in a cycle.

[0024] After adopting the above technical scheme, the present invention can intuitively analyze the evolution process of the microstructure of polycrystalline nickel strengthened by magnetic field synergistic laser shock wave, reveal the strengthening mechanism of magnetic field synergistic laser shock wave from the atomic microscopic level, and obtain tensile properties and specific damping properties, thereby providing guidance for analyzing the process of strengthening polycrystalline nickel by magnetic field synergistic laser shock wave; in addition, the corresponding conditions or parameters in the simulation process can be changed, and the basis and direction for optimizing the process of strengthening polycrystalline nickel by magnetic field synergistic laser shock wave can be provided according to the simulation results. Therefore, the simulation method in the present invention is conducive to promoting the application potential of magnetic field in laser modification technology, and providing scientific basis and technical support for the development and application of anti-fatigue manufacturing technology of key aviation components. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a flow chart of a simulation method of strengthening nickel metal by using magnetic field in coordination with laser shock wave of the present invention;

[0026] Figure 2 Figure 1. Polycrystalline nickel model diagram established for the embodiment;

[0027] Figure 3 The microstructure diagram of the magnetic field coordinated laser shock model at different times in the embodiment;

[0028] Figure 4 The microstructure diagram of the laser shock model at different times in the comparative example;

[0029] Figure 5 A comparison diagram of the tensile properties of the magnetic field coordinated laser shock model in the embodiment and the laser shock model in the comparative example;

[0030] Figure 6 A comparison of the specific damping performance of the magnetic field coordinated laser shock model in the embodiment and the laser shock model in the comparative example

[0031] in: Figure 2 (a) is the grain distribution diagram in the polycrystalline nickel model;

[0032] Figure 2 (b) is the atomic distribution diagram in the polycrystalline nickel model;

[0033] Figure 3 (a) is a microstructure diagram of grains at different times in the magnetic field coordinated laser shock model in the embodiment;

[0034] Figure 3 (b) is a microscopic structure diagram of atoms in the magnetic field synergistic laser shock model at different times in the embodiment;

[0035] Figure 4 (a) is the microstructure diagram of the grains in the laser shock model in the comparative example at different times;

[0036] Figure 4 (b) is the microstructure diagram of atoms in the laser shock model in the comparative example at different times. DETAILED DESCRIPTION

[0037] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments in conjunction with the accompanying drawings.

[0038] like Figure 1 As shown, a simulation method for strengthening nickel metal by using a magnetic field in coordination with laser shock waves comprises:

[0039] Step S1, generating a polycrystalline nickel model using molecular dynamics software;

[0040] Step S2, performing preliminary relaxation on the polycrystalline nickel model by using the cg conjugate gradient method to obtain an energy minimized system;

[0041] Step S3, setting the model boundary, constant magnetic field conditions and parameters, applying the Langevin method to the magnetic spin, controlling the model temperature and magnetic damping parameters, performing symmetric integration on the particle spin, and relaxing the energy-minimizing system to an equilibrium state in conjunction with the potential function;

[0042] Step S4, using the piston method to generate laser shock waves to induce plastic deformation, the impact direction is changed to a contraction boundary condition, the ensemble is set to the NVE ensemble, and the piston is set to impact the polycrystalline nickel model at a constant speed;

[0043] Step S5, changing the model ensemble that has completed the stress wave loading stage to the NPT ensemble, removing the influence of the magnetic field, and performing temperature and pressure control simulation on the model until the shock wave is completely unloaded and the first relaxation is completed;

[0044] Step S6, removing the center of mass velocity of the model that has completed the first relaxation or adjusting all atomic velocities to 0, performing temperature and pressure control simulation under the NPT ensemble, simulating until the system energy reaches stability and the global stress is 0, and completing the second relaxation;

[0045] Step S7, visualizing the microstructure of the polycrystalline nickel model during the simulation process;

[0046] Step S8, performing a tensile test and a specific damping performance test simulation on the model that has completed the second relaxation, respectively, to obtain the tensile performance and the specific damping performance.

[0047] The magnetic field cooperates with the laser impact, and the model particles are charged, but the model is electrically balanced. The charged particles are moved by the laser impact, or the moving charges are affected by the magnetic field. The charged particles move in a circle or spiral perpendicular to the plane formed by the particle velocity and the magnetic field direction. Compared with the electric field, it is more complicated and mainly relies on the spin-orbit coupling effect generated by the magnetic field and the mechanical effect of the laser shock wave to strengthen the metal material.

[0048] The following will introduce the scheme involved in the above embodiment in detail in combination with the simulation process in the specific embodiment; and will demonstrate the advantages of the scheme involved in the above embodiment in combination with the comparative example.

[0049] Example:

[0050] A simulation method for strengthening nickel metal by using magnetic field in coordination with laser shock wave, comprising:

[0051] (a) Based on the lattice constant, the molecular dynamics modeling software Atomsk is used to generate a data file of the nickel unit cell. Metallic nickel has a face-centered cubic (FCC) structure with a lattice constant of 3.52. The terminal run command is set to atomsk–create fcc3.52file1.cfg to generate the nickel unit cell.

[0052] (b) Create a parameter file and set the dimensions of the nickel polycrystalline model in the x, y, and z directions to be And set 13 grains in the model, and use the random command in the code running file to randomly assign the center position and grain orientation of the grains.

[0053] (c) The data file of the nickel element unit cell is converted into a polycrystalline nickel model by using the -warp command in the terminal according to the parameter file. The nickel unit cell is filled into a polycrystalline nickel model by the Voronoi tessellation method. Figure 2 shown.

[0054] (d) The polycrystalline nickel model is initially relaxed using the CG conjugate gradient method to obtain an energy-minimized system. The energy minimization uses the CG conjugate gradient method, where at each iteration the force gradient is combined with information from the previous iteration to calculate a new orientation that is conjugate to the previous orientation.

[0055] (e) Set the model boundary to a periodic boundary, and use the spin / atom command to set the magnetic spin vector of the polycrystalline nickel model. The Bohr magneton of nickel is 3.2μB, and the initial spin direction is the z axis. Use the hybrid potential command hybrid / overlay eam / fsspin / exchange to set the potential function to Ni_v6_2.0.eam, and the magnetic field cutoff radius is The constant magnetic field strength is set to 5×107T and the magnetic field direction is in the Z direction through the procession / spin command; fix_modify energy changes the energy calculation method and adds the potential energy caused by the magnetic field to the potential energy of the system as part of the thermodynamic output; the system temperature and transverse magnetic damping parameters are controlled through the langevin / spin and nve / spin commands, and the spin and atomic movement are integrated. The system temperature is set to 300K and the transverse magnetic damping parameter is 0.01.

[0056] (f) Use the Langevin method for magnetic spin, control the model temperature and magnetic damping parameters, combine the nve / spin command to perform symmetric integration on the particle spin, and use the potential function to relax the energy-minimized system to the equilibrium state.

[0057] (g) Laser shock wave induced plastic deformation was generated using the piston method. The impact direction was changed to the contraction boundary condition. The ensemble was set to the NVE ensemble and the piston was set as the bottom of the model. Impact the model body at a constant speed of 1.5 km / s.

[0058] (h) The model ensemble that completes the stress wave loading stage is changed to the NPT ensemble, the magnetic field influence is removed, and the model is temperature and pressure controlled. The pressure control adopts non-coupled pressure control. The pressure is not controlled in the impact direction, but only in the other two directions. The impact direction is still a contraction boundary condition. The simulation is carried out until the shock wave is completely unloaded and the first relaxation is completed.

[0059] (i) Remove the center of mass velocity of the model that has completed the first relaxation or adjust all atomic velocities to 0, and perform temperature and pressure control simulation under the NPT ensemble. At this time, the pressure control method is coupled pressure control, and the simulation is completed until the system energy reaches stability and the global stress is 0, and the second relaxation is completed.

[0060] (j) Visualization of the microstructure of the polycrystalline nickel model during the above simulation process (using the Common Neighbor Analysis method to color different crystal structures and analyze the microstructure, the microstructure diagrams at different times are shown in Figure 2). Figure 3 As shown. During the simulation process, the dump command is used to export the model at different times. All processes can be visualized and analyzed using the ovito software)

[0061] (k) The model that has completed the second relaxation is subjected to a tensile test and a specific damping performance test simulation. The tensile test is simulated using the deform method, with the strain rate set to 10^11 / s, the strain rate set to 15%, and the temperature controlled to 300K. The specific damping performance test uses the deform method to apply tensile and compressive cyclic loads to the model, with the temperature controlled to 300K and the strain rate set to 10^10 / s. After the tensile strain rate reaches 2%, a cycle of compression-stretching simulation is performed, and the specific damping performance is calculated based on the ratio of lost energy to maximum stored energy in one cycle.

[0062] (l) The data information of the tensile test and specific damping performance test simulation process were input into the visualization software for post-processing, and finally the technical advantages of magnetic field synergistic laser shock strengthening were analyzed.

[0063] Comparative Example:

[0064] The difference between this comparative example and the embodiment is that no magnetic field is applied, and only the laser is used to simulate the impact on the polycrystalline nickel model. Figure 4 Microstructure diagram at different times during the laser shock process.

[0065] The tensile properties and specific damping performance test simulation results of the comparative examples and embodiments are shown in Table 1, and the comparison diagram is shown in Figure 5 and Figure 6 As shown in the figure, by comparison, compared with single laser shock, the tensile strength of the magnetic field synergistic laser shock model is increased by 10.0%, and the specific damping performance is improved by 11.9%. Figure 3 and Figure 4 ) The comparison results are shown in Tables 2 and 3. Compared with the single laser shock, the phase change ratio of the magnetic field synergistic laser shock model has no obvious difference, but the dislocation line length increases significantly, especially for the Other type and 1 / 6 <112> Type dislocation.

[0066] Table 1 Comparison of model performance under different processing methods

[0067]

[0068] Table 2 Microstructure proportion of laser shock at 4ps

[0069]

[0070] Table 3 Dislocation length at 4ps after laser shock

[0071]

[0072] Based on the above ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the technical concept of the present invention through the above description. The technical scope of the present invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A simulation method for strengthening nickel metal by magnetic field synergistic with laser shock wave, characterized in that: include: Step S1, generating a polycrystalline nickel model using molecular dynamics software; Step S2, performing preliminary relaxation on the polycrystalline nickel model by using the cg conjugate gradient method to obtain an energy minimized system; Step S3, setting the model boundary, constant magnetic field conditions and parameters, applying the Langevin method to the magnetic spin, controlling the model temperature and magnetic damping parameters, performing symmetric integration on the particle spin, and relaxing the energy-minimizing system to an equilibrium state in conjunction with the potential function; Step S4, using the piston method to generate laser shock waves to induce plastic deformation, the impact direction is changed to a contraction boundary condition, the ensemble is set to the NVE ensemble, and the piston is set to impact the polycrystalline nickel model at a constant speed; Step S5, changing the model ensemble that has completed the stress wave loading stage to the NPT ensemble, removing the influence of the magnetic field, and performing temperature and pressure control simulation on the model until the shock wave is completely unloaded and the first relaxation is completed; Step S6, removing the center of mass velocity of the model that has completed the first relaxation or adjusting all atomic velocities to 0, performing temperature and pressure control simulation under the NPT ensemble, simulating until the system energy reaches stability and the global stress is 0, and completing the second relaxation; Step S7, visualizing the microstructure of the polycrystalline nickel model during the simulation process; Step S8, performing a tensile test and a specific damping performance test simulation on the model that has completed the second relaxation, respectively, to obtain the tensile performance and the specific damping performance.

2. The method for simulating the strengthening of nickel metal by a magnetic field in coordination with laser shock waves according to claim 1, characterized in that: Step S1 specifically includes: Step S11, generating a data file of a nickel element unit cell using molecular dynamics modeling software according to the lattice constant; Step S12, establishing a parameter file, setting the dimensions of the nickel polycrystalline model in the x, y, and z directions and the number of grains, and randomly assigning the center position and grain orientation of the grains; Step S13, the data file of the nickel element unit cell is converted into a polycrystalline nickel model according to the parameter file to realize the periodicity of polycrystalline nickel.

3. The method for simulating the strengthening of nickel metal by magnetic field coordinated laser shock wave according to claim 1, characterized in that: In step S3, the model boundary, constant magnetic field conditions and parameters are set; specifically: Set the model boundary to a periodic boundary, set the polycrystalline nickel magnetic spin vector, potential function, magnetic field cutoff radius, magnetic field strength and direction, change the energy calculation method, control the system temperature, damping, and integrate spin and atomic movement.

4. The method for simulating the strengthening of nickel metal by a magnetic field in coordination with laser shock waves according to claim 1, characterized in that: In step S5, during the temperature and pressure control simulation process, non-coupled pressure control is adopted, and pressure control is not performed in the impact direction, and pressure control is performed only in the other two directions, and the impact direction is still a contraction boundary condition.

5. The method for simulating strengthening of nickel metal by magnetic field coordinated laser shock wave according to claim 1, characterized in that: In step S6, coupled pressure control is adopted during the temperature and pressure control simulation process.

6. The method for simulating strengthening of nickel metal by magnetic field coordinated laser shock wave according to claim 1, characterized in that: In step S8, the tensile test is simulated using the deform method.

7. The method for simulating strengthening of nickel metal by magnetic field coordinated laser shock wave according to claim 1, characterized in that: In step S8, the specific damping test process is to use the deform method to apply tensile and compressive cyclic loads to the model to obtain a tensile-compressive stress-strain curve, and calculate the specific damping performance based on the ratio of lost energy to maximum stored energy in a cycle.

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