Laser shock micro-mesoscale simulation method for benchmarking experiment

Abstract

The invention belongs to the technical field of engineering and theoretical research of a laser shock technology, and particularly relates to a laser shock micro-mesoscale simulation method for a benchmarking experiment, which is suitable for simulation research of laser shock and comprises the following steps: determining laser energy density I0 of laser shock of the benchmarking experiment; calculating the energy density I of shock waves generated by the laser shock material; calculating the equivalent piston speed UP of the induced shock wave; and performing simulation by taking the equivalent piston speed UP as a boundary condition. According to the invention, the simulation boundary conditions can be conveniently and accurately corresponding to the experimental parameters, so that the simulation accuracy is improved; material parameters involved in the parameter conversion process can be obtained through various low-cost modes such as a high-speed impact experiment and simulation, and it is avoided that pressure field distribution is determined directly through an expensive laser impact experiment; the method is high in portability and suitable for micro-mesoscale laser shock simulation of any platform.

Description

Technical Field

[0001] This invention belongs to the field of engineering and theoretical research technology of laser shock technology, specifically involving a micro-to-mesoscale simulation method for laser shock based on benchmark experiments, which is applicable to the simulation research of laser shock. Background Technology

[0002] Current simulation methods for simulating laser shock mainly include: (1) Applying an equivalent pressure load: A time-varying pressure pulse load is directly applied to the laser spot area on the material surface. The amplitude and spatiotemporal distribution (temporal shape and spatial distribution) of this pressure pulse are highly dependent on theoretical models or experimental data, without considering coupling with the dynamic response of the material. This method is suitable for laser shock simulation of macroscopic materials with well-defined impact constitutive relations.

[0003] (2) Applying an equivalent impact velocity / displacement load: Instead of applying force directly, an initial high velocity is given to the surface layer of the material (by applying velocity or displacement boundary conditions), causing the material to compress itself and generate an inwardly propagating shock wave. This shock wave is determined by the mechanical properties of the material itself, and is theoretically more self-consistent. This method is suitable for laser shock simulation of micro- to mesoscale materials with complex and unclear impact constitutive relations.

[0004] Applications: The main application is to simulate the laser shock process, including molecular dynamics simulation and finite element simulation. It can simulate the propagation of shock waves induced by laser shock on the surface of materials within the material, so as to carry out theoretical research or engineering prediction. For example, it can be used to study the impact constitutive relationship of nanomaterials and predict the residual stress field and fatigue life of industrial parts after laser shock strengthening.

[0005] Objective drawbacks of existing technologies: ① For parts or materials with complex structures, there is often a lack of experimental data on laser shock pressure fields, making it difficult to determine the simulation boundary conditions and thus difficult to carry out macroscopic laser shock simulation.

[0006] ② Existing micro- to mesoscale laser shock simulations typically do not consider the correspondence between velocity or displacement boundary conditions and experimental parameters, which weakens the accuracy of the simulation results. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a laser shock micro-mesoscale simulation method for benchmark experiments.

[0008] This invention is implemented by providing a laser shock micro-to-mesoscale simulation method for benchmark experiments, comprising the following steps: Step 1: Determine the laser energy density for the benchmark experiment laser shock.I 0; Step 2: Calculate the energy density of the shock wave generated by the laser-induced shock to the material. I ; Step 3: Calculate the equivalent piston velocity of the induced shock wave. U P ; Step 4: At equivalent piston speed U P Simulate the boundary conditions.

[0009] Preferably, in step 1, for a single laser shock experiment, the laser energy density is... I 0 is: in, E It is the energy of the laser emitted by the laser. d It refers to the diameter of a circular laser spot, or the diameter of a non-circular laser spot after it has been converted into a circular spot. τ It is the pulse width of the laser.

[0010] Preferably, in step 2, the energy density of the shock wave... I for: Here, α is the efficiency of the interaction between the laser and the material, and its value is material-dependent.

[0011] Preferably, in step 3, the pressure, density, and energy of the region inside the material disturbed by the shock wave are respectively P S , ρ S and E S The pressure, density, and energy of the region unaffected by the shock wave are respectively P 0、 ρ 0 and E 0. Both regions satisfy the laws of conservation of mass, momentum, and energy: shock wave velocity inside the material U S and the equivalent piston velocity of the induced shock wave U P Satisfying the impact-rain-button relationship, its state equation is: in, C 0 and S 1 represents the material's property parameters; The peak pressure of the shock wave generated in a single laser shock experiment is determined according to Fabbro's theoretical model: in Z The impedance of the material; For simulations at the micro-metascale, it is approximated that the pressure on the simulated boundary material is the peak pressure. By combining equations (1), (2), (4), (6), and (7), the laser energy density in the benchmark experiment is achieved. I Equivalent piston speed in 0-axis simulation U P The conversion.

[0012] Preferably, in step 4, a micro-to-metascale target material model is constructed using simulation software to achieve an equivalent piston speed. U P Alternatively, equivalent boundary conditions can be used as simulation boundary conditions to simulate the generation of shock waves. The propagation of laser-induced shock waves and the dynamic response of materials can be analyzed through numerical calculation and post-processing.

[0013] Compared with the prior art, the advantages of the present invention are as follows: ① It can easily and accurately correspond the boundary conditions of the simulation to the experimental parameters, thus improving the accuracy of the simulation; ②The material parameters involved in the parameter conversion process can be obtained through various low-cost methods such as high-speed impact experiments and simulations, avoiding the direct determination of the pressure field distribution through expensive laser impact experiments; ③ The method is highly portable and applicable to micro- to mesoscale laser shock simulation on any platform. Attached Figure Description

[0014] Figure 1 A schematic diagram illustrating the principle of generating shock waves within a material by applying an equivalent impact velocity to compress it. Figure 2 This is a schematic diagram illustrating the application of this method in Example 1; Figure 3 This is a schematic diagram illustrating the application of this method in Example 2. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0016] This invention provides a method for simulating laser shock at the micro-meta-scale in benchmark experiments, comprising the following steps: Step 1: Determine the laser energy density for the benchmark experiment laser shock. I 0; For a single laser shock experiment, the laser energy density I 0 is: in, E It is the energy of the laser emitted by the laser. d It refers to the diameter of a circular laser spot, or the diameter of a non-circular laser spot after it has been converted into a circular spot. τ It is the pulse width of the laser.

[0017] Step 2: Calculate the energy density of the shock wave generated by the laser-induced shock to the material. I : When a laser beam strikes the surface of a target material, it interacts with the material, inducing a shock wave that propagates into the material's interior. This shock wave possesses an energy density... I : Here, α is the efficiency of the interaction between the laser and the material, and its value is material-dependent.

[0018] Step 3: Calculate the equivalent piston velocity of the induced shock wave. U P ; like Figure 1 As shown, the piston plane moves at a velocity U P Along the compression of the target material, a velocity will be generated. U S A shock wave propagating into the material causes abrupt changes in the material's internal physical parameters at the shock wave front. The shock wave front divides the material into a region ① disturbed by the shock wave and a region ② undisturbed by the shock wave. The pressure, density, and energy in region ① are respectively... P S , ρ S and E S The pressure, density, and energy in region ② are respectively P 0、 ρ 0 and E 0 satisfies the laws of conservation of mass, momentum, and energy: shock wave velocity inside the material U S and the equivalent piston velocity of the induced shock wave U P Satisfying the impact-rain-button relationship, its state equation is: in, C 0 and S 1 represents the material's property parameters; The peak pressure of the shock wave generated in a single laser shock experiment is determined according to Fabbro's theoretical model: in Z The impedance of the material; For simulations at the micro-to-mesoscale, where the size is in the micrometer or even nanometer range, far smaller than a laser spot in the millimeter range, the pressure on the simulated boundary material can be approximated (due to...). P 0 is usually the reference pressure, so it typically refers to 0 here. P S All of these are peak pressures. By combining equations (1), (2), (4), (6), and (7), the laser energy density in the benchmark experiment is achieved. I Equivalent piston speed in 0-axis simulation U P The conversion.

[0019] Step 4: At equivalent piston speed U P Simulate for boundary conditions: A micro- to mesoscale target material model was constructed using simulation software, with an equivalent piston velocity. U P Alternatively, equivalent boundary conditions can be used as simulation boundary conditions to simulate the generation of shock waves. The propagation of laser-induced shock waves and the dynamic response of materials can be analyzed through numerical calculation and post-processing.

[0020] To further improve the simulation calculation speed, parallel computing platforms or software packages can be used to conduct laser shock simulations for benchmark experiments.

[0021] Example 1: Microscale laser shock simulation using the large-scale parallel molecular dynamics simulation software LAMMPS as a platform: like Figure 2 As shown, the target material is nanoscale single-crystal α-Ti with an HCP-type atomic arrangement. The boundary condition is a piston composed of an infinitely large rigid plane moving at a velocity... U P Impact along a specific crystal orientation. This velocity... U P Determined by combining equations (1), (2), (4), (6), and (7). The required material parameters are: C 0 = 5.65 S 1 = 1.01, α = 0.3, Z = 0.281 * 10 6 g∙cm -2 ∙s -1 .

[0022] Example 2: Mesoscale laser shock simulation using the commercial finite element software ANSYS: like Figure 3 As shown, the target material is micron-sized bulk α-titanium, and the boundary condition is to rigidly constrain one of its surfaces with a constant strain rate. ε ( ε × L=U P ) compressing material. This speed U P Determined by combining equations (1), (2), (4), (6), and (7). The required material parameters are: C 0 = 5.65 S 1 = 1.01, α = 0.3, Z = 0.281 * 10 6 g∙cm -2 ∙s -1 .

[0023] The technical innovations of this method include at least the following: 1. The energy density of the laser shock experiment is converted into the impact velocity or equivalent boundary conditions (such as strain rate) of the micro-mesoscopic simulation by using the momentum conservation equation (4) and the Yugongnu state equation (6), and the laser shock micro-mesoscopic simulation is carried out based on this.

[0024] 2. Conducting laser shock micro-mesoscopic simulations for benchmark experiments using molecular dynamics and finite element simulation software as platforms.

[0025] 3. Conduct laser shock micro-mesoscopic simulations for benchmark experiments using parallel computing platforms or software packages.

[0026] 4. Conduct laser shock micro-mesoscopic simulations for benchmark experiments and perform subsequent post-processing analysis.

[0027] Compared with existing technologies, this patent has at least one of the following advantages: 1. High accuracy of laser shock simulation.

[0028] 2. Significantly improves computational efficiency.

[0029] 3. It has strong applicability and scalability.

Claims

1. A method of laser shock micro-mesoscale simulation of a benchmark experiment, characterized in that, The method comprises the following steps: Step 1 : Determining the laser energy density for the laser impact of the reference experiment I 0; Step 2: Calculate the energy density of the shock wave generated by the laser impacting the material I ; Step 3: Calculate the equivalent piston velocity of the induced shock wave U P ; Step 4: at equivalent piston speed U P The simulation is performed for boundary conditions.

2. The method of claim 1, wherein, In the step 1, for one laser shot experiment, the laser energy density I 0 is: wherein, E is the energy of the laser light emitted by the laser, d is the diameter of the circular laser spot or the diameter after the non-circular spot is equivalent to a circular spot, τ is the pulse width of the laser.

3. The method of claim 2, wherein, In step 2, the energy density of the shock wave I is: Where a is the efficiency of the laser and material interaction, which is material dependent.

4. The method of claim 3, wherein, The pressure, density and energy of the region disturbed by the shock wave in the material in step 3 are respectively P S , ρ S and E S , the pressure, density and energy of the region not disturbed by the shock wave are respectively P 0、 ρ 0 and E 0, both regions satisfy the mass, momentum and energy conservation law: Shock wave speed in material U S Equivalent piston velocity of the induced shock wave U P The state equation that satisfies the shock rain condition is wherein C 0 and S 1 are material property parameters; The pressure peak of the shock wave generated by one laser impact experiment is determined according to the theoretical model of Fabbro: wherein Z Z is the impedance of the material; For micro-meso scale simulation, it is approximately considered that the pressure on the simulation boundary material is the peak pressure. Combined with equations (1), (2), (4), (6), (7), the conversion of the laser energy density I 0 to the equivalent piston velocity in simulation is realized. U P ​ 5. The method of claim 1, wherein, In step 4, a micro-meso scale target material model is constructed using simulation software to simulate the generation of the shock wave, the propagation of the laser-induced shock wave and the dynamic response of the material by numerical calculation and post-processing analysis, with the equivalent piston velocity U P or an equivalent boundary condition as a simulation boundary condition.

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