A method for simulating the quality of the post-laser impact collaborative grinding surface of an additive part

Abstract

This invention provides a method for simulating and calculating the surface quality of additive parts after laser shock calendering (LSC) combined with grinding, relating to the field of additive manufacturing technology. The method includes: calculating the time-varying impact pressure and spatial distribution during the LSC process and fitting it into a polynomial; calculating the grinding force and grinding heat flux under different grinding parameters and fitting them into a polynomial; establishing an additive part model in finite element software and applying an initial residual stress field; calculating the residual stress field after LSC by calling the impact pressure polynomial through the VDLOAD subroutine; using this residual stress field as the initial state, sequentially coupling the grinding temperature field and grinding force field through the DFLUX, DLOAD, and UTRACLOAD subroutines to calculate the final residual stress field after the combined process; establishing a morphology mathematical model based on the grinding kinematics model and abrasive grain distribution characteristics to calculate the three-dimensional surface morphology and roughness value; and quantitatively predicting the surface residual stress and surface morphology after the combined process, providing theoretical guidance for process parameter optimization, thereby reducing costs and increasing efficiency.

Description

Technical Field

[0001] This invention relates to the field of additive manufacturing technology, and in particular to a method for simulating and calculating the surface quality of additive parts after laser shock colliding grinding. Background Technology

[0002] Additive manufacturing, due to its high degree of freedom in forming, near-net-shape characteristics, and strong customization capabilities, is currently widely used in the rapid manufacturing and repair of complex and irregularly shaped, high-end components. Its small subsequent processing allowance and high degree of automation significantly reduce material and labor costs, making it a promising technology for the future. During additive manufacturing, a high-energy laser beam is generated above the material, rapidly melting and accumulating the powder. The molten metal solidifies to form complex shapes. In this process, a non-uniform temperature field is created in the molten pool, subjecting the material to unsteady, long-term thermal cycling loads. When the upper molten pool expands due to heat and contracts due to cooling, it is strongly constrained by the solidified, high-rigidity matrix layer below, preventing free deformation and easily generating high levels of residual tensile stress. When the local tensile stress exceeds the strength limit of the additive manufacturing process, cracks easily form, severely affecting the mechanical properties and fatigue life of the additive components. Furthermore, additive manufacturing uses a layered stacking process, which creates distinct layered steps on curved / sloping surfaces. The greater the layer thickness and the smaller the inclination angle, the more pronounced the surface steps become. Some incompletely melted metal powder adheres to the component surface after cooling, easily forming protruding particles. These factors reduce the surface precision of the additive part, resulting in poor surface morphology and significantly increasing surface roughness. High levels of residual tensile stress, poor surface morphology, and surface roughness on the surface of additive parts are problems that need to be addressed in the field of additive manufacturing post-processing.

[0003] In the post-processing of residual surface stress, surface shot peening is commonly used to improve the surface stress state. Compared to traditional mechanical shot peening, laser shock peening (LSP) can typically introduce a larger and deeper residual stress layer; moreover, the size and position of the laser spot can be precisely controlled, enabling the treatment of areas that are difficult or impossible to treat with traditional processes, thus eliminating the need for specialized design of strengthening equipment and processes for different parts. The process of introducing residual compressive stress into the material surface through laser shock peening essentially involves introducing plastic deformation in the impact area, forming micro-pits of a certain depth. However, this can alter the surface morphology and surface roughness to some extent, thus affecting surface accuracy. In terms of post-processing improvement of surface morphology and surface roughness, grinding (AP), as a final surface finishing process, can improve the surface morphology of the workpiece, giving it a ground appearance, and is one of the important means to ensure the surface morphology and surface accuracy of materials. However, the mechanical plastic deformation caused by abrasive removal and the thermoplastic deformation caused by grinding heat can easily lead to the formation of residual tensile stress.

[0004] As the above analysis shows, the residual stress, surface morphology, and surface roughness of additive components can be improved by laser shock blasting and grinding, respectively. However, to avoid the seesaw effect of sacrificing surface accuracy to improve residual stress and disrupting the surface stress state to ensure surface accuracy, an accurate recommendation method for different LSP and AP co-processing parameters for additive component surfaces with different initial residual stresses is crucial.

[0005] Currently, the recommended steps for synergistic process parameters from an experimental perspective are cumbersome, including: laser preparation of additive parts followed by laser shock peening; grinding with different parameters; and characterization of residual stress and surface morphology using various testing devices. For surfaces with different initial residual stresses, each set of personalized LSP-AP synergistic strengthening process parameters requires multiple processes including additive preparation, shock peening, and grinding, consuming significant material and time costs. Furthermore, the coordinated operation of multiple devices increases equipment wear and tear costs. A method for numerically simulating the surface residual stress and surface morphology of additive parts after laser shock peening synergistic grinding could provide a new approach to solving this problem. However, quantitative numerical simulation methods for laser shock peening synergistic grinding have not yet formed a complete system, representing a technological gap. Related numerical studies mostly focus on numerical simulations of single laser shock peening or single grinding processes, such as predicting residual compressive stress distribution by constructing a dynamic model of laser shock peening, or analyzing the formation law of grinding residual stress through a grinding thermo-mechanical coupling model. However, from the perspective of processing synergy, single-process simulation ignores the secondary reconstruction effect of the residual compressive stress field introduced by laser shock during grinding, failing to reflect the coupling mechanism between the two processes and unable to simulate the surface morphology of the synergistic process. Therefore, existing single-process simulation methods cannot provide precise support for parameter optimization of the laser shock and grinding synergistic process, and are insufficient to meet the requirements for precise control of residual stress and surface morphology of additive parts. Therefore, it is necessary to establish a numerical simulation method for laser shock synergistic grinding to achieve quantitative calculation of residual stress and surface morphology during the synergistic process, providing theoretical guidance for process parameter optimization, and thus maximizing the strengthening advantages of the synergistic process while ensuring surface quality. Summary of the Invention

[0006] This invention proposes a method for simulating and calculating the surface quality of additive parts after laser shock synergistic grinding, aiming to solve the technical problems that existing single-process numerical simulations cannot reflect the secondary reconstruction effect of grinding on the residual stress field of laser shock strengthening, and cannot simultaneously predict the surface residual stress and surface morphology after synergistic processing.

[0007] This invention provides a method for simulating and calculating the surface quality of additive parts after laser shock galvanizing and grinding, the method comprising the following steps: Step S1: Based on the time-varying characteristics of laser power and the change in plasma thickness, calculate the impact pressure distributed over time and space during the laser shock strengthening process, and fit the impact pressure into a polynomial form; Step S2: Establish a mathematical model of grinding force and a mathematical model of grinding heat based on grinding parameters, calculate the grinding force and grinding heat flow under different combinations of grinding parameters, and fit the calculation results into a polynomial form; Step S3: Establish an additive part model in the finite element software and apply an initial residual stress field. Call the impact pressure polynomial fitted in step S1 through the user-defined subroutine VDLOAD to simulate the laser shock strengthening process and calculate the surface residual stress field after laser shock strengthening. Step S4: Using the residual stress field calculated in step S3 as the initial state, the grinding heat flux polynomial fitted in step S2 is called through the user-defined subroutine DFLUX, and the grinding force polynomial fitted in step S2 is called through the user-defined subroutines DLOAD and UTRACLOAD. The grinding temperature field and grinding force field are applied sequentially and coupled to simulate the secondary reconstruction effect of grinding on the residual stress field after laser shock strengthening, and the final surface residual stress field after laser shock synergistic grinding is calculated. Step S5: Based on the kinematic model of grinding and the characteristics of abrasive grain distribution, establish a mathematical model for simulating grinding morphology, including grinding speed, grinding depth and feed rate, and obtain the three-dimensional surface morphology data and surface roughness value through numerical calculation.

[0008] Furthermore, the specific method for calculating the impact pressure distributed over time and space during laser shock strengthening based on the time-varying characteristics of laser power and the change in plasma thickness, and fitting the impact pressure into a polynomial form, as described in step S1, includes: The laser shock time is discretized into multiple small time steps. Within each time step, the laser power and the initial plasma thickness are assumed to be constant. The time-varying shock pressure is then solved by accumulating the values ​​time by time step. Within the energy absorption range, when the initial plasma thickness... L When the value is 0, the instantaneous impact pressure P generated by LSP and the plasma thickness at time τ are calculated using the following formula; When the initial plasma thickness L When the value is a non-zero constant, the instantaneous impact pressure P generated by LSP and the plasma thickness at time τ are calculated. The calculated time-varying impact pressure is fitted with a polynomial multiple times to obtain the fitting coefficients of the polynomial. To address the spatial distribution of the laser spot, a spatial distribution model of the shock wave pressure is established: for a circular spot, the characteristics of the Gaussian distribution are used to determine the pressure at other locations, thus establishing a spatial distribution model of laser-induced shock wave pressure. For a square light spot, based on the pressure distribution of its circumscribed circular light spot, the pressure outside the effective area of ​​the square light spot is set to zero, thus obtaining the spatial distribution of the impact pressure of the square light spot.

[0009] Furthermore, in step S2, the specific methods for establishing a mathematical model of grinding force and a mathematical model of grinding heat based on grinding parameters, calculating the grinding force and grinding heat flow under different combinations of grinding parameters, and fitting the calculation results into a polynomial form include: S2-1: Calculate the number of abrasive grains per unit volume of the grinding wheel Nv; S2-2: Calculate the total number of abrasive grains participating in grinding instantaneously on the surface of the grinding wheel; S2-3: Calculate the number of abrasive grains under different cutting conditions in the grinding contact area; The range of values ​​for the grinding contact area length and abrasive grain diameter is divided into multiple equal parts. Based on the probability distribution of abrasive grains appearing in the grinding contact area, the number of abrasive grains in each state at each position is calculated. S2-3: Calculate the plowing force and cutting force of a single abrasive grain respectively; The total grinding force is obtained by summing the grinding forces of all abrasive grains in the plowing and cutting states within the grinding arc zone. The total grinding force is then fitted with a polynomial to obtain the fitting coefficients of the fitted polynomial. S2-4: Calculate grinding heat flux; The total heat flux generated during grinding is distributed to the chips, workpiece, grinding wheel, and cutting fluid in a certain proportion. The heat distribution coefficient between the workpiece and the grinding wheel is calculated at any position in the contact area to obtain the fitting coefficient.

[0010] Furthermore, the specific method for establishing an additive part model and applying an initial residual stress field in the finite element software as described in step S3, and simulating the laser shock strengthening process by calling the impact pressure polynomial fitted in step S1 through the user-defined subroutine VDLOAD, and calculating the surface residual stress field after laser shock strengthening, includes: (1) Initial residual stress application stage of additive parts: Based on the geometry of the actual additive part, a solid model is established in the finite element software, and the corresponding material parameters are set according to the material type of the actual additive part. The mesh of the area to be strengthened by laser shock is locally refined, and the calculation unit adopts 3D stress unit that supports standard calculation. Apply a completely fixed constraint to the surface of the additive part to be laser shock hardening; The residual stress distribution on the surface of the additive part was determined by experiment, and the measured residual stress data was used as the initial stress condition applied to the model. Set up a static general analysis step to make the residual stress field inside the model reach a self-equilibrium state. Compare the calculated residual stress distribution with the measured results, and repeatedly correct the initial stress field until the two match well. (2) Calculation stage of laser shock strengthening of pre-fabricated residual stress surface: A solid model of the additive part was established in the finite element software, material parameters were set, and the Johnson-Cook constitutive model was used in the material parameter module to characterize the nonlinear constitutive relationship between material stress and strain under high strain rate. The mesh is refined at the laser shock strengthening location, and the calculation unit adopts 3D stress element that supports explicit calculation; The laser shock load is applied in Pressure mode. Based on the impact pressure polynomial coefficients calculated in step S1, combined with the set overlap rate and laser scanning path, a VDLOAD subroutine is written and called in Pressure mode. Set up the Dynamic Explicit analysis step to perform a trial calculation, add stress output and energy output in the output request, submit the calculation, view the kinetic energy results, and take the time when the kinetic energy tends to stabilize as the reference value for the duration of a single laser pulse. Based on the reference value for the duration of a single laser pulse, set the total duration of multiple laser shock enhancements at arbitrary locations, submit the calculation, and save the results. Copy the above model, convert the elements to 3D stress elements that support Standard calculations, cancel the Pressure loading mode, retain the constraints, load the results obtained from the previous calculation as the initial state, modify the analysis step to a static general analysis step, and submit the calculation to obtain the steady-state calculation results of the residual stress field on the surface after laser shock strengthening.

[0011] Further, in step S4, using the residual stress field calculated in step S3 as the initial state, the grinding heat flux polynomial fitted in step S2 is called through the user-defined subroutine DFLUX, and the grinding force polynomial fitted in step S2 is called through the user-defined subroutines DLOAD and UTRACLOAD, sequentially coupling the grinding temperature field and the grinding force field to simulate the secondary reconstruction effect of grinding on the residual stress field after laser shock strengthening. The specific method for calculating the final surface residual stress field after laser shock synergistic grinding includes: (1) Grinding temperature field calculation stage: Copy the finite element model of the residual stress field on the surface after laser shock strengthening in step S3, and set the corresponding thermophysical parameters according to the material type of the actual additive part. Replace the element type with a Heat Transfer element that supports heat transfer calculations, and add thermal boundary conditions and constraints according to the actual situation; The DFLUX subroutine is written based on the polynomial coefficients obtained from the grinding heat flux calculation in step S2, and referenced in the form of Surface heat flux when the load is applied. Select the Heat Transfer analysis step, add thermal output to the output request, and call the written DFLUX subroutine when submitting the calculation to obtain the grinding temperature field distribution. (2) Calculation stage of grinding thermo-mechanical coupling: Copy the finite element model of the surface residual stress field calculated in step S3 after laser shock strengthening, and set the corresponding material parameters according to the material type of the actual additive part; The residual stress field after laser shock strengthening calculated in step S3 is loaded into the initial analysis step in the form of the initial state. The grinding temperature field calculated in step S4-4 is loaded into the current analysis step in the form of a predefined temperature field using a sequential thermo-coupling method. Based on the multiple polynomial coefficients calculated from the normal grinding force and tangential grinding force in step S2, write the DLOAD subroutine and the UTRACLOAD subroutine respectively, and reference the subroutine in Pressure form and Surface traction form respectively when applying load; Set up a Dynamic implicit analysis step to calculate the effect of grinding thermo-mechanical coupling on the residual stress field of the surface after laser shock strengthening. Add stress output to the output request and call the written DLOAD and UTRACLOAD subroutines when submitting the calculation. (3) Steady-state result acquisition stage: The simulation model of laser shock synergistic grinding effect obtained by the thermo-mechanical coupling calculation of surface grinding after laser shock strengthening is replicated. The element type is converted to 3D stress element that supports Standard calculation. The Pressure and Surfacetraction loading modes are canceled, the predefined fields are canceled, and the constraint conditions are retained. Modify the analysis step to Static General, and the result obtained after submitting the calculation is the final surface residual stress field after laser shock co-grinding.

[0012] Furthermore, the specific method for establishing a grinding morphology simulation mathematical model based on the kinematic model of grinding and abrasive grain distribution characteristics, including grinding speed, grinding depth, and feed rate, and obtaining surface three-dimensional morphology data and surface roughness values ​​through numerical calculation as described in step S5 includes: (1) Establishment of the mathematical model of grinding morphology: Based on the kinematic relationship between adjacent abrasive grains, the motion trajectory equation of a single abrasive grain in the global coordinate system is established. The protrusion height of the abrasive grains on the grinding wheel surface is set to a random distribution, and a Gaussian distribution model is used to describe the variation law of the abrasive grain protrusion height. The actual cutting radius when the abrasive grains actually participate in cutting is expressed as the sum of the grinding wheel radius and the abrasive grain protrusion height. Based on the trajectory equation of the abrasive grains across the workpiece surface, the height value of each point on the workpiece surface is determined, forming a surface topology matrix. The value of each element in the matrix represents the surface height at the corresponding position. (2) Numerical calculation of surface roughness: In the surface topology matrix, along the direction perpendicular to the grinding feed speed, a set of vectors is extracted according to the set sampling length. This set of vectors represents the surface profile curve where the sampling position is located. The calculation is performed iteratively from the highest point to the lowest point of the vector set, and a reference line is determined by gradually decreasing thresholds, so that the area of ​​the surface profile curve above and below the reference line is equal, and the reference line is used as the baseline. Record the height of the baseline, and calculate the average absolute value of the deviation of each position in the sampling vector from the height of the baseline. This average value is the surface roughness Ra value. Compared with the prior art, the present invention has the following advantages: This invention proposes for the first time a sequentially coupled numerical simulation method for the synergistic process of laser shock annealing (LSA) and grinding. Using the residual stress field after LSA as the initial state, it quantitatively simulates the secondary reconstruction effect of grinding on the LSA residual stress field through user-defined subroutines by sequentially applying grinding heat flux and grinding force. This overcomes the limitation of single-process simulations in failing to reflect the coupling mechanism between the two processes. This invention can simultaneously output the final surface residual stress distribution cloud map, surface 3D morphology, and surface roughness Ra value after LSA-Grinding, solving the problem that existing methods cannot simultaneously evaluate the comprehensive impact of the two processes on surface quality. This provides a theoretical basis for process optimization in engineering that "ensures surface accuracy without damaging the stress state." This invention requires only minimal adjustments to material parameters through additive manufacturing, LSA, and grinding experiments. Surface quality results under different process parameter combinations can be quickly screened through numerical calculations, avoiding significant material consumption, equipment wear and tear, and labor costs, thus significantly shortening the development cycle of the synergistic process. This invention is applicable to the combined simulation of different materials (such as 316L stainless steel), different initial residual stress states, different laser shock parameters (spot shape, overlap rate, scanning path, number of impacts), and different grinding parameters (grinding speed, grinding depth, feed rate). It can quickly recommend the optimal laser shock synergistic grinding process parameters for additive parts with specific initial states. Experimental verification (taking 316L stainless steel as an example) shows that the error between the final surface residual stress simulated by this invention and the measured value is within a reasonable range, and the simulated surface roughness Ra value trend is consistent with the experimental value, which can meet the accuracy requirements for parameter initial selection and optimization in engineering applications.

[0013] Based on the implementation methods provided in the above aspects, this application can be further combined to provide more implementation methods. Attached Figure Description

[0014] The above and other objects, features, and advantages of exemplary embodiments of the present invention will become readily apparent upon reading the following detailed description with reference to the accompanying drawings. In the drawings, several embodiments of the invention are illustrated by way of example and not limitation, with the same or corresponding reference numerals denoteing the same or corresponding parts, wherein: Figure 1 A flowchart of a method for simulating and calculating the surface quality of an additive part after laser shock colliding grinding is provided by the present invention; Figure 2 A comparison graph showing the change of actual laser power and simulated power over time; Figure 3 The figure shows the simulation results of LSP impact pressure changing over time. Figure 4 Flowchart for LSP impact pressure calculation; Figure 5A schematic diagram of the spatial distribution of energy in a laser shock-enhanced spot. Figure 6 A simplified diagram of the motion trajectory of adjacent abrasive grains on the surface of the grinding wheel; Figure 7 This is a simulation result of the spatial distribution of the shock wave pressure from a square light spot. Figure 8 This is a schematic diagram of the mesh refinement strategy for the finite element model of an additive part. Figure 9 This is a schematic diagram of the LSP scan path (S-shaped). Figure 10 Figure showing the results of applying initial residual stress to the additive surface. Figure 11 shows the calculation results of residual stress on the LSP surface. Figure (a) shows the distribution of residual stress on the surface; Figure (b) shows the distribution of residual stress along the depth direction. Figure 12 This is a diagram showing the residual stress distribution on the surface after LSP-AP co-processing. Figure 13 shows the comparison between LSP-AP surface morphology simulation and experiment. Figure (a) shows the surface morphology simulation results; Figure (b) shows the surface morphology experimental results. Detailed Implementation

[0015] The exemplary embodiments disclosed in this application will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of this application are shown in the drawings, it should be understood that this application can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of this application and to fully convey the scope of this application to those skilled in the art. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art.

[0016] This invention provides a method for simulating and calculating the surface quality of additive parts after laser shock galvanizing and grinding, the method comprising the following steps: (1) Calculation of LSP impact pressure: Based on relevant theories, the laser impact pressure is calculated using MATLAB programming software. The calculated pressure is fitted in the form of multiple polynomials, and the polynomial coefficients are output.

[0017] (2) Calculation of AP characteristic grinding heat and grinding force: The grinding heat flow and grinding force generated by the grinding wheel under different grinding parameters were calculated using MATLAB programming software, and the calculation results were fitted in multiple polynomial form.

[0018] (3) Calculation of residual stress on LSP surface: Based on the polynomial coefficients calculated in step (1), the user-defined subroutine VDLOAD in ABAQUS finite element software is used to program the process parameters such as laser shock pressure, shock position, and overlap rate, and then participate in the calculation of residual stress on the surface after LSP.

[0019] (4) Calculation of surface residual stress: Based on the heat flux polynomial coefficients obtained in step (2), the temperature field distribution of the grinding process is pre-calculated using the user-defined subroutine DFLUX. The residual stress field obtained in step (3) is used as the initial state, and the above-mentioned grinding temperature field is introduced. At the same time, the user-defined subroutines DLOAD and UTRACLOAD are used to program and load the grinding force polynomial coefficients calculated in step (2). On this basis, the update and iteration calculation of the LSP residual stress field by the AP coupled thermodynamic action is completed.

[0020] (5) LSP-AP Surface Morphology and Roughness Simulation: Based on relevant theories, MATLAB programming software was used to simulate and characterize the surface morphology of the grinding process under the above grinding parameters. The overall flowchart of the simulation is as follows: Figure 1 As shown.

[0021] The specific calculation process is as follows: S1: LSP Impact Pressure Calculation 1. Fitting the laser power curve In laser shock peening (LSP) processes, an absorption layer is often used to efficiently generate plasma, while a confinement layer is used to further restrict the escape of shock energy. Laser energy is captured by the absorption layer in the gap between the target and the confinement layer. The absorption layer vaporizes after being heated by the laser, transforming into plasma. Because the plasma is confined by the confinement layer and cannot diffuse freely, its internal pressure rises rapidly. When the pressure generated by the plasma reaches a certain threshold, a shock wave is generated, which propagates within both the target and the confinement layer. Therefore, the plasma layer thickness is a crucial factor affecting the shock pressure, and the pulsed laser power is the key factor determining the plasma layer thickness. Based on the actual laser energy curve shape, a method is considered... The mathematical form is used for fitting, where t is time, and A and n are parameters that need to be adjusted according to the actual laser power, such as... Figure 2 The image shows a comparison between a real pulse obtained using this method and a simulation result.

[0022] 2. LSP Impact Pressure Calculation When the laser power is in the energy absorption range I When 0 is a constant and the initial plasma thickness L is 0, the instantaneous impact pressure P generated by the LSP and τ The plasma thickness at time t can be calculated using the following formula: (1) in, Z The reduced acoustic impedance coefficient can be obtained from Perform calculations. Z 1. Z 2. Acoustic impedance of the target material and acoustic impedance coefficient of the confinement layer, respectively. When the initial plasma thickness... L When the value is non-zero constant, the instantaneous impact pressure generated by LSP P as well as τ The plasma thickness at time t can be calculated using the following formula: (2) In the formula P 0 is the assumption L When the value is zero, the resulting impact pressure is calculated using the same LSP power. Here, formula (1) is used for calculation. P When the value is 0, the 2α+3 term can be replaced by the value 3.

[0023] At the end of laser irradiation, a plasma of a certain thickness will still exist, but it will no longer receive replenishment of laser energy. Within this energy release range, the plasma's internal energy will continue to be converted into mechanical energy to "push aside the confinement layer / target material." At this point, the shock wave pressure... and plasma thickness The following equations can be used to solve for: (3) In the formula: For specific heat ratio, The duration of the laser pulse.

[0024] Formulas (1)-(3) for solving the impact pressure and the instantaneous plasma thickness are all based on the assumption that the laser power and the initial plasma thickness are constant. However, in actual processes, the laser power is time-varying and not a constant value. Therefore, in the actual calculation, this paper discretizes the impact time into a sufficient number of small time steps, assumes that the laser power and the initial plasma thickness are constant values ​​in each time step, and solves by accumulating the results time by time to approximate the time-varying impact pressure at any moment. Figure 3 The simulation result of the impact pressure obtained using this method. The impact pressure P ( ) is calculated using formulas (1)-(3). t This requires fitting using multiple polynomials to facilitate subsequent calculation steps; its expression can be written as: (4) in, for n The fitting coefficients of the order-1 fitting polynomial.

[0025] The calculation of impact pressure in this step can be summarized as follows: Figure 4 The flowchart shown.

[0026] 3. Spatial distribution of laser pressure In LSP (Laser Shock Wave) processes, laser spot shapes are typically either circular or square. The instantaneous pressure at the spot center can be determined using the calculation method described above. When dealing with circular spots, the pressure at other locations can be determined based on the characteristics of a Gaussian distribution. For a circular spot, the spatial distribution model of the laser shock wave pressure is as follows: (5) In the formula: P space Distance from the center of the light spot r Peak shock wave pressure at the location; r 0 is the radius of the light spot; P( t ( ) represents the instantaneous impact pressure at the center of the light spot. For example... Figure 5 This represents the spatial distribution of the impact energy of a circular single-spot LSP laser.

[0027] When dealing with a square spot, the laser pressure of the circular spot circumscribed by the square spot can be calculated first according to formula (5) based on half the length of its diagonal. Then, the pressure at the outer position of the square spot is recorded as zero according to the actual action area of ​​the square spot. In this way, the general method of calculating square and circular spots can be used.

[0028] S2: Calculation of grinding heat and grinding force in AP characteristic grinding Based on grinding theory, a mathematical model coupling grinding parameters (grinding speed, depth of cut, and feed rate) is constructed to characterize the variation laws of normal grinding force, tangential grinding force, and grinding heat flux. A calculation program is developed using MATLAB software to perform numerical calculations of grinding force and grinding heat under any combination of grinding parameters. Based on the calculated data, a multi-order polynomial fitting algorithm is used for data regression analysis, ultimately establishing a continuous function model relating grinding force, grinding heat, and grinding process parameters.

[0029] 1. Number of abrasive grains per unit volume of grinding wheel N v calculate (6) in, This represents the total volume of all abrasive grains within a unit volume of the grinding wheel. d gx It is the diameter of the abrasive grain. It is the maximum abrasive grain diameter d max With minimum abrasive diameter d min difference, σ It is the standard deviation of the abrasive grain diameter fluctuation.x The abrasive grain diameter deviates from the average abrasive grain diameter. d mean The difference, i.e. x = d gx -d mean ,by P g ( x This indicates that the surface deviation of the grinding wheel from the average value is... x The frequency of abrasive grain appearance; once the grinding wheel is determined, d max , d min , σ , d mean All of these can be obtained through actual measurements, and thus can be determined. N v The value; 2. Calculation of the total number of abrasive grains participating in grinding instantaneously on the grinding wheel surface. The total number of abrasive grains in the grinding zone (the total number of abrasive grains that participate in grinding on the grinding wheel surface instantaneously) can be calculated by the following formula. (7) in h cu,max The maximum undeformed cutting thickness, v s Let be the linear velocity of the grinding wheel. To solve formula (7), calculations must be performed first. h cu,max The contact state between abrasive grains and material in the grinding contact zone can be categorized into non-contact state, sliding state, plowing state, and cutting state. The instantaneous contact state of the abrasive grains can be determined by the depth of cut of the abrasive grains at that moment. h cuz Distinguishing: Coefficient , These represent the critical depth of cut coefficients for plowing and cutting states, respectively. The critical depth of cut for plowing action is... The critical depth of cut for the cutting action is Based on the critical depth of cut, assuming that the height of the abrasive grain protrusions follows a uniform distribution, with... P g (y) represents the probability of its occurrence, which can be obtained by combining formulas (6) and (7) with the following system of equations (8). h cu,max The value of .

[0030] (8) In finding h cu,max Then, by using formula (7) again, the solution can be obtained. N total .

[0031] 3. Calculation of the number of abrasive grains under different cutting conditions in the grinding contact zone. Contact area length The range of values ​​for abrasive grain diameter Divide into a sufficient number of equal parts (e.g., N equal parts). P g ( l a The value () represents the probability of abrasive grains appearing in the grinding contact area, and it is assumed that they follow a uniform distribution. (The above is a simplified representation of the probability.) i Represents any position in space ( i The range is 0 to N). Therefore, we have , , as well as and , Since the intervals between each segment are small enough, for ease of calculation, The position parameter can be used in the middle of each interval. This is used to obtain the contact type of the abrasive grains at that location. The number of abrasive grains in each state at that location can be represented as follows: (9) in according to To calculate, It is the grinding depth. It is the diameter of the grinding wheel; 4. Grinding force calculation Depending on the different states of the abrasive grains during grinding, grinding forces can be divided into frictional force, plowing force, and cutting force. Compared to plowing force and cutting force, frictional force is very small. Therefore, for ease of calculation, the influence of frictional force is ignored when calculating grinding forces in this paper.

[0032] (1) The plowing force of each abrasive grain in the tangential and normal directions can be calculated using the following formula: (10) in, It is the coefficient of friction of the plow. It refers to the Brinell hardness of the material. It is a correction factor added to the grinding force calculation to correct for some factors that are not fully considered, such as thermal effects and abrasive grain shape effects. α It is the instantaneous entry angle, which can be determined by... calculate.

[0033] (2) Tangential and normal cutting forces of a single abrasive grain: (11) in For the shear strength of the material, It is the angle of friction. . It is the shear angle. During grinding, the abrasive grains' cutting edges come into contact with the workpiece surface through compression, removing material through cutting action. The angle between the cutting edge of the abrasive grain and the workpiece surface is defined as the cutting edge angle. Using the critical cutting edge angle condition It can determine the minimum cutting edge angle required for the cutting action to occur. Instantaneous cutting edge angle It can be done calculate.

[0034] (3). Calculation of total grinding force: The above method can be used to calculate each component of the grinding force of a single abrasive grain. By summing the abrasive grain grinding forces under different conditions within all calculated grinding arc zones, the total grinding force at any point can be obtained. The result of the total grinding force is fitted using a multi-order polynomial.

[0035] (12) in, , for n The fitting coefficients of the order-1 fitting polynomial.

[0036] (4) Calculation of grinding heat flow: Total heat flux generated during grinding ( , b The heat distribution (based on the width of the grinding wheel) is allocated proportionally to the chips, workpiece, grinding wheel, and cutting fluid. The heat distribution coefficient between the workpiece and the grinding wheel is: (13) in, and These are the thermal conductivity of the abrasive particles and the workpiece, respectively. It is the density of the workpiece. It is the specific heat of the workpiece. This is the effective contact radius between the abrasive grain and the workpiece. For alumina and CBN grinding wheels, The same value is used for calculation, generally 15 μm.

[0037] Residual heat in the workpiece This can be expressed as, (14) in, It is the extreme value of grinding temperature. It is the boiling point of the cutting fluid. and These are the thermal conductivity coefficients of the cutting fluid and the workpiece material, respectively. It can be obtained through the following formula, Where C is related to the Pecklet number, , α w This is the thermal diffusivity. It can be further obtained from the following formula: (15) The method described above can be used to calculate the contact area at any location. ,pass n Fitting it with an order polynomial: (16) In the formula, represents the fitting coefficient.

[0038] S3: Calculation of residual stress on LSP surface The LSP process is characterized by the generation of high-intensity loads by the laser spot within an extremely short time, causing the material to deform at an extremely high strain rate. Furthermore, the non-uniform temperature field resulting from the rapid heating and cooling of the high-energy-density laser beam during additive manufacturing can easily induce high levels of residual tensile stress near the surface of the additive part. To address these characteristics, this patent requires multi-step coupled calculations when using ABAQUS to calculate the residual stress on the additive surface after LSP. The key simulation details are as follows: 1. Application of initial residual stress in additive parts (1) Modeling: Based on the actual geometry of the additive part, a finite element model is established in ABAQUS, and the corresponding parameters are set according to the material type of the actual additive part.

[0039] (2) Mesh and element: To ensure calculation accuracy, the mesh can be locally refined in the subsequent LSP action area; the element used for calculation must be a 3D stress element that supports Standard calculation.

[0040] (3) Constraints: Apply complete fixed constraints to the surface of the additive part to which LSP is to be implemented.

[0041] (4) Measurement of residual stress: The distribution of residual stress on the surface of the additive part is determined by experiment.

[0042] (5) Calculation of the analysis step: The measured residual stress data is applied to the model as the initial stress condition. Then, a static general analysis step is set, and the analysis step duration is set (this step is a steady-state analysis, and the time can be set as needed, or it can be set to 1 second) to make the residual stress field inside the model reach a self-equilibrium state. The calculated residual stress distribution is compared with the measured results, and the initial stress field is repeatedly corrected until the two match well.

[0043] 2. Calculation of LSP on precast residual stress surfaces (1) Modeling: In ABAQUS, a solid model is built according to the actual shape of the additive part, and the corresponding parameters are set according to the material type of the actual additive part. In the material parameter module, the Johnson-Cook constitutive model is used to demonstrate the nonlinear constitutive relationship between material stress and strain under high strain rate of LSP.

[0044] (2) Mesh and Elements: To ensure computational accuracy, mesh refinement can be considered at the locations where LSP is applied during mesh construction. The elements used for computation must be 3D stress elements that support explicit computation.

[0045] (3) Loading and Constraints: The laser shock load is applied in Pressure mode. Based on the polynomial coefficients calculated in S1, the required overlap ratio and laser path are added, and a VDLOAD subroutine is written and called in Pressure mode. Constraints are added according to the actual situation. If you want to easily implement the loading of arbitrary shock paths and arbitrary laser shock parameters, you need to write a user-defined program VDLOAD to achieve this; otherwise, the load needs to be reset every time you change a set of parameters and paths.

[0046] (4) Analysis Step and Trial Calculation: First, perform a trial calculation using a single laser shock. The analysis step should be set to Dynamic Explicit, and the analysis step duration should initially be a relatively large value (e.g., if the duration of a single laser pulse is t, the trial calculation duration could be 5t). Add a Stresses output request in Field Output Requests; add an Energy output request in History Output Requests, and submit the calculation. Check the ALLKE (kinetic energy) result in the calculated results, and take the time when the kinetic energy result tends to stabilize as the reference value for the duration of a single laser pulse in the simulation.

[0047] (5) Modify the calculation time and obtain steady-state results: Based on the reference value of the duration of a single laser pulse obtained in “4. Analysis Step and Trial Calculation”, set the total time length for multiple LSPs at arbitrary positions, submit the calculation and save the results; copy the model again, replace the elements in the copied model with 3D stress elements that support Standard calculation, cancel the Pressure mode in loading, retain the constraints, load the results calculated above in the Initialstate form in Predefined Field, modify the analysis step to Static General analysis step, there are no special requirements for the calculation time (1s is sufficient), and the result obtained after submitting the calculation is the steady-state calculation result of the residual stress on the surface after LSP.

[0048] S4: Calculation of residual stress on LSP-AP surface: The characteristic of the LSP-AP synergistic process is that an AP process is further applied to the LSP surface, so that the LSP-reinforced surface retains the grinding morphology while minimizing changes to the stress state of the LSP-reinforced surface, i.e., preventing the generation of high-level tensile stress. To address this characteristic, this patent requires multi-step coupled calculations when using ABAQUS to calculate the residual stress on the additive surface after LSP-AP synergistic reinforcement. The key simulation details are as follows: 1. Grinding Temperature Calculation: Copy the model used in S3 to calculate the residual stress on the LSP-reinforced additive manufacturing surface, and set the corresponding parameters according to the material type of the actual additive part. Replace the element type with the Heat Transfer element in the standard module that supports heat transfer calculation. Add thermal boundary conditions and constraints as needed. Write the DFLUX subroutine based on the polynomial coefficients obtained from the grinding heat flux calculation in S2, and reference this subroutine in the form of Surface heat flux when applying loads. After selecting Heat Transfer in the analysis step, add a Thermal output request in Field Output Requests, and select the written subroutine when submitting the calculation.

[0049] 2. LSP Surface Grinding Thermo-Mechanical Coupling Calculation: Copy the model used in S3 to calculate the residual stress on the LSP-reinforced additive surface, and set the corresponding parameters according to the material type of the actual additive part. Load the stress results calculated from S3 into the Initial step in the Predefined field as initialstate. The grinding thermo-mechanical coupling effect is added using sequential thermo-mechanical coupling; load the temperature calculation results from the previous step "Grinding Temperature Calculation" into the current analysis step in the Predefined field as Temperature. Write the polynomial coefficients calculated from the normal and tangential grinding forces in S2 into the DLOAD and UTRACLOAD subroutines respectively, and reference these subroutines in Pressure and Surface traction forms when applying loads. The calculation of the effect of grinding thermo-mechanical coupling on the residual stress on the LSP surface in this step requires calculation using the Dynamic implicit analysis step. Add a Stress output request in Field Output Requests, and select the written subroutine when submitting the calculation.

[0050] The DLOAD and UTRACLOAD subroutines can respectively apply normal and tangential grinding forces. These subroutines were written because the grinding force generated during grinding varies with grinding parameters (depth of cut, feed rate, and wheel speed) and is a moving load. Without using subroutines, it would be difficult to apply such a dynamic load through the ABAQUS panel input.

[0051] This invention requires sequential thermo-mechanical coupling to further couple the calculation of grinding force and grinding heat on a laser-shocked surface with pre-existing residual stress. In ABAQUS, thermo-mechanical coupling calculations can only be achieved through simultaneous thermo-mechanical coupling and sequential thermo-mechanical coupling. One of the challenges in simulating laser-shock co-grinding is the long computation time and difficulty in achieving convergence. Simultaneous thermo-mechanical coupling requires solving multiple differential equations simultaneously, such as heat transfer calculations and stress-strain calculations, which easily leads to convergence issues and is computationally intensive and time-consuming. Our proposed sequential thermo-mechanical method first calculates the grinding temperature, then uses the temperature result as a load, combined with grinding forces written in DLOAD and UTRACLOAD subroutines, for calculation. This is equivalent to solving for the heat transfer result, reducing the number of equations to be solved simultaneously, reducing computational load, and easily achieving convergence.

[0052] 3. Obtain steady-state calculation results: Copy the LSP-AP synergistic simulation model obtained from "LSP surface grinding thermo-mechanical coupling calculation". In the copied model, replace the elements with 3D stress elements that support Standard calculation, cancel the Pressure and Surface traction modes in the loading, cancel the predefined field in the Predefined field, retain the constraints, modify the analysis step to Static General analysis step, and there are no special requirements for the calculation time (1 second is sufficient). The result obtained after submitting the calculation is the steady-state calculation result of the surface residual stress after LSP-AP.

[0053] S5: LSP-AP surface morphology and roughness simulation: Applying the process parameters for calculating LSP-AP reinforced surface residual stress as described earlier using ABAQUS, a mathematical model for simulating grinding morphology, incorporating three factors—grinding speed, depth of cut, and feed rate—is established based on grinding kinematics and material forming theory. MATLAB software is then used to program and calculate the three-dimensional surface morphology data of the material under these grinding parameters, and the surface roughness Ra is output.

[0054] Figure 6 This is a simplified diagram of the motion model of any two adjacent abrasive grains on the surface of a grinding wheel. Assume the first abrasive grain... The movement begins from the lowest point of contact with the workpiece. and Let be the local coordinate system to which the abrasive grain trajectory belongs. It is also the global coordinate system.

[0055] (17) In equation (17): , abrasive grains The coordinates; The actual radius of the abrasive grain's location; ; For the corner; For feed rate; For turning The time of the angle; abrasive grains The radius of the grinding wheel; The distance between each abrasive grain on the surface of the grinding wheel ; indicates the grinding wheel grit size; This refers to the number of grinding wheel structures. After the abrasive grains pass over the workpiece, each point on the workpiece surface... Height can be determined by express.

[0056] Equation (17) is rearranged to obtain the abrasive trajectory of any abrasive grain in the global coordinate system: (18) In the formula, Represents the topology matrix elements of the workpiece surface along The spacing of the directions. The height of each abrasive grain protrusion on the surface of the grinding wheel varies randomly. This patent uses a Gaussian distribution to describe the variation of the abrasive grain protrusion height. According to this formula (17), the actual cutting radius when the abrasive grain actually participates in cutting should be the sum of the grinding wheel radius and the height of the abrasive grain protrusion.

[0057] The above grinding morphology formula was calculated using MATLAB software. The specific steps are as follows. (1) Store the calculated results in a matrix, where the value of each element in the matrix represents the surface height at that location.

[0058] (2) By taking values ​​from a row or column in the matrix, a set of vectors can be obtained. This set of vectors represents the surface profile curve where the value is located. When calculating the surface roughness Ra value of a ground surface, a measurement curve is usually taken along the direction perpendicular to the grinding feed speed, and the calculation result of this sampling curve represents the surface roughness Ra value at the sampling location. Similarly, in the surface topography matrix, a set of vectors is taken along the direction perpendicular to the grinding feed speed, according to the required sampling length.

[0059] (3) Starting from the highest point of the vector set and continuing to the lowest point, perform a loop calculation. The calculation involves decreasing the vector by a certain small value to obtain a reference straight line with a certain height. The area of ​​the contour curve above and below this line is equal. This reference straight line is the baseline. Record the height of the baseline and calculate the average value of the deviation of each position in the sampling vector from the height of the baseline. This average value is the surface roughness Ra value. Example

[0060] The following detailed explanation of the invention is illustrated with a specific example. The example uses additively manufactured 316L stainless steel with an initial surface residual tensile stress of 200 MPa. The LSP-AP parameters are: laser power density... Laser shock peening was performed on the target surface using an "S"-shaped scanning sequence, with a spot overlap rate of 50% and three shocks at the same location; AP parameters were as follows. , and .

[0061] In numerical simulations, the Johnson-Cook constitutive model is widely used in studies of explosive impacts and instantaneous impacts to describe the strain hardening process of materials during impact. The simplified formula for this model is: (19) In the formula, The equivalent plastic stress is expressed in MPa. The initial yield strength; These are the strain hardening parameters of the material; The strain hardening index; The equivalent plastic strain of the material; The strain rate strengthening coefficient of the material; This is the equivalent plastic strain rate; The reference strain rate is shown in Table 1. The material parameters involved in the calculation process of this example are listed in Table 1.

[0062] Table 1 Relevant Material Parameters

[0063] Based on the S1 step simulation of a square light spot with a side length of 4mm, the spatial distribution shape of the shock wave pressure is as follows: Figure 7 As shown, To calculate the surface residual stress of 316L stainless steel after LSP treatment, a Johnson-Cook constitutive model of the 316L stainless steel material was established. The initial residual tensile stress field after laser additive manufacturing, loaded in step S3, was used as the initial condition for the laser shock simulation, with full constraints applied to the bottom surface of the target. A 12 mm × 12 mm × 4 mm cubic finite element model was established in Abaqus. Considering that laser shock strengthening would cause deformation of the near-surface layer of the material at a certain high strain rate, the mesh was refined within a 1 mm thick area at the top of the target to ensure computational accuracy and improve computational efficiency. The mesh size in this region was 0.1 mm × 0.1 mm × 0.05 mm. For other locations, a mesh size of 0.1 mm × 0.1 mm × 0.3 mm was used. The mesh settings are as follows: Figure 8 As shown. (Based on laser power density) Laser shock peening was performed on the target surface in an "S"-shaped scanning sequence, with a spot overlap rate of 50% and three shocks at the same location. The scanning path of the LSP is as follows. Figure 9 As shown.

[0064] According to step S3, the additive surface with a measured residual tensile stress of approximately 200 MPa is applied to the model surface, and the result is as follows. Figure 10 As shown, the steady-state initial residual stress field of the additive surface simulated according to step S3 is approximately 200 MPa.

[0065] Figure 11 shows the residual stress distribution on the surface and in the depth direction of the material after LSP (Laminated Stress Processing). It can be seen that LSP induces residual compressive stress on the surface of the additive part, and the residual tensile stress distribution near the surface of the material is also improved. After LSP strengthening, the maximum residual compressive stress on the material surface reaches 446 MPa, and a residual compressive stress layer with a thickness exceeding 1 mm is formed in the depth direction. LSP treatment can effectively convert the residual tensile stress near the surface of the 316L stainless steel target material produced by LSP into compressive stress.

[0066] Based on this LSP, the AP effect is further coupled according to steps S2 and S4, using the corresponding grinding process parameters ( , and The simulation results of the tangential residual stress obtained from the processing are as follows: Figure 12 As shown in the figure, after the additively manufactured 316L surface with an initial stress of 200 MPa is treated with AP, the LSP-strengthened areas of the surface can still maintain a stable residual stress level, and most of the areas do not exceed 10 MPa; the tangential residual stress at the center of the model is approximately -17 MPa, while the tangential residual stress at the center of the cube under experimental conditions is -5 MPa.

[0067] Using the grinding parameters, the workpiece grinding surface morphology obtained in step S5 is shown in Figure 13, and the experimental results are also shown in Figure 13. The surface roughness Ra values ​​obtained under experimental conditions and simulation calculations are 1.58 μm and 1.31 μm, respectively. This indicates that the LSP-AP synergistic strengthening process under these parameters can indeed achieve a grinding morphology on the workpiece surface while preserving the improved residual stress level. Furthermore, the calculation method proposed in this patent has a certain degree of accuracy. Although there are still deviations in calculation precision, it meets the requirements for initial parameter selection in engineering applications and can provide important reference value for the optimal selection of LSP-AP parameters in engineering.

[0068] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method of simulating the quality of the post-laser impact synergistic grinding surface of an additive piece, characterized in that, The method includes the following steps: Step S1: Based on the time-varying characteristics of laser power and the change in plasma thickness, calculate the impact pressure distributed over time and space during the laser shock strengthening process, and fit the impact pressure into a polynomial form; Step S2: Establish a mathematical model of grinding force and a mathematical model of grinding heat based on grinding parameters, calculate the grinding force and grinding heat flow under different combinations of grinding parameters, and fit the calculation results into a polynomial form; Step S3: Establish an additive part model in the finite element software and apply an initial residual stress field. Call the impact pressure polynomial fitted in step S1 through the user-defined subroutine VDLOAD to simulate the laser shock strengthening process and calculate the surface residual stress field after laser shock strengthening. Step S4: Using the residual stress field calculated in step S3 as the initial state, the grinding heat flux polynomial fitted in step S2 is called through the user-defined subroutine DFLUX, and the grinding force polynomial fitted in step S2 is called through the user-defined subroutines DLOAD and UTRACLOAD. The grinding temperature field and grinding force field are applied sequentially and coupled to simulate the secondary reconstruction effect of grinding on the residual stress field after laser shock strengthening, and the final surface residual stress field after laser shock synergistic grinding is calculated. Step S5: Based on the kinematic model of grinding and the characteristics of abrasive grain distribution, establish a mathematical model for simulating grinding morphology, including grinding speed, grinding depth and feed rate, and obtain the three-dimensional surface morphology data and surface roughness value through numerical calculation.

2. The method of claim 1, wherein, The specific method described in step S1 for calculating the impact pressure distributed over time and space during laser shock strengthening based on the time-varying characteristics of laser power and the change in plasma thickness, and fitting this impact pressure into a polynomial form, includes: The laser shock time is discretized into multiple small time steps. Within each time step, the laser power and the initial plasma thickness are assumed to be constant. The time-varying shock pressure is then solved by accumulating the values ​​time by time step. Within the energy absorption range, when the initial plasma thickness L is 0, the instantaneous impact pressure P generated by the LSP and the plasma thickness at time τ are calculated using the following formula: Where Z is the refracted acoustic impedance coefficient, I0 is the laser power, and α is the instantaneous angle of entry; When the initial plasma thickness L is a non-zero constant, the instantaneous impact pressure P generated by the LSP and the plasma thickness at time τ can be calculated by the following formula: where P0 is the pressure when L is assumed to be zero, is the initial plasma thickness; t is time, L(t) is the real-time thickness of the plasma at time t, and P1(t) is the instantaneous pressure generated at time t. The calculated time-varying impact pressure is fitted using a polynomial, and its expression is as follows: wherein, is the fitted coefficient for the ith term of the n order polynomial fit of P(t); To address the spatial distribution of the laser spot, a spatial distribution model of the shock wave pressure is established: For a circular spot, the Gaussian distribution is used to determine the pressure at other locations. The spatial distribution model of the laser-induced shock wave pressure is as follows: where P space is the peak shock pressure at a distance r from the center of the spot; r0is the spot radius; P(t) is the instantaneous shock pressure at the center of the spot; For a square light spot, based on the pressure distribution of its circumscribed circular light spot, the pressure outside the effective area of ​​the square light spot is set to zero, thus obtaining the spatial distribution of the impact pressure of the square light spot.

3. The method of claim 1, wherein, In step S2, the specific methods for establishing a mathematical model of grinding force and a mathematical model of grinding heat based on grinding parameters, calculating the grinding force and grinding heat flow under different combinations of grinding parameters, and fitting the calculation results into a polynomial form include: S2-1: Calculate the number of abrasive grains per unit volume of the grinding wheel, Nv; in, d is the total volume of all abrasive grains within a unit volume of the grinding wheel. gx It is the diameter of the abrasive grain. It is the maximum abrasive grain diameter d max With minimum abrasive diameter d min The difference, σ is the standard deviation of the abrasive grain diameter fluctuation, and x is the deviation of the abrasive grain diameter from the average abrasive grain diameter d. mean The difference, i.e., x=d gx -d mean , with P g (x) represents the frequency of abrasive grains on the grinding wheel surface that deviate from the average value by x; when the grinding wheel is determined, d max d min , σ, d mean All of these can be obtained through actual measurements, and thus N can be determined. v The value; S2-2: Calculate the total number of abrasive grains participating in grinding instantaneously on the surface of the grinding wheel; The total amount of abrasive grains in the grinding zone can be calculated using the following formula: where h cu,max is the maximum undeformed cutting thickness, v s is the wheel linear speed; the contact state between the abrasive grain and the material in the grinding contact zone can be divided into non-contact state, sliding state, plowing state and cutting state; S2-3: Calculate the number of abrasive grains under different cutting conditions in the grinding contact area; Dividing the range of values ​​for the grinding contact zone length and abrasive grain diameter into multiple equal parts, and based on the probability distribution of abrasive grains appearing in the grinding contact zone, the number of abrasive grains in each state at each location can be expressed as: in, according to To calculate, It is the grinding depth. It is the diameter of the grinding wheel; S2-3: Calculate the plowing force and cutting force of a single abrasive grain respectively: The tangential and normal tillage forces of a single abrasive grain can be calculated using the following formulas: in, It is the coefficient of friction of the plow. It refers to the Brinell hardness of the material. It is a correction factor added to the grinding force calculation, where α is the instantaneous angle of entry; Tangential and normal cutting forces of a single abrasive grain: in, For the shear strength of the material, It is the angle of friction. It is the shear angle; The angle between the cutting edge of the abrasive grain and the workpiece surface is called the cutting edge angle; Instantaneous cutting edge angle; The total grinding force is obtained by summing the grinding forces of all abrasive grains in the plowing and cutting states within the grinding arc region, and then fitting this total grinding force as a polynomial. ； in, , These are the fitting coefficients before the i-th term of the n-th polynomial when fitting tangential and normal grinding forces, respectively; S2-4: Calculate grinding heat flux; The total heat flux generated during grinding is distributed to the chips, workpiece, grinding wheel, and cutting fluid in a certain proportion. The heat distribution coefficient between the workpiece and the grinding wheel is as follows: in, and These are the thermal conductivity of the abrasive particles and the workpiece, respectively. It is the density of the workpiece. It is the specific heat of the workpiece. It is the effective contact radius between the abrasive grains and the workpiece; Residual heat in the workpiece It can be represented as: in, It is the extreme value of grinding temperature. It is the boiling point of the cutting fluid. and These are the thermal conductivity coefficients of the cutting fluid and the workpiece material, respectively. The method described above can be used to calculate the contact area at any location. Fit it using an nth-order polynomial: in, represents the fitting coefficient.

4. The method for simulating and calculating the surface quality of an additive part after laser shock calendering, as described in claim 1, is characterized in that... The specific method for establishing an additive part model and applying an initial residual stress field in the finite element software as described in step S3, and simulating the laser shock strengthening process by calling the impact pressure polynomial fitted in step S1 through the user-defined subroutine VDLOAD, and calculating the surface residual stress field after laser shock strengthening, includes: (1) Initial residual stress application stage of additive parts: Based on the geometry of the actual additive part, a solid model is established in the finite element software, and the corresponding material parameters are set according to the material type of the actual additive part. The mesh of the area to be strengthened by laser shock is locally refined, and the calculation unit adopts 3D stress unit that supports standard calculation. Apply a completely fixed constraint to the surface of the additive part to be laser shock hardening; The residual stress distribution on the surface of the additive part was determined by experiment, and the measured residual stress data was used as the initial stress condition applied to the model. Set up a static general analysis step to make the residual stress field inside the model reach a self-equilibrium state. Compare the calculated residual stress distribution with the measured results, and repeatedly correct the initial stress field until the two match well. (2) Calculation stage of laser shock strengthening of pre-fabricated residual stress surface: A solid model of the additive part was established in the finite element software, material parameters were set, and the Johnson-Cook constitutive model was used in the material parameter module to characterize the nonlinear constitutive relationship between material stress and strain under high strain rate. The mesh is refined at the laser shock strengthening location, and the calculation unit adopts 3D stress element that supports explicit calculation; The laser shock load is applied in Pressure mode. Based on the impact pressure polynomial coefficients calculated in step S1, combined with the set overlap rate and laser scanning path, a VDLOAD subroutine is written and called in Pressure mode. Set up the Dynamic Explicit analysis step to perform a trial calculation, add stress output and energy output in the output request, submit the calculation, view the kinetic energy results, and take the time when the kinetic energy tends to stabilize as the reference value for the duration of a single laser pulse. Based on the reference value for the duration of a single laser pulse, set the total duration of multiple laser shock enhancements at arbitrary locations, submit the calculation, and save the results. Copy the above model, convert the elements to 3D stress elements that support Standard calculations, cancel the Pressure loading mode, retain the constraints, load the results obtained from the previous calculation as the initial state, modify the analysis step to a static general analysis step, and submit the calculation to obtain the steady-state calculation results of the residual stress field on the surface after laser shock strengthening.

5. The method for simulating and calculating the surface quality of an additive part after laser shock calendering, as described in claim 1, is characterized in that... In step S4, using the residual stress field calculated in step S3 as the initial state, the grinding heat flux polynomial fitted in step S2 is called through the user-defined subroutine DFLUX, and the grinding force polynomial fitted in step S2 is called through the user-defined subroutines DLOAD and UTRACLOAD. The grinding temperature field and grinding force field are applied sequentially and coupled to simulate the secondary reconstruction effect of grinding on the residual stress field after laser shock strengthening. The specific method for calculating the final surface residual stress field after laser shock synergistic grinding includes: (1) Grinding temperature field calculation stage: Copy the finite element model of the residual stress field on the surface after laser shock strengthening in step S3, and set the corresponding thermophysical parameters according to the material type of the actual additive part. Replace the element type with a Heat Transfer element that supports heat transfer calculations, and add thermal boundary conditions and constraints according to the actual situation; The DFLUX subroutine is written based on the polynomial coefficients obtained from the grinding heat flux calculation in step S2, and referenced in the form of Surface heat flux when the load is applied. Select the Heat Transfer analysis step, add thermal output to the output request, and call the written DFLUX subroutine when submitting the calculation to obtain the grinding temperature field distribution. (2) Calculation stage of grinding thermo-mechanical coupling: Copy the finite element model of the surface residual stress field calculated in step S3 after laser shock strengthening, and set the corresponding material parameters according to the material type of the actual additive part; The residual stress field after laser shock strengthening calculated in step S3 is loaded into the initial analysis step in the form of the initial state. The grinding temperature field calculated in step S4-4 is loaded into the current analysis step in the form of a predefined temperature field using a sequential thermo-coupling method. Based on the multiple polynomial coefficients calculated from the normal grinding force and tangential grinding force in step S2, write the DLOAD subroutine and the UTRACLOAD subroutine respectively, and reference the subroutine in Pressure form and Surface traction form respectively when applying load; Set up a Dynamic implicit analysis step to calculate the effect of grinding thermo-mechanical coupling on the residual stress field of the surface after laser shock strengthening. Add stress output to the output request and call the written DLOAD and UTRACLOAD subroutines when submitting the calculation. (3) Steady-state result acquisition stage: The simulation model of laser shock synergistic grinding effect obtained by the thermo-mechanical coupling calculation of surface grinding after laser shock strengthening is replicated. The element type is converted to 3D stress element that supports Standard calculation. The Pressure and Surface traction loading modes are canceled, the predefined fields are canceled, and the constraint conditions are retained. Modify the analysis step to Static General, and the result obtained after submitting the calculation is the final surface residual stress field after laser shock co-grinding.

6. The method for simulating and calculating the surface quality of an additive part after laser shock galvanizing and grinding according to claim 1, characterized in that, The specific method described in step S5 for establishing a mathematical model of grinding morphology simulation based on the kinematic model of grinding and abrasive grain distribution characteristics, including grinding speed, grinding depth, and feed rate, and obtaining surface three-dimensional morphology data and surface roughness values ​​through numerical calculation includes: (1) Establishment of the mathematical model of grinding morphology: Based on the kinematic relationship between adjacent abrasive grains, the motion trajectory equation of a single abrasive grain in the global coordinate system is established: in, , abrasive grains coordinates The actual radius of the abrasive grain's location. For the corner; For feed rate; For turning The time of the angle; abrasive grains The radius of the grinding wheel; This refers to the distance between the abrasive grains on the surface of the grinding wheel. Indicates the grinding wheel grit size; The number of grinding wheel structures; , Abrasive grains The difference between the x and y coordinates of the origin; The protrusion height of the abrasive grains on the grinding wheel surface is set to a random distribution, and a Gaussian distribution model is used to describe the variation law of the abrasive grain protrusion height. The actual cutting radius when the abrasive grains actually participate in cutting is expressed as the sum of the grinding wheel radius and the abrasive grain protrusion height. Based on the trajectory equation of the abrasive grains across the workpiece surface, the height value of each point on the workpiece surface is determined, forming a surface topology matrix. The value of each element in the matrix represents the surface height at the corresponding position. (2) Numerical calculation of surface roughness: In the surface topology matrix, along the direction perpendicular to the grinding feed speed, a set of vectors is extracted according to the set sampling length. This set of vectors represents the surface profile curve where the sampling position is located. The calculation is performed iteratively from the highest point to the lowest point of the vector set, and a reference line is determined by gradually decreasing thresholds, so that the area of ​​the surface profile curve above and below the reference line is equal, and the reference line is used as the baseline. Record the height of the baseline, and calculate the average absolute value of the deviation of each position from the baseline height in the sampling vector. This average value is the surface roughness Ra value.

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