Aerospace thin-wall part laser cladding remanufacturing process chain optimization method

Abstract

The invention relates to the technical field of laser cladding repair of thin-walled parts, in particular to an aerospace thin-walled part laser cladding remanufacturing process chain optimization method. The method comprises the following steps that S1, a CAD model is established according to the damage shape of the thin-wall part, and the CAD model is sliced and layered; s2, establishing a heat-force-stress coupling simulation model, and optimizing a temperature field, a stress field and a deformation field in the laser cladding process; s3, writing a laser cladding path code, and carrying out laser cladding; s4, numerical control milling is conducted on the cladding layer area, and cladding layer errors are calculated; and S5, a low-plasticity ultrasonic rolling technology is adopted for conducting strengthening and finish machining on the repaired surface, stress concentration generated by laser cladding and milling is eliminated through sound wave rolling, and metal surface layer nanocrystallization is achieved. According to the aerospace thin-wall part laser cladding remanufacturing process chain optimization method, through finite element simulation, numerical control and sound wave rolling technologies, the repairing precision and performance of the thin-wall part are improved, and the reliability under extreme conditions is ensured.

Description

Technical Field

[0001] The invention relates to the technical field of laser cladding repair of thin-walled parts, and in particular to a method for optimizing a laser cladding remanufacturing process chain for aerospace thin-walled parts. Background Art

[0002] A laser cladding remanufacturing process chain optimization method for aerospace thin-walled parts aims to achieve high performance and long life of repaired parts by integrating advanced simulation technology and precision machining technology, and to achieve high optimization and quality control of the machining process by using multi-physics field simulation and intelligent control strategy.

[0003] The existing laser cladding repair technology for thin-walled parts is difficult to accurately control when dealing with complex shapes and thin-walled structures. It is easy to produce high thermal stress and deformation due to the difficulty in accurately controlling the heat-affected zone, which will lead to defects in the bonding interface between the repair layer and the substrate, and uneven surface accuracy and mechanical properties. In summary, a method for optimizing the laser cladding remanufacturing process chain for aerospace thin-walled parts is provided. Summary of the invention

[0004] The purpose of the present invention is to provide a method for optimizing the laser cladding remanufacturing process chain of aerospace thin-walled parts, so as to solve the problems raised in the above background technology that the heat-affected zone is difficult to accurately control, high thermal stress and deformation are easily generated, which will lead to defects in the bonding interface between the repair layer and the substrate, and uneven surface accuracy and mechanical properties.

[0005] To achieve the above object, the present invention aims to provide a method for optimizing the laser cladding remanufacturing process chain of aerospace thin-walled parts, comprising the following steps:

[0006] S1. Establish a 3D CAD model of the required repair shape according to the damaged shape of the thin-walled part, and vertically slice and layer the 3D CAD model according to the thickness of 0.2 mm to 0.5 mm;

[0007] S2. Establish and solve the thermal-mechanical-stress coupling simulation model through finite element simulation software to optimize the temperature field, stress field and deformation field during laser cladding;

[0008] S3 writes the laser cladding path code according to the multi-physics field simulation results, performs laser cladding according to the optimized path, and forms a multi-layer deposition pattern;

[0009] S4. After laser cladding, CNC milling is performed on the cladding layer and its surrounding area, the error of the cladding layer is calculated, and the processing parameters are adjusted;

[0010] S5. After laser cladding and CNC machining, the low-plasticity ultrasonic rolling process is used to strengthen and finish the repaired surface. Through ultrasonic rolling, the stress concentration caused by laser cladding and milling is eliminated, and the metal surface nano-crystallization is achieved.

[0011] As a further improvement of the technical solution, the specific steps involved in establishing a three-dimensional CAD model of the desired repair shape in S1 and vertically slicing and layering the three-dimensional CAD model are as follows:

[0012] S1.1. Use CAD software to perform 3D modeling of damaged thin-walled parts to ensure the actual workpiece geometry and damage area;

[0013] S1.2. Mark the area that needs to be repaired by laser cladding in the 3D CAD model, and describe and mark the part that needs to be repaired in detail according to the scope and depth of the damage;

[0014] S1.3. Considering the material properties, equipment capabilities and repair requirements, select the slice thickness for vertical slicing and layering to generate a cross-sectional view of each layer S i ;

[0015] S1.4, the cross-sectional view of each layer S i Data is exported as 2D vector graphics V i , and according to the two-dimensional vector graph V i Plan the laser cladding path.

[0016] As a further improvement of the present technical solution, in S2, a thermal-mechanical-stress coupling simulation model is established and solved by finite element simulation software, and the temperature field, stress field and deformation field in the laser cladding process are optimized to determine the cladding sequence with the minimum temperature gradient in the single-layer multi-pass laser cladding process. The specific steps involved are as follows:

[0017] S2.1. Use finite element simulation software to establish a thermal-mechanical-stress coupling simulation model, input the process parameters and material properties of laser cladding, use a double ellipsoid heat source model to define the heat source distribution during laser cladding, and set the boundary conditions and initial conditions of the model, including heat conduction, convection and radiation;

[0018] S2.2, analyze the temperature field distribution during laser cladding, calculate the temperature field distribution T(x, y, z, t), analyze the thermal stress and residual stress distribution caused by temperature change, calculate the stress distribution σ, analyze the deformation of the workpiece during laser cladding, and calculate the deformation ∈;

[0019] S2.3, through the temperature gradient Minimization strategy optimizes the cladding sequence and calculates the temperature difference at each cladding position Optimize cladding sequence through stress gradient Minimization strategy optimizes the cladding path and calculates the stress difference at each cladding position Optimize cladding path.

[0020] As a further improvement of the present technical solution, the heat source model in S2.1 is used to describe the input and distribution of heat energy during the laser cladding process. The mathematical formulas involved in the heat source model are as follows:

[0021] Heat source distribution in the front half of the ellipsoid:

[0022]

[0023] Heat source distribution in the rear half of the ellipsoid:

[0024]

[0025] Among them, q f represents the heat flow distribution inside the front half of the ellipsoid; q r Represents the heat flow distribution inside the rear half ellipsoid; a f 、a r are the two semi-axes of the front hemisphere and the back hemi-ellipsoid, respectively, and are the other two semi-axes of the front hemisphere and the back hemi-ellipsoid, and the two short semi-axes of the two ellipsoids are equal; f f 、f r represents the heat input share in the front and rear hemi-ellipsoids, f f +f r =1;

[0026] The thermal-mechanical-stress coupling simulation model is used to simulate and analyze the temperature field, stress field and deformation field in the laser cladding process. The mathematical model formula involved in the thermal-mechanical-stress coupling simulation model is as follows:

[0027] Heat conduction equation:

[0028]

[0029] Where ρ is the material density; c p is the specific heat capacity; k is the thermal conductivity; T is the temperature; t is the time; Q is the internal heat source term, which is provided by the heat source model formula;

[0030] Thermal stress equation:

[0031] σ=Eα(T-T0);

[0032] Wherein, σ is stress; E is elastic modulus; α is thermal expansion coefficient; T is temperature; T0 is reference temperature;

[0033] Strain-displacement relationship:

[0034]

[0035] Among them, ∈ is strain and u is displacement.

[0036] As a further improvement of the technical solution, the temperature field distribution analysis during the laser cladding process is performed in S2.2, and the temperature field distribution T(x, y, z, t) is calculated. According to the heat source model formula and the heat conduction equation in S2.1, the temperature field distribution T(x, y, z, t) is obtained by discretization using the finite element method;

[0037] The thermal stress and residual stress distribution caused by temperature change are analyzed, and the stress distribution σ is calculated. The temperature field distribution T (x, y, z, t) is used as input, and the stress field distribution σ is calculated according to the thermal stress equation;

[0038] The deformation of the workpiece during the laser cladding process is analyzed, the deformation amount ∈ is calculated, the calculated stress field σ is used as input, the displacement field u(x, y, z) is calculated according to the strain-displacement relationship, and the deformation amount ∈ is calculated according to the displacement field u(x, y, z).

[0039] As a further improvement of the technical solution, the S2.3 is carried out by temperature gradient Minimization strategy optimizes the cladding sequence and calculates the temperature difference at each cladding position Optimize cladding sequence through stress gradient Minimization strategy optimizes the cladding path and calculates the stress difference at each cladding position The specific steps involved in optimizing the cladding path are as follows:

[0040] S2.3.1. Select i units at each cladding position and determine the instantaneous surface temperature T of these units. 上 , the instantaneous temperature of the lower surface T 下 and stress σ 上 and σ 下 ;

[0041] S2.3.2. Calculate the temperature difference Δt and stress difference Δσ for each unit:

[0042] Δt=T 上 -T 下 ;

[0043] Δσ=σ 上 -σ 下 ;

[0044] S2.3.3. Calculate the average temperature difference of each cladding area and the mean stress difference

[0045] S2.3.4. After each laser cladding is completed, select the average temperature difference The minimum pass is the position of the next laser cladding, and the average stress difference is selected The smallest path is the optimal cladding path.

[0046] As a further improvement of the technical solution, in S3, the laser cladding path code is written according to the multi-physical field simulation results, and laser cladding is performed according to the optimized path to form a multi-layer deposition pattern. The specific steps involved are as follows:

[0047] S3.1, obtaining the cladding path and sequence from step S2, including the position, sequence, temperature gradient and stress gradient of each cladding, determining the laser power, scanning speed and cladding material supply rate of each cladding according to the simulation results, and writing the laser cladding path code using Python programming language, the code including laser start and stop control, laser scanning path and cladding material supply control;

[0048] S3.2. Prepare the laser cladding equipment, set the laser power, scanning speed and cladding material supply rate according to the programmed path code, load the programmed path code into the laser cladding control system, check and verify the path and parameters, and perform the actual laser cladding operation according to the path code;

[0049] S3.3. According to the simulation results and actual cladding conditions, the laser power, scanning speed and cladding material supply rate of each layer are fine-tuned, and laser cladding is performed layer by layer according to the path code to form a multi-layer accumulation pattern.

[0050] As a further improvement of the technical solution, the specific steps of performing CNC milling on the cladding layer and its surrounding area after laser cladding in S4, calculating the error of the cladding layer and adjusting the processing parameters are as follows:

[0051] S4.1. Use a 3D scanner to scan the surface of the cladding layer, obtain its actual shape and size, and generate point cloud data P scan ={(x i ,y i , z i )}, and compare the point cloud data with the original CAD model to calculate the difference between the actual shape of the cladding layer and the target shape;

[0052] S4.2. For each scanning point, calculate the point cloud data P scan ={(x i ,y i , z i )} and the corresponding points of the CAD model, and then perform statistical analysis on the errors;

[0053] S4.3. Determine the CNC milling path based on the scanning data and error analysis results, and use CAM software to generate the CNC milling path P NC, set the process parameters of CNC milling, including cutting speed, feed rate and cutting depth.

[0054] As a further improvement of this technical solution, the point cloud data P is calculated in S4.2 scan ={(x i ,y i , z i )} and the corresponding point of the CAD model, and then the mathematical formula involved in the error statistical analysis is as follows:

[0055]

[0056] Among them, (x i，scan ,y i，scan , z i,scan ) is the scanning point coordinate; (x i，CAD ,y i，CAD , z i，CAD ) is the coordinate of the CAD model point, e i is the error of each point cloud data;

[0057] Error statistical analysis:

[0058] Average Error:

[0059] Mean Square Error:

[0060] Standard Deviation:

[0061] As a further improvement of the technical solution, the low-plasticity ultrasonic rolling process is used in S5 to strengthen and finish the repaired surface. The stress concentration caused by laser cladding and milling is eliminated by ultrasonic rolling to achieve nano-crystallization of the metal surface. The specific steps involved are as follows:

[0062] S5.1. Select an ultrasonic generator and roller, and adjust the ultrasonic frequency, amplitude, roller pressure and feed speed according to the material characteristics and specific needs of the repair area;

[0063] S5.2. Apply uniform pressure to make the surface of the material undergo small and continuous plastic deformation with the assistance of high-frequency vibration of ultrasound;

[0064] S5.2. Conduct detailed inspection of the repaired area, including surface roughness measurement and hardness test.

[0065] Compared with the prior art, the present invention has the following beneficial effects:

[0066] 1. In this method of optimizing the laser cladding remanufacturing process chain for aerospace thin-walled parts, the accuracy and integrity of the repair layer can be significantly improved through the combination of finite element simulation, CNC machining and sonic rolling. At the same time, the microstructure of the material is optimized, its comprehensive mechanical properties are enhanced, and the reliability and durability of the repaired thin-walled parts under extreme working conditions are ensured.

[0067] 2. In this laser cladding remanufacturing process chain optimization method for aerospace thin-walled parts, a refined multi-step quality control and intelligent feedback adjustment system are used to achieve full chain optimization from design to processing, effectively reduce processing defects, improve remanufacturing efficiency and yield, and ultimately achieve a performance level equivalent to or even exceeding that of the original components. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] Figure 1 The figure is a flow chart of the overall method of the present invention. DETAILED DESCRIPTION

[0069] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0070] Example:

[0071] See also Figure 1 As shown, this embodiment provides a method for optimizing the laser cladding remanufacturing process chain of aerospace thin-walled parts, including the following steps:

[0072] S1. Establish a 3D CAD model of the required repair shape according to the damaged shape of the thin-walled part, and vertically slice and layer the 3D CAD model according to the thickness of 0.2 mm to 0.5 mm;

[0073] The specific steps involved in establishing a three-dimensional CAD model of the desired repair shape in S1 and vertically slicing and layering the three-dimensional CAD model are as follows:

[0074] S1.1. Use CAD software to perform 3D modeling of damaged thin-walled parts to ensure the actual workpiece geometry and damage area;

[0075] S1.2. Mark the area that needs to be repaired by laser cladding in the 3D CAD model, and describe and mark the part that needs to be repaired in detail according to the scope and depth of the damage;

[0076] S1.3. Considering the material properties, equipment capabilities and repair requirements, select the slice thickness for vertical slicing and layering to generate a cross-sectional view of each layer S i ;

[0077] S1.4, the cross-sectional view of each layer S i Data is exported as 2D vector graphics V i , and according to the two-dimensional vector graph V i Plan the laser cladding path.

[0078] S2. Establish and solve the thermal-mechanical-stress coupling simulation model through finite element simulation software to optimize the temperature field, stress field and deformation field during laser cladding;

[0079] In S2, a thermal-mechanical-stress coupling simulation model is established and solved by finite element simulation software, and the temperature field, stress field and deformation field in the laser cladding process are optimized to determine the cladding sequence with the minimum temperature gradient in the single-layer multi-pass laser cladding process, so as to reduce the deformation in the cladding process, improve the cladding quality and reduce the subsequent processing workload; the specific steps involved are as follows:

[0080] S2.1. Use finite element simulation software to establish a thermal-mechanical-stress coupling simulation model, input the process parameters and material properties of laser cladding, use a double ellipsoid heat source model to define the heat source distribution during laser cladding, and set the boundary conditions and initial conditions of the model, including heat conduction, convection and radiation;

[0081] S2.2, analyze the temperature field distribution during laser cladding, calculate the temperature field distribution T(x, y, z, t), analyze the thermal stress and residual stress distribution caused by temperature change, calculate the stress distribution σ, analyze the deformation of the workpiece during laser cladding, and calculate the deformation ∈;

[0082] S2.3, through the temperature gradient Minimization strategy optimizes the cladding sequence and calculates the temperature difference at each cladding position Optimize cladding sequence through stress gradient Minimization strategy optimizes the cladding path and calculates the stress difference at each cladding position Optimize cladding path.

[0083] The heat source model in S2.1 is used to describe the input and distribution of heat energy during laser cladding. The mathematical formulas involved in the heat source model are as follows:

[0084] Heat source distribution in the front half of the ellipsoid:

[0085]

[0086] Heat source distribution in the rear half of the ellipsoid:

[0087]

[0088] Among them, q f represents the heat flow distribution inside the front half of the ellipsoid; q r Represents the heat flow distribution inside the rear half ellipsoid; a f 、a r are the two semi-axes of the front hemisphere and the back hemi-ellipsoid, respectively, and are the other two semi-axes of the front hemisphere and the back hemi-ellipsoid, and the two short semi-axes of the two ellipsoids are equal; f f 、f r represents the heat input share in the front and rear hemi-ellipsoids, f f +f r =1;

[0089] The thermal-mechanical-stress coupling simulation model is used to simulate and analyze the temperature field, stress field and deformation field in the laser cladding process. The mathematical model formula involved in the thermal-mechanical-stress coupling simulation model is as follows:

[0090] Heat conduction equation:

[0091]

[0092] Where ρ is the material density; c p is the specific heat capacity; k is the thermal conductivity; T is the temperature; t is the time; Q is the internal heat source term, which is provided by the heat source model formula;

[0093] Thermal stress equation:

[0094] σ=Eα(T-T0);

[0095] Wherein, σ is stress; E is elastic modulus; α is thermal expansion coefficient; T is temperature; T0 is reference temperature;

[0096] Strain-displacement relationship:

[0097]

[0098] Among them, ∈ is strain and u is displacement.

[0099] In S2.2, the temperature field distribution during the laser cladding process is analyzed, and the temperature field distribution T(x, y, z, t) is calculated. According to the heat source model formula and the heat conduction equation in S2.1, the temperature field distribution T(x, y, z, t) is obtained by discretization using the finite element method;

[0100] The finite element method discretization refers to dividing the continuous physical domain into many non-overlapping subdomains, converting complex continuous problems into a combination of multiple simple subproblems, and solving each subproblem in a limited, discretized area. Specifically, in the calculation of the temperature field distribution T (x, y, z, t), the discretization steps are as follows:

[0101] First, it involves dividing the complex three-dimensional space into multiple small units, then establishing a local mathematical model based on the heat conduction equation for each unit, and connecting adjacent units through nodes to form an overall algebraic equation system. Then, a numerical algorithm is used to solve this large set of equations to obtain the temperature value of each point in space at each time node, thereby describing in detail the temperature field distribution T (x, y, z, t) during the laser cladding process. This technology is of great significance for accurately predicting temperature changes, controlling thermal effects and optimizing process parameters to avoid heat-induced defects.

[0102] The thermal stress and residual stress distribution caused by temperature change are analyzed, and the stress distribution σ is calculated. The temperature field distribution T (x, y, z, t) is used as input, and the stress field distribution σ is calculated according to the thermal stress equation:

[0103] The deformation of the workpiece during the laser cladding process is analyzed, the deformation amount ∈ is calculated, the calculated stress field σ is used as input, the displacement field u(x, y, z) is calculated according to the strain-displacement relationship, and the deformation amount ∈ is calculated according to the displacement field u(x, y, z).

[0104] The S2.3 is through the temperature gradient Minimization strategy optimizes the cladding sequence and calculates the temperature difference at each cladding position Optimize cladding sequence through stress gradient Minimization strategy optimizes the cladding path and calculates the stress difference at each cladding position The specific steps involved in optimizing the cladding path are as follows:

[0105] S2.3.1. Select i units at each cladding position and determine the instantaneous surface temperature T of these units. 上 , the instantaneous temperature of the lower surface T 下 and stress σ 上 and σ 下 ;

[0106] S2.3.2. Calculate the temperature difference Δt and stress difference Δσ for each unit:

[0107] Δt=T 上 -T 下 ;

[0108] Δσ=σ 上 -σ 下 ;

[0109] S2.3.3. Calculate the average temperature difference of each cladding area and the mean stress difference

[0110] S2.3.4. After each laser cladding is completed, select the average temperature difference The minimum pass is the position of the next laser cladding, and the average stress difference is selected The smallest path is the optimal cladding path.

[0111] S3 writes the laser cladding path code according to the multi-physics field simulation results, performs laser cladding according to the optimized path, and forms a multi-layer deposition pattern;

[0112] In the S3, the laser cladding path code is written according to the multi-physics field simulation results, and the laser cladding is performed according to the optimized path to form a multi-layer deposition pattern. The specific steps involved are as follows:

[0113] S3.1, obtaining the cladding path and sequence from step S2, including the position, sequence, temperature gradient and stress gradient of each cladding, determining the laser power, scanning speed and cladding material supply rate of each cladding according to the simulation results, and writing the laser cladding path code using Python programming language, the code including laser start and stop control, laser scanning path and cladding material supply control;

[0114] For example:

[0115]

[0116] S3.2. Prepare the laser cladding equipment, set the laser power, scanning speed and cladding material supply rate according to the programmed path code, load the programmed path code into the laser cladding control system, check and verify the path and parameters, and perform the actual laser cladding operation according to the path code;

[0117] S3.3. According to the simulation results and actual cladding conditions, the laser power, scanning speed and cladding material supply rate of each layer are fine-tuned, and laser cladding is performed layer by layer according to the path code to form a multi-layer accumulation pattern.

[0118] S4. After laser cladding, CNC milling is performed on the cladding layer and its surrounding area, the error of the cladding layer is calculated, and the processing parameters are adjusted;

[0119] The specific steps involved in performing CNC milling on the cladding layer and its surrounding area after laser cladding in S4, calculating the error of the cladding layer and adjusting the processing parameters are as follows:

[0120] S4.1. Use a 3D scanner to scan the surface of the cladding layer, obtain its actual shape and size, and generate point cloud data P scan ={(x i ,y i , z i )}, and compare the point cloud data with the original CAD model to calculate the difference between the actual shape of the cladding layer and the target shape;

[0121] S4.2. For each scanning point, calculate the point cloud data P scan ={(x i ,y i , z i )} and the corresponding points of the CAD model, and then perform statistical analysis on the errors;

[0122] S4.3. Determine the CNC milling path based on the scanning data and error analysis results, and use CAM software to generate the CNC milling path P NC , set the process parameters of CNC milling, including cutting speed, feed rate and cutting depth.

[0123] The point cloud data P is calculated in S4.2 scan ={(x i ,y i , z i )} and the corresponding point of the CAD model, and then the mathematical formula involved in the error statistical analysis is as follows:

[0124]

[0125] Among them, (x i，scan ,y i，scan , z i，scan ) is the scanning point coordinate; (x i，CAD ,y i，CAD , z i，CAD ) is the coordinate of the CAD model point, e i is the error of each point cloud data;

[0126] Error statistical analysis:

[0127] Average Error:

[0128] Mean Square Error:

[0129] Standard Deviation:

[0130] S5. After laser cladding and CNC machining, the low-plasticity ultrasonic rolling process is used to strengthen and finish the repaired surface. Through ultrasonic rolling, the stress concentration caused by laser cladding and milling is eliminated, and the metal surface nano-crystallization is achieved.

[0131] In S5, a low-plasticity ultrasonic rolling process is used to strengthen and fine-process the repaired surface. Ultrasonic rolling is used to eliminate stress concentration caused by laser cladding and milling, and nano-crystallization of the metal surface is achieved. The specific steps involved are as follows:

[0132] S5.1. Select an ultrasonic generator and roller, and adjust the ultrasonic frequency, amplitude, roller pressure and feed speed according to the material characteristics and specific needs of the repair area;

[0133] S5.2. Apply uniform pressure to make the surface of the material undergo small and continuous plastic deformation with the assistance of high-frequency vibration of ultrasound;

[0134] S5.2. Conduct detailed inspection of the repaired area, including surface roughness measurement and hardness test;

[0135] Among them, the ultrasonic rolling is a precision processing technology that uses ultrasonic vibration energy combined with a roller to perform cold plastic deformation on the workpiece surface. Special emphasis is placed on "low plasticity" ultrasonic rolling, which means that it can improve surface properties through only slight plastic deformation while keeping the material's microstructure basically unchanged.

[0136] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and descriptions are only preferred examples of the present invention and are not intended to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A laser cladding remanufacturing process chain optimization method for aerospace thin-walled parts, Features: The following steps are involved: S1. Establish a 3D CAD model of the required repair shape according to the damaged shape of the thin-walled part, and vertically slice and layer the 3D CAD model according to the thickness of 0.2 mm to 0.5 mm; S2. Establish and solve the thermal-mechanical-stress coupling simulation model through finite element simulation software to optimize the temperature field, stress field and deformation field during laser cladding; S3 writes the laser cladding path code according to the multi-physics field simulation results, performs laser cladding according to the optimized path, and forms a multi-layer deposition pattern; S4. After laser cladding, CNC milling is performed on the cladding layer and its surrounding area, the error of the cladding layer is calculated, and the processing parameters are adjusted; S5. After laser cladding and CNC machining, the low-plasticity ultrasonic rolling process is used to strengthen and finish the repaired surface. Through ultrasonic rolling, the stress concentration caused by laser cladding and milling is eliminated, and the metal surface nano-crystallization is achieved.

2. The method for optimizing the laser cladding remanufacturing process chain of aerospace thin-walled parts according to claim 1, Features: The specific steps involved in establishing a three-dimensional CAD model of the desired repair shape in S1 and vertically slicing and layering the three-dimensional CAD model are as follows: S1.

1. Use CAD software to perform 3D modeling of damaged thin-walled parts to ensure the actual workpiece geometry and damage area; S1.

2. Mark the area that needs to be repaired by laser cladding in the 3D CAD model, and describe and mark the part that needs to be repaired in detail according to the scope and depth of the damage; S1.

3. Considering the material properties, equipment capabilities and repair requirements, select the slice thickness for vertical slicing and layering to generate a cross-sectional view of each layer S i ; S1.4, the cross-sectional view of each layer S i Data is exported as 2D vector graphics V i , and according to the two-dimensional vector graph V i Plan the laser cladding path.

3. The method for optimizing the laser cladding remanufacturing process chain of aerospace thin-walled parts according to claim 1, Features: In S2, a thermal-mechanical-stress coupling simulation model is established and solved by finite element simulation software, and the temperature field, stress field and deformation field in the laser cladding process are optimized to determine the cladding sequence with the minimum temperature gradient in the single-layer multi-pass laser cladding process, so as to reduce the deformation in the cladding process, improve the cladding quality and reduce the subsequent processing workload; the specific steps involved are as follows: S2.

1. Use finite element simulation software to establish a thermal-mechanical-stress coupling simulation model, input the process parameters and material properties of laser cladding, use a double ellipsoid heat source model to define the heat source distribution during laser cladding, and set the boundary conditions and initial conditions of the model, including heat conduction, convection and radiation; S2.2, analyze the temperature field distribution during laser cladding, calculate the temperature field distribution T(x, y, z, t), analyze the thermal stress and residual stress distribution caused by temperature change, calculate the stress distribution σ, analyze the deformation of the workpiece during laser cladding, and calculate the deformation ∈; S2.3, through the temperature gradient Minimization strategy optimizes the cladding sequence and calculates the temperature difference at each cladding position Optimize cladding sequence through stress gradient Minimization strategy optimizes the cladding path and calculates the stress difference at each cladding position Optimize cladding path.

4. The method for optimizing the laser cladding remanufacturing process chain of aerospace thin-walled parts according to claim 3, Features: The heat source model in S2.1 is used to describe the input and distribution of heat energy during laser cladding. The mathematical formulas involved in the heat source model are as follows: Heat source distribution in the front half of the ellipsoid: Heat source distribution in the rear half of the ellipsoid: Among them, q f represents the heat flow distribution inside the front half of the ellipsoid; q r Represents the heat flow distribution inside the rear semi-ellipsoid; a f 、a r are the two semi-axes of the front hemisphere and the rear hemi-ellipsoid, respectively, and are the other two semi-axes of the front hemisphere and the rear hemi-ellipsoid, and the two short semi-axes of the two ellipsoids are equal; f f 、f r represents the heat input share in the front and rear hemi-ellipsoids, f f +f r =1; The thermal-mechanical-stress coupling simulation model is used to simulate and analyze the temperature field, stress field and deformation field in the laser cladding process. The mathematical model formula involved in the thermal-mechanical-stress coupling simulation model is as follows: Heat conduction equation: Where ρ is the material density; c p is the specific heat capacity; k is the thermal conductivity; T is the temperature; t is the time; Q is the internal heat source term, which is provided by the heat source model formula; Thermal stress equation: σ=Eα(TT 0 ); Where, σ is stress; E is elastic modulus; α is thermal expansion coefficient; T is temperature; T 0 is the reference temperature; Strain-displacement relationship: Among them, ∈ is strain and u is displacement.

5. The method for optimizing the laser cladding remanufacturing process chain of aerospace thin-walled parts according to claim 3, Features: In S2.2, the temperature field distribution during the laser cladding process is analyzed, and the temperature field distribution T (x, y, z, t) is calculated. According to the heat source model formula and the heat conduction equation in S2.1, the temperature field distribution T (x, y, z, t) is obtained by discretization using the finite element method; The thermal stress and residual stress distribution caused by temperature change are analyzed, and the stress distribution σ is calculated. The temperature field distribution T (x, y, z, t) is used as input, and the stress field distribution σ is calculated according to the thermal stress equation; The deformation of the workpiece during the laser cladding process is analyzed, the deformation amount ∈ is calculated, the calculated stress field σ is used as input, the displacement field u(x, y, z) is calculated according to the strain-displacement relationship, and the deformation amount ∈ is calculated according to the displacement field u(x, y, z).

6. The method for optimizing the laser cladding remanufacturing process chain of aerospace thin-walled parts according to claim 3, Features: The S2.3 is through the temperature gradient Minimization strategy optimizes the cladding sequence and calculates the temperature difference at each cladding position Optimize cladding sequence through stress gradient Minimization strategy optimizes the cladding path and calculates the stress difference at each cladding position The specific steps involved in optimizing the cladding path are as follows: S2.3.

1. Select i units at each cladding position and determine the instantaneous surface temperature T of these units. 上 , the instantaneous temperature of the lower surface T 下 and stress σ 上 and σ 下 ; S2.3.

2. Calculate the temperature difference Δt and stress difference Δσ for each unit: Δt=T 上 -T 下 ; Ds = s 上 -s 下 ; S2.3.

3. Calculate the average temperature difference of each cladding area and the mean stress difference S2.3.

4. After each laser cladding is completed, select the average temperature difference The minimum pass is the position of the next laser cladding, and the average stress difference is selected The smallest path is the optimal cladding path.

7. The method for optimizing the laser cladding remanufacturing process chain of aerospace thin-walled parts according to claim 1, Features: In the S3, the laser cladding path code is written according to the multi-physics field simulation results, and the laser cladding is performed according to the optimized path to form a multi-layer deposition pattern. The specific steps involved are as follows: S3.1, obtaining the cladding path and sequence from step S2, including the position, sequence, temperature gradient and stress gradient of each cladding, determining the laser power, scanning speed and cladding material supply rate of each cladding according to the simulation results, and writing the laser cladding path code using Python programming language, the code including laser start and stop control, laser scanning path and cladding material supply control; S3.

2. Prepare the laser cladding equipment, set the laser power, scanning speed and cladding material supply rate according to the programmed path code, load the programmed path code into the laser cladding control system, check and verify the path and parameters, and perform the actual laser cladding operation according to the path code; S3.

3. According to the simulation results and actual cladding conditions, the laser power, scanning speed and cladding material supply rate of each layer are fine-tuned, and laser cladding is performed layer by layer according to the path code to form a multi-layer accumulation pattern.

8. The method for optimizing the laser cladding remanufacturing process chain of aerospace thin-walled parts according to claim 1, Features: The specific steps involved in performing CNC milling on the cladding layer and its surrounding area after laser cladding in S4, calculating the error of the cladding layer and adjusting the processing parameters are as follows: S4.

1. Use a 3D scanner to scan the surface of the cladding layer, obtain its actual shape and size, and generate point cloud data P scan ={(x i ,y i , z i )}, and compare the point cloud data with the original CAD model to calculate the difference between the actual shape of the cladding layer and the target shape; S4.

2. For each scanning point, calculate the point cloud data P scan ={(x i ,y i , z i )} and the corresponding points of the CAD model, and then perform statistical analysis on the errors; S4.

3. Determine the CNC milling path based on the scanning data and error analysis results, and use CAM software to generate the CNC milling path P NC , set the process parameters of CNC milling, including cutting speed, feed rate and cutting depth.

9. The method for optimizing the laser cladding remanufacturing process chain of aerospace thin-walled parts according to claim 8, Features: The point cloud data P is calculated in S4.2 scan ={(x i ,y i , z i )} and the corresponding point of the CAD model, and then the mathematical formula involved in the error statistical analysis is as follows: Among them, (x i，scan ,y i，scan ,z i，scan ) is the scanning point coordinate; (x i，CAD ,y i，CAD ,z i，CAD ) is the coordinate of the CAD model point, e i is the error of each point cloud data; Error statistical analysis: Average Error: Mean Square Error: Standard Deviation:

10. The method for optimizing the laser cladding remanufacturing process chain of aerospace thin-walled parts according to claim 1, Features: In S5, a low-plasticity ultrasonic rolling process is used to strengthen and fine-process the repaired surface. Ultrasonic rolling is used to eliminate stress concentration caused by laser cladding and milling, and nano-crystallization of the metal surface is achieved. The specific steps involved are as follows: S5.

1. Select an ultrasonic generator and roller, and adjust the ultrasonic frequency, amplitude, roller pressure and feed speed according to the material characteristics and specific needs of the repair area; S5.

2. Apply uniform pressure to make the surface of the material undergo small and continuous plastic deformation with the assistance of high-frequency vibration of ultrasound; S5.

2. Conduct detailed inspection of the repaired area, including surface roughness measurement and hardness test.

Images