Method for analyzing residual stress field of laser shot peening of aviation aluminum alloy with texture

Abstract

A kind of method for analyzing residual stress field of laser shot peening of aviation aluminum alloy containing texture, based on X-ray diffraction method, grain orientation information and laser shot peening finite element simulation result analysis residual stress, using chemical milling to strip layer, based on X-ray diffraction, grain orientation information and ABAQUS laser shot peening finite element simulation, the residual stress field generated by laser shot peening of 2024T351 aluminum alloy is analyzed, it is a complete method suitable for residual stress analysis of strong texture material, the method is aimed at the problem of layer-by-layer stripping of material, the anisotropy phenomenon caused by grain preferred orientation and the problem of poor data reliability, the method of analyzing residual stress by X-ray diffraction is optimized in details, including the combined application of chemical milling stripping layer, residual stress calculation considering grain orientation information and data screening.The present application makes the inner surface of chemical milling window flat by plane layer-by-layer stripping, which has a positive effect on improving the accuracy of residual stress test, and reliable stress data is obtained.

Description

Technical Field

[0001] This invention relates to the field of stress detection technology, specifically a method for analyzing the residual stress field generated by laser peening of 2024T351 aluminum alloy using chemical milling for delamination, X-ray diffraction and grain orientation information, and combined with ABAQUS laser peening finite element simulation results. Background Technology

[0002] Laser peening, similar in principle to traditional shot peening, is an advanced technology that utilizes the release of residual stress fields to achieve forming. In laser peening, the residual stress field of the material is generated by shock waves induced by a high-energy laser beam acting on the material surface and propagating into the material, causing uneven elastoplastic deformation. Compared to traditional shot peening, it has advantages such as introducing a deeper residual compressive stress layer, shorter preparation cycle, and controllable parameters. This means that laser peening has stronger forming capabilities, better fatigue resistance of the formed workpiece, and higher forming efficiency. Theoretically, it can achieve precise forming, showing great potential in the aerospace manufacturing field. Testing and analyzing the residual stress field introduced inside the workpiece by laser peening can not only provide a reference for forming control but also help in evaluating workpiece performance improvement.

[0003] Currently, X-ray diffraction is the most commonly used non-destructive testing method for residual stress measurement. However, its application in detecting residual stress from shot peening has many limitations. For example, to obtain the residual stress inside the workpiece, material needs to be removed while maintaining the surface finish and preserving the original residual stress. This process is generally achieved through electrolysis, but practice shows that electrolytic delamination is difficult to control, resulting in a smooth but uneven surface, which negatively impacts the accuracy of X-ray diffraction for residual stress measurement. Furthermore, traditional X-ray diffraction methods, when testing the residual stress of strongly textured materials, suffer from limitations in diffraction angle 2θ and crystal plane characteristics (sinθ). 2 ψ exhibits a nonlinear relationship, and using classical formulas to calculate stress at this point will result in unpredictable errors. Furthermore, X-ray diffraction is affected by numerous factors, leading to multiple sources of error in the measured data. However, due to limitations imposed by the swing angle and stress gradient, it is difficult to improve the accuracy of single-point testing of residual stress in laser-peened parts by increasing the amount of test data, resulting in extremely large measurement errors.

[0004] Regarding the problem of residual stress testing in laser-peened parts, an invention patent with publication number CN 108827513 B discloses a method for detecting planar residual stress in thin plates treated by laser shot peening. This method uses a designed cutting method to prevent deformation of the cut surface caused by gravity, thereby obtaining a more accurate planar residual stress value. However, this method is only applicable to the testing of residual stress in thin plates, and still requires X-ray diffraction analysis to obtain the distribution of microscopic residual stress. There is no corresponding solution for highly textured materials.

[0005] To address the problem of residual stress analysis in strongly textured materials using X-ray diffraction, invention publication CN105021331A discloses a method for measuring residual stress in polycrystalline materials based on the full X-ray diffraction spectrum. This method utilizes the full X-ray diffraction spectrum to obtain the grain orientation volume fraction, and uses this to correct the measured strain, thus reducing the influence of preferred grain orientation on the residual stress measurement results. It is a method for correcting the mean strain value, but it does not reflect the influence of texture on material properties. Invention publication CN112326084A discloses a method for measuring residual stress in textured materials using X-rays. This method, in a specific crystal plane along a strongly textured orientation direction, uses the measured d... ψ -sin 2 By analyzing the linear segment of the ψ curve, the weighted Young's modulus and lattice distortion are obtained, and the residual stress value of the strongly textured material can be calculated. However, this method requires high experimental conditions, and the calculation accuracy depends on d. ψ -sin 2 The number of points in the ψ curve that conform to a linear relationship is limited, and there are restrictions on the direction of stress testing, which poses certain difficulties in practical applications. Liu Yushu of Shanghai Jiaotong University published an article entitled "ODF Analysis of Residual Stress in Textured Materials" in the Journal of Materials Research, Vol. 9, No. 6, 1995, which elaborated on the basic principle of the ODF method for analyzing residual stress in textured materials. The key feature of this method is that it uses low-order texture coefficients to express the anisotropy of the macroscopic elasticity of textured materials, and then calculates the macroscopic elastic properties of the materials. However, the calculation process of low-order texture coefficients is cumbersome and involves a lot of mathematics, so it has not been widely used. Summary of the Invention

[0006] To overcome the shortcomings of existing technologies, such as inapplicability to textured materials and unsuitability for engineering applications, this invention proposes a method for analyzing the residual stress field of laser shot peening on textured aerospace aluminum alloys.

[0007] The specific process of the laser shot peening residual stress field analysis method for textured aerospace aluminum alloys proposed in this invention is as follows:

[0008] Step 1, Pretreatment of aluminum alloy test blocks:

[0009] The pretreatment of the aluminum alloy test block includes the following:

[0010] The first step is to measure and record the external dimensions of the aluminum alloy test block.

[0011] The second step is to remove oil from the surface of the aluminum alloy test block. This is done using a degreasing solution.

[0012] The third step is to apply and cure the protective adhesive. Apply the protective adhesive layer by layer evenly to each surface of the aluminum alloy test block, with a total thickness of 0.2 mm.

[0013] The fourth step is to obtain the initial test surface H0 of the aluminum alloy specimen. The chemical milling protective coating in the center test area of ​​the laser-peened surface of the aluminum alloy specimen is removed; the exposed surface of the aluminum alloy specimen is taken as the initial test surface H0; the distance h0 from the initial test surface H0 to the surface of the chemical milling protective coating is measured.

[0014] Fifth step: Establish the initial test block coordinate system G0.

[0015] An initial test block coordinate system G0 is established on the initial test surface H0. The origin O0 of the initial test block coordinate system G0 is located at the geometric center of the initial test surface H0; the three coordinate axes X of this initial test block coordinate system are... G0 Y G0 and Z G0 The three mutually perpendicular sides of the aluminum alloy test block to be tested are parallel to each other, where Z... G0 Perpendicular to the laser-peened surface outwards.

[0016] After steps one through five of step 1, the pretreatment of the aluminum alloy test block is completed.

[0017] Step 2: Collect X-ray diffraction data of the initial test surface H0 test point:

[0018] The test point O'0 of the initial test surface H0 is located at the geometric center of the initial test surface.

[0019] X-ray diffraction analysis was performed at the test points using the Proto-iXRD residual stress analysis system. G0 Y G0 The specific process for acquiring X-ray diffraction data in two directions is as follows:

[0020] The first step is to place the aluminum alloy test block.

[0021] The second step is to focus.

[0022] The third step is to collect data from the initial surface H0 test point O'0 along the X direction. G0 X-ray diffraction data in the direction.

[0023] A measurement coordinate system is defined on the test surface H0 by coordinate system rotation transformation. Specifically,

[0024] The initial test block coordinate system G0 revolves around the Y-axis in the coordinate system of the aluminum alloy test block. G0 Rotate the axis counterclockwise ψ j Angle, to obtain the measurement coordinate system Recorded as The three coordinate axes of each measurement coordinate system are denoted as X. L0xj YL0xj and Z L0xj Where the superscript 0 represents the initial test block coordinate system G0; For Y G0 With Y L0xj The angle between them, which is 0° here, ψ j The normal angle of the crystal plane where diffraction occurs, i.e., the angle between the crystal plane normal and the Z-axis. G0 The included angle of the axes satisfies ψ i =β i -20.5°, ψ i+9 =β i +20.5°, i=1,2,……,9, then the subscript j=1,2,……,18, where β i This is the reference angle for the swing head of the X-ray diffractometer.

[0025] The acquisition method was set to multiple exposure, with a single exposure time of 2 seconds and 10 exposures.

[0026] Using the Proto-iXRD residual stress analysis system, in each measurement coordinate system X-ray diffraction data were acquired at the initial surface H0 test point O'0, and the values ​​of each Z-axis at the initial surface H0 test point O'0 were read. L0xj To lattice strain j = 1, 2, ..., 18.

[0027] The fourth step is to collect data from the initial surface H0 test point O'0 along the Y direction. G0 X-ray diffraction data in the direction.

[0028] Centered on the origin of the test block coordinate system G0, the aluminum alloy test block on the worktable is rotated around Z... G0 The axis rotates 90°.

[0029] Repeat the focusing process described in step two of this step.

[0030] A measurement coordinate system is defined on the test surface H0 by coordinate system rotation transformation. The specific process is as follows:

[0031] The initial test block coordinate system G0 first revolves around the Z coordinate system of the aluminum alloy test block. G0 Rotate the axis counterclockwise The angle is used to obtain the rotated transition coordinate system, and then the obtained transition coordinate system is rotated counterclockwise around the Y-axis of the transition coordinate system by ψ. j Angle, to obtain the measurement coordinate system Recorded as The three coordinate axes of each measurement coordinate system are denoted as X. L0yj Y L0yj and Z L0yjThe superscript 0 represents the initial test surface; For Y G0 With Y L0yj The angle between them is 90°; ψ j Let be the normal angle of the crystal plane where diffraction occurs, satisfying ψ i =β i -20.5°, ψ i+9 =β i +20.5°, i=1,2,……,9, then the subscript j=1,2,……,18, where β i This is the reference angle for the swing head of the X-ray diffractometer.

[0032] Using the Proto-iXRD residual stress analysis system, in each measurement coordinate system X-ray diffraction data were acquired at the initial surface H0 test point O'0, and the lattice strain in each ZL0yj direction at the initial surface H0 test point O'0 was read.

[0033] After steps one through four of step 2, the Z values ​​at test point O0 are obtained. L0xj To lattice strain and Z L0yj To lattice strain j = 1, 2, ..., 18.

[0034] Step 3, obtain the first test surface H1 of the aluminum alloy specimen:

[0035] The first step is to prepare the chemical milling fluid.

[0036] The second step is to prepare for peeling.

[0037] The third step is chemical milling to remove the layers.

[0038] The fourth step is cleaning.

[0039] Step 5: Determine the first test surface H1 and the corresponding chemical milling depth z1. The surface of the aluminum alloy test block exposed after the first chemical milling peeling is denoted as the first test surface H1. The chemical milling depth z1 = h1 - h0. h1 is the distance from the test surface H1 to the surface of the chemically milled adhesive coating; h0 is the distance from the initial test surface H0 to the surface of the chemically milled adhesive coating.

[0040] Step 6: Establish the test block coordinate system G1. The three coordinate axes of this test block coordinate system are denoted as X, Y, Z, F, G, and C. G1 Y G1 and Z G1 The origin O1 of the test block coordinate system G1 coincides with the geometric center of the test surface H1, and the coordinate axis X... G1 Y G1 and Z G1The direction is relative to the X coordinate in the initial test block coordinate system G0. G0 Y G0 and Z G0 They are in the same direction.

[0041] Step 4: Collect X-ray diffraction data at test point H1 on the first test surface:

[0042] The test point O'1 on the first test surface H1 is located at the geometric center of the first test surface.

[0043] X-ray diffraction analysis was performed at the test points using the Proto-iXRD residual stress analysis system. G1 Y G1 The specific process for acquiring X-ray diffraction data in two directions is as follows:

[0044] The first step is to place the aluminum alloy test block.

[0045] The second step is to focus.

[0046] The third step is to collect data from test point O'1 on the first test surface H1 along the X-axis. G1 X-ray diffraction data in the direction.

[0047] Establish a measurement coordinate system Recorded as The three coordinate axes in the diagram are denoted as X, X, and X. L1xj Y L1xj and Z L1xj Its coordinate origin coincides with the coordinate origin of the test block coordinate system G1, and the coordinate axis X... L1xj Y L1xj and Z L1xj The directions are respectively relative to the measurement coordinate system X in L0xj Y L0xj and Z L0xj The directions are consistent, and the subscripts j = 1, 2, ..., 18.

[0048] Using the Proto-iXRD residual stress analysis system, in each measurement coordinate system The X-ray diffraction data of test point O'1 on the first test surface H1 was acquired, and the Z values ​​of each test point O'1 on the first test surface H1 were read. L1xj To lattice strain j = 1, 2, ..., 18.

[0049] Fourth step, collect data at test point O'1 on the first test surface H1 along the Y-axis. G1 X-ray diffraction data in the direction.

[0050] Centered on the origin of the test block coordinate system G1, the aluminum alloy test block on the worktable is rotated around Z...G1 The axis rotates 90°.

[0051] Repeat the focusing process described in step two of this step.

[0052] Establish a measurement coordinate system Recorded as The three coordinate axes in the diagram are denoted as X, X, and X. L1yj Y L1yj and Z L1yj Its coordinate origin coincides with the coordinate origin of the test block coordinate system G1, and the coordinate axis X... L1yj Y L1yj and Z L1yj The directions are respectively relative to the measurement coordinate system X in L0yj Y L0yj and Z L0yj The directions are consistent, and the subscripts j = 1, 2, ..., 18.

[0053] Using the Proto-iXRD residual stress analysis system, in each measurement coordinate system L 1 yj The X-ray diffraction data of test point O'1 on the first test surface H1 was acquired, and the Z values ​​of each test point O'1 on the first test surface H1 were read. L1yj To lattice strain j = 1, 2, ..., 18.

[0054] After steps one through four of step 4, the Z values ​​at test point O'1 on the first test surface H1 are obtained. L1xj To lattice strain and Z L1yj To lattice strain j = 1, 2, ..., 18.

[0055] Step 5, obtain the second test surface H2 of the aluminum alloy specimen:

[0056] The first step is chemical milling to remove the layers.

[0057] The second step is cleaning.

[0058] The third step is to determine the second test surface H2 and its corresponding chemical milling depth z2. The surface of the aluminum alloy test block exposed after the first chemical milling peeling is designated as the second test surface H2. The chemical milling depth z2 = h2 - h0. Here, h2 is the distance from the test surface H2 to the surface of the chemically milled adhesive coating, and h0 is the distance from the initial test surface H0 to the surface of the chemically milled adhesive coating.

[0059] The fourth step is to establish the test block coordinate system G2. The three coordinate axes of this test block coordinate system are denoted as X, Y, Z, and F. G2 YG2 and Z G2 The origin O2 of the test block coordinate system G2 coincides with the geometric center of the test surface H2, and the coordinate axis X is made to be... G2 Y G2 and Z G2 The direction is relative to the X coordinate in the initial test block coordinate system G0. G0 Y G0 and Z G0 They are in the same direction.

[0060] Step 6: Obtain the remaining test surfaces H of the aluminum alloy specimen. i and the lattice strain at the test point:

[0061] Repeat step 5 to sequentially chemically mill and peel off the surface of the aluminum alloy test block, obtaining the remaining test surfaces H in turn. i .

[0062] After each chemical milling delamination, repeat step 4 and test each of the resulting test surfaces H in sequence. i Test point O' i X-ray diffraction data were acquired at the location, and the remaining test surfaces H were obtained respectively. i Test point O' i Z at each location Lixj To lattice strain and Z Liyj To lattice strain Where i = 0, 1, 2, ..., n, j = 1, 2, ..., 18, and the value of n must satisfy z n-1 Less than 2mm, and z n ≥2mm.

[0063] Step 7, calculate the measured value of residual stress:

[0064] The test point O' obtained through steps 2 to 6 i Z at each location Lixj To lattice strain and Z Liyj To lattice strain Calculate the measured stress by combining grain orientation information. Where i = 1, 2, ..., n, j = 1, 2, ..., 18, and the value of n must satisfy z n-1 Less than 2mm, z n ≥2mm.

[0065] The grain orientation information is represented by the three Euler angles γ1, α, and γ2 of the grain.

[0066] The coordinate system of each grain is established based on the grain orientation information. For example... Figure 2As shown, the grain coordinate system C k The origin of this grain coordinate system is located at the geometric center of the grain; the three coordinate axes X and Y of this grain coordinate system are... Ck Y Ck Z Ck Parallel to the three mutually perpendicular sides of the grain, it can be passed through The Euler transformation is parallel to the coordinate system G of the test block. Here, k = 1, 2, ..., i = 1, 2, ..., n, and the value of n must satisfy z... n-1 Less than 2mm, z n ≥2mm.

[0067] The specific process for calculating the measured stress is as follows.

[0068] The first step is to approximate the grain orientation distribution using a three-dimensional normal distribution function, where the grain orientation distribution function is:

[0069]

[0070] Where P represents the three Euler angles (γ1, α, γ2) indicating grain orientation; E is the mean vector of P; D is the covariance matrix of P; and the superscript T is the matrix operator, indicating transpose.

[0071] The second step is to use the test block coordinate system G. i Below, the macroscopically averaged flexibility constant matrix S of the aluminum alloy specimen is calculated. G (6×6); where 6×6 is the matrix order:

[0072]

[0073] in, The macroscopically averaged flexibility constant matrix of the aluminum alloy specimen under the Reuss constant stress model is obtained from equation (3); This is the macroscopically averaged flexibility constant matrix of the aluminum alloy specimen under the Voigt constant strain model.

[0074] The third step is to calculate the test point O based on the least squares method. i Measured stress at the location The σ 11 and σ 22 For X G Y G Principal stresses in two directions; σ 12 For X G OY G Shear stress in a plane, i = 1, 2, ..., n

[0075] Step 8: Determine the residual stress distribution curve:

[0076] The first step was to establish the laser shot peening impact model of the 2024T351 aluminum alloy using the preprocessing module of the ABAQUS finite element software.

[0077] The second step is to calculate the laser shot peening impact model of 2024T351 aluminum alloy using ABAQUS finite element software.

[0078] The third step is to calculate the rebound model of the 2024T351 aluminum alloy laser shot peening.

[0079] The fourth step is to extract the simulation data.

[0080] Fifth step, replace the subscript of stress S with the suffix pq, pq = 11, 22, 12, and modify the S obtained in step 8, fourth step. pq The data were fitted with a sixth-order polynomial, as shown in equation (15), to obtain the residual stress S. pq Distribution curve y along depth z pq (z).

[0081]

[0082] Step 9, Filtering:

[0083] Replace the stress subscript S obtained in step 8 and the measured residual stress subscript σ obtained in step 7 with the suffix pq, pq = 11, 22, 12.

[0084] For residual stress S pq Distribution curve y along depth z pq (z) is translated so that it is aligned with the test point O of the aluminum alloy specimen. i Measured residual stress σ at the location pq By minimizing the sum of squared errors between them, the scale curve y is obtained. pq '(z)

[0085] The measured residual stress value σ pq Compared to the scale curve y pq The error of '(z) is used as an index, and the measured residual stress value σ with the largest error is taken as the index. pq Begin elimination, retaining 70% of σ. pq Data points. Nine data points with large errors were removed.

[0086] This concludes the analysis of the residual stress field of the laser shot peening of the textured aerospace aluminum alloy.

[0087] This invention addresses the problem of detecting and analyzing the residual stress field generated by laser shot peening of 2024T351 aluminum alloy. It proposes a method for analyzing residual stress based on X-ray diffraction, grain orientation information, and finite element simulation results of laser shot peening, using chemical milling for delamination.

[0088] In this invention, the residual compressive stress layer introduced by laser shot peening is relatively deep. When analyzing it using X-ray diffraction, it is necessary to peel off the material layer by layer to obtain the residual stress along the thickness direction. This process is often achieved by electrolytic etching. However, electrolytic etching requires high precision in electrolytic parameters and chemical reagent concentrations, which is difficult to control in practical applications. Furthermore, the surface curvature after etching is difficult to control, which leads to diffraction line broadening, changes in peak position, and inaccurate diffraction line intensity, seriously affecting the accuracy of residual stress testing. In contrast, this invention uses chemical milling to peel off the layer by uniformly etching downwards in the area covered by the chemical milling fluid. This allows for planar layer-by-layer peeling, resulting in a smooth inner surface of the chemical milling window, which has a positive effect on improving the accuracy of residual stress testing.

[0089] The basic principle of X-ray diffraction for determining residual stress is to approximate macroscopic strain with lattice strain and assume that the material is isotropic, thereby obtaining the residual stress. However, when the material has strong texture, the grain orientation is preferentially distributed, and the material exhibits anisotropic characteristics in both elastoplastic deformation. Therefore, in order to address the problem of strong texture in rolled materials, adjusting the material property parameters in conjunction with grain orientation during the X-ray diffraction determination of residual stress can, to a certain extent, reduce the influence of texture on the determination of residual stress.

[0090] X-ray diffraction for residual stress measurement requires stringent conditions regarding the material's surface condition and microstructure, resulting in unreliable and poorly repeatable data. By obtaining sufficient data through multiple measurements and then filtering the data using ABAQUS finite element simulation results, more reliable stress data can be obtained.

[0091] This invention utilizes chemical milling for delamination and analyzes the residual stress field generated by laser peening of 2024T351 aluminum alloy based on X-ray diffraction (XRD), grain orientation information, and ABAQUS laser peening finite element simulation. It is a complete method suitable for residual stress analysis of strongly textured materials. This method addresses the issues of layer-by-layer material removal, material anisotropy caused by preferred grain orientation, and poor data reliability. It involves detailed discussions and modifications to the X-ray diffraction method for residual stress analysis, including the combined application of chemical milling delamination, residual stress calculation considering grain orientation information, and data screening based on ABAQUS finite element simulation.

[0092] like Figure 3 and Figure 4As shown, compared with the stress data 3 obtained by the traditional XRD method, the consistency between the measured residual stress value 5 obtained by this invention and the polynomial fitting curve 6 of the simulated data is improved by 47.1%. The scale curve 7 is obtained by translating the polynomial fitting curve 6 of the simulated data, which minimizes the sum of squared errors between the measured residual stress value 5 and the scale curve 7, further improving the consistency between the measured residual stress value 5 and the scale curve 7 by 27.5%. Finally, based on the scale curve 7, 30% of the large error stress data in the point set 5 is removed, and the consistency between the remaining stress data, i.e., the stress data 8 after removing the large error data points, and the scale curve 7 is further improved by 87.6%. Attached Figure Description

[0093] Figure 1 This is a schematic diagram showing the relationship between the test block coordinate system G and the measurement coordinate system L.

[0094] Figure 2 This is a schematic diagram showing the relationship between the sample coordinate system G and the crystal coordinate system C.

[0095] Figure 3 This is a schematic diagram showing the screening of measured residual stress values.

[0096] Figure 4 This is a schematic diagram of the measured residual stress values ​​after screening.

[0097] Figure 5 This is a schematic diagram of the technical solution of the present invention.

[0098] Figure 6 This is a flowchart of the present invention.

[0099] In the figure: 1. Distance from laser-peened surface; 2. Residual stress; 3. Stress data measured by conventional XRD method; 4. Stress data obtained by simulation; 5. Measured residual stress value obtained by the present invention; 6. Polynomial fitting curve of simulation data; 7. Scale curve; 8. Measured residual stress value after removing large error data points. Detailed Implementation

[0100] This embodiment is a method for testing and analyzing the residual stress field of laser shot peening on textured aerospace aluminum alloys.

[0101] The test piece is a 2024-T351 aluminum alloy specimen that has undergone laser peening. Its dimensions are 100mm × 100mm × 50mm. A square laser-peened area is located in the center of the 100mm × 100mm face of the aluminum alloy specimen, with an outer dimension of 50mm × 50mm. The laser peening uses a 4mm × 4mm square laser spot with a laser energy of 30J and a spot spacing of 3.4mm. The residual stress field analysis and calculation steps are as follows:

[0102] Step 1, Pretreatment of aluminum alloy test blocks:

[0103] The pretreatment of the aluminum alloy test block includes the following:

[0104] Ⅰ. Measure and record the external dimensions of the aluminum alloy test block. In this embodiment, the length, width, and height of the aluminum alloy test block are 100mm × 100mm × 50mm.

[0105] II. Degreasing of the aluminum alloy test block surface. A cage with an inner cavity slightly larger than the aluminum alloy test block is constructed by binding acid and alkali resistant 316 stainless steel wire; the aluminum alloy test block is placed in the cage and completely immersed in the degreasing solution for 15 minutes to remove surface oil.

[0106] The degreasing solution is composed of sodium hydroxide, sodium phosphate, sodium silicate and water, and its ratio is sodium hydroxide:sodium phosphate:sodium silicate:water = 1:4:3:100, and the unit of the ratio is parts by mass.

[0107] To degrease the aluminum alloy test block, a 2L degreasing solution needs to be prepared. To prepare the solution, weigh out 20g of sodium hydroxide, 80g of sodium phosphate, and 60g of sodium silicate according to the mass ratio of sodium hydroxide, sodium phosphate, sodium silicate, and water, and place them in a stainless steel container. Divide 2000ml of water into two equal portions. Add one portion of water to the stainless steel container and stir thoroughly until homogeneous. Then add the other portion of water to the stainless steel container and stir thoroughly until homogeneous, thus obtaining the degreasing solution.

[0108] Place the stainless steel container containing the degreasing solution in a water bath. Set the water bath temperature to 100℃ to heat the degreasing solution. When the degreasing solution temperature reaches 70℃, set the water bath temperature to 90℃ to maintain the degreasing solution at this temperature.

[0109] The aluminum alloy test block was immersed in a degreasing solution at 70°C for 15 minutes to remove surface oil.

[0110] III. Applying and Curing the Adhesive. Stir the localized electroplating protective adhesive produced by Green Chemical until there are no obvious lumps, and then evenly brush it layer by layer onto each surface of the aluminum alloy test block. The total thickness of the protective adhesive is 0.2 mm. When brushing, the brushing directions of adjacent layers of milling protective adhesive should be perpendicular at 90°. After each layer of the protective adhesive is applied, it needs to dry at room temperature for 60 minutes. The aluminum alloy test block after adhesive application should be cured at room temperature for 8 hours.

[0111] IV. Obtain the initial test surface H0 of the aluminum alloy specimen. Use a chisel to remove the chemical milling protective coating from the center 20mm × 20mm area of ​​the laser-peeled surface of the aluminum alloy specimen to be tested, and use the exposed aluminum alloy specimen surface as the initial test surface H0.

[0112] Measure the distance h0 from the initial test surface H0 to the surface of the chemically milled adhesive coating.

[0113] V. Establish the initial test block coordinate system G0.

[0114] An initial test block coordinate system G0 is established on the initial test surface H0. The origin O0 of the initial test block coordinate system G0 is located at the geometric center of the initial test surface H0; the three coordinate axes X of this initial test block coordinate system are... G0 Y G0 and Z G0 The three mutually perpendicular sides of the aluminum alloy test block to be tested are parallel to each other, where Z... G0 Perpendicular to the laser-peened surface outwards.

[0115] After the above steps, the pretreatment of the aluminum alloy test block is completed.

[0116] Step 2: Collect X-ray diffraction data of the initial test surface H0 test point:

[0117] The test point O'0 of the initial test surface H0 is located at the geometric center of the initial test surface.

[0118] X-ray diffraction analysis was performed at the test points using the Proto-iXRD residual stress analysis system. G0 Y G0 The specific process for acquiring X-ray diffraction data in two directions is as follows:

[0119] The first step is to place the aluminum alloy specimen. The aluminum alloy specimen is placed on the horizontal stage of the Proto-iXRD residual stress analysis system, and the oscillating plane of the X-ray diffractometer in the Proto-iXRD residual stress analysis system is aligned with the X-ray... G0 OZ G0 The faces are parallel;

[0120] The second step is to focus. The specific method is as follows:

[0121] The X-ray diffractometer's tilting head, equipped with a focusing needle, is moved downwards until it contacts the test point O'0. The tilting head is then moved upwards by 20 mm. The focusing needle is replaced with a 1 mm × 3 mm collimating tube. The tilting head is then moved downwards by 20 mm to complete the focusing operation.

[0122] The third step is to collect data from the initial surface H0 test point O'0 along the X direction. G0 X-ray diffraction data in the direction.

[0123] In this embodiment, the swing reference angle β of the X-ray diffractometer's swing head is set. i; i=1,2,...,9; β1=-27.00°, β2=-20.50°, β3=-10.92°, β4=-1.13°, β5=0°, β6=1.13°, β7=10.92°, β8=20.50°, β9=27.00°.

[0124] A measurement coordinate system is defined on the test surface H0 by coordinate system rotation transformation. Specifically,

[0125] The initial test block coordinate system G0 revolves around the Y-axis in the coordinate system of the aluminum alloy test block. G0 Rotate the axis counterclockwise ψ j Angle, to obtain the measurement coordinate system Recorded as The three coordinate axes of each measurement coordinate system are denoted as X. L0xj Y L0xj and Z L0xj Where the superscript 0 represents the initial test block coordinate system G0; For Y G0 With Y L0xj The angle between them, which is 0° here, ψ j The normal angle of the crystal plane where diffraction occurs, i.e., the angle between the crystal plane normal and the Z-axis. G0 The included angle of the axes satisfies ψ i =β i -20.5°, ψ i+9 =β i +20.5°, i=1,2,……,9, then the subscript j=1,2,……,18.

[0126] The acquisition method was set to multiple exposure, with a single exposure time of 2 seconds and 10 exposures.

[0127] Using the Proto-iXRD residual stress analysis system, in each measurement coordinate system X-ray diffraction data were acquired at the initial surface H0 test point O'0, and the values ​​of each Z at the initial test point O'0 were read. L0xj To lattice strain j = 1, 2, ..., 18.

[0128] The fourth step is to collect data from the initial surface H0 test point O'0 along the Y direction. G0 X-ray diffraction data in the direction.

[0129] Centered on the origin of the test block coordinate system G0, the aluminum alloy test block on the worktable is rotated around Z... G0 The axis rotates 90°.

[0130] Focusing. The focusing process is the same as the focusing process in the second step of this procedure.

[0131] The reference angle β of the swing head of the X-ray diffractometer i The data acquisition method and other parameter settings are the same as those in step three of this procedure. A measurement coordinate system is defined on the test surface H0 through coordinate system rotation transformation. Specifically,

[0132] The initial test block coordinate system G0 first revolves around Z. G0 Rotate the axis counterclockwise The angle is used to obtain the rotated transition coordinate system, and then the obtained transition coordinate system is rotated counterclockwise around the Y-axis of the transition coordinate system by ψ. j Angle, to obtain the measurement coordinate system Recorded as The three coordinate axes of each measurement coordinate system are denoted as X. L0yj Y L0yj and Z L0yj The superscript 0 represents the initial test surface; For Y G0 With Y L0yj The angle between them is 90°; ψ j Let ψ be the normal angle of the crystal plane where diffraction occurs, i.e., the angle between the crystal plane normal and the Z-axis of the sample coordinate system, satisfying ψ i =β i -20.5°, ψ i+9 =β i +20.5°, i=1,2,……,9, then the subscript j=1,2,……,18.

[0133] The initial surface H0 test point O'0 and Z were read using XrdWin software. L0yj To lattice strain

[0134] This concludes step 2, obtaining the Z values ​​at test point O'0 on the initial surface H0. L0xj To lattice strain and Z L0yj To lattice strain j = 1, 2, ..., 18.

[0135] Step 3, obtain the first test surface H1 of the aluminum alloy specimen:

[0136] The first step is to prepare the chemical milling fluid. The chemical milling fluid is prepared from sodium hydroxide, triethanolamine, sodium sulfide, and water, with a sodium hydroxide:triethanolamine:sodium sulfide:water ratio of 28:7:4:200. The unit of measurement is parts by mass. In this embodiment, a total of 2L of chemical milling fluid was prepared in a stainless steel container.

[0137] The second step is peeling preparation. A stainless steel container filled with chemical milling fluid is placed in a water bath, and the temperature of the water bath is adjusted to stabilize the temperature of the chemical milling fluid at 70°C.

[0138] The third step is chemical milling to remove the delamination. The aluminum alloy test block to be tested is placed in an iron cage and immersed in the chemical milling solution for 6 minutes to perform chemical milling.

[0139] The fourth step is to clean the aluminum alloy test block.

[0140] Rinse the aluminum alloy test block that has undergone the first chemical milling and delamination with room temperature tap water.

[0141] After rinsing, immerse the aluminum alloy test block in a 40% nitric acid solution for 10 seconds. After immersion, rinse again with room temperature tap water until no nitric acid residue remains on the surface of the test block. After cleaning, dry the surface of the aluminum alloy test block.

[0142] Step 5: Determine the first test surface H1 and its corresponding chemical milling depth. The surface of the aluminum alloy test block exposed after the first chemical milling peel is taken as the first test surface H1. The distance h1 from the test surface H1 to the surface of the chemical milling adhesive coating is measured. The total thickness of the material removed by chemical milling peeling z1 = h1 - h0 is called the chemical milling depth, where h0 is the distance from the initial test surface H0 to the surface of the chemical milling adhesive coating.

[0143] Step 6: Establish the test block coordinate system G1. The three coordinate axes of this test block coordinate system are denoted as X, Y, Z, F, G, and C. G1 Y G1 and Z G1 The origin O1 of the test block coordinate system G1 coincides with the geometric center of the test surface H1, and the coordinate axis X... G1 Y G1 and Z G1 The direction is relative to the X coordinate in the initial test block coordinate system G0. G0 Y G0 and Z G0 They are in the same direction.

[0144] Step 4: Collect X-ray diffraction data at test point H1 on the first test surface.

[0145] The test point O'1 on the first test surface H1 is located at the geometric center of the first test surface.

[0146] X-ray diffraction analysis was performed at the test points using the Proto-iXRD residual stress analysis system. G1 Y G1 The specific process for acquiring X-ray diffraction data in two directions is as follows:

[0147] The first step is to place the aluminum alloy specimen. Place the aluminum alloy specimen on the horizontal stage of the Proto-iXRD residual stress analysis system, and align the swing plane of the X-ray diffractometer in the Proto-iXRD residual stress analysis system with the X-ray diffractometer. G1 OZ G1 The faces are parallel;

[0148] The second step is to focus. The specific method is as follows:

[0149] The X-ray diffractometer's tilting head, equipped with a focusing needle, is moved downwards until it contacts the test point O'1. The tilting head is then moved upwards by 20 mm. The focusing needle is replaced with a 1 mm × 3 mm collimating tube. The tilting head is then moved downwards by 20 mm to complete the focusing operation.

[0150] The third step is to collect data from test point O'1 on the first test surface H1 along the X-axis. G1 X-ray diffraction data in the direction.

[0151] The reference angle β of the swing head of the X-ray diffractometer i The data acquisition method and other parameter settings are the same as those in step 2, i = 1, 2, ..., 9.

[0152] Establish a measurement coordinate system Recorded as The three coordinate axes in the diagram are denoted as X, X, and X. L1xj Y L1xj and Z L1xj Its coordinate origin coincides with the coordinate origin of the test block coordinate system G1, and the coordinate axis X... L1xj Y L1xj and Z L1xj The directions are respectively relative to the measurement coordinate system X in L0xj Y L0xj and Z L0xj The directions are consistent, and the subscripts j = 1, 2, ..., 18.

[0153] Using the Proto-iXRD residual stress analysis system, in each measurement coordinate system The X-ray diffraction data of test point O'1 on the first test surface H1 was acquired, and the Z values ​​of each test point O'1 on the first test surface H1 were read. L1xj To lattice strain j = 1, 2, ..., 18.

[0154] Fourth step, collect data at test point O'1 on the first test surface H1 along the Y-axis. G1 X-ray diffraction data in the direction.

[0155] Centered on the origin of the test block coordinate system G1, the aluminum alloy test block on the worktable is rotated around Z... G1 The axis rotates 90°.

[0156] The focusing process described herein is the same as the focusing process in the second step of this procedure.

[0157] The reference angle β of the swing head of the X-ray diffractometer i The data acquisition method and other parameter settings are the same as those in step three of this procedure.

[0158] Establish a measurement coordinate system Recorded as The three coordinate axes in the diagram are denoted as X, X, and X. L1yj Y L1yj and Z L1yj Its coordinate origin coincides with the coordinate origin of the test block coordinate system G1, and the coordinate axis X... L1yj Y L1yj and Z L1yj The directions are respectively relative to the measurement coordinate system X in L0yj Y L0yj and Z L0yj The directions are consistent, and the subscripts j = 1, 2, ..., 18.

[0159] Using the Proto-iXRD residual stress analysis system, in each measurement coordinate system The X-ray diffraction data of test point O'1 on the first test surface H1 was acquired, and the Z values ​​of each test point O'1 on the first test surface H1 were read. L1yj To lattice strain .

[0160] After the above steps, the Z values ​​at test point O'1 on the first test surface H1 are obtained. L1xj To lattice strain and Z L1yj To lattice strain j = 1, 2, ..., 18.

[0161] Step 5, obtain the second test surface H2 of the aluminum alloy specimen:

[0162] Repeat step 3 to obtain the first test surface H1 of the aluminum alloy specimen, and obtain the second test surface H2 of the aluminum alloy specimen. Specifically:

[0163] The first step is to place the aluminum alloy test block to be tested into an iron cage and immerse it in the chemical milling fluid obtained in the second step of step 3 for 6 minutes to perform chemical milling.

[0164] The second step is cleaning, which is the same as the fourth step in step 3.

[0165] The third step is to determine the second test surface H2 and the corresponding chemical milling depth z2. The surface of the aluminum alloy test block exposed after the first chemical milling peeling is taken as the second test surface H2, and the depth h2 from the second test surface H2 to the surface of the chemical milling adhesive coating is measured; then the chemical milling depth z2 = h2 - h0.

[0166] The fourth step is to establish the test block coordinate system G2. The three coordinate axes of this test block coordinate system are denoted as X, Y, Z, and F. G2 Y G2 and Z G2 The origin O2 of the test block coordinate system G2 coincides with the geometric center of the test surface H2, and the coordinate axis X is made to be... G2 Y G2 and Z G2 The direction is relative to the X coordinate in the initial test block coordinate system G0. G0 Y G0 and Z G0 They are in the same direction.

[0167] Step 6: Obtain the remaining test surfaces H of the aluminum alloy specimen. i and the lattice strain at the test point:

[0168] Repeat step 5 to sequentially chemically mill and peel off the surface of the aluminum alloy test block, obtaining the remaining test surfaces H in turn. i .

[0169] After each chemical milling delamination, repeat step 4 and test each of the resulting test surfaces H in sequence. i Test point O' i X-ray diffraction data were acquired at the location, and the remaining test surfaces H were obtained respectively. i Test point O' i Z at each location Lixj To lattice strain and Z Liyj To lattice strain Where i = 0, 1, 2, ..., n, j = 1, 2, ..., 18, and the value of n must satisfy z n-1 Less than 2mm, and z n ≥2mm.

[0170] Step 7, calculate the measured value of residual stress:

[0171] Through steps 2 to 6, the test points O' are obtained respectively. i Z at each location Lixj To lattice strain and Z Liyj To lattice strain Combined with grain orientation information, the measured stress was calculated. Where i = 1, 2, ..., n, j = 1, 2, ..., 18, and the value of n must satisfy z n-1 Less than 2mm, z n ≥2mm.

[0172] The grain orientation information was obtained through electron backscatter diffraction, totaling 532,303 sets. Each set of grain orientation information is represented by three Euler angles γ1, α, and γ2 of the grain, denoted as γ1, α, α, α. Where k = 1, 2, ..., 532303, i = 1, 2, ..., n, and the value of n must satisfy z n-1 Less than 2mm, z n ≥2mm.

[0173] The coordinate system of each grain is established based on the grain orientation information. For example... Figure 2 As shown, the grain coordinate system C k The origin of this grain coordinate system is located at the geometric center of the grain; the three coordinate axes X and Y of this grain coordinate system are... Ck Y Ck Z Ck Parallel to the three mutually perpendicular sides of the grain, it can be passed through The Euler transformation is parallel to the coordinate system G of the test block.

[0174] The specific process for calculating the measured value of residual stress is as follows.

[0175] The first step is to approximate the grain orientation distribution using a three-dimensional normal distribution function, where the grain orientation distribution function is:

[0176]

[0177] Where P is a vector (γ1, α, γ2) consisting of three Euler angles representing grain orientation; E is the mean vector of P; D is the covariance matrix of P; and the superscript T is a matrix operator that represents transpose.

[0178] The second step is to calculate the macroscopically averaged flexibility constant matrix of the aluminum alloy specimen in the specimen coordinate system G. (6×6); where 6×6 is the matrix order.

[0179]

[0180] in, The macroscopically averaged flexibility constant matrix of the aluminum alloy specimen under the Reuss constant stress model is obtained from equation (3); The macroscopically averaged flexibility constant matrix of the aluminum alloy specimen under the Voigt constant strain model is obtained from equation (4):

[0181]

[0182]

[0183] in, The stiffness constant matrix of the aluminum alloy specimen, which is the macroscopic average, is obtained from equation (5):

[0184]

[0185] In equations (2) to (5), S is the flexible constant matrix; C is the rigid constant matrix; Represents the average macroscopic flexibility constant matrix; The matrix represents the average macroscopic stiffness constant; the superscript G represents the specimen coordinate system; the superscript C represents the grain coordinate system; the subscript R is the Reuss constant stress model; the subscript V is the Voigt constant strain model; M a is the double transformation matrix from the grain coordinate system to the test block coordinate system constructed based on A(3×3); f(P) is the grain orientation distribution function.

[0186] In equation (5), C C (6×6) is the rigidity constant matrix in the aluminum alloy grain coordinate system.

[0187]

[0188] In equation (3), in each grain coordinate system C k Below, the flexibility constant matrix S of single-crystal aluminum alloy C (6×6) can be determined by formula (7).

[0189] S C =(C C ) -1 (7)

[0190] The single transformation matrix A (3×3) from each grain coordinate system C to the test block coordinate system G is determined by formula (8).

[0191]

[0192] Double transformation matrix M a The construction of (6×6) is as shown in formula (9).

[0193]

[0194] Where γ1, α, and γ2 are three Euler angles representing the orientation of each grain. The subscripts in formula (9) are denoted as ij, i = 1, 2, 3, j = 1, 2, 3, a ij Let be the element in the i-th row and j-th column of the single transformation matrix A (3×3).

[0195] The third step is to calculate the test point O'. iMeasured stress at the location The σ 11 and σ 22 For X G Y G Principal stresses in two directions; σ 12 For X G OY G The shear stress in the plane, i = 1, 2, ..., n, where the value of n must satisfy z n-1 Less than 2mm, z n ≥2mm.

[0196] According to Hooke's Law, at test point O... strain in direction Represented as,

[0197]

[0198] in, To measure the normal stress in the Z direction under coordinate system L; The average macroscopic flexibility constant matrix in the measurement coordinate system L; σ = [σ 11 σ 22 σ 33 σ 23 σ 12 σ 13 ] T , is the stress vector composed of stress tensor components; superscript L indicates the measurement coordinate system; superscript G indicates the specimen coordinate system; Each is a matrix The element in row 3, column 1; row 3, column 2; ...; row 3, column 6; denoted as... M b It is the double transformation matrix from the test block coordinate system to the measurement coordinate system constructed based on B(3×3).

[0199] Among them, the single coordinate transformation matrix B (3×3) from the test block coordinate system G to the measurement coordinate system L is,

[0200]

[0201] In equation (11), Angle Y L axis and Y G The angle between the axes, ψ is Z. L Axis and Z G The included angle of the axis.

[0202] Construct a dual-coordinate transformation factor matrix M based on B(3×3). b (6×6) is as follows:

[0203]

[0204] In formula (12), the subscripts are denoted as ij, i = 1, 2, 3, j = 1, 2, 3, b ij It is the element in the i-th row and j-th column of the single transformation matrix B (3×3) from the test block coordinate system to the measurement coordinate system.

[0205] In equation (10), the average macroscopic flexibility constant matrix under the measurement coordinate system L is... It can be obtained from equation (13).

[0206]

[0207] in, The matrix represents the average macroscopic flexibility constant; the superscript G represents the test block coordinate system; the superscript L represents the measurement coordinate system; M b This is a double transformation matrix constructed based on B(3×3); the superscript T is a matrix operator.

[0208] The residual stress measured by XRD is considered as a plane stress state, that is, only σ in the stress tensor is considered as a plane stress state. 11 σ 22 σ 12 If all three components are non-zero, then in principle only three equations are needed to obtain all target values. However, X-ray diffraction measurement involves random errors. To reduce measurement errors and improve measurement accuracy, the measured residual stress values ​​at each test point are solved using the least squares method. Equation (10) can be written as:

[0209]

[0210] For equation (14), the numerical subscripts for strain ε and measurement coordinate system L are denoted as j. For test point O' i Z Lixj Towards lattice strain, Refers to the coordinate system used for measurement. For test point O' i Z Liyj Towards lattice strain, For each measurement coordinate system, i = 1, 2, ..., n, where the value of n must satisfy z n-1 Less than 2mm, z n ≥2mm, j=1,2,……,18.

[0211] Solving equation (14) yields the test point O' of the aluminum alloy specimen. i Measured residual stress at the location

[0212] Step 8: Determine the residual stress distribution curve:

[0213] The first step involved establishing a laser shot peening impact model of the 2024T351 aluminum alloy using the preprocessing module of the ABAQUS finite element software. A semi-infinite body model was used to approximate the laser shot peening specimen, meaning that all surfaces except the shot-peened surface were covered with CIN3D8 elements. The constitutive model of the material was selected from 2024T351 aluminum alloy at 10... 6 The Johnson-Cook model is used at a strain rate of / s; considering the high speed and instantaneous characteristics of the laser peening process, a dynamic explicit analysis method is selected for simulation; the laser peening process is simplified as a force loading process, which is realized through Analytical Field and Tabular.

[0214] The second step involves calculating the laser shot peening impact model of 2024T351 aluminum alloy using the ABAQUS finite element software; and creating an impact model job using the job-create command. This yields the odb result file of the 2024T351 aluminum alloy laser shot peening impact simulation.

[0215] The third step is the calculation of the rebound model of the 2024T351 aluminum alloy laser shot peening. The obtained 2024T351 aluminum alloy laser shot peening impact simulation ODB result file is imported into ABAQUS as a model; CIN3D8 elements are removed; the static analysis method is selected; the job-create command is used to create an impact model job, resulting in the ODB result file of the 2024T351 aluminum alloy laser shot peening finite element simulation.

[0216] The fourth step involves extracting simulation data using the ABAQUS finite element software post-processing module. In ABAQUS's visualization section, open the .odb result file of the laser shot peening finite element simulation of the 2024T351 aluminum alloy, and extract the X-direction residual stress S of the center elements at depths of 0 to 2 mm from the shot-peened surface. 11 ,Y-direction residual stress S 22 and the residual shear stress S on the YOZ surface 12 data.

[0217] Fifth step, replace the subscript of stress S with the suffix pq, pq = 11, 22, 12, and use existing technology to process the S obtained in step 8, fourth step. pq The data were fitted with a sixth-order polynomial, as shown in equation (15), to obtain the residual stress S. pq Distribution curve y along depth z pq (z), as shown by curve 6 in the figure.

[0218]

[0219] Step 9, Filtering:

[0220] Replace the stress subscript S obtained in step 8 and the measured residual stress subscript σ obtained in step 7 with the suffix pq, pq = 11, 22, 12.

[0221] For residual stress S pq Distribution curve y along depth z pq (z) is translated so that it is aligned with the test point O of the aluminum alloy specimen. i Measured residual stress σ at the location pq By minimizing the sum of squared errors between them, the scale curve y is obtained. pq '(z), as shown by curve 7 in the figure.

[0222] The measured residual stress value σ pq Compared to the scale curve y pq The error of '(z) is used as an index, and the measured residual stress value σ with the largest error is taken as the index. pq Begin elimination, retaining 70% of σ. pq Data points. In this embodiment, nine data points with large errors are removed.

[0223] This concludes the analysis of the residual stress field of the laser shot peening of the textured aerospace aluminum alloy.

Claims

1. A method for analyzing the residual stress field of laser shot peening on textured aerospace aluminum alloys, characterized in that, Step 1, Pretreatment of aluminum alloy test blocks: The pretreatment of the aluminum alloy test block includes the following: The first step is to measure and record the external dimensions of the aluminum alloy test block; The second step is to remove oil from the surface of the aluminum alloy test block: the surface is degreased using a degreasing solution. The third step is to apply the adhesive and allow it to cure. The protective adhesive was evenly brushed onto each surface of the aluminum alloy test block layer by layer, and the total thickness of the protective adhesive was 0.2 mm. The fourth step is to obtain the initial test surface H0 of the aluminum alloy specimen; and to remove the chemical milling protective coating in the center test area of ​​the laser shot peened surface of the aluminum alloy specimen. The exposed surface of the aluminum alloy specimen was used as the initial test surface H0; Measure the distance h0 from the initial test surface H0 to the surface of the chemically milled adhesive coating; Fifth step: Establish the initial test block coordinate system G0; Step 2: Collect X-ray diffraction data of the initial test surface H0 test point: The test point O'0 of the initial test surface H0 is located at the geometric center of the initial test surface; X-ray diffraction analysis was performed at the test points using the Proto-iXRD residual stress analysis system. G0 Y G0 The specific process for acquiring X-ray diffraction data in two directions is as follows: The first step is to place the aluminum alloy test block; The second step is to focus; The third step is to collect data from the initial surface H0 test point O'0 along the X direction. G0 X-ray diffraction data in the direction; A measurement coordinate system is defined on the test surface H0 by coordinate system rotation transformation. The acquisition method was set to multiple exposure, with a single exposure time of 2 seconds and 10 exposures. Using the Proto-iXRD residual stress analysis system, in each measurement coordinate system X-ray diffraction data were acquired at the initial surface H0 test point O'0, and the Z values ​​at the initial surface H0 test point O'0 were read. L0xj To lattice strain j＝1,2,……,18； The fourth step is to collect data from the initial surface H0 test point O'1 along the Y direction. G0 X-ray diffraction data in the direction; Centered on the origin of the test block coordinate system G0, the aluminum alloy test block on the worktable is rotated around Z... G0 Rotate the axis 90°; Repeat the focusing process described in step two of this step; A measurement coordinate system is defined on the test surface H0 by coordinate system rotation transformation. Using the Proto-iXRD residual stress analysis system, in each measurement coordinate system X-ray diffraction data were acquired at the initial surface H0 test point O'0, and the Z values ​​at the initial surface H0 test point O'0 were read. L0yj To lattice strain j = 1, 2, ..., 18; Step 3, obtain the first test surface H1 of the aluminum alloy specimen: The first step is to prepare the chemical milling fluid; The second step is to prepare for peeling. The third step is chemical milling to remove the layers; The fourth step is cleaning; Step 5: Determine the first test surface H1 and the corresponding chemical milling depth z1; the surface of the aluminum alloy test block exposed after the first chemical milling peeling is recorded as the first test surface H1; the chemical milling depth z1 = h1 - h0; where h1 is the distance from the test surface H1 to the surface of the chemical milling adhesive coating; h0 is the distance from the initial test surface H0 to the surface of the chemical milling adhesive coating; Step 6: Establish the test block coordinate system G1; the three coordinate axes of this test block coordinate system are denoted as X, Y, X, and X respectively. G1 Y G1 and Z G1 The origin O1 of the test block coordinate system G1 coincides with the geometric center of the test surface H1, and the coordinate axis X... G1 Y G1 and Z G1 The direction is relative to the X coordinate in the initial test block coordinate system G0. G0 Y G0 and Z G0 The directions are consistent; Step 4, collect X-ray diffraction data of the test point H1 on the first test surface: The test point O'1 on the first test surface H1 is located at the geometric center of the first test surface; X-ray diffraction analysis was performed at the test points using the Proto-iXRD residual stress analysis system. G1 Y G1 The specific process for acquiring X-ray diffraction data in two directions is as follows: The first step is to place the aluminum alloy test block; The second step is to focus; The third step is to collect data from test point O'1 on the first test surface H1 along the X-axis. G1 X-ray diffraction data in the direction; Establish a measurement coordinate system on the test surface H1 Using the Proto-iXRD residual stress analysis system, in each measurement coordinate system The X-ray diffraction data of test point O'1 on the first test surface H1 was acquired, and the Z values ​​of each test point O'1 on the first test surface H1 were read. L1xj To lattice strain Fourth step, collect data at test point O'1 on the first test surface H1 along the Y-axis. G1 X-ray diffraction data in the direction; Centered on the origin of the test block coordinate system G1, the aluminum alloy test block on the worktable is rotated around Z... G1 Rotate the axis 90°; repeat the focusing process described in step two of this step; Establish a measurement coordinate system on the test surface H1 Using the Proto-iXRD residual stress analysis system, in each measurement coordinate system The X-ray diffraction data of test point O'1 on the first test surface H1 was acquired, and the Z values ​​of each test point O'1 on the first test surface H1 were read. L1yj To lattice strain Step 5, obtain the second test surface H2 of the aluminum alloy specimen: The first step is chemical milling to remove the layers; The second step is cleaning; The third step is to determine the second test surface H2 and the corresponding chemical milling depth z2; the surface of the aluminum alloy test block exposed after the first chemical milling peeling is recorded as the second test surface H2; the chemical milling depth z2 = h2 - h0; where h2 is the distance from the test surface H2 to the surface of the chemical milling adhesive coating, and h0 is the distance from the initial test surface H0 to the surface of the chemical milling adhesive coating. The fourth step is to establish the test block coordinate system G2; the three coordinate axes of this test block coordinate system are denoted as X, Y, X, and X respectively. G2 Y G2 and Z G2 The origin O2 of the test block coordinate system G2 coincides with the geometric center of the test surface H2, and the coordinate axis X is made to be... G2 Y G2 and Z G2 The direction is relative to the X coordinate in the initial test block coordinate system G0. G0 Y G0 and Z G0 The directions are consistent; Step 6: Obtain the remaining test surfaces H of the aluminum alloy specimen. i and the lattice strain at the test point: Repeat step 5 to sequentially chemically mill and peel off the surface of the aluminum alloy test block, obtaining the remaining test surfaces H in turn. i ; After each chemical milling delamination, repeat step 4 and test each of the resulting test surfaces H in sequence. i Test point O' i X-ray diffraction data were acquired at the location, and the remaining test surfaces H were obtained respectively. i Test point O' i Z at each location Lixj To lattice strain and Z Liyj To lattice strain Where i = 0, 1, 2, ..., n, j = 1, 2, ..., 18, and the value of n must satisfy z n-1 Less than 2mm, and z n ≥2mm; Step 7, calculate the measured value of residual stress: The test point O' obtained through steps 2 to 6 i Z at each location Lixj To lattice strain and Z Liyj To lattice strain Combined with grain orientation information, the measured stress was calculated. Where i = 1, 2, ..., n, j = 1, 2, ..., 18, and the value of n must satisfy z n-1 Less than 2mm, z n ≥2mm; The grain orientation information is represented by the three Euler angles γ1, α, and γ2 of the grain; Each grain coordinate system is established using the grain orientation information; grain coordinate system C k The origin of this grain coordinate system is located at the geometric center of the grain; the three coordinate axes X and Y of this grain coordinate system are... Ck Y Ck Z Ck The three sides, parallel to each other and perpendicular to the grain, can be accessed via Z. Ck X Gi Z Gi - Euler transformation and the test block coordinate system G i Parallel, where k = 1, 2, ... i = 1, 2, ..., n, where the value of n must satisfy z n-1 Less than 2mm, z n ≥2mm; Calculation of test point O' of aluminum alloy specimen based on least squares method i Measured residual stress at the location Step 8: Determine the residual stress distribution curve: The first step was to establish the laser shot peening impact model of the 2024T351 aluminum alloy using the preprocessing module of the ABAQUS finite element software. The second step is to calculate the laser shot peening impact model of 2024T351 aluminum alloy using ABAQUS finite element software. The third step is to calculate the rebound model of the 2024T351 aluminum alloy laser shot peening. The fourth step is to extract the simulation data; Fifth step, replace the subscript of stress S with the suffix pq, pq = 11, 22, 12, and modify the S obtained in step 8, fourth step. pq The data were fitted with a sixth-order polynomial, as shown in equation (15), to obtain the residual stress S. pq Distribution curve y along depth z pq (z); Step 9, Filtering: Replace the stress subscript S obtained in step 8 and the measured residual stress subscript σ obtained in step 7 with the suffix pq, pq = 11, 22, 12; For residual stress S pq Distribution curve y along depth z pq (z) is translated so that it is aligned with the test point O of the aluminum alloy specimen. i Measured residual stress σ at the location pq By minimizing the sum of squared errors between them, the scale curve y is obtained. pq '(z) Using the measured residual stress value σ pq Compared to the scale curve y pq The error of '(z) is used as an index, and the measured residual stress value σ with the largest error is taken as the index. pq Begin elimination, retaining 70% of σ. pq Data points; remove 9 data points with large errors; This concludes the analysis of the residual stress field of the laser shot peening of the textured aerospace aluminum alloy.

2. The method for analyzing the residual stress field of laser shot peening on textured aerospace aluminum alloys as described in claim 1, characterized in that, The initial surface H0 test point O'0 was collected along X... G0 When obtaining X-ray diffraction data in the direction of the sample, specifically, the initial sample coordinate system G0 is rotated around the Y-axis of the aluminum alloy sample coordinate system. G0 Rotate the axis counterclockwise ψ j Angle, to obtain the measurement coordinate system Recorded as The three coordinate axes of each measurement coordinate system are denoted as X. L0xj Y L0xj and Z L0xj Wherein, the superscript 0 represents the initial test block coordinate system G0; For Y G0 With Y L0xj The angle between them, which is 0° here, ψ j The normal angle of the crystal plane where diffraction occurs, i.e., the angle between the crystal plane normal and the Z-axis. G0 The included angle of the axes satisfies ψ i =β i -20.5°, ψ i+9 =β i +20.5°, i=1,2,……,9, then the subscript j=1,2,……,18, where β i The reference angle for the swing head of the X-ray diffractometer; The acquisition method was set to multiple exposure, with a single exposure time of 2 seconds and 10 exposures.

3. The method for analyzing residual stress fields in laser shot peening of textured aerospace aluminum alloys as described in claim 1, characterized in that, The initial surface H0 test point O'0 was collected along the Y... G0 The specific process for obtaining X-ray diffraction data in the direction is as follows: the initial sample coordinate system G0 first revolves around the Z coordinate system of the aluminum alloy sample. G0 Rotate the axis counterclockwise The angle is used to obtain the rotated transition coordinate system, and then the obtained transition coordinate system is rotated counterclockwise around the Y-axis of the transition coordinate system by ψ. j Angle, to obtain the measurement coordinate system Recorded as The three coordinate axes of each measurement coordinate system are denoted as X. L0yj Y L0yj and Z L0yj ; where the superscript 0 represents the initial test surface; For Y G0 With Y L0yj The angle between them is 90°; ψ j Let be the normal angle of the crystal plane where diffraction occurs, satisfying ψ i =β i -20.5°, ψ i+9 =β i +20.5°, i=1,2,……,9, then the subscript j=1,2,……,18, where β i This is the reference angle for the swing head of the X-ray diffractometer.

4. The method for analyzing residual stress fields in laser shot peening of textured aerospace aluminum alloys as described in claim 1, characterized in that, The first test surface H1 test point O'1 is collected along X... G1 When dealing with X-ray diffraction data in a specific direction; Establish a measurement coordinate system Recorded as The three coordinate axes in the diagram are denoted as X, X, and X. L1xj Y L1xj and Z L1xj Its coordinate origin coincides with the coordinate origin of the test block coordinate system G1, and the coordinate axis X... L1xj Y L1xj and Z L1xj The directions are respectively relative to the measurement coordinate system X in L0xj Y L0xj and Z L0xj The directions are consistent, and the subscripts j = 1, 2, ..., 18.

5. The method for analyzing residual stress fields in laser shot peening of textured aerospace aluminum alloys as described in claim 1, characterized in that, Establish a measurement coordinate system Recorded as The three coordinate axes in the diagram are denoted as X, X, and X. L1yj Y L1yj and Z L1yj Its coordinate origin coincides with the coordinate origin of the test block coordinate system G1, and the coordinate axis X... L1yj Y L1yj and Z L1yj The directions are respectively relative to the measurement coordinate system X in L0yj Y L0yj and Z L0yj The directions are consistent, and the subscripts j = 1, 2, ..., 18.

6. The method for analyzing residual stress fields in laser shot peening of textured aerospace aluminum alloys as described in claim 1, characterized in that, The specific process for calculating the measured value of residual stress in step 7 is as follows; The first step is to approximate the grain orientation distribution using a three-dimensional normal distribution function, where the grain orientation distribution function is: Where P represents the three Euler angles (γ1, α, γ2) indicating grain orientation; E is the mean vector of P; D is the covariance matrix of P; and the superscript T is the matrix operator, indicating transpose. The second step is to use the test block coordinate system G. i Below, the macroscopically averaged flexibility constant matrix of the aluminum alloy specimen is calculated. The 6×6 represents the matrix order. in, The macroscopically averaged flexibility constant matrix of the aluminum alloy specimen under the Reuss constant stress model is obtained from equation (3); This represents the macroscopically averaged flexibility constant matrix of the aluminum alloy specimen under the Voigt constant strain model. The third step is to calculate the test point O based on the least squares method. i Measured stress at the location σ 11 and σ 22 For X G Y G Principal stresses in two directions; σ 12 For X G OY G The shear stress in the plane, i = 1, 2, ..., n, where the value of n must satisfy z n-1 Less than 2mm, z n ≥2mm; According to Hooke's Law, at test point O... strain in direction Represented as, in, To measure the normal stress in the Z direction under coordinate system L; The average macroscopic flexibility constant matrix in the measurement coordinate system L; σ = [σ 11 σ 22 σ 33 σ 23 σ 12 σ 13 ] T , is the stress vector composed of stress tensor components; superscript L indicates the measurement coordinate system; superscript G indicates the specimen coordinate system; Each is a matrix The element in row 3, column 1; row 3, column 2; ...; row 3, column 6; denoted as... M b This is the double transformation matrix from the test block coordinate system to the measurement coordinate system, constructed based on B(3×3); Among them, the single coordinate transformation matrix B (3×3) from the test block coordinate system G to the measurement coordinate system L is, In equation (11), Angle Y L axis and Y G The angle between the axes, ψ is Z. L Axis and Z G The included angle of the axis; Construct a dual-coordinate transformation factor matrix M based on B(3×3). b (6×6) is as follows: In formula (12), the subscripts are denoted as ij, i = 1, 2, 3, j = 1, 2, 3, b ij The element in the i-th row and j-th column of the single transformation matrix B (3×3) from the test block coordinate system to the measurement coordinate system; In equation (10), the average macroscopic flexibility constant matrix under the measurement coordinate system L is... It can be obtained from equation (13). in, The matrix represents the average macroscopic flexibility constant; the superscript G represents the test block coordinate system; the superscript L represents the measurement coordinate system; M b This is a double transformation matrix constructed based on B(3×3); the superscript T represents matrix operators; The residual stress measured by XRD is considered as a plane stress state, that is, only σ in the stress tensor is considered as a plane stress state. 11 σ 22 σ 12 If all three components are non-zero, then in principle only three equations are needed to obtain all target values. However, X-ray diffraction measurement involves random errors. To reduce measurement errors and improve measurement accuracy, the measured residual stress values ​​at each test point are solved using the least squares method. Equation (10) can be written as: For equation (14), the numerical subscripts for strain ε and measurement coordinate system L are denoted as j. For test point O' i Z Lixj Towards lattice strain, Refers to the coordinate system used for measurement. For test point O' i Z Liyj Towards lattice strain, For each measurement coordinate system, The value of n must be such that z n-1 Less than 2mm, z n ≥2mm, j=1,2,……,18; Solving equation (14) yields the test point O' of the aluminum alloy specimen. i Measured residual stress at the location 7. The method for analyzing residual stress fields in laser shot peening of textured aerospace aluminum alloys as described in claim 1, characterized in that, The initial test block coordinate system G0 established in step 1 is on the initial test surface H0; the origin O0 of the initial test block coordinate system G0 is located at the geometric center of the initial test surface H0; the three coordinate axes X of this initial test block coordinate system are... G0 Y G0 and Z G0 The three mutually perpendicular sides of the aluminum alloy test block to be tested are parallel to each other, where Z... G0 Perpendicular to the laser-peened surface outwards.

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