Method for measuring residual stress of aluminum alloy sheet

Abstract

The application discloses a kind of measurement methods of residual stress of aluminum alloy sheet, belong to metal residual stress measurement technical field.It includes the following steps: step one, using three-dimensional scanner to scan the surface three-dimensional point cloud data of sheet to be measured;Step two, using adsorption system to apply adsorption force to sheet to be measured, make sheet to be measured produce deformation, then use three-dimensional scanner to scan the surface three-dimensional point cloud data of sheet to be measured after deformation;Step three, using software to process three-dimensional point cloud data before and after adsorption respectively, obtain the curvature of sheet to be measured before and after applying adsorption force by numerical fitting, calculate curvature variation;Step four, curvature variation is substituted into the function equation of calibrated residual stress-curvature variation, and the residual stress of sheet to be measured can be obtained.The application overcomes the problem that traditional ultrasonic detection method cannot detect when detecting sheet because ultrasonic wave is easy to penetrate and difficult to receive echo signal;Solve the deficiency that macroscopic determination cannot give specific stress value.

Description

Technical Field

[0001] This invention belongs to the field of metal residual stress measurement technology, specifically relating to a method for measuring residual stress in aluminum alloy thin plates. Background Technology

[0002] During the rolling and quenching processes of aluminum alloy sheets, residual stress is inevitably generated within the material. The presence of residual stress can lead to problems such as warping, cracking, and dimensional instability in the sheets, severely impacting product performance and service life. Therefore, accurately measuring the residual stress in aluminum alloy sheets is crucial for optimizing processing techniques and improving product quality.

[0003] Generally, there are two main categories of methods for detecting residual stress: destructive testing (DPT) and non-destructive testing (NDT). DPT involves locally damaging the workpiece to release residual stress, thus achieving stress detection. However, this method damages the workpiece and is therefore unsuitable for online inspection of in-service workpieces. NDT utilizes the principle of acoustoelasticity for stress detection; commonly used methods include the critical refractive longitudinal wave (LCR wave) and the Lamb wave method.

[0004] The LCR wave method measures stress by utilizing the characteristic that the propagation speed of a critically refracted longitudinal wave changes with the residual stress on the surface of a material. However, the LCR wave method is susceptible to the influence of the material's surface condition (such as surface roughness) and can only measure residual stress within a certain depth range on the material's surface, making it unsuitable for stress detection in ultra-thin sheet metal workpieces. The Lamb wave method measures stress by utilizing the principle that the propagation characteristics (such as wave velocity and frequency) of a Lamb wave in a thin plate change due to the influence of residual stress within the plate. That is, by analyzing the changes in the propagation characteristics of the Lamb wave, the distribution of residual stress within the thin plate can be inferred. However, the Lamb wave method essentially also inverts residual stress by analyzing the changes in various modes within the workpiece, and therefore is also unsuitable for stress detection in ultra-thin sheet metal workpieces.

[0005] For aluminum alloy sheets thinner than 0.5 mm, traditional ultrasonic testing methods are unsuitable for residual stress detection because the emitted ultrasonic waves may penetrate the sheet, preventing the reception of ultrasonic echo signals. To address this, many researchers have studied macroscopic methods for determining residual stress and internal stress testing methods. The macroscopic method involves placing a relatively flat aluminum alloy sheet vertically, shaking the top, and observing the direction and amplitude of the swing along the length to determine residual stress. While this method allows for non-destructive testing of residual stress, it only provides a macroscopic assessment and cannot give specific stress values. The internal stress testing method involves removing a certain thickness of the sheet through chemical etching or cutting, disrupting the original stress balance and causing the sheet to bend. The magnitude of the internal stress is then calculated by measuring the warp value. Although this method is low-cost and requires simple equipment, it is difficult to control the uniformity of etching and cutting for aluminum alloy sheets thinner than 0.5 mm, leading to reduced testing accuracy.

[0006] In summary, the main problems with residual stress detection in thin plates less than 0.5mm thick are: 1. Traditional ultrasonic testing methods are prone to signal penetration when testing aluminum alloy thin plates less than 0.5mm thick, making it difficult to receive echo signals and thus impossible to detect. 2. Although macroscopic methods for determining residual stress can achieve non-destructive testing, they only provide a macroscopic assessment and cannot give specific stress values. Summary of the Invention

[0007] This invention addresses the technical problems existing in the detection of residual stress in thin plates with a thickness of less than 0.5 mm by providing a method for measuring residual stress in aluminum alloy thin plates.

[0008] The present invention provides a method for measuring the residual stress of a thin aluminum alloy plate with a thickness ≤ 0.5 mm. The method includes the following steps: Step 1: Scanning the three-dimensional point cloud data of the surface of the thin plate using a 3D scanner; Step 2: Applying an adsorption force to the thin plate using an adsorption system to induce elastic deformation, and then scanning the three-dimensional point cloud data of the deformed surface using a 3D scanner; Step 3: Converting the three-dimensional point cloud data into a planar surface patch to obtain a reverse model with a continuous surface patch structure; then sectioning the reverse model, extracting and fitting the section lines to obtain the curvature of the thin plate before and after applying the adsorption force, and thus obtaining the change in curvature; Step 4: Substituting the change in curvature into a pre-calibrated function equation of residual stress - change in curvature to obtain the residual stress of the thin plate.

[0009] The basic principle of this invention is to use an adsorption system to adsorb the thin plate under test. The release of stress will cause the thin plate under test to deform. As the thin plate under test deforms, the curvature of the surface also changes accordingly. During the adsorption process, it is ensured that no additional residual stress is generated and that the boundary conditions and adsorption force are consistent. By using a pre-calibrated functional equation of residual stress and curvature change, it is only necessary to obtain the change in surface curvature of the thin plate under test before and after the adsorption force is applied. Then, the residual stress value can be obtained by substituting it into the calibrated functional equation of residual stress and curvature change.

[0010] Preferably, in step four, the residual stress-curvature change function equation is calibrated using a residual stress calibration specimen. This specimen is obtained by stretching a zero-stress specimen. The zero-stress specimen has the same material and size as the thin plate to be tested, and the adsorption force applied to the residual stress calibration specimen during calibration is consistent with that applied to the thin plate. The calibration process includes the following steps: S1. Applying different residual stresses to the zero-stress specimen using a stretching method, and confirming the residual stress value using a pinhole method, thereby obtaining the residual stress calibration specimen; scanning the residual stress calibration specimen using a 3D scanner. Surface three-dimensional point cloud data; then, an adsorption system is used to apply adsorption force to the residual stress calibration sample, and a three-dimensional scanner is used to scan the surface three-dimensional point cloud data of the residual stress calibration sample after adsorption; S2, the obtained three-dimensional point cloud data of the residual stress calibration sample before and after adsorption are fitted to obtain the curvature of the residual stress calibration sample before and after applying adsorption force, and then the curvature change of the residual stress calibration sample before and after applying adsorption force under different residual stresses is obtained; S3, the residual stress-curvature change function equation is obtained by fitting the data of different residual stresses and curvature changes of the residual stress calibration sample.

[0011] Preferably, steps S1 and S2 are repeated 3-5 times to obtain multiple sets of curvature change data under the same residual stress, and the average value is calculated. By averaging multiple sets of curvature change data under the same residual stress, the calibration equation can be more accurate.

[0012] Preferably, in step S2, the process of fitting the three-dimensional point cloud data of the obtained residual stress calibration sample before and after adsorption includes the following steps: (1) using post-processing software to perform "patch processing" on the obtained three-dimensional point cloud data of the residual stress calibration sample before and after adsorption, converting the three-dimensional point cloud data into a patch form with a planar structure, and obtaining a reverse model with a continuous patch structure; (2) then using solid modeling software to cut the reverse model, extracting and fitting the cut section line, obtaining the curvature of the residual stress calibration sample before and after applying adsorption force, and then obtaining the curvature change.

[0013] Preferably, the adsorption system includes an air compressor, an air pipe, a vacuum gauge, and a vacuum suction cup; the vacuum gauge is equipped with a regulating valve, one end of the vacuum gauge is connected to the air compressor through the air pipe, and the other end is connected to the vacuum suction cup through the air pipe; the air compressor is used to generate negative pressure and transmit the negative pressure to the vacuum suction cup through the air pipe; the vacuum gauge can display the negative pressure generated by the air compressor and ensure that the negative pressure is the same for each test through the regulating valve; the vacuum suction cup is used to apply adsorption force to the thin plate to be tested and the residual stress calibration sample.

[0014] The present invention has the following beneficial effects: (1) It uses a three-dimensional scanner to perform three-dimensional inspection on aluminum alloy thin plates with a thickness of less than 0.5 mm, and calculates the residual stress using the empirical equation of curvature-residual stress, thereby overcoming the problem that traditional ultrasonic testing methods cannot detect such thin plates because ultrasonic waves can easily penetrate and it is difficult to receive echo signals. (2) It solves the shortcomings of the macroscopic residual stress judgment method, which can only make macroscopic judgments and cannot give specific stress values, and provides a detection method that can obtain specific stress values. (3) The present invention belongs to non-destructive testing and relies on optical measurement, so it is not limited by the detection of workpiece thickness. Attached Figure Description

[0015] Figure 1 This is a fitting graph of the residual stress-curvature change of the residual stress calibration specimen (h=0.3mm) in Example 1 of the present invention;

[0016] Figure 2 This is a fitted image of the point cloud data of the thin plate (h=0.3mm) before deformation in Embodiment 1 of the present invention;

[0017] Figure 3 This is a fitted image of the point cloud data of the thin plate (h=0.3mm) under test after deformation in Embodiment 1 of the present invention;

[0018] Figure 4 This is a fitting graph of the residual stress-curvature change of the residual stress calibration specimen (h=0.4mm) in Example 2 of the present invention.

[0019] Figure 5 This is a fitted image of the point cloud data of the thin plate (h=0.4mm) before deformation in Embodiment 2 of the present invention;

[0020] Figure 6 This is a fitted image of the point cloud data of the thin plate (h=0.4mm) under test after deformation in Embodiment 2 of the present invention;

[0021] Figure 7 This is a fitting graph of the residual stress-curvature change of the residual stress calibration specimen (h=0.5mm) in Example 3 of the present invention.

[0022] Figure 8This is a fitted image of the point cloud data before deformation in Embodiment 3 of the present invention (h=0.5mm);

[0023] Figure 9 This is a fitted image of the point cloud data after deformation in Embodiment 3 of the present invention (h=0.5mm);

[0024] Figure 10 This is a schematic diagram of the adsorption system device of the present invention.

[0025] In the diagram, 1 is an air compressor; 2 is an air pipe; 3 is a vacuum gauge; and 4 is a vacuum suction cup. Detailed Implementation

[0026] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0027] Example 1

[0028] A method for measuring residual stress in aluminum alloy thin plates, using an adsorption system such as... Figure 10 As shown, the adsorption system includes an air compressor 1, an air pipe 2, a vacuum gauge 3, and a vacuum suction cup 4. The vacuum gauge 3 is equipped with a regulating valve. One end of the vacuum gauge 3 is connected to the air compressor 1 via the air pipe 2, and the other end is connected to the vacuum suction cup 4 via the air pipe 2. The air compressor 1 generates negative pressure and transmits this negative pressure to the vacuum suction cup 4 through the air pipe 2. The vacuum gauge 3 displays the negative pressure generated by the air compressor 1 and ensures that the negative pressure remains consistent for each test through the regulating valve. The vacuum suction cup 4 applies adsorption force to the thin plate under test and the residual stress calibration sample. In this embodiment, the negative pressure generated by the air compressor on the vacuum suction cup is -0.028 MPa.

[0029] The residual stress calibration specimen is obtained by tensile treatment of the zero-stress specimen. A certain residual stress is applied to the zero-stress specimen by the tensile method, thereby obtaining the residual stress calibration specimen under this residual stress. The zero-stress specimen is a rectangular thin plate of 2024 aluminum alloy in the T4 state after heat treatment at 120℃ for 24h, with a length L=160mm, width D=80mm, and thickness h=0.3mm. The data area of ​​the zero-stress specimen is a circular area with a diameter of 46mm. The thin plate to be tested is a rectangular thin plate of 2024 aluminum alloy in the T4 state, with a length L=160mm, width D=80mm, and thickness h=0.3mm. The test area of ​​the thin plate to be tested is a circular area with a diameter of 46mm.

[0030] The measurement method includes the following steps: Step 1, scanning the three-dimensional point cloud data of the surface of the thin plate to be tested using a 3D scanner; Step 2, applying an adsorption force to the thin plate to be tested using an adsorption system to induce elastic deformation, and then scanning the three-dimensional point cloud data of the deformed surface of the thin plate to be tested using a 3D scanner; Step 3, converting the three-dimensional point cloud data into a planar surface patch form to obtain a reverse model with a continuous surface patch structure; then, sectioning the reverse model, extracting and fitting the section lines to obtain the curvature of the thin plate to be tested before and after applying the adsorption force as -0.1502m. -1 and 2.4183m -1 The fitting results are as follows Figure 2 and Figure 3 As shown, the curvature change is 2.5685m according to the fitting results. -1 Step 4: Substitute the curvature change into the pre-calibrated residual stress-curvature change function equation to obtain the residual stress of the thin plate under test.

[0031] In step four, the residual stress-curvature change function equation is calibrated using a residual stress calibration sample. The calibration process includes the following steps: S1. Apply different residual stresses to the zero-stress sample using the tensile method, and confirm the residual stresses as 10 MPa, 20 MPa, 40 MPa, 60 MPa, 80 MPa and 100 MPa by measuring with the pinhole method, thereby obtaining the residual stress calibration sample with the corresponding residual stress. Use a 3D scanner to scan the surface 3D point cloud data of the residual stress calibration sample; then use an adsorption system to apply adsorption force to the residual stress calibration sample, and use a 3D scanner to scan the surface 3D point cloud data of the residual stress calibration sample after adsorption; S2. Fit the obtained 3D point cloud data of the residual stress calibration sample before and after adsorption. The processing includes the following steps: (1) Use post-processing software (Geomagic) Controlx) performs “patch processing” on the three-dimensional point cloud data of the residual stress calibration sample before and after adsorption, respectively, and converts the three-dimensional point cloud data into a patch form with a planar structure to obtain a reverse model with a continuous patch structure; (2) then uses solid modeling software (UG) to cut the reverse model, extracts and fits the cut section line to obtain the curvature of the residual stress calibration sample before and after the adsorption force is applied, and then obtains the curvature change. S3. Fit the data of different residual stresses and curvature changes of the residual stress calibration sample to obtain the function equation of residual stress-curvature change. During the calibration process, repeat the operation of steps S1 and S2 3 times to obtain multiple sets of curvature change data under the same residual stress, and calculate the average value. The residual stress and the average curvature change under the corresponding residual stress are shown in Table 1, and the fitting figure is shown in Table 2. Figure 1As shown, the fitted function equation is Δk = -0.0097Δσ + 2.4205, where Δk is the curvature change and Δσ is the residual stress.

[0032] Based on the residual stress-curvature function equation Δk=-0.0097Δσ+2.4205, the residual stress value of the thin plate under test is calculated to be -15.25MPa.

[0033] Table 1. Residual stress Δσ—curvature change Δk data of residual stress calibration specimens.

[0034] Residual stress (MPa) Curvature before deformation Curvature after deformation <![CDATA[Change in curvature Δk (m -1 )]]> 10 0.1190 2.4895 2.3705 20 0.0818 2.2878 2.206 40 0.1216 2.1784 2.0568 60 0.1962 1.9396 1.7434 80 -0.0353 1.5958 1.6311 100 -0.0629 1.4445 1.5074

[0035] Example 2

[0036] A method for measuring residual stress in aluminum alloy thin plates, using the same adsorption system as in Example 1. The difference lies in that the zero-stress sample is a rectangular 2024 aluminum alloy thin plate in the T4-treated state after heat treatment at 120°C for 24 hours, with a length L = 160 mm, width D = 80 mm, and thickness h = 0.4 mm. The data area of ​​the zero-stress sample is a circular region with a diameter of 46 mm. The thin plate to be tested is a rectangular 2024 aluminum alloy thin plate in the T4-treated state, with a length L = 160 mm, width D = 80 mm, and thickness h = 0.4 mm. The test area of ​​the thin plate to be tested is a circular region with a diameter of 46 mm.

[0037] The measurement method includes the following steps: Step 1: Scan the three-dimensional point cloud data of the surface of the thin plate to be tested using a 3D scanner; Step 2: Apply an adsorption force to the thin plate to be tested using an adsorption system to induce elastic deformation, and then scan the three-dimensional point cloud data of the deformed surface of the thin plate to be tested using a 3D scanner; Step 3: Convert the three-dimensional point cloud data into a planar surface patch form to obtain a reverse model with a continuous surface patch structure; then section the reverse model, extract and fit the section lines to obtain the curvature of the thin plate to be tested before and after applying the adsorption force as -0.0924m. -1 and 2.4132m -1 The fitting results are as follows Figure 5 and Figure 6 As shown, the fitting results further yielded a curvature change of 2.5056m. -1 Step 4: Substitute the curvature change into the pre-calibrated residual stress-curvature change function equation to obtain the residual stress of the thin plate under test.

[0038] In step four, the residual stress-curvature change function equation is calibrated using a residual stress calibration sample. The calibration process includes the following steps: S1. Apply different residual stresses to the zero-stress sample using the tensile method, and confirm the residual stresses as 10 MPa, 20 MPa, 40 MPa, 60 MPa, 80 MPa and 100 MPa by measuring with the pinhole method, thereby obtaining the residual stress calibration sample with the corresponding residual stress. Use a 3D scanner to scan the surface 3D point cloud data of the residual stress calibration sample; then use an adsorption system to apply adsorption force to the residual stress calibration sample, and use a 3D scanner to scan the surface 3D point cloud data of the residual stress calibration sample after adsorption; S2. Fit the obtained 3D point cloud data of the residual stress calibration sample before and after adsorption. The processing includes the following steps: (1) Use post-processing software (Geomagic) Controlx) performs “patch processing” on the three-dimensional point cloud data of the residual stress calibration sample before and after adsorption, respectively, and converts the three-dimensional point cloud data into a patch form with a planar structure to obtain a reverse model with a continuous patch structure; (2) then uses solid modeling software (UG) to cut the reverse model, extracts and fits the cut section line to obtain the curvature of the residual stress calibration sample before and after the adsorption force is applied, and then obtains the curvature change. S3. Fit the data of different residual stresses and curvature changes of the residual stress calibration sample to obtain the function equation of residual stress-curvature change. During the calibration process, repeat the operation of steps S1 and S2 4 times to obtain multiple sets of curvature change data under the same residual stress, and calculate the average value. The residual stress and the average curvature change under the corresponding residual stress are shown in Table 2, and the fitting figure is shown in Table 2. Figure 4 As shown, the fitted function equation is Δk = -0.0106Δσ + 2.3619, where Δk is the curvature change and Δσ is the residual stress.

[0039] Based on the residual stress-curvature function equation Δk=-0.0106Δσ+2.3619, the residual stress value of the thin plate under test is calculated to be -13.56MPa.

[0040] Table 2. Residual stress Δσ—curvature change Δk data of residual stress calibration specimens.

[0041] Residual stress (MPa) Curvature before deformation Curvature after deformation <![CDATA[Change in curvature Δk (m -1 )]]> 10 0.0624 2.3074 2.245 20 -0.2187 1.8892 2.1079 40 -0.2009 1.8568 2.0577 60 -0.1792 1.5141 1.6933 80 0.0043 1.4193 1.415 100 0.1771 1.5285 1.3514

[0042] Example 3

[0043] A method for measuring residual stress in aluminum alloy thin plates, using the same adsorption system as in Example 1. The difference lies in that the zero-stress sample is a rectangular 2024 aluminum alloy thin plate in the T4-treated state after heat treatment at 120℃ for 24 hours, with a length L = 160 mm, width D = 80 mm, and thickness h = 0.5 mm. The data area of ​​the zero-stress sample is a circular region with a diameter of 46 mm. The thin plate to be tested is a rectangular 2024 aluminum alloy thin plate in the T4-treated state, with a length L = 160 mm, width D = 80 mm, and thickness h = 0.5 mm. The test area of ​​the thin plate to be tested is a circular region with a diameter of 46 mm.

[0044] The measurement method includes the following steps: Step 1, scanning the three-dimensional point cloud data of the surface of the thin plate to be tested using a 3D scanner; Step 2, applying an adsorption force to the thin plate to be tested using an adsorption system to induce elastic deformation, and then scanning the three-dimensional point cloud data of the deformed surface of the thin plate to be tested using a 3D scanner; Step 3, converting the three-dimensional point cloud data into a planar surface patch form to obtain a reverse model with a continuous surface patch structure; then, sectioning the reverse model, extracting and fitting the section lines to obtain the curvature of the thin plate to be tested before and after applying the adsorption force as -0.0419m. -1 and 2.3271m -1 The fitting results are as follows Figure 8 and Figure 9 As shown, the fitting results further yielded a curvature change of 2.369m. -1 Step 4: Substitute the curvature change into the pre-calibrated residual stress-curvature change function equation to obtain the residual stress of the thin plate under test.

[0045] In step four, the residual stress-curvature change function equation is calibrated using a residual stress calibration sample. The calibration process includes the following steps: S1. Apply different residual stresses to the zero-stress sample using the tensile method, and confirm the residual stresses as 10 MPa, 20 MPa, 40 MPa, 60 MPa, 80 MPa and 100 MPa by measuring with the pinhole method, thereby obtaining the residual stress calibration sample with the corresponding residual stress. Use a 3D scanner to scan the surface 3D point cloud data of the residual stress calibration sample; then use an adsorption system to apply adsorption force to the residual stress calibration sample, and use a 3D scanner to scan the surface 3D point cloud data of the residual stress calibration sample after adsorption; S2. Fit the obtained 3D point cloud data of the residual stress calibration sample before and after adsorption. The processing includes the following steps: (1) Use post-processing software (Geomagic) Controlx) performs “patch processing” on the three-dimensional point cloud data of the residual stress calibration sample before and after adsorption, respectively, and converts the three-dimensional point cloud data into a patch form with a planar structure to obtain a reverse model with a continuous patch structure; (2) then uses solid modeling software (UG) to cut the reverse model, extracts and fits the cut section line to obtain the curvature of the residual stress calibration sample before and after the adsorption force is applied, and then obtains the curvature change. S3. Fit the data of different residual stresses and curvature changes of the residual stress calibration sample to obtain the function equation of residual stress-curvature change. During the calibration process, repeat the operation of steps S1 and S2 5 times to obtain multiple sets of curvature change data under the same residual stress, calculate the average value, the residual stress and the average curvature change under the corresponding residual stress are shown in Table 3, and the fitting figure is shown in Table 3. Figure 7 As shown, the fitted function equation is Δk = -0.0104Δσ + 2.2448, where Δk is the curvature change and Δσ is the residual stress.

[0046] Based on the residual stress-curvature function equation Δk=-0.0104Δσ+2.2448, the residual stress value of the thin plate under test is calculated to be -11.94MPa.

[0047] Table 3. Residual stress Δσ—curvature change Δk data for residual stress calibration specimens.

[0048] Residual stress (MPa) Curvature before deformation Curvature after deformation <![CDATA[Amount of curvature change Δk (m -1 )]]> 10 0.0679 2.2809 2.213 20 -0.0418 2.0352 2.077 40 0.0575 1.7750 1.7175 60 -0.0644 1.4748 1.5392 80 -0.0155 1.4130 1.4285 100 -0.0159 1.2565 1.2724 .

Claims

1. A method for measuring residual stress in aluminum alloy thin plates, characterized in that, The thickness of the aluminum alloy sheet is ≤0.5mm; the measurement method includes the following steps: Step 1, using a 3D scanner to scan the 3D point cloud data of the surface of the sheet to be measured; Step 2, using an adsorption system to apply an adsorption force to the sheet to be measured, causing the sheet to undergo elastic deformation, and then using a 3D scanner to scan the 3D point cloud data of the deformed surface of the sheet to be measured; Step 3, converting the 3D point cloud data into a planar structure of surface patches to obtain a reverse model with a continuous surface patch structure. Next, the reverse model is sectioned, and the section line is extracted and fitted to obtain the curvature of the thin plate under test before and after the adsorption force is applied, and then the curvature change is obtained; Step 4: Substitute the curvature change into the pre-calibrated residual stress-curvature change function equation to obtain the residual stress of the thin plate under test. In step four, the residual stress-curvature change function equation is calibrated using a residual stress calibration specimen. This specimen is obtained by stretching a zero-stress specimen. The zero-stress specimen has the same material and dimensions as the thin plate under test. During calibration, the adsorption force applied to the residual stress calibration specimen is consistent with that applied to the thin plate under test. The calibration process includes the following steps: S1. Applying different residual stresses to the zero-stress specimen using a stretching method, and confirming the residual stress value using a pinhole method, thereby obtaining the residual stress calibration specimen; scanning the surface of the residual stress calibration specimen using a 3D scanner. Three-dimensional point cloud data; then, an adsorption system is used to apply adsorption force to the residual stress calibration sample, and a three-dimensional scanner is used to scan the three-dimensional point cloud data of the surface of the residual stress calibration sample after adsorption; S2, the obtained three-dimensional point cloud data of the residual stress calibration sample before and after adsorption are fitted to obtain the curvature of the residual stress calibration sample before and after the adsorption force is applied, and then the curvature change of the residual stress calibration sample before and after the adsorption force is applied under different residual stresses is obtained; S3, the data of different residual stresses and curvature changes of the residual stress calibration sample are fitted to obtain the functional equation of residual stress-curvature change. In step S2, the process of fitting the three-dimensional point cloud data of the obtained residual stress calibration sample before and after adsorption includes the following steps: (1) Using post-processing software, the three-dimensional point cloud data of the obtained residual stress calibration sample before and after adsorption are processed into "surface patches", and the three-dimensional point cloud data are converted into a surface patch with a planar structure to obtain a reverse model with a continuous surface patch structure; (2) Then, the reverse model is cut by solid modeling software, and the cut section line is extracted and fitted to obtain the curvature of the residual stress calibration sample before and after the adsorption force is applied, and then the curvature change is obtained. The adsorption system includes an air compressor, an air pipe, a vacuum gauge, and a vacuum suction cup. The vacuum gauge is equipped with a regulating valve. One end of the vacuum gauge is connected to the air compressor via the air pipe, and the other end is connected to the vacuum suction cup via the air pipe. The air compressor generates negative pressure and transmits the negative pressure to the vacuum suction cup through the air pipe. The vacuum gauge displays the negative pressure generated by the air compressor and ensures that the negative pressure is the same for each test through the regulating valve. The vacuum suction cup is used to apply adsorption force to the thin plate to be tested and the residual stress calibration sample.

2. The method for measuring residual stress in aluminum alloy thin plates according to claim 1, characterized in that, Repeat steps S1 and S2 3-5 times to obtain multiple sets of curvature change data under the same residual stress, and calculate the average value.

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