Residual stress testing device and testing method for crane welding joint

Abstract

The invention relates to a residual stress testing device and testing method for a crane welding joint, the residual stress testing device comprises a rack, a mounting assembly, a load detection module, a displacement detection module and a processing module, the top of the rack is rotatably provided with two switching arms arranged at a right angle, and one switching arm is provided with an indentation instrument; an image acquisition module is arranged at the bottom of the other adapter arm; the mounting assembly is arranged at the bottom of the rack and is used for mounting a to-be-tested welding joint; the load detection module is used for detecting a pressure load applied to the surface of the to-be-detected welding joint by an indenter of the indenter; the displacement detection module is used for detecting the axial displacement of an indenter of the indenter; and the processing module is used for acquiring the residual stress according to the image before the load is applied to the to-be-tested position on the to-be-tested welding joint and the image after the load is applied to the to-be-tested position. According to the invention, the accuracy of test results is ensured.

Description

Technical Field

[0001] The invention relates to the technical field of residual stress testing, and in particular to a residual stress testing device and a testing method for a crane welding joint. Background Art

[0002] The crane industry plays a vital role in modern industry. It is an indispensable equipment in engineering construction, logistics and transportation, and many manufacturing processes. With the development of the global economy and the continuous advancement of infrastructure construction, the demand for cranes continues to grow, and their safety and reliability have become the focus of attention in the industry. As the weak link in the crane structure, the quality of the welded joint directly affects the safety performance and service life of the whole machine. Therefore, residual stress testing of crane welded joints to ensure welding quality is an important part of ensuring the safe operation of cranes.

[0003] The residual stress test of crane welding joints is an important part of ensuring the quality and safety of welding structures. Existing residual stress test technologies for welding joints include X-ray diffraction (XRD), ultrasonic testing (UT), magnetic particle testing (MT), electrical testing, neutron diffraction, electron backscatter diffraction (EBSD) and synchrotron X-ray diffraction. X-ray diffraction uses X-rays to irradiate the surface of the material and calculates the residual stress by measuring the change in the lattice spacing of the crystal. It has the advantages of non-destructive testing and high precision, but the equipment is expensive and the operation is complicated. The ultrasonic testing method evaluates the internal structure and stress state by transmitting and receiving the propagation characteristics of ultrasonic waves in the material. It is suitable for large-volume materials and can detect deep defects, but it is sensitive to surface roughness. The magnetic particle testing method uses the aggregation phenomenon of magnetic powder at the defect under the action of a magnetic field to detect surface and near-surface defects. It is simple to operate and has low cost, but it can only detect surface or near-surface defects and cannot quantify residual stress. The electrical testing method pastes strain gauges on the surface of the material and infers the residual stress by measuring the strain change. The principle is simple and the cost is relatively low, but it is a destructive test and requires contact with the surface of the material. Neutron diffraction is similar to X-ray diffraction, but uses neutron beams instead of X-rays. It can perform stress analysis deep inside the material and measure the three-dimensional stress distribution inside the material and perform non-destructive testing, but the equipment is expensive and requires a special neutron source. Electron backscatter diffraction infers residual stress by analyzing changes in crystal orientation on the surface of the sample under a scanning electron microscope. It has high resolution and can provide crystal structure information, but it is limited to laboratory use and sample preparation is complex and costly. Synchrotron X-ray diffraction uses high-intensity X-rays generated by synchrotron radiation light sources to perform diffraction experiments to obtain more accurate residual stress data. It has high precision and high resolution and can study microstructures, but requires expensive large-scale experimental equipment support and is extremely costly.

[0004] Although there are many residual stress testing methods, ranging from traditional mechanical release methods to modern non-destructive testing technologies such as X-ray diffraction, neutron diffraction, ultrasonic testing, magnetic particle testing, electron backscatter diffraction, and synchrotron radiation X-ray diffraction, these technologies have their own advantages and can meet the needs of scientific research and industrial fields for residual stress analysis of welded joints to varying degrees. However, a significant challenge is that most existing residual stress testing methods are mainly designed for laboratory environments, and they rely on stable and controllable experimental conditions such as temperature, humidity, sample preparation status, etc. to ensure the accuracy and repeatability of the test results.

[0005] In contrast, crane welded joints face a complex and changeable working environment in service, including dynamic loads, environmental corrosion, and temperature differences, all of which may affect the state and distribution of residual stress. It becomes extremely difficult to accurately measure residual stress directly under such field conditions. First, field tests are often limited by space, making it difficult to deploy large-scale precision testing equipment; second, the uncertainty of the field environment increases the variability of test results and reduces the reliability of the data; third, some high-precision test methods, such as neutron diffraction or synchrotron radiation X-ray diffraction, are almost impossible to implement in the actual workplace of the crane due to their high dependence on facilities.

[0006] Therefore, it is necessary to provide a residual stress testing device and a testing method for crane welding joints to solve the above problems. Summary of the invention

[0007] The invention provides a residual stress testing device and a testing method for a crane welding joint, so as to solve the existing problems.

[0008] A residual stress testing device and testing method for crane welding joints of the present invention adopts the following technical scheme, including: A frame is provided on which two transfer arms are rotatably arranged at a right angle to the top, one of which is provided with an indenter, which is used to apply a load to a position to be tested on the welded joint to be tested; an image acquisition module is provided at the bottom of the other transfer arm, which is used to acquire images of the position to be tested on the welded joint to be tested before and after the load is applied; A mounting assembly, which is arranged at the bottom of the frame and is used to mount the welding joint to be tested; A load detection module, used to detect the pressure load applied by the indenter on the surface of the weld joint to be tested; A displacement detection module is arranged on one side of the frame and is used to detect the axial displacement of the indenter; and a processing module for obtaining residual stress according to the image before and after the load is applied to the position to be tested on the welded joint to be tested.

[0009] Preferably, the transfer arm is rotatably connected to the frame via a vertically arranged transmission shaft, a steering gear is arranged on the frame, and an output shaft of the steering gear is transmission-connected to the transmission shaft.

[0010] Preferably, the mounting assembly includes: a U-shaped support ring and connecting ears arranged on both sides of the bottom of the frame, the connecting ears are provided with mounting holes, the end of the U-shaped support ring is passed through the mounting hole, and one end of the U-shaped support ring passing through the mounting hole is connected by an external thread and a nut.

[0011] Preferably, the mounting assembly comprises: A support base, wherein the frame is arranged on the support base; A stage, which is slidably disposed on a support seat and on which a positioning component for positioning the welding joint to be tested is disposed; And a linear motor, an output end of which is connected to the stage.

[0012] Preferably, the indenter comprises: a driver, an output end of the driver is vertically downward and connected to a load sensor, and the other end of the load sensor is connected to a clamp of an indenter, wherein the indenter is a quadrangular pyramid indenter.

[0013] A residual stress testing method for a crane welding joint comprises: Grind the test position of the weld joint to be tested and perform surface polishing; Primer is sprayed on the position to be tested. After the primer is air-dried, paint is used on the primer to make spots so that a uniform speckle pattern is formed on the surface of the position to be tested of the welded joint to be tested; and the speckle pattern before the load is applied to the surface of the position to be tested is collected; Applying an indentation load to the surface of the position to be measured, and collecting a speckle pattern of the indentation contour area after the load is applied to the surface of the position to be measured; Determine the type of residual stress at the position to be measured according to the diagonal length of the indentation contour area on the surface of the position to be measured; According to the speckle pattern before and after the load is applied to the surface of the position to be measured, the displacement change amount and the strain change amount of the speckle in the indentation contour area in the speckle pattern after the load is applied relative to the speckle in the speckle pattern before the load is applied are determined; A finite element model of the indentation test under the influence of residual stress is established. Horizontal stress is applied to the finite element model according to the type of residual stress, and an indentation test is carried out at the position to be tested. The magnitude of the horizontal stress is adjusted until the displacement change and strain change of the experimental indentation contour area obtained by the indentation test relative to the speckle in the speckle pattern before the load is applied are the same as the displacement change and strain change corresponding to the speckle in the speckle pattern before the load is applied in the indentation contour area obtained by the finite element simulation. At this time, the magnitude of the horizontal stress input in the finite element model is the magnitude of the residual stress obtained from the weld joint test in the experiment.

[0014] Preferably, the step of determining the type of residual stress at the position to be measured is: If the indentation contour area at the position to be measured is a square contour area, there is no residual stress at the position to be measured; If the diagonal of the indentation contour area at the position to be measured is elongated relative to the diagonal of the square contour area, residual stress exists in the diagonal elongation direction, and the residual stress type is tensile residual stress; If the diagonal of the indentation contour area at the position to be measured is shortened relative to the diagonal of the square contour area, residual stress exists in the direction of the shortened diagonal, and the residual stress type is compressive residual stress.

[0015] Preferably, the stress applied by adjusting the indentation area in the finite element model is used as the residual stress existing in the weld joint to be tested during the test.

[0016] Preferably, the indentation depth of the indenter and the indentation depth during the indentation test are 30 μm.

[0017] Preferably, the position to be measured is ground to a surface roughness of less than 0.2 μm, and then the surface is polished until mechanical grinding marks are eliminated.

[0018] The beneficial effects of the present invention are: Through the integrated design of image acquisition module and indenter, the image acquisition of residual indentation and the indentation test function are realized by using two rotating adapter arms. Since the indentation depth is extremely small (set to 30μm), the cone indentation test method has almost no damage to the in-service structure. The in-service test can be directly carried out on the welding joints of the crane main beam after many years of service, without cutting the residual stress test specimens on the equipment in service, thus avoiding the damage to the in-service equipment itself when cutting the residual stress test specimens; avoiding the residual stress release phenomenon of welding residual stress after cutting the specimens. The residual stress of the engineering structure itself and the residual stress on the residual stress test specimen cut from the engineering structure are not exactly the same. The in-service test through the in-service test avoids the interference of residual stress release on the correctness of the test results, thereby ensuring the accuracy of the test results. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 This is a schematic diagram of a residual stress testing device for a crane welding joint according to Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of a residual stress testing device for a crane welding joint according to Embodiment 2 of the present invention; Figure 3 It is a measured indentation diagram in an embodiment of the present invention; Figure 4 is a schematic diagram of the indentation contour area in an embodiment of the present invention; Figure 5 Schematic diagram of the effect of residual stress on indentation morphology in an embodiment of the present invention; Figure 6 is a schematic diagram of a finite element model of a welded joint in an embodiment of the present invention; Figure 7 The present invention is a flowchart of a residual stress testing method for a crane welding joint in an embodiment of the present invention.

[0021] In the figure: 1. Indenter; 2. Load sensor; 3. Grating scale fixing plate; 4. Indenter; 5. Displacement sensor; 6. Adapter arm; 7. Image acquisition module; 8. Frame; 9. Fixing bolts; 10. Linear motor; 11. Stage. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] Example 1 Embodiment 1 of a residual stress testing device and testing method for a crane welding joint of the present invention, as shown in Figure 1As shown, it includes: a frame 8, a mounting assembly, a load detection module, a displacement detection module, an image acquisition module and a processing module. The frame 8 is provided with two adapter arms 6 which are rotatably arranged at the top and are arranged at a right angle. One of the adapter arms 6 is provided with an indenter 1, and the indenter 1 is used to apply a load to a position to be tested on the welded joint to be tested; an image acquisition module 7 is provided at the bottom of the other adapter arm 6, and the image acquisition module 7 is used to collect images of the position to be tested on the welded joint to be tested before and after the load is applied; the mounting assembly is provided at the bottom of the frame 8, and is used to install the welded joint to be tested; the load detection module is used to detect the indenter The pressure load applied by the indenter 4 to the surface of the weld joint to be tested; the displacement detection module adopts a displacement sensor, which is arranged on one side of the frame 8 and is used to detect the axial displacement of the indenter 4 of the indenter, that is, the indentation depth of the indenter 4 can be measured; the processing module is used to obtain the residual stress according to the image before and after the pressure is applied to the test position on the weld joint to be tested, that is, due to the effect of the indentation, the speckle in the middle of the indentation will fail, and the position change of the speckle around the indentation is measured according to the change of the displacement of the speckle around the indentation, and the displacement and strain change are determined by combining the results of a large number of speckles. Therefore, the residual stress calculation is completed through comparative analysis.

[0024] The transfer arm 6 is rotatably connected to the frame 8 via a vertically arranged transmission shaft, a steering gear is arranged on the frame 8, and an output shaft of the steering gear is transmission-connected to the transmission shaft.

[0025] Among them, the installation component includes: a U-shaped support ring and connecting ears arranged on both sides of the bottom of the frame 8, the connecting ears are provided with mounting holes, the end of the U-shaped support ring is passed through the mounting hole, and one end of the U-shaped support ring passing through the mounting hole is connected by an external thread and a nut 9.

[0026] Among them, the indenter 1 includes: a driver, the output end of the driver is vertically downward and connected to a load sensor 2, the other end of the load sensor 2 is connected to the clamp of the indenter 4, wherein the indenter 4 is a four-sided pyramid indenter; a grating scale fixing plate 3 is also arranged between the load sensor 2 and the clamp of the indenter 4, and a grating scale is fixed on the grating scale fixing plate 3. When the driver drives the grating scale fixing plate 3 to move in the vertical direction, the reading of the grating scale is the axial displacement of the indenter 4.

[0027] It should be noted that in the device shown in Example 1, the U-shaped support ring and the nut 9 are used to Figure 1 The device shown is fixed on the main beam of the crane to be tested, and can be used to test the position to be tested of the welding joint of the in-service crane. In this mode, the test device can be directly installed at the position to be tested of the crane to perform real-time or regular inspection of the welding joint to ensure its safety and reliability.

[0028] Example 2 The difference between Example 2 and Example 1 is only in the installation components, such as Figure 2 As shown, the installation components of this embodiment 2 include: a support seat, a stage 11 and a linear motor 10, wherein the frame 8 is arranged on the support seat; the stage 11 is slidably arranged on the support seat, and a positioning component for positioning the sample to be tested is arranged on the stage 11, and the positioning component includes a plurality of pin holes arranged on the stage 11, the pin holes are used to install positioning pins, and the positioning pins are used to limit the position of the welding joint to be tested on the stage 11, and the connection method is that the positioning pins align the sample to be tested with the hole and install it on the hole of the base; the output end of the linear motor 10 is connected to the stage 11. It should be noted that under the test device of embodiment 2, it is mainly used to realize the development of new products or residual stress analysis of accident parts in the laboratory state, and in the laboratory mode, the test device is mainly used in the laboratory environment, so as to realize more detailed analysis or calibration.

[0029] Combined with Figure 1 The residual stress test method of welded joints of in-service cranes, such as Figure 7 As shown, the specific test steps of the device using Example 1 include: S1. Surface treatment of the position to be tested; The position to be tested of the weld joint to be tested is ground and the surface is polished; specifically, the position to be tested is ground until the surface roughness is less than 0.2 μm, and then the surface is polished until the mechanical grinding marks are eliminated.

[0030] S2, creating speckles on the surface of the position to be measured; Primer is sprayed on the position to be tested. After the primer is air-dried, paint is used on the primer to make spots, so that a uniform speckle pattern is formed on the surface of the position to be tested of the weld joint to be tested. In this embodiment, white primer is sprayed on the position to be tested by spraying paint. After the white primer is air-dried, black paint is used on the white primer to make spots, and the spraying concentration is controlled to form a uniform speckle pattern on the surface of the sample to be tested. The speckle pattern is as shown in FIG. Figure 3 As shown, the black points are speckles, and the speckle diameter is controlled within 10μm.

[0031] S3, collecting the speckle pattern before applying the load; The steering gear is controlled to drive the adapter arm 6 to rotate so that the image acquisition module is located directly above the position to be measured. The image acquisition module is used to collect the original speckle information of the position to be measured to obtain the speckle pattern before the load is applied.

[0032] S4, collecting the speckle pattern after the load is applied; The steering gear is controlled to drive the transfer arm 6 to rotate so that the indenter 1 is located directly above the position to be tested. The driving actuator of the indenter drives the indenter 4 to apply a load to the surface of the position to be tested of the weld joint to be tested. That is, the driving actuator of the indenter drives the indenter 4 to press downward at a speed of 0.1 mm / min, and the pressing depth is set to 30 μm. After the pressing process is completed, the indenter is automatically raised to the initial position at a speed of 1 mm / min. The indenter 4 forms the following at the position to be tested. Figure 3 The quadrilateral indentation shown in the figure is completed at this time. The steering gear is controlled to drive the adapter arm 6 to rotate so that the image acquisition module is located directly above the position to be measured. The image acquisition module collects the speckle pattern after the load is applied to the surface of the position to be measured, as shown in FIG. Figure 4 The quadrilateral indentation contour area in the speckle pattern is extracted by computer.

[0033] S5. Determine the type of residual stress at the position to be measured; According to the diagonal length of the quadrilateral indentation contour area, determine the type of residual stress at the position to be measured. The specific steps are: Figure 5 Analyze the indentation contour area shown in the figure. At the position of the welding joint far away from the weld, the indentation will maintain a square contour due to low or no residual stress. If there is tensile residual stress at the position of the indentation, the indentation contour will change due to the residual stress, and the diagonal length of the indentation will be stretched. If there is compressive residual stress at the position of the indentation, the indentation contour will change due to the residual stress, and the diagonal length of the indentation will be compressed.

[0034] S6, determining a displacement change and a strain change of the speckle pattern after the load is applied relative to the speckle in the speckle pattern before the load is applied; Specifically, based on the speckle pattern before and after the load is applied, a computer is used to analyze the change in the speckle position around the indentation contour area after the load is applied relative to the speckle position in the speckle pattern before the load is not applied, and the computer software is used to convert the change in the speckle position into a change in the indentation contour, thereby accurately determining the displacement change and strain change.

[0035] S7, obtaining residual stress; Establish a finite element model of the indentation test under the influence of residual stress on the material to be tested. The finite element model is as follows: Figure 6As shown, horizontal stress is applied in the finite element model and an indentation test is performed at the position to be tested, and the magnitude of the horizontal stress is adjusted until the displacement change and strain change of the experimental indentation profile area obtained by the indentation test relative to the corresponding area of ​​the speckle pattern before the load is applied are the same as the displacement change and strain change of the indentation profile area obtained by the finite element simulation relative to the corresponding area of ​​the speckle pattern before the load is applied. At this time, the magnitude of the horizontal stress input in the finite element model is the magnitude of the residual stress obtained from the welding joint test in the experiment, thereby realizing the measurement of the residual stress value of the welding joint to be tested.

[0036] In this embodiment, when the residual stress type confirmed in step 6 is tensile residual stress, the material data of the base material of the weld joint is input into the finite element model of the weld joint, the loading hole on the left side of the finite element model is fixed, and a horizontal tensile force is applied to the right side of the loading hole at an interval of 10N, that is, when the residual stress type is tensile residual stress, the horizontal stress is horizontal tensile stress, and the pressing head 4 of the same size as in step 4 is used to simulate the pressing process, and the horizontal tensile stress F is continuously increased. tensile until the displacement change and strain change of the experimental indentation profile area obtained by the indentation experiment relative to the corresponding area of ​​the speckle pattern before the load is applied are the same as the displacement change and strain change of the indentation profile area obtained by the finite element simulation relative to the corresponding area of ​​the speckle pattern before the load is applied. At this time, the horizontal tensile stress input in the finite element model is the residual stress obtained by the welding joint test in the experiment; when the residual stress type confirmed in step 5 is compressive residual stress, the material data of the weld joint base material is input into the finite element model of the weld joint, the loading hole on the left side of the finite element model is fixed, and a horizontal pressure is applied to the left in the loading hole on the right side at an interval of 10N, that is, when the residual stress type is tensile residual stress, the horizontal stress is horizontal compressive stress, and the indenter 4 of the same size as in step 4 is used to simulate the indentation process, and the horizontal compressive stress F is continuously increased. pressure until the displacement change and strain change of the experimental indentation contour area obtained by the indentation experiment relative to the corresponding area of ​​the speckle pattern before the load is applied are the same as the displacement change and strain change of the indentation contour area obtained by the finite element simulation relative to the corresponding area of ​​the speckle pattern before the load is applied. At this time, the magnitude of the horizontal compressive stress input in the finite element model is the magnitude of the residual stress obtained from the weld joint test in the experiment.

[0037] Use attached Figure 2 The steps of the device for residual stress testing of laboratory welded joint specimens are as follows: Step 1: Adopt Figure 2The device shown places the sample to be tested or the disassembled and cut welding joint on the stage 11, and fixes the test piece with residual stress with screws; the subsequent test steps are the same as steps 2 to 6 of the test process of Example 1.

[0038] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A residual stress testing device for crane welding joints, characterized in that: include: A frame is provided on which two transfer arms are rotatably arranged at a right angle to the top, one of which is provided with an indenter, which is used to apply a load to a position to be tested on the welded joint to be tested; an image acquisition module is provided at the bottom of the other transfer arm, which is used to acquire images of the position to be tested on the welded joint to be tested before and after the load is applied; A mounting assembly, which is arranged at the bottom of the frame and is used to mount the welding joint to be tested; A load detection module, used to detect the pressure load applied by the indenter on the surface of the weld joint to be tested; A displacement detection module is arranged on one side of the frame and is used to detect the axial displacement of the indenter; and a processing module for obtaining residual stress according to the image before and after the load is applied to the position to be tested on the welded joint to be tested.

2. A residual stress testing device for crane welding joints according to claim 1, characterized in that: The transfer arm is rotatably connected to the frame through a vertically arranged transmission shaft, a steering gear is arranged on the frame, and an output shaft of the steering gear is transmission-connected to the transmission shaft.

3. A residual stress testing device for crane welding joints according to claim 1, characterized in that: The mounting assembly includes: a U-shaped support ring and connecting ears arranged on both sides of the bottom of the frame, the connecting ears are provided with mounting holes, the end of the U-shaped support ring is inserted into the mounting hole, and one end of the U-shaped support ring passing through the mounting hole is connected by an external thread and a nut.

4. A residual stress testing device for crane welding joints according to claim 1, characterized in that: The installation components include: A support base, wherein the frame is arranged on the support base; A stage, which is slidably disposed on a support seat and on which a positioning component for positioning the welding joint to be tested is disposed; And a linear motor, an output end of which is connected to the stage.

5. The residual stress testing device for crane welding joints according to claim 1 is characterized in that: The indenter comprises: a driver, an output end of the driver is vertically downward and connected to a load sensor, and the other end of the load sensor is connected to a clamp of an indenter, wherein the indenter is a quadrangular pyramid indenter.

6. A residual stress testing method for crane welding joints, characterized in that: include: Grind the test position of the weld joint to be tested and perform surface polishing; Primer is sprayed on the position to be tested. After the primer is air-dried, paint is used on the primer to make spots so that a uniform speckle pattern is formed on the surface of the position to be tested of the welded joint to be tested; and the speckle pattern before the load is applied to the surface of the position to be tested is collected; Applying an indentation load to the surface of the position to be measured, and collecting a speckle pattern of the indentation contour area after the load is applied to the surface of the position to be measured; Determine the type of residual stress at the position to be measured according to the diagonal length of the indentation contour area on the surface of the position to be measured; Determine the displacement change and strain change of the indentation contour area in the speckle pattern after the load is applied relative to the corresponding area in the speckle pattern before the load is applied, based on the speckle pattern before and after the load is applied on the surface of the position to be measured; A finite element model of the indentation test under the influence of residual stress on the material to be tested is established. Horizontal stress is applied to the finite element model according to the type of residual stress, and an indentation test is carried out at the position to be tested. The magnitude of the horizontal stress is adjusted until the displacement change and strain change of the experimental indentation contour area obtained by the indentation test relative to the corresponding area of ​​the speckle pattern before the load is applied are the same as the displacement change and strain change of the indentation contour area obtained by the finite element simulation relative to the corresponding area of ​​the speckle pattern before the load is applied. At this time, the magnitude of the horizontal stress input in the finite element model is the magnitude of the residual stress obtained from the welding joint test in the experiment.

7. A residual stress testing method for crane welding joints according to claim 1, characterized in that: The steps to determine the type of residual stress at the location to be measured are: If the indentation contour area at the position to be measured is a square contour area, there is no residual stress at the position to be measured; If the diagonal of the indentation contour area at the position to be measured is elongated relative to the diagonal of the square contour area, residual stress exists in the diagonal elongation direction, and the residual stress type is tensile residual stress; If the diagonal of the indentation contour area at the position to be measured is shortened relative to the diagonal of the square contour area, residual stress exists in the direction of the shortened diagonal, and the residual stress type is compressive residual stress.

8. The residual stress testing method for crane welding joints according to claim 1 is characterized in that: The tensile stress or compressive stress applied in the adjusted finite element model is used as the residual stress existing in the welded joint to be tested during the test.

9. A residual stress testing method for crane welding joints according to claim 1, characterized in that: The indentation depth of the indenter and the indentation depth during the indentation test were 30 μm.

10. A residual stress testing method for crane welding joints according to claim 1, characterized in that: The position to be tested is ground until the surface roughness is less than 0.2 μm, and then the surface is polished until the mechanical grinding marks are eliminated.

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