Equipment and method for studying residual compressive stress introduced into workpiece after surface strengthening

Abstract

The present invention relates to the technical field of residual compressive stress detection of workpieces, specifically to a device and method for studying the introduction of residual compressive stress into workpieces after surface strengthening. In order to solve the problem in the prior art that there is a lack of a device for studying the introduction of residual compressive stress into workpieces after surface strengthening that integrates the bonding of strain gauges and high-speed blind hole drilling and a corresponding method for studying the introduction of residual compressive stress, a new device and method for studying the introduction of residual compressive stress into workpieces after surface strengthening are provided, including a biaxial mobile platform, an adsorption mechanism, a cleaning mechanism, a gluing mechanism, a six-axis robot, and a pressing mechanism, which realizes the study of the introduction of residual compressive stress into workpieces after surface strengthening, and improves the accuracy of residual compressive stress detection of workpieces after surface strengthening by correcting the calculated value of residual compressive stress.

Description

Technical Field

[0001] The present invention relates to the technical field of residual compressive stress detection of workpieces, and in particular to equipment and methods for studying residual compressive stress introduced into workpieces after surface strengthening. Background Art

[0002] Ultrasonic rolling, laser shock and shot peening are key technologies for improving the surface properties of materials. They enhance the fatigue strength and corrosion resistance of materials by introducing residual compressive stress on the surface of materials, and play an important role in key fields such as aviation and aerospace. Excessive strengthening may increase the surface roughness of the material and generate non-uniform residual compressive stress, thereby introducing cracks and affecting the integrity and reliability of the workpiece, while insufficient strengthening may lead to insufficient introduction of residual compressive stress, reduce the fatigue life and crack resistance of the workpiece, and thus affect its service performance. The introduction of residual compressive stress research can reveal the stress state inside the workpiece, help identify its potential problems, and balance the strengthening effect by optimizing process parameters to ensure the performance and safety of the strengthened workpiece during service.

[0003] At present, the methods introduced for residual compressive stress research include X-ray diffraction technology, neutron diffraction technology, blind hole method, ultrasonic technology, profile method and crack flexibility method. X-ray diffraction technology is suitable for surface residual compressive stress detection. When measuring the stress distribution of 0-2mm, layer-by-layer corrosion is required. The corrosion depth control is difficult and the cycle is long. In addition, X-ray diffraction technology and neutron diffraction technology are expensive to operate, and the experimental and application costs are high. Ultrasonic technology measurement is difficult to achieve 0-2mm stress distribution detection, and is not suitable for residual compressive stress research of workpieces after surface strengthening. The profile method and crack flexibility method are suitable for stress detection at a certain distance from the workpiece surface, and have poor characterization capabilities for workpiece surface stress. The blind hole method is widely used due to its advantages such as little damage to the workpiece, no impact on the performance of the workpiece, and simplicity.

[0004] The conventional blind hole method is to stick a strain gauge on the measuring part of the workpiece surface, and then drill a blind hole to cause changes in the surrounding stress field. The strain values ​​in the x and y directions are collected by the collector, and finally the residual compressive stress in the x and y directions are solved according to the strain value. This method is now mainly used for the study of residual compressive stress of non-surface-strengthened workpieces. For surface-strengthened workpieces, the stress value distribution corresponding to the gradient-drilled blind hole needs to be collected (such as 0-2mm gradient-drilled blind hole processing, assuming that the depth of each blind hole drilling is 0.05mm, that is, a total of 40 blind hole depths of 0.05-0.1-…-1.95-2mm are required, and the corresponding stress value needs to be collected after each blind hole drilling). However, the conventional blind hole method is poorly applicable to the study of residual compressive stress of surface-strengthened workpieces and has low accuracy.

[0005] For example, the device described in the prior art, whose publication number is CN108457948A and the patent name is "Automatic Pasting Device for Resistance Three-axis Resistance Strain Gauge", is aimed at non-surface-hardened workpieces. The device also includes grinding and dust removal stations, while the surface of the workpiece after surface hardening does not require grinding and dust removal, but it needs to be cleaned; at the same time, the conventional blind hole drilling part in the prior art is generally completed by a separate device, and the blind hole drilling in the prior art is all low-speed drilling, which is easy to generate mechanical processing stress and cutting thermal stress, and is easy to affect the release of residual compressive stress inside the workpiece after surface hardening. Therefore, there is an urgent need for a device for studying the introduction of residual compressive stress into the workpiece after surface hardening, which integrates the pasting of strain gauges and high-speed blind hole drilling, and a corresponding method for studying the introduction of residual compressive stress. Summary of the invention

[0006] In order to solve the problem in the prior art that there is a lack of a device for studying the introduction of residual compressive stress into a workpiece after surface strengthening and a corresponding method for studying the introduction of residual compressive stress, the present invention provides a new device and method for studying the introduction of residual compressive stress into a workpiece after surface strengthening, which integrates the bonding of strain gauges and high-speed blind hole drilling.

[0007] The present invention is achieved by adopting the following technical solutions:

[0008] A device for studying the residual compressive stress introduced into a workpiece after surface strengthening, comprising:

[0009] The adsorption mechanism is used to adsorb and fix the workpiece after surface strengthening. The adsorption mechanism is also provided with an oil spraying component for cooling the workpiece after surface strengthening:

[0010] A cleaning mechanism, which is used to achieve dead-angle cleaning of the workpiece after surface strengthening;

[0011] A gluing mechanism, which is used to glue the position on the surface of the workpiece where the strain gauge needs to be glued after the surface strengthening;

[0012] The feeding mechanism includes a six-axis robot and a strain gauge storage table. The strain gauge storage table is used to store strain gauges. The six-axis robot has two end effectors, which are an air-floating spindle and a strain gauge suction nozzle. The strain gauge suction nozzle is used to absorb the strain gauges on the strain gauge storage table. The air-floating spindle is equipped with a drill bit.

[0013] A pressing mechanism, which is used to press the strain gauge attached to the workpiece after surface strengthening;

[0014] A collector, used for connecting with the strain gauge to collect strain values;

[0015] A double-axis moving mechanism, the adsorption mechanism is fixed to the double-axis moving mechanism, and the double-axis moving mechanism is used to drive the adsorption mechanism to move in the front-back and left-right directions and move it to the corresponding positions of the cleaning mechanism, the gluing mechanism, the six-axis robot, the strain gauge storage table, and the pressing mechanism;

[0016] The PLC controller is used to control the two-axis moving mechanism, cleaning mechanism, gluing mechanism, six-axis robot, and pressing mechanism to perform corresponding actions.

[0017] Furthermore, the pressing mechanism includes a fixed frame and a guide rail, a slider, and a pressing assembly fixed on the fixed frame. The guide rail and the slider are arranged in the up and down directions and are adaptively connected. The pressing assembly is located on one side of the slider. The pressing assembly includes a fixed plate, a lower connecting plate, two support plates, a driving gear, a driven gear, a motor, a pressing roller, a pressing shaft, a fixed shaft, an anti-sticking paper tape, a conveying roller, and a collecting roller. The lower connecting plate is horizontally arranged and fixed to the side of the slider. A pressing hole is opened on the lower connecting plate. The fixing plate is vertically arranged and inserted into the pressing hole. The motor is fixed to the upper end of the right side of the fixing plate. The motor shaft is rotatably connected to the fixing plate and extends to the left side of the upper connecting plate. The driven gear and the conveying roller are both located on the left side of the fixed plate and are both fixed to the motor shaft. The fixed shaft is vertically fixed to the lower end of the left side of the fixed plate. A collecting roller and a driven gear meshing with the driving gear are rotatably sleeved on the fixed shaft. The driven gear is fixed to the collecting roller. The two support plates are distributed on the left and right and are vertically fixed to the bottom surface of the lower connecting plate. The two ends of the pressing shaft are rotatably connected to the two support plates respectively. The middle part of the pressing shaft is sleeved with a pressing roller. The pressing roller, conveying roller and collecting roller are adaptively arranged and are provided with wire grooves adapted to the anti-sticking paper tape. One end of the anti-sticking paper tape is fixed to the conveying roller, and the other end of the anti-sticking paper tape is fixed to the collecting roller after passing around the pressing roller.

[0018] When pressing, the motor is started, and the motor shaft rotates to drive the driving gear and the conveying roller to rotate. The driving gear rotates to drive the driven gear to rotate. The driven gear rotates to drive the collecting roller to rotate. The pressing roller is forced to rotate through the anti-sticking paper tape, so that the strain gauge is rolled and pressed by the pressing roller. Among them, the conveying roller is used to convey new anti-sticking paper tape, and the collecting roller is used to collect the used anti-sticking paper tape to prevent glue from sticking to the pressing roller and affecting the next use. At the same time, the up and down position of the pressing roller is controlled by the PLC control slider to ensure the pressing force.

[0019] Furthermore, the pressing assembly also includes an upper connecting plate arranged parallel to the lower connecting plate, the upper connecting plate is located above the lower connecting plate and fixed to the side of the slider, and guide rods are fixed at the four corners between the upper connecting plate and the lower connecting plate, which improves the stability of the pressing mechanism and ensures vertical pressing of the pressing roller.

[0020] Furthermore, a six-dimensional force sensor is provided at the end of the six-axis robot, and the output end of the six-dimensional force sensor is connected to the PLC controller. Firstly, it is used to detect the initial pressing force when the six-axis robot sticks the strain gauge to prevent damage to the strain gauge when the initial pressing force is too large, and at the same time it is also convenient to achieve the constancy of the initial pressing force and improve the consistency of the sticking strain gauge. Secondly, it is used to collect cutting force to facilitate the setting of drilling zero position, that is, when the drill bit has not cut the surface strengthened workpiece, the cutting force is 0, when the drill bit just cuts the surface strengthened workpiece, the cutting force changes, and the cutting position at this time is the drilling zero position.

[0021] Furthermore, the adsorption mechanism, cleaning mechanism, gluing mechanism, six-axis robot, strain gauge storage table, and pressing mechanism are placed in sequence along the left and right directions and are all located in front of the dual-axis moving mechanism, and the layout is standardized and more reasonable.

[0022] The method for studying the introduction of residual compressive stress into a workpiece after surface strengthening using the above-mentioned equipment comprises the following steps:

[0023] 1) The workpiece after surface strengthening is adsorbed and fixed on the adsorption mechanism;

[0024] 2) The PLC controller controls the dual-axis moving mechanism to drive the adsorption mechanism to move to the corresponding position of the cleaning mechanism, and the cleaning mechanism cleans the workpiece after surface strengthening without dead angles;

[0025] 3) The PLC controller controls the dual-axis moving mechanism to drive the adsorption mechanism to move to the corresponding position of the gluing mechanism. The PLC controller controls the gluing mechanism to apply glue to the position where the strain gauge needs to be pasted on the workpiece after surface strengthening and controls the glue output of the gluing mechanism;

[0026] 4) The PLC controller controls the dual-axis moving mechanism to drive the adsorption mechanism to move to the corresponding position of the feeding mechanism. The six-axis robot adsorbs the strain gauge from the strain gauge storage table through the strain gauge suction nozzle and attaches the adsorbed strain gauge to the specified position of the workpiece after surface strengthening, and then performs preliminary pressing on the strain gauge to complete the initial adhesion of the strain gauge;

[0027] 5) The PLC controller controls the biaxial moving mechanism to drive the adsorption mechanism to move to the corresponding position of the pressing mechanism. The PLC controller controls the pressing mechanism to press the strain gauge pasted on the workpiece after surface strengthening to complete the final pasting of the strain gauge;

[0028] 6) Connect the collector to the strain gauge, the PLC controller controls the dual-axis moving mechanism to drive the adsorption mechanism to move to the corresponding position of the six-axis robot drill bit, the PLC controller controls the movement of the air-floating spindle of the six-axis robot, the air-floating spindle drives the drill bit to perform gradient high-speed blind hole drilling on the surface-enhanced workpiece, and at the same time cooperates with the oil injection component on the adsorption mechanism to spray oil to cool the surface-enhanced workpiece, and collects the corresponding x-direction measured strain value and y-direction measured strain value through the collector;

[0029] 7) According to the measured strain values ​​in the x-direction and the measured strain values ​​in the y-direction obtained in step 6), the corresponding residual compressive stress values ​​are calculated. The specific calculation method is as follows:

[0030] a. Set up the uniaxial tensile stress finite element simulation adapted to the gradient high-speed blind hole drilling process in step 6), obtain the corresponding x-direction simulation strain value and y-direction simulation strain value through the uniaxial tensile stress finite element simulation, and calculate the stress calibration constant through formula ① and stress calibration constant ,

[0031] ①

[0032] in, is the stress calibration constant, is the stress calibration constant, is the elastic modulus, is the simulated strain value in the x direction, is the simulated strain value in the y direction, is the simulation value of uniaxial tensile stress;

[0033] b. Calculate the shape change specific energy according to formula ②, establish the first curve diagram of the relationship between the blind hole depth and the uniaxial tensile stress simulation value and the shape change specific energy, and establish the relationship between the blind hole depth and the shape change specific energy and stress calibration constant. The second curve of the relationship is used to establish the calibration constants of blind hole depth, shape change specific energy and stress The third curve graph,

[0034] ②

[0035] in, is the shape change specific energy, is Poisson's ratio;

[0036] c. The stress calibration constant corresponding to the simulated uniaxial tensile stress value equal to 0.6 times the yield strength of the workpiece after surface strengthening and stress calibration constant The stress calibration constants are and stress calibration constant values , using the stress calibration constant to determine the value , stress calibration constant value The corresponding uniaxial tensile stress theoretical value is inversely calculated according to formula ③, and the fourth curve diagram of the relationship between the blind hole depth and the uniaxial tensile stress simulation value and the uniaxial tensile stress theoretical value is established.

[0037] ③

[0038] in, is the theoretical value of uniaxial tensile stress;

[0039] d. Use the measured strain values ​​in the x-direction and y-direction collected in step 6) and the stress calibration constant value calibrated in step c) to determine the value. , stress calibration constant value , the first residual compressive stress value in the x direction is calculated according to formula ④, the calculated first residual compressive stress value in the x direction is used as the theoretical value of uniaxial tensile stress and is placed in the fourth curve chart established in step c to match the corresponding uniaxial tensile stress simulation value,

[0040] ④

[0041] in, is the first residual compressive stress value in the x direction, is the measured strain value in the x direction, is the measured strain value in the y direction;

[0042] e. Place the uniaxial tensile stress simulation value matched in step d in the first curve graph to match the corresponding shape change specific energy, and then place the matched shape change specific energy in the second curve graph and the third curve graph to match the corresponding stress calibration constant respectively. and stress calibration constant , and finally use the matching stress calibration constant and stress calibration constant The measured strain value in the x direction and the measured strain value in the y direction obtained in step 6) are used to calculate the second residual compressive stress value in the x direction and the second residual compressive stress value in the y direction according to formula ⑤, and the calculated second residual compressive stress value in the x direction and the second residual compressive stress value in the y direction are respectively used as the final residual compressive stress values.

[0043] ⑤

[0044] in, is the second residual compressive stress value in the x direction, is the second compressive residual stress value in the y direction.

[0045] Further, in step c, the calibrated yield stress determined by the stress-increased uniaxial tensile test is used as the yield strength of the workpiece after surface strengthening. The uniaxial tensile stress in the stress-increased uniaxial tensile test is increased multiple times. Each time the uniaxial tensile stress is increased, a strain data collection time is stopped. When the strain data within a certain strain data collection time increases continuously for the first time, the corresponding uniaxial tensile stress at this time is determined to be the calibrated yield stress of the workpiece after surface strengthening. The determination method of the calibrated yield stress in this part is determined based on the phenomenon of the uniaxial stress-increased tensile test, that is, when the uniaxial tensile stress reaches a certain value in the yield stage, the uniaxial tensile stress no longer increases and the strain value continues to increase, indicating that the workpiece begins to undergo plastic deformation after surface strengthening at this time, so the corresponding uniaxial tensile stress at this time is determined as the calibrated yield stress of the workpiece after surface strengthening, avoiding the error level of the result caused by using the yield strength in the national standard.

[0046] Furthermore, in the uniaxial tensile stress finite element simulation in step a, the finite element simulation grid is divided according to the actual strain gauge acquisition area, so that the calculated stress calibration constant and stress calibration constant It is more consistent with the actual working principle of the strain gauge, thereby further improving the accuracy of the residual compressive stress value finally calculated.

[0047] Furthermore, a plurality of blind holes whose depths match the processing depths of the gradient height drilling blind holes in step 6) are distributed in the simulation model of the surface-strengthened workpiece in the uniaxial tensile stress finite element simulation, so as to reduce the number of simulations.

[0048] Furthermore, the first curve graph, the second curve graph, the third curve graph and the fourth curve graph are all established by smooth curve fitting using MATLAB programming, which reduces workload and has a small error.

[0049] The beneficial effects of the present invention are as follows: 1) Two end effectors are arranged on the six-axis robot, which are a strain gauge nozzle and an air-floating spindle respectively. The air-floating spindle is used to realize high-speed drilling, and the workpiece after surface strengthening is cooled in cooperation with the oil injection assembly, thereby reducing the influence of the mechanical processing stress and cutting thermal stress generated in the low-speed drilling process of the conventional blind hole method on the release of the residual compressive stress inside the workpiece after surface strengthening. At the same time, the strain gauge nozzle is used to grasp the strain gauge, and the structure is compact and easy to implement; 2) By arranging a collecting roller, a pressing roller, a conveying roller, and an anti-sticking paper in the pressing mechanism The tape realizes the rolling pressing of the strain gauge pasted on the workpiece after surface strengthening and the real-time replacement of the anti-sticking paper tape; 3) The cleaning mechanism is added to realize the cleaning of the workpiece after surface strengthening; 4) The automation of the equipment is realized through the PLC controller; 5) A feasible method for studying the introduction of residual compressive stress into the workpiece after surface strengthening is provided, and the accuracy of residual compressive stress detection on the workpiece after surface strengthening is improved by correcting the residual compressive stress value; 6) For the first time, it is proposed to determine the yield strength through stress-increased uniaxial tensile test, so as to avoid the error influence of the yield strength in the national standard on the result. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0051] 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, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0052] Figure 1 It is a schematic diagram of the overall structure of the device of the present invention;

[0053] Figure 2 is a structural schematic diagram of the adsorption mechanism;

[0054] Figure 3 It is a structural schematic diagram of the cleaning mechanism;

[0055] Figure 4 It is a structural diagram of a six-axis robot;

[0056] Figure 5 It is a structural schematic diagram of the strain gauge storage station;

[0057] Figure 6 is a structural schematic diagram of a pressing mechanism;

[0058] Figure 7 It is a partial enlarged schematic diagram of the pressing mechanism;

[0059] Figure 8 It is a schematic diagram of the finite element simulation grid divided according to the actual strain gauge acquisition area;

[0060] Fig. 9 It is a schematic diagram of the workpiece model after surface strengthening in the uniaxial tensile stress finite element simulation;

[0061] Fig.10 The first curve diagram of the relationship between the blind hole depth, the uniaxial tensile stress simulation value, and the shape change specific energy established in step b;

[0062] Fig.11 A second curve diagram of the relationship between the blind hole depth, shape change specific energy, and stress calibration constant A established in step b;

[0063] Fig.12 The third curve diagram of blind hole depth, shape change specific energy and stress calibration constant B established in step b;

[0064] Fig.13 A fourth curve chart of the relationship between the blind hole depth and the uniaxial tensile stress simulation value and the uniaxial tensile stress theoretical value established in step c;

[0065] Fig.14 It is a schematic diagram of the relationship between the residual compressive stress value and the blind hole depth obtained by the detection method described in the present invention and a schematic diagram of the relationship between the residual compressive stress value and the blind hole depth measured by the ABAQUS ultrasonic rolling finite element simulation method.

[0066] In the figure: 1-adsorption mechanism, 101-oil injection assembly, 2-cleaning mechanism, 201-high-pressure cleaning head, 202-air gun, 3-gluing mechanism, 4-six-axis robot, 401-air floating spindle, 402-strain gauge nozzle, 403-drill bit, 404-six-dimensional force sensor, 5-strain gauge storage table, 501-strain gauge, 6-pressing mechanism, 601-guide rail, 602-slider, 603-fixed plate, 604-upper connecting plate, 605-support plate, 606-lower connecting plate, 607-driving gear, 608-guide rod, 609-fixed frame, 610-pressing roller, 611-anti-sticking paper tape, 612-transmission roller, 613-collecting roller, 614-pressing shaft, 615-pressing hole, 7-double-axis moving mechanism, 8-workpiece after surface strengthening. DETAILED DESCRIPTION

[0067] In order to more clearly understand the above-mentioned objectives, features and advantages of the present invention, the scheme of the present invention will be further described below. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0068] In the description, it should be noted that the terms "first" and "second" are only used for descriptive purposes and should not be understood as indicating or implying relative importance. It should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be internal communication between two elements. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0069] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present invention, rather than all of the embodiments.

[0070] The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0071] like Figure 1-7 As shown, a device for studying the residual compressive stress introduced into a workpiece after surface strengthening comprises:

[0072] The adsorption mechanism 1 is used for adsorbing and fixing the workpiece 8 after surface strengthening. The adsorption mechanism 1 is also provided with an oil spraying component 101 for spraying oil for cooling the workpiece 8 after surface strengthening:

[0073] A cleaning mechanism 2, which is used to achieve dead-angle cleaning of the workpiece 8 after surface strengthening;

[0074] A gluing mechanism 3, which is used to glue the position on the surface of the workpiece 8 where the strain gauge 501 needs to be glued after the surface strengthening;

[0075] The feeding mechanism includes a six-axis robot 4 and a strain gauge storage platform 5. The strain gauge storage platform 5 is used to store strain gauges 501. The six-axis robot 4 has two end effectors, namely, an air-floating spindle 401 and a strain gauge suction nozzle 402. The strain gauge suction nozzle 402 is used to absorb the strain gauge 501 on the strain gauge storage platform 5. The air-floating spindle 401 is equipped with a drill 403.

[0076] A pressing mechanism 6, which is used to press the strain gauge 501 attached to the workpiece 8 after surface strengthening;

[0077] A collector, used to connect to the strain gauge 501 to collect strain values;

[0078] A double-axis moving mechanism 7, the adsorption mechanism 1 is fixed to the double-axis moving mechanism 7, and the double-axis moving mechanism 7 is used to drive the adsorption mechanism 1 to move in the front-back and left-right directions and move it to the corresponding positions of the cleaning mechanism 2, the gluing mechanism 3, the six-axis robot 4, the strain gauge storage table 5, and the pressing mechanism 6;

[0079] The PLC controller is used to control the two-axis moving platform, the cleaning mechanism 2, the gluing mechanism 3, the six-axis robot 4, and the pressing mechanism to perform corresponding actions.

[0080] In specific implementation, the pressing mechanism 6 includes a fixed frame 609 and a guide rail 601 fixed on the fixed frame 609, a slider 602, and a pressing assembly. The guide rail 601 and the slider 602 are arranged in the up and down direction and are adaptively connected. The pressing assembly is located on one side of the slider 602. The pressing assembly includes a fixed plate 603, a lower connecting plate 606, two support plates 605, a driving gear 607, a driven gear, a motor, a pressing roller 610, a pressing shaft 614, a fixed shaft, an anti-sticking paper tape 611, a conveying roller 612, and a collecting roller 613. The lower connecting plate 606 is horizontally arranged and fixed to the side of the slider 602. A pressing hole 615 is opened on the lower connecting plate 606. The fixed plate 603 is vertically arranged and inserted into the pressing hole 615. The motor is fixed to the upper end of the right side of the fixed plate 603. The motor shaft is rotatably connected to the fixed plate 603 and extends to the upper connecting plate 60 4, the driving gear 607 and the conveying roller 612 are both located on the left side of the fixed plate 603 and are both sleeved on the motor shaft, the fixed shaft is vertically fixed to the lower end of the left side of the fixed plate 603, and the collecting roller 613 and the driven gear meshing with the driving gear 607 are rotatably sleeved on the fixed shaft, and the driven gear is fixed to the collecting roller 613, the two supporting plates 605 are distributed on the left and right and are both vertically fixed to the bottom surface of the lower connecting plate 606, the two ends of the pressing shaft 614 are rotatably connected to the two supporting plates 605 respectively, and the middle part of the pressing shaft 614 is sleeved with a pressing roller 610, the pressing roller 610, the conveying roller 612, and the collecting roller 613 are adaptively arranged and are all provided with a wire groove adapted to the anti-sticking paper tape 611, one end of the anti-sticking paper tape 611 is fixed to the conveying roller 612, and the other end of the anti-sticking paper tape 611 is fixed to the collecting roller 613 after bypassing the pressing roller 610.

[0081] When pressing, the motor is started, and the motor shaft rotates to drive the driving gear 607 and the transmission roller 612 to rotate. The driving gear 607 rotates to drive the driven gear to rotate. The driven gear rotates to drive the collecting roller 613 to rotate. The pressing roller 610 is forced to rotate through the anti-sticking paper tape 611, so that the strain gauge 501 is rolled and pressed by the pressing roller 610. Among them, the transmission roller 612 is used to transmit new anti-sticking paper tape 611, and the collecting roller 613 is used to collect the used anti-sticking paper tape 611 to prevent glue from sticking to the pressing roller 610 and affecting the next use. At the same time, the upper and lower positions of the pressing roller 610 are controlled by the PLC control slider 602 to ensure the pressing force.

[0082] In a specific implementation, the pressing assembly also includes an upper connecting plate 604 arranged parallel to the lower connecting plate 606. The upper connecting plate 604 is located above the lower connecting plate 606 and is fixed to the side of the slider 602. Guide rods 608 are fixed at the four corners between the upper connecting plate 604 and the lower connecting plate 606, thereby improving the stability of the pressing mechanism 6 and ensuring vertical pressing of the pressing roller 610.

[0083] During specific implementation, a six-axis force sensor 404 is provided at the end of the six-axis robot 4, and the output end of the six-axis force sensor 404 is connected to the PLC controller. Firstly, it is used to detect the initial pressing force when the six-axis robot 4 is pasting the strain gauge 501, to prevent the strain gauge 501 from being damaged when the initial pressing force is too large, and at the same time, it is also convenient to achieve the constancy of the initial pressing force and improve the consistency of pasting the strain gauge 501. Secondly, it is used to collect cutting force to facilitate the setting of drilling zero position, that is, when the drill bit 403 has not cut the workpiece 8 after surface strengthening, the cutting force is 0, when the drill bit 403 just cuts the workpiece 8 after surface strengthening, the cutting force changes, and the cutting position at this time is the drilling zero position.

[0084] In this specific embodiment, the adsorption mechanism 1, the cleaning mechanism 2, the gluing mechanism 3, the six-axis robot 4, the strain gauge storage table 5, and the pressing mechanism 6 are placed in sequence along the left and right directions and are all located on the front side of the dual-axis movable platform, and the layout is standardized and more reasonable.

[0085] In this specific embodiment, the cleaning mechanism 2 includes a high-pressure cleaning head 201 and an air gun 202. The high-pressure cleaning head 201 is used to clean the workpiece 8 after surface strengthening, and the air gun 202 is used to blow and dry the surface of the workpiece 8 after surface strengthening, thereby improving the cleaning efficiency of the workpiece 8 after surface strengthening.

[0086] The method for studying the introduction of residual compressive stress into the workpiece 8 after surface strengthening using the above-mentioned equipment comprises the following steps:

[0087] 1) The workpiece 8 after surface strengthening is adsorbed and fixed on the adsorption mechanism 1;

[0088] 2) The PLC controller controls the dual-axis moving mechanism to drive the adsorption mechanism 1 to move to the corresponding position of the cleaning mechanism 2, and the cleaning mechanism 2 cleans the workpiece 8 after surface strengthening without dead angles;

[0089] 3) The PLC controller controls the biaxial moving mechanism to drive the adsorption mechanism 1 to move to the corresponding position of the gluing mechanism 3. The PLC controller controls the gluing mechanism 3 to apply glue to the position where the strain gauge 501 needs to be pasted on the workpiece 8 after surface strengthening and controls the glue output of the gluing mechanism 3;

[0090] 4) The PLC controller controls the two-axis moving mechanism to drive the adsorption mechanism 1 to move to the corresponding position of the feeding mechanism, and the six-axis robot 4 adsorbs the strain gauge 501 from the strain gauge storage table 5 through the strain gauge suction nozzle 402 and attaches the adsorbed strain gauge 501 to the specified position of the surface-strengthened workpiece 8, and then performs preliminary pressing on the strain gauge 501 to complete the initial attachment of the strain gauge 501;

[0091] 5) The PLC controller controls the biaxial moving mechanism to drive the adsorption mechanism 1 to move to the corresponding position of the pressing mechanism 6. The PLC controller controls the pressing mechanism 6 to press the strain gauge 501 pasted on the workpiece 8 after surface strengthening, thereby completing the final pasting of the strain gauge 501.

[0092] 6) Connect the collector to the strain gauge 501, the PLC controller controls the two-axis moving mechanism to drive the adsorption mechanism 1 to move to the corresponding position of the drill 403 at the end of the six-axis robot 4, the PLC controller controls the air-floating spindle 401 of the six-axis robot 4 to move, the air-floating spindle 401 drives the drill 403 to perform 0-2mm gradient high-speed blind hole drilling on the surface-strengthened workpiece 8, the 0-2mm gradient high-speed blind hole drilling is divided into 40 blind hole depths, namely 0.05-0.1-…-1.95-2mm, respectively, and at the same time cooperate with the oil injection component 101 on the adsorption mechanism 1 to spray oil to cool the surface-strengthened workpiece 8, and collect the corresponding x-direction measured strain value and y-direction measured strain value through the collector;

[0093] 7) According to the measured strain values ​​in the x-direction and the measured strain values ​​in the y-direction obtained in step 6), the corresponding residual compressive stress values ​​are calculated. The specific calculation method is as follows:

[0094] a. Set up the uniaxial tensile stress finite element simulation adapted to the gradient high-speed blind hole drilling process in step 6). The uniaxial tensile stress in the uniaxial tensile stress finite element simulation is set to 0-5-10-…100MPa, a total of 20 uniaxial tensile stresses. The corresponding x-direction simulation strain value and y-direction simulation strain value are obtained through the uniaxial tensile stress finite element simulation. The stress calibration constant is calculated by formula ① and stress calibration constant ,

[0095] ①

[0096] Among them, A is the stress calibration constant, B is the stress calibration constant, E is the elastic modulus, is the simulated strain value in the x direction, is the simulated strain value in the y direction, is the simulation value of uniaxial tensile stress;

[0097] b. Calculate the shape change specific energy according to formula ②, and establish the first curve diagram of the relationship between the blind hole depth, the uniaxial tensile stress simulation value, and the shape change specific energy. Fig.10 As shown, the calibration constants of blind hole depth, shape change, specific energy and stress are established. The second curve diagram of the relationship is as follows Fig.11 As shown, the calibration constants of blind hole depth, shape change, specific energy and stress are established. The third curve is as follows Fig.12 As shown,

[0098] ②

[0099] in, is the shape change specific energy, is Poisson's ratio;

[0100] c. The stress calibration constant corresponding to the 8 yield strength of the workpiece after surface strengthening is 0.6 times the simulated value of uniaxial tensile stress. and stress calibration constant The stress calibration constants are and stress calibration constant values , using the stress calibration constant to determine the value , stress calibration constant value The corresponding uniaxial tensile stress theoretical value is inversely calculated according to formula ③, and the fourth curve diagram of the relationship between the blind hole depth and the uniaxial tensile stress simulation value and the uniaxial tensile stress theoretical value is established as shown in Fig.13 As shown,

[0101] ③

[0102] in, is the theoretical value of uniaxial tensile stress;

[0103] d. Use the measured strain values ​​in the x-direction and y-direction collected in step 6) and the stress calibration constant calibrated in step c to determine the value. , stress calibration constant value , calculate the first residual compressive stress value in the x direction according to formula ④, use the calculated first residual compressive stress value in the x direction as the theoretical value of uniaxial tensile stress and match it with the corresponding uniaxial tensile stress simulation value in the fourth curve diagram established in step c,

[0104] ④

[0105] in, is the first residual compressive stress value in the x direction, is the measured strain value in the x direction, is the measured strain value in the y direction;

[0106] e. Place the uniaxial tensile stress simulation value matched in step d in the first curve graph to match the corresponding shape change specific energy, and then place the matched shape change specific energy in the second curve graph and the third curve graph to match the corresponding stress calibration constant respectively. and stress calibration constant , and finally use the matching stress calibration constant and stress calibration constant The measured strain value in the x direction and the measured strain value in the y direction obtained in step 6) are used to calculate the second residual compressive stress value in the x direction and the second residual compressive stress value in the y direction according to formula ⑤, and the calculated second residual compressive stress value in the x direction and the second residual compressive stress value in the y direction are respectively used as the final residual compressive stress values.

[0107] ⑤

[0108] in, is the second residual compressive stress value in the x direction, is the second compressive residual stress value in the y direction.

[0109] In specific implementation, in step c, the calibrated yield stress determined by the stress-increased uniaxial tensile test is used as the yield strength of the workpiece after surface strengthening. The uniaxial tensile stress in the stress-increased uniaxial tensile test is increased multiple times. Each time the uniaxial tensile stress is increased, a strain data collection time is stopped. When the strain data within a certain strain data collection time increases continuously for the first time, the corresponding uniaxial tensile stress at this time is determined as the calibrated yield stress of the workpiece 8 after surface strengthening. The determination method of the calibrated yield stress of this part is determined based on the phenomenon of the uniaxial stress-increased tensile test, that is, when the uniaxial tensile stress reaches a certain value in the yield stage, the uniaxial tensile stress no longer increases and the strain value continues to increase, indicating that the workpiece 8 after surface strengthening begins to undergo plastic deformation at this time, so the corresponding uniaxial tensile stress at this time is determined as the calibrated yield stress of the workpiece 8 after surface strengthening, avoiding the influence of the yield strength in the national standard on the results.

[0110] When implementing it, Figure 8 As shown, in the uniaxial tensile stress finite element simulation in step a, the finite element simulation grid is divided according to the acquisition area of ​​the actual strain gauge 501, so that the calculated stress calibration constant and stress calibration constant This is more consistent with the actual working principle of the strain gauge 501, thereby further improving the accuracy of the residual compressive stress value finally calculated.

[0111] When implementing it, Fig. 9 As shown, a plurality of blind holes whose depths match the processing depths of the gradient height drilling blind holes in step 6) are distributed in the simulation model of the surface-strengthened workpiece 8 in the uniaxial tensile stress finite element simulation, so as to reduce the number of simulations.

[0112] In specific implementation, the first curve graph, the second curve graph, the third curve graph and the fourth curve graph are all established by smooth curve fitting using MATLAB programming, which reduces workload and has small errors.

[0113] In order to verify the accuracy of the final residual compressive stress value obtained by the method described in the present invention, two experiments are now conducted:

[0114] Experiment 1: The residual compressive stress value in the x direction of the surface layer of the workpiece 8 after surface strengthening obtained by the X-ray diffraction technology is -120MPa±15, while the residual compressive stress value in the x direction of the surface layer of the workpiece after surface strengthening obtained by the method of the present invention is -106MPa, which is basically consistent with the allowable error value of the residual compressive stress value;

[0115] Experiment 2: The second residual compressive stress value in the x direction obtained by the method described in the present invention and the second residual pressure value in the y direction The residual compressive stress value in the X direction obtained by ABAQUS uniaxial tension finite element simulation method and the residual compressive stress values ​​in the Y direction For comparison, Fig.14 As shown, the second residual compressive stress value in the x direction obtained by the method described in the present invention can be obtained. and the second residual pressure value in the y direction The residual compressive stress value in the X direction obtained by ABAQUS uniaxial tension finite element simulation method and the residual compressive stress values ​​in the Y direction The results are basically consistent, and the difference between the residual compressive stress values ​​of the two is within ±20MPa, which is in line with the allowable error value of the residual compressive stress value, proving that the method described in the present invention is indeed feasible and the residual pressure value obtained by the method described in the present invention is highly accurate.

[0116] The above is only a specific implementation of the present invention, which enables those skilled in the art to understand or implement the present invention. Although detailed descriptions are given with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments, and they should all be covered by the protection scope of the claims.

Claims

1. Equipment for studying the residual compressive stress introduced into workpieces after surface strengthening, characterized in that: include: An adsorption mechanism (1) is used for adsorbing and fixing the workpiece (8) after surface strengthening, and the adsorption mechanism (1) is also provided with an oil spraying component (101) for spraying oil to cool the workpiece (8) after surface strengthening; A cleaning mechanism (2) for achieving dead-angle-free cleaning of the workpiece (8) after surface strengthening; A gluing mechanism (3) for gluing the position on the surface of the workpiece (8) after surface strengthening where the strain gauge (501) needs to be glued; A loading mechanism, comprising a six-axis robot (4) and a strain gauge storage platform (5), wherein the strain gauge storage platform (5) is used to store strain gauges (501), the six-axis robot (4) has two end effectors, namely, an air-floating spindle (401) and a strain gauge suction nozzle (402), the strain gauge suction nozzle (402) is used to absorb the strain gauge (501) on the strain gauge storage platform (5), and a drill bit (403) is provided on the air-floating spindle (401); A pressing mechanism (6) is used to press a strain gauge (501) attached to a workpiece (8) after surface strengthening. The pressing mechanism (6) comprises a fixing frame (609), a guide rail (601) fixed to the fixing frame (609), a slider (602), and a pressing assembly. The guide rail (601) and the slider (602) are arranged in an up-down direction and are adaptively connected. The pressing assembly is located on one side of the slider (602). The pressing assembly comprises a fixing plate (603), two support plates (605), and a lower connecting plate (606). , a driving gear (607), a driven gear, a motor, a pressing roller (610), a pressing shaft (614), a fixed shaft, an anti-sticking paper tape (611), a conveying roller (612), a collecting roller (613), a lower connecting plate (606) arranged horizontally and fixed to the side of the slider (602), a pressing hole (615) is opened on the lower connecting plate (606), the fixed plate (603) is arranged vertically and inserted into the pressing hole (615), the motor is fixed to the upper end of the right side of the fixed plate (603), and the motor shaft rotates to connect The fixed plate (603) is connected to the fixed plate (603) and extends to the left side of the fixed plate (603). The driving gear (607) and the transmission roller (612) are both located on the left side of the fixed plate (603) and are both sleeved on the motor shaft. The fixed shaft is vertically fixed to the lower end of the left side of the fixed plate (603). The fixed shaft is rotatably sleeved with a collection roller (613) and a driven gear meshing with the driving gear (607). The driven gear is fixed to the collection roller (613). The two support plates (605) are distributed on the left and right and are both vertically fixed to the lower connecting plate (606). The bottom surface of the pressing shaft (614) is rotatably connected to the two support plates (605) at both ends, and a pressing roller (610) is sleeved on the middle of the pressing shaft (614). The pressing roller (610), the conveying roller (612), and the collecting roller (613) are adaptively arranged and are provided with a wire groove adapted to the anti-sticking paper tape (611). One end of the anti-sticking paper tape (611) is fixed to the conveying roller (612), and the other end of the anti-sticking paper tape (611) is fixed to the collecting roller (613) after passing the pressing roller (610); A collector, used for connecting to the strain gauge (501) to collect strain values; A double-axis moving mechanism (7), wherein the adsorption mechanism (1) is fixed to the double-axis moving mechanism (7), and the double-axis moving mechanism (7) is used to drive the adsorption mechanism (1) to move in the front-back and left-right directions and to move the adsorption mechanism (1) to corresponding positions of the cleaning mechanism (2), the gluing mechanism (3), the six-axis robot (4), the strain gauge storage table (5), and the pressing mechanism (6); The PLC controller is used to control the two-axis moving mechanism (7), the cleaning mechanism (2), the gluing mechanism (3), the six-axis robot (4), and the pressing mechanism (6) to perform corresponding actions.

2. The device for studying the residual compressive stress introduced into the workpiece after surface strengthening according to claim 1 is characterized in that: The pressing assembly further comprises an upper connecting plate (604) arranged in parallel with the lower connecting plate (606); the upper connecting plate (604) is located above the lower connecting plate (606) and is fixed to the side of the slider (602); guide rods (608) are fixed at the four corners between the upper connecting plate (604) and the lower connecting plate (606).

3. The device for studying the residual compressive stress introduced into the workpiece after surface strengthening according to claim 2 is characterized in that: A six-axis force sensor (404) is provided at the end of the six-axis robot (4), and an output end of the six-axis force sensor (404) is connected to a PLC controller.

4. The device for studying the residual compressive stress introduced into the workpiece after surface strengthening according to claim 3 is characterized in that: The adsorption mechanism (1), the cleaning mechanism (2), the gluing mechanism (3), the six-axis robot (4), the strain gauge storage table (5), and the pressing mechanism (6) are arranged in sequence along the left-right direction and are all located in front of the dual-axis moving mechanism.

5. A method for studying the introduction of residual compressive stress into a workpiece after surface strengthening, the method being implemented by the device for studying the introduction of residual compressive stress into a workpiece after surface strengthening as claimed in claim 1, characterized in that: The steps include: 1) Adsorbing and fixing the workpiece (8) after surface strengthening onto the adsorption mechanism (1); 2) The PLC controller controls the dual-axis moving mechanism (7) to drive the adsorption mechanism (1) to move to the corresponding position of the cleaning mechanism (2), and the cleaning mechanism (2) cleans the workpiece (8) after surface strengthening without any dead angle; 3) The PLC controller controls the biaxial moving mechanism (7) to drive the adsorption mechanism (1) to move to the corresponding position of the gluing mechanism (3), and the PLC controller controls the gluing mechanism (3) to apply glue to the position of the workpiece (8) after surface strengthening where the strain gauge (501) needs to be pasted, and controls the glue output of the gluing mechanism (3); 4) The PLC controller controls the two-axis moving mechanism (7) to drive the adsorption mechanism (1) to move to the corresponding position of the feeding mechanism, and the six-axis robot (4) adsorbs the strain gauge (501) from the strain gauge storage table (5) through the strain gauge suction nozzle (402) and attaches the adsorbed strain gauge (501) to the specified position of the surface-strengthened workpiece (8), and then performs preliminary pressing on the strain gauge (501) to complete the initial attachment of the strain gauge (501); 5) The PLC controller controls the biaxial moving mechanism (7) to drive the adsorption mechanism (1) to move to the corresponding position of the pressing mechanism (6), and the PLC controller controls the pressing mechanism (6) to press the strain gauge (501) pasted on the workpiece (8) after surface strengthening, thereby completing the final pasting of the strain gauge (501); 6) connecting the acquisition instrument to the strain gauge (501), the PLC controller controls the dual-axis moving mechanism (7) to drive the adsorption mechanism (1) to move to the corresponding position of the drill bit (403) of the six-axis robot (4), the PLC controller controls the air-floating spindle (401) of the six-axis robot (4) to move, the air-floating spindle (401) drives the drill bit (403) to perform gradient high-speed blind hole drilling on the surface-strengthened workpiece (8), and at the same time cooperates with the oil injection component (101) on the adsorption mechanism (1) to perform oil injection cooling on the surface-strengthened workpiece (8), and collects the corresponding x-direction measured strain value and y-direction measured strain value through the acquisition instrument; 7) According to the measured strain values ​​in the x-direction and the measured strain values ​​in the y-direction obtained in step 6), the corresponding residual compressive stress values ​​are calculated. The specific calculation method is as follows: a. Set up the uniaxial tensile stress finite element simulation adapted to the gradient high-speed blind hole drilling process in step 6), obtain the corresponding x-direction simulation strain value and y-direction simulation strain value through the uniaxial tensile stress finite element simulation, and calculate the stress calibration constant through formula ① and stress calibration constant , ① in, is the stress calibration constant, is the stress calibration constant, is the elastic modulus, is the simulated strain value in the x direction, is the simulated strain value in the y direction, is the simulation value of uniaxial tensile stress; b. Calculate the shape change specific energy according to formula ②, establish the first curve diagram of the relationship between the blind hole depth and the uniaxial tensile stress simulation value and the shape change specific energy, and establish the relationship between the blind hole depth and the shape change specific energy and stress calibration constant. The second curve of the relationship is used to establish the calibration constants of blind hole depth, shape change specific energy and stress The third curve graph, ② in, is the shape change specific energy, is Poisson’s ratio; c. The stress calibration constant corresponding to the simulated uniaxial tensile stress value equal to 0.6 times the yield strength of the surface-hardened workpiece (8) and stress calibration constant They are stress calibration constant values and stress calibration constant values , using the stress calibration constant to determine the value , stress calibration constant value The corresponding uniaxial tensile stress theoretical value is inversely calculated according to formula ③, and the fourth curve diagram of the relationship between the blind hole depth and the uniaxial tensile stress simulation value and the uniaxial tensile stress theoretical value is established. ③ in, is the theoretical value of uniaxial tensile stress; d. Use the measured strain values ​​in the x-direction and y-direction collected in step 6) and the stress calibration constant value calibrated in step c) to determine the value. , stress calibration constant value , the first residual compressive stress value in the x direction is calculated according to formula ④, the calculated first residual compressive stress value in the x direction is used as the theoretical value of uniaxial tensile stress and is placed in the fourth curve diagram established in step c to match the corresponding uniaxial tensile stress simulation value, ④ in, is the first residual compressive stress value in the x direction, is the measured strain value in the x direction, is the measured strain value in the y direction; e. Place the uniaxial tensile stress simulation value matched in step d in the first curve graph to match the corresponding shape change specific energy, and then place the matched shape change specific energy in the second curve graph and the third curve graph to match the corresponding stress calibration constant respectively. and stress calibration constant , and finally use the matching stress calibration constant and stress calibration constant The measured strain value in the x direction and the measured strain value in the y direction obtained in step 6) are used to calculate the second residual compressive stress value in the x direction and the second residual compressive stress value in the y direction according to formula ⑤, and the calculated second residual compressive stress value in the x direction and the second residual compressive stress value in the y direction are respectively used as the final residual compressive stress values. ⑤ in, is the second residual compressive stress value in the x direction, is the second compressive residual stress value in the y direction.

6. The method for studying the residual compressive stress introduced into the workpiece after surface strengthening according to claim 5 is characterized in that: In step c, a calibrated yield stress determined by a stress-increased uniaxial tensile test is used as the yield strength of the workpiece (8) after surface strengthening. The uniaxial tensile stress in the stress-increased uniaxial tensile test is increased multiple times. Each time the uniaxial tensile stress is increased, a strain data collection time is paused. When the strain data within a certain strain data collection time shows a continuous increase for the first time, the corresponding uniaxial tensile stress at this time is determined to be the calibrated yield stress of the workpiece (8) after surface strengthening.

7. The method for studying residual compressive stress introduced into a workpiece after surface strengthening according to claim 6, characterized in that: In the uniaxial tensile stress finite element simulation in step a, the finite element simulation grid is divided according to the actual acquisition area of ​​the strain gauge (501).

8. The method for studying residual compressive stress introduced into a workpiece after surface strengthening according to claim 7, characterized in that: In the simulation model of the surface-hardened workpiece (8) in the uniaxial tensile stress finite element simulation, there are multiple blind holes whose depths match the depths of the gradient height drilling blind holes in step 6).

9. The method for studying the residual compressive stress introduced into the workpiece after surface strengthening according to claim 8, characterized in that: The first curve graph, the second curve graph, the third curve graph and the fourth curve graph are all established by smooth curve fitting using MATLAB programming.

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