Rail standard specimen calibration stress applying device and applying method

Abstract

This invention belongs to the field of non-destructive testing technology for rail transit calibration, specifically relating to a stress application device and method for calibrating standard rail specimens. It addresses the problems of existing testing machines in applying stress to standard rail specimens, such as large random systematic errors, bulky size, inability to simulate the stress on specific rail sections, difficulty in switching between tension and compression, and inflexible use in field or small laboratories. The device includes a hydraulic cylinder assembly, a force transmission module, and multiple wedges. The force transmission module includes two clamps with C-shaped openings for holding the rail web or rail head of the standard rail specimen. The two clamps are detachably connected to both ends of the hydraulic cylinder assembly. When the clamps are held at the corresponding positions on the standard rail specimen, gaps are formed between the inner sides of the left and right side walls of the clamps and the left and right side walls of the rail web, and the wedges are correspondingly fitted into these gaps.

Description

Technical Field

[0001] This invention belongs to the field of non-destructive testing technology for rail transit calibration, specifically relating to a stress application device and method for calibrating standard rail specimens. Background Technology

[0002] In the rail transit sector, changes in ambient temperature (high and low temperature cycles) and train loads can generate significant internal stress within the rails. If this internal stress exceeds a safe threshold, it can easily lead to rail deformation, accelerated fatigue crack propagation, and damage to track geometry, seriously threatening train operation safety. In railway preventative maintenance, regularly conducting stress testing on the rails is a key technical means for implementing "condition-based maintenance" and preventing major rail breakage accidents.

[0003] Before conducting on-site stress testing, it is essential to calibrate the testing instruments (such as ultrasonic stress meters and magnetoelastic instruments) using standard rail specimens to ensure the accuracy and reliability of the on-site measurement data. Calibration is essentially "calibration," which involves exciting the standard rail specimen with a set of known stress values ​​while simultaneously recording the instrument's response signal to plot a stress-signal calibration curve. However, the industry currently lacks dedicated calibration devices capable of applying quantitative, controllable, and variable-direction (tensile / compressive) stress to standard rail specimens. Existing technologies often employ material testing machines or simple loading fixtures. Taking material testing machines as an example, the degree of eccentricity in loading the standard rail specimen is greatly affected by the specimen clamping position and the straightness of the rail head surface, constituting a random systematic error rather than a fixed proportional error. This error changes with each clamping, cannot be eliminated by a single correction factor, and suffers from problems such as large size, inability to simulate the stress on specific rail sections, difficulty in switching between tension and compression, and inflexibility in on-site or small laboratory settings. Summary of the Invention

[0004] This invention provides a stress application device and method for calibrating standard rail specimens, solving the problems of large random systematic errors, large size, inability to simulate the stress of specific rail sections, difficulty in switching between tension and compression, and inflexible use in the field or small laboratory in the prior art. The clamping and wedge structures of this device closely fit the shape of the rail web and rail head of the standard rail specimen, avoiding stress concentration and loading eccentricity, and ensuring the accuracy and repeatability of the calibration results.

[0005] This invention is achieved through the following technical solution: A stress application device for calibrating standard rail specimens, characterized in that it includes a hydraulic cylinder assembly, a force transmission module, and multiple wedges; The force transmission module includes two clamps, each with a C-shaped latch. The clamps are used to hold the rail web or rail head of the standard rail specimen. The two clamps are detachably connected to both ends of the hydraulic cylinder assembly. When the clamping device is held at the corresponding position of the rail standard specimen, the inner sides of the left and right side walls of the clamping device form gaps with the left and right side walls of the web of the rail standard specimen, and the wedge block is correspondingly assembled in the gap.

[0006] Furthermore, it also includes a movable protective cover for covering or exposing the hydraulic cylinder assembly and force transmission module.

[0007] Furthermore, the protective cover is gantry-shaped, and the bottom of the left and right side walls of the protective cover are slidably connected to guide rails via sliders, and the guide rails are fixed to the ground.

[0008] Furthermore, the hydraulic cylinder assembly includes two hydraulic cylinders distributed on the left and right sides. The outer sides of the left and right side walls of the clamping member are provided with two ear plates distributed vertically and horizontally. The bottom end of the fixed housing of the hydraulic cylinder and the top end of the hydraulic rod are provided with connecting blocks with insertion holes. When the connecting blocks are inserted into the gap formed by the two ear plates, they are connected as one unit by a pin.

[0009] Furthermore, the inner sides of the left and right side walls of the clamp are provided with limiting grooves that extend through the front and rear. When the clamp is held at the corresponding position of the standard rail specimen, the inclined surface of the wedge is inserted into the limiting groove.

[0010] Furthermore, one side of one of the guide rails is provided with a vertical plate extending along its length, the top surface of the vertical plate is provided with a rack, the side wall of the protective cover is provided with a drive motor, and the output shaft of the drive motor is provided with a gear that meshes with the rack for transmission.

[0011] Furthermore, it also includes a visual monitoring module, which includes at least one camera and a data storage unit. The camera is located on the top inner side of the protective cover, and its field of view covers the loading area.

[0012] A method for applying calibration stress to a standard rail specimen, comprising the following steps, using the aforementioned standard rail specimen calibration stress application device to apply calibration stress to the standard rail specimen: S10. Clamp the two clamps at the corresponding positions of the standard rail specimen, and detachably connect the two clamps to both ends of the hydraulic cylinder assembly. S20. In low-pressure mode, control the hydraulic cylinder assembly to start, causing the clamp to move to the initial position, and then depressurize the hydraulic cylinder assembly. S30. Select the assembly position of the wedge block in the gap according to the required stress type; When the required tensile stress is applied, the wedge is fitted into the gap from the outside of the clamp to achieve temporary fixation between the clamp and the standard rail specimen; When compressive stress is required, the wedge is installed from the inside of the clamp into the gap to temporarily fix the clamp to the standard rail specimen; S40. Based on the target rail stress value required for the standard rail specimen, calculate the target oil pressure value required for the hydraulic cylinder assembly. S50. Control the hydraulic cylinder assembly to apply stress to the standard rail specimen until the hydraulic cylinder assembly reaches the target oil pressure value calculated in S40. At this time, the stress applied to the standard rail specimen by the two clamps reaches the target rail stress value, and the hydraulic cylinder assembly enters the pressure holding state. S60. The testing instrument is calibrated using a standard rail specimen that has reached the target rail stress value. S70. After completing the calibration of the testing instruments, depressurize the hydraulic cylinder assembly.

[0013] Furthermore, in step S40, the formula for calculating the target oil pressure value P is as follows: ; in, The target rail stress value, This refers to the cross-sectional area of ​​the standard rail specimen. This represents the effective area of ​​the hydraulic cylinder piston.

[0014] Furthermore, it also includes a movable protective cover that covers the hydraulic cylinder assembly, the rail standard specimen, and the force transmission module when stress is applied to the rail standard specimen.

[0015] The beneficial effects achieved by this invention compared with the prior art are as follows: 1. The rail standard specimen calibration stress application device described in this invention fills a gap in the field and is specialized. Compared with the general universal material testing machine, the clamping and wedge structure of this device closely fits the shape of the rail web and rail head of the rail standard specimen, avoiding stress concentration and loading eccentricity, and ensuring the accuracy and repeatability of the calibration results. The rail standard specimen calibration stress application method of the present invention uses the above-mentioned rail standard specimen calibration stress application device to apply calibration stress to the rail standard specimen. It does not require the replacement of any major components. By simply adjusting the position of the wedge block, tensile stress or compressive stress can be generated on the same device, which greatly simplifies the operation process. 2. This invention is a dual-purpose device that can quickly switch between tensile and compressive stresses. By utilizing different installation directions of the wedges, without replacing any major components, tensile or compressive stresses can be generated on the same device simply by adjusting the position of the wedges. This invention greatly simplifies the operation process, reduces equipment costs and size, and is especially suitable for on-site or mobile laboratory use. 3. The stress value is precise and controllable and can be quantified and calibrated. Based on the hydraulic principle and area conversion formula of the hydraulic cylinder, the operator can directly calculate the oil supply pressure of the servo precision control hydraulic system according to the rail stress value required for calibration. This realizes quantitative, precise and continuous control of stress, and provides a reliable metrological benchmark for the accurate calibration of stress detection instruments. 4. The protective cover is used to cover or expose the hydraulic cylinder assembly and force transmission module to avoid accidental contact or inadequate protection. It is especially suitable for high-frequency calibration scenarios and eliminates the risk of human error from the source.

[0016] 5. The visual monitoring module enables process traceability. The protective cover houses a high-definition camera that can monitor rail deformation, wedge displacement, and clamping status in real time, recording the entire loading process. This video data can be used for post-process analysis, operational review, fault diagnosis, and quality traceability during calibration, significantly improving the equipment's intelligence and data-driven capabilities. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the working state of the rail standard specimen calibration stress application device described in this invention; Figure 2 This is a schematic diagram of the assembly of the card component and the standard rail specimen described in this invention; Figure 3 This is a schematic diagram of the wedge block installation position under tensile stress as described in this invention; Figure 4 This is a schematic diagram of the wedge block installation position under compressive stress as described in this invention; In the diagram: 1. Hydraulic cylinder assembly, 2. Clamping piece, 3. Standard rail specimen, 4. Gap, 5. Wedge block, 6. Protective cover, 7. Guide rail, 8. Ear plate, 9. Connecting block, 10. Pin, 11. Limiting groove, 12. Vertical plate, 13. Rack, 14. Camera, 15. Data storage unit, 16. Hydraulic station, 17. Hydraulic rod. Detailed Implementation

[0018] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0019] In the description of the invention, it should be understood that the terms "front", "rear", "up", "down", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the invention.

[0020] Example 1 This embodiment discloses a stress application device for calibrating standard rail specimens, such as... Figure 1 As shown, it mainly includes a servo precision control hydraulic system, a force transmission module, a protective cover 6, a guide rail 7, a vision monitoring module, and four wedges 5.

[0021] The servo precision control hydraulic system is used to generate tensile or compressive stress along the length of the standard rail specimen. It mainly includes a hydraulic cylinder assembly 1, a hydraulic station 16, and oil pipes. In this embodiment, the hydraulic cylinder assembly 1 consists of two hydraulic cylinders distributed on the left and right. The hydraulic station 16 is connected to each hydraulic cylinder through oil pipes, thereby enabling precise control of the hydraulic cylinder fluid.

[0022] like Figure 2 As shown, the force transmission module mainly includes two clamps 2, which are made of steel. Each clamp has a C-shaped jaw and an overall U-shaped structure. The clamps 2 are used to hold the rail web or rail head of the standard rail specimen 3. The inner contour of the clamps 2 conforms to the outer contour of the rail web or rail head of the standard rail specimen to uniformly transmit the load. The two clamps 2 are detachably connected to both ends of the hydraulic cylinder assembly 1. Since the hydraulic cylinder assembly 1 includes two hydraulic cylinders, two parallel ear plates 8 are welded to the outer sides of both the left and right side walls of the clamps 2. The ear plates 8 have pre-drilled through-hole mounting holes. Each hydraulic cylinder's fixed housing bottom and hydraulic rod 17 top end are equipped with a connecting block 9 with an insertion hole. When the connecting block 9 is inserted into the gap formed by the two ear plates 8, a pin 10 passes through the ear plates 8 and the connecting block 9 sequentially to connect them as a single unit, facilitating disassembly.

[0023] When the clamping piece 2 is held at the corresponding position of the standard rail specimen 3, gaps 4 are formed between the inner sides of the left and right side walls of the clamping piece 2 and the left and right side walls of the web of the standard rail specimen 3, and the wedge 5 is correspondingly assembled in the gaps 4. In order to limit the wedge 5 and prevent it from falling off during the test, a limiting groove 11 extending through the front and back is machined on the inner sides of the left and right side walls of the clamping piece 2. When the clamping piece 2 is held at the corresponding position of the standard rail specimen 3, the wedge 5 is inserted into the gap 4 along the limiting groove 11, so that the plane of the wedge 5 contacts the web surface of the standard rail specimen, and the inclined surface of the wedge 5 contacts the limiting groove 11.

[0024] The protective cover 6 is used to cover or expose the hydraulic cylinder assembly 1 and the force transmission module. During testing, covering with the protective cover reduces the risk of accidents and improves operator safety. The protective cover 6 is gantry-shaped. To facilitate movement, two guide rails 7 are fixed to the ground, allowing the bottom of the left and right sidewalls of the protective cover 6 to slide onto the guide rails 7 via sliders. A vertical plate 12 extending along the length of one of the guide rails 7 is mounted on one side. A rack 13 is mounted on the top surface of the vertical plate 12. A drive motor, which is a conventional geared motor, is mounted on the sidewall of the protective cover 6. The output shaft of the drive motor is equipped with a gear, which meshes with the rack 13 for transmission. The drive motor controls the rotation of the gear, enabling the protective cover 6 to move back and forth.

[0025] The visual monitoring module is used to observe and record in real time the extension and retraction of hydraulic rods, as well as the state changes of the standard rail specimen during stress. The visual monitoring module mainly includes at least one camera 14 and a data storage unit 15. The field of view of the camera 14 covers the loading area. The camera 14 is electrically connected to the data storage unit 15 to transmit the captured image signals of the loading area to the data storage unit 15 for local caching and storage. The data storage unit 15 is electrically connected to a host computer interface, allowing the host computer to read and retrieve the image data stored in the data storage unit 15.

[0026] It also includes an electrical interlock module, which connects the protective cover 6 to the servo precision control hydraulic system. This ensures that the servo precision control hydraulic system cannot be activated if the protective cover does not completely cover the hazardous parts, and that the protective cover cannot be moved during loading. It mainly includes a position sensor and an interlock controller. The position sensor detects the coverage status of the protective cover, and the interlock controller controls the power supply circuit of the hydraulic station and the locking status of the protective cover drive motor based on the position sensor signal. This integrates an electric protective cover, video monitoring, and an electrical interlock mechanism, significantly improving operational safety and process traceability.

[0027] The working principle of the stress application device for calibrating standard rail specimens described in this embodiment is as follows: Prepare a standard rail specimen 3. Clamp the standard rail specimen 3 at the corresponding positions (generally the rail head or rail web) using the two clamps 2. The two clamps 2 are detachably connected to both ends of the hydraulic cylinder assembly 1. Select the assembly position of the wedge 5 in the gap 4 according to the required stress type. When tensile stress needs to be applied to the standard rail specimen 3, assemble the wedge 5 from the outside of the clamp 2 into the gap 4 to temporarily fix the clamp 2 and the standard rail specimen 3. When compressive stress is required, assemble the wedge 5 from the inside of the clamp 2 into the gap 4 to temporarily fix the clamp 2 and the standard rail specimen 3. After the wedge 5 is temporarily fixed, apply stress to the standard rail specimen 3 by activating the hydraulic cylinder assembly 1. When the target rail stress value is reached, calibrate the testing instrument using the standard rail specimen 3. This involves using a set of known stress values ​​to excite a standard rail specimen while simultaneously recording the instrument's response signal, thereby plotting a "stress-signal" calibration curve to calibrate the testing instrument.

[0028] The rail standard specimen calibration stress application device described above fills a gap in the field and is specialized. Compared with general universal testing machines, the clamping and wedge structure of this device closely fits the shape of the rail web and rail head of the rail standard specimen, avoiding stress concentration and loading eccentricity, and ensuring the accuracy and repeatability of calibration results. It is a dual-purpose device that can quickly switch between tensile and compressive stresses. By using different installation directions of the wedges, tensile or compressive stresses can be generated on the same device without replacing any major components. This invention greatly simplifies the operation process, reduces equipment cost and size, and is especially suitable for field or mobile laboratory use.

[0029] Example 2 Taking the calibration and testing instrument for applying tensile stress to standard rail specimens as an example, this embodiment discloses a method for applying calibration stress to standard rail specimens. The rail standard specimen calibration stress application device described in Example 1 is used to apply calibration tensile stress to the rail standard specimen 3, including the following steps: S10. Clamp the web of the rail standard test piece 3 with the two clamps 2 respectively, and connect the two opposite clamps 2 to the two ends of the hydraulic cylinder and the hydraulic rod respectively with pins. S20. In low-pressure mode, the hydraulic cylinder assembly 1 is started by controlling the hydraulic station to move the clamp 2 to the initial position. At this time, the hydraulic rod is fully retracted. Finally, the hydraulic cylinder assembly 1 is depressurized. S30, such as Figure 3 As shown, four wedges 5 are assembled from the outside of the two clips 2 into the gap 4 to temporarily fix the clips 2 and the standard rail specimen 3. S40, control the movement of the protective cover 6 so that the protective cover covers the hydraulic cylinder assembly 1 and the force transmission module. At the same time, start the visual monitoring module and calculate the target oil pressure value required for the hydraulic cylinder assembly 1 based on the target rail stress value required for the standard rail specimen 3. In this step, the formula for calculating the target oil pressure value P is as follows: ; in, The target rail stress value, Let be the cross-sectional area of ​​standard rail specimen 3. The effective area of ​​the hydraulic cylinder piston; S50, control the hydraulic cylinder assembly 1 to apply stress to the rail standard specimen 3 until the hydraulic cylinder assembly 1 reaches the target oil pressure value calculated in S40. At this time, the stress applied to the rail standard specimen 3 by the two clamps 2 reaches the target rail stress value, and the hydraulic cylinder assembly 1 enters the pressure holding state. S60. The testing instrument is calibrated using a standard rail specimen 3 that has reached the target rail stress value. S70. After completing the calibration of the testing instrument, depressurize the hydraulic cylinder assembly 1 to reset the protective cover.

[0030] The above method enables the tensile stress calibration of standard rail specimens. The stress value is precise, controllable, and quantifiable. Based on the hydraulic principle and area conversion formula of the hydraulic cylinder, the operator can directly calculate the oil supply pressure of the servo precision control hydraulic system according to the required rail stress value for calibration. This achieves quantitative, precise, and continuous control of stress, providing a reliable metrological benchmark for the accurate calibration of stress testing instruments.

[0031] Example 3 Taking the calibration and testing instrument for applying compressive stress to standard rail specimens as an example, this embodiment discloses a method for applying calibration stress to standard rail specimens. The standard rail specimen calibrating stress is applied to the standard rail specimen 3 using the calibration stress application device described in Example 1, including the following steps: S10. Clamp the rail head of the standard rail specimen 3 with the two clamps 2 respectively, and connect the two opposite clamps 2 to the two ends of the hydraulic cylinder and hydraulic rod respectively with pins. S20. In low-pressure mode, the hydraulic cylinder assembly 1 is started by controlling the hydraulic station to move the clamp 2 to the initial position. At this time, the hydraulic rod is fully extended. Finally, the hydraulic cylinder assembly 1 is depressurized. S30, such as Figure 4 As shown, four wedges 5 are assembled from the inside of the two clips 2 into the gap 4 to temporarily fix the clips 2 and the standard rail specimen 3. S40, control the movement of the protective cover 6 so that the protective cover covers the hydraulic cylinder assembly 1 and the force transmission module. At the same time, start the visual monitoring module and calculate the target oil pressure value required for the hydraulic cylinder assembly 1 based on the target rail stress value required for the standard rail specimen 3. In this step, the formula for calculating the target oil pressure value P is as follows: ; in, The target rail stress value, Let be the cross-sectional area of ​​standard rail specimen 3. The effective area of ​​the hydraulic cylinder piston; S50, control the hydraulic cylinder assembly 1 to apply stress to the rail standard specimen 3 until the hydraulic cylinder assembly 1 reaches the target oil pressure value calculated in S40. At this time, the stress applied to the rail standard specimen 3 by the two clamps 2 reaches the target rail stress value, and the hydraulic cylinder assembly 1 enters the pressure holding state. S60. The testing instrument is calibrated using a standard rail specimen 3 that has reached the target rail stress value. S70. After completing the calibration of the testing instrument, depressurize the hydraulic cylinder assembly 1 to reset the protective cover.

[0032] The above method enables the calibration of compressive stress on standard rail specimens. The stress value is precise, controllable, and quantifiable. Based on the hydraulic principle and area conversion formula of the hydraulic cylinder, the operator can directly calculate the oil supply pressure of the servo precision control hydraulic system according to the required rail stress value for calibration. This achieves quantitative, precise, and continuous control of stress, providing a reliable metrological benchmark for the accurate calibration of stress testing instruments.

Claims

1. A stress application device for calibrating standard rail specimens, characterized in that, Includes a hydraulic cylinder assembly (1), a force transmission module, and multiple wedges (5); The force transmission module includes two clamps (2), each clamp (2) having a C-shaped bayonet. The clamps (2) are used to clamp the rail web or rail head of the standard rail specimen (3). The two clamps (2) are detachably connected to both ends of the hydraulic cylinder assembly (1). When the clamp (2) is held in the corresponding position of the rail standard test piece (3), the inner side of the left and right side walls of the clamp (2) and the left and right side of the web of the rail standard test piece (3) form a gap (4), and the wedge (5) is correspondingly assembled in the gap (4).

2. The stress application device for calibrating standard rail specimens according to claim 1, characterized in that, It also includes a movable protective cover (6) for covering or exposing the hydraulic cylinder assembly (1) and the force transmission module.

3. The stress application device for calibrating standard rail specimens according to claim 2, characterized in that, The protective cover (6) is gantry-shaped, and the bottom of the left and right side walls of the protective cover (6) is slidably connected to the guide rail (7) by a slider, and the guide rail (7) is fixed on the ground.

4. The stress application device for calibrating standard rail specimens according to claim 1, characterized in that, The hydraulic cylinder assembly (1) includes two hydraulic cylinders distributed on the left and right. The outer sides of the left and right side walls of the clamp (2) are provided with two ear plates (8) distributed vertically and horizontally. The bottom end of the fixed housing of the hydraulic cylinder and the top end of the hydraulic rod are provided with connecting blocks (9) with insertion holes. When the connecting block (9) is inserted into the gap formed by the two ear plates (8), they are connected as one unit by a pin (10).

5. The stress application device for calibrating standard rail specimens according to any one of claims 1-4, characterized in that, The inner sides of the left and right side walls of the clamp (2) are provided with a limiting groove (11) that extends through the front and back. When the clamp (2) is clamped at the corresponding position of the standard rail test piece (3), the inclined surface of the wedge (5) is inserted into the limiting groove (11).

6. The stress application device for calibrating standard rail specimens according to claim 3, characterized in that, One of the guide rails (7) has a vertical plate (12) extending along its length on one side. The top surface of the vertical plate (12) is provided with a rack (13). The side wall of the protective cover (6) is provided with a drive motor. The output shaft of the drive motor is provided with a gear that meshes with the rack (13).

7. The stress application device for calibrating standard rail specimens according to claim 3 or 6, characterized in that, It also includes a visual monitoring module, which includes at least one camera (14) and a data storage unit (15). The camera (14) is located on the top inner side of the protective cover (6), and the field of view of the camera (14) covers the loading area.

8. A method for applying calibration stress to a standard rail specimen (3), characterized in that, The calibration stress is applied to the rail standard specimen (3) using the calibration stress application device according to any one of claims 1-7, comprising the following steps: S10. Clamp the corresponding positions of the standard rail specimen (3) with the two clamps (2) respectively, and detachably connect the two clamps (2) to both ends of the hydraulic cylinder assembly (1); S20. In low-pressure mode, control the hydraulic cylinder assembly (1) to start so that the clamp (2) moves to the initial position, and then depressurize the hydraulic cylinder assembly (1). S30. Select the assembly position of the wedge (5) in the gap (4) according to the required stress type; When the required tensile stress is applied, the wedge (5) is fitted from the outside of the clamp (2) into the gap (4) to achieve temporary fixation between the clamp (2) and the standard rail specimen (3); When compressive stress is required, the wedge (5) is assembled from the inside of the clamp (2) into the gap (4) to achieve temporary fixation between the clamp (2) and the standard rail specimen (3); S40. Based on the target rail stress value required by the standard rail specimen (3), calculate the target oil pressure value required for the hydraulic cylinder assembly (1); S50, control the hydraulic cylinder assembly (1) to apply stress to the rail standard test piece (3) until the hydraulic cylinder assembly (1) reaches the target oil pressure value calculated in S40. At this time, the stress applied by the two clamps (2) to the rail standard test piece (3) reaches the target rail stress value, and the hydraulic cylinder assembly (1) enters the pressure holding state. S60. The testing instrument is calibrated using a standard rail specimen (3) that has reached the target rail stress value. S70. After completing the calibration of the testing instrument, depressurize the hydraulic cylinder assembly (1).

9. The method for applying calibration stress to the standard rail specimen (3) according to claim 8, characterized in that, In step S40, the formula for calculating the target oil pressure value P is as follows: ； in, The target rail stress value, The cross-sectional area of ​​the standard rail specimen (3) is given. This represents the effective area of ​​the hydraulic cylinder piston.

10. The method for applying calibration stress to the standard rail specimen (3) according to claim 9, characterized in that, It also includes a movable protective cover (6) which is used to cover the hydraulic cylinder assembly (1), the rail standard specimen (3) and the force transmission module when stress is applied to the rail standard specimen (3).

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