High-temperature fretting fatigue test device

Abstract

The utility model discloses a high-temperature fretting fatigue testing device, which belongs to the technical field of tenon connection structure testing and comprises an upper clamp and a lower clamp which are used for fixing a tenon sample and applying acting force to the tenon sample, and a digital integrated circuit (DIC) camera used for observing material deformation and crack progress of the tenon sample, a micro-motion cushion block used for supporting a tenon sample is arranged in the upper clamp, the upper clamp is sleeved with an electromagnetic induction coil, the electromagnetic induction coil is located at the contact area of the tenon sample and the micro-motion cushion block, an observation window is arranged between every two adjacent turns of coils of the electromagnetic induction coil, and the DIC camera faces the observation window and is as high as the observation window; the observation window is reserved between the two turns of coils, and the material deformation and crack initiation progress of the tenon sample can be recorded in real time through the DIC camera; and the clamp is connected with the bearing seat through the joint bearing, so that self-centering of the tenon sample can be realized, deflection torque is prevented from being introduced, and the shape control precision of a friction surface of a contact area is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of mortise and tenon connection structure testing, in particular to a high-temperature fretting fatigue testing device. Background Art

[0002] During operation, aircraft engine turbine blades are subject to complex loads, primarily low-frequency centrifugal loads generated by the blade's mass during high-speed rotation, aerodynamic loads caused by airflow acting on the blade, thermal loads caused by uneven temperature distribution across the blade, and high-frequency vibration loads. These complex loads are transmitted to the tenon joint between the blade and the disc, causing typical fretting fatigue. Under fretting fatigue conditions, the blade tenon can fracture at the contact root, leading to engine failure and even aircraft accidents.

[0003] To improve the lifespan of aircraft engines and reduce the occurrence of fretting failures in tenon joints, it is necessary to identify the factors that influence fretting fatigue life. Compared to traditional mechanical property testing techniques, DIC (Digital Image Correlation) is a novel testing method that enables real-time measurement of material strain during testing, allowing the correlation of macroscopic mechanical behavior with microscopic damage mechanisms. Furthermore, aircraft engine turbine blades are exposed to high temperatures in actual operation, and the impact of creep and oxidation on the blade tenon joints also requires analysis. To rationally evaluate the fretting fatigue performance of tenon joints, researchers have conducted tests to analyze the fretting fatigue performance of turbine blade materials. Existing fretting fatigue testing systems suffer from complex structures, high production costs, and inconvenience. In summary, existing fretting fatigue testing methods are divided into material-level and structural simulator testing methods. Material-level simulations are often oversimplified and can only be used for qualitative studies. These simulations often differ from actual component fatigue damage results and fail to simulate real-world operating conditions. Direct testing using structural simulators, however, is costly due to the complex specimen structure. In addition, high-temperature test chambers are often in a black box state, and the fatigue damage behavior of materials cannot be captured in real time during the test.

[0004] Therefore, how to design a high-temperature fretting fatigue test device to monitor the plastic deformation and fatigue cracks in the contact area of ​​the tenon specimen in real time and provide accurate data support for the fretting fatigue damage mechanism analysis of the tenon structure is a technical problem that technical personnel in this field urgently need to solve. Utility Model Content

[0005] The purpose of this utility model is to address the defects and shortcomings in the existing technology and provide a high-temperature fretting fatigue testing device to monitor the plastic deformation and fatigue cracks in the contact area of ​​the tenon specimen in real time, providing accurate data support for the analysis of the fretting fatigue damage mechanism of the tenon structure.

[0006] In order to achieve the above purpose, the technical solution adopted by the utility model is:

[0007] The utility model provides a high-temperature micro-motion fatigue testing device, comprising an upper clamp and a lower clamp for fixing a tenon sample and applying a force to the tenon sample, and a DIC camera for observing the material deformation and crack progression of the tenon sample, wherein the interior of the upper clamp is provided with a micro-motion pad for supporting the tenon sample, the exterior of the upper clamp is provided with an electromagnetic induction coil, the electromagnetic induction coil is located in the contact area between the tenon sample and the micro-motion pad, and an observation window is provided between two adjacent turns of the electromagnetic induction coil, and the DIC camera faces the observation window and is at the same height as the observation window.

[0008] Preferably, a first mounting groove is provided inside the upper clamp, and the first mounting groove passes through the front surface and / or rear surface of the upper clamp. A second mounting groove is provided inside the lower clamp, and the second mounting groove passes through the top surface of the lower clamp. The first mounting groove passes through the bottom surface of the upper clamp, and the second mounting groove is connected to the first mounting groove to form a placement space for the tenon sample.

[0009] Preferably, the tenon sample is installed in the placement space in a detachable manner.

[0010] Preferably, the lower edge of the upper clamp is provided with a skirt for connecting the left and right halves of the upper clamp, a through groove is provided between the skirt and the front surface and / or rear surface of the upper clamp, the through groove is connected to the second mounting groove, and an installation space is provided between the portion of the front surface and / or rear surface of the upper clamp where the skirt is not provided and the top surface of the skirt, the installation space is respectively connected to the first mounting groove and the through groove, and the projection of the installation space on the front and rear surfaces of the upper clamp is not less than the size of the first mounting groove.

[0011] Preferably, a pad installation groove is provided on the first installation groove, and the micro-motion pad is detachably installed in the pad installation groove.

[0012] Preferably, the micro-motion pads are provided on both the left and right sides of the first mounting slot, and the tenon portion of the tenon specimen is hung on the micro-motion pads;

[0013] The lower clamp is connected to the rest of the tenon sample except the tenon part through a positioning pin; the front and rear sides of the lower clamp are provided with threaded holes connected to the second mounting groove, and a limiting bolt is provided in each of the threaded holes, and the end of the limiting bolt abuts against the tenon sample to limit the setting position of the tenon sample in the lower clamp.

[0014] Preferably, it also includes an upper bearing seat, a lower bearing seat, an upper joint bearing and a lower joint bearing, the upper bearing seat and the lower bearing seat are respectively connected to the fatigue testing machine, the upper fixture is connected to the upper bearing seat through the upper joint bearing, and the lower fixture is connected to the lower bearing seat through the lower joint bearing.

[0015] Preferably, the electromagnetic induction coil is a coil that is not easily deformed, an end of the electromagnetic induction coil extends out of the upper fixture and is connected to a fixed-position heating device, and the electromagnetic induction coil and the upper fixture conduct heat non-contactly.

[0016] Preferably, the heating device is provided with an infrared temperature sensor, and the infrared temperature sensor and the heating device are connected to form negative feedback.

[0017] Preferably, the heating device is placed on a supporting mechanism, which includes a supporting platform, a supporting column and a clamp. The supporting column and the clamp are respectively fixedly connected to the supporting platform. The clamp is mounted on the pillar of the fatigue testing machine and can slide up and down along the pillar of the fatigue testing machine.

[0018] Compared with the prior art, the utility model has achieved the following technical effects:

[0019] 1. The utility model sets an electromagnetic induction coil at the contact area between the tenon specimen and the micro-motion pad, and sets an observation window between two adjacent turns of the electromagnetic induction coil. The DIC camera faces the observation window and is at the same height as the observation window, so that the DIC camera can observe the material deformation and crack initiation progress of the tenon specimen in real time through the observation window. The observed results are closer to the actual service conditions of the engine blade tenon structure and the stress field distribution in the actual working environment, providing accurate data support for the analysis of the micro-motion fatigue damage mechanism of the tenon structure.

[0020] Other technical solutions of the utility model have achieved the following technical effects compared with the prior art:

[0021] 2. The micro-motion plane accuracy of the test specimen is crucial for post-experimental observation and characterization. Conventional methods are prone to uneven loading and misalignment due to fatigue loading, making it impossible to effectively control the shape and position of the wear marks on the tenon specimen. The utility model uses a spherical bearing with a high degree of freedom to be set between the bearing seat and the fixture to achieve self-centering of the tenon specimen, avoiding errors and deflection torque caused by over-positioning of the fixture or asymmetric or misaligned specimen clamping, thereby improving the shape control accuracy of the friction surface in the contact area. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 Schematic diagram of the overall structure of a high-temperature fretting fatigue testing device disclosed in a specific embodiment of the present invention;

[0024] Figure 2 This is a structural schematic diagram of a tenon specimen fixture module in a high-temperature fretting fatigue testing device disclosed in a specific embodiment of the present invention;

[0025] Figure 3 It is a schematic cross-sectional structural diagram of a tenon specimen fixture module in a high-temperature fretting fatigue testing device disclosed in a specific embodiment of the present invention;

[0026] Figure 4 A schematic diagram of the working state of a high-temperature fretting fatigue testing device disclosed in a specific embodiment of the present invention;

[0027] Figures 5 and 6 This is a schematic diagram of the enlarged structure of the fitting between the fixture and the tenon specimen in a high-temperature fretting fatigue testing device disclosed in a specific embodiment of the present invention.

[0028] Among them, 1. Upper bearing seat; 2. Locating pin; 3. Upper joint bearing; 4. Upper fixture; 5. Tenon specimen; 6. Clamp; 7. Electromagnetic induction coil; 8. Limit bolt; 9. Lower fixture; 10. Lower joint bearing; 11. Lower bearing seat; 12. Support column; 13. Support platform; 14. Heating equipment; 15. Infrared temperature sensor; 16. First mounting slot; 17. Skirt; 18. Through slot; 19. Second mounting slot; 20. Micro-motion pad; 21. Fatigue testing machine; 22. DIC camera; 23. Bracket. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0030] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0031] like Figures 1 to 6 As shown, the present invention provides a high-temperature fretting fatigue testing apparatus comprising an upper fixture 4 and a lower fixture 9 for securing and applying force to a tenon specimen 5, and a DIC camera 22 for observing material deformation and crack progression in the tenon specimen 5. The upper fixture 4 is internally provided with a fretting pad 20 for supporting the tenon specimen 5. An electromagnetic induction coil 7 is externally sheathed on the upper fixture 4. The electromagnetic induction coil 7 is located in the contact area between the tenon specimen 5 and the fretting pad 20, and an observation window is provided between two adjacent turns of the electromagnetic induction coil 7. The DIC camera 22 faces the observation window and is positioned at the same height as the observation window. During operation, the tenon specimen 5 is sprayed with a speckle pattern and mounted within the upper fixture 4 and lower fixture 9. The DIC camera 22 is adjusted to be at the same height as the observation window and activated, allowing the DIC camera 22 to observe the material deformation and crack initiation progression of the tenon specimen 5 in real time through the observation window. In one embodiment, the two turns of the coil near the contact area between the tenon sample 5 and the fine-motion pad 20 are spaced one centimeter apart in the vertical direction to form an observation window. The DIC camera 22 is mounted on a bracket 23, and the bracket 23 can be adjusted so that the DIC camera 22 faces the observation window and is at the same height as the observation window. Figure 5 This is a schematic diagram of the structure; Figure 6 It is a side view structural diagram.

[0032] The tenon specimen 5 consists of a tenon portion and a remaining portion. The tenon portion is T-shaped, and the remaining portion is rod-shaped or columnar. The upper fixture 4 is internally provided with a first mounting slot 16 for mounting the tenon portion. The first mounting slot 16 extends through the front and / or rear surfaces of the upper fixture 4. The lower fixture 9 is internally provided with a second mounting slot 19. The second mounting slot 19 extends through the top surface of the lower fixture 9. The first mounting slot 16 extends through the bottom surface of the upper fixture 4. The second mounting slot 19 communicates with the first mounting slot 16 to form a placement space for the tenon specimen 5. The tenon specimen 5 is removably mounted within the placement space, allowing for easy replacement of the specimen 5 after testing and repeating the experiment.

[0033] Since the contact area between the tenon specimen 5 and the micro-motion pad 20 is located inside the upper fixture 4, and the first mounting groove 16 penetrates the bottom surface, front surface and / or rear surface of the upper fixture 4, dividing the bottom portion of the upper fixture 4 into left and right parts, when tensile stress is applied to the tenon specimen 5, the left and right parts tend to deform outward and separate from each other, affecting the mechanical properties and service life of the upper fixture 4. For this reason, in one embodiment, the lower edge of the upper fixture 4 is provided with a skirt 17 for connecting the left and right halves of the upper fixture 4, a through groove 18 is provided between the skirt 17 and the front surface and / or rear surface of the upper fixture 4, and the through groove 18 is connected to the second mounting groove 19, and an installation space is provided between the portion of the front surface and / or rear surface of the upper fixture 4 where the skirt 17 is not provided and the top surface of the skirt 17, and the installation space is respectively connected to the first mounting groove 16 and the through groove 18, and the projection of the installation space on the front and rear surfaces of the upper fixture 4 is not less than the size of the first mounting groove 16. By providing the skirt 17, the overall stress condition of the upper clamp 4 can be greatly optimized, the deformation stiffness of the upper clamp 4 can be increased, and the mechanical properties and service life of the upper clamp 4 can be improved. When in use, first install the remaining part of the tenon sample 5 into the second installation groove 19, and the tenon part passes through the through groove 18 and is placed in the installation space. Move the tenon sample 5 back and forth so that the tenon part passes through the first installation groove 16 and is hung on the micro-motion pad 20, thereby completing the installation of the tenon sample 5. In one embodiment, the material of the upper clamp 4 is W18Cr4V tungsten high-speed steel, which can still maintain a fatigue strength of 500MPa at a high temperature of 500°C. The lowermost side of the upper clamp 4 is surrounded by an 8mm thick skirt 17, and the remaining parts are made of 316L stainless steel.

[0034] A pad mounting groove is also provided on the first mounting groove 16, and a micro-motion pad 20 is detachably mounted in the pad mounting groove. Specifically, the micro-motion pad 20 is clearance-matched with the pad mounting groove, with a deviation of 0.01 mm. The micro-motion pad 20 can move back and forth along the pad mounting groove, and the width of the micro-motion pad 20 is set to be at least 2 mm larger than the thickness of the tenon portion of the tenon sample 5, ensuring that the tenon portion of the tenon sample 5 is in complete contact with the micro-motion pad 20. After the test, the micro-motion pad 20 and the tenon sample 5 are replaced so that the contact conditions of the micro-motion pad 20 and the tenon sample 5 are the same during each experiment, thereby ensuring that the test conditions are consistent during multiple tests, improving the accuracy of the test results, and compared with replacing the upper fixture 4, replacing the micro-motion pad 20 can greatly reduce the test cost.

[0035] Micro-motion pads 20 are provided on the left and right sides of the first mounting groove 16, and the tenon part of the tenon sample 5 is hung on the micro-motion pads 20; the lower clamp 9 is connected to the rest of the tenon sample 5 through the positioning pin 2; and the front and rear sides of the lower clamp 9 are provided with threaded holes connected to the second mounting groove 19, and a limiting bolt 8 is provided in each threaded hole. The limiting bolt 8 passes through the threaded hole and abuts against the tenon sample 5. When in use, the limiting bolts 8 on both sides are screwed in the same number of turns and the end of the limiting bolt 8 abuts against the tenon sample 5, so that the tenon sample 5 is adjusted and fixed to the middle position of the clamp.

[0036] The high-temperature micro-motion fatigue testing device provided by the present invention also includes an upper bearing seat 1, a lower bearing seat 11, an upper spherical bearing 3 and a lower spherical bearing 10. The upper bearing seat 1 and the lower bearing seat 11 are respectively connected to the fatigue testing machine 21. The upper fixture 4 is connected to the upper bearing seat 1 through the upper spherical bearing 3, and the lower fixture 9 is connected to the lower bearing seat 11 through the lower spherical bearing 10. In one embodiment, the upper bearing seat 1 and the lower bearing seat 11 both include a fixedly connected cylindrical rod and a U-shaped seat. The cylindrical rod is connected to the V-block in the chuck of the fatigue testing machine 21. The U-shaped seat is connected to the spherical bearing through a locating pin 2. The other end of the spherical bearing is threadedly connected to the upper fixture 4 and the lower fixture 9. The upper bearing seat 1 and the lower bearing seat 11 both have the function of hindering temperature transfer, so as to reduce the heat transfer of the heating device 14 and protect the fatigue testing machine 21.

[0037] Furthermore, the electromagnetic induction coil 7 is a coil that is not easily deformed. The end of the electromagnetic induction coil 7 extends out of the upper clamp 4 and is connected to the fixed heating device 14. The electromagnetic induction coil 7 and the upper clamp 4 conduct heat non-contactly. Specifically, a safety distance of 1 cm is left between the electromagnetic induction coil 7 and the upper clamp 4. The heating device 14 is provided with an infrared temperature sensor 15. The infrared temperature sensor 15 and the heating device 14 are connected to form negative feedback, that is, the infrared temperature sensor 15 on the heating device 14 controls the start and stop of the heating device 14, and controls the temperature of the tenon sample 5 at the required test temperature (about 500°C), realizing PID negative feedback control of the temperature, ensuring the constant temperature condition in the electromagnetic induction coil 7, and having a simple structure and low cost. In one embodiment, the electromagnetic induction coil 7 and the heating device 14 are detachably connected, and a safety distance of 20 cm is provided between the upper clamp 4 and the heating device 14 to ensure the safety of the entire experiment. The heating device 14 is a high-frequency electromagnetic induction heating device 14.

[0038] The heating device 14 is placed on a support mechanism, which includes a support platform 13, a support column 12, and a clamp 6 for adjusting the height of the support platform 13. The support column 12 is fixed to the bottom of the support platform 13, and the clamp 6 is fixed to both sides of the support platform 13. The clamp 6 can move up and down relative to the support column of the fatigue testing machine 21. Specifically, the clamp 6 is an annular structure that is mounted on the support column of the fatigue testing machine 21. The end of the annular structure is provided with a lug, and the lug is provided with a threaded hole. A threaded connector passes through the threaded hole to lock the annular structure. When the height needs to be adjusted, the threaded connector is loosened to allow the clamp 6 to move up and down relative to the support column. When it moves to the appropriate position, the threaded connector is tightened to secure the clamp 6 to the support column.

[0039] Working Principle: Tenon specimen 5 and micro-motion pad 20, adjusted in position and preloaded with 100N, are placed in the test chamber. Heating device 14 is then turned on and adjusted to the desired test temperature. After maintaining the preset temperature for ten minutes, the servo cylinder of fatigue testing machine 21 is activated. The servo cylinder applies a tensile fatigue load to tenon specimen 5 via the lower spherical plain bearing 10. A DIC camera 22 observes the strain field distribution and crack initiation progress in real time in the contact area through an observation window.

[0040] It should be noted that it is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, from all perspectives, the embodiments should be regarded as illustrative and non-restrictive, and the scope of the present invention is defined by the appended claims rather than the above description. Therefore, it is intended that all changes that fall within the meaning and range of equivalents of the claims be included in the present invention, and any reference signs in the claims should not be regarded as limiting the claims involved.

Claims

1. A high-temperature fretting fatigue test device, characterized by: The invention comprises an upper clamp and a lower clamp for fixing the tenon sample and applying force to the tenon sample, and a DIC camera for observing the material deformation and crack progression of the tenon sample. The interior of the upper clamp is provided with a micro-motion pad for supporting the tenon sample. The exterior of the upper clamp is provided with an electromagnetic induction coil, which is located in the contact area between the tenon sample and the micro-motion pad. An observation window is provided between two adjacent turns of the electromagnetic induction coil. The DIC camera faces the observation window and is at the same height as the observation window.

2. The high-temperature fretting fatigue testing device according to claim 1, characterized in that: A first mounting groove is provided inside the upper clamp, and the first mounting groove passes through the front surface and / or rear surface of the upper clamp. A second mounting groove is provided inside the lower clamp, and the second mounting groove passes through the top surface of the lower clamp. The first mounting groove passes through the bottom surface of the upper clamp, and the second mounting groove is connected to the first mounting groove to form a placement space for the tenon sample.

3. The high-temperature fretting fatigue testing device according to claim 2, characterized in that: The tenon sample is installed in the placement space in a detachable manner.

4. The high-temperature fretting fatigue testing device according to claim 3, characterized in that: The lower edge of the upper clamp is provided with a skirt for connecting the left and right halves of the upper clamp, a through groove is provided between the skirt and the front surface and / or rear surface of the upper clamp, the through groove is connected to the second mounting groove, and an installation space is provided between the portion of the front surface and / or rear surface of the upper clamp where the skirt is not provided and the top surface of the skirt, the installation space is respectively connected to the first mounting groove and the through groove, and the projection of the installation space on the front and rear surfaces of the upper clamp is not less than the size of the first mounting groove.

5. The high temperature fretting fatigue testing device according to claim 2, characterized in that: A pad installation groove is provided on the first installation groove, and the micro-motion pad is detachably installed in the pad installation groove.

6. The high temperature fretting fatigue testing device according to claim 5, characterized in that: The micro-motion pads are provided on both the left and right sides of the first mounting slot, and the tenon portion of the tenon specimen is hung on the micro-motion pads; The lower clamp is connected to the rest of the tenon sample except the tenon part through a positioning pin; the front and rear sides of the lower clamp are provided with threaded holes connected to the second mounting groove, and a limiting bolt is provided in each of the threaded holes, and the end of the limiting bolt abuts against the tenon sample to limit the setting position of the tenon sample in the lower clamp.

7. The high temperature fretting fatigue testing device according to any one of claims 1 to 6, characterized in that: It also includes an upper bearing seat, a lower bearing seat, an upper joint bearing and a lower joint bearing. The upper bearing seat and the lower bearing seat are respectively connected to the fatigue testing machine. The upper fixture is connected to the upper bearing seat through the upper joint bearing, and the lower fixture is connected to the lower bearing seat through the lower joint bearing.

8. The high temperature fretting fatigue testing device according to claim 1, characterized in that: The electromagnetic induction coil is a coil that is not easily deformed. The end of the electromagnetic induction coil extends out of the upper fixture and is connected to a fixed heating device, and the electromagnetic induction coil and the upper fixture conduct heat in a non-contact manner.

9. The high-temperature fretting fatigue testing device according to claim 8, characterized in that: The heating device is provided with an infrared temperature sensor, and the infrared temperature sensor and the heating device are connected to form a negative feedback.

10. The high temperature fretting fatigue testing device according to claim 8, characterized in that: The heating device is placed on a supporting mechanism, which includes a supporting platform, a supporting column and a clamp. The supporting column and the clamp are respectively fixedly connected to the supporting platform. The clamp is sleeved on the pillar of the fatigue testing machine and can slide up and down along the pillar of the fatigue testing machine.

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