A fretting fatigue life test device and method under high temperature and high frequency vibration conditions considering surface integrity

Abstract

The present invention provides a fretting fatigue life test device and method under high-temperature and high-frequency vibration conditions considering surface integrity, belonging to the technical field of fretting fatigue tests, and comprising an axial load loading device, a vibrator tooling and a high-temperature component. The present invention simulates thermal load through the high-temperature component, simulates axial centrifugal force through the axial load loading device, simulates normal centrifugal force, pneumatic load and high-frequency vibration through the vibrator tooling, obtains specimens with different surface integrity by changing processing parameters, and respectively changes surface topography features, residual stress distribution and microhardness to conduct fretting fatigue tests. The present invention can approximately simulate the stress condition of a tenon groove and tenon head under the actual working environment, and can conduct fretting fatigue tests on a simulated part of the tenon groove and tenon head structure in cooperation with a conventional uniaxial fatigue testing machine; it can fully consider the differences in surface integrity parameters and effectively carry out fretting fatigue tests on fatigue specimens.

Description

Technical Field

[0001] The present invention belongs to the technical field of fretting fatigue test, and relates to a fretting fatigue life test device and method under high temperature and high frequency vibration conditions considering surface integrity. Background Technique

[0002] During the operation of an aeroengine, the dovetail connection structure of the turbine disk is subjected to the combined action of centrifugal force, thermal load, aerodynamic load and vibration load. In the full-disk tests of multiple engine models, fretting fatigue failure occurs in the dovetail connection structure. The main reason is that the dovetail groove and dovetail contact area bear multiaxial alternating stress, resulting in cyclic plastic deformation of surface asperities at macro and micro scales, which in turn triggers crack initiation and crack propagation, reducing the fatigue performance of the dovetail connection structure.

[0003] In a new generation of aeroengines, the thermal load of the turbine disk exceeds 600 °C and the vibration frequency reaches above 2500 Hz. The high temperature load will accelerate the creep deformation and fretting wear of the dovetail groove and dovetail. The high frequency vibration will accelerate the cumulative rate of plastic deformation of surface asperities on the contact surface of the dovetail groove and dovetail, thereby accelerating the crack initiation and propagation on the contact surface. In addition, the surface integrity parameters of the contact surface of the dovetail connection structure have a significant impact on the fretting fatigue life: the change of surface topography will affect the oxidation rate and crack propagation path of the contact surface; the increase of surface hardness can effectively reduce wear and alleviate the initiation and propagation of cracks; surface residual tensile stress accelerates crack propagation, and surface residual compressive stress reduces the crack propagation rate.

[0004] To simulate the actual contact conditions of the dovetail groove and dovetail contact surface, a scaled-down form is usually adopted, but the size effect results in an unrealistic simulation and complex processing. In recent years, it has been found that the processing quality of the contact surface, especially surface integrity, has a significant impact on fretting fatigue. For this reason, a multi-axial fretting fatigue test device based on a flat fatigue specimen 31 is designed, which is of great significance for simulating high temperature and high frequency vibration conditions and studying the influence of surface integrity on fretting fatigue and the establishment and verification of life prediction models.

[0005] At present, there are already some related patented technologies for the fretting fatigue of the tenon joint parts of turbine blades, but there are still certain limitations. For the "High and low cycle composite fretting fatigue test device and method for the tenon joint part of turbine blades" disclosed in the Chinese invention patent application No. CN202310849957.2, the above technology conducts tests through a scaled-down specimen of the turbine mortise and tenon. However, due to the limitations of the structural characteristics of the scaled-down specimen, it is difficult to machine a contact surface with specific surface integrity parameters, and thus it is impossible to systematically study the influence law of surface integrity on fretting fatigue damage. For the "A fretting fatigue test method and device" disclosed in the Chinese invention patent application No. CN202210462522.8, the above technology adopts the design of a fretting pad and a flat specimen, but its test conditions cannot simulate the coupling effect of high-frequency vibration and thermal load. For the "A method and system for predicting the fatigue life of superalloys based on surface integrity" disclosed in the Chinese invention patent application No. CN 202210030260.8, the fatigue test method considering surface integrity proposed above is only applicable to conventional fatigue experiments and is difficult to meet the requirements of fretting fatigue life assessment. Summary of the Invention

[0006] In order to overcome the deficiencies of the prior art, the present invention provides a fretting fatigue life test device and method under high temperature and high-frequency vibration conditions considering surface integrity, which can fully consider the differences in surface integrity parameters, effectively carry out the fretting fatigue test of fatigue specimens, and serve and support the establishment of a fretting fatigue life prediction model considering surface integrity parameters.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] A fretting fatigue life test device under high temperature and high-frequency vibration conditions considering surface integrity, the fretting fatigue life test device includes the following parts: an axial load loading device 1, a vibrator tooling 2, and a high-temperature component 3. The axial load loading device 1 is used to simulate axial centrifugal force, the vibrator tooling 2 is used to simulate normal centrifugal force, pneumatic load, and high-frequency vibration, and the high-temperature component 3 is used to simulate thermal load. The vibrator tooling 2 is fixed on the support column 12 of the axial load loading device 1 by means of a connecting ear and a bolt through a tooling platform 14; the high-temperature component 3 is fixed on the support column 12 by means of a pin 5 and a connecting ear 6. After removing the glass window of the high-temperature furnace 4 in the high-temperature component 3, the fatigue specimen 31, the fretting pad 21, the movable fixture 20, and the fixed fixture 33 on the vibrator tooling 2 are connected to the high-temperature pull rod 10 in the axial load loading device 1 by means of pin connection and placed in the high-temperature furnace 4. Specifically as follows:

[0009] The axial load loading device 1 includes a cross beam 11, a hydraulic cylinder 7, a support column 12, a wedge block 9, a high-temperature tie rod 10, a fatigue specimen 31, and a hydraulic fixture 8. The hydraulic fixture 8 is connected to the hydraulic cylinder 7 by means of threaded connection. The wedge block 9 is installed in the hydraulic fixture 8 in a clearance fit manner. The high-temperature tie rod 10 is installed in the wedge block 9 and achieves a fastening fit through the pressure provided by the hydraulic cylinder 7. The movement of the piston rod of the hydraulic cylinder 7 provides tensile force for the high-temperature tie rod 10 to simulate axial centrifugal force and achieve axial loading.

[0010] The high-temperature component 3 includes a high-temperature furnace 4, a connecting ear 6, and a pin 5. The high-temperature furnace 4 is in interference fit with the support column 12 of the axial load loading device 1 through the connecting ear 6, ensuring the stability of the high-temperature furnace 4 during the test. During the installation process, the observation window of the high-temperature furnace 4 is kept parallel to the end face of the cross beam 11 to ensure the parallelism of the fatigue specimen 31 and the fretting pad 21, so as to achieve reliable fretting displacement.

[0011] The excitation tooling 2 includes an exciter 13, an excitation rod 15, a pressure sensor 26, a movable fixture 20, a fixed fixture 33, a slide rail slider 16, a slide rail lead screw 18, a slide rail base 19, a tooling platform 14, a vibration loading block 17, a micro-motion pad 21, a thermocouple 22, a micro hydraulic cylinder 23, a right support seat 24, a force transmission lead screw 25, a cooling system 27, a normal load loading block 28, a force transmission guide rail 29, a left support seat 30, a fatigue specimen 31, and a fixture lead screw 32. Specifically: The excitation rod 15 is fixed to the exciter 13 by a threaded method, and the exciter 13 is installed on the tooling platform 14 by bolts; The slide rail slider 16 is installed on the slide rail base 19 by the slide rail lead screw 18, the vibration loading block 17 is fixed to the slide rail slider 16 by bolts, the micro hydraulic cylinder 23 is installed on the slide rail base 19 by bolts, and the piston rod of the micro hydraulic cylinder 23 pushes the vibration loading block 17 to apply a normal load, where the normal load includes an aerodynamic load and a normal centrifugal force, and at the same time the excitation rod 15 drives the vibration loading block 17 to generate high-frequency vibration; On the left side of the left support seat 30, the fixture lead screw 32 is threadedly connected to the fixed fixture 33 and maintains a fixed distance, and the movable fixture 20 is installed on the fixture lead screw 32 and is located between the fixed fixture 33 and the left support seat 30; The micro-motion pads 21 are respectively placed at the clamping positions of the movable fixture 20 and the fixed fixture 33, located between the movable fixture 20 and the fixed fixture 33, and the fatigue specimen 31 is placed between the two micro-motion pads 21; The upper end of the fixed fixture 33, the upper end of the fatigue specimen 31, and the upper high-temperature pull rod 10 are connected in the part order by pins, and the lower end of the fatigue specimen 31 is also connected to the lower high-temperature pull rod 10 by a pin. After installation, the upper and lower high-temperature pull rods 10 and the movable fixture 20 are adjusted to ensure the parallelism between the movable fixture 20 and the fatigue specimen 31; The left support seat 30 is threadedly connected to the right support seat 24 through the force transmission guide rail 29. The force transmission lead screw 25, the normal load loading block 28, the cooling system 27, the pressure sensor 26, and the vibration loading block 17 are placed between the left support seat 30 and the right support seat 24. The force transmission lead screw 25 connects the normal load loading block 28 and the vibration loading block 17 to slide on the force transmission guide rail 29, and the pressure sensor 26 is installed between the normal load loading block 28 and the vibration loading block 17; The cooling system 27 is installed between the observation window of the high-temperature furnace 4 and the pressure sensor 26 to isolate heat and protect the safety of the test equipment and the test personnel. The thermocouple 22 is bonded to the fatigue specimen 31 in the high-temperature furnace 4 by high-temperature glue to measure the experimental temperature of the fatigue specimen 31. The cooling system 27 is a water-cooling system.

[0012] A fretting fatigue life test method under high temperature and high-frequency vibration conditions considering surface integrity. This fretting fatigue life test method is realized based on the above-mentioned fretting fatigue life test device. Specifically: First, fatigue specimens 31 with different surface integrity parameters are prepared by controlling different processing parameters. Second, a white light interferometer, X-ray diffraction method, small hole method residual stress detection method, and nano-indentation are used to measure key parameters such as the three-dimensional topography characteristics, residual stress distribution, and microhardness of the specimen surface before the test. Third, under high temperature and high-frequency vibration conditions, the test cycle gradient is set according to the logarithmic distribution law to carry out the fretting fatigue test. Fourth, after the test is completed, each surface integrity parameter of the specimen surface after the test is measured again, and the evolution law of the parameters with the fretting cycle is obtained through comparative analysis. It specifically includes the following steps:

[0013] Step 1: Prepare fatigue specimens 31 and fretting pads 21 with different surface integrity parameters under different processing parameters to prepare for subsequent fretting fatigue tests.

[0014] Step 2: Measure the surface topography characteristics, residual stress distribution, and microhardness of the surface of the fatigue specimen 31 before the test through a white light interferometer, X-ray diffraction method, small hole method residual stress detection method, and nano-indentation respectively.

[0015] Step 3: During the application of the axial load, the high-temperature tie rod 10 is rigidly connected to the fatigue specimen 31 through the pin 5, and the hydraulic clamp 8 of the axial load loading device 1 accurately transmits the set load to the high-temperature tie rod 10, so as to apply an axial centrifugal force load on the fatigue specimen 31.

[0016] Step 4: During the application of the normal load and the vibration load, the micro hydraulic cylinder 23 provides a normal load for the fretting pad 21 and the fatigue specimen 31 to form a pre-tightening force. The vibration loading block 17 and the normal load loading block 28 transmit the pre-tightening force and vibration to the movable fixture 20 through the force transmission guide rail 29 and finally act on the fretting pad 21 and the fatigue specimen 31; at the same time, the exciter 13 transmits high-frequency vibration through the force transmission lead screw 25 to realize the composite loading of the normal load and high-frequency vibration; the fretting pad 21 and the fatigue specimen 31 are tightly fitted through the movable fixture 20 and the fixed fixture 33. However, during the test, the fatigue specimen 31 will deform, resulting in a small gap between the mating surfaces, which will cause the pre-tightening force to decay. Therefore, the micro hydraulic cylinder 23 is designed to monitor and compensate the pre-tightening force in real time through a closed-loop control system to maintain the constancy of the normal load.

[0017] Step 5: The thermal load is applied through the high-temperature furnace 4 to provide a stable and controllable temperature environment for the fretting fatigue test. Inside the high-temperature furnace 4, there are arranged a fretting pad 21, a movable fixture 20, a fixed fixture 33, a thermocouple 22, a force transmission lead screw 25, a normal load loading block 28, a force transmission guide rail 29, a left support seat 30, a fatigue specimen 31, and a fixture lead screw 32.

[0018] Step 6: Considering the long test period, set the test period gradient according to the logarithmic distribution law; within each period gradient, conduct fretting fatigue tests on the fatigue specimens 31 with the same surface integrity parameters under high temperature and high-frequency vibration conditions.

[0019] Step 7: Use a white light interferometer, X-ray diffraction method, small hole method residual stress detection method, and nanoindentation technology to measure the surface integrity parameters of different fatigue specimens 31 after the test; according to the test period gradient, analyze the variation laws of surface topography characteristics, residual stress distribution, and microhardness, and further reveal the differential effects of different surface integrity states on fatigue damage behavior.

[0020] The beneficial effects of the present invention are as follows:

[0021] (1) Through the closed-loop feedback control system of the micro hydraulic cylinder and the pressure sensor, the present invention dynamically compensates the normal load loss caused by fretting wear in real time, realizing the constant loading of the normal load at the fretting contact interface.

[0022] (2) The present invention uses a vibrator tooling to accurately simulate a high-frequency vibration load of 2500 Hz, breaking through the limitation of the frequency response range of traditional test equipment;

[0023] (3) By designing fretting fatigue tests with different fretting periods, the present invention can systematically study the dynamic evolution laws of surface integrity parameters such as surface roughness and residual stress during the fretting fatigue process, and further reveal the influence laws of surface integrity parameters on the fretting fatigue damage mechanism. Description of the Drawings

[0024] Figure 1 is the overall view of the fretting fatigue life test device of the present invention.

[0025] Figure 2 is the schematic diagram of the high-temperature component providing thermal load in the present invention patent.

[0026] Figure 3 is the schematic diagram of the axial load loading device providing axial centrifugal force in the present invention patent.

[0027] Figure 4 is the schematic diagram of a vibrator tooling platform provided in the present invention patent.

[0028] Figure 5 is the flow chart of the fretting fatigue life test method of the present invention.

[0029] In the figure: 1 Axial load loading device; 2 Vibration exciter tooling; 3 High-temperature component; 4 High-temperature furnace; 5 Plug pin; 6 Connecting ear; 7 Hydraulic cylinder; 8 Hydraulic fixture; 9 Wedge block; 10 High-temperature tie rod; 11 Cross beam; 12 Support column; 13 Vibration exciter; 14 Tooling platform; 15 Vibration rod; 16 Slide rail slider; 17 Vibration loading block; 18 Slide rail lead screw; 19 Slide rail base; 20 Movable fixture; 21 Micro-motion pad; 22 Thermocouple; 23 Micro hydraulic cylinder; 24 Right support seat; 25 Force transmission lead screw; 26 Pressure sensor; 27 Cooling system; 28 Normal load loading block; 29 Force transmission guide rail; 30 Left support seat; 31 Fatigue specimen; 32 Fixture lead screw; 33 Fixed fixture. Detailed implementation manners

[0030] Next, in combination with the design concept of the present invention, the technical solutions in the design process of the present invention will be clearly and completely described.

[0031] A fretting fatigue life test device under high temperature and high-frequency vibration conditions considering surface integrity, the fretting fatigue life test device includes the following parts: an axial load loading device 1, a vibration exciter tooling 2, and a high-temperature component 3. The axial load loading device 1 is used to simulate axial centrifugal force, the vibration exciter tooling 2 is used to simulate normal centrifugal force, pneumatic load, and high-frequency vibration, and the high-temperature component 3 is used to simulate thermal load. The vibration exciter tooling 2 is fixed on the support column 12 in the way of connecting ear and bolt through the tooling platform 14, and the high-temperature component 3 is fixed on the support column 12 of the axial load loading device 1 through the plug pin 5 and the connecting ear 6. The glass window of the high-temperature furnace 4 in the high-temperature component 3 is removed, and the fatigue specimen 31, the micro-motion pad 21, the movable fixture 20, and the fixed fixture 33 on the vibration exciter tooling 2 are connected to the high-temperature tie rod 10 in the axial load loading device 1 by plug pin connection and placed in the high-temperature furnace 4.

[0032] Refer to Figure 3 As shown, the axial load loading device 1 includes a cross beam 11, a hydraulic cylinder 7, a support column 12, a wedge block 9, a high-temperature tie rod 10, a fatigue specimen 31, and a hydraulic fixture 8. The hydraulic fixture 8 is connected to the hydraulic cylinder 7 by threaded connection. The wedge block 9 is installed in the hydraulic fixture 8 with clearance fit. The high-temperature tie rod 10 is placed in the wedge block 9 and is tightly fitted by the pressure provided by the hydraulic cylinder 7. In the axial loading process, the movement of the piston rod of the hydraulic cylinder 7 provides tensile force for the high-temperature tie rod 10 to simulate axial centrifugal force, and the movement frequency of the piston rod can be changed to make the frequency of the axial centrifugal force controllable, so as to control the fretting frequency in the fretting fatigue process.

[0033] Refer to Figure 2As shown, the high-temperature component 3 includes a high-temperature furnace 4, connecting lugs 6, and pins 5. The high-temperature furnace 4 is in interference fit with the support column 12 of the axial load loading device 1 through the connecting lugs 6, ensuring the stability and detachability of the high-temperature furnace 4 during the test. During the installation process, the observation window of the high-temperature furnace 4 is kept parallel to the end face of the cross beam 11 to ensure the parallelism of the fatigue specimen 31 and the fretting pad 21, so as to achieve reliable fretting displacement. The high-temperature furnace can simulate thermal loads below 1200 °C at most. The thermocouple 22 is bonded to the fatigue specimen 31 in the high-temperature furnace 4 with high-temperature glue to measure the experimental temperature of the fatigue specimen 31.

[0034] Reference Figure 4 As shown, the installation process of the fatigue specimen 31 and the fretting pad 21 is as follows: The excitation rod 15 is connected to the exciter 13 in a threaded manner, and the exciter 13 is installed on the tooling platform 14 by bolts; The slide rail slider 16 is installed on the slide rail base 19 through the slide rail lead screw 18, the vibration loading block 17 is installed on the slide rail slider 16 by bolts, the micro hydraulic cylinder 23 is installed on the slide rail base 19 by bolts, and the piston rod of the micro hydraulic cylinder 23 pushes the vibration loading block 17 to apply a normal load, and the excitation rod 15 drives the vibration loading block 17 to apply high-frequency vibration; The left support seat 30 is connected to the fixed fixture 33 in a threaded manner through the fixture lead screw 32 on the left side to fix the distance between the two. The movable fixture 20 is placed on the fixture lead screw, and its position is between the fixed fixture 33 and the left support seat 30. The fretting pads 21 are respectively placed at the clamping positions of the movable fixture 20 and the fixed fixture 33. The positions of the two fretting pads 21 are between the movable fixture 20 and the fixed fixture 33. The fatigue specimen 31 is placed between the two fretting pads 21. The upper end of the fixed fixture 33, the upper end of the fatigue specimen 31, and the upper high-temperature pull rod 10 are connected in sequence by pins according to the order of the parts. The lower end of the fatigue specimen 31 is connected to the lower high-temperature pull rod 10 by a pin. After the installation is completed, the upper and lower high-temperature pull rods 10 and the movable fixture 20 are adjusted to ensure the parallelism of the movable fixture 20 and the fatigue specimen 31.

[0035] Reference Figure 4As shown, the installation process of the loading device for the fatigue specimen 31 and the fretting pad 21 is as follows: The left support base 30 is threadedly connected to the right support base 24 through the force transmission guide rail 29. The force transmission screw 25, the normal load loading block 28, the cooling system 27, the pressure sensor 26, and the vibration loading block 17 are arranged between the left support base 30 and the right support base 24. The force transmission screw 25 connects the normal load loading block 28 and the vibration loading block 17 and slides on the force transmission guide rail 29. The pressure sensor 26 is installed between the normal load loading block 28 and the vibration loading block 17. The micro hydraulic cylinder 23 realizes feedback control with the pressure sensor 26. The pressure range of the normal load is F±f. When the normal load is not within the range of F - f ≤ Ft ≤ F + f, the micro hydraulic cylinder 23 compensates by increasing or decreasing the force output to ensure the reliability of the normal load loading in the fretting fatigue test. Here, F is the normal load and f is the preload attenuation value.

[0036] Reference Figure 4 As shown, since the glass observation window of the high-temperature furnace 4 is removed, heat will overflow. To protect the safety of the test equipment and the testers, the cooling system 27 is bolted to the tooling platform 14, and its function is to isolate the heat overflowing from the observation window of the high-temperature furnace between the observation window of the high-temperature furnace 4 and the pressure sensor 26.

[0037] A fretting fatigue life test method under high-temperature and high-frequency vibration conditions realized based on the above-mentioned fretting fatigue life test device. The fretting fatigue life test method includes the following steps: First, prepare fatigue specimens 31 with different surface integrity parameters by controlling different processing parameters. Second, use a white light interferometer, X-ray diffraction method, small hole method residual stress detection method, and nanoindentation to measure key parameters such as the three-dimensional topography characteristics, residual stress distribution, and microhardness of the surface of the fatigue specimen 31 before the test. Third, under high-temperature and high-frequency vibration conditions, carry out the fretting fatigue test using the method of discrete fretting cycles. Fourth, after the test is completed, measure the surface integrity parameters of the surface of the fatigue specimen 31 again, and obtain the evolution law of the parameters with the fretting cycle through comparative analysis. Specifically:

[0038] Step 1: Prepare fatigue specimens 31 and fretting pads 21 with different surface integrity parameters under different processing parameters to prepare for the subsequent fretting fatigue test;

[0039] Step 2: Measure the surface topography characteristics, residual stress distribution, and microhardness of the surface of the fatigue specimen 31 before the test through a white light interferometer, X-ray diffraction method, small hole method residual stress detection method, and nanoindentation;

[0040] Step 3: During the axial load application process, the high-temperature tie rod 10 is rigidly connected to the fatigue specimen 31 through the pin 5. The hydraulic fixture 8 of the axial load loading device 1 accurately transmits the set load to the high-temperature tie rod 10, thereby applying an axial centrifugal force load to the fatigue specimen 31.

[0041] Step 4: During the normal load and vibration load application processes, the micro hydraulic cylinder 23 provides a normal load for the micro motion pad 21 and the fatigue specimen 31 to form a pre-tightening force. The vibration loading block 17 and the normal load loading block 28 conduct the pre-tightening force and vibration to the movable fixture 20 through the force transmission guide rail 29 and finally act on the micro motion pad 21 and the fatigue specimen 31; meanwhile, the vibrator 13 transmits high-frequency vibration through the force transmission lead screw 25 to achieve the combined loading of the normal load and high-frequency vibration; the micro motion pad 21 and the fatigue specimen 31 are tightly fitted through the movable fixture 20 and the fixed fixture 33. However, during the test, the fatigue specimen 31 will deform, resulting in a small gap between the mating surfaces, which will cause the attenuation of the pre-tightening force. Therefore, the micro hydraulic cylinder 23 is designed to monitor and compensate the pre-tightening force in real time through a closed-loop control system to maintain the constancy of the normal load.

[0042] Step 5: The thermal load is applied through the high-temperature furnace 4 to provide a stable and controllable temperature environment for the fretting fatigue test. Inside the high-temperature furnace 4, there are arranged the micro motion pad 21, the fatigue specimen 31, the movable fixture 20, the fixed fixture 33, the micro motion pad 21, the thermocouple 22, the force transmission lead screw 25, the normal load loading block 28, the force transmission guide rail 29, the left support seat 30, the fatigue specimen 31, and the fixture lead screw 32.

[0043] Step 6: Considering the long test cycle, the test cycle gradient is set according to the logarithmic distribution law; within each cycle gradient, the fretting fatigue test under high-temperature and high-frequency vibration conditions is carried out on the fatigue specimens 31 with the same surface integrity parameters.

[0044] Step 7: The white light interferometer, X-ray diffraction method, small hole method residual stress detection method, and nano-indentation technology are used to measure the surface integrity parameters of different fatigue specimens 31 after the test; according to the test cycle gradient, the variation laws of the surface topography characteristics, residual stress distribution, and microhardness are analyzed, and further, the differential effects of different surface integrity states on the fatigue damage behavior are revealed.

[0045] The fretting fatigue test method of this embodiment has been described in detail in the fretting fatigue test device of the above embodiment and will not be elaborated here.

[0046] It should be understood that the present invention is not limited in its application to the detailed construction and arrangement of components set forth in this specification. The present invention is capable of other embodiments and of being practiced and carried out in various ways. The foregoing variations and modifications fall within the scope of the present invention. It should be understood that the invention as disclosed and defined in this specification extends to all alternative combinations of two or more separate features mentioned or evident in the text or drawings. All such different combinations constitute various alternative aspects of the present invention. The embodiments described in this specification illustrate the best mode known for practicing the invention and will enable those skilled in the art to utilize the invention.

Claims

1. A fretting fatigue life test device under high temperature and high-frequency vibration conditions considering surface integrity, characterized in that, The fretting fatigue life test device includes the following parts: an axial load loading device (1), a vibrator tooling (2), and a high-temperature component (3); the axial load loading device (1) is used to simulate axial centrifugal force, the vibrator tooling (2) is used to simulate normal centrifugal force, pneumatic load, and high-frequency vibration, and the high-temperature component (3) is used to simulate thermal load; the vibrator tooling (2) is fixed on the support column (12) of the axial load loading device (1) through a tooling platform (14); the high-temperature component (3) is fixed on the support column (12); the fatigue specimen (31), the fretting pad (21), the movable fixture (20), and the fixed fixture (33) on the vibrator tooling (2) are connected to the high-temperature tie rod (10) in the axial load loading device (1) by means of pin connection and placed in a high-temperature furnace (4). The excitation device tooling (2) includes an exciter (13), an excitation rod (15), a pressure sensor (26), a movable fixture (20), a fixed fixture (33), a slide rail slider (16), a slide rail lead screw (18), a slide rail base (19), a tooling platform (14), a vibration loading block (17), a micro-motion pad (21), a thermocouple (22), a micro hydraulic cylinder (23), a right support seat (24), a force transmission lead screw (25), a cooling system (27), a normal load loading block (28), a force transmission guide rail (29), a left support seat (30), a fatigue specimen (31), and a fixture lead screw (32); specifically: the excitation rod (15) is fixed to the exciter (13), and the exciter (13) is installed on the tooling platform (14); the slide rail slider (16) is installed on the slide rail base (19) through the slide rail lead screw (18), the vibration loading block (17) is fixed to the slide rail slider (16), the micro hydraulic cylinder (23) is installed on the slide rail base (19), and the piston rod of the micro hydraulic cylinder (23) pushes the vibration loading block (17) to apply a normal load, where the normal load includes an aerodynamic load and a normal centrifugal force, and at the same time the excitation rod (15) drives the vibration loading block (17) to generate high-frequency vibration; the left side of the left support seat (30) is connected to the fixed fixture (33) through the fixture lead screw (32) and maintains a fixed distance, and the movable fixture (20) is installed on the fixture lead screw (32) and is located between the fixed fixture (33) and the left support seat (30); the micro-motion pads (21) are respectively arranged at the clamping positions of the movable fixture (20) and the fixed fixture (33), located between the movable fixture (20) and the fixed fixture (33), and the fatigue specimen (31) is placed between the two micro-motion pads (21); the upper end of the fixed fixture (33), the upper end of the fatigue specimen (31), and the upper high-temperature pull rod (10) are connected in sequence, the lower end of the fatigue specimen (31) is connected to the lower high-temperature pull rod (10), and after installation, the upper and lower high-temperature pull rods (10) and the movable fixture (20) are adjusted to ensure the parallelism between the movable fixture (20) and the fatigue specimen (31); the left support seat (30) is connected to the right support seat (24) through the force transmission guide rail (29), the force transmission lead screw (25), the normal load loading block (28), the cooling system (27), the pressure sensor (26), and the vibration loading block (17) are placed between the left support seat (30) and the right support seat (24), the force transmission lead screw (25) connects the normal load loading block (28) and the vibration loading block (17) to slide on the force transmission guide rail (29), and the pressure sensor (26) is installed between the normal load loading block (28) and the vibration loading block (17); a cooling system (27) is installed between the observation window of the high-temperature furnace (4) and the pressure sensor (26); the thermocouple (22) is bonded to the fatigue specimen (31) in the high-temperature furnace (4) through high-temperature glue to measure the experimental temperature of the fatigue specimen (31).

2. The fretting fatigue life test device under high temperature and high frequency vibration conditions considering surface integrity according to claim 1, characterized in that The axial load loading device (1) includes a cross beam (11), a hydraulic cylinder (7), a support column (12), a wedge block (9), a high-temperature tie rod (10), a fatigue specimen (31) and a hydraulic fixture (8); the hydraulic fixture (8) is connected to the hydraulic cylinder (7), the wedge block (9) is installed in the hydraulic fixture (8) in a clearance fit manner, the high-temperature tie rod (10) is installed in the wedge block (9) and achieves a tight fit through the pressure provided by the hydraulic cylinder (7); the movement of the piston rod of the hydraulic cylinder (7) provides a tensile force for the high-temperature tie rod (10) to simulate the axial centrifugal force and achieve axial loading.

3. A fretting fatigue life test device under high temperature and high frequency vibration conditions considering surface integrity according to claim 1, characterized in that, The high-temperature component (3) includes a high-temperature furnace (4), a connecting ear (6) and a pin (5); the high-temperature furnace (4) is in an interference fit with the support column (12) of the axial load loading device (1) through the connecting ear (6) and the pin (5), and the observation window of the high-temperature furnace (4) is kept parallel to the end face of the cross beam (11) during the installation process to ensure the parallelism of the fatigue specimen (31) and the fretting pad (21).

4. A fretting fatigue life test method implemented by a fretting fatigue life test device under high temperature and high frequency vibration conditions according to any one of claims 1-3, characterized in that, The fretting fatigue life test method includes the following steps: First, prepare fatigue specimens (31) with different surface integrity parameters; Second, measure the key parameters on the surface of the fatigue specimen (31) before the test; Third, under the conditions of high temperature and high-frequency vibration, set the test cycle gradient according to the logarithmic distribution law and carry out the fretting fatigue test; Finally, after the test is completed, measure the surface integrity parameters of the fatigue specimen (31) on each surface again, and obtain the evolution law of the surface integrity parameters with the fretting cycle through comparative analysis.

5. The fretting fatigue life test method according to claim 4, wherein The fretting fatigue life test method includes the following steps: Step 1: Prepare fatigue specimens (31) and fretting pads (21) with different surface integrity parameters under different processing process parameters; Step 2: Measure the key parameters on the surface of the fatigue specimen (31) before the test through a white light interferometer, X-ray diffraction method, small hole method residual stress detection method and nano-indentation respectively. The key parameters include surface topography characteristics, residual stress distribution and microhardness; Step 3: During the application of the axial load, the high-temperature tie rod (10) is rigidly connected to the fatigue specimen (31) through the pin (5), and the hydraulic fixture (8) of the axial load loading device (1) accurately transmits the set load to the high-temperature tie rod (10) to apply an axial centrifugal force on the fatigue specimen (31). Step 4: During the application of the normal load and the vibration load, the micro hydraulic cylinder (23) provides a normal load for the micro motion pad (21) and the fatigue specimen (31) to form a pre-tightening force. The vibration loading block (17) and the normal load loading block (28) transmit the pre-tightening force and vibration to the movable fixture (20) through the force transmission guide rail (29) and finally act on the micro motion pad (21) and the fatigue specimen (31); at the same time, the vibration exciter (13) transmits high-frequency vibration through the force transmission lead screw (25) to realize the combined loading of the normal load and the high-frequency vibration; the micro motion pad (21) and the fatigue specimen (31) are tightly fitted through the movable fixture (20) and the fixed fixture (33); the micro hydraulic cylinder (23) is designed to monitor and compensate the pre-tightening force in real time through a closed-loop control system to maintain the constancy of the normal load; Step 5: Apply a thermal load through the high-temperature furnace (4) to provide a stable and controllable temperature environment for the fretting fatigue test; Step 6: Set the test cycle gradient according to the logarithmic distribution law; within each cycle gradient, conduct fretting fatigue tests on the fatigue specimens (31) with the same surface integrity parameters under high-temperature and high-frequency vibration conditions; Step 7: Measure the surface integrity parameters of different fatigue specimens (31) after the test; according to the test cycle gradient, analyze the change laws of the surface topography characteristics, residual stress distribution, and microhardness, and further reveal the differential effects of different surface integrity states on the fatigue damage behavior.

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