Ultrahigh-cycle fatigue experiment device capable of realizing thermal gradient environment

Abstract

The invention discloses an ultra-high-cycle fatigue test device capable of realizing a thermal gradient environment. The ultra-high-cycle fatigue test device comprises an ultrasonic fatigue test device, a tensile test device, a high-temperature environment device, a cooling system, a temperature test device and a microscopic monitoring device, the ultrasonic fatigue test devices are arranged on the upper and lower sides of the high-temperature environment device; the tensile test device is located above the ultrasonic fatigue test device, and the cooling system is connected with the interior of the sample. According to the invention, the comprehensive service behavior test under the conditions of high temperature environment, thermal gradient and multi-stress ratio ultra-high cycle fatigue can be carried out at the same time, multiple functions are integrated, the test under complex conditions is carried out on the same experimental platform, and the performance evaluation of an aero-engine material under more real conditions is realized; the influence of the thermal gradient condition on the service strength and the failure mechanism is explored, and cooperative test research on the service behavior of the engine blade material under the influence of multiple factors such as super-long life fatigue under the high-temperature thermal gradient is realized.

Description

An ultra-high cycle fatigue testing device capable of realizing a thermal gradient environment Technical Field

[0001] This invention belongs to the technical field of high-temperature alloy fatigue testing devices, specifically relating to an ultra-high cycle fatigue testing device that can realize a thermal gradient environment. Background Technology

[0002] Aero-engines, as cutting-edge products in the equipment manufacturing field, embody a nation's technological level and comprehensive national strength, and are one of the core technologies affecting national air transport, defense security, and maintaining strategic advantage. Turbine blades, as key components of aero-engines, directly impact engine lifespan due to their service safety. Accident analysis shows that high-cycle fatigue accounts for approximately 25% of accidents in gas turbine engines, with long-life fatigue fracture of turbine blades being one of the main causes of major accidents. The failure of blade materials during ultra-long service life is influenced not only by complex stress states but also by the crucial external working environment. During ultra-long service life, turbine blade materials are subject to the dual influence of complex stress states and the external working environment. Blades operate at temperatures reaching 2000℃, requiring cooling gas convection in internal channels and film cooling through external pores. Although current cooling technologies can reduce blade temperatures by 400-600℃, the temperature difference between the internal and surface still induces additional stress, resulting in multiaxial compressive and tensile stresses, making the thermal gradient environment a key factor in studying blade fatigue behavior.

[0003] Currently, thermal gradient environments have been applied in low-cycle thermomechanical fatigue testing using hydraulic servo fatigue testing machines. Studies have shown that thermal gradients induce different failure mechanisms, which differ significantly from material damage and failure assessment under conventional uniform high-temperature conditions. However, existing thermomechanical fatigue research has the following shortcomings: First, thermomechanical fatigue experiments under thermal gradient conditions are technically challenging, and research is scarce and lacks systematicity; second, existing experiments typically employ strain-controlled cyclic loading, where the maximum applied stress often exceeds the material's yield strength under high-temperature conditions.

[0004] Existing research on the ultra-long-life fatigue behavior of blade materials under service conditions is very limited, and is mainly limited to the study of single influencing factors. It fails to fully explore key scientific issues such as crack initiation and propagation, micro-area damage mechanisms, and microstructural stability under the coupled environment of high-temperature thermal gradients, low-cycle deformation, and long-life fatigue. Furthermore, current experimental techniques cannot achieve ultra-long-life fatigue testing of blade materials under multiple coupled conditions, resulting in a lack of in-depth understanding of the ultra-long-life fatigue behavior of blade materials under real service conditions.

[0005] The drawback of existing technologies is that current ultrasonic vibration fatigue testing systems cannot accurately simulate fatigue loading under high-temperature thermal gradient environments. This limitation makes it difficult to accurately reproduce the material behavior in actual service environments when conducting ultrasonic fatigue tests under high-temperature thermal gradient conditions. Current ultrasonic fatigue testing systems, mainly composed of transducers, amplification systems, and specimens, suffer from the following main problems: 1. Inability to conduct ultrasonic fatigue tests under high-temperature thermal gradients: Traditional ultrasonic fatigue testing systems cannot simulate the real fatigue state of aero-engine blades under high-temperature and thermal gradient environments, limiting the study of blade material behavior in complex environments; 2. Loading frequency limitation: Traditional high-temperature thermal gradient fatigue testing systems typically have loading frequencies below 100 Hz, while achieving 10 Hz is much more difficult. 9 For ultra-high cycle fatigue loading exceeding one cycle, the existing 50 Hz high-frequency fatigue testing machine requires approximately 230 days. This significantly increases the time and effort required for scientific research, hindering the acceleration of equipment or component development.

[0006] The shortcomings of existing technologies in terms of structural integrity and reliability of aero-engines severely restrict the development process of engines. Therefore, studying the ultra-long-life fatigue, creep strength, and failure mechanisms of blade materials under thermal gradient conditions, and establishing the theoretical and physical correlation between material microstructure and long-life fatigue behavior, has become a necessary condition for ensuring the safe and stable operation of aircraft. Therefore, designing a test device capable of conducting ultra-long-life fatigue tests under high-temperature thermal gradients has become an urgent need. Summary of the Invention

[0007] The purpose of this invention is to address the aforementioned shortcomings in the prior art by providing an ultra-high cycle fatigue testing device capable of realizing a thermal gradient environment. This solves the problem that existing ultrasonic vibration fatigue testing systems cannot accurately simulate fatigue loading under high temperature thermal gradient conditions. This limitation makes it difficult to accurately reproduce the material behavior in actual service environments when conducting ultrasonic fatigue tests under high temperature thermal gradient conditions.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is: an ultra-high cycle fatigue testing device capable of realizing a thermal gradient environment, comprising an ultrasonic fatigue testing device, a tensile testing device, a high-temperature environment device, a cooling system, a temperature testing device, and a microscopic monitoring device; the ultrasonic fatigue testing device is disposed on the upper and lower sides of the high-temperature environment device, and the ultrasonic fatigue testing device fixes the sample inside the high-temperature environment device; the tensile testing device is located above the ultrasonic fatigue testing device and applies a load to the sample through the ultrasonic fatigue testing device; the cooling system is connected to the interior of the sample to cool the interior of the sample; the temperature testing device and the microscopic monitoring device respectively collect the temperature information and physical change information of the sample.

[0009] Furthermore, the tensile testing apparatus includes a tensile machine; a servo-hydraulic fatigue testing machine is mounted on the top of the tensile machine, and the servo-hydraulic fatigue testing machine is connected to the ultrasonic fatigue testing apparatus via an upper square fixed frame.

[0010] Furthermore, the high-temperature environment device is a high-temperature environment chamber, which is a sealed structure and is fixed to the stretching machine by interference fit, and has a built-in heating structure; the high-temperature environment chamber adopts a split design, which includes an upper chamber and a lower chamber.

[0011] Furthermore, the sample is dog-bone shaped with a hollow tubular interior; the sample is placed vertically inside the high-temperature environmental chamber.

[0012] Furthermore, the ultrasonic fatigue testing device includes a transducer, an amplitude transformer, an upper amplifier, an upper extension rod, a lower amplifier, and a lower extension rod arranged coaxially; the lower end of the upper extension rod and the upper end of the lower extension rod are respectively threaded to the upper and lower ends of the sample; the upper end of the upper extension rod is connected to one end of the upper amplifier, and the lower end of the lower extension rod is connected to one end of the lower amplifier; the other end of the upper amplifier is threaded to one end of the amplitude transformer, and the other end of the amplitude transformer is threaded to the transducer; simultaneously, the upper amplifier is bolted to the upper square fixed frame, and the lower amplifier is clamped to the lower square fixed frame by an interference fit.

[0013] Furthermore, both the upper and lower chambers of the high-temperature environmental chamber are provided with openings. The upper and lower extension rods pass through these openings and are connected to the sample, and the openings are sealed with high-temperature asbestos. The interiors of both the upper and lower extension rods are hollow tubular structures, forming cooling channels with the hollow interiors of the upper and lower extension rods and the sample. The opening on the upper extension rod is an air inlet connected to the cooling system, and the lower end of the lower extension rod is an air outlet. The air inlet and outlet are located on the zero-vibration displacement surfaces of the upper and lower extension rods, respectively. Further, the cooling system includes an air compressor, an air dryer, a metering valve, an air pressure gauge, and a cooling channel. The air outlet of the cooling channel is connected to the air inlet on the cooling pipe, and the air inlet of the cooling channel is connected to the air compressor. The air dryer, metering valve, and air pressure gauge are all installed on the cooling channel.

[0014] Furthermore, the lower square fixing frame is fixed to the tensile testing machine; the upper square fixing frame is connected to the output shaft of the servo hydraulic fatigue testing machine.

[0015] Furthermore, the temperature testing device is connected to an external computer and includes patch-type temperature sensors disposed on the hollow inner wall and outer wall of the sample, thermocouple sensors disposed in a high-temperature environment chamber, and temperature sensors disposed at the air inlet and outlet.

[0016] Furthermore, the microscopic monitoring device includes a far-field optical microscope and an infrared thermal imager; the far-field optical microscope and the infrared thermal imager are positioned facing the monitoring windows on both sides of the high-temperature environment chamber, and both the far-field optical microscope and the infrared thermal imager are clamped on the stretching machine support by fixing rings.

[0017] This invention first requires a deep coupling connection between the high-temperature environmental chamber, cooling system, temperature testing device, and ultrasonic fatigue testing device. The outer high-temperature environmental chamber provides the high-temperature environment for the experiment, forming the basis for realizing the thermal gradient of the material. The specimen is designed as a tube, with its inner diameter connected to the cooling system. Compressed cold air is used to cool the interior of the specimen, creating a temperature difference between the inner and outer surfaces, thus achieving the thermal gradient difference between the material's inner and outer surfaces. The inner ultrasonic fatigue testing device and temperature testing device enable low-stress, ultra-long-life loading and environmental temperature control. Their coordinated operation requires a stable external high-temperature environment to prevent temperature changes from affecting the resonant frequency of the internal ultrasonic vibration, causing errors in the experimental results. Simultaneously, the ultrasonic vibration system and connecting components must possess sufficient strength and stiffness to ensure the accuracy of the load applied by the fatigue testing system. Therefore, high-strength steel with good stiffness and strength is used to construct the connection device between the two systems. Based on finite element analysis, considering the influence of the thermal gradient, the displacement response of the stressed section of the ultrasonic fatigue testing device is obtained, eliminating the influence of the connection between the two systems on the test results.

[0018] Regarding the realization of the thermal gradient environment, the project will construct a small high-temperature environment chamber to achieve a 1000℃ high-temperature environment, and design an extension rod for ultrasonic vibration to ensure that the transducer and amplifier are not affected by the high-temperature environment. To achieve the internal thermal gradient environment of the sample, the extension rod and fatigue sample will be redesigned, with cooling pipes installed inside. The air inlet and outlet of the pipes will be located at the zero-vibration displacement surfaces of the upper and lower extension rods, respectively, to facilitate connection with external compressed cold air and to minimize the impact of the inlet and outlet connection pipes on the vibration frequency of the extension rod.

[0019] In terms of temperature control for the high-temperature environmental chamber and the sample, the furnace temperature is measured using thermocouple sensors. Due to the sample's own vibration, a temperature rise effect occurs, and its surface temperature is measured using both an infrared thermal imager and a patch-type temperature sensor. The internal wall temperature of the sample is also measured using a specially designed small patch sensor. Simultaneously, the heat dissipation process of the sample during stable loading is simulated and analyzed using the finite element method, and the accuracy of temperature monitoring is ensured by comparing the simulation results with experimental data. Furthermore, a coordinated control program for ultrasonic stress loading, sample outer wall temperature, and inner wall temperature has been developed. This program achieves rapid response and automatic adjustment of stress and temperature by adjusting the ultrasonic amplitude, the high-temperature chamber, and the cooling system power.

[0020] The ultra-high cycle fatigue testing apparatus provided by this invention, capable of realizing a thermal gradient environment, has the following beneficial effects: 1. This invention achieves a high-temperature thermal gradient through the synergistic effect of a high-temperature environment device and a cooling system. The high-temperature environment device heats the outer surface of the specimen to a set ambient temperature, while the cooling system cools the interior of the tubular specimen with compressed cold air, thereby creating a temperature difference between the inner and outer surfaces of the specimen and achieving a controllable thermal gradient. Through the above design, this invention not only simplifies the design of the testing apparatus but also significantly improves the accuracy and reliability of the test, making it particularly suitable for high-temperature gradient environments in ultra-long life fatigue testing.

[0021] 2. Currently, the effects of thermal gradient and ultra-long life fatigue are relatively independent, and there is no precedent for coupled testing. This invention can better meet the working conditions of nickel-based superalloys under high temperature conditions for long-term service, realize the coordinated test study of the service behavior of engine blade materials under the influence of multiple factors such as thermal gradient and low stress ultra-long life fatigue, and solve the problem that it is difficult to design ultrasonic vibration thermal gradient under high temperature conditions.

[0022] 3. This invention designs a high-temperature environment device precisely matched to the ultrasonic loading system, achieving external temperature conditions up to 1000℃. The influence of the high-temperature environment on the operating frequency and vibration amplitude of the ultrasonic vibration system is analyzed to ensure the loading stability and stress control accuracy of the extension rod and the specimen. Furthermore, an extension rod with internal hollow cooling pipes is designed, and its influence on vibration frequency and stress distribution is studied based on finite element analysis, achieving precise fatigue loading under high-temperature conditions.

[0023] 4. This invention develops a patch-type temperature sensor for measuring the surface temperature inside a sample, and studies its stability and influencing factors under thermal gradient conditions. A quantitative relationship is established between ultrasonic loading stress, external ambient chamber temperature, cooling system, and sample surface / internal temperature. Optical microscopy and infrared thermal imaging are used to investigate the relationship between sample surface heat dissipation and local fatigue damage. A macroscopic material damage evaluation method based on local temperature changes, vibration frequency evolution, and surface crack behavior is established, achieving high-precision closed-loop temperature control and low-energy continuous high-frequency testing, ensuring system safety. Attached Figure Description

[0024] Figure 1 is a schematic diagram of the structure of the ultra-high cycle fatigue test device that can realize a thermal gradient environment according to an embodiment of the present invention.

[0025] Figure 2 is a schematic diagram of the microscopic monitoring device according to an embodiment of the present invention.

[0026] Figure 3 is a schematic diagram of the connection between the sample and the cooling system in an embodiment of the present invention.

[0027] Figure 4 is a schematic diagram of the sample structure in an embodiment of the present invention.

[0028] Figure 5 is a structural block diagram of an embodiment of the present invention.

[0029] The components include: 1. Tensile testing machine; 2. Servo hydraulic fatigue testing machine; 3. Upper square fixed frame; 4. High temperature environment chamber; 5. Sample; 6. Transducer; 7. Amplifier rod; 8. Upper amplifier; 9. Upper extension rod; 10. Lower amplifier; 11. Lower extension rod; 12. Lower square fixed frame; 13. Air inlet; 14. Air outlet; 15. Patch-type temperature sensor; 16. Temperature sensor; 17. Far-field optical microscope; 18. Infrared thermal imager. Detailed Implementation

[0030] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0031] This embodiment of the ultra-high cycle fatigue testing device enables a thermal gradient environment. This embodiment constructs a coupled fatigue testing system based on a high-temperature chamber and ultrasonic vibration acceleration. A heating device is installed inside the sealed high-temperature environment chamber 4, while a cooling system is provided externally. Compressed cold air is used to cool the interior of the specimen, achieving ultra-long life fatigue testing under a high-temperature thermal gradient. Referring to Figures 1 and 5, it specifically includes: an ultrasonic fatigue testing device, a tensile testing device, a high-temperature environment device, a cooling system, a temperature testing device, and a microscopic monitoring device. The ultrasonic fatigue testing device is located on the upper and lower sides of the high-temperature environment device, fixing the specimen 5 inside the high-temperature environment device. The tensile testing device is located above the ultrasonic fatigue testing device and applies a load to the specimen 5 through the ultrasonic fatigue testing device. The cooling system is connected to the interior of the specimen 5 to cool its interior. The temperature testing device and the microscopic monitoring device respectively collect temperature information and physical change information of the specimen 5.

[0032] In some embodiments, the tensile testing apparatus includes a tensile machine 1, a servo-hydraulic fatigue testing machine 2 mounted on top of the tensile machine 1, and the servo-hydraulic fatigue testing machine 2 connected to the ultrasonic fatigue testing apparatus via an upper square fixed frame 3. The servo-hydraulic fatigue testing machine 2 is used to apply a tensile-torsional mechanical load with a given mechanical strain to the specimen 5.

[0033] In some embodiments, the high-temperature environment device is a high-temperature environment chamber 4, which is a sealed structure and is fixed to the stretching machine 1 by interference fit, and has a built-in heating structure; the high-temperature environment chamber 4 adopts a split design, which includes an upper chamber and a lower chamber.

[0034] In one specific embodiment, a temperature sensor 16 is installed inside the high-temperature environment chamber 4 to collect real-time ambient temperature data. The upper and lower parts of the high-temperature environment chamber 4 have openings for installing hollow extension rods. The extension rods pass through the openings and are sealed around the openings with high-temperature asbestos to achieve heat preservation and isolation from external air. Monitoring windows are provided on both sides of the high-temperature environment chamber 4 for the original optical microscope and infrared thermal imager 18 to observe and measure the surface of the sample 5, obtaining relevant surface temperature and physical change information.

[0035] In some embodiments, referring to Figures 3 and 4, the sample 5 is dog bone shaped with a hollow tubular interior, and the sample 5 is vertically placed inside the high-temperature environment chamber 4.

[0036] In one specific embodiment, in order to accurately measure the temperature difference between the inner and outer surfaces of the sample 5, patch-type temperature sensors 15 are installed on the inner and outer surfaces respectively. Through this design, the temperature changes of the inner and outer surfaces of the sample 5 can be monitored in real time during the test, providing basic data for subsequent experiments and further analyzing the distribution of the thermal gradient field.

[0037] In some embodiments, the ultrasonic fatigue testing apparatus includes a transducer 6, an amplitude transformer 7, an upper amplifier 8, an upper extension rod 9, a lower amplifier 10, and a lower extension rod 11 arranged coaxially. The lower end of the upper extension rod 9 and the upper end of the lower extension rod 11 are threadedly connected to the upper and lower ends of the sample 5, respectively. The upper end of the upper extension rod 9 is connected to one end of the upper amplifier 8, and the lower end of the lower extension rod 11 is connected to one end of the lower amplifier 10. The other end of the upper amplifier 8 is threadedly connected to one end of the amplitude transformer 7, and the other end of the amplitude transformer 7 is threadedly connected to the transducer 6. Meanwhile, the upper amplifier 8 is bolted to the upper square fixed frame 3, and the lower amplifier 10 is clamped to the lower square fixed frame 12 by an interference fit.

[0038] In one specific embodiment, both the upper and lower chambers of the high-temperature environmental chamber 4 are provided with openings. The upper extension rod 9 and the lower extension rod 11 pass through the openings and are connected to the sample 5, respectively. The openings are sealed with high-temperature asbestos. The interiors of the upper extension rod 9 and the lower extension rod 11 are hollow tubular structures, and the hollow interiors of the upper extension rod 9, the lower extension rod 11, and the sample 5 form cooling pipes. The opening on the upper extension rod 9 is an air inlet 13, which is connected to the cooling system. The lower end of the lower extension rod 11 is an air outlet 14. The air inlet 13 and the air outlet 14 are located on the zero-vibration displacement surfaces of the upper and lower extension rods 11, respectively.

[0039] In one specific embodiment, temperature sensors 16 are also installed at the air inlet 13 and the air outlet 14 respectively. The sensors are connected to a computer via a data cable to monitor and calculate the air temperature difference between the air inlet 13 and the air outlet 14 in real time, thereby obtaining the heat conversion efficiency.

[0040] In one specific embodiment, the lower square fixing frame 12 is fixed to the tensile testing machine 1; the upper square fixing frame 3 is connected to the output shaft of the servo hydraulic fatigue testing machine 2.

[0041] In one specific embodiment, considering the convenience of replacing the test specimen, the lower amplifier 10 is designed to be detachable, which greatly simplifies the difficulty of replacing the test specimen.

[0042] In one specific embodiment, the sample 5 is fixed between the upper amplifier 8 and the lower amplifier 10, which are symmetrically positioned, and the design is completely symmetrical to ensure that the zero displacement surface in the middle of the sample 5 is at the position of maximum stress.

[0043] In one specific embodiment, the hollow sample 5 and the transducer 6 (using a piezoelectric ceramic transducer 6) resonate at the same frequency, forming a unified resonant system. The amplitude rod 7 is threadedly connected to the transducer 6 and can move vertically through the tensile machine 1 connected at the upper end.

[0044] In one specific embodiment, the ultrasonic fatigue testing device transmits ultrasonic vibrations through a piezoelectric ceramic transducer 6 and an amplitude transformer 7. An extension rod coaxially connected to the amplitude transformer 7 is used to transmit the amplitude and introduce a flow of cold air inside. An infrared thermal imager 18 and a temperature sensor 16 are used to measure the internal and external surface temperatures of the specimen 5 in real time. The high-temperature environmental chamber 4 adopts a split design and is equipped with a side window for temperature monitoring. Through this structure, compressed cold air is introduced into the specimen, creating a temperature difference between the inside and outside, resulting in a thermal gradient in the specimen, thereby simulating fatigue damage in actual service environments.

[0045] In one specific embodiment, the ultrasonic fatigue testing apparatus and stress control system convert a 50Hz electrical signal into a 20kHz ultrasonic signal using an ultrasonic generator. This signal is then converted into a mechanical vibration signal by a piezoelectric ceramic transducer 6. An amplitude transformer 7 amplifies the amplitude, ensuring the specimen 5 reaches the required displacement amplitude, thus achieving the ultrasonic fatigue test. Stress control is achieved by adjusting the power of the ultrasonic generator. After ABAQUS simulation correction, the system ensures the accuracy of maintaining the stress level under a thermal gradient environment. The computer system records the vibration cycles and temperature data in real time, determining the fatigue type of the specimen 5 based on the vibration cycles. Ultra-high cycle fatigue requires a vibration cycle count of 10 cycles. 7 More than once.

[0046] In some embodiments, referring to FIG3, the cooling system includes an air compressor, an air dryer, a metering valve, an air pressure gauge, and a cooling channel; the air outlet 14 of the cooling channel is connected to the air inlet 13 on the cooling pipe, the air inlet 13 of the cooling channel is connected to the air compressor, and the air dryer, the metering valve, and the air pressure gauge are all installed on the cooling channel.

[0047] In one specific embodiment, cold air is introduced into the cooling pipe of the extension rod to cool the inner surface of the sample 5. Simultaneously, an air dryer is used to remove water vapor from the compressed air, ensuring that the impact of water vapor on fatigue damage is minimized. By calculating the temperature difference between the inlet and outlet air 14, the temperature change of the inner surface of the specimen can be effectively calculated.

[0048] In some embodiments, the temperature testing device is connected to an external computer and includes a patch-type temperature sensor 15 disposed on the hollow inner wall of the sample 5 and the outer wall of the sample 5, a thermocouple sensor disposed in the high-temperature environment chamber 4, and a temperature sensor 16 disposed on the air inlet 13 and the air outlet 14.

[0049] In some embodiments, referring to FIG2, the microscopic monitoring device includes a far-field optical microscope 17 and an infrared thermal imager 18; the far-field optical microscope 17 and the infrared thermal imager 18 are positioned facing the monitoring windows on both sides of the high-temperature environment chamber 4, and both the far-field optical microscope 17 and the infrared thermal imager 18 are clamped on the support of the stretching machine 1 by a fixing ring.

[0050] In one specific embodiment, during the test, a tensile tester 1 applies an average stress to the sample 5 to achieve different stress ratios. A high-temperature environmental chamber 4 heats the sample 5, maintaining a high temperature on its outer surface. Simultaneously, a cooling system injects cold air into the hollow sample 5 through a hollow extension rod to lower the temperature of its inner surface. This creates a temperature gradient between the inner and outer surfaces of the sample 5, which better reflects the actual working conditions of nickel-based superalloys. During the test, a far-field optical microscope 17 observes the sample 5, and an infrared thermal imager 18 and thermocouples monitor the temperature of the inner and outer surfaces. Finite element simulation and calculation are used to obtain the thermal gradient change from the surface to the interior of the sample 5. Fatigue testing under the combined effects of temperature gradient and ultra-high cycle time effectively reflects the working conditions of nickel-based superalloys under high-temperature conditions for extended periods.

[0051] Although specific embodiments of the invention have been described in detail with reference to the accompanying drawings, this should not be construed as limiting the scope of protection of this patent. Various modifications and variations that can be made by a person skilled in the art without inventive effort within the scope described in the claims still fall within the scope of protection of this patent.

Claims

1. A high-cycle fatigue testing device capable of realizing a thermal gradient environment, characterized in that: The device includes an ultrasonic fatigue testing apparatus, a tensile testing apparatus, a high-temperature environment apparatus, a cooling system, a temperature testing device, and a microscopic monitoring device. The ultrasonic fatigue testing apparatus is positioned on the upper and lower sides of the high-temperature environment apparatus, and it fixes the specimen inside the apparatus. The tensile testing apparatus is located above the ultrasonic fatigue testing apparatus and applies a load to the specimen. The cooling system is connected to the interior of the specimen to cool its internal components. The temperature testing device and the microscopic monitoring device collect the specimen's temperature and physical change information, respectively.

2. The ultra-high cycle fatigue test apparatus capable of realizing a thermal gradient environment according to claim 1, characterized in that: The tensile testing apparatus includes a tensile machine; a servo-hydraulic fatigue testing machine is mounted on the top of the tensile machine, and the servo-hydraulic fatigue testing machine is connected to the ultrasonic fatigue testing apparatus through an upper square fixed frame.

3. The ultra-high cycle fatigue test apparatus capable of realizing a thermal gradient environment according to claim 1, characterized in that: The high-temperature environment device is a high-temperature environment chamber, which is a sealed structure that is fixed to the stretching machine by interference fit and has a built-in heating structure. The high-temperature environment chamber adopts a split design, which includes an upper chamber and a lower chamber.

4. The ultra-high cycle fatigue test apparatus capable of realizing a thermal gradient environment according to claim 1, characterized in that: The sample is dog bone shaped with a hollow tubular interior; the sample is placed vertically inside the high-temperature environment chamber.

5. The ultra-high cycle fatigue test apparatus capable of realizing a thermal gradient environment according to claim 2, characterized in that: The ultrasonic fatigue testing device includes a transducer, an amplitude transformer, an upper amplifier, an upper extension rod, a lower amplifier, and a lower extension rod arranged coaxially. The lower end of the upper extension rod and the upper end of the lower extension rod are threaded to the upper and lower ends of the specimen, respectively. The upper end of the upper extension rod is connected to one end of the upper amplifier, and the lower end of the lower extension rod is connected to one end of the lower amplifier. The other end of the upper amplifier is threaded to one end of the amplitude transformer, and the other end of the amplitude transformer is threaded to the transducer. Meanwhile, the upper amplifier is bolted to the upper square fixed frame, and the lower amplifier is clamped to the lower square fixed frame by an interference fit.

6. The ultra-high cycle fatigue test apparatus capable of realizing a thermal gradient environment according to claim 5, characterized in that: The upper and lower chambers of the high-temperature environmental chamber are both provided with openings. The upper and lower extension rods pass through the openings and are connected to the sample, and the openings are sealed with high-temperature asbestos. The interiors of the upper and lower extension rods are hollow tubular structures, and the hollow interiors of the upper and lower extension rods and the sample form a cooling pipe. The opening on the upper extension rod is an air inlet, which is connected to the cooling system, and the lower end of the lower extension rod is an air outlet. The air inlet and outlet of the pipes are located on the zero-vibration displacement surfaces of the upper and lower extension rods, respectively.

7. The ultra-high cycle fatigue test apparatus capable of realizing a thermal gradient environment according to claim 6, characterized in that: The cooling system includes an air compressor, an air dryer, a metering valve, an air pressure gauge, and a cooling channel; the air outlet of the cooling channel is connected to the air inlet on the cooling pipe, and the air inlet of the cooling channel is connected to the air compressor; the air dryer, the metering valve, and the air pressure gauge are all installed on the cooling channel.

8. The ultra-high cycle fatigue test apparatus capable of realizing a thermal gradient environment according to claim 5, characterized in that: The lower square fixed frame is fixed to the tensile testing machine; the upper square fixed frame is connected to the output shaft of the servo hydraulic fatigue testing machine.

9. The ultra-high cycle fatigue test apparatus capable of realizing a thermal gradient environment according to claim 5, characterized in that: The temperature testing device is connected to an external computer and includes patch-type temperature sensors installed on the inner wall of the hollow sample and the outer wall of the sample, thermocouple sensors installed in a high-temperature environment chamber, and temperature sensors installed at the air inlet and air outlet.

10. The ultra-high cycle fatigue test apparatus capable of realizing a thermal gradient environment according to claim 5, characterized in that: The microscopic monitoring device includes a far-field optical microscope and an infrared thermal imager; the far-field optical microscope and the infrared thermal imager are positioned facing the monitoring windows on both sides of the high-temperature environment chamber, and both the far-field optical microscope and the infrared thermal imager are clamped on the stretching machine support by fixing rings.

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