In-situ high-resolution microscopic characterization equipment for ultrahigh-cycle fatigue test and design method thereof

Abstract

The invention belongs to the related technical field of ultrahigh-cycle fatigue tests of materials, and discloses in-situ high-resolution microscopic characterization equipment for an ultrahigh-cycle fatigue test and a design method of the in-situ high-resolution microscopic characterization equipment. In the equipment, an ultrasonic fatigue test device comprises an ultrahigh-cycle fatigue assembly and a supporting block, and in the ultrahigh-cycle fatigue assembly, the supporting block is connected with the ultrahigh-cycle fatigue assembly; the amplitude-change pole extends into the vacuum cavity of the electron microscope device; the sealing device comprises a hollow corrugated pipe, a first sealing end cover and a second sealing end cover, the hollow corrugated pipe penetrates through the supporting block and extends to a bin opening of the vacuum cavity, the first sealing end cover is fixedly attached to the surface of the vacuum cavity, the second sealing end cover is fixedly attached to the supporting block, and the ultrahigh-cycle fatigue assembly extends to the vacuum cavity through the hollow corrugated pipe; the external fine adjustment device enables the displacement zero point of the test piece to be located in an observable area by adjusting the position of the supporting block; the electron microscope device is used for carrying out in-situ observation on the test piece. Based on the equipment, high-resolution in-situ observation of the microcosmic continuous whole process of crack initiation and expansion in the ultrahigh-cycle fatigue test can be realized.

Description

Technical Field

[0001] This invention belongs to the technical field of ultra-high cycle fatigue testing of materials, and more specifically, relates to an in-situ high-resolution microscopic characterization device for ultra-high cycle fatigue testing and its design method. Background Technology

[0002] In the research and development of key equipment such as aero-engines and high-speed rail, ultra-high frequency (greater than 10) 7 High-cycle fatigue (HCFL) has become a significant factor affecting the service life and reliability of materials. HCFL testing is an important method for studying the fatigue characteristics of materials under high-cycle loading. In HCFL, understanding the deformation behavior and microscopic deformation mechanism is crucial for accurately predicting HCFL life. However, studying the microscopic deformation mechanism of HCFL requires the use of high-resolution microscopy techniques.

[0003] Currently, ultrasonic ultra-high cycle fatigue research typically employs in-situ experiments using optical microscopy. However, optical microscopy has limited magnification and low resolution, making it impossible to achieve higher resolution and more precise observation and characterization of ultra-high cycle fatigue fracture features. Although electron microscopy can be used to observe and characterize ultra-high cycle test samples, this method can currently only observe the final result of crack formation after the experiment, and cannot achieve high-resolution in-situ observation of the continuous process of crack initiation and propagation. This method has limited applicability for studying the microscopic deformation mechanism of ultra-high cycle fatigue.

[0004] It is evident that there is currently a lack of technical means to perform high-resolution in-situ characterization of ultrasonic ultra-high cycle fatigue testing. Therefore, developing in-situ observation techniques and experimental equipment for the entire microscopic continuous process of crack initiation and propagation in ultra-high cycle fatigue testing is a core technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] In view of the above-mentioned defects or improvement needs of the existing technology, the present invention provides an in-situ high-resolution microscopic characterization device and its design method for ultra-high cycle fatigue testing. Its purpose is to perform high-resolution in-situ characterization of ultrasonic ultra-high cycle fatigue testing, so as to realize high-resolution in-situ observation of the entire microscopic continuous process of crack initiation and propagation in ultra-high cycle fatigue testing.

[0006] To achieve the above objectives, the following technical solution is proposed.

[0007] According to a first aspect of the present invention, an in-situ high-resolution microscopic characterization device for ultra-high cycle fatigue testing is provided, comprising: an ultrasonic fatigue testing device, an electron microscope device, a sealing device, and an external fine-tuning device; The ultrasonic fatigue testing device includes an ultra-high cycle fatigue component and a support block supporting the ultra-high cycle fatigue component. The ultra-high cycle fatigue component includes an ultrasonic transducer and an amplitude transformer. The end of the amplitude transformer is used to connect to the test piece. One end of the amplitude transformer connected to the test piece extends into the vacuum cavity of the electron microscope device. The ultrasonic transducer is used to generate ultrasonic energy and apply it to the test piece through the amplitude transformer to perform fatigue testing on the test piece. The sealing device includes a hollow bellows and a first sealing end cap and a second sealing end cap, which are bent and extended from both ends of the hollow bellows. The hollow bellows passes through the support block and extends to the opening of the vacuum chamber where it connects to the amplitude transformer. The first sealing end cap is fixedly attached to the outer surface of the vacuum chamber, and the second sealing end cap is fixedly attached to the outer surface of the support block. The ultra-high cycle fatigue component is covered by the second sealing end cap and extends into the vacuum chamber through the hollow space of the hollow bellows. The sealing device is used to seal the opening of the vacuum chamber where it connects to the ultra-high cycle fatigue component to ensure the airtightness of the vacuum chamber. The external fine-tuning device is located outside the vacuum chamber and is used to adjust the position of the specimen by adjusting the position of the support block so that the zero displacement point of the specimen in the fatigue test is located within the electron beam landing point area of ​​the electron microscope device. The electron microscope device is used for in-situ observation of the specimen.

[0008] According to a second aspect of the present invention, a method for designing an in-situ high-resolution microscopic characterization device for ultra-high cycle fatigue testing is provided, comprising: S1. Based on the distance from the electron beam landing area of ​​the electron microscope device to the vacuum chamber opening, determine the length of the amplitude transformer and the length of the specimen, so that the specimen at the end of the amplitude transformer extends into the electron beam landing area. S2. Optimize the side profile and cross-sectional dimensions of the amplitude transformer to make the amplification factor of the amplitude transformer reach the preset value; S3. Solve the zero displacement position of the current amplitude rod and the natural frequency of the axial mode of the specimen through finite element analysis. If the fatigue test requirements are not met, optimize the side profile and cross-sectional dimensions of the specimen until the fatigue test requirements are met. The fatigue test requirements are that the zero displacement position of the amplitude rod coincides with the middle position of the specimen and the natural frequency of the axial mode of the specimen reaches the expected design frequency. S4, design parameters of the output amplitude rod and specimen, to complete the design of in-situ high-resolution microscopic characterization equipment.

[0009] In summary, compared with the prior art, the technical solutions conceived in this invention have the following main advantages: 1. The in-situ high-resolution microscopic characterization device proposed in this invention has an opening in the vacuum chamber of an electron microscope device. After the specimen is connected to the end of the amplitude transformer, it extends directly into the electron microscope device through the opening of the vacuum chamber. An external fine-tuning system is used to adjust the zero-point position of the surface displacement of the specimen to be within the electron beam landing area of ​​the electron microscope device, and microscopic observation and characterization of microscopic deformation mechanisms are carried out. Moreover, in order to solve the influence of the vacuum chamber opening on the vacuum chamber sealing performance, this invention also designs a unique sealing device. The amplitude transformer extends into the vacuum chamber through the hollow bellows of the sealing device, and the hollow bellows achieves the sealing of the vacuum chamber and the pipeline through the sealing end caps at both ends. This solves the vacuum sealing problem caused by extending the amplitude transformer into the electron microscope device. Furthermore, this invention also sets up an external fine-tuning device. This external fine-tuning device drives the sealing device passing through the support block by adjusting the support block, thereby realizing the position adjustment of the ultra-high cycle fatigue component, so that the specimen at the end of the amplitude transformer is within the observation range of the electron microscope device. Based on the in-situ high-resolution micro-characterization equipment, it is possible to realize in-situ high-resolution real-time observation and characterization of the entire process of crack initiation and propagation in ultra-high cycle fatigue specimens based on electron microscopy. This breaks through the limitation that traditional test systems cannot achieve high-resolution in-situ characterization and provides a new technical means for further in-depth research on the quantitative correlation between ultra-high cycle fatigue theory and micro-deformation mechanism. 2. The in-situ high-resolution microscopic characterization device design method proposed in this invention, in order to achieve the coincidence of the specimen's midpoint and the zero-point displacement position within an adjustable electron microscopy observation range, firstly performs a coarse adjustment design to determine the length so that the specimen is within the electron microscopy observation range and the magnification factor of the amplitude transformer reaches a preset value. Then, a fine-tuning specimen design is performed to ensure the zero-point displacement position is at the midpoint of the specimen, achieving the coincidence of the two points and both being within the electron microscopy observation range. Through the above design method, the dimensional parameters of the specimen and the amplitude transformer are designed and controlled to ensure that the specimen's midpoint and the zero-point displacement position coincide within an adjustable electron microscopy observation range. Since the zero-point displacement position on the specimen is in a relatively static state during ultrasonic excitation, the entire process of ultrasonic ultra-high cycle fatigue can ultimately be observed in situ at high resolution using electron microscopy. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of the structure of an in-situ high-resolution microscopic characterization device for ultra-high cycle fatigue testing according to an embodiment of the present invention. Figure 2 This is a schematic diagram of the structure of the first sealing end cap in one embodiment of the present invention; Figure 3 This is a schematic diagram of the structure of the second sealing end cap in one embodiment of the present invention; Figure 4 This is a schematic diagram of the structure of a specimen in one embodiment of the present invention; Figure 5This is a flowchart of the steps of the in-situ high-resolution microscopic characterization device design method in one embodiment of the present invention; In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein: 1-Vacuum chamber, 2-Ultra-high cycle fatigue component, 3-Support block, 4-Hollow bellows, 5-First sealing end cap, 6-Second sealing end cap, 7-External fine-tuning device. Detailed Implementation

[0011] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0012] Example 1 This invention provides an in-situ high-resolution microscopic characterization device for ultra-high cycle fatigue testing.

[0013] like Figure 1 The diagram shows a schematic of an in-situ high-resolution microscopic characterization device for ultra-high cycle fatigue testing according to an embodiment of the present invention. The device includes: an ultrasonic fatigue testing device, an electron microscope device (with a vacuum chamber 1), a sealing device, and an external fine-tuning device.

[0014] The ultrasonic fatigue testing device includes an ultra-high cycle fatigue component 2 and a support block 3 supporting the ultra-high cycle fatigue component. The ultra-high cycle fatigue component 2 includes an ultrasonic transducer and an amplitude transformer. The end of the amplitude transformer is used to connect to the test specimen. One end of the amplitude transformer connected to the test specimen extends into the vacuum chamber 1 of the electron microscope device. The ultrasonic transducer is used to generate ultrasonic energy and apply it to the test specimen through the amplitude transformer to conduct fatigue tests on the test specimen. Specifically, the ultrasonic transducer can convert low-frequency voltage into a voltage-adjustable high-frequency sinusoidal electrical signal. The amplitude transformer is connected to the ultrasonic transducer and is used to transmit and amplify the ultrasonic energy generated by the ultrasonic transducer, so that the test specimen achieves the expected fatigue stress range through the amplified amplitude.

[0015] The sealing device includes a hollow bellows 4 and a first sealing end cap 5 and a second sealing end cap 6 extending from both ends of the hollow bellows in a direction away from the central axis. The hollow bellows 4 can be seamlessly welded to the end caps at both ends to achieve vacuum sealing. The hollow bellows 4 passes through the support block 3 and extends to the opening of the vacuum chamber 1 where it connects to the amplitude transformer. The first sealing end cap 5 is fixed to the outer surface of the vacuum chamber 1, and the second sealing end cap 6 is fixed to the outer surface of the support block 3. The ultra-high cycle fatigue component 2 is covered by the second sealing end cap 6 and extends into the vacuum chamber 1 through the hollow space of the hollow bellows 4. The sealing device is used to seal the opening of the vacuum chamber 1 where it connects to the ultra-high cycle fatigue component 2 to ensure the airtightness of the vacuum chamber 1.

[0016] The external fine-tuning device 7 is located outside the vacuum chamber 1 and is used to adjust the position of the specimen by adjusting the position of the support block 3 so that the zero displacement point of the specimen in the fatigue test is located in the electron beam landing area of ​​the electron microscope device.

[0017] Electron microscopes are used for in-situ observation of specimens.

[0018] The above-described in-situ high-resolution microscopic characterization equipment features an opening in the vacuum chamber of an electron microscope. The specimen, connected to the end of the amplitude transformer, extends directly into the electron microscope through this opening. An external fine-tuning system adjusts the zero-point displacement of the specimen surface to be within the electron beam landing area of ​​the electron microscope, enabling microscopic observation and characterization of microscopic deformation mechanisms. Furthermore, to address the impact of the vacuum chamber opening on the vacuum chamber's sealing performance, a unique sealing device is designed. The ultrasonic fatigue testing device extends into the vacuum chamber through a hollow bellows within this sealing device, which is sealed at both ends to achieve a seal between the vacuum chamber and the pipeline. This solves the vacuum sealing problem caused by extending the amplitude transformer into the electron microscope. Additionally, the invention includes an external fine-tuning device. This device adjusts the support block, thereby driving the sealing device through it and adjusting the position of the ultrasonic fatigue testing device, ensuring the specimen at the end of the amplitude transformer is within the observable range of the electron microscope. Based on in-situ high-resolution microscopic characterization equipment, it is possible to realize in-situ high-resolution real-time observation and characterization of the entire process of crack initiation and propagation in ultra-high cycle fatigue specimens based on electron microscopy. This breaks through the limitation of traditional test systems that cannot achieve high-resolution in-situ characterization, and provides a new technical means for further in-depth research on the quantitative correlation between ultra-high cycle fatigue theory and microscopic deformation mechanism.

[0019] In one embodiment, the amplitude transformer is a composite amplitude transformer with multiple segments along its length. That is, the amplitude transformer adopts a multi-section composite design to adjust the magnitude of the half-wavelength of the displacement change, so that a zero-displacement position exists in the specimen, i.e., a relatively stationary position during vibration. This allows for accurate quantitative characterization of the ultra-high cycle fatigue deformation behavior and deformation mechanism. In one embodiment, the zero-displacement position of the vibration can be selected at the mid-section of the specimen, while ensuring that the center of the specimen can be observed within the visible working range of the electron microscope system (i.e., the range hit by the electron beam) through an external fine-tuning device.

[0020] In one embodiment, the support block 3 can be a solid aluminum plate bracket.

[0021] In one embodiment, the outer ring of the first sealing end cap 5 near the edge of the end cap has screw holes for positioning and fixing, and the inner ring of the first sealing end cap 5 near the hollow area of ​​the hollow bellows is provided with a rubber strip surrounding the hollow area. When the vacuum chamber 1 is evacuated, under the action of the device's own gravity and the internal pressure difference, the rubber strip is flattened and adsorbed at the opening of the vacuum chamber 1 where it connects to the ultra-high cycle fatigue component, thereby achieving a vacuum seal.

[0022] Specifically, such as Figure 2 The diagram shown is a schematic diagram of the structure of the first sealing end cap in one embodiment of the present invention. The outer ring of the first sealing end cap 5 located at the vacuum chamber opening of the electron microscope has two screw holes for positioning and fixing. The inner ring has a small circular groove, in which a rubber strip that fits well is installed. When vacuuming, the rubber strip is flattened and adsorbed at the interface of the vacuum chamber opening by the device's own weight and the pressure difference between the inside and outside of the air, thereby achieving a vacuum seal.

[0023] In the above embodiments, the first sealing end cap 5 achieves sealing through automatic adsorption caused by vacuum, avoiding the impact of possible rigid contact caused by bolt connection and improving sealing performance.

[0024] like Figure 3 The diagram shown is a schematic diagram of the structure of the second sealing end cap in one embodiment of the present invention. In this embodiment, the second sealing end cap 6 is fixed to the support block by bolts and flanges, and a sealing rubber gasket is provided on the inner wall of the second sealing end cap 6 that covers the ultra-high cycle fatigue component. The sealing rubber gasket improves the sealing performance when the second sealing end cap 6 and the ultra-high cycle fatigue component are covered.

[0025] Hollow corrugated pipes can be made of metal. Understandably, hollow corrugated pipes should have a certain thickness to ensure that they do not deform or collapse under the vacuum conditions of an electron microscope.

[0026] The above sealing device can maintain the vacuum state of vacuum chamber 1 when the vacuum pump of the electron microscope is in operation.

[0027] In one embodiment, the support block 3 is placed on the external fine-tuning device 7. Specifically, the external fine-tuning device 7 can be connected to the upper support block 3 by bolts. The support block 3 fixes the ultra-high cycle fatigue component 2. That is, the external fine-tuning device 7 needs to bear the weight of the ultra-high cycle fatigue component 2 and the support block 3. The external fine-tuning device 7 can move in multiple directions (up, down, left, right). By adjusting the external fine-tuning device 7, the observation position of the specimen at the end of the amplitude transformer rod in the electron microscope device can be adjusted to ensure that the relative static position of the displacement zero point can be observed in real time. It should be emphasized that, in order not to affect the basic performance of the electron microscope, this invention does not use the fine-tuning device built into the electron microscope itself, but designs a separate external fine-tuning device to ensure that, within the adjustable distance range, the microscopic deformation behavior and its corresponding physical mechanism near the displacement zero point of ultrasonic ultra-high cycle fatigue can be characterized using the electron microscope.

[0028] In one embodiment, a specimen with a tangential plane is further provided to facilitate in-situ electron microscopy ultra-high cycle fatigue testing, such as... Figure 4 The diagram shows a schematic of the specimen in one embodiment of the present invention. The specimen is a symmetrical structure obtained by cutting the side of a dog-bone shaped specimen. The dog-bone shaped specimen includes a cylindrical test section, a flared variable cross section, and a cylindrical resonant section from the middle to both sides. The radius of the resonant section is larger than that of the test section. The cutting includes forming two first machining surfaces of the same size and opposite positions on the upper and lower sides of the dog-bone shaped specimen, and forming two second machining surfaces of the same size and opposite positions on the left and right sides of the dog-bone shaped specimen. The first machining surface has a first arc surface that is tangent to the cylindrical test section from the flared variable cross section at both ends, and a plane connecting the two first arc surfaces. The second machining surface is a second arc surface located in the test section.

[0029] In the above embodiments, the designed specimen can obtain the maximum stress at the observation surface at the center position. The ultra-high cycle fatigue fracture of the specimen is more likely to occur at the mid-section position, which is more conducive to observing the failure mechanism of the material and studying the initiation and propagation mechanism of ultra-high cycle cracks. It solves the problem that cracks may occur at any position in the test section, which is not conducive to in-situ observation of crack fracture surfaces. In other words, the specimen design provided in this embodiment realizes that when the specimen is subjected to ultrasonic ultra-high cycle fatigue testing, the fracture surface occurs at the middle position of the test area. Setting the observation surface at the middle position of the test area improves the accuracy of quantitative analysis of the microscopic characterization of the specimen.

[0030] Preferably, the radius R1 of the first arc surface and the radius R2 of the second arc surface satisfy the following condition: the value of R1 is in the range of [0.8R2, 1.2R2].

[0031] Preferably, the maximum processing depth h of the first processing surface and the diameter d of the resonant section satisfy the following condition: the range of h is... .

[0032] Within the above value range, it helps to significantly reduce the number of calculation iterations to determine the final specimen size.

[0033] It should be noted that other specimens can also be used instead, in principle any ultra-high cycle fatigue specimen with a planar section is acceptable.

[0034] Example 2 This invention provides a design method for the in-situ high-resolution microscopic characterization device for ultra-high cycle fatigue testing provided in the above embodiments.

[0035] Understandably, the components of the in-situ high-resolution microscopic characterization equipment are fixed, as described in the above embodiments. It includes an ultrasonic fatigue testing device, an electron microscope device, a sealing device, and an external fine-tuning device. The parameters of the electron microscope device, the sealing device, and the external fine-tuning device are all fixed. The design focus of the in-situ high-resolution microscopic characterization equipment is to design the parameters of the amplitude transformer and its matching specimen parameters so that the middle position of the specimen coincides with the zero displacement position and is located in the electron beam landing area.

[0036] like Figure 5 The diagram shown is a flowchart of the design method for an in-situ high-resolution microscopic characterization device according to an embodiment of the present invention. The following is a summary of the steps. Figure 5 This design method will be explained in detail.

[0037] S1. Based on the distance from the electron beam landing area of ​​the electron microscope device to the vacuum chamber opening, determine the length of the amplitude transformer and the length of the specimen, so that the specimen at the end of the amplitude transformer extends into the electron beam landing area.

[0038] Specifically, a sample can be initially selected and placed at the end of the amplitude transformer. Then, the length of the amplitude transformer is determined so that it can extend into the vacuum cavity and the sample at its end can be in the electron beam landing area.

[0039] S2. Optimize the side profile and cross-sectional dimensions of the amplitude transformer to make the amplification factor of the amplitude transformer reach the preset value.

[0040] Specifically, the amplification factor (amplitude amplification factor) of the amplitude transformer refers to the ratio of the output amplitude to the input amplitude. It is used to describe the amplitude transformer's ability to amplify vibration energy. The amplitude transformer amplifies the vibration energy and then applies it to the specimen at its end to achieve fatigue testing of the specimen.

[0041] Specifically, the number of segments and the material of the amplitude transformer can be determined in advance. After determining the above parameters, the side profile and cross-sectional dimensions of the amplitude transformer can be optimized to make the amplification factor of the amplitude transformer reach the preset value.

[0042] More specifically, the optimization goal can be to achieve a preset value in the magnification system, and by combining gradient optimization and non-gradient optimization algorithms, the side profile and cross-sectional dimensions of the amplitude transformer can be optimized.

[0043] Based on the above steps, the overall dimensions can be roughly adjusted, the length of the specimen and the overall dimensions of the amplitude transformer can be determined, the amplification factor of the amplitude transformer can be made to reach the preset value, and the specimen can be located in the electron beam landing area.

[0044] S3. Solve the zero displacement position of the current amplitude rod and the natural frequency of the axial mode of the specimen through finite element analysis. If the fatigue test requirements are not met, optimize the side profile and cross-sectional dimensions of the specimen until the fatigue test requirements are met. The fatigue test requirements are that the zero displacement position of the amplitude rod coincides with the middle position of the specimen and the natural frequency of the axial mode of the specimen reaches the expected design frequency.

[0045] Specifically, for the amplitude transformer and its specimen, a geometric model is established for the whole. The zero-displacement position of the amplitude transformer is solved using the finite element method. Furthermore, the axial mode natural frequencies of the current specimen are obtained through finite element analysis. If the fatigue test requirements are not met, the side profile and cross-sectional dimensions of the specimen are optimized until they are satisfied. Specifically, the travel limit of the external fine-tuning device can be considered to ensure that within the travel limit of the external fine-tuning device, the zero-displacement position of the amplitude transformer coincides with the middle position of the specimen and is within the observable range.

[0046] While the coarse adjustments achieved positioning of the specimen within the electron beam landing region, the zero-displacement point may not be located in the center of the specimen. Therefore, fine adjustments are necessary to optimize the specimen's side profile and cross-sectional dimensions, ensuring that the zero-displacement point coincides with the center of the specimen and both are within the electron beam landing region. Furthermore, the specimen's axial mode natural frequency must reach the expected design frequency.

[0047] S4, design parameters of the output amplitude rod and specimen, to complete the design of in-situ high-resolution microscopic characterization equipment.

[0048] The design method proposed in this invention, in order to achieve the coincidence of the specimen's midpoint and the zero-point displacement position within an adjustable electron microscopy observation range, first performs a coarse adjustment design to determine the length so that the specimen is within the electron microscopy observation range and the amplification factor of the amplitude transformer reaches a preset value. Then, a fine adjustment design is performed to ensure the zero-point displacement position is at the specimen's midpoint, achieving the coincidence of both points within the electron microscopy observation range. By designing and controlling the dimensional parameters of the specimen and the amplitude transformer using the above method, the coincidence of the specimen's midpoint and the zero-point displacement position within the adjustable electron microscopy observation range is ensured. Since the zero-point displacement position on the specimen is in a relatively static state during ultrasonic excitation, high-resolution in-situ observation of the entire process of ultrasonic high-cycle fatigue using electron microscopy is ultimately achieved.

[0049] After completing the parameter design using the above method, an in-situ high-resolution microscopic characterization device can be built and in-situ high-resolution microscopic characterization of ultra-high cycle fatigue tests can be performed using the following method: 1. Prepare the characterization surface of the ultra-high cycle fatigue specimen by polishing and other micro-characterization surface treatments, and make micro-marks near the preset zero displacement position by indentation and other methods. 2. Connect the amplitude transformer to the ultrasonic transducer, and install the ultra-high cycle fatigue specimen to be observed and quantitatively characterized at the end of the amplitude transformer; further, extend the ultrasonic fatigue testing device into the vacuum cavity of the electron microscope device so that the specimen is within the observation range of the electron microscope; 3. Connect a sealing device at the interface between the ultrasonic fatigue testing device and the electron microscope device to ensure the vacuum environment requirements of high-resolution electron microscopy; 4. Fine-tune the ultrasonic fatigue testing device and the position of the specimen using an external fine-tuning device, adjust the specimen to the optimal observation position in the electron microscope system until the marked position on the specimen surface is determined, and then fix the fine-tuning device to lock the system position. 5. On an external computer, use the ultrasonic high-frequency control system to set the ultrasonic fatigue test conditions and control parameters, and then conduct the high-frequency fatigue test; 6. Utilize electron microscopy to conduct microscopic observations of the fatigue behavior of ultra-high cycle fatigue specimens, enabling in-situ observation of the entire process from crack initiation to propagation failure in ultra-high cycle fatigue. In addition, high-resolution quantitative characterization techniques (such as high-resolution DIC and high-resolution EBSD) can be combined to accurately and quantitatively characterize the mechanical behavior and microscopic deformation mechanism during the ultra-high cycle fatigue failure process.

[0050] In summary, this invention enables simultaneous in-situ observation during ultra-high cycle fatigue testing, thus introducing ultra-high cycle fatigue research into a new stage of quantitative characterization of micromechanics. It allows for real-time observation of microscopic dislocation slip and the failure process of materials during ultra-high cycle fatigue. This in-situ, real-time, high-resolution technology facilitates in-depth research into the physical principles of long-life, safe service of key materials, and provides more comprehensive theoretical and experimental technical support for the study of ultra-high cycle fatigue performance of materials under extreme environments.

[0051] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. It should be noted that the terms "in one embodiment," "for example," and "again" are intended to illustrate the present invention and are not intended to limit the present invention.

[0052] The above embodiments merely illustrate several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. An in-situ high-resolution micro-characterization apparatus for ultra-high cycle fatigue testing, characterized by, The application relates to an ultrasonic fatigue test device, an electron microscope device, a sealing device and an external fine adjustment device. The ultrasonic fatigue test device comprises an ultrasonic fatigue test assembly and a supporting block supporting the ultrasonic fatigue test assembly, the ultrasonic fatigue test assembly comprises an ultrasonic transducer and a variable amplitude rod, the end of the variable amplitude rod is used for connecting a test piece, one end of the variable amplitude rod connected to the test piece extends into a vacuum cavity of the electron microscope device, the ultrasonic transducer is used for generating ultrasonic wave energy and acting on the test piece through the variable amplitude rod to perform a fatigue test on the test piece. The sealing device comprises a hollow bellows and first and second sealing end covers respectively bent and extended from the two end portions of the hollow bellows, the hollow bellows passes through the supporting block and extends to the vacuum cavity to access the barrel opening of the variable amplitude rod, the first sealing end cover is fixedly attached to the outer surface of the vacuum cavity, the second sealing end cover is fixedly attached to the outer surface of the supporting block, the ultrasonic fatigue test assembly is covered on the second sealing end cover and extends into the vacuum cavity through the hollow space of the hollow bellows, and the sealing device is used for sealing the barrel opening of the ultrasonic fatigue test assembly accessing the vacuum cavity to ensure the airtightness of the vacuum cavity. The external fine adjustment device is located outside the vacuum cavity and is used for adjusting the position of the test piece by adjusting the position of the supporting block, so that the displacement zero point of the test piece in the fatigue test is located in the electron beam landing point area of the electron microscope device. The electron microscope device is used for in-situ observation of the test piece. The outer ring of the first sealing end cover close to the end cover edge has a threaded hole for positioning and fixing, and the inner ring of the first sealing end cover close to the hollow region of the hollow bellows is provided with a rubber ring surrounding the hollow region; when the vacuum cavity is vacuumized, under the action of the gravity of the device itself and the pressure difference of the internal pressure, the rubber ring is flattened and adsorbed at the barrel opening of the vacuum cavity to realize vacuum sealing.

2. The in-situ high resolution micro-characterization apparatus of claim 1, wherein, The supporting block is placed on the external fine adjustment device, and the observation position of the test piece at the end of the variable amplitude rod in the electron microscope device is adjusted by adjusting the external fine adjustment device.

3. The in-situ high resolution micro-characterization apparatus of claim 1, wherein, The displacement zero point is located at the middle position of the test piece.

4. The in-situ high resolution micro-characterization apparatus of claim 1, wherein, The test piece is a center-symmetrical structure obtained by cutting the side surface of a dog bone type test piece, the dog bone type test piece sequentially comprises a cylindrical test section, a horn-shaped variable cross-section section and a cylindrical resonance section from the middle to both sides, and the radius of the resonance section is greater than that of the test section, the cutting comprises forming two first machining surfaces with the same size and opposite positions on the upper and lower side surfaces of the dog bone type test piece and forming two second machining surfaces with the same size and opposite positions on the left and right side surfaces of the dog bone type test piece, the first machining surface has a first circular arc surface tangent to the cylindrical test section from the horn-shaped variable cross-section section at both ends and a plane connecting the two first circular arc surfaces, and the second machining surface is a second circular arc surface located at the test section.

5. The apparatus of claim 4, wherein, The variable amplitude rod is a composite variable amplitude rod, and the composite variable amplitude rod has a plurality of segments along the length direction.

6. The apparatus of claim 5, wherein, The circular arc radius R1 of the first circular arc surface and the circular arc radius R2 of the second circular arc surface satisfy: the value range of R1 is [0.8R2, 1.2R2]; the maximum machining depth h of the first machining surface and the diameter d of the resonance section satisfy: the value range of h is .

7. The in-situ high resolution micro-characterization apparatus of claim 1, wherein, The application relates to an ultrasonic fatigue test device, an electron microscope device, a sealing device and an external fine adjustment device.

8. A method for designing an in-situ high-resolution micro-characterization apparatus for ultra-high cycle fatigue testing according to any one of claims 1 to 7, characterized in that, ​ S1, determining the length of the variable amplitude rod and the length of the test piece according to the distance from the electron beam landing area of the electron microscope device to the vacuum cavity port, so that the test piece at the end of the variable amplitude rod extends into the electron beam landing area; S2, optimizing the side profile and cross-sectional size of the variable amplitude rod, so that the amplification coefficient of the variable amplitude rod reaches a preset value; S3, solving the displacement zero point position of the current variable amplitude rod and the axial mode natural frequency of the test piece by finite element analysis, if the fatigue test requirement is not met, then optimizing the side profile and cross-sectional size of the test piece until the fatigue test requirement is met, the fatigue test requirement is that the displacement zero point position of the variable amplitude rod coincides with the middle position of the test piece and the axial mode natural frequency of the test piece reaches the expected design frequency; S4, outputting the design parameters of the variable amplitude rod and the test piece, and completing the design of the in-situ high-resolution micro characterization equipment.

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