In-situ fretting corrosion fatigue testing machine and method based on synchrotron radiation diffraction and three-dimensional imaging

Abstract

The present invention relates to an in-situ fretting corrosion fatigue testing machine and method based on synchrotron radiation diffraction and three-dimensional imaging, and belongs to the field of fretting corrosion fatigue testing. The testing machine includes an axial fatigue loading system, a fretting loading system and a corrosion environment control system; the axial fatigue loading system includes a driving device, a load control device, and a load sensing device; the load sensing device is used to measure the axial force and normal force in real time; the driving device is used to drive the load control device to enable the load control device to achieve axial displacement; the load control device is used to perform axial fatigue loading on the sample; the fretting loading system includes a fretting wear device. The testing machine is used to realize the real-time three-dimensional imaging characterization of material wear spots and crack shapes under fretting corrosion environment and the characterization of residual stress evolution law.

Description

Technical Field

[0001] The invention belongs to the field of fretting corrosion fatigue testing, and relates to an in-situ fretting corrosion fatigue testing machine and method based on synchrotron radiation diffraction and imaging technology. Background Art

[0002] Fretting fatigue refers to a failure mode in which the contact interface undergoes micrometer-level relative movement due to external alternating stress, which accelerates the initiation and expansion of fatigue cracks, thereby affecting its fatigue strength and life. When fretting fatigue and corrosion damage coexist, the effects of the two are not simply superimposed, but there is an obvious interaction between the two types of damage, and its intensity has exceeded the consequences of the simple action of alternating stress and corrosive medium. Affected by corrosive media, the fretting fatigue life of materials has been greatly reduced, posing a great challenge to the safe use of major engineering equipment. Fretting corrosion fatigue is widely present in many national economic industries such as marine machinery, aerospace, and rail transportation. Especially under harsh natural conditions such as marine atmosphere and urban acid rain, the fretting corrosion fatigue damage of components is very prominent. Therefore, it is of great theoretical and practical significance to explore the failure behavior and mechanism of fretting corrosion fatigue damage.

[0003] At present, researchers at home and abroad mainly use scanning electron microscopy, optical microscopy and transmission electron microscopy to observe and analyze the surface morphology and fracture of wear spots and corrosion pits of fretting fatigue failure specimens, and then infer the fretting fatigue damage mechanism. However, surface observation and destructive section research alone cannot obtain the evolution law of wear spots and cracks in the fretting fatigue process, resulting in the fretting fatigue damage mechanism of materials still being unknown. In order to study the evolution of wear spots / corrosion pits and cracks in three-dimensional space and the interaction between corrosive media and fatigue loads during fretting fatigue, it is necessary to observe the fretting fatigue process in situ and in real time. In recent years, the material characterization technology based on synchrotron radiation light source has developed rapidly. Due to its high brightness, high collimation, high polarization, narrow pulse and other characteristics, it can accurately capture the defects and microstructure distribution characteristics in the sample at the submicron spatial scale and the picosecond time scale. It is a new type of ultra-high resolution microscopic imaging technology to realize in-situ, dynamic, non-destructive and visualized research on the microstructure of various materials. The use of synchrotron radiation light source imaging technology can observe the process and evolution of fretting corrosion fatigue damage and fracture in situ and in real time, which has irreplaceable scientific significance for the accurate assessment of material strength and life.

[0004] In addition, the existence of residual stress has an important influence on the fatigue life of components. Generally, residual tensile stress reduces fatigue life, and residual compressive stress can prevent cracks from initiating. Therefore, exploring the evolution law of residual stress in fretting corrosion fatigue is an important basis for studying fretting corrosion fatigue. Studies have shown that during fretting fatigue loading, the depth and width of residual stress in the fretting wear area can reach hundreds of microns. At present, there are a variety of non-destructive detection methods that can be used to characterize the evolution of residual stress, including laboratory X-ray diffraction (XRD), neutron diffraction (ND), synchrotron radiation diffraction, etc. Among them, the laboratory X-ray diffraction method has poor penetration ability, and the penetration depth is generally around 10 microns, which cannot characterize the residual stress evolution law inside the material in situ; the resolution of the neutron diffraction method is at the millimeter level, and it cannot accurately measure the residual stress distribution in the micron-level micron-wear area; and the resolution of synchrotron X-ray diffraction can be adjusted between a few microns and hundreds of microns, and it has the characteristics of high stability, high throughput, small beam diameter, quasi-coherence, etc., and has stronger penetration. Combined with the in-situ micron-corrosion fatigue testing machine compatible with the synchrotron diffraction line station, it can effectively obtain the residual stress distribution and evolution law in the micron-level micron-wear area.

[0005] Currently, in the field of fretting corrosion fatigue testing, commercial fatigue testing machines on the market are mainly used to carry out tests in combination with the sample environment. However, their size and weight are huge, and there are components such as metal support arms around the test samples, which cannot meet the imaging and diffraction requirements of synchrotron radiation light sources. Therefore, commercial fatigue testing machines cannot be directly used for synchrotron radiation light sources. Summary of the invention

[0006] The technical problems to be solved by the present invention are:

[0007] In order to avoid the shortcomings of the prior art, the present invention provides an in-situ fretting corrosion fatigue testing machine and method suitable for synchrotron radiation light source imaging and diffraction, so as to meet the relevant conditions required for synchrotron radiation light source experiments, thereby realizing real-time three-dimensional imaging characterization of material wear spots and crack shapes under fretting corrosion environments and characterization of residual stress evolution laws.

[0008] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0009] An in-situ fretting corrosion fatigue testing machine based on synchrotron radiation diffraction and three-dimensional imaging, characterized in that it includes an axial fatigue loading system, a fretting loading system and a corrosion environment control system;

[0010] The axial fatigue loading system comprises a driving device, a load control device, and a load sensing device; the load sensing device is used to measure the axial force and the normal force in real time; the driving device is used to drive the load control device to enable the load control device to achieve axial displacement; the load control device is used to perform axial fatigue loading on the sample;

[0011] The fretting loading system includes a fretting wear device; the fretting wear device is two identical fretting pads that are symmetrical about the central axis of the sample and horizontally positioned 45 degrees downward, and the two fretting pads are connected to two identical moving magnet voice coil motors to achieve normal loading, so that the fretting pads and the sample surface are kept in close contact during the entire experiment, ensuring that the electromagnetic loading device cooperates with the two fretting pads to achieve fretting fatigue testing;

[0012] The corrosion environment control system includes an environment control device and a data acquisition and control device; the environment control device is used to provide a corrosion environment of full immersion, peripheral immersion, and salt spray for the sample; the data acquisition and control device is used to collect measurement data and control the drive device.

[0013] A further technical solution of the present invention is as follows: the axial fatigue loading system comprises a chassis, an xy micro-displacement platform, an axial force sensor, a PMMA support cover, a lower clamp, an upper clamp, an electromagnetic loading device, an electric hydraulic cylinder, an upper end cover, an upper support rod, and a lower support rod; the xy micro-displacement platform is fixed on the chassis to ensure the overall coaxiality of the testing machine after clamping the sample; the axial force sensor is installed on the upper end of the xy micro-displacement platform to monitor the axial loading force of the collected sample; the lower support rod is fixed on the xy micro-displacement platform, and a PMMA support cover is installed on the upper end of the lower support rod; a clamp and a lower clamp are respectively installed on the upper and lower sides of the PMMA support cover to clamp the sample; an upper support rod is installed above the PMMA support cover to support the upper end cover; the electromagnetic loading device is fixed on the upper end of the upper clamp to apply axial force to the sample to achieve axial fatigue loading; the electric hydraulic cylinder is fixed above the electromagnetic loading device to control the axial displacement of the upper end part of the sample of the axial fatigue loading system to facilitate the replacement of the sample.

[0014] A further technical solution of the present invention is as follows: the micro-motion loading system comprises a micro-motion pad, a moving magnet voice coil motor and a normal force sensor; two identical normal force sensors are installed on the top of the micro-motion pad to monitor the micro-force applied by the micro-motion pad of the sample; the two micro-motion pads are connected to two identical moving magnet voice coil motors, which are in turn connected to a computer terminal, and the two micro-motion pads are controlled to generate normal displacement through computer input signals to ensure that the micro-motion pad is in close contact with the sample during the entire loading process to achieve micro-motion fatigue testing.

[0015] A further technical solution of the present invention is that the top height of the micro-motion pad is the same as the micro-motion wear area of ​​the sample.

[0016] A further technical solution of the present invention is as follows: the environment control device adopts a "bottom-in, top-out" circulation mode, and can create a full immersion, surrounding immersion, and salt spray corrosion environment in the test chamber by controlling the state of the two-position four-way solenoid valve and the state of the liquid inlet.

[0017] A further technical solution of the present invention is as follows: the environmental control device also includes heating by clustered tubular electric heating tubes to accelerate the corrosion rate, and simultaneously using thermocouples to measure the temperature in the corrosion solution cavity, thereby realizing the micro-corrosion fatigue damage test.

[0018] A further technical solution of the present invention: the corrosive environment control system includes a liquid inlet, an upper liquid outlet, a lower liquid outlet, a corrosive medium cavity, a solution tank, an overflow valve, a filter, a hydraulic pump, a one-way valve, a two-position four-way solenoid valve, a clustered tubular electric heating tube, a thermocouple, and a central processing unit; the two interfaces at the upper end of the two-position four-way solenoid valve are respectively connected to the liquid inlet 4 and the lower liquid outlet, the two interfaces at the lower end are respectively connected to the one-way valve and the solution tank, the upper liquid outlet is directly connected to the solution tank, the clustered tubular electric heating tube is fixed to the lower cover of the cavity by fasteners, and a thermocouple is installed at the lower cover of the cavity to monitor the temperature in the corrosive medium cavity, the central processing unit is respectively connected to the clustered tubular electric heating tube, the thermocouple, the axial force sensor, the normal force sensor and the electric hydraulic cylinder, and is uniformly controlled by the central processing unit.

[0019] An in-situ fretting corrosion fatigue test method based on synchrotron radiation diffraction and three-dimensional imaging, characterized by the following steps:

[0020] Step 1: After the upper fixture clamps the sample, adjust the xy micro-displacement platform so that the lower fixture is aligned with the sample's center of gravity and clamps the sample. The electromagnetic loading device is adjusted to adjust the sample's height in the vertical direction and properly match the X-ray height. The laser positioning system is used to accurately locate the sample test position to ensure that the X-ray can pass through the PMMA support cover through the sample's area of ​​interest and be received by the ray receiver;

[0021] Step 2: Turn on the environmental control device through the central controller, connect the hydraulic pump and the clustered tubular electric heating tube, and use the thermocouple to measure the temperature in the corrosive medium cavity and transmit the data to the central controller. When the temperature in the corrosive medium cavity reaches the test requirements, the clustered tubular electric heating tube is disconnected. The designed corrosive solution cavity can provide three corrosive environment conditions: full immersion, peripheral immersion, and salt spray;

[0022] Step 3: After the corrosion environment is set, the corrosion fretting fatigue test is started. During the test, the axial movement of the electromagnetic loading device is controlled by the electric hydraulic cylinder to achieve axial fatigue actuation of the sample. At the same time, the fretting pad causes fretting wear on the sample, causing the internal cracks of the sample to open. At the same time, the axial force sensor collects the axial force data through the signal line and uploads it to the data acquisition card of the central controller, and then transmits it to the computer for recording;

[0023] Step 4: Start the X-ray emission device of the light source while ensuring that the X-ray will not be blocked, and control the light source rotating table to rotate the main body of the test device and the sample in the main body 180°; during this process, the high-energy X-rays emitted by the light source pass through the PMMA support cover, and after passing through the sample rotated 180°, they are received by the X-ray detector, thereby realizing 180° image processing of the sample; re-apply fatigue load to the specimen within the specified period, and repeat the above steps until the specified test period is reached;

[0024] Step 5: For the imaging line station, the reconstruction of the internal three-dimensional morphology of the material is completed to capture the crack initiation and propagation process during the fretting corrosion fatigue test; for the diffraction line station, the residual stress distribution information in the fretting wear area of ​​the material can be obtained to explore the evolution law of residual stress in fretting corrosion fatigue.

[0025] A further technical solution of the present invention: The three corrosive environmental conditions described in step 2: full immersion, peripheral immersion, and salt spray, are specifically:

[0026] a) Under full immersion corrosion conditions, the two-position four-way solenoid valve is in the energized state, at which time the liquid inlet is open and the lower liquid outlet is closed, and the corrosive solution forms a circulation loop in the order of solution tank-filter-hydraulic pump-check valve-liquid inlet-corrosive solution chamber-upper liquid outlet-solution tank;

[0027] b) Under the condition of circumferential immersion corrosion, the central controller controls the two-position four-way solenoid valve to be in a periodic on-off state. At this time, the liquid inlet is open, the lower liquid outlet is closed, and the circulation mode of the corrosion solution is the same as in a);

[0028] c) Under salt spray corrosion conditions, first replace the liquid inlet with an atomizing nozzle, adjust the flow rate of the hydraulic pump to the maximum, and adjust the maximum pressure of the overflow valve to ensure the safety of the test. At this time, the central controller controls the two-position four-way solenoid valve to be in a periodic on-off state. When the solenoid valve is energized, the atomizing nozzle atomizes the corrosive solution flowing through, forming a salt spray environment in the corrosive solution cavity; when the solenoid valve is de-energized, the lower liquid outlet is opened to discharge the atomized solution beads back into the solution tank.

[0029] The beneficial effects of the present invention are:

[0030] The in-situ fretting corrosion fatigue testing machine and method based on synchrotron radiation diffraction and imaging technology provided by the present invention have the following advantages:

[0031] 1. The present invention is a lightweight, compact in-situ imaging mechanical loading tester for fretting fatigue and corrosion coupling. It is small in size and weighs less than 20kg (light weight), can be well compatible with advanced light sources, meet the weight and size requirements of the sample platform, and can rotate 180° with the light source rotating platform.

[0032] 2. The present invention adopts an electric hydraulic cylinder as a driving mechanism, and drives the electromagnetic loading system to produce axial displacement through a high-precision load sensor, thereby realizing reciprocating circulation of the specimen, and applying tangential stress on the surface of the specimen through the micro-motion pad to cause micro-motion wear.

[0033] 3. The micro-motion pad is at an angle of 45° to the horizontal direction, and both ends of the micro-motion pad are relatively thin, thus ensuring that the synchrotron radiation light source can easily penetrate the sample during horizontal irradiation, and ultimately obtain three-dimensional imaging results.

[0034] 4. By controlling the on and off of the solenoid valve, the corrosion environment chamber of the testing machine can switch between three working states. Each working state is independent of each other and does not interfere with each other, ensuring that accurate results can be obtained when conducting fretting corrosion fatigue tests under various working conditions.

[0035] 5. The heater adopts clustered tubular electric heating elements, which have the advantages of fast thermal response, high temperature control accuracy, high comprehensive thermal efficiency and high heating temperature.

[0036] 6. The moving magnet voice coil motor can provide a static maximum load of ±750N, a dynamic maximum load of ±1250N, and a load accuracy of 0.001N; it can provide a displacement stroke of 40mm, and a displacement accuracy of 0.1μm; it can provide an actuation frequency of 0.001~50Hz, and the operation can remain stable for a long time, clean and noiseless.

[0037] 7. The main structure of the test equipment can rotate with the rotation of the synchrotron radiation source. A large-diameter circular hole is provided on its base to facilitate the lead-out of pipes and wires.

[0038] 8. Two sealing rings are installed on the upper and lower parts of the corrosion chamber to prevent the leakage of the corrosive medium, ensure the closed operating environment of the corrosion chamber, and enable the testing machine to operate normally and efficiently to ensure the accuracy of the test results. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0040] Figure 1 Schematic diagram of the overall structure of the in-situ fretting corrosion fatigue testing machine based on synchrotron radiation light source diffraction and three-dimensional imaging.

[0041] Figure 2 The overall structural assembly diagram of the in-situ fretting corrosion fatigue testing machine based on synchrotron radiation light source diffraction and three-dimensional imaging.

[0042] Figure 3 Three-dimensional image of the overall structure of the in-situ fretting corrosion fatigue testing machine based on synchrotron radiation light source diffraction and three-dimensional imaging.

[0043] Figure 4 Exploded image of the corrosion chamber of an in-situ fretting corrosion fatigue testing machine based on synchrotron radiation light source diffraction and three-dimensional imaging.

[0044] Figure 5 Diagram of the corrosion cavity pipeline of the in-situ fretting corrosion fatigue testing machine based on synchrotron radiation light source diffraction and three-dimensional imaging.

[0045] The reference numerals are as follows:

[0046] 1-sample rotating table; 2-chassis; 3-xy micro-displacement platform; 4-liquid inlet; 5-axial force sensor; 6-lower fixture; 7-micro-motion pad; 8-sample; 9-upper fixture; 10-electromagnetic loading system; 11-electric hydraulic cylinder; 12-upper end cover; 13-upper support rod; 14-upper liquid outlet; 15-corrosive medium cavity; 16-PMMA support cover; 17-lower liquid outlet; 18-moving magnetic voice coil motor; 19-lower support rod; 20-normal force sensor; 21-solution tank; 22-filter; 23-hydraulic pump; 24-overflow valve; 25-check valve; 26-two-position four-way electromagnetic; 27-central controller; 28-thermocouple; 29-clustered tubular electric heating tube. DETAILED DESCRIPTION

[0047] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0048] like Figure 1As shown, the present invention provides an in-situ fretting corrosion fatigue testing machine based on synchrotron radiation diffraction and imaging technology, which is composed of a driving device, a load control device, a load sensing device, a fretting wear device, an environmental control device, and a data acquisition and control device. It is an in-situ fretting corrosion fatigue testing device that can observe the material damage evolution process under the coupling of fretting fatigue and corrosion in real time. The load sensing device is used to measure the axial force and normal force in real time; the driving device uses an electric hydraulic cylinder to drive the load control device so that the load control device can achieve axial displacement; the load control device uses an electromagnetic loading system to perform axial fatigue loading on the sample, and the electric hydraulic cylinder is connected to the electromagnetic loading system; the fretting wear device is two identical fretting pads that are symmetrical about the central axis of the sample and horizontally positioned at 45° downward. The two fretting pads are connected to two identical moving magnetic voice coil motors to achieve normal loading, so that the fretting pads and the sample surface are kept in contact during the entire experiment. Maintain close contact to ensure that the electromagnetic loading system cooperates with the two micro-motion pads to realize micro-motion fatigue test; the environmental control device adopts a "bottom-in and top-out" circulation mode, and can create a full immersion, circumferential immersion, and salt spray corrosion environment in the test chamber by controlling the state of the two-position four-way solenoid valve and the state of the liquid inlet, and can also be heated by clustered tubular electric heating tubes to accelerate the corrosion rate, and use thermocouples to measure the temperature in the corrosion solution chamber, thereby realizing micro-motion corrosion fatigue damage test; the data acquisition and control device simultaneously controls the electric hydraulic cylinder, solenoid valve, electric heating tube and other components. By carrying out synchrotron radiation in-situ three-dimensional imaging and diffraction experiments on the damage evolution behavior of materials during micro-motion corrosion fatigue loading, and simultaneously using load sensing devices to quantitatively measure the applied load, the evolution law of defects, damage and residual stress inside the material during micro-motion corrosion fatigue loading with the number of cycles is obtained, providing indispensable high-end technical equipment for revealing the micro-motion corrosion fatigue damage mechanism of materials.

[0049] The driving device, load control device and load sensing device constitute an axial fatigue loading system; the micro-motion wear device constitutes a micro-motion loading system; the environmental control device and the data acquisition and control device constitute a corrosion environment control system. The axial fatigue loading system includes a chassis 2, an xy micro-displacement platform 3, an axial force sensor 5, a PMMA support cover 16, a lower fixture 6, an upper fixture 9, an electromagnetic loading device 10, an electric hydraulic cylinder 11, an upper end cover 12, an upper support rod 13, and a lower support rod 19; the micro-motion loading system includes a micro-motion pad 7, a moving magnetic voice coil motor 18, and a normal force sensor 20; the corrosion environment control system includes a liquid inlet 4, an upper liquid outlet 15, a lower liquid outlet 18, a corrosive medium cavity 16, a solution tank 21, an overflow valve 24, a filter 22, a hydraulic pump 23, a one-way valve 25, a two-position four-way electromagnetic valve 26, a clustered tubular electric heating tube 29, a thermocouple 28, and a central processing unit 27. The micro-motion loading system can ensure that the micro-motion pad 7 and the surface of the sample 8 maintain close contact during the entire experimental process, and ensure that the axial fatigue loading system cooperates with the two micro-motion pads 7 to realize the micro-motion fatigue test; through the control of the corrosion environment control system, three corrosion environment conditions of full immersion, peripheral immersion and salt spray can be provided, and cooperate with the axial fatigue loading system and the micro-motion loading system to carry out in-situ micro-motion corrosion fatigue test. In the axial fatigue loading system, the xy micro-displacement platform 3 is fixed to the chassis 2 by screws, so as to ensure the overall coaxiality of the testing machine after clamping the sample 8; the axial force sensor 5 is installed on the upper end of the xy micro-displacement platform 3, so as to monitor the axial loading force of the sample; the lower support rod 19 is fixed to the xy micro-displacement platform 3 by screws, and the PMMA support cover 16 is installed on the upper end of the lower support rod 19; the upper and lower sides of the PMMA support cover 16 are respectively provided with a clamp 6 and a lower clamp 9, which are fixed by screws for clamping the sample 8; the upper support rod 13 is installed above the PMMA support cover 16 by screws for supporting the upper end cover 12, and the connection between the upper end cover 12 and the upper support rod 13 is still screw connection; the electromagnetic loading system 10 is fixed to the upper end of the upper clamp 6 by screws, so as to apply axial force to the sample to realize axial fatigue loading; the electric hydraulic cylinder 11 is fixed above the electromagnetic loading system 10 by screws, so as to control the axial displacement of the upper end part of the sample of the axial fatigue loading system, so as to facilitate the replacement of the sample 8. In the micro-motion loading system, two identical micro-motion pads 7 are symmetrically installed horizontally at a 45° angle downward about the central axis of the sample. Two identical normal force sensors 20 are installed on the top of the micro-motion pads 7 to monitor the micro-force applied by the micro-motion pads of the sample. The top height of the micro-motion pads 7 is the same as the micro-motion wear area of ​​the sample. The two micro-motion pads 7 are connected to two identical moving magnetic voice coil motors 18, which are connected to the computer terminal. The two micro-motion pads 7 are controlled to produce normal displacement through computer input signals to ensure that the micro-motion pads 7 are in close contact with the sample 8 during the entire loading process to achieve micro-motion fatigue testing. In the corrosion environment control system, the corrosion solution circulation adopts a "bottom-in and top-out" circulation method.The corrosive solution is extracted from the solution tank 21 through the pipeline, flows into the corrosive medium cavity through the filter 22, the hydraulic pump 23, the two-position four-way solenoid valve 26, and the liquid inlet, and then returns to the solution tank 21 through the pipeline through the lower liquid outlet. Among them, the liquid inlet 4 and the lower liquid outlet 18 are installed on the lower cover of the cavity, and the upper liquid outlet 15 is installed on the upper cover of the cavity. The upper liquid outlet 15 is used to observe the liquid height after the liquid is stable; the overflow valve 24 is installed on the hydraulic pump branch to control the maximum pressure of the liquid in the pipeline to ensure safety during the test; the liquid inlet 4 and the upper and lower liquid outlets are all equipped with rubber gaskets for sealing. The two interfaces at the upper end of the two-position four-way solenoid valve 26 are connected to the liquid inlet 4 and the lower liquid outlet 18 respectively, and the two interfaces at the lower end are connected to the one-way valve 25 and the solution tank 21 respectively, and the upper liquid outlet 15 is directly connected to the solution tank 21. The clustered tubular electric heating tube 29 is fixed to the lower cover of the cavity by fasteners, and a thermocouple 28 is installed at the lower cover of the cavity to monitor the temperature in the corrosive medium cavity. The central processor 27 is respectively connected to the clustered tubular electric heating tube 29, the thermocouple 28, the axial force sensor 5, the normal force sensor 20 and the electric hydraulic cylinder 11, and is uniformly controlled by the central processor 27.

[0050] The process of building the test machine is as follows:

[0051] 1) The xy micro-displacement platform 3 is placed on the chassis 2, and can be made to make a planar micro-displacement relative to the chassis 2. Its function is as follows: when the sample 8 is fixed by the upper clamp 9 and needs to be aligned with the lower clamp 6, the chassis 2 can be adjusted to make a planar micro-displacement so that the center of gravity of the upper and lower clamps coincide, thereby avoiding inaccurate measurement caused by eccentric loading of the sample 8.

[0052] 2) The chassis 2 is supported by support columns to support the PMMA support cover 16 in the middle and the upper end cover 12 at the top. The upper end cover 12 is connected to the electric hydraulic cylinder 11 below. The electric hydraulic cylinder 11 is connected to the upper fixture 9 below to clamp the sample 8. The sample 8 is connected to the lower fixture 6 below. The lower fixture 6 is connected to the axial force sensor 5 to measure the tensile and compressive loads on the sample 8.

[0053] 3) The sample rotating table 1 is a sample rotating platform for the synchrotron radiation device, and the chassis 2 is the base of the test machine for holding the sample part, wherein the sample rotating table 1 and the chassis 2 are relatively separated from each other, but they need to be connected during the test. Install the chassis 2 on the sample rotating table 1.

[0054] 4) A closed corrosive medium chamber 15 is installed inside the PMMA support cover 16, and a micro-motion pad 7 is installed at the lower end of the closed corrosive medium chamber 15. The upper and lower ends of the micro-motion pad 7 are flat, and its top part is connected to the sample 8 and has a certain interference fit with the sample 8. Its top part is tangent to the sample 8 and is compressed to a certain extent. Its lower end is installed on the lower fixture 6, and its upper end is installed on the upper fixture 9.

[0055] 5) A liquid inlet 4 is installed on the lower right side of the corrosive medium chamber 15 and connected to the pipeline and the wire. An upper liquid outlet 14 and a lower liquid outlet 17 are installed on the upper left and lower left parts of the corrosive medium chamber 15. The upper liquid outlet 14 and the lower liquid outlet 17 are connected to the pipeline and the wire in the same way as the liquid inlet 4. A clustered tubular electric heating tube 29 is installed in the corrosive chamber to heat the corrosive medium chamber 15.

[0056] 6) The end of the micro-motion pad 7 is connected to the normal force sensor 20, and the symmetrical micro-motion pad 7 needs to be connected to the same normal force sensor. The tail of the micro-motion pad 7 is respectively connected to two moving magnet voice coil motors 18, one of which is connected to the central processing unit 27. Data collection and control are performed through the central processing unit 27. At this time, the test machine is built.

[0057] The present invention also proposes a new characterization method for in-situ fretting corrosion fatigue damage evolution using synchrotron radiation light source diffraction and three-dimensional imaging, comprising the following steps:

[0058] 1) First, complete the assembly and connection of various parts according to the structural description of the above-mentioned in-situ fretting corrosion fatigue testing machine, ensure that the sample rotating table 2 is coaxial with the axis of the testing machine body and the clamped sample 8 and does not rotate relative to each other; and place it on the sample test table of the light source imaging or diffraction line station.

[0059] 2) After the upper clamp 9 clamps the sample, adjust the xy micro-displacement platform 2 so that the lower clamp 6 is aligned with the center of gravity of the sample and clamps the sample. The electromagnetic loading device 12 is adjusted to adjust the height of the sample in the vertical direction and properly match the X-ray height. The laser positioning system is used to accurately locate the sample test position to ensure that the X-ray can pass through the PMMA support cover 16 through the sample area of ​​interest and be received by the radiation receiver.

[0060] 3) The environmental control device is turned on by the central controller 27, the hydraulic pump 23 and the clustered tubular electric heating tube 29 are connected, and the temperature in the corrosive medium chamber 15 is measured by the thermocouple 28 and the data is transmitted to the central controller. When the temperature in the corrosive medium chamber reaches the test requirements, the clustered tubular electric heating tube is disconnected. The designed corrosive solution chamber can provide three corrosive environment conditions: full immersion, peripheral immersion, and salt spray.

[0061] a) Under full immersion corrosion conditions, the two-position four-way solenoid valve is in the energized state, at which time the liquid inlet 4 is open and the lower liquid outlet 17 is closed, and the corrosive solution forms a circulation loop in the order of solution tank-filter-hydraulic pump-check valve-liquid inlet-corrosive solution chamber-upper liquid outlet-solution tank.

[0062] b) Under the condition of cyclic immersion corrosion, the central controller controls the two-position four-way solenoid valve to be in a periodic on-off state. At this time, the liquid inlet is open, the lower liquid outlet is closed, and the circulation mode of the corrosion solution is the same as in a.

[0063] c) Under the salt spray corrosion condition, first replace the liquid inlet with an atomizing nozzle, adjust the flow rate of the hydraulic pump to the maximum, and adjust the maximum pressure of the overflow valve 24 to ensure the safety of the test. At this time, the central controller controls the two-position four-way solenoid valve to be in a periodic on-off state. When the solenoid valve is energized, the atomizing nozzle atomizes the corrosive solution flowing through, forming a salt spray environment in the corrosive solution cavity; when the solenoid valve is de-energized, the lower liquid outlet is opened to discharge the atomized solution beads back into the solution tank.

[0064] 4) After the corrosion environment is set, the corrosion micro-motion fatigue test is started. During the test, the axial movement of the electromagnetic loading system is controlled by the electric hydraulic cylinder to achieve axial fatigue actuation of the sample 8. At the same time, the micro-motion pad achieves micro-motion wear on the sample, so that the internal cracks of the sample open. At the same time, the axial force sensor 5 transmits the collected axial force data to the data acquisition card of the central controller through the signal line, and then transmits it to the computer for recording.

[0065] 5) While ensuring that the X-rays will not be blocked, start the X-ray emission device of the light source, control the light source rotating platform 1, and rotate the test device body and the sample 8 in the body 180°; during this process, the high-energy X-rays emitted by the light source pass through the acrylic support cover 16, and after passing through the sample 8 that rotates 180°, they are received by the X-ray detector, thereby achieving 180° image processing of the sample. Reapply fatigue load to the specimen within the specified period, and repeat the above steps until the specified test period is reached.

[0066] 6) After the test, the central processor is used to control the electric hydraulic cylinder 11 to cause the electromagnetic loading device to produce axial displacement to achieve unloading of the sample. At the same time, the screws of the upper clamp 9 and the lower clamp 6 are loosened to remove the sample 8.

[0067] 7) For the imaging line station, the reconstruction of the internal three-dimensional morphology of the material is completed, and the crack initiation and propagation process during the fretting corrosion fatigue test is captured; for the diffraction line station, the residual stress distribution information in the fretting wear area of ​​the material can be obtained, which is used to explore the evolution law of residual stress in fretting corrosion fatigue.

[0068] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should be included in the protection scope of the present invention.

Claims

1. An in-situ fretting corrosion fatigue testing machine based on synchrotron radiation diffraction and three-dimensional imaging, characterized in that: Including axial fatigue loading system, micro-motion loading system and corrosion environment control system; The axial fatigue loading system comprises a driving device, a load control device, and a load sensing device; the load sensing device is used to measure the axial force and the normal force in real time; the driving device is used to drive the load control device to enable the load control device to achieve axial displacement; the load control device is used to perform axial fatigue loading on the sample; The fretting loading system includes a fretting wear device; the fretting wear device is two identical fretting pads that are symmetrical about the central axis of the sample and horizontally positioned 45 degrees downward, and the two fretting pads are connected to two identical moving magnet voice coil motors to achieve normal loading, so that the fretting pads and the sample surface are kept in close contact during the entire experiment, ensuring that the electromagnetic loading device cooperates with the two fretting pads to achieve fretting fatigue testing; The corrosion environment control system includes an environment control device and a data acquisition and control device; the environment control device is used to provide a corrosion environment of full immersion, peripheral immersion, and salt spray for the sample; the data acquisition and control device is used to collect measurement data and control the drive device.

2. The in-situ fretting corrosion fatigue testing machine based on synchrotron radiation diffraction and three-dimensional imaging according to claim 1, characterized in that: The axial fatigue loading system comprises a chassis (2), an xy micro-displacement platform (3), an axial force sensor (5), a PMMA support cover (16), a lower clamp (6), an upper clamp (9), an electromagnetic loading device (10), an electric hydraulic cylinder (11), an upper end cover (12), an upper support rod (13), and a lower support rod (19); the xy micro-displacement platform (3) is fixed on the chassis (2) and is used to ensure the overall coaxiality of the testing machine after clamping the sample (8); the axial force sensor (5) is installed on the upper end of the xy micro-displacement platform (3) and is used to monitor the axial loading force of the sample; the lower support rod (19) is fixed on the xy micro-displacement platform (3), and a PMMA support cover (16) is installed on the upper end of the lower support rod (19); a clamp (9) and a lower clamp (6) are installed on the upper and lower sides of the PMMA support cover (16) respectively, for clamping the sample (8); an upper support rod (13) is installed above the PMMA support cover (16) for supporting the upper end cover (12); an electromagnetic loading device (10) is fixed on the upper end of the upper clamp (9) for applying an axial force to the sample to achieve axial fatigue loading; an electric hydraulic cylinder (11) is fixed above the electromagnetic loading device (10) for controlling the axial displacement of the upper end portion of the sample of the axial fatigue loading system, so as to facilitate the replacement of the sample (8).

3. The in-situ fretting corrosion fatigue testing machine based on synchrotron radiation diffraction and three-dimensional imaging according to claim 1, characterized in that: The micro-motion loading system comprises a micro-motion pad (7), a moving magnet voice coil motor (18), and a normal force sensor (20); two identical normal force sensors (20) are installed on the top of the micro-motion pad (7) for monitoring the micro-force applied by the micro-motion pad of the sample; the two micro-motion pads (7) are connected to two identical moving magnet voice coil motors (18), which are in turn connected to a computer terminal, and the two micro-motion pads (7) are controlled to generate normal displacement through computer input signals, thereby ensuring that the micro-motion pad (7) is in close contact with the sample (8) during the entire loading process, so as to realize a micro-motion fatigue test.

4. The in-situ fretting corrosion fatigue testing machine based on synchrotron radiation diffraction and three-dimensional imaging according to claim 3, characterized in that: The top height of the micro-motion pad (7) is the same as the micro-motion wear area of ​​the sample (8).

5. The in-situ fretting corrosion fatigue testing machine based on synchrotron radiation diffraction and three-dimensional imaging according to claim 1, characterized in that: The environmental control device adopts a "bottom-in, top-out" circulation mode, and can create a full immersion, surrounding immersion, and salt spray corrosion environment in the test chamber by controlling the state of the two-position four-way solenoid valve and the state of the liquid inlet.

6. The in-situ fretting corrosion fatigue testing machine based on synchrotron radiation diffraction and three-dimensional imaging according to claim 5, characterized in that: The environmental control device also includes heating through a clustered tubular electric heating tube to accelerate the corrosion rate, and simultaneously using a thermocouple to measure the temperature in the corrosion solution cavity, thereby realizing the fretting corrosion fatigue damage test.

7. The in-situ fretting corrosion fatigue testing machine based on synchrotron radiation diffraction and three-dimensional imaging according to claim 6, characterized in that: The corrosive environment control system comprises a liquid inlet (4), an upper liquid outlet (14), a lower liquid outlet (17), a corrosive medium chamber (15), a solution tank (21), a one-way valve (25), a two-position four-way solenoid valve (26), a clustered tubular electric heating tube (29), a thermocouple (28), and a central processing unit (27); two interfaces at the upper end of the two-position four-way solenoid valve (26) are respectively connected to the liquid inlet (4) and the lower liquid outlet (17), and two interfaces at the lower end are respectively connected to the one-way valve (25) and the solution tank (21). The upper liquid outlet (14) is directly connected to the solution tank (21), the clustered tubular electric heating tube (29) is fixed to the lower cover of the cavity by fasteners, and a thermocouple (28) is installed at the lower cover of the cavity to monitor the temperature in the corrosive medium cavity (15). The central processing unit (27) is respectively connected to the clustered tubular electric heating tube (29), the thermocouple (28), the axial force sensor (5), the normal force sensor (20) and the electric hydraulic cylinder (11), and is uniformly controlled by the central processing unit (27).

8. An in-situ fretting corrosion fatigue test method based on synchrotron radiation diffraction and three-dimensional imaging, characterized in that Here are the steps: Step 1: After the upper fixture (9) clamps the sample, the xy micro-displacement platform (2) is adjusted so that the lower fixture (6) is aligned with the center of gravity of the sample and clamps the sample. The electromagnetic loading device (12) is adjusted to adjust the height of the sample in the vertical direction and properly match the height of the X-ray. The laser positioning system is used to accurately locate the sample test position to ensure that the X-ray can pass through the PMMA support cover (16) and pass through the sample area of ​​interest and be received by the radiation receiver; Step 2: The environment control device is turned on through the central controller (27), the hydraulic pump (23) and the clustered tubular electric heating tube (29) are turned on, and the temperature in the corrosive medium chamber (15) is measured by the thermocouple (28) and the data is transmitted to the central controller. When the temperature in the corrosive medium chamber (15) reaches the test requirements, the clustered tubular electric heating tube (29) is disconnected. The designed corrosive solution chamber can provide three kinds of corrosive environment conditions: full immersion, peripheral immersion, and salt spray; Step 3: After the corrosion environment is set, the corrosion micro-motion fatigue test is started; during the test, the axial movement of the electromagnetic loading device is controlled by controlling the electric hydraulic cylinder, thereby achieving axial fatigue actuation of the sample (8), and at the same time, the micro-motion pad achieves micro-motion wear on the sample, so that the internal cracks of the sample open, and at the same time, the axial force sensor (5) collects the axial force data through the signal line and uploads it to the data acquisition card of the central controller, and then transmits it to the computer for recording; Step 4: while ensuring that the X-rays are not blocked, the light source X-ray emission device is started, and the sample rotating table is controlled to rotate the test device body and the sample (8) in the body 180 degrees; during this process, the high-energy X-rays emitted by the light source pass through the PMMA support cover (16), and after passing through the sample (8) rotated 180 degrees, are received by the X-ray detector, thereby achieving 180 degrees of image processing of the sample (8); within a specified period, the fatigue load is reapplied to the specimen, and the above steps are repeated until the specified test period is reached; Step 5: For the imaging line station, the reconstruction of the internal three-dimensional morphology of the material is completed to capture the crack initiation and propagation process during the fretting corrosion fatigue test; for the diffraction line station, the residual stress distribution information in the fretting wear area of ​​the material can be obtained to explore the evolution law of residual stress in fretting corrosion fatigue.

9. The in-situ fretting corrosion fatigue test method based on synchrotron radiation diffraction and three-dimensional imaging according to claim 8, characterized in that: The three corrosive environmental conditions described in step 2: full immersion, weekly immersion, and salt spray, are specifically: a) Under full immersion corrosion conditions, the two-position four-way solenoid valve is in an energized state, at which time the liquid inlet (4) is opened and the lower liquid outlet (17) is closed, and the corrosion solution forms a circulation loop in the order of solution tank - filter - hydraulic pump - check valve - liquid inlet - corrosion solution chamber - upper liquid outlet - solution tank; b) Under the condition of cyclic immersion corrosion, the central controller controls the two-position four-way solenoid valve to be in a periodic on-off state; at this time, the liquid inlet is opened, the lower liquid outlet is closed, and the circulation mode of the corrosion solution is the same as in a); c) Under the salt spray corrosion condition, first replace the liquid inlet with an atomizing nozzle, adjust the flow rate of the hydraulic pump to the maximum, and adjust the maximum pressure of the overflow valve (24) to ensure the safety of the test. At this time, the central controller controls the two-position four-way solenoid valve to be in a periodic on-off state; when the solenoid valve is energized, the atomizing nozzle atomizes the corrosive solution flowing through, forming a salt spray environment in the corrosive solution chamber; when the solenoid valve is de-energized, the lower liquid outlet is opened to discharge the atomized solution beads back into the solution tank.

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