Three-point bending high-temperature fatigue test instrument and method based on X-ray in-situ imaging

Abstract

According to the three-point bending high-temperature fatigue test instrument and method based on X-ray in-situ imaging, an extreme thermal field is applied to a sample based on halogen lamp infrared radiation focusing heating, a clamp ascends and descends through a servo hydraulic cylinder, and axial displacement of the ends of the sample is converted into bending moments at the two ends through the rotation characteristic of a connecting rod mechanism; therefore, a monotonous or cyclic bending external load is applied to the sample. Meanwhile, an oxidizing or inert test gas atmosphere is provided. And the acoustic emission system monitors the material damage failure starting time in real time. The device is small in size, high in precision and fast in response, and provides technical support for the damage evolution process characterization and failure damage mechanism research test of the tested sample under the heat-force-oxygen multi-field coupling action by combining a three-dimensional high-temporal-spatial-resolution X-ray characterization technology.

Description

Technical Field

[0001] The invention relates to the technical field of material fatigue testing, and in particular to a three-point bending high-temperature fatigue testing instrument and method based on X-ray in-situ imaging. Background Art

[0002] For the heat-bearing structures of hypersonic vehicles, scramjet engines, launch vehicle engines and heavy-duty gas turbines, their key hot-end structural components are in harsh environments such as high temperature, oxidation, high impact and high vibration for a long time. Take the engine blades as an example. They are in a high temperature and high pressure environment during service, and at the same time bear huge tensile loads caused by high-speed rotation, bending loads caused by high-speed airflow, and reciprocating bending vibrations caused by airflow excitation forces. Extreme high temperature environments and complex mechanical loads place stringent requirements on the strength, stiffness, high temperature resistance, oxidation resistance and fatigue resistance of existing metal materials, and even reaching their use limits still cannot meet service requirements. Ceramic-based composites have developed into a new strategic material to replace traditional metal materials in the aerospace field due to their excellent properties such as high strength, corrosion resistance, high temperature resistance, fatigue resistance, high specific stiffness and specific strength.

[0003] However, unlike metal materials, the multiphase heterogeneous microstructure of ceramic-based composite materials makes them exhibit more complex and diverse damage accumulation processes and failure modes under the aforementioned heat-mechanics-oxygen multi-field coupling. At the macroscopic scale, the mechanical properties are non-uniform, strongly nonlinear and temperature-dependent, which poses challenges to the prediction of their service performance and reliability evaluation. Due to the limitations of three-dimensional characterization technology and high-temperature mechanical testing technology, current research mainly focuses on in-situ and ex-situ observation of material surface damage and monotonic tension, compression, bending and shear tests under room temperature. There are problems such as unclear internal microscopic damage mechanism and inability of test conditions to simulate real service conditions. For example, Chinese patent 201611080310.4 discloses a four-point bending fatigue in-situ mechanical testing device, which can be combined with a scanning microscope to monitor the micromechanical behavior and degeneration damage mechanism of materials in real time in situ, but it is still a damage observation method limited to the sample surface. Chinese patent 202110637763.7 discloses a three-point bending test device, but the load is only transferred through simple contact between the sample and the fixture, so problems such as displacement of the sample and inability to reverse the load will occur in fatigue tests. Chinese patent 201911125914.X discloses a three-point bending fatigue test fixture that supports negative stress ratios. It solves the above problems by locking both ends of the sample under test, but lacks a relevant material internal damage monitoring module.

[0004] In addition, the above-mentioned devices and experimental methods do not take into account the service environment of the tested samples, and cannot provide material damage and service performance test data under real working conditions. Structural reliability design is based on reliability test data, and obtains the internal laws followed by the service performance of components through probability statistical analysis, thereby guiding its static strength design, fatigue strength design and limited life design, etc. However, the existing material reliability test equipment, methods and databases rarely consider the real application scenarios of components, which will lead to problems such as inaccuracy, unreliability and pseudo-safety in the reliability evaluation system established based on them.

[0005] In summary, there is currently no in-situ test device that is compatible with a high-resolution X-ray platform and can simultaneously provide extreme high temperatures (above 1500°C), special atmospheres (oxidation or oxygen-suppressing environments) and high-frequency bending fatigue loads. Due to the limitations of the above-mentioned equipment and technology, the evolution process of bending fatigue damage of composite materials under extreme high temperature and oxidation conditions has not yet been explored, and the actual use limit remains to be verified. Therefore, based on characterization and testing technologies such as high-resolution X-rays, acoustic emission, DIC and DVC, a miniature high-temperature three-point bending fatigue experimental device is designed to in-situ characterize the complex failure behaviors of matrix cracking, interface debonding, fiber fracture, pore connectivity and crack propagation of composite materials under near-service conditions, which is of great significance for revealing the multi-scale mechanical behavior and deformation damage mechanism inside the material and establishing a more accurate and complete macroscopic mechanical property evaluation system based on microstructural characteristics. Based on this research background, the present invention discloses an in-situ extreme high-temperature three-point bending fatigue test method and equipment combined with high-resolution X-ray characterization and acoustic emission-assisted monitoring. Summary of the invention

[0006] The purpose of the present invention is to provide a three-point bending high-temperature fatigue test instrument and method based on X-ray in-situ imaging, which is designed to be compatible with a high-resolution X-ray platform and simultaneously provide an extreme high-temperature oxidation or oxygen suppression special atmosphere above 1500°C and high-frequency bending fatigue loads as well as acoustic emission auxiliary monitoring and applied to the tested samples, so as to accurately reveal the multi-scale mechanical behavior and deformation damage mechanism inside the material.

[0007] The object of the present invention is achieved in that:

[0008] The servo hydraulic cylinder 7 is mounted on the adapter base 8, the adapter base is mounted on the five-axis sample stage 9, and the five-axis sample stage is mounted on the support table 10; the sealed housing is composed of an upper cavity 18 and a lower cavity 23 and a polyetherimide X-ray transmissive support flange ring 15: the upper and lower cavities are shaped as a regular hexagonal pyramid and an inverted regular hexagonal pyramid, respectively, and the two are symmetrical up and down, the support flange ring 15 is composed of a short pipe joint fixedly connected between two plate flanges, and the outer surfaces of the two plate flanges are respectively provided with water inlet and water outlet annular water cooling channels 22 located inside the bolt holes, and the support flange ring is connected between the upper and lower cavities by bolts;

[0009] Three halogen lamps 20 are inserted from ports of three non-adjacent side panels of the upper cavity and fixed with bolts, and another three halogen lamps 20 are inserted from ports of another three non-adjacent side panels of the lower cavity and fixed with bolts, and the infrared radiation of the six halogen lamps providing an extremely high temperature of 1500°C is focused on a point on the central axis of the above-mentioned closed shell;

[0010] The sealed shell is provided with a thermocouple and a gas concentration monitoring probe mounting seat 26 and a gas pipeline interface 27;

[0011] The support table is provided with a halogen lamp controller 1, an X-ray transmitter 3, an X-ray receiver 13 with a built-in image collector; an acoustic receiving system 4, a high-temperature optical two-color thermometer 24 for testing the temperature of the sample under test, an exhaust pump 3, a high-pressure gas cylinder 6 equipped with a pressure reducing valve 5, a fatigue loading controller 12 and a water cooler 14;

[0012] The hydropower wireless slip ring 25 is mounted on the servo hydraulic cylinder body;

[0013] The lower loading unit 16 is: a connecting rod 16b with a lower flange passes through the middle hole of the connecting flange 16a from bottom to top and is sleeved on the connecting flange 16a in a tight fit, or the lower flange of the connecting rod is fixedly connected to the connecting flange by screws, the pull rod 16c is formed by integrating a vertically arranged hinge seat and an outer convex neck of a horizontal circular plate, the middle column at the top of the connecting rod passes through the central hole of the horizontal circular plate of the pull rod from bottom to top and the two are fixedly connected by nuts, the swing rod 16d is composed of a horizontal rod member fixed on the left side of the vertical plate, the left end of the horizontal rod member is movably sleeved on the fixed axis of the hinge seat of the pull rod, an acoustic wave sensor 16e is arranged in the groove socket hole on the right side of the vertical plate of the horizontal rod member, and a pressing plate 16f and a water-cooled back plate 16g with a water-cooling channel therein are successively fixed to the right side of the vertical plate of the swing rod by bolts;

[0014] The upper loading unit 19 is: the upper connecting rod 19b with a flange at the lower part is screwed from bottom to top on the connecting flange 19a with internal threads; the upper tie rod 19c, the upper swing rod 19d, the upper pressing plate 19f and the upper water-cooled back plate 19g are respectively the same in shape, structure and connection method as the tie rod 16c, the swing rod 16d, the pressing plate 16f and the water-cooled back plate 16g and are symmetrically arranged up and down; the horizontal circular plate of the upper tie rod is fixedly connected to the flange of the upper tie rod by bolts;

[0015] The outlet of the water chiller is connected to the water cooling channel on the support flange ring and the water cooling back plate of the lower loading unit and the upper water cooling back plate of the upper loading unit through a hydroelectric wireless slip ring, so as to deliver cooling water to cool the support flange ring and the acoustic wave sensor when the upper and lower loading units clamp the sample to be tested and rotate with the five-axis sample stage;

[0016] The halogen lamp controller 1 is connected to 6 halogen lamps via a hydroelectric wireless slip ring to maintain the supply of working power to the halogen lamps when the closed housing rotates with the five-axis sample stage;

[0017] The upper connecting rod 19b of the upper loading unit extends out of the cavity top plate, and a spherical pad is mounted on the upper connecting rod between the connecting flange 19a with an inner screw and the top surface of the upper cavity top plate, and another spherical pad 28 is mounted on the upper connecting rod between the bottom surface of the upper cavity top plate and the flange of the upper connecting rod 19b;

[0018] The connection flange 16a of the lower loading unit is fixedly connected to the flange on the piston rod of the servo hydraulic cylinder through bolts, and a bellows for sealing is sleeved on the middle opening of the top plate of the lower cavity of the closed shell and the piston rod of the servo hydraulic cylinder;

[0019] The sealing shell is fixed on the top of the servo hydraulic cylinder body via a bracket, and the piston rod in the servo hydraulic cylinder can be freely extended and retracted to enter or move out of the sealing shell.

[0020] Compared with the prior art, the present invention has the following technical features and advantages:

[0021] 1. The present invention is an in-situ bending fatigue test device with light weight, compact structure and accurate control ( Figure 1 and 2 ), which can simultaneously provide extreme high temperatures above 1500°C, oxidation / oxygen inhibition test environments, monotonic / cyclic bending fatigue loads and auxiliary damage monitoring, and meet the requirements of high-resolution X-ray characterization platforms for weight, size, and installation, with good compatibility.

[0022] 2. The sample environment chamber of the present invention is a double-layer hollow hexagonal pyramid structure and is divided into two parts, the outer layer is made of titanium alloy to provide the main bearing capacity, and the inner layer is a reflective insulation material, which increases the infrared radiation flux on the sample surface while providing thermal insulation functions. The inclined cavity wall as a whole serves as a positioning surface, which reduces the difficulty of mechanical processing while making it easy to ensure the positioning dimensions and angles of each key space. The upper and lower cavities are connected by an X-ray transmission-support flange ring, which is made of polyetherimide. It reduces the absorption of X-rays while meeting the bearing and sealing requirements in high temperature environments. The circular ring shape meets the requirements for uniform penetration of X-rays and does not affect the subsequent image data processing. At the same time, a water cooling channel is provided at the flange ring-chamber connection to prevent the chamber and flange ring from overheating and failing.

[0023] 3. The present invention is based on the halogen lamp infrared radiation focused heating technology to quickly apply an external extreme heat field to the sample. The heating module has a simple structure, is easy to install, has a fast heating speed, does not damage the sample, is suitable for all kinds of materials, and the size of the hot zone and the temperature are continuously adjustable. ( Figure 3). Specifically, three halogen lamps are evenly distributed in the upper and lower chambers, respectively, and a spatial array is formed along a sphere centered on the observation area of ​​the sample to be tested, wherein the axis of the halogen lamp passes through the center of the sphere and the lamp body can be moved closer to or farther away from the center of the sphere along the axis to adjust the size of the focused hot zone. Two quartz glass observation windows are also arranged in the upper and lower chambers, respectively, which facilitate visual inspection of the internal conditions of the chamber while meeting the requirements of heat resistance, load bearing and sealing. In addition, a thermocouple and a gas concentration monitoring probe mounting base and a gas pipeline interface are also arranged in the upper and lower chambers, respectively. The spherical array of halogen lamps and observation windows not only provides a uniform and extremely high temperature thermal field, but also provides sufficient interfaces and optical paths for sample clamping, multi-angle remote temperature measurement, visual observation and potential DIC-assisted observation, and has the advantages of high experimental operation flexibility and strong expandability.

[0024] 4. The thermocouple mounting seat of the present invention has a radial fine-tuning nut, which can manually adjust the insertion length of the thermocouple to change the temperature measurement area. It is also equipped with a high-temperature optical two-color thermometer to remotely measure the temperature outside the cavity through a quartz glass observation window. The two sets of temperature measurement systems can be compared with each other to ensure the accuracy of temperature measurement. The gas pipeline interface is externally connected to a special gas source such as oxidation or oxygen suppression, and the concentration signal obtained by the gas monitoring probe is fed back to control its on and off.

[0025] 5. The bending fatigue sample described in the present invention adopts a vertical orientation strategy, and the longitudinal axis of the sample is coaxial with the longitudinal axis of the testing machine to avoid the excessive long side size of the sample hindering the transmission of X-rays. At the same time, it greatly saves the radial size requirements of the device, which is beneficial to reducing the volume and weight of the device. The sample is fixed in the center of the chamber by the upper and lower loading units. The upper and lower loading units are in a right-angle C shape, where the distal inflection point (the inflection point of the C shape away from the sample) is fixed at an angle of 90 degrees, and the proximal inflection point (the inflection point of the C shape close to the sample) is a hinged structure with a variable angle. The ends of the loading units (16e-g and 19e-g) are connected by tightening screws and tightening pads to constrain all degrees of freedom of the sample ends. After clamping the sample, according to the rotation characteristics of the connecting rod mechanism, the load applied in the vertical direction can be converted into a bending load applied to the sample in the horizontal direction by converting the axial displacement of the distal end (16b) into the rotation around the axis of the proximal loading beam (16d). Figure 4 As shown in the figure, the sum of the interior angles of the quadrilateral remains unchanged. When the angle of the hinge point changes, the angle between the sample and the two loading unit pendulums 16d and 19d will change. Since the sample and the ends of the loading unit are fully constrained and consolidated, the angle remains unchanged. Therefore, the change in angle is borne by the middle of the sample, that is, the middle of the sample bears the bending load. The loading unit has the characteristics of simple structure, stable load transmission, and tight clamping. It can apply a reasonable range of bending moment to the sample and meet the bending fatigue test conditions.

[0026] 6. The connection between the upper and lower loading units and the sample is built with a micro water cooling channel and an acoustic wave sensor, which can monitor the acoustic emission events caused by internal damage of the sample during fatigue loading in real time while ensuring that the acoustic wave sensor is in a safe working temperature condition. Figure 5 As shown. The upper loading unit end is equipped with a spherical pad structure to provide coaxial adjustment freedom, and is fixed to the top of the upper chamber through a sealing gasket. The lower loading unit is driven by a servo hydraulic cylinder and can be raised and lowered along its longitudinal axis. At the same time, a dynamic sealing structure is provided at the connection between its end and the environmental chamber to ensure good air tightness of the chamber.

[0027] 7. The centering clamp of the present invention ( Figure 6 ) with spherical pad structure ( Figure 7 ) can ensure the accurate spatial positioning of the loading unit, prevent the axis of the clamped sample from deviating from the rotation axis of the sample stage, ensure that the sample is in a reasonable loading and imaging position, and improve the characterization and measurement quality during the experiment. In addition, the servo hydraulic cylinder is equipped with water and electric slip rings on the outside to reduce the impact of pipeline pulling on the X-ray image data acquisition process when the sample rotates with the test machine.

[0028] 8. The servo hydraulic cylinder described in the present invention has the advantages of high rigidity, zero friction, high frequency response, smooth operation, high coaxiality, and ultra-long life. It can provide an axial load of up to 5kN and a loading frequency of 50Hz. The servo hydraulic cylinder is driven by a silent oil source system. The silent oil source system adopts an integrated design of oil pump motor group + oil source cooling system. The entire motor pump group is immersed in hydraulic oil. The vibration and heat generated during operation are discharged in real time through the hydraulic oil, thereby achieving a significant reduction in system noise and the risk of overheating and damage to the motor pump group. The working principle diagram is as follows Figure 8 shown.

[0029] 9. In order to accurately capture the initiation stage of material damage during the test, the present invention has a dual control system inside and outside the experimental lead room and an auxiliary acoustic emission monitoring module. It can monitor the starting moments of complex failure behaviors such as matrix cracking, fiber breakage, interface debonding and sliding inside the tested sample in real time outside the experimental lead room and remotely and quickly suspend mechanical loading to maintain the material damage state. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the overall structure of the extreme high temperature bending fatigue test equipment that is compatible with the high-resolution X-ray three-dimensional characterization platform.

[0031] Figure 2 This is a schematic diagram of the main structure of the extreme high temperature bending fatigue test equipment based on X-ray three-dimensional in-situ imaging.

[0032] Figure 3 It is a schematic diagram of the spatial arrangement and imaging principle of the temperature and mechanical loading modules in extreme high temperature monotonic and cyclic bending tests.

[0033] Figure 4 It is a schematic diagram of the state when the lower loading unit moves up to the vertex and down to the end point.

[0034] Figure 5 Schematic diagram of specimen clamping in extreme high temperature monotonic and cyclic bending tests.

[0035] Figure 5a yes Figure 5 A partial cross-sectional view of .

[0036] Figure 6 Schematic diagram of the sample centering fixture in extreme high temperature monotonic and cyclic bending tests.

[0037] Figure 7 This is a diagram of the center structure of the fixture spherical surface in extreme high temperature monotonic and cyclic bending tests.

[0038] Figure 8 It is the schematic diagram of hydraulic loading. DETAILED DESCRIPTION

[0039] Figure 1 Among them, 1. halogen lamp controller 2. X-ray transmitter 3. exhaust pump 4. sound receiving system 5. pressure reducing valve 6. high-pressure gas cylinder 7. servo hydraulic cylinder 8. adapter base 9. five-axis sample table 10. support table 11. hydraulic oil pump 12. fatigue loading controller 13. X-ray receiver 14. water chiller 15. polyetherimide X-ray transmission-support flange ring 16. lower loading unit 17. measured sample 18. upper cavity 19. upper loading unit 20. halogen lamp 21. quartz glass observation window 22. water cooling channel 23. lower cavity 24. high-temperature optical two-color thermometer 25. hydropower wireless slip ring.

[0040] Figure 2 7, servo hydraulic cylinder 8, adapter base 15, polyetherimide X-ray transmission-support flange ring 16, lower loading unit 18, upper cavity 19, upper loading unit 20, halogen lamp 21, quartz glass observation window 23, lower cavity 26, thermocouple and gas concentration monitoring probe mounting seat 27, gas pipeline interface.

[0041] Figure 3 2, X-ray transmitter 13, X-ray receiver 15, polyetherimide X-ray transmission-support flange ring 16, lower loading unit 17, sample to be tested 19, upper loading unit 20, halogen lamp

[0042] Figure 516a, (lower loading unit) connecting flange 16b, (lower loading unit) connecting rod 16c, (lower loading unit) pull rod 16d, (lower loading unit) swing rod 16e, (lower loading unit) acoustic wave sensor jack 16f, (lower loading unit) pressing plate 16g, (lower loading unit) water-cooled back plate 17, tested sample 19a, upper loading unit connecting flange 19b with internal thread, (upper loading unit) upper connecting rod 19c, (upper loading unit) upper pull rod 19d, (upper loading unit) upper swing rod 19e, (upper loading unit) acoustic wave sensor jack 19f, (upper loading unit) upper pressing plate 19g, (upper loading unit) upper water-cooled back plate

[0043] Figure 6 16a, (lower loading unit) connecting flange 16b, (lower loading unit) connecting rod 16c, (lower loading unit) tie rod 19a, (upper loading unit) connecting flange 19b with internal thread, (upper loading unit) upper connecting rod 19c, (upper loading unit) upper tie rod 19h, centering clamp

[0044] Figure 7 18, upper cavity 19a, (upper loading unit) connecting flange 19b with internal thread, (upper loading unit) connecting rod 19c, (upper loading unit) pull rod 28, spherical pad 29, fastening screw

[0045] Figure 1 Shown is a three-point bending high-temperature fatigue test instrument based on X-ray in-situ imaging, characterized in that a servo hydraulic cylinder is mounted on an adapter base, the adapter base is mounted on a five-axis sample stage, and the five-axis sample stage is mounted on a support platform; the sealed shell is composed of an upper cavity and a lower cavity and a polyetherimide X-ray transmissive support flange ring: the upper and lower cavities are shaped like a regular hexagonal pyramid and an inverted regular hexagonal pyramid, respectively, and the two are symmetrical up and down, the support flange ring is composed of a short pipe joint fixedly connected between two plate flanges, and the outer surfaces of the two plate flanges are respectively provided with water inlet and water outlet annular water cooling channels located on the inner side of the bolt holes, and the support flange ring is connected between the upper and lower cavities by bolts;

[0046] Three halogen lamps are inserted from ports of three non-adjacent side panels of the upper cavity and fixed with bolts, and another three halogen lamps are inserted from ports of another three non-adjacent side panels of the lower cavity and fixed with bolts, and the infrared radiation of the six halogen lamps providing an extremely high temperature of 1500°C is focused on a point on the central axis of the above-mentioned closed shell;

[0047] The sealed shell is provided with a thermocouple and a gas concentration monitoring probe mounting seat and a gas pipeline interface;

[0048] The support table is equipped with a halogen lamp controller, an X-ray transmitter, an X-ray receiver with a built-in image collector; an acoustic receiving system, a high-temperature optical two-color thermometer for testing the temperature of the sample being tested, an exhaust pump, a high-pressure gas cylinder equipped with a pressure reducing valve, a fatigue loading controller, and a water cooler;

[0049] The hydropower wireless slip ring is mounted on the servo hydraulic cylinder body;

[0050] The lower loading unit is: a connecting rod with a lower flange passes through the middle hole of the connecting flange from bottom to top and is sleeved on the connecting flange in a tight fit, or the lower flange of the connecting rod is fixedly connected to the connecting flange by screws, the pull rod is integrated with a vertically arranged hinge seat and an outer convex neck of a horizontal circular plate, the middle column at the top of the connecting rod passes through the central hole of the horizontal circular plate of the pull rod from bottom to top and the two are fixedly connected by nuts, the swing arm is composed of a horizontal rod member fixed on the left side of the vertical plate, the left end of the horizontal rod member is movably sleeved on the fixed axis of the hinge seat of the pull rod, an acoustic wave sensor is arranged in the groove socket hole on the right side of the vertical plate of the horizontal rod member, and a pressing plate and a water-cooling back plate with a water-cooling channel therein are successively fixed to the right side of the vertical plate of the swing arm by bolts;

[0051] The upper loading unit is: the upper connecting rod with a flange at the lower part is screwed from bottom to top on the connecting flange with internal threads; the upper tie rod, the upper swing rod, the upper pressing plate and the upper water-cooled back plate are respectively the same in shape, structure and connection mode as the tie rod, the swing rod, the pressing plate and the water-cooled back plate and are symmetrically arranged up and down; the horizontal circular plate of the upper tie rod is fixedly connected with the flange of the upper tie rod by bolts;

[0052] The outlet of the water chiller is connected to the water cooling channel on the support flange ring and the water cooling back plate of the lower loading unit and the upper water cooling back plate of the upper loading unit through a hydroelectric wireless slip ring, so as to deliver cooling water to cool the support flange ring and the acoustic wave sensor when the upper and lower loading units clamp the sample to be tested and rotate with the five-axis sample stage;

[0053] The above-mentioned halogen lamp controller is connected to 6 halogen lamps via a hydroelectric wireless slip ring to maintain the supply of working power to the halogen lamps when the closed housing rotates with the five-axis sample stage;

[0054] The upper connecting rod of the upper loading unit extends out of the cavity top plate, and a spherical pad is sleeved on the upper connecting rod between the connecting flange with an inner screw and the top surface of the upper cavity top plate, and another spherical pad is sleeved on the upper connecting rod between the bottom surface of the upper cavity top plate and the flange of the upper connecting rod;

[0055] The connection flange of the lower loading unit is fixedly connected with the flange on the piston rod of the servo hydraulic cylinder through bolts, and a bellows for sealing is sleeved on the middle opening of the top plate of the lower cavity of the closed shell and the piston rod of the servo hydraulic cylinder;

[0056] The sealing shell is fixed on the top of the servo hydraulic cylinder body through the bracket, and the piston rod in the servo hydraulic cylinder can be freely extended and retracted into or out of the sealing shell. (See Figure 2 Figure 3 Figure 5 )

[0057] The acoustic wave sensors arranged in the upper and lower loading units collect the burst or continuous acoustic wave signals of the tested sample during the bending fatigue loading test, and continue to transmit them to the acoustic receiving system (signal amplification, processing and recording modules).

[0058] The outlet of the water cooler is connected to the water cooling chambers at the rear of the six halogen lamps and the pressure sensor of the servo hydraulic cylinder through a hydroelectric wireless slip ring to cool the halogen lamps and the pressure sensor.

[0059] The upper and lower chambers are composed of a top plate and six side plates. Three halogen lamps are respectively installed on the first, third and fifth side plates of the upper chamber, and the other three halogen lamps are respectively installed on the second, fourth and sixth side plates of the lower chamber. Figure 2 The top view direction is numbered in counterclockwise order from the first side plates of the upper and lower cavities), and 6 halogen lamps focus infrared radiation on a point of the sample to be tested from six directions respectively;

[0060] Quartz glass observation windows are respectively arranged on the 2nd and 4th side plates of the upper cavity and the 3rd and 5th side plates of the lower cavity; the upper and lower cavities are both made of composite plates with an outer layer of titanium alloy and an inner layer of reflective insulation material.

[0061] The high-pressure gas cylinder contains nitrogen, argon or oxygen; the exhaust pump inlet and the pressure reducing valve outlet are respectively connected to the gas pipeline interface on the closed shell through pipelines, and are respectively used to empty the closed shell and to input nitrogen, argon or oxygen into the closed shell.

[0062] The support platform is provided with a hydraulic oil pump connected with the servo hydraulic cylinder and a fatigue loading controller for controlling the start and stop of the servo hydraulic cylinder.

[0063] Six fastening screws are screwed onto the internally threaded connection flange of the upper loading unit, and the lower ends of the fastening screws are pressed onto the spherical pads to prevent the connection flange from loosening and enhance the shaft sealing effect at the upper connecting rod position.

[0064] See also Figure 6 The method also comprises a centering clamp for coaxial calibration of the upper and lower loading units: the outer sides of the upper and lower parts of the cylinder respectively have a sleeve for being sleeved with the convex neck of the upper pull rod and the pull rod of the upper and lower loading units, and the center positions of the top and bottom surfaces of the cylinder respectively have a central axis, and the two central axes respectively penetrate into the central holes of the horizontal circular plates of the upper pull rod and the pull rod to perform coaxial calibration of the upper and lower loading units.

[0065] 1. Complete the device construction process

[0066] 1) If Figure 2 As shown, the adapter base 8 is placed on the five-axis sample stage 9, the servo hydraulic cylinder 7 is placed on the adapter base 8, the lower cavity 23 is placed on the servo hydraulic cylinder 7, and the lower loading unit 16 is placed on the lower cavity 23, and they are fixed and connected with screws. The lower loading unit 16c is connected and fastened with the (upper loading unit) 19c by the centering clamp 19h, and then the upper cavity 18 is connected and fastened with the lower cavity 23 by the polyetherimide X-ray transmission-support flange ring 15. The fatigue loading controller 12 and the hydraulic oil pump 11 are started in sequence, and the servo hydraulic cylinder 7 is started in the upper computer control software, so that the lower loading unit 16c rises and drives the (upper loading unit) 19c to press against 19b, press against the spherical pad 28, and then press against the upper cavity 18 through the centering clamp 19h. At this time, the (upper loading unit) 19b is connected to the upper cavity 18 by the fastening screw 29 and the (upper loading unit) connecting flange 19a with internal threads. The servo hydraulic cylinder 7 is controlled in the upper computer software to lower the lower loading unit 16 and remove the centering clamp. The above process can complete the construction of the loading host and the coaxiality calibration of the loading units (16c and 19c).

[0067] 2) Insert the six halogen lamps 20 through the corresponding ports of the upper cavity 18 and the lower cavity 23 and fix them with screws. Install the four quartz glass observation windows 21 on the corresponding ports of the upper cavity 18 and the lower cavity 23 and fix them with screws. Figure 1 The thermocouple and gas concentration monitoring probe mounting base 26 and gas pipeline interface 27 not shown are installed in the corresponding ports of the upper cavity 18 and the lower cavity 23 and fixedly connected by screws, such as Figure 2 As shown. The output and input pipelines of the water chiller 14 are connected to the corresponding ports on the halogen lamp 20, the water cooling channel 22 and the water-electric wireless slip ring 25 respectively. The output and input lines of the halogen lamp controller 1 are connected to the corresponding ports on the halogen lamp 20 and the water-electric wireless slip ring 25 respectively. The output and input lines of the sound receiving system 4 are connected to the corresponding ports on the lower cavity 23.

[0068] 3) Install the pressure reducing valve 5 on the high-pressure gas cylinder 6, open the control valve of the high-pressure gas cylinder 6 and let it stand for 10 minutes. After no abnormality, close the control valve of the high-pressure gas cylinder 6 for subsequent use. Connect the input end of the exhaust pump 3 and the output end of the pressure reducing valve 5 to the corresponding ports on the upper cavity 18 and the lower cavity 23 respectively. By removing the halogen lamp 20, insert the two ends of the sample 17 to be tested into the corresponding grooves at the ends of the lower loading unit 16 and the (upper loading unit) 19 through its mounting seat, and lock the sample 17 to the lower loading unit 16 and the (upper loading unit) 19 with screws. Adjust the vertical (Z-direction) height, position in the XY plane, and inclination of the horizontal plane relative to the X and Y axes of the five-axis sample stage 9 so that the X-rays emitted by the X-ray transmitter 2 just pass through the polyetherimide X-ray transmission-support flange ring 15 and the middle of the sample 17 to be tested and are received by the X-ray receiver 13, and the sample axis remains vertical and located at the center of the sample and the field of view during the 360-degree rotation. The position and height of the high-temperature optical two-color thermometer 24 are adjusted to meet the normal working distance conditions and to be aligned with the measured object. At this point, the experimental device is built.

[0069] 2. X-ray-based in-situ bending fatigue damage 3D characterization test steps

[0070] 1) First, assemble and connect all parts of the test machine on the five-axis sample stage 9 of the X-ray characterization system, adjust the height of the five-axis sample stage 9 according to the height of the X-ray, and accurately locate the sample test position through the laser positioning system to ensure that the X-ray passes through the area of ​​interest of the sample. Calibrate the sample stage and the axis of the test machine, and then determine the test parameters such as the imaging field size, X-ray energy and exposure time according to the material, size and test purpose of the sample to be tested.

[0071] 2) Before the test begins, the two ends of the sample 17 to be tested are respectively inserted into the corresponding grooves at the ends of the lower loading unit 16 and (upper loading unit) 19 by disassembling the halogen lamp 20 and inserting the two ends of the sample 17 to be tested from its mounting seat, and the sample 17 to be tested is locked with the lower loading unit 16 and (upper loading unit) 19 by screws. Subsequently, the gas in the closed chamber formed by the polyetherimide X-ray transmission-support flange ring 15, the upper cavity 18 and the lower cavity 23 is discharged through the exhaust pump 3, and then the pressure reducing valve 5 and the high-pressure gas cylinder 6 valve are opened to fill in a specific gas (such as nitrogen or argon or oxygen), and this process is repeated three times to ensure that the closed chamber is in the target gas environment. After the gas environment adjustment is completed, the pressure reducing valve 5 and the high-pressure gas cylinder 6 valve are closed to avoid gas flow inside the cavity to reduce convective heat exchange.

[0072] 3) Start the fatigue loading controller 12 and the hydraulic oil pump 11 in sequence, and start the servo hydraulic cylinder 7 in the upper computer control software to lower the lower loading unit 16. Figure 5As shown, according to the rotation characteristics of the connecting rod mechanism, the axial displacement of the distal end (16b) will be converted into the rotation of the proximal loading beam (16d) around the axis, thereby applying an appropriate preload bending load to the sample. Subsequently, the halogen lamp 20 heats the test section of the sample 17 under the control of the halogen lamp controller 1, and the water cooler 14 is started to ensure that the servo hydraulic cylinder 7, the polyetherimide X-ray transmission-support flange ring 15, the halogen lamp 20, the upper cavity 18, the quartz glass observation window 21, and the lower cavity 23 are at room temperature. The sample temperature is monitored in real time by a high-temperature optical two-color thermometer 24.

[0073] 4) The sample is kept at the target temperature for 10 minutes to ensure that it is heated evenly. Then, the X-ray transmitter 2 and the X-ray receiver 13 are turned on, and the five-axis sample stage 9 is controlled to rotate and drive the test machine body and the internal sample 17 to rotate 180 degrees at a constant speed. During the rotation, the X-rays emitted by the X-ray transmitter 2 and passing through the polyetherimide X-ray transmission-support flange ring 15 and the sample 17 are received by the X-ray receiver 13 to collect image data, that is, the initial state record of the sample is completed for comparison with the subsequent damage state.

[0074] 5) According to the experimental purpose and experimental materials, determine the stress loading conditions in the experiment and start the experiment. For monotonic bending test, the recommended axial displacement loading rate is 0.5mm / min. For bending fatigue test, the recommended loading frequency range is 30-50Hz to ensure that the experimental time is reasonable and it is easy to find and record the damage failure evolution in time. The schematic diagram of the bending state of the sample when the lower loading unit 16 moves up to the top and down to the end is as follows Figure 4 shown.

[0075] 6) After a certain size of monotonous bending loading or a certain number of fatigue cycle loading, when the acoustic receiving system 4 collects a burst or continuous signal or a microstructure change in the real-time X-ray transmission projection image, it indicates that the sample 17 under test is damaged. At this time, the servo hydraulic cylinder 7 is controlled to stop loading and keep the loading level unchanged, so that the sample remains in the current damage state without further deterioration, and at the same time, the damage characteristics are clearly visible. The five-axis sample table 9 is controlled to rotate and drive the test machine body and the internal sample 17 to rotate 180 degrees at a constant speed. During the rotation, the X-ray receiver 13 receives the X-rays emitted by the X-ray transmitter 2 and passing through the polyetherimide X-ray transmission-support flange ring 15 and the sample 17 under test to collect image data, that is, the damage state record of the sample under test is completed.

[0076] 7) After completing 180-degree imaging of the current damage state of the sample 17 under test, resume the monotonic or cyclic bending loading of the sample 17 under test, and repeat the above operation until the expected damage state or cycle number is reached, and turn off the X-ray emitter 2. Reconstruct the obtained image data to complete the three-dimensional morphology characterization of the internal material, and three-dimensionally display the evolution of material damage during the monotonic or cyclic bending loading test.

Claims

1. A three-point bending high temperature fatigue test instrument based on X-ray in-situ imaging, characterized in that: The servo hydraulic cylinder (7) is mounted on an adapter base (8), the adapter base is mounted on a five-axis sample stage (9), and the five-axis sample stage is mounted on a support platform (10); the sealed housing comprises an upper cavity (18), a lower cavity (23), and a polyetherimide X-ray transmissive support flange ring (15); the upper and lower cavities are shaped as a regular hexagonal pyramid and an inverted regular hexagonal pyramid, respectively, and the two are symmetrical in the upper and lower parts; the support flange ring (15) is composed of a short pipe joint fixedly connected between two plate flanges, and the outer surfaces of the two plate flanges are respectively provided with annular water cooling channels (22) with water inlets and water outlets on the inner sides of the bolt holes, and the support flange ring is connected between the upper and lower cavities by bolts; Three halogen lamps (20) are inserted from ports of three non-adjacent side panels of the upper cavity and fixed by bolts, and another three halogen lamps (20) are inserted from ports of another three non-adjacent side panels of the lower cavity and fixed by bolts, and the infrared radiation of the six halogen lamps providing an extremely high temperature of 1500° C. is focused on a point on the central axis of the above-mentioned closed shell; The sealed shell is provided with a thermocouple and a gas concentration monitoring probe mounting seat (26) and a gas pipeline interface (27); The support platform is provided with a halogen lamp controller (1), an X-ray transmitter (3), an X-ray receiver (13) with a built-in image collector; an acoustic receiving system (4), a high-temperature optical two-color thermometer (24) for testing the temperature of a sample under test, an exhaust pump (3), a high-pressure gas cylinder (6) equipped with a pressure reducing valve (5), a fatigue loading controller (12), and a water cooler (14); The hydroelectric wireless slip ring (25) is sleeved on the servo hydraulic cylinder body; The lower loading unit (16) is: a connecting rod (16b) with a lower flange passes through the middle hole of the connecting flange (16a) from bottom to top and is mounted on the connecting flange (16a) in a tight fit, or the lower flange of the connecting rod is fixedly connected to the connecting flange by screws, the pull rod (16c) is formed by integrating a vertically arranged hinge seat and an outer convex neck of a horizontal circular plate, the middle column at the top of the connecting rod passes through the central hole of the horizontal circular plate of the pull rod from bottom to top and the two are fixedly connected by nuts, the swing rod (16d) is composed of a horizontal rod fixed on the left side of the vertical plate, the left end of the horizontal rod is movably mounted on the fixed axis of the hinge seat of the pull rod, an acoustic wave sensor (16e) is arranged in the groove socket hole on the right side of the vertical plate of the horizontal rod, and a pressing plate (16f) and a water-cooling back plate (16g) with a water-cooling channel therein are fixed to the right side of the vertical plate of the swing rod in sequence by bolts; The upper loading unit (19) comprises an upper connecting rod (19b) having a flange at the bottom, the upper part of which is screwed from bottom to top on a connecting flange (19a) with internal threads; an upper pull rod (19c), an upper swing rod (19d), an upper pressing plate (19f) and an upper water-cooled back plate (19g) are respectively the same in shape, structure and connection method as the pull rod (16c), the swing rod (16d), the pressing plate (16f) and the water-cooled back plate (16g) and are symmetrically arranged up and down; a horizontal circular plate of the upper pull rod is fixedly connected to the flange of the upper pull rod by bolts; The outlet of the water chiller is connected to the water cooling channel on the support flange ring and the water cooling back plate of the lower loading unit and the upper water cooling back plate of the upper loading unit through a hydroelectric wireless slip ring, so as to deliver cooling water to cool the support flange ring and the acoustic wave sensor when the upper and lower loading units clamp the sample to be tested and rotate with the five-axis sample stage; The halogen lamp controller (1) is connected to six halogen lamps via a hydroelectric wireless slip ring to maintain the supply of working power to the halogen lamps when the closed housing rotates with the five-axis sample stage; The upper connecting rod (19b) of the upper loading unit extends out of the cavity top plate, and a spherical pad is sleeved on the upper connecting rod between the connecting flange (19a) with an inner thread and the top surface of the upper cavity top plate, and another spherical pad (28) is sleeved on the upper connecting rod between the bottom surface of the upper cavity top plate and the flange of the upper connecting rod (19b); The connection flange (16a) of the lower loading unit is fixedly connected to the flange on the piston rod of the servo hydraulic cylinder through bolts, and a bellows for sealing is sleeved on the middle opening of the top plate of the lower cavity of the closed housing and the piston rod of the servo hydraulic cylinder; The sealing shell is fixed on the top of the servo hydraulic cylinder body via a bracket, and the piston rod in the servo hydraulic cylinder can be freely extended and retracted to enter or move out of the sealing shell.

2. The three-point bending high temperature fatigue test instrument and method based on X-ray in-situ imaging according to claim 1 is characterized in that: The acoustic wave sensors arranged in the upper and lower loading units collect the burst or continuous acoustic wave signals of the tested sample during the bending fatigue loading test, and continue to transmit them to the acoustic receiving system (signal amplification, processing and recording modules).

3. The three-point bending high temperature fatigue test instrument and method based on X-ray in-situ imaging according to claim 1 is characterized in that: The outlet of the water cooler is connected to the water cooling chambers at the rear of the six halogen lamps and the pressure sensor of the servo hydraulic cylinder through a hydroelectric wireless slip ring to cool the halogen lamps and the pressure sensor.

4. The three-point bending high temperature fatigue test instrument and method based on X-ray in-situ imaging according to claim 1 is characterized in that: The upper and lower chambers are composed of a top plate and six side plates, three halogen lamps are respectively mounted on the first, third and fifth side plates of the upper chamber, and another three halogen lamps are respectively mounted on the second, fourth and sixth side plates of the lower chamber, and the six halogen lamps focus infrared radiation on a point of the sample to be tested from six directions; Quartz glass observation windows (21) are respectively arranged on the second and fourth side plates of the upper cavity and the third and fifth side plates of the lower cavity; the upper and lower cavities are both made of composite plates with an outer layer of titanium alloy and an inner layer of reflective heat insulation material.

5. The three-point bending high temperature fatigue test instrument and method based on X-ray in-situ imaging according to claim 1 is characterized in that: The high-pressure gas cylinder (7) contains nitrogen, argon or oxygen; the inlet of the exhaust pump (3) and the outlet of the pressure reducing valve (5) are respectively connected to the gas pipeline interface (27) on the closed shell through pipelines, and are respectively used to empty the closed shell and to input nitrogen, argon or oxygen into the closed shell.

6. The three-point bending high temperature fatigue test instrument and method based on X-ray in-situ imaging according to claim 1 is characterized in that: The support platform is provided with a hydraulic oil pump (11) connected to the servo hydraulic cylinder and a fatigue loading controller (12) for controlling the start and stop of the servo hydraulic cylinder.

7. The three-point bending high temperature fatigue test instrument and method based on X-ray in-situ imaging according to claim 1 is characterized in that: Six fastening screws (29) are screwed onto the internally threaded connection flange of the upper loading unit, and the lower ends of the fastening screws are pressed onto the spherical pads to prevent the connection flange (19a) from loosening and to enhance the shaft sealing effect at the upper connecting rod position.

8. The three-point bending high temperature fatigue test instrument and method based on X-ray in-situ imaging according to claim 1 is characterized in that: The invention also comprises a centering clamp (19h) for coaxial calibration of the upper and lower loading units: the outer sides of the upper and lower parts of the cylinder respectively have a sleeve for being sleeved with the convex neck of the upper pull rod and the pull rod of the upper and lower loading units, and the center positions of the top and bottom surfaces of the cylinder respectively have a central axis, and the two central axes respectively penetrate into the central holes of the horizontal circular plates of the upper pull rod and the pull rod to perform coaxial calibration of the upper and lower loading units.

9. A method for constructing an experimental instrument according to any one of claims 1 to 8, characterized in that: The following steps are involved: 1) placing the transfer base (8) on the five-axis sample table (9), placing the servo hydraulic cylinder (7) on the transfer base (8), placing the lower cavity (23) on the servo hydraulic cylinder (7), placing the lower loading unit (16) on the lower cavity (23), and fixing them with screws; connecting the lower loading unit (16c) and the upper loading unit (19c) with a centering clamp (19h), and then connecting the upper cavity (18) and the lower cavity (23) with a polyetherimide X-ray transmission-support flange ring (15); starting the fatigue loading controller (12) and the hydraulic oil pump (11) in turn, and in the upper computer control software The servo hydraulic cylinder (7) is started to make the lower loading unit (16c) rise and drive the upper loading unit (19c) to press against (19b) and against the spherical pad (28) and then against the upper cavity (18) through the centering clamp (19h); at this time, the upper loading unit (19b) is connected to the upper cavity (18) by the fastening screw (29) and the upper loading unit connecting flange (19a) with internal threads; the servo hydraulic cylinder (7) is controlled in the upper computer software to make the lower loading unit (16) descend and remove the centering clamp; through the above process, the loading host can be built and the coaxiality calibration of the loading units (16c) and (19c) can be completed; 2) inserting six halogen lamps (20) from the corresponding ports of the upper cavity (18) and the lower cavity (23) and fixing them with screws; installing four quartz glass observation windows (21) at the corresponding ports of the upper cavity (18) and the lower cavity (23) and fixing them with screws; installing the thermocouple and gas concentration monitoring probe mounting seat (26) and the gas pipeline interface (27) not shown in FIG. 1 at the corresponding ports of the upper cavity (18) and the lower cavity (23) and fixing them with screws, as shown in FIG. 2; connecting the output and input pipelines of the water cooler (14) to the corresponding ports on the halogen lamp (20), the water cooling channel (22) and the water-electric wireless slip ring (25); connecting the output and input lines of the halogen lamp controller (1) to the corresponding ports on the halogen lamp (20) and the water-electric wireless slip ring (25); connecting the output and input lines of the sound receiving system (4) to the corresponding ports on the lower cavity (23); 3) Install the pressure reducing valve 5 on the high-pressure gas cylinder (6), open the control valve of the high-pressure gas cylinder (6) and let it stand for 10 minutes. After no abnormality is found, close the control valve of the high-pressure gas cylinder (6) for subsequent use; connect the input end of the exhaust pump (3) and the output end of the pressure reducing valve 5 to the corresponding ports on the upper cavity (18) and the lower cavity (23) respectively; remove the halogen lamp (20) and insert the two ends of the sample to be tested (17) into the corresponding grooves at the ends of the lower loading unit (16) and the upper loading unit (19) through its mounting seat, and screw the sample to be tested (17) to the lower loading unit (16) and the upper loading unit (19) The unit (19) is locked; the vertical (Z-direction) height, the position in the XY plane and the inclination angle of the horizontal plane relative to the X and Y axes of the five-axis sample stage (9) are adjusted so that the X-rays emitted by the X-ray emitter (2) just pass through the polyetherimide X-ray transmission-support flange ring (15) and the middle of the sample (17) to be measured and are received by the X-ray receiver (13), and the sample axis remains vertical and is located at the center of the sample and the field of view during the 360-degree rotation; the position and height of the high-temperature optical two-color thermometer (24) are adjusted so that it meets the normal working distance conditions and is aligned with the target to be measured; at this time, the experimental device is completed.

10. A test method of the experimental instrument according to any one of claims 1 to 8, characterized in that: The method comprises the following steps: firstly, assembling and connecting the various parts of the test machine on the five-axis sample stage (9) of the X-ray characterization system, adjusting the height of the five-axis sample stage (9) according to the height of the X-ray, accurately positioning the sample test position by a laser positioning system, and ensuring that the X-ray passes through the sample area of ​​interest; calibrating the sample stage and the axis of the test machine, and then determining the imaging field size, X-ray energy, exposure time and other test parameters according to the material, size and test purpose of the sample to be tested; 1) Before the test begins, the two ends of the sample to be tested (17) are respectively inserted into the corresponding grooves at the ends of the lower loading unit (16) and the upper loading unit (19) by disassembling the halogen lamp (20) and inserting the two ends of the sample to be tested (17) from its mounting seat, and the sample to be tested (17) is locked with the lower loading unit (16) and the upper loading unit (19) by screws; then the gas in the closed chamber formed by the polyetherimide X-ray transmission-support flange ring (15), the upper cavity (18) and the lower cavity (23) is discharged through the exhaust pump (3), and then the pressure reducing valve (5) and the high-pressure gas cylinder (6) valve are opened to fill in a specific gas (such as nitrogen, argon or oxygen), and this process is repeated three times to ensure that the closed chamber is in the target gas environment; after the gas environment adjustment is completed, the pressure reducing valve (5) and the high-pressure gas cylinder (6) valve are closed to avoid gas flow inside the cavity, so as to reduce convective heat exchange; 2) Start the fatigue loading controller (12) and the hydraulic oil pump (11) in sequence, start the servo hydraulic cylinder (7) in the upper computer control software, and lower the lower loading unit (16); as shown in FIG5 , according to the rotation characteristics of the connecting rod mechanism, the axial displacement of the distal end (16b) will be converted into the rotation of the proximal loading beam (16d) around the axis, thereby applying an appropriate preload bending load to the sample; then, the halogen lamp (20) heats the test section of the sample (17) under the control of the halogen lamp controller (1), and at the same time, the water cooler (14) is started to ensure that the servo hydraulic cylinder (7), the polyetherimide X-ray transmission-support flange ring (15), the halogen lamp (20), the upper cavity (18), the quartz glass observation window (21), and the lower cavity (23) are at room temperature; the sample temperature is monitored in real time by a high-temperature optical two-color thermometer (24); 3) The sample is kept at the target temperature for 10 minutes to ensure that it is heated evenly, and then the X-ray transmitter (2) and the X-ray receiver (13) are turned on, and the five-axis sample stage (9) is controlled to rotate and drive the test machine body and the sample to be tested (17) inside to rotate 180 degrees at a constant speed. During the rotation process, the X-rays emitted by the X-ray transmitter (2) and passing through the polyetherimide X-ray transmission-support flange ring (15) and the sample to be tested (17) are received by the X-ray receiver (13) to collect image data, that is, the initial state record of the sample to be tested is completed, so as to prepare for comparison and study of subsequent damage states; 4) According to the experimental purpose and experimental materials, the stress loading conditions in the experiment are determined, and the experiment is started; for the monotonic bending test, the recommended axial displacement loading rate is 0.5 mm / min, and for the bending fatigue test, the recommended loading frequency range is 30 to 50 Hz, so as to ensure that the experimental time is reasonable and it is easy to find and record the damage failure evolution in time; the schematic diagram of the bending state of the sample when the lower loading unit (16) moves up to the top and down to the end is shown in FIG4; 5) After a certain magnitude of monotonic bending loading or a certain number of fatigue cycle loading, when the acoustic receiving system (4) collects a burst or continuous signal or a microstructural change appears in the real-time X-ray transmission projection image, it indicates that the sample (17) under test is damaged. At this time, the servo hydraulic cylinder (7) is controlled to stop loading and keep the loading level unchanged, so that the sample remains in the current damage state and does not deteriorate further, while ensuring that the damage characteristics are clearly visible; the five-axis sample stage (9) is controlled to rotate and drive the test machine body and the sample (17) under test to rotate 180 degrees at a uniform speed. During the rotation, the X-ray receiver (13) receives the X-rays emitted by the X-ray transmitter (2) and passing through the polyetherimide X-ray transmission-support flange ring (15) and the sample (17) under test to collect image data, thus completing the record of the damage state of the sample under test; VI) After completing 180-degree imaging of the current damage state of the sample under test (17), resume the monotonic or cyclic bending loading of the sample under test (17), and repeat the above operation until the expected damage state or cycle number is reached, and turn off the X-ray emitter (2); reconstruct the obtained image data to complete the three-dimensional morphology characterization of the internal material, and three-dimensionally display the material damage evolution process during the monotonic or cyclic bending loading test.

Images