A 4D-CT under coupling low temperature and acoustic emission infinite rotation loading system

Abstract

The present application relates to the technical field of in-situ testing device of material mechanical properties, and particularly relates to a 4D-CT coupled low temperature and acoustic emission infinite rotation loading system, which comprises a system base, a loading system and a heat insulation sleeve from bottom to top; the loading system comprises a lower opening shell and a loading motor, the loading motor drives a down rod to move up and down, the down rod is sealed and penetrates through the shell to extend into the heat insulation sleeve; the heat insulation sleeve is provided with a partition plate; a loading platform is arranged on the down rod, an upper pressing rod and an upper pressing plate are fixed in sequence above the loading platform opposite to the loading platform and below the partition plate; a lower electric slip ring assembly is arranged on the loading system shell, and an upper electric slip ring assembly is arranged on the upper part of the heat insulation sleeve; a mechanical slip ring assembly is arranged at the top end of the heat insulation sleeve, and a low temperature nitrogen inlet pipe penetrates through the mechanical slip ring stator to enter the heat insulation sleeve. The present application can complete infinite rotation of the loading area without pipeline winding during CT scanning, and realizes closed loop control of the temperature of the upper and lower ends of the sample and double channel synchronous acquisition of the damage acoustic emission signal.

Description

Technical Field

[0001] This invention relates to the field of in-situ testing devices for the mechanical properties of materials. Specifically, it relates to an ultra-low temperature infinite rotation uniaxial loading system that is compatible with 4D-CT (four-dimensional computed tomography) imaging and has acoustic emission damage monitoring capabilities. It is particularly suitable for multi-scale, dynamic, and visualized research on the damage evolution mechanism of aerospace materials, composite materials, and energy geological materials in extreme low-temperature service environments such as deep space, polar regions, and LNG storage facilities. Background Technology

[0002] With the development of deep resources, polar engineering, and underground liquefied natural gas (LNG) storage projects, the mechanical behavior of rock materials under low-temperature environments has become a fundamental issue requiring in-depth understanding in geotechnical engineering and energy geology. Numerous experimental studies have shown that under low-temperature to frozen conditions, the pore water or fissure water in rocks undergoes a phase change and freezes, expanding in volume by approximately 9%. This alters the cementation strength between mineral particles, macroscopically manifesting as increased compressive strength and elastic modulus, but significantly enhanced brittleness and decreased fracture toughness. Simultaneously, freeze-thaw cycles exacerbate the initiation and connection of microcracks, leading to progressive damage to the rock structure. Therefore, accurately characterizing the internal damage evolution process of rocks under low-temperature and thermo-pressure coupled conditions is of significant scientific value for revealing the aforementioned engineering instability mechanisms.

[0003] Traditional cryogenic mechanics tests for rocks often employ conventional uniaxial hydraulic devices in conjunction with cryogenic environmental chambers. The sealed chamber is cooled as a whole by a refrigeration compressor or liquid nitrogen spray, and the sample is subjected to axial loading until failure. While this testing method can obtain macroscopic mechanical parameters such as stress-strain curves at low temperatures, it has significant technical limitations: the cryogenic environmental chamber is bulky and has a complex insulation structure, making it difficult to integrate into the rotating sample stage of a computed tomography (CT) scanner; the metal walls and insulation layer of the environmental chamber almost completely block X-ray penetration, making simultaneous CT scanning during loading impossible. Researchers can only remove the sample after the experiment for "post-experimental" observation, unable to capture the intermediate evolution of damage. More importantly, even if the environmental chamber is simplified to an open cooling structure, the external pipelines such as refrigeration pipes, loading drive cables, and sensor leads remain stationary, preventing the sample stage from achieving continuous 360° infinite rotation (a fundamental requirement for continuous temporal data acquisition in 4D-CT imaging). Existing devices can only perform limited reciprocating rotations, which not only results in low scanning efficiency but also introduces mechanical gap impacts and temperature fluctuations at each reversal moment, causing motion artifacts in CT reconstructed images that are difficult to correct. This severely restricts uninterrupted, high-fidelity dynamic observation of the entire process of low-temperature damage to rocks.

[0004] In recent years, CT technology with temporal dimension (4D) imaging capabilities has opened up new avenues for rock mechanics research. 4D-CT, through continuous 360° rotation of the sample stage and rapid tomographic reconstruction, can acquire three-dimensional image sequences of the evolution of key features of the sample, such as internal pore structure, microcrack network, and particle displacement, over time during the entire stress process, elevating damage research from static "dissection" to dynamic "video recording." Especially for media highly sensitive to temperature and pressure, such as hydrate-bearing sediments or permafrost, 4D-CT can capture in situ the morphological changes at the hydrate decomposition front, the growth and disappearance of ice lenses, and the initiation and expansion of microcracks under temperature gradients. However, to achieve the integration of 4D-CT with low-temperature loading of rocks, a clever rotational connection design is necessary to prevent all peripheral pipelines, such as the cooling medium delivery pipeline, loading drive cable, and temperature sensor leads, from tangling during the infinite rotation of the sample stage. This is currently the biggest technical bottleneck hindering the practical application of in-situ rock CT testing devices.

[0005] Furthermore, the damage process of rock materials at low temperatures is usually accompanied by abundant acoustic emission signals. Acoustic emission technology, by detecting transient elastic waves generated by microfractures, can invert the crack initiation time, spatial location, and failure mode in real time, providing early warning capabilities for brittle rock failure. However, in ultra-low temperature environments, the sensitivity of conventional acoustic emission probes drops sharply, and the coupling medium between the probe and the rock sample is prone to brittle fracture and failure at low temperatures. More critically, multi-channel acoustic emission signal lines, together with other pipelines, form a complex cable control system, which inevitably becomes entangled and pulled during continuous rotation of the CT, severely restricting the in-situ realization of real-time acoustic emission monitoring of rock damage at low temperatures. Currently, there is a lack of a rock mechanics testing system that integrates ultra-low temperature environment, uniaxial loading, dynamic acoustic emission monitoring, and infinite rotation of 4D-CT, which urgently needs to be developed.

[0006] In summary, there is currently a lack of rock mechanics testing systems that integrate ultra-low temperature environment, uniaxial loading, and dynamic acoustic emission monitoring, while also being compatible with infinite rotation of 4D-CT. The necessity of developing such a device lies in the fact that only by overcoming the bottlenecks in functional integration and rotation compatibility can the entire lifecycle damage process of rocks, from microcrack initiation to macroscopic failure, be fully captured under continuous dynamic scanning conditions. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention proposes an infinitely rotating loading system for 4D-CT coupling cryogenics and acoustic emission, comprising, from bottom to top, a system base, a loading system, and a heat-insulating sleeve. The system base can be fixed to a CT turntable. The loading system includes a cylindrical outer shell with a lower opening fixed to the system base. A loading motor is installed inside the outer shell, driving a downward pressure rod to move up and down. The downward pressure rod extends through the outer shell and into the heat-insulating sleeve. The heat-insulating sleeve has upper and lower openings, and its bottom is detachably connected to the loading system outer shell by bolts. The heat-insulating sleeve is divided into two interconnected cavities by a partition plate. A stage is installed on the downward pressure rod in the lower cavity. Above the stage, an upper pressure rod and an upper pressure plate are fixed sequentially below the partition plate. The sample is installed between the stage and the upper pressure plate. The stage and the upper pressure plate each integrate a complete heating, temperature measurement, and acoustic emission monitoring unit. On the partition plate, an air inlet is provided around the upper pressure rod to connect the upper and lower cavities. An exhaust valve is provided in the lower cavity. A lower electric slip ring assembly is provided on the outer shell of the loading system, and an upper electric slip ring assembly is provided on the upper part of the heat insulation sleeve. A mechanical slip ring assembly is provided at the top of the heat insulation sleeve. The mechanical slip ring rotor is fixedly sleeved on the top of the heat insulation sleeve, and the mechanical slip ring stator can rotate relative to the mechanical slip ring rotor. The low-temperature nitrogen inlet pipe passes through the mechanical slip ring stator and enters the heat insulation sleeve.

[0008] Preferably, a radiation source is arranged on one side of the CT turntable, and a detector is arranged on the other side. The radiation source and the detector are at least directly facing the sample in the heat insulation sleeve. The sample is imaged by n cycles of CT scanning through the continuous n×360° rotation of the CT turntable.

[0009] Preferably, a loading motor is fixed on the system base inside the housing. The output shaft of the loading motor faces vertically upward and is connected to the lead screw nut through a transmission shaft. The lead screw nut and the lead rod cooperate to form a ball screw pair, which converts the rotational motion of the lead screw nut into the linear lifting motion of the lead rod. A pressure rod is connected to the upper end of the lead rod, and a pressure sensor is set at the connection between the lead rod and the pressure rod.

[0010] Preferably, a lower resistance wire and a lower temperature sensor are embedded inside the stage near the sample clamping end, and a lower acoustic emission probe coupling groove is provided for fixing the lower acoustic emission probe; the upper pressure plate is correspondingly embedded with an upper resistance wire and an upper temperature sensor, and an upper acoustic emission probe coupling groove is provided for fixing the upper acoustic emission probe.

[0011] Preferably, the lower slip ring assembly includes an outer lower slip ring cylinder that is relatively stationary and an inner lower slip ring cylinder that rotates together with the loading system housing. The lower slip ring assembly is equipped with a motor positive power interface, a motor negative power interface, a motor signal control interface, a pressure sensor signal acquisition port, a lower resistance wire positive power interface, a lower resistance wire negative power interface, a lower acoustic emission probe signal acquisition port, and a lower temperature sensor signal acquisition port. The loading motor is connected to an external power supply device through the motor positive and negative power interfaces. The motor signal control interface not only provides motor drive commands to the loading motor but also reads the loading motor rotation data and lead screw parameters, thereby indirectly obtaining loading displacement information. The pressure sensor signal acquisition port is used to connect to a pressure sensor to detect the axial load during the loading process in real time.

[0012] Preferably, the lower acoustic emission probe signal acquisition port and the lower temperature sensor signal acquisition port are used to connect the lower acoustic emission probe and the lower temperature sensor, respectively; the lower resistance wire positive power interface and the lower resistance wire negative power interface are used to connect the lower resistance wire; and the connecting wire passes through the loading system housing in a sealed manner.

[0013] Preferably, the lower part of the heat insulation sleeve is frustum-shaped, and the upper part is cylindrical. An upper electric slip ring assembly is provided on the upper part of the cylindrical part of the heat insulation sleeve. The upper electric slip ring assembly includes an outer upper electric slip ring cylinder that is relatively stationary and an inner upper electric slip ring cylinder that rotates with the heat insulation sleeve. The side of the outer upper electric slip ring cylinder is provided with an upper temperature sensor signal acquisition port, an upper acoustic emission probe signal acquisition port, an upper resistance wire negative power interface, and an upper resistance wire positive power interface. The upper acoustic emission probe signal acquisition port and the upper temperature sensor signal acquisition port are used to connect the upper acoustic emission probe and the upper temperature sensor, respectively. The upper resistance wire negative power interface and the upper resistance wire positive power interface are used to connect the upper resistance wire.

[0014] Preferably, an inner heat insulation cylinder is fixed on the lower surface of the partition plate, around the outer periphery of the air inlet. The interior of the inner heat insulation cylinder is a low-temperature nitrogen channel, which physically separates the low-temperature nitrogen from the upper slip ring assembly.

[0015] Preferably, a solenoid valve is connected in series with the low-temperature nitrogen inlet pipe inside the upper cavity of the heat insulation sleeve.

[0016] The beneficial technical effects of this invention are as follows: Through the coordinated design of the upper and lower electric slip ring assemblies and the top mechanical slip ring assembly, this invention integrates the loading motor drive, resistance wire heating power supply, temperature sensor signal, acoustic emission probe signal, and low-temperature nitrogen pipeline into the rotation-stationary interface transmission, enabling the core loading area to complete n×360° infinite rotation during CT scanning without pipeline entanglement. The stage and upper pressure plate integrate independent resistance heating wires, temperature sensors, and acoustic emission probes, achieving closed-loop temperature control at both ends of the sample and dual-channel synchronous acquisition of damage acoustic emission signals. This system solves the problems of large size, interference with X-ray imaging, and inability to rotate continuously in traditional low-temperature loading devices. It can perform 4D-CT dynamic imaging and real-time acoustic emission monitoring of the initiation and propagation process of microcracks inside materials such as rocks under low-temperature conditions below -100℃ and uniaxial loading conditions, offering significant advantages such as precise temperature control, continuous imaging, and multi-dimensional synchronous damage information. Attached Figure Description

[0017] The accompanying drawings, which constitute the present invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0018] Figure 1 This is a schematic diagram of the overall structure of the present invention. Figure 2 This is a schematic cross-sectional view of the overall structure of the present invention.

[0019] In the diagram: 1. CT turntable; 2. X-ray source; 3. Detector; 4. System base; 5. Lower electric slip ring assembly; 6. Loading system; 7. Sample; 8. Upper electric slip ring assembly; 9. Mechanical slip ring assembly; 10. Thermal insulation sleeve; 5-1. Lower electric slip ring outer cylinder; 5-2. Motor positive power interface; 5-3. Motor negative power interface; 5-4. Motor signal control interface; 5-5. Pressure sensor signal acquisition port; 5-6. Lower resistance wire positive power interface; 5-7. Lower resistance wire negative power interface; 5-8. Lower acoustic emission probe signal acquisition port; 5-9. Lower temperature sensor signal acquisition port; 6-1. Loading motor; 6-2. Drive shaft; 6-3. Nut; 6-4. Lead screw; 6-5. Pressure sensor... 6-6. Lower pressure rod; 7-1. Stage; 7-2. Lower resistance wire; 7-3. Lower acoustic emission probe; 7-4. Lower temperature sensor; 7-5. Upper temperature sensor; 7-6. Upper acoustic emission probe; 7-7. Upper resistance wire; 7-8. Upper pressure plate; 8-1. Upper slip ring outer cylinder; 8-2. Upper temperature sensor signal acquisition port; 8-3. Upper acoustic emission probe signal acquisition port; 8-4. Upper resistance wire negative power interface; 8-5. Upper resistance wire positive power interface; 9-1. Solenoid valve; 9-2. Low-temperature nitrogen inlet pipe; 9-3. Mechanical slip ring stator; 9-4. Mechanical slip ring rotor; 10-1. Air inlet; 10-2. Inner heat insulation cylinder; 10-3. Exhaust valve; 10-4. Bolt. Detailed Implementation

[0020] To provide a clearer understanding of the technical features, objectives, and beneficial effects of this invention, the technical solution of this invention is described in detail below, but this should not be construed as limiting the scope of implementation of this invention. Unless otherwise specified, the methods used in this invention are conventional methods in this technical field.

[0021] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0022] like Figures 1-2 As shown, this invention proposes an infinitely rotating loading system for coupling cryogenics and acoustic emission under 4D-CT. The system includes, from bottom to top, a system base 4, a loading system 6, and a heat insulation sleeve 10. The system base 4 can be coaxially fixed to the worktable surface of the CT turntable 1 by bolts. A radiation source 2 is arranged on one side of the CT turntable 1, and a detector 3 is arranged on the other side. The radiation source 2 and the detector 3 are at least directly facing the position of the sample 7 in the heat insulation sleeve 10. The sample 7 is imaged by n cycles of CT scanning through the continuous n×360° rotation of the CT turntable 1.

[0023] The loading system 6 includes a cylindrical outer shell (bell-shaped) with an open bottom. The outer shell is coaxially fixed on the system base 4. Inside the outer shell, a loading motor 6-1 is fixed on the system base 4. The output shaft of the loading motor 6-1 is vertically upward and connected to a lead screw 6-3 via a transmission shaft 6-2. The lead screw 6-3 and the lead screw 6-4 cooperate to form a ball screw pair, which can convert the rotational motion of the lead screw 6-3 into the linear lifting motion of the lead screw 6-4. A pressure rod 6-6 is connected to the upper end of the lead screw 6-4. A pressure sensor 6-5 is provided at the connection between the lead screw 6-4 and the pressure rod 6-6. The pressure rod 6-6 is sealed through the outer shell and extends into the heat insulation sleeve 10.

[0024] The heat insulation sleeve 10 has openings at the top and bottom, with the lower part being a frustum and the upper part being a cylinder. The bottom of the lower frustum is coaxially fixed to the outer shell of the loading system 6 by bolts 10-4. The upper cylindrical part of the heat insulation sleeve 10 is provided with a partition plate, which divides the heat insulation sleeve 10 into two connected cavities. In the lower cavity, a stage 7-1 is provided on the lower pressure rod 6-6. Above the stage 7-1, an upper pressure rod and an upper pressure plate 7-8 are fixed in sequence below the partition plate. The sample 7 is installed between the stage 7-1 and the upper pressure plate 7-8. The stage 7-1 is supported by the lower pressure rod 6-6 and applies an axial load to the sample 7. Both the stage 7-1 and the upper pressure plate 7-8 are direct-load structures, and each integrates a complete heating, temperature measurement, and acoustic emission monitoring unit. Specifically, a lower resistance wire 7-2 and a lower temperature sensor 7-4 are embedded inside the stage 7-1 near the sample 7 clamping end, and a coupling groove for a lower acoustic emission probe 7-3 is provided for fixing the lower acoustic emission probe 7-3. Correspondingly, an upper resistance wire 7-7 and an upper temperature sensor 7-5 are embedded inside the upper pressure plate 7-8, and a coupling groove for an upper acoustic emission probe 7-6 is provided for fixing the upper acoustic emission probe 7-6. On the partition plate, an air inlet 10-1 connecting the upper and lower chambers is provided circumferentially on the upper pressure rod, and an exhaust valve 10-3 is also provided in the lower chamber.

[0025] A lower electric slip ring assembly 5 is provided on the outer shell of the loading system 6. The lower electric slip ring assembly 5 includes an outer lower electric slip ring cylinder 5-1 that is relatively stationary and an inner lower electric slip ring cylinder that rotates together with the outer shell of the loading system 6. The lower electric slip ring assembly 5 is provided with a motor positive power interface 5-2, a motor negative power interface 5-3, a motor signal control interface 5-4, a pressure sensor signal acquisition port 5-5, a lower resistance wire positive power interface 5-6, a lower resistance wire negative power interface 5-7, a lower acoustic emission probe signal acquisition port 5-8, and a lower temperature sensor signal acquisition port 5-9. These interfaces transmit multiple signals and power currents from the rotating end to the stationary end to the external controller through the sliding contact of the internal conductive ring and the alloy brush filament. The drive current for the loading motor 6-1 is provided by the motor positive power interface 5-2 and the motor negative power interface 5-3. The motor signal control interface 5-4 not only provides motor drive commands to the loading motor 6-1, but also reads the rotation data of the loading motor 6-1 and the parameters of the lead screw 6-4, thereby indirectly obtaining the loading displacement information without the need for an additional displacement sensor. The pressure sensor signal acquisition port 5-5 is used to connect to the pressure sensor 6-5, which detects the axial load during the loading process in real time. The lower acoustic emission probe signal acquisition port 5-8 and the lower temperature sensor signal acquisition port 5-9 are used to connect to the lower acoustic emission probe 7-3 and the lower temperature sensor 7-4, respectively. The lower resistance wire positive power interface 5-6 and the lower resistance wire negative power interface 5-7 are used to connect to the lower resistance wire 7-2, and the connecting wires pass through the outer shell of the loading system 6 in a sealed manner.

[0026] An upper slip ring assembly 8 is provided on the upper part of the cylindrical portion of the heat insulation sleeve 10. The upper slip ring assembly includes an outer upper slip ring cylinder 8-1 that is relatively stationary on the outside and an inner upper slip ring cylinder that rotates together with the heat insulation sleeve 10. The side of the outer upper slip ring cylinder 8-1 is provided with an upper temperature sensor signal acquisition port 8-2, an upper acoustic emission probe signal acquisition port 8-3, an upper resistance wire negative power interface 8-4, and an upper resistance wire positive power interface 8-5. The upper acoustic emission probe signal acquisition port 8-3 and the upper temperature sensor signal acquisition port 8-2 are respectively used to connect the upper acoustic emission probe 7-6 and the upper temperature sensor 7-5. The upper resistance wire negative power interface 8-4 and the upper resistance wire positive power interface 8-5 are used to connect the upper resistance wire 7-7. On the lower surface of the partition plate, an inner heat insulation cylinder 10-2 is fixed around the air inlet 10-1. The interior of the inner heat insulation cylinder 10-2 is a low-temperature nitrogen channel. After the low-temperature nitrogen is introduced through the air inlet 10-1, it flows downward along the annular channel between the inner heat insulation cylinder 10-2 and the upper pressure rod. After forced convection heat exchange with the sample 7 and its fixture, it is discharged from the exhaust valve 10-3 at the bottom to avoid pressure imbalance between the inside and outside. The inner heat insulation cylinder 10-2 physically separates the low-temperature nitrogen from the upper electric slip ring assembly 8 to prevent the low-temperature nitrogen from directly impacting the electronic components and contact pairs in the upper electric slip ring and causing adverse effects.

[0027] The power supply for the lower resistance wire 7-2 and the upper resistance wire 7-7 is led out through the lower slip ring assembly 5 and the upper slip ring assembly 8, respectively. With the cooling effect of low-temperature nitrogen, independent closed-loop control of the temperature at both ends of the sample 7 is achieved. The lower acoustic emission probe 7-3 and the upper acoustic emission probe 7-6 receive the transient elastic waves generated by the micro-fractures from both ends of the sample 7, and finally transmit them to the external acoustic emission acquisition instrument.

[0028] A mechanical slip ring assembly 9 is provided at the top of the heat insulation sleeve 10. The mechanical slip ring assembly 9 includes a mechanical slip ring stator 9-3 and a mechanical slip ring rotor 9-4, which are coaxially fitted and can rotate relative to each other. The mechanical slip ring stator 9-3 is on top and the mechanical slip ring rotor 9-4 is on the bottom. The mechanical slip ring rotor 9-4 is fixedly sleeved on the top of the heat insulation sleeve 10 and rotates with the heat insulation sleeve 10. Since the mechanical slip ring stator 9-3 can rotate relative to the mechanical slip ring rotor 9-4, it can remain stationary when the mechanical slip ring rotor 9-4 rotates. The low-temperature nitrogen inlet pipe 9-2 passes through the mechanical slip ring stator 9-3 and enters the upper cavity of the heat insulation sleeve 10. In the upper cavity of the heat insulation sleeve 10, a solenoid valve 9-1 is connected in series with the low-temperature nitrogen inlet pipe 9-2. The solenoid valve 9-1 is used to precisely adjust the flow rate of the low-temperature nitrogen, thereby achieving temperature control in conjunction with the resistance wire heating. The low-temperature nitrogen inlet pipe 9-2 adopts a vacuum insulated hose to minimize the loss of cold energy during the transportation process.

[0029] The working process of this system is described in detail below. Before the test, loosen bolt 10-4, remove the heat insulation sleeve 10, place sample 7 on the stage 7-1, then reinstall the heat insulation sleeve 10 and tighten bolt 10-4. Control the loading motor 6-1 to apply a certain initial load to sample 7 to prevent sample 7 from moving or falling off during subsequent operations. Low-temperature nitrogen is supplied, entering the heat insulation sleeve 10 through the low-temperature nitrogen inlet pipe 9-2 to cool sample 7 and the fixture. Based on the temperature signals fed back by the upper temperature sensor 7-5 and the lower temperature sensor 7-4, the heating power of the upper resistance wire 7-7 and the lower resistance wire 7-2 are adjusted respectively to lower sample 7 to the target low temperature (e.g., -100℃) at a preset cooling rate. At the same time, the acoustic emission probe begins background noise acquisition and calibration. Once the temperature and acoustic emission data acquisition stabilize, the loading motor 6-1 is driven to rotate, which in turn pushes the lead screw 6-4 and the pressure rod 6-6 upwards via the transmission shaft 6-2 and the lead screw nut 6-3, applying an axial load to the sample 7. During the loading process, the pressure sensor 6-5 and the number of rotations of the loading motor 6-1 provide the axial load and axial displacement signals, respectively.

[0030] Throughout the loading process, the CT turntable 1 drives the system base 4, the lower slip ring inner cylinder of the lower slip ring assembly 5, the loading system 6, the sample 7, the upper slip ring inner cylinder of the upper slip ring assembly 8, the rotor of the mechanical slip ring assembly 9, and the heat insulation sleeve 10 to rotate infinitely n×360°. Since the lower slip ring outer cylinder 5-1, the upper slip ring outer cylinder 8-1, and the stator of the mechanical slip ring assembly 9 remain stationary, all electrical cables and cryogenic nitrogen pipelines do not twist or become entangled. During continuous rotation, the X-ray source 2 and detector 3 rapidly project tomographic images onto the sample 7, and the CT control and reconstruction computer reconstructs a three-dimensional image sequence of the sample's internal microstructure in real time based on the projection data. Simultaneously, the lower acoustic emission probe 7-3 and the upper acoustic emission probe 7-6 completely record the acoustic emission characteristic parameters of each stage of crack initiation and propagation in the sample. This achieves synchronous dynamic characterization of the force, heat, sound, and image multi-physics fields of the same sample under uniaxial loading in a cryogenic environment.

[0031] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. An infinite rotational loading system for coupling cryogenics and acoustic emission under 4D-CT, characterized in that, The system comprises, from bottom to top, a system base, a loading system, and a heat insulation sleeve. The system base can be fixed to a CT turntable. The loading system includes a cylindrical outer shell with a lower opening, fixed to the system base. A loading motor is installed inside the outer shell, driving a downward pressure rod to move up and down. The downward pressure rod extends through the outer shell and into the heat insulation sleeve. The heat insulation sleeve has upper and lower openings, and its bottom is detachably connected to the loading system outer shell by bolts. The heat insulation sleeve is divided into two connected cavities by a partition plate. In the lower cavity, a stage is installed on the downward pressure rod. Above the stage, below the partition plate, are sequentially fixed... It has an upper pressure rod and an upper pressure plate, and the sample is installed between the stage and the upper pressure plate. The stage and the upper pressure plate each integrate a complete heating, temperature measurement and acoustic emission monitoring unit. On the partition plate, there is an air inlet hole connecting the upper cavity and the lower cavity in the circumferential direction of the upper pressure rod, and an exhaust valve is provided in the lower cavity. A lower electric slip ring assembly is provided on the outer shell of the loading system, and an upper electric slip ring assembly is provided on the upper part of the heat insulation sleeve. A mechanical slip ring assembly is provided at the top of the heat insulation sleeve. The mechanical slip ring rotor is fixedly sleeved on the top of the heat insulation sleeve, and the mechanical slip ring stator can rotate relative to the mechanical slip ring rotor. The low-temperature nitrogen inlet pipe passes through the mechanical slip ring stator and enters the heat insulation sleeve.

2. The infinite rotational loading system for coupling cryogenics and acoustic emission under 4D-CT as described in claim 1, characterized in that, A radiation source is arranged on one side of the CT turntable, and a detector is arranged on the other side. The radiation source and detector are at least directly facing the sample in the heat insulation sleeve. The sample is imaged by n cycles of CT scanning through the continuous n×360° rotation of the CT turntable.

3. The infinite rotational loading system for coupling cryogenics and acoustic emission under 4D-CT according to claim 1 or 2, characterized in that, Inside the housing, a loading motor is fixed on the system base. The output shaft of the loading motor faces vertically upward and is connected to the lead screw nut through a transmission shaft. The lead screw nut and the lead rod cooperate to form a ball screw pair, which converts the rotational motion of the lead screw nut into the linear lifting motion of the lead rod. A pressure rod is connected to the upper end of the lead rod, and a pressure sensor is set at the connection between the lead rod and the pressure rod.

4. The infinite rotational loading system for coupling cryogenics and acoustic emission under 4D-CT according to claim 3, characterized in that... Inside the stage, near the sample clamping end, there is a lower resistance wire and a lower temperature sensor, and a lower acoustic emission probe coupling slot for fixing the lower acoustic emission probe; inside the upper pressure plate, there is a corresponding upper resistance wire and an upper temperature sensor, and an upper acoustic emission probe coupling slot for fixing the upper acoustic emission probe.

5. The infinite rotational loading system for coupling cryogenics and acoustic emission under 4D-CT according to claim 4, characterized in that... The lower slip ring assembly includes an outer lower slip ring cylinder that is relatively stationary and an inner lower slip ring cylinder that rotates together with the loading system housing. The lower slip ring assembly is equipped with a motor positive power interface, a motor negative power interface, a motor signal control interface, a pressure sensor signal acquisition port, a lower resistance wire positive power interface, a lower resistance wire negative power interface, a lower acoustic emission probe signal acquisition port, and a lower temperature sensor signal acquisition port. The loading motor is connected to an external power supply device through the motor positive and negative power interfaces. The motor signal control interface not only provides motor drive commands to the loading motor but also reads the loading motor rotation data and lead screw parameters, thereby indirectly obtaining loading displacement information. The pressure sensor signal acquisition port is used to connect to a pressure sensor to detect the axial load during the loading process in real time.

6. The infinite rotational loading system for coupling cryogenics and acoustic emission under 4D-CT according to claim 5, characterized in that... The lower acoustic emission probe signal acquisition port and the lower temperature sensor signal acquisition port are used to connect the lower acoustic emission probe and the lower temperature sensor, respectively. The lower resistance wire positive power interface and the lower resistance wire negative power interface are used to connect the lower resistance wire. The connecting wire passes through the loading system housing in a sealed manner.

7. The infinite rotational loading system for coupling cryogenics and acoustic emission under 4D-CT according to claim 1 or 6, characterized in that... The lower part of the heat insulation sleeve is frustum-shaped, and the upper part is cylindrical. An upper electric slip ring assembly is provided on the upper part of the cylindrical part of the heat insulation sleeve. The upper electric slip ring assembly includes an outer upper electric slip ring cylinder that is relatively stationary and an inner upper electric slip ring cylinder that rotates with the heat insulation sleeve. The side of the outer upper electric slip ring cylinder is provided with an upper temperature sensor signal acquisition port, an upper acoustic emission probe signal acquisition port, an upper resistance wire negative power interface, and an upper resistance wire positive power interface. The upper acoustic emission probe signal acquisition port and the upper temperature sensor signal acquisition port are used to connect the upper acoustic emission probe and the upper temperature sensor, respectively. The upper resistance wire negative power interface and the upper resistance wire positive power interface are used to connect the upper resistance wire.

8. The infinite rotational loading system for coupling cryogenics and acoustic emission under 4D-CT according to claim 1, characterized in that... On the lower surface of the partition plate, an inner heat insulation cylinder is fixed around the air inlet. The interior of the inner heat insulation cylinder is a low-temperature nitrogen channel, which physically separates the low-temperature nitrogen from the upper slip ring assembly.

9. The infinite rotational loading system for coupling cryogenics and acoustic emission under 4D-CT according to claim 1, characterized in that... Inside the upper cavity of the heat insulation sleeve, a solenoid valve is connected in series with the low-temperature nitrogen inlet pipe.

Images