A dynamic scanning loading device and implementation method

Abstract

This invention discloses a dynamic scanning loading device and its implementation method, which can perform specimen loading in stages. Each stage is divided into several orders of magnitude based on its characteristics, thus achieving graded loading. During the entire loading process, after each order of magnitude is completed, the loading system automatically pauses further pressurization and, while maintaining the load constant, activates a rotation system, causing the specimen to rotate under pressure. Simultaneously, a CT scanner connected to the control system is activated to perform a 360-degree omnidirectional scan of the rotating specimen. The loading order of magnitude is progressively increased until the specimen is completely damaged. Therefore, this invention can achieve 360-degree scanning reconstruction of the internal damage of concrete using relatively simple devices and operating techniques, thereby constructing a dynamic three-dimensional damage model of the specimen.

Description

Technical Field

[0001] The invention belongs to the technical field of test loading, in particular to a dynamic scanning loading device and an implementation method thereof. Background Art

[0002] Since the 1980s, CT technology has been used to study the internal meso- and microscopic structures of materials such as rock, stone, soil, and concrete, as well as the development of micropores and microcracks. In recent years, a new approach to studying the mechanical properties of concrete has been to scan concrete slices and use image reconstruction technology to obtain the true three-dimensional configuration of concrete, generate a three-dimensional finite element model, and then use the idea of ​​mesoscopic numerical simulation to study the mechanical behavior of concrete.

[0003] The scanning methods of existing CT equipment are generally directional scanning and circumferential scanning. Due to the large scale of the loading instrument used for the test specimen, the scanning device cannot perform real-time 360-degree scanning of the deformation state of the specimen at various angles during the test due to the rigidity of the scanning method of the existing CT equipment, that is, it is impossible to capture all-round image information of the loaded specimen, resulting in the inaccurate description of the nonlinear mechanical behavior of materials such as concrete and the actual failure morphology at each loading stage. Therefore, the existing loading method combined with the current CT scanning method is used to scan the material during the loading process, which will have a great impact on the acquisition of the true situation of its internal morphology and structural dynamic changes. However, the real three-dimensional configuration of concrete at each loading stage is crucial to revealing the microscopic fracture process of concrete materials, analyzing its loading behavior and further evaluating the performance of concrete. In order to better obtain the three-dimensional configuration of concrete during the loading process, the CT scanning loading device still needs to be improved.

[0004] In view of the current industrial CT scanning method, one is that the CT machine is fixed and directional X-rays are emitted to scan the specimen, but the commonly used test loading press is also a fixed device, and the specimen cannot be rotated during the loading process. This causes the specimen to always face the CT device with one face or one angle during the entire loading process, resulting in the inability to achieve full-angle accurate scanning of the specimen; the other is a gantry-type CT scanning device. Due to the existence of the specimen loading machine, this type of CT cannot be used for scanning during the loading process, and thus a true dynamic three-dimensional damage model cannot be constructed.

[0005] In addition, there is currently no test loading machine in the industry that can be linked with a CT instrument. The test loading process requires manual judgment on whether a certain loading stage has been reached, and then the CT is manually started to perform a unidirectional scan of the test block in that state.

[0006] Therefore, there is a need for a dynamic scanning loading device and implementation method, which can perform loading according to the divided levels under a fixed CT machine scanning angle, and when the specimen is loaded to a certain level and the loading load is kept unchanged, the specimen is rotated 360 degrees at a certain rotation speed, thereby constructing a dynamic three-dimensional damage model of the specimen. Summary of the invention

[0007] The technical problem to be solved by the present invention is to provide a dynamic scanning loading device and implementation method in view of the deficiencies of the above-mentioned prior art. The dynamic scanning loading device and implementation method can load the specimen in stages, and divide each stage into several levels according to the characteristics of different stages, so as to realize graded loading. In the whole loading process, after the device loads one level, the loading system will automatically stop the pressurization and start the rotation system while keeping the load unchanged, so that the test block starts to rotate under the pressurization state, and at the same time start the CT scanner connected to the control system to perform a 360-degree full-range scan of the specimen in the rotating state, and gradually increase the loading level until the specimen is completely damaged. Therefore, the invention can realize the 360-degree scanning reconstruction of the internal damage of concrete through a relatively simple device and operation technology, and then construct a dynamic three-dimensional damage model of the specimen.

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

[0009] A method for implementing dynamic scanning loading includes the following steps:

[0010] Step 1: Determine the ultimate load: Estimate the ultimate load f of the concrete specimen according to the compressive strength grade of the concrete specimen material. p .

[0011] Step 2: Loading mode classification, which includes force loading mode and displacement loading mode; according to the ultimate load f determined in step 1 p , the loading mode is divided; assuming that the loading force borne by the concrete specimen is F, the specific division method is:

[0012] A. When 0≤F≤80%f p When the load is increased, the force loading mode is adopted, and the load increase rate range is f1~f2; among them, f1<f2, f1 is the lower limit of the load increase rate, and f2 is the upper limit of the load increase rate; f1 and f2 are determined according to the compressive strength grade of the concrete specimen material.

[0013] B. When F>80%f pWhen the displacement loading mode is adopted, the displacement increase rate range is s1~s2; among which, s1<s2, s1 is the lower limit of the displacement increase rate, and s2 is the upper limit of the displacement increase rate; s1 and s2 are determined according to the compressive strength grade of the concrete specimen material.

[0014] Step 3, specimen clamping: The concrete specimen is vertically mounted between the upper pressing plate and the lower pressing plate in the dynamic scanning loading device, and the concrete specimen can rotate synchronously with the upper pressing plate and the lower pressing plate.

[0015] Step 4: Load by force: The axial loading mechanism in the dynamic scanning loading device applies force load to the concrete specimen according to the set load increase rate until the loading force F borne by the concrete specimen reaches 80% f p During the loading process, the pressure sensor detects the loading force F borne by the concrete specimen in real time. When F reaches the set CT scanning point, the axial loading mechanism suspends the axial loading, and the rotating mechanism in the dynamic scanning loading device drives the concrete specimen to rotate 360°. The CT scanning equipment performs CT scanning on each height section of the concrete specimen and obtains the cross-sectional scanning image of the concrete specimen.

[0016] Step 5, loading by displacement: the axial loading mechanism in the dynamic scanning loading device applies a force load to the concrete specimen according to the set displacement increase rate until the concrete specimen is destroyed; during the loading process, the pressure sensor detects the loading force F borne by the concrete specimen in real time. When F reaches the set CT scanning point, the axial loading mechanism suspends the axial loading, and the rotating mechanism in the dynamic scanning loading device drives the concrete specimen to rotate 360°. The CT scanning equipment performs CT scanning on each height section of the concrete specimen and obtains a cross-sectional scanning image of the concrete specimen.

[0017] Step 6: Observe and analyze the cross-sectional scanning images of the concrete specimens in chronological order to obtain the damage variation pattern of the concrete specimens over time.

[0018] The specific loading method in step 4 is:

[0019] Step 4-1, set the CT scan frequency: 0~80%f p According to 10% f p A CT scan is performed at a frequency of

[0020] Step 4-2, primary loading: The axial loading mechanism in the dynamic scanning loading device applies a force load to the concrete specimen through the upper pressing plate at an upper limit of the load increase rate f2.

[0021] Step 4-3, primary loading force detection: During the loading process, the pressure sensor detects the loading force F borne by the concrete specimen in real time.

[0022] Step 4-4, a CT scan: when F = 10% f p 、20%f p 、30%f p 、40%f p and 50%f p When the axial loading mechanism stops axial loading, the rotating mechanism in the dynamic scanning loading device drives the concrete specimen to rotate 360°. The CT scanning equipment performs CT scanning on each height section of the concrete specimen and obtains the cross-sectional scanning image of the concrete specimen.

[0023] Step 4-5, secondary loading: The axial loading mechanism in the dynamic scanning loading device applies a force load to the concrete specimen through the upper pressing plate at the lower limit of the load increase rate f1.

[0024] Step 4-6, secondary loading force detection: During the loading process, the pressure sensor detects the loading force F borne by the concrete specimen in real time.

[0025] Step 4-7, Second CT Scan: When F = 60% f p 、70%f p and 80%f p When the axial loading mechanism stops axial loading, the rotating mechanism in the dynamic scanning loading device drives the concrete specimen to rotate 360°. The CT scanning equipment performs CT scanning on each height section of the concrete specimen and obtains the cross-sectional scanning image of the concrete specimen.

[0026] The specific loading method in step 5 is:

[0027] Step 5-1, set the CT scan frequency: between 80% and 100% f p According to 2% f p A CT scan is performed at a frequency of

[0028] Step 5-2, primary loading: The axial loading mechanism in the dynamic scanning loading device applies a force load to the concrete specimen through the upper pressing plate at an upper limit of the displacement increase rate s2.

[0029] Step 5-3, primary loading force detection: During the loading process, the pressure sensor detects the loading force F borne by the concrete specimen in real time.

[0030] Step 5-4, a CT scan: when F = 82% f p , 84%f p 、86%f p 、88%f p and 90%f pWhen the axial loading mechanism stops axial loading, the rotating mechanism in the dynamic scanning loading device drives the concrete specimen to rotate 360°. The CT scanning equipment performs CT scanning on each height section of the concrete specimen and obtains the cross-sectional scanning image of the concrete specimen.

[0031] Step 5-5, secondary loading: the axial loading mechanism in the dynamic scanning device applies a force load to the concrete specimen through the upper pressing plate at a lower limit of the displacement increase rate s2.

[0032] Step 5-6, secondary loading force detection: During the loading process, the pressure sensor detects the loading force F borne by the concrete specimen in real time.

[0033] Step 5-7, Second CT Scan: When F = 92% f p , 94%f p , 96%f p 、98%f p and 100% f p When the axial loading mechanism stops axial loading, the rotating mechanism in the dynamic scanning loading device drives the concrete specimen to rotate 360°. The CT scanning equipment performs CT scanning on each height section of the concrete specimen and obtains the cross-sectional scanning image of the concrete specimen.

[0034] A dynamic scanning loading device comprises an axial loading mechanism, a rotating mechanism and a bearing frame.

[0035] The axial loading mechanism includes a guide assembly, a rotation drive assembly, a loading conduction assembly and a top plate.

[0036] The guide assembly comprises a guide arm and a guide plate, and is used for providing a path for the loading conduction assembly in a vertical direction and limiting its rotational freedom.

[0037] The first rotation drive component includes a loading motor, a loading large pulley and a loading synchronous belt; the loading synchronous belt is arranged between the loading motor and the loading large pulley, and is used to transmit the rotation drive of the loading motor to the loading large pulley.

[0038] The loading transmission component includes a ball screw, a sensor pressure plate and a sensor fixing seat; the top end of the ball screw is fixedly connected to the guide arm, and the ball screw is coaxially inserted in the loading large pulley to convert the rotational torque provided by the rotating drive component into a loading pressure in the vertical direction.

[0039] The sensor pressing plate is coaxially arranged below the ball screw, and a sensor fixing seat is fixedly arranged at the bottom end of the sensor pressing plate; the sensor pressing plate and the sensor fixing seat are fixedly arranged below the ball screw.

[0040] The rotating mechanism comprises a second rotating drive assembly, an upper pressing plate, a lower pressing plate and an intermediate guide plate.

[0041] The upper part of the middle guide plate is fixedly connected to the sensor fixing seat.

[0042] The second rotation drive assembly includes a rotating spindle, a rotating motor, an upper rotation drive assembly and a lower rotation drive assembly; the rotating motor synchronously drives the upper rotation drive assembly and the lower rotation drive assembly to rotate through the rotating spindle, and the upper rotation drive assembly is arranged above the middle guide plate, and the middle guide plate is used to drive the upper rotation drive assembly as a whole to move in the vertical direction.

[0043] The bearing frame comprises a lower platen and a plurality of columns, wherein the plurality of columns are vertically arranged above the lower platen in the circumferential direction; a top plate is fixedly arranged above the top ends of the columns, and a middle guide plate is horizontally slidably arranged on the plurality of columns and the rotating spindle.

[0044] The sensor pressure plate is a spoke-type pressure sensor, which is used to detect the loading force F borne by the concrete specimen in real time.

[0045] The guide structure also includes a guide bearing, which is arranged at the front end of the guide arm, and the guide arm is slidably connected with the guide plate through the guide bearing.

[0046] The first rotary drive component also includes a rotary sleeve and a limit bearing seat.

[0047] The rotating sleeve is coaxially arranged inside the loading pulley, and the rotating sleeve is rotationally connected with the roller screw through a nut.

[0048] The limiting bearing sleeve is coaxially arranged on the outside of the rotating sleeve and is fixedly connected to the top plate. The limiting bearing sleeve is used to limit the freedom of movement of the rotating sleeve in the vertical direction.

[0049] The upper rotary drive assembly comprises a bearing pressure seat, a guide key, an upper rotary driving wheel, a fixed pad, a pull plate, an upper synchronous belt, an upper rotary large pulley, a secondary transmission shaft 1 and an upper rotary bearing seat.

[0050] The guide key is vertically arranged on the rotating main shaft, and the rotating main shaft is slidingly connected with the upper rotating driving wheel through the guide key.

[0051] The bearing pressure seat is arranged above the upper rotating driving wheel, the fixed pad is arranged below the upper rotating driving wheel and is fitted with the middle guide plate, and the bearing pressure plate and the fixed pad are both slidably connected with the rotating main shaft.

[0052] The upper and lower ends of the pull plate are respectively fixedly connected with a bearing pressure seat and an intermediate guide plate, which are used to ensure that the position of the rotating driving wheel relative to the intermediate guide plate in the vertical direction remains stable.

[0053] The upper rotating driving wheel is connected with the upper rotating large pulley through the upper synchronous belt, the upper rotating large pulley is coaxially sleeved on the secondary transmission shaft one, and the upper rotating large pulley is fixedly connected with the secondary transmission shaft one through a flat key.

[0054] The upper rotary bearing end seat is sleeved on the secondary transmission shaft 1 and is used to limit the freedom of movement of the secondary transmission shaft 1 in the vertical direction.

[0055] The lower part of the secondary transmission shaft is fixedly connected with the upper pressing plate through a cylindrical pin.

[0056] The lower rotary drive assembly comprises a lower rotary driving wheel, a main shaft bearing, a bearing end cover, a fastening screw, a lower synchronous belt, a lower large pulley, a second secondary transmission shaft and a lower rotary bearing seat.

[0057] The main shaft bearing sliding sleeve is arranged on the rotating main shaft, the main shaft bearing is arranged inside the upper layer of the lower table through the bearing end cover, and the lower rotating driving wheel is arranged at the bottom end of the rotating main shaft through the fastening screw.

[0058] The lower rotating driving wheel is connected with the lower rotating large pulley through the lower synchronous belt, the lower rotating large pulley is coaxially sleeved on the secondary transmission shaft 2, and the lower rotating large pulley is fixedly connected with the secondary transmission shaft 2 through a flat key.

[0059] The upper portion of the secondary transmission shaft 2 is fixedly connected to the lower pressure plate through a cylindrical pin.

[0060] The loading large pulley, the upper rotating large pulley and the lower rotating large pulley are all planetary reducers, which are used to reduce the motor speed and increase the output torque at the same time.

[0061] The present invention has the following beneficial effects:

[0062] 1. Under the condition of a fixed CT scanning angle, the present invention can rotate the specimen 360 degrees at a certain rotation speed when the specimen is loaded to a certain level and the loading load is kept unchanged, thereby realizing a full-angle accurate scanning of the specimen and constructing a real dynamic three-dimensional damage model of the specimen.

[0063] 2. The present invention estimates the ultimate load according to the compressive strength grade of the concrete specimen, divides the loading mode into force loading and displacement loading based on the material deformation characteristics of the concrete specimen when under pressure, and performs segmented loading according to the loading rates in different modes to ensure that the internal crack development speed of the concrete specimen is stable when under pressure. The automatic control device scans and records the damage conditions inside the specimen under different states while loading step by step, avoiding the influence of errors caused by human judgment and manual operation.

[0064] 3. Under the condition of a fixed CT scanning angle, the present invention can rotate the specimen 360 degrees at a certain rotation speed while keeping the loading load unchanged after the specimen is loaded to different levels, and ensure stable rotation while carrying a large loading load, thereby realizing full-angle precise scanning of the specimen and constructing a real dynamic three-dimensional damage model of the specimen. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 It is a structural schematic diagram of a dynamic scanning loading device of the present invention.

[0066] Figure 2 A schematic diagram of the working posture of the CT scanner in the present invention is shown.

[0067] Figure 3 A cross-sectional view of the axial loading mechanism of the present invention is shown.

[0068] Figure 4 The schematic diagram of the structure of the axial loading mechanism in the present invention is shown.

[0069] Figure 5 A cross-sectional view of the rotating mechanism of the present invention is shown.

[0070] Figure 6 The schematic diagram of the structure of the rotating mechanism in the present invention is shown.

[0071] Among them are:

[0072] 10. Axial loading mechanism;

[0073] 11. Guide assembly; 111. Guide arm; 112. Guide plate; 113. Guide bearing;

[0074] 12. Rotation drive assembly 1; 121. Loading motor; 122. Loading large pulley; 123. Loading synchronous belt; 124. Limit bearing seat; 125. Rotating sleeve;

[0075] 13. Loading transmission assembly; 131. Ball screw; 132. Sensor pressure plate; 133. Sensor fixing seat;

[0076] 14. Top plate;

[0077] 20. Rotating mechanism;

[0078] 21. Rotating drive assembly 2; 211. Rotating spindle; 212. Rotating motor;

[0079] 213. Upper rotating drive assembly; 213a. Bearing pressure seat; 213b. Guide key; 213c. Upper rotating driving wheel; 213d. Fixed pad; 213e Pull plate; 213f. Upper synchronous belt; 213g. Upper rotating large pulley; 213h. Secondary transmission shaft 1; 213i. Upper rotating bearing seat;

[0080] 214. Lower rotating drive assembly; 214a. Lower rotating driving wheel; 214b. Main shaft bearing; 214c. Bearing end cover; 214d. Fastening screw; 214e. Lower synchronous belt; 214f. Lower rotating large pulley; 214g. Secondary transmission shaft 2; 214h. Lower rotating bearing seat;

[0081] 22. Upper pressing plate;

[0082] 23. Lower pressure plate;

[0083] 24. Middle guide plate;

[0084] 30. Loading frame;

[0085] 31. Step down;

[0086] 32. Pillar. DETAILED DESCRIPTION

[0087] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific preferred embodiments.

[0088] In the description of the present invention, it should be understood that the terms "left side", "right side", "upper part", "lower part" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. "First", "second" and the like do not indicate the importance of the components, and therefore cannot be understood as limiting the present invention. The specific dimensions used in this embodiment are only for illustrating the technical solution, and do not limit the scope of protection of the present invention.

[0089] As shown in the figure, a dynamic scanning loading device includes an axial loading mechanism 10 , a rotating mechanism 20 and a carrying frame 30 .

[0090] The axial loading mechanism is used to apply axial loading to the concrete specimen, and the axial loading mechanism includes a guide component 11, a rotation drive component 12, a loading conduction component 13 and a top plate 14.

[0091] The first rotary drive component includes a loading motor 121, a loading large pulley 122 and a loading synchronous belt 123. The rotary drive component provides a loading driving force for the loading device through the loading motor. In this embodiment, the loading motor is preferably a servo motor, which can measure the accurate displacement of the loading conduction component without the need for other external displacement sensors. The loading synchronous belt is arranged between the loading motor and the loading large pulley, and the loading synchronous belt is used to transmit the rotational drive of the loading motor to the loading large pulley. In this embodiment, the loading large pulley is preferably a planetary reducer, and the loading large pulley can reduce the rotational transmission ratio between the loading motor and the loading large pulley, and at the same time increase the output torque provided by the loading large pulley to the loading conduction component, so as to meet the larger loading range required by the loading device.

[0092] The loading transmission component includes a ball screw 131, a sensor pressure plate 132 and a sensor fixing seat 133. The ball screw is coaxially inserted on the loading large pulley to convert the rotational driving force provided by the rotational driving component 1 into an axial loading force in the vertical direction. The maximum loading range of this dynamic scanning loading device is set to 100KN, which can be achieved by using a ball screw loading, and the force control accuracy is 1 / 5000, which is more economical than the hydraulic servo loading method.

[0093] The sensor pressure plate is coaxially arranged below the ball screw. In this embodiment, the sensor pressure plate is preferably a spoke-type pressure sensor, which has high measurement accuracy and good lateral resistance, and can transmit the axial loading force provided by the ball screw while detecting the loading force F borne by the concrete specimen in real time. The sensor fixing seat is fixedly arranged below the sensor pressure plate to transmit the axial loading force to the rotating mechanism as a whole.

[0094] The first rotary drive assembly also includes a rotary sleeve 125 and a limit bearing seat 126. The rotary sleeve is coaxially arranged inside the loading pulley, and the rotary sleeve is located between the loading pulley and the ball screw. The rotary sleeve is rotatably connected to the roller screw through a nut. The limit bearing sleeve is coaxially arranged outside the rotary sleeve and fixedly connected to the top plate. The limit bearing sleeve is used to limit the freedom of movement of the rotary sleeve in the vertical direction.

[0095] The guide assembly includes a guide arm 111, a guide plate 112 and a guide bearing 113. The guide assembly is used to limit the rotational freedom of the load transmission assembly. The guide bearing is slidably arranged on the guide plate. The guide bearing is located at the front end of the guide arm. The guide arm is slidably connected to the guide plate through the guide bearing. The bottom end of the guide arm is fixedly connected to the top end of the ball screw. Since the rotation of the rotating sleeve tends to drive the ball screw to rotate, a circumferential torque will also be applied to the guide arm. At this time, several torques generated by a small force fixed at the far end of the guide arm can offset the torque of the ball screw acting on the guide arm, that is, the guide plate can offset the rotational torque of the guide arm in the horizontal plane, and at the same time can provide a moving path in the vertical direction for the ball screw and the guide arm.

[0096] The rotating mechanism is used to drive the compressed concrete specimen to rotate axially when the axial loading mechanism provides the axial loading load. The rotating mechanism includes a rotating drive component 21, an upper pressing plate 22, a lower pressing plate 23 and an intermediate guide plate 24.

[0097] The bearing frame includes a lower plate 31 and a plurality of columns 32, wherein the plurality of columns are vertically arranged above the lower plate; a top plate is fixedly arranged above the top of the columns, and an intermediate guide plate is horizontally slidably arranged on the plurality of columns and the rotating spindle. The upper part of the intermediate guide plate is fixedly connected to the sensor fixing seat, and can slide in the vertical direction under the pressure of the sensor fixing seat. In this embodiment, the loading device adopts a frame structure, the axial loading mechanism is placed on the upper part, and the sensor pressure plate is connected and arranged between the axial loading mechanism and the rotating mechanism, which has high measurement accuracy while ensuring excellent anti-lateral performance.

[0098] The second rotary drive assembly includes a rotary spindle 211, a rotary motor 212, an upper rotary drive assembly 213 and a lower rotary drive assembly 214. The rotary motor drives the upper rotary drive assembly and the lower rotary drive assembly to rotate synchronously through the rotary spindle. The upper rotary drive assembly is arranged above the middle guide plate, and the middle guide plate is used to drive the upper rotary drive assembly to move in the vertical direction as a whole.

[0099] The upper rotation drive assembly includes a bearing press seat 213a, a guide key 213b, an upper rotation driving wheel 213c, a fixed pad 213d, a pull plate 213e, an upper synchronous belt 213f, an upper rotation large pulley 213g, a secondary transmission shaft 1 213h and an upper rotation bearing seat 213i. The guide key is vertically arranged on the rotation main shaft, and the rotation main shaft is slidably connected with the upper rotation driving wheel through the guide key.

[0100] The bearing pressure seat is arranged above the upper rotating driving wheel, the fixed pad is arranged below the upper rotating driving wheel and is fitted with the middle guide plate, and the bearing pressure plate and the fixed pad are both slidably connected with the rotating main shaft.

[0101] The upper and lower ends of the pull plate are respectively fixedly connected with a bearing pressure seat and an intermediate guide plate, which are used to ensure that the position of the rotating driving wheel relative to the intermediate guide plate in the vertical direction remains stable.

[0102] The upper rotating driving wheel is connected to the upper rotating large pulley through the upper synchronous belt, the upper rotating large pulley is coaxially sleeved on the secondary transmission shaft 1, and the upper rotating large pulley is fixedly connected to the secondary transmission shaft 1 through a flat key. The upper rotating bearing end seat is sleeved on the secondary transmission shaft 1 to limit the freedom of movement of the secondary transmission shaft 1 in the vertical direction. The lower part of the secondary transmission shaft 1 is fixedly connected to the upper pressure plate through a cylindrical pin.

[0103] The lower rotating drive assembly includes a lower rotating driving wheel 214a, a main shaft bearing 214b, a bearing end cover 214c, a fastening screw 214d, a lower synchronous belt 214e, a lower rotating large pulley 214f, a secondary transmission shaft 214g and a lower rotating bearing seat 214h. The main shaft bearing sliding sleeve is arranged on the rotating main shaft, the main shaft bearing is arranged inside the upper layer of the lower platen through the bearing end cover, and the lower rotating driving wheel is arranged at the bottom end of the rotating main shaft through the fastening screw. The lower rotating driving wheel is connected to the lower rotating large pulley through the lower synchronous belt, the lower rotating large pulley is coaxially sleeved on the secondary transmission shaft 2, and the lower rotating large pulley is fixedly connected to the secondary transmission shaft 2 through a flat key. The upper part of the secondary transmission shaft 2 is fixedly connected to the lower pressure plate through a cylindrical pin.

[0104] In this embodiment, the upper rotating large pulley and the lower rotating large pulley are preferably planetary reducers. The rotating mechanism has the same principle as the axial loading mechanism. The rotating mechanism drives the rotating main shaft to rotate through the rotating motor. The rotating main shaft drives the upper rotating driving wheel and the lower rotating driving wheel to rotate synchronously. The rotating driving wheel drives the upper rotating large pulley and the lower rotating large pulley to passively rotate, thereby driving the secondary transmission shaft to rotate synchronously. Since the diameters of the upper rotating large pulley and the lower rotating large pulley are much larger than the secondary rotating shaft, the torque acting on the upper rotating pulley and the lower rotating pulley has been amplified many times when it is transmitted to the secondary rotating shaft. Therefore, the servo motor can easily realize the rotation of the test piece and the upper and lower pressure plates.

[0105] A method for implementing dynamic scanning loading of the present invention comprises the following steps:

[0106] Step 1: Determine the ultimate load: Estimate the ultimate load f of the concrete specimen according to the compressive strength grade of the concrete specimen material. p .

[0107] Step 2: Loading mode classification, which includes force loading mode and displacement loading mode; according to the ultimate load f determined in step 1 p , the loading mode is divided; assuming that the loading force borne by the concrete specimen is F, the specific division method is:

[0108] A. When 0≤F≤80%fp When the load is increased, the force loading mode is adopted, and the load increase rate range is f1~f2; among them, f1<f2, f1 is the lower limit of the load increase rate, and f2 is the upper limit of the load increase rate; f1 and f2 are determined according to the compressive strength grade of the concrete specimen material.

[0109] B. When F>80%f p When the displacement loading mode is adopted, the displacement increase rate range is s1~s2; among which, s1<s2, s1 is the lower limit of the displacement increase rate, and s2 is the upper limit of the displacement increase rate; s1 and s2 are determined according to the compressive strength grade of the concrete specimen material.

[0110] Step 3, specimen clamping: The concrete specimen is vertically mounted between the upper pressing plate and the lower pressing plate in the dynamic scanning loading device, and the concrete specimen can rotate synchronously with the upper pressing plate and the lower pressing plate.

[0111] Step 4: Load by force: The axial loading mechanism in the dynamic scanning loading device applies force load to the concrete specimen according to the set load increase rate until the loading force F borne by the concrete specimen reaches 80% f p During the loading process, the pressure sensor detects the loading force F borne by the concrete specimen in real time. When F reaches the set CT scanning point, the axial loading mechanism suspends the axial loading, and the rotating mechanism in the dynamic scanning loading device drives the concrete specimen to rotate 360°. The CT scanning equipment performs CT scanning on each height section of the concrete specimen and obtains the cross-sectional scanning image of the concrete specimen.

[0112] Step 4-1, set the CT scan frequency: 0~80%f p According to 10% f p A CT scan is performed at a frequency of

[0113] Step 4-2, primary loading: The axial loading mechanism in the dynamic scanning loading device applies a force load to the concrete specimen through the upper pressing plate at an upper limit of the load increase rate f2.

[0114] Step 4-3, primary loading force detection: During the loading process, the pressure sensor detects the loading force F borne by the concrete specimen in real time.

[0115] Step 4-4, a CT scan: when F = 10% f p 、20%f p and 30% f p When the axial loading mechanism stops axial loading, the rotating mechanism in the dynamic scanning loading device drives the concrete specimen to rotate 360°. The CT scanning equipment performs CT scanning on each height section of the concrete specimen and obtains the cross-sectional scanning image of the concrete specimen.

[0116] The specific loading rate in the force loading stage is determined according to the material properties and relevant specifications. At the same time, when the force is loaded, the loading force F reaches f p Before 30% of the load, the material is in the elastic deformation stage, no cracks appear inside the material, and the internal changes are relatively simple. The loading rate can be appropriately increased. In this stage, the loading rate can be loaded according to the upper limit value, that is, f2 is taken as the loading rate.

[0117] Step 4-5, secondary loading: The axial loading mechanism in the dynamic scanning loading device applies a force load to the concrete specimen through the upper pressing plate at the lower limit of the load increase rate f1.

[0118] Step 4-6, secondary loading force detection: During the loading process, the pressure sensor detects the loading force F borne by the concrete specimen in real time.

[0119] Step 4-7, Second CT Scan: When F = 40% f p 、50%f p 60%f p 、70%f p and 80%f p When the axial loading mechanism stops axial loading, the rotating mechanism in the dynamic scanning loading device drives the concrete specimen to rotate 360°. The CT scanning equipment performs CT scanning on each height section of the concrete specimen and obtains the cross-sectional scanning image of the concrete specimen.

[0120] The load F reaches f p When the loading rate is between 30% and 80%, cracks appear inside the material and the deformation enters the inelastic stage. At this stage, the loading rate needs to be appropriately reduced to slow down the crack development process and load according to the lower limit, that is, take f1 as the loading rate.

[0121] When the applied load reaches f p After 80% of the cracks in the material have been developed, the internal cracks enter the rapid development stage and the loading mode is converted to displacement loading.

[0122] Step 5, loading by displacement: the axial loading mechanism in the dynamic scanning loading device applies a force load to the concrete specimen according to the set displacement increase rate until the concrete specimen is destroyed; during the loading process, the pressure sensor detects the loading force F borne by the concrete specimen in real time. When F reaches the set CT scanning point, the axial loading mechanism suspends the axial loading, and the rotating mechanism in the dynamic scanning loading device drives the concrete specimen to rotate 360°. The CT scanning equipment performs CT scanning on each height section of the concrete specimen and obtains a cross-sectional scanning image of the concrete specimen.

[0123] Step 5-1, set the CT scan frequency: between 80% and 100% f p According to 2% f p A CT scan is performed at a frequency of

[0124] Step 5-2, primary loading: The axial loading mechanism in the dynamic scanning loading device applies a force load to the concrete specimen through the upper pressing plate at an upper limit of the displacement increase rate s2.

[0125] Step 5-3, primary loading force detection: During the loading process, the pressure sensor detects the loading force F borne by the concrete specimen in real time.

[0126] Step 5-4, a CT scan: when F = 82% f p , 84%f p 、86%f p 、88%f p and 90%f p When the axial loading mechanism stops axial loading, the rotating mechanism in the dynamic scanning loading device drives the concrete specimen to rotate 360°. The CT scanning equipment performs CT scanning on each height section of the concrete specimen and obtains the cross-sectional scanning image of the concrete specimen.

[0127] When loading is performed according to displacement, the force is f p The 80% to 90% stage and f p 90% to the ultimate load f p Compared with this stage, the crack development speed is relatively low. If the displacement loading rate specified in the relevant specifications is generally s1~s2 per second, the force at f p In the stage of 80% to 90% of the loading rate, the upper limit s2 is taken as the loading rate. p 90% to the ultimate load f p In this stage, the upper limit s1 is taken as the loading rate.

[0128] Step 5-5, secondary loading: the axial loading mechanism in the dynamic scanning device applies a force load to the concrete specimen through the upper pressing plate at a lower limit of the displacement increase rate s1;

[0129] Step 5-6, secondary loading force detection: During the loading process, the pressure sensor detects the loading force F borne by the concrete specimen in real time;

[0130] Step 5-7, Second CT Scan: When F = 92% f p , 94%f p , 96%f p 、98%f p and 100% f pWhen the axial loading mechanism stops axial loading, the rotating mechanism in the dynamic scanning loading device drives the concrete specimen to rotate 360°. The CT scanning equipment performs CT scanning on each height section of the concrete specimen and obtains the cross-sectional scanning image of the concrete specimen.

[0131] Step 6: Observe and analyze the cross-sectional scanning images of the concrete specimens in chronological order to obtain the damage variation pattern of the concrete specimens over time.

[0132] The dynamic scanning loading device of the present invention can automatically control loading, pausing, maintaining load rotation, starting a CT scanner to scan a specimen, and continuing loading after relevant parameters are input before the test. The test personnel can also manually load and control rotation through corresponding buttons on the control panel according to the actual situation during the test.

[0133] Under the condition of fixed CT scanning angle, after the specimen is loaded to a certain level, the applied load is kept unchanged, and the specimen is rotated at a certain rotation speed. The rotation speed of the rotation system can be adjusted as needed according to the deformation of the specimen, the scanning speed of the CT device, and the degree of reconstruction of the three-dimensional deformation state of the specimen. If the scanning speed of the CT is slow or the reconstruction requirements for the internal changes of the specimen during the pressure process are high, the rotation speed of the rotation system can be reduced accordingly, and the slowest can reach 15min / r. If the scanning speed of the CT is fast or the reconstruction requirements for the internal changes of the specimen during the pressure process are relatively low, the rotation speed of the rotation system can be increased accordingly, and the fastest can reach 1min / r.

[0134] The preferred embodiments of the present invention are described in detail above; however, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various equivalent transformations can be made to the technical solutions of the present invention, and these equivalent transformations all belong to the protection scope of the present invention.

Claims

1. A method for implementing dynamic scanning loading, characterized in that: The following steps are included: Step 1: Determine the ultimate load: Estimate the ultimate load f of the concrete specimen according to the compressive strength grade of the concrete specimen material. p ; Step 2, loading mode division, loading mode includes force loading mode and displacement loading mode; According to the limit load f determined in step 1 p , the loading mode is divided; if the loading force borne by the concrete specimen is F, the specific division method is: A, when 0≤F≤80%f p When the load is loaded by force, the load increase rate range is f1~f2; where f1<f2, f1 is the lower limit of the load increase rate, and f2 is the upper limit of the load increase rate; f1 and f2 are determined according to the compressive strength grade of the concrete specimen material; B. When F>80%f p When the displacement loading mode is adopted, the displacement increase rate range is s1~s2; wherein, s1<s2, s1 is the lower limit of the displacement increase rate, and s2 is the upper limit of the displacement increase rate; s1 and s2 are determined according to the compressive strength grade of the concrete specimen material; Step 3, specimen clamping: the concrete specimen is vertically mounted between the upper pressing plate and the lower pressing plate in the dynamic scanning loading device, and the concrete specimen can rotate synchronously with the upper pressing plate and the lower pressing plate; Step 4, force loading: the axial loading mechanism in the dynamic scanning loading device applies a force load to the concrete specimen according to the set load increase rate until the loading force F borne by the concrete specimen reaches 80%f p ; During the loading process, the pressure sensor detects the loading force F borne by the concrete specimen in real time. When F reaches the set CT scanning point, the axial loading mechanism suspends the axial loading, and the rotating mechanism in the dynamic scanning loading device drives the concrete specimen to rotate 360°. The CT scanning equipment performs CT scanning on each height section of the concrete specimen and obtains the cross-sectional scanning image of the concrete specimen; Step 5, loading by displacement: The axial loading mechanism in the dynamic scanning loading device applies force load to the concrete specimen according to the set displacement increase rate until the concrete specimen is destroyed; During the loading process, the pressure sensor The sensor detects the loading force F borne by the concrete specimen in real time. When F reaches the set CT scanning point, the axial loading mechanism suspends the axial loading, and the rotating mechanism in the dynamic scanning loading device drives the concrete specimen to rotate 360°. The CT scanning equipment performs CT scanning on each height section of the concrete specimen and obtains the cross-sectional scanning image of the concrete specimen; Step 6, observe and analyze the cross-sectional scanning image of the concrete specimen in chronological order, so as to obtain the destruction change law of the concrete specimen over time; The specific loading method in step 4 is: Step 4-1, set the CT scanning frequency: between 0 and 80% f p According to 10% f p frequency, perform a CT scan once; Step 4-2, one loading: the axial loading mechanism in the dynamic scanning loading device applies a force load to the concrete specimen through the upper pressure plate at the upper limit of the load increase rate f2; Step 4-3, one loading force detection: during the loading process, the pressure sensor detects the loading force F borne by the concrete specimen in real time; Step 4-4, one CT scan: when F = 10% f p 、20%f p 、30%f p 、40%f p and 50%f p When the axial loading mechanism stops axial loading, the rotating mechanism in the dynamic scanning loading device drives the concrete specimen to rotate 360°, and the CT scanning equipment performs CT scanning on each height section of the concrete specimen and obtains the cross-sectional scanning image of the concrete specimen; Step 4-5, secondary loading: the axial loading mechanism in the dynamic scanning loading device applies a force load to the concrete specimen through the upper pressure plate at the lower limit of the load increase rate f1; Step 4-6, secondary loading force detection: during the loading process, the pressure sensor detects the loading force F borne by the concrete specimen in real time; Step 4-7, secondary CT scanning: when F=60%f p 、70%f p and 80%f p When the axial loading mechanism stops axial loading, the rotating mechanism in the dynamic scanning loading device drives the concrete specimen to rotate 360°, and the CT scanning equipment performs CT scanning on each height section of the concrete specimen and obtains the cross-sectional scanning image of the concrete specimen; the specific loading method in step 5 is: step 5-1, setting the CT scanning frequency: between 80% and 100% f p According to 2% f p frequency, perform a CT scan once; Step 5-2, one loading: the axial loading mechanism in the dynamic scanning loading device applies a force load to the concrete specimen through the upper pressure plate at the upper limit of the displacement increase rate s2; Step 5-3, one loading force detection: during the loading process, the pressure sensor detects the loading force F borne by the concrete specimen in real time; Step 5-4, one CT scan: when F = 82% f p , 84%f p 、86%f p 、88%f p and 90%f p When the axial loading mechanism stops axial loading, the rotating mechanism in the dynamic scanning loading device drives the concrete specimen to rotate 360°, and the CT scanning equipment performs CT scanning on each height section of the concrete specimen and obtains the cross-sectional scanning image of the concrete specimen; Step 5-5, secondary loading: the axial loading mechanism in the dynamic scanning device applies a force load to the concrete specimen through the upper pressure plate at the lower limit of the displacement increase rate s2; Step 5-6, secondary loading force detection: during the loading process, the pressure sensor detects the loading force F borne by the concrete specimen in real time; Step 5-7, secondary CT scanning: when F=92%f p , 94%f p , 96%f p 、98%f p and 100% f p When the axial loading mechanism stops axial loading, the rotating mechanism in the dynamic scanning loading device drives the concrete specimen to rotate 360°. The CT scanning equipment performs CT scanning on each height section of the concrete specimen and obtains the cross-sectional scanning image of the concrete specimen.

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