CN113252515A - Test method of wet inter-particle liquid bridge tensile-compression mechanical property tester - Google Patents
Test method of wet inter-particle liquid bridge tensile-compression mechanical property tester Download PDFInfo
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Abstract
The invention discloses a test method of a wet inter-particle liquid bridge tensile-compression mechanical property tester, which comprises the initial setting of the tester, a liquid bridge test for controlling the volume of a liquid bridge, a liquid bridge test for controlling the suction force of a matrix, and the setting of the types of the liquid bridge tests, namely the liquid bridge tensile test, the liquid bridge compression test and the liquid bridge tensile-compression cycle test, through a control system. The method of the invention can not only carry out the stretching and compression of the liquid bridge and the cyclic test of the liquid bridge in a set range under the condition of automatically and accurately controlling the volume of the liquid bridge or the absorption of the matrix, but also monitor the change rule of the key geometric parameters of the meniscus in the whole process by combining an industrial electron microscope and a corresponding image processing method.
Description
Technical Field
The invention relates to an electromechanical device of geotechnical engineering, in particular to a method for determining an interaction rule of wet particles and water in unsaturated soil, and particularly relates to a test method of a wet particle liquid bridge tensile-compression mechanical property tester.
Background
Research on hydraulic and mechanical properties of unsaturated soil is the foundation and key for geotechnical structure design and performance evaluation. The existing research does not fully reveal the physical mechanism, and the macro test under different test conditions reflects unclear action mechanism, so that the design and construction optimization of the geotechnical structure is limited, and further investment waste or potential safety hazard is caused. Therefore, unsaturated soil is taken as a spherical wet particle aggregate, the moisture state among wet particles is represented by a liquid bridge, the understanding of the mesomechanics mechanism of the unsaturated soil can be improved by researching the interaction mechanism of the wet particles and water, the intrinsic requirement of the development of the mechanics theory of the unsaturated soil is met, and the external requirement of the construction of geotechnical structures is met. The test equipment for completely, stably and reliably acquiring the mechanical characteristic parameters of the liquid bridge between the wet particles is researched and developed, and necessary data support can be provided for characterization of the macroscopic hydraulic power and the mechanical characteristics of unsaturated soil. So far, scholars mostly adopt a Young-Laplace equation numerical solution and a semi-analytic-semi-numerical method to research the geometric properties and the stress state of a liquid bridge between wet particles, the two methods for indirectly simulating the mechanical properties of the liquid bridge have limited applicability, and the geometric properties-mechanical property change rule and the key parameter determination method of the liquid bridge are also important contents for the description of the microstructure mechanical properties of unsaturated soil. Therefore, it is important to directly measure the surface (meniscus) shape parameters of the liquid bridge and the evolution law of the capillary force by adopting a test method. The existing liquid bridge mechanical property testing technology basically takes liquid bridge tension as a testing condition, but in geotechnical engineering practice (such as sudden drop and sudden rise of water level of an earth dam), most of the interaction between wet particles in unsaturated soil and water shows a hysteresis phenomenon, which is mainly controlled by the hysteresis mechanical property of the liquid bridge between the wet particles under the tension-compression condition on a microscopic scale, but the testing technology is rarely researched and developed.
The existing wet inter-particle liquid bridge mechanical property testing equipment is mainly a wet inter-particle liquid bridge tensile mechanical property instrument for controlling the volume of a liquid bridge.
For example, the title published by Springer by Lambert of Belgian university for purposes in micro assembly, modeling, Simulation, Experiments, and Case Study, Chapter 17 (4. 2007) "Test bed and characterization" discloses a platform for testing the mechanical properties of a liquid bridge between wet particles, wherein the instrument can fix the wet particles on a section of cantilever beam, make the cantilever beam to be flexible by stretching the liquid bridge between the wet particles, measure the corresponding Capillary force by combining the rigidity of the beam, and monitor the change process of the liquid bridge shape by the imaging technology of an industrial electron microscope (CCD). However, the test platform cannot control and collect capillary force data in the liquid bridge compression process, and the liquid bridge formed by manually dropping liquid by using a pipette among wet particles has poor symmetry, so that the initial conditions of a liquid bridge tensile test are easily influenced.
For example, the "Experimental Verification of Capillary Force and Water Retention between the two devices" published by Lu et al in the Journal of Engineering Mechanics discloses a Capillary Force testing technique based on a glass fiber cantilever and a rigid Capillary, which is equipped with a high-precision controller, an optical microscope, and a digital video microscope, and the Capillary Force is measured by the deflection of the glass fiber cantilever when the inter-particle liquid bridge is stretched, and the geometry analysis is performed by image processing. However, this technique cannot record the capillary force in real time, and cannot realize the compression of the liquid bridge and the liquid bridge tension-compression cycle test.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a test method of a wet inter-particle liquid bridge tensile-compression mechanical property tester, which can be used for carrying out liquid bridge tensile and compression and a circulation test within a set range under the condition of automatically and accurately controlling the volume of a liquid bridge or the absorption force of a matrix and monitoring the change rule of key geometric parameters of a meniscus in the whole process by combining an industrial electron microscope and a corresponding image processing method.
In order to achieve the purpose, the invention adopts the following technical scheme:
a test method of a wet inter-particle liquid bridge tensile-compression mechanical property tester comprises the following steps:
1) opening the control system and the data acquisition and image processing system, returning the numerical value of the high-precision balance to zero, and adjusting the video image displayed by the data acquisition and image processing system; respectively installing upper particles and lower particles on an upper support and a lower support, wherein the upper particles are provided with openings, placing the lower support on a high-precision balance, and connecting the upper support with a position adjusting device;
starting a first stepping motor, wherein the first stepping motor drives a first lead screw to rotate, and the first lead screw rotates to drive a first nut to rotate, so that a first pull rod fixed on the first lead screw is driven to move up and down, and the distance between particles is adjusted; the first knob is rotated to drive the first gear to rotate, and the first gear rotates to drive the first racks which are meshed with each other to move forwards and backwards in the groove; the second knob is rotated to drive the second gear to rotate, and the second gear rotates to drive the mutually meshed second racks to move left and right in the groove, so that the upper support fixed on the second racks is driven to adjust the front, back and left and right positions; in the process of adjusting the distance between the particles and the front, back, left and right positions of the upper support, real-time monitoring is carried out according to a data acquisition and image processing system;
2) the following two tests were performed:
A. the liquid bridge test for controlling the volume of the liquid bridge comprises the steps of injecting liquid into a liquid bridge volume controller, controlling the liquid bridge volume controller to inject liquid into a pipeline through a control system, exhausting gas through an exhaust valve of the liquid bridge volume controller, closing the exhaust valve of the liquid bridge volume controller, injecting liquid into an upper support through a pipeline communicated with the liquid bridge volume controller, and exhausting the gas in an upper particle hole and an upper support; setting the liquid volume through a control system, and controlling a liquid bridge volume controller to inject liquid to the upper particles;
B. controlling the liquid bridge test of the substrate suction, pouring liquid into the beaker, opening a corresponding stop valve after the liquid fully flows into the pipeline, so that the liquid flows into a measuring cylinder, wherein the measuring cylinder is used for reading the liquid level in the beaker; then opening a stop valve in a pipeline communicated with the upper support, opening an exhaust valve of the upper support after liquid flows into the upper support, exhausting gas in the upper support, preventing bubbles from being generated in the test, and then closing the exhaust valve; the height of the beaker is adjusted by a lifting platform, liquid flows out from the upper particles to form a liquid bridge, and the substrate suction is controlled according to the height difference between the liquid level of the beaker and the central section of the formed liquid bridge;
3) setting the type of the liquid bridge test by the control system:
A. in the liquid bridge tensile test, the control system controls the tension and compression device to move the upper support downwards to enable the upper particles and the lower particles to approach each other to form a liquid bridge and approach to a state of not contacting each other, the tension rate is set, the data acquisition and image processing system records real-time data of the high-precision balance and displacement data and video images of the whole process of liquid bridge tension, the control system starts to stretch until the liquid bridge breaks, and then the data acquisition and image processing system processes the data and the images;
B. the method comprises the following steps of performing a liquid bridge tensile test, obtaining a liquid bridge tensile initial position and an end point position to be fractured, respectively setting the liquid bridge tensile initial position and the end point position to be fractured as the end point position and the initial position of the liquid bridge compressive test through a control system, setting a tensile rate, recording real-time data of a high-precision balance and displacement data and video images of the whole liquid bridge compression process through a data acquisition and image processing system, starting the test through the control system, moving an upper particle from top to bottom to compress a liquid bridge, enabling the particles to approach each other, and processing the data and the images through the data acquisition and image processing system;
C. a liquid bridge stretching-compressing cycle test, wherein the liquid bridge stretching test step is firstly carried out to obtain the stretching initial position of the liquid bridge and the terminal position of the liquid bridge to be fractured, the initial position of the liquid bridge stretching and the final position of the liquid bridge to be broken are respectively set as the initial position and the final position of the liquid bridge compression test by a control system, the upper support is controlled by the control system to move downwards by the tension and compression device, so that the upper particles and the lower particles are close to each other to form a liquid bridge, and approaching to the state of not contacting, setting the stretching rate and cycle times, recording the real-time data of the high-precision balance and the displacement data and video images of the whole process of stretching-compressing the liquid bridge by the data acquisition and image processing system, and starting the test by a control system, enabling the upper particles to move circularly, alternately performing stretching-compressing cycles, and processing data and images by a data acquisition and image processing system.
Data and image processing includes calculation of liquid bridge capillary force and image processing:
the calculation method of the liquid bridge capillary force comprises the following steps: recording readings of lower pedestal and lower particle placement on high precision balance prior to liquid bridge formation
Recording the reading of the high-precision balance during the test of the stretching, compressing and stretching-compressing cycle of the liquid bridge after the liquid bridge is formed
Capillary force
Is formula (1):
the image processing method of the liquid bridge comprises the following steps: firstly, acquiring high-definition pictures of different positions of particles in a liquid bridge fracture process by using a first CCD and a second CCD, guiding the high-definition pictures into Image J software for binarization processing, improving the definition of the pictures until the liquid bridge and the particles are clear in outline and easy to distinguish, so that the particle outline and the liquid bridge outline can be conveniently drawn by using AutoCAD software, positioning the particles to determine the circle center, measuring the radius of the particles in the pictures, and determining a picture scale by combining the actual radius of the particles; after the liquid bridge contour is determined, approximating the contour of the liquid bridge by using a circle by using a least square method, selecting an optimal circle through goodness of fit, and calculating the curvature radius of the meniscus by matching with a picture scale; and (3) approximating the liquid bridge contour line by using a circle by using a least square method, connecting the centers of the left and right optimal circles, and matching with a picture scale to obtain the narrowest neck section of the liquid bridge, so that the narrowest neck radius can be calculated.
The principle of upper and lower particle and liquid selection:
selecting sodium-calcium glass polishing round balls with soil or sand as particles, wherein the diameter range is 2-5 mm; when a small-volume liquid bridge test is carried out, in order to simulate the actual condition of the project, water is selected by a liquid bridge for testing; when a large-volume liquid bridge test is carried out, the liquid bridge selects glycerol for testing, and the specific indexes of the glycerol are as follows: at 25 ℃, the viscosity is 800 mPa.s, the surface tension is 61.9mN/m, and the relative density is 1.255.
Compared with the existing wet inter-particle liquid bridge mechanical property test method, the method has the beneficial effects that:
1. the liquid bridge test under the condition of controlling the volume of the liquid bridge and the liquid bridge test under the condition of controlling the suction force of the matrix can be respectively realized through the switch of the stop valve; when a liquid bridge test is carried out under the condition of controlling the volume of the liquid bridge, the volume of the liquid bridge is set through a control system, and a liquid bridge volume controller automatically injects quantitative liquid into an upper support; when the liquid bridge test is carried out under the condition of controlling the substrate suction force, the liquid level difference is controlled by the substrate suction force control device, so that the control of the substrate suction force is realized.
2. The control system can control the tension and compression device, set the type, the tension rate, the cycle times, the initial position and the final position of the tension and compression of the liquid bridge, and realize the tension test and the compression test of the liquid bridge and the tension-compression cycle test of the liquid bridge in a given range.
3. The position of the upper support can be adjusted through the position adjusting device and the data acquisition and image processing system, so that a liquid bridge with good symmetry and without influencing the initial test condition is formed. Meanwhile, the data acquisition and image processing system is also used for acquiring mechanical parameter data and video images and processing the data and the video images by software.
Drawings
FIG. 1 is a flow chart of an image processing method;
FIG. 2 is a schematic diagram of the system of the present invention;
FIG. 3 is an overview of the system of the present invention;
FIG. 4 is a block diagram of a liquid bridge volume controller;
FIG. 5 is a cross-sectional view taken along line A-A of FIG. 4;
FIG. 6 is a cross-sectional view taken along line B-B of FIG. 4;
FIG. 7 is a view showing the structure of the drawing and pressing device;
FIG. 8 is a front view of the position adjustment device;
FIG. 9 is a top view of the position adjustment device configuration;
FIG. 10 is a front view of the upper bracket;
FIG. 11 is a left side view of the upper mount;
FIG. 12 is a top plan view of the upper mount;
FIG. 13 is a front view of the lower bracket;
FIG. 14 is a top view of the lower support;
wherein, C, an actuating system, D, a matrix suction control device, E, a data acquisition and image processing system, 1, a control system, 2, a liquid bridge volume controller, 3, a first stop valve, 4, a tension and compression device, 5, a position adjusting device, 6, a first end through joint, 7, a third stop valve, 8, a first three-way pipe joint, 9, a fifth stop valve, 10, a second end through joint, 11, a beaker, 12, a measuring cylinder, 13, a second stop valve, 14, a lower support, 15, an upper support, 16, a computer, 17, a third end through joint, 18, a second three-way pipe joint, 19, a fourth end through joint, 20, a first CCD, 21, a high-precision balance, 22, a second CCD, 23, a fifth end through joint, 24, a fourth stop valve, 25, a sixth stop valve, 26, a lifting platform, 27, a fifth end through joint, 28, 29, a third pressure ring, 30, T-shaped plunger, 31, a column barrel, 32, a second press ring, 33, a collar, 34, a first guide key, 35, a first guide cylinder, 36, a first press ring, 37, a first bearing box, 38, a first stepping motor, 39, a second O-shaped sealing ring, 40, a second key ring, 41, a first O-shaped sealing ring, 42, a first screw nut, 43, a first lead screw, 44, a first key ring, 45, a second stepping motor, 46, a second bearing box, 47, a third key ring, 48, a second guide cylinder, 49, a second lead screw, 50, a second screw nut, 51, a pull rod, 52, a sealing ring, 53, a fifth press ring, 54, a fourth press ring, 55, a second guide key, 56, a first rack, 57, a first gear, 58, a first knob, 59, a second knob, 60, a second gear, 61 and a second rack.
Detailed Description
The invention is further illustrated with reference to the following figures and examples.
The structures, proportions, sizes, and other dimensions shown in the drawings and described in the specification are for understanding and reading the present disclosure, and are not intended to limit the scope of the present disclosure, which is defined in the claims, and are not essential to the art, and any structural modifications, changes in proportions, or adjustments in size, which do not affect the efficacy and attainment of the same are intended to fall within the scope of the present disclosure. In addition, the terms "upper", "lower", "left", "right", "middle" and "one" used in the present specification are for clarity of description, and are not intended to limit the scope of the present invention, and the relative relationship between the terms and the terms is not to be construed as a scope of the present invention.
As shown in fig. 1-14, the testing method of the wet inter-particle liquid bridge tensile-compression mechanical property tester comprises the following steps:
1) opening the control system 1 and the data acquisition and image processing system E, resetting the numerical value of the high-precision balance 21 to zero, and adjusting a video image displayed by the data acquisition and image processing system E; respectively installing upper particles and lower particles on an upper support 15 and a lower support 14, wherein the upper particles are provided with openings, placing the lower support 14 on a high-precision balance 21, and connecting the upper support 15 with a position adjusting device 5;
starting the second stepping motor 45, driving the second lead screw 49 to rotate by the second stepping motor 45, driving the second nut 50 to rotate by the second lead screw 49, thereby driving the pull rod 51 fixed on the second lead screw to move up and down and adjusting the distance between particles; the first knob 58 is rotated to drive the first gear 57 to rotate, and the first gear 57 rotates to drive the first racks 56 which are meshed with each other to move forwards and backwards in the groove; the second knob 59 is rotated to drive the second gear 60 to rotate, the second gear 60 rotates to drive the second racks 61 which are meshed with each other to move left and right in the groove, so that the upper support 15 fixed on the second racks 61 is driven to adjust the front, back and left and right positions, and real-time monitoring is carried out according to the data acquisition and image processing system E in the process of adjusting the distance of particles and the front, back and left and right positions of the upper support 15.
2) The following two tests were performed:
A. the liquid bridge test for controlling the volume of the liquid bridge comprises the steps of firstly injecting liquid into a liquid bridge volume controller 2, opening a first stop valve 3, closing second to fourth stop valves 13, 7 and 24, controlling the liquid bridge volume controller 2 to inject liquid into a pipeline through a control system 1, exhausting gas in the liquid bridge volume controller 2 through the first stop valve 3, and then closing the first stop valve 3; the second stop valve 13 and the third stop valve 7 are opened to inject liquid into the upper support 15 and discharge gas to the upper particle hole and the third stop valve 7, and then the third stop valve 7 is closed; the liquid volume is set through the control system 1, and the liquid bridge volume controller 2 is controlled to inject liquid to the upper particles;
B. a liquid bridge test for controlling the suction force of the substrate is carried out, wherein the second to sixth stop valves 13, 7, 24, 9 and 25 are closed, liquid is poured into the beaker 11, the fifth stop valve 9 and the sixth stop valve 25 are opened after the liquid fully flows into the pipeline, the liquid flows into the measuring cylinder 12, and the measuring cylinder 12 is used for reading the liquid level in the beaker; the fourth stop valve 24 is opened, the third stop valve 7 is opened after the liquid flows into the upper support 15, the gas in the upper support 15 is discharged, bubbles are prevented from being generated in the test, and then the third stop valve 7 is closed; the height of the beaker 11 is adjusted by the lifting platform 26, liquid flows out from the upper particles to form a liquid bridge, and the substrate suction is controlled according to the height difference between the liquid level of the beaker and the central section of the formed liquid bridge;
3) setting the type of the liquid bridge test by the control system:
A. in the liquid bridge tensile test, the control system 1 controls the tension and compression device 4 to move the upper support 15 downwards to enable the upper particles and the lower particles to approach each other to form a liquid bridge and approach to a state of not contacting each other, the tension rate is set, the data acquisition and image processing system E records real-time data of a high-precision balance and displacement data and video images of the whole liquid bridge tension process, the control system 1 starts to stretch until the liquid bridge breaks, and then the data acquisition and image processing system E stops, and software programs of the data acquisition and image processing system E process the data and the images;
B. the method comprises the following steps of liquid bridge compression test, wherein a liquid bridge tensile test step is firstly carried out to obtain a liquid bridge tensile initial position and an end point position to be fractured, the liquid bridge tensile initial position and the end point position to be fractured are respectively set as the end point position and the initial position of the liquid bridge compression test through a control system 1, the tensile rate is set, a data acquisition and image processing system E records real-time data of a high-precision balance 21 and displacement data and video images of the whole liquid bridge compression process, the test is started through the control system 1, upper particles move from top to bottom to compress a liquid bridge, the particles are close to each other, and the data and the images are processed through a software program of the data acquisition and image processing system E;
C. a liquid bridge stretching-compressing cycle test, wherein the liquid bridge stretching test step is firstly carried out to obtain the stretching initial position of the liquid bridge and the terminal position of the liquid bridge to be fractured, the initial position of the liquid bridge stretching and the final position of the liquid bridge to be fractured are respectively set as the initial position and the final position of the liquid bridge compression test by the control system 1, the control system 1 controls the tension-compression device 4 to move the upper support 15 downwards, so that the upper particles and the lower particles are close to each other to form a liquid bridge, and approaching to a state of not contacting, setting a stretching rate and cycle times, recording real-time data of the high-precision balance 21 and displacement data and video images of the whole process of stretching-compressing the liquid bridge by a data acquisition and image processing system E, the test is started by controlling the system 1, the upper particles are moved circularly, the stretching-compressing cycles are alternately carried out, the data and images are processed by software programs of the data acquisition and image processing system E.
The data and image processing includes calculation of liquid bridge capillary force and image processing of liquid bridge capillary force.
The calculation method of the liquid bridge capillary force comprises the following steps: the reading of the placement of the lower support 14 and the lower particle on the high precision balance 21 is recorded before the liquid bridge is formed
Recording the indication of the high precision balance 21 during the test cycle of stretching, compressing, stretching-compressing after the liquid bridge is formedNumber of
Capillary force
Is formula (1):
the processing method of the liquid bridge image (fig. 1 image processing method flow chart) is as follows: firstly, acquiring high-definition pictures of different positions of particles in a liquid bridge fracture process by using a first CCD and a second CCD, guiding the high-definition pictures into Image J software for binarization processing, improving the definition of the pictures until the liquid bridge and the particles are clear in outline and easy to distinguish, so that the particle outline and the liquid bridge outline can be conveniently drawn by using AutoCAD software, positioning the particles to determine the circle center, measuring the radius of the particles in the pictures, and determining a picture scale by combining the actual radius of the particles; after the liquid bridge contour is determined, approximating the contour of the liquid bridge by using a circle by using a least square method, selecting an optimal circle through goodness of fit, and calculating the curvature radius of the meniscus by matching with a picture scale; and (3) approximating the liquid bridge contour line by using a circle by using a least square method, connecting the centers of the left and right optimal circles, and matching with a picture scale to obtain the narrowest neck section of the liquid bridge, so that the narrowest neck radius can be calculated.
Wherein the principle of selecting the upper particles, the lower particles and the liquid is as follows: the particles are sodium calcium glass polishing round balls with soil or sand as physical properties, the diameter range is 2-5 mm, if the particle size is too large, the liquid bridge is greatly influenced by gravity, and if the particle size is too small, the liquid dropping operation is difficult; when a small-volume liquid bridge test is carried out, in order to simulate the actual condition of the project, water is selected by a liquid bridge for testing; when carrying out the bulky liquid bridge experiment, because the less difficult shaping of liquid bridge and easy evaporation of making of water surface tension, the liquid bridge is selected the glycerine and is tested, and the concrete index of glycerine is: the viscosity (25 ℃) is 800 mPas, the surface tension is 61.9mN/m, and the relative density is 1.255.
As shown in fig. 1 and 2, the wet inter-particle liquid bridge tensile-compression mechanical property tester includes an actuating system C capable of axially stretching and compressing, a liquid bridge volume controller 2, a matrix suction control device E, a control system 1 and a data acquisition and image processing system D. The control system 1 respectively controls the actuating system C and the liquid bridge volume controller 2, the liquid bridge volume controller 2 is connected with the actuating system C, the actuating system C is connected with the matrix suction control device E, and the data acquisition and image processing system D acquires data generated by the actuating system C;
the actuating system C comprises a tension and compression device 4, a position adjusting device 5, an upper support 15 and a lower support 14 which are arranged in sequence from top to bottom. The liquid bridge volume controller 2 comprises a cylinder body with an opening at the front end, an end socket 28 with a hole at the center is arranged at the opening end of the cylinder body, and a power mechanism is arranged at the rear end of the cylinder body and connected with a T-shaped plunger mechanism in the shell and can drive the T-shaped plunger mechanism to reciprocate; a sealing ring is embedded in the inner side of the cylinder body, so that the cylinder body, the end socket and the T-shaped plunger form an independent closed space, and liquid in the independent closed space can be injected out when the T-shaped plunger moves upwards;
the position adjusting device 5 comprises an upper group of gear rack mechanisms and a lower group of gear rack mechanisms which are fixedly connected, and racks of the two groups of gear rack mechanisms are arranged vertically; the rack of the upper gear rack mechanism is fixedly connected with the bottom of the tension and compression device 4, the rack of the lower gear rack mechanism is fixedly connected with the upper support 15, and the upper support and the lower support are correspondingly arranged in a matching manner.
As shown in fig. 2 and 3, the matrix suction control device E, the liquid bridge volume controller 2 and the actuating system C are the core parts of the instrument and comprise a tension and compression device 4, a position adjusting device 5, an upper support 15 and a lower support 14; the lower part of the tension and compression device 4 is connected with a position adjusting device 5, the lower part of the position adjusting device 5 is connected with an upper support 15, the left opening of the upper support 15 is connected with a first port of a second three-way pipe joint 18 through a fourth through joint 19 and a second stop valve 13, a second port of the second three-way pipe joint 18 is connected with a liquid bridge volume controller 2 through a third through joint 17, a third port is connected with a first stop valve 3, the right opening of the upper support 15 is connected with a first port of a first three-way pipe joint 8 through a fifth through joint 23 and a fourth stop valve, one port of the other two ports of the first three-way pipe joint 8 is communicated with a beaker 11 through a fifth stop valve 9 and a second through joint 10, the other port is communicated with a sixth stop valve 25, the end straight joint 27 is communicated with the measuring cylinder 12, the beaker 11 is arranged on the lifting platform 26, and the beaker 11, the measuring cylinder 12 and the lifting platform 26 form a substrate suction control device E.
As shown in fig. 4 to 6, the hydraulic bridge volume controller 2 is composed of a head 28, a third press ring 29, a T-shaped plunger 30, a column casing 31, a second press ring 32, a collar 33, a first guide key 34, a first guide cylinder 35, a first press ring 36, a first bearing box 37, a first stepping motor 38, a second key ring 40, a first screw 42, a first lead screw 43, and a first key ring 44.
The first stepping motor 38 is connected with a first lead screw 43 through a first bearing box 37 and drives the first lead screw 43 to rotate, the first lead screw 43 penetrates through a first nut 42, the first lead screw 43 and the first nut 42 are matched for use, corresponding spiral grains are arranged on the outer side of the first lead screw 43 and the inner side of the first nut 42, a first guide key 34 is connected to the left side of the first nut 42, when the first stepping motor 38 drives the first lead screw 43 to rotate, the first nut 42 moves up and down along with the first lead screw, a first guide cylinder 35 is arranged outside the first nut 42, the first guide cylinder 35 is connected with the first bearing box 37 through a first pressing ring 36 and a first key ring 44, the first key ring 44 is nested in a groove on the outer side of the lower end of the first guide cylinder 35, and then is fixed through the first pressing ring 36; a guide groove is formed in the inner side of the first guide cylinder 35 and corresponds to the first guide key 34, so that the first screw 42 cannot rotate along with the first lead screw 43 when moving vertically in the first guide cylinder 35; the T-shaped plunger 30 is arranged on the first screw nut 42 and moves up and down along with the movement of the first screw nut 42; the column casing 31 is connected with the first guide casing 35 through a lantern ring 33 and a second press ring 32, the lantern ring 33 is nested outside the first guide casing 35 and the column casing 31, and then the column casing is fixed through the second press ring 32; the end socket 28 is connected with the column casing 35 through a second key ring 40 and a third press ring 29, the second key ring 40 is nested in a groove on the outer side of the upper end of the column casing 35, and then the second key ring is fixed through the third press ring 29; the center of the seal head 28 is provided with an opening for discharging liquid; two first O-shaped sealing rings 41 are embedded in the inner side of the lower end of the column tube 35, and a second O-shaped sealing ring 39 is embedded in the inner side of the upper end of the column tube 35, so that the column tube 35, the seal head 28 and the T-shaped plunger 30 form an independent closed space, and liquid can be injected when the T-shaped plunger 30 faces upwards.
As shown in fig. 7, the tension/compression device 4 includes a second stepping motor 45, a second bearing box 46, a third key ring 47, a second guide cylinder 48, a second lead screw 49, a second nut 50, a pull rod 51, a seal ring 52, a fifth compression ring 53, a fourth compression ring 54, and a second guide key 55.
The second stepping motor 45 is connected with a second lead screw 49 through a bearing in a second bearing box 46, the second lead screw 49 penetrates through a second nut 50, the second lead screw 49 and the second nut 50 are matched for use, the outer side of the second lead screw 49 and the inner side of the second nut 50 are provided with corresponding spiral lines, the right side of the second nut 50 is connected with a second guide key 55, when the second stepping motor 45 drives the second lead screw 49 to rotate, the second nut 50 moves up and down along with the second lead screw, a second guide cylinder 48 is arranged outside the second nut 50, the second guide cylinder 48 is connected with the second bearing box 46 through a fourth pressing ring 54 and a third key ring 47, and the third key ring 47 is nested in a groove in the outer side of the upper end of the second guide cylinder 48 and then fixed by the fourth pressing ring 54; a guide groove is formed in the inner side of the second guide cylinder 48 and corresponds to the second guide key 55, so that the second nut 50 cannot rotate along with the second lead screw 49 when moving vertically in the second guide cylinder 48; the pull rod 51 is arranged on the second nut 50 and moves up and down along with the second nut 50; the seal ring 52 is fitted to the inner side of the upper end of the guide cylinder and then fixed by a fifth press ring 53. The tension and compression device is connected with the position adjusting device 5 through a pull rod 51, and the control system 1 controls the tension and compression device 4 to apply vertical displacement.
As shown in fig. 8 and 9, the position adjustment device 5 includes a first rack 56, a first gear 57, a second knob 58, a first knob 59, a second gear 60, and a second rack 61. The above components are all mounted in the housing, the first knob 59 is supported and mounted in a longitudinal groove on the housing and can reciprocate along the longitudinal groove; the second knob 58 is supported for mounting in a transverse slot in the housing and is capable of reciprocating movement along the transverse slot.
The components are divided into two groups, a first rack 56, a first gear 57 and a first knob 59 are in one group, a second rack 61, a second gear 60 and a second knob 58 are in one group, the first rack 56 and the second rack 61 are arranged vertically, each group of the first gear 57 is meshed with the first rack 56, the second rack 61 is meshed with the second gear 60, the first rack 56 is fixed on the second rack 61, the upper support 15 is fixed under the second rack 61, the first gear 57 and the second gear 60 are respectively connected with the first knob 59 and the second knob 58, the first gear 57 and the second gear 61 are rotated by the first knob 59 and the second knob 58 to drive the first rack 59 and the second gear 60 to perform linear motion, so as to control the front and back movement and the left and right movement of the upper support 15, the first rack 56 is connected with a pull rod 51 of the tension and compression device 4, the second rack 61 is connected with the upper support 15, the upper support 15 and the lower support 14 are centered by combining a data acquisition and image processing system D, and a liquid bridge with good symmetry and without influencing the initial conditions of the test is formed in the test.
As shown in fig. 2, the control system 1 controls the tension and compression device 4 to set the test type, the stretching rate, the initial and final positions and the cycle number to perform the liquid bridge test.
As shown in fig. 2, 3, 10-14, the upper opening of the upper support 15 is connected with the third stop valve 7 through the first end straight-through joint 6, when the third stop valve 7 is opened, the gas in the upper support 15 is discharged, the generation of bubbles in the test is prevented, and then the third stop valve 7 is closed; the lower opening is used for installing the upper particles and injecting liquid into the upper particles; the left opening is connected with the liquid bridge volume controller 2 through a fourth-end straight joint 19, and a passage is formed through the opening and closing of a second stop valve 13 and is used for carrying out a liquid bridge test under the condition of controlling the volume of the liquid bridge; the right opening is connected with a matrix suction control device E through a fifth end straight-through joint 23, and a passage is formed through opening and closing of a fourth stop valve 24 and is used for performing a liquid bridge test under the condition of controlling the suction of the liquid bridge matrix.
As shown in fig. 2 and 3, the data acquisition and image processing system is mainly composed of a computer 16, a high-precision balance 21, a first CCD20 and a second CCD 22.
The lower support 14 is arranged on the high-precision balance 21, the first CCD20 and the second CCD22 are connected with the computer 16, and mechanical parameter data and video images in the liquid bridge test process are recorded and processed through a software program.
As shown in fig. 2, 10-14, during the test, two spherical particles are respectively arranged on an upper support 15 and a lower support 14, the upper spherical particles are provided with holes for injecting liquid, the positions of the particles are observed by a data acquisition and image processing system D, and the two particles are centered by a position adjusting device 5, so that a liquid bridge with good symmetry and without influencing the initial condition of the test is formed.
Although the embodiments of the present invention have been described with reference to the accompanying drawings, it is not intended to limit the scope of the present invention, and it should be understood by those skilled in the art that various modifications and variations can be made without inventive efforts by those skilled in the art based on the technical solution of the present invention.
Claims (6)
1. A test method of a wet inter-particle liquid bridge tensile-compression mechanical property tester is characterized by comprising the following steps:
1) setting a tester initially, namely respectively installing upper and lower particles to be tested in the tester, adjusting the upper and lower particles to be tested in place, and monitoring in real time;
2) the following two tests were performed:
A. the liquid bridge test for controlling the volume of the liquid bridge comprises the steps that liquid is injected into a liquid bridge volume controller, a control system controls the liquid bridge volume controller to inject liquid into a pipeline, gas is exhausted through an exhaust valve of the liquid bridge volume controller, then the exhaust valve of the liquid bridge volume controller is closed, the liquid is injected into an upper support through a pipeline communicated with the liquid bridge volume controller, and the gas in an upper particle hole and an upper support is exhausted; setting the liquid volume through a control system, and controlling a liquid bridge volume controller to inject liquid to the upper particles;
B. controlling the liquid bridge test of the substrate suction, pouring liquid into the beaker, and opening the corresponding stop valve after the liquid fully flows into the pipeline to ensure that the liquid flows into the measuring cylinder; then opening a stop valve in a pipeline communicated with the upper support, opening an exhaust valve of the upper support after liquid flows into the upper support, exhausting gas in the upper support, preventing bubbles from being generated in the test, and then closing the exhaust valve; the height of the beaker is adjusted by a lifting platform, liquid flows out from the upper particles to form a liquid bridge, and the substrate suction is controlled according to the height difference between the liquid level of the beaker and the central section of the formed liquid bridge;
3) setting the type of the liquid bridge test by the control system:
A. in the liquid bridge tensile test, the control system controls the tension and compression device to move the upper support downwards to enable the upper particles and the lower particles to approach each other to form a liquid bridge and approach to a state of not contacting each other, the tension rate is set, the data acquisition and image processing system records real-time data of the high-precision balance and displacement data and video images of the whole process of liquid bridge tension, the control system starts to stretch until the liquid bridge breaks, and then the data acquisition and image processing system processes the data and the images;
b, performing a liquid bridge compression test, namely firstly performing the liquid bridge tension test step to obtain a liquid bridge tension initial position and an end point position to be fractured, respectively setting the liquid bridge tension initial position and the end point position to be fractured as the end point position and the initial position of the liquid bridge compression test through a control system, setting a tension rate, recording real-time data of a high-precision balance and displacement data and video images of the whole liquid bridge compression process by a data acquisition and image processing system, starting the test through the control system, moving the upper particles from top to bottom to compress the liquid bridge, enabling the particles to approach each other, and processing the data and the images through the data acquisition and image processing system;
C. a liquid bridge stretching-compressing cycle test, wherein the liquid bridge stretching test step is firstly carried out to obtain the stretching initial position of the liquid bridge and the terminal position of the liquid bridge to be fractured, the initial position of the liquid bridge stretching and the final position of the liquid bridge to be broken are respectively set as the initial position and the final position of the liquid bridge compression test by a control system, the upper support is controlled by the control system to move downwards by the tension and compression device, so that the upper particles and the lower particles are close to each other to form a liquid bridge, and approaching to the state of not contacting, setting the stretching rate and cycle times, recording the real-time data of the high-precision balance and the displacement data and video images of the whole process of stretching-compressing the liquid bridge by the data acquisition and image processing system, and starting the test by a control system, enabling the upper particles to move circularly, alternately performing stretching-compressing cycles, and processing data and images by a data acquisition and image processing system.
2. The testing method according to claim 1, wherein in the step 1), the control system and the data acquisition and image processing system are opened, the high-precision balance value is reset to zero, and the video image displayed by the data acquisition and image processing system is adjusted; respectively installing upper particles and lower particles on an upper support and a lower support, wherein the upper particles are provided with openings, the lower support is arranged on a high-precision balance, and the upper support is connected with a position adjusting device;
starting a second stepping motor, driving a second screw rod to rotate by the second stepping motor, driving a second nut to rotate by the second screw rod, and driving the pull rod fixed on the second screw rod to move up and down to adjust the distance between particles; the first knob is rotated to drive the first gear to rotate, and the first gear rotates to drive the first racks which are meshed with each other to move forwards and backwards in the groove; the second knob is rotated to drive the second gear to rotate, the second gear rotates to drive the mutually meshed second racks to move left and right in the groove, so that the upper support fixed on the second rack is driven to adjust the front, back and left and right positions, and the upper support comprises the first knob, the second knob, and two groups of mutually meshed gears and racks; and in the process of adjusting the distance between the particles and the front, back, left and right positions of the upper support, real-time monitoring is carried out according to a data acquisition and image processing system.
3. The assay of claim 1, wherein the data and image processing comprises calculation of liquid bridge capillary forces and image processing.
4. The test method according to claim 3, wherein the liquid bridge capillary force is calculated by: recording readings of lower pedestal and lower particle placement on high precision balance prior to liquid bridge formation
Recording the reading of the high-precision balance during the test of the stretching, compressing and stretching-compressing cycle of the liquid bridge after the liquid bridge is formed
Capillary force
Is formula (1):
5. a test method according to claim 3, wherein the liquid bridge image is processed as follows: firstly, acquiring high-definition pictures of different positions of particles in a liquid bridge fracture process by using a first industrial electron microscope and a second industrial electron microscope, guiding the high-definition pictures into Image J software for binarization processing, improving the definition of the pictures until the liquid bridge and the particles are clear in outline and easy to distinguish, so that the particle outline and the liquid bridge outline can be conveniently drawn by using AutoCAD software, the particles are positioned to determine the circle center, the particle radius in the pictures is measured, and the picture scale is determined by combining the actual radius of the particles; after the liquid bridge contour is determined, approximating the contour of the liquid bridge by using a circle by using a least square method, selecting an optimal circle through goodness of fit, and calculating the curvature radius of the meniscus by matching with a picture scale; and (3) approximating the liquid bridge contour line by using a circle by using a least square method, connecting the centers of the left and right optimal circles, and matching with a picture scale to obtain the narrowest neck section of the liquid bridge, so that the narrowest neck radius can be calculated.
6. The assay method of claim 1, wherein the upper and lower particles and the liquid are selected from the group consisting of:
selecting sodium-calcium glass polishing round balls with soil or sand as particles, wherein the diameter range is 2-5 mm; when a small-volume liquid bridge test is carried out, in order to simulate the actual condition of the project, water is selected by a liquid bridge for testing; when a large-volume liquid bridge test is carried out, the liquid bridge selects glycerol for testing, and the specific indexes of the glycerol are as follows: at 25 ℃, the viscosity is 800 mPa.s, the surface tension is 61.9mN/m, and the relative density is 1.255.
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