CN113049386B - High-ductility cement-based composite material displacement control load holding device and method - Google Patents

High-ductility cement-based composite material displacement control load holding device and method Download PDF

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CN113049386B
CN113049386B CN202110332252.4A CN202110332252A CN113049386B CN 113049386 B CN113049386 B CN 113049386B CN 202110332252 A CN202110332252 A CN 202110332252A CN 113049386 B CN113049386 B CN 113049386B
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clamp
wedge
test piece
shaped clamp
screw rod
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CN113049386A (en
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刘何稚
王强
葛亮
吴迪
卢贝
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China Three Gorges International Corp
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China Three Gorges International Corp
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N3/02—Details
    • G01N3/04—Chucks
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0014—Type of force applied
    • G01N2203/0016—Tensile or compressive
    • G01N2203/0017—Tensile
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/02—Details not specific for a particular testing method
    • G01N2203/06—Indicating or recording means; Sensing means
    • G01N2203/067—Parameter measured for estimating the property
    • G01N2203/0676—Force, weight, load, energy, speed or acceleration
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/02—Details not specific for a particular testing method
    • G01N2203/06—Indicating or recording means; Sensing means
    • G01N2203/067—Parameter measured for estimating the property
    • G01N2203/0682—Spatial dimension, e.g. length, area, angle
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A30/00—Adapting or protecting infrastructure or their operation
    • Y02A30/30—Adapting or protecting infrastructure or their operation in transportation, e.g. on roads, waterways or railways

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  • Life Sciences & Earth Sciences (AREA)
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Abstract

A displacement control load holding device and method for a high-ductility cement-based composite material comprise a test piece clamping mechanism and a tensile measuring mechanism, wherein a dog bone test piece is clamped by an upper clamp and a lower clamp of the test piece clamping mechanism, the upper end of a screw rod is in sliding fit with an upper wedge-shaped clamp, the lower end of the screw rod is fixedly connected with a lower wedge-shaped clamp, the fixed end of a displacement sensor is fixedly connected with the upper clamp, a telescopic end of the displacement sensor is abutted against the lower clamp, two ends of a diameter-changing section of the dog bone test piece are respectively matched with wedge-shaped grooves of the upper wedge-shaped clamp and the lower wedge-shaped clamp, and load is transferred to the test piece clamping mechanism and the tensile measuring mechanism after the dog bone test piece is pulled. The invention overcomes the problem that the later test data is unreal because the original high-ductility cement-based composite material retracts after being unloaded in the test and micro-crack information cannot be reflected visually, and has the advantages of simple structure, no unloading of the dog bone test piece in a strain state, contribution to developing the crack distribution and water permeability test of the high-ductility cement-based composite material and simple and convenient operation.

Description

High-ductility cement-based composite material displacement control load holding device and method
Technical Field
The invention belongs to the technical field of material tests, and relates to a displacement control load-holding device and method for a high-ductility cement-based composite material.
Background
The concrete is a simple material which is most widely applied in the world at present by virtue of the advantages of rich raw materials, good plasticity, high cost performance and the like. However, concrete has obvious brittleness characteristics, the tension-compression ratio is generally 1/10-1/14, and the ultimate tensile strain is only 0.01% -0.015%. The high-ductility cement-based material is a novel fiber-reinforced cement-based composite material designed based on fracture mechanics and micromechanics, is different from the brittleness characteristic of common concrete, has ultrahigh ductility, is a bendable cement-based material, and has the ultimate tensile strain reaching 3-5 percent which is 300-500 times that of the common concrete. Different from the macroscopic cracking mode that only a single crack appears when the traditional cement-based material bears tensile load, when the first microcrack of the high-ductility cement-based composite material appears and develops to a certain degree, the new microcrack can be regenerated, and the process is repeated for a plurality of times until a certain microcrack is locally expanded, and the test piece is finally damaged.
The high-ductility cement-based composite material has good crack width control capability and self-healing capability, the permeability coefficient of the material can be remarkably reduced due to the characteristics, and the dynamic modulus, the rigidity, the uniaxial tensile capability and the like of the cracked material can be effectively recovered, so that the high-ductility cement-based composite material is very important for improving the durability of a building and prolonging the service life of a project.
At present, researchers at home and abroad conduct related researches on the crack distribution and the water permeability of the material. However, the above researches are carried out based on the unloading of the test piece, and the material or the crack can be retracted due to the unloading of the test, so that the micro-crack width information obtained by the test cannot objectively reflect the micro-crack distribution of the high-ductility cement-based composite material.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a displacement control load holding device and method for a high-ductility cement-based composite material, the device and method are simple in structure, an upper clamp and a lower clamp of a test piece clamping mechanism are adopted to clamp a dog bone test piece, the upper end of a screw is in sliding fit with an upper wedge-shaped clamp, the lower end of the screw is fixedly connected with a lower wedge-shaped clamp, the fixed end of a displacement sensor is fixedly connected with the upper clamp, a telescopic end of the displacement sensor is abutted against the lower clamp, two ends of a diameter-changing section of the dog bone test piece are respectively matched with wedge-shaped grooves of the upper wedge-shaped clamp and the lower wedge-shaped clamp, the load of the dog bone test piece is transferred to the test piece clamping mechanism and a tensile measuring mechanism after the dog bone test piece is pulled, the dog bone test piece is kept not to be unloaded in a strain state, crack distribution and water permeability tests for the high-ductility cement-based composite material are facilitated, and the operation is simple and convenient.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows: a displacement control load holding device for a high-ductility cement-based composite material comprises a test piece clamping mechanism and a tensile measuring mechanism; the tensile measuring mechanism is positioned between the upper wedge-shaped clamp and the lower wedge-shaped clamp of the test piece clamping mechanism, the upper ends of the screws on two sides of the tensile measuring mechanism are in sliding fit with the upper wedge-shaped clamp of the test piece clamping mechanism, and the lower ends of the screws are fixedly connected with the lower wedge-shaped clamp; the fixed end of the displacement sensor is fixedly connected with the upper clamp, and the telescopic end of the displacement sensor is abutted against the lower clamp; after the upper wedge-shaped clamp and the lower wedge-shaped clamp bear load, a limiting nut at the upper end of the screw is abutted against the upper wedge-shaped clamp to transfer the load to the tensile measuring mechanism.
The test piece clamping mechanism comprises an upper wedge-shaped clamp, a lower wedge-shaped clamp and wedge-shaped grooves arranged on the upper wedge-shaped clamp and the lower wedge-shaped clamp.
The ends, with smaller cross sections, of the wedge-shaped grooves in the upper wedge-shaped clamp and the lower wedge-shaped clamp are mutually symmetrical, and the ends, far away from the ends with smaller cross sections, of the upper wedge-shaped clamp and the lower wedge-shaped clamp are provided with connecting plates.
The lower side surface of the upper wedge-shaped clamp is provided with a through hole which is in sliding fit with the screw rod, and the upper side surface of the lower wedge-shaped clamp is provided with a threaded hole which is in threaded fit with the screw rod.
The stretching measurement mechanism comprises an upper clamp and a lower clamp, and the screw rods are located on two sides of clamping holes of the upper clamp and the lower clamp.
And the two ends of the screw rod are respectively provided with a fixing nut and a limiting nut, the fixing nut is fixedly connected with the screw rod, and the limiting nut is in threaded fit with the screw rod.
And the fixing nut and the limiting nut on the screw rod are respectively positioned on the lower part of the lower side surface of the lower clamp and the upper part of the upper side surface of the upper clamp.
The upper clamp and the lower clamp are of a combined structure and respectively composed of two clamping plates which are symmetrical to each other, and the fastener penetrates through the two clamping plates to form a whole.
The mounting holes are formed in the two ends of the clamping plate of the upper clamp respectively, the fixed end of the displacement sensor is matched with the mounting holes, and the locking screw penetrates through the mounting holes to be abutted and locked with the displacement sensor.
The control method of the displacement control load-holding device for the high-ductility cement-based composite material comprises the following steps:
s1, clamping, namely clamping two ends of a uniform straight line section of a dog bone test piece by an upper clamp and a lower clamp respectively; the displacement sensors are positioned at the two ends of the upper clamp and are fixedly connected with the upper clamp;
s2, inserting, namely inserting the upper end of the screw rod into the through hole on the lower side surface of the upper wedge-shaped clamp, and at the moment, not connecting the lower end of the screw rod with the lower wedge-shaped clamp;
s3, buckling, namely buckling the diameter-variable sections at the two ends of the dog bone test piece into wedge-shaped grooves of the upper wedge-shaped clamp and the lower wedge-shaped clamp respectively;
s4, connecting, namely pulling out the upper end of the screw rod downwards for a certain distance from the through hole of the upper wedge-shaped clamp, enabling the lower end of the screw rod to correspond to the threaded hole of the lower wedge-shaped clamp, and applying knob force of the fixing nut to drive the screw rod to rotate to be matched with the threaded hole of the lower wedge-shaped clamp until the fixing nut is abutted against and locked with the upper side face of the lower wedge-shaped clamp;
s5, preparing a test, wherein the stretching end of the universal material mechanics testing machine is connected with the connecting plate of the upper wedge-shaped clamp, and the fixed seat of the universal material mechanics testing machine is connected with the connecting plate of the lower wedge-shaped clamp; the displacement sensor and the universal material mechanics testing machine are connected with the PLC control system; resetting the displacement sensor to zero;
s6, testing, namely, a universal material mechanics testing machine upwards stretches the upper wedge-shaped clamp at the upper part, and the uniform straight line segment of the dog bone test piece is stretched and deformed, extended and cracked in the stretching process;
s7, displacement, in the S6, after the dog bone test piece is pulled, the displacement sensor transmits the sensed displacement data to the PLC control system, and meanwhile, the PLC control system records the tension of the universal material mechanics testing machine;
s8, limiting, repeating S6 in sequence, and rotating the limiting nut to enable the limiting nut to be abutted against the lower side face of the upper wedge-shaped clamp after the universal material mechanics testing machine reaches a testing set value; at the moment, a limit nut and a fixed nut (26) of the screw respectively abut against the upper wedge-shaped clamp and the lower wedge-shaped clamp;
s9, unloading and holding the load, removing the connection between the universal material mechanics testing machine and the upper wedge-shaped clamp and the lower wedge-shaped clamp, transferring the tensile load to the test piece clamping mechanism and the tensile measuring mechanism, and keeping the tensioned dog bone test piece not to be unloaded in a strain state; and then observing the crack distribution pattern of the test piece.
A displacement control load holding device and method for a high-ductility cement-based composite material comprise a test piece clamping mechanism and a tensile measuring mechanism, wherein a dog bone test piece is clamped by an upper clamp and a lower clamp of the test piece clamping mechanism, the upper end of a screw rod is in sliding fit with an upper wedge-shaped clamp, the lower end of the screw rod is fixedly connected with a lower wedge-shaped clamp, the fixed end of a displacement sensor is fixedly connected with the upper clamp, a telescopic end of the displacement sensor is abutted against the lower clamp, two ends of a diameter-changing section of the dog bone test piece are respectively matched with wedge-shaped grooves of the upper wedge-shaped clamp and the lower wedge-shaped clamp, and load is transferred to the test piece clamping mechanism and the tensile measuring mechanism after the dog bone test piece is pulled. The invention overcomes the problem that the later test data is unreal because the original high-ductility cement-based composite material retracts after being unloaded in the test and micro-crack information cannot be reflected visually, and has the advantages of simple structure, no unloading of the dog bone test piece in a strain state, contribution to developing the crack distribution and water permeability test of the high-ductility cement-based composite material and simple and convenient operation.
Drawings
The invention is further illustrated by the following examples in conjunction with the accompanying drawings:
FIG. 1 is a schematic structural diagram of the present invention.
Fig. 2 is a schematic top view of fig. 1.
Fig. 3 is a test state diagram of the present invention.
Fig. 4 is a schematic structural view of the upper clamp of the present invention.
FIG. 5 is a schematic view of the structure of the dog bone test piece of the present invention.
In the figure: the device comprises an upper wedge clamp 11, a lower wedge clamp 12, a wedge groove 13, a connecting plate 14, a screw 21, an upper clamp 22, a lower clamp 23, a fixing nut 24, a limiting nut 25, a displacement sensor 26 and a dog bone test piece 3.
Detailed Description
As shown in fig. 1 to 5, a displacement control load holding device for a high-ductility cement-based composite material comprises a test piece clamping mechanism and a tensile measurement mechanism; the tensile measuring mechanism is positioned between an upper wedge-shaped clamp 11 and a lower wedge-shaped clamp 12 of the test piece clamping mechanism, the upper ends of screw rods 21 on two sides of the tensile measuring mechanism are in sliding fit with the upper wedge-shaped clamp 11 of the test piece clamping mechanism, and the lower ends of the screw rods 21 are fixedly connected with the lower wedge-shaped clamp 12; the fixed end of the displacement sensor 26 is fixedly connected with the upper clamp 22, and the telescopic end of the displacement sensor is abutted against the lower clamp 23; after the upper wedge clamp 11 and the lower wedge clamp 12 bear load, the limiting nut 25 at the upper end of the screw 21 is abutted against the upper wedge clamp 11, and the load is transferred to the tensile measuring mechanism. Simple structure, last anchor clamps 22 and 23 centre gripping dog bone test pieces 3 of lower anchor clamps through test piece fixture, the upper end and the last wedge clamp 11 sliding fit of screw rod 21, the screw rod 21 lower extreme is connected fixedly with lower wedge clamp 12, displacement sensor 26's stiff end is connected fixedly with last anchor clamps 22, flexible end is contradicted with lower anchor clamps 23, dog bone test pieces 3's reducing section both ends cooperate with the wedge groove 13 of last wedge clamp 11 and lower wedge clamp 12 respectively, shift test piece fixture and tensile measurement mechanism with the load after pulling through dog bone test pieces 3, keep dog bone test pieces not off-load under the strain state, be favorable to developing crack distribution and the water permeability test to high ductility cement based composite, and easy operation is convenient.
In a preferred scheme, the test piece clamping mechanism comprises an upper wedge clamp 11, a lower wedge clamp 12 and a wedge-shaped groove 13 which is arranged on the upper wedge clamp 11 and the lower wedge clamp 12. Simple structure, during the installation, the reducing section of dog bone 3 is detained in the wedge-shaped groove 13 of last wedge-shaped clamp 11 and lower wedge-shaped clamp 12, carries on spacingly to dog bone 3.
In a preferable scheme, the ends of the wedge grooves 13 of the upper wedge clamp 11 and the lower wedge clamp 12 with smaller cross sections are symmetrical with each other, and the connecting plates 14 are arranged at the ends of the upper wedge clamp 11 and the lower wedge clamp 12 far away from the ends with smaller cross sections. Simple structure, during the use, after dog bone test piece 3 is drawn, its stress point is located the tapered section of wedge groove 13 and dog bone test piece 3, and both ends bear the loading force.
In a preferable scheme, a through hole is arranged on the lower side surface of the upper wedge clamp 11 and is in sliding fit with the screw rod 21, and a threaded hole is arranged on the upper side surface of the lower wedge clamp 12 and is in threaded fit with the screw rod 21. The structure is simple, during installation, the upper end of the screw 21 is in sliding fit with the through hole on the lower side surface of the upper wedge-shaped clamp 11, so that the lower end of the screw has telescopic allowance, and the dog bone test piece 3 can be conveniently buckled in; after the tension, the upper end of the screw 21 slides with the through hole, so that the screw 21 is not affected when the dog bone test piece 3 stretches.
In a preferred embodiment, the stretch measuring mechanism includes an upper clamp 22 and a lower clamp 23, and the screw 21 is located on two sides of a clamping hole of the upper clamp 22 and the lower clamp 23. Simple structure, during the use, the even straightway of dog bone test piece 3 is held to upper clamp 22 and lower clamp 23, and screw rod 21 does not contact with upper clamp 22 and lower clamp 23.
In a preferred scheme, two ends of the screw 21 are respectively provided with a fixing nut 24 and a limiting nut 25, the fixing nut 24 is fixedly connected with the screw 21, and the limiting nut 25 is in threaded fit with the screw 21. Simple structure, during the use, fixation nut 24 on the screw rod 21 rather than fixed, exert fixation nut 24 knob power during the connection and drive screw rod 21 rotatory, and stop nut 25 and screw rod 21 screw-thread fit are convenient for adjust stop nut 25's limiting position.
In a preferred scheme, the fixing nut 24 and the limiting nut 25 on the screw 21 are respectively positioned at the lower side of the lower clamp 23 and the upper side of the upper clamp 22. The structure is simple, during installation, after the upper clamp 22 and the lower clamp 23 clamp the dog bone test piece 3, the fixing nut 24 is positioned at the lower part of the lower side surface of the lower clamp 23, and an operation space is reserved when the operation screw 21 rotates to be connected with the lower wedge clamp 12; the limiting nut 25 is positioned at the upper part of the upper side surface of the upper clamp 22, and is driven to rotate to abut against the lower side surface of the upper wedge clamp 11 after the stretching is finished, so that the tensile stress of the upper wedge clamp is transferred, and the test piece clamping mechanism and the tensile measuring mechanism bear the load together after the stress is transferred.
In a preferred embodiment, the upper clamp 22 and the lower clamp 23 are of a combined structure, and each of the combined structure is composed of two clamping plates which are symmetrical to each other, and the fastening member penetrates through the two clamping plates to form a whole. Simple structure, during the use, the both ends of the even straightway of upper clamp 22 and lower clamp 23 centre gripping dog bone test piece, when even straightway takes place the displacement, the corresponding emergence of distance between upper clamp plate 22 and the lower plate 23 changes, is convenient for survey the tensile volume of even straightway.
In the preferred scheme, the mounting holes are respectively arranged at the two ends of the clamping plate of the upper clamp 22, the fixed end of the displacement sensor 26 is matched with the mounting holes, and the locking screw penetrates through the mounting holes to be abutted and locked with the displacement sensor 26. Simple structure, during the use, displacement sensor 26 stiff end and through-hole cooperation are locked by locking screw, improve the stability of displacement sensor 26 survey data.
In a preferred embodiment, the method for controlling the displacement control load-holding device of the high-ductility cement-based composite material comprises the following steps:
s1, clamping, namely clamping two ends of a uniform straight line section of a dog bone test piece 3 by an upper clamp 22 and a lower clamp 23 respectively; the displacement sensor 26 is positioned at two ends of the upper clamp 22 and is fixedly connected with the upper clamp;
s2, inserting, namely inserting the upper end of the screw rod 21 into a through hole in the lower side face of the upper wedge-shaped clamp 11, wherein the lower end of the screw rod 21 is not connected with the lower wedge-shaped clamp 12;
s3, buckling, namely buckling the variable diameter sections at the two ends of the dog bone test piece 3 into the wedge-shaped grooves 13 of the upper wedge-shaped clamp 11 and the lower wedge-shaped clamp 12 respectively;
s4, connecting, namely pulling out the upper end of the screw rod 21 downwards for a certain distance from the through hole of the upper wedge-shaped clamp 11, enabling the lower end of the screw rod 21 to correspond to the threaded hole of the lower wedge-shaped clamp 12, applying knob force of the fixing nut 24 to drive the screw rod 21 to rotate to be matched with the threaded hole of the lower wedge-shaped clamp 12 until the fixing nut 24 is abutted and locked with the upper side face of the lower wedge-shaped clamp 12;
s5, preparing a test, wherein the stretching end of the universal material mechanics testing machine is connected with the connecting plate 14 of the upper wedge clamp 11, and the fixed seat of the universal material mechanics testing machine is connected with the connecting plate 14 of the lower wedge clamp 12; the displacement sensor 26 and the universal material mechanics testing machine are connected with the PLC control system; resetting and zeroing the displacement sensor 26;
s6, testing, namely, a universal material mechanics testing machine upwards stretches the upper wedge-shaped clamp 11 on the upper part, and the uniform straight line segment of the dog bone test piece is stretched and deformed, extended and cracked in the stretching process;
s7, displacement, in S6, after the dog bone test piece is pulled, the displacement sensor 26 transmits the sensed displacement data to the PLC control system, and meanwhile, the PLC control system records the tension of the universal material mechanics testing machine;
s8, limiting, repeating S6 in sequence, and rotating the limiting nut 25 to enable the limiting nut to be abutted against the lower side face of the upper wedge-shaped clamp 11 after the universal material mechanics testing machine reaches a testing set value; at this time, the limit nut 25 and the fixing nut 26 of the screw 21 respectively abut against the upper wedge clamp 11 and the lower wedge clamp 12;
s9, unloading and holding load, relieving the connection between the universal material mechanics testing machine and the upper wedge-shaped clamp 11 and the lower wedge-shaped clamp 12, transferring tensile load to the test piece clamping mechanism and the tensile measurement mechanism, and keeping the tensioned dog bone test piece not to be unloaded in a strain state; and then observing the crack distribution pattern of the test piece. The method is simple and convenient to operate, and the device can solve the problem of retraction of the material and the microcracks caused by unloading when a uniaxial tensile test is carried out on the high-ductility cement-based composite material, obtain the distribution pattern of the microcracks of the high-ductility cement-based material in a load-holding state, and further lay a foundation for analyzing the characteristic relationship between the distribution pattern of the microcracks and strain and the influence of different microcrack distribution patterns and permeability.
When the high-ductility cement-based composite material displacement control load-holding device and the method are installed and used, the upper clamp 22 and the lower clamp 23 of the test piece clamping mechanism clamp the dog bone test piece 3, the upper end of the screw rod 21 is in sliding fit with the upper wedge-shaped clamp 11, the lower end of the screw rod 21 is fixedly connected with the lower wedge-shaped clamp 12, the fixed end of the displacement sensor 26 is fixedly connected with the upper clamp 22, the telescopic end of the displacement sensor is abutted against the lower clamp 23, two ends of the diameter-changing section of the dog bone test piece 3 are respectively matched with the wedge-shaped grooves 13 of the upper wedge-shaped clamp 11 and the lower wedge-shaped clamp 12, the load of the dog bone test piece 3 is transferred to the test piece clamping mechanism and the tensile measurement mechanism after being pulled, the dog bone test piece is kept not to be unloaded in a strain state, crack distribution and water permeability tests on the high-ductility cement-based composite material can be conveniently carried out, and the operation is simple and convenient.
During installation, the variable-diameter section of the dog bone 3 is buckled into the wedge-shaped grooves 13 of the upper wedge-shaped clamp 11 and the lower wedge-shaped clamp 12 to limit the dog bone 3.
When the dog bone test piece is used, after the dog bone test piece 3 is pulled, the stress point is positioned at the tapered section of the wedge-shaped groove 13 and the dog bone test piece 3, and the two ends bear loading force.
During installation, the upper end of the screw 21 is in sliding fit with the through hole on the lower side surface of the upper wedge-shaped clamp 11, so that the lower end of the screw has telescopic allowance, and the dog bone test piece 3 can be conveniently buckled in; after the tension, the upper end of the screw 21 slides with the through hole, so that the screw 21 is not affected when the dog bone test piece 3 stretches.
When the dog bone test piece is used, the upper clamp 22 and the lower clamp 23 clamp the uniform straight line segment of the dog bone test piece 3, and the screw 21 is not in contact with the upper clamp 22 and the lower clamp 23.
During the use, the fixation nut 24 on the screw rod 21 is rather than fixed, and exert fixation nut 24 knob power and drive screw rod 21 rotatory during the connection, and the limit nut 25 is with screw rod 21 screw-thread fit, is convenient for adjust the limit position of limit nut 25.
During installation, after the upper clamp 22 and the lower clamp 23 clamp the dog bone test piece 3, the fixing nut 24 is positioned at the lower part of the lower side surface of the lower clamp 23, and an operation space is reserved when the operation screw 21 rotates to be connected with the lower wedge clamp 12; and the limiting nut 25 is positioned at the upper part of the upper side surface of the upper clamp 22, and is driven to rotate to abut against the lower side surface of the upper wedge-shaped clamp 11 after the stretching is finished, so that the tensile stress of the upper wedge-shaped clamp is transferred, and the test piece clamping mechanism and the tensile measuring mechanism bear the load together after the stress is transferred.
During the use, the both ends of the even straightway of upper clamp 22 and lower clamp 23 centre gripping dog bone test piece, when even straightway takes place the displacement, the corresponding emergence of distance between upper clamp plate 22 and the lower clamp plate 23 changes, is convenient for survey the tensile volume of even straightway.
When the device is used, the fixed end of the displacement sensor 26 is matched with the through hole and locked by the locking screw, so that the stability of data measured by the displacement sensor 26 is improved.
The above-described embodiments are merely preferred technical solutions of the present invention, and should not be construed as limiting the present invention, and the embodiments and features in the embodiments in the present application may be arbitrarily combined with each other without conflict. The protection scope of the present invention is defined by the claims, and includes equivalents of technical features of the claims. I.e., equivalent alterations and modifications within the scope hereof, are also intended to be within the scope of the invention.

Claims (7)

1. A high-ductility cement-based composite material displacement control load holding device is characterized in that: the device comprises a test piece clamping mechanism and a tensile measurement mechanism; the tensile measuring mechanism is positioned between an upper wedge clamp (11) and a lower wedge clamp (12) of the test piece clamping mechanism, the upper ends of screw rods (21) on two sides of the tensile measuring mechanism are in sliding fit with the upper wedge clamp (11) of the test piece clamping mechanism, and the lower ends of the screw rods (21) are fixedly connected with the lower wedge clamp (12); the fixed end of the displacement sensor (26) is fixedly connected with the upper clamp (22), and the telescopic end of the displacement sensor is abutted against the lower clamp (23); after the upper wedge-shaped clamp (11) and the lower wedge-shaped clamp (12) bear loads, a limiting nut (25) at the upper end of the screw rod (21) is abutted against the upper wedge-shaped clamp (11) to transfer the loads to a tensile measuring mechanism;
the test piece clamping mechanism comprises an upper wedge clamp (11), a lower wedge clamp (12) and wedge-shaped grooves (13) which are arranged on the upper wedge clamp (11) and the lower wedge clamp (12);
the ends, with smaller cross sections, of the wedge-shaped grooves (13) on the upper wedge-shaped clamp (11) and the lower wedge-shaped clamp (12) are mutually symmetrical, and a connecting plate (14) is arranged at the end, far away from the end with smaller cross section, of the upper wedge-shaped clamp (11) and the lower wedge-shaped clamp (12);
the stretching measuring mechanism comprises an upper clamp (22) and a lower clamp (23), and the screw rod (21) is positioned on two sides of a clamping hole of the upper clamp (22) and the clamping hole of the lower clamp (23).
2. The displacement control load-holding device for the high ductility cement-based composite material as claimed in claim 1, wherein: the lower side surface of the upper wedge-shaped clamp (11) is provided with a through hole which is in sliding fit with the screw rod (21), and the upper side surface of the lower wedge-shaped clamp (12) is provided with a threaded hole which is in threaded fit with the screw rod (21).
3. The high-ductility cement-based composite material displacement control load-holding device as claimed in claim 1, characterized in that: and two ends of the screw rod (21) are respectively provided with a fixing nut (24) and a limiting nut (25), the fixing nut (24) is fixedly connected with the screw rod (21), and the limiting nut (25) is in threaded fit with the screw rod (21).
4. The high ductility cement-based composite material displacement control load-holding device as claimed in claim 3, wherein: and the fixing nut (24) and the limiting nut (25) on the screw rod (21) are respectively positioned on the lower side surface of the lower clamp (23) and the upper side surface of the upper clamp (22).
5. The displacement control load-holding device for the high ductility cement-based composite material as claimed in claim 1, wherein: the upper clamp (22) and the lower clamp (23) are of a combined structure and respectively composed of two clamping plates which are symmetrical to each other, and the fastening piece penetrates through the two clamping plates to form a whole.
6. The displacement control load-holding device for the high ductility cement-based composite material as claimed in claim 1, wherein: the mounting holes are formed in the two ends of the clamping plate of the upper clamp (22) respectively, the fixed end of the displacement sensor (26) is matched with the mounting holes, and the locking screw penetrates through the mounting holes to be abutted and locked with the displacement sensor (26).
7. The method for controlling the displacement control load-holding device of the high ductility cement-based composite material according to any one of claims 1~6, comprising the steps of:
s1, clamping, namely clamping two ends of a uniform straight line section of a dog bone test piece (3) by an upper clamp (22) and a lower clamp (23) respectively; the displacement sensors (26) are positioned at the two ends of the upper clamp (22) and are fixedly connected with the upper clamp;
s2, inserting, namely inserting the upper end of the screw rod (21) into a through hole in the lower side surface of the upper wedge-shaped clamp (11), wherein the lower end of the screw rod (21) is not connected with the lower wedge-shaped clamp (12);
s3, buckling, namely buckling the variable diameter sections at the two ends of the dog bone test piece (3) into wedge-shaped grooves (13) of the upper wedge-shaped clamp (11) and the lower wedge-shaped clamp (12) respectively;
s4, connecting, namely pulling out the upper end of the screw rod (21) downwards for a certain distance from the through hole of the upper wedge-shaped clamp (11), enabling the lower end of the screw rod (21) to correspond to the threaded hole of the lower wedge-shaped clamp (12), applying knob force of the fixing nut (24) to drive the screw rod (21) to rotate to be matched with the threaded hole of the lower wedge-shaped clamp (12) until the fixing nut (24) is abutted and locked with the upper side face of the lower wedge-shaped clamp (12);
s5, preparing a test, wherein the stretching end of a universal material mechanics testing machine is connected with the connecting plate (14) of the upper wedge clamp (11), and a fixed seat of the universal material mechanics testing machine is connected with the connecting plate (14) of the lower wedge clamp (12); the displacement sensor (26) and the universal material mechanics testing machine are connected with the PLC control system; resetting the displacement sensor (26) to zero;
s6, testing, namely, a universal material mechanics testing machine upwards stretches the upper wedge-shaped clamp (11) at the upper part, and the uniform straight line segment of the dog bone test piece is stretched and deformed, extended and cracked in the stretching process;
s7, displacement, in S6, after the dog bone test piece is pulled, the displacement sensor (26) transmits the sensed displacement data to the PLC control system, and meanwhile, the PLC control system records the tension of the universal material mechanics testing machine;
s8, limiting, repeating S6 in sequence, and rotating the limiting nut (25) to enable the limiting nut to be abutted against the lower side face of the upper wedge-shaped clamp (11) after the universal material mechanics testing machine reaches a testing set value; at the moment, a limiting nut (25) and a fixing nut (24) of the screw (21) are respectively abutted against the upper wedge-shaped clamp (11) and the lower wedge-shaped clamp (12);
s9, unloading and holding load, namely relieving the connection between the universal material mechanics testing machine and the upper wedge-shaped clamp (11) and the lower wedge-shaped clamp (12), transferring tensile load to the test piece clamping mechanism and the tensile measuring mechanism, and keeping the tensioned dog bone test piece not to be unloaded in a strain state; and then observing the crack distribution pattern of the test piece.
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