CN111413203A - A kind of concrete uniaxial tensile test fixture and test method - Google Patents

Abstract

The invention discloses a concrete uniaxial tensile test fixture and a test method, comprising two clamp bodies with the same structure. The jaws are matched and connected, and the other end is connected with the specimen holder; the jaw connection and the specimen holder are connected by tenon and mortise; the clamping end of the concrete specimen is embedded in the specimen holder, The clamping end of the concrete specimen and the specimen clamping piece are connected by surface contact and tight fitting; the present invention adopts the surface contact fitting connection between the clamping end of the concrete specimen and the specimen clamping piece, which effectively eliminates the need for local The stress concentration reduces the damage of the specimen, ensures that the tensile fracture surface of the concrete specimen occurs in the middle of the specimen, and plays a positive role in improving the test accuracy; the jaw connector and the specimen holder are connected by tenon and mortise. , Improve the stability of the structure, the installation and disassembly is simple, and the efficiency and measurement accuracy of the tensile test are effectively improved.

Description

A kind of concrete uniaxial tensile test fixture and test method

technical field

The invention belongs to the technical field of concrete testing, and particularly relates to a concrete uniaxial tensile test fixture and a testing method.

Background technique

Concrete is currently the most widely used material in construction projects, and the strength of concrete components needs to be tested by means of experiments. Tensile performance is an important mechanical property of concrete materials, and its tensile strength can be obtained by uniaxial tensile test.

At present, there are three main test methods for concrete tensile properties: split pull test, straight pull test and flexural pull test. Among them, the test data measured by the direct tensile test is the most accurate, and can most directly reflect the tensile strength and strain changes of concrete, so as to obtain the stress-strain relationship of the concrete material. However, due to the natural brittleness of concrete materials, in uniaxial tensile tests, the selection of fixtures and the way of clamping the specimen and fixtures are critical to the accuracy and success rate of the test.

In the direct tensile test, the existing specimen clamping methods mainly include the stick-steel type, the three-point type, the soft-contact type and the hard-contact type. Among them, the stick-steel type is to use an adhesive to hold the two ends of the concrete specimen with the tensile force. The extension shaft is bonded, and the adhesive is epoxy resin-based adhesive steel; its disadvantages: the epoxy resin bonding method needs to melt the epoxy resin, which is harmful to the human body and pollutes the environment; the three-point type is installed on the cylindrical The three bolt holes of the shaped shell are used to tighten the clamping of the specimen by the rotation of the bolt; its disadvantage is that the force exerted by the three bolt action points and the length of the screwed bolt cannot be quantified, which is easy to cause eccentricity and test. The stress concentration at the end of the component; the soft contact type is lined with an elastic sheet on the contact surface of the fixture and the test piece. Although this design has a certain effect on preventing stress concentration, when studying the stress-strain relationship of concrete, the elasticity The strain of the thin sheet will cause huge errors in the test results, and this method cannot meet the needs of concrete constitutive research; the hard contact type uses two bolts to clamp the concrete specimen, and its disadvantages: it is easy to cause stress concentration, and the end of the specimen is damaged. It is difficult to make the tensile failure surface occur in the middle of the specimen, and the tensile test error is too large due to the bending deformation of the bolt during the tensile process.

In terms of the connection between the clamp and the common servo universal machine, most of the existing technologies use metal rods for connection, and the disadvantage is: when the direction of the metal rod structure is parallel to the axial stretching direction, it will be under the action of the axial force. A non-negligible strain is generated, and the generation of this additional strain will have a greater impact on the stress-strain relationship in the study of concrete tensile, thereby causing the measured test data to lose accuracy.

SUMMARY OF THE INVENTION

In view of the technical problems existing in the prior art, the present invention provides a concrete uniaxial tensile test fixture and a test method, so as to solve the non-negligible stress concentration between the concrete specimen and the fixture in the prior art, which is easy to cause concrete The root of the specimen breaks or the creep failure phenomenon occurs in the contact part with the fixture, which eventually leads to the technical problem of failure of the tensile test.

To achieve the above object, the technical scheme adopted in the present invention is:

The invention provides a concrete uniaxial tensile test fixture, which includes two clamping bodies with the same structure, the two clamping bodies are respectively arranged at both ends of a concrete specimen, and the concrete specimen is fixedly installed in the tensile test by the clamping bodies on board;

The clamp specifically includes a jaw connector and a specimen holder, one end of the jaw connector is connected with the jaw of the tensile testing machine, and the other end is connected with the specimen holder; the jaw connector is clamped with the specimen Tenon-and-mortise connection is adopted between the pieces; the clamping end of the concrete specimen is embedded in the specimen clamping piece, and the clamping end of the concrete specimen and the specimen clamping piece are connected by surface contact and tight fit.

Further, the jaw connector includes a connector bottom plate and a connector middle plate; one side of the connector bottom plate is connected with the specimen holder, and the connector bottom plate is evenly provided with a first tenon-and-mortise structure, through the first tenon-and-mortise structure. The structure is fixedly connected with the specimen holder; the other side of the bottom plate of the connector is connected to the middle plate of the connector, one end of the middle plate of the connector is vertically fixed and connected to the middle of the bottom plate of the connector, and the other end is connected to the tensile testing machine. The jaws mate with the connection.

Further, the jaw connector also includes two sets of reinforced bodies, and the two sets of reinforced bodies are symmetrically arranged on both sides of the middle plate of the connector; each set of reinforced bodies includes two reinforced plates, and the two reinforced plates are vertical. It is arranged in parallel between the bottom plate of the connecting piece and the middle plate of the connecting piece, one end of the stiffening plate is fixedly connected with the bottom plate of the connecting piece, and the other end is fixedly connected with the connecting piece.

Further, the connection between the intermediate plate of the connecting piece and the bottom plate of the connecting piece is provided with rounded corners.

Further, the bottom plate of the connector and the middle plate of the connector adopt an integrated structure.

Further, the specimen holder includes a symmetrically arranged first specimen holder and a second specimen holder, and the first specimen holder and the second specimen holder are detachably connected;

The side of the first specimen clamping block is provided with a first curved groove, the side of the second specimen clamping block is provided with a second curved groove, and the first curved groove and the second curved groove are matched and connected to form a curved fixed groove; The clamping end of the specimen is embedded in the curved surface fixing groove, and the clamping end of the concrete specimen and the curved surface fixing groove are connected by surface contact and tight fit;

A second mortise-and-mortise structure is evenly arranged at the ends of the first and second test piece clamping blocks, and is detachably and fixedly connected to the jaw connector through the second mortise and tenon structure.

Further, the curved surface fixing groove is a circular truncated cavity structure with one large end and one small end;

The concrete specimen includes an upper clamping end, a middle test section and a lower clamping end; the upper clamping end and the lower clamping end are respectively arranged at both ends of the middle test section, and both the upper clamping end and the lower clamping end are large at one end. A circular cone-shaped structure with a small end, the upper clamping end or the lower clamping end is arranged in the curved surface fixing groove, and the outer wall of the upper clamping end or the lower clamping end is in close contact with the inner wall of the curved surface fixing groove.

Further, the specimen holder also includes fasteners, the fasteners are horizontally arranged in the first specimen clamping block and the second specimen clamping block, and the first specimen clamping block and the second specimen clamping block are connected by the fasteners. The specimen clamps are fixedly connected together;

The fasteners include high-strength bolts and nuts. The high-strength bolts horizontally penetrate the first and second specimen clamping blocks in sequence. The nuts are sleeved on the ends of the high-strength bolts, and the nuts and the high-strength bolts are connected by threads.

The present invention also provides a concrete uniaxial tensile test method, using the concrete uniaxial tensile test fixture, and the specific steps are as follows:

First, make a concrete specimen according to the test requirements; then insert the two ends of the concrete specimen into two specimen holders respectively, and install a jaw connector at the end of each specimen holder. Tenon-and-mortise connection is used between the mouth connector and the specimen holder; then the jaw connector is fixedly installed at the jaw of the tensile testing machine, and the distance between the two chucks of the tensile testing machine is adjusted to make the concrete The clamping end of the specimen and the specimen holder are connected by surface contact and tight fit; the tensile testing machine is started to carry out the concrete uniaxial tensile test.

Compared with the prior art, the beneficial effects of the present invention are:

The invention provides a concrete uniaxial tensile test fixture. By arranging a specimen clamping piece, the clamping end of the concrete specimen and the specimen clamping piece are connected by surface contact, effectively eliminating local stress. Concentration reduces the damage of the concrete specimen due to stress concentration, improves the reliability and stability of the test process, ensures that the tensile fracture surface of the concrete specimen occurs in the middle of the specimen, and actively promotes the improvement of the test accuracy. Function; the jaw connector adopts tenon and mortise connection between the specimen holding parts, which reduces the complexity of the structure, improves the stability of the structure, and is easy to install and disassemble, which effectively improves the measurement accuracy of the tensile test.

Further, the jaw connector adopts the combination of the connector bottom plate and the connector middle plate. By setting the connector middle plate, the plate structure is used instead of the existing rod structure to connect with the jaws of the tensile testing machine, which not only improves the structure. It also effectively reduces the adverse effect on the test results caused by the additional strain caused by the fixture structure during the tensile process, and improves the accuracy of the tensile test results.

Further, by arranging stiffened plates on both sides of the middle plate of the connecting piece, the structural strength of the jaw connecting piece is effectively improved, and the occurrence of structural failure during the test is prevented.

Further, the connection between the middle plate of the connector and the bottom plate of the connector is connected by means of rounded corners, which effectively disperses stress concentration and improves the reliability of the jaw connector.

Further, by adopting the integrated structure of the middle plate of the connector and the bottom plate of the connector, the strength and stability of the structure are improved, and the accuracy of the test results is ensured.

Further, the specimen holder is connected by two symmetrically arranged specimen clamps, which facilitates the disassembly and installation between the concrete specimen and the specimen holder, is convenient to operate, and improves the test efficiency; the two specimen clamps The surface fixing groove is formed in cooperation with each other, and the clamping end of the concrete specimen is in close contact with the surface of the curved fixing groove, which effectively eliminates the effect of local stress concentration and reduces the damage caused by the stress concentration at the end of the concrete specimen.

Further, the clamping end of the concrete specimen and the curved surface fixing groove are set to a structure with one large end and one small end, which ensures the reliability of the connection between the concrete specimen and the curved surface fixing groove, and improves the connection between the concrete specimen and the curved surface fixing groove. The contact area between the two parts eliminates the local stress concentration, and at the same time effectively improves the clamping force of the specimen holder.

Further, high-strength bolts are used to connect the two specimen clamping blocks, which ensures the stability of the structure and facilitates the installation and removal of concrete specimens.

The invention also provides a concrete uniaxial tensile test method, the test operation steps are simple, the concrete specimen and the specimen holder, the specimen holder and the jaw connection, and the jaw connection and the tensile testing machine The installation and disassembly process is simple and the reliability is high, which effectively improves the measurement accuracy of the uniaxial tensile test.

To sum up, the concrete uniaxial tensile test fixture and the test method according to the present invention can realize the accurate measurement of the tensile test data of the concrete specimen, the clamping is convenient, and the structure is simple; the present invention can be directly used in The uniaxial tensile test of concrete is carried out on a common type of servo universal testing machine, which can minimize the local stress concentration generated during the tensile test and eliminate the additional strain generated by the fixture itself during the tensile process. Uniform stress is applied during the stretching process, thereby improving the accuracy of the tensile test database and making up for the vacancies and deficiencies in the prior art.

Description of drawings

Fig. 1 is the three-dimensional structure schematic diagram of a kind of concrete uniaxial tensile test fixture of the present invention;

Fig. 2 is a perspective view of a concrete uniaxial tensile test fixture according to the present invention;

3 is a top view of a concrete uniaxial tensile test fixture according to the present invention;

4 is a cross-sectional view of the A-A surface of a concrete uniaxial tensile test fixture according to the present invention;

5 is a schematic structural diagram of a jaw connector in a concrete uniaxial tensile test fixture according to the present invention;

6 is a schematic structural diagram of a specimen holder in a concrete uniaxial tensile test fixture according to the present invention;

7 is a schematic structural diagram of a specimen clamping block in a concrete uniaxial tensile test fixture according to the present invention;

8 is a schematic diagram of the three-dimensional structure of the specimen in a concrete uniaxial tensile test fixture according to the present invention;

9 is a sectional view of a specimen in a concrete uniaxial tensile test fixture according to the present invention;

10 is a perspective view of the assembly structure of a concrete uniaxial tensile test fixture according to the present invention;

11 is a front view of the assembly structure of a concrete uniaxial tensile test fixture according to the present invention.

Among them, 1 clamp body, 2 concrete specimen; 11 jaw connector, 12 specimen holder; 111 connector base plate, 112 connector middle plate, 113 reinforcement body, 114 first tenon-and-mortise structure; 121 No. One specimen clamp, 122 second specimen clamp, 123 high-strength bolts, 124 nuts, 125 first curved grooves, 126 second curved grooves, 127 curved fixed grooves, 128 second tenon-and-mortise structures; 21 upper clamping end , 22 middle test section, 23 lower clamping end.

Detailed ways

In order to make the technical problems, technical solutions and beneficial effects solved by the present invention clearer, the following geometric drawings and embodiments will further describe the present invention in detail. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

As shown in the accompanying drawings 1-11, the present invention provides a concrete uniaxial tensile test fixture, which includes two clamping bodies 1 with the same structure, and the two clamping bodies 1 are respectively arranged at both ends of the concrete specimen 2. The clamp body 1 fixes the concrete specimen 2 on the tensile testing machine.

The clamp body 1 includes a jaw connector 11 and a specimen holder 12. One end of the jaw connector 11 is connected with the jaws of the tensile testing machine, and the other end is connected with the specimen holder 12; the jaw connector 11 and the specimen holder 12 are connected by mortise and tenon; They are connected by surface contact and tight fit.

The jaw connector 11 includes a connector bottom plate 111 , a connector middle plate 112 and two sets of stiffeners 113 ; one side of the connector bottom plate 111 is connected with the specimen holder 12 , and the other side of the connector bottom plate 111 is connected with The middle plate 112 of the connector is connected; one end of the middle plate 112 of the connector is vertically and fixedly connected with the middle of the bottom plate 111 of the connector, and the other end is connected with the jaws of the tensile testing machine; by setting the middle plate 112 of the connector, the test During the process, the middle plate 112 of the connector is connected with the jaws of the tensile testing machine, and the plate structure is used instead of the existing rod structure to connect with the jaws of the tensile testing machine, which not only improves the stability of the structure, but also effectively reduces During the tensile test, the additional strain caused by the fixture structure adversely affects the test results, which improves the accuracy of the tensile test results.

Two sets of stiffeners 113 are symmetrically arranged on both sides of the middle plate 112 of the connector, each set of stiffeners 113 includes two stiffeners, and the two stiffeners are vertically parallel to the bottom plate 111 of the connector and in the connector. Between the position plates 112, one end of the stiffened plate is fixedly connected with the connecting piece bottom plate 111, and the other end is fixedly connected with the connecting piece 112; by arranging stiffened plates on both sides of the middle position plate 112 of the connecting piece, the jaw connection is effectively improved The structural strength of the part 11 is avoided to avoid structural failure and deformation during the test.

Preferably, the connection between the middle plate 112 of the connector and the bottom plate 111 of the connector is set with rounded corners, and the connection between the middle plate 112 of the connector and the bottom plate 111 of the connector is connected by rounded corners, which is effective. Disperses stress concentration and improves the reliability of jaw connections. .

Preferably, the connector bottom plate 111 and the connector middle plate 112 adopt an integrated structure; by using the connector middle plate and the connector bottom plate to adopt an integrated structure, the strength and stability of the structure are improved, and the accuracy of the test results is ensured sex.

The specimen holder 12 includes a first specimen holder 121, a second specimen holder 122 and fasteners. The first specimen holder 121 and the second specimen holder 122 are symmetrically arranged. The block 121 and the second specimen clamping block 122 are detachably connected by fasteners; the specimen clamping piece is connected by two symmetrically arranged specimen clamping blocks, which is convenient for the concrete specimen 2 and the specimen clamping piece 12 It is easy to operate and improve the test efficiency. The fasteners are horizontally arranged in the first specimen clamping block 121 and the second specimen clamping block 122, and the first specimen clamping block 121 and the second specimen clamping block 122 are fixedly connected together by the fasteners; The firmware includes high-strength bolts 123 and nuts 124. The high-strength bolts 123 horizontally penetrate the first specimen clamping block 121 and the second specimen clamping block 122 in sequence. The nut 124 is sleeved on the end of the high-strength bolt 123. Threaded connection is used between 123.

The first tenon-and-mortise structure 114 is evenly arranged on the base plate 111 of the connecting piece, and the first tenon-and-mortise structure 114 on the base plate 111 of the connecting piece is arranged at the contact end with the specimen holder 12; the first specimen holder 121 and the second The end of the specimen clamping block 122 is evenly provided with a second tenon and mortise structure 128 , and the second tenon and mortise structure 128 on the first specimen clamping block 121 or the second specimen clamping block 122 is arranged in contact with the base plate 111 of the connector. The first tenon-and-mortise structure 114 and the second tenon-and-mortise structure 128 are cooperatively connected to realize the cooperative connection between the jaw connector 11 and the specimen holder 12, and the jaw connector 11 and the specimen holder 12 The tenon-and-mortise connection is adopted between them, which optimizes the complexity of the fixture structure and improves the stability of the structure. There are few operation steps in the use process, and the installation and disassembly are simple, which effectively improves the measurement accuracy of the tensile test.

The side wall of the first specimen clamping block 121 is provided with a first curved groove, the side wall of the second specimen clamping block 122 is provided with a second curved groove, and the first curved groove and the second curved groove are matched and connected to form a curved fixed groove; The clamping end of the concrete specimen 2 is embedded in the curved surface fixing groove; preferably, the curved surface fixing groove is a truncated cavity structure with one large end and one small end, and a surface is used between the clamping end of the concrete specimen 2 and the curved surface fixing groove. Contact tight fit connection;

The concrete specimen 2 includes an upper clamping end 21, a middle test section 22 and a lower clamping end 23; the upper clamping end 21 and the lower clamping end 23 are respectively arranged at both ends of the middle test section 22, and the upper clamping end 21 and The lower clamping end 23 is a circular cone-shaped structure with one large end and one small end. The upper clamping end 21 or the lower clamping end 23 is matched and arranged in the curved surface fixing groove. The inner walls of the fixing grooves are in close contact.

The invention also provides a concrete uniaxial tensile test method, the specific steps are as follows:

First, according to the test requirements, make the concrete specimen 2; then insert the two ends of the concrete specimen 2 into the two specimen holders 12 respectively, and install jaws at the end of each specimen holder 12 The connection piece 11, the jaw connection piece 11 and the specimen holder 12 are connected by tenon and mortise; then the jaw connection piece 11 is fixedly installed at the jaw of the tensile testing machine, and the two clamps of the tensile testing machine are adjusted. The distance between the heads, so that the clamping end of the concrete specimen 2 and the specimen clamping element 12 are closely connected by surface contact; start the tensile testing machine to carry out the concrete uniaxial tensile test.

The concrete uniaxial tensile test fixture of the present invention can reduce the damage of the clamping end of the concrete specimen due to stress concentration during the test clamping process, and can reduce the error caused by the structure of the test fixture and even The eliminated test fixture has a pivotal significance for accurately measuring the results of the uniaxial tensile test of concrete materials; the tensile test fixture of the present invention is convenient to hold and has a simple structure, and can be directly used for common models of servo universal testing machines. Concrete uniaxial tensile test, which can minimize the local stress concentration generated during the test and eliminate the additional strain generated by the fixture itself during the tensile process, so that the specimen is uniformly stressed during the tensile process, thereby improving the tensile strength. The accuracy of the tensile test database makes up for the vacancies and deficiencies in the existing technology; as a special brittle material, the traditional clamping method in the tensile test will produce non-negligible effects at the jaws of the concrete specimen and the fixture. Stress concentration, which will cause damage to the concrete material in the early stage of the test, and then cause the root of the specimen to break during the test, or the phenomenon of creep rupture in the contact part with the jaws of the fixture, which will eventually lead to the failure of the test or loss of test accuracy. In addition, most of the fixtures used in the existing concrete uniaxial tensile tests use metal rod structures. When the direction of the metal rod structure is parallel to the axial tensile direction, the axial force Under the action of , a non-negligible strain will be generated, and this additional strain generation will have a great impact on the stress-strain relationship when studying concrete tension; and in the present invention, by setting the middle plate of the connector, the connection will be connected during the test process. The middle plate 112 is connected with the jaws of the tensile testing machine, and the plate structure is used instead of the existing rod structure to connect with the jaws of the tensile testing machine, which not only improves the stability of the structure, but also effectively reduces the tensile testing process. The additional strain caused by the structure of the fixture has an adverse effect on the test results, which improves the accuracy of the tensile test results.

There are two main aspects of stress concentration in engineering tests, that is, the damage to the specimen material leads to the reduction of the effective stress surface, and the second is the stress concentration caused by the contact method between the fixture and the specimen; when there is point contact or line contact between the specimen and the fixture, both It is possible to generate local stress concentration; the present invention adopts the design of surface contact between the specimen and the fixture, and the clamping end of the concrete specimen and the curved surface of the curved surface fixing groove of the specimen clamping block are matched with each other, and the specimen adheres to the block. The curved surface fixing groove can completely wrap the clamping end of the specimen and fit each other, which can effectively solve the problem of damage to the specimen caused by the stress concentration generated by the fixture during the clamping process of the specimen.

Example

This embodiment provides a concrete uniaxial tensile test fixture, which includes two clamping bodies 1 with the same structure. The two clamping bodies 1 are respectively arranged at both ends of the concrete specimen 2, and the concrete specimen 2 is held by the clamping bodies 1. Fixed installation on the tensile testing machine.

The clamp body 1 includes a jaw connector 11 and a specimen holder 12. One end of the jaw connector 11 is connected with the jaws of the tensile testing machine, and the other end is connected with the specimen holder 12; the jaw connector 11 and the specimen holder 12 are connected by mortise and tenon; They are connected by surface contact and tight fit.

The jaw connector 11 includes a connector bottom plate 111 , a connector middle plate 112 and two sets of stiffeners 113 ; the connector middle plate 112 is vertically fixed on the connector bottom plate 111 to form a “⊥” structure as a jaw The main structure of the connector 11; the center plate 112 of the connector and the central axis of the concrete specimen 2 are arranged to coincide; A stiffened plate, two stiffened plates are vertically and parallelly arranged between the connecting piece bottom plate 111 and the connecting piece middle plate 112 , one end of the stiffening plate is fixedly connected to the connecting piece bottom plate 111 , and the other end is fixedly connected to the connecting piece 112 . At the connection between the middle plate 112 of the connector and the bottom plate 111 of the connector, the stress concentration of the fixture structure during the test is reduced by means of rounding.

The specimen holder 12 includes a first specimen holder 121, a second specimen holder 122, four sets of high-strength bolts 123 and nuts 124, and the first specimen holder 121 and the second specimen holder 122 are symmetrically arranged. Four horizontal bolt holes are evenly arranged on the first specimen clamping block 121 and the second specimen clamping block 122 , four groups of high-strength bolts 123 pass through the horizontal bolt holes, and nuts 124 are fixedly sleeved on the high-strength bolts 123 . At the end, the detachable and fixed connection between the first specimen clamping block 121 and the second specimen clamping block 122 is realized; the side wall of the first specimen clamping block 121 is provided with a first curved groove 125, and the second specimen clamping block 122 A second curved groove 126 is provided on the side wall of the 126 . The first curved groove 125 and the second curved groove 126 are matched and connected to form a curved fixed groove 127 . Coincidence; the clamping end of the concrete specimen 2 is embedded in the curved surface fixing groove 127; It adopts surface contact and tight fit connection;

In the present embodiment, the concrete specimen is a dumbbell-shaped specimen whose two ends are truncated. The concrete specimen 2 includes an upper clamping end 21, a middle test section 22 and a lower clamping end 23; the upper clamping end 21 and The lower clamping ends 23 are respectively arranged at both ends of the middle test section 22. The upper clamping end 21 and the lower clamping end 23 are both circular truncated structures with one large end and one small end. The upper clamping end 21 or the lower clamping end 23 are matched with each other. Set in the curved surface fixing groove, the outer wall of the upper clamping end 21 or the lower clamping end 23 is in close contact with the inner wall of the curved surface fixing groove, which reduces the stress concentration on the contact surface. The test piece is subjected to uniform uniaxial tension, so that the fracture surface is generated on the middle test section 22, thereby improving the test accuracy.

The jaw connector 11 is fixed on the tensile chuck of the common servo universal testing machine, and the jaw connector 11 and the specimen holder 12 are connected by matching tenon and mortise; the end of the connector base plate 111 is provided with a first In the tenon-and-mortise structure 114 , the end of the first specimen clamping block 121 or the second specimen clamping block 122 is provided with a second tenon-and-mortise structure 128 .

In this embodiment, the bottom plate 111 of the connector, the middle plate 112 of the connector, and the two sets of stiffeners 113 are all made of steel plates; the first clamp block 121 and the second clamp block 122 are square steel blocks .

In the concrete uniaxial tensile test method described in this embodiment, the uniaxial tensile test is carried out by clamping the concrete specimen on a common servo universal machine as follows:

The mixed concrete was cast according to the shape of the pre-designed concrete specimen, put into a standard concrete curing box for curing for 28 d, and then the concrete specimen was taken out for concrete tensile test. The two jaw connectors of the two clamping bodies are respectively fixed on the upper and lower stretching pliers of the ordinary servo universal machine by clamping the stretching jaws of the ordinary servo universal machine on the connecting piece middle plate of the jaw connecting piece. The upper clamping end of the concrete specimen is assembled in the two specimen clamping blocks, and four high-strength bolts are horizontally inserted into the four bolt holes of the two specimen clamping blocks, and the upper clamping end of the concrete specimen is subjected to Position and fix, and fasten the connection with nuts; assemble the lower clamping end of the concrete specimen in the other two specimen clamping blocks, and use four high-strength bolts to horizontally insert the four bolt holes of the two specimen clamping blocks In the middle, the lower clamping end of the concrete specimen is positioned and fixed, and is fastened and connected by nuts; the two specimen clamping blocks on the upper and lower clamping ends are respectively connected by the tenon-and-mortise structure and the matching jaws. The pieces are securely attached by sliding in. Adjust the distance between the upper and lower tension clamps of the ordinary servo universal machine, so that the outer wall surface of the clamping end of the concrete specimen and the inner wall surface of the specimen clamping piece are in contact with each other. At this point, the installation process of the specimen and the fixture is completed; then start the ordinary servo universal machine. To carry out the tensile test, the tensile forceps of the ordinary servo universal machine will transmit the tensile force to the curved surfaces of the two clamping ends of the concrete specimen through the jaw connector and the specimen holder. The segment axial force is the resultant external force on the upper and lower clamping ends.

In this embodiment, during the whole test process, the outer wall surface of the upper and lower clamping ends of the concrete specimen is closely fitted with the inner wall surface of the specimen clamping part, and the method of applying uniform surface force is used to replace the traditional method of applying uniform surface force on the upper and lower clamping ends of the concrete specimen. The point force application method can minimize the local stress concentration caused by the contact between the concrete specimen and the fixture, so that the damage of the concrete specimen at the root is reduced and the fracture surface occurs in the middle test section of the concrete specimen. . At the same time, in the connection method with the servo universal machine tensile forceps, the middle plate structure of the connector is used to avoid the use of rod structure in the fixture design, so that the strength test, especially in the tensile test, eliminates the need for rods. The additional strain generated by the structure makes it possible to use this fixture not only to measure the tensile strength of the concrete specimen, but also to accurately obtain the stress-strain relationship of the concrete specimen in the tensile test, which provides a basis for related theoretical research. an effective test method. In this implementation, the tenon-and-mortise structure is adopted, which can effectively limit the torsion generated during the stretching process, and the fixture installation and disassembly is simple and quick; the invention purpose of accurately measuring the tensile test data of the concrete specimen can be achieved, and the operation The process is simple, which can greatly improve the test work efficiency and reduce the test cost.

Obviously, the above-mentioned embodiment is only one of the embodiments that can realize the technical solution of the present invention, and the scope of protection claimed in the present invention is not only limited by this embodiment, but also included in the technical scope disclosed in the present invention. Variations, substitutions, and other implementations will readily occur to those skilled in the art.

Claims (9)

1. The clamp for the uniaxial concrete tensile test is characterized by comprising two clamp bodies (1) with the same structure, wherein the two clamp bodies (1) are respectively arranged at two ends of a concrete test piece (2), and the concrete test piece (2) is fixedly arranged on a tensile testing machine through the clamp bodies (1);

the clamp body (1) comprises a jaw connecting piece (11) and a test piece clamping piece (12), one end of the jaw connecting piece (11) is connected with a jaw of the tensile testing machine in a matched mode, and the other end of the jaw connecting piece is connected with the test piece clamping piece (12); the jaw connecting piece (11) and the test piece clamping piece (12) are connected through mortise and tenon joints; the clamping end of the concrete test piece (2) is embedded into the test piece clamping piece (12), and the clamping end of the concrete test piece (2) is in close fit connection with the test piece clamping piece (12) through surface contact.

2. The concrete uniaxial tension test fixture as claimed in claim 1, wherein the jaw connector (11) comprises a connector bottom plate (111) and a connector middle plate (112);

one side of the connecting piece bottom plate (111) is connected with the test piece clamping piece (12), the connecting piece bottom plate (111) is uniformly provided with first tenon-and-mortise structures (114), and the first tenon-and-mortise structures (114) are matched and fixedly connected with the test piece clamping piece (12); the other side of the connecting piece bottom plate (111) is connected with the connecting piece middle plate (112), one end of the connecting piece middle plate (112) is vertically and fixedly connected with the middle part of the connecting piece bottom plate (111), and the other end of the connecting piece middle plate is matched and connected with a jaw of the tensile testing machine.

3. The concrete uniaxial tension test fixture as claimed in claim 2, wherein the jaw connector (111) further comprises two groups of reinforcement bodies (113), and the two groups of reinforcement bodies (113) are symmetrically arranged at two sides of the connector neutral plate (112); each group of the reinforcing rib bodies (113) comprises two reinforcing rib plates, the two reinforcing rib plates are vertically arranged between the connecting piece bottom plate (111) and the connecting piece middle plate (112) in parallel, one ends of the reinforcing rib plates are fixedly connected with the connecting piece bottom plate (111), and the other ends of the reinforcing rib plates are fixedly connected with the connecting piece (112).

4. The concrete uniaxial tension test fixture as recited in claim 2, characterized in that the connecting part of the connecting piece neutral plate (112) and the connecting piece bottom plate (111) is arranged by a fillet.

5. The concrete uniaxial tension test fixture as recited in claim 2, wherein the connecting piece bottom plate (111) and the connecting piece neutral plate (112) are of an integral structure.

6. The concrete uniaxial tension test fixture as recited in claim 1, characterized in that the test piece clamping piece (12) comprises a first test piece clamping block (121) and a second test piece clamping block (122) which are symmetrically arranged, and the first test piece clamping block (121) and the second test piece clamping block (122) are detachably connected;

a first curved surface groove is formed in the side edge of the first test piece clamping block (121), a second curved surface groove is formed in the side edge of the second test piece clamping block (122), and the first curved surface groove and the second curved surface groove are connected in a matched mode to form a curved surface fixing groove; the clamping end of the concrete test piece (2) is embedded in the curved surface fixing groove, and the clamping end of the concrete test piece (2) is in close fit connection with the curved surface fixing groove in a surface contact manner;

the end parts of the first test piece clamping block (121) and the second test piece clamping block (122) are uniformly provided with second mortise and tenon structures (128), and the second mortise and tenon structures (128) are detachably and fixedly connected with the jaw connecting piece (1).

7. The concrete uniaxial tension test fixture of claim 6, wherein the curved surface fixing groove is a truncated cone-shaped cavity structure with a large end and a small end;

the concrete test piece (2) comprises an upper clamping end (21), a middle test section (22) and a lower clamping end (23); go up exposed core (21) and lower exposed core (23) and set up respectively at the both ends of middle part test section (22), go up exposed core (21) and exposed core (23) down and be the round platform type structure that one end is big one end is little, go up exposed core (21) or exposed core (23) cooperation setting down in the curved surface fixed slot, go up exposed core (21) or the outer wall in exposed core (23) and the inner wall in curved surface fixed slot in close contact with down.

8. The concrete uniaxial tension test fixture as recited in claim 6, characterized in that the test piece clamping piece (12) further comprises a fastener, the fastener is horizontally arranged in the first test piece clamping block (121) and the second test piece clamping block (122) in a penetrating manner, and the first test piece clamping block (121) and the second test piece clamping block (122) are fixedly connected together through the fastener;

the fastener comprises a high-strength bolt (123) and a nut (124), the high-strength bolt (123) sequentially and horizontally penetrates through the first test piece clamping block (121) and the second test piece clamping block (122), the nut (124) is sleeved at the end of the high-strength bolt (123), and the nut (124) is in threaded connection with the high-strength bolt (123).

9. A concrete uniaxial tension test method, which is characterized in that the concrete uniaxial tension test fixture of any one of claims 1-8 is used, and the concrete uniaxial tension test fixture comprises the following concrete steps:

firstly, manufacturing a concrete sample (2) according to test requirements; then embedding two ends of the concrete test piece (2) into the two test piece clamping pieces (12), installing a jaw connecting piece (11) at the end part of each test piece clamping piece (12), and connecting the jaw connecting piece (11) and the test piece clamping pieces (12) in a mortise-tenon manner; then fixedly installing a jaw connecting piece (11) at a jaw of a tensile testing machine, and adjusting the distance between two chucks of the tensile testing machine to ensure that the clamping end of the concrete test piece (2) is in close fit connection with the test piece clamping piece (12) by adopting surface contact; and starting a tensile testing machine to perform a concrete uniaxial tensile test.

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