CN111413203A - Concrete uniaxial tension test fixture and test method - Google Patents

Concrete uniaxial tension test fixture and test method Download PDF

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Publication number
CN111413203A
CN111413203A CN202010346215.4A CN202010346215A CN111413203A CN 111413203 A CN111413203 A CN 111413203A CN 202010346215 A CN202010346215 A CN 202010346215A CN 111413203 A CN111413203 A CN 111413203A
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China
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test
piece
test piece
concrete
clamping
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姚尧
鲁昊
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Xian University of Architecture and Technology
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Xian University of Architecture and Technology
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Priority to CN202010346215.4A priority Critical patent/CN111413203A/en
Publication of CN111413203A publication Critical patent/CN111413203A/en
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N3/00Investigating strength properties of solid materials by application of mechanical stress
    • G01N3/08Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N3/00Investigating strength properties of solid materials by application of mechanical stress
    • G01N3/02Details
    • G01N3/04Chucks

Abstract

The invention discloses a concrete uniaxial tensile test fixture and a test method, which comprise two fixture bodies with the same structure, wherein each fixture body comprises a jaw connecting piece and a test piece clamping piece; the jaw connecting piece and the test piece clamping piece are connected through mortise and tenon joints; the clamping end of the concrete test piece is embedded in the test piece clamping piece, and the clamping end of the concrete test piece and the test piece clamping piece are in close fit connection by adopting surface contact; according to the invention, the clamping end of the concrete test piece is in surface contact fit connection with the test piece clamping piece, so that local stress concentration is effectively eliminated, the damage of the test piece is reduced, the tensile fracture surface of the concrete test piece is ensured to be generated in the middle of the test piece, and the positive promotion effect on improving the test precision is achieved; the jaw connecting piece and the test piece clamping piece are connected in a mortise-tenon mode, so that the stability of the structure is improved, the mounting and dismounting are simple, and the efficiency and the measurement precision of a tensile test are effectively improved.

Description

Concrete uniaxial tension test fixture and test method
Technical Field
The invention belongs to the technical field of concrete tests, and particularly relates to a clamp and a test method for a concrete uniaxial tensile test.
Background
Concrete materials are the most widely used materials in the current building engineering, and the strength of concrete members needs to be tested through test means. Tensile properties are important mechanical properties of concrete materials, and the tensile strength can be obtained by uniaxial tensile test.
At present, the concrete tensile property test methods mainly comprise three methods: split pull test, straight pull test and bend pull test. The test data measured by the direct tensile test is the most accurate, and the tensile strength and the strain change of the concrete can be most directly reflected, so that the stress-strain relation of the concrete material is obtained. However, due to the natural brittleness of the concrete material, the selection of the clamp and the way of clamping the test piece and the clamp in the uniaxial tensile test become critical to the accuracy and success rate of the test.
In a direct tensile test, the existing test piece clamping modes mainly comprise a sticky steel type, a three-point type, a soft contact type and a hard contact type; the steel-bonding mode is that two end faces of a concrete sample are bonded with a tensile shaft through a bonding agent, and the bonding agent adopts epoxy resin-based steel-bonding glue; the disadvantages are as follows: the epoxy resin bonding method needs to melt the epoxy resin, is harmful to human bodies and pollutes the environment; the three-point type is that the tightness of clamping a test piece is realized by the rotation of bolts through three bolt holes arranged on a cylindrical shell; the disadvantages are as follows: force applied by three bolt action points and the length of a screwed bolt cannot be quantized, so that eccentricity and stress concentration at the end part of a test piece are easily caused; the soft contact type is characterized in that an elastic sheet is attached to a contact surface of a clamp and a test piece in a lining mode, although the design has a certain effect on preventing stress concentration, when the stress-strain relation of concrete is researched, the strain of the elastic sheet causes huge errors to a test result, and the method cannot meet the requirement of concrete constitutive research; hard contact is through two bolts centre gripping concrete sample, its shortcoming: stress concentration is easily caused, the end part of the test piece is broken, the tensile failure surface is difficult to occur in the middle of the test piece, and the tensile test error is easily caused to be overlarge due to the bending deformation of the bolt in the tensile process.
In the aspect of matched connection of the clamp and a common servo universal machine, the metal rod system is mostly adopted for connection in the prior art, and the defects are as follows: when the direction of the metal rod structure is parallel to the axial stretching direction, the metal rod structure generates non-negligible strain under the action of axial force, and the generation of the additional strain can generate great influence on the stress-strain relation during the research of concrete stretching, so that the accuracy of the measured test data is lost.
Disclosure of Invention
Aiming at the technical problems in the prior art, the invention provides a clamp for a concrete uniaxial tensile test and a test method, and aims to solve the technical problem that the tensile test fails due to the fact that the root of a concrete test piece is easy to break or the contact part of the concrete test piece and the clamp generates a creep failure phenomenon because of non-negligible stress concentration between the concrete test piece and the clamp in the prior art.
In order to achieve the purpose, the invention adopts the technical scheme that:
the invention provides a concrete uniaxial tensile test fixture which comprises two fixture bodies with the same structure, wherein the two fixture bodies are respectively arranged at two ends of a concrete test piece, and the concrete test piece is fixedly arranged on a tensile testing machine through the fixture bodies;
the clamp body comprises a jaw connecting piece and a test piece clamping piece, one end of the jaw connecting piece is connected with a jaw of the tensile testing machine in a matching way, and the other end of the jaw connecting piece is connected with the test piece clamping piece; the jaw connecting piece and the test piece clamping piece are connected through mortise and tenon joints; the clamping end of the concrete test piece is embedded into the test piece clamping piece, and the clamping end of the concrete test piece is in close fit connection with the test piece clamping piece through surface contact.
Further, the jaw connecting piece comprises a connecting piece bottom plate and a connecting piece middle plate; one side of the connecting piece bottom plate is connected with the test piece clamping piece, and the connecting piece bottom plate is uniformly provided with a first tenon-and-mortise structure which is matched and fixedly connected with the test piece clamping piece through the first tenon-and-mortise structure; the other side of the connecting piece bottom plate is connected with the connecting piece middle plate, one end of the connecting piece middle plate is vertically and fixedly connected with the middle part of the connecting piece bottom plate, and the other end of the connecting piece middle plate is matched and connected with a jaw of the tensile testing machine.
Furthermore, the jaw connecting piece also comprises two groups of reinforcement bodies which are symmetrically arranged at two sides of the middle plate of the connecting piece; each group of the reinforced bodies comprises two reinforced plates, the two reinforced plates are vertically arranged between the connecting piece bottom plate and the connecting piece middle plate in parallel, one end of each reinforced plate is fixedly connected with the connecting piece bottom plate, and the other end of each reinforced plate is fixedly connected with the connecting piece.
Furthermore, the connecting part of the connecting piece middle plate and the connecting piece bottom plate is arranged by adopting a guide circular angle.
Furthermore, the connecting piece bottom plate and the connecting piece middle plate adopt an integrated structure.
Further, the test piece clamping piece comprises a first test piece clamping block and a second test piece clamping block which are symmetrically arranged, and the first test piece clamping block is detachably connected with the second test piece clamping block;
the side edge of the first test piece clamping block is provided with a first curved surface groove, the side edge of the second test piece clamping block is provided with a second curved surface groove, and the first curved surface groove and the second curved surface groove are matched and connected to form a curved surface fixing groove; the clamping end of the concrete sample is embedded in the curved surface fixing groove, and the clamping end of the concrete sample 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 and the second test piece clamping block are uniformly provided with second tenon-and-mortise structures, and the second tenon-and-mortise structures are detachably and fixedly connected with the jaw connecting piece.
Furthermore, the curved surface fixing groove is a circular truncated cone-shaped cavity structure with a large end and a small end;
the concrete test piece comprises an upper clamping end, a middle test section and a lower clamping end; go up the exposed core and the exposed core sets up respectively at the both ends of middle part test section, go up exposed core and exposed core down and be the round platform type structure that one end is big one end is little, go up exposed core or the exposed core cooperation setting down in the curved surface fixed slot, go up the exposed core of exposed core or the outer wall in exposed core and the inner wall in contact with in curved surface fixed slot down.
The test piece clamping piece further comprises a fastening piece, the fastening piece horizontally penetrates through the first test piece clamping block and the second test piece clamping block, and the first test piece clamping block and the second test piece clamping block are fixedly connected together through the fastening piece;
the fastener comprises a high-strength bolt and a nut, the high-strength bolt sequentially and horizontally penetrates through the first test piece clamping block and the second test piece clamping block, the nut is sleeved at the end of the high-strength bolt, and the nut is in threaded connection with the high-strength bolt.
The invention also provides a concrete uniaxial tension test method, which utilizes the concrete uniaxial tension test clamp and comprises the following concrete steps:
firstly, manufacturing a concrete sample according to test requirements; then, two ends of the concrete test piece are respectively embedded into the two test piece clamping pieces, a jaw connecting piece is arranged at the end part of each test piece clamping piece, and the jaw connecting pieces and the test piece clamping pieces are connected in a mortise-tenon mode; then fixedly installing the jaw connecting piece at the jaw of the 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 is in close fit connection with the test piece clamping piece by adopting surface contact; and starting a tensile testing machine to perform a concrete uniaxial tensile test.
Compared with the prior art, the invention has the beneficial effects that:
the invention provides a concrete uniaxial tensile test fixture, which is characterized in that a test piece clamping piece is arranged, and a clamping end of a concrete test piece is in surface contact fit connection with the test piece clamping piece, so that local stress concentration is effectively eliminated, the damage of the concrete test piece caused by the stress concentration is reduced, the reliability and the stability of the test process are improved, the tensile fracture surface of the concrete test piece is ensured to be generated in the middle of the test piece, and the positive promotion effect on improving the test precision is achieved; the jaw connecting piece is connected between the test piece clamping pieces through the mortise and tenon joint, the complexity of the structure is reduced, the stability of the structure is improved, the installation and the disassembly are simple, and the measurement precision of a tensile test is effectively improved.
Furthermore, the jaw connecting piece adopts the connecting piece bottom plate and the combination of the connecting piece neutral plate, and through setting up the connecting piece neutral plate, the jaw connecting piece adopts the plate structure to replace the existing rod structure and tensile testing machine is connected, thereby not only improving the stability of the structure, but also effectively reducing the adverse effect on the test result caused by the additional strain generated by the clamp structure, and improving the accuracy of the tensile test result.
Furthermore, the reinforcing plates are arranged on the two sides of the middle plate of the connecting piece, so that the structural strength of the jaw connecting piece is effectively improved, and the phenomenon of structural failure in the test process is prevented.
Furthermore, the connecting part between the connecting piece middle plate and the connecting piece bottom plate is connected in a fillet mode, so that stress concentration is effectively dispersed, and the reliability of the jaw connecting piece is improved.
Furthermore, the connecting piece middle plate and the connecting piece bottom plate are of an integrated structure, so that the strength and stability of the structure are improved, and the accuracy of a test result is ensured.
Furthermore, the test piece clamping piece is matched and connected by adopting two symmetrically arranged test piece clamping blocks, so that the concrete test piece and the test piece clamping piece are convenient to disassemble and assemble, the operation is convenient, and the test efficiency is improved; the two test piece clamping blocks are matched to form a curved surface fixing groove, the clamping end of the concrete test piece is in close fit connection with the curved surface fixing groove in a surface contact mode, the effect of local stress concentration is effectively eliminated, and damage to the end portion of the concrete test piece due to stress concentration is reduced.
Furthermore, the clamping end and the curved surface fixing groove of the concrete test piece are set to be of a structure with one large end and one small end, so that the reliability of connection between the concrete test piece and the curved surface fixing groove is ensured, the contact area between the concrete test piece and the curved surface fixing groove is increased, local stress concentration is eliminated, and meanwhile, the clamping acting force of the test piece clamping piece is effectively increased.
Furthermore, the two test piece clamping blocks are connected through high-strength bolts, so that the stability of the structure is ensured, and the concrete test piece is convenient to install and remove.
The invention also provides a concrete uniaxial tensile test method, which has simple test operation steps, simple mounting and dismounting processes between the concrete test piece and the test piece clamping piece, between the test piece clamping piece and the jaw connecting piece and between the jaw connecting piece and the tensile testing machine, high reliability and effectively improved measurement precision of the uniaxial tensile test.
In conclusion, the concrete uniaxial tensile test fixture and the test method can realize accurate measurement of tensile test data of a concrete sample, are convenient to clamp and have simple structures; the invention can be directly used on a servo universal testing machine with a common model to carry out concrete uniaxial tension test, can reduce local stress concentration generated in the tension test process to the maximum extent and eliminate additional strain generated by the clamp in the tension process, so that the concrete test piece is uniformly stressed in the tension process, thereby improving the accuracy of a tension test database and making up the vacancy and the deficiency in the prior art.
Drawings
FIG. 1 is a schematic perspective view of a concrete uniaxial tension test fixture according to the present invention;
FIG. 2 is a perspective view of a concrete uniaxial tension test fixture according to the present invention;
FIG. 3 is a top view of a concrete uniaxial tension test fixture according to the present invention;
FIG. 4 is a cross-sectional view of the A-A side of a concrete uniaxial tension test fixture according to the present invention;
FIG. 5 is a schematic structural view of a jaw connector in a concrete uniaxial tension test fixture according to the present invention;
FIG. 6 is a schematic structural view of a test piece clamping member in the concrete uniaxial tensile test fixture according to the present invention;
FIG. 7 is a schematic structural view of a test piece clamping block in the concrete uniaxial tensile test fixture according to the present invention;
FIG. 8 is a schematic view of a three-dimensional structure of a test piece in the fixture for uniaxial concrete tensile test according to the present invention;
FIG. 9 is a cross-sectional view of a test piece in a fixture for uniaxial concrete tensile test according to the present invention;
FIG. 10 is a perspective view of an assembled structure of a concrete uniaxial tension test fixture according to the present invention;
FIG. 11 is a front view of an assembly structure of the concrete uniaxial tension test fixture of the invention.
Wherein, 1, the fixture body, 2 concrete test pieces; 11 jaw connecting pieces and 12 test piece clamping pieces; the structure comprises a 111 connecting piece bottom plate, a 112 connecting piece middle plate, a 113 reinforcing body and a 114 first tenon-and-mortise structure; 121, a first test piece clamping block, 122 a second test piece clamping block, 123 high-strength bolts, 124 nuts, 125 a first curved surface groove, 126 a second curved surface groove, 127 a curved surface fixing groove and 128 a second mortise and tenon structure; 21 upper clamping end, 22 middle test section and 23 lower clamping end.
Detailed Description
In order to make the technical problems, technical solutions and advantageous effects of the present invention more apparent, the following geometric drawings and embodiments are further described in detail. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
As shown in the accompanying drawings 1-11, the invention provides a concrete uniaxial tensile test fixture, which comprises two fixture bodies 1 with the same structure, wherein the two fixture 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 fixture 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 matching way, 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 sample 2 is embedded in the sample clamping piece 12, and the clamping end of the concrete sample 2 is in close fit connection with the sample clamping piece 12 through surface contact.
The jaw connecting piece 11 comprises a connecting piece bottom plate 111, a connecting piece middle plate 112 and two groups of reinforcing bodies 113; one side of the connecting piece bottom plate 111 is connected with the test piece clamping piece 12, and 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 neutral plate 112 is vertically and fixedly connected with the middle part of the connecting piece bottom plate 111, and the other end is matched and connected with a jaw of the tensile testing machine; through setting up connecting piece neutral plate 112, be connected connecting piece neutral plate 112 and tensile test machine's keeping silent in the testing process, adopt the plate structure to replace current rod structure and tensile test machine's keeping silent to be connected, not only improved the stability of structure, still effectively reduced the tensile test in-process, because of the additional strain that the anchor clamps structure produced is to the adverse effect that the test result led to the fact, improved the accuracy of tensile test result.
The two groups of reinforcing bodies 113 are symmetrically arranged on two sides of the connecting piece neutral plate 112, each group of reinforcing bodies 113 comprises two reinforcing plates which are vertically arranged between the connecting piece bottom plate 111 and the connecting piece neutral plate 112 in parallel, one end of each reinforcing plate is fixedly connected with the connecting piece bottom plate 111, and the other end of each reinforcing plate is fixedly connected with the connecting piece 112; the reinforcing plates are arranged on the two sides of the connecting piece middle plate 112, so that the structural strength of the jaw connecting piece 11 is effectively improved, and structural failure and deformation in the test process are avoided.
Preferably, the connecting part of the connecting piece neutral plate 112 and the connecting piece bottom plate 111 is arranged by a rounded corner, and the connecting part between the connecting piece neutral plate 112 and the connecting piece bottom plate 111 is connected by a rounded corner, so that stress concentration is effectively dispersed, and the reliability of the jaw connecting piece is improved. .
Preferably, the connecting piece bottom plate 111 and the connecting piece middle plate 112 adopt an integrated structure; through adopting the integral type structure with connecting piece median plate and connecting piece bottom plate, improved the intensity and the stability of structure, ensured the accuracy of test result.
The test piece clamping piece 12 comprises a first test piece clamping block 121, a second test piece clamping block 122 and a fastener, the first test piece clamping block 121 and the second test piece clamping block 122 are symmetrically arranged, and the first test piece clamping block 121 and the second test piece clamping block 122 are detachably connected through the fastener; the test piece clamping piece adopts the test piece clamping blocks which are symmetrically arranged to be matched and connected, so that the concrete test piece 2 and the test piece clamping piece 12 can be conveniently disassembled and assembled, the operation is convenient, and the test efficiency is improved. The fastener horizontally penetrates through the first test piece clamping block 121 and the second test piece clamping block 122, 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.
The connecting piece bottom plate 111 is uniformly provided with first tenon-and-mortise structures 114, and the first tenon-and-mortise structures 114 on the connecting piece bottom plate 111 are arranged at the contact end with the test piece clamping piece 12; 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 on the first test piece clamping block 121 or the second test piece clamping block 122 are arranged at the contact end with the connecting piece bottom plate 111; first tenon fourth of twelve earthly branches structure 114 and second tenon fourth of twelve earthly branches structure 128 cooperation are connected, have realized keeping silent the connecting piece 11 and have been connected with the cooperation between the test piece holder 12, adopt tenon fourth of twelve earthly branches to be connected between keeping silent the connecting piece 11 and the test piece holder 12, have optimized the complexity of anchor clamps structure, have improved the stability of structure, and operating procedure is few in the use, and the installation is simple with the dismantlement, has effectively improved tensile test's measurement accuracy.
The side wall of the first test piece clamping block 121 is provided with a first curved surface groove, the side wall of the second test piece clamping block 122 is provided with a second curved surface groove, and the first curved surface groove and the second curved surface groove are matched and connected to form a curved surface fixing groove; the clamping end of the concrete sample 2 is embedded in the curved surface fixing groove; preferably, the curved surface fixing groove is a circular truncated cone-shaped cavity structure with a large end and a small end, and the clamping end of the concrete sample 2 is in close fit connection with the curved surface fixing groove in a surface contact manner;
the concrete sample 2 comprises an upper clamping end 21, a middle test section 22 and a lower clamping end 23; go up exposed core 21 and 23 and set up respectively at the both ends of middle part test section 22, go up exposed core 21 and 23 and be the round platform type structure that one end is big one end is little down exposed core, go up exposed core 21 or 23 cooperation settings of exposed core down in the curved surface fixed slot, go up exposed core 21 or 23 outer wall of exposed core and the inner wall in curved surface fixed slot in close contact with down.
The invention also provides a concrete uniaxial tension test method, which comprises the following specific steps:
firstly, manufacturing a concrete sample 2 according to test requirements; then, two ends of the concrete sample 2 are respectively embedded into the two sample clamping pieces 12, a jaw connecting piece 11 is arranged at the end part of each sample clamping piece 12, and the jaw connecting pieces 11 and the sample clamping pieces 12 are connected 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 sample 2 is in close fit connection with the sample clamping piece 12 by adopting surface contact; and starting a tensile testing machine to perform a concrete uniaxial tensile test.
The concrete uniaxial tensile test fixture has the advantages that damage caused by stress concentration is reduced at the clamping end of a concrete sample in the test clamping process, errors caused by the structure of the test fixture can be reduced or even eliminated, and the concrete uniaxial tensile test fixture has great significance for accurately measuring the result of a concrete material uniaxial tensile test; the tensile test fixture disclosed by the invention is convenient to clamp and simple in structure, can be directly used for a servo universal testing machine of a common model to carry out a concrete uniaxial tensile test, can reduce local stress concentration generated in the test process to the maximum extent and eliminate additional strain generated by the fixture in the tensile process, so that a test piece is uniformly stressed in the tensile process, the accuracy of a tensile test database is improved, and the vacancy and the deficiency in the prior art are made up; concrete is used as a special brittle material, the clamping method in the traditional tensile test can generate non-negligible stress concentration at the jaw position of a concrete test piece and a clamp, which can cause the concrete material to be damaged in the early stage of the test, further cause the root part of the test piece to be broken in the test, or cause the creep damage on the contact part of the test piece and the jaw of the clamp, and finally cause the test to fail or lose the result of the test accuracy; in addition, most of the clamps adopted in the existing concrete uniaxial tension test adopt a metal rod structure, when the direction of the metal rod structure is parallel to the axial tension direction, the metal rod structure can generate non-negligible strain under the action of axial force, and the additional strain generation can generate great influence on the stress-strain relation during the concrete tension research; in the invention, the connecting piece neutral plate 112 is connected with the jaw of the tensile testing machine in the testing process by arranging the connecting piece neutral plate, and the plate structure is adopted to replace the existing rod structure to be connected with the jaw of the tensile testing machine, so that the stability of the structure is improved, the adverse effect on the testing result caused by the additional strain generated by the clamp structure in the tensile testing process is effectively reduced, and the accuracy of the tensile testing result is improved.
Stress concentration in an engineering test mainly has two aspects, namely that the effective stress surface is reduced due to damage of a test piece material, and stress concentration is caused by a contact mode of a clamp and the test piece; when the test piece is in point contact or line contact with the clamp, local stress concentration is possibly generated; the test piece and the clamp are designed to be in surface contact, the clamping end of the concrete test piece is matched with the curved surface of the curved surface fixing groove of the test piece clamping block, the curved surface fixing groove of the test piece holding block can completely wrap the test piece clamping end and is mutually attached, and the problem that the test piece is damaged due to stress concentration generated by the clamp in the test piece clamping process can be effectively solved.
Examples
The embodiment provides a concrete uniaxial tensile test anchor clamps, including two anchor clamps bodies 1 that the structure is the same, two anchor clamps bodies 1 set up respectively at the both ends of concrete sample 2, through anchor clamps bodies 1 with concrete sample 2 fixed mounting on tensile testing machine.
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 matching way, 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 sample 2 is embedded in the sample clamping piece 12, and the clamping end of the concrete sample 2 is in close fit connection with the sample clamping piece 12 through surface contact.
The jaw connecting piece 11 comprises a connecting piece bottom plate 111, a connecting piece middle plate 112 and two groups of reinforcing bodies 113, wherein the connecting piece middle plate 112 is vertically and fixedly arranged on the connecting piece bottom plate 111 to form an ⊥ structure and serves as a main body structure of the jaw connecting piece 11, the connecting piece middle plate 112 is arranged in a mode of being overlapped with a central axis of the concrete sample 2, the two groups of reinforcing bodies 113 are respectively arranged on two sides of the connecting piece middle plate 112, each group of reinforcing bodies 113 comprises two reinforcing plates, the two reinforcing plates are vertically and parallelly arranged between the connecting piece bottom plate 111 and the connecting piece middle plate 112, one ends of the reinforcing plates are fixedly connected with the connecting piece bottom plate 111, the other ends of the reinforcing plates are fixedly connected with the connecting piece 112, and stress concentration of a clamp structure in a test process is reduced at the connecting position of the connecting piece middle plate 112 and.
The test piece clamping piece 12 comprises a first test piece clamping block 121, a second test piece clamping block 122, four groups of high-strength bolts 123 and nuts 124, the first test piece clamping block 121 and the second test piece clamping block 122 are symmetrically arranged, four horizontal bolt holes are uniformly formed in the first test piece clamping block 121 and the second test piece clamping block 122 respectively, the four groups of high-strength bolts 123 penetrate through the horizontal bolt holes, and nuts 124 are fixedly sleeved at the end parts of the high-strength bolts 123 to realize the detachable fixed connection of the first test piece clamping block 121 and the second test piece clamping block 122; the side wall of the first test piece clamping block 121 is provided with a first curved surface groove 125, the side wall of the second test piece clamping block 122 is provided with a second curved surface groove 126, the first curved surface groove 125 and the second curved surface groove 126 are matched and connected to form a curved surface fixing groove 127, and the central axis of the curved surface fixing groove 127 is vertically arranged and is overlapped with the central axis of the concrete test piece 2; the clamping end of the concrete sample 2 is embedded in the curved surface fixing groove 127; the curved surface fixing groove 127 is a circular truncated cone-shaped cavity structure with a large end and a small end, and the clamping end of the concrete sample 2 is in close fit connection with the curved surface fixing groove 127 by surface contact;
in the embodiment, the concrete test piece is a dumbbell-shaped test piece with two truncated cone-shaped ends, and 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 clamping end 23 and set up respectively at the both ends of middle part test section 22 down, it is the little round platform type structure of the big one end of one end to go up exposed core 21 and clamping end 23 down, it sets up in the curved surface fixed slot to go up exposed core 21 or clamping end 23 cooperation down, the outer wall of exposed core 21 or clamping end 23 down and the inner wall in close contact with of curved surface fixed slot, the stress concentration of contact surface has been reduced, learn to make the test piece receive even unipolar pulling force at tensile test in-process according to the atress analysis, make the fracture surface produce on middle part test section 22, thereby improve experimental precision.
The jaw connecting piece 11 is fixed on a tensile chuck of a common servo universal testing machine, and the jaw connecting piece 11 is connected with the test piece clamping piece 12 through matched mortise and tenon joints; the end of the connecting piece bottom plate 111 is provided with a first mortise and tenon structure 114, the end of the first test piece clamping block 121 or the end of the second test piece clamping block 122 is provided with a second mortise and tenon structure 128, and the first mortise and tenon structure 114 is connected with the second mortise and tenon structure 128 in a matched manner.
In this embodiment, the connecting member bottom plate 111, the connecting member middle plate 112, and the two sets of reinforcement bodies 113 are made of steel plates; the first test piece clamping block 121 and the second test piece clamping block 122 are both square steel blocks.
In the concrete uniaxial tension test method of this embodiment, a concrete sample is clamped on a common servo universal machine to perform a uniaxial tension test in the following manner:
and (3) performing injection molding on the stirred concrete according to the shape of a pre-designed concrete sample, putting the concrete sample into a standard concrete curing box for curing for 28d, and taking out the concrete sample for a concrete tensile test. The two jaw connecting pieces of the two clamp bodies are respectively fixed on the upper and lower stretching pliers of the common servo universal machine. Assembling the upper clamping end of the concrete test piece in two test piece clamping blocks, horizontally inserting four high-strength bolts into four bolt holes of the two test piece clamping blocks, positioning and fixing the upper clamping end of the concrete test piece, and fastening and connecting the upper clamping end of the concrete test piece through nuts; assembling the lower clamping end of the concrete test piece in the other two test piece clamping blocks, horizontally inserting four high-strength bolts into four bolt holes of the two test piece clamping blocks, positioning and fixing the lower clamping end of the concrete test piece, and fastening and connecting the lower clamping end of the concrete test piece through nuts; and the two test piece clamping blocks on the upper clamping end and the lower clamping end are fixedly connected in a sliding-in mode through the mortise and tenon joint structure and the jaw connecting piece matched with the mortise and tenon joint structure. Adjusting the distance between an upper drawing clamp and a lower drawing clamp of a common servo universal machine to enable the outer wall curved surface of the clamping end of the concrete test piece and the inner wall curved surface of the test piece clamping piece to be mutually attached until the installation process of the test piece and the clamp is finished; and then starting a common servo universal machine to carry out a tensile test, wherein the tensile clamp of the common servo universal machine transmits tensile force to the curved surfaces of the two clamping ends of the concrete test piece through the jaw connecting piece and the test piece clamping piece, and the axial force of the middle test section is the combined external force applied to the upper and lower clamping ends through stress analysis.
This embodiment is at whole test process, and the outer wall curved surface of the upper and lower exposed core of concrete sample closely laminates with the inner wall curved surface of test piece holder, and the mode of applying the uniform surface power replaces the mode of applying of traditional point power at the upper and lower exposed core of concrete sample, and the local stress that can furthest reduction concrete sample and anchor clamps produced because of the contact concentrates for the damage of concrete sample at the root reduces and makes the fracture surface take place at the middle part test section department of concrete sample. Meanwhile, the connecting piece middle-position plate structure is adopted to be connected in the connecting mode of the universal servo machine stretching pliers, the rod system structure is prevented from being used in the design of the clamp, and therefore in the strength test, particularly in the stretching test, the additional strain generated by the rod system structure is eliminated, the clamp can be used for measuring the tensile strength of the concrete test piece, meanwhile, the stress-strain relation of the concrete test piece in the stretching test can be accurately obtained, and an effective test means is provided for relevant theoretical research. In the implementation, the mortise and tenon type structure is adopted, so that the twisting generated in the stretching process can be effectively limited, and the clamp is simple and quick to mount and dismount; the invention can realize the aim of accurately measuring the tensile test data of the concrete test piece, has simple operation process, and can greatly improve the test working efficiency and reduce the test cost.
It should be understood that the above-described embodiments are only one of the embodiments that can implement the technical solution of the present invention, and the scope of the present invention is not limited by the embodiments, but includes any variations, substitutions and other embodiments that can be easily conceived by those skilled in the art within the technical scope of the present invention disclosed.

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.
CN202010346215.4A 2020-04-27 2020-04-27 Concrete uniaxial tension test fixture and test method Pending CN111413203A (en)

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