A device for measuring small circumferential strain of a concrete cylinder specimen

Abstract

The present application relates to the technical fields of strain measurement, in particular to a device for measuring the micro hoop strain of a concrete cylinder specimen. In order to solve the problem that the existing method for measuring the micro hoop strain of a specimen is difficult to test the micro hoop strain of the specimen, a new device for measuring the micro hoop strain of a concrete cylinder specimen is provided, which comprises a first arc-shaped frame and a second arc-shaped frame, and the first arc-shaped frame and the second arc-shaped frame are both provided with a hoop support part, the two hoop support parts are symmetrically distributed left and right, the front end of the first arc-shaped frame is fixed with a first extension part, the front end of the second arc-shaped frame is fixed with a second extension part, a clamping spring is arranged between the first extension part and the second extension part, the left side of the second extension part extends leftward with a connecting part, the connecting part is fixed with a supporting leg, and the connecting part is also fixed with a displacement sensor. The device has simple structure, low manufacturing cost and is convenient to use.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of strain measurement, in particular to a device for measuring the micro hoop strain of a concrete cylinder specimen. BACKGROUND

[0002] During the stress process of a concrete cylinder specimen (hereinafter referred to as a specimen), significant axial compression deformation and corresponding hoop strain (hoop expansion deformation) will be generated. Accurate measurement of the hoop strain of the specimen is of great significance for mastering the material properties of the specimen and establishing a structural relationship model. Most of the existing methods for measuring the micro hoop strain of the specimen use strain gauges for measurement, but strain gauges cannot be used for testing high-temperature specimens. In addition, some existing methods for measuring the micro hoop strain of the specimen use rigid clamps in combination with LVDT displacement meters for measurement, but displacement meters are difficult to test the micro hoop strain of the specimen, and have low testing sensitivity. At the same time, under the condition that the structural size is fixed or the connection mode is single, it is often impossible to be compatible with specimens of different sizes or different boundary conditions, and the versatility is poor. SUMMARY

[0003] In order to solve the problem that the existing method for measuring the micro hoop strain of the specimen is difficult to test the micro hoop strain of the specimen, a new device for measuring the micro hoop strain of a concrete cylinder specimen is provided.

[0004] The present application is implemented by using the following technical scheme:

[0005] A device for measuring the micro hoop strain of a concrete cylinder specimen, comprising first and second arc-shaped frames symmetrically distributed left and right, the rear end of the first arc-shaped frame is hinged to the rear end of the second arc-shaped frame, and the hinge shaft is arranged along the height direction, the first and second arc-shaped frames are each provided with a hoop support part arranged along the radial direction, the two hoop support parts are symmetrically distributed left and right, and the first and second arc-shaped frames are respectively provided with first and second radial adjustment structures for realizing the sliding of the two hoop support parts along the radial direction and being fixed after being fitted with the specimen, the front end of the first arc-shaped frame and the front end of the second arc-shaped frame form a deformation expansion interval, the front end of the first arc-shaped frame is fixed with a first extension part arranged along the front and back directions, the front end of the second arc-shaped frame is fixed with a second extension part arranged along the front and back directions, a clamping spring is arranged between the first and second extension parts, a connecting part extends leftward from the left side of the second extension part, a support leg arranged along the height direction is fixed on the connecting part, and a displacement sensor arranged along the left and right directions is also fixed on the connecting part, and the probe of the displacement sensor abuts against the right side of the first extension part.

[0006] In use, the cylindrical test piece is placed between the first and second arc-shaped frames, and the device is supported as a whole by the support legs to keep the device stable in the height direction, then the radial positions of the two annular support parts are adjusted by the two radial adjustment structures, so that the two opposite ends of the two annular support parts are in contact with the test piece, and at the same time the elastic tension provided by the clamping spring is used to maintain the contact between the two annular support parts and the test piece, so as to realize the initial positioning of the device and the test piece. When the test piece has a small annular strain, the annular strain of the test piece can be deduced from the value measured by the displacement sensor, and the specific principle and deduction process are as follows:

[0007] When the test piece has an annular strain, the strain amplification is realized by using the triangular transformation relationship in the geometric structure of the device, the hinge shaft between the rear end of the first arc-shaped frame and the rear end of the second arc-shaped frame is taken as the vertex O, the straight line where the displacement sensor is located is taken as the base, and the two opposite ends of the two annular support parts are taken as the points on the two oblique sides to construct an isosceles triangle, the distance between the two annular support parts is defined as , the length of the base of the isosceles right triangle is defined as , the height is , the top angle is , the vertical distance from the vertex O to any one of the annular support parts is , and the horizontal section line with a height of from the vertex O is taken, and the length of the horizontal section line can be represented as:

[0008] ①

[0009] When the device is driven by the annular deformation of the test piece to produce a small rotation angle , the length of the horizontal section line also changes accordingly, so the differential of is obtained, and the length increment of the horizontal section line is:

[0010] ②

[0011] When the device is driven by the annular deformation of the test piece to produce a small rotation angle , the distance between the two annular support parts also changes accordingly, and the change amount is , and the length of the base of the isosceles triangle also changes accordingly, and the change amount is , according to formula ②, it is obtained:

[0012] ③

[0013] ④

[0014] Divide formula ③ and formula ④ to obtain the geometric amplification coefficient of the device:

[0015] 5

[0016] From formula 5, the geometric amplification factor of the device is determined by the distance between the two ring support parts , and , which can be calculated by formula 5 from the displacement measured by the displacement sensor , which is the ring strain of the test piece that the present application ultimately obtains.

[0017] Further, the line connecting the two ring support parts passes through the center of the test piece. The structure is specific and standardized, which ensures the stability of the structure during testing, thereby further improving the testing sensitivity of the device.

[0018] Further, the first extension part and the second extension part are both telescopic tubes that can stretch and contract in the front-back direction. From formula 5, when the distance between the two ring support parts is constant, the geometric amplification factor of the device changes, and when the length of the first extension part and the second extension part changes, the geometric amplification factor of the device also changes, thereby further improving the measurement sensitivity of the device to the ring strain of the test piece.

[0019] Further, the first radial adjustment structure includes a first adjustment hole and a first threaded hole provided on the first arc-shaped frame, the first adjustment hole is arranged in the left-right direction and is adapted to the corresponding ring support part, the first threaded hole is arranged in the height direction and is adapted to a first jacking bolt for positioning and fixing the corresponding ring support part, and the first adjustment hole is in communication with the first threaded hole; the second radial adjustment structure includes a second adjustment hole and a second threaded hole provided on the second arc-shaped frame, the second adjustment hole is arranged in the left-right direction and is adapted to the corresponding ring support part, the second threaded hole is arranged in the height direction and is adapted to a second jacking bolt for positioning and fixing the corresponding ring support part, and the second adjustment hole is in communication with the second threaded hole. The specific and standardized first radial adjustment structure and second radial adjustment structure are simple in structure and are convenient for being applied to the measurement of the ring strain of test pieces of different sizes. When in use, the first jacking bolt and the second jacking bolt are loosened, the corresponding ring support part is pushed until it is attached to the test piece, and finally the first jacking bolt and the second jacking bolt are tightened.

[0020] Further, the clamping spring is a retainer spring, which is convenient for providing elastic tension to maintain the attachment between the two ring support parts and the test piece.

[0021] Further, the first and second extension parts are respectively provided with first and second clamping through holes arranged along the left-right direction, the first and second clamping through holes are respectively matched with the two end parts (which are rod-shaped parts in the art) of the holder spring, the first and second extension parts are respectively provided with third and fourth threaded holes arranged along the height direction, the first clamping through hole is communicated with the third threaded hole, the second clamping through hole is communicated with the fourth threaded hole, and the third and fourth threaded holes are respectively matched with third and fourth tightening bolts for positioning the two end parts of the holder spring. In use, the third and fourth tightening bolts are loosened, the two end parts of the holder spring are adjusted to extend into the first and second clamping through holes to the appropriate positions, and then the third and fourth tightening bolts are tightened to tighten the two end parts of the holder spring, so as to realize the adjustment of the clamping force.

[0022] Further, the connecting part is provided with a through hole arranged along the height direction and matched with the support leg, the left side surface of the connecting part is provided with a connecting threaded hole communicated with the through hole and arranged along the left-right direction, the connecting threaded hole is matched with a connecting bolt for tightening the support leg, and in use, the fixing height of the support leg is adjusted according to the actual arrangement environment, so as to realize the height support of the overall device, and the applicability is strong.

[0023] Further, the rigidity coefficient of the holder spring is not less than 5 N / mm, so as to ensure that the device has enough clamping force and resilience during the measurement process.

[0024] Further, the two opposite end parts of the two annular support parts are respectively provided with rubber pads for enhancing the friction and preventing the damage to the surface of the test piece.

[0025] Further, the displacement sensor is fixed to the front side surface of the connecting part through the quick release structure, so as to facilitate the installation and disassembly of the displacement sensor during the later maintenance and replacement of the displacement sensor.

[0026] The beneficial effects of the present application are as follows: 1) the device mainly comprises two annular support parts, a displacement sensor, a first arc-shaped frame and a geometric structure formed by the first arc-shaped frame, and strain amplification is realized by using the triangular transformation relationship in the geometric structure, so that the small annular strain generated by the test piece is converted into an amplified displacement change that can be observed by the displacement sensor, thereby effectively improving the response sensitivity of the device; 2) each connecting part in the device is provided with a connecting structure for adapting to the size of the test piece, which can be compatible with test pieces of different sizes and has strong versatility; 3) the device ensures clamping of the test piece through the spring fixer, and is stable in installation, while avoiding damage to the test piece, and is suitable for micro-deformation measurement with high requirements for the surface integrity of the test piece; 4) the overall structure of the device is compact, facilitating laboratory mobile deployment or rapid use on the engineering site; 5) the device can be applied to the testing of high-temperature test pieces, and has strong applicability; 6) the device has simple structure, low manufacturing cost and is convenient to use. BRIEF DESCRIPTION OF DRAWINGS

[0027] The drawings incorporated into the specification and forming a part of the specification, show embodiments consistent with the present application, and together with the specification serve to explain the principles of the present application.

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced as follows, and obviously, other drawings can also be obtained by those skilled in the art without creative labor.

[0029] Figure 1 The overall structure schematic diagram of the device of the present application is shown in the figure.

[0030] Figure 2 The measurement principle schematic diagram of the device of the present application is shown in the figure.

[0031] In the figure: 1-first arc-shaped frame, 2-second arc-shaped frame, 3-hinge shaft, 4-annular support part, 5-first extension part, 6-second extension part, 7-clamping spring, 8-connection part, 9-support leg, 10-displacement sensor, 11-first jacking bolt, 12-second jacking bolt, 13-third jacking bolt, 14-fourth jacking bolt, 15-connection bolt. DETAILED DESCRIPTION

[0032] In order to more clearly understand the above-mentioned purposes, features and advantages of the present application, the scheme of the present application will be further described below. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0033] In the description, it needs to be explained that the terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance. It needs to be explained that unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0034] In the following description, many specific details are set forth in order to provide a thorough understanding of the present application, but the present application can also be implemented in other ways different from those described herein; obviously, the examples in the description are only some of the embodiments of the present application, not all the embodiments.

[0035] The specific embodiments of the present application will be described in detail below in conjunction with the accompanying drawings.

[0036] As Figure 1 shown, a device for measuring the small circumferential strain of a concrete cylindrical test piece, comprising a first arc-shaped frame 1 and a second arc-shaped frame 2 which are symmetrically distributed left and right, the rear end of the first arc-shaped frame 1 is hinged with the rear end of the second arc-shaped frame 2 and the hinge shaft 3 is arranged along the height direction, the first arc-shaped frame 1 and the second arc-shaped frame 2 are both provided with a circumferential support part 4 arranged along the radial direction, the two circumferential support parts 4 are symmetrically distributed left and right, and the first arc-shaped frame 1 and the second arc-shaped frame 2 are respectively provided with a first radial adjusting structure and a second radial adjusting structure for realizing the radial sliding of the two circumferential support parts 4 and being able to be fixedly positioned after being fitted with the test piece, the front end of the first arc-shaped frame 1 and the front end of the second arc-shaped frame 2 form a deformation expansion interval, the front end of the first arc-shaped frame 1 is fixed with a first extension part 5 arranged along the front and back direction, the front end of the second arc-shaped frame 2 is fixed with a second extension part 6 arranged along the front and back direction, the first extension part 5 and the second extension part 6 are provided with a clamping spring 7, the left side of the second extension part 6 extends leftwardly with a connecting part 8, the connecting part 8 is fixed with a support leg 9 arranged along the height direction, and the connecting part 8 is also fixed with a displacement sensor 10 arranged along the left and right direction in the axial direction, and the probe of the displacement sensor 10 abuts against the right side surface of the first extension part 5.

[0037] In use, the cylindrical specimen is placed between the first arc-shaped frame 1 and the second arc-shaped frame 2, and the entire device is supported by the support legs 9 to maintain its stability in the height direction. Then, the radial positions of the two circumferential support parts 4 are adjusted by two radial adjustment structures so that the two opposite ends of the two circumferential support parts 4 are in contact with the specimen. At the same time, the clamping spring 7 provides elastic tension to maintain the contact between the two circumferential support parts 4 and the specimen, thus achieving the initial positioning of the device and the specimen. During measurement, when the specimen experiences a small circumferential strain, the circumferential strain of the specimen can be deduced from the value measured by the displacement sensor 10. The specific principle and deduction process are as follows:

[0038] When the specimen undergoes circumferential strain, the strain is amplified using the trigonometric transformations in the device's geometry, such as... Figure 2 As shown, an isosceles triangle is constructed with the hinge axis 3 between the rear ends of the first arc-shaped frame 1 and the rear ends of the second arc-shaped frame 2 as vertex O, the straight line where the displacement sensor 10 is located as the base, and the two opposite ends of the two circumferential support parts 4 as points on the two hypotenuses. The distance between the two circumferential support parts 4 is defined as... The base length of the isosceles right triangle is defined as... Gao Wei The vertex is The vertical distance between vertex O and any circumferential support 4 is 1. Take any distance from vertex O with a height of The horizontal intercept, the length of which can be expressed as:

[0039] ①

[0040] When the device is driven by the circumferential deformation of the specimen, a small rotation angle is generated. At that time, the length of the horizontal section also changes accordingly, therefore... By taking the differential, we can obtain the increment in length of the horizontal intercept:

[0041] ②

[0042] When the device is driven by the circumferential deformation of the specimen, a small rotation angle is generated. At the same time, the distance between the two circumferential support parts 4 also changes accordingly, and the amount of change is... The length of the base of the isosceles triangle also changes accordingly, and the amount of change is... According to formula ②, we can derive:

[0043] ③

[0044] ④

[0045] Dividing formula ③ and formula ④, the geometric amplification factor of the device is obtained :

[0046] ⑤

[0047] From formula ⑤, the geometric amplification factor of the device is only determined by and , The displacement sensor 10 measures the distance change between the two ring support parts 4, which can be inversely deduced by formula ⑤ , That is, the ring strain of the test piece that the present application ultimately obtains.

[0048] In specific implementation, the line connecting the two ring support parts 4 passes through the center of the test piece. The structure is specific and standardized to ensure the stability of the structure during testing, thereby further improving the testing sensitivity of the device.

[0049] In specific implementation, the first extension part 5 and the second extension part 6 are both telescopic tubes that can stretch and contract in the front-back direction. As can be seen from formula ⑤, when is constant, changes, the geometric amplification factor of the device changes, and when the length of the first extension part 5 and the second extension part 6 changes, will also change, and the geometric amplification factor of the device will also change, thereby further improving the measurement sensitivity of the device to the ring strain of the test piece.

[0050] In specific implementation, the first radial adjustment structure includes a first adjustment hole and a first threaded hole provided on the first arc-shaped frame 1. The first adjustment hole is arranged in the left-right direction and is adapted to the corresponding ring support part 4. The first threaded hole is arranged in the height direction and is adapted to the first jamming bolt 11 for positioning and fixing the corresponding ring support part 4. The first adjustment hole and the first threaded hole are in communication. The second radial adjustment structure includes a second adjustment hole and a second threaded hole provided on the second arc-shaped frame 2. The second adjustment hole is arranged in the left-right direction and is adapted to the corresponding ring support part 4. The second threaded hole is arranged in the height direction and is adapted to the second jamming bolt 12 for positioning and fixing the corresponding ring support part 4. The second adjustment hole and the second threaded hole are in communication. The specific and standardized first radial adjustment structure and second radial adjustment structure are simple in structure and are suitable for measuring the ring strain of test pieces of different sizes. When in use, the first jamming bolt 11 and the second jamming bolt 12 are loosened, the corresponding ring support part 4 is pushed until it is attached to the test piece, and finally the first jamming bolt 11 and the second jamming bolt 12 are tightened.

[0051] In actual implementation, the clamping spring 7 is a holder spring, which is used to provide elastic tension to maintain the fit between the two annular support portions 4 and the test piece.

[0052] In the embodiment, the first and second extension portions 5 and 6 are respectively provided with first and second clamping through holes arranged along the left-right direction, which are adapted to the two end portions of the holder spring (which are rod-shaped portions in the art), and are respectively provided with third and fourth threaded holes arranged along the height direction, the first clamping through hole is communicated with the third threaded hole, and the second clamping through hole is communicated with the fourth threaded hole, and the third and fourth threaded holes are adapted to third and fourth jacking bolts 13 and 14 respectively used to position the two end portions of the holder spring. In use, the third and fourth jacking bolts 13 and 14 are loosened, and the extension amounts of the two end portions of the holder spring into the first and second clamping through holes are adjusted to appropriate positions, and then the third and fourth jacking bolts 13 and 14 are tightened to jacking the two end portions of the holder spring, so as to adjust the clamping force.

[0053] In the embodiment, the connecting portion 8 is provided with a through hole arranged along the height direction and adapted to the support leg 9, and the left side surface of the connecting portion 8 is provided with a connecting threaded hole communicated with the through hole and arranged along the left-right direction, and the connecting threaded hole is adapted to a connecting bolt 15 used to jacking the support leg 9, and in use, the fixed height of the support leg 9 is adjusted according to the actual arrangement environment, so as to realize the height support of the overall device, and the applicability is strong.

[0054] In the embodiment, the rigidity coefficient of the holder spring is not less than 5 N / mm, so as to ensure that the device has enough clamping force and resilience during the measurement process.

[0055] In the embodiment, the two opposite end portions of the two annular support portions 4 are respectively provided with rubber pad layers, which are used to enhance the friction and prevent the damage to the surface of the test piece.

[0056] In the embodiment, the displacement sensor 10 is fixed to the front side surface of the connecting portion 8 through a quick release structure, which is convenient for the installation and disassembly of the displacement sensor 10 during the later maintenance and replacement of the displacement sensor 10.

[0057] The above description is merely one specific implementation of the application, and thus the technical solutions recorded in the foregoing embodiments can be modified or some or all of the technical features can be substituted equivalently by those skilled in the art, without departing from the scope of the technical solutions of the embodiments, and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the embodiments, and should be included in the protection scope of the claims.

Claims

1. A device for measuring minute circumferential strain in a concrete cylindrical specimen, characterized in that, The system includes a first arc-shaped frame (1) and a second arc-shaped frame (2) symmetrically distributed on the left and right. The rear end of the first arc-shaped frame (1) is hinged to the rear end of the second arc-shaped frame (2), and the hinge axis (3) is arranged along the height direction. Both the first arc-shaped frame (1) and the second arc-shaped frame (2) are provided with circumferential support parts (4) arranged radially. The two circumferential support parts (4) are symmetrically distributed on the left and right. The two circumferential support parts (4) are respectively provided with a first radial adjustment structure and a second radial adjustment structure between them and the first arc-shaped frame (1) and the second arc-shaped frame (2) to enable the two circumferential support parts (4) to slide radially and be positioned and fixed after sliding to fit with the specimen. A deformation expansion gap is formed between the front end of the first arc-shaped frame (1) and the front end of the second arc-shaped frame (2). The front end of the first arc frame (1) is fixed with a first extension (5) arranged in the front-back direction, and the front end of the second arc frame (2) is fixed with a second extension (6) arranged in the front-back direction. A clamping spring (7) is provided between the first extension (5) and the second extension (6). The left side of the second extension (6) extends to the left with a connecting part (8). A support leg (9) arranged in the height direction is fixed on the connecting part (8). A displacement sensor (10) arranged in the left-right direction is also fixed on the connecting part (8), and the probe of the displacement sensor (10) abuts against the right side of the first extension (5). The line connecting the two circumferential support parts (4) passes through the center of the specimen. The first extension (5) and the second extension (6) are both telescopic tubes that can extend and retract in the front-back direction.

2. The device for measuring minute circumferential strain of a concrete cylindrical specimen according to claim 1, characterized in that, The first radial adjustment structure includes a first adjustment hole and a first threaded hole on the first arc frame (1). The first adjustment hole is arranged in the left-right direction and is adapted to the corresponding circumferential support (4). The first threaded hole is arranged in the height direction and is adapted to a first tightening bolt (11) for positioning and fixing the corresponding circumferential support (4). The first adjustment hole and the first threaded hole are connected. The second radial adjustment structure includes a second adjustment hole and a second threaded hole on the second arc frame (2). The second adjustment hole is arranged in the left-right direction and is adapted to the corresponding circumferential support (4). The second threaded hole is arranged in the height direction and is adapted to a second tightening bolt (12) for positioning and fixing the corresponding circumferential support (4). The second adjustment hole and the second threaded hole are connected.

3. The device for measuring minute circumferential strain of a concrete cylindrical specimen according to claim 2, characterized in that, The clamping spring (7) is a retainer spring.

4. The device for measuring minute circumferential strain of a concrete cylindrical specimen according to claim 3, characterized in that, The first extension (5) and the second extension (6) are respectively provided with a first clamping through hole and a second clamping through hole arranged in the left and right direction. The first clamping through hole and the second clamping through hole are respectively adapted to the two ends of the retainer spring. The first extension (5) and the second extension (6) are also respectively provided with a third threaded hole and a fourth threaded hole arranged in the height direction. The first clamping through hole communicates with the third threaded hole, and the second clamping through hole communicates with the fourth threaded hole. The third threaded hole and the fourth threaded hole are respectively provided with a third tightening bolt (13) and a fourth tightening bolt (14) for positioning the two ends of the retainer spring.

5. The device for measuring minute circumferential strain of a concrete cylindrical specimen according to claim 4, characterized in that, The connecting part (8) is provided with a through hole arranged along the height direction and adapted to the support leg (9). The left side of the connecting part (8) is provided with a connecting thread hole that communicates with the through hole and is arranged along the left and right directions. The connecting thread hole is fitted with a connecting bolt (15) for tightening the support leg (9).

6. The device for measuring minute circumferential strain of a concrete cylindrical specimen according to claim 5, characterized in that, The stiffness coefficient of the retainer spring shall not be less than 5 N / mm.

7. The device for measuring minute circumferential strain of a concrete cylindrical specimen according to claim 6, characterized in that, Rubber pads are provided on the two opposite ends of the two circumferential support parts (4).

8. The device for measuring minute circumferential strain of a concrete cylindrical specimen according to claim 7, characterized in that, The displacement sensor (10) is fixed to the front side of the connector (8) by a quick-release structure.

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