Tensioning regulation and control device and method for mechanical property detection of prestressed material in laboratory

Abstract

The invention discloses a tension regulation and control device and method for detecting the mechanical property of a prestressed material in a laboratory. The tension regulation and control device comprises a prestress adjustable and controllable bracket, an anchoring device and a distance measuring device, the prestress-adjustable support comprises a screw rod and at least two top plates, and the top plates are connected to the screw rod in a fastened mode through nuts. The anchoring devices are used for fixing a test piece, the number of the anchoring devices is two, and each anchoring device abuts against the outer side of at least one top plate; and the distance measuring device is used for measuring the distance between any two points on the test piece between the two anchoring devices. The tension regulation and control device provided by the invention is reasonable in overall structural design, small in size, convenient to operate and accurate to control, and meets actual test requirements. According to the method for detecting the mechanical property of the prestressed material in the laboratory, the technical problems that in the prior art, a tension regulation and control device for a large structure cannot be used for convenient operation and precise control of a small test piece in the laboratory, and cannot be used in cooperation with existing detection equipment are solved.

Description

Technical Field

[0001] The invention belongs to the technical field of laboratory testing of prestressed materials, and in particular relates to a tensioning control device and method for testing the mechanical properties of prestressed materials in a laboratory. Background Art

[0002] With the continuous development of technology in the fields of materials and engineering, some high-performance new materials, such as fiber-reinforced resin-based composite materials, are being innovatively applied in some construction projects as new prestressed structural components. At present, the short-term / long-term performance testing and evaluation methods of these new prestressed material components replacing existing structures are still under research and improvement to promote the further development and long-term safe application of new material components.

[0003] Traditional engineering material testing and evaluation methods are mostly laboratory test methods for a mechanical property or a mechanical property coupled with environmental factors. Based on the service characteristics of new prestressed structural components, it is urgent to carry out experimental testing and evaluation technology for the mechanical properties of new materials under prestress coupling, as well as the comprehensive properties coupled with environmental factors, in order to more comprehensively evaluate the service characteristics of new prestressed structural materials. At present, there is still a lack of prestressed tensioning and control devices and supporting test methods for laboratory material testing. Prestressed material tensioning devices in the prior art are mostly used in prestressed engineering structures. The anchoring and tensioning devices correspond to large prestressed components and cannot match the existing testing equipment in the laboratory; if they are simply scaled into small-sized devices, they cannot meet the precise control requirements of tensioning of small specimens in laboratory tests.

[0004] For example, patent CN101851985B discloses a method for prestressing a hinged anchor and a high-strength fiber composite sheet. The structural design of the tensioning device and the anchoring operation method are relatively complex, and the tensioning instrument matched with the device is a jack, which cannot be operated on a small test specimen in the laboratory, and the large tension range of the jack cannot meet the demand for precise control of the small tension range of the small specimen.

[0005] Therefore, it is urgent to develop a tensioning control device and test method for laboratory prestressed material mechanical properties testing that is small in size, easy to operate, and precisely controlled, which can match the conventional laboratory material properties testing machine, so as to realize prestressed coupling detection experiments of various types of materials. Summary of the invention

[0006] In order to solve the above technical problems, the present invention improves the existing technology and optimizes the tension control device for testing the mechanical properties of prestressed materials. The specific scheme is as follows:

[0007] In a first aspect, the present invention provides a tensioning and regulating device for testing the mechanical properties of prestressed materials in a laboratory, characterized in that the tensioning and regulating device comprises a prestressed and adjustable bracket, an anchoring device and a distance measuring device;

[0008] The prestressed adjustable bracket includes a screw and at least two top plates, the top plates are fastened to the screw by nuts, and the position of the top plates on the screw is adjustable; the anchoring device includes a clamp and a wedge-shaped clip, the wedge-shaped clip is arranged in the clamp, and the inclination angle of the wedge-shaped clip is 1°-1.5°;

[0009] The anchoring device is used to fix the test piece, and two anchoring devices are provided, and each anchoring device abuts against the outer side of at least one top plate;

[0010] The distance measuring device is used to measure the distance between any two points on the test piece between the two anchoring devices.

[0011] Furthermore, at least two top plates are provided between the two anchoring devices.

[0012] Furthermore, the anchoring device includes a clamp and a wedge-shaped clip, wherein the wedge-shaped clip is arranged in the middle of the clamp and is in close contact with the specimen. The wedge-shaped clip can not only ensure that the stress is evenly distributed on the clamp, reduce local stress concentration, and avoid local damage caused by excessive stress, but also the wedge-shaped clip will increase the surface friction with the specimen when subjected to force, ensuring that the specimen will not slip off.

[0013] Furthermore, the surface of the wedge-shaped clamping piece that fits the test piece is provided with corrugated protrusions.

[0014] The design of the corrugated protrusion not only prevents the surface of the wedge-shaped clamp from being too sharp and causing damage to the specimen, but also improves the friction between the wedge-shaped clamp and the specimen.

[0015] Furthermore, the inner surface of the wedge-shaped clamp is padded with sandpaper, which can increase the friction force during clamping, improve the gripping force between the prestressed specimen and the wedge-shaped clamp, and ensure the stability and reliability of the anchoring device.

[0016] Furthermore, the anchoring device is suitable for new prestressed structural materials such as carbon fiber reinforced composite materials, which have ultra-high tensile strength (>3000Mpa) and easy brittle fracture.

[0017] Furthermore, the cross section of the clamp is rectangular, and a square groove for placing a wedge-shaped clamp is provided inside, which is used to clamp a test piece with a rectangular cross section.

[0018] Preferably, the clamp uses two sets of clamping plates, and the clamping plates are provided with double rows of connecting bolts for fastening the entire clamping plates to ensure uniform stress distribution at the clamping ends.

[0019] Furthermore, the inclination angle of the wedge-shaped clip in the square groove is 1°-1.5°.

[0020] Preferably, when the prestress required for the anchoring specimen is less than 1000 MPa, the inclination angle may be 1°.

[0021] Preferably, when the prestress required for the anchoring specimen is higher than 1000 MPa, the inclination angle is greater than 1°.

[0022] More preferably, when the required prestress for the anchoring specimen is higher than 1000 MPa, the inclination angle is 1.5°

[0023] Furthermore, the width of the wedge-shaped clip does not exceed 2 cm; the length does not exceed 10 cm; and the maximum thickness is less than or equal to 2 cm.

[0024] Furthermore, the cross section of the clamp is circular, and a circular channel matching the wedge-shaped clamp is provided inside for clamping a test piece with a circular cross section.

[0025] Preferably, the clamp is a circular sleeve.

[0026] Furthermore, the inclination angle of the wedge-shaped clip in the circular channel is 1°.

[0027] Preferably, when the diameter of the test piece is less than or equal to 5 mm, the number of wedge-shaped clamps is two.

[0028] Preferably, when the diameter of the specimen is greater than 5 mm, the number of wedge-shaped clamps is two or more.

[0029] More preferably, when the diameter of the specimen is greater than 5 mm, the number of the wedge-shaped clamps is three, and the inclination angle of the wedge-shaped clamps is designed to be 1°.

[0030] When the stress is too large or the stress is concentrated, the specimen is easily crushed; when the stress is too small or the stress clamping is insufficient, the anchor device and the specimen are easy to slip during the tensioning process.

[0031] Furthermore, the wedge-shaped clip does not exceed 8 cm; the diameter does not exceed 5 cm; and the wall thickness of the outer sleeve does not exceed 0.5 cm.

[0032] Furthermore, a through hole for the test piece to pass through is provided at the center of the top plate.

[0033] Furthermore, the two anchoring devices are respectively close to the ends of the specimen, and the two ends of the specimen extend out of the anchoring devices for a distance, so that the universal testing machine can clamp the two ends of the specimen.

[0034] Furthermore, the screw rods are passed through the four corners of the top plate, and the screw rods are arranged parallel to the test piece.

[0035] Preferably, the number of the screws is 4.

[0036] Furthermore, the nut includes an upper nut and a lower nut symmetrically arranged on both sides of the top plate, and is used to fasten the position of the top plate.

[0037] Preferably, there are 8 nuts on each top plate, and the nuts are on the screw rods to ensure that the relative position of the top plates does not slip.

[0038] Furthermore, the distance measuring device is selected from one of a strain gauge, a video extensometer, a fully automatic extensometer and a manual distance measuring device.

[0039] Preferably, a strain gauge is attached to the surface of the specimen, and a lead wire is connected to the lead-out end of the strain gauge.

[0040] Preferably, a video extensometer or fully automatic extensometer is used in conjunction with a universal testing machine to synchronize the loading speed and load force to accurately measure strain and displacement. Video extensometers or fully automatic extensometers are highly accurate, easy to use, fast in response, and highly reliable.

[0041] More preferably, compared with the method of connecting the strain gauge to the external lead wire, it may not be possible in the environmental chamber; the video extensometer and the fully automatic extensometer must be used in conjunction with the universal testing machine. Therefore, although the accuracy of the manual distance measuring device is relatively low, this method of measuring prestress relaxation is more feasible in the coupling test of the long-term environmental test chamber. The manual distance measuring device is highly flexible and can directly observe the surface condition and subtle changes of the material, which helps to find potential problems or abnormalities.

[0042] Furthermore, the manual distance measuring device includes but is not limited to a ruler and a vernier caliper. Any manual distance measuring device that can measure the length of a test piece between two anchoring devices is applicable to the present invention.

[0043] Furthermore, the prestressed adjustable bracket and the anchoring device are made of quenched and tempered steel material.

[0044] Preferably, the prestressed adjustable bracket and anchor device are made of quenched and tempered 45 steel, which is not only corrosion-resistant and high-strength, but also not easy to deform, and can meet the requirements of placing the tensioning and regulating device as a whole in an environmental coupling test box.

[0045] The test material specimens include various material specimens with rectangular or circular cross-sections; material types include metals, inorganic / organic materials and composite materials.

[0046] Preferably, there is a certain margin between the two top plates compared to the maximum measuring range of the test specimen.

[0047] In a second aspect, the present invention provides a method for testing the mechanical properties of prestressed materials in a laboratory, the method comprising the following steps:

[0048] S1. Mark two points at a certain distance on the material specimen to be tested, and record the distance L0 between the two points;

[0049] S2. Use a tensioning and regulating device to fix the material specimen to be tested: first, insert the material specimen to be tested into the top plate of the prestressed adjustable bracket; then fix the two ends of the material specimen to be tested in the prestressed adjustable bracket through anchoring devices, and the two anchoring devices are respectively located on the outside of the two top plates; when the anchoring devices are fixed, the two ends of the material specimen to be tested need to extend out of the anchoring devices to a certain position, and the extended part is used for reliable clamping on the universal testing machine;

[0050] S3. Fix both ends of the material specimen to be tested on the universal testing machine: adjust the relative position of the top plate on the prestressed adjustable bracket, and loosen the nut on the prestressed adjustable bracket; then place the tensioning control device as a whole on the universal testing machine, and fix both ends of the material specimen to be tested on the universal testing machine, with the two marked points located between the two anchoring devices;

[0051] S4. Start the universal testing machine and apply prestress to the test material specimen by adjusting the equipment parameters of the universal testing machine;

[0052] S5. When the prestress reaches the required value, keep the universal testing machine in tension state, use the distance measuring device to measure the distance L1 between two points of the material specimen to be tested in the tension equilibrium state of the universal testing machine, record the corresponding stress value F1, and draw the stress / strain curve of the material specimen to be tested based on L0, L1, and F1;

[0053] S6. Adjust the top plates on both sides of the tension control device to be close to the inner side of the anchor device, tighten the upper and lower nuts on the top plate, so that the top plate is closely abutted against the anchor device on the same side to maintain the prestress applied to the material specimen to be tested;

[0054] S7. Finally, the universal testing machine unloads the load, and when the test material specimen in the tensioning device is stable, the distance L2 between two points of the test material specimen is measured again by the distance measuring device, and the actual prestress value F2 is determined by comparing the stress / strain curve; then, the tensioning control device and the test material specimen with prestress applied fixed inside are taken out of the universal testing machine as a whole.

[0055] The basic principle of the prestressed system evaluation method is based on the stress / strain curve during the material stretching and / or relaxation process. That is, the principle that the stress corresponding to different strains can be determined. When the stress / strain curves of the material stretching and relaxation processes within the target stress range are consistent, only the tensile stress-strain curve can be referred to.

[0056] Furthermore, the method further comprises the following steps:

[0057] S8. Take out the tensioning control device together with the prestressed material specimen to be tested fixed inside it from the universal testing machine and carry out the prestress coupling detection test.

[0058] Preferably, the equipment used for the prestressed coupling detection test is conventional equipment in the art, including but not limited to impact test equipment, bending test equipment, and environmental coupling test chamber.

[0059] The tensioning control device and method for testing the mechanical properties of prestressed materials in the laboratory are designed based on the principle of the prestressed system evaluation method. The length of the tensioned test specimen is limited to not retract by the prestressed adjustable bracket and anchor device in the tensioning control device, so as to effectively control the prestress. The tensioning control device is used together with the prestressed material specimen to be tested fixed inside it and other testing equipment to realize the prestressed coupling performance test of multiple types of laboratory material testing machines.

[0060] Compared with the prior art, the beneficial effects of the present invention include:

[0061] 1. The present invention provides a tensioning control device for laboratory prestressed material mechanical property testing and a method for laboratory prestressed material mechanical property testing, which overcomes the technical problems in the prior art that the tensioning device cannot be matched with the existing laboratory testing equipment and cannot be accurately controlled when testing smaller specimens in the laboratory.

[0062] 2. The present invention provides a tensioning and regulating device for testing the mechanical properties of prestressed materials in laboratories. The device has a simple overall structure and a small size, and is convenient for being placed on various types of storage tables. The length of the specimen to be tested and the size of the prestressed clamp can be flexibly adjusted. During tensioning and regulation, the device can be used in combination with a universal testing machine to meet the precise control requirements of small test specimens in laboratories.

[0063] 3. The present invention provides a tensioning and regulating device for laboratory prestressed material mechanical property testing, which adopts a prestressed adjustable bracket and an anchoring device to meet actual testing needs, is easy to operate, and can stably clamp the prestress.

[0064] 4. The present invention provides a tensioning control device for laboratory prestressed material mechanical property testing. Since the clamping force of the anchoring device is large, it can ensure that the clamp and the clamped specimen do not slip. At the same time, the stress distribution at both ends of the anchoring is uniform, which can reduce damage to the clamped specimen. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0066] Figure 1 It is a schematic diagram of the overall structure of the tensioning and regulating device;

[0067] Figure 2 It is a schematic diagram of the structure of one end of the rectangular clamp of the anchoring device;

[0068] Figure 3 It is the right view of the rectangular clamp of the anchoring device;

[0069] Figure 4 It is a top view of the circular clamp of the anchoring device;

[0070] Figure 5 It is a schematic diagram of the wedge-shaped clip structure;

[0071] Figure 6 This is a schematic diagram of the overall structure of the tensioning and regulating device of Example 1;

[0072] Figure 7 Figure 1 is a prestressed impact test effect diagram; Figure (a) is a prestressed specimen impact damage effect diagram; Figure (b) is a prestressed specimen impact damage effect diagram;

[0073] The reference numerals in the figure are as follows: 1-prestressed adjustable bracket; 101-screw; 102-top plate; 103-nut; 2-anchoring device; 201-clamp; 202-wedge-shaped clip; 203-bolt; 204-corrugated protrusion; 3-test piece. DETAILED DESCRIPTION

[0074] The technical scheme of the present invention is described clearly and completely below in conjunction with the embodiments and drawings. The described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0075] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and the like are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", and the like may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0076] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0077] The present invention provides a tensioning and regulating device for testing the mechanical properties of prestressed materials in a laboratory, the tensioning and regulating device comprising a prestressed and adjustable support 1, an anchoring device 2 and a distance measuring device (not shown in the figure);

[0078] like Figure 1 As shown, the prestressed adjustable bracket 1 includes a screw rod 101 and at least two top plates 102, the top plates 102 are fastened to the screw rod 101 by nuts 103, and the position of the top plates on the screw rod is adjustable; the anchoring device 2 is used to fix the specimen, and two anchoring devices 2 are provided, each anchoring device 2 is at least abutted against the outer side of one top plate, and the top plate is used to limit the slippage of the anchoring device to prevent the specimen from shrinking; the anchoring device 2 includes a clamp 201 and a wedge-shaped clamp 202, the wedge-shaped clamp 202 is arranged in the clamp 201, and the inclination angle of the wedge-shaped clamp 202 is 1°-1.5°; the distance measuring device is used to measure the distance between any two points on the specimen 3 between the two anchoring devices 2, and the prestress borne by the specimen is determined by the change in the distance between any two points; the surface of the wedge-shaped clamp 202 that is in contact with the specimen 3 is provided with a corrugated protrusion 204; the inner surface of the wedge-shaped clamp 202 is also padded with sandpaper.

[0079] like Figure 2-3 As shown, the clamp 201 has a rectangular cross section and is provided with a square groove for placing a wedge-shaped clamp 202; the inclination angle of the wedge-shaped clamp 202 in the square groove is 1°-1.5°. The clamp 201 uses a set of clamps, and a double row of connecting bolts 203 are provided on the clamps.

[0080] When the required prestress for the anchor specimen is less than 1000 MPa, the inclination angle can be 1°.

[0081] When the required prestress of the anchor specimen is higher than 1000MPa, the inclination angle is 1.5°

[0082] The width of the wedge-shaped clip 202 does not exceed 2 cm; the length does not exceed 10 cm; and the maximum thickness is less than or equal to 2 cm.

[0083] The steps of installing the rectangular clamp 201 and the wedge-shaped clamp 202 are as follows: the raised ends of the upper and lower wedge-shaped clamps are attached to the surface of the test material specimen 3 to be tested, with the small end of the wedge-shaped clamp facing inward and the large end facing outward, and then the wedge-shaped clamp 202 and the test material specimen 3 to be tested are placed as a whole in the square groove of the clamp 201. Finally, the relative positions of the test material specimen 3 to be tested and the wedge-shaped clamp 202 are adjusted, and they are connected and tightened with the connecting bolts 203.

[0084] like Figure 4 As shown, the clamp 201 has a circular cross section and is provided with a circular channel inside to match the wedge-shaped clamp 202; the inclination angle of the wedge-shaped clamp 202 in the circular channel is 1°; and there are two or more wedge-shaped clamps 202. The clamp 201 adopts a circular sleeve.

[0085] When the diameter of the test piece is less than or equal to 5 mm, the number of wedge-shaped clamping pieces 202 is two.

[0086] When the diameter of the specimen is greater than 5 mm, the number of the wedge-shaped clamping pieces 202 is more than two.

[0087] When the diameter of the specimen is greater than 5 mm, the number of wedge-shaped clamps 202 is three, and the inclination angle of the wedge-shaped clamps 202 is designed to be 1°.

[0088] The steps of installing the circular fixture 201 and the wedge-shaped clamp 202 are as follows: wrap the test material specimen 3 with the wedge-shaped clamp 202, then cover it with a circular sleeve, then adjust the relative positions of the test material specimen 3 and the wedge-shaped clamp 202, tighten the circular sleeve, and complete the tightening.

[0089] The material specimen 3 to be tested and the anchoring device 2 are mechanically connected without any gluing process, which not only avoids the operational inconvenience caused by gluing and the stress relaxation at the gluing point that easily interferes with the overall test analysis, shortens the production cycle, but also can effectively ensure the efficiency of the anchoring device 2.

[0090] A through hole for the specimen to pass through is provided at the center of the top plate 102; the two anchoring devices 2 are respectively close to the two ends of the specimen 3, and the two ends of the specimen 3 extend out of the anchoring devices 2 for a distance.

[0091] The screw rods 101 are passed through the four corners of the top plate 102, and the screw rods 101 are arranged parallel to the test piece 3. The number of the screw rods 101 is 4; the nuts 103 include an upper nut 103 and a lower nut 103 symmetrically arranged on both sides of the top plate 102; the number of nuts 103 on each top plate 102 is 8.

[0092] The distance measuring device is selected from one of a strain gauge, a video extensometer, a fully automatic extensometer and a manual distance measuring device.

[0093] The prestressed adjustable bracket 1 and the anchoring device 2 are made of quenched and tempered steel material.

[0094] The invention also provides a method for testing the mechanical properties of prestressed materials in a laboratory.

[0095] The tensioning control device of the present invention is used in conjunction with a universal testing machine and an environmental coupling test chamber. In the test, it is necessary to first use the tensioning control device and the universal testing machine in the present application to apply prestress to the material to be tested, and then use the environmental test chamber to perform a prestress coupling experimental test on the material.

[0096] The universal testing machine is a device specially designed for measuring the mechanical properties of materials. It integrates multiple functions such as stretching, bending, compression, and shearing. It consists of a frame, a fixture, and a force sensor. The universal testing machine clamps the material to be tested and applies a certain tensile stress through the upper and lower fixtures, which can accurately control the prestress applied to the material to be tested.

[0097] The environmental coupling test chamber in this application is an advanced test equipment that can apply multiple environmental factors simultaneously or sequentially, including high and low temperature, water bath, seawater immersion, freeze-thaw, ultraviolet and other environments. It is mainly used to evaluate the attenuation law of tensile strength, bending / shear and impact resistance of the test material after a certain period of time, and then predict the degree of characteristic attenuation of the test material during long-term service.

[0098] In order to better understand the technical solution of the present invention, the following specific implementation is selected to illustrate the present invention is used for laboratory prestressed material multi-type environmental weather resistance test, prestressed material impact resistance test and prestressed material bending resistance test and other mechanical property tests.

[0099] In this embodiment, the length of the test material specimen 3 is measured by a video extensometer. The video extensometer is used in conjunction with a universal testing machine, and the camera of the video extensometer is vertically aligned with the material specimen 3 to be tested, ensuring that the camera's field of view covers the measurement area of ​​the material specimen 3 to be tested, and at the same time, the optical axis of the camera should be parallel or perpendicular to the axis of the material specimen 3 to be tested, reducing the viewing angle error.

[0100] Example 1

[0101] like Figure 6 As shown, the prestressed adjustable bracket 1 used in Example 1 includes two top plates 102 and four screws 101, and each top plate 102 is provided with eight nuts 103; the anchoring device 2 uses two sets of clamping plates, and the wedge-shaped clamping piece 202 and the material specimen 3 to be tested are integrally placed in the square groove of the clamp 201. The prestressed adjustable bracket and the anchoring device used in Example 1 are both made of quenched and tempered 45 steel.

[0102] S1. Mark two points at a certain distance on the material specimen 3 to be tested, and record the distance between the two points L0 = 100mm;

[0103] S2. Use the tensioning and regulating device to fix the material specimen 3 to be tested: first, insert the material specimen 3 to be tested into the top plate 102 of the prestressed adjustable bracket 1; then fix the two ends of the material specimen 3 to be tested in the prestressed adjustable bracket 1 through the anchoring devices 2, and the two anchoring devices 2 are respectively located on the outside of the two top plates 102; when the anchoring devices 2 are fixed, the two ends of the material specimen 3 to be tested need to extend out of the anchoring devices 2 to a certain position, and the extended portion is used for reliable clamping on the universal testing machine;

[0104] S3. Fix both ends of the material specimen 3 to be tested on the universal testing machine: adjust the relative position of the top plate 102 on the prestressed adjustable bracket 1, and loosen the nut 103 on the prestressed adjustable bracket 1; then place the tensioning and regulating device as a whole on the universal testing machine, and fix both ends of the material specimen 3 to be tested on the universal testing machine, and the two marked points are located between the two anchoring devices 2;

[0105] S4. Start the universal testing machine, and apply prestress to the test material specimen 3 by adjusting the equipment parameters of the universal testing machine;

[0106] S5. When the prestress reaches the required value, keep the universal testing machine in tension state, use the video extensometer to measure the distance L1=102mm between two points of the material specimen to be tested in the tension equilibrium state of the universal testing machine, record the corresponding stress value F1=30kN, and draw the stress / strain curve of the material specimen to be tested based on L0, L1, and F1; (Generally, F1 is within 60% of the maximum breaking stress value Fmax of the material, F1=(20%~60%)Fmax, Fmax does not exceed 100kN)

[0107] S6. Adjust the top plates 102 on both sides of the tension control device close to the inner side of the anchor device 2, tighten the upper and lower nuts 103 on the top plate, so that the top plate 102 is closely abutted with the anchor device on the same side to maintain the prestress applied to the material specimen 3 to be tested;

[0108] S7. Finally, the universal testing machine unloads the load, and when the test material specimen 3 in the tensioning device is stable, the distance L2=102 mm between two points of the test material specimen 3 is measured again by the video extensometer, and the actual prestress value F2=30 kN is determined by comparing the stress / strain curve; then, the tensioning control device and the test material specimen to be tested fixed therein and applied with prestress are taken out from the universal testing machine as a whole;

[0109] S8. Confirm that the prestress of the tensioning and regulating device is effectively controlled to more than 98%, and match the prestressed material specimen 3 to be tested together with the tensioning and regulating device with the existing material performance testing machine in the laboratory.

[0110] Prestressed impact resistance test:

[0111] Prestressed material impact resistance test steps: prestress is applied to the material specimen to be tested according to the steps of Example 1, the tensioning control device and the prestressed material specimen 3 fixed inside the device are placed on the test bench as a whole, and are firmly connected to the storage table, and mechanical performance tests such as prestressed material impact resistance test or prestressed material bending resistance test are performed;

[0112] like Figure 7 As shown in the figure, under the same material, the specimens without prestressing were used as the control group, and the impact resistance tests were carried out on the specimens with prestressing and the specimens without prestressing respectively; Figure 7 (a) and Figure 7 From the experimental results of (b), it can be seen that under the same material, when prestressed or not, that is, under different prestresses, the impact damage resistance is significantly different after being subjected to the same impact capacity.

[0113] Environmental weathering test:

[0114] Environmental weather resistance test steps: Take 4 identical specimens of the material to be tested, and apply prestress to the specimens of the material to be tested according to the steps of Example 1 respectively. The tensioning control device together with the specimen of the material to be tested 3 with prestress fixed inside are placed as a whole in an environmental test box, and the environmental weather resistance test performance of the prestressed material is tested under different temperature conditions. The specimen without prestress is used as the control group, and the prestressed material is subjected to an environmental weather resistance test at different temperatures for 30 minutes. According to the experimental results in Table 1, it can be seen that: at different temperatures within the same time, the tensile strength of different prestressed materials is significantly different.

[0115] Table 1 Test results of tensile strength of material specimens at different temperatures

[0116]

[0117] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A tensioning control device for testing the mechanical properties of prestressed materials in a laboratory, characterized in that: The tensioning and regulating device comprises a prestressed adjustable bracket, an anchoring device and a distance measuring device; The prestressed adjustable support comprises a screw rod and at least two top plates, wherein the top plates are fastened to the screw rod by nuts, and the position of the top plates on the screw rod is adjustable; The anchoring device is used to fix the test piece, and two anchoring devices are provided, each anchoring device abuts against at least one outer side of the top plate; the anchoring device comprises a clamp and a wedge-shaped clip, and the wedge-shaped clip is arranged in the clamp, and the inclination angle of the wedge-shaped clip is 1°-1.5°; The distance measuring device is used to measure the distance between any two points on the test piece between the two anchoring devices.

2. The tensioning control device according to claim 1, characterized in that: The surface of the wedge-shaped clamping piece that is fitted with the test piece is provided with corrugated protrusions; and the inner surface of the wedge-shaped clamping piece is padded with sandpaper.

3. The tensioning control device according to claim 2, characterized in that: The clamp has a rectangular cross section and is provided with a square groove inside for accommodating a wedge-shaped clamp.

4. The tensioning control device according to claim 2, characterized in that: The cross section of the clamp is circular, and a circular channel matching the wedge-shaped clamp is arranged inside; the inclination angle of the wedge-shaped clamp in the circular channel is 1°; and the number of the wedge-shaped clamps is two or more.

5. The tensioning control device according to claim 1, characterized in that: A through hole for the test piece to pass through is arranged at the center of the top plate.

6. The tensioning control device according to claim 1, characterized in that: The screw rods are arranged on the four corners of the top plate, and the screw rods are parallel to the test piece; preferably, the number of the screw rods is 4.

7. The tensioning control device according to claim 1, characterized in that: The nuts include an upper nut and a lower nut symmetrically arranged on both sides of the top plate; preferably, the number of nuts on each top plate is 8.

8. The tensioning control device according to claim 1, characterized in that: The distance measuring device is selected from one of a strain gauge, a video extensometer, a fully automatic extensometer and a manual distance measuring device.

9. The tensioning control device according to any one of claims 1 to 7, characterized in that: The prestressed adjustable bracket and anchoring device are made of quenched and tempered steel material.

10. A method for testing the mechanical properties of prestressed materials in a laboratory, characterized in that: The method comprises the following steps: S1. Mark two points at a certain distance on the material specimen to be tested and record the distance between the two points; S2. Using the tensioning control device described in any one of claims 1-9 to fix the test material specimen; S3. Fix both ends of the material specimen to be tested on the universal testing machine; S4. Start the universal testing machine, and apply and maintain prestress to the test material specimen through the universal testing machine; S5. Use a distance measuring device to measure the distance between two points of the test piece of the material to be tested in the tension equilibrium state of the universal testing machine, record the corresponding stress value, and draw a stress / strain curve; S6. Adjust the top plates on both sides of the tension control device to be close to the inner side of the anchor device, and tighten the upper and lower nuts on the top plate to make the top plate closely abut against the anchor device on the same side; S7. The universal testing machine unloads the load, and when the test material specimen in the tensioning and regulating device is stable, the distance between two points of the test material specimen is measured again by the distance measuring device, and the actual prestress value is determined by comparing the stress / strain curve.

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