A double-break bending experiment device

Abstract

The utility model discloses a kind of double-breakpoint bending experimental device in the technical field of anti-bending detection, including pressing plate device and force application device, pressing plate device is clamped and protected to flat plate test piece, and ensure its stability, force application device is hydraulic press, hydraulic force is applied to test piece, the device has two pressing plate devices, pressing plate device is fixedly installed on force application device, and two sets of pressing plate device all have two force rods respectively, four point positions are formed by force rod, can be misaligned to flat plate test piece Pressing force, flat plate test piece is directly pressed to two point positions reverse break, to carry out anti-bending strength test on fiber reinforced cement-based composite material efficiently, device is simple and convenient, easy to operate, twice results are obtained by once pressing, also can slow down cracking rate, obtain stable test curve, detection process time consumption reduces by half, increase the spring and elastic pad of buffer, can ensure that flat plate test piece two break points do not affect secondary stress each other.

Description

Technical Field

[0001] This utility model relates to the field of bending resistance testing technology, and in particular to a double-breakpoint bending test device. Background Technology

[0002] New fiber-reinforced cement-based composite materials have advantages such as high ductility, high strength, and good durability. They are currently commonly used in reinforcement projects and are widely applied in bridge engineering, earthquake-resistant engineering, and building repair projects. By combining materials with different properties, the bonding of concrete and different fibers forms a unified whole, which improves the strength and toughness of the composite material and avoids the eccentric stress that occurs in traditional reinforced concrete structures due to changes in the stress state.

[0003] The use of these new composite materials requires prior performance testing. Compressive strength is a crucial parameter for concrete performance; for example, eccentric compression and tension can be converted into flexural or bending strength through stress analysis. Testing these performance parameters can significantly improve the stability and safety of structures. Therefore, ductility and high flexural strength are also primary parameters to be tested for concrete materials.

[0004] Currently, the testing methods for the mechanical properties of high-ductility fiber-reinforced cementitious composites require the fabrication of flat test specimens before testing. The testing methods mainly include three-point flexural strength and four-point flexural strength.

[0005] Regardless of the testing method, a hydraulic press is used to press and break the flat test piece. The bottom two points bear the load of the test piece, while the top is pressed by a hydraulic testing machine to measure the force applied when the piece breaks. A test piece with only one pressing point at the top is considered a three-point bending test, while one with two pressing points at the top is considered a four-point bending test. Whether it's a three-point or four-point bending test, the point of force application at the top is always between the two bearing points at the bottom.

[0006] The drawbacks of the two detection methods are: 1. Ordinary concrete flexural strength testers can only measure the flexural strength value once per test, and the two halves of the specimen formed after flexural strength are small and difficult to clamp, so they have to be discarded. This results in low utilization of sample blocks, increases the number of test operation steps, and is time-consuming and labor-intensive. 2. Existing testing methods have limited flexural strength testing cycles. Increasing the number of tests would increase testing costs, especially for high-ductility, ultra-high-performance concrete. This type of concrete tends to have high consistency, and the amount of concrete used when making test specimens is small, resulting in uneven molding and bearing structure, which leads to deviations in test results and inaccurate experimental data. 3. Although the existing device has a simple bending resistance operation, it requires a large number of tests, a lot of manpower, high cost, outdated equipment, and low work efficiency. This results in a long test process, cumbersome test work, repeated use of the device, large workload, and long cycle.

[0007] Based on this, the present invention designs a double-breakpoint bending test device to solve the above problems. Utility Model Content

[0008] The purpose of this invention is to provide a double-breakpoint bending test device. This device has two pressure plate devices, upper and lower, which are fixedly installed on the force application device. Each of the upper and lower pressure plate devices has two force-bearing rods, forming four points. These rods can apply pressure to the flat plate test piece in a staggered manner, directly causing the flat plate test piece to bend in opposite directions at two points. This allows for efficient testing of the flexural strength of fiber-reinforced cement-based composite materials. The device is simple and easy to operate, obtaining two results with a single press. It can also slow down the cracking rate, obtain a stable test curve, and reduce the testing time by half. Although the results are bidirectional, both the upper and lower sides are stress-bearing. Furthermore, the addition of buffer springs and elastic pads ensures that the two breakpoints of the flat plate test piece do not affect the secondary force application.

[0009] This invention is implemented as follows: a double-breakpoint bending test device, comprising: Pressure plate device and force application device; The pressure plate device includes a base plate, a spring, and a force-bearing rod; Each of the aforementioned pressure plate devices is equipped with two force-bearing rods and two sets of guard plates; The base plate is a sturdy flat plate erected horizontally. A side guard is provided with a vertically upward protrusion on the left side edge of the base plate, a splash guard is provided with a vertically protruding front edge of the base plate, and multiple protective plates are also provided with a vertically upward protrusion on the front and rear sides of the top of the base plate. Each pair of the guard plates forms a group, and the guard plates in the same group are symmetrically arranged on the front and rear sides of the base plate, and the axes of the guard plates in the same group coincide in the front and rear direction; The force-bearing rod is a straight rod, which is mounted on the top of the base plate. A force-bearing rod is also clamped between the same group of guard plates. The force-bearing rod is horizontally arranged in the front-back direction, and one of the force-bearing rods is located on the top of the right edge of the base plate. An elastic pad is fitted at the bottom of the force-bearing rod. The elastic pad has a U-shaped groove structure with an open top, and the force-bearing rod is locked in the groove of the elastic pad. The spring is fixed to the top of the base plate, and the upper end of the spring is locked to the elastic pad and the force rod. The force-applying device includes a support base and a hydraulic rod; the support base is a fixed base, the hydraulic rod is the force-applying end of the hydraulic testing machine, the hydraulic rod is vertically arranged, and the support base is located directly below the hydraulic rod; Each of the support base and the hydraulic rod is equipped with a pressure plate device. The two pressure plate devices have the same structure, and the front-to-back and left-to-right directions of the upper and lower pressure plate devices are opposite. The force-bearing rods of the two pressure plate devices are parallel to each other, and the force-bearing rods of the upper and lower pressure plate devices are staggered. The horizontal distance s between the axes of every two staggered force-bearing rods is the same.

[0010] Furthermore, the force-bearing rod is a solid circular steel rod, and the force-bearing rod on each pressure plate device is horizontally arranged in the front-to-back direction.

[0011] Furthermore, the elastic pad is a semi-circular elongated rubber pad, and the thickness of the elastic pad is between 5-15mm; The U-shaped groove of the elastic pad is interference-fitted with the force-bearing rod, and the diameter of the force-bearing rod is between 10-30mm.

[0012] Furthermore, an annular washer is fixed to the top of the spring; a locking rod is provided inside the spring, the locking rod is a screw, and the nut end of the locking rod is engaged with the bottom of the washer; A screw hole is provided on the outer wall of the force-bearing rod, and the threaded end of the locking rod passes through the washer and the elastic pad and is locked inside the screw hole of the force-bearing rod.

[0013] Furthermore, one or two springs are provided between the force-bearing rod and the base plate, and the spring axes on each force-bearing rod are on the same straight line.

[0014] Furthermore, the distance between the two force-bearing rods on the same pressure plate device is 2s, the diameter of each force-bearing rod is less than s, and the distance s ranges from 3 to 5 cm; The guard plate and the load-bearing rod are fitted with a clearance, and the clearance range is 0.5-1mm.

[0015] Furthermore, it also includes an energy-absorbing pad, which is a sponge pad, and the energy-absorbing pad is laid all over the force-applying pressure surface of the base plate, and the energy-absorbing pad does not obstruct the force-bearing rod.

[0016] Furthermore, the base plate is made of high-strength steel plate, and the side guards and protective plates are also made of steel plate; The splash guard is a transparent PVC partition.

[0017] The beneficial effects of this utility model are: 1. This utility model has a pressure plate device on each of the upper and lower sides of the force application device, and the flat plate test piece is placed and clamped by the pressure plate device to form a stable force state. At the same time, each pressure plate device has two force rods. By pressing the upper and lower four force rods together, four staggered and opposite force positions are formed in the upper and lower directions, forming double fracture positions. Thus, the flat plate test piece can be pressed once to obtain two fracture forces. One force application can obtain two test results. It can also slow down the cracking rate, obtain a stable test curve, and effectively improve the detection efficiency. 2. By breaking the material at two points in opposite directions, bidirectional stress data is obtained. This bidirectional breaking simulation allows for more complex engineering applications, supplementing missing data and providing richer mechanical property data for material testing, thus enabling a more comprehensive understanding of material properties. 3. This device also incorporates springs, energy-absorbing pads, and elastic pads, all of which buffer the impact of breakage, especially during the first breakage of the flat plate test piece. This effectively prevents the two different breakage data from interfering with each other, and avoids the flat plate test piece from falling or bouncing away when it breaks, ensuring that the second test can proceed normally. In addition, the addition of side guards and front splash guards can also effectively prevent concrete debris from flying out when the flat plate test piece breaks, providing a certain degree of protection. Attached Figure Description

[0018] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0019] Figure 1 This is a schematic diagram of the overall structure of this utility model; Figure 2 This is a top view of the load-bearing rod at the top of the base plate of this utility model; Figure 3 This is a schematic diagram of the internal front structure of the two mating pressure plate devices of this utility model; Figure 4 This is a schematic diagram of the external front structure of the two mating pressure plate devices of this utility model; Figure 5 This is a schematic diagram of the spring of this utility model in the assembled state at the bottom of the elastic pad.

[0020] The attached diagram lists the components represented by each number as follows: 1-Base plate, 11-Side guard, 12-Splash guard, 13-Guard plate, 2-Spring, 21-Washer, 22-Energy-absorbing pad, 23-Locking rod, 3-Force-bearing rod, 31-Elastic pad, 4-Support seat, 41-Hydraulic rod. Detailed Implementation

[0021] Please see Figures 1 to 5As shown, this utility model provides a double-breakpoint bending test device. In order to better understand the above technical solution, the above technical solution will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] In a specific embodiment of the technical solution of this utility model: Includes pressure plate device and force application device; The pressure plate device includes a base plate 1, a spring 2, and a force-bearing rod 3; Each pressure plate device is equipped with two force-bearing rods 3 and two sets of guard plates 13; The base plate 1 is a sturdy flat plate erected horizontally. A side guard 11 is vertically protruding upward from the left side edge of the base plate 1, and a splash guard 12 is vertically protruding from the front edge of the base plate 1. Multiple protective plates 13 are also vertically installed upward from the front and rear sides of the top of the base plate 1. The height of the side guard 11 can be lower than the height of the protective plate 13, and the height difference does not exceed 5mm. The height of the side guard 11 can also be the same as the height of the protective plate 13, mainly to protect the sides of the flat plate test piece.

[0023] The base plate 1 is made of high-strength steel plate, and the side guards 11 and guard plates 13 are also made of steel plates; The splash guard 12 is a transparent PVC partition. When needed, the splash guard 12 has toughness and elasticity to absorb impact energy, thereby reducing the kinetic energy of flying concrete debris and effectively reducing hazards. The splash guard 12 can also be made of rubber and silicone, just avoid using brittle materials.

[0024] Two guard plates 13 form a group, and the guard plates 13 in the same group are symmetrically arranged on the front and rear sides of the base plate 1, and the axes of the guard plates 13 in the same group coincide in the front and rear direction. The force-bearing rod 3 is a solid steel circular straight rod, and each force-bearing rod 3 on each pressure plate device is horizontally arranged in the front-back direction. The force-bearing rod 3 is mounted on the top of the base plate 1, and a force-bearing rod 3 is sandwiched between the same set of guard plates 13. The force-bearing rod 3 is horizontally arranged in the front-back direction, and one force-bearing rod 3 is located at the top of the right edge of the base plate 1. An elastic pad 31 is fitted at the bottom of the force-bearing rod 3. The elastic pad 31 has a U-shaped groove structure with an open top, and the force-bearing rod 3 is locked in the groove of the elastic pad 31. The elastic pad 31 is a semi-circular strip of rubber, and the thickness of the elastic pad 31 is between 5-15mm. The U-shaped groove of the elastic pad 31 and the force-bearing rod 3 are interference fit. The diameter of the force-bearing rod 3 is between 10-30mm, which makes the force-bearing rod 3 and the elastic pad 31 securely and stably clamped together.

[0025] A ring-shaped washer 21 is fixed at the top of the spring 2; a locking rod 23 is provided inside the spring 2. The locking rod 23 is a screw, and the nut end of the locking rod 23 is engaged with the bottom of the washer 21. A threaded hole is formed on the outer wall of the force-bearing rod 3. The threaded end of the locking rod 23 passes through the washer 21 and the elastic pad 31 and is locked inside the threaded hole of the force-bearing rod 3. Therefore, both the force-bearing rod 3 and the elastic pad 31 are locked by the locking rod 23. The nut end of the lower end of the locking rod 23 is engaged with the washer 21, which locks the upper end of the spring 2 to the force-bearing rod 3 and the elastic pad 31. The lower end of the spring 2 can also form an elastic connection, which plays a buffering role. This allows the elastic pad 31, which is prone to fatigue, to be replaced. The locking rod 23 can be easily disassembled to replace the elastic pad 31, and the damaged force-bearing rod 3 can also be replaced.

[0026] Spring 2 is fixed to the top of base plate 1, and the upper end of spring 2 is locked to elastic pad 31 and force rod 3. One or two springs 2 are set between force rod 3 and base plate 1. The axis of spring 2 set on each force rod 3 is on the same straight line, so that force rod 3 forms buffer force and elastic support on base plate 1 through spring 2. Springs with high hardness are required to have sufficient support force to ensure the stability of force rod 3. The function is the same as the buffer spring on automobile chassis, which can provide stable support and buffer shock absorption. Therefore, spring 2 needs to meet the test force strength of flat plate test piece.

[0027] The top of the base plate 1 also needs to be covered with an energy-absorbing pad 22. The energy-absorbing pad 22 is a sponge pad. The energy-absorbing pad 22 is laid on the force-applying pressure surface of the base plate 1. That is, the energy-absorbing pad 22 of the pressure plate device at the top of the support seat 4 is laid on the top of the base plate 1, while the energy-absorbing pad 22 of the pressure plate device at the bottom of the hydraulic rod 41 is laid on the bottom of the base plate 1. The energy-absorbing pad 22 does not cover the force-bearing rod 3. The energy-absorbing pad 22 plays a supplementary role in the gap between the force-bearing rods 3. The flat plate test piece is placed on top of the energy-absorbing pad 22.

[0028] The force-applying device includes a support base 4 and a hydraulic rod 41; the support base 4 is a fixed base, the hydraulic rod 41 is the force-applying end of the hydraulic testing machine, the hydraulic rod 41 is vertically arranged, and the support base 4 is located directly below the hydraulic rod 41. A pressure plate device is installed on the support base 4 and the hydraulic rod 41. The two pressure plate devices have the same structure, and the front-to-back and left-to-right directions of the upper and lower pressure plate devices are opposite. The force-bearing rods 3 of the two pressure plate devices are parallel to each other, and the force-bearing rods 3 of the upper and lower pressure plate devices are staggered. The horizontal distance s between the axes of every two staggered force-bearing rods 3 is the same.

[0029] The distance between the two force rods 3 on the same pressure plate device is 2s, and the diameter of each force rod 3 is less than s. The purpose of this design is to ensure that the force rods 3 maintain a certain distance when pressing down, so that the test plate can be pressed and broken. If the distance between the force rods 3 is too close, the pressing force on the plate will be affected by the force rods 3 on the upper and lower sides. The distance s between the force rods 3 of this device needs to be kept within the range that does not affect the accuracy of the test. The distance s can be in the range of 3-5cm. The guard plate 13 and the load-bearing rod 3 are fitted with a clearance, and the clearance range is 0.5-1mm.

[0030] It should be noted that: Existing methods for testing concrete strips or flat plates, whether three-point or four-point bending tests, only involve a single bend. The bottom is supported on the left and right sides, while the hydraulic rod 41 at the top presses down in the middle, causing the flat plate test piece to break only downwards from the middle. Figure 3 As shown, this device applies opposing forces at two points (3) on the two interlocking, jacked middle force-bearing rods, thus causing the test specimen to fracture bidirectionally. Each press yields two sets of fracture data, and these data are in opposite directions—a feature not found in existing technologies, which typically apply forces unidirectionally. This bidirectional fracture method significantly increases the testing efficiency of the test specimen, resulting in more fracture results and more comprehensive test curve data. Furthermore, it simulates the flexural strength of concrete under extreme conditions. The first fracture yields conventional data, while the second fracture yields high-strength data indicating greater resistance to fracture. This not only increases experimental efficiency but also provides richer data, supporting research on the flexural strength of concrete.

[0031] In use, the two pressure plate devices are installed stably, and then the flat plate test piece is placed on top of the two force-bearing rods 3. After alignment, ensure that the flat plate test piece is within the range of the side guards 11, splash guards 12 and guard plates 13 on both sides. Then, start the hydraulic rod 41 to press. At this time, the flat plate test piece will be bent by one of the force-bearing rods 3. However, the bending will not completely break it. At this time, the broken part of the flat plate test piece has lost its support. If pressure is continued, the other force point of the flat plate test piece will also bend, forming two bending effects and two data points, thus completing the bending test.

[0032] The four load-bearing rods 3 are of the same length and in the same direction. They all need to be set horizontally and parallel to each other.

[0033] The four load-bearing rods are distributed alternately, with the center-to-center distance between the upper and lower rods being 100mm and the center-to-center distance between the upper and lower rods being 50mm.

[0034] The final result is a symmetrical stress structure diagram centered on the test specimen. The two pressure plate devices are located at the top and bottom ends of the test specimen, and the concrete test specimen must be wrapped in all directions. The side guards 11 and the protective plates 13 must be clamped around the test specimen to ensure that the test specimen does not slip out. Each force rod 3 must be in contact with the force-bearing surface of the test specimen to ensure uniform stress during the test.

[0035] The U-shaped elastic pad 31 ensures that it wraps around the force-bearing rod 3 and does not come into direct contact with the flexural strength test piece during the test, ensuring that the test piece and the force-bearing rod 3 are in hard contact, thus avoiding energy transfer or loss during the stress process of the test piece; the outer side of the force-bearing rod 3 and the spring 2 are tightly wrapped into a whole, absorbing the energy of vibration during the test and maintaining overall stability.

[0036] Thus, through various buffer components, the second flexural strength test is ensured to be unaffected by the failure of the first flexural strength test; the energy-absorbing pad 22 sponge is evenly distributed on the inner side of the side guard 11 to prevent the fragments after the failure of the first flexural strength test from directly contacting the pressure plate device and generating vibrations that are detrimental to the second flexural strength test.

[0037] Furthermore, it should be noted in the description of this utility model that terms such as "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," "outer," "front," "back," "top," and "bottom" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0038] While specific embodiments of the present invention have been described above, those skilled in the art should understand that the specific embodiments described are merely illustrative and not intended to limit the scope of the present invention. Equivalent modifications and variations made by those skilled in the art in accordance with the spirit of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A double-breakpoint bending test apparatus, characterized in that, include: Pressure plate device and force application device; The pressure plate device includes a base plate (1), a spring (2), and a force-bearing rod (3); Each of the pressure plate devices is provided with two force-bearing rods (3) and two sets of guard plates (13); The base plate (1) is a sturdy flat plate erected horizontally. A side guard (11) is provided on the left side edge of the base plate (1) with a vertical upward protrusion. A splash guard (12) is provided on the front edge of the base plate (1). Multiple guard plates (13) are also provided on the front and rear sides of the top of the base plate (1) with a vertical upward protrusion. Each pair of the guard plates (13) forms a group, and the guard plates (13) in the same group are symmetrically arranged on the front and rear sides of the base plate (1), and the axes of the guard plates (13) in the same group coincide in the front and rear direction; The force-bearing rod (3) is a straight rod. The force-bearing rod (3) is mounted on the top of the base plate (1), and a force-bearing rod (3) is sandwiched between the same group of guard plates (13). The force-bearing rod (3) is set horizontally in the front-back direction, and one of the force-bearing rods (3) is set on the top of the right side edge of the base plate (1). An elastic pad (31) is fitted at the bottom of the force-bearing rod (3). The top of the elastic pad (31) is an open long strip U-shaped groove. The force-bearing rod (3) is locked in the groove of the elastic pad (31). The spring (2) is fixed on the top of the base plate (1), and the upper end of the spring (2) is locked with the elastic pad (31) and the force rod (3); The force-applying device includes a support base (4) and a hydraulic rod (41); the support base (4) is a fixed base, the hydraulic rod (41) is the force-applying end of the hydraulic testing machine, the hydraulic rod (41) is vertically arranged, and the support base (4) is located directly below the hydraulic rod (41); A pressure plate device is installed on each of the support base (4) and the hydraulic rod (41). The two pressure plate devices have the same structure, and the front-to-back and left-to-right directions of the upper and lower pressure plate devices are opposite. The force rods (3) of the two pressure plate devices are parallel to each other, and the force rods (3) of the upper and lower pressure plate devices are staggered. The horizontal distance s between the axes of each two staggered force rods (3) is the same.

2. The double-breakpoint bending test apparatus according to claim 1, characterized in that: The force-bearing rod (3) is a solid circular steel rod, and the force-bearing rod (3) on each pressure plate device is horizontally arranged in the front-back direction.

3. The double-breakpoint bending test apparatus according to claim 1, characterized in that: The elastic pad (31) is a semi-circular strip of rubber, and the thickness of the elastic pad (31) is between 5-15 mm. The U-shaped groove of the elastic pad (31) is interference-fitted with the force rod (3), and the diameter of the force rod (3) is between 10-30mm.

4. The double-breakpoint bending test apparatus according to claim 1, characterized in that: A ring-shaped washer (21) is fixed at the top of the spring (2); a locking rod (23) is provided inside the spring (2), the locking rod (23) is a screw, and the nut end of the locking rod (23) is fitted into the bottom of the washer (21); The outer wall of the force-bearing rod (3) has a screw hole, and the threaded end of the locking rod (23) passes through the washer (21) and the elastic pad (31) and is locked inside the screw hole of the force-bearing rod (3).

5. The double-breakpoint bending test apparatus according to claim 1, characterized in that: One or two springs (2) are provided between the force-bearing rod (3) and the base plate (1), and the axes of the springs (2) provided on each force-bearing rod (3) are on the same straight line.

6. The double-breakpoint bending test apparatus according to claim 1, characterized in that: The distance between the two force rods (3) on the same pressure plate device is 2s, the diameter of each force rod (3) is less than s, and the distance s ranges from 3 to 5 cm; The guard plate (13) and the force-bearing rod (3) are in clearance fit, and the clearance range is 0.5-1mm.

7. The double-breakpoint bending test apparatus according to claim 1, characterized in that: It also includes an energy-absorbing pad (22), which is a sponge pad. The energy-absorbing pad (22) is spread on the force-pressing surface between the base plate (1) and the test piece. The energy-absorbing pad (22) does not block the force-bearing rod (3).

8. The double-breakpoint bending test apparatus according to claim 1, characterized in that: The base plate (1) is a high-strength steel plate, and the side guards (11) and guard plates (13) are also steel plates.

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