Creep testing device, tension and compression creep testing system and testing method

Abstract

The present invention provides a creep testing device and a testing system and method using the device. The creep testing device at least includes a device frame, a specimen fixture, a load loading mechanism and a linear displacement sensor. The specimen is placed in the middle of the specimen fixture. One end of the specimen fixture is a fixed end, and the position of the fixed end relative to the device frame remains unchanged, and the other end is a movable end; the load loading mechanism at least includes a pulley block and a load. The tensile and compressive creep testing system provided by the present invention includes a sealable box body, the box body is provided with a box door, the box body is provided with a constant temperature and humidity device, and the box body is provided with the creep testing device of the present invention. The long-term automatic collection, storage and display of pure tensile and pure compressive creep of bamboo / wood-based materials in a high-precision controllable climate environment can be realized, and through the simple transformation of the specimen fixture and the pulley block, the free switching of tensile and compressive creep can be realized on a set of systems, realizing a substantial miniaturization and lightweight of the equipment.

Description

Technical Field

[0001] The invention relates to a physical and mechanical property testing device for bamboo / wood-based materials and to a tension-compression creep testing system. Background Art

[0002] Wood, bamboo or bamboo-based materials are the only renewable green materials among the four major building materials. However, although creep performance, one of the important indicators for measuring its long-term service performance, has been studied for more than half a century, there is still much controversy in both the academic and engineering circles about its occurrence and development mechanism and its quantitative prediction. In particular, the normal creep (Normal Creep) and mechanical adsorption creep (Mechanical Sorptive Creep, referred to as MSC) of such materials in natural service environments (i.e. variable temperature and humidity environments) have always been hot and difficult issues in academic research. Among them, the test system that can simultaneously simulate the natural service environment and can automatically measure, present and save the creep deformation is the key to studying such issues.

[0003] In the prior art, static bending creep is often used to study the creep of wood or bamboo, such as the Chinese invention patent application "Creep test device, wood creep test system and test method" (application number 2020102392173) submitted by the applicant on March 30, 2020, which discloses a creep test device and a test system for the improved creep test device of the present invention. The wood creep test system provided by the present invention can simultaneously test a certain number of specimens during the creep test of wood. The entire system of the present invention can perform long-term, continuous and stable detection, recording and display of the general creep and complex wetting creep deflection, shrinkage and swelling, and environmental temperature and humidity parameters of wood, providing an experimental basis and a test platform for the exploration of the behavior laws and creep mechanisms of wood MSC.

[0004] However, the problem that cannot be avoided when using a single static flexure creep to study wood / bamboo is that, from the perspective of stress analysis, the static flexure creep of the material is actually the coupling of the compression creep of the upper part of the material and the tensile creep of the lower part. The special anisotropic material properties of wood and bamboo lead to the great differences in their mechanical properties under tension, compression and static flexure stress. For example, the tensile elastic modulus of most wood is 1.1-1.2 times the bending elastic modulus and about 1.1 times the compressive elastic modulus. More importantly, the basic physical and mechanical properties of wood in this stress direction are inconsistently affected by the variable temperature and humidity environment. Therefore, using a single static flexure creep to study the creep properties of wood / bamboo is bound to cover up the special creep laws and properties of wood / bamboo under pure tension and pure compression stress. In addition, the huge differences in the sensitivity of wood / bamboo to environmental temperature and humidity in tension and compression, dry shrinkage and wet swelling, and environmental temperature and humidity make this research method also have major problems from the perspective of scientific research.

[0005] The current research on the creep performance of bamboo-based materials under the tension / compression mode is still in its early stages. Due to the limitations of the environmental temperature and humidity control system and its space, most of the current research focuses on the creep test of simple specimens under indoor or outdoor conditions, and lacks research on the tension / compression creep under the condition that the environmental temperature and humidity can be greatly controlled. If the creep test is performed using the existing tension / compression instrument, the equipment is expensive, the test method is single, and the test content and measured data are even more lackluster. Therefore, the existing technology lacks a device for creep testing in the tension / compression mode that can realize the automatic collection, processing, storage and intuitive presentation of test creep data, which greatly restricts the in-depth and development of related research. Summary of the invention

[0006] In order to overcome the above-mentioned defects, the present invention provides a creep testing device and a testing system using the device, which can realize the long-term automatic collection, storage and display of pure tensile and pure compressive creep of bamboo / wood-based materials in a high-precision controllable climate environment. The creep test accuracy reaches 0.001mm, which fully meets the accuracy requirements of wood / bamboo creep testing. Moreover, through simple transformation of the specimen fixture and the pulley set, free switching between tensile and compressive creep can be achieved in a set of system, realizing substantial miniaturization and lightweight of the equipment.

[0007] The present invention is achieved through the following technical solutions:

[0008] A creep test device comprises at least a device frame, a specimen fixture, a load-loading mechanism and a linear displacement sensor. The specimen fixture, the load-loading mechanism and the linear displacement sensor are all arranged on the device frame, wherein the specimen fixture is used to place a specimen for creep test, the specimen is placed in the middle of the specimen fixture, one end of the specimen fixture is a fixed end, the position of the fixed end relative to the device frame remains unchanged, and the other end is a movable end; the load-loading mechanism comprises at least a pulley block and a load, the pulley block has at least one movable pulley and a plurality of fixed pulleys, the load is connected to the movable end on the specimen fixture after passing through the pulley block through a steel wire rope, and a force is applied to the specimen of the creep test through the specimen fixture at the movable end, and the direction of the force is in the same straight line as the axis of the specimen; the linear displacement sensor collects displacement data of the specimen during creep test.

[0009] The device frame comprises a top plate and a bottom plate which are arranged opposite to each other, and the top plate and the bottom plate are fixedly connected by at least four mutually parallel supporting rods.

[0010] The direction of the applied force of the specimen fixture is parallel to the direction of the support rod. The load loading mechanism is arranged above the specimen fixture, and the fixed pulley of the load loading mechanism is fixed on the top plate.

[0011] Furthermore, fixture base plates are fixedly provided at both ends of the specimen fixture, and four support rods pass vertically through the fixture base plates, wherein the fixture base plate located at the fixed end is fixed in position relative to the support rods, and the fixture base plate located at the movable end can drive the movable end of the specimen fixture to slide along the direction of the support rods, thereby applying a tensile or compressive force to the specimen on the specimen fixture.

[0012] As the tensile creep test device of the present invention, the fixture seat plate near the bottom plate on the specimen fixture can be fixedly connected to the bottom plate as a fixed end, and the fixture seat plate at the movable end is connected to the steel wire rope of the load loading mechanism. When the load passes through the steel wire rope and the pulley block, a force is generated on the movable end. Since the fixture seat plate at the movable end is on the side close to the top plate relative to the specimen, a tensile force is generated on the specimen.

[0013] As the compression creep test device of the present invention, the fixture seat plate on the specimen fixture away from the bottom plate can be fixedly connected to the bottom plate as the fixed end, and the fixture seat plate at the movable end is connected to the steel wire rope of the load loading mechanism. When the load passes through the steel wire rope and the pulley block, a force is generated on the movable end. Since the fixture seat plate at the movable end is on the side close to the bottom plate relative to the specimen, a compressive force is generated on the specimen.

[0014] Furthermore, a load seat plate parallel to the fixture seat plate is provided at the end of the wire rope, four support rods pass vertically through the load seat plate respectively, the load seat plate and the support rods are slidably matched, and the load seat plate is fixedly connected to the fixture seat plate at the moving end of the specimen fixture. The force of the pulley block can be evenly applied to the moving end of the specimen fixture through the load seat plate, ensuring that the force is stable and effective.

[0015] The movable pulley is arranged above the load base plate, and the movable pulley is rotatably connected with the load base plate, that is, the load base plate is equivalent to a part of the movable pulley and moves with the movable pulley.

[0016] There are two fixed pulleys, wherein the first fixed pulley is arranged above the movable pulley, and the second fixed pulley is arranged at one side, the first fixed pulley and the second fixed pulley are both rotatably connected to the top plate, and the axles of the first fixed pulley, the second fixed pulley and the movable pulley are parallel to each other. The first fixed pulley and the movable pulley are arranged up and down, which can ensure that the force transmitted from the load through the wire rope can act vertically on the load seat plate.

[0017] The movable pulley and the first fixed pulley are both three-wheel pulleys, and the second fixed pulley is a single-wheel pulley. The wire rope is wound between the movable pulley and the first fixed pulley, and finally passed over the second fixed pulley. There are two ways to wind the wire rope between the movable pulley and the first fixed pulley, that is, the end of the wire rope is either connected to the hook of the movable pulley or to the hook of the first fixed pulley. In this way, two load force amplification ratios of 1:7 or 1:6 can be generated.

[0018] Preferably, the end of the wire rope is connected to the hook of the movable pulley, and after the wire rope is wound three times between the movable pulley and the first fixed pulley, it is led out from the movable pulley and then wound over the second fixed pulley, and the front end of the wire rope is vertically downwardly connected to the load. This can produce a 1:7 force amplification effect.

[0019] The present invention provides two linear displacement sensors, which are respectively fixedly connected to the nearest support rods through sensor brackets, and the probes of the linear displacement sensors are in opposite directions; a pair of receiving platforms are provided in the middle of the specimen on the specimen fixture, one end of the receiving platform is fixedly connected to the specimen, and the other end extends to the front of the probe of the linear displacement sensor. The receiving platform is fixed at both ends of the effective section of the specimen, and the test value obtained by the linear displacement sensor is the change amount of the effective section of the specimen.

[0020] As the tensile creep testing device of the present invention, further, the specimen fixture is a pair of tensile clamps, which are respectively fixed on the fixture base plates, each tensile clamp is provided with an open slot, the open slots of the two tensile clamps are opposite, and the two ends of the specimen are respectively confined in the open slots of the tensile clamps.

[0021] The inner walls on both sides of the opening groove are provided with anti-slip grooves, which can effectively prevent the displacement of the test piece in the opening groove due to the acting force.

[0022] In order to better prevent the specimen from moving in the direction of the force due to the force in the open groove, the open groove is a dovetail groove.

[0023] The inner wall of the opening groove is smooth, and a wedge-shaped slider is provided between the specimen and the inner walls on both sides of the opening groove. The side projection of the wedge-shaped slider is a right-angle trapezoid. The side of the wedge-shaped slider that fits the specimen is a vertical surface, and anti-slip grooves are provided on the vertical surface. The vertical surface of the wedge-shaped slider contacts and clamps the specimen. The two ends of the specimen do not need to be processed into the same cross-sectional shape (trapezoidal) as the opening groove, but can be directly processed into a pair of parallel planes, reducing the difficulty of processing the specimen. The anti-slip grooves on the vertical surface can prevent the displacement of the specimen relative to the wedge-shaped slider in the direction of the force.

[0024] A tightening bolt is provided at the bottom of the stretching clamp seat at a position corresponding to the wedge-shaped slider. The tightening bolt passes through the bottom of the stretching clamp seat and presses against the bottom of the wedge-shaped slider. The tightening bolt is threadedly matched with the stretching clamp seat. The wedge-shaped slider is pushed toward the notch of the opening slot by the tightening bolt, which can generate lateral pressure on both sides of the end of the specimen, thereby obtaining a better specimen restriction effect.

[0025] Limit rods are respectively arranged at the open ends of the opening groove, and the two ends of the limit rods are fixedly connected to the tensile clamp seat. The limit rods can not only strengthen the clamping force of the wedge-shaped sliders on both sides of the end of the specimen, but also prevent the wedge-shaped sliders from sliding in the opening groove.

[0026] As the compression creep test device of the present invention, further, the specimen fixture is a pair of pressure plates, the pressure plates are respectively fixed on the fixture base plate, each pressure plate is provided with a limit groove, the limit grooves of the two pressure plates are opposite, and the two ends of the specimen are respectively limited in the limit grooves of the pressure plates. The limit groove can prevent the displacement of the specimen in the non-force direction.

[0027] The tensile and compressive creep testing system provided by the present invention comprises a sealable box body, the box body is provided with a box door, the box body is provided with a constant temperature and humidity device, and at least one creep testing device of the present invention is arranged in the box body.

[0028] A frame for fixing a creep test device is provided in the box body. At least one creep test device is provided on the frame. The top of the device frame of the creep test device is horizontally fixed on the top of the frame. The lengths of the top plate and the bottom plate of the device frame are both equal to the width of the top of the frame.

[0029] The lengths of the fixture seat plate and the load seat plate are equal and both are smaller than the length of the bottom plate; there are six support rods, two of which are close to the box door and connect the top plate and the bottom plate, and the other four support rods connect the top plate and the bottom plate and pass through the fixture seat plate and the load seat plate.

[0030] The load of the load-loading mechanism is arranged on the side close to the box door.

[0031] The first fixed pulley and the second fixed pulley of the load-loading mechanism are arranged from the inside to the outside along the center line of the longer direction of the top plate, and the movable pulley is located directly below the first fixed pulley; the first fixed pulley, the movable pulley, the load seat plate, the fixture seat plate, the specimen fixture and the axis line and center of gravity of the specimen are all on the same vertical line, so as to ensure that the force can be effectively transmitted to the specimen.

[0032] A lifting device is arranged just below the load and is placed on the bottom plate.

[0033] The lifting device is a jack.

[0034] A cushion is placed on the bottom plate directly below the load. The cushion is mainly used to prevent damage to the equipment caused by the load falling when the specimen is broken by the load during the test.

[0035] The present invention uses the above-mentioned tensile and compressive creep testing system to test the method, comprising the following steps:

[0036] Step 1, select a specimen fixture according to the test purpose, install the specimen to be tested on the specimen fixture, fix the fixture base plate at the fixed end of the specimen fixture, and fix the fixture base plate at the movable end of the specimen fixture to the load base plate;

[0037] Step 2, installing the receiving platform on the test piece, fixing the position of the linear displacement sensor, and placing the probes of the linear displacement sensor against the surface of the receiving platform respectively;

[0038] Step 3, place the lifting device on the bottom plate, use the lifting device to lift the load and connect it to the wire rope;

[0039] Step 4, lower the lifting device until the load is suspended in the air, remove the lifting device, and lay a buffer pad on the bottom plate under the load;

[0040] Step 5, close the box door, start the constant temperature and humidity device to control the temperature and humidity in the box, and monitor the data in real time;

[0041] Step 6, inputting the temperature, humidity, wind speed in the box and the displacement signal of the test piece collected in step 5 into the computer for data storage, processing, analysis and display. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a three-dimensional schematic diagram of the tensile creep testing device of the present invention.

[0043] Figure 2 It is a schematic side view of the tensile creep testing device of the present invention.

[0044] Figure 3 It is a three-dimensional schematic diagram of the compression creep testing device of the present invention.

[0045] Figure 4 It is a schematic side view of the compression creep testing device of the present invention.

[0046] Figure 5 It is a schematic diagram of the specimen fixture of the tensile creep test device of the present invention.

[0047] Figure 6 It is a schematic diagram of the tensile clamp seat of the tensile creep testing device of the present invention.

[0048] Figure 7 It is a schematic diagram of the specimen fixture of the compression creep test device of the present invention.

[0049] Figure 8 It is a schematic diagram of the pressure plate of the compression creep testing device of the present invention.

[0050] Fig. 9 It is a schematic diagram of the structure of the fixture base plate of the creep testing device of the present invention.

[0051] Fig.10 It is a schematic diagram of the structure of the creep testing system of the present invention.

[0052] Fig.11 It is a schematic diagram of the box structure of the creep testing system of the present invention.

[0053] Fig.12 It is a schematic diagram of the frame structure of the creep testing system of the present invention.

[0054] Fig.13 This is a state diagram of the creep test system rack of the present invention.

[0055] Fig.14 It is a schematic diagram of the connection structure between the first fixed pulley, the second fixed pulley and the top plate.

[0056] Fig.15 It is a schematic diagram of the connection structure between the movable pulley and the load seat plate.

[0057] Fig.16 It is a schematic diagram of the connection structure between the stretching clamp seat and the fixture seat plate.

[0058] Fig.17 It is a schematic diagram of the connection structure between the pressure plate and the fixture base plate. DETAILED DESCRIPTION

[0059] Combination Figures 1 to 5 As shown, the creep testing device of the present invention at least includes a device frame 100, a specimen fixture 200, a load loading mechanism 300 and a linear displacement sensor 400, and the specimen fixture 200, the load loading mechanism 300 and the linear displacement sensor 400 are all arranged on the device frame 100.

[0060] In this embodiment, the device frame 100 includes a top plate 110 and a bottom plate 120 which are arranged opposite to each other in an upper and lower direction. The top plate 110 and the bottom plate 120 are fixedly connected by at least four supporting rods 130 which are parallel to each other.

[0061] The specimen fixture 200 is used to place a specimen 201 for creep testing. The specimen 201 is placed in the middle of the specimen fixture 200. One end of the specimen fixture 200 is a fixed end 202, and the position of the fixed end 202 relative to the device frame 100 remains unchanged. The other end is a movable end 203.

[0062] In order to facilitate the connection between the specimen fixture 200 and the device frame 100, fixture base plates 204 are fixed at both ends of the specimen fixture 200, and four support rods 130 pass vertically through the fixture base plates 204, such as Figure 1 and Figure 3 The fixture base plate 204 is rectangular, and the support rods 130 pass through the four corners of the fixture base plate 204. The fixture base plate 204 at the fixed end 202 is fixed relative to the support rod 130, and the fixture base plate 204 at the movable end 203 can drive the movable end 203 of the specimen fixture 200 to slide along the direction of the support rod 130, thereby applying a tensile or compressive force to the specimen 201 on the specimen fixture 200.

[0063] As long as a force acts on the moving end 203, a force can be generated on the test piece 201. As for which end is used as the fixed end and which end is used as the moving end, and whether the creep test is a tensile creep test or a compressive creep test, the movement of one end can be restricted while the other end is allowed to move relatively. According to the direction of movement, the same device can be applied to different creep tests.

[0064] The force is provided by the load loading mechanism 300, which at least includes a pulley block and a load 301. The pulley block has at least one movable pulley 302 and a plurality of fixed pulleys. The load loading mechanism 300 is disposed above the specimen fixture 200, and the fixed pulley of the load loading mechanism 300 is fixed on the top plate 110. The load 301 passes through the pulley block through the steel wire rope 303 and is connected to the movable end 203 on the specimen fixture 201, and applies a force to the specimen 201 of the creep test through the specimen fixture 200 at the movable end 203. The direction of the force is in the same straight line as the axis of the specimen 201, and the direction of the force applied by the specimen fixture 200 is parallel to the direction of the support rod 130, so that the displacement of the movable end 203 can be achieved.

[0065] like Figure 1 and Figure 2 As shown, when a tensile creep test is required, the fixture base plate 204 on the specimen fixture 200 close to the bottom plate 120 can be fixedly connected to the bottom plate 120 as the fixed end 202, and the fixture base plate 204 of the mobile end 203 is connected to the steel wire rope 303 of the load loading mechanism 300. When the load 301 passes through the steel wire rope 303 and the pulley block, a force is generated on the mobile end 203. The fixture base plate 204 of the mobile end 203 is on the side of the top plate 110 relative to the specimen, so when the mobile end 203 is pulled, it is pulled in the direction of the top plate 110, and a tensile force is generated on the specimen 201.

[0066] like Figure 3 and Figure 4 As shown, when a compression creep test is required, the fixture base plate 204 on the specimen fixture 200 away from the bottom plate 120 can be fixedly connected to the bottom plate 120 as the fixed end 202, and the fixture base plate 204 of the mobile end 203 is connected to the steel wire rope 303 of the load loading mechanism 300. When the load 301 passes through the steel wire rope 303 and the pulley block, a force is generated on the mobile end 203. The fixture base plate 204 of the mobile end 203 is on the side close to the bottom plate 120 relative to the specimen. When the mobile end 203 is pulled, it is still pulled in the direction of the top plate 110, so a compressive force is generated on the specimen 201 at this time.

[0067] When performing a tensile test, the fixture base plate 204 of the fixed end 202 can be directly fixedly connected to the base plate 120 by bolts, and the fixture base plate 204 of the movable end 203 can be directly connected to the wire rope 303 to complete the test.

[0068] However, when performing the compression test, the load-applying mechanism 300 in this embodiment cannot generate a force in the direction of the bottom plate 120. In order to compress the specimen, the clamp seat plate 204 close to the top plate 110 can only be fixed, and then the compression force is generated by pulling the clamp seat plate 204 close to the bottom plate 120. If the clamp seat plate 204 is directly fixedly connected to the support rod, it is not easy to achieve, because the friction between the support rod and the clamp seat plate must be minimized during the experiment, and the surface of the support rod must be smooth. The surface of the support rod 130 cannot be damaged by using a limiting structure or a locking structure just to fix the clamp seat plate 204.

[0069] In addition, the force of the load-adding mechanism 300 bypasses the nearest fixture base plate 204 and then is connected to the fixture base plate 204 close to the bottom plate 120 , which makes it difficult to ensure that the force can act on the specimen 201 effectively and accurately.

[0070] Therefore, in this embodiment, a load seat plate 304 parallel to the fixture seat plate 204 is provided at the end of the steel wire 303, and the structure of the load seat plate 304 is substantially the same as that of the fixture seat plate 204. Four support rods 130 also vertically pass through the four corners of the load seat plate 304, respectively, and the load seat plate 304 and the support rods 130 are slidably matched. The load seat plate 304 is fixedly connected to the fixture seat plate 204 of the moving end 203 of the specimen fixture 200, driving it to move along the support rods 130. The force of the pulley block can be evenly applied to the moving end 203 of the specimen fixture 200 through the load seat plate 304, ensuring that the force is stable and effective.

[0071] In this embodiment, the structure of the fixture base plate 204 is as follows: Fig. 9 , near the four corners, there are through holes 215 for the support rods 130 to pass through. On the diagonal lines near the corners, there are four through holes 216, which are for bolts to pass through to connect the clamp base plate 204 with the bottom plate 120. The structure of the load base plate 304 is the same as that of the clamp base plate 204, and the positions and sizes of the through holes are the same.

[0072] like Figure 1 As described above, when performing a tensile test, the load seat plate 304 is fixedly connected to the nearest fixture seat plate 204. Figure 3 , Figure 4When performing a compression test, the load base plate 304 is fixedly connected to the fixture base plate 204 near the bottom plate 120 by a pair of bolts 214 passing through two through holes 216 on the same diagonal line, while the fixture base plate 204 near the load base plate 304 is fixedly connected to the bottom plate 120 by a pair of bolts 313 passing through two through holes 216 on another diagonal line. In addition to connecting two components, the bolts 214 and 213 need to pass through a fixture base plate. In order to avoid interference, the diameter of the through hole 216 should be larger than the diameter of the bolts 214 and 213.

[0073] The movable pulley 302 in this embodiment is arranged above the load base plate 304, and the movable pulley 302 is rotatably connected to the load base plate 304. That is, the load base plate 304 is equivalent to a part of the movable pulley 302 and moves with the movable pulley 302.

[0074] Combination Figure 1 and Figure 3 There are two fixed pulleys, wherein the first fixed pulley 305 is arranged above the movable pulley 302, and the second fixed pulley 306 is arranged on one side. The first fixed pulley 305 and the second fixed pulley 306 are both rotatably connected to the top plate 110, and the axles of the first fixed pulley 305, the second fixed pulley 306 and the movable pulley 302 are parallel to each other. The first fixed pulley 305 and the movable pulley 302 are arranged up and down, which can ensure that the force transmitted from the load 301 through the wire rope 303 can act vertically on the load seat plate 304.

[0075] The movable pulley 302 and the first fixed pulley 305 are both three-wheel pulleys, and the second fixed pulley is a single-wheel pulley 306. The wire rope 303 is wound between the movable pulley 302 and the first fixed pulley 305, and finally passed over the second fixed pulley 306. There are two ways to wind the wire rope 303 between the movable pulley 302 and the first fixed pulley 305, that is, the end of the wire rope 303 is either connected to the hook of the movable pulley 302 or connected to the hook of the first fixed pulley 305. In this way, two load 301 force amplification ratios of 1:7 or 1:6 can be generated.

[0076] In this embodiment, the end of the steel wire 303 is first connected to the hook of the movable pulley 302, and the steel wire 303 is wound three times between the movable pulley 302 and the first fixed pulley 305, and then drawn out from the movable pulley 302 and wound over the second fixed pulley 306, and the front end of the steel wire 303 is vertically downwardly connected to the load 301. In this way, a 1:7 force amplification effect can be generated.

[0077] The linear displacement sensor 400 collects displacement data of the test piece 201 during the creep test.

[0078] Combination Figure 1 , 4 , 5 and Figure 7The present invention has two linear displacement sensors 400, which are respectively fixedly connected to the nearest support rod 130 through a sensor bracket 401. Whether it is a tensile creep test or a compressive creep test, it is necessary to test the change of the effective section of the test piece 201, so the probes of each group of linear displacement sensors 400 are in opposite directions.

[0079] A pair of receiving platforms 402 are provided in the middle of the specimen 201 on the specimen fixture 200, one end of the receiving platform 402 is fixedly connected to the specimen 201, and the other end is respectively extended in front of the probe of the linear displacement sensor 400. The receiving platform 402 is fixed at both ends of the effective section of the specimen 201, and the test value obtained by the linear displacement sensor 400 is the change amount of the effective section of the specimen 201.

[0080] As the tensile creep test device of the present invention, Figure 5 As shown, the specimen fixture 200 is a pair of tensile clamp seats 205, and the tensile clamp seats 205 are respectively fixed on the fixture base plate 204, combined with Figure 6 Each stretching clamp seat 205 is provided with an open slot 206 , the open slots 206 of the two stretching clamp seats 205 are opposite to each other, and the two ends of the specimen 201 are respectively confined in the open slots 206 of the stretching clamp seats 205 .

[0081] Anti-slip grooves 207 may be directly provided on the inner walls of both sides of the opening groove 206 , and the anti-slip grooves 207 may effectively prevent the displacement of the test piece 201 in the opening groove 206 due to the acting force.

[0082] In order to better prevent the test piece 201 from moving in the opening groove 206 along the direction of the force due to the force, the opening groove 206 is a dovetail groove.

[0083] The inner wall of the opening groove 206 is smooth. A wedge-shaped slider 208 is provided between the specimen 201 and the inner walls of the opening groove 206 on both sides. The side projection of the wedge-shaped slider 208 is a right-angled trapezoid. The side of the wedge-shaped slider 208 that is in contact with the specimen 201 is a vertical surface, and an anti-slip pattern 207 is provided on the vertical surface. The vertical surface of the wedge-shaped slider 208 contacts and clamps the specimen 201. The two ends of the specimen 201 do not need to be processed into the same cross-sectional shape (trapezoidal) as the opening groove 206, and can be directly processed into a pair of parallel planes, thereby reducing the processing difficulty of the specimen 201. The anti-slip pattern 207 on the vertical surface can prevent the displacement of the specimen 201 relative to the wedge-shaped slider 208 in the direction of the force.

[0084] A tightening bolt 209 is provided at the bottom of the stretching clamp seat 205 at a position corresponding to the wedge-shaped slider 208. The tightening bolt 209 passes through the bottom of the stretching clamp seat 205 and presses against the bottom of the wedge-shaped slider 208. The tightening bolt 209 is threadedly engaged with the stretching clamp seat 205. The wedge-shaped slider 208 is pushed toward the notch of the opening groove 206 by the tightening bolt 209, which can generate lateral pressure on both sides of the end of the test piece 201, thereby obtaining a better effect of restricting the test piece 201.

[0085] Limiting rods 210 are respectively provided at the open ends of the opening slot 206, and the two ends of the limiting rod 210 are fixedly connected to the tensile clamp seat 205. The limiting rod 210 can not only strengthen the clamping force of the wedge-shaped sliders 208 on both sides of the end of the specimen 201, but also prevent the wedge-shaped sliders 208 from sliding in the opening slot 206.

[0086] As the compression creep test device of the present invention, Figure 7 As shown, the specimen fixture 200 is a pair of pressure plates 211, which are respectively fixed on the fixture base plate 204 and combined with Figure 8 Each pressing plate 211 is provided with a limiting groove 212. The limiting grooves 212 of the two pressing plates 211 are opposite to each other, and the two ends of the test piece 201 are respectively limited in the limiting grooves 212 of the pressing plates 211. The limiting grooves 212 can prevent the displacement of the test piece 201 in the non-force direction.

[0087] In this embodiment, the movable pulley 302 and the load base plate 304, the two fixed pulleys and the top plate 110, and the specimen fixture and the fixture base plate 204 are fixedly connected by a connection column 150, an annular connection groove 151 and a latch 152 respectively fixedly provided on the bottom or shell of each component. Figures 14 to 17 As shown, a connecting column 150 is provided on the first fixed pulley 305 and the second fixed pulley 306, respectively, and an annular connecting groove 151 is provided on the corresponding position of the top plate 110; a connecting column 150 is provided on the movable pulley 302, and an annular connecting groove 151 is provided on the corresponding position of the load seat plate 304; a connecting column 150 is provided on the stretching clamp seat 205, and an annular connecting groove 151 is provided on the corresponding position of the clamp seat plate 204; a connecting column 150 is provided on the pressure plate 211, and an annular connecting groove 151 is provided on the corresponding position of the clamp seat plate 204. For each group of components to be connected, after the connecting column 150 on the component is inserted into the annular connecting groove 151, the plug 152 is inserted into the pin hole reserved on the connecting column 150 and the annular connecting groove 151, so that the connection between the two is achieved.

[0088] This detachable connection mode, especially for the specimen fixture 200, makes it convenient and quick to replace the tensile clamp seat 205 and the pressure plate 211, and the specimen fixture can be arbitrarily selected and adjusted according to needs.

[0089] The tensile and compressive creep testing system provided by the present invention is as follows: Fig.10 As shown, it includes a sealable box 500, the box 500 is provided with a box door 501, the box 500 is provided with a constant temperature and humidity device, and at least one creep test device of the present invention is arranged in the box 500.

[0090] A rack 502 for fixing the creep test device is provided in the box 500. At least one creep test device is provided on the rack 502. The top of the device frame 100 of the creep test device is horizontally fixed on the top of the rack 502. The lengths of the top plate and the bottom plate of the device frame 100 are equal to the width of the top of the rack 502.

[0091] like Fig.12 As shown, the rack 502 is a rectangular frame structure, including a pair of top beams 506, four side columns 512 and a pair of bottom beams 505 at the bottom. Between the side columns 512 on both sides, a number of ribs 513 are evenly spaced from top to bottom. On the inner walls of both sides of the box 500, a number of slide bars 503 are evenly spaced from top to bottom. The ribs 513 on the rack 502 are set according to the slide bars 503 in the box 500. The spacing of the ribs 513 is equal to the spacing of the slide bars 503. When the rack 502 is pushed into the box 500, the ribs 513 are aligned with the slide bars 503 and then pushed in. The slide bars 503 serve as the slide rails of the ribs 513 and also as the bearing of the entire rack 502.

[0092] In actual application, the bottom of the rack 502 does not contact the bottom plate in the box 500, including the creep test device, which is suspended in the box 500 because the bottom plate in the box 500 is thin and cannot bear a heavy load. Moreover, the creep test device is suspended, which is more conducive to more uniform climate parameters in the box 500.

[0093] Since the top beam 506 of the frame 502 has to bear the weight of the entire creep test device, the top beam 506 can be made of a larger diameter round steel to have a stronger bearing capacity. Since the frame 502 is a rectangular structure and the creep test needs to be kept naturally vertical, in addition to ensuring that the top beam 506 does not deform, the frame 502 as a whole cannot deform either. In order to adjust the frame 502, the bottom beam 505 is two rods of variable length, and each bottom beam 505 is two rods connected by threads, and the length can be adjusted.

[0094] Preferably, two connecting beams 504 are further provided along the diagonal direction on the inner side of the rack 502 . The connecting beams 504 are also two rods connected by threads. The level of the rack 502 can be adjusted by adjusting the length.

[0095] The various components of the rack 502 are connected by bolts, and the screw holes are all bar-shaped holes, so that the fixing positions of the bolts can be adjusted.

[0096] like Fig.13 As shown, in this embodiment, two creep testing devices are arranged in the box 500, and both tensile and compressive creep tests can be performed on the same material at the same time.

[0097] Combination Figures 1 to 4 As shown, the lengths of the fixture seat plate 204 and the load seat plate 304 are equal and both are smaller than the length of the bottom plate 120; there are six support rods 130, of which two support rods 130 on the side close to the box door 501 connect the top plate 110 and the bottom plate 120, and the other four support rods 130 connect the top plate 110 and the bottom plate 120, and pass through the fixture seat plate 204 and the load seat plate 304.

[0098] The load 301 of the load loading mechanism is arranged on the side close to the box door 501 so as to control the load application force.

[0099] The first fixed pulley 305 and the second fixed pulley 306 of the load loading mechanism 300 are arranged from the inside to the outside along the center line of the longer direction of the top plate 110, and the movable pulley 302 is located directly below the first fixed pulley 305; the axis and center of gravity of the first fixed pulley 305, the movable pulley 302, the load seat plate 304, the fixture seat plate 204, the specimen fixture 200 and the specimen 201 are all on the same vertical line, so that it can be ensured that the force can be effectively transmitted to the specimen.

[0100] like Fig.13 As shown, a lifting device 507 is provided directly below the load 301, and the lifting device 507 is placed on the bottom plate 120. The lifting device 507 in this embodiment is a jack, and a scissor jack can be selected.

[0101] A buffer pad 508 is laid on the bottom plate 120 directly below the load 301. The buffer pad 508 is mainly used to prevent the load 301 from falling and causing damage to the equipment when the test piece is broken by the load 301 during the test.

[0102] The box 500 of this embodiment, i.e., the environmental climate box, uses the German BINDER KMF720 environmental climate box, and the linear displacement sensor uses the F50-10LVDT displacement sensor of Shenzhen Walker Intelligent System Co., Ltd. The box 500 is also provided with an air intake system, a wind speed regulating device and a temperature and humidity sensor, as well as a temperature and humidity alarm device, a computer and a power supply for the test system arranged outside the box 500. The wind speed regulating device includes a hot wire anemometer and a speed regulator. Through the wind speed regulating device and the temperature and humidity sensor, the ability to stably generate, transport, maintain and discharge wet air with a specific humidity and temperature in a quantitative, constant speed and directional manner is formed to ensure that the wood specimen can stably absorb or discharge gaseous moisture; it also has the ability to regulate the humidity, temperature and flow rate of the wet air and their variation range, and the relative humidity control accuracy of the wet air is not greater than ±2%, and the temperature control accuracy is not greater than ±0.1°C. In actual implementation, in order to prevent the daily changes in the humidity and temperature of the surrounding environment of the box from affecting the humidity and temperature inside the box, especially the impact of opening the door, and to try to maintain the consistency between the temperature and humidity of the experimental operation space outside the box and the parameters inside the box, the test can be carried out in an environment equipped with a humidifier / dehumidifier and air conditioner. The ambient temperature around the box can be adjusted in the range of 10 to 40°C, with an accuracy of ±1°C; the relative humidity can be adjusted in the range of 40 to 80%, with an accuracy of ±5%.

[0103] The present invention uses the above-mentioned tensile and compressive creep testing system to test the method, comprising the following steps:

[0104] Step 1, select a specimen fixture according to the test purpose, install the specimen to be tested on the specimen fixture, fix the fixture base plate at the fixed end of the specimen fixture, and fix the fixture base plate at the movable end of the specimen fixture to the load base plate;

[0105] Step 2, installing the receiving platform on the test piece, fixing the position of the linear displacement sensor, and placing the probes of the linear displacement sensor against the surface of the receiving platform respectively;

[0106] Step 3, place the lifting device on the bottom plate, use the lifting device to lift the load and connect it to the wire rope;

[0107] Step 4, lower the lifting device until the load is suspended in the air, remove the lifting device, and lay a buffer pad on the bottom plate under the load;

[0108] Step 5, close the box door, start the constant temperature and humidity device to control the temperature and humidity in the box, and monitor the data in real time;

[0109] Step 6, inputting the temperature, humidity, wind speed in the box and the displacement signal of the test piece collected in step 5 into the computer for data storage, processing, analysis and display.

[0110] like Fig.10As shown, the present invention uses a transmitter 509 and a data conductor 510 to input the above-collected temperature, humidity, and displacement signals into a computer 511, and then the real-time storage, real-time processing, analysis, and display of the data can be realized through a program software compiled based on the VB language. Among them, the collected real-time raw data is in text format and stored in the form of a database for real-time data processing and analysis by the software. At the same time, the data can also be exported at any time to copy it into a backup, which is convenient for offline processing and analysis of the data. The data is obtained by the temperature and humidity sensor, and after being recorded and processed by the supporting software, a real-time coordinate diagram with time as the horizontal scale and the temperature and relative humidity in the box as the vertical scale can be obtained. After the above-mentioned raw displacement data is processed in real time by the software, a continuous coordinate diagram with time as the horizontal scale and the static bending deflection and the swelling and shrinkage of the specimen as the vertical scale is formed for real-time monitoring and control.

Claims

1. Creep testing device, characterized in that, At least includes a device frame, a specimen fixture, a load-loading mechanism and a linear displacement sensor, wherein the specimen fixture, the load-loading mechanism and the linear displacement sensor are all arranged on the device frame, wherein: The device frame includes a top plate and a bottom plate which are arranged opposite to each other, and the top plate and the bottom plate are fixedly connected by at least four mutually parallel support rods; The specimen fixture is used to place the specimen for creep test. The specimen is placed in the middle of the specimen fixture. A fixture base plate is fixed at both ends of the specimen fixture. Four support rods pass vertically through the fixture base plate. One end of the specimen fixture is a fixed end. The position of the fixture base plate at the fixed end relative to the support rod remains unchanged. The other end of the specimen fixture is a movable end. The fixture base plate at the movable end can slide along the direction of the support rod. The direction of the applied force of the specimen fixture is parallel to the direction of the support rod, the load loading mechanism is arranged above the specimen fixture, and the fixed pulley of the load loading mechanism is fixed on the top plate; The load loading mechanism includes at least a pulley block and a load. The pulley block has at least one movable pulley and a plurality of fixed pulleys. The load is connected to the movable end of the specimen fixture after passing through the pulley block via a steel wire rope, and a force is applied to the specimen of the creep test via the specimen fixture at the movable end. The direction of the force is in the same straight line as the axis of the specimen. The linear displacement sensor collects the displacement data of the specimen during the creep test. Two linear displacement sensors are provided. The linear displacement sensors are respectively fixedly connected to the nearest support rods through sensor brackets, and the probes of the linear displacement sensors are in opposite directions. A pair of receiving platforms are provided in the middle of the specimen on the specimen fixture, one end of the receiving platform is fixedly connected to the specimen, and the other end extends to the front of the probes of the linear displacement sensors.

2. The creep testing device according to claim 1, characterized in that: The fixture base plate on the specimen fixture close to the bottom plate is fixedly connected to the bottom plate as a fixed end, and the fixture base plate at the movable end is connected to the steel wire rope of the load loading mechanism.

3. The creep testing device according to claim 1, characterized in that: The fixture base plate on the specimen fixture far away from the bottom plate is fixedly connected to the bottom plate as a fixed end, and the fixture base plate at the movable end is connected to the steel wire rope of the load loading mechanism.

4. The creep testing device according to claim 2 or 3, characterized in that: A load base plate parallel to the fixture base plate is provided at the end of the wire rope, and four support rods pass vertically through the load base plate respectively. The load base plate and the support rods are slidably matched, and the load base plate is fixedly connected to the fixture base plate at the moving end of the specimen fixture.

5. The creep testing device according to claim 4, characterized in that: The movable pulley is arranged above the load seat plate, and the movable pulley is rotatably connected with the load seat plate.

6. The creep testing device according to claim 5, characterized in that: There are two fixed pulleys, wherein the first fixed pulley is arranged above the movable pulley, and the second fixed pulley is arranged at one side, the first fixed pulley and the second fixed pulley are both rotatably connected to the top plate, and the axles of the first fixed pulley, the second fixed pulley and the movable pulley are parallel to each other.

7. The creep testing device according to claim 6, characterized in that: The movable pulley and the first fixed pulley are both three-wheel pulleys, and the second fixed pulley is a single-wheel pulley.

8. The creep testing device according to claim 7, characterized in that: The end of the wire rope is connected to the hook of the movable pulley. After the wire rope is wound three times between the movable pulley and the first fixed pulley, it is led out from the movable pulley and then wound over the second fixed pulley. The front end of the wire rope is vertically downward to connect the load.

9. The creep testing device according to claim 2, characterized in that: The specimen fixture is a pair of tensile clamps, which are respectively fixed on the fixture base plates. Each tensile clamp is provided with an open slot, the open slots of the two tensile clamps are opposite, and the two ends of the specimen are respectively confined in the open slots of the tensile clamps.

10. The creep testing device according to claim 2, characterized in that: The inner walls on both sides of the opening groove are provided with anti-slip grooves.

11. The creep testing device according to claim 9, characterized in that: The opening slot is a dovetail slot.

12. The creep testing device according to claim 11, characterized in that: The inner wall of the opening groove is smooth, and a wedge-shaped slider is provided between the test piece and the inner walls on both sides of the opening groove. The side projection of the wedge-shaped slider is a right-angled trapezoid, and the side of the wedge-shaped slider that fits the test piece is a vertical surface, and anti-slip grooves are provided on the vertical surface.

13. The creep testing device according to claim 12, characterized in that: A tightening bolt is arranged on the bottom of the stretching clamp seat at a position corresponding to the wedge-shaped slider. The tightening bolt passes through the bottom of the stretching clamp seat and presses against the bottom of the wedge-shaped slider. The tightening bolt is threadedly matched with the stretching clamp seat.

14. The creep testing device according to claim 12, characterized in that: Limiting rods are respectively arranged at the open ends of the opening groove, and the two ends of the limiting rods are fixedly connected with the stretching clamp seat.

15. The creep testing device according to claim 3, characterized in that: The specimen fixture is a pair of pressure plates, which are respectively fixed on the fixture base plates. Each pressure plate is provided with a limiting groove, and the limiting grooves of the two pressure plates are opposite to each other. The two ends of the specimen are respectively limited in the limiting grooves of the pressure plates.

16. A tension and compression creep test system, comprising a sealable box, a door, and a constant temperature and humidity device, characterized in that: At least one creep testing device according to any one of claims 1 to 15 is arranged in the box.

17. The tension and compression creep testing system according to claim 16, characterized in that: A frame for fixing a creep test device is provided in the box body. At least one creep test device is provided on the frame. The top of the device frame of the creep test device is horizontally fixed on the top of the frame. The lengths of the top plate and the bottom plate of the device frame are both equal to the width of the top of the frame.

18. The tension and compression creep testing system according to claim 17, characterized in that: The lengths of the fixture seat plate and the load seat plate are equal and both are smaller than the length of the bottom plate; there are six support rods, two of which are close to the box door and connect the top plate and the bottom plate, and the other four support rods connect the top plate and the bottom plate and pass through the fixture seat plate and the load seat plate.

19. The tension and compression creep testing system according to claim 18, characterized in that: The load of the load-loading mechanism is arranged on the side close to the box door.

20. The tension and compression creep testing system according to claim 19, characterized in that: The first fixed pulley and the second fixed pulley of the load loading mechanism are arranged from the inside to the outside along the center line of the longer direction of the top plate, and the movable pulley is located directly below the first fixed pulley; the first fixed pulley, the movable pulley, the load seat plate, the fixture seat plate, the specimen fixture and the axis line and center of gravity of the specimen are all on the same vertical line.

21. The tension and compression creep testing system according to claim 20, characterized in that: A lifting device is arranged just below the load and is placed on the bottom plate.

22. The tension and compression creep testing system according to claim 21, characterized in that: The lifting device is a jack.

23. The tension and compression creep testing system according to claim 21, characterized in that: A cushion is placed on the bottom plate directly under the load.

24. A testing method using the tension and compression creep testing system according to any one of claims 16 to 23, characterized in that: The steps include: Step 1, select a specimen fixture according to the test purpose, install the specimen to be tested on the specimen fixture, fix the fixture base plate at the fixed end of the specimen fixture, and fix the fixture base plate at the movable end of the specimen fixture to the load base plate; Step 2, installing the receiving platform on the test piece, fixing the position of the linear displacement sensor, and placing the probes of the linear displacement sensor against the surface of the receiving platform respectively; Step 3, place the lifting device on the bottom plate, use the lifting device to lift the load and connect it to the wire rope; Step 4, lower the lifting device until the load is suspended in the air, remove the lifting device, and lay a buffer pad on the bottom plate under the load; Step 5, close the box door, start the constant temperature and humidity device to control the temperature and humidity in the box, and monitor the data in real time; Step 6, inputting the temperature, humidity, wind speed in the box and the displacement signal of the test piece collected in step 5 into the computer for data storage, processing, analysis and display.

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