Environmental-tensile loading-bending fatigue coupling test device and test method for FRP rods

Abstract

The present invention discloses an environment-tensile loading-bending fatigue coupling test device for FRP rods and a test method thereof, comprising a metal pedestal, a servo motor, an eccentric cam, a driven roller, a driven push rod, a spring sleeve, a spring, a bending pressure sensor, a bending support, a loading reaction frame, a height adjustment mechanism, a hollow pressure sensor, a hollow jack, a loading gasket, an anchor sleeve, an anchor clip assembly and an environmental hose. The anchored FRP rod crosses the loading reaction frame, and the two ends are respectively fixedly connected to the hollow pressure sensor and the hollow jack, and the tensile loading effect is realized under the action of the hollow jack. The driven push rod drives the bending support to realize up and down reciprocating simple harmonic linear motion under the action of the eccentric cam and the spring, and an environmental solution is injected into the environmental hose to realize the environment-tensile loading-bending fatigue coupling test of the FRP rod. The present invention is simple to operate and meets the residual tensile strength test requirements of the FRP rod after the coupling effect.

Description

Technical Field

[0001] The invention relates to the field of experimental equipment for material fatigue testing, and in particular to an environment-tensile loading-bending fatigue coupling test device for FRP rods and a test method thereof. Background Art

[0002] Cable structures are the core load-bearing components of large-span bridges, large-span space structures, marine moorings, submarine optical cables and other projects. Traditional cables are made of steel wires, which have problems such as excessive weight and poor corrosion resistance. Fiber-reinforced plastic (FRP) rods have the advantages of light weight, high strength and corrosion resistance, and are an important material to break through the limitations of traditional steel wires.

[0003] However, in actual engineering applications, in order to effectively fix the FRP rod to the structure, the two ends of the rod need to be anchored, and then the anchored end becomes the fixed end support; at this time, under the influence of wind and waves, the FRP rod at the anchored end will be subjected to the coupling of tensile load and bending fatigue. Under the long-term coupling effect, it is easy for the FRP rod to accumulate damage such as delamination, fiber breakage, and resin damage, resulting in a decrease in the strength and stiffness of the material, which in turn poses a serious threat to the safety of life and property.

[0004] The bending fatigue test of materials is often carried out by modifying the fixture of large-scale tension-tension fatigue testing equipment. However, the procurement cost of such testing equipment is extremely high, the testing and maintenance costs are high, the test operation is complicated, and the site requirements are large. It is not suitable for a large number of tests on small-sized, low bending load specimens such as FRP rods. At the same time, it is difficult for such testing equipment to carry out FRP rod tensile loading-bending fatigue coupling tests. On the one hand, this is because the testing equipment itself lacks a tensile loading module; on the other hand, the shear and compression resistance of FRP rods is poor. In order to prevent the two ends of the FRP rod from being damaged prematurely during the tensile process, its tensile loading must be anchored, and the existing loading device does not have an anchoring function. Therefore, in view of the above problems, it is of great significance to develop an environmental-tensile loading-bending fatigue coupling test device and its testing method for FRP rods.

[0005] The existing tensile loading-bending fatigue coupling test devices have the following problems: (1) The stretching and bending of the material are completed in sequence, rather than true tensile loading-bending fatigue; (2) It is only a fixture or accessory attached to the traditional fatigue testing machine, and it is difficult to complete the fatigue test independently; (3) It is impossible to effectively anchor the FRP rod, making it difficult to achieve tensile loading for the FRP rod; (4) The achieved bending fatigue does not strictly follow simple harmonic motion, and does not meet the existing national standard for bending fatigue of FRP materials (GB / T 35465.5-2020); (5) The equipment that can complete the test is too complicated and the cost is too high; (6) Due to the limitation of the design structure, the designed target specimen size is too small, and the upper limit of the tensile load that can be provided is too small, which makes it difficult to apply to FRP rods with long size, large tensile load, and residual strength tensile test; (7) It is difficult to achieve the three coupling effects of environment-tensile loading-bending fatigue. Summary of the invention

[0006] Based on the shortcomings of the existing tensile loading-bending fatigue coupling test device, the purpose of the present invention is to provide an environmental-tensile loading-bending fatigue coupling test device and a testing method for FRP rods, which can realize strict simple harmonic bending fatigue loading test on FRP rods in accordance with the national standard: GB / T 35465.5-2020, including three types of coupling loading: tensile loading-bending fatigue coupling loading and environmental-tensile loading-bending fatigue, and can meet the residual tensile strength test requirements of FRP rods after coupling.

[0007] The technical solution adopted by the present invention is as follows: an environmental-tensile loading-bending fatigue coupling test device for FRP rods, comprising a metal pedestal, a servo motor, an eccentric cam, a driven roller, a driven push rod, a spring sleeve, a spring, a bending pressure sensor, a bending support, a loading reaction frame, a height adjustment mechanism, a hollow pressure sensor, a hollow jack, a loading gasket, an anchor sleeve, an anchor clip assembly and an environmental hose, wherein the bottom of the loading reaction frame is connected to the chassis of the metal pedestal through the height adjustment mechanism, and the The back of the load-bearing reaction frame is slidably connected to the slideway on the side wall of the metal pedestal, the back of the spring sleeve is fixedly connected to the side wall of the metal pedestal, and the two ends of the FRP rod are clamped by the anchor clip assembly and pressed into the anchor sleeve for anchoring; the hollow pressure sensor and the hollow jack are relatively fixed on both sides of the load-bearing reaction frame respectively; the anchored FRP rod crosses the load-bearing reaction frame, one end of which is fixedly connected to the hollow pressure sensor through a load-bearing gasket, and the other end of which is fixedly connected to the hollow jack through another load-bearing gasket. Then, the stretching and holding function is realized under the action of the hollow jack; the servo motor is fixed on the top of the metal pedestal, and the eccentric cam is connected to the power output shaft of the servo motor, and eccentrically rotates under the action of the servo motor; the driven roller is in close contact with the eccentric cam, and the driven roller is rotatably connected to the roller fork fixedly connected to the upper section of the driven push rod; the lower section of the driven push rod is sleeved with a spring, and a spring limiting pressure plate is fixedly connected between the upper section and the lower section of the driven push rod; the lower section of the driven push rod is located in the spring sleeve, and the spring limiting pressure plate and the spring sleeve are connected to each other. The spring is confined in the spring sleeve, the lower end of the driven push rod is fixedly connected to the bending pressure sensor, the bending pressure sensor is detachably fixedly connected to the upper end of the bending support, and the lower end of the bending support is in contact with the FRP rod; the driven push rod drives the bending support to realize up and down reciprocating simple harmonic linear motion under the action of the eccentric cam and the spring, thereby realizing the tensile loading-bending fatigue coupling test of the FRP rod; the environmental hose is sleeved on the surface of the FRP rod, and the environmental solution is injected into it, thereby realizing the environmental-tensile loading-bending fatigue coupling test.

[0008] Furthermore, the eccentricity of the eccentric cam is the bending amplitude, and a plurality of eccentric holes with eccentricities are arranged on the disk surface of the eccentric cam for connecting with the output shaft of the servo motor. The servo motor adjusts the speed and number of rotations of the servo motor through the controller to achieve control of the frequency and number of cycles of bending fatigue.

[0009] Furthermore, the FRP rod and the anchor clip assembly are pressed into the anchor sleeve, and the inner side inclination angle of the anchor sleeve is smaller than the outer side inclination angle of the anchor clip assembly, so that during the pressing process, the anchoring area of ​​the FRP rod is continuously clamped by the anchor clip assembly from the end to the inside, thereby achieving effective anchoring of the FRP rod.

[0010] Furthermore, the outer side inclination angle of the anchor clip assembly is 1.2°, and the inner side inclination angle of the anchor sleeve is 1.1°; the diameter of the clip rod groove inside the anchor clip assembly is consistent with the diameter of the FRP rod, ensuring close contact between the FRP rod and the clip rod groove.

[0011] Furthermore, the anchor clip assembly includes two clip bodies, and the radial cross-section of each clip body is a minor arc, so that there is still a gap in the middle when the two halves of the clip body clamp the FRP rod, so as to ensure that there is clamping space during the pre-pressure application process.

[0012] Furthermore, the device also includes a dynamic data acquisition instrument, which is electrically connected to the bending pressure sensor and the hollow pressure sensor respectively. The hollow pressure sensor is used to collect the size of the load-bearing force in real time, and the bending pressure sensor is used to collect the size of the bending force in real time; the actual load size of each sensor should not exceed 80% of the sensor range; the sampling frequency of the dynamic acquisition instrument should satisfy the requirement of at least 10 sampling points in a single cycle.

[0013] Another object of the present invention is to provide a test method using the above test device, the steps are as follows:

[0014] In the first step, the environmental hose is fixed at the mid-span position of the FRP rod, and distilled water, acid, alkali or salt solution is injected into the environmental hose;

[0015] The second step is to clamp the anchor clip assembly at both ends of the FRP rod according to the required anchor type requirements, adjust the free section length to the required span, and use a press to pre-press the two together into the anchor sleeve to complete the anchoring;

[0016] The third step is to pass the anchored FRP rod through the hollow pressure sensor, the load-bearing reaction frame, and the hollow jack in sequence, and screw the anchor sleeves at both ends into the load-bearing gasket so that the bending support acts on the mid-span position of the FRP rod;

[0017] The fourth step is to adjust the initial stroke of the hollow jack, and then apply tension to the FRP rod so that the reading of the hollow pressure sensor reaches the required tensile load, and at the same time, the bending support acts on the mid-span position of the FRP rod;

[0018] Step 5: Select the eccentric cam with the required eccentricity and fix it on the servo motor, adjust and fix the height of the load-bearing reaction frame so that the FRP rod is in pressure-free contact with the lower end of the bending support when it is in the highest position;

[0019] The sixth step is to turn on the servo motor to start the environmental-tensile load-bending fatigue test until completion, obtain the load-time curve of the whole process, and test the residual tensile strength of the FRP rod through the tensile test to obtain the residual tensile strength-cycle number logarithmic curve.

[0020] The present invention has the following advantages and beneficial effects: the present invention can realize rapid switching of various bending fatigue amplitudes, frequencies, number of cycles, and spans; the test device and test method have the advantage of simple operation and can be applied to FRP rods of various types and diameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The overall diagram of a tensile loading-bending fatigue coupling test device for FRP rods;

[0022] Figure 2 This is a schematic diagram of a metal pedestal;

[0023] Figure 3 It is a schematic diagram of an eccentric cam;

[0024] Figure 4 is a schematic diagram of a driven roller;

[0025] Figure 5 It is a schematic diagram of the driven ejector rod;

[0026] Figure 6 It is a schematic diagram of the spring guide;

[0027] Figure 7 is a schematic diagram of a curved support;

[0028] Figure 8 is the cross-sectional view of the curved support;

[0029] Fig. 9 It is a schematic diagram of the three-dimensional structure of the bottom of the load-bearing reaction frame;

[0030] Fig.10 It is a schematic diagram of a hollow pressure sensor;

[0031] Fig.11 It is a schematic diagram of a hollow jack;

[0032] Fig.12 It is a schematic diagram of the load-bearing gasket;

[0033] Fig.13 Schematic diagram of the anchored FRP rod coupled to the environment;

[0034] Fig.14 Schematic diagram of the FRP rod clamped by the anchor clip;

[0035] Fig.15 is a schematic diagram of an anchor sleeve;

[0036] Fig.16 is a cross-sectional view of the anchor sleeve;

[0037] Fig.17 is a schematic diagram of the anchor clip;

[0038] Fig.18 It is the axial cross-sectional view of the anchor clip;

[0039] Fig.19 Schematic diagram of the radial section of the FRP rod clamped by the anchor clip.

[0040] Among them, 1-metal pedestal, 2-servo motor, 3-eccentric cam, 4-driven roller, 5-driven push rod, 6-spring sleeve, 7-spring, 8-bending pressure sensor, 9-bending support, 10-load-bearing reaction frame, 11-height adjustment mechanism, 12-hollow pressure sensor, 13-hollow jack, 14-load-bearing gasket, 15-anchor sleeve, 16-anchor clip assembly, 17-FRP rod; 18-environmental hose; 201-motor support, 202-pedestal chassis, 203-height adjustment slot, 204-height adjustment bolt slot; 301-cam plate, 302-eccentric hole; 401-roller, 402-roller bearing, 403 roller limit slot; 501-roller fork, 502-upper section of driven push rod, 503-spring limit pressure piece, 504-driven Lower section of push rod, 505-sensor pressing piece; 601-limit baffle, 602-limit middle cylinder, 603-limit hole; 901-support push rod, 902-semicircular groove; 1001-support plate, 1002-support rod, 1003-support plate hole, 1004-support bolt, 1005-support nut, 1006-height adjustment hole; 1201-sensor body, 1202-sensor connection hole, 1203-sensor middle hole; 1301-oil cylinder, 1302-pull column, 1303-middle hole, 1304-oil inlet, 1305-fixing hole; 1401-gasket body, 1402-gasket thread; 1501-sleeve body, 1502-sleeve thread, 1503-sleeve middle hole; 1601-clip body, 1602-clip rod groove; DETAILED DESCRIPTION

[0041] The present invention is further described in detail below in conjunction with the accompanying drawings and specific practical cases. The implementation cases herein are used to explain the present invention but do not limit the present invention.

[0042] Example 1

[0043] An environmental-tensile loading-bending fatigue coupling test device for FRP rods, comprising a metal pedestal 1, a servo motor 2, an eccentric cam 3, a driven roller 4, a driven push rod 5, a spring sleeve 6, a spring 7, a bending pressure sensor 8, a bending support 9, a loading reaction frame 10, a height adjustment mechanism 11, a hollow pressure sensor 12, a hollow jack 13, a loading gasket 14, an anchor sleeve 15, an anchor clip assembly 16 and an environmental hose 18. The bottom of the loading reaction frame 10 is connected to the chassis of the metal pedestal 1 through the height adjustment mechanism 11. The loading reaction frame 10 is connected to the chassis of the metal pedestal 1 through the height adjustment mechanism 11. The back of the frame 10 is slidably connected to the slideway on the side wall of the metal pedestal 1, the back of the spring sleeve 6 is fixedly connected to the side wall of the metal pedestal 1, and the two ends of the FRP rod 17 are clamped by the anchor clip assembly 16 and pressed into the anchor sleeve 15 for anchoring; the hollow pressure sensor 12 and the hollow jack 13 are relatively fixed on both sides of the load-bearing reaction frame 10 respectively; the anchored FRP rod 17 crosses the load-bearing reaction frame 10, one end of which is fixedly connected to the hollow pressure sensor 12 through a load-bearing gasket, and the other end of which is fixedly connected to the hollow jack 13 through another load-bearing gasket, The stretching and holding function is realized under the action of the hollow jack 13; the servo motor 2 is fixed on the top of the metal pedestal 1, and the eccentric cam 3 is connected to the power output shaft of the servo motor 2, and eccentrically rotates under the action of the servo motor 2; the driven roller 4 is in close contact with the eccentric cam 3, and the driven roller 4 is rotatably connected to the roller fork 501 fixedly connected to the upper section of the driven push rod 5; the lower section of the driven push rod 5 is sleeved with a spring 7, and a spring limiting pressing plate 503 is fixedly connected between the upper and lower sections of the driven push rod 5; the lower section of the driven push rod 5 is located in the spring sleeve 6, and the spring limiting pressing plate 503 and the spring 7 are confined in the spring sleeve 6, the lower end of the driven push rod 5 is fixedly connected to the bending pressure sensor 8, the bending pressure sensor 8 is detachably fixedly connected to the upper end of the bending support 9, and the lower end of the bending support 9 is in contact with the FRP rod 17; the driven push rod 5 drives the bending support 9 to realize up and down reciprocating simple harmonic linear motion under the action of the eccentric cam 3 and the spring 7, thereby realizing the tensile loading-bending fatigue coupling test of the FRP rod 17; the environmental hose 18 is sleeved on the surface of the FRP rod 17, and the environmental solution is injected into it, thereby realizing the environment-tensile loading-bending fatigue coupling test.

[0044] The height adjustment mechanism of this embodiment uses four height adjustment bolts to be threadedly connected to the load-bearing reaction frame 10 through the height adjustment holes 1006, and is limited in the four height adjustment bolt grooves 204 of the metal pedestal 1 to achieve bottom support for the load-bearing reaction frame 10; two groups of support bolts 1004 are respectively installed on the support plates 1001 on both sides of the load-bearing reaction frame, and the two groups of support bolts 1004 respectively pass through the two rows of height adjustment grooves 203 on the side wall of the metal pedestal 1, and are fixed to the side wall of the metal pedestal 1 through two support nuts 1005 to achieve lateral constraint of the load-bearing reaction frame 10; the height of the load-bearing reaction frame 10 can be adjusted by adjusting the screw-in depth of the height adjustment bolts to adapt to bending requirements under different amplitudes.

[0045] The speed control module of this embodiment includes a servo motor and a controller. In this invention device, the number of rotations of the servo motor per second is the frequency of bending fatigue. After the test starts, the number of rotations of the servo motor is the number of cycles of bending fatigue. Therefore, by adjusting the speed and number of rotations of the servo motor through the controller, the frequency and number of cycles of bending fatigue can be controlled.

[0046] The simple harmonic motion module of this embodiment includes a driven roller, a driven push rod, a spring, a spring sleeve, a bending pressure sensor and a bending support. The spring provides an upward force, and the eccentric cam provides a downward force. Under the action of the two, the simple harmonic motion module realizes the conversion of circular motion to upward and downward reciprocating simple harmonic linear motion. The roller limit groove should be slightly larger than the eccentric cam; the diameter of the spring pressure plate should be consistent with the maximum outer diameter of the spring, and the inner diameter of the limit middle cylinder of the spring sleeve should be slightly larger than the spring, and the inner diameter of the limit hole of the spring sleeve should be slightly larger than the diameter of the upper section of the driven push rod and the lower section of the driven push rod to ensure the stability of the up and down reciprocating motion. The diameter of the semicircular groove at the lower end of the bending support should be consistent with the diameter of the FRP rod. By replacing semicircular grooves of different diameters, FRP rods of various diameters can be tested. During the test, the maximum pressure on the spring should be less than 80% of the elastic limit of the spring.

[0047] The sample anchoring module of this embodiment includes an anchor sleeve, an anchor clip assembly and an FRP rod. The working mechanism of the sample anchoring module is that the FRP rod and the anchor clip assembly are pressed into the anchor sleeve under the pre-pressure of the press. Because the inner side of the anchor sleeve and the outer side of the anchor clip assembly have an inclination angle, and the former is smaller than the latter, the anchoring area of ​​the FRP rod is continuously clamped from the end to the inside during the pressing process. Under the joint action of mechanical bite force and friction force, the effective anchoring of the FRP rod is achieved. The inclination angle of the outer side of the anchor clip assembly should be 1.2°; the diameter of the clip rod groove inside the anchor clip assembly is consistent with the diameter of the FRP rod to ensure close contact between the FRP rod and the clip rod groove; the anchor clip assembly is composed of two clip bodies, and its radial cross-section should be a minor arc, so that there is still a gap in the middle when the two clip bodies clamp the FRP rod to ensure that there is clamping space during the application of pre-pressure. The inner inclination angle of the anchor sleeve should be 1.1°; the inner diameter of the anchor sleeve at the minimum point should be consistent with the outer diameter of the anchor clip assembly at the minimum point to ensure that the preload is evenly applied throughout the anchor; the applied preload should reach 50% of the theoretical maximum tensile load of the FRP rod. The length of the middle free section of the FRP rod should not be less than 40 times the diameter, and should not be less than 380mm, that is, it meets the requirements, so as to facilitate the static test of the residual tensile strength of the FRP rod; by adjusting the length of the free section, the bending fatigue span can be adjusted, and the two are equal in size. The anchoring method of the device of the present invention can be changed according to the test requirements, and commonly used methods include clip-type anchoring, bonding anchoring, composite anchoring, etc.; when anchoring, the length of the middle free section of the FRP rod should not be less than 40 times the diameter, and should not be less than 380mm, that is, it meets the requirements of the tensile test specification (ASTM D7205 / D7205M), so as to facilitate the static test of the residual tensile strength of the FRP rod; by adjusting the length of the free section, the bending fatigue span can be adjusted, and the two are equal in size.

[0048] The tensile load-bearing module of this embodiment includes a load-bearing reaction frame, a hollow pressure sensor, a hollow jack and a load-bearing gasket. By passing the anchored FRP rod through the tensile load-bearing module, the anchor sleeve is screwed into the load-bearing gasket, and the tensile load-bearing effect is achieved under the tensioning action of the hollow jack. The pressure indication displayed by the hollow pressure sensor, that is, the tensile load size, can be adjusted by adjusting the thrust stroke of the hollow jack; by adjusting the initial stroke of the hollow jack, the bending fatigue action position of the FRP rod can be adjusted. The inner diameters of the support plate hole of the load-bearing reaction frame, the hollow pressure sensor, and the hollow jack should all be larger than the maximum outer diameter of the anchor sleeve to ensure the smooth passage of the anchor sleeve; the outer diameter of the load-bearing gasket should be larger than the outer diameter of the jack top column to achieve reaction force holding; during the bending fatigue process, if the tensile load decreases, the hollow jack load should be supplemented.

[0049] The data acquisition module of this embodiment includes a bending pressure sensor, a hollow pressure sensor and a dynamic data acquisition instrument. The hollow pressure sensor is used to collect the magnitude of the tensile load force in real time, and the bending pressure sensor is used to collect the magnitude of the bending force in real time. During the test, the actual load size should not exceed 80% of the sensor range to ensure the long-term service life of the sensor. At the same time, the sampling frequency of the bending pressure sensor and the dynamic data acquisition instrument should satisfy at least 10 sampling points in a single cycle to ensure that there is an obvious cycle during data processing.

[0050] The environmental coupling module of this embodiment includes an environmental hose. By adding distilled water, acid, alkali, and salt solution into the environmental hose before the test, the three coupling effects of environment-tensile loading-bending fatigue can be achieved; at the same time, the environmental hose also has the function of protecting the surface of the FRP rod from mechanical wear by the bending support.

[0051] This embodiment can be applicable to various types of FRP rods, including thermosetting fiber composite rods and thermoplastic fiber composite rods according to the type of matrix, and including carbon fiber composite rods, glass fiber composite rods, basalt fiber composite rods, etc. according to the type of fiber; this device is applicable to fiber composite rods of various diameters, but it should be ensured that the bending failure load of the sample should not exceed 80% of the maximum bending force that the speed control module can provide.

[0052] In order to ensure the reliability of each component of this device during the bending fatigue test, the eccentric cam, driven roller, driven push rod, spring sleeve, bending pressure sensor, and bending support components should be made of wear-resistant and non-deformable materials; at the same time, lubricating oil should be applied to the moving parts of the components to reduce the friction of the components.

[0053] Example 2

[0054] A method for coupling tensile loading-bending fatigue testing of carbon fiber composite rods is as follows:

[0055] A 5mm diameter carbon fiber composite rod needs to be subjected to a tensile loading-bending fatigue coupling test. The tensile loading condition is: the loading level is 60% of the tensile limit load; the bending fatigue condition is: the amplitude is 1.5mm, the maximum number of cycles is 2 million times, the frequency is 5Hz, and the span is 400mm. It is known that the tensile limit load of this CFRP rod is 50kN.

[0056] The specific test steps are as follows: clamp two symmetrical anchor clips at both ends of the CFRP rod, with the larger diameter end of the clips arranged toward the end of the rod, adjust the free section length of the CFRP rod to 400mm, and take the inner diameter of the clip rod groove to 5mm; use a press to press the two ends of the CFRP rod and the anchor clips into the anchor sleeve, and apply a preload of 25kN to achieve the anchoring of the CFRP rod; pass the anchored CFRP rod through the hollow pressure sensor, the load-bearing reaction frame, and the hollow jack in turn, and screw the anchor sleeves at both ends into the load-bearing gaskets; adjust the initial stroke of the hollow jack and add oil so that the reading of the hollow pressure sensor reaches 30kN, and the bending support can act on the span of the CFRP rod; select the eccentricity of 1 A .5mm cam is fixed on the servo motor, and the height of the load-holding reaction frame is adjusted and fixed so that the CFRP rod can contact the lower end of the bending support without pressure when it is in the highest position. The diameter of the semicircular groove of the bending support is 5mm; the servo motor controller is adjusted, the frequency is selected to be 5Hz, the number of cycles is 2 million times, the servo motor power is turned on, and the tensile load-bending fatigue coupling test is started until completion to obtain the load-time curve of the whole process; the above test steps are repeated, and the number of cycles is adjusted to 500,000 times, 1 million times, and 1.5 million times in turn, and the anchored CFRP rod is removed, and the residual tensile strength of all CFRP rods is tested by tensile test, and finally the residual tensile strength-cycle number logarithmic curve is obtained.

[0057] Example 3

[0058] A salt solution-tensile loading-bending fatigue coupling test method for glass fiber composite rods is as follows:

[0059] Now it is necessary to conduct a salt solution-tensile holding-bending fatigue coupling test on a 10mm diameter glass fiber composite rod. The required conditions for tensile holding are: the holding level is 80% of the tensile limit load; the required conditions for bending fatigue are: amplitude of 5mm, maximum number of cycles is 2 million times, frequency is 10Hz, span is 500mm, bonding anchorage is required, and salt solution environment coupling is required. It is known that the tensile limit load of this GFRP rod is 30kN.

[0060] The specific test steps are as follows: fix the environmental hose in the middle of the span of the FRP rod, and inject the salt solution into the environmental hose with a syringe; use bonding anchors at both ends of the GFRP rod, and adjust the free section length of the GFRP rod to 500mm, and the inner diameter of the clip rod slot to 10mm; use a press to press the two ends of the GFRP rod and the anchor clip into the anchor sleeve, and apply a pre-pressure of 15kN to achieve the anchoring of the GFRP rod; pass the anchored GFRP rod through the hollow pressure sensor, the load-bearing reaction frame, and the hollow jack in turn, and screw the anchor sleeves at both ends into the load-bearing gasket; adjust the initial stroke of the hollow jack and add oil so that the reading of the hollow pressure sensor reaches 24kN, and the bending support can act on the middle of the span of the GFRP rod; Select cams with an eccentricity of 5 mm in turn and fix them on the servo motor. Adjust and fix the height of the load-holding reaction frame so that the GFRP rod can be in pressure-free contact with the lower end of the bending support when it is in the highest position. The diameter of the semicircular groove of the bending support is 10 mm. Adjust the servo motor controller, select a frequency of 10 Hz and a cycle number of 2 million times. Turn on the servo motor power supply and start the tensile load-bending fatigue coupling test until completion to obtain the load-time curve of the whole process. Repeat the above test steps, adjust the cycle number to 500,000 times, 1 million times, and 1.5 million cycles in turn, remove the anchored GFRP rod, and test the residual tensile strength of all GFRP rods through a tensile test, and finally obtain the residual strength-cycle number logarithmic curve.

Claims

1. An environmental-tensile loading-bending fatigue coupling test device for FRP rods, comprising a metal pedestal (1), a servo motor (2), an eccentric cam (3), a driven roller (4), a driven push rod (5), a spring sleeve (6), a spring (7), a bending pressure sensor (8), a bending support (9), a loading reaction frame (10), a height adjustment mechanism (11), a hollow pressure sensor (12), a hollow jack (13), a loading gasket (14), an anchor sleeve (15), an anchor clip assembly (16) and an environmental hose (18), characterized in that: The bottom of the load-bearing reaction frame (10) is connected to the chassis of the metal pedestal (1) through a height adjustment mechanism (11); the back of the load-bearing reaction frame (10) is slidably connected to the slideway on the side wall of the metal pedestal (1); the back of the spring sleeve (6) is fixedly connected to the side wall of the metal pedestal (1); the two ends of the FRP rod (17) are clamped by an anchor clip assembly (16) and then pressed into the anchor sleeve (15) for anchoring; the hollow pressure sensor (12) and the hollow jack (13) are respectively fixed relatively to the load-bearing reaction frame (10). The two sides of the frame (10); the anchored FRP rod (17) crosses the load-bearing reaction frame (10), one end of which is fixedly connected to the hollow pressure sensor (12) through a load-bearing gasket, and the other end of which is fixedly connected to the hollow jack (13) through another load-bearing gasket, thereby realizing the tensile load-bearing effect under the action of the hollow jack (13); the servo motor (2) is fixed on the top of the metal pedestal (1), and the eccentric cam (3) is connected to the power output shaft of the servo motor (2), and performs eccentric rotation under the action of the servo motor (2); the driven roller The wheel (4) is in close contact with the eccentric cam (3); the driven roller (4) is rotatably connected to a roller fork (501) fixedly connected to the upper section of the driven push rod (5); the lower section of the driven push rod (5) is sleeved with a spring (7); a spring limiting pressing piece (503) is fixedly connected between the upper section and the lower section of the driven push rod (5); the lower section of the driven push rod (5) is located in the spring sleeve (6); the spring limiting pressing piece (503) and the spring (7) are restricted in the spring sleeve (6); the lower end of the driven push rod (5) is fixed to the bending pressure sensor (8) The bending pressure sensor (8) is detachably fixedly connected to the upper end of the bending support (9), and the lower end of the bending support (9) is in contact with the FRP rod (17); the driven push rod (5) drives the bending support (9) to realize up and down reciprocating simple harmonic linear motion under the action of the eccentric cam (3) and the spring (7), thereby realizing the tensile loading-bending fatigue coupling test of the FRP rod (17); the environmental hose (18) is sleeved on the surface of the FRP rod (17), and the environmental solution is injected into it, thereby realizing the environmental-tensile loading-bending fatigue coupling test.

2. The environment-tensile loading-bending fatigue coupling test device for FRP rods according to claim 1, characterized in that: The eccentricity of the eccentric cam (3) is the bending amplitude. A plurality of eccentric holes with eccentricities are arranged on the disk surface of the eccentric cam (3) for connecting with the output shaft of the servo motor (2). The rotation speed and the number of rotations of the servo motor (2) are adjusted by a controller to achieve control of the frequency and the number of cycles of bending fatigue.

3. The environment-tensile loading-bending fatigue coupling test device for FRP rods according to claim 2, characterized in that: The FRP rod (17) and the anchor clip assembly (16) are pressed into the anchor sleeve (15), and the inner side tilt angle of the anchor sleeve (15) is smaller than the outer side tilt angle of the anchor clip assembly (16), so that during the pressing process, the anchoring area of ​​the FRP rod (17) is continuously clamped by the anchor clip assembly (16) from the end to the inside, thereby achieving effective anchoring of the FRP rod.

4. The environment-tensile loading-bending fatigue coupling test device for FRP rods according to claim 3, characterized in that: The outer side inclination angle of the anchor clip assembly (16) is 1.2°, and the inner side inclination angle of the anchor sleeve (15) is 1.1°; the diameter of the clip rod groove (1602) inside the anchor clip assembly (16) is consistent with the diameter of the FRP rod (17), ensuring close contact between the FRP rod (17) and the clip rod groove (1602).

5. The environment-tensile loading-bending fatigue coupling test device for FRP rods according to claim 4, characterized in that: The anchor clip assembly (16) includes two clip bodies (1601), and the radial cross-section of each clip body (1601) is a minor arc, so that there is still a gap in the middle when the two clip bodies (1601) clamp the FRP rod, thereby ensuring that there is clamping space during the pre-pressure application process.

6. An environment-tensile loading-bending fatigue coupling test device for FRP rods according to any one of claims 1 to 5, characterized in that: It also includes a dynamic data acquisition instrument, which is electrically connected to the bending pressure sensor (8) and the hollow pressure sensor (12) respectively. The hollow pressure sensor (12) is used to collect the magnitude of the load-bearing force in real time, and the bending pressure sensor (8) is used to collect the magnitude of the bending force in real time. The actual load magnitude of each sensor should not exceed 80% of the sensor range. The sampling frequency of the dynamic acquisition instrument should satisfy the requirement of having at least 10 sampling points in a single cycle.

7. A method for coupling environmental-tensile loading-bending fatigue testing for FRP rods obtained from the testing device according to claim 6, characterized in that: Here are the steps: The first step is to fix the environmental hose (18) at the mid-span position of the FRP rod (17), and inject distilled water, acid, alkali or salt solution into the environmental hose (18); The second step is to clamp the anchor clip assembly (16) at both ends of the FRP rod (17) according to the required anchoring type requirements, adjust the free section length to the required span, and use a press to pre-press the two together into the anchor sleeve (15) to complete the anchoring; The third step is to pass the anchored FRP rod (17) through the hollow pressure sensor (12), the load-bearing reaction frame (10), and the hollow jack (13) in sequence, and screw the anchor sleeves at both ends into the load-bearing gasket (14) so ​​that the bending support (9) acts on the mid-span position of the FRP rod (17); The fourth step is to adjust the initial stroke of the hollow jack (13), and then apply tension to the FRP rod (17) so that the reading of the hollow pressure sensor (12) reaches the required tensile load, and at the same time, the bending support (9) acts on the mid-span position of the FRP rod (17); Step 5: Select an eccentric cam (3) with a desired eccentricity and fix it on the servo motor (2); adjust and fix the height of the load-bearing reaction frame (10) so that the FRP rod (17) is in pressure-free contact with the lower end of the curved support (9) at the highest position; The sixth step is to turn on the servo motor (2) to start the environment-tensile load-bending fatigue test until it is completed, obtain the load-time curve of the whole process, and test the residual tensile strength of the FRP rod (17) through a tensile test to obtain a residual tensile strength-cycle number logarithmic curve.

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