Steel cable axial stress test system, calibration platform and detection method

Abstract

The invention discloses a steel cable axial stress test system, a calibration platform and a detection method, the steel cable axial stress test system is composed of a stress loading test bench and a liftable temperature loading device, the stress loading test bench can stretch a steel cable within a certain size, and the liftable temperature loading device can safely load the temperature of the steel cable; the liftable temperature loading device comprises a constant-temperature sleeve and a lifting mechanism; the steel cable axial stress calibration platform comprises an inductance resistance measuring device, a data acquisition and analysis upper computer and a detachable sensor, the detachable sensor is arranged on a measured steel cable in a sleeving manner, and the detachable sensor is completely wrapped by a constant-temperature sleeve; a detection coil of the detachable sensor is connected with the inductance resistance measuring device; the inductance and resistance measuring device communicates with the data acquisition and analysis upper computer in real time, the inductance value and the resistance value of the steel cable under alternating current excitation are measured in real time, and the inductance value or the resistance value under multiple frequencies is adopted to form a set of information to represent the axial stress value of the steel cable.

Description

Technical Field

[0001] The present invention relates to the technical field of steel cable axial stress detection, and particularly relates to a steel cable axial stress testing system, a calibration platform and a detection method. Background Art

[0002] Due to its high strength, good toughness, light weight, and the fact that it will not suddenly break in a whole bundle under overload and can transmit load over a long distance, steel cables are widely used in fields such as bridge engineering, mechanical traction equipment, and building engineering structures. However, during service, steel cables are under various adverse static and dynamic loads for a long time, and inevitably suffer cumulative damages such as wear, fatigue, and corrosion, which reduce their load-bearing capacity, and may even cause some steel wires to break, endangering life and property safety.

[0003] Most existing steel cable axial stress testing systems apply a certain tensile force to the steel cable through a floor-standing tensile loading device (such as a tensile testing machine), and on this basis, measure the single inductance value of the steel cable through a coil sensor on the steel cable. There are four aspects that need to be improved: First, longitudinally installing and arranging the sensor requires a corresponding adhesive or fixing structure, and the sensor is prone to slip downward during the stretching process; second, the stress loading device needs to be applicable to steel cables of various specifications; third, existing steel cable axial stress loading devices usually detect the axial stress of steel cables at room temperature and cannot meet the requirements of detecting the axial stress of steel cables at different temperatures; fourth, it is difficult to accurately reflect the axial stress condition of the steel cable only by detecting the single inductance value of the detection coil in the existing AC excitation measurement method.

[0004] If stress detection can be carried out on vulnerable structures such as bridge steel cables in advance, and early warning, reinforcement, and repair are carried out in a timely manner, it is entirely possible to avoid accidents. Therefore, timely and effective monitoring of the axial stress state of steel cables and mastering the law of its axial stress change are of great significance for ensuring the safe operation of steel cable structures and preventing major accidents. Summary of the Invention

[0005] Aiming at the deficiencies in the prior art, the present invention provides a steel cable axial stress testing system, a calibration platform and a detection method.

[0006] The first object of the present invention is to provide a steel cable axial stress testing system, including: a stress loading test bench and a liftable temperature loading device;

[0007] The stress loading test bench includes a left backing plate and a right backing plate which are arranged relatively parallel. Sleeves are coaxially arranged on the left backing plate and the right backing plate. A hollow jack that pushes out to the right is provided on the right side of the right backing plate. The steel cable to be tested passes through the sleeve of the left backing plate, the sleeve of the right backing plate, and the hollow jack. Anchor plates are sleeved on the left and right ends of the steel cable to be tested, and the anchor plates are fixed to the steel cable to be tested through wedge-shaped clamping pieces. The left anchor plate is located on the left side of the left backing plate, and the ejecting end of the hollow jack abuts against the right anchor plate. A detachable sensor is sleeved on the steel cable to be tested between the left backing plate and the right backing plate.

[0008] The liftable temperature loading device includes a constant temperature sleeve and a lifting mechanism that drives the constant temperature sleeve to adjust its height. The constant temperature sleeve contains an internal heating wire, a fiberglass blanket, and a heat insulation layer. The constant temperature sleeve is sleeved on the detachable sensor. Heat insulation layers are provided at both ends of the constant temperature sleeve, and central holes for the steel cable to be tested to pass through and for the detection coil of the detachable sensor to lead out are provided in the middle of the heat insulation layers at both ends. Based on the adjustment of the lifting mechanism, a certain gap is left between the constant temperature sleeve and the heat insulation layers at both ends and the detachable sensor and the steel cable to be tested.

[0009] As a further improvement of the present invention, the stress loading test bench further includes: an electro-hydraulic pump main body, a second motor, a solenoid valve, a pressure measuring device, and an oil pipeline.

[0010] The second motor is connected to the electro-hydraulic pump main body. A solenoid valve and a pressure measuring device are installed at the oil outlet end of the electro-hydraulic pump main body. The oil outlet of the electro-hydraulic pump main body is connected to the pressure maintaining valve installed at the oil inlet of the hollow jack through the oil pipeline.

[0011] As a further improvement of the present invention, a test bench main frame is provided between the left backing plate and the right backing plate. The left backing plate and the right backing plate are installed on the test bench bottom plate to form a horizontal frame structure. A plurality of bolt holes are provided on the test bench bottom plate, and it can be fixed to a heavier thick plate through bolts to ensure the stable loading of stress in a larger range of the test bench. Further, the material of the bolts is 40Cr.

[0012] As a further improvement of the present invention, the main frame structure in the stress loading test bench is used for the installation and fixation of the steel cable to be tested and the stress loading mechanism. Thin layer sleeves with different sizes and smooth interiors need to be provided at the perforations of the backing plates on both sides of the test bench to meet the centering and adapt to the stress loading of steel cables of various specifications.

[0013] As a further improvement of the present invention, the lifting mechanism includes a first motor, a worm and worm gear transmission device, and an upper fixing plate and a temperature loading mechanism bottom plate which are arranged parallel up and down.

[0014] The constant temperature sleeve is placed on the upper fixing plate. The axial length of the constant temperature sleeve should cover the steel cable as much as possible. Longitudinal connecting plates are provided on both the left and right sides at the bottom of the upper fixing plate and on both the left and right sides at the top of the temperature loading mechanism bottom plate. An X-shaped frame is provided between the upper and lower longitudinal connecting plates on the left side, and an X-shaped frame is provided between the upper and lower longitudinal connecting plates on the right side. The central rotation points of the two X-shaped frames are connected by a central connecting rod; the X-shaped frame is composed of two side connecting plates that rotate around the central rotation point. The upper end of one side connecting plate is fixed on the upper longitudinal connecting plate, and the lower end slides in the horizontal chute of the lower longitudinal connecting plate. The upper end of the other side connecting plate slides in the horizontal chute of the upper longitudinal connecting plate, and the lower end is fixed on the lower longitudinal connecting plate; the four endpoints of the two X-shaped frames on both sides are connected by a transverse connecting rod;

[0015] The output end of the first motor is connected to the worm end of the worm and gear transmission device to control the horizontal extension and retraction of the output shaft of the worm and gear transmission device; the worm and gear transmission device is placed on the transmission device bottom plate. The output shaft of the worm and gear transmission device is connected to one end of the lifting push rod through a connector, and the other end of the lifting push rod is connected to one end of the transverse connecting rod in the horizontal chute of the lower longitudinal connecting plate; based on the horizontal extension and retraction of the output shaft of the worm and gear transmission device, the transverse connecting rod is driven to reciprocate in the horizontal chute of the lower longitudinal connecting plate to realize the lifting movement of the upper fixing plate.

[0016] As a further improvement of the present invention, the hollow jack can withstand the set pressure value and maintain the numerical stability within a certain time. The maximum load it can withstand is not less than 30 tons; the liftable temperature loading device further includes a control device for the heating element to heat the constant temperature sleeve through the control device; one realizable way is: the outer layer of the constant temperature sleeve is a heat insulation layer, the inner layer is provided with a heating element, and a temperature sensor for detecting temperature is also provided in the constant temperature sleeve. The heating element and the temperature sensor are connected to the controller; the controller controls the constant temperature sleeve to reach the set temperature value and can maintain this temperature value within a certain time. The temperature heating range is 10°C - 80°C.

[0017] As a further improvement of the present invention, the present invention can realize the tensile test of single-strand steel strand cables or parallel wire cables of different specifications within a certain size. At the same time, the steel cable can also be replaced with a steel wire rope or other pipe column type test pieces.

[0018] As a further improvement of the present invention, the main frame structure of the stress loading test bench and the bottom plate need to be integrally manufactured to ensure that there is no relative movement between the two during the stress loading process; the inner and outer surfaces of the thin-layer sleeves on both sides of the pads should be smooth and the length should be greater than the thickness of the pads.

[0019] The second object of the present invention is to provide a calibration platform for the axial stress of a steel cable, which is used for measuring the electromagnetic parameters and characterizing the axial stress value when the axial stress of the steel cable changes; it includes: a data acquisition and analysis host computer, an inductance and resistance measuring device, a detachable sensor, and the above-mentioned steel cable axial stress test system;

[0020] The inductance and resistance measuring device is connected to both ends of the detection coil through Kelvin clamps. The inductance and resistance measuring device is equipped with a real-time data display screen, and the inductance and resistance measuring device can adjust the amplitude of the excitation signal and the magnitude of the measurement frequency; the data acquisition and analysis host computer communicates with the inductance and resistance measuring device, and the data acquisition and analysis host computer can control the inductance and resistance measuring device to simultaneously collect the inductance values and resistance values at both ends of the detection coil at multiple frequencies under AC excitation to establish the relationship between the measurement parameters and the axial stress value of the steel cable.

[0021] As a further improvement of the present invention, the measurable frequency range of the inductance and resistance measuring device is 10 Hz to 100 kHz; the data acquisition and analysis host computer issues commands to control the frequency conversion and data acquisition of the inductance and resistance measuring device, and the program of the data acquisition and analysis host computer has functions of multi-frequency data acquisition, analysis, and drawing.

[0022] As a further improvement of the present invention, the detachable sensor includes a detachable sensor skeleton and a detection coil. A skeleton inner hole is provided in the middle of the detachable sensor skeleton. The detachable sensor skeleton is composed of two sensor half-skeletons arranged in half. A first positioning boss, a second positioning boss, a first positioning groove, and a second positioning groove are provided on one sensor half-skeleton. The other sensor half-skeleton is provided with a first positioning groove corresponding to the first positioning boss of one sensor half-skeleton, a second positioning groove corresponding to the second positioning boss, a first positioning boss corresponding to the first positioning groove, and a second positioning boss corresponding to the second positioning groove; the two sensor half-skeletons arranged in half are clamped on the steel cable to be measured and fixed by cable ties, and the detection coil is wound on the detachable sensor skeleton.

[0023] As a further improvement of the present invention, a winding groove is provided in the middle of the detachable sensor skeleton. Cable tie slots and shield positioning slots are sequentially provided on both the left and right sides of the winding groove. A partition is provided between the winding groove and the cable tie slots, and a wire outlet hole is provided on the partition;

[0024] An inner heat insulation layer, a detection coil, an outer heat insulation layer, and a shielding layer are sequentially wound on the winding groove from the inside to the outside. High-temperature cable ties are placed in the cable tie slots, and a shielding cover is provided on the outermost layer and fixed in the shield positioning slots.

[0025] As a further improvement of the present invention, the material of the detachable sensor skeleton is made of high-temperature resistant resin material, and is installed and arranged along the axial direction of the steel cable. Cable ties can be used to fasten the sensor at the reserved position. If there is a gap between the sensor and the steel cable, it can be positioned and partially filled with high-temperature resistant insulating tape.

[0026] The third object of the present invention is to provide a method for detecting axial stress of a steel cable, comprising:

[0027] Step 1, assembling the cable axial stress test system;

[0028] Specifically include:

[0029] Install and fix the stress loading test bench, including the installation of the horizontal main frame, the fixing of the bottom plate, the installation of the pad and the installation of the thin sleeve; pass the tested steel cable through the pads and thin sleeves on both sides of the test bench, reserve a good length at one end, and then pass the hollow jack through the tested steel cable, and the left end of the jack should be against the right pad; put anchor plates on both ends of the tested steel cable, and after one end is fixed, the bottom of the anchor plate should be against the pad, and after the other end is fixed, the bottom of the anchor plate should be against the upper end of the jack, and the clips should be tightened by pulling or hammering;

[0030] The detachable sensor frame is fixed along the axial direction of the steel cable and fastened with a cable tie, and then the inner insulation layer, the detection coil (enameled wire), the outer insulation layer and the shielding layer are wound on the winding groove of the detachable sensor frame from the inside to the outside in sequence; the two ends of the enameled wire are led out from the wire hole and the paint is removed with a knife, and then the two ends are tinned; the Kelvin clamp is clamped on the two ends of the tinned enameled wire;

[0031] The thermostatic sleeve of the liftable temperature loading device (the thermostatic sleeve can be selected as a pair-mounted structure) is wrapped around the sensor, and the two ends of the detection coil are led out from the central holes of the insulation layer on both sides of the thermostatic sleeve; the thermostatic sleeve is placed on the upper fixing plate, and the height of the upper fixing plate is adjusted to leave a partial gap between the inner wall of the sleeve and the sensor (i.e., they are not in contact with each other), so as to facilitate tensile loading;

[0032] Establish a communication connection between the data acquisition and analysis host computer and the inductance and resistance measuring device, the connection mode can be wired or wireless;

[0033] Step 2: Enable the inductance and resistance measuring device, the data acquisition and analysis host computer, the stress loading test bench, and the liftable temperature loading device, input the cross-sectional area of ​​the steel cable into the data acquisition and analysis host computer, install and fix the steel cable, and debug the test system to ensure the stability of stress and temperature loading and the accuracy of real-time data acquisition;

[0034] Step 3: Load the jack to the specified bearing capacity F1, close the pressure-holding valve to maintain the stability of the tensile force value, adjust the temperature in the specified form, and after maintaining each temperature value for t1 time, turn off the heating device to prevent interference with the detection signal. Then, quickly use the host computer software to perform frequency conversion and data acquisition on the inductance and resistance measurement device. In this step, a total of n1 frequency points are collected. At each frequency, the inductance value and resistance value are collected n2 times, and the collection interval for each time is t2. The average value of the multiple collection data at each frequency point is taken as the inductance value and resistance value at that frequency point, and the temperature difference T1 before and after the data acquisition of the inductance and resistance measurement device is recorded. The values of t1, n1, n2, and t2 can be controlled to ensure that the temperature difference T1 is within the range allowed by the experiment. In this step, the host computer continuously issues commands to modify the frequency and receive data to the data measurement module through the serial port. The frequency increases in logarithmic form. After each frequency modification, multiple groups of inductance and resistance values are read, the average value of each group of data is calculated and stored, and finally, the average values of inductance and resistance at different frequencies are exported in the form of an excel table.

[0035] Step 4: Open the pressure-holding valve, and sequentially set the loading values of the jack to F2, F3, F4... Fn. Repeat Step 3 each time a loading value is set. After the data acquisition under the loading of Fn is completed, this step ends.

[0036] Step 5: Repeat Steps 3 to 4 multiple times.

[0037] Step 6: Analyze and process the data through the host computer program to obtain the specified axial stress value, the electromagnetic parameter value of the steel cable under test at a certain temperature, and the fitting relationship diagram between each parameter value and frequency and axial stress. A curve formed by the inductance values or resistance values at multiple frequencies is used to characterize the axial stress.

[0038] Step 7: Quantitatively analyze the relationship between the collected parameters and stress under this measurement device. By referring to the relationship formula between the collected parameters and stress, installing the same sensors and measurement devices on the steel cables under test of the same specification can realize the detection of the axial stress of the steel cables under test.

[0039] As a further improvement of the present invention, the detection accuracies of inductance and resistance should be within 0.001 μH and 0.001 μΩ respectively, and the update speed of the detection data can be adjusted.

[0040] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0041] The stress loading test platform of the present invention is a horizontal frame structure, which is convenient for the installation and arrangement of detection sensors, and is economical, reliable, and reasonable in structure. It can meet the stress loading of different specifications of steel cables or other pipe-shaped ferromagnetic materials within a certain size range.

[0042] The present invention realizes the temperature and height adjustment of the constant temperature sleeve by sleeving a liftable temperature loading device on the sensor, so as to meet the axial stress detection of the steel cable at different temperatures; by adjusting the height of the constant temperature sleeve, a certain gap is ensured between the inner wall of the sleeve and the sensor and the steel cable when loading the steel cable, ensuring the safe loading of stress under variable temperature conditions.

[0043] The test method of the present invention is novel, economical and efficient. The measurement of magnetic parameters and the characterization of axial stress values can be completed by using a single detection coil, and the detachable sensor is suitable for the axial stress detection of the in-service steel cable that has been installed and fixed.

[0044] The test method of the present invention can collect electromagnetic parameter information under various conditions by using an upper computer, and uses the inductance value or AC resistance value at different frequencies to form multiple information to characterize the axial stress value, that is, multiple data characterize one axial stress value, making up for the deficiency of characterizing axial stress with a single piece of information. Description of the Drawings

[0045] Figure 1 It is a schematic structural diagram of a steel cable axial stress test system disclosed by the present invention;

[0046] Figure 2 It is an installation schematic diagram of a steel cable axial stress calibration platform disclosed by the present invention;

[0047] Figure 3A 、 Figure 3B It is a schematic diagram of the detachable sensor skeleton disclosed by the present invention;

[0048] Figure 4 It is an installation schematic diagram of the sensor disclosed by the present invention;

[0049] Figure 5 It is a schematic flow chart of a steel cable axial stress detection method disclosed by the present invention;

[0050] Figure 6 It is a working flow chart of the data acquisition and analysis upper computer disclosed by the present invention;

[0051] Figure 7 It is a schematic diagram of characterizing axial tension with multiple information disclosed by the present invention.

[0052] In the figure:

[0053] 1. Wedge clip; 2. Anchor plate; 3. Hollow jack; 4. Pressure maintaining valve; 5. Right side backing plate; 6. Main frame of test bench; 7. Detection coil; 8. Detachable sensor skeleton; 8-1. Inner hole of skeleton; 8-2. First positioning boss; 8-3. Tie strap slot; 8-4. Wire winding slot; 8-5. Wire outlet hole; 8-6. Shielding cover positioning slot; 8-7. First positioning slot; 8-8. Second positioning boss; 8-9. Second positioning slot; 9. Bolt hole; 10. Test bench bottom plate; 11. Sleeve; 12. Left side backing plate; 13. Steel cable to be measured; 14. Temperature loading mechanism; 14-1. Insulation layers on both sides; 14-2. Constant temperature sleeve; 14-3. Upper fixing plate; 14-4. Horizontal connecting rod; 14-5. First motor; 14-6. Worm and worm gear transmission device; 14-7. Connector; 14-8. Bottom plate of transmission device; 14-9. Lifting push rod; 14-10. Longitudinal connecting plate; 14-11. Side connecting plate; 14-12. Bottom plate of temperature loading mechanism; 14-13. Horizontal sliding groove; 14-14. Central connecting rod; 15. Main body of electro-hydraulic pump; 16. Second motor; 17. Solenoid valve; 18. Pressure measuring device; 19. Oil pipeline; 20. Data acquisition and analysis host computer; 21. Kelvin clamp; 22. Inductance and resistance measuring device; 23. Real-time data display screen; 24. High-temperature resistant tie strap; 25. Surrounding shielding layer; 26. Outer heat insulation layer; 27. Inner heat insulation layer. Detailed implementation manners

[0054] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0055] The present invention discloses a steel cable axial stress testing system, a calibration platform and a detection method. The system applies tensile force to the steel cable to be tested through a hollow jack. A detachable sensor is sleeved on the steel cable to be tested, and a constant temperature sleeve is sleeved on the detachable sensor. A lifting mechanism for controlling its lifting is provided at the bottom of the constant temperature sleeve; the detection coil of the detachable sensor is connected to an inductance resistance measuring device, and the inductance resistance measuring device communicates with a data acquisition and analysis upper computer; by measuring the inductance value and resistance value of the steel strand under the AC excitation of the inductance resistance measuring device, multiple information such as the inductance value or resistance value at different frequencies is used to characterize the axial stress value. The present invention can provide stress loading and temperature loading for the steel cable to be tested, can keep the stress unchanged and adopt temperature gradient change, and can also keep the temperature unchanged and adopt stress gradient change; instructions are sent through the upper computer, detection data is collected in real time through the inductance resistance measuring device, stress loading is provided through the jack, and temperature change is provided through the constant temperature sleeve with adjustable height, so as to realize stress testing and magnetic parameter acquisition of the steel cable or other pipe columns.

[0056] The following further describes the present invention in detail with reference to the accompanying drawings:

[0057] As Figure 1 shown, the present invention provides a steel cable axial stress testing system, including: a stress loading test bench, a liftable temperature loading device; wherein,

[0058] The stress loading test bench includes a left cushion plate 12 and a right cushion plate 5 which are arranged relatively parallel. A test bench main frame 6 is provided between the left cushion plate 12 and the right cushion plate 5. The left cushion plate 12 and the right cushion plate 5 are installed on a test bench bottom plate 10 to form a horizontal frame structure. Multiple bolt holes 9 are provided on the test bench bottom plate 10, and it can be fixed on a heavier thick plate through bolts to ensure the stable loading of stress over a larger range of the test bench. Further, the material of the bolts is 40Cr. The main frame structure in the stress loading test bench is used for the installation and fixation of the steel cable to be tested and the stress loading mechanism. Different-sized thin-layer sleeves need to be set at the perforations of the cushion plates on both sides of the test bench to meet the centering requirement and adapt to the stress loading of various specifications of steel cables. Coaxial sleeves 11 are provided on the left cushion plate 12 and the right cushion plate 5. A hollow jack 3 that protrudes to the right is provided on the right side of the right cushion plate 5. The steel cable 13 to be tested passes through the sleeve 11 of the left cushion plate 12, the sleeve 11 of the right cushion plate 5, and the hollow jack 3. Anchor plates 2 are sleeved on the left and right ends of the steel cable 13 to be tested, and the anchor plates 2 are fixed to the steel cable 13 to be tested through wedge grips 1. The left anchor plate 2 is located on the left side of the left cushion plate 12. The fixed end of the hollow jack 3 abuts against the right cushion plate 5, and the jacking end abuts against the right anchor plate 2. Different tensile forces are applied to the steel cable 13 to be tested based on the hollow jack 3. Further, the main frame structure of the stress loading test bench and the bottom plate need to be integrally manufactured to ensure that there is no relative movement between the two during the stretching process. The inner and outer surfaces of the thin-layer sleeves of the cushion plates on both sides should be smooth and the length should be greater than the thickness of the cushion plates. Further, the thin-layer sleeves 11 have various specifications of inner diameters for tensile tests of steel cables with different diameters. The steel cable can also be replaced with steel strands, wire ropes, and other tubular test pieces. Further, the hollow jack 3 can withstand the set pressure value and maintain the stability of the value within a certain period of time, and the maximum weight it can withstand is not less than 30 tons.

[0059] The stress loading test bench of the present invention further includes: an electro-hydraulic pump main body 15, a second motor 16, a solenoid valve 17, a pressure measuring device 18, an oil delivery pipe 19, and a pressure maintaining valve 4. The second motor 16 is connected to the electro-hydraulic pump main body 15. A solenoid valve 17 and a pressure measuring device 18 are installed at the oil outlet end of the electro-hydraulic pump main body 15. The oil outlet of the electro-hydraulic pump main body 15 is connected to the pressure maintaining valve 4 installed at the oil inlet of the hollow jack 3 through the oil delivery pipe 19. The pressure maintaining valve 4 is used to ensure the continuous stability of the oil pressure in the jack, which is opened during pressurization and closed during pressure stabilization.

[0060] A detachable sensor is sleeved on the steel cable 13 to be tested between the left cushion plate 12 and the right cushion plate 5 of the present invention; such as Figure 3A , Figure 3B and Figure 4As shown, the detachable sensor includes a detachable sensor skeleton 8 and a detection coil 7. A skeleton inner hole 8-1 is provided in the middle of the detachable sensor skeleton 8. The detachable sensor skeleton 8 is composed of two sensor half-skeletons arranged in half. A first positioning boss 8-2, a second positioning boss 8-8, a first positioning groove 8-7, and a second positioning groove 8-9 are provided on one sensor half-skeleton. On the other sensor half-skeleton, there are a first positioning groove 8-7 corresponding to the first positioning boss 8-2 of one sensor half-skeleton, a second positioning groove 8-9 corresponding to the second positioning boss 8-8, a first positioning boss 8-2 corresponding to the first positioning groove 8-7, and a second positioning boss 8-8 corresponding to the second positioning groove 8-9. The two sensor half-skeletons arranged in half are clamped on the steel cable 13 to be measured and fixed by a cable tie 24. The detection coil 7 is wound around the detachable sensor skeleton 8. Further, a wire winding groove 8-4 is provided in the middle of the detachable sensor skeleton 8. On both the left and right sides of the wire winding groove 8-4, there are successively a cable tie clamping groove 8-3 and a shield cover positioning groove 8-6. A partition is provided between the wire winding groove 8-4 and the cable tie clamping groove 8-3, and a wire outlet hole 8-5 is provided on the partition. An inner heat insulation layer 26, a detection coil 7, an outer heat insulation layer 27, and a shielding layer 25 are successively wound on the wire winding groove 8-4 from the inside to the outside. The high-temperature resistant cable tie 24 is placed in the cable tie clamping groove 8-3, and the outermost layer is covered with a shield cover and the shield cover is fixed in the shield cover positioning groove 8-6. Further, the material of the detachable sensor skeleton uses a high-temperature resistant resin material, which is installed and arranged along the axial direction of the steel cable. The sensor can be fastened with a cable tie at the reserved position. If there is a gap between the sensor and the steel cable, positioning and partial filling can be carried out through a high-temperature resistant insulating tape.

[0061] The liftable temperature loading device of the present invention includes a constant temperature sleeve 14-2 and a lifting mechanism for driving the constant temperature sleeve 14-2 to adjust its height. The constant temperature sleeve 14-2 contains a heating device and a heat insulation layer. The constant temperature sleeve 14-2 is sleeved on a detachable sensor. Heat insulation layers 14-1 are provided at both ends of the constant temperature sleeve 14-2, and a central hole for the measured steel cable to pass through and for the detection coil of the detachable sensor to lead out is provided in the middle of the heat insulation layers 14-1 at both ends. Based on the adjustment of the lifting mechanism, a certain gap is left between the constant temperature sleeve 14-2 and the heat insulation layers 14-1 at both ends, the detachable sensor, and the measured steel cable 13. Specifically: The lifting mechanism includes a first motor 14-5, a worm and worm gear transmission device 14-6, and an upper fixing plate 14-3 and a temperature loading mechanism bottom plate 14-12 that are arranged parallel up and down; the constant temperature sleeve 14-2 is placed on the upper fixing plate 14-3. Longitudinal connecting plates 14-10 are provided on both the left and right sides of the bottom of the upper fixing plate 14-3 and on both the left and right sides of the top of the temperature loading mechanism bottom plate 14-12. An X-shaped frame is provided between the upper and lower longitudinal connecting plates on the left side, and an X-shaped frame is provided between the upper and lower longitudinal connecting plates on the right side. The central rotation points of the two X-shaped frames are connected by a central connecting rod 14-14; the X-shaped frame is composed of two side connecting plates 14-11 that rotate around the central rotation point. The upper end of one side connecting plate 14-11 is fixed on the upper longitudinal connecting plate, and the lower end slides in the horizontal chute 14-13 of the lower longitudinal connecting plate. The upper end of the other side connecting plate slides in the horizontal chute 14-13 of the upper longitudinal connecting plate, and the lower end is fixed on the lower longitudinal connecting plate; the four endpoints of the two side X-shaped frames are connected by a transverse connecting rod 14-4; the output end of the first motor 14-5 is connected to the turbine end of the worm and worm gear transmission device 14-6 to control the horizontal extension and retraction of the worm of the worm and worm gear transmission device 14-6; the worm and worm gear transmission device 14-6 is placed on the transmission device bottom plate 14-8, and one end of the lifting push rod 14-9 is connected to the worm end of the worm and worm gear transmission device 14-6 through a connector 14-7. Specifically, the extended worm of the worm and worm gear transmission device 14-6 is connected to the bearing in the connector 14-7; the other end of the lifting push rod 14-9 is connected to one end of the transverse connecting rod 14-4 in the horizontal chute of the lower longitudinal connecting plate; based on the horizontal extension and retraction of the worm of the worm and worm gear transmission device 14-6, the transverse connecting rod 14-4 is driven to reciprocate in the horizontal chute 14-13 of the lower longitudinal connecting plate to realize the lifting movement of the upper fixing plate 14-3. Further, the transverse connecting rod 14-4 and the central connecting rod 14-14 include a rod body and nuts. Both ends of the rod body have threads. After the rod body of the transverse connecting rod 14-4 passes through the longitudinal connecting plate 14-10 and the side connecting plate 14-11, nuts are covered and tightened. The central connecting rod 14-14 passes through all the side connecting rods 14-11 and then nuts are covered and tightened.Furthermore, the liftable temperature loading device of the present invention further includes a control device, which is used to heat the constant temperature sleeve. One achievable way is that the outer layer of the constant temperature sleeve is a heat insulation layer, the inner layer is provided with a heating element, and a temperature sensor for detecting temperature is also provided in the constant temperature sleeve. The heating element and the temperature sensor are connected to the controller. The controller controls the constant temperature sleeve to reach the set temperature value and can maintain this temperature value within a certain period of time. The temperature heating range is 10°C - 80°C.

[0062] As Figure 2 shown, the present invention provides a calibration platform for axial stress of steel cables, which is used for magnetic parameter measurement and axial stress value calibration of steel cables. It includes: a data acquisition and analysis host computer 20, an inductance and resistance measurement device 22, and the above-mentioned axial stress loading device for steel cables. The inductance and resistance measurement device 22 is connected to both ends of the detection coil 7 through Kelvin clamps 21, and a real-time data display screen 23 is provided on the inductance and resistance measurement device 22. The data acquisition and analysis host computer 20 communicates with the inductance and resistance measurement device 22. The data acquisition and analysis host computer can control the inductance and resistance measurement device to simultaneously collect the inductance values and resistance values at both ends of the detection coil at multiple frequencies under AC excitation to characterize the axial stress value of the steel cable.

[0063] Furthermore, the measurable frequency range of the inductance and resistance measurement device 22 of the present invention is 10 Hz - 100 kHz. The acquisition of the inductance and resistance measurement device is controlled by issuing commands from the data acquisition and analysis host computer 20. The program of the data acquisition and analysis host computer should have functions of multi-frequency data acquisition, analysis, and drawing.

[0064] Furthermore, the data acquisition and analysis host computer 20 of the present invention is also connected to the constant temperature sleeve 14-2, the first motor 14-5, the second motor 16, and the solenoid valve 17. It can read the real-time temperature inside the constant temperature sleeve 14-2, accurately adjust the height of the constant temperature sleeve, accurately adjust the rotation speeds of the first motor 14-5 and the second motor 16, accurately control the operation state of the solenoid valve 17, receive the readings of the pressure measurer 18 in real time, and perform data interaction with the inductance and resistance measurement device 22 in real time.

[0065] As Figure 5 shown, the present invention provides a method for detecting axial stress of steel cables. This detection method is realized based on the above-mentioned calibration platform for axial stress of steel cables, and includes:

[0066] The specifications, stress state and detection principle of the actual steel cable are determined through field research and literature research to ensure the rationality of the method; a detachable sensor skeleton is designed according to the size and specifications. The skeleton material can be selected from high-temperature resistant resin materials, and the wire diameter, number of turns, inner diameter and other parameters of the coil are optimized to make it easy to install; the multi-frequency acquisition program of the host computer is used to test the inductance resistance measurement device to ensure the accuracy of the real-time acquisition data;

[0067] This detection method is applicable to the detection of axial stress of steel cables at room temperature and the detection of axial stress of steel cables under force-temperature. The detection of axial stress of steel cables at room temperature does not require the opening of the temperature loading device; the specific steps of the detection of axial stress of steel cables under force-temperature are as follows:

[0068] Step 1, assembling the cable axial stress test system;

[0069] Specifically include:

[0070] Install and fix the stress loading test bench, including the installation of the horizontal main frame, the fixing of the bottom plate, the installation of the pad and the installation of the thin sleeve; pass the tested steel cable 13 through the pads 12, 5 and the thin sleeve 11 on both sides of the test bench, reserve a good length at one end, and then pass the hollow jack 3 through the tested steel cable 13, and the left end of the jack should be against the right pad 5; put the anchor plates 2 on both ends of the tested steel cable 13, after one end is fixed, the bottom of the anchor plate should be against the left pad 12, and after the other end is fixed, the bottom of the anchor plate should be against the upper end of the jack, and the clip is tightened by pulling or hammering; install and fix the detachable sensor skeleton along the axial direction of the steel cable and tighten it with a cable tie, and then from the inside to the outside on the winding groove of the detachable sensor skeleton An inner insulation layer, a detection coil (enameled wire), an outer insulation layer and a shielding layer are wound in sequence; the two ends of the enameled wire are led out from the wire hole and then the paint is removed with a knife, and then the two ends are tinned; the Kelvin clamp 21 is clamped at the two ends of the tinned enameled wire; the constant temperature sleeve of the temperature loading mechanism (the constant temperature sleeve can be selected as a pair-mounted structure) is wrapped around the sensor, and the two ends of the detection coil are led out from the central hole of the insulation layer on both sides of the constant temperature sleeve; the constant temperature sleeve is placed on the upper fixed plate, and the height of the upper fixed plate is adjusted to leave a partial gap between the inner wall of the sleeve and the sensor (that is, they do not touch each other), which is convenient for axial stress loading; a communication connection is established between the data acquisition and analysis host computer and the data measurement module of the inductance and resistance measurement device, and the connection method can be wired or wireless;

[0071] Step 2, start the inductance resistance measuring device 22, the data acquisition and analysis host computer 20, the stress loading test bench, and the temperature loading device, input the cross-sectional area of ​​the steel cable into the host computer and debug the test system to ensure the stability of stress and temperature loading and the accuracy of real-time data acquisition, so that it is suitable for the tested steel cable 13;

[0072] Step 3: Load the jack 3 to the specified bearing capacity F1 and maintain stability. Adjust the temperature in a specified form. After each temperature value is maintained for t1 time, turn off the heating device to prevent interference with the detection signal, and quickly use the host computer software to perform frequency conversion and data acquisition on the inductance and resistance measuring device 22;

[0073] In this step, a total of n2 frequency points are collected. At each frequency, the inductance value and resistance value are collected n2 times, and the collection interval for each time is t2. The average value of the multiple collection data at each frequency point is taken as the inductance value and resistance value at that frequency point, and the temperature difference T1 before and after the data collection of the inductance and resistance measuring device 22 is recorded; t1, n1, n2, and t2 can be controlled to ensure that the temperature difference T1 is within the range allowed by the experiment;

[0074] As Figure 6 shown, in this step, the host computer 20 continuously issues commands to modify the frequency and receive data to the data measurement module through the serial port. The frequency increases in a logarithmic form. After each frequency modification, multiple groups of inductance and resistance values are read, the average value of each group of data is calculated and stored, and finally the average values of inductance and resistance at different frequencies are exported in the form of an excel table;

[0075] Step 4: Set the loading values of the jack 3 to F2, F3, F4... Fn in sequence. Each time a loading value is set, repeat the steps of the fifth step. After the data collection under the load of Fn is completed, this step ends;

[0076] Step 5: Repeat the processes of Step 3 and Step 4 m times. Each time Step 4 ends, it is regarded as the end of the processes of Step 3 and Step 4;

[0077] Step 6: By analyzing and processing the exported data through the host computer 20, the inductance values and resistance values at each frequency under different tensile force values can be obtained. As Figure 7 shown, the current axial stress value can be characterized by the curves of inductance values or resistance values at multiple frequencies; after multiple groups of experiments, the electromagnetic parameter values of the steel cable to be measured under specified tensile force values and temperatures can be analyzed, as well as the fitting curve graphs of each parameter value with frequency and tensile force.

[0078] Step 7: Quantitatively analyze the relationship between the collected parameters and the stress under this measuring device. By referring to the relational expression between the collected parameters and the stress, installing the same sensors and measuring devices on the steel cable to be measured with the same specifications can realize the detection of the axial stress of the steel cable to be measured.

[0079] The above is only the preferred embodiment of the present invention and is not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A steel cable axial stress testing system, characterized in that Including: A stress loading test bench and a liftable temperature loading device; The stress loading test bench includes a left cushion plate and a right cushion plate which are arranged relatively parallel. Sleeves are coaxially arranged on the left cushion plate and the right cushion plate. A hollow jack that ejects to the right is arranged on the right side of the right cushion plate. The steel cable to be measured passes through the sleeve of the left cushion plate, the sleeve of the right cushion plate and the hollow jack. Anchor plates are sleeved on the left and right ends of the steel cable to be measured, and the anchor plates and the steel cable to be measured are fixed by clamping pieces. The left anchor plate is located on the left side of the left cushion plate, and the ejecting end of the hollow jack abuts against the right anchor plate. A detachable sensor is sleeved on the steel cable to be measured between the left cushion plate and the right cushion plate; The liftable temperature loading device includes a constant temperature sleeve and a lifting mechanism that drives the constant temperature sleeve to adjust its height. The constant temperature sleeve contains internal heating wires, fiberglass blankets and a heat preservation layer. The constant temperature sleeve is sleeved on the detachable sensor. Heat preservation layers are also arranged at both ends of the constant temperature sleeve. Central holes for the steel cable to be measured to pass through and for the detection coil of the detachable sensor to lead out are arranged in the middle of the heat preservation layers at both ends. Based on the adjustment of the lifting mechanism, a certain gap is left between the constant temperature sleeve and the heat preservation layers at both ends and the detachable sensor and the steel cable to be measured.

2. The cable axial stress testing system according to claim 1, wherein The stress loading test bench further includes: an electro-hydraulic pump main body, a second motor, a solenoid valve, a pressure measurer and an oil pipeline; The second motor is connected to the electro-hydraulic pump main body. A solenoid valve and a pressure measurer are installed at the oil outlet end of the electro-hydraulic pump main body. The opening and closing of the solenoid valve are controlled by a host computer, and the pressure value of the pressure measurer can be accurately transmitted to the host computer.

3. The cable axial stress test system according to claim 1, characterized in that A test bench main frame is arranged between the left cushion plate and the right cushion plate. The left cushion plate and the right cushion plate are installed on a test bench bottom plate. Sleeves of various specifications can be installed inside the left cushion plate and the right cushion plate to be applicable to steel cables of different specifications. A plurality of bolt holes are arranged on the test bench bottom plate for installation and fixation.

4. The cable axial stress testing system according to claim 1, characterized in that, The lifting mechanism includes a first motor, a worm and worm gear transmission device, and an upper fixing plate and a temperature loading mechanism bottom plate which are arranged parallel up and down; The constant temperature sleeve is placed on the upper fixing plate. Longitudinal connecting plates are arranged on the left and right sides of the bottom of the upper fixing plate and on the left and right sides of the top of the temperature loading mechanism bottom plate. An X-shaped frame is arranged between the upper and lower longitudinal connecting plates on the left side, and an X-shaped frame is arranged between the upper and lower longitudinal connecting plates on the right side. The central rotation points of the two X-shaped frames are connected by a central connecting rod. The X-shaped frame is composed of two side connecting plates that rotate around the central rotation point. The upper end of one side connecting plate is fixed on the upper longitudinal connecting plate, and the lower end slides in the horizontal chute of the lower longitudinal connecting plate. The upper end of the other side connecting plate slides in the horizontal chute of the upper longitudinal connecting plate, and the lower end is fixed on the lower longitudinal connecting plate. The four endpoints of the two X-shaped frames on both sides are connected by a transverse connecting rod; The output end of the first motor is connected to the worm end of the worm and gear transmission device to control the horizontal extension and retraction of the output shaft of the worm and gear transmission device; the worm and gear transmission device is placed on the transmission device bottom plate, and the output shaft of the worm and gear transmission device is connected to one end of the lifting push rod through a connector, and the other end of the lifting push rod is connected to one end of a transverse connecting rod in the horizontal chute of the lower longitudinal connecting plate; based on the horizontal extension and retraction of the output shaft of the worm and gear transmission device, the transverse connecting rod is driven to reciprocate in the horizontal chute of the lower longitudinal connecting plate, so as to realize the lifting movement of the upper fixing plate.

5. A calibration platform for the axial stress of a steel cable, which is used for measuring the magnetic parameters of the steel cable and characterizing the axial stress value; characterized in that, Comprising: an inductance and resistance measuring device, a data acquisition and analysis host computer, a detachable sensor, and a steel cable axial stress testing system according to any one of claims 1 to 4; The inductance and resistance measuring device is connected to both ends of the detection coil through Kelvin clamps, and a real-time data display screen is provided on the inductance and resistance measuring device; The data acquisition and analysis host computer communicates with the inductance and resistance measuring device, and the data acquisition and analysis host computer can control the inductance and resistance measuring device to simultaneously collect the inductance values and resistance values at both ends of the detection coil at multiple frequencies under AC excitation to characterize the steel cable axial stress value; The detachable sensor includes a detachable sensor skeleton and a detection coil. A skeleton inner hole is provided in the middle of the detachable sensor skeleton. The detachable sensor skeleton is composed of two sensor half skeletons arranged in half. A first positioning boss, a second positioning boss, a first positioning groove, and a second positioning groove are provided on one sensor half skeleton, and a first positioning groove corresponding to the first positioning boss of one sensor half skeleton, a second positioning groove corresponding to the second positioning boss, a first positioning boss corresponding to the first positioning groove, and a second positioning boss corresponding to the second positioning groove are provided on the other sensor half skeleton; the two sensor half skeletons arranged in half are clamped on the steel cable to be measured and fixed by cable ties, and the detection coil is wound on the detachable sensor skeleton.

6. The cable axial stress calibration platform according to claim 5, wherein A wire winding groove is provided in the middle of the detachable sensor skeleton. Cable tie slots and shield positioning slots are sequentially provided on both the left and right sides of the wire winding groove. A partition is provided between the wire winding groove and the cable tie slots, and a wire outlet hole is provided on the partition; An inner heat insulation layer, a detection coil, an outer heat insulation layer, and a shielding layer are sequentially wound on the wire winding groove from the inside to the outside. The cable tie is placed in the cable tie slot, and a shielding cover is provided on the outermost layer and fixed in the shield positioning slot.

7. A method for detecting the axial stress of a steel cable as described in claim 5, characterized in that, Comprising: Step 1, assemble the steel cable axial stress calibration platform; Step 2, start the inductance and resistance measuring device, the data acquisition and analysis host computer, the detachable sensor, the stress loading test bench, and the liftable temperature loading device. Input the cross-sectional area of the steel cable into the data acquisition and analysis host computer, install and fix the steel cable, and debug the calibration platform. Step 3: Load the jack to the specified bearing capacity F1, close the solenoid valve to maintain the stability of the tensile force value, adjust the temperature in the specified form, close the heating device after maintaining each temperature value for t1 time; use the host computer software to perform frequency conversion and data acquisition on the inductance and resistance measurement device; among them, a total of n1 frequency points are collected in this step, the inductance value and resistance value are collected n2 times at each frequency, the collection interval for each time is t2, the average value of the multiple collection data at each frequency point is taken as the inductance value and resistance value at that frequency point, and the temperature difference T1 before and after the data acquisition of the inductance and resistance measurement device is recorded; in this step, the host computer continuously issues commands to modify the frequency and receive data to the data measurement module through the serial port, the frequency increases logarithmically, multiple groups of inductance and resistance values are read after each frequency modification, the average value of each group of data is calculated and stored, and finally the average values of inductance and resistance at different frequencies are exported in the form of an excel table; Step 4: Open the solenoid valve, sequentially set the loading values of the jack to F2, F3, F4... Fn, and repeat Step 3 each time a loading value is set. After the data acquisition under the loading of Fn is completed, end this step; Step 5: Repeat Steps 3 to 4 multiple times; Step 6: Analyze and process the measured data through the host computer program to obtain the specified axial stress value of the steel cable, the electromagnetic parameter value of the measured steel cable at the temperature, and the fitting relationship diagram between each parameter value and the frequency and axial stress value. Use the inductance value or resistance value at multiple frequencies to form a curve to characterize the axial stress of the steel cable; Step 7: Quantitatively analyze the relationship between the collected parameters and the stress under this measurement device. By comparing the relationship formula between the collected parameters and the stress, installing the same sensor and measurement device on the steel cable to be measured with the same specification can realize the detection of the axial stress of the steel cable to be measured.

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