Device and method for measuring the nonlinear coefficient and attenuation coefficient of surface waves on main beams

Abstract

This invention discloses a measuring device and method for detecting the nonlinear coefficient and attenuation coefficient of surface waves on a main beam, relating to the technical field of cranes. It solves the problem of difficulty in online measurement of fatigue damage state assessment parameters for crane main beams. The device includes: a piezoelectric surface wave transducer and two dual-electrode piezoelectric thin-film sensors, both pressed firmly onto the surface of the steel plate to be tested; the dual-electrode piezoelectric thin-film sensor closer to the piezoelectric surface wave transducer is designated as sensor number one, and the dual-electrode piezoelectric thin-film sensor farther from the transducer is designated as sensor number two; the piezoelectric surface wave transducer is used to excite surface waves, and sensors number one and two are used to receive surface waves. In this invention, the measuring device is fixed using magnets, making it easy to install and remove, reliably fixed, and compact, adaptable to the working environment of cranes.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of cranes, in particular to a measuring device and method for detecting nonlinear coefficient and attenuation coefficient of surface wave of a girder. BACKGROUND

[0002] A crane is an important cargo handling tool, which repeatedly completes the lifting and unloading process of heavy objects in work, so that the metal structure of the crane bears alternating load. It is estimated that more than 70% of the failure cases of metal structures under alternating load are caused by fatigue damage. Fatigue failure is sudden, and once the crane occurs fatigue failure during lifting heavy objects, it will lead to heavy objects falling off, even the whole crane overturning, which may cause significant economic losses and casualties. The girder is an important stressed component of the crane, therefore, reasonable evaluation and fatigue life prediction of the fatigue damage state of the crane girder can effectively reduce the risk of crane fatigue failure, reduce the occurrence of crane safety accidents, and improve the safety of the crane.

[0003] In the existing detection method of crane fatigue damage, the ultrasonic method is the preferred method for evaluating the fatigue damage of the crane due to its strong penetration, good directivity and easy implementation of online measurement. Influenced by factors such as surface roughness and stress concentration, the initiation of fatigue cracks of the girder is generally from the surface or near the surface. The ultrasonic surface wave is a kind of ultrasonic wave mainly propagating on the surface of solid medium, which is suitable for detecting the fatigue damage state of the girder. The nonlinear coefficient of the surface wave is sensitive to the early fatigue of the material, which is an important parameter for characterizing the early fatigue damage of the crane girder. The attenuation coefficient of the surface wave is sensitive to the middle and late fatigue of the material, which is an important parameter for characterizing the middle and late fatigue damage of the crane girder. The commonly used materials of the crane girder are Q235B and Q355B, and in the process of measuring the fatigue damage state evaluation parameters, the electromagnetic ultrasonic transducer is convenient for fixing the sensor, but the electromagnetic ultrasonic transducer has low efficiency, which is 20-40dB lower than the piezoelectric transducer. The excitation process and receiving process of the traditional piezoelectric transducer both need to use coupling agent, and the amplitude of the surface wave measured is unstable due to the influence of the coupling state, which directly affects the measurement result of the attenuation coefficient, and at the same time, it is not convenient for fixing the sensor. At present, most of the piezoelectric transducers in China are based on the imported RAM-5000 SNAP nonlinear high-energy ultrasonic test system, which has large volume and high price, and it is difficult to realize the online measurement of the fatigue damage state evaluation parameters of the crane girder. SUMMARY

[0004] In view of the above problem that it is difficult to realize the online measurement of the fatigue damage state evaluation parameters of the crane girder, the purpose of the present application is to provide a measuring device and method for detecting nonlinear coefficient and attenuation coefficient of surface wave of a girder.

[0005] To achieve the above object, the technical scheme adopted by the present application is:

[0006] A measuring device for detecting nonlinear coefficient and attenuation coefficient of a girder surface wave, comprising: an excitation device 1 and a receiving device 2, both of which are connected to the surface of a steel plate 3 to be measured by magnetic attraction;

[0007] The excitation device 1 comprises a piezoelectric surface wave transducer 104, and the receiving device 2 comprises two double-electrode piezoelectric film sensors 203; the piezoelectric surface wave transducer 104 and the double-electrode piezoelectric film sensors 203 are both pressed against the surface of the steel plate 3 to be measured, and the center point of the piezoelectric surface wave transducer 104 and the center points of the two double-electrode piezoelectric film sensors 203 are located on the same straight line; the two double-electrode piezoelectric film sensors 203 are both encapsulated by an insulating layer.

[0008] The double-electrode piezoelectric film sensor 203 closer to the piezoelectric surface wave transducer 104 is a first sensor 2031, and the double-electrode piezoelectric film sensor 203 farther from the piezoelectric surface wave transducer 104 is a second sensor 2032; the piezoelectric surface wave transducer 104 is used for exciting surface waves, and the first sensor 2031 and the second sensor 2032 are used for receiving surface waves.

[0009] The above-mentioned measuring device for detecting nonlinear coefficient and attenuation coefficient of a girder surface wave, wherein the excitation device 1 further comprises two magnets 101, a guide plate 102, two hole-supporting rods 103, a support plate 109 and two long screws 110; the support plate 109 and the guide plate 102 are arranged in parallel; the support plate 109 is arranged above the guide plate 102; the support plate 109 is provided with two through holes; the guide plate 102 is provided with two mounting holes and a limiting groove matched with the piezoelectric surface wave transducer 104; each mounting hole is penetrated by a hole-supporting rod 103; each magnet 101 is provided with a threaded hole; each long screw 110 is screwed into the threaded hole of a magnet 101 after penetrating the through hole of the support plate 109 and the hole-supporting rod 103 from top to bottom; the upper end of each hole-supporting rod 103 abuts against the lower surface of the support plate 109; the lower end of each hole-supporting rod 103 abuts against the upper surface of the magnet 101.

[0010] The two long screws 110 are arranged in parallel and perpendicularly to the guide plate 102.

[0011] The measuring device for nonlinear coefficient and attenuation coefficient of the main girder surface wave detection, wherein the exciting device 1 further comprises a cylindrical pressing block 105 and a screw rod 108, the supporting plate 109 is provided with a threaded hole between the two through holes; the middle part of the screw rod 108 is provided with a threaded section, the middle part of the screw rod 108 is assembled with the threaded hole of the supporting plate 109 by screwing, the cylindrical pressing block 105 is rotatably installed at the lower end of the screw rod 108; the cylindrical pressing block 105 is arranged above the piezoelectric surface wave transducer 104, and the piezoelectric surface wave transducer 104 is pressed on the upper surface of the steel plate 3 by rotating the screw rod 108 to realize the downward movement of the cylindrical pressing block 105.

[0012] The measuring device for nonlinear coefficient and attenuation coefficient of the main girder surface wave detection, wherein the exciting device 1 further comprises a thrust bearing 106 and a sealing cover 107, the upper surface of the cylindrical pressing block 105 is provided with a circular groove matched with the thrust bearing 106, the lower end of the screw rod 108 is rotatably connected with the cylindrical pressing block 105 through the thrust bearing 106; the sealing cover 107 is provided with a sealing through hole matched with the middle part of the screw rod 108, the lower surface of the sealing cover 107 is connected with the upper surface of the cylindrical pressing block 105; the sealing cover 107 is used for sealing the thrust bearing 106; the screw rod 108 can freely rotate around its own axis in the sealing through hole of the sealing cover 107.

[0013] The measuring device for measuring nonlinear coefficient and attenuation coefficient of girder surface wave detection, wherein the receiving device 2 further comprises a body 201, two magnets 207, two long screws 208, two compression springs 209, two cylindrical nuts 211 and a support plate 212, the upper side middle part of the body 201 is provided with an upper notch groove, the bottom side middle part of the body 201 is provided with a lower notch groove, two guide holes 210 are formed in the body 201 and penetrate the upper notch groove and the lower notch groove; the support plate 212 is arranged above the upper notch groove, the support plate 212 is provided with a threaded hole and two through holes; each magnet 207 is provided with a threaded hole; each long screw 208 is screwed into the threaded hole of a magnet 207 after penetrating the through hole of the support plate 212 and the guide hole 210 of the body 201 from top to bottom; the two magnets 207 are located in the lower notch groove; each long screw 208 is assembled with a cylindrical nut 211, the cylindrical nut 211 is located in the upper notch groove, and the cylindrical nut 211 is used for locking the long screw 208 and the support plate 212; the upper part of each guide hole 210 is provided with an upper variable diameter section with an increased outer diameter, and the lower part of each guide hole 210 is provided with a lower variable diameter section with an increased outer diameter; the inner diameter of the upper variable diameter section matches the outer diameter of the cylindrical nut 211, so that the cylindrical nut 211 can axially displace in the upper variable diameter section; each long screw 208 is sleeved with a compression spring 209, the upper end of the compression spring 209 abuts against the variable diameter position of the lower variable diameter section of the guide hole 210 of the body 201, and the lower end of the compression spring 209 abuts against the magnet 207.

[0014] The two long screws 208 are parallel to each other and perpendicular to the support plate 212.

[0015] The measuring device for measuring nonlinear coefficient and attenuation coefficient of girder surface wave detection, wherein the receiving device 2 further comprises two triangular pressing blocks 202 and two pressing plates 204, the bottom plate of the body 201 is provided with two strip-shaped holes; each strip-shaped hole is mounted with a double-electrode piezoelectric film sensor 203; the two pressing plates 204 are mounted in the body 201, the bottom surface of each pressing plate 204 is mounted with a triangular pressing block 202, and each triangular pressing block 202 is used for pressing the double-electrode piezoelectric film sensor 203 in the strip-shaped hole of the body 201; the two double-electrode piezoelectric film sensors 203 are arranged on the two sides of the lower notch groove.

[0016] The measuring device for detecting nonlinear coefficient and attenuation coefficient of the main girder surface wave, wherein the receiving device 2 further comprises two covers 205 and a signal line plug connector 206, the two covers 205 are respectively arranged on the two sides of the upper notch groove and are mounted on the upper surface of the body 201, and the signal line plug connector 206 is mounted on any one of the covers 205; and the two double-electrode piezoelectric film sensors 203 are connected with the signal line plug connector 206 through a circuit.

[0017] The measuring device for detecting nonlinear coefficient and attenuation coefficient of the main girder surface wave, wherein the receiving device 2 further comprises a pressing screw 215, a threaded segment is arranged at the middle part of the pressing screw 215, the middle part of the pressing screw 215 is threadedly assembled with a threaded hole of the supporting plate two 212, and the lower end of the pressing screw 215 is rotationally connected with the groove bottom of the upper notch groove; the body 201 is lowered and the two double-electrode piezoelectric film sensors 203 are pressed on the upper surface of the steel plate 3 to be measured by rotating the pressing screw 215.

[0018] The receiving device 2 further comprises an angle disc 214 and a displacement scale plate 213, the upper end of the pressing screw 215 is connected with the angle disc 214, and the upper surface of the supporting plate two 212 is connected with the displacement scale plate 213; the displacement distance of the body 201 is read through the angle disc 214 and the displacement scale plate 213.

[0019] The measuring device for detecting nonlinear coefficient and attenuation coefficient of the main girder surface wave, wherein the receiving device 2 further comprises a sealing cover two 216 and a thrust bearing two 217, a circular groove matched with the thrust bearing two 217 is arranged at the middle part of the groove bottom of the upper notch groove, the lower end of the pressing screw 215 is rotationally connected with the body 201 through the thrust bearing two 217, the sealing cover two 216 is provided with a sealing through hole matched with the middle part of the pressing screw 215, and the lower surface of the sealing cover two 216 is connected with the groove bottom of the upper notch groove; the sealing cover two 216 is used for sealing the thrust bearing two 217, and the pressing screw 215 can freely rotate around its own axis in the sealing through hole of the sealing cover two 216.

[0020] A measuring method for detecting nonlinear coefficient and attenuation coefficient of the main girder surface wave, which is suitable for the measuring device for detecting nonlinear coefficient and attenuation coefficient of the main girder surface wave, and comprises the following steps:

[0021] S1: selecting a measuring position on the lower cover plate of the crane main girder;

[0022] S2: magnetically connecting the receiving device 2 with the lower cover plate, and pressing the two double-electrode piezoelectric film sensors 203 on the surface to be measured of the steel plate 3 to be measured by adjusting the receiving device 2;

[0023] S3: coating a coupling agent on the piezoelectric surface wave transducer 104.

[0024] S4: Adjust the position of the piezoelectric surface wave transducer 104 so that the center point of the piezoelectric surface wave transducer 104 and the center points of the two double-electrode piezoelectric film sensors 203 are on the same straight line;

[0025] S5: Magnetically connect the excitation device 1 to the lower cover plate, and press the piezoelectric surface wave transducer 104 against the surface of the steel plate 3 to be measured by adjusting the excitation device 1;

[0026] S6: The double-electrode piezoelectric film sensor 203 closer to the piezoelectric surface wave transducer 104 is the first sensor 2031, and the double-electrode piezoelectric film sensor 203 farther from the piezoelectric surface wave transducer 104 is the second sensor 2032; measure the distance between the piezoelectric surface wave transducer 104 and the first sensor 2031 using a steel ruler , and record it; measure the distance between the first sensor 2031 and the second sensor 2032 using a steel ruler , and record it;

[0027] S7: The piezoelectric surface wave transducer 104 excites surface waves, and the first sensor 2031 and the second sensor 2032 receive the surface waves; obtain the time waveform diagrams of the surface wave signals measured by the first sensor 2031 and the second sensor 2032; calculate the time difference between the time instants corresponding to the wave peaks of two adjacent groups of signals

[0028] Calculate the speed of the surface wave :

[0029]

[0030] wherein: is the speed of the surface wave, is the distance between the first sensor 2031 and the second sensor 2032;

[0031] Calculate the wave number , wherein:

[0032]

[0033] wherein: is the circular frequency of the surface wave, is the speed of the surface wave;

[0034] And the circular frequency of the surface wave , is the frequency of the piezoelectric surface wave transducer 104;

[0035] ​After the formula is combined, the wave number is calculated :

[0036]

[0037] S8: According to the surface wave signal measured by the first sensor 2031, the amplitude of the fundamental wave and the amplitude of the second harmonic are obtained after Fourier spectrum analysis ; ;

[0038] Substitute the definition formula of the nonlinear coefficient of the surface wave:

[0039]

[0040] In the formula: The nonlinear coefficient of the surface wave is And The amplitudes of the fundamental wave and the second harmonic are respectively, The wave number is The distance between the piezoelectric surface wave transducer 104 and the first sensor 2031 is;

[0041] The nonlinear coefficient of the surface wave is calculated ;

[0042] S9: According to the surface wave signal measured by the second sensor 2032, the amplitude of the fundamental wave frequency domain is obtained after Fourier spectrum analysis ;

[0043] S10: Calculate the attenuation coefficient ;

[0044]

[0045] In the formula: The attenuation coefficient is The distance between the first sensor 2031 and the second sensor 2032 is And The amplitudes of the surface wave measured by the first sensor 2031 and the second sensor 2032 are respectively;

[0046] Here The amplitude of the fundamental wave obtained in step S8 is .

[0047] The application has the following positive effects compared with the prior art due to the adoption of the above-mentioned technology:

[0048] (1) In the application, both double-electrode piezoelectric film sensors are packaged with an insulating layer, have an insulating film on the surface, and the whole body is made of an insulating material, which can protect the surface wave signal amplifier from being damaged by the voltage signal in the main beam steel plate;

[0049] (2) In the present application, the piezoelectric surface wave transducer is a narrow frequency transducer, and different frequency transducers can be selected according to measurement requirements; the double-electrode piezoelectric film sensor is a wide frequency sensor, and the fundamental wave and the second harmonic can be measured simultaneously; in the measurement process, when different frequency transducers are selected as the surface wave excitation source, the sensor does not need to be replaced;

[0050] (3) In the present application, two surface wave receiving sensors are used simultaneously, so that the measurement result of the attenuation coefficient is not affected by the coupling effect of the transducer; the two receiving sensors are connected in parallel and share an amplifier, which avoids the influence of different amplification powers on the measurement result of the surface wave amplitude.

[0051] (4) In the present application, the measurement device is fixed by a magnet, which is convenient to disassemble and assemble, reliable in fixation, small in size, can effectively eliminate the influence of gravity and other external environmental factors on the detection process and detection accuracy, does not cause damage to the surface of the steel plate to be measured in the entire detection process, can adapt to the working environment of the crane, and the equipment cost is much lower than that of the imported RAM-5000 SNAP nonlinear high-energy ultrasonic testing system. BRIEF DESCRIPTION OF DRAWINGS

[0052] Figure 1 is a structural schematic diagram of a measurement device for detecting the nonlinear coefficient and the attenuation coefficient of a main beam according to the present application.

[0053] Figure 2 is a structural schematic diagram of an excitation device of a measurement device for detecting the nonlinear coefficient and the attenuation coefficient of a main beam according to the present application and an internal enlarged view thereof.

[0054] Figure 3 is a structural schematic diagram of a receiving device of a measurement device for detecting the nonlinear coefficient and the attenuation coefficient of a main beam according to the present application from a first perspective and an internal enlarged view thereof.

[0055] Figure 4 is a structural schematic diagram of a receiving device of a measurement device for detecting the nonlinear coefficient and the attenuation coefficient of a main beam according to the present application from a second perspective and an internal enlarged view thereof.

[0056] Figure 5 is a principle diagram of nonlinear coefficient calculation according to the present application.

[0057] Figure 6 is a time waveform diagram for example illustration.

[0058] Figure 7 is a left signal sensor spectrum diagram for example illustration.

[0059] Figure 8 is a right signal sensor spectrum diagram for example illustration. Figure 6The two groups of signals are respectively subjected to spectrum analysis.

[0060] In the drawings: 1, excitation device; 2, receiving device; 3, steel plate to be tested; 101, magnet one; 102, guide plate; 103, hole support rod; 104, piezoelectric surface wave transducer; 105, cylindrical pressing block; 106, thrust bearing one; 107, sealing cover one; 108, screw rod; 109, support plate one; 110, long screw rod one; 201, body; 202, triangular pressing block; 203, double-electrode piezoelectric film sensor; 204, pressing plate; 205, cover; 206, signal line plug connector; 207, magnet two; 208, long screw rod two; 209, compression spring; 210, guide hole; 211, cylindrical nut; 212, support plate two; 213, displacement scale plate; 214, angle disc; 215, compression screw rod; 216, sealing cover two; 217, thrust bearing two; 2031, No. 1 sensor; 2032, No. 2 sensor. DETAILED DESCRIPTION

[0061] The application will be further described below in conjunction with the drawings and specific embodiments, but not as a limitation of the application.

[0062] Please refer to Figures 1 to 5 , which shows a measuring device for detecting the non-linear coefficient and attenuation coefficient of a girder surface wave, wherein, Figure 1 is a schematic diagram of an online measuring device for fatigue damage state evaluation parameters, which mainly includes three parts of an excitation device 1 of a surface wave, a receiving device 2 of a surface wave and a steel plate 3 to be tested.

[0063] Further, in a preferred embodiment, the excitation device 1 of a surface wave is as shown in Figure 2 , the magnet one 101 is provided with a threaded hole matched with the long screw rod one 110, the hole support rod 103 is internally provided with upper and lower through holes, facilitating the long screw rod one 110 to pass through, the thrust bearing one 106 is used to bear the axial force of the cylindrical pressing block 105, the sealing cover one 107 is used to seal the thrust bearing one 106, the screw rod 108 can freely rotate around its own axis in the sealing hole of the sealing cover one 107, the middle of the support plate one 109 is provided with a threaded hole, and both sides are through holes for the long screw rod one 110 to pass in, the screw rod 108 is assembled with the threaded hole by screwing, the cylindrical pressing block 105 is installed at the lower end of the screw rod 108, and the displacement of the cylindrical pressing block 105 is realized by rotating the screw rod 108;

[0064] Further, in a preferred embodiment, the long screw rod 110 is connected with the magnet 101 through the hole support rod 103, so that the surface wave excitation device 1 can be adsorbed on the crane girder steel plate as a whole. The guide plate 102 has two installation holes for passing through the hole support rod 103, and the guide plate 102 is closely attached to the piezoelectric surface wave transducer 104, so as to ensure that the propagation direction of the surface wave is fixed during the measurement. The screw rod 108 can drive the cylindrical pressing block 105 to move up and down as a whole through the interaction with the threaded hole of the support plate 109, and press the piezoelectric surface wave transducer 104, so as to ensure that the position of the piezoelectric surface wave transducer 104 is fixed during the measurement.

[0065] Further, in a preferred embodiment, the surface wave receiving device 2 is as shown in Figure 3 and Figure 4 The double-electrode piezoelectric film sensor 203 is packaged with an insulating layer, the thrust bearing 217 is used to bear the axial force of the body 201 along the pressing screw 215, and the magnet 207 has threaded holes matched with the long screw rod 208.

[0066] Further, in a preferred embodiment, as shown in Figure 3 Since the crane girder steel plate is a conductor and may be electrified, the body 201 of the receiving device is made of insulating material, and the surface wave receiving device uses two double-electrode piezoelectric film sensors 203 packaged with insulating layers to protect the surface wave signal amplifier from being damaged by the voltage signal in the girder steel plate. The distance between the two double-electrode piezoelectric film sensors 203 is known. The pressing plate 204 presses the double-electrode piezoelectric film sensor 203 against the surface of the strip-shaped hole of the body 201 through the triangular pressing block 202, the double-electrode piezoelectric film sensor 203 extends out of the strip-shaped hole of the body 201, and the pressing plate 204 is connected with the body 201 through bolts. The cover 205 is fixed with a signal line plug connector 206, the electrodes of the two double-electrode piezoelectric film sensors 203 are connected with the signal line plug connector 206 in parallel. The two groups of magnets 207 are connected with the two groups of long screw rods 208 through threaded holes. The upper and lower surfaces of the two groups of compression springs 209 are in contact with the body 201 and the magnet 207 respectively. The guide hole 210 is a circular hole passing through the metal cylinder of the body 201, and can slide relative to the outer surface of the cylindrical nut 211. The two groups of long screw rods 208 are fixed by the cylindrical nut 211 after passing through the two through holes of the support plate 212.

[0067] Further, in a preferred embodiment, as shown in Figure 4The angle disc 214 is fixed on the pressing screw 215, and the pressing screw 215 moves up and down through the threaded hole in the middle of the support plate two 212. The displacement scale plate 213 has scales, and the tightening depth of the pressing screw can be roughly read according to the height of the angle disc 214. The surface of the angle disc 214 is divided according to the angle, and the pressing screw 215 moves down by one pitch distance, and the angle disc 214 rotates 360 degrees. According to the angle position of the angle disc 214, the tightening depth of the pressing screw 215 can be read with high precision. The sealing cover two 216 can prevent particles from entering and damaging the thrust bearing two 217, and the thrust bearing two 217 can reduce the tightening resistance of the pressing screw 215. When the receiving device 2 is in a non-working state, the pressing screw 215 is in an upward position, and the body 201 is in a suspended state under the action of the upward force of the two groups of compression springs 209; when the receiving device 2 is in a working state, the body 201 is subjected to a downward force by rotating the pressing screw 215, so that the two groups of compression springs 209 are further compressed, and the two groups of double-electrode piezoelectric film sensors 203 are in full contact with the surface of the main beam steel plate to be measured. The readings on the displacement scale plate 213 and the angle disc 214 at this time are recorded to ensure that the two groups of piezoelectric film sensors 203 are subjected to the same pressure in the next working state, and to reduce the measurement error caused by different surface pressures of the piezoelectric film sensors.

[0068] The above is only a preferred embodiment of the present application, and does not limit the implementation and protection scope of the present application.

[0069] The present application has the following implementation based on the above:

[0070] In a further embodiment of the present application, the calculation of the nonlinear coefficient:

[0071] The definition formula of the nonlinear coefficient of the surface wave is:

[0072] (1)

[0073] In the formula: is the nonlinear coefficient of the surface wave, and are the amplitudes of the fundamental wave and the second harmonic wave respectively, is the wave number, , is the circular frequency of the surface wave, is the velocity of the surface wave, is the propagation distance.

[0074] As can be seen from formula 1: the circular frequency of the surface wave is determined by the frequency of the transducer , which is a known quantity. To calculate the nonlinear coefficient, the velocity of the surface wave and the propagation distance Amplitude of fundamental and second harmonic waves and Four unknowns.

[0075] The schematic diagram for calculating nonlinear coefficients is as follows: Figure 5 As shown. After the excitation device 1 is magnetically attached to the surface of the steel plate 3 under test, the position of the piezoelectric surface wave transducer 104 is determined. After the receiving device 2 is magnetically attached to the surface of the steel plate 3 under test, the positions of sensor 2031 and sensor 2032 are determined. Based on the surface wave signal measured by sensor 2031, Fourier spectrum analysis is performed to obtain the amplitude of the fundamental wave. and the amplitude of the second harmonic It can be measured using a steel ruler. Figure 5 Propagation distance in The values, and the distance between sensor 2031 and sensor 2032. Based on the time waveforms of the surface wave signals measured by sensor 2031 and sensor 2032, the time difference between the corresponding moments of two adjacent signal peaks can be calculated. The velocity of surface acoustic waves . Wave number At this point, all the parameters in formula (1) are known quantities, and the nonlinear coefficients can be calculated. .

[0076] In a further embodiment of the present invention, the attenuation coefficient is calculated as follows:

[0077] (2)

[0078] In the formula: The attenuation coefficient is... The distance between two measurement points. and These are the amplitudes of the surface wave measured at two points. Corresponding to this measuring device, The distance between sensor 2031 (No. 1) and sensor 2032 (No. 2) was measured using a steel ruler. and The amplitudes of the surface waves were measured by sensor 2031 and sensor 2032, respectively.

[0079] In a further embodiment of the present invention, the operation steps are as follows:

[0080] 1. Choose the measurement position on the lower cover plate of the crane girder, and fix the receiving device 2 on the lower cover plate of the crane girder by using the magnet 207 of the receiving device 2. Rotate the compression screw 215, and through the interaction with the threaded hole in the support plate 212, the bottom of the compression screw 215 is pressed on the thrust bearing 217, and the body 201 is pushed downward to compress the compression spring 209 until the two double-electrode piezoelectric film sensors 203 are pressed on the surface to be measured.

[0081] 2. The scale of the displacement scale plate 213 can roughly determine the compression degree of the sensor, and on this basis, the angle value of the angle disc 214 can accurately determine the compression degree of the double-electrode piezoelectric film sensor 203. The scale value and the angle value of the angle disc 214 are recorded respectively, so as to compare the compression degree of the double-electrode piezoelectric film sensor 203 in the future measurement, and reduce the measurement error.

[0082] 3. Preliminarily determine the installation position of the excitation device 1, and coat the coupling agent below the piezoelectric surface wave transducer 104. Adjust the position of the excitation device 1, so that the center of the piezoelectric surface wave transducer 104 of the excitation device 1 is on a straight line with the center of the two double-electrode piezoelectric film sensors 203 of the receiving device 2, and fix the excitation device 1 on the lower cover plate of the crane girder by using the magnet 101 of the excitation device 1.

[0083] 4. Push the cylindrical pressing block 105 downward by rotating the screw 108, and press the piezoelectric surface wave transducer 104 on the lower cover plate of the crane girder.

[0084] 5. Measure the distance between the edge of the piezoelectric surface wave transducer 104 and the first sensor 2031 by using a steel ruler , and record the value; measure the distance between the first sensor 2031 and the second sensor 2032 by using a steel ruler , and record the value, which is fixed.

[0085] 6. Excite the surface wave by using the piezoelectric surface wave transducer 104, and receive the surface wave by the first sensor 2031 and the second sensor 2032. Since the first sensor 2031 and the second sensor 2032 are in parallel relationship, two signals will be displayed on the time waveform diagram of the surface wave signal.

[0086] 7. According to the time waveform diagram of the surface wave signal, the time difference between the corresponding time of the wave peaks of two adjacent groups of signals can be calculated , and the speed of the surface acoustic wave is . By substituting the frequency of the piezoelectric surface wave transducer 104 , the wave number can be calculated .

[0087] 8、According to the surface wave signal measured by the first sensor 2031, the amplitude of the fundamental wave and the amplitude of the second harmonic can be obtained after Fourier spectrum analysis. .

[0088] 9、The above measured data is brought into formula (1), and the nonlinear coefficient of the surface wave can be calculated.

[0089] 10、Since the first sensor 2031 and the second sensor 2032 are in parallel, two groups of signals will be displayed on the time waveform diagram of the surface wave signal, and the fundamental wave frequency domain amplitude of the first sensor 2031 is recorded as A1, and the fundamental wave frequency domain amplitude of the second sensor 2032 is recorded as A2. According to formula (2), the attenuation coefficient of the surface wave can be calculated.

[0090] 11、After the measurement is completed, the compression screw 215 is reversely rotated, and the body 201 is driven to move upward under the restoring force of the compression spring 209. The double-electrode piezoelectric film sensor 203 is driven by the body 201 to separate from the surface of the crane main beam. In the non-working state, the position of the double-electrode piezoelectric film sensor 203 is higher than that of the magnet 207, so as to protect the double-electrode piezoelectric film sensor 203 and avoid unnecessary bumps.

[0091] In a further embodiment of the present application, the double-electrode piezoelectric film sensor 203 has an insulating film on the surface, and the body 201 is an insulating shell, which can protect the surface wave signal amplifier from being damaged by the voltage signal in the main beam steel plate.

[0092] In a further embodiment of the present application, the piezoelectric surface wave transducer 104 is a narrow-frequency transducer, and different frequency transducers can be selected according to the measurement requirements. The double-electrode piezoelectric film sensor 203 is a wide-frequency sensor, which can measure the fundamental wave and the second harmonic simultaneously. In the measurement process, when different frequency transducers are selected as the surface wave excitation source, the double-electrode piezoelectric film sensor 203 does not need to be replaced.

[0093] In a further embodiment of the present application, two surface wave receiving sensors are used simultaneously, so that the measurement result of the attenuation coefficient is not affected by the coupling effect of the transducer.

[0094] In a further embodiment of the present application, the two receiving sensors are connected in parallel and share an amplifier, which avoids the influence of different amplification powers on the measurement result of the surface wave amplitude.

[0095] ​​​​In a further embodiment of the present invention, the measuring device is fixed with a magnet, which is convenient to install and remove, reliable to fix, small in size, and can be adapted to the working environment of cranes. The equipment cost is far lower than that of the imported RAM-5000 SNAP nonlinear high-energy ultrasonic testing system.

[0096] In a further embodiment of the present invention, combined with Figures 6 to 8 The following example illustrates the measuring device and method for detecting the nonlinear coefficient and attenuation coefficient of the main beam surface wave according to the present invention:

[0097] Figure 6 The graph shows time-wavelength waveforms. The waveform on the left was measured by sensor 1 (2031), and the waveform on the right was measured by sensor 2 (2032). The distance between the two sensors is 40 mm, and the center frequency of the transducer in the experiment was 1 MHz. The surface wave velocity can be calculated based on the time difference between the two waveforms.

[0098]

[0099] The nonlinear coefficient is calculated using the following formula:

[0100] (1)

[0101] In the formula: For the nonlinear coefficients of surface waves, and These are the amplitudes of the fundamental wave and the second harmonic, respectively. For wave number, , The angular frequency of the surface wave. For the velocity of surface waves, For the distance of propagation.

[0102] It can be seen from Equation 1 that the angular frequency of the surface wave is... The frequency of the transducer Given that the surface wave velocity is a known quantity, to calculate the nonlinear coefficient, it is necessary to measure the surface wave velocity. Distance of transmission Amplitude of fundamental and second harmonic waves and Four unknowns.

[0103] The nonlinear coefficient is calculated using sensor #1: The spectrum of the waveform on the left is shown below. Figure 7 As shown, the vertical axis of the fundamental frequency (1MHz) can be used to obtain... From the ordinate of the second harmonic (2MHz), we can obtain Distance of transmission The distance between the piezoelectric surface wave transducer 104 and sensor 2031 was measured using a steel ruler. Therefore, only the wavenumber remains. unknown.

[0104]

[0105]

[0106] Among them, the velocity of surface waves It has been measured that, by Figure 7 It can be known that the frequency of the fundamental wave Since the frequency is 1 MHz, the wavenumber can be calculated. Therefore, all the unknowns in Formula 1 have been obtained, and the nonlinear coefficients can be calculated.

[0107] Calculation of attenuation coefficient

[0108] (2)

[0109] In the formula: The attenuation coefficient is... The distance between two measurement points. and These are the amplitudes of the surface wave measured at two points. Corresponding to this measuring device, The distance between sensor 2031 (No. 1) and sensor 2032 (No. 2) was measured using a steel ruler. and The amplitudes of the surface waves were measured by sensor 2031 and sensor 2032, respectively.

[0110] right Figure 6 The two sets of signals were subjected to spectral analysis, and the results are as follows: Figure 8 As shown, the black curve is the spectrum of the waveform on the left, and the red curve is... Figure 6 The spectrum of the waveform on the right side of the graph. In the graph, the vertical axis of the peak point of the black curve is... The ordinate of the peak point of the red curve is , The distance between sensor 2031 and sensor 2032 is a known quantity. Therefore, all the unknowns in formula (2) are known, and the attenuation coefficient of the surface wave can be calculated.

[0111] The above are merely preferred embodiments of the present invention and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should recognize that any equivalent substitutions and obvious changes made based on the description and illustrations of the present invention should be included within the protection scope of the present invention.

Claims

1. A measuring device for detecting nonlinear coefficient and attenuation coefficient of a girder surface wave, characterized by, The application relates to a surface wave excitation and receiving device for measuring the surface quality of a steel plate. The device comprises an excitation device (1) and a receiving device (2), both of which are connected to the surface of the steel plate (3) to be measured by magnetic attraction. The excitation device (1) comprises a piezoelectric surface wave transducer (104), and the receiving device (2) comprises two double-electrode piezoelectric film sensors (203); the piezoelectric surface wave transducer (104) and the double-electrode piezoelectric film sensors (203) are pressed against the surface of the steel plate (3) to be measured, and the center point of the piezoelectric surface wave transducer (104) and the center points of the two double-electrode piezoelectric film sensors (203) are located on the same straight line; the two double-electrode piezoelectric film sensors (203) are both encapsulated by an insulating layer. The double-electrode piezoelectric film sensor (203) close to the piezoelectric surface wave transducer (104) is a first sensor (2031), and the double-electrode piezoelectric film sensor (203) far from the piezoelectric surface wave transducer (104) is a second sensor (2032); the piezoelectric surface wave transducer (104) is used for exciting surface waves, and the first sensor (2031) and the second sensor (2032) are used for receiving surface waves.

2. The apparatus for measuring nonlinear coefficient and attenuation coefficient of a girder surface wave according to claim 1, wherein The excitation device (1) further comprises two magnets (101), a guide plate (102), two hole supporting rods (103), a supporting plate (109) and two long screws (110); the supporting plate (109) and the guide plate (102) are arranged in parallel; the supporting plate (109) is arranged above the guide plate (102); the supporting plate (109) is provided with two through holes; the guide plate (102) is provided with two mounting holes and a limiting groove matched with the piezoelectric surface wave transducer (104); each mounting hole is penetrated by a hole supporting rod (103); each magnet (101) is provided with a threaded hole; each long screw (110) is penetrated through the through hole of the supporting plate (109) and the hole supporting rod (103) from top to bottom and is screwed in the threaded hole of the magnet (101); the upper end of each hole supporting rod (103) abuts against the lower surface of the supporting plate (109); and the lower end of each hole supporting rod (103) abuts against the upper surface of the magnet (101).

3. The apparatus for measuring nonlinear coefficient and attenuation coefficient of a girder surface wave according to claim 2, wherein The excitation device (1) further comprises a cylindrical pressing block (105) and a screw rod (108); the supporting plate (109) is provided with a threaded hole between the two through holes; the middle part of the screw rod (108) is provided with a threaded section; the middle part of the screw rod (108) is assembled with the threaded hole of the supporting plate (109) by screwing; the cylindrical pressing block (105) is rotatably arranged at the lower end of the screw rod (108); the cylindrical pressing block (105) is arranged above the piezoelectric surface wave transducer (104); and the cylindrical pressing block (105) is lowered by rotating the screw rod (108) and is pressed against the upper surface of the steel plate (3) to press the piezoelectric surface wave transducer (104).

4. The apparatus for measuring nonlinear coefficient and attenuation coefficient of a girder surface wave according to claim 3, wherein The exciting device (1) further comprises a thrust bearing I (106) and a sealing cover I (107), the middle part of the upper surface of the cylindrical pressing block (105) is provided with a circular groove matched with the thrust bearing I (106), the lower end of the screw rod (108) is rotatably connected with the cylindrical pressing block (105) through the thrust bearing I (106); the sealing cover I (107) is provided with a sealing through hole matched with the middle part of the screw rod (108), the lower surface of the sealing cover I (107) is connected with the upper surface of the cylindrical pressing block (105); the sealing cover I (107) is used for sealing the thrust bearing I (106); the screw rod (108) can freely rotate around its own axis in the sealing through hole of the sealing cover I (107).

5. The apparatus for measuring nonlinear coefficient and attenuation coefficient of a girder surface wave according to claim 1, wherein The receiving device (2) further comprises a body (201), two magnets II (207), two long screw rods II (208), two compression springs (209), two cylindrical nuts (211) and a support plate II (212), the top middle part of the body (201) is provided with an upper notched groove, the bottom middle part of the body (201) is provided with a lower notched groove, the body (201) is provided with two guide holes (210) penetrating the upper notched groove and the lower notched groove; the support plate II (212) is arranged above the upper notched groove, the support plate II (212) is provided with a threaded hole and two through holes; each magnet II (207) is provided with a threaded hole; each long screw rod II (208) passes through a through hole of the support plate II (212) and a guide hole (210) of the body (201) from top to bottom and is screwed in the threaded hole of a magnet II (207); the two magnets II (207) are located in the lower notched groove; each long screw rod II (208) is provided with a cylindrical nut (211), the cylindrical nut (211) is located in the upper notched groove, and the cylindrical nut (211) is used for locking the long screw rod II (208) and the support plate II (212); the upper part of each guide hole (210) is provided with an upper variable diameter section with an increased outer diameter, and the lower part of each guide hole (210) is provided with a lower variable diameter section with an increased outer diameter; the inner diameter of the upper variable diameter section matches the outer diameter of the cylindrical nut (211), so that the cylindrical nut (211) can axially displace in the upper variable diameter section; each long screw rod II (208) is provided with a compression spring (209), the upper end of the compression spring (209) abuts against the variable diameter position of the lower variable diameter section of the guide hole (210) of the body (201), and the lower end of the compression spring (209) abuts against the magnet II (207).

6. The apparatus for measuring nonlinear coefficient and attenuation coefficient of a girder surface wave according to claim 5, wherein The receiving device (2) further comprises two triangular pressing blocks (202) and two pressing plates (204), the bottom plate of the body (201) is provided with two strip-shaped holes; one double-electrode piezoelectric film sensor (203) is arranged in each strip-shaped hole; the two pressing plates (204) are arranged in the body (201), the bottom surface of each pressing plate (204) is provided with a triangular pressing block (202), and each triangular pressing block (202) is used for pressing a double-electrode piezoelectric film sensor (203) in a strip-shaped hole of the body (201); and the two double-electrode piezoelectric film sensors (203) are arranged on the two sides of the lower notch groove respectively.

7. The apparatus for measuring nonlinear coefficient and attenuation coefficient of a girder surface wave according to claim 6, wherein The receiving device (2) further comprises two covers (205) and a signal line plug connector (206), the two covers (205) are arranged on the two sides of the upper notch groove and are arranged on the upper surface of the body (201); the signal line plug connector (206) is arranged on any one cover (205); and the two double-electrode piezoelectric film sensors (203) are connected with the signal line plug connector (206) through a circuit.

8. The apparatus for measuring nonlinear coefficient and attenuation coefficient of a girder surface wave according to claim 7, wherein The receiving device (2) further comprises a pressing screw (215), the middle part of the pressing screw (215) is provided with a threaded section, the middle part of the pressing screw (215) is screw-connected with the threaded hole of the second supporting plate (212), and the lower end of the pressing screw (215) is rotationally connected with the groove bottom of the upper notch groove; the body (201) is lowered and the two double-electrode piezoelectric film sensors (203) are pressed on the upper surface of the steel plate (3) by rotating the pressing screw (215). The receiving device (2) further comprises an angle disc (214) and a displacement scale plate (213), the upper end of the pressing screw (215) is connected with the angle disc (214), and the upper surface of the second supporting plate (212) is connected with the displacement scale plate (213); the displacement distance of the body (201) is read through the angle disc (214) and the displacement scale plate (213).

9. The apparatus for measuring nonlinear coefficient and attenuation coefficient of a girder surface wave according to claim 8, wherein The receiving device (2) further comprises a second sealing cover (216) and a second thrust bearing (217), the middle part of the groove bottom of the upper notch groove is provided with a circular groove matched with the second thrust bearing (217), the lower end of the pressing screw (215) is rotationally connected with the body (201) through the second thrust bearing (217), the second sealing cover (216) is provided with a sealing through hole matched with the middle part of the pressing screw (215), and the lower surface of the second sealing cover (216) is connected with the groove bottom of the upper notch groove; the second sealing cover (216) is used for sealing the second thrust bearing (217), and the pressing screw (215) can freely rotate around the axis in the sealing through hole of the second sealing cover (216).

10. A method of measuring nonlinear coefficient and attenuation coefficient of a surface wave of a girder, which is applied to the measuring apparatus of nonlinear coefficient and attenuation coefficient of a surface wave of a girder according to any one of claims 1 to 9, characterized by, The method comprises the following steps: S1: selecting a measurement position on the lower cover plate of the crane girder; S2: magnetically connecting the receiving device (2) with the lower cover plate, and pressing the two double-electrode piezoelectric film sensors (203) on the measured surface of the steel plate (3) by adjusting the receiving device (2); S3: coating a coupling agent on the piezoelectric surface wave transducer (104); S4: adjust the position of the piezoelectric surface wave transducer (104) so that the center point of the piezoelectric surface wave transducer (104) and the center points of the two double-electrode piezoelectric film sensors (203) are located on the same straight line; S5: magnetically connect the excitation device (1) with the lower cover plate, and press the piezoelectric surface wave transducer (104) on the surface to be measured of the steel plate (3) by adjusting the excitation device (1); S6: The double-electrode piezoelectric film sensor (203) close to the piezoelectric surface wave transducer (104) is No. 1 sensor (2031), and the double-electrode piezoelectric film sensor (203) far from the piezoelectric surface wave transducer (104) is No. 2 sensor (2032); use a steel ruler to measure the distance between the piezoelectric surface wave transducer (104) and No. 1 sensor (2031) and record; use a steel ruler to measure the distance between No. 1 sensor (2031) and No. 2 sensor (2032) and record; S7: the piezoelectric surface wave transducer (104) excites a surface wave, the first sensor (2031) and the second sensor (2032) receive the surface wave; a time waveform diagram of the surface wave signals measured by the first sensor (2031) and the second sensor (2032) is obtained; and a time difference between time instants corresponding to two adjacent groups of signal wave crests is calculated according to the time waveform diagram of the surface wave signals measured by the first sensor (2031) and the second sensor (2032) ; Calculating the speed of a surface wave : In the formula: is the velocity of the surface wave, is the distance between the first sensor (2031) and the second sensor (2032); Computing the wave number wherein: wherein: is the circular frequency of the surface wave, is the velocity of the surface wave; And the surface wave's circular frequency , is the frequency of the piezoelectric surface wave transducer (104); After combining the equations, the wave number is calculated : S8: obtaining the amplitude of the fundamental wave and the amplitude of the second harmonic wave after Fourier spectrum analysis of the surface wave signal measured by the first sensor (2031) and the second harmonic wave ; Substitute the definition formula of the nonlinear coefficient of the surface wave: wherein: is the nonlinear coefficient of the surface wave, and are the amplitudes of the fundamental and second harmonic waves, respectively, is the wave number, is the distance between the piezoelectric surface wave transducer (104) and the first sensor (2031); Computing a nonlinear coefficient of a surface wave ; S9: obtaining the fundamental frequency domain amplitude from the surface wave signal measured by the second sensor (2032) after Fourier spectrum analysis ; S10: Calculate attenuation coefficient ; In the formula: is the attenuation coefficient, is the distance between the first sensor (2031) and the second sensor (2032), and are the amplitudes of the surface wave measured by the first sensor (2031) and the second sensor (2032), respectively. Here To obtain the amplitude of the fundamental wave in step S8 .

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