CN113009554B - Method and device for detecting bolt group connection loosening condition based on SH0 guided wave - Google Patents
Method and device for detecting bolt group connection loosening condition based on SH0 guided wave Download PDFInfo
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- CN113009554B CN113009554B CN202110259693.6A CN202110259693A CN113009554B CN 113009554 B CN113009554 B CN 113009554B CN 202110259693 A CN202110259693 A CN 202110259693A CN 113009554 B CN113009554 B CN 113009554B
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Abstract
The invention discloses an SH guided wave detection method and device for bolt looseness detection. Processing to obtain the guided wave frequency dispersion characteristic of the flat plate, coupling three transducers on the surface of the flat plate connected with the bolt group, exciting two guided waves by one transducer, receiving guided wave signals by the two transducers, calculating the distance between emission and reception, obtaining guided wave propagation time according to the distance and the wave velocity, and setting an energy calculation time interval by combining with a time interval; and calculating an energy characteristic value in a calculation time interval, calculating a quantitative value of the looseness of the bolt group, comparing the quantitative value with the quantitative value under the connection of the initial bolt group to obtain a percentage parameter, and detecting the looseness according to the percentage parameter. The invention realizes the rapid detection and long-time monitoring of the connecting piece, is suitable for the detection of the connection condition of the bolt groups with different bolt numbers, has more simple transducer, is reasonable in design, can realize the long-time bolt loosening monitoring, and is very effective for the monitoring of the flat connecting piece which has a surface coating and works for a long time.
Description
Technical Field
The invention relates to a nondestructive testing method and a nondestructive testing device for bolt connection loosening conditions, in particular to a method and a device for testing bolt group bolt loosening conditions based on SH guided waves, and belongs to the technical field of nondestructive testing.
Background
The bolt connection is a common mechanical connection mode, and is widely applied to the assembly of bridges, railways and mechanical equipment due to the simple connection mode, high connection strength and reliable connection. However, the bolt often encounters vibration impact during working, and the bolt connection is usually in a tensile state during working, so that the bolt can loosen after working for a period of time. If the bolt is not loosened and is not timely solved and screwed, serious accidents such as bolt fracture, bolt group connection failure and the like are caused, and great personnel and property losses are brought. For example, bolt loosening is a significant cause of threat to the safe operation of railways and bridges. In order to avoid accidents caused by bolt loosening in connection of mechanical structures such as bridges and the like, a method for effectively monitoring connection of in-service bolt groups in a nondestructive mode must be sought.
At present, a plurality of nondestructive detection technologies for bolt looseness exist, and conventional detection comprises the following steps: vibration detection, impedance, ultrasound, acoustic modulation, and the like. However, the conventional monitoring technology has a small detection range and low detection efficiency, and meanwhile, long-time and long-distance off-line monitoring cannot be realized. For large-scale equipment such as bridges and rails, a vibration detection method has certain detection limitation on the large-scale components, and vibration in the detection process easily causes additional bolt loosening and structural damage. The impedance method is a method in which the impedance value of a bolt changes when the bolt connection is loosened and the bolt loosening is detected by measuring the impedance value, but this method requires mounting an impedance piece on each bolt, and is inefficient and costly. The impedance method and the ultrasonic method can not detect the connection condition of the whole bolt group, so that when the bolt with limited installation space is encountered, the method can not detect the connection condition of the bolt; for the sound modulation technology, the operation mode is complex, and the detection effect is influenced by many factors, so the technology is still in the laboratory stage at present. Therefore, the above nondestructive testing technologies cannot realize online real-time monitoring of the bolt group mechanism in work.
The ultrasonic guided wave technology is also widely applied to the field of bolt looseness detection, and has the advantages of wide detection range, high detection efficiency, real-time monitoring and the like. The ultrasonic guided waves propagating in the flat panel can be divided into Lamb waves and SH guided waves, and currently the most commonly used are A0, S0 (Lamb waves) and SH0 (SH waves). The main object for bolt looseness detection research at present is Lamb waves, but Lamb waves have large attenuation in the propagation process because the vibration direction of mass points is vertical to a flat plate plane in the propagation process, and especially for some bridge members with multiple layers of paint, the Lamb detection distance is very limited. Meanwhile, for the outdoor work piece to be detected, when the weather such as rain occurs, the surface of the member will also have great influence on detection of Lamb, and false alarm or missing report is likely to occur. And Lamb guided waves are usually generated and received by the excitation of a piezoelectric transducer, the piezoelectric transducer has a large volume, certain influence can be caused on the normal operation of a measured piece, the detection cost is high due to the high price of the piezoelectric transducer, and the energy conversion efficiency of the piezoelectric transducer is greatly influenced by the temperature. Therefore, the bolt looseness detection technology including Lamb guided wave detection technology still faces a lot of difficulties at present. SH guided waves are the horizontal shear type of ultrasonic guided waves, and the mode of vibration of particles during propagation is parallel to the plane of the plate. Therefore, the device is less susceptible to the influence of mediums such as paint, accumulated water and the like on the surface of the measured piece in the transmission process. The current SH guided wave can be excited and received by using a magnetostrictive transducer, and the magnetostrictive transducer can realize the excitation and the reception of the SH guided wave according to the magnetostrictive and inverse magnetostrictive principles. The magnetostrictive transducer consists of a pre-magnetized iron-cobalt strip and a coil, which are coupled together by a coupling agent. When the magnetostrictive transducer is arranged on the tested piece, the magnetostrictive transducer is arranged on the surface of the tested piece by using the coupling agent, and the excitation and the reception of the SH guided waves can be realized without scraping off coatings such as paint on the surface.
In summary, a method for detecting and monitoring bolt loosening conditions of a bolt group based on SH guided waves excited by a magnetostrictive transducer is absent in the prior art.
Disclosure of Invention
In order to solve the problems in the background art and solve the defects in the detection of the bolt loosening condition of the existing bolt group, the invention provides an SH guided wave detection method for diagnosing the bolt connection condition of the bolt group with a coating, according to the change of the actual contact area at the contact position caused by the loosening of the bolt, the propagation of SH0 guided wave at the contact position is influenced, and based on the received SH guided wave signal, a standard value for bolt tightening is determined by using a reference-free method, so that the quantitative detection of the bolt group connection condition can be realized.
The method can realize the rapid detection of the whole loosening condition of the bolt group, has high detection efficiency, and can monitor the loosening condition of the bolt group for a long time without stopping production under the condition of lower cost.
The invention is realized by the following technical scheme:
1. a monitoring method for bolt group connection loosening conditions based on SH guided waves comprises the following steps:
1) Calculating the SH0 guided wave frequency dispersion characteristic of the flat plate by a semi-analytic finite element method according to the geometrical parameters and the material mechanical parameters of the flat plate structure connected by the bolt group; the SH0 guided wave dispersion characteristic includes the wave velocity of the SH0 guided wave, and the wave velocity includes the group velocity and the phase velocity. SH0 guided waves are guided in the 0 th order mode.
The two flat plates are connected through a bolt group, and are made of the same material.
2) An excitation transducer, a reference receiving transducer and a transmission receiving transducer are coupled on the surfaces of two flat plates connected by a bolt group, the excitation transducer excites two SH0 guided waves which are simultaneously transmitted along two directions respectively, the two SH0 guided waves are transmitted towards the reference receiving transducer and the transmission receiving transducer respectively, the reference receiving transducer and the transmission receiving transducer receive two guided wave signals, and the distance d between the reference receiving transducer and the excitation transducer is calculated 1 The distance between the transmitting and receiving transducer and the exciting transducer is d 2 ；
Thus, three identical magnetostrictive transducers are coupled to the surfaces of two flat plates connected by a bolt group by using a coupling agent, one of the magnetostrictive transducers is used as an excitation transducer for exciting an SH0 guided wave propagating to both sides, and the remaining two magnetostrictive transducers are used as receiving transducers for receiving a secondary excitation waveThe excitation transducer propagates SH0 guided waves. The distances of the two receiving transducers from the excitation transducer are respectively denoted as d 1 And d 2 . When SH0 guided wave is propagated on the flat board, the flat board itself can also have certain attenuation to the energy of guided wave, in order to reduce the influence of the difference of propagation path to the attenuation of guided wave signal, and then produce the influence to the detection effect, when arranging the transducer, d 1 And d 2 The difference between should be as small as possible.
Exciting an excitation transducer arranged on the flat plate to excite an SH0 guided wave propagating along a plane parallel to the flat plate, and propagating by an SH0 guided wave propagation distance d in which the propagation direction is a positive direction 1 And then received by one of the receiving transducers, which is referred to as the reference receiving transducer. SH0 guided wave propagating along the negative propagation direction at a propagation distance d 2 And then received by another receiving transducer, which is denoted as the propagating receiving transducer.
3) According to the obtained distance d 1 And a distance d 2 And the group velocity of the SH0 guided wave velocity in the SH0 guided wave frequency dispersion characteristics calculated in the step 1) is obtained, and the time t required by the two SH0 guided waves to propagate to the respective receiving transducers is obtained 1 And t 2 Then, the time interval delta t of a complete waveform signal is determined according to the central frequency and the periodicity of the SH0 guided wave excited by the excitation transducer, and an energy calculation time interval [ t ] is further set for the received SH0 signal 1 ，t 1 +Δt]And [ t 2 ，t 2 +Δt]；
4) The SH0 guided wave signals received by the reference receiving transducer and the propagation receiving transducer are respectively in a time interval of [ t 1 ，t 1 +Δt]And [ t 2 ，t 2 +Δt]The energy characteristic values calculated by the reference receiving transducer and the propagation receiving transducer are respectively E TRF And E TTR The method is used as a quantitative calculation basis for subsequently calculating the loosening condition of the bolt group;
5) The energy characteristic value E obtained in the step 4) is processed TRF And E TTR And calculating to obtain a quantitative value I under the condition that the bolt group is loosened at the moment BL ；
6) Processing the quantitative value I obtained in the step 5) in real time BL Quantitative value I in the case of initial bolt group connection BL0 And comparing to obtain the percentage parameter of the bolt group loosening under the real-time condition, and further detecting the connection loosening condition of the bolt group according to the percentage parameter.
Quantitative value I in the case of initial bolt group connection BL0 Obtained by the same way as in the steps 1) to 5) described above, just after the bolt group has been installed.
In the step 2), the reference receiving transducer and the excitation transducer are arranged on one of the flat plates connected by the bolt group in a coupling mode, and the propagation receiving transducer is arranged on the other flat plate connected by the bolt group.
And the excitation transducer is arranged midway, but not strictly bisecting, between the reference receiving transducer and the propagation receiving transducer in terms of the position of the transducers.
In the step 2), the position of the excitation transducer is arranged closer to the connection area of the bolt group than the reference receiving transducer and the propagation receiving transducer, and the reference receiving transducer and the propagation receiving transducer are respectively away from the excitation transducer by a distance d 1 And d 2 The difference between the two signals is set to be as small as possible, and the difference is specifically set to be zero optimal so as to reduce the influence of the attenuation of the flat plate to the SH0 guided wave on the detection result.
In the step 3), the reference receiving transducer receives the SH0 guided wave transmitted by the same flat plate in the bolt group contact area, and the transmission receiving transducer receives the SH0 guided wave transmitted by the bolt group contact area and crossing the two flat plates. The guided wave propagating across the two plates is a portion of the guided wave.
The energy characteristic values received by the reference receiving transducer and the propagation receiving transducer in the step 4) are calculated by adopting the following formulas:
wherein i =1, 2; i =1 represents the receiving transduction now referred to as referenceI =2 represents the waveform signal of the SH0 guided wave received by the i-th receiving transducer at this time for the propagation receiving transducer 4, v (x) represents the waveform signal of the SH0 guided wave received by the i-th receiving transducer at this time, f s Representing the sampling frequency of the guided wave detector, E 1 Is marked as E TRF ，E 2 Is marked as E TTR ；
Considering that when an SH0 guided wave excited in one of the plates propagates through the region of the bolt group connection position, the contact between the two plates caused by the bolt tightening force causes a part of energy in the propagating SH0 guided wave to penetrate into the other plate and continue to propagate forwards until being received by the propagation receiving transducer, but the energy of the penetrated guided wave caused by the contact is far less than that of the propagating SH0 guided wave generated by the original excitation at the moment. And the energies of the guided waves propagating on the plate in two directions are equal, so that the guided wave energy E received by the reference receiving transducer is used TRF Instead of guided wave energy in the areas not passing through the bolt set contact.
In the step 5), the characteristic value E is used TRF And E TTR On the basis, a quantitative value I for detecting the loosening condition of the bolt group BL The following formula is used for the calculation of (c):
wherein, E TRF Representing a characteristic value of energy calculated with reference to the receiving transducer, E TTR Representing the energy characteristic value calculated by the transmitting and receiving transducer.
The step 6) is to process the quantitative value I obtained by real-time processing BL And a quantitative value I in the case of an initial bolt group connection BL0 And (4) dividing to obtain a percentage parameter, comparing the percentage parameter with a preset percentage threshold value, and alarming the loosening of the bolt group.
The percentage threshold is based on the initial quantitative value I in the case of the initial connection BL And determining the safety factor and connection reliability of the component. Calculated quantitative value I BL The device can also be used for monitoring the loosening condition of the bolt group, namely every other bolt groupPerforming detection once in a period of time, and detecting the obtained quantitative value I BL Stored in the computer.
The exciting transducer and the reference receiving transducer arranged in the step 2) and the propagation receiving transducer use the same magnetostrictive transducer. The present invention considers that when the object to be inspected is two flat plates connected by a bolt group, in terms of the positions of three transducers, an excitation transducer and a reference receiving transducer are mounted on the surface of one of the flat plates, and a propagation receiving transducer is mounted on the surface of the other flat plate, while the excitation transducer is mounted at an intermediate position between the reference receiving transducer and the propagation receiving transducer, not necessarily at a position exactly bisected. When a plurality of flat plate mechanisms are connected simultaneously by using the bolt group connecting piece, the looseness detection of the bolt group can be realized by selecting any two flat plate members according to the same installation mode.
The excitation transducer in the step 2) is installed to be as close to the bolt group as possible, and the distances from the reference receiving transducer to the excitation transducer and from the propagation receiving transducer to the reference receiving transducer are the same as possible.
2. A detection apparatus for bolt group connects not hard up condition based on SH0 guided wave:
the device comprises an excitation transducer, a reference receiving transducer, a propagation receiving transducer and a guided wave detector, wherein the two flat plates are connected through a bolt group, the excitation transducer, the reference receiving transducer and the propagation receiving transducer are arranged on the two flat plates, the excitation transducer is arranged at a position close to the bolt group, the reference receiving transducer and the propagation receiving transducer are positioned at two sides of the excitation transducer, the reference receiving transducer and the propagation receiving transducer are respectively arranged on the two flat plates, and the excitation transducer and the reference receiving transducer are arranged on the same flat plate; the excitation transducer, the reference receiving transducer and the propagation receiving transducer are all connected to the guided wave detector.
The guided wave detector comprises a power amplification module, a signal generator, a time delay module, a pre-amplification module, a signal acquisition module and a filter unit; the computer is connected to the excitation transducer sequentially through the signal generator and the power amplification module, the reference receiving transducer and the transmission receiving transducer are connected to the signal synchronization module sequentially through the pre-amplification module, the signal acquisition module and the filter unit respectively, and are connected to the computer through the signal synchronization module.
The excitation transducer, the reference receiving transducer and the transmission receiving transducer are all SH0 guided-wave magnetostrictive transducers.
The computer synchronously receives the signals of the two channels received by the reference receiving transducer and the propagation receiving transducer through the signal synchronization module, and simultaneously makes the channels of the reference receiving transducer and the propagation receiving transducer independent and free of coupling.
The coupling agent is epoxy resin or double-sided adhesive tape, and meanwhile, dry coupling devices such as an air bag clamp and the like can also be used.
The invention has the following main beneficial effects:
according to the invention, by using the SH0 guided wave excited by the magnetostrictive transducer, certain influence is generated on the transmission energy percentage of the guided wave according to the change of the contact area caused by bolt loosening. Therefore, the connection condition of the bolt group at the moment can be quantitatively detected and monitored by researching the condition of the guided wave signals respectively received by the reference receiving transducer and the propagation receiving transducer. The SH guided wave is used for overcoming the influence of a paint spraying coating on the surface of the bolt group and severe weather, and the reliability and the practicability of detection are improved. Meanwhile, the magnetostrictive transducer has small volume and low cost, and can be effectively used for monitoring the loosening condition of the bolt group for a long time.
Drawings
FIG. 1 is a diagram of a detection apparatus for the method of the present invention.
Fig. 2 is a graph of SH0 guided wave signals received by the reference receiving transducer and the propagating receiving transducer.
FIG. 3 is a quantitative value I calculated when the tightening condition of the bolt group is changed BL A trend graph of the change.
In the figure: 1. plate, 2, propagation receiving transducer, 3, bolt group, 4, excitation transducer, 5, reference receiving transducer.
Detailed Description
The invention is further illustrated by the following figures and examples.
As shown in fig. 1, the device comprises an excitation transducer 4, a reference receiving transducer 5, a propagation receiving transducer 2 and a guided wave detector, wherein the two flat plates 1 are connected through a bolt group 3, the excitation transducer 4, the reference receiving transducer 5 and the propagation receiving transducer 2 are arranged on the two flat plates 1, the excitation transducer 4 is arranged close to the bolt group 3, the reference receiving transducer 5 and the propagation receiving transducer 2 are positioned at two sides of the excitation transducer 4, the reference receiving transducer 5 and the propagation receiving transducer 2 are respectively arranged on the two flat plates 1, and the excitation transducer 4 and the reference receiving transducer 5 are arranged on the same flat plate 1; the excitation transducer 4, the reference receiving transducer 5 and the propagation receiving transducer 2 are all connected to a guided wave detector.
As shown in fig. 1, the guided wave detector includes a power amplification module, a signal generator, a delay module, a pre-amplification module, a signal acquisition module, and a filter unit; the computer is connected to the excitation transducer 4 through the signal generator and the power amplification module in sequence, and the excitation transducer 4 couples the elastic strain of the ultrasonic guided wave into the flat plate 1 through the coupling agent; the reference receiving transducer 5 and the transmission receiving transducer 2 are respectively connected to the signal synchronization module after passing through the pre-amplification module, the signal acquisition module and the filter unit of each path in sequence and are connected to the computer through the signal synchronization module; the computer controls the acquisition synchronization among a plurality of data acquisition channels through the data synchronization module. Finally, the acquired two-channel signals need to be processed and filtered through a band-pass filter, and the frequency doubling phenomenon caused by contact is eliminated.
The excitation transducer 4, the reference receiving transducer 5 and the propagation receiving transducer 2 are all magnetostrictive transducers of SH0 guided waves and are used for being coupled on the surface of the flat plate 1 for exciting and receiving the SH0 guided waves.
The computer receives the signals of the two channels received by the reference receiving transducer 5 and the propagation receiving transducer 2 synchronously through the signal synchronization module, and simultaneously, the channels of the reference receiving transducer 5 and the propagation receiving transducer 2 are independent and are not coupled.
The pre-amplification module is a broadband weak signal amplifier, the maximum gain of the pre-amplification module reaches 100dB, and the requirement of ultrasonic guided wave monitoring on the gain of the pre-amplification module can be met.
The data acquisition module is a multi-channel data acquisition module, and can adopt an ADC unit integrated in a DSP chip to realize analog-to-digital conversion. In addition, the acquisition time sequence of the data acquisition module is controlled by the synchronous receiving module. In order to ensure the integrity of the ultrasonic guided wave signal, the sampling frequency is 10 times of the frequency of the sinusoidal pulse signal.
The synchronous receiving module is realized by software and is used for controlling two channels of the data acquisition module to acquire the received signals at the same time.
The filtering module is a band-pass filter, and in consideration of the problem that the contact problem of the bolt 3 connection causes the generation of frequency doubling, the band-pass filter taking the excitation frequency as the center frequency is used for filtering the received guided wave signal.
The magnetostrictive transducers 2, 4 and 5 couple the guided elastic strain to the surface of the flat plate 1 through a coupling agent or through a dry coupling device, preferably an epoxy adhesive or a double-sided adhesive, and preferably the dry coupling device can be an air bag clamp.
The two channels in the SH guided wave receiving unit are mutually independent, and the preprocessing of signals is finished through two identical amplifying module devices and two identical band-pass filter modules respectively, namely, the two received signals directly have no interference with each other, the processed waveforms are simultaneously displayed on an oscilloscope, the two waveform signals at the moment are processed according to the method for calculating the energy value provided by the invention, and the obtained quantitative value I is obtained BL The display is on the detector, so that the operator can conveniently make judgment.
As shown in FIG. 1, the implementation method of the invention comprises the following steps:
1) According to the geometric parameters (wall thickness) and the material mechanical property parameters such as Young modulus, poisson's ratio, density and the like of the flat plate 1 connected with the bolt group 3 to be measured, the frequency dispersion characteristic of the SH0 modal guided wave for detection is calculated by a semi-analytic finite element method.
2) 3 identical magnetostrictive transducers are pasted on the surfaces of two flat plates 1 connected by a bolt group 3 by using a coupling agent and respectively used as an excitation transducer 4, a reference receiving transducer 5 and a propagation receiving transducer 2.
Wherein, the exciting transducer 4 is firstly coupled on the surface of the right plate of the plate 1 connected by the bolt group 3 by using coupling agent, and the coupling position is as close as possible to the bolt group 3 under the condition of permission.
Then, the reference receiving transducer 5 is coupled on the surface of the right plate 1 opposite to the excitation transducer 4 by using the coupling agent, but the coupling position is far away from the bolt group 3, and the distance d between the reference receiving transducer 5 and the excitation transducer 4 is recorded 1 。
Then, the transmitting and receiving transducer 2 is coupled on the surface of the left panel 1 of the other panel connected by the bolt group 3 by using a coupling agent, and the distance d between the transmitting and receiving transducer 2 and the exciting transducer 4 is recorded 2 The installation of the exciter transducer 4 and the receiving transducers 2 and 5 is completed so far, and at this time, the propagation receiving transducer 2 and the exciter transducer 4 are not on the same plate 1, the reference receiving transducer 5 and the exciter transducer 4 are coupled on the same plate 1, and the exciter transducer 4 is located in the middle of the propagation receiving transducer 2 and the reference receiving transducer 5. When the SH0 guided wave propagates on the flat plate 1, the flat plate 1 can attenuate the energy of the guided wave to a certain degree, and when the transducers 2, 4 and 5 are arranged, d 1 And d 2 The difference between the two should be as small as possible to reduce the influence of the difference of the propagation paths on the attenuation of the guided wave signal, and thus on the detection effect.
3) The wave velocity of the SH0 mode guided wave obtained according to the frequency dispersion characteristic in the step 1 and the distance d between the reference receiving transducer 5 and the excitation transducer 4 measured in the step 2 1 And the distance d of the transmitting receiving transducer 2 from the exciting transducer 4 2 The time at which SH0 reaches the two receiving transducers 2 and 5 is calculated and recorded as t 1 And t 2 。
As shown in FIG. 2, the time interval Δ t required to receive a complete waveform is then calculated based on the center frequency and the number of cycles of the excited SH0 guided wave, and thus the parameters for the waveformThe computation interval of the SH0 guided wave waveform signal received by the test receiving transducer 5 is [ t ] 1 ，t 1 +Δt]And the calculation interval for the SH0 guided wave waveform signal received by the transmission and reception transducer 2 is [ t 2 ，t 2 +Δt]。
4) When the SH0 guided wave is excited by the excitation transducer 4, the SH0 guided wave will propagate forward along both positive and negative directions of the propagation direction. SH0 guided wave propagating in the forward direction at t 1 The time of day is received by the reference receiving transducer 5; SH0 guided wave propagating in the negative direction at t 2 The time instants are received by the transmitting receiving transducer 2. Then, calculating the energy characteristic value E of the SH0 guided wave signal received by the reference receiving transducer according to the time calculation interval in the step 3 TRF And transmitting the energy characteristic value E of the SH0 guided wave signal received by the receiving transducer TTR As a criterion for the calculation of quantitative values for subsequent detections. The concrete formula is as follows:
5) According to the calculated energy characteristic value E TRF And E TTR Calculating the energy percentage of SH0 guided wave transmission under the condition that the bolt group 3 is connected, namely the quantitative value IB under the condition that the bolt group 3 is connected at the moment L . The concrete formula is as follows:
as shown in FIG. 3, it is demonstrated that the quantitative values I calculated under different conditions when the total pretension of the bolt group 3 is changed BL The obtained change curve graph accords with the Hertz contact theory. And at this time the quantitative value I BL Can approximately represent the percentage change in the total pretension of the bolt set 3 at that time. The quantitative value I obtained at this time BL Can be used to evaluate the loosening of the bolt set 3 at this time.
Under the conditions of detection and monitoring, the quantitative value I can be determined according to the specific safety factor and connection requirement grade of the structure BL Is manually calibrated, for example for a bridge construction, it is assumed that a connection failure occurs when the total tightening torque of the connection of the bolt set 3 is lost by 10%. Then, during the detection and monitoring process, the measured quantitative value I BL Change to the initial quantitative value I BL And when the loss is 90%, 10% is lost, so that the maintenance and troubleshooting can be carried out, and the safe operation of the bridge can be guaranteed.
The specific example conditions are as follows:
1) Two flat structures 1 connected by a bolt group 3 are selected, and the bolt group 3 consists of four identical pairs of bolts. The thus-joined flat plate 1 had a length of 1.5m, a width of 0.3m, a thickness of 0.008m, a Young's modulus of 210GPa, a Poisson's ratio of 0.28, and a density of 7800kg/m 3 . The wave velocity of the SH0 guided wave under the frequency of 80KHz is calculated and obtained by a semi-analytic finite element method and is 3140m/s.
2) According to the arrangement and installation positions of the excitation transducer 4, the reference receiving transducer 5 and the propagation receiving transducer 2, the distances d between the reference receiving transducer 5 and the propagation receiving transducer 2 and the excitation transducer 4 are obtained 1 And d 2 And then according to the wave velocity calculated in the step 1, obtaining the time d of the SH0 guided wave reaching the reference receiving transducer 5 and the transmitting receiving transducer 2 1 And d 2 . Meanwhile, according to the fact that the excited guided wave is a 3-cycle 80KHz guided wave, the energy calculation time interval delta t is obtained through calculation. Therefore, the calculation interval for determining the SH0 guided-wave waveform signal received by the reference receiving transducer 5 is [ t ] 1 ，t 1 +Δt]And the calculation interval for the SH0 guided wave waveform signal received by the transmission and reception transducer 2 is [ t 2 ，t 2 +Δt]。
3) Calculating the reference energy value E of the reference receiving transducer 5 and the propagation receiving transducer 2 at the moment based on the calculation interval calculated in the step 2 TRF And propagation energy value E TTR 。
4) Based on the reference energy value E calculated in the step 3 TRF And propagation energy value E TTR Finally obtaining a quantitative value I detected and obtained under the connection state of the bolt group 3 at the moment BL 。
5) Detecting the obtained quantitative value I BL And a quantitative value I of an initial state of complete tightening of the bolt group 3 BL By comparison, the percentage of the bolt group 3 that is substantially loose at this time can be determined. And at the moment, the bolt can be reminded to overhaul and tighten according to the set bolt loss threshold.
Quantitative value I obtained by detection BL Not only can be used for detecting the looseness of the bolt group 3, but also can be used for measuring quantitative values I measured at different moments BL And the monitoring device is stored in a computer and used for monitoring the connection condition of the bolt group 3.
In the implementation, the loosening condition of the bolt group is detected at intervals, and the quantitative value I obtained by each detection BL The storage is in the detector, can be used for the not hard up long-time monitoring of the condition of bolt group, and the not hard up emergence of discovery bolted connection that can be timely and quick. When in the detection and monitoring process, the measured quantitative value I BL When the percentage of the bridge is over the calibrated threshold value, an alarm is sent to remind the staff to carry out maintenance and troubleshooting treatment, so that the safe operation of the bridge is guaranteed.
The invention realizes the rapid detection and long-time monitoring of the connecting piece, is suitable for the detection of the connection condition of the bolt groups with different bolt numbers, has more simple transducer, is reasonable in design, can realize the long-time bolt loosening monitoring, and is very effective for the monitoring of the flat connecting piece which has a surface coating and works for a long time.
The foregoing detailed description is intended to illustrate rather than to limit the invention, and all changes and modifications that come within the spirit of the invention and the scope of the appended claims are intended to be embraced therein.
Claims (10)
1. A method for detecting bolt group connection loosening condition based on SH0 guided waves comprises the following steps:
1) According to the structural geometric parameters and the material mechanics parameters of the flat plate (1) connected by the bolt group (3), calculating by a semi-analytic finite element method to obtain the SH0 guided wave frequency dispersion characteristic of the flat plate (1);
2) The excitation transducer (4), the reference receiving transducer (5) and the propagation receiving transducer (2) are coupled on the surfaces of two flat plates (1) connected by the bolt group (3), the excitation transducer (4) excites two SH0 guided waves which are simultaneously propagated along two directions respectively, the two SH0 guided waves are propagated towards the reference receiving transducer (5) and the propagation receiving transducer (2) respectively, the reference receiving transducer (5) and the propagation receiving transducer (2) receive two guided wave signals, and the distance between the reference receiving transducer (5) and the excitation transducer (4) is calculated to be d 1 The distance between the transmitting and receiving transducer (2) and the exciting transducer (4) is d 2 ；
3) According to the obtained distance d 1 And a distance d 2 And the group velocity of the SH0 guided wave velocity in the SH0 guided wave frequency dispersion characteristics calculated in the step 1) is obtained, and the time t required by the two SH0 guided waves to propagate to the respective receiving transducers is obtained 1 And t 2 Then, the time interval delta t of a complete waveform signal is determined according to the central frequency and the periodicity of the SH0 guided wave excited by the excitation transducer (4), and then the energy calculation time interval [ t ] is set for the received SH0 signal 1 ，t 1 +Δt]And [ t 2 ，t 2 +Δt]；
4) SH0 guided wave signals received by the reference receiving transducer (5) and the propagation receiving transducer (2) are respectively in a time interval of [ t 1 ，t 1 +Δt]And [ t 2 ，t 2 +Δt]Calculating energy characteristic values in the region, wherein the energy characteristic values calculated by the reference receiving transducer (5) and the propagation receiving transducer (2) are respectively E TRF And E TTR ；
5) The energy characteristic value E obtained in the step 4) is used TRF And E TTR And calculating to obtain a quantitative value I under the condition that the bolt group (3) is loosened at the moment VL ；
6) Processing the quantitative value I obtained in the step 5) in real time BL Quantitative value I in the case of connection to the initial set of bolts (3) BL0 And comparing to obtain the percentage parameter of the loosening of the bolt group (3) under the real-time condition, and further detecting the connection loosening condition of the bolt group (3) according to the percentage parameter.
2. The method for detecting the loose condition of the connection of the bolt group based on the SH0 guided waves according to claim 1, characterized in that: in the step 2), the reference receiving transducer (5) and the excitation transducer (4) are coupled and arranged on one of the flat plates connected by the bolt group (3), and the propagation receiving transducer (2) is arranged on the other flat plate (1) connected by the bolt group (3).
3. The method for detecting the bolt group connection loosening condition based on the SH0 guided wave according to claim 1, is characterized in that: in the step 2), the excitation transducer (4) is arranged at a position closer to the connection region of the bolt group (3).
4. The method for detecting the bolt group connection loosening condition based on the SH0 guided wave according to claim 1, is characterized in that: in the step 3), the reference receiving transducer (5) receives the SH0 guided wave transmitted by the same flat plate (1) in the contact area of the bolt group (3), and the transmission receiving transducer (2) receives the SH0 guided wave transmitted by the two flat plates (1) in the contact area of the bolt group (3).
5. The method for detecting the loose condition of the connection of the bolt group based on the SH0 guided waves according to claim 1, characterized in that: the energy characteristic values received by the reference receiving transducer (5) and the propagation receiving transducer (2) in the step 4) are calculated by adopting the following formulas:
wherein i =1, 2; i =1 represents the reference receiving transducer (5) at this time, i =2 represents the propagation receiving transducer (2) at this time, V (x) represents the group velocity of the SH0 guided wave received by the i-th receiving transducer at this time, f s Representing the sampling frequency of the guided wave detector, E 1 Is marked as E TRF ，E 2 Is marked as E TTR ；
In the step 5), the looseness condition of the bolt group (3) is detectedMagnitude I BL The following formula is used for the calculation of (c):
wherein, W TRF Representing an energy characteristic value, E, calculated with reference to the receiving transducer (5) TTR Representing the energy characteristic value calculated by the transmitting and receiving transducer (2).
6. The method for detecting the bolt group connection loosening condition based on the SH0 guided wave according to claim 1, is characterized in that: the step 6) is to specifically process the quantitative value I obtained by real-time processing BL Quantitative value I in the case of connection to the initial set of bolts (3) BL0 And (4) dividing to obtain a percentage parameter, comparing the percentage parameter with a preset percentage threshold value, and alarming the loosening of the bolt group.
7. The detection device for detecting the bolt group connection looseness based on the SH0 guided wave, which is applied to the detection method of claim 1, is characterized in that: the device comprises an excitation transducer (4), a reference receiving transducer (5), a propagation receiving transducer (2) and a guided wave detector, wherein the two flat plates (1) are connected through a bolt group (3), the excitation transducer (4), the reference receiving transducer (5) and the propagation receiving transducer (2) are arranged on the two flat plates (1), the excitation transducer (4) is arranged at a position close to the bolt group (3), the reference receiving transducer (5) and the propagation receiving transducer (2) are positioned at two sides of the excitation transducer (4), the reference receiving transducer (5) and the propagation receiving transducer (2) are respectively arranged on the two flat plates (1), and the excitation transducer (4) and the reference receiving transducer (5) are arranged on the same flat plate (1); the excitation transducer (4), the reference receiving transducer (5) and the propagation receiving transducer (2) are all connected to the guided wave detector.
8. The SH0 guided wave-based detection device for detecting the bolt group connection loosening condition as claimed in claim 7, wherein: the guided wave detector comprises a power amplification module, a signal generator, a delay module, a pre-amplification module, a signal acquisition module and a filter unit; the computer is connected to the excitation transducer (4) sequentially through the signal generator and the power amplification module, the reference receiving transducer (5) and the transmission receiving transducer (2) are connected to the signal synchronization module sequentially through the pre-amplification module, the signal acquisition module and the filter unit respectively, and are connected to the computer through the signal synchronization module.
9. The SH0 guided wave-based detection device for detecting the bolt group connection loosening condition as claimed in claim 7, wherein: the excitation transducer (4), the reference receiving transducer (5) and the propagation receiving transducer (2) are all SH0 guided-wave magnetostrictive transducers.
10. The SH0 guided wave-based detection device for detecting the bolt group connection loosening condition as claimed in claim 7, wherein: the computer synchronously receives the signals of the two channels received by the reference receiving transducer (5) and the propagation receiving transducer (2) through the signal synchronization module, and simultaneously, the channels of the reference receiving transducer (5) and the propagation receiving transducer (2) are independent and are not coupled.
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