1. A shore bridge front pull rod joint damage monitoring and positioning method based on ultrasonic guided waves is characterized by comprising the following steps:

(1) a rectangular sensor array for defect monitoring is distributed in the front pull rod joint area;

(2) judging whether the structure is damaged or not by using the difference between the reference signal and the damage signal acquired by the rectangular sensor array unit;

(3) and defects are reconstructed by adopting an ellipse positioning algorithm and a data fusion method, so that the monitoring and positioning of the defects in the front pull rod of the shore bridge are realized.

2. The shore bridge front pull rod joint damage monitoring and positioning method based on the ultrasonic guided waves as claimed in claim 1, wherein the specific method in the step (1) is as follows:

in the front pull rod joint area of the shore bridge, 2N piezoelectric sensors are symmetrically arranged on two symmetrical sides of a rectangle with the central connecting line of stress release holes of the front pull rod joint as a symmetrical axis, and N is more than or equal to 6;

each piezoelectric sensor T on one of the sides of a rectangle_iI is 1 and … … N, which are used as excitation sensors to send out excitation ultrasonic guided waves;

piezoelectric sensor T on the other rectangular side_jJ ═ N +1, … … 2N, as receiving sensors,receiving the collected signals, sequentially collecting the reference signal as the received signal without defect and the monitor signal as the received signal with defect to obtain 2N²A group signal.

3. The shore bridge front drawbar joint damage monitoring and positioning method based on ultrasonic guided waves according to claim 2, characterized in that the excitation signal of the excitation sensor is a 5-cycle sine wave signal modulated by a hanning window.

4. The shore bridge front pull rod joint damage monitoring and positioning method based on the ultrasonic guided waves as claimed in claim 2 or 3, wherein the specific method in the step (2) is that in the monitoring process:

when the structure is defect-free, the sensor T is excited_iThe ultrasonic guided waves excited to transmit propagate in the plate and are received by the receiving transducer T_jReceiving, wherein the monitoring signal is not different from the reference signal, and the defect scattering signal is the difference between the monitoring signal and the reference signal, and the amplitude value is theoretically zero in the oscillogram;

when a defect D is present in the structure, the sensor T is excited_iThe ultrasonic guided wave excited by the excitation can be scattered after encountering the defect D, and a part of scattered signals can be received by the receiving sensor T_jReceiving, wherein the monitoring signal and the reference signal have difference due to a defect D, the amplitude of the defect scattering signal in the oscillogram is not zero, and a defect reflection echo exists; whether the defects exist in the monitored object can be judged by observing the defect scattering signals.

5. The shore bridge front drawbar joint damage monitoring and positioning method based on ultrasonic guided waves according to claim 4, characterized in that the ellipse positioning algorithm in step (3) comprises the following specific steps:

ultrasonic guided wave can be obtained from defect scattering signal from first excitation sensor T₁Past the defect D to the first receiving sensor T₂And the group velocity v of the ultrasonic guided waves_gObtaining the defect D and the first defect according to the dispersion curveAn excitation sensor T₁First receiving sensor T₂Is equal to v_g×t；

From the geometric relationship of the ellipse, the location of the defect D is at the first excitation sensor T₁First receiving sensor T₂An ellipse with L as the major axis as the focus;

similarly, each group of sensor array units can determine an elliptical track with L as the major axis, and the intersection point of all the elliptical tracks is the position of the defect D.

6. The shore bridge front drawbar joint damage monitoring and positioning method based on ultrasonic guided waves according to claim 4, characterized in that the data fusion method in step (3) comprises the following specific steps:

firstly, the plate structure of the shore bridge front pull rod joint is divided into discrete units, and the ultrasonic signals are obtained from an excitation sensor T according to the geometric trigonometric relation_i(x_i,y_i) Where it begins to propagate to each discrete point (x, y) in the structure, again to be received by the sensor T_j(x_j,y_j) Time of reception t_ij(x, y) is calculated as follows:

wherein i, j is the number of the piezoelectric sensor, and detects the signal t_ijEnvelope amplitude S corresponding to time (x, y)_ij(T) assigning to each discrete point (x, y) in the plate, the excitation sensor T is obtained_iExcitation reception sensor T_jDetecting imaging result S at reception_ij(t_ij(x,y))；

The number of the sensor arrays is 2N, and the sensors T are excited_iAnd a receiving sensor T_jAs an array unit, there is 2N in total²The positioning units add the amplitude values of each discrete point corresponding to all the positioning units by a data fusion method to obtain a plate structure defect imaging result I (x, y), and the calculation formula is as follows:

Background

The world economy globalization promotes the rapid development of international trade, and more than 90% of the international trade is completed by waterway transportation according to statistics, while container transportation becomes the main force of ocean transportation. With the increasing container throughput, the shore container crane (shore bridge for short) is developing towards high speed and large scale. The front pull rod of the shore bridge has a supporting effect on the girder, and the normal work of the shore bridge can be directly influenced. The edge of a stress release hole of the front pull rod is easy to generate microcracks under the action of cyclic load, the front pull rod is difficult to check because of being in a high-altitude position, and once the fine cracks are not checked, the front pull rod can be extended and cracked or even broken due to long-term accumulation, so that economic loss and casualties are caused. The detection means commonly used at present include visual inspection, ultrasonic detection, penetration detection, magnetic particle detection and the like, the detection efficiency is low, the detection is required to be carried out in a shutdown state, and the detection result cannot be mastered in real time on the operation condition of the shore bridge. The ultrasonic guided wave has the advantages of long propagation distance, small attenuation, high defect identification capability and the like, gets rid of the limitation that the conventional detection needs point-by-point scanning, and is suitable for real-time monitoring of the damage of inaccessible areas such as the front pull rod and the like under the condition that the shore bridge is not stopped.

Therefore, it is very necessary to develop a shore bridge front pull rod joint damage monitoring and positioning method based on ultrasonic guided waves.

Disclosure of Invention

The invention aims to provide a shore bridge front pull rod joint damage monitoring and positioning method based on ultrasonic guided waves, which utilizes the ultrasonic guided wave technology to realize monitoring and positioning of defects on a front pull rod joint. The rectangular sensor array layout method suitable for monitoring the defects of the front pull rod joint area is provided, whether the structure is damaged or not is judged by using the difference between a reference signal and a damage signal acquired by a sensor array unit, and the signals are simple and clear and are convenient to analyze; and further reconstructing the defects by adopting an ellipse positioning algorithm and a data fusion method, thereby realizing the monitoring and positioning of the defects in the front pull rod of the shore bridge.

In order to achieve the purpose, the invention adopts the following design scheme:

a shore bridge front pull rod joint damage monitoring and positioning method based on ultrasonic guided waves comprises the following steps;

(1) a rectangular sensor array for defect monitoring is distributed in the front pull rod joint area;

(2) judging whether the structure is damaged or not by using the difference between the reference signal and the damage signal acquired by the rectangular sensor array unit;

(3) and defects are reconstructed by adopting an ellipse positioning algorithm and a data fusion method, so that the monitoring and positioning of the defects in the front pull rod of the shore bridge are realized.

Further, the specific method in the step (1) is as follows:

in the front pull rod joint area of the shore bridge, 2N piezoelectric sensors are symmetrically arranged on two symmetrical sides of a rectangle with the central connecting line of stress release holes of the front pull rod joint as a symmetrical axis, and N is more than or equal to 6;

each piezoelectric sensor T on one of the sides of a rectangle_iI is 1 and … … N, which are used as excitation sensors to send out excitation ultrasonic guided waves;

piezoelectric sensor T on the other rectangular side_jJ is N +1, … … 2N, and is a reception sensor for receiving and acquiring signals, sequentially acquiring a reference signal as a reception signal in the case of no defect and a monitor signal as a reception signal in the case of defect, and obtaining 2N in total²A group signal.

Preferably, the excitation signal of the excitation sensor is a 5-cycle sine wave signal modulated by a Hanning window.

Further, the specific method in the step (2) is that, in the monitoring process:

when the structure is defect-free, the sensor T is excited_iThe ultrasonic guided waves excited to transmit propagate in the plate and are received by the receiving transducer T_jReceiving, wherein the monitoring signal is not different from the reference signal, and the defect scattering signal is the difference between the monitoring signal and the reference signal, and the amplitude value is theoretically zero in the oscillogram;

when a defect D is present in the structure, the sensor T is excited_iThe ultrasonic guided wave excited by the excitation can be scattered after encountering the defect D, and a part of scattered signals can be received by the receiving sensor T_jWhen received, the monitor signal and the reference signal will have a defect DThe difference exists, the amplitude of the defect scattering signal in the oscillogram is not zero, and a defect reflection echo exists; whether the defects exist in the monitored object can be judged by observing the defect scattering signals.

The ellipse positioning algorithm in the step (3) comprises the following specific steps:

ultrasonic guided wave can be obtained from defect scattering signal from first excitation sensor T₁Past the defect D to the first receiving sensor T₂And the group velocity v of the ultrasonic guided waves_gFrom the dispersion curve, the defect D and the first excitation sensor T are determined₁First receiving sensor T₂Is equal to v_g×t；

From the geometric relationship of the ellipse, the location of the defect D is at the first excitation sensor T₁First receiving sensor T₂An ellipse with L as the major axis as the focus;

similarly, each group of sensor array units can determine an elliptical track with L as the major axis, and the intersection point of all the elliptical tracks is the position of the defect D.

The data fusion method in the step (3) comprises the following specific steps:

firstly, the plate structure of the shore bridge front pull rod joint is divided into discrete units, and the positioning precision is higher when the number of the units is larger. From the geometrical trigonometric relationship, the ultrasonic signal is excited from the transducer T_i(x_i,y_i) Where it begins to propagate to each discrete point (x, y) in the structure, again to be received by the sensor T_j(x_j,y_j) Time of reception t_ij(x, y) is calculated as follows:

wherein i, j is the number of the piezoelectric sensor, and detects the signal t_ijEnvelope amplitude S corresponding to time (x, y)_ij(T) assigning to each discrete point (x, y) in the plate, the excitation sensor T is obtained_iExcitation reception sensor T_jDetection at receptionImaging result S_ij(t_ij(x,y))；

The number of the sensor arrays is 2N, and the sensors T are excited_iAnd a receiving sensor T_jAs an array unit, there is 2N in total²The positioning units add the amplitude values of each discrete point corresponding to all the positioning units by a data fusion method to obtain a plate structure defect imaging result I (x, y), and the calculation formula is as follows:

the invention adopts the technical scheme, and achieves the following effects:

the monitoring and the positioning of the regional defects of the front pull rod joint of the shore bridge under the condition of no shutdown are realized, the time and labor waste of conventional manual inspection are avoided, the front pull rod joint can be monitored in real time only by installing the sensor array once, the efficiency is high, and the cost and the labor intensity are low.

Drawings

FIG. 1 is a schematic view of the elliptical positioning principle of the present invention;

FIG. 2 is a graph of ultrasonic guided wave group velocity dispersion for a 25mm thick web of an embodiment;

FIG. 3 is a schematic diagram of a sensor array propagation path according to an embodiment;

FIG. 4 illustrates the received signals of the sensing paths 1-9 of an embodiment;

FIG. 5 is a reference signal for sensing paths 1-12 of an embodiment;

FIG. 6 is a monitoring signal when the sensing paths 1-12 of the embodiment are defective;

FIG. 7 illustrates defect scatter signals from sensing paths 1-12 according to an exemplary embodiment;

FIG. 8 shows the elliptical positioning results of the path 1-12 cells of the embodiment;

FIG. 9 shows the result of ellipse positioning of the embodiment;

FIG. 10 is a comparison graph of the imaging of a real through crack calculated in the example.

Detailed Description

The present invention is further illustrated by the following examples and figures, and the following examples are illustrative and not limiting, and are not intended to limit the scope of the present invention.

The invention aims to provide a shore bridge front pull rod joint damage monitoring and positioning method based on ultrasonic guided waves, which utilizes the ultrasonic guided wave technology to realize monitoring and positioning of defects on a front pull rod joint. The rectangular sensor array layout method suitable for monitoring the defects of the front pull rod joint area is provided, whether the structure is damaged or not is judged by using the difference between a reference signal and a damage signal acquired by a sensor array unit, and the signals are simple and clear and are convenient to analyze; further, an ellipse positioning algorithm and a data fusion method shown in fig. 1 are adopted to reconstruct the defects, so that the monitoring and positioning of the defects in the front pull rod of the shore bridge are realized. The method is specifically realized by the following steps:

FIG. 2 is a schematic diagram of a front tie rod joint area defect monitoring system, which comprises an industrial computer, a self-developed 64-channel signal excitation receiver, a piezoelectric transducer array (PZT) and a front tie rod of a monitoring object. The monitoring object front pull rod is of an H-shaped structure and is composed of a middle web plate and flange plates on two sides, the material is Q235, and the thickness of the web plate is 25 mm. Figure 3 shows the ultrasonic guided wave group velocity dispersion curve of a web 25mm thick of the monitored object. The sensor selects circular piezoelectric ceramics (PZT) with the diameter of 12mm and the thickness of 0.48mm, 16 piezoelectric sensor units are arranged to form a sparse sensor array, the number of the sparse sensor array is 1-16, and the sensor is arranged as shown in figure 2. Because the test object is an in-service crane and damage cannot be simulated by destructive methods such as grooving, punching and the like, the test method adopts AB glue to bond a stainless steel column with the diameter of 10mm on the edge surface of the stress release hole to serve as a simulation defect. The excitation signal is a hanning window modulated 5-cycle sine wave centered at 150 kHz.

First, reference signal acquisition is carried out, the propagation path of the sensor is shown in FIG. 4, and the sensor T_i(i-1, … … 8) as excitation, sensor T_j(j ═ i +1, i +2, … … 16) as received acquisition signals, for a total of 64 sets of reference signals. Then the diameter of the edge of the stress release hole at the left side of the front pull rod is pasted asThe 10mm stainless steel column is used as a simulation defect, the method is the same as the reference signal acquisition method, and 64 groups of monitoring signals are acquired.

In order to avoid complex modal analysis, the test performs data processing by using the mode with the highest speed, so that the wave speed of the 1 st direct wave packet is only required to be calculated. The wave velocity calculation is performed by taking the reference signal when the No. 1 sensor is excited, the No. 9 sensor receives the reference signal, and the excitation frequency is 150kHz as an example. Fig. 4 shows the received signals 1-9, and it can be distinguished from fig. 5 that the 1 st wave packet is a crosstalk signal synchronized with the excitation signal, the 2 nd wave packet is a direct wave signal of the mode with the fastest speed, and the following wave packet is a superposition of direct waves of other modes and end reflected waves, and no analysis is performed. First, the wave velocity of the direct wave is calculated by a time-of-flight method, and it is known that the distance L between the excitation and reception sensors is 200mm, the propagation time Δ t of the direct wave is 43.51 μ s (in fig. 5, the initial excitation time is subtracted from the packet time No. 2), and the corresponding wave velocity V of the direct wave is L/Δ t 4597 m/s. From the group velocity dispersion curve of the web given in fig. 3, the theoretical group velocity of the S1 mode corresponding to the frequency of 150kHz is 4494, which is substantially identical to the direct wave velocity calculated in this experiment, and differs by 2.3%. Therefore, the direct wave can be judged to be the S1 mode of Lamb, and the actual propagation group velocity is 4597 m/S.

Then, the collected original detection signals are analyzed, fig. 6 and 7 respectively show the excitation of the sensor No. 1, the reception of the sensor No. 12, and the reception signals under the non-defective and defective conditions, and the reception signals under the two conditions are subtracted to obtain the scattering signal containing the defect information, as shown in fig. 8. As can be seen from fig. 8, there is a significant defect reflection echo in the signal, which indicates that the method can achieve the monitoring of the defect in the front drawbar joint area.

The scattered signals on the sensing path are processed by an ellipse positioning algorithm, that is, the defect can be positioned on an ellipse track which takes the sensor 1 and the sensor 12 as a focus and takes the defect echo propagation distance as a major axis according to the excitation, the sensor receiving position and the propagation time of the defect reflected echo, and the positioning result is shown in fig. 9. Where the box represents the location of the sensor and the cross indicates the location of the defect. It can be seen that the color of the elliptical track at or near the position of the simulated defect is darker, which indicates that the method can realize elliptical positioning of the simulated defect.

In order to realize the positioning of the defect in the structure, data fusion needs to be performed on the unit positioning results of the sensor array, and all the unit positioning results are added and fused according to the formula (6-2), so as to obtain the defect positioning result based on the sensor array, as shown in fig. 10. As can be seen from the positioning results, the position with the darkest color in the figure is matched with the actual position of the simulated defect. Therefore, the ultrasonic guided wave monitoring method for the defects of the shore bridge front pull rod joint can be used for monitoring and positioning the defects of the front pull rod joint area.