JPH01248049A - Cracking change detecting method and monitoring system therefor - Google Patents

Abstract

PURPOSE:To enable the detection on the changes in cracking range generated in a conductor surface at a remote point, by arranging an electromagnetic coil as opposed to a cracking part of the surface to detect a change in the voltage of an LC circuit with the LC circuit containing the coil being resonated. CONSTITUTION:An electromagnetic coil 4 is arranged as opposed to a cracking part 2 of a conductor surface 1 and an LC oscillation circuit composed of the coil 4 and a capacitor 5 is resonated. As the coil 4 is excited, a magnetic flux 3 generated causes an eddy current 21 in a conductor surface 1. When any cracking part 2 exists in the conductor surface 1, the current 21 at a part where the magnetic fluxes 3 cross is divided by the cracking part 2, while according as the extent of a cracking increases, the number of lines of magnetic force causing the electric current 21 in the magnetic flux 3 decreases. Thus, a reversely excited magnetic flux due to the current 21 reduces to cause a change in the resonance frequency, increasing impedance of the LC circuit. As a result, any change in cracking can be detected by measuring a voltage output of the LC circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a crack change detection method and a crack change monitoring system. The present invention relates to a detection method and a monitoring system for monitoring safety.

[Prior Art] Cracks often occur in structural members such as bridges due to static or dynamic external forces acting on them over time. This crack causes stress concentration in the member, and there is a risk that the crack will further develop and cause a fatal defect in the structure.

In particular, bridge components are exposed to large environmental conditions due to changes in temperature and humidity, and are subject to dynamic stress every time a train or automobile passes by, resulting in cracks in many places. The cracks develop and cause serious safety problems.

Therefore, if a crack occurs, it can be detected early and
It is necessary to diagnose the fatigue of structures by measuring the degree of change in the cracks.

Conventionally, there is a method for inspecting the extent of crack growth in bridges made of steel members, which utilizes the phenomenon of magnetic polarization at f(L) cracks, which involves attaching magnetic particles to the cracks. A method of inspecting the degree of cracking has been adopted by measuring the tendency of magnetic particles to concentrate at that location.

[Problems to be Solved by the Invention] However, the above-described method of attaching magnetic particles for inspection has the following problems.

First of all, according to the rules regarding bridge maintenance and inspection by JR companies, etc., in principle, demagnetization must be performed after the inspection is completed.
In particular, it is mandatory to demagnetize anything that affects instruments. This demagnetization work is performed by placing an electromagnetic coil energized with alternating current opposite the location where the magnetic particles are attached.
This method gradually reduces the current to zero, but it has been pointed out that it is dangerous due to the poor footing of bridges, and is extremely inefficient. Furthermore, there is a limit to the ability to inspect a large number of crack occurrence locations, and it is almost impossible to constantly monitor the degree of change in cracks.

Furthermore, according to the above-mentioned magnetic powder adhesion method, because it utilizes the magnetic polarization phenomenon of cracks, it may be applicable to steel members, but it cannot be applied to non-conductive members such as concrete members of bridges. be.

Therefore, the present invention provides a crack change detection method that does not use materials that affect instruments such as magnetic particles, and that does not require the detection object to be a conductive member or a non-conductive member. , was created with the aim of providing a system that can remotely monitor crack growth data detected by this method.

[Means for Solving the Problems] The basic configuration of the crack change detection method of the present invention is shown in FIG. The present invention relates to a method of detecting a voltage change in the LC circuit based on a change in the crack width of the conductor surface 1 in a state in which the LC oscillation circuit constituted by the TL8i coil 4 and the capacitor 5 resonates.

This crack change detection method can also be applied to the case where a crack has occurred or a non-conductive member.
As shown in the figure, a conductor film 8 is additionally formed on both edges of the crack 7 of the non-conductive member 6, and an electromagnetic coil is attached to both conductor films 8 in order to cause the magnetic flux 3 to cross in the same manner as shown in FIG. 4
are installed facing each other to detect voltage changes in the LC oscillation circuit.

The basic configuration of the crack change monitoring system is shown in Figure 3.
In the detection method described above, a plurality of sensors (s
r~S,, ), and are remotely connected to each sensor (S+~Sn), TF of each sensor (S+~Sn), magnetic coil 4
and an excitation circuit 9 including a capacitor 5 constituting an LC oscillation circuit, an input control means 10 for time-divisionally inputting the output data of each sensor (S+ to Sn), a storage means 11, and an input control means lO. Regarding each data of the storage control means 12 and the input control means 10 to be stored in separate areas (M, to M,) of the storage means 11, the previous data (Da) stored in the storage means 11 and the data input this time are Comparison means 13 for comparing data (Db) with data (Db), data rewriting means 14 for rewriting data (Da) in storage means 11 to data (Db) when the comparison result of comparison means 13 is Da to Db, storage means 11 a data processing device 16 equipped with a communication means 15 for communicating and transferring each data; and a central monitoring device that is installed remotely to the data processing device 16 and monitors the data transferred from the data processing device 16 via a communication line 17. The system includes a device 18.

[Operation] The crack change detection method of the present invention detects crack changes based on the following principle.

When the electromagnetic coil 4 is excited, the resulting magnetic flux 3 generates an eddy current 21 in the conductor surface 1. This eddy current 21 is generated as a concentric current in a direction perpendicular to the magnetic flux 3 and in a direction that generates a reverse excitation magnetic flux that cancels the magnetic flux 3 of the electromagnetic coil 4. If there is a crack 2 on the conductor surface l, the thin current 21 in the part where the magnetic flux 3 intersects is divided by the crack 2, and as the width of the crack increases, the eddy current 21 in the magnetic flux 3 increases. The number of magnetic lines of force that generate this decreases.

Therefore, in a state in which the LC oscillation circuit resonates, as the crack width increases, the reverse excitation magnetic flux due to each eddy current 21 becomes smaller, the resonance frequency changes, and the impedance of the LC circuit increases.

As a result, changes in the crack can be detected by measuring the voltage output of the LC circuit.

On the other hand, in the case of a cracked member or a non-conductive member, the magnetic flux 3 of the electromagnetic coil 4 causes an eddy current 2
1 will not occur, or if a conductive film 8 is additionally formed on both edges of the crack 7 of the non-conductive member 6 as shown in FIG.
As in the previous case, an eddy current 22 is generated in the conductor film 8.
occurs, and changes in cracks can be detected.

The conductor film 8 may be formed by pasting aluminum foil, spraying conductor particles such as silver particles, or applying conductor paint.

The crack change monitoring system of the present invention remotely monitors data from a plurality of crack change detection units using the method described above.

Sensors (S+ to Sn), which are electromagnetic coils installed in each crack of the structural member, are made to resonate by an excitation circuit 9, and the output of each sensor (S, to Sn) is sent to a data processing device 16. is input.

The data processing device 16 causes the input control means 10 and the memory control means 12 to store the detection data of each sensor (S□ to S7) in separate areas of the memory means 11, but the data of each area and the newly input data are stored in separate areas of the memory means 11. Each detection data is compared with the comparison means 13.
If the two data are different, the data rewriting means 14 rewrites the detected data in the corresponding area of the storage means 11 with the newly inputted detected data. That is, each piece of data in the storage means 11 is updated sequentially, and new crack data of structural members are always stored in the storage means 11.

Since this data processing device 16 is connected to the central monitoring device 18 via the communication line 17, it is possible to transfer each data in the storage device 11 to the central monitoring device 18 side by the communication means 15 at any time or when necessary. This makes it possible to intensively monitor changes in each crack in the structural member using a CRT, recorder, etc. provided on the central monitoring device 18 side.

[Example] Hereinafter, the present invention will be explained in detail using FIGS. 4 to 13.

In this embodiment, the present invention is applied to a system for intensively monitoring the progress of cracks that have occurred in the constituent members of a railway bridge, as shown in FIG.

In the figure, 31 is a train, 32 is a bridge, and bridge 3
Sensors (electromagnetic coils) are placed at each crack occurrence location in the component parts of 2.
(S1 to Sn) are installed facing each other, and each sensor (SI to Sn
) is connected to a data processing device 33 installed on the side of the track, and is further connected to the data processing device 33 and a central monitoring device 34.
They are connected via switched lines installed along the railroad tracks.

In general, cracks are likely to occur in the structural members of the bridge 32 at the joints 36 of each girder plate, as shown in Figure 5, and at the joints of reinforcing members that reinforce the joints of the girder plates, as shown in Figure 6. It is 37. This is because when a load is applied to the bridge 32, stress tends to concentrate on each of the joints 36 and 37, resulting in increased fatigue.

Whether the sensor (S+ to Sn) is attached to the cracked area or the manner of attachment is shown in Figure 7 or 8.
As shown in the figure. In each figure, 38 is a sensor body with a built-in electromagnetic coil, 39 is a curved face plate made of transparent resin, and 40
is the lead wire of the electromagnetic coil, and each sensor (S, ~Sn
) is the shaft of the sensor body 38 or the crack 41a on the member surface 41.
It is attached via a curved surface plate 39 so as to pass through.

In addition, FIG. 7 shows the case where the member is made of steel, and FIG. 8 shows the case where the member is made of concrete. In the latter case, the sensor (
S, ~Sn) are installed.

Furthermore, the detailed installation of the sensors (S+ to Sn) is shown in the sectional view of FIG. As is clear from the figure,
An O-ring 43 is attached to a groove on the peripheral edge of the curved face plate 39, and the entire sensor (S+ to Sn) is fixed to the member surface 41 with an adhesive 44 in a sealed state to prevent rainwater etc. from entering the measuring section. .

FIG. 10 shows a circuit section for detecting the progress of the crack 41a. In this example, a Colpitts oscillator circuit is used, and the fundamental resonance frequency is f = (1/2π), (1/L) ((1/
Control C1 and C2 as (:1)÷(1/(:2)) and excite the electromagnetic coil L while initially adjusting f.
The circuit is configured to detect a potential difference in the circuit. In this circuit, as explained in the principle in the "Operation" column, as the crack width grows, the magnitude of the thin current generated in the member surface 41 or the aluminum foil 42 changes, and as a result, the resonant frequency of the LC circuit changes. The impedance increases and the output voltage increases.

FIG. 11 shows a system circuit diagram of the crack growth monitoring system.

The data processing device 33 includes amplifiers (50-1 to 50-n) that include the Colpitts oscillation circuit and an amplifier circuit that amplifies the voltage output of each sensor (S+ to Sn);
- n) output data (n channels) in a time-divisional manner; an A/D converter 52 that quantizes the analog data selected by the multiplexer; and an A/D converter 52 that quantizes the analog data selected by the multiplexer;
t to mn), a comparator 54 that compares the quantized detection data with the detection data previously stored in the RAM 53, a memory selector 55 that selects a memory area of the RAM 53, and a data processing device 3.
ROM56 that stores the operation program of 3, each amplifier (
50-1 to 50-n), a floppy disk drive (FDD) 58 for saving data in the RAM 53, a timer 59, a system phone 60 equipped with a communication interface (R3-232C), and a CPU 61. , CPU61 is ROM5
Each unit is controlled via the lotus control line based on the program No. 6.

Further, this data processing device 33 is connected to a central monitoring device 34 via an exchange line 35, and both devices can communicate through their respective system phones 60.degree. 34a.

The operation process of the system of this embodiment will be explained below with reference to the flowchart of FIG.

First, in this system, each sensor (s 1 to Sn
) is always quantized by an A/D converter 52 via an amplifier (50-1 to n) and a multiplexer 51. Also, under this condition, the CPU 61 or each amplifier (5
0-1 to n) are operating normally.

At this point, when the timer 59 measures the time when the train 31 passes the bridge, the A/D converter 52 starts to take in data (steps
Each detection data of n) is compared with the data stored in the RAM 53 at the time of the previous measurement (step 2). That is, A
/D converter 52 data or sensor (S, ) data (D
ip+1), the memory area (m,) of the RAM 53 is selected by the memory selector 55, and the previously stored data (Di,) of the previous sensor (S,) and the current data (D+, , l) are compared.

As a result, if D , , = D , □1, then R
The data (Dip) of AM53 is left as is (Steup ■ → ■), but if it is D, 608.1, RA
The memory area (m□) of M53 is rewritten to data (D, , l) (step ■■).

This procedure is executed for all channels, and as each crack 41a of the member develops, the output of the sensor installed at that crack 41a changes, so the data in the memory area of the RAM 53 corresponding to that sensor is updated. will be done.

Then, the timer 59 runs out for a predetermined period of time (when the train 31 reaches the M5 beam 32)
After counting the time it takes to complete the process, all the data in the RAM 53 is saved to the FDD 58 (step ■),
Wait until the next train passes.

As a result of the above, the progress data of each crack 41a of the bridge 32, which is updated every time a train 31 passes, is stored in the FDD 58.As shown in the flowchart of FIG. System phone 3 from the 34 side
4a instructs the data processing device 33 to request data via the switched line 35 (step ■), the CPU 61 detecting this data request signal reads out the data stored in the FDD 5B and centrally transfers the data via the switched line 35. The information is transferred to the monitoring device 34 side (step ■ [shares]).

As a result, the central monitoring device 34 can check the crack width of each crack 41a of the bridge 32 using the latest data, or if the condition is becoming dangerous for train operation, check the crack width of each crack 41a of the bridge 32. Measures will be taken.

In this embodiment, data transfer from the FDD 58 is executed after waiting for a data request from the central monitoring device 34 side, or every time the timer 59 on the data processing device 33 side counts a certain period of time, the data processing device 33 It is also possible to have data on the FDD 5B periodically transferred from the side to the central monitoring device 34 side.

[Effects of the Invention] Since the present invention is configured as described above,
It has the following effects.

The crack change detection method of claim (1) makes it possible to electrically detect a change in crack width generated on a conductor surface at a remote location without using additional materials such as magnetic particles. As a result, it is no longer necessary to go to each crack occurrence location in a structure member every time an inspection is carried out, and the claim (2), which is particularly characterized by the danger and poor work efficiency associated with inspection work for bridges, etc., is eliminated. The crack change detection method makes it possible to electrically detect changes in cracks even when the crack is occurring in a non-conductive member, and is particularly effective when the structural member is concrete. Become.

The crack change monitoring system of claim (3) makes it possible to centrally monitor changes in multiple cracks occurring in a large-scale structure from a remote location, and facilitates comprehensive diagnosis of the entire structure. . As a result, immediate measures can be taken to ensure the safety of the structure. In particular, when detecting changes in cracks in railways and expressway bridges, communication lines are often installed along railways and roads, and by using these as data transmission lines, extremely efficient central Build a monitoring system.

[Brief explanation of the drawing]

Figures 1 and 2 show the basic configuration of the crack change detection method, Figure 3 shows the basic configuration of the crack change monitoring system, and Figure 4 shows the application of the crack change monitoring system to railway bridges. Figures 5 and 6 are perspective views of bridge structural members, Figures 7 and 8 are perspective views showing how the sensors are installed, Figure 9 is a sectional view of the same, and Figure 10 FIG. 11 is a circuit diagram of the crack change detection section, FIG. 11 is a system circuit diagram of the crack change monitoring system, and FIG. 12 is a flowchart showing the operating process of the system. l...Conductor surface 2...Crack part 3...Magnetic flux 4...
・TL81 coil 5... Capacitor 6... Non-conductive member 7... Crack 8... Conductor film 21.22.
・Eddy current

Claims (3)

[Claims] (1) Electromagnetic coils are installed facing each other to cause magnetic flux to cross the cracks in the conductor surface, and the LC oscillation circuit made up of the electromagnetic coils and the capacitor is resonated. A crack change detection method characterized by detecting voltage changes in a circuit. (2) In the case where the cracked member is a non-conductive member, a claim in which a conductive film is additionally formed on both edges of the cracked part, and electromagnetic coils are installed facing each other to cause magnetic flux to cross between the two conductive films. The crack change detection method in item (1). (3) In the crack change detection method according to claim (1) or (2), a plurality of sensors are provided in which electromagnetic coils are installed facing each other in a plurality of cracks of a structural member, and each sensor is remotely connected. , an excitation circuit including the electromagnetic coil of each sensor and a capacitor constituting the LC oscillation circuit, an input control means for time-divisionally inputting the output data of each sensor, a storage means, and a separate storage means for storing each input data of the input control means. Regarding each data of the storage control means and input control means to be stored in the area of
a comparison means for comparing a) with the currently input data (Db); a data rewriting means for rewriting the data (Da) in the storage means to data (Db) when the comparison result of the comparison means is Da≠Db; A data processing device equipped with a communication means for communicating and transferring each data stored in the storage means, and a central monitoring device installed remotely from the data processing device to monitor the data transferred from the data processing device via a communication line. A crack change monitoring system characterized by: