JP2020169965A - Acoustic diagnostic device of multiple-train pulse electromagnetic force - Google Patents

Abstract

To provide an acoustic diagnostic device of multiple-train pulse electromagnetic force, which is for non-destructive inspection and which can perform quick and mass measurement by generating multiple trains of pulses in a short period.SOLUTION: An acoustic diagnostic device of multiple-train pulse electromagnetic force includes a pulse coil 2, a multiple-train pulse supply circuit 1, a sensor 11, and a measurement analysis part 15. The circuit 1 includes: a charge/discharge capacitor 3 for plurally and intermittently supplying a charge to the pulse coil 2; a thyristor 4 for making a forward-direction discharge current i flow to the pulse coil 2 by inputting a gate signal; a diode 5 for an inversion current, which is parallely connected to the thyristor 4; and a DC high-voltage power supply 10 for charging the charge/discharge capacitor 3.SELECTED DRAWING: Figure 1

Description

The present invention is non-destructive using multiple pulsed electromagnetic force that can detect an object to be inspected (for example, fine peeling of a joint portion between a metal material and a CFRP, an internal defect of reinforced concrete) in a short time and with high accuracy. Regarding acoustic diagnostic equipment.

Non-destructive inspection is an inspection technique that detects the internal scratches, surface scratches, or deterioration of the object to be inspected "without damaging the object". A wide variety of materials are used for industrial products and various equipment according to their purposes, and they are in operation every day. Since operating products and equipment deteriorate over time, it is important to use them for as long as possible while checking their safety.

Non-destructive testing can be applied to the processing process from the time of the material, the inspection of the product at the time of completion, the inspection at the time of construction of the equipment, the maintenance inspection, etc., so that the reliability and life of the product or equipment can be extended. You can. The main non-destructive inspection applications include nuclear power plants, plants, railways, aircraft, bridges, buildings (reinforced concrete), and underground buried objects.
The main non-destructive inspection methods are visual inspection, radiation transmission inspection, ultrasonic flaw detection inspection, magnetic flaw detection inspection, penetrant inspection, eddy current flaw detection inspection, strain measurement, leak test, acoustic emission method (hereinafter referred to as AE method). , Infrared inspection method, acoustic diagnosis method using pulsed electromagnetic force, etc.

Among the above, the acoustic diagnostic method using the pulse electromagnetic force generates an elastic wave in the inspection object by applying a pulse magnetic field generated from the pulse coil, and the elastic wave is installed on the surface of the inspection object. This is a method of detecting internal defects and surface defects by converting them into electrical signals using a sensor (piezoelectric element sensor, etc.) and then analyzing them. In general, elastic waves mainly have high frequency components in the ultrasonic region (several tens of kHz to several MHz).

The device (Patent Document 1) used in the acoustic diagnostic method includes a pulse coil 200 installed close to the surface of the inspection object 600, and a charge / discharger connected in series to the pulse coil 200 via a switch 400. A sensor 700 (acoustic signal) installed in parallel with the charging / discharging capacitor 300, a diode 500 connected in parallel to the charging / discharging capacitor 300, and a predetermined distance L from the pulse coil 200, and in contact with the surface of the inspection object 600. An acoustic emission sensor, an acceleration sensor, or a microphone that converts an electric signal into an electric signal, a current source 100 that supplies a current for charging the charging / discharging capacitor 300, and a measurement that measures and analyzes an output waveform from the sensor 700. It is composed of an analysis unit 150 (AD conversion device 120, amplifier 130 and waveform analysis device 140).

When the charging / discharging capacitor 300 by the current source 100 is completed, the switch 400 is turned on according to the instruction from the control device 400a, and the forward discharge current i is instantly flowed from the charging / discharging capacitor 300 to the pulse coil 200. A pulsed magnetic field is generated from the pulse coil 200. From this pulsed magnetic field, an eddy current U is generated in the conductor 601 near the surface of the object to be inspected 600, and the Lorentz force due to the eddy current U and the pulsed magnetic field acts on the conductor 601. If the conductor 601 is a magnetic material, in addition to the Lorentz force, a magnetic force due to a magnetic field gradient and a strain due to magnetostriction are applied to the conductor 601. Due to these complex factors, elastic wave D is generated from the conductor 601.
When the inspection object 600 has a defect N, the elastic wave D changes to a waveform caused by the defect N as compared with a waveform without the defect N. The elastic wave D is measured and analyzed by the measurement analysis unit 150 to detect the presence / absence, position, size, etc. of the defect N.

Japanese Patent No. 3738424

In the circuit (FIG. 7) used in Patent Document 1, when the electric charge is discharged from the charging / discharging capacitor 300 to the pulse coil 200, the reverse current −i passing through the pulse coil 200 is connected in parallel to the charging / discharging capacitor 300. After the pulsed magnetic field is generated, no electric charge remains in the charging / discharging capacitor 300. Therefore, when the charge / discharge capacitor 300 is discharged in the forward direction, the charge / discharge capacitor 300 becomes 0 V, and when the charge / discharge capacitor 300 is to be charged in preparation for the next discharge, the charge starts from 0 V. As a result, the charging time becomes long, and rapid and large-scale measurement is hindered.
Here, the waveforms of the forward discharge current i and the charge current are shown in the upper left graph of FIG. 7. In this case, the discharge time is 0.3 ms to 0.4 ms, and the charge time is about 5 seconds. It was.

Therefore, in order to shorten the charging time, (1) the boost transformer that generates the high voltage of the current source 100 is increased in pressure and capacity, and (2) the capacity of the bridge circuit that rectifies the voltage from the boost transformer is increased. (3) It is necessary to increase the capacity of the limiting resistor that limits the charging current, and (4) in some cases, it is necessary to adopt a multi-channel system with a plurality of capacitors and a charging circuit. All of these mean a significant increase in device size, weight and power consumption. For this reason, the continuous pulse generation circuit applied to the non-destructive acoustic diagnosis must be large and heavy, and consume a large amount of power.
However, the non-destructive acoustic diagnostic apparatus is required to be applied to all sites, and a lightweight and compact handy type is required. The more the measurement data, the higher the accuracy of the measurement result. Therefore, the charging / discharging capacitor is required to have a short charging time.

The present invention has been made in view of such problems of the conventional device, and by improving the circuit configuration, the charging time of the charging / discharging capacitor can be significantly shortened, and multiple pulses can be generated in a short time. This provides a multi-pulse electromagnetic force acoustic diagnostic apparatus for non-destructive inspection, which enables rapid and large-scale measurement.

The present invention (multi-shot pulse electromagnetic force acoustic diagnostic apparatus) has solved the above problems by using the following techniques. The invention according to claim 1 (FIGS. 1 (a) (b) and 2 (a) (b))
A pulse coil 2 that generates an eddy current U at the inspection target portion 21 of the inspection target 20 and
A multi-repeated pulse supply circuit 1 that supplies discharge currents i (-i) in the forward direction and the reverse direction following the pulse coil 2 at predetermined intervals.
A sensor 11 that is separated from the pulse coil 2 and placed in contact with or close to the inspection object 20 to record an elastic wave D caused by the eddy current U and convert it into an electric signal.
It is composed of a measurement analysis unit 15 that analyzes an output electric signal from the sensor 11 and outputs data for estimating the presence or absence of an internal defect N in the inspection object 20.
The multiple pulse supply circuit 1
A charging / discharging capacitor 3 connected to the pulse coil 2 and intermittently supplying the charged charge to the pulse coil 2 a plurality of times as a discharge current i (−i) in the forward direction and the subsequent reverse direction.
It is connected between the pulse coil 2 and the charge / discharge capacitor 3, and the forward discharge current i is passed through the pulse coil 2 by inputting a gate signal, and the forward discharge passes through the pulse coil 2. A thyristor 4 for charging the charging / discharging capacitor 3 with the opposite polarity,
A discharge current-i in the reverse direction is passed through the pulse coil 2 from the charge / discharge capacitor 3 connected in antiparallel to the psyllista 4 and charged in the opposite polarity, and the discharge current in the reverse direction passes through the pulse coil 2. An inverting current diode 5 for positively charging the charging / discharging capacitor 3 with -i,
It is characterized in that it is composed of a DC high-voltage power supply 10 which is connected to the charging / discharging capacitor 3 and charges the charging / discharging capacitor 3.

The invention according to claim 2 (FIGS. 1 (a) (b) and 2 (a) (b)) is the multiple-pulse electromagnetic force acoustic diagnostic apparatus according to claim 1.
The measurement analysis unit 15
An AD conversion device 12 that AD-converts and digitizes an acoustic analog signal from the sensor 11 and outputs this acoustic digital data.
A CPU 14 that numerically analyzes the acoustic digital data in order to nondestructively estimate the presence or absence of defects in the inspection object 20.
A memory 13 for storing acoustic digital data and numerically analyzed data is provided.
The CPU 14 performs a process of separating a response waveform for each pulse magnetic field from the captured acoustic digital data, a process of adding a plurality of separated response waveforms, dividing by the number of pulses and averaging, and obtains an averaged response waveform. It is characterized by having a function of outputting.

The invention according to claim 3 is the multiple pulse electromagnetic force acoustic diagnostic apparatus according to claim 2.
The averaged response waveform is subjected to a Fourier transform process, and the averaged Fourier transform result is output.

The invention according to claim 4 is the multiple pulse electromagnetic force acoustic diagnostic apparatus according to claim 2.
The CPU 14 replaces the addition of the separated response waveforms and the averaging process of dividing by the number of pulses, which is performed after the process of separating the response waveforms for each pulse magnetic field from the captured acoustic digital data.
It is characterized by performing a Fourier transform process on a plurality of separated response waveforms, adding a plurality of Fourier transform results, dividing by the number of pulses and averaging, and outputting the averaged Fourier transform result. ..

The invention according to claim 5 is the multiple pulse electromagnetic force acoustic diagnostic apparatus according to any one of claims 1 to 4.
The gate signal to the thyristor 4 is used as a signal for processing to separate a response waveform for each pulse magnetic field from the captured acoustic digital data.

According to the present invention, since the inverting current diode 5 is connected to the thylister 4 in antiparallel, most of the forward discharge current i flowing from the charge / discharge capacitor 3 to the pulse coil 2 is the charge / discharge. The capacitor 3 is charged in the opposite polarity, and the charge charged in the opposite polarity flows in the pulse coil 2 in the opposite direction as the inverting current (-i), and the charging / discharging capacitor 3 is passed through the inverting current diode 5. Is charged as a forward charge (Fig. 5).
As described above, the charge / discharge capacitor 3 is charged by the returned charge (indicated as the backflow current amount in FIG. 5), so that the charge by the DC high-voltage power supply 10 is the balance (necessary charge). Amount and display) is sufficient. In other words, the increased amount shortens the charging time. Therefore, a large amount of acoustic data can be obtained in a short time, and by averaging these data, the measurement work time can be shortened and the measurement accuracy can be improved.

(A) is an explanatory diagram of a first embodiment of the multiple-pulse electromagnetic force acoustic diagnostic apparatus of the present invention, and (b) is a modified example thereof. (A) is an explanatory diagram of a second embodiment of the multiple-pulse electromagnetic force acoustic diagnostic apparatus of the present invention, and (b) is a modified example thereof. It is sectional drawing which shows the inspection state of the dissimilar material joint body in this invention. (A) is a cross-sectional view showing an inspection state of a laminated body having an internal defect in the present invention, and (b) is a sectional view showing an inspection state of a reinforced concrete having an internal defect in the present invention. It is a figure of the charge waveform and the discharge waveform at the time of discharge of this invention. (A) is a correlation diagram between the intermittently recorded acoustic waveform diagram, the discharge current, and the thyristor-on signal for isolation, and (b) is each response waveform to the pulse magnetic field separated by the pulse synchronization signal. It is explanatory drawing of the prior art.

Hereinafter, the present invention will be described with reference to the illustrated examples.
1 and 2 are schematic configurations of the multi-pulse electromagnetic force acoustic diagnostic apparatus of the present invention, FIG. 1 (a) is a first embodiment, FIG. 1 (b) is a modified example thereof, and FIG. 2 (a) is. The second embodiment and FIG. 6B are modifications thereof. In each case, the circuit configuration is slightly different, but the effects are the same.
The multi-shot pulse electromagnetic force acoustic diagnostic apparatus of FIGS. 1 and 2 has a multi-shot pulse in which a discharge pulse current i (-i) in a forward (reverse) direction is applied to the pulse coil 2 via a power cable. The supply circuit 1, the sensor 11 attached in contact with or slightly separated from the surface of the inspection object 20, the measurement analysis unit 15 connected to the sensor 11 with a signal cable, the DC high voltage power supply 10, and the necessary It is composed of a display device 16 provided according to the above.

The pulse coil 2 is composed of a single coil composed of spirally wound electric wires. A core may be used in the pulse coil 2.
The pulse coil 2 is attached with a gap (height) H provided on the surface of the inspection object 20. At the time of inspection, the gap H is kept constant.

The sensor 11 is a known sensor, which is an instrument that detects an elastic wave D (acoustic signal) generated in an inspection object 20 and converts it into an analog electric signal. As the sensor 11, for example, an AE sensor that converts an acoustic signal into an electric signal, an acceleration sensor, an optical measurement sensor, or a microphone is used. A microphone is used here. The sensor 11 is installed in contact with or slightly separated from the measurement surface of the inspection object 20.

The measurement analysis unit 15 includes an AD conversion device 12 that AD-converts an acoustic analog signal from the sensor 11 and digitizes it, a CPU 14 including a calculation device that numerically analyzes the acoustic digital signal, and digital from the AD conversion device 12. A memory 13 for storing the digitized acoustic signal and the calculation result by the CPU 14 is provided.

The measurement and analysis unit 15 samples the output waveform of the sensor 11, amplifies it with an amplifier (not shown), and removes unnecessary signals such as noise with a filter (not shown). The output waveform filtered by the AD conversion device 12 is A / D converted, and the A / D converted digital data is stored in the memory 13.
Then, the measurement analysis unit 15 reads the acoustic digital data from the memory 13 at any time, and the CPU 14 performs a predetermined calculation according to a program having a predetermined signal processing procedure (for example, an average processing calculation program described later). The result is stored in the memory 13 or displayed via the display device 16.

The average processing calculation program is stored in the memory 13, and the CPU 14 reads and uses it at any time. This will be described with reference to FIG.
The upper waveform diagram of FIG. 6A is a diagram in which a series of acoustic digital waveforms recorded by the sensor 11 and A / D converted stored in the memory 13 are output to the display device 16 in a short time. It is a figure which shows the relationship between the acoustic signal with respect to a plurality of pulse magnetic fields stored intermittently, a pulse synchronization signal, and a discharge pulse current i (−i).
Since acoustic signals for a plurality of pulse magnetic fields are connected in the series of acoustic digital waveforms, a pulse synchronization signal (gate signal of the thylister 4) is used to separate each acoustic signal for the plurality of pulse magnetic fields. A forward discharge pulse current i flows at the same time as the input of the pulse synchronization signal (gate signal of the thyristor 4).

The first of the average processing calculation programs is
(1) A step of separating each response waveform to a pulse magnetic field caused by a pulse current i (-i) from a series of acoustic digital signals read from the memory 13 with reference to a pulse synchronization signal.
(2) Multiple response waveforms separated, a step of adding numerically and dividing by the number of pulses to average the response waveforms.
(3) A step of obtaining an averaged spectrum by performing an FFT (Fourier transform such as Fast Fourier Transform) on the averaged response waveform.
(4) The obtained averaged spectrum is displayed on the display device 16 or another calculation process (for example, peak detection that enables non-destructive estimation of the existence, position, size, etc. of the defect N). It has a function consisting of steps to output to the calculation process).

The second of the average processing arithmetic programs is
(1) A step of separating each response waveform to a pulse magnetic field caused by a pulse current i (-i) from a series of acoustic digital signals read from the memory 13 with reference to a pulse synchronization signal.
(2) A step of obtaining a spectrum by performing an FFT (Fourier transform such as Fast Fourier Transform) on the separated response waveform.
(3) A step of numerically adding a plurality of FFT-transformed spectra and dividing by the number of pulses to average the response waveform or spectrum.
(4) Display the averaged spectrum on the display device 16 or perform peak detection that enables non-destructive estimation of the existence, position, size, etc. of the defect N in another calculation process (for example, It has a function consisting of steps to output to the calculation process).

An embodiment of the multiple pulse supply circuit 1 is as shown in FIGS. 1 (a) and 2 (b) and 2 (a) and 2 (b) as described above, and the operations are the same.
In FIG. 1A, one line of the pulse coil 2 is connected to the positive terminal of the DC high voltage power supply 10, and the other line is connected to the negative terminal.
The charging / discharging capacitor 3 is installed between both lines and is connected to the pulse coil 2 at both lines.
The thyristor 4 is connected between one connection end of the charging / discharging capacitor 3 and the positive side connection end of the pulse coil 2 in one line of the pulse coil 2 (plus side in the embodiment of the figure). The cathode side is connected to the pulse coil 2 side, and the anode side is connected to the charge / discharge capacitor 3 side. That is, the forward discharge current i from the charge / discharge capacitor 3 is connected so as to be supplied to the pulse coil 2. A control device 4a for turning on / off the thyristor 4 is connected to the gate of the thyristor 4.

The inverting current diode 5 is connected to the thyristor 4 in antiparallel, and is connected to the thyristor 4 so as to flow an inverting discharge current (−i) in the opposite direction.
The DC high-voltage power supply 10 is connected to the charging / discharging capacitor 3 as described above, and charges the charging / discharging capacitor 3.

When a gate signal is input to the thyristor 4, a forward discharge pulse current i flows from the charge / discharge capacitor 3 to the pulse coil 2. Although a part of the forward discharge pulse current i is consumed, most of the forward discharge pulse current i flows into the charging / discharging capacitor 3 and charges it in the opposite polarity. Immediately after charging with the opposite polarity is completed, the battery is discharged in the opposite direction, and a part of the discharge pulse current −i in the reverse direction flows into the charging / discharging capacitor 3 which is partially consumed by the pulse coil 2 and is charged positively. The charge charged to the positive electrode is about 1/2 of the initial charge, and re-discharging is possible by replenishing the consumed amount (FIG. 5).

FIG. 1B is a modification of FIG. 1A, in which the thyristor 4 is connected to one of the charging / discharging capacitors 3 in the other line of the pulse coil 2 (minus side in the embodiment of the drawing). It is connected between the end and the positive side connection end of the pulse coil 2, its cathode side is connected to the charge / discharge capacitor 3 side, and the anode side is connected to the pulse coil 2 side. The inverting current diode 5 is connected to the thyristor 4 in antiparallel. The action is the same as in FIG. 1 (a).

FIG. 2A shows a second embodiment of the multiple pulse supply circuit 1 of the present invention, in which a set of a thyristor 4 and an inverting current diode 5 connected in parallel with respect to FIG. 1A, and charging / discharging The positions of the capacitors 3 are reversed, one connection end of the charge / discharge capacitor 3 is connected to the pulse coil 2, and the other connection end is connected to the anode side of the thyristor 4. The action is the same as in FIG. 1 (a).

FIG. 2B is a modification of FIG. 2A, in which the other line of the pulse coil 2 (minus side in the embodiment of the figure) is connected to one end of the charging / discharging capacitor 3 and the pulse coil. The connection end on the minus side of 2 is connected, the anode side of the thyristor 4 is connected to the pulse coil 2 side, and the cathode side thereof is connected to the charge / discharge capacitor 3 side. The inverting current diode 5 is connected to the thyristor 4 in antiparallel. The action is the same as in FIG. 1 (a).

Since the operation of each embodiment of the multiple-shot pulse supply circuit 1 of the present invention is the same, the multiple-shot pulse supply circuit 1 of FIG. 1A will be used as a representative example below.

Next, the measurement of the inspection object 20 using this apparatus will be described. The pulse coil 2 and the sensor 11 separated from the pulse coil 2 by a certain distance L are measured at a plurality of points at regular intervals within the measurement range.
When the measurer presses the measurement start button (not shown) of the device to start the measurement, the thyristor 4 is turned on from the control device 4a in response to the fact that the charging / discharging capacitor 3 has been charged at a later time. A gate signal is output, and a forward discharge current i flows from the charging / discharging capacitor 3 to the pulse coil 2. As a result, as already described, elastic waves D due to "composite of Lorentz force, magnetic field gradient and magnetostriction" are generated in the highly conductive material 20a in the non- or low conductive material 20b (20c) covering the high conductive material 20a. (Fig. 3). This elastic wave D is recorded in the sensor 11 together with the noise, and an acoustic analog signal on which the noise analog signal is superimposed is output from the sensor 11.
At the same time, the gate signal is sent to the CPU 14 and stored in the memory 13.

Since the charging / discharging by the charging / discharging capacitor 3 is repeated in a short time, a large amount of acoustic analog signals are output from the sensor 11 in a short time.
Then, the acoustic analog signal on which the noise analog signal is superimposed is amplified, A / D converted, and sequentially stored in the memory 13.
Such measurement is performed at each measurement point of the inspection object 20.

The inspection object 20 includes a high conductive material 20a, a non-conductive material 20b, and a low conductive material 20c alone or a combination thereof. However, the non-conductive material 20b alone is not a target.
The highly conductive material 20a, generally a metallic material such as alloy steel or aluminum, which is a material of electric conductivity exceeds 10 ⁶ S / m.
The non-conductive material 20b is a material having an electric conductivity of less than 10 ^-4 S / m, and ceramics, GFRP (glass fiber reinforced plastic), plastics and the like are typical examples.
The low conductivity material 20c is a material having an electric conductivity in the range of 10 ^-4 to 10 ⁴ S / m, and is a CFRP (carbon fiber reinforced plastic), CFRC (carbon fiber reinforced concrete), CNF composite material (carbon nano). Typical examples of the fiber composite material include a composite in which carbon nanofibers are dispersed in a polymer material such as polyethylene or polypropylene), a CNT composite material (carbon nanotube composite material), and a solid polymer electrolytic film.

The simple substance of the high conductive material 20a is, for example, a metal block, a metal pipe, or a laminate of the low conductive material 20c (sheets, films, single plates, etc., which are laminated and bonded to each other. There is a CFRP in which prepregs of carbon fiber woven fabrics are laminated in different fiber directions and cured).
As a bonded body (a material in which two or more materials having different properties are firmly bonded at an interface while maintaining their respective phases to improve characteristics such as strength, rigidity, and weight reduction, and combined / composited). Examples thereof include a bonded body in which a non-conductive material 20b is bonded to a highly conductive material 20a, and a bonded body in which a low conductive material 20c is bonded to a highly conductive material 20a.
Examples of the structure include a structure in which a highly conductive material 20a such as a reinforcing bar is embedded inside a non-conductive material 20b such as concrete, such as reinforced concrete.

A single defect N includes a crack.
Defects N in the joint include partial boundary peeling of the adhesive joint between the inner layer material and the outer shell, or the adhesive joint of different material structures, delamination / internal peeling inside the outer shell, and reduction of the inner layer material. Examples include meat and fatigue cracks.
Examples of the defect N of the laminate include delamination and transverse cracks.
Taking reinforced concrete as an example, the defect N of the structure includes the generation of a gap between the reinforcing bar and the concrete due to rust or corrosion of the reinforcing bar 20a.

Although the bonding using an adhesive has been described as a typical example for joining the bonded body and the laminated body, fusion bonding may also be used. Further, the delamination is, for example, a portion where the joint portion between the layers is peeled off by an impact or the like after joining, but also includes a poorly fused portion where the joining is incomplete due to the presence of air bubbles or foreign matter.

Next, a method of installing the pulse coil 2 and the sensor 11 in this inspection will be described. FIG. 3 schematically shows a case where an inspection object (joint) 20 having an internal defect N is used. In this case, a boundary peeling having a width K is provided in the adhesive joint portion S as an internal defect N. Of course, the internal defect N is not limited to the boundary peeling, and there are the above-mentioned ones. Here, boundary peeling is taken as a typical example. Then, a reference body (not shown) having no internal defect N, which is a comparison standard for the inspection object 20, is used. The reference body has the same structure as the inspection object 20 except for the internal defect N.

The method of installing the pulse coil 2 and the sensor 11 in this inspection (inspection object 20, reference body) is the same as that of the laminated body (single body) and the structure (FIGS. 4 (a) and 4 (b)). .. The standard for inspection is the standard body having the same structure as the object 20 to be inspected and having no internal defects.
In either case, when the inspection object 20 is a bonded body or a structure (FIGS. 3 and 4 (b)), the pulse coil 2 is viewed from the upper surface of the non-or low conductive material 20b / 20c, which is the measurement surface thereof. Install them apart (or in contact with each other), and in the case of a laminated body (single unit: FIG. 4 (a)), install them apart (or in contact with each other) from one surface. Let H be the separation height.

When the inspection object 20 is a bonded body or a structure as described above, the sensor 11 is installed in contact with or slightly separated from the surface (that is, the pulsed magnetic field irradiation surface) on the non-or low conductive material 20b / 20c side. To. When the inspection object 20 is a laminated body (single substance), it is installed in contact with or slightly separated from the surface (pulse magnetic field irradiation surface).
In relation to the pulse coil 2, the sensor 11 is installed at a position separated from the pulse coil 2 by a distance L.

Although the outline of this inspection has been described, it will be described in more detail below. The charge / discharge capacitor 3 is charged by the DC high-voltage power supply 10, the start button (not shown) of the present device is pressed, and the thyristor 4 is turned on according to the instruction of the control device 4a. At the same time, the electric charge accumulated in the charging / discharging capacitor 3 becomes a forward discharge pulse current i, which flows through the thyristor 4 to the pulse coil 2. When the forward discharge pulse current i is applied to the pulse coil 2, a pulse magnetic field is generated from the pulse coil 2 side toward the inside of the inspection object 20 (or the reference body).

The remaining forward discharge pulse current i that has passed through the pulse coil 2 and has not been consumed flows into the charge / discharge capacitor 3 and is charged in the opposite polarity, and then the charge in the opposite polarity is used for charging / discharging. An inverting discharge current (−i) is generated in the reverse direction from the capacitor 3, and flows in the reverse direction through the pulse coil 2. Then, the remaining unconsumed inverting discharge current (−i) passes through the inverting current diode 5 and returns to the charging / discharging capacitor 3. This returned charge (indicated as the amount of backflow current in FIG. 5) is increased, the remaining charge (indicated as the required charge amount in FIG. 5) is sufficient for charging for the next discharge, and the increased amount shortens the charging time. As a result, the charge / discharge interval can be significantly shortened as compared with the conventional device, and a large amount of data can be obtained at the same measurement time.
In the embodiment shown in FIG. 5, the discharge time in the forward and reverse directions is 0.3 ms, the charge time is 200 ms, and the conventional circuit of FIG. 6 (only forward discharge is 0.15 ms). , Charging time is 5 seconds) and can be charged and discharged in a shorter time.

As described above, the pulse due to the forward (reverse) direction discharge pulse current i (-i) Pulses in the forward direction (or in the reverse direction from the internal direction) in the internal direction of the inspection object 20 (or reference body) from the coil 2 side. When a magnetic field is generated, this pulsed magnetic field is weaker than the highly conductive material 20a (or the highly conductive material 20a) of the inspection object 20 (or the reference body) on the opposite side of the inspection surface, but has low conductivity. A forward (reverse) eddy current U is induced in the material 20c).
Then, the highly conductive material 20a (or the low conductive material 20c) is excited by the interaction force between the magnetic field and the pulsed magnetic field accompanying the eddy current U, and in the case of a bonded body, the high conductive material 20a (or low) is excited. Conductive material 20c), in the case of a laminated body (single unit), from the whole (particularly within the range where eddy current U is generated), from a structure such as reinforced concrete, it is elastic from the reinforcing bar which is the highly conductive material 20a inside. Wave D is emitted. This elastic wave D is transmitted in concrete which is a non- or low conductive material 20b / 20c (FIGS. 3 and 4 (b)).
On the other hand, when the inspection object 20 (or the reference body) is a laminated body, an eddy current U is generated in the inspection object 20, and an elastic wave D caused by this eddy current U is transmitted to the inspection surface (FIG. 4 (FIG. 4). a)).

The elastic wave D has a frequency component of several kHz to several tens of kHz. In metal materials, many signals having a frequency component of 100 kHz to 300 kHz are mainly emitted. Since a high frequency signal has a large attenuation in air, the elastic wave D mainly propagates in the material. In this case, if the highly conductive material 20a is a magnetic material, the force associated with the magnetic energy is also added to the exciting force to strengthen the elastic wave D. (Note that the eddy current U in the reverse direction is subsequently generated after the end of the eddy current U in the forward direction, but does not interfere with each other.)

As described above, the elastic wave D transmitted to the inspection surface is detected by the sensor 11 installed on the surface of the non- or low conductive material 20b / 20c, and this is converted into an acoustic analog signal. The sensor 11 outputs this to an amplifier (not shown) installed in the measurement analysis unit 15. The output acoustic analog signal is amplified by the amplifier and then output to the AD converter 12.
The amplified acoustic analog signal is converted into a digital signal by the AD conversion device 12, output to the memory 13, and stored.
A series of input acoustic data (acoustic data intermittently recorded with respect to the time axis (FIG. 6A)), data related to a pulse synchronization signal, and other data related to measurement are input to the memory 13. It is remembered.

In order to improve the measurement result, the CPU 14 needs to divide a large amount of a series of acoustic data at one measurement point into response waveforms for the discharge pulse current i (−i) and perform averaging processing.
Therefore, a series of acoustic data and data related to the pulse synchronization signal are read from the memory 13, and the captured acoustic data is divided into response waveforms for each discharge pulse current i (−i) with reference to the pulse synchronization signal.

The averaging process is as described above.

The obtained averaged response waveform or spectrum is stored in the memory 13 and displayed on the display device 16 as necessary, or / and is output to another calculation process shown in (a) to (d) below.

It should be noted that the data of the reference body having no internal defects is obtained in advance by the same procedure as described above and stored in the memory 13.

After that, the reference data (waveform of the reference elastic wave and its reference FFT spectrum) and the inspection data (waveform of the inspection elastic wave and its inspection FFT spectrum) are compared, and the following inspection data for the reference data ( B) Select one or more items shown in (d) to (d), compare the results of the selected items, extract the characteristic portion thereof, and estimate the presence or absence of the internal defect N of the inspection object 20. This is the same for any of the bonded body, laminated body, structure, and simple substance.
(A) Difference between the sound intensity appearing in the waveform of the reference elastic wave and the sound intensity appearing in the waveform of the elastic wave of the inspection object 20 (b) The elastic wave of the inspection object 20 with respect to the waveform of the reference elastic wave. Waveform time lag (c) Damped state of the waveform of the elastic wave of the inspection object 20 with respect to the waveform of the reference elastic wave (d) Frequency of the waveform of the elastic wave of the inspection object 20 with respect to the waveform of the reference elastic wave

Based on the above results (a) to (d) of the non-destructive inspection using this device, the presence or absence of the defect N of the inspection object 20, and the position and size of the defect N if any, are estimated. In the present invention, since a large amount of data can be obtained in a short time, a more accurate inspection result can be obtained by performing an average processing calculation.

1: Multiple pulse supply circuit, 2: Pulse coil, 3: Charging / discharging capacitor, 4: Cylister, 4a: Control device, 5: Inverting current diode, 10: DC high voltage power supply, 11: Sensor, 12: AD Conversion device, 13: Memory, 14: CPU, 15: Measurement and analysis unit, 16: Display device, 20: Inspection object, 20a: Highly conductive material, 20b: Non-conductive material, 20c: Low conductivity material, 21 : Inspection target part, 100: Current source, 200: Pulse coil, 300: Charging / discharging capacitor, 400: Switch, 400a: Control device, 500: Diode, 600: Inspection target, 700: Sensor, D: Elastic wave, H: Gap (height), K: Defect width, L: Spacing, N: Defect, U: Vortex current i: Forward discharge current (pulse current), -i: Reverse discharge current (pulse current)

Claims (5)

A pulse coil that generates an eddy current at the inspection target site of the inspection target,
A multi-shot pulse supply circuit that supplies discharge currents in the forward direction and the reverse direction following the pulse coil at predetermined intervals, and
A sensor that is separated from the pulse coil and placed in contact with or close to the inspection object to record elastic waves caused by the eddy current and convert them into electrical signals.
In a multi-pulse electromagnetic force acoustic diagnostic apparatus composed of a measurement analysis unit that analyzes an output electric signal from the sensor and outputs data for estimating the presence or absence of internal defects in the inspection object.
The multiple pulse supply circuit
A charging / discharging capacitor connected to the pulse coil and intermittently supplying the charged charge to the pulse coil multiple times as a discharge current in the forward direction and the subsequent reverse direction.
It is connected between the pulse coil and the charge / discharge capacitor, the forward discharge current is passed through the pulse coil by inputting a gate signal, and the forward discharge current that has passed through the pulse coil is charged / discharged. A thyristor that charges the capacitor with the opposite polarity,
A discharge current in the reverse direction is passed through the pulse coil from the charge / discharge capacitor which is connected in antiparallel to the thyristor and charged in the opposite polarity, and the discharge current in the reverse direction that has passed through the pulse coil is passed through the pulse coil. Inverted current capacitor that charges positively
A multi-shot pulse electromagnetic force acoustic diagnostic apparatus comprising a DC high-voltage power supply connected to the charging / discharging capacitor and charging the charging / discharging capacitor. The measurement analysis department
An AD conversion device that AD-converts and digitizes the acoustic analog signal from the sensor and outputs this acoustic digital data,
A CPU that numerically analyzes the acoustic digital data in order to nondestructively estimate the presence or absence of defects in the inspection object.
Equipped with a memory for storing acoustic digital data and numerically analyzed data
The CPU performs a process of separating a response waveform for each pulse magnetic field from the captured acoustic digital data, a process of adding a plurality of separated response waveforms, dividing by the number of pulses and averaging, and obtains the averaged response waveform. The multi-pulse electromagnetic force acoustic diagnostic apparatus according to claim 1, wherein the device has a function of outputting. The multi-pulse electromagnetic force acoustic diagnostic apparatus according to claim 2, wherein the averaged response waveform is subjected to a Fourier transform process and the averaged Fourier transform result is output. The CPU replaces the addition of the separated response waveforms and the averaging process of dividing by the number of pulses, which is performed after the process of separating the response waveforms for each pulse magnetic field from the captured acoustic digital data.
It is characterized by performing a Fourier transform process on a plurality of separated response waveforms, adding a plurality of Fourier transform results, dividing by the number of pulses and averaging, and outputting the averaged Fourier transform result. The multi-pulse electromagnetic force acoustic diagnostic apparatus according to claim 2. The multi-pulse electromagnetic force acoustic diagnostic apparatus according to any one of claims 1 to 4, wherein the gate signal to the thyristor is a signal for processing to separate a response waveform for each pulse magnetic field from the captured acoustic digital data. ..

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