JP2002116112A - Nondestructive inspection method and nondestructive inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nondestructive inspection device having a simple structure and capable of accurately measuring. SOLUTION: A sine wave oscillator 1 is arranged for generating a sine wave signal having a frequency continuously changing in a prescribed frequency range, and while the sine wave signal from this sine wave oscillator 1 is transduced into mechanical vibration and is impressed on an inspection object tile 10, mechanical vibration generated by the inspection object tile 10 is detected at a point separate from the impressing point, the detected mechanical vibration is transduced into an electric signal, the transduced electric signal and the sine wave signal from the sine wave oscillator 1 are multiplied together, and a defect of the inspection object tile 10 is detected on the basis of the electric signal obtained thereby.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-destructive inspection method and a non-destructive inspection apparatus for non-destructively detecting a peeling of a tile used on a wall surface of a building or a defect of concrete of the building.

[0002]

2. Description of the Related Art Conventionally, there has been a long-awaited need for a method of detecting in advance an accident in which a tile used on a wall surface of a building is peeled and dropped due to a change over time or the like. Japanese Patent Application Laid-Open No. 2000-131290 and Japanese Patent Application Laid-Open No. 2000-131290.

Japanese Patent Application Laid-Open No. 07-209262 discloses a method of hitting an object to be inspected with a hammer, converting the hitting sound at that time into a digital signal, and analyzing the digital signal with a computer.

More specifically, an object to be inspected is hit with a hitting means such as a hammer, and a crest factor is calculated from a reflection sound obtained at that time. When the crest factor is equal to or more than a first predetermined value, the object to be inspected is The object is determined to be sound, and when the crest factor is less than the first predetermined value, the expected frequency is calculated from the reflected sound, and the deviation between the expected frequency and the expected frequency of the sound defendant inspection object is smaller than the second predetermined value. Sometimes, it is determined that the inspected object is sound, and when the deviation is equal to or greater than the second predetermined value, it is determined that the inspected object is defective.

In Japanese Patent Application Laid-Open No. 2000-131290,
A method of analyzing the frequency of an impact sound using a plurality of bandpass filters is disclosed.

More specifically, an external force when an external force is applied to the object to be inspected by a hammer to generate a tapping sound is detected by an excitation force sensor, and a ratio between the result and an external force reference value is obtained. The tapping sound generated from the object to be inspected is detected by a microphone, the result is separated into a time-series signal for each frequency by a band-pass filter, further rectified, and a peak hold is applied to the instantaneous maximum in each frequency band. Extract the value. The maximum value is corrected based on the ratio calculated earlier, and the comparator compares the vibration value with a preset vibration reference value to output a comparison result signal when the value deviates from a predetermined relationship. However, if there are three or more, an alarm is issued. That is, the maximum value of the time-series signal for each of a plurality of frequency bands is extracted and compared.

On the other hand, there is an apparatus in which an object to be inspected is hit using a vibrator instead of hitting with a hammer. For example, in Japanese Unexamined Patent Application Publication No. 59-94062, a vibrator is driven by an alternating current generated by an oscillator to strike an object to be inspected.
In the device disclosed in this publication, a vibration having a continuously changing frequency is applied to an object to be inspected by a vibrator, and a resonance point at the natural frequency is measured by a vibrator.

[0008]

The conventional nondestructive inspection method has the following problems. In other words, the main test is a sensitivity test, in which the inspector strikes the tile surface with a hammer or the like and determines the difference in the sound at that time.However, in this method, quantitative judgment is difficult due to individual differences and skills of the inspector, and The accuracy and reproducibility were incomplete.

There have been some attempts to mechanically and electrically process this determination, but all of them have required a large-sized apparatus or an expensive measuring instrument. For example, JP-A-07-
The method disclosed in Japanese Patent Publication No. 209262 requires an apparatus and a computer for hitting a tile to be inspected with a hammer and processing the hitting sound with a computer. In the method disclosed in Japanese Patent Application Laid-Open No. 2000-131290, the structure is complicated because a plurality of band-pass filters are prepared for analyzing the frequency. Also,
Since the hammering sound is collected by a microphone, accurate measurement cannot be performed if there is another noise source that causes noise.

In the method disclosed in Japanese Patent Application Laid-Open No. 59-94062, an object to be inspected is vibrated and only the resonance frequency at that time is measured. Otherwise, it is difficult to make a more accurate determination, and extra inspection costs such as labor costs are required.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a nondestructive inspection method and a nondestructive inspection apparatus which have a simple structure and can perform accurate measurement.

[0012]

According to the non-destructive inspection method of the present invention, a sine wave signal whose frequency changes with time in a predetermined range is generated, and this sine wave signal is converted into mechanical vibration to be applied to the object. The mechanical vibration generated in the inspection object is detected at a point separated from the application point of the mechanical vibration while being applied to the inspection object, and the detected mechanical vibration is converted into an electric signal, and further converted into an electric signal. And the sine wave signal, and detecting a defect of the inspection object based on an electric signal obtained thereby.

According to this method, since the sine wave signal is used and the excitation signal and the reception signal are multiplied,
Defect detection processing is simplified, and highly accurate measurement is possible.

The nondestructive inspection apparatus according to the present invention comprises: a vibration signal generating means for repeatedly generating a sine wave signal whose frequency changes with time in a predetermined range; and a sine wave generated by the vibration signal generation. Mechanical vibration applying means for converting a signal into mechanical vibration and applying the same to the object to be inspected, and detecting mechanical vibration generated in the object to be inspected at a point separated from the point of application of the mechanical vibration, Mechanical vibration detecting means for outputting an electric signal corresponding to the detected value; multiplying a sine wave signal generated by the excitation signal generating means by a detection signal detected by the mechanical vibration detecting means; Signal multiplying means for outputting the result.

According to this configuration, since a sine wave signal is used, the defect detection processing is simplified, the apparatus can be simplified, and highly accurate measurement can be performed.

The nondestructive inspection apparatus of the present invention is the above nondestructive inspection apparatus, further comprising frequency range switching means for switching a frequency range, wherein the excitation signal generating means is switched by the frequency range switching means. A sine wave signal is repeatedly generated in a frequency band of the range.

According to this configuration, the frequency range in which the sine wave signal is changed can be arbitrarily changed, so that the optimum frequency range for the measurement is selected in accordance with the physical characteristics such as the structure and the material of the inspection object. This allows for more accurate measurements.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a nondestructive inspection device according to one embodiment of the present invention. In this figure, the nondestructive inspection device according to the present embodiment includes a sine wave oscillator 1, first and second amplifiers 2, 3, a multiplier 4, and a piezoelectric speaker 5 for excitation.
, A receiving piezoelectric speaker 6 and a low-pass filter 7.

The sine wave oscillator 1 repeatedly generates a sine wave signal whose frequency continuously changes in a predetermined frequency range (for example, 1 kHz to 20 kHz). First amplifier 2
Amplifies the sine-wave signal from the sine-wave oscillator 1 to a level at which the vibration piezoelectric speaker 6 can be driven.
Output as r. The second amplifier 3 amplifies the sine wave signal from the receiving piezoelectric speaker 5 to a level usable by the multiplier 4, and outputs the amplified signal as a received signal Vi. The multiplier 4 multiplies the excitation signal Vr from the first amplifier 2 by the received signal Vi from the second amplifier 3 and outputs the result.

The vibrating piezoelectric speaker 5 includes a first amplifier 2
Is converted into mechanical vibration and applied to the tile to be inspected (object to be inspected) 10. The receiving piezoelectric speaker 6 uses a piezoelectric element, and converts a mechanical signal into an electric signal and outputs it. The excitation piezoelectric speaker 5 and the reception piezoelectric speaker 5 are spaced apart from each other on the inspection target tile 10. The low-pass filter 7 removes cos (2ωt + α + β) from the output signal from the multiplier 4 as described below.

In such a configuration, the sine wave oscillator 1
Is amplified by the first amplifier 2 and output as the excitation signal Vr to the excitation piezoelectric speaker 5, and mechanical vibration is applied to the tile 10 to be inspected.
The excitation signal Vr is also output to the multiplier 4. When a mechanical vibration is applied to the inspection tile 10, the vibration is received by the receiving piezoelectric speaker 6, and a signal having a level corresponding to the magnitude of the vibration at that time is output to the second amplifier 3. You. Then, the signal is amplified by the second amplifier 3 to obtain the received signal Vi. The received signal Vi is multiplied by the excitation signal Vr from the first amplifier 2 by the multiplier 4. Then, the output of the multiplier 4 is sent to the low-pass filter 7, and the low-pass filter 7 outputs cos (2ωt + α + β).
The component is removed to obtain the output voltage Vo.

This output voltage Vo is a signal reflecting the amplitude and phase of the received signal Vi with respect to the frequency change of the excitation signal Vr. Therefore, this output voltage Vo is equal to the tile 1 to be inspected.
This indicates a simple frequency characteristic of 0. Since the frequency characteristics of the normal tile and the peeled tile are greatly different, the peeled tile can be easily distinguished.

The above operation principle can be expressed as follows using mathematical expressions. Vr = sin (ωt + α) Vi = sin (ωt + β) where ωt is a frequency and α and β are phase shifts. Vr × Vi = sin (ωt + α) × sin (ωt + β) = １ ／ [cos (β−α) −cos (2ωt + α + β)] (1)

The cos (β-α) part in the above equation (1) is
This is a DC component that changes according to the phase difference, and includes the amplitude component of the received signal Vi. Also, cos (2ωt
+ Α + β) represents the original vibration signal Vr and the received signal Vr.
This is a signal having a frequency twice as high as i. Since the information on the required frequency characteristics is the amplitude (magnitude) of the received signal Vi,
Only cos (β-α) in the equation (1) is sufficient. Therefore,
After passing through the low-pass filter 7, cos (2ωt + α +
The component of β) may be removed. In this way, the frequency characteristics appear in the output voltage Vo in the form of a voltage.

FIG. 2 is a diagram showing waveforms of the output voltage Vo of a normal tile and a tile having a peeled portion. In this case, (a) is an output voltage waveform in a normal tile, and (b) is an output voltage waveform in a tile having a peeled portion. Normal tiles are in contact with the entire surface of the building, so the excited energy is absorbed and does not return much to the receiving side.However, the tiles that have peeled off are only partially in contact with the building. The exfoliated portion does not absorb the excited energy, and the frequency characteristics of the vibration of the tile itself can be observed. Therefore, the output voltage Vo
By observing the difference in the frequency characteristics appearing in the above, it is possible to determine the separation of the tile.

As described above, according to the nondestructive inspection apparatus of the present embodiment, the excitation signal Vr of a sine wave whose frequency continuously changes is used for excitation of the tile 10 to be inspected.
Normal tiles and peeled tiles can be distinguished with simple processing and high accuracy. Also, by multiplying the excitation signal Vr and the reception signal Vi, noise components unrelated to the excitation signal Vr can be removed from the reception signal Vi, and highly accurate measurement can be performed by simple signal processing. Further, since the processing is simple, the apparatus can be simplified. In particular, since the amplifiers, multipliers, and the like to be used can be easily realized with inexpensive semiconductors currently on the market, they can be manufactured at low cost. In addition, since it is not necessary to measure a large number of basic data, it is possible to reduce labor costs and the like.

In the above embodiment, a sine wave in a single frequency range is used. However, a frequency range switch (not shown) for switching the frequency range is provided to select a sine wave in a plurality of frequency ranges. You may make it selectable. In this case, the sine wave oscillator 1 has a function of repeatedly generating a sine wave signal in the frequency band of the range switched by the frequency range switch. In this way, by enabling sine waves in a plurality of frequency ranges to be selected alternatively,
An optimum frequency range for measurement can be selected according to physical characteristics such as the structure and material of the tile 10 to be inspected, thereby enabling more accurate measurement.

Further, in the above embodiment, the detection of the peeling tile has been described. However, it is needless to say that the defect of the concrete can be detected. .

[0029]

As described above, according to the present invention,
Since a sine wave excitation signal is used to excite the object to be inspected, it is possible to provide a nondestructive inspection apparatus that has a simple structure and can perform accurate measurement.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a nondestructive inspection device according to an embodiment of the present invention.

FIGS. 2A and 2B are diagrams showing an example of a measurement result by the nondestructive inspection device of FIG. 1; FIG. 2A is an output voltage waveform diagram of a normal tile; FIG. is there.

[Explanation of symbols]

 Reference Signs List 1 sine wave oscillator 2, 3 amplifier 4 analog multiplier 5 piezoelectric speaker for excitation 6 piezoelectric speaker for reception 7 low-pass filter 10 tile to be inspected

Claims (3)

[Claims] 1. A sine wave signal whose frequency changes with time in a predetermined range is generated, and the sine wave signal is converted into mechanical vibration and applied to an object to be inspected, while applying the mechanical vibration. A mechanical vibration generated in the object to be inspected at a point away from the point is detected, the detected mechanical vibration is converted into an electric signal, and the converted electric signal is multiplied by the sine wave signal. A non-destructive inspection method, wherein a defect of the inspection object is detected based on an electrical signal obtained. 2. A vibration signal generating means for repeatedly generating a sine wave signal whose frequency changes with time in a predetermined range, and converting the sine wave signal generated by the vibration signal generation into mechanical vibration. Mechanical vibration applying means for applying to the object to be inspected, and detecting mechanical vibration generated in the object to be inspected at a point separated from the point of application of the mechanical vibration, and generating electricity corresponding to the detected value. A mechanical vibration detecting means for outputting a signal, a signal for multiplying a sine wave signal generated by the excitation signal generating means and a detection signal detected by the mechanical vibration detecting means, and outputting a result thereof A non-destructive inspection device, comprising: multiplication means. 3. A frequency range switching means for switching a frequency range, wherein the excitation signal generating means repeatedly generates a sine wave signal in a frequency band of the range switched by the frequency range switching means. Claim 2
Non-destructive inspection equipment.