JP4056224B2 - Nondestructive inspection method and nondestructive inspection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a nondestructive inspection method and a nondestructive inspection device for nondestructively detecting peeling of tiles used on a wall surface of a building or a defect of concrete in a building.
[0002]
[Prior art]
Conventionally, there has been a strong demand for a method for detecting in advance the danger that a tile used for a wall of a building will be peeled and dropped due to changes over time. For example, Japanese Patent Application Laid-Open No. 07-209262 and There are some which are indicated by JP, 2000-131290, A.
[0003]
Japanese Patent Application Laid-Open No. 07-209262 discloses a method in which an object to be inspected is hit with a hammer, and the hitting sound at that time is converted into a digital signal and analyzed by a computer.
[0004]
More specifically, the object to be inspected is hit with a hammer or other hitting means, the crest factor is calculated from the reflected sound obtained at that time, and the object to be inspected is healthy when the crest factor is equal to or greater than a first predetermined value When the crest factor is less than the first predetermined value, the expected frequency is calculated from the reflected sound. When the deviation between the expected frequency and the expected frequency of the sound object to be inspected is smaller than the second predetermined value, the target frequency is calculated. The inspection object is determined to be healthy, and when the deviation is greater than or equal to a second predetermined value, it is determined that the inspection object is defective.
[0005]
Japanese Patent Application Laid-Open No. 2000-131290 discloses a method of analyzing the frequency of impact sound using a plurality of bandpass filters.
[0006]
More specifically, the external force when an external force is applied to the object to be inspected with a hammer to generate a hitting sound is detected by an excitation force sensor, and the ratio between the result and the external force reference value is obtained while the object to be inspected is detected. The sound generated by an object is detected by a microphone, and the result is separated into time-series signals for each frequency by a bandpass filter, and further rectified to extract the instantaneous maximum value in each frequency band by peak hold. To do. The maximum value is corrected based on the ratio calculated earlier, and compared with the vibration reference value set in advance in the comparator, when the result is out of the predetermined relationship, a comparison result signal is issued, and the alarm device counts the number of comparison result signals. However, for example, when there are three or more, an alarm is given. The maximum value of the time series signal for each of a plurality of frequency bands is extracted and compared.
[0007]
On the other hand, there is one in which an object to be inspected is hit using a vibrator instead of hitting with a hammer. For example, in the one disclosed in Japanese Patent Application Laid-Open No. 59-94062, an object to be inspected is hit by driving an exciter with an alternating current generated by an oscillator. In the apparatus disclosed in this publication, a vibration having a continuously changing frequency is applied to an object to be inspected by a vibration exciter, and a resonance point at the natural frequency is measured by a vibration sensor.
[0008]
[Problems to be solved by the invention]
By the way, the conventional nondestructive inspection method has the following problems. In other words, an inspector hits the tile surface with a hammer or the like, and the sensory test is mainly used to determine the difference in the hitting sound at that time, but this method makes quantitative determination difficult due to individual differences and skills of the inspector. It was incomplete in terms of accuracy and reproducibility.
[0009]
In addition, there are some attempts to mechanically and electrically process this determination, but all of them require a large-sized apparatus or an expensive measuring instrument. For example, the method disclosed in Japanese Patent Application Laid-Open No. 07-209262 requires a device and a computer for hitting a tile to be inspected with a hammer and for processing the hitting sound with a computer. Further, in the method disclosed in Japanese Patent Laid-Open No. 2000-131290, the structure is complicated because a plurality of bandpass filters are prepared in order to analyze the frequency. In addition, since the hammering sound is collected by a microphone, accurate measurement cannot be performed if there are other noise sources.
[0010]
In the method disclosed in Japanese Patent Application Laid-Open No. 59-94062, the object to be inspected is vibrated and only the resonance frequency at that time is measured. Therefore, it is difficult to make a more accurate determination, and this requires extra expenses such as labor costs.
[0011]
The present invention has been made in view of such circumstances, and an object of the present invention is to provide a nondestructive inspection method and a nondestructive inspection apparatus capable of measuring with a simple structure and high accuracy.
[0012]
[Means for solving the problems]
The nondestructive inspection method of the present invention generates a sine wave signal whose frequency changes with time in a predetermined range, converts the sine wave signal into mechanical vibration, and applies it to tile or concrete, while the machine Obtained by detecting mechanical vibration generated in the tile or concrete at a point separated from the point where the mechanical vibration is applied, converting the detected mechanical vibration into an electric signal, and multiplying it with the sine wave signal. The level of the electric signal is compared with a threshold value which is gradually increased every time the sine wave signal is repeatedly generated, and the degree of peeling of the tile or the defect of the concrete is determined.
[0013]
According to this method, a sine wave signal whose frequency changes over time within a predetermined range is used as the excitation signal, and reception in which the frequency changes over time within a predetermined range similarly to this sine wave signal. Multiplying the signal and comparing the resulting electrical signal level with a predetermined threshold to determine the presence of tile flaking or concrete defects, simplifying the tile or concrete defect detection process, and Highly accurate measurement is possible for tiles or concrete . In particular, the degree of deterioration of the tile or concrete can be determined by changing the threshold value .
[ 0014 ]
The nondestructive inspection apparatus of the present invention includes an excitation signal generating means for repeatedly generating a sine wave signal whose frequency changes with time within a predetermined range, and a sine wave signal generated by the excitation signal generating means. a mechanical vibration applying means for applying a tile or concrete is converted into mechanical vibration by detecting the mechanical vibration generated by the tile or concrete at a point remote from the point of applying the mechanical vibration, the detected value A mechanical vibration detecting means for outputting an electrical signal according to the frequency, and a result obtained by multiplying the sine wave signal generated by the excitation signal generating means by the detection signal detected by the mechanical vibration detecting means. a signal multiplying means for outputting, the pressure and the threshold switching means mutabilis signal generating means changes the threshold value of each repeatedly generates a sine wave, the output value with a threshold value changed by said threshold switching means of said signal multiplier means And comparing and determining means for determining the extent of defects of the release or the concrete of the tile by comparing, notification of outputting an alarm when the comparison and determination means determines that there is a defect of peeling or the concrete of the tile And means for comparing.
[ 0015 ]
According to this configuration, a sine wave signal whose frequency changes over time in a predetermined range is used as the excitation signal, and reception in which the frequency changes over time in the predetermined range as with this sine wave signal. Multiply the signal and compare the resulting electrical signal level with a predetermined threshold to determine the presence or absence of tile flaking or concrete defects, simplifying the tile flaking or concrete defect detection process. In addition to simplifying the device, it is possible to perform highly accurate measurements on tiles or concrete . In particular, by changing the threshold value, the degree of tile peeling or concrete defects can be determined.
[ 0016 ]
The nondestructive inspection apparatus of the present invention comprises a frequency range switching means for switching a frequency range in the nondestructive inspection apparatus, and the excitation signal generating means has a frequency in a range switched by the frequency range switching means. A sine wave signal is repeatedly generated in the band.
[ 0017 ]
According to this configuration, since the frequency range for changing the sine wave signal can be arbitrarily changed, the optimum frequency range for measurement can be selected according to physical characteristics such as the structure or material of the tile or concrete , This allows for more accurate measurements on tiles or concrete .
[ 0018 ]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the nondestructive inspection apparatus according to the first embodiment of the present invention. In this figure, the nondestructive inspection apparatus according to the present embodiment includes a sine wave oscillator 1, first and second amplifiers 2, 3, an analog multiplier 4, a vibrating piezoelectric speaker 5, and a receiving device. A piezoelectric speaker 6, a low-pass filter 7, a comparator 8, an alarm output unit 9, and a speaker 10 are configured.
[ 0019 ]
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). The first amplifier 2 amplifies the sine wave signal from the sine wave oscillator 1 to a level at which the excitation piezoelectric speaker 5 can be driven and outputs it as the excitation signal Vr. The second amplifier 3 amplifies the sine wave signal from the reception piezoelectric speaker 6 to a level that can be used by the analog multiplier 4 and outputs the amplified signal as a reception signal Vi. The analog multiplier 4 multiplies the excitation signal Vr from the first amplifier 2 and the reception signal Vi from the second amplifier 3 and outputs the result.
[ 0020 ]
The excitation piezoelectric speaker 5 converts the excitation signal Vr from the first amplifier 2 into mechanical vibration and applies it to the tile 11 to be inspected . The receiving piezoelectric speaker 6 uses a piezoelectric element, converts a mechanical signal into an electric signal, and outputs it. The vibrating piezoelectric speaker 5 and the receiving piezoelectric speaker 6 are spaced apart from each other on the tile 11 to be inspected. The low-pass filter 7 outputs a signal (voltage Vo) obtained by removing cos (2ωt + α + β) described below from the output signal from the analog multiplier 4.
[ 0021 ]
The comparator 8 compares the output voltage Vo from the low-pass filter 7 with a predetermined threshold value (reference voltage Vref). In this case, the output of the comparator 8 becomes H level when the output voltage Vo exceeds the threshold value. The alarm output unit 9 monitors the output of the comparator 8 and outputs an audio signal for sounding an alarm sound from the speaker 10 when it is detected that the level has become H level.
[ 0022 ]
In such a configuration, the sine wave signal generated by the sine wave oscillator 1 is amplified by the first amplifier 2 and output to the oscillating piezoelectric speaker 5 as the oscillating signal Vr. Mechanical vibration is applied to the. The excitation signal Vr is also output to the analog multiplier 4. When mechanical vibration is applied to the tile 11 to be inspected, 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. The Then, it is amplified by the second amplifier 3 to obtain a reception signal Vi, and this reception signal Vi and the excitation signal Vr from the first amplifier 2 are multiplied by the analog multiplier 4. Then, the cos (2ωt + α + β) component is removed from the output of the analog multiplier 4 by the low-pass filter 7 to obtain the output voltage Vo.
[ 0023 ]
The output voltage Vo from the low-pass filter 7 is compared with a predetermined threshold value by the comparator 8, and when the threshold voltage is exceeded, an alarm signal is output from the alarm output unit 9 and an alarm sound is output from the speaker 19. Is done.
[ 0024 ]
Here, the output voltage Vo from the low-pass filter 7 is a signal reflecting the amplitude and phase of the reception signal Vi with respect to the frequency change of the excitation signal Vr. Therefore, this output voltage Vo represents a simple frequency characteristic of the tile 11 to be inspected. Since the frequency characteristics of the normal tile and the peeled tile are greatly different, it is possible to easily distinguish the peeled tile.
[ 0025 ]
The above operation principle is expressed as follows using mathematical formulas.
Vr = sin (ωt + α)
Vi = sin (ωt + β)
Where ωt is the frequency and α and β are the phase shifts.
Vr × Vi = sin (ωt + α) × sin (ωt + β)
= 1/2 [cos (β−α) −cos (2ωt + α + β)] (1)
[ 0026 ]
The cos (β−α) portion of the expression (1) is a direct current component that changes in accordance with the phase difference, and includes the amplitude component of the reception signal Vi. The portion of cos (2ωt + α + β) is a signal having a frequency twice that of the original excitation signal Vr and the reception signal Vi. Since the required frequency characteristic information is the amplitude (magnitude) of the received signal Vi, only cos (β−α) in the equation (1) is sufficient. Therefore, the component of cos (2ωt + α + β) may be removed by passing through the low-pass filter 7. In this way, frequency characteristics appear in the form of voltage in the output voltage Vo.
[ 0027 ]
Here, FIG. 2 is a diagram showing a waveform of the output voltage Vo of a normal tile and a tile having a peeling 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 full contact with the building, so the excited energy is absorbed and does not return to the receiver side very much, but only a part of the tiles with peeled parts are in contact with the building. Therefore, the peeled portion does not absorb the excited energy, and the frequency characteristics of the vibration of the tile itself can be observed. Therefore, it is possible to determine the separation of tiles by observing the difference in frequency characteristics appearing in the output voltage Vo.
[ 0028 ]
As described above, according to the nondestructive inspection apparatus of the present embodiment, the sinusoidal excitation signal Vr whose frequency continuously changes is used for the excitation of the tile 11 to be inspected. In addition, the normal tile and the peeled tile can be distinguished with high accuracy. Further, 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 high-precision measurement can be performed with simple signal processing. Furthermore, since the process is simple, the apparatus can be simplified. In particular, amplifiers and analog multipliers to be used can be easily realized with inexpensive semiconductors currently on the market, and can be manufactured at low cost. In addition, since it is not necessary to measure a large amount of basic data, labor costs can be saved.
[ 0029 ]
FIG. 3 is a block diagram showing a configuration of a nondestructive inspection apparatus according to the second embodiment of the present invention. In this figure, parts common to those in FIG. The nondestructive inspection apparatus according to the present embodiment includes a microcomputer (hereinafter referred to as a microcomputer) 12 and a display 13 instead of the alarm output unit 9 and the speaker 10 of the nondestructive inspection apparatus of the first embodiment.
[ 0030 ]
Each time a sine wave signal is repeatedly generated from the sine wave transmitter 1, the microcomputer 12 sequentially increases the threshold value, that is, the reference voltage Vref given to the comparator 8, and detects the peak value of the output voltage Vo. . After the peak value is detected, the degree of peeling of the inspection tile 11 with respect to the peak value is displayed on the display 13. For example, the degree of peeling is divided from “0”, which is not at all, to “10”, which is completely peeled off, and the numerical value is displayed on the display unit 13 or the display unit 13 is composed of 10 light emitting diodes. The number of light emitting diodes is made to emit light in accordance with the degree of.
[ 0031 ]
The method of detecting the peak value by changing the threshold value Vref using the microcomputer 12 is to separate the time series signal for each frequency by a band pass filter, and further rectify and instantaneously in each frequency band by peak hold. Compared with the method of extracting the maximum value, the cost can be significantly reduced. As in the first embodiment, a threshold value that can be estimated as defective may be determined, and an alarm may be output when the threshold value is exceeded.
[ 0032 ]
Here, FIG. 4 is a diagram showing an example of a measurement result in an actually manufactured nondestructive inspection apparatus, where (a) is an output voltage waveform diagram in a normal tile, and (b) is in a tile having a peeled portion. It is an output voltage waveform diagram. In the normal tile, the peak value is within approximately ± 2 (V), but in the peeled tile, the peak value is increased to ± 8 (V).
[ 0033 ]
FIG. 5 is a diagram showing an example of the result of measuring 10 tiles with the threshold value set to 4 (V), (a) is a peak voltage distribution diagram in a normal tile, and (b) is a diagram. It is a peak voltage distribution figure in the tile with a peeling part.
[ 0034 ]
FIG. 6 is a diagram showing an example in which six tiles are measured and each peak value is graphed. (A) is a graph showing the relationship between the adhesive strength and the + side peak voltage, and (b). These are graphs showing the relationship between the adhesive strength and the negative peak voltage. By taking this graph, the adhesive strength of the tile can be determined nondestructively.
[ 0035 ]
In the first and second embodiments, a sine wave having a single frequency range is used. However, a sine wave having a plurality of frequency ranges is provided by providing a frequency range switch (not shown) for switching the frequency range. May be selected alternatively. In this case, the sine wave oscillator 1 has a function of repeatedly generating a sine wave signal in the frequency band in the range switched by the frequency range switch. As described above, by selecting a sine wave having a plurality of frequency ranges, the optimum frequency range for measurement is selected in accordance with the physical characteristics such as the structure and material of the tile 11 to be inspected. This allows for more accurate measurements.
[0036]
In the first and second embodiments described above, the detection of the peeling tile has been described, but it is needless to say that the present invention can also detect a defect in concrete.
[ 0037 ]
【The invention's effect】
As described above, according to the present invention, a sine wave signal whose frequency changes over time within a predetermined range is used as a vibration signal for tiles or concrete , and a predetermined signal is provided in the same manner as the sine wave signal. Multiplying the received signal whose frequency changes over time in the range, and comparing the level of the electric signal obtained thereby with a predetermined threshold value, it is judged whether there is any tile peeling or concrete defect , so tile peeling Alternatively, it is possible to provide a non-destructive inspection method and apparatus capable of performing a measurement with a simple and accurate structure suitable for inspection of defects in concrete . In particular, the degree of peeling of the tile or the defect of the concrete can be determined by changing the threshold value for comparison.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a nondestructive inspection apparatus according to a first embodiment of the present invention.
2A and 2B are diagrams illustrating an example of measurement results obtained by the nondestructive inspection apparatus in FIG. 1, wherein FIG. 2A is an output voltage waveform diagram in a normal tile, and FIG. 2B is an output voltage waveform diagram in a tile having a peeled portion. is there.
FIG. 3 is a block diagram showing a configuration of a nondestructive inspection apparatus according to a second embodiment of the present invention.
4A and 4B are diagrams illustrating an example of a measurement result obtained by the nondestructive inspection apparatus in FIG. 3, in which FIG. 4A is an output voltage waveform diagram in a normal tile, and FIG. 4B is an output voltage waveform diagram in a tile having a peeled portion. is there.
5A and 5B are diagrams illustrating an example of measurement results obtained by the nondestructive inspection apparatus of FIG. 3, wherein FIG. 5A is a peak voltage distribution diagram in a normal tile, and FIG. 5B is a peak voltage distribution diagram in a tile having a peeled portion. is there.
6 is a diagram showing an example of measurement results obtained by the nondestructive inspection apparatus of FIG. 3, wherein (a) is a graph showing the relationship between the adhesive strength and the peak voltage characteristics (+ side) of each of a plurality of tiles; ) Is a graph showing the relationship between the adhesive strength of each of the plurality of tiles and the peak voltage characteristic (− side).
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Sinusoidal oscillator 2 1st amplifier 3 2nd amplifier 4 Analog multiplier 5 Piezoelectric speaker 6 for excitation 6 Piezoelectric speaker 7 for reception Low pass filter 8 Comparator 9 Alarm output part 10 Speaker 11 Tile to be examined 12 Microcomputer 13 Display

Claims (3)

A sine wave signal whose frequency changes over time in a predetermined range is generated, and the sine wave signal is converted into mechanical vibration and applied to the tile or concrete, while being separated from the point where the mechanical vibration is applied. Mechanical vibration generated in the tile or concrete at a point is detected, the detected mechanical vibration is converted into an electric signal and multiplied by the sine wave signal, and the level of the electric signal obtained thereby is determined as the sine wave signal. A non-destructive inspection method, wherein the degree of peeling of the tile or the degree of defect of the concrete is determined by comparing with a threshold value which is increased little by little each time the is repeatedly generated . A vibration signal generating means for repeatedly generating a sine wave signal whose frequency changes over time within a predetermined range, and a tile or a sine wave signal generated by the vibration signal generating means by converting it into mechanical vibration Mechanical vibration applying means for applying to the concrete, and mechanical vibration generated in the tile or concrete at a point separated from the point to which the mechanical vibration is applied, and an electric signal corresponding to the detected value is output. Mechanical vibration detecting means; signal multiplying means for multiplying the sine wave signal generated by the excitation signal generating means by the electrical signal detected by the mechanical vibration detecting means and outputting the result; The threshold value switching means that changes the threshold value every time the excitation signal generation means repeatedly generates a sine wave signal, and the output value of the signal multiplication means is compared with the threshold value changed by the threshold value switching means. Comparing / determining means for judging the degree of tile peeling or the concrete defect, and a notifying means for outputting an alarm when the comparing / judging means determines that the tile peeling or the concrete defect exists. A non-destructive inspection device characterized by The frequency range switching means for switching a frequency range is provided, and 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. The nondestructive inspection apparatus according to 2.

Images