JP3492217B2 - Non-destructive inspection equipment for welds - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for inspecting welds for cracks, slag inclusions and other defects, and more particularly to a non-destructive inspection apparatus for welds capable of improving inspection reliability.

[0002]

2. Description of the Related Art As a nondestructive inspection apparatus for a welded portion of a welded structure, a method using ultrasonic flaw detection or magnetic flaw detection is widely used. Further, as a tapping sound inspection device for inspecting the state of a target object by tapping sound, there is, for example, one disclosed in Japanese Patent Application Laid-Open No. 6-3336 for inspecting peeling of a tile on a wall. In this method, a striking device strikes a wall to which tiles are attached, detects a striking sound generated, converts the striking sound into an electric signal, and extracts a component of a predetermined frequency band related to diagnosis through a bandpass filter. It is checked whether or not the peak value of the extracted signal voltage in the AC state exceeds a predetermined reference value, and if it exceeds, a warning is output to the screen display device.

[0003]

As described above, when ultrasonic flaw detection is used, flat plate-shaped defects can be easily detected.
The ability to detect spherical defects such as blowholes is low. Further, in the magnetic flaw detection, the application target is limited to those having magnetism, and the magnetic powder must be used whether it is dry type or wet type, so that operability is poor. Further, in the conventional hammering sound inspection device, since the frequency of the maximum level of the frequency band in the sound pressure signal generated by striking, that is, the sound pressure of the frequency that is the main component is simply compared, the complex frequency is characterized. In the inspection of the tapping sound, it was not possible to detect the abnormality accurately when the characteristics of the abnormality appeared in frequencies other than the main component.

Further, since the maximum level in the frequency band is targeted for evaluation, it is not possible to distinguish between a sound pressure that is a characteristic of tapping, that is, a sound pressure that occurs momentarily and a sound pressure that has a long decay and a low level. was there. Because of these
Even if the above-described tapping sound inspection device is applied to the inspection of the welded portion, it is difficult to accurately detect the defect.

The present invention has been made to solve the above problems, and an object thereof is to obtain a non-destructive inspection device for a welded portion as follows. a. The reliability of the inspection can be improved by comparing the state of vibration generated by impact with the reference state. b. Inexpensive and high-speed processing is possible. c. It can be miniaturized and can flexibly respond to changing conditions.

D. It is possible to prevent the influence of variations in external force applied to the object. e. It is possible to prevent noise from the surroundings and the influence of noise.
As a further improvement, f. It is possible to know when an external force outside the proper range is given or when the input exceeds the proper range. g. The amplification factor of the amplifier can be easily set to an appropriate value. h. The vibration reference value can be set easily and accurately, and the reliability of the inspection can be improved.

[0007]

In order to achieve the above-mentioned object, in the nondestructive inspection apparatus for a welded portion according to the present invention, the vibration generated from the welded portion to which an external force is applied is detected as a vibration signal. Signal detecting means, a converting means for converting the vibration signal into a time series signal for each of a plurality of predetermined frequency bands, an extracting means for extracting the maximum value of the time series signal for each frequency band, and presetting each maximum value. The comparison means for comparing with the vibration reference value for each frequency band is provided. The vibration signal is converted into a time-series signal for each of multiple frequency bands, and the maximum value of each time-series signal is extracted, so that the frequency resolution of the vibration signal is improved and the maximum value of the time-series signal is detected with good sensitivity. Can be extracted. Therefore, it is possible to accurately grasp the characteristics of the loud sound or vibration immediately after the occurrence, which is also the characteristics of the impact, and perform the comparison.

Further, the conversion means is a plurality of bandpass filters that pass the frequency components of a predetermined frequency band of the vibration signal, and the extraction means rectifies the frequency components that have passed through the respective bandpass filters and each of the rectified frequency components. It is characterized in that the maximum value among the peak values is extracted as the maximum value. If the conversion means is a bandpass filter, the processing can be performed at high speed, and the device is simple and inexpensive. In particular, if an analog bandpass filter is used, the processing speed can be increased. A digital bandpass filter can be downsized and can flexibly respond to changing conditions. Further, since the extraction means extracts the maximum value from the rectified frequency component, it is possible to detect even when the negative sign portion of the vibration signal has the maximum value, and it is possible to accurately compare even when the vibration signal is rapidly attenuated.

Further, the converting means is a wavelet converting means for wavelet converting the vibration signal, and the extracting means is for extracting the maximum value for each frequency band based on the conversion result by the wavelet converting means. The wavelet transform means can improve the characteristics when separating into time series signals for each frequency band, and improve the reliability of inspection.

The transforming means is a short time fast Fourier transforming means for performing a short time fast Fourier transform of the vibration signal,
The extraction means is characterized by extracting the maximum value for each frequency band based on the conversion result by the short-time fast Fourier transform means. The use of short-time fast Fourier transform means improves the frequency resolution.

Further, external force detecting means for detecting the magnitude of the applied external force is provided, and at least one of the vibration signal, the time series signal, the maximum value and the vibration reference value is corrected according to the magnitude of the external force. It is characterized in that a correction means is provided. The correction is performed according to the magnitude of the external force to prevent the comparison by the comparing means from being influenced by the variation in the magnitude of the external force. Further, for example, by performing different correction depending on the external force for each frequency band, it is possible to compare with high reliability even an object in which the distribution of frequency components changes according to the applied external force.

Further, an external force detecting means for detecting the magnitude of the applied external force is provided, and at least one of a signal detecting means, a converting means, an extracting means and a comparing means when the magnitude of the external force exceeds a predetermined value. It is characterized in that a command means for commanding the start of the operation is provided. Since the operation is not started until a command is issued, there is no risk of erroneously processing ambient noise, vibration, noise, etc. when there is no command as a vibration signal. Therefore, the influence of these can be prevented and the reliability of the inspection is improved.

Further, an external force detecting means for detecting the magnitude of the applied external force as an external force signal is provided, and a ratio calculating means for obtaining a ratio obtained by dividing the external force signal by a preset external force reference value, and the above ratio. Correction means for changing the relationship between the maximum value and the vibration reference value in the comparison means by correcting at least one of the vibration signal, the time-series signal, the maximum value, and the vibration reference value, and the ratio is within a predetermined range. And a ratio inspecting unit for inspecting whether or not the ratio is within. The ratio calculating means inspects whether the ratio between the external force and the external force reference value is within a predetermined range, that is, whether the external force applied to the object, that is, the exciting force is too small or too large. Make sure that you have given an improper external force. If the excitation force is too small or too large, it is possible to prevent an erroneous inspection when the frequency characteristics of the vibration generated by the object are different. If you know that you have given an inappropriate external force, you can apply the external force again.
It can be operated without much nerve and the operability is improved.

Further, external force signal amplifying means for amplifying the external force signal and outputting it as an amplified external force signal and vibration signal amplifying means for amplifying the vibration signal and outputting it as an amplified vibration signal are provided, and the ratio calculating means is provided for amplifying the external force signal. A range over detection means for detecting that the crest value of at least one of the amplified external force signal and the amplified vibration signal exceeds a predetermined value is assumed to be used as the external force signal and the conversion means uses the amplified vibration signal as the vibration signal. It is characterized by being provided. In order to ensure the reliability of the measurement, it is detected that the amplified external force signal or the amplified vibration signal exceeds a predetermined value, that is, that a large signal that saturates the external force signal amplification means or the vibration signal amplification means is input. To do.

Further, it is characterized in that an amplification factor automatic setting means for automatically setting the amplification factor of at least one of the external force signal amplification means and the vibration signal amplification means is provided. The amplification factor can be easily set so that the amplified external force signal and the amplified vibration signal are in an appropriate output range, and the operability is improved. Further, it is possible to prevent the S / N ratio from being lowered and improve the reliability of the inspection.

The comparison means is characterized in that the comparison is made on the basis of a vibration reference value set based on a vibration signal generated when an external force is applied to the welded portion in a predetermined state. The vibration reference value can be easily set according to the condition of the welded portion, and the reliability of the inspection is enhanced.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1. An embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a block diagram of a nondestructive inspection device for welded portions. Reference numeral 1 is a welded portion of a steel structure, and 2 is a hammer that strikes the welded portion 1 to generate a hammering sound. Reference numeral 11 denotes an exciting force sensor which is attached to the hammer 2 and serves as an external force detecting means for converting an exciting force as an external force applied to the welded portion 1 into an electric signal. 12 is an exciting force sensor 11
An amplifier that amplifies the electric signal converted by the amplifier 13 is a rectifier that converts the signal amplified by the amplifier 12 into a direct current.

Reference numeral 14 is a peak hold for holding the maximum value of the DC signal output from the rectifier, and 15 is a ratio calculator for obtaining the ratio between the peak hold output and the external force reference value stored in the reference value setting device 16. . A trigger detector 17 detects a trigger from the DC signal output from the rectifier 13.

Reference numeral 19 is a ratio determiner for determining the ratio obtained by the ratio calculator 15. Reference numeral 20 is an automatic range setting device for automatically setting the amplification factor of the amplifier 12 from the maximum value output from the peak hold 14. Reference numeral 21 is a range over detector for detecting a range over from the maximum value output from the peak hold 14.

Reference numeral 3 denotes a microphone which is attached to the hammer 2 and serves as a signal detecting means for converting a tapping sound generated by a welded portion hit by the hammer into an electric signal. Reference numeral 4 denotes an amplifier for amplifying the electric signal converted by the microphone 3. Reference numeral 5 is an analog BPF as a conversion means for separating the signal obtained from the amplifier 4 for each frequency band. The analog BPF 5 covers 9 octaves of 31.25 Hz to 16 kHz so as to substantially cover the human audible range of 20 Hz to 20 kHz, and provides a total of 28 bands for giving a resolution of 1/3 octave.

Reference numeral 6 is a rectifier for rectifying a signal for each frequency band obtained from the analog BPF 5 and converting it into a direct current.
Reference numeral 7 is a peak hold serving as an extraction unit that holds the maximum value of the output from the rectifier 6, and 8 is a corrector that corrects the maximum value output by the peak hold 7 from the ratio obtained from the ratio calculator 15. 9 is the output of the compensator 8 and the reference value setting device 1
The comparator compares the sound pressure reference value as the vibration reference value stored in 0 with a predetermined method, that is, a predetermined comparison reference. Reference numeral 18 denotes an alarm device as a determination means that outputs an alarm when an overall inspection is performed based on the comparison result from each comparator 9 and it is inspected as abnormal.

Reference numeral 31 is a rectifier for converting the signal amplified by the amplifier 4 into direct current. Reference numeral 32 is a peak hold that holds the maximum value of the output from the rectifier 31, and 33 is an automatic range setting device that automatically sets the amplification factor of the amplifier 4 from the maximum value output from the peak hold 32. Reference numeral 34 is a range over detector that detects a range over from the maximum value output from the peak hold 32.

Next, the reference value setting mode for setting the external force reference value and the sound pressure reference value by the object serving as a reference for the operation, that is, the sound weld 1 having no defect will be described. It is confirmed by, for example, ultrasonic flaw detection and X-ray inspection that the welded portion 1 has no defects such as cracks and blow holes.

First, the amplification factors of the amplifier 4 and the amplifier 12 are minimized. In this state, the sound welded portion 1 is struck by the hammer 2, the generated impact sound is converted into an electric signal by the microphone 3, and the amplifier 4, the rectifier 31, the peak hold 32 are provided.
Then, the maximum value of the sound pressure signal that does not pass the analog BPF 5 is obtained.

This maximum value is input to the automatic range setting device 33 and the gain of the amplifier 4 is set so as to obtain an appropriate measurement range. Similarly, after the vibration generated on the hammer by impact is converted into an electric signal by the excitation force sensor 11, the maximum value of the vibration signal is obtained by the amplifier 12, the rectifier 13 (not passing through the analog BPF 5) and the peak hold 14. This maximum value Is input to the automatic range setting device 20, and the gain of the amplifier 12 is set so as to obtain an appropriate measurement range.

The appropriate measurement range is, for example, the correction based on the difference in exciting force as in this embodiment. If the range is 1/2 to 2 times, the maximum value is 2 compared with the reference value. Since it is necessary to accept double input, the signal level input in this reference value setting mode is 5
The gain is set to be 0%.

In this way, the amplification rates of both vibration and sound are set by the first first impact in the reference value setting mode.

Next, a hammer 2 strikes the sound welded portion 1 which is a reference object. At this time, the vibration generated in the hammer 2 is converted into an electric signal by the excitation force sensor 11, and the amplifier 12 gives the gain set by the first impact in the reference value setting mode. The amplified signal is converted into direct current by the rectifier 13. Trigger detector 1
Reference numeral 7 compares the DC signal from the rectifier 13 with a preset reference value, and outputs a trigger when the DC signal exceeds this reference value.

The peak hold 14 records the maximum value of the DC signal input from the rectifier 13. At this time, the operation of the peak hold 14 is started by the trigger signal from the trigger detector 17. Such recording of the maximum value is performed for a certain period of time until the vibration generated by the hammer due to the impact is attenuated to some extent, and thereafter the output from the peak hold 14 is stored in the reference value setting device 16 as the external force reference value.

Similarly, a sound wave generated by striking is converted into an electric signal by the microphone 3, and the amplifier 4 gives a gain set by the first striking in the first reference value setting mode. A plurality of the amplified sound pressure signals are provided and input to the analog BPF 5 which is set to pass different frequency bands, and separated into time series signals for each frequency band.

The time series signals separated for each frequency band by the analog BPF 5 are converted into DC signals by the rectifier 6 and input to the peak hold 7. The maximum value recording operation of the DC signal from the rectifier 6 of the peak hold 7 is performed by the trigger detector 7
Starting with the trigger signal from, the sound pressure attenuation of the object is performed for a certain period of time like the vibration peak hold 14. In this way, the instantaneous maximum value for each frequency band is recorded.

After the end of the fixed time until the sound pressure is attenuated, the maximum value recorded by the peak hold 7 for each frequency band is stored in the reference setter 10 as the sound pressure reference value. By the operation of the reference value setting mode, the reference value setting device 16 stores the external force reference value, which is information indicating the strength of impact,
The reference value setting device 10 stores a sound pressure reference value, which is information indicating an instantaneous maximum sound pressure in each frequency band of tapping.

Next, the inspection mode for inspecting the object will be described. First, the hammer 2 hits the welded portion 1 as the inspection object. At this time, as in the reference value setting mode, the vibration generated in the hammer 2 is converted into an electric signal by the excitation force sensor 11, amplified by the amplifier 12, and the rectifier 13 is used.
Is converted to direct current.

Similarly, the trigger detector 17 also performs trigger output from the DC signal from the rectifier 13, and the peak hold 14
Records the maximum value of the DC signal for a fixed time from the trigger output to vibration damping. In the case of the inspection mode, the maximum value recorded in the peak hold 14 is input to the ratio calculator 15 after a fixed time until the vibration damping, and the ratio calculator 15 sets the maximum value from the peak hold 14 and the reference value setter. The ratio with the external force reference value stored in 16 is calculated and output.

Similarly to the reference value setting mode, the sound wave generated by striking is converted into an electric signal by the microphone 3, amplified by the amplifier 4, separated by the analog BPF 5 into a time series signal for each frequency band, and rectified by the rectifier 6. It is converted into a DC signal and input to the peak hold 7. The peak hold 7 records the maximum value of the DC signal for a fixed time from the trigger output to the sound pressure attenuation.

In the inspection mode, the maximum value recorded by the peak hold 7 is input to the compensator 8 after a fixed time until the sound pressure is attenuated, and the compensator 8 selects an appropriate value from the ratio obtained from the ratio calculator 15. A correction value is calculated, and the maximum value obtained from the peak hold 7 is corrected by this correction value and output.

At this time, assuming that the correction of the vibration level and the sound pressure is performed in proportion, for example, when a ratio of twice the reference value is obtained by calculation, the maximum value recorded in the peak hold 7 is compared. Divide by a value of 2. In other words, if the excitation force in the inspection mode is doubled with respect to the excitation force in the reference value setting mode, the sound pressure generated in each frequency band is also doubled. Divide by 2 to convert the value into the excitation force in the reference value setting mode.

The maximum value thus corrected is compared by the comparator 9 with the sound pressure reference value stored in the reference value setting unit 10 based on a predetermined method or a predetermined comparison standard.
In this embodiment, a comparison result signal is output to the alarm device 18 when the corrected maximum value deviates from a predetermined relationship set in advance.

The predetermined relationship at this time means that, for example, in a certain band, when the corrected maximum value is within a range of, for example, 80% to 120% with respect to the sound pressure reference value of the band, it is normal. When it is out of the range, the comparison reference is set so that it is out of the range and a comparison result signal is output. Further, in another band, the comparison result signal is not output, assuming that the range of 70% to 110% is normal with respect to the sound pressure reference value of the band, and the comparison result signal is output when it is out of the range. Set the comparison standard.

Further, when the sound pressure reference value is smaller than the overall sound pressure, the comparison result signal should not be erroneously output in the frequency band which is not the main component by taking measures such as releasing the lower limit of the range. To do.

The alarm device 18 inputs the comparison result signal from the comparator 9 in each frequency band, and the determination standard is set so that it is determined to be abnormal when the number of comparison result signals exceeds a preset number, for example, two. When it is determined that there is an abnormality, an alarm is output to the outside.

The ratio determiner 19 outputs a correction range outside alarm when the ratio calculated by the ratio calculator 15 exceeds a predetermined relationship. The predetermined relationship at this time is set to, for example, 1/2 to 2 times. Then, when there is an input less than 1/2 or more than twice, an out-of-correction range alarm is output.

If the excitation force changes extremely, the frequency component of the generated sound changes greatly, which makes correction difficult. When the vibration force is extremely weak or extremely strong, as in the case of this weld inspection, a sound unrelated to the weld defect, which is the purpose of inspection, is generated and the reliability of the inspection is improved. It will be greatly reduced. However, by providing a range limitation for the correction by the excitation force in this way, it is possible to reliably inspect even an object in which the frequency characteristic of the hitting sound generated when the excitation force changes extremely, It is possible to prevent an erroneous inspection due to an extreme change in excitation force.

The correction is performed by correcting the relationship between the waveform analysis result and the sound pressure reference value, that is, the sound pressure reference value stored in the reference value setting unit 10 of the comparator 9 according to the magnitude of the vibration signal. The output of the amplifier 12 and each analog B
One or more of the output of the PF 5, the output of the rectifier 6, or the sound pressure reference value stored in the reference value setting device 10 may be corrected.

Further, when the magnitude of vibration detected by the exciting force sensor 11 exceeds a predetermined value, the peak hold 1
4. Since the peak hold 7 as the extraction means is provided with the trigger detector 17 for instructing the start of the operation, it is possible to reduce the influence of noise from the surroundings and improve the reliability of the inspection.

Although the trigger signal of the trigger detector 17 is given to the peak hold 7, the microphone 3, the amplifier 4, the analog BPF 5 as the converting means, the rectifier 6, the corrector 8 as the correcting means, and the comparing means. The same effect can be obtained even if the storage operation of the maximum value is started or the comparison operation is started by giving the same to the comparator 9 or the like.

In each of the reference value setting mode and the inspection mode, the range over detector 21 inputs the maximum value obtained from the peak hold 14 for the vibration signal, and when the maximum value exceeds the predetermined relationship, the range over is detected. Output an alarm. The range over detector 34 inputs the maximum value obtained from the peak hold 7 for a sound signal, and outputs a range over alarm when the measurement signal exceeds a predetermined relationship.

The predetermined relationship at this time is set, for example, as 99% of the measurement range. In this case, when a signal exceeding 99% is input, a range over alarm is output.

Further, by setting an appropriate measurement range in the first first impact in the reference value setting mode, the trouble of manually setting the measurement range is eliminated and the operability is improved. Furthermore, when setting manually, if the range is not appropriate, the S / N ratio will decrease and the reliability of the inspection will decrease, but this will not occur because the range is automatically set. Therefore, it is possible to obtain a hammering sound inspection device with improved inspection reliability.

Further, by outputting the range over alarm immediately before the input of each signal is saturated, it is possible to prevent the erroneous determination due to the saturation of the amplifier and to obtain the tapping sound inspection device with improved inspection reliability. Becomes Note that the inspection can be performed at high speed by using the analog BPF.

Embodiment 2. FIG. 2 is a configuration diagram of a nondestructive inspection device for a welded portion showing another embodiment of the present invention. In FIG. 2, the following points are different from those shown in FIG. 1, but other configurations are the same as those shown in FIG. The maximum value of the sound pressure extracted by the peak hold 7 for each frequency band is corrected by the corrector 8 and then input to the reference setting device 10, and the reference setting device 10 outputs the maximum value of the input maximum value. Obtain the average value for each frequency band and use this as the sound pressure reference value, and also find the range of variation of the maximum value,
The difference is that it has a function of determining a comparison standard based on the range of the variation.

Next, the operation will be described. First, a sound arbitrary welded portion 1 is hit with a hammer 2. At this time, the vibration generated in the hammer 2 is detected as an external force applied to the welded portion 1 by the excitation force sensor 11, converted into an electric signal, and the peak hold 14 extracts the maximum value. Peak hold 14
The maximum value extracted at is stored in the reference setter 16 as an external force reference value. At this time, the ratio calculator 15 outputs ratio 1. These are the same as those shown in the embodiment of FIG. The soundness of the welded portion 1 is confirmed by X-ray inspection, magnetic flaw detection, ultrasonic flaw detection, or the like, as described in the first embodiment.

On the other hand, the maximum value of the sound pressure signal extracted by the peak hold 7 passes through the corrector 8 as it is and is input to the reference setting device 10 because the ratio output from the ratio calculator 15 is 1. It is stored as a pressure reference value.

Next, the average value of the maximum values of the sound pressure signal is calculated and used as the sound pressure reference value. Also, the variation of the maximum value is obtained. Welding portions 1 whose soundness is not completely secured but which are considered to be sound and have no defects are selected at 100 locations along the welding portion and are hit to obtain 100 pieces of data. The maximum value of the sound pressure obtained for each hit, that is, the maximum value of each frequency band extracted by the peak hold 7 is corrected by the corrector 8 by the ratio calculated by the ratio calculator 15 each time, and the reference value is corrected. It is stored in the value setter 10. That is, if the ratio is 1.2, it is assumed that the external force applied this time is 1.2 times the external force when the external force reference value was stored in the reference setter 16 first, and divided by 1.2. Normalize. In this way, 100 pieces of data are obtained for each frequency band.

Then, the average value of the maximum values, the range of variation of the maximum values, and the standard deviation σ are obtained for each frequency band. Then, if there is data that exceeds three times the standard deviation σ, it is determined that there is a defect, this data is excluded, the average value of the maximum values is calculated again, and this is used as the sound pressure reference value, and the range of variation is calculated. . For example, in the frequency band number A1, the sound pressure reference value is set to 100 and 95 to 110, and in the frequency band number A2, from 90 to 105, the range of variation is obtained for all 28 bands. By doing so, it is possible to prevent the data having a defect in the welded portion from being incorporated into the sound pressure reference value or the comparison reference. In addition, when it is expected that there may be a case where the variation of the normal data obtained in the reference value setting mode may be exceeded, a margin of about ± 10% may be provided to prevent erroneous determination.

Then, the comparator 9 does not output the comparison result signal if it is within the variation range determined as described above, and if it exceeds this, the comparison reference is determined so that the comparison result signal is output to the alarm device 18.

Even if the alarm 18 is normal, there is a possibility that the alarm 18 may overflow from the data obtained from the 100 welds. Therefore, it is not inspected as abnormal by only issuing one comparison result signal. When 3 or more are inspected as abnormal, a judgment standard is set so that an alarm is issued.

As described above, the range of variation of the maximum value of the time-series signal for each frequency band of the vibration signal is obtained from a sufficient number of data by striking the welded portion which seems to be sound, and compared based on this. By doing so, if there is an appropriate defect in the welded part, an abnormality will appear somewhere in the above frequency band and protrude from the comparison reference, so that the defect can be reliably detected. The comparison standard set by the above method can be further corrected and learned by the data obtained in the actual inspection later.

Third Embodiment Although the analog BPF is used to obtain the maximum value for each frequency band in the first embodiment, a digital BPF may be used. In this embodiment, a case where a digital BPF is used will be described based on the configuration diagram of FIG. In FIG. 3, 51 is an A / D converter that converts an analog signal from the rectifier 13 into a digital signal, and 52 is an A / D converter that converts an analog signal from the amplifier 4 into a digital signal. 53 is an A / D converter 5
It is a maximum value calculator for calculating the maximum value of the output of 1.

Reference numeral 61 is a digital BPF as a conversion means for converting a digital signal into a time series signal for each frequency band. The digital BPF 61 has a frequency range of 31.25 to 16,000 Hz so as to substantially cover the human audible range of 20 to 20,000 Hz as in the embodiment of FIG.
A total of 28 bands are provided by targeting the octave and providing resolution for each 1/3 octave. Reference numeral 62 is a rectifier for rectifying the AC signal from the digital BPF, and 63 is a maximum value calculator as an extracting means for extracting the maximum value from the rectified digital signal.

Reference numeral 64 denotes a corrector, which corrects the maximum value output by the maximum value calculator 63 based on the ratio obtained from the ratio calculator 15 and outputs a correction value. Reference numeral 65 denotes a comparator, which compares the output of the corrector 64 with the sound pressure reference value stored in the reference value setting device 66 by a predetermined method. The rectifier 62, the peak hold circuit 63, the corrector 64, the comparator 65, and the reference value setter 66 are digital BPs provided for all 28 bands.
28 pieces are provided corresponding to each F61.

Reference numeral 41 is a maximum value calculator, which extracts the maximum value from the digital signal from the A / D converter 52 rectified by the rectifier 31. Since other configurations are the same as those shown in FIG. 1, corresponding components are designated by the same reference numerals and description thereof will be omitted.

Next, the operation will be described. First, a reference value setting mode for setting each reference value using a reference object will be described. The A / D converter 51 converts the analog DC signal from the rectifier 13 into a digital signal. At this time, the A / D converter 51 starts its operation in response to the trigger signal from the trigger detector 17, and continues for a certain period of time until the vibration generated by the hammer 2 is attenuated to a predetermined value or less. . The maximum value calculator 53 extracts the maximum value of the digital signal from the A / D converter 51, and this maximum value is stored in the reference value setter 16 as the external force reference value.

Similarly, the sound wave generated by striking is converted into an electric signal by the microphone 3, given an appropriate gain by the amplifier 4, and then converted into a digital signal by the A / D converter 52. At this time, the A / D converter 52 starts its operation in response to the trigger signal from the trigger detector 17, and operates for a certain period of time until the sound pressure generated by the impact of the object is attenuated to a predetermined value or less. This converted digital signal is
The signals are input to 28 digital BPFs 61 set to pass different frequency bands, and separated into time series signals for each frequency band.

The time series signals separated for each frequency band by the digital BPF 61 are converted into DC signals by the rectifier 62 and input to the maximum value calculator 63. Maximum value calculator 63
Extracts the maximum value of this DC signal and outputs the reference value setter 66.
To store. In this way, the instantaneous maximum value for each frequency band is extracted, and the reference value setter 66 is used as the sound pressure reference value.
Stored in.

By the operation of the reference value setting mode as described above, the reference value setting device 16 stores the external force reference value which is the information indicating the strength of the impact, and the reference value setting device 66 stores each frequency band of the tapping sound. A sound pressure reference value, which is information indicating the instantaneous maximum sound pressure at, is stored.

Next, the inspection mode for inspecting the object will be described. First, the welder 1 which is the object by the hammer 2
Hit. At this time, as in the reference value setting mode,
The vibration generated in the hammer 2 is converted into an electric signal by the exciting force sensor 11, amplified by the amplifier 12, and converted into direct current by the rectifier 13. Similarly, the trigger detector 17 also outputs a trigger signal from the DC signal from the rectifier 13, and the A / D converter 5
Reference numeral 1 converts a DC signal into a digital signal for a fixed time from trigger output to vibration damping. The maximum value calculator 53 extracts and outputs the maximum value of the digital signal.

In the inspection mode, the maximum value extracted by the maximum value calculator 53 is input to the ratio calculator 15, which calculates the maximum value and the external force reference value stored in the reference value setting device 16. And the ratio is calculated and output.

Similarly to the reference value setting mode, the sound wave generated by striking is converted into an electric signal by the microphone 3, amplified by the amplifier 4, and converted into a digital signal by the A / D converter 52. At this time, the operation of the A / D converter 52 is started by the trigger signal from the trigger detector 17, and is performed for a fixed time until the sound pressure is attenuated. The digital signal is separated into time series signals for each frequency band by the digital BPF 61, converted into a DC signal by the rectifier 62, and input to the maximum value calculator 63. The maximum value calculator 63 extracts and outputs the maximum value of the DC signal.

In the inspection mode, the maximum value extracted by the maximum value calculator 63 is input to the corrector 64 and the corrector 6
4 calculates an appropriate correction value based on the ratio obtained from the ratio calculator 15, corrects the maximum value obtained from the maximum value calculator 63, and outputs it.

The corrected maximum value is compared by the comparator 65 with the sound pressure reference value stored in the reference value setting unit 66, and when the predetermined maximum value is not satisfied, the comparison result signal is output by the alarm unit 18. Is output to. The predetermined relationship to set is
Similar to the embodiment shown in FIG. 1, in a certain band, for example, when the corrected maximum value is within the range of 80% to 120% with respect to the sound pressure reference value of the band, the comparison result signal is regarded as normal. When the value is out of this range, that is, when it is less than 80% and more than 120%, it is set as abnormal and the comparison result signal is output. Also other,
In a certain band, when the sound pressure reference value of the band is out of the range of 70% to 110%, the comparison result signal is output as being out of the range.

When the sound pressure reference value is smaller than the overall sound pressure, the comparison result signal is not erroneously output in the frequency band which is not the main component by taking measures such as canceling the comparison on the lower limit side. To When the number of the input comparison result signals exceeds a preset number, for example, two, the alarm device 18 sounds a buzzer as a notification and blinks a lamp to give an alarm.

As described above, by using the digital BPF 61 as a method for obtaining a time-series signal for each frequency band, the device can be downsized, and since the processing is performed by software (S / W), the filter characteristics are changed and the frequency band for diagnosis is used. It is possible to flexibly deal with the addition of.

Fourth Embodiment FIG. 4 is a configuration diagram of a nondestructive inspection device for a welded portion showing another embodiment of the present invention. In the embodiment of FIG. 3, the digital BPF is used to obtain the maximum value for each frequency band, but a wavelet transform may be used. Hereinafter, the case of using the wavelet transform will be described based on the configuration diagram of FIG.

In this embodiment, a wavelet transform calculator 71 is provided to obtain a time series signal for each frequency band, and other operations are as shown in FIG.
This is the same as the embodiment. Since the effective value of the wavelet transform is calculated by the analytical calculation, it is not necessary to provide a rectifying means.

In the figure, reference numeral 71 denotes a wavelet transform as a transforming means.
An arithmetic unit, which expands or contracts the basis function (mother wavelet) to separate the digital sound pressure signal into time series signals for each frequency band. The wavelet-transformed signals are provided with 28 sets of maximum value calculators 6
3, the corrector 64, and the comparator 65.

The comparator 65 is compared with the sound pressure reference value stored in the reference value setting unit 66 as in the case shown in FIGS. 1 and 3, and if the preset relationship is established, The comparison result signal is output to the alarm device 18.

At this time, by selecting an appropriate basis function in accordance with the measured waveform and the phenomenon to be observed, the frequency separation characteristic is improved and the reliability of the inspection can be improved. Further, the apparatus can be downsized by using the wavelet transform calculator.

Embodiment 5. FIG. 5 is a block diagram of a nondestructive inspection device for a welded portion showing another embodiment of the present invention. In the embodiment of FIG. 3, the digital BPF is used to obtain the maximum value for each frequency band.
You may use T. Hereinafter, the case of using the short-time FFT will be described with reference to FIG. In this embodiment, a short-time FFT calculator 81 is provided to obtain a time series signal for each frequency band.

Other operations are similar to those of the embodiment shown in FIG. Since the short-time FFT calculates the effective value by its analytical calculation, it is not necessary to provide a rectifying means. In FIG. 5, 81 is a short-time FF as a conversion means.
T (STFT: Short-Time Fourier)
-Transform) arithmetic unit, which is adapted to obtain a time-series signal for each frequency band.

As described above, the short time F which is the Fourier transformer
The frequency resolution can be improved by providing the FT calculator 81 and determining the time series signal for each frequency band.

Therefore, by utilizing the excellent resolution of the short-time FFT, the reliability of diagnosis can be improved when the characteristic of the change in frequency appears due to the structure of the welded portion. Further, the device can be downsized by using the FFT calculator for a short time.

Further, in each of the above-described embodiments, the hammer is used to apply the external force, but the external force may be applied by other means, for example, the electromagnetic force or the cylinder may be used to apply the exciting force.

In each of the above-described embodiments, the external force is detected by the excitation force sensor 11 and the impact sound is detected by the microphone 3. However, a vibration detector is used instead of the microphone for impact sound. Good. In each of the above-mentioned embodiments, those of audible frequencies are called sounds and those of a wider frequency range are called vibrations. However, in the present invention, the inspection device is not limited to sounds, but sounds and vibrations. No distinction is made, and the one due to vibration is included.

Although an alarm is issued by the alarm device 18, each signal in such an inspection or a calculated value, for example, each sound pressure reference value stored in the setting device 10 in the embodiment of FIG. And a normal or abnormal range set as a reference for comparison set in the comparator 9, a correction value calculated by the ratio calculator 15, a corrected maximum value from each corrector 8 in the inspection, and the like in the form of dots or bands. It is also possible to improve the operability by making it easy to confirm by displaying the color on the CRT and coloring the color out of the range with red or the like.

The maximum value corrected by the corrector 8 can also be shown in the normal range so as to be visually recognized. At this time, if the comparison result deviates from the predetermined relationship, the maximum value detected at that time may be displayed in red.

Further, instead of the sound pressure reference value and the comparison reference shown in the third to fifth embodiments, the sound pressure reference value and the comparison reference obtained by the same defining method as those shown in the second embodiment are used. You can also

[0088]

Since the present invention is constructed as described above, it has the following effects.

Signal detecting means for detecting the vibration generated from the welded portion to which an external force is applied as a vibration signal, a converting means for converting the vibration signal into a time series signal for each of a plurality of predetermined frequency bands, and a time series signal Since the extraction means for extracting the maximum value for each frequency band and the comparison means for comparing each maximum value with the vibration reference value for each preset frequency band are provided,
It is possible to accurately grasp the frequency distribution of the large sound pressure immediately after the generation, which is also a characteristic of the tapping sound, and improve the reliability of comparison.

Further, the converting means is a plurality of bandpass filters that pass the frequency components of a predetermined frequency band of the vibration signal, and the extracting means rectifies the frequency components that have passed through the respective bandpass filters, and each of the rectified frequency components. Since the maximum value among the peak values is extracted as the maximum value, if the conversion means is a bandpass filter, the processing can be performed at high speed, and the apparatus is simple and inexpensive.
Further, since the extraction means extracts the maximum value from the rectified frequency component, it is possible to detect even when the negative sign portion of the vibration signal has the maximum value, and it is possible to accurately compare even when the vibration signal is rapidly attenuated.

Further, the transforming means is wavelet transforming means for wavelet transforming the vibration signal, and the extracting means is characterized by extracting the maximum value for each frequency band based on the transform result by the wavelet transforming means. It is possible to improve the characteristics when separating into time series signals for each frequency band, and it is possible to improve the reliability of comparison and inspection.

Since the transforming means is the short-time fast Fourier transforming means and the extracting means is to extract the maximum value for each frequency band based on the transforming result by the short-time fast Fourier transforming means, the frequency resolution is improved. be able to.

Further, external force detecting means for detecting the magnitude of the applied external force is provided, and at least one of the vibration signal, the time series signal, the maximum value and the vibration reference value is corrected according to the magnitude of the external force. Since the correction means is provided, by correcting according to the magnitude of the external force,
In the comparison by the comparison means, it is possible to prevent the influence of the variation in the magnitude of the external force, and the reliability of the comparison is improved.

Further, external force detecting means for detecting the magnitude of the applied external force is provided, and at least one of the signal detecting means, the converting means, the extracting means, and the comparing means when the magnitude of the external force exceeds a predetermined value. It is characterized by the provision of command means for instructing the start of operation, and does not start operation until a command is issued, so there is a risk of erroneously processing ambient noise, vibration, noise, etc. as a vibration signal when there is no command There is no. Therefore, the influence of these can be prevented and the reliability of the inspection is improved.

Further, an external force detecting means for detecting the magnitude of the applied external force as an external force signal is provided, and a ratio calculating means for obtaining a ratio obtained by dividing the external force signal by a preset external force reference value, and the above ratio. Correction means for changing the relationship between the maximum value and the vibration reference value in the comparison means by correcting at least one of the vibration signal, the time-series signal, the maximum value, and the vibration reference value, and the ratio is within a predetermined range. Since it is characterized in that a ratio inspecting means for inspecting whether or not it is within the range is provided, it can be understood that an improper external force that is out of a predetermined range is applied, and the reliability of comparison can be improved. it can.

Further, an external force signal amplifying means for amplifying the external force signal and outputting it as an amplified external force signal, and a vibration signal amplifying means for amplifying the vibration signal and outputting it as an amplified vibration signal are provided, and the ratio calculating means is adapted to output the amplified external force signal. A range over detection means for detecting that the crest value of at least one of the amplified external force signal and the amplified vibration signal exceeds a predetermined value is assumed to be used as the external force signal and the conversion means uses the amplified vibration signal as the vibration signal. Since it is provided, it is detected that the amplified external force signal or the amplified vibration signal exceeds a predetermined value, that is, a large signal that saturates the external force signal amplification means or the vibration signal amplification means is detected. Therefore, the reliability of the inspection can be secured.

Further, since the automatic amplification factor setting means for automatically setting the amplification factor of at least one of the external force signal amplifying means and the vibration signal amplifying means is provided, the amplified external force signal and the amplified vibration signal are The amplification factor can be easily set to obtain an appropriate output range, and operability is improved.
Further, it is possible to prevent the S / N ratio from being lowered and improve the reliability of the inspection.

The comparison means is characterized in that the comparison is made on the basis of the vibration reference value set based on the vibration signal generated when the external force is applied to the welded portion in the predetermined state. It is possible to easily set the vibration reference value according to the state of the welded portion and improve the reliability of the inspection.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a nondestructive inspection device for a welded portion, which is an embodiment of the present invention.

FIG. 2 is a configuration diagram of a nondestructive inspection device for a welded portion which is another embodiment of the present invention.

FIG. 3 is a configuration diagram of a nondestructive inspection device for a welded portion which is another embodiment of the present invention.

FIG. 4 is a configuration diagram of a nondestructive inspection device for a welded portion which is another embodiment of the present invention.

FIG. 5 is a configuration diagram of a nondestructive inspection device for a welded portion which is another embodiment of the present invention.

[Explanation of symbols]

1 welded part, 2 hammer, 3 microphone, 4 amplifier, 5 analog BPF, 6 rectifier, 7 peak hold circuit, 8 corrector, 9 comparator, 10 reference value setting device, 11 excitation force sensor, 12 amplifier, 13 rectifier , 14 Peak hold, 15 Ratio calculator, 16
Reference value setter, 17 trigger detector, 18 alarm device, 1
9 ratio determiner, 20 range automatic setting device, 21 range over detector, 31 rectifier, 32 peak hold, 33 range automatic setting device, 34 range over detector, 41 maximum value calculator, 51, 52 A / D converter ,
53 maximum value calculator, 61 digital BPF, 62 rectifier, 63 maximum value calculator, 64 corrector, 65 comparator, 66 reference value setter, 71 wavelet transform calculator, 81 short time FFT calculator.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-58-129251 (JP, A) JP-A-54-127385 (JP, A) JP-A 61-23966 (JP, A) JP-A 8- 177530 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01N 29/00-29/28 G01H 1/00-17/00

Claims (10)

(57) [Claims] 1. A signal detecting means for detecting a vibration generated from a welded portion to which an external force is applied as a vibration signal, a converting means for converting the vibration signal into a time-series signal for each of a plurality of predetermined frequency bands, and Non-destructive inspection of a welded portion including extraction means for extracting the maximum value of a time-series signal for each frequency band, and comparison means for comparing each maximum value with a preset vibration reference value for each frequency band. apparatus. 2. The conversion means is a plurality of bandpass filters that pass a frequency component of a predetermined frequency band of the vibration signal,
The extraction means is for rectifying the frequency component that has passed through each of the bandpass filters and extracting the maximum value of the peak values of the rectified frequency component as the maximum value. Non-destructive inspection device for the welded part. 3. The converting means is a wavelet converting means for wavelet converting the vibration signal, and the extracting means is for extracting the maximum value for each frequency band based on the conversion result by the wavelet converting means. Item 1. A nondestructive inspection device for a welded part according to item 1. 4. The transforming means is a short-time fast Fourier transforming means for subjecting the vibration signal to a short-time fast Fourier transform, and the extracting means extracts the maximum value for each frequency band based on the transform result by the short-time fast Fourier transforming means. The non-destructive inspection device for a welded part according to claim 1, wherein the non-destructive inspection device is a welded part. 5. An external force detecting means for detecting the magnitude of the applied external force is provided, and at least one of a vibration signal, a time series signal, a maximum value, and a vibration reference value is corrected according to the magnitude of the external force. The non-destructive inspection device for a welded part according to claim 1, further comprising a correction means. 6. An external force detecting means for detecting the magnitude of the applied external force is provided, and at least one of a signal detecting means, a converting means, an extracting means, and a comparing means when the magnitude of the external force exceeds a predetermined value. The nondestructive inspection device for a welded part according to claim 1, further comprising a command means for commanding the start of the operation. 7. An external force detecting means for detecting the magnitude of the applied external force as an external force signal is provided, and a ratio calculating means for obtaining a ratio obtained by dividing the external force signal by a preset external force reference value, and the ratio Correction means for changing the relationship between the maximum value and the vibration reference value in the comparison means by correcting at least one of the vibration signal, the time series signal, the maximum value and the vibration reference value based on The non-destructive inspection device for a welded part according to claim 1, further comprising a ratio inspection means for inspecting whether or not it is within the range. 8. An external force signal amplifying means for amplifying an external force signal and outputting it as an amplified external force signal, and a vibration signal amplifying means for amplifying a vibration signal and outputting it as an amplified vibration signal. Is used as an external force signal, the converting means is used as the vibration signal of the amplified vibration signal, and a range for detecting that the peak value of at least one of the amplified external force signal and the amplified vibration signal exceeds a predetermined value. The nondestructive inspection device for a welded part according to claim 7, further comprising an over detection means. 9. The non-welded portion according to claim 8, further comprising: an automatic amplification factor setting unit for automatically setting the amplification factor of at least one of the external force signal amplification unit and the vibration signal amplification unit. Destruction inspection device. 10. The comparison means performs comparison based on a vibration reference value set based on a vibration signal generated when an external force is applied to a welded portion in a predetermined state. The nondestructive inspection device for a welded part according to any one of claims 1 to 9.