CA2055285A1 - Method and apparatus for performing ultrasonic flaw detection - Google Patents
Method and apparatus for performing ultrasonic flaw detectionInfo
- Publication number
- CA2055285A1 CA2055285A1 CA002055285A CA2055285A CA2055285A1 CA 2055285 A1 CA2055285 A1 CA 2055285A1 CA 002055285 A CA002055285 A CA 002055285A CA 2055285 A CA2055285 A CA 2055285A CA 2055285 A1 CA2055285 A1 CA 2055285A1
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- echo signal
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- flaw detection
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- 238000001514 detection method Methods 0.000 title claims abstract description 70
- 238000000034 method Methods 0.000 title claims abstract description 23
- 239000000523 sample Substances 0.000 claims abstract description 78
- 230000007547 defect Effects 0.000 claims abstract description 26
- 230000005540 biological transmission Effects 0.000 claims abstract description 23
- 238000004458 analytical method Methods 0.000 claims abstract description 13
- 239000000463 material Substances 0.000 claims description 14
- 230000004044 response Effects 0.000 claims description 3
- 230000006870 function Effects 0.000 description 8
- 238000012360 testing method Methods 0.000 description 6
- 238000002592 echocardiography Methods 0.000 description 3
- 238000012545 processing Methods 0.000 description 3
- 230000035945 sensitivity Effects 0.000 description 3
- 229910000831 Steel Inorganic materials 0.000 description 2
- 238000007796 conventional method Methods 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- 230000006399 behavior Effects 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/04—Analysing solids
- G01N29/11—Analysing solids by measuring attenuation of acoustic waves
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/34—Generating the ultrasonic, sonic or infrasonic waves, e.g. electronic circuits specially adapted therefor
- G01N29/348—Generating the ultrasonic, sonic or infrasonic waves, e.g. electronic circuits specially adapted therefor with frequency characteristics, e.g. single frequency signals, chirp signals
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2291/00—Indexing codes associated with group G01N29/00
- G01N2291/04—Wave modes and trajectories
- G01N2291/044—Internal reflections (echoes), e.g. on walls or defects
Abstract
Abstract of the Disclosure According to a method of performing ultrasonic flaw detection, a pulse signal is output to an ultrasonic probe attached through an ultrasonic wave propagation medium to an object to be tested, a reflected wave of the ultrasonic wave incident on the object is received by the ultrasonic probe to obtain an echo signal. The carrier frequency of the pulse signal is set so that the peak frequency of the echo signal becomes a predeter-mined frequency, and then the cycle count of the pulse signal is set so that the frequency bandwidth of the echo signal becomes a predetermined bandwidth. A defect present in the object is detected in accordance with the echo signal output from the ultrasonic probe.
According to an apparatus for performing ultrasonic flaw detection, an ultrasonic transmitter transmits a pulse signal having a designated carrier frequency and a designated cycle count to an ultrasonic probe. An ultrasonic receiver receives the echo signal output from the ultrasonic probe. The peak frequency and the fre-quency bandwidth of the echo signal received by the ultrasonic receiving unit are detected by a signal anal-ysis unit. A transmission control unit designates the carrier frequency and the cycle count of the pulse sig-nal output from the ultrasonic transmission unit so that the detected peak frequency and the detected frequency bandwidth become a flaw detection condition peak frequency and a flaw detection condition frequency bandwidth, respectively.
According to an apparatus for performing ultrasonic flaw detection, an ultrasonic transmitter transmits a pulse signal having a designated carrier frequency and a designated cycle count to an ultrasonic probe. An ultrasonic receiver receives the echo signal output from the ultrasonic probe. The peak frequency and the fre-quency bandwidth of the echo signal received by the ultrasonic receiving unit are detected by a signal anal-ysis unit. A transmission control unit designates the carrier frequency and the cycle count of the pulse sig-nal output from the ultrasonic transmission unit so that the detected peak frequency and the detected frequency bandwidth become a flaw detection condition peak frequency and a flaw detection condition frequency bandwidth, respectively.
Description
2~5~5 The present lnventlon relates to an ultrasonlc flaw detectlon method for detecting a defect present in a test ob~ect by uslng an ultrasonic probe, and an ultra-sonic flaw detection apparatus employing thls method and, more particularly, to a method and apparatus for performing ultrasonic flaw detection, in which a peak frequency and a frequency bandwidth of an echo signal obtained from the ultrasonic probe attached to the ob;ect are independently controlled.
In an ultrasonic flaw detection apparatus for detecting defects or flaws present on the surface of or inside a steel plate by using an ultrasonic wave, an impulse signal obtained by utilizing discharge charac-teristics or the like of, e.g., a charge circuit is applied to an ultrasonic probe attached to the surface of the ob~ect. An ultrasonic wave is transmitted from the ultrasonic probe to the inside of the ob;ect. When a defect is present, upon propagation of the ultrasonic wave inside the object, a reflected wave is generated.
The ultrasonic probe detects this reflected wave and outputs it as an echo signal. The level of the echo signal output from the ultrasonic probe corresponds to the size and shape of the defect. Therefore, the presence/absence of the defect and its size and shape are detected in accordance with this signal level.
In this conventional apparatus, even if flaw ;~S~ 35 detectors havlng the same technlcal speclflcatlons and ultrasonlc probes havlng the same technical speclflca-tions are used, and even if the same defect is detected by these components, if a plurallty of channels are present, the same results cannot be expected between the channels due to the following reason. The properties of an object are not always uniform, and ultrasonic probes do not necessarily have identical characteristics. For these reasons, differences occur between the character-istics of the channels. As a result, frequency charac-teristics such as operating frequencies and frequency bands of the respective channeis are fixed to different values.
A wide-band probe has advantages in that the echo width of a receivsd echo signal is sharp, and that an S/N ratio obtained with an attenuating material is higher than that of a narrow-band probe. Since the electrical impedance of this wide-band probe, however, is low, the differences in characteristics have large influences on output waveforms. Variations in frequency characteristics such as operating frequency characteris-tics and frequency bandwidths therefore occur between the respective probes. In a multichannel ultrasonic flaw detection apparatus having a probe array consisting of a plurality of ultrasonic probes, it is impossible to obtain a uniform flaw detection sensitivity of the object as a whole.
2~5~35 In additlon, when an ultrasonlc probe i8 replaced with a new one, dlfferences in characterlstlcs between the ultrasonic probes are present. For this reason, ad~ustment must be performed in accordance wlth these dlfferences ln characteristics and deterioratlon over time in each ultrasonic probe. The ad~ustment opera-tions are time-consuming and cumbersome and requlre much labor.
.~
; An ultrasonic flaw detection method called a CS
method (Controlled Signal Technique) is proposed ln which an impulse signal is not applied to an ultrasonic probe. According to this CS method, as shown in Fig. llA, a tone-burst pulse signal obtained by extract-lng a carrler wave having a predetermined carrier fre-quency fc every predetermined time interval is applied to the ultrasonic probe. Some techniques of the CS
method are introduced in Published Unexamined Japanese Patent Application Nos. 62-180267 and 62-54160 and Published Examined Japanese Patent Application No. 59-10501.
The tone-burst pulse signal has frequency charac-teristics as shown in Fig. llB. Frequency components a in a narrow band centered on a peak frequency fp are present, as shown in Fig. 12. For the sake of comparison, a characteristic curve indicated by a dotted line is a frequency characteristic curve obtained when an impulse signal is applied. When the carrier ~5~35 frequency fc Of the lmpulse signal to be applled to the ultrasonic probe ls changed, the peak frequency fp of the echo signal changes accordingly. For example, when the carrier frequency fc f the pulse slgnal is changed in an order of 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, and 7 MHz, the peak frequency fp of the echo signal changes in an order of 3, 3.s, 4, 4.5, 5, 5.5, 6, 6.5, and 7 MHz accordingly, as shown in Fig. 13.
A cycle count N representing the number of waves included in the pulse signal ~s increased, the ratio of the components of the carrier frequency fc to other fre-quency components of the pulse signal is increased. As a result, the bandwidth of the pulse signal is narrowed, and a steep frequency characteristic curve is obtained.
Fig. 14A shows a pulse signal waveform for N = 1.
Fig. 14B shows a frequency characteristic curve of the pulse signal shown in Fig. 14A. Figs. 15A and 15B show a signal waveform and frequency characteristics for N = 5. Figs. 16A and 16B show a signal waveform and frequency characteristics for N = 10.
It is thus understood that the bandwidth of the pulse signal is decreased with an increase in cycle count N of the pulse signal. When the cycle count N
is changed, the frequency bandwidth W of the ultra-sonic waves applied to the object can be changed to an arbitrary value.
In practice, a uniform flaw detection sensitivity Z ~ ~ ~7~ 5 in the entire detection range of an object in a multichannel ultrasonic flaw detection apparatus having an array of a plurality of ultrasonic probes must be realized. At the same time, adjustment operatlons based on the differences in characteristics upon replacement of a probe and the deterioration over time in each probe must be performed. It is very difficult to control that the frequency characteristics such as the peak frequency fp and the frequency bandwidth W of the echo signal out-put from the ultrasonic probe satisfy the aboveconditions.
It is an object of the present invention to inde-pendently control parameters of echo signal frequency characteristics matching with flaw detection conditions determined by physical conditions such as a material of a test object, and finally, to provide a method and apparatus for performing ultrasonic flaw detection capable of performing sensitivity adjustment between channels and greatly improving flaw detection accuracy even in a multichannel ultrasonic flaw detection apparatus.
In order to achieve the above object, according to an ultrasonic flaw detection method of the present invention, a pulse signal is transmitted to an ultrasonic probe attached to the object to cause an ultrasonic wave to be incident on the ob;ect, and a reflected wave of the ultrasonic wave incident on the z~ s ob~ect is received by the ultrasonlc probe, thereby obtaining an echo signal. A carrier frequency of the pulse signal is set so that the peak frequency of the echo signal is set to be a predetermined frequency, and the cycle count of the pulse signal is determined so that the frequency bandwidth of the echo signal is set to be a predetermined bandwidth. A defect present in the object is detected in accordance with the signal level of the echo signal output from the ultrasonic probe.
According to experimental results, even if the carrier frequency of the pulse signal is changed, the frequency bandwidth of the echo signal is almost not changed. At the same time, even if the cycle count of the pulse signal is changed, the peak frequency f of the echo signal is almost not changed. In consideration of this, the peak frequency of the echo signal is con-trolled by only the carrier frequency of the pulse signal, and the frequency bandwidth of the echo signal is controlled by only the cycle count of the pulse signal. Therefore, the peak frequency and the frequency bandwidth of the echo signal can be independently controlled.
In order to achieve the above ob;ect according to the present invention, there is provided an ultrasonic flaw detection apparatus comprising an ultrasonic wave transmission unit for outputting a pulse signal having a deslgnated carrler frequency and a deslgnated cycle count, an ultrasonlc probe, attached to a test ob~ect, for outputting an ultrasonic wave to the object ln response to the pulse slgnal lnput from the ultrasonic transmlssion unit and for outputting an echo signal upon receptlon of a reflected wave of the ultrasonlc wave, an ultrasonlc wave reception unit for receiving the echo signal output from the ultrasonic probe, a signal analy-sis unit for detecting a peak frequency and a low-frequency bandwidth of the echo signal received by the ultrasonic reception unit, and a transmission control unit for designating the carrier frequency and the cycle count of the pulse signal output from the ultrasonic wave transmission unit so that the peak frequency and the frequency bandwidth which are detected by the signal analysis unit are set to be an optimal peak frequency and an optimal frequency bandwidth, respectively.
The peak frequency and the frequency bandwidth of the echo signal output from the ultrasonic probe can be controlled to an optimal peak frequency and an optimal frequency bandwidth which are determined by, e.g., the material of a test object of interest. As a result, the flaw detection for the object can be performed in opti-mal flaw detection conditions.
This invention can be more fully understood from the following detailed description when taken in con-junction with the accompanying drawings, in which:
~c`sr~ 35 Fig. 1 is a block dlagram showlng a schematlc arrangement of an ultrasonlc flaw detection apparatus employing an ultrasonlc flaw detectlon method accordlng to an embodlment of the present invention;
Flg. 2A is a waveform chart showing a pulse signal in the apparatus shown in Fig. l;
Fig. 2B ls a waveform chart showing an echo signal ln the apparatus shown in Fig. l;
Fig. 2C is a graph showing frequency characterls-tics of the echo signal in the apparatus shown ln Fig. l;
Fig. 3 is a flow chart showing an operation of the ultrasonic flaw detection apparatus shown in Fig. l;
Fig. ~ is a flow chart showing an operation of an ultrasonic flaw detection apparatus according to another embodiment of the present invention;
Figs. 5A and 5B are graphs each showing an echo signal waveform and a frequency characteristic curve which are measured by a conventional method;
Figs. 6A and 6B are graphs each showing an echo signal waveform and a frequency characteristic curve which are measured by the method of the embodiment;
Fig. 7 is a graph showing an echo signal waveform representing a sample defect and a frequency character-istlc curve whlch are measured by the method of the embodiment;
Fig. 8 is a graph showing a relationship between z~ s the carrier frequency and echo frequency which are meas-ured by the method of the embodiment;
Flg. 9A ls a graph showlng the echo frequency and echo bandwidth as a function of the carrier frequency;
5Fig. 9B is a graph showing the echo frequency and echo bandwidth as a function of the cycle count;
Fig. 9C ls a graph showing the echo frequency and echo bandwidth as a function of the carrier frequency;
Fig. 9D is a graph showing the echo frequency and - 10echo bandwidth as a function of the cycle count;
Fig. loA ls a graph showing the echo frequency and echo bandwidth as a function of the carrier frequency;
Fig. lOB is a graph showing the echo frequency and echo bandwidth as a function of the cycle count;
15Fig. lOC is a graph showing the echo frequency and echo bandwidth as a function of the carrier frequency;
Fig. lOD is a graph showing the echo frequency and echo bandwidth as a function of the cycle count;
Fig. llA is a waveform chart showing a tone-burst 20pulse slgnal;
Fig. llB is a graph showing a frequency character-istic curve of the pulse signal shown in Fig. llA;
Fig. 12 is a graph showing frequency characteristic curves of echo signals of the tone-burst pulse signal 25and an impulse signal;
Fig. 13 is a graph showing a relationship between the carrier frequency of the tone-burst pulse signal and - 1 0 - 2~ 35 the peak frequency of the echo 9 lgnal;
Figs. 14A and 14B are graphs showing a relationship between the pulse signal waveform and the frequency characteristics when the cycle count of the tone-burst pulse signal cycle count is 1;
Figs. 15A and 15B are graphs showing a relationship between the pulse signal waveform and the frequency characteristics when the cycle count of the tone-burst pulse signal cycle count is 5; and Figs. 16A and 16B are graphs showing a relationship between the pulse signal waveform and the frequency characteristics when the cycle count of the tone-burst pulse signal cycle count is 10.
A description will be made on the basis of experi-mental results so as to prove that a peak frequency fpand a frequency bandwidth W of an echo signal output from an ultrasonic probe can be independently controlled.
For example, when a tone-burst pulse signal a hav-ing the carrier frequency fc and the cycle count N, asshown in Fig. 2A, is applied to an ultrasonic probe attached to tne surface of a test object, an ultrasonic wave is incident from the ultrasonic probe onto the object. If a defect is present in the object, this ultrasonic wave is reflected by this defect, and a reflected wave is incident on the ultrasonic probe.
As a result, an echo signal b having a waveform shown in - 1 1 - 2~ 3S
Fig. 2B is output from the ultrasonic probe.
The frequency of this echo slgnal b ls analyzed to obtain a frequency characterlstlc curve c shown in Fig. 2C. The frequency at the maximum signal level of thls frequency characteristic curve c is defined as the peak frequency fp. Frequencies at levels 6 dB below the maximum signal level of the frequency characteristic curve c are defined as -6-dB lower frequencles fH and fL. A width at a position 6 dB below the maxlmum signal ; 10 level of the frequency characteristlc curve c is defined as a frequency bandwidth W (= fH ~ fL) Experimental values showing changes in characteris-tic values fp, fH, fL, and W of the echo signal b output from one ultrasonic probe A, which values are obtained by independently changing the carrier frequency fc and the cycle count N of the pulse signal a applied to the ultrasonic probe A, are shown in Figs. 9A to 9D.
~ Fig. 9A is a graph showing changes in the peak fre-- quency fp and the -6-dB lower frequencies fH and fL when the cycle count N is fixed and the carrier frequency fc is changed within the range of 2 to 4 MHz. Fig. 9C is a graph showing changes in the frequency bandwidth W when the cycle count N is fixed and the carrier frequency fc is changed in the range of 2 to 4 MHz.
Fig. 9B is a graph showing changes in the peak frequency fp and the -6-dB lower frequencies fH and fL
when the carrier frequency fc is fixed and the cycle :
2~%~5 count N is changed in the range of 1 to 5. Fig. 9D is a graph showing changes in the frequency bandwidth W when the carrier frequency fc ls fixed and the cycle count N
is changed ln the range of 1 to 5.
As is apparent from the experimental results shown ln Figs. 9A to 9D, even if the carrier frequency fc of the pulse slgnal a is changed, the frequency bandwidth W
of the echo signal b is almost not changed. Even if the cycle count N of the pulse signal a is changed, the peak frequency fp of the echo signal b ls almost not changed.
That is, the peak frequency fp of the echo signal b is changed by only the carrier frequency fc of the pulse signal a. The frequency bandwidth W of the echo signal b is controlled by only the cycle count N of the pulse signal a. Therefore, the peak frequency fp and the fre-quency bandwidth W of the echo signal b can be independ-ently controlled.
In the ultrasonic probe A shown in the experiment of Figs. 9A to 9D, even if the cycle count N is changed, the peak frequency fp is almost not changed. When the frequency bandwidth W is adjusted to a target frequency bandwidth after the peak frequency fp is adjusted to a target frequency, flaw detection conditions for the object can be set by a single operation.
Experimental results obtained using an ultrasonic probe B having different specifications from those of the ultrasonic probe A shown in Figs. 9A to 9D are shown ;~s~ ~s in Flgs. lOA to lOD. That ls, Flgs. lOA to lOD show changes ln respective characteristlc values fp, fH, fL, and W of an echo slgnal b output from the ultrasonlc probe B when a carrler frequency fc and the cycle count N of the pulse slgnal a applied to the ultrasonlc probe B are independently changed. Note that the carrler fre-quency fc Of the pulse slgnal a is set sllghtly hlgher than that applied to the ultrasonic probe A, and other condltions are the same as those in the ultrasonlc probe A.
As is apparent from the experimental results shown in Figs. lOA to lOD, the peak frequency fp and the fre-quency bandwidth W of the echo signal b are independ-ently controlled. In Figs. lOA to lOD, when the cycle count N is changed, the peak frequency fp is slightly changed, so that a plurality of adjustment operations are required to obtain target frequency characteristics.
As shown ln Fig. lOB, however, since the degree of change in peak frequency fp is very small, adjustment need only be repeated a maximum of several times.
When the carrler frequency fc and the cycle count N
of the pulse signal a applled to the ultrasonic probe are changed, the peak frequency fp and the frequency bandwidth W of the echo slgnal b obtalned upon detection of a defect by the ultrasonic probe can be independently controlled. The frequ~ncy characteristics of the echo signal b can be easily matched with optimal flaw - 14 - 2~ S
detection condltions, thereby greatly lmprovlng flaw detection precislon.
There are provided a technlque for matching the frequency bandwidth W with an optimal frequency bandwidth determlned by the material of an ob~ect after the peak frequency fp of the echo signal b is matched with an optimal frequency determined by the material of the object, and a technique for matching the peak fre-quency with an optimal value after the frequency bandwidth is matched with an optlmal value. In either technique, the target peak frequency and frequency bandwidth can be obtained.
Control of the peak frequency can be performed independently of control of the frequency bandwidth.
Fig. 1 is a block diagram showing a schematic arrangement of an ultrasonic flaw detection apparatus employing a flaw detection method of this embodiment.
An ob;ect 1 is a steel plate or the like. For example, a vertical ultrasonic probe 2 is attached to the surface of the ob;ect 1. The tone-burst signal a having the carrier frequency fc and the cycle count N, as shown in Fig. 2A, is applied from an ultrasonic transmission unit 3 to the ultrasonic probe 2. If a defect or flaw is present in the ob;ect 1, the echo sig-nal b shown in Fig. 2B is output from the ultrasonicprobe 2 to an ultrasonic receiving unit 4.
A transmission control unit 5 comprises, e.g., 2C~5~?~5 a microcomputer. The transmlsslon control unlt 5 con-trols the carrler frequency fc and the cycle count N of the pulse si~nal a output from the ultrasonlc transmis-sion unit 3 in accordance with flaw detection conditions stored in a flaw detection condition memory 6. A signal analysis unit 7 has, e.g., an FFT (Fast-Fourier Transform) functlon and analyzes the frequency of the echo signal b received by the ultrasonic recelving unit 4 and feeds back the analysis result to the transmission control unit 5. The signal analysls unlt 7 also deter-mines the presence/absence of a defect in accordance with the level of the input echo signal b. In addition, the signal analysis unit 7 can also calculate the size of a defect and display it on a display unlt 8.
The flaw detectlon condition memory 6 stores, in units of materials of the objects 1, the optimal peak frequency fp and the optimal frequency bandwidth W of the echo signal b output from the ultrasonic probe 2 attached to the ob;ect 1. Various conditions such as allowable ranges ~fm and ~Wm of the peak frequency fp and the frequency bandwidth W are also stored in the flaw detection condition memory 6.
When a flaw detection condition command is input from a keyboard (not shown) to the transmission control unit 5, the carrier frequency fc and the cycle count N
of the pulse signal a are set in accordance with a flow chart in Fig. 3.
z~ a5 .
If this ultrasonlc flaw detectlon apparatus ls a multichannel apparatus, a large number of probes 2 are regarded to be arranged on one ob~ect 1. Peak frequen-cies fp and frequency bandwldths W of echo slgnals b obtained from all channels except for a reference chan-nel must be matched with those of the reference channel.
In this case, in step P (program step) 1, the transmission control unit 5 transmits a transmission command to the ultrasonic transmission unit 3 of the reference channel to cause the ultrasonic transmission unit 3 to output a pulse signal a having a carrier fre-quency fc and a cycle count N which are currently set in the ultrasonic transmission unit 3. The ultrasonic receiving unit 4 receives the echo signal b output from the ultrasonic probe 2. The signal analysis unit 7 per-forms frequency analysis of the received echa signal to obtain the peak frequency fp, the -6-dB lower frequen-cies fH and fL, and the frequency bandwidth W of the input echo signal. The transmission control unit 5 stores these values, i.e., fp, fH, fL, and w as flaw detectlon conditions in the flaw detection condition memory 6. The flow then advances to step P3.
When the echo signals b of all the channels except for the reference channel are to be matched with spe-cific flaw detection conditions, the transmissioncontrol unit 5 reads out frequency characteristics such as the optimal peak frequency fp and the optimal 2~ s frequency bandwidth W stored ~P2) in the flaw detectlon condltion memory 6.
In step P3, the transmlsslon control unlt 5 reads out the allowable ranges Qfm and ~Wm from the flaw detection condition memory 6 and sets them in, e.g., a buffer memory, thereby setting parameter control steps ~f and ~N. The carrier frequency fc and the cycle count N of the ultrasonic transmission unit 3 are set to ini-tlal values.
In step P4, the transmission control unit 5 causes the ultrasonic transmission unit 3 to output the pulse signal a having the set carrier frequency fc and the set cycle count N to the ultrasonic probe 2. The ultrasonic receiving unit 4 receives an echo signal b from the ultrasonic probe 2. The signal analysis unit 7 performs frequency analysis of the echo signal b to obtain the peak frequency fp and the frequency bandwidth W. In step P5, the transmission control unit 5 compares the peak frequency fp of the echo signal b with the peak frequency fp as one of the preset flaw detection conditions. If the difference between the measured peak frequency fp and the peak frequency fp as the flaw detection condition does not fall within the allowable range ~fm in step P6, the carrier frequency fc of the pulse slgnal a is changed by the small frequency ~f in step P7. The flow then returns to step P4, and another pulse signal a is then output.
z~ s When the dlfference between the measured peak fre-quency fp and the measured peak frequency fp falls wlthin the allowable range ~fm ln step P6, the transmls-slon control unlt 5 compares the measured frequency bandwldth W with the frequency bandwldth W as one of the flaw detection condltions in step P8. If the difference between the measured frequency bandwidth w and the fre-quency bandwidth W as one of the flaw detection condi-tions does not fall wlthln the allowable range ~Wm ln step P9, the cycle count N of the pulse slgnal a ls changed by the small cycle count ~N in step P10. The flow then returns to step P4, and another pulse signal a is output.
When the difference between the measured frequency bandwldth w and the frequency bandwidth W as the flaw detectlon condltlon falls wlthln the allowable range QWm in step P9, flaw detection condition setup processing for this channel is completed.
As shown ln Fig. 4, setup processing of the fre-quency bandwldth W may be performed before setup proc-essing of the peak frequency fp.
Effects of the ultrasonlc flaw detection apparatus having the above arrangement wlll be described with ref-erence to Figs. 5A to 6B.
2s Figs. 5A and 5s are graphs showing signal waveforms and frequency characteristics of echo signals b obtained by flaw detection using two ultrasonic probes C and D
2~ s having identical technlcal specifications. The ultra-sonic probes C and D are driven such that the same lmpulse signal as in the conventional apparatus is applied to the ob~ect 1 having a reference defect or 5 flaw. As shown in Figs. 5A and 5B, even if these ultra-sonic probes have the identical speclficatlons, a dif-ference occurs between the resultant echo signals b.
Peak frequencies fp are different from each other between the echo signals by about 0.5 MHz, and their frequency bandwidths W are also slightly different from each other.
Figs. 6A and 6B are graphs showing signal waveforms and frequency characteristics of echo signals b obtained when flaw detection is performed using the above two ultrasonic probes C and D. The carrier frequencies fc and the cycle counts N of the pulse signals a are set by control as shown in Fig. 3 so that the peak frequencies fp and the frequency bandwidths W of the resultant echo signals b coincide with each other. As is understood from Figs. 6A and 6B, even if a characteristic differ-ence is present between the ultrasonic probes C and D, the flaw detection conditions represented by the peak frequencies fp and the frequency bandwidths w of the output echo signals _ can coincide with each other.
That is, flaw detection errors between the channels in the multichannel ultrasonic flaw apparatus can be minimized.
X~ 35 Figs. 7 and 8 are graphs obtalned when flaw detec-tion is performed after two dlfferent lateral test holes A and B are formed. An ob~ect 1 comprises a hlgh atten-uation materlal in which correlation between the lateral hole diameter and the signal level of an echo signal is lost. The ultrasonic flaw detection method of the above embodiment ls applied to this ob~ect 1. As shown in Fig. 7, an echo signal b obtained upon detection of the lateral hole can maintain a single frequency.
That is, an optimal peak frequency fp of the echo signal is set to be an optimal value determined by the material of this ob;ect 1, and its frequency bandwidth W
is set narrow, thereby minimizing noise echoes, caused by the structure of the ob;ect 1, included in the echo signal b. The S/N ratio of the echo signal b can be largely increased, and flaw detection precision can be greatly improved.
There is often an object having flaw detection characteristics which make it difficult to detect a defect due to a low S/N ratio caused by high attenuation (caused ~y ultrasonic scattering) and drill echoes.
This object has a small frequency difference between the peak frequency fp of the echo signal output by a wave reflected by a defect and the peak frequency of the echo signal of structural noise such as drill echoes caused by the composition of the material structure of the ob;ect 1.
2~5~ 5 The tone-burst pulse signal b ls used to ad~ust the carrier frequency fc f the pulse slgnal b to slightly shift the peak frequency fp of the echo signal obtained upon detection of a defect from the peak frequency of the echo signal of the structural noise. At the same time, the cycle count N is ad~usted to be an appropriate value, and the frequency bandwidth W of the echo signal b is set to be minimized. In principle, then, the S~N
ratio of the echo signal b output from the ultrasonic probe 2 can be greatly improved as compared with the conventional technique using the impulse signal.
As shown in Fig. 8, even if the carrier frequency fc Of the pulse signal a is changed, the peak frequency fp and the -6-ds lower fre~uencies fH and fL have the same tendency as the experimental results shown in Figs. 9A and lOA. Even if the object comprises a high attenuation material, the peak frequency fp and the frequency bandwidth W of the echo signal b can be independently controlled. Therefore, control is not complicated, and the setup operations of the ultrasonic flaw detection conditions can be facilitated.
The present invention has been applied to the method and apparatus for performing ultrasonic flaw detection to detect a defect or flaw present in an ob~ect. However, the principle of the present invention is applicable to a wide range of flaw detection.
For example, the present invention is applicable to - 22 - ~C ~ S
an ultrasonic tester, an ultrasonlc flaw detection unlt, and an ultrasonic dlagnosis apparatus, all of which use a pulse echo method.
When ad~ustment and uniform control in the fre-quency range of transmisslon pulses applled to objectsare established, the present invention is also applica-ble to the following regions:
(a) Flaw discrimination by frequency optimization for a boundary damage of various types of bonding mate-rials and coating materials, or damage evaluation in afrequency range; and (b) Applications to evaluation of material proper-ties by means of pulse propagation behavior analysis in ~onsideration of information of the frequency region.
In an ultrasonic flaw detection apparatus for detecting defects or flaws present on the surface of or inside a steel plate by using an ultrasonic wave, an impulse signal obtained by utilizing discharge charac-teristics or the like of, e.g., a charge circuit is applied to an ultrasonic probe attached to the surface of the ob~ect. An ultrasonic wave is transmitted from the ultrasonic probe to the inside of the ob;ect. When a defect is present, upon propagation of the ultrasonic wave inside the object, a reflected wave is generated.
The ultrasonic probe detects this reflected wave and outputs it as an echo signal. The level of the echo signal output from the ultrasonic probe corresponds to the size and shape of the defect. Therefore, the presence/absence of the defect and its size and shape are detected in accordance with this signal level.
In this conventional apparatus, even if flaw ;~S~ 35 detectors havlng the same technlcal speclflcatlons and ultrasonlc probes havlng the same technical speclflca-tions are used, and even if the same defect is detected by these components, if a plurallty of channels are present, the same results cannot be expected between the channels due to the following reason. The properties of an object are not always uniform, and ultrasonic probes do not necessarily have identical characteristics. For these reasons, differences occur between the character-istics of the channels. As a result, frequency charac-teristics such as operating frequencies and frequency bands of the respective channeis are fixed to different values.
A wide-band probe has advantages in that the echo width of a receivsd echo signal is sharp, and that an S/N ratio obtained with an attenuating material is higher than that of a narrow-band probe. Since the electrical impedance of this wide-band probe, however, is low, the differences in characteristics have large influences on output waveforms. Variations in frequency characteristics such as operating frequency characteris-tics and frequency bandwidths therefore occur between the respective probes. In a multichannel ultrasonic flaw detection apparatus having a probe array consisting of a plurality of ultrasonic probes, it is impossible to obtain a uniform flaw detection sensitivity of the object as a whole.
2~5~35 In additlon, when an ultrasonlc probe i8 replaced with a new one, dlfferences in characterlstlcs between the ultrasonic probes are present. For this reason, ad~ustment must be performed in accordance wlth these dlfferences ln characteristics and deterioratlon over time in each ultrasonic probe. The ad~ustment opera-tions are time-consuming and cumbersome and requlre much labor.
.~
; An ultrasonic flaw detection method called a CS
method (Controlled Signal Technique) is proposed ln which an impulse signal is not applied to an ultrasonic probe. According to this CS method, as shown in Fig. llA, a tone-burst pulse signal obtained by extract-lng a carrler wave having a predetermined carrier fre-quency fc every predetermined time interval is applied to the ultrasonic probe. Some techniques of the CS
method are introduced in Published Unexamined Japanese Patent Application Nos. 62-180267 and 62-54160 and Published Examined Japanese Patent Application No. 59-10501.
The tone-burst pulse signal has frequency charac-teristics as shown in Fig. llB. Frequency components a in a narrow band centered on a peak frequency fp are present, as shown in Fig. 12. For the sake of comparison, a characteristic curve indicated by a dotted line is a frequency characteristic curve obtained when an impulse signal is applied. When the carrier ~5~35 frequency fc Of the lmpulse signal to be applled to the ultrasonic probe ls changed, the peak frequency fp of the echo signal changes accordingly. For example, when the carrier frequency fc f the pulse slgnal is changed in an order of 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, and 7 MHz, the peak frequency fp of the echo signal changes in an order of 3, 3.s, 4, 4.5, 5, 5.5, 6, 6.5, and 7 MHz accordingly, as shown in Fig. 13.
A cycle count N representing the number of waves included in the pulse signal ~s increased, the ratio of the components of the carrier frequency fc to other fre-quency components of the pulse signal is increased. As a result, the bandwidth of the pulse signal is narrowed, and a steep frequency characteristic curve is obtained.
Fig. 14A shows a pulse signal waveform for N = 1.
Fig. 14B shows a frequency characteristic curve of the pulse signal shown in Fig. 14A. Figs. 15A and 15B show a signal waveform and frequency characteristics for N = 5. Figs. 16A and 16B show a signal waveform and frequency characteristics for N = 10.
It is thus understood that the bandwidth of the pulse signal is decreased with an increase in cycle count N of the pulse signal. When the cycle count N
is changed, the frequency bandwidth W of the ultra-sonic waves applied to the object can be changed to an arbitrary value.
In practice, a uniform flaw detection sensitivity Z ~ ~ ~7~ 5 in the entire detection range of an object in a multichannel ultrasonic flaw detection apparatus having an array of a plurality of ultrasonic probes must be realized. At the same time, adjustment operatlons based on the differences in characteristics upon replacement of a probe and the deterioration over time in each probe must be performed. It is very difficult to control that the frequency characteristics such as the peak frequency fp and the frequency bandwidth W of the echo signal out-put from the ultrasonic probe satisfy the aboveconditions.
It is an object of the present invention to inde-pendently control parameters of echo signal frequency characteristics matching with flaw detection conditions determined by physical conditions such as a material of a test object, and finally, to provide a method and apparatus for performing ultrasonic flaw detection capable of performing sensitivity adjustment between channels and greatly improving flaw detection accuracy even in a multichannel ultrasonic flaw detection apparatus.
In order to achieve the above object, according to an ultrasonic flaw detection method of the present invention, a pulse signal is transmitted to an ultrasonic probe attached to the object to cause an ultrasonic wave to be incident on the ob;ect, and a reflected wave of the ultrasonic wave incident on the z~ s ob~ect is received by the ultrasonlc probe, thereby obtaining an echo signal. A carrier frequency of the pulse signal is set so that the peak frequency of the echo signal is set to be a predetermined frequency, and the cycle count of the pulse signal is determined so that the frequency bandwidth of the echo signal is set to be a predetermined bandwidth. A defect present in the object is detected in accordance with the signal level of the echo signal output from the ultrasonic probe.
According to experimental results, even if the carrier frequency of the pulse signal is changed, the frequency bandwidth of the echo signal is almost not changed. At the same time, even if the cycle count of the pulse signal is changed, the peak frequency f of the echo signal is almost not changed. In consideration of this, the peak frequency of the echo signal is con-trolled by only the carrier frequency of the pulse signal, and the frequency bandwidth of the echo signal is controlled by only the cycle count of the pulse signal. Therefore, the peak frequency and the frequency bandwidth of the echo signal can be independently controlled.
In order to achieve the above ob;ect according to the present invention, there is provided an ultrasonic flaw detection apparatus comprising an ultrasonic wave transmission unit for outputting a pulse signal having a deslgnated carrler frequency and a deslgnated cycle count, an ultrasonlc probe, attached to a test ob~ect, for outputting an ultrasonic wave to the object ln response to the pulse slgnal lnput from the ultrasonic transmlssion unit and for outputting an echo signal upon receptlon of a reflected wave of the ultrasonlc wave, an ultrasonlc wave reception unit for receiving the echo signal output from the ultrasonic probe, a signal analy-sis unit for detecting a peak frequency and a low-frequency bandwidth of the echo signal received by the ultrasonic reception unit, and a transmission control unit for designating the carrier frequency and the cycle count of the pulse signal output from the ultrasonic wave transmission unit so that the peak frequency and the frequency bandwidth which are detected by the signal analysis unit are set to be an optimal peak frequency and an optimal frequency bandwidth, respectively.
The peak frequency and the frequency bandwidth of the echo signal output from the ultrasonic probe can be controlled to an optimal peak frequency and an optimal frequency bandwidth which are determined by, e.g., the material of a test object of interest. As a result, the flaw detection for the object can be performed in opti-mal flaw detection conditions.
This invention can be more fully understood from the following detailed description when taken in con-junction with the accompanying drawings, in which:
~c`sr~ 35 Fig. 1 is a block dlagram showlng a schematlc arrangement of an ultrasonlc flaw detection apparatus employing an ultrasonlc flaw detectlon method accordlng to an embodlment of the present invention;
Flg. 2A is a waveform chart showing a pulse signal in the apparatus shown in Fig. l;
Fig. 2B ls a waveform chart showing an echo signal ln the apparatus shown in Fig. l;
Fig. 2C is a graph showing frequency characterls-tics of the echo signal in the apparatus shown ln Fig. l;
Fig. 3 is a flow chart showing an operation of the ultrasonic flaw detection apparatus shown in Fig. l;
Fig. ~ is a flow chart showing an operation of an ultrasonic flaw detection apparatus according to another embodiment of the present invention;
Figs. 5A and 5B are graphs each showing an echo signal waveform and a frequency characteristic curve which are measured by a conventional method;
Figs. 6A and 6B are graphs each showing an echo signal waveform and a frequency characteristic curve which are measured by the method of the embodiment;
Fig. 7 is a graph showing an echo signal waveform representing a sample defect and a frequency character-istlc curve whlch are measured by the method of the embodiment;
Fig. 8 is a graph showing a relationship between z~ s the carrier frequency and echo frequency which are meas-ured by the method of the embodiment;
Flg. 9A ls a graph showlng the echo frequency and echo bandwidth as a function of the carrier frequency;
5Fig. 9B is a graph showing the echo frequency and echo bandwidth as a function of the cycle count;
Fig. 9C ls a graph showing the echo frequency and echo bandwidth as a function of the carrier frequency;
Fig. 9D is a graph showing the echo frequency and - 10echo bandwidth as a function of the cycle count;
Fig. loA ls a graph showing the echo frequency and echo bandwidth as a function of the carrier frequency;
Fig. lOB is a graph showing the echo frequency and echo bandwidth as a function of the cycle count;
15Fig. lOC is a graph showing the echo frequency and echo bandwidth as a function of the carrier frequency;
Fig. lOD is a graph showing the echo frequency and echo bandwidth as a function of the cycle count;
Fig. llA is a waveform chart showing a tone-burst 20pulse slgnal;
Fig. llB is a graph showing a frequency character-istic curve of the pulse signal shown in Fig. llA;
Fig. 12 is a graph showing frequency characteristic curves of echo signals of the tone-burst pulse signal 25and an impulse signal;
Fig. 13 is a graph showing a relationship between the carrier frequency of the tone-burst pulse signal and - 1 0 - 2~ 35 the peak frequency of the echo 9 lgnal;
Figs. 14A and 14B are graphs showing a relationship between the pulse signal waveform and the frequency characteristics when the cycle count of the tone-burst pulse signal cycle count is 1;
Figs. 15A and 15B are graphs showing a relationship between the pulse signal waveform and the frequency characteristics when the cycle count of the tone-burst pulse signal cycle count is 5; and Figs. 16A and 16B are graphs showing a relationship between the pulse signal waveform and the frequency characteristics when the cycle count of the tone-burst pulse signal cycle count is 10.
A description will be made on the basis of experi-mental results so as to prove that a peak frequency fpand a frequency bandwidth W of an echo signal output from an ultrasonic probe can be independently controlled.
For example, when a tone-burst pulse signal a hav-ing the carrier frequency fc and the cycle count N, asshown in Fig. 2A, is applied to an ultrasonic probe attached to tne surface of a test object, an ultrasonic wave is incident from the ultrasonic probe onto the object. If a defect is present in the object, this ultrasonic wave is reflected by this defect, and a reflected wave is incident on the ultrasonic probe.
As a result, an echo signal b having a waveform shown in - 1 1 - 2~ 3S
Fig. 2B is output from the ultrasonic probe.
The frequency of this echo slgnal b ls analyzed to obtain a frequency characterlstlc curve c shown in Fig. 2C. The frequency at the maximum signal level of thls frequency characteristic curve c is defined as the peak frequency fp. Frequencies at levels 6 dB below the maximum signal level of the frequency characteristic curve c are defined as -6-dB lower frequencles fH and fL. A width at a position 6 dB below the maxlmum signal ; 10 level of the frequency characteristlc curve c is defined as a frequency bandwidth W (= fH ~ fL) Experimental values showing changes in characteris-tic values fp, fH, fL, and W of the echo signal b output from one ultrasonic probe A, which values are obtained by independently changing the carrier frequency fc and the cycle count N of the pulse signal a applied to the ultrasonic probe A, are shown in Figs. 9A to 9D.
~ Fig. 9A is a graph showing changes in the peak fre-- quency fp and the -6-dB lower frequencies fH and fL when the cycle count N is fixed and the carrier frequency fc is changed within the range of 2 to 4 MHz. Fig. 9C is a graph showing changes in the frequency bandwidth W when the cycle count N is fixed and the carrier frequency fc is changed in the range of 2 to 4 MHz.
Fig. 9B is a graph showing changes in the peak frequency fp and the -6-dB lower frequencies fH and fL
when the carrier frequency fc is fixed and the cycle :
2~%~5 count N is changed in the range of 1 to 5. Fig. 9D is a graph showing changes in the frequency bandwidth W when the carrier frequency fc ls fixed and the cycle count N
is changed ln the range of 1 to 5.
As is apparent from the experimental results shown ln Figs. 9A to 9D, even if the carrier frequency fc of the pulse slgnal a is changed, the frequency bandwidth W
of the echo signal b is almost not changed. Even if the cycle count N of the pulse signal a is changed, the peak frequency fp of the echo signal b ls almost not changed.
That is, the peak frequency fp of the echo signal b is changed by only the carrier frequency fc of the pulse signal a. The frequency bandwidth W of the echo signal b is controlled by only the cycle count N of the pulse signal a. Therefore, the peak frequency fp and the fre-quency bandwidth W of the echo signal b can be independ-ently controlled.
In the ultrasonic probe A shown in the experiment of Figs. 9A to 9D, even if the cycle count N is changed, the peak frequency fp is almost not changed. When the frequency bandwidth W is adjusted to a target frequency bandwidth after the peak frequency fp is adjusted to a target frequency, flaw detection conditions for the object can be set by a single operation.
Experimental results obtained using an ultrasonic probe B having different specifications from those of the ultrasonic probe A shown in Figs. 9A to 9D are shown ;~s~ ~s in Flgs. lOA to lOD. That ls, Flgs. lOA to lOD show changes ln respective characteristlc values fp, fH, fL, and W of an echo slgnal b output from the ultrasonlc probe B when a carrler frequency fc and the cycle count N of the pulse slgnal a applied to the ultrasonlc probe B are independently changed. Note that the carrler fre-quency fc Of the pulse slgnal a is set sllghtly hlgher than that applied to the ultrasonic probe A, and other condltions are the same as those in the ultrasonlc probe A.
As is apparent from the experimental results shown in Figs. lOA to lOD, the peak frequency fp and the fre-quency bandwidth W of the echo signal b are independ-ently controlled. In Figs. lOA to lOD, when the cycle count N is changed, the peak frequency fp is slightly changed, so that a plurality of adjustment operations are required to obtain target frequency characteristics.
As shown ln Fig. lOB, however, since the degree of change in peak frequency fp is very small, adjustment need only be repeated a maximum of several times.
When the carrler frequency fc and the cycle count N
of the pulse signal a applled to the ultrasonic probe are changed, the peak frequency fp and the frequency bandwidth W of the echo slgnal b obtalned upon detection of a defect by the ultrasonic probe can be independently controlled. The frequ~ncy characteristics of the echo signal b can be easily matched with optimal flaw - 14 - 2~ S
detection condltions, thereby greatly lmprovlng flaw detection precislon.
There are provided a technlque for matching the frequency bandwidth W with an optimal frequency bandwidth determlned by the material of an ob~ect after the peak frequency fp of the echo signal b is matched with an optimal frequency determined by the material of the object, and a technique for matching the peak fre-quency with an optimal value after the frequency bandwidth is matched with an optlmal value. In either technique, the target peak frequency and frequency bandwidth can be obtained.
Control of the peak frequency can be performed independently of control of the frequency bandwidth.
Fig. 1 is a block diagram showing a schematic arrangement of an ultrasonic flaw detection apparatus employing a flaw detection method of this embodiment.
An ob;ect 1 is a steel plate or the like. For example, a vertical ultrasonic probe 2 is attached to the surface of the ob;ect 1. The tone-burst signal a having the carrier frequency fc and the cycle count N, as shown in Fig. 2A, is applied from an ultrasonic transmission unit 3 to the ultrasonic probe 2. If a defect or flaw is present in the ob;ect 1, the echo sig-nal b shown in Fig. 2B is output from the ultrasonicprobe 2 to an ultrasonic receiving unit 4.
A transmission control unit 5 comprises, e.g., 2C~5~?~5 a microcomputer. The transmlsslon control unlt 5 con-trols the carrler frequency fc and the cycle count N of the pulse si~nal a output from the ultrasonlc transmis-sion unit 3 in accordance with flaw detection conditions stored in a flaw detection condition memory 6. A signal analysis unit 7 has, e.g., an FFT (Fast-Fourier Transform) functlon and analyzes the frequency of the echo signal b received by the ultrasonic recelving unit 4 and feeds back the analysis result to the transmission control unit 5. The signal analysls unlt 7 also deter-mines the presence/absence of a defect in accordance with the level of the input echo signal b. In addition, the signal analysis unit 7 can also calculate the size of a defect and display it on a display unlt 8.
The flaw detectlon condition memory 6 stores, in units of materials of the objects 1, the optimal peak frequency fp and the optimal frequency bandwidth W of the echo signal b output from the ultrasonic probe 2 attached to the ob;ect 1. Various conditions such as allowable ranges ~fm and ~Wm of the peak frequency fp and the frequency bandwidth W are also stored in the flaw detection condition memory 6.
When a flaw detection condition command is input from a keyboard (not shown) to the transmission control unit 5, the carrier frequency fc and the cycle count N
of the pulse signal a are set in accordance with a flow chart in Fig. 3.
z~ a5 .
If this ultrasonlc flaw detectlon apparatus ls a multichannel apparatus, a large number of probes 2 are regarded to be arranged on one ob~ect 1. Peak frequen-cies fp and frequency bandwldths W of echo slgnals b obtained from all channels except for a reference chan-nel must be matched with those of the reference channel.
In this case, in step P (program step) 1, the transmission control unit 5 transmits a transmission command to the ultrasonic transmission unit 3 of the reference channel to cause the ultrasonic transmission unit 3 to output a pulse signal a having a carrier fre-quency fc and a cycle count N which are currently set in the ultrasonic transmission unit 3. The ultrasonic receiving unit 4 receives the echo signal b output from the ultrasonic probe 2. The signal analysis unit 7 per-forms frequency analysis of the received echa signal to obtain the peak frequency fp, the -6-dB lower frequen-cies fH and fL, and the frequency bandwidth W of the input echo signal. The transmission control unit 5 stores these values, i.e., fp, fH, fL, and w as flaw detectlon conditions in the flaw detection condition memory 6. The flow then advances to step P3.
When the echo signals b of all the channels except for the reference channel are to be matched with spe-cific flaw detection conditions, the transmissioncontrol unit 5 reads out frequency characteristics such as the optimal peak frequency fp and the optimal 2~ s frequency bandwidth W stored ~P2) in the flaw detectlon condltion memory 6.
In step P3, the transmlsslon control unlt 5 reads out the allowable ranges Qfm and ~Wm from the flaw detection condition memory 6 and sets them in, e.g., a buffer memory, thereby setting parameter control steps ~f and ~N. The carrier frequency fc and the cycle count N of the ultrasonic transmission unit 3 are set to ini-tlal values.
In step P4, the transmission control unit 5 causes the ultrasonic transmission unit 3 to output the pulse signal a having the set carrier frequency fc and the set cycle count N to the ultrasonic probe 2. The ultrasonic receiving unit 4 receives an echo signal b from the ultrasonic probe 2. The signal analysis unit 7 performs frequency analysis of the echo signal b to obtain the peak frequency fp and the frequency bandwidth W. In step P5, the transmission control unit 5 compares the peak frequency fp of the echo signal b with the peak frequency fp as one of the preset flaw detection conditions. If the difference between the measured peak frequency fp and the peak frequency fp as the flaw detection condition does not fall within the allowable range ~fm in step P6, the carrier frequency fc of the pulse slgnal a is changed by the small frequency ~f in step P7. The flow then returns to step P4, and another pulse signal a is then output.
z~ s When the dlfference between the measured peak fre-quency fp and the measured peak frequency fp falls wlthin the allowable range ~fm ln step P6, the transmls-slon control unlt 5 compares the measured frequency bandwldth W with the frequency bandwldth W as one of the flaw detection condltions in step P8. If the difference between the measured frequency bandwidth w and the fre-quency bandwidth W as one of the flaw detection condi-tions does not fall wlthln the allowable range ~Wm ln step P9, the cycle count N of the pulse slgnal a ls changed by the small cycle count ~N in step P10. The flow then returns to step P4, and another pulse signal a is output.
When the difference between the measured frequency bandwldth w and the frequency bandwidth W as the flaw detectlon condltlon falls wlthln the allowable range QWm in step P9, flaw detection condition setup processing for this channel is completed.
As shown ln Fig. 4, setup processing of the fre-quency bandwldth W may be performed before setup proc-essing of the peak frequency fp.
Effects of the ultrasonlc flaw detection apparatus having the above arrangement wlll be described with ref-erence to Figs. 5A to 6B.
2s Figs. 5A and 5s are graphs showing signal waveforms and frequency characteristics of echo signals b obtained by flaw detection using two ultrasonic probes C and D
2~ s having identical technlcal specifications. The ultra-sonic probes C and D are driven such that the same lmpulse signal as in the conventional apparatus is applied to the ob~ect 1 having a reference defect or 5 flaw. As shown in Figs. 5A and 5B, even if these ultra-sonic probes have the identical speclficatlons, a dif-ference occurs between the resultant echo signals b.
Peak frequencies fp are different from each other between the echo signals by about 0.5 MHz, and their frequency bandwidths W are also slightly different from each other.
Figs. 6A and 6B are graphs showing signal waveforms and frequency characteristics of echo signals b obtained when flaw detection is performed using the above two ultrasonic probes C and D. The carrier frequencies fc and the cycle counts N of the pulse signals a are set by control as shown in Fig. 3 so that the peak frequencies fp and the frequency bandwidths W of the resultant echo signals b coincide with each other. As is understood from Figs. 6A and 6B, even if a characteristic differ-ence is present between the ultrasonic probes C and D, the flaw detection conditions represented by the peak frequencies fp and the frequency bandwidths w of the output echo signals _ can coincide with each other.
That is, flaw detection errors between the channels in the multichannel ultrasonic flaw apparatus can be minimized.
X~ 35 Figs. 7 and 8 are graphs obtalned when flaw detec-tion is performed after two dlfferent lateral test holes A and B are formed. An ob~ect 1 comprises a hlgh atten-uation materlal in which correlation between the lateral hole diameter and the signal level of an echo signal is lost. The ultrasonic flaw detection method of the above embodiment ls applied to this ob~ect 1. As shown in Fig. 7, an echo signal b obtained upon detection of the lateral hole can maintain a single frequency.
That is, an optimal peak frequency fp of the echo signal is set to be an optimal value determined by the material of this ob;ect 1, and its frequency bandwidth W
is set narrow, thereby minimizing noise echoes, caused by the structure of the ob;ect 1, included in the echo signal b. The S/N ratio of the echo signal b can be largely increased, and flaw detection precision can be greatly improved.
There is often an object having flaw detection characteristics which make it difficult to detect a defect due to a low S/N ratio caused by high attenuation (caused ~y ultrasonic scattering) and drill echoes.
This object has a small frequency difference between the peak frequency fp of the echo signal output by a wave reflected by a defect and the peak frequency of the echo signal of structural noise such as drill echoes caused by the composition of the material structure of the ob;ect 1.
2~5~ 5 The tone-burst pulse signal b ls used to ad~ust the carrier frequency fc f the pulse slgnal b to slightly shift the peak frequency fp of the echo signal obtained upon detection of a defect from the peak frequency of the echo signal of the structural noise. At the same time, the cycle count N is ad~usted to be an appropriate value, and the frequency bandwidth W of the echo signal b is set to be minimized. In principle, then, the S~N
ratio of the echo signal b output from the ultrasonic probe 2 can be greatly improved as compared with the conventional technique using the impulse signal.
As shown in Fig. 8, even if the carrier frequency fc Of the pulse signal a is changed, the peak frequency fp and the -6-ds lower fre~uencies fH and fL have the same tendency as the experimental results shown in Figs. 9A and lOA. Even if the object comprises a high attenuation material, the peak frequency fp and the frequency bandwidth W of the echo signal b can be independently controlled. Therefore, control is not complicated, and the setup operations of the ultrasonic flaw detection conditions can be facilitated.
The present invention has been applied to the method and apparatus for performing ultrasonic flaw detection to detect a defect or flaw present in an ob~ect. However, the principle of the present invention is applicable to a wide range of flaw detection.
For example, the present invention is applicable to - 22 - ~C ~ S
an ultrasonic tester, an ultrasonlc flaw detection unlt, and an ultrasonic dlagnosis apparatus, all of which use a pulse echo method.
When ad~ustment and uniform control in the fre-quency range of transmisslon pulses applled to objectsare established, the present invention is also applica-ble to the following regions:
(a) Flaw discrimination by frequency optimization for a boundary damage of various types of bonding mate-rials and coating materials, or damage evaluation in afrequency range; and (b) Applications to evaluation of material proper-ties by means of pulse propagation behavior analysis in ~onsideration of information of the frequency region.
Claims (12)
1. A method of performing ultrasonic flaw detection, comprising the steps of:
outputting a pulse signal to an ultrasonic probe attached to an object to be tested and causing an ultra-sonic wave to be incident on the object;
causing said ultrasonic probe to receive a reflected wave of the ultrasonic wave incident on the object to obtain an echo signal;
setting a carrier frequency of the pulse signal so that a peak frequency of the echo signal becomes a pre-determined frequency;
setting a cycle count of the pulse signal so that a frequency bandwidth of the echo signal becomes a prede-termined bandwidth; and detecting a defect present in the object in accor-dance with the echo signal output from said ultrasonic probe.
outputting a pulse signal to an ultrasonic probe attached to an object to be tested and causing an ultra-sonic wave to be incident on the object;
causing said ultrasonic probe to receive a reflected wave of the ultrasonic wave incident on the object to obtain an echo signal;
setting a carrier frequency of the pulse signal so that a peak frequency of the echo signal becomes a pre-determined frequency;
setting a cycle count of the pulse signal so that a frequency bandwidth of the echo signal becomes a prede-termined bandwidth; and detecting a defect present in the object in accor-dance with the echo signal output from said ultrasonic probe.
2. A method of performing ultrasonic flaw detection, comprising the steps of:
outputting a pulse signal to an ultrasonic probe attached to an object to be tested and causing an ultra-sonic wave to be incident on the object;
causing said ultrasonic probe to receive a reflected wave of the ultrasonic wave incident on the object to obtain an echo signal;
setting a cycle count of the pulse signal so that a frequency bandwidth of the echo signal becomes a pre-determined bandwidth;
setting a carrier frequency of the pulse signal so that a peak frequency of the echo signal becomes a pre-determined frequency; and detecting a defect present in the object in accor-dance with the echo signal output from said ultrasonic probe.
outputting a pulse signal to an ultrasonic probe attached to an object to be tested and causing an ultra-sonic wave to be incident on the object;
causing said ultrasonic probe to receive a reflected wave of the ultrasonic wave incident on the object to obtain an echo signal;
setting a cycle count of the pulse signal so that a frequency bandwidth of the echo signal becomes a pre-determined bandwidth;
setting a carrier frequency of the pulse signal so that a peak frequency of the echo signal becomes a pre-determined frequency; and detecting a defect present in the object in accor-dance with the echo signal output from said ultrasonic probe.
3. A method of performing ultrasonic flaw detection, comprising the steps of:
outputting a pulse signal to an ultrasonic probe attached to an object to be tested and causing an ultra-sonic wave to be incident on the object;
causing said ultrasonic probe to receive a reflected wave of the ultrasonic wave incident on the object to obtain an echo signal;
setting a carrier frequency of the pulse signal independently of a frequency bandwidth of the echo sig-nal so that a peak frequency of the echo signal becomes a predetermined frequency;
setting a cycle count of the pulse signal independ-ently of the peak frequency of the echo signal so that the frequency bandwidth of the echo signal becomes a predetermined bandwidth; and detecting a defect present in the object in accordance with the echo signal output from said ultra-sonic probe.
outputting a pulse signal to an ultrasonic probe attached to an object to be tested and causing an ultra-sonic wave to be incident on the object;
causing said ultrasonic probe to receive a reflected wave of the ultrasonic wave incident on the object to obtain an echo signal;
setting a carrier frequency of the pulse signal independently of a frequency bandwidth of the echo sig-nal so that a peak frequency of the echo signal becomes a predetermined frequency;
setting a cycle count of the pulse signal independ-ently of the peak frequency of the echo signal so that the frequency bandwidth of the echo signal becomes a predetermined bandwidth; and detecting a defect present in the object in accordance with the echo signal output from said ultra-sonic probe.
4. A method according to claim 3, wherein the step of controlling the carrier frequency of the pulse signal and the step of controlling the cycle count of the pulse signal are repeated at least once each.
5. An apparatus for performing ultrasonic flaw detection, comprising ultrasonic transmitting means for outputting a pulse signal having a designated carrier frequency and a designated cycle count, an ultrasonic probe, attached to an object to be tested, for outpu-tting an ultrasonic wave to the object in response to the pulse signal input from said ultrasonic transmitting means and for outputting an echo signal, ultrasonic receiving means for receiving the echo signal output from said ultrasonic probe, signal analyzing means for detecting a peak frequency and a frequency bandwidth of the echo signal received by said ultrasonic receiving means, and transmission control means for designating the carrier frequency and the cycle count of the pulse signal output from said ultrasonic transmitting means so that the detected peak frequency and the detected fre-quency bandwidth become the predetermined peak frequency and the predetermined frequency bandwidth, respectively.
6. An apparatus according to claim 5, further com-prising flaw detection condition memory means for stor-ing an optimal peak frequency and an optimal frequency bandwidth in units of materials of the objects.
7. An apparatus according to claim 6, wherein said flaw detection condition memory means stores the optimal peak frequency and the optimal frequency bandwidth in units of materials of the objects, and all-owable ranges of the optimal peak frequency and the optimal frequency bandwidth, and said transmission control means designates to change the carrier frequency and the cycle count of the pulse signal when the peak frequency and the frequency bandwidth of the echo signal fall outside the allowable ranges.
8. An apparatus according to claim 6, wherein said signal analyzing means incorporates a fast Fourier transform circuit for performing frequency analysis of the echo signal and calculates the peak frequency and the frequency bandwidth of the echo signal by using said fast Fourier transform circuit.
9. An apparatus for performing ultrasonic flaw detection, comprising ultrasonic transmitting means for outputting a pulse signal having a designated carrier frequency and a designated cycle count, an ultrasonic probe, attached through an ultrasonic wave propagation medium to an object to be tested, for outputting an ultrasonic wave to the object in response to the pulse signal input from said ultrasonic transmitting means and for outputting an echo signal, ultrasonic receiving means for receiving the echo signal output from said ultrasonic probe, signal analyzing means for detecting a peak frequency and a frequency bandwidth of the echo signal received by said ultrasonic receiving means, flaw detection condition memory means for storing a flaw detection condition peak frequency and a flaw detection condition frequency bandwidth of the echo signal, and transmission control means for designating the carrier frequency and the cycle count of the pulse signal output from said ultrasonic transmitting means so that the detected peak frequency and the detected frequency bandwidth become the flaw detection condition peak fre-quency and the flaw detection condition frequency bandwidth, respectively.
10. An apparatus according to claim 9, further com-prising display means for displaying the detected peak frequency and the detected frequency bandwidth of the echo signal.
11. An apparatus according to claim 9, wherein said signal analyzing means incorporates a fast Fourier transform circuit for performing frequency analysis of the echo signal and calculates the peak frequency and the frequency bandwidth of the echo signal by using said fast Fourier transform circuit.
12. An apparatus according to claim 11, further comprising display means for determining a level of the echo signal, determining the presence/absence of a defect, calculating a size of the defect, and display-ing the size of the defect.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP30990190 | 1990-11-14 | ||
| JP2-309901 | 1990-11-14 | ||
| JP3160676A JPH04348275A (en) | 1990-11-14 | 1991-07-01 | Ultrasonic flaw detection |
| JP3-160676 | 1991-07-01 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2055285A1 true CA2055285A1 (en) | 1992-05-15 |
Family
ID=26487102
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002055285A Abandoned CA2055285A1 (en) | 1990-11-14 | 1991-11-12 | Method and apparatus for performing ultrasonic flaw detection |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US5309765A (en) |
| EP (1) | EP0485960B1 (en) |
| JP (1) | JPH04348275A (en) |
| CA (1) | CA2055285A1 (en) |
| DE (1) | DE69127742T2 (en) |
Families Citing this family (20)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4224035A1 (en) * | 1992-07-21 | 1994-01-27 | Siemens Ag | Ultrasound test method for flaw location - using frequency modulated chirp signal whose instantaneous frequency time characteristic is matched to transfer function of transmission path |
| US5511424A (en) * | 1994-02-15 | 1996-04-30 | The Babcock & Wilcox Company | Remote preamplifier and impedance matching circuit for electromagnetic acoustic transducer |
| FR2723446B1 (en) * | 1994-08-08 | 1996-10-25 | Aerospatiale | AUTOMATED SOUND CONTROL PROCESS FOR COMPLEX PARTS, FOR DETECTION OF SHALLOW DEFECTS |
| US5864058A (en) * | 1994-09-23 | 1999-01-26 | Baroid Technology, Inc. | Detecting and reducing bit whirl |
| CA2169307C (en) * | 1994-12-12 | 2003-10-14 | David A. Hutchins | Non-contact characterization and inspection of materials using wideband air coupled ultrasound |
| US5831157A (en) * | 1996-09-18 | 1998-11-03 | The Boeing Company | Digital bond tester |
| US6160756A (en) | 1998-06-15 | 2000-12-12 | Guigne International Limited | Seabed sonar matrix system |
| US6856918B2 (en) | 2001-11-26 | 2005-02-15 | Lockheed Martin Corporation | Method to characterize material using mathematical propagation models and ultrasonic signal |
| US6996480B2 (en) * | 2002-06-14 | 2006-02-07 | University Of South Carolina | Structural health monitoring system utilizing guided lamb waves embedded ultrasonic structural radar |
| EP2148196A1 (en) * | 2005-07-07 | 2010-01-27 | Kabushiki Kaisha Toshiba | Laser-based apparatus for ultrasonic flaw detection |
| JP5226231B2 (en) * | 2007-03-13 | 2013-07-03 | 株式会社東芝 | Ultrasonic diagnostic equipment |
| JP4853545B2 (en) * | 2009-05-25 | 2012-01-11 | 株式会社デンソー | In-vehicle communication device and communication system |
| WO2011103450A1 (en) | 2010-02-18 | 2011-08-25 | Rolls-Royce Corporation | Ultrasonic apparatus and method for determining the crystallographic texture of a polycrystalline material |
| US9753014B2 (en) | 2011-02-18 | 2017-09-05 | Rolls-Royce Corporation | Detection and measurement of defect size and shape using ultrasonic fourier-transformed waveforms |
| JP6189227B2 (en) * | 2013-02-20 | 2017-08-30 | 株式会社東芝 | Ultrasonic flaw detector and its evaluation method |
| CN103175900B (en) * | 2013-03-19 | 2016-02-17 | 中国科学院声学研究所 | A kind of phased-array non-destructive inspection device and system |
| US9594061B2 (en) * | 2014-02-11 | 2017-03-14 | Orbital Atk, Inc. | Methods and apparatus for detecting defects in an object of interest |
| CN104655727A (en) * | 2015-02-06 | 2015-05-27 | 北京航空航天大学 | Concrete nondestructive testing equipment based on nonlinear second harmonics theory |
| JP6933595B2 (en) * | 2018-03-14 | 2021-09-08 | 株式会社東芝 | Diagnostic equipment, diagnostic robots, diagnostic methods and programs |
| CN110658261A (en) * | 2019-10-10 | 2020-01-07 | 天津科技大学 | Structural health monitoring frequency selection method based on ultrasonic guided waves |
Family Cites Families (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4052889A (en) * | 1976-06-10 | 1977-10-11 | Adaptronics, Inc. | System for measurement of subsurface fatigue crack size |
| US4364273A (en) * | 1980-02-15 | 1982-12-21 | Redding Robert J | Apparatus for locating interfaces in media |
| JPS5910501A (en) * | 1982-07-07 | 1984-01-20 | Hirotoshi Miyajima | Agent for preserving plant and its preparation |
| DE3380939D1 (en) * | 1982-10-06 | 1990-01-11 | Welding Inst | ACOUSTIC DETECTING DEFECTS IN STRUCTURES. |
| JPS59171540A (en) * | 1983-03-18 | 1984-09-28 | 富士通株式会社 | Measurement utilizing spectrum shape |
| GB2143036B (en) * | 1983-07-08 | 1986-10-15 | Atomic Energy Authority Uk | Ultrasonic resonance for detecting changes in elastic properties |
| DE3504210A1 (en) * | 1985-02-07 | 1986-08-07 | Kraftwerk Union AG, 4330 Mülheim | DEVICE FOR DETERMINING SURFACE CRACKS |
| JPS6254160A (en) * | 1985-09-03 | 1987-03-09 | Nippon Kokan Kk <Nkk> | Ultrasonic test equipment |
| JPS62180267A (en) * | 1986-02-05 | 1987-08-07 | Mitsubishi Electric Corp | Ultrasonic flaw detecting device |
| DE3779621T2 (en) * | 1987-03-31 | 1993-02-11 | Benjamin Gavish | METHOD AND DEVICE FOR MONITORING SMALL PIK SHIFTINGS IN A FREQUENCY SPECTRUM. |
-
1991
- 1991-07-01 JP JP3160676A patent/JPH04348275A/en active Pending
- 1991-11-12 EP EP91119287A patent/EP0485960B1/en not_active Expired - Lifetime
- 1991-11-12 US US07/790,471 patent/US5309765A/en not_active Expired - Fee Related
- 1991-11-12 CA CA002055285A patent/CA2055285A1/en not_active Abandoned
- 1991-11-12 DE DE69127742T patent/DE69127742T2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| EP0485960A3 (en) | 1992-10-21 |
| DE69127742D1 (en) | 1997-10-30 |
| DE69127742T2 (en) | 1998-04-09 |
| JPH04348275A (en) | 1992-12-03 |
| US5309765A (en) | 1994-05-10 |
| EP0485960B1 (en) | 1997-09-24 |
| EP0485960A2 (en) | 1992-05-20 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Discontinued |