JP4746365B2 - Surface inspection method - Google Patents

Description

The present invention is not affected by noise, and an improvement in measurable front surface inspecting method with high accuracy even in minute defect depth.

  In many cases, the method of inspecting material surface layer defects and measuring material properties are measured using surface waves, which are elastic waves propagating along the surface of the material.

  The method of performing defect inspection using this surface wave is to send a surface wave by contacting the surface of the object to be inspected via an ultrasonic wave propagation medium and receive it using the probe, The presence or absence of a defect is determined by the presence or absence of an echo from the defect opening.

  Further, for example, Non-Patent Document 1 also describes a method of detecting the delay time of a signal component passing through the opening of a defect and an ultrasonic component reflected or diffracted at the edge of the defect and measuring the depth of the defect. ing.

  On the other hand, using the characteristics of surface waves, transmitters and receivers are individually installed at the positions where the defects are sandwiched, and the depth of the defects is estimated based on fluctuations in the surface waves that pass through the defects. For example, Japanese Patent Application Laid-Open No. H10-228707 discloses a technique for performing this.

  In this technique, as shown in FIG. 10, a signal is transmitted from an oscillator 1 that transmits a signal having a predetermined frequency f, is converted into a surface wave by a transmitting ultrasonic probe 2, and is transmitted to an inspected object TP. To do.

  The surface wave SR propagates through the surface of the inspection object TP, and if there is a defect C in the inspection object TP, it interacts with the defect C and becomes a transmitted wave ST, which is received by the receiving ultrasonic probe 3. The This received signal is received by the receiver 4 and processed by the data analysis device 5 to calculate the presence / absence of the defect C and its depth.

  Note that a contact probe using a piezoelectric effect is used for transmission / reception. In this case, the ultrasonic wave propagation medium 6 is applied between the inspection object TP and the transmission / reception probes 2 and 3.

This technology uses the fact that the penetration depth (defect) depth of surface waves changes depending on the frequency f, and the attenuation factor for each frequency of the surface wave that has passed through the defects in the surface layer of the material estimates the defect depth. It is. That is, a waveform including several different frequencies f ₁ , f ₂ ,..., Fn is used as a transmission wave, and for each frequency of the reception wave that has passed through a defect in the material surface layer with reference to the reception wave that has propagated through the healthy part. The attenuation rate α (f) is obtained, and the depth of the defect C is calculated according to the ratio of the attenuation rate amount.

  As described above, in Patent Document 1, by using the transmission method and calculating the attenuation factor of the surface wave for each frequency, the depth as well as the presence or absence of a defect can be obtained.

  As a technique for obtaining the depth of a defect from a frequency component of a transmitted wave, for example, Patent Document 2 proposes identifying the transfer characteristic of a surface wave.

  In this method, two reception ultrasonic probes are provided, and a surface wave SR incident on a defect by a reception probe close to the transmission probe is received by a reception probe far from the transmission probe. Then, the surface wave ST transmitted through the defect C is detected, and the transfer characteristic of the surface wave in the defective portion is obtained from these two signals.

For example, when the power spectrum of the surface wave signal incident on the defect is R (f) and the power spectrum of the surface wave signal transmitted through the defect C is T (f), the frequency component changes due to the defect, that is, the transfer function H ( f)
[Equation 2]
H (f) = T (f) / R (f)
The depth of the defect is identified theoretically or with reference to the calibration test result obtained in advance from the response time and cutoff frequency of the transfer function H (f).

  This technology also proposes to use a plurality of receiving ultrasonic probes to simultaneously detect a defect, identify its position, and measure the depth of the defect.

  Furthermore, the same operation is possible even if a plurality of transmitting ultrasonic probes are used instead of a plurality of receiving ultrasonic probes, and a laser ultrasonic method or an electromagnetic wave is used as a surface wave transmitting / receiving method. It also discloses the use of the law.

  Furthermore, for example, Patent Literature 2 is disclosed as another method for obtaining the depth of the defect C from the frequency component of the transmitted wave. This Patent Document 2 is an improvement of the above-mentioned Patent Document 1.

  That is, in Patent Document 1, when the length of the defect C becomes smaller than the width of the surface wave beam passing through the defect C, the attenuation amount of the surface wave is affected by both the depth and the length of the defect (surface wave beam Part of the defect is transmitted through the defect and attenuated and mixed with the component that does not transmit the remaining defect), so both cannot be detected separately. Detection was inaccurate.

However, in Patent Document 2, various depths having a sufficient length compared to the power spectrum R (f) of the transmitted wave (incident wave to the defect of Patent Document 1) transmitted through the healthy portion and the width of the surface wave beam. The power spectrum Tc (f, h) of the transmitted wave that has passed through the defect h is obtained in advance by a calibration test. Then, the transmission power spectrum T (f, h) that has passed through the defect of unknown length and depth is measured, and using the coefficient K,
[Equation 3]
T (f, h) = K × Tc (f, h) + (1−k) × R (f)
And the parameter K related to the defect length and the defect depth h are estimated by regression calculation.

  Further, Patent Document 3 is disclosed as another method for obtaining the depth of the defect from the frequency component of the transmitted wave.

This technology uses ultrasonic waves containing multiple frequency components, normalizes them with the amount of ultrasonic waves that pass through the object under test, and determines the type and depth of surface defects from the normalized frequency distribution pattern of the transmitted amount. Is detected.
JP-A-10-213573 JP 2000-180418 A Japanese Patent Laid-Open No. 2001-4599 Japanese Patent Laid-Open No. 2001-4600 Published by Yugoro Ishii, “New Edition of Nondestructive Inspection Engineering”, Sangyo Publishing, 1993, P242

  The techniques disclosed in Patent Documents 1 to 4 focus on the attenuation of the frequency component of the surface wave that has passed through the defect and measure the depth of the defect. However, the defect depth can be accurately planned. It is valid.

  However, even the techniques disclosed in Patent Documents 1 to 4 have some problems.

  There is noise as a first problem.

  As shown in FIG. 11, when the frequency f is taken on the horizontal axis and the power P is taken on the vertical axis, as shown in FIG. 11, when noise is added to the true power spectrum shown by the broken line, the noise problem is shown by the solid line. This results in a jagged parabola and a relatively large measurement error between the true power spectrum.

  In particular, the techniques disclosed in Patent Documents 1 and 3 focus on a discrete and effective number of frequencies, and the defect depth based on the attenuation rate α (f) or transmission power T (f, h) at each frequency. The effect of noise was large just by adopting the method of estimating the error, the measurement was errored, and I was completely anxious about the measured value.

  The second problem is measurement accuracy.

  Defect depths that can be measured for depth depend on the band characteristics of the probe or transmitter / receiver, or the attenuation characteristics of each material frequency, and the accuracy of measurement becomes worse for relatively shallow or relatively deep defects. Yes.

  Such problems will now be explained in detail.

  In general, a surface wave has the property of being localized in the surface layer portion for one wavelength. The penetration (defect) depth of the surface wave of each frequency in a material having a surface wave velocity of 2900 m / s, for example, stainless steel, varies significantly from 0.1 MHz to 100 MHz as shown in FIG. It is a depth diagram.

  For example, the techniques disclosed in Patent Documents 3 and 4 use ultrasonic waves having a band up to 10 MHz and having a peak at 6 MHz. When this peak frequency of 6 MHz is plotted in FIG. 12, the penetration depth is about 0.5 mm. For this reason, when measuring the depth of a minute defect having a defect depth of 0.5 mm or less, the frequency band is a frequency region higher than 6 MHz. For this reason, the evaluation is performed with a weaker signal power as compared with a defect depth evaluation of 0.5 mm or more. This means a reduction in the signal-to-noise ratio (SN ratio) of the signal to be evaluated. As a result, for example, a defect depth of 0.3 mm or less that mainly evaluates a 10 MHz surface wave component and a 6 MHz surface wave component are mainly evaluated. The measurement accuracy is different from the defect depth of 0.5 mm. In other words, the accuracy of the estimation of the defect depth is worse for a minute defect.

  If an ultrasonic signal having a broad and flat power spectrum distribution from a low frequency to a high frequency band is used as the intensity of the transmitted / received ultrasonic signal, such a problem does not occur.

  However, it takes a lot of cost to realize a broadband characteristic using an ultrasonic probe using a normal piezoelectric element. As for the high frequency band, even if an ultrasonic signal with a wide and flat power spectrum distribution can be oscillated, the propagation attenuation in the material differs depending on the frequency, so the signal intensity in the high frequency region also decreases during signal reception. However, the measurement accuracy of the minute defect depth is deteriorated.

  For this reason, the techniques disclosed in Patent Document 2 and Patent Document 4 are a method of evaluating using the entire power spectrum distribution of the transmitted defect wave, and the measurement accuracy is poor as in Patent Document 1 and Patent Document 3. .

The present invention has been made in view of such circumstances, the front surface inspection without being affected by noise, and to defects of small depth, you allow more accurate depth measurements It aims to provide a method.

Further, in order to achieve the above object, the surface inspection method according to the present invention is based on the attenuation rate of the intensity of the transmitted wave in the frequency band in which the defect of the object to be inspected is transmitted using the surface wave. In a surface inspection method for estimating the depth of a defect, a step of calculating a power spectrum of a transmitted wave that passes through the defect of the object to be inspected, integrating a power spectrum of the transmitted wave in a frequency band to be evaluated, and integrating the integration A step of calculating a value, a step of calculating a defect depth of the object to be inspected by collating the calculated integrated value with a calibration integral value-defect depth conversion means prepared in advance, and calculating Displaying the defect depth of the object to be inspected.

Engaging Ru front surface inspection method according to the present invention, a transmitting ultrasonic transducer for transmitting a surface acoustic wave to the defect of the inspection object, an ultrasonic probe for receiving for receiving a transmitted wave transmitted through the defect, the It is equipped with a defect evaluation device that calculates the depth of the defect based on the transmitted wave from the receiving ultrasonic probe, and incorporates an algorithm for calculating and estimating the defect depth into this defect evaluation device. Of these steps, the calculated power spectrum is integrated, and the frequency weighting calculation is performed. Therefore, the depth of the defect can be accurately estimated without being affected by noise.

Hereinafter will be described a code of one embodiment of the fastening Ru front surface inspection method according to the present invention were subjected to drawings and by reference.

  FIG. 1 is a conceptual diagram showing a first embodiment of a surface inspection apparatus according to the present invention.

  The surface inspection apparatus according to the present embodiment includes a transmission ultrasonic probe 12 and a reception ultrasonic probe 13 which are brought into contact with an object to be inspected 10 via ultrasonic propagation layers 11a and 11b. And a transmitter 14 connected to the transmitting ultrasonic probe 12, and a defect evaluation device 16 a is provided on the receiving ultrasonic probe 13 with a receiver 15. A signal having the frequency f is transmitted to the inspected object 10 by the transmitting ultrasonic probe 12 instead of the surface wave SR.

  The surface wave SR transmitted to the inspected object 10 propagates through the surface of the inspected object 10, and if there is a defect C on the surface, it becomes a transmitted wave ST attenuated by the defect C, and the receiving ultrasonic wave The probe 13 receives the signal.

  This received signal is received by the receiver 15 and processed by the defect evaluation device 16a to calculate the presence / absence of the defect C and its depth.

That is, as shown in FIG. 8, when the transmitting ultrasonic probe 12 and the receiving ultrasonic probe 13 detect the defective portions C ₁ , C ₂ , and C ₃ during scanning of the inspection object 10, The waveforms of the detected defective portions C ₁ , C ₂ , C _{3 and} the waveform of the healthy portion are represented as shown in FIG.

  Here, FIG. 9 shows the measurement position on the horizontal axis and the defect depth on the vertical axis, and is a diagram showing the evaluation index of the defective part when the defect of the healthy part is zero.

As described above, in the present embodiment, the defect depths d ₁ , d ₂ ,... Of the defect portions C ₁ , C ₂ , C ₃ are determined based on the defect depth zero (0) of the healthy portion in the inspection object 10. Calculated as an evaluation index.

  Note that this embodiment uses the fact that the penetration (defect) depth of the surface wave SR changes depending on the frequency f, so that for each frequency of the transmitted wave ST transmitted through the defect C in the surface layer portion of the inspection object 10. The defect depth is estimated from the attenuation rate. However, the present invention is not limited to this example. For example, as shown in FIG. 2, an ultrasonic transmission laser that irradiates the inspection target 10 with laser light GL modulated in a pulse shape. When the device 17 and the laser beam GL are irradiated to the object 10 to be inspected, the surface layer portion is vaporized or thermally expanded, and an ultrasonic wave is generated by the distortion, and the generated surface wave SR passes through the defect C. When the transmitted laser beam ST reaches the reception position while vibrating, the frequency, phase, and reflection direction of the irradiated received laser beam DLD are changed by the vibration, and the received ultrasonic wave DLI as the change information is received by the ultrasonic wave. Receiving laser device 18 , Based on the information from the ultrasonic receiving laser apparatus 18 may be used surface inspection apparatus including the defect evaluation apparatus 16b for processing the presence and its depth of defect C of the device under test 10.

  Thus, the use of laser ultrasonic waves is effective in that broadband ultrasonic waves can be transmitted and received.

  By the way, the defect evaluation apparatuses 16a and 16b shown in FIGS. 1 and 2 incorporate processing and procedures for estimating the depth of the defect C occurring in the inspection object 10.

  FIG. 3 is a block diagram showing a first embodiment of the surface inspection method according to the present invention, which is a processing procedure for estimating the depth of the defect C occurring in the inspection object 10.

  In the surface inspection method according to the present embodiment, when the inspection object 10 has a defect C, the surface 10 is transmitted therethrough and an attenuated transmission signal is received (step 1), and the received signal is converted from analog to digital ( Step 2) After conversion into a digital signal, the evaluation time region is cut out (step 3).

  For example, as shown in FIG. 7, this cut-out is performed by evaluating, for example, a longitudinal wave or the like of a peak value of a surface wave or an amplitude waveform in a predetermined time zone.

  When the specific region to be investigated is cut out (step 3), the power spectrum T (f) in the time domain to be evaluated, that is, the frequency function is calculated (step 4), and the integrated value I of the power spectrum in the evaluation frequency domain is calculated. Is calculated (step 5).

  This integral value I is not a power spectrum T (f) that passes through defects at discrete frequencies, but an integral value in a frequency band specified as an object to be evaluated.

The integral value I is expressed as follows: when the minimum frequency in the specified frequency band is f _L and the maximum frequency is f _H ,

It can be obtained from the following formula.

Also, when considering digital values, the digital integrated value J over the entire frequency band is

Is an evaluation index.

Note that the integral value I and its digital integral value J in the frequency band specified as described above are normalized using the power spectrum R (f) of the surface wave SR of the healthy part, and the normalized integral value I _norm and The standardized digital integral value J _norm is

May be used as an evaluation index, or an integrated value I _norm−1 and a standardized digital integrated value J _norm−1 in a specific frequency band standardized by another method are expressed as follows:

May be used as an evaluation index.

  When the integral value I of the power spectrum is calculated (step 5), in the present embodiment, an integral value / defect depth conversion relationship diagram is prepared in advance with a test piece or the like (step 6). The integrated value I of the frequency is plotted on the defect depth conversion relationship diagram to calculate the integrated value / defect depth converted value (step 7).

  Then, the depth of the defect C occurring in the inspection object 10 is displayed on a display or the like (step 8).

  As described above, in the present embodiment, the power spectrum in the frequency region to be evaluated is integrated, and this integrated value I is collated with a previously prepared integrated value defect depth conversion relationship diagram, Since the depth of the defect C is estimated, the depth of the defect can be accurately estimated without being affected by noise.

  FIG. 4 shows a second surface inspection method according to the present invention, which is a processing procedure for estimating the depth of the defect C of the inspection object 10 incorporated in the defect evaluation apparatuses 16a and 16b shown in FIGS. It is a block diagram which shows embodiment.

In the surface inspection method according to the present embodiment, when an evaluation index of an evaluation target region is obtained, the frequency band in the target region to be evaluated is weighted (frequency variation distribution becomes clearer) in the power spectrum (f) of the transmission signal at each frequency f. The transmission power spectrum E (f) normalized by multiplying the weight function W (f) with
E (f) = W (f) × T (f)
And the weight function W (f) of the power spectrum R (f) of the passing wave that passes through the healthy part of the object 10 and the power spectrum T (f) of the transmitted wave that passes through the defect part. It applies to both.

  Here, as one example of the weighting function W (f), an inverse function of the power spectrum R (f) of the passing wave in the healthy part of the device under test 10 is applied.

The normalized passing power spectrum E (f) at this time is

Can be expressed as

The weight function W (f) is
[Equation 10]
W (f) = f ⁿ
And can be applied by replacement.

Thus replacing the weighting function W (f) is the f ⁿ frequency f, the change of the specific frequency of interest to be evaluated becomes remarkably sharp, metrics become clearer.

  Here, n can be determined arbitrarily. For example, when it is desired to pay attention to a high frequency region that enhances the detection sensitivity of a minute defect, a number of n ≧ 1 may be employed.

  When the dominant attenuation factor in the propagation path can be specified as the transition in the material or the scattering by the crystal grains, the attenuation due to the transition is generally proportional to the frequency f, and the attenuation due to the grain boundary scattering is the frequency f. It is preferable to adopt n = 2 or n = 4 from the proportional physical model.

When applying such a weighting function W (f), the present embodiment first calculates a power spectrum R (f) in the time domain to be evaluated on the investigation specific object in the healthy part 19 of the object 10 to be inspected. (Step 4a) Of the calculated power spectrum R (f), the evaluation frequencies f ₁ , f ₂ ,..., F _n are multiplied by a weight function, and the frequencies f ₁ , f _{2 ,.} It performs weighting calculation (step _{4a 1, 4a 2, ...,} 4a n), the frequency _{f 1,} f 2 to be the evaluation, ..., attenuation of _{f n α (f 1),} α (f 2), ... , Α (f _n ) is calculated (steps 4b ₁ , 4b ₂ ,..., 4b _n ).

When the attenuation amounts α (f ₁ ), α (f ₂ ),..., Α (f _n ) of the frequencies f ₁ , f ₂ ,..., F _n to be evaluated are calculated (steps 4 b ₁ , 4 b ₂ ,. , 4b _n ), in this embodiment, a database of attenuation defect depths is created in advance using a test piece or the like (step 6a), and the frequencies f ₁ , f ₂ ,. attenuation of _{f n α (f 1),} α (f 2), ..., checks the alpha _{(f n),} calculates the defect depth conversion value (step 7a).

  Then, the depth of the defect C occurring in the inspection object 10 is displayed on a display or the like (step 8a).

Further, in the present embodiment, the power spectrum T (f) is calculated for the defective portion 20 of the inspection object 10 in the same manner as described above (step 4b), and the frequencies f ₁ , f ₂ ,. It performs weighting calculation of f _n (step _{4c 1, 4c 2, ...,} 4c n), the frequency _{f 1,} f 2 to be evaluated and each, ..., attenuation of _{f n α (f 1),} α (f 2 ,..., Α (f _n ) are calculated (steps 4d ₁ , 4d ₂ ,..., 4d _n ), and the attenuation amount α (f ₁ ), α is added to the previously created database (step 6b). (F ₂ ),..., Α (f _n ) are collated, a defect depth converted value is calculated, and this data information is displayed (step 7b, step 8b).

  Since other steps are the same as those in the first embodiment, the same reference numerals or subscripts “a” and “b” are only added, and redundant description is omitted.

As described above, in the present embodiment, the weighting calculation of the evaluation frequencies f ₁ , f ₂ ,..., F _n is performed on both the healthy part 19 and the defective part 20 of the inspection object 10 (steps 4 a ₁ , 4 a ₂ ,. 4a _n ), attenuation amounts α (f ₁ ), α (f ₂ ),..., Α (f _n ) of the frequencies f ₁ , f ₂ ,..., F _n to be evaluated are calculated (steps 4 b ₁ , 4 b). ₂ ,..., 4 b _n ) and the calculated attenuation amounts α (f ₁ ), α (f ₂ ),..., Α (f _n ) are collated with a database (steps 6 a and 6 b) created in advance, and defects are detected. Since the depth converted value is calculated (steps 7a and 7b), even if the defect C of the inspection object 10 is very small, it can be detected with high accuracy.

  FIG. 5 shows a third example of the surface inspection method according to the present invention, which is a processing procedure for estimating the depth of the defect C of the inspection object 10 incorporated in the defect evaluation apparatuses 16a and 16b shown in FIGS. It is a block diagram which shows embodiment.

  The surface inspection method according to the present embodiment calculates the power spectrum T (f) in the time domain to be evaluated (step 4), and then calculates the product of the calculated power spectrum T (f) and the weighting function W (f). (Step 5a), and further, the integrated value of the weighted power spectrum W (f) × T (f) in the frequency domain to be evaluated is calculated (Step 5b), and the integrated value of the weighted power spectrum prepared in advance-defects The integral value of the above-mentioned weighted power spectrum W (f) × T (f) is collated with the conversion function (step 6c) indicating the depth relationship, and the integral value-defect depth conversion value is obtained (step 7c). The defect depth from the integrated value-defect depth conversion value is displayed (step 8c).

Here, the integrated value I of the weighted power spectrum W (f) × T (f) in step 5b can be obtained as the evaluation index by the following equation.

Also, when considering digital values, the digital integrated value J over the entire frequency band is

Can be obtained as an evaluation index.

The integrated value and digital integrated value J in the frequency band specified above are normalized using the power spectrum R (f) of the surface wave SR of the healthy part 19 of the device under test 10, and the normalized integrated value I _norm and Standardized digital integral value J _norm

As an evaluation index, or an integrated value I _norm−1 and a standardized digital integrated value J _norm−1 in a specific frequency band standardized by other methods,

As an evaluation index.

Further, when the power spectrum T (f) of the transmission signal transmitted through the defect portion 20 of the inspection object 10 is standardized, the integral value I _momentum of the transmitted wave transmitted through the defect portion 20 and the standardized digital integration value J _momentum are obtained. ,

  Alternatively, a value obtained by further normalizing these with R (f) or an integral value thereof may be used as the evaluation index.

  Further, since the other steps are the same as those in the first embodiment, the same reference numerals or subscripts a, b, and c are attached, and redundant description is omitted.

  Thus, the present embodiment calculates the power spectrum T (f) in the time domain to be evaluated (step 4), and calculates the product of the calculated power spectrum T (f) and the weighting function W (f) ( Step 5a), the integral value of the weighted power spectrum W (f) × T (f) in the evaluation frequency region is calculated (Step 5b), and the defect depth of the inspection object 10 is converted and estimated (Step 6c, Step 7c). Therefore, the depth of the defect can be accurately estimated without being affected by noise.

  FIG. 6 shows a fourth of the surface inspection method according to the present invention, which is a processing procedure for estimating the depth of the defect C of the inspection object 10 incorporated in the defect evaluation apparatuses 16a and 16b shown in FIGS. It is a block diagram which shows embodiment.

The surface inspection method according to the present embodiment is divided into three steps of a calibration test piece defect depth calculation unit 21, an actual machine sound part data information collection unit 22, and an actual machine defect depth calculation unit 23, and a calibration test piece defect. The depth calculation unit 21 derives the evaluation index-defect depth conversion function g ^-1 (I), and the derived evaluation index-defect depth conversion function g ^-1 (I) and the actual machine healthy part data information collection unit. The integration function of the weighted power spectrum W (f) × T (f) in the evaluation frequency region of the actual machine defect depth calculation unit 23 and the conversion function indicating the relationship between the integrated value of the corrected weighted power spectrum derived in 22 and the defect depth. The integral value-defect depth conversion value is obtained from the value I, and the depth of the actual machine defect is estimated.

  The processing procedures in the calibration specimen defect depth calculation unit 21, the actual machine sound part data information collection unit 22, and the actual machine defect depth calculation unit 23 are the steps 1 to 3 shown in the first to third embodiments. Since 8c is the same as one of the steps, a duplicate description is omitted here.

However, the calibration specimen defect depth calculation unit 21 derives the evaluation index-defect depth conversion function g ⁻¹ (I) by the following processing procedure.

First, comprises normal area (defect depth _d 0 = 0), at least two different known depths _{d 1,} d 2, ..., to prepare the calibration test piece having a defect _{d n.} Here, the defect length has a sufficiently long defect length compared to the width of the surface wave beam to be used, and the maximum depth _dn is deeper than the maximum depth to be inspected in an actual inspection operation. ing.

  Further, it is desirable that the calibration test piece not only has the above-described defects, but also has a surface condition and ultrasonic characteristics (such as sound speed and attenuation characteristics) that are as equal as possible to the object 10 to be actually inspected. If the current state of the object to be inspected 10 cannot be specified, the surface state and ultrasonic characteristics (sound speed, attenuation characteristics, etc.) may be simulated as much as possible based on manufacturing data.

In this calibration test pieces, each defect depth d _1, d 2, _..., the transmitted surface wave measured with respect to d _n, by applying the first embodiment to the result calculated value in the third embodiment, calibration An integrated value I ^c (d) or a digital integrated value J ^c (d) (represented by I ^c (d) in the following description for the sake of simplicity) is calculated as an evaluation index. The relationship between the obtained integrated value I ^c (d) and the known defect depth d is fitted in a function form, and an evaluation index-defect depth conversion function g ⁻¹ (I) is obtained from the result g (d).

  In actual inspections, the measurement conditions such as sensitivity must be as constant as possible as in the calibration test, but the following procedure is taken in consideration of unavoidable changes.

First, at the time of actual inspection, a transmitted surface wave of a healthy part is measured at a part where it can be guaranteed that there is no defect, and the calculated value in the first to third embodiments is applied to the result, and zero (0 ) Evaluation index I (0). This is compared with zero (0) data I ^c (0) in the calibration specimen, and the evaluation index-defect depth conversion function g ⁻¹ (I) is recalibrated.

The recalibration method depends on the difference between the calibration condition and the actual measurement condition.
I = g (d) − (I ^c (0) −I (0))
Alternatively, β = I (0) / I ^c (0) is introduced,
[Equation 17]
I = β · g (d)
And its inverse function g ⁻¹ (I) or J ⁻¹ (I).

  As described above, according to the present embodiment, when the actual machine defect depth is estimated, the calibration test piece defect depth calculation unit 21, the actual machine sound part data information collection unit 22, and the actual machine defect depth calculation unit 23 divided into three are divided. The defect depth is calculated from the conversion function derived by each and the integral value of the weighted power spectrum W (f) × T (f) and the defect depth is estimated, so that the defect is accurately detected without being affected by noise. Can be estimated.

The conceptual diagram which shows 1st Embodiment of the surface inspection apparatus which concerns on this invention. The conceptual diagram which shows 2nd Embodiment of the surface inspection apparatus which concerns on this invention. The block diagram which shows 1st Embodiment of the surface inspection method which concerns on this invention. The block diagram which shows 2nd Embodiment of the surface inspection method which concerns on this invention. The block diagram which shows 3rd Embodiment of the surface inspection method which concerns on this invention. The block diagram which shows 4th Embodiment of the surface inspection method which concerns on this invention. The figure which shows the cut-out as an evaluation object area | region among the waveforms of the surface wave applied to the surface inspection method which concerns on this invention. The figure which shows the position of the defect detected during the to-be-inspected object scan of the ultrasonic probe for transmission, and the ultrasonic probe for reception in the surface inspection apparatus which concerns on this invention. The surface inspection apparatus which concerns on this invention WHEREIN: The figure which shows the evaluation parameter | index of a defective part when a healthy part is made into the waveform when a surface wave propagates the healthy part and defect of a to-be-inspected object. The conceptual diagram which shows the conventional surface inspection apparatus. The power spectrum comparison diagram which compares the power spectrum distribution of an ideal surface wave with the power spectrum distribution actually measured. The penetration depth diagram which shows the relationship between a frequency and the defect depth of a to-be-inspected object.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transmitter 2 Transmission ultrasonic probe 3 Reception ultrasonic probe 4 Receiver 5 Data analysis apparatus 10 Inspected object 11a, 11b Ultrasonic propagation layer 12 Transmission ultrasonic probe 13 Reception ultrasonic wave Probe 14 Transmitter 15 Receiver 16a, 16b Defect evaluation device 17 Ultrasonic transmission laser device 18 Ultrasonic reception laser device 19 Sound portion 20 Defect portion 21 Calibration test piece defect depth calculation portion 22 Actual device sound portion data information Collection unit 23 Actual machine defect depth calculation unit

Claims (6)

In a surface inspection method for estimating a defect depth of an object to be inspected from an attenuation rate of intensity of a transmitted wave in a frequency band in which the defect of the object to be inspected is transmitted using a surface wave, the defect of the object to be inspected is transmitted. Calculating the power spectrum of the transmitted wave to be integrated, integrating the power spectrum of the transmitted wave in the frequency band to be evaluated, calculating the integrated value thereof, and a previously prepared integral value for calibration-defect Comparing the calculated integral value with a depth conversion means to calculate the defect depth of the object to be inspected, and displaying the calculated defect depth of the object to be inspected. Surface inspection method. In the surface inspection method for estimating the defect depth of the inspection object from the attenuation rate of the intensity of the transmitted wave in the frequency band that has transmitted the defect of the inspection object using the surface wave, the depth of the defect of the inspection object In estimating the length, the step of dividing the region of the object to be inspected into a healthy part and a defective part, calculating a power spectrum of a transmitted wave that passes through the separated healthy part, and for each frequency component to be evaluated in the healthy part A step of calculating a weighting function that gives a weight to the component, a step of calculating a power spectrum of a transmitted wave that passes through the classified defect portion, and a weighting function that gives a weight to each frequency component to be evaluated in the defect portion and steps to evaluate the value and the division defect portion weighting the power spectrum of each frequency component to be evaluated in the normal area that the division Steps and attenuation for calibrating prepared in advance to calculate the attenuation of each frequency component to be voted to the value of weighting the power spectrum of each can frequency components - the calculated attenuation in the database of defect depth A surface inspection method comprising: a step of calculating the defect depth of the inspection object by comparing the above and a step of displaying the calculated defect depth of the inspection object. In a surface inspection method for estimating a defect depth of an object to be inspected from an attenuation rate of intensity of a transmitted wave in a frequency band in which the defect of the object to be inspected is transmitted using a surface wave, the defect of the object to be inspected is transmitted. A power spectrum of the transmitted wave to be calculated; a step of calculating a product of the power spectrum of the transmitted wave and a weighting function; a step of calculating an integral value of the weighted power spectrum in a frequency domain to be evaluated; The step of calculating the defect depth of the object to be inspected by comparing the calculated integral value of the weighted power spectrum with the weighted power spectrum integral value for calibration-defect depth conversion means previously calculated, and And a step of displaying a defect depth of the object to be inspected. In the surface inspection method for estimating the defect depth of the inspection object from the attenuation rate of the intensity of the transmitted wave in the frequency band that has transmitted the defect of the inspection object using the surface wave, the depth of the defect of the inspection object is the estimation to step calibration test strip defect depth calculating step, is divided into a actual healthy section data information acquisition process and the actual defect depth calculating step, the calibration test strip defect depth calculating steps sectioned, to be evaluated A step of calculating a power spectrum in the time domain, a step of calculating a product of the power spectrum and a weighting function, a step of calculating an integrated value of the weighted power spectrum in the frequency domain to be evaluated, and a conversion function from the depth of the defect deriving, in the actual sound unit data information collection step that is divided, scan to calculate the power spectrum of the time to be evaluated area And-up, calculating a product of the weighting function the power spectrum, and calculating the integral value of the weighted power spectrum in the frequency domain to be evaluated, healthy specimens in the calibration test strip defect depth calculating step integral value of weighting the power spectrum data corrected based on the - calculating deriving the conversion function of the defect depth, in the actual defect depth calculating step was divided, the power spectrum of the time domain to be evaluated A step of calculating a product of the power spectrum and a weighting function, a step of calculating an integrated value of the weighted power spectrum in the frequency domain to be evaluated, and the weighted power spectrum derived in the actual machine healthy part data information collecting step The calculated weighting parameter is used as the integral value-defect depth conversion function. Step a, surface inspection method characterized by comprising the steps of calculating by said displaying the defect depth of the device under test to calculate the defect depth of the object to be inspected by matching an integral value of over spectrum. When the frequency is f and the natural number is n,
[Equation 1]
W (f) = f ⁿ
The surface inspection method according to claim 2 , wherein the surface inspection method is a function form of Frequency of the transmission wave table Mencken described Of waveform, any one of claims 1, 2, 3, 4, characterized in that selects either one surface wave peak value and the longitudinal Survey method.

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