KR101964758B1 - Non-contact nonlinear ultrasonic diagnosis apparatus - Google Patents

Abstract

The ultrasonic diagnostic apparatus of the present invention comprises an irradiating unit for generating ultrasonic waves propagated from a first surface to a second surface of an object to be inspected; A first receiving unit for receiving a first reflected signal of the ultrasonic wave reflected from the second surface; A second receiving unit for receiving a second reflected signal in which a time inverse signal of the first reflected signal is reflected on the second surface; And a processing unit for calculating a nonlinear parameter value of the subject using the second reflected signal.

Description

[0001] NON-CONTACT NONLINEAR ULTRASONIC DIAGNOSIS APPARATUS [0002]

The present invention relates to an ultrasonic nondestructive diagnosis apparatus for inspecting defects of an object by using ultrasonic waves.

Among the nondestructive testing methods, ultrasound testing is a representative technique for detecting defects in industrial facilities and evaluating reliability. In an ultrasonic test, nonlinear defects such as cracks are the most difficult defects to examine. For microcracks, it is a common practice to identify the diffraction wave at the tip of the crack or the reflected wave at the crack surface to perform defect inspection.

However, in the case of a closed crack or a partially closed crack, it is very difficult to detect a defect because the diffraction signal at the crack tip is very weak or the reflection signal of the crack face does not appear.

Although phased array ultrasound studies have been developed to focus a beam onto a defect and thereby enhance the detection signal, it is difficult to expect an improvement in the detection of cracks, which are nonlinear defects.

It is also possible to consider a method of detecting a nonlinear component occurring when a crack surface is opened or closed by radiating a strong incident wave and by the incident wave. However, in the case of a closed crack, nonlinearity due to crack opening / The component output is so weak that it is difficult to perform a successful inspection.

Korean Patent Registration No. 1414520 discloses a technique for determining presence or absence of a small structure by vibrating a structure by applying signals of different frequencies.

Korean Patent Registration No. 1414520

The present invention is intended to provide an ultrasonic diagnostic apparatus capable of reliably acquiring a nonlinear parameter value necessary for grasping an abnormality of an object.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not intended to limit the invention to the precise forms disclosed. Other objects, which will be apparent to those skilled in the art, It will be possible.

The ultrasonic diagnostic apparatus of the present invention comprises an irradiating unit for generating ultrasonic waves propagated from a first surface to a second surface of an object to be inspected; A first receiving unit for receiving a first reflected signal of the ultrasonic wave reflected from the second surface; A second receiving unit for receiving a second reflected signal in which a time inverse signal of the first reflected signal is reflected on the second surface; And a processing unit for calculating a nonlinear parameter value of the subject using the second reflected signal.

According to the present invention, the absolute value of the nonlinear parameter of the damaging material can be measured using ultrasound in a noncontacting method, focusing wave received in reflection mode, and focused beam based on advanced signal processing techniques.

A practical nonlinear ultrasonic diagnostic technique of a new concept capable of accurately predicting the degree of damage of the material by the absolute value of the nonlinear parameter can be provided.

1 is a schematic view showing an ultrasonic diagnostic apparatus of the present invention.
Fig. 2 is a schematic diagram showing the processing section of the present invention. Fig.
3 is a schematic diagram illustrating an ultrasonic beam focusing process by the time reversing process of the present invention.
4 is a frequency spectrum of a comparative example.
5 is a schematic view showing the ultrasonic diagnostic method of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The sizes and shapes of the components shown in the drawings may be exaggerated for clarity and convenience. In addition, terms defined in consideration of the configuration and operation of the present invention may be changed according to the intention or custom of the user, the operator. Definitions of these terms should be based on the content of this specification.

FIG. 1 is a schematic view showing an ultrasonic diagnostic apparatus of the present invention, and FIG. 2 is a schematic view showing a processing section 150 of the present invention.

The nonlinear ultrasound method for observing the second harmonic generated when a single-frequency ultrasound of a strong intensity is incident on a damage material (hereinafter referred to as the subject 10) such as plastic deformation, fatigue, and creep is an effective method for early detection of damage It is known. Nonlinear sonography, however, remains at the laboratory level, using the longitudinal wave and transmission methods, to find the correlation between the relative nonlinear parameter values and the degree of damage.

The ultrasonic diagnostic apparatus of the present invention excites an ultrasonic wave by a non-contact method and measures the nonlinear parameter value of the test object (specimen) 10 by using a focused beam based on the longitudinal wave received in the reflection mode and advanced signal processing technology To a practical novel nonlinear ultrasonic diagnostic technique capable of accurately predicting the degree of damage of the subject (10).

In order to perform diagnosis such as detecting the damage position of the subject in an actual field, it is required to measure the absolute nonlinear parameter value through calibration of the receiving module that receives the signal passing through the subject. The calibrating operation of the receiving module is performed using the second harmonic component included in the signal. However, in the case of the known nonlinear ultrasonic testing method, the measured second harmonic component has a critical limit of almost zero. Therefore, the existing nonlinear ultrasonic inspection method can not be used in an actual field where various noises that make it difficult to detect the second harmonic are scattered, and is applied only in a laboratory where noise can be excluded.

The ultrasonic diagnostic apparatus of the present invention may be for calculating a nonlinear parameter value of the subject 10 by generating a second harmonic that can be detected regardless of noise.

The ultrasonic diagnostic apparatus of the present invention includes an irradiation unit 110, a first receiving unit 131, a second receiving unit 132, a transmitting unit 133, a processing unit (not shown) 150).

The irradiating unit 110 can generate ultrasonic waves propagated from the first surface 11 to the second surface (bottom surface) 12 of the test object 10. The first surface 11 and the second surface 12 may be on different sides and the first surface 11 is the upper surface of the subject 10 and the second surface 12 is the surface of the subject 10, Lt; / RTI >

The irradiating unit 110 may include a laser irradiator for irradiating the laser toward the first surface 11 at a position spaced apart from the subject 10. [ Ultrasonic waves passing through the subject 10 can be generated by the excitation of the laser beam irradiated on the first surface 11.

According to the irradiation unit 110 spaced from the subject 10, the position at which ultrasonic waves are generated on the first surface 11 can be easily changed. Also, the ultrasonic waves generated by the laser excitation have an advantage of excellent spatial resolution.

The first receiving unit 131 may receive the first reflected signal reflected from the second surface 12 by the ultrasonic waves.

The transmission unit 133 can generate the time reversal signal of the first reflection signal and transmit it to the second surface 12.

The second receiving unit 132 may receive the second reflected signal reflected from the second surface 12 by the time inverse signal of the first reflected signal.

The processing unit 150 can calculate the nonlinear parameter value of the subject 10 using the second reflected signal.

The first receiving unit 131, the second receiving unit 132, and the transmitting unit 133 may be formed at the same position on the first side 11. For example, the first surface 11 of the subject 10 may be provided with a transceiver 130 serving as both a transmitting and a receiving unit in which a first receiving unit 131, a second receiving unit 132, and a transmitting unit 133 are integrally formed . The first receiving unit 131, the second receiving unit 132, and the transmitting unit 133 may be provided on the first surface 11 in a plurality of ways.

The ultrasonic waves generated by the irradiation unit 110 can be reflected at the P position on the second surface 12 of the object 10. Since the second surface 12 is a portion bounded by another medium such as air or a supporting plate, the first or second reflected signal reflected on the second surface 12 may have a fine crack on the inside of the subject 10 A second harmonic component having a very large magnitude in comparison with the reflected signal may be included. The second harmonic component included in the signal reflected on the second surface 12 can be distinguished from the noise, so that it can be easily grasped even in the actual field where the noise is mixed.

A plurality of transmitting units 133 or a plurality of probes 130 disposed on the first surface 11 of the test object 10 generate a focusing beam to be focused at the P position to obtain a second harmonic component stronger than the noise can do.

The array type transducer 130 having more than four channels can be brought into close contact with the first surface 11 of the test object 10 for reliable beam focusing and a time reversing method can be applied for beam focusing. The time reversal signal to which the time reversal method is applied can be accurately focused at the P position of the second surface 12.

Since the signal radiated from the probe 130 to the subject 10 is time reversed, the ultrasound beam can be accurately focused at the P position where the nonlinear defect exists even though the prior information including the characteristics of the subject 10 is not known.

The transducer 130 extracts a signal of a specific mode of interest from among a nonlinear component signal caused by a boundary surface, a multimode of a Lamb wave, or a nonlinear component signal caused by reflected waves of various modes in the flat plate- And time reverses it. This allows precise beam focusing at the desired location, allowing accurate analysis optimized for a variety of inspection purposes.

3 is a schematic diagram illustrating an ultrasonic beam focusing process by the time reversing process of the present invention. Although FIG. 1 shows the time reversal method for the array transducers in which the N probes 130 are arranged, the embodiment of the present invention is not limited to the array transducer. Can be implemented.

1, one of the N probes 130 provided in the array transducer is excited. The excited incident wave propagates to the object 10.

Referring to the second drawing of FIG. 1, a scatter signal reflected at the P position of the second surface 12 corresponding to the interface of the subject 10 is received by each transducer 130. The difference in the distance from the respective transducers 130 arranged on the first surface 11 to the second surface 12 depends on the medium characteristics of the subject 10, the surface geometry of the subject 10, A difference in the amount of time delay of the echo signal, and a waveform difference of each probe 130. [

According to the time reversal method of the present invention, data on the difference in time delay amount and waveform difference is required, but knowledge of the prior information is not required at all.

The difference in time delay amount and waveform difference between the respective transducers 130 is determined by the surface geometry of the subject 10 and the distance from each transducer 130 to the P position Dictionary information such as difference is already included. Therefore, by calculating the amount of time delay from the signals radiated and obtained from the transducer 130 and using the time reversal processing, it becomes possible to detect the P position without knowing the prior information such as the surface geometry or the medium characteristics.

The prior information on the geometrical shape and the physical properties of the subject 10 can be restored by using the signals returned by propagating the inside of the subject 10 without knowing prior information of the array transducer or the subject 10 at all . The time reversal method is based on the property that the propagation time of the ultrasonic waves is constant for the array transducer or the subject 10 even if no advance information is input to the array transducer or the subject.

1, a waveform (first reflected signal) acquired by the N transducers 130 is converted into a time reversal signal based on the difference in time delays between the transducers 130 without acquiring the prior information, . Each transducer 130 causes a new waveform (time reversing signal) that has been time reversed to be incident on the subject 10. The time reversed ultrasound beam is accurately focused at the P position.

The original signal received in the time reversal process of the received signal can be used as is, or the nonlinear signal of the particular mode of interest can be selectively extracted and the time reversal processed, and the P position can be analyzed accurately.

Referring to FIG. 1, the ultrasound beam (time reversal signal) concentrated at the P position is again received (second reflected signal) at each probe 130. The acquired waveform is a waveform with improved signal-to-noise ratio and contains accurate information (including coordinates, size) about the P position.

That is, when each transducer 130 is excited in a time reversed state reflecting the time delay amount calculated by the time reversal method, the excited ultrasonic waves are propagated to converge at the P position. When the ultrasonic wave is focused at the P position, the signal-to-noise ratio is improved, so that a clean defect image can be obtained.

It is preferable that the signal reception time of the first reception unit 131 is longer than the signal transmission time of the investigation unit 110 in order to improve the inspection accuracy of the nonlinear defect. As the reception time of the first reflection signal becomes longer, the peak amplitude of the harmonic component increases, so that pure harmonic components can be extracted without noise.

The first reflected signal may be input to the processing unit 150. [ The processing unit 150 can Fourier transform the first reflection signal of the received time domain and extract the harmonic spectrum using the window function in the frequency domain if the frequency spectrum is obtained. The processing unit 150 can generate a time inverse signal by transforming the extracted harmonic spectrum into time domain after time inverse processing. The processing unit 150 may amplify the time reversal signal and then provide it to the transmission unit 133.

The transmission unit 133 can redirect the time reversal signal provided from the processing unit 150 toward the subject 10.

The first reflected signal contains information about nonlinear defects such as the interface. Therefore, the time reversed signal obtained by performing the time reversal processing on the first reflection signal can be accurately focused on the P position having the nonlinear characteristic according to the time reversal processing without knowing the prior information at all. The time reversal signal propagated to the P position can be reflected at the P position again and can be obtained at each probe 130.

The processing unit 150 may process the first reflection signal or the second reflection signal received by each of the transducers 130. The processing unit 150 may analyze the second reflected signal to extract the fundamental frequency component and the second harmonic component, and may calculate the nonlinear parameter value using the second harmonic component.

The processing unit 150 may multiply the fundamental frequency component or the second harmonic component by the transfer function of the probe 130 to convert the fundamental frequency component or the second harmonic component to an absolute displacement. The processing unit 150 may calculate the nonlinear parameter value by synthesizing the second reflected signal by applying a time delay to the probe 130. [ The processing unit 150 can calculate the nonlinear parameter value by correcting the rotation or attenuation of the second reflected signal.

The processing unit 150 includes an oscilloscope 151, a processing module 153, a multi-channel function generator 155, a multi-channel amplifier 157, an impedance matching unit 159 matching may be provided.

The oscilloscope 151 may monitor and provide the first or second reflected signal received from the probe 130 to the processing module 153.

The processing module 153 may process the first reflected signal to provide it to the multi-channel frequency generator, or may calculate the nonlinear parameter value of the subject 10 using the second reflected signal.

The processing module 153 may be provided with a probe calibration module, a time reversing signal processing module, a received signal processing module, an absolute displacement calculation module, a nonlinear parameter value calculation module, and a diffraction and attenuation correction module.

The probe calibration module can calibrate the receiving frequency of the probe 130, etc. in order to grasp the absolute displacement of the second harmonic component.

The time reversal signal processing module may apply the time reversal method to the first reflected signal received by each transducer 130. [

The received signal processing module may process the first reflected signal or the second reflected signal. For example, the received signal processing module may apply a time delay to a plurality of second reflected signals obtained from the plurality of transducers 130, and then synthesize the received signals.

The absolute displacement calculation module may calculate the absolute displacement of the second harmonic component or the like by multiplying the fundamental frequency component or the second harmonic component by the transfer function of the probe 130. [

The nonlinear parameter value calculation module can calculate the nonlinear parameter value? As shown in Equation (1) using the calculated absolute displacement.

The diffraction and attenuation correction module can correct the diffraction and attenuation factors included in the second reflection signal and the like.

The detailed operation and mathematical model of the probe calibration module, the received signal processing module, the absolute displacement calculation module, the nonlinear parameter value calculation module, the diffraction and attenuation correction module and the mathematical model are described in the paper 'Review of Second Harmonic Generation Measurement Techniques for Material State Determination in Metals' Nondestruct Eval. DOI 10.1007 / s10921-014-0273-5.

The multi-channel frequency generator may generate a time reversal signal assigned to a plurality of probes 130 installed on the first surface 11 using the result of processing the first reflected signal.

The multi-channel amplifier can amplify the time reversal signal assigned to each probe 130. [

The impedance matcher is to prevent the time reversal signal from being reflected on the first surface 11 and returning to the processing unit 150.

4 is a frequency spectrum of a comparative example.

In the case of a comparison signal reflected at the defect 20 within the object 10 rather than at the P position of the second surface 12, the magnitude of the second harmonics is determined by the spectrum of the fundamental frequency).

Therefore, it is impossible to calculate the nonlinear parameter value by using the comparison signal for the defect 20 in the inspection object 10 in the actual field where the noise exists.

According to the present invention, the first reflected signal may include a second harmonic component having a very large magnitude since it is reflected on the second surface 12. Therefore, the second harmonic component can be separately processed in spite of the presence of various noises, so that it is possible to calculate the nonlinear parameter value even in the actual field. The non-linear parameter value can be used for defect detection in the inspection object 10 in the future.

5 is a schematic view showing the ultrasonic diagnostic method of the present invention.

First, ultrasonic waves can be radiated to the first surface 11 of the subject 10 by the laser excitation of the irradiation unit 110. [

Ultrasonic waves passing through the inside of the subject 10 can be received by a plurality of transducers 130 disposed on the first surface 11 by being reflected by the second surface 12 (first reflected signal).

When the first reflection signal received by each transducer 130 is inverted and retransmitted, a beam (time inverse signal) may be focused on the reflection position P of the second surface 12.

The second reflected signal, which is the time reversal signal reflected at the position P, is received by each transducer 130, and after the signal processing, the fundamental frequency component and the second harmonic component can be obtained.

It is possible to multiply the transmission function of each transducer 130 to convert it into an absolute displacement, and synthesize the reception wave by applying a time delay to the transducer 130.

The nonlinear parameter values before the diffraction / attenuation correction are obtained, and the final nonlinear parameter values can be obtained by correcting the diffraction and attenuation.

The ultrasonic diagnostic apparatus according to the present invention uses only one surface of the subject 10 through the application of the non-contact type excitation and reflection method, so that the applicability to the field is very high. It is not necessary to know the specification of the array transducer 130 or the geometrical shape and physical properties of the subject 10 in advance because the reflected signal is propagated through the inside of the subject 10 for beam focusing. The absolute nonlinear parameter value of the subject 10 can be measured through calibration of the probe 130 and diffraction and attenuation correction can be applied to provide a more accurate nonlinear parameter value. Since the nonlinear ultrasonic diagnostic apparatus is constituted by using the array transducer 130 of at least four channels, productivity is high.

The ultrasonic diagnostic apparatus of the present invention shoots a non-contact type laser at the top of the specimen for initial excitation and receives the reflected signal from the bottom of the specimen with the array type probe disposed on the specimen. And extracting the second harmonic (nonlinear component) signal and then measuring the nonlinear parameter.

In summary, ultrasonic generation of a specimen through a non-contact laser excitation (laser irradiation at a position separated by a specimen), receiving a first reflection signal reflected from the bottom of the specimen using a plurality of array transducers arranged in a single transducer, The first reflected signal is simultaneously retransmitted after time reversal (at this time, a high voltage is applied to the array probe to generate a nonlinear ultrasonic wave on the specimen), a second reflected signal acquisition on the bottom of the specimen, 2 Harmonic component acquisition, nonlinear parameter calculation can be done in order.

After time reversal, it is important to concentrate the signal at a specific point on the bottom of the specimen through simultaneous retransmission.

While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined by the appended claims. Accordingly, the true scope of the present invention should be determined by the following claims.

10: subject to be inspected 11: first surface
12 ... second side 20 ... defect
110 ... irradiation unit 130 ... probe
131 ... first receiving unit 132 ... second receiving unit
133 ... transmission unit 150 ... processing unit
151 ... Oscilloscope 153 ... processing module
155 ... Multi-channel function generator
157 ... multi-channel amplifier 159 ... impedance matching device

Claims (6)

An irradiating unit for generating ultrasonic waves propagated from the first surface to the second surface of the object to be inspected;
A first receiving unit for receiving a first reflected signal of the ultrasonic wave reflected from the second surface;
A transmitter configured to generate a time reversal signal of the first reflected signal and transmit the generated signal to the second surface;
A second receiver for receiving the second reflection signal, the time reversal signal being reflected from the second surface;
And a processing unit for calculating a nonlinear parameter value of the subject using the second reflected signal,
Wherein the first receiving unit, the second receiving unit, and the transmitting unit are all formed on the first surface,
An array transducer in which the first receiver, the second receiver, and the transmitter are integrally formed on the first surface,
Wherein the irradiating unit includes a laser irradiator for irradiating a laser toward the first surface at a position spaced apart from the object to be inspected,
The ultrasonic wave is generated by excitation of the laser beam irradiated on the first surface,
The time reversed signal obtained by time-reversing the first reflection signal received by the array transducer is simultaneously retransmitted through the array transducer,
Wherein when the time reversal signal is retransmitted, a high voltage for generating nonlinear ultrasonic waves in the subject is applied to the array transducer,
Wherein the processor analyzes the second reflected signal to extract a fundamental frequency component and a second harmonic component, and calculates the nonlinear parameter value using the second harmonic component.
delete delete delete The method according to claim 1,
The processing unit may multiply the fundamental frequency component and the second harmonic component by a transfer function of the transducer to convert the basic frequency component and the second harmonic component into absolute displacements and apply a time delay to the transducer to synthesize the second reflected signal to calculate the non- Ultrasonic diagnostic equipment.
6. The method of claim 5,
And the processing unit corrects the diffraction or attenuation of the second reflected signal to calculate the nonlinear parameter value.

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