JP2012122729A - Method and apparatus for material deterioration detection using ultrasonic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect an initial stage of creep damage in metallic materials with high sensitivity.SOLUTION: In a transmitting-receiving part 12 of a material deterioration detection apparatus, an array type ultrasonic sensor 11 is driven by a phased array system. Ultrasonic of the frequency centering the specific frequency is transmitted through a test object 10. The reflected wave is received by the array type ultrasonic sensor 11, converted into an electric signal and fed into the transmitting-receiving part 12. A reception signal relating to a reception waveform from a specific direction is composited and then a waveform information included in the reception signal after the composition is time-frequency analyzed using a calculator 12A. A harmonic waveform information on a multiple component of the specific frequency is extracted and based on the information a flaw detection image is generated using the calculator 12A. Based on the image data, a flaw detection image with display color gradation matching the degree of damage is displayed on a display part 13. A damage state is evaluated by referring to a relationship among the display, a predetermined a gradation level of display colors (corresponding to the magnitude of a harmonic waveform) and the damage state.

Description

  The present invention belongs to a technical field in which the degree of deterioration of a material is inspected using ultrasonic waves, and particularly belongs to a technical field suitable for detecting creep damage of a metal material used under high temperature and stress.

  With the aging of thermal power plants, technology that can diagnose non-destructively the soundness (degree of creep damage) of structural materials such as piping under high temperature and stress has become important. On the other hand, in a thermal power plant having a high operating temperature, a steel material having a high chromium ratio (hereinafter also referred to as high chromium steel) is used as a structural material by welding. However, a characteristic of high chromium steel is that deterioration progresses from the inside at the weld heat affected zone at the weld location.

  Therefore, it is necessary to inspect the progress of the deterioration. A replica method is known as a method for nondestructive inspection of structural materials. Since the replica method is a method for nondestructively observing the structure of the metal surface of the structural material, the damage state of the surface of the structural material can be grasped, but there is a problem that the damage state inside the structural material cannot be inspected.

  As a method for answering the problem, a method for inspecting the inside of a metallic structural material using ultrasonic waves has been proposed. This method pays attention to the property that ultrasonic waves are reflected, scattered, and diffracted at the position of a crack generated by creeping voids in a structural material caused by creep or by joining voids.

  For example, in Patent Document 1 below, an ultrasonic wave is incident on a metal material, and an ultrasonic noise signal is time-divided by a time width corresponding to a position in the depth direction of the metal material, and for each time-divided noise signal, A method for calculating a frequency spectrum and calculating a value indicating the degree of progress of a defect corresponding to the depth direction based on the frequency spectrum is disclosed.

  In Patent Document 2 below, an ultrasonic transmission probe and an ultrasonic reception probe are arranged with a flaw interposed therebetween, and an ultrasonic wave is transmitted into a metal material to receive a diffracted wave from the flaw. There is disclosed a method for determining whether a scratch in a metal material is caused by creep damage based on a distribution state of a diffracted wave detected by a touch element, presence / absence of a void by a replica method, and the distribution state thereof.

  Furthermore, as a method for detecting an initial deterioration state, a technique for extracting a harmonic component of a frequency to be transmitted is known. For example, Patent Document 3 below shows a method of creating an image of a transmission frequency component and a harmonic component of a backscattered wave or surface wave of an ultrasonic probe, and evaluating a remaining life from the ratio of both. Yes.

  Patent Document 4 below discloses an apparatus that transmits an ultrasonic wave using an array type ultrasonic sensor, receives an ultrasonic wave including a harmonic component of a transmission frequency, and generates an image based on the received wave. Has been.

WO2007 / 110900 Publication JP 2001-153865 A JP 2005-128018 A Japanese Patent Laid-Open No. 11-276478

  The technique disclosed in Patent Document 1 is a method for displaying a specific frequency band having a high sensitivity in the gap in a limited manner, and is expected to have a low sensitivity for a relatively early gap in a closed state. is there. In addition, the technique disclosed in Patent Document 2 is generally applied to the TOFD method (Time-of-flight Diffraction method) used for crack detection and dimension measurement. Although it is an appropriate method for the creep damage, the initial creep damage in which the voids are not completely connected is unlikely to cause ultrasonic diffraction and is expected to have low sensitivity.

  Further, Patent Document 3 is a method of imaging using information of harmonic components of transmission frequency components using a single ultrasonic probe, which is in a closed state compared to Patent Documents 1 and 2. Sensitivity may be high for relatively early voids. However, in order to visualize the inspection result, it is necessary to mechanically scan a single ultrasonic probe, and the resolution of the damaged position may not be sufficient.

  Patent Document 4 discloses a method for generating an image of a harmonic component using an array type ultrasonic sensor, but there is no description regarding a method for detecting damage.

  Accordingly, an object of the present invention is to provide a material that is highly sensitive to the initial state of creep damage in a metal structural material and that can image a damage position with high resolution without mechanically scanning a flaw detection sensor. It is an object to provide a degradation detection method and apparatus.

  A feature of the method of the present invention for achieving the above object is that a waveform centering on a specific frequency from the array type ultrasonic sensor in the inspection object by driving the array type ultrasonic sensor by a phased array method in the deterioration detecting device. And the reflected wave from the inspection object generated by the transmission is received by the array-type ultrasonic sensor, and the received waveform obtained by the reception is subjected to frequency analysis by a computer. The waveform information of a higher harmonic waveform is extracted, data for constructing a flaw detection image by a computer is generated based on the extracted waveform information, and the flaw detection image is visualized by display means based on the data This is a material deterioration detection method using sound waves.

  In order to achieve the above object, the apparatus of the present invention is characterized in that an array type ultrasonic sensor is driven by a phased array method, and transmitting / receiving means for transmitting and receiving ultrasonic waves having a waveform centered on a specific frequency within an inspection object. The frequency analysis is performed on the received waveform received by the transmission / reception means, and the waveform processing means for extracting the waveform information of the harmonic waveform higher than the specific frequency, and the flaw detection image is constructed from the extracted waveform information This is a material deterioration detection apparatus using ultrasonic waves, comprising flaw detection image information generation means for generating information for the purpose and display means for visualizing the flaw detection image based on the flaw detection image information.

  According to the present invention, it is possible to detect deterioration of a metal material at an initial stage.

It is a block diagram of the whole structure of the material degradation detection apparatus by the Example of this invention. It is a flowchart figure which shows the material degradation detection method by the Example of this invention. It is a schematic diagram which shows the relationship between the content of the two-dimensional display screen by the material degradation detector by the Example of this invention, and the welded joint shape of a test object. It is the figure which showed an example of the waveform of the received signal of the material degradation detection apparatus by the Example of this invention. It is a figure explaining the result of having analyzed the frequency of the received signal of the material deterioration detection apparatus by the Example of this invention. It is a figure which shows the relationship between the display image of the material degradation detection apparatus by the Example of this invention, and the welded joint shape of test object.

  In an embodiment of the present invention, in an apparatus for inspecting damage in a metal material using an array type ultrasonic sensor as an ultrasonic probe, an electronic delay is given to each vibration element of the ultrasonic probe. A drive signal is given to operate an array type ultrasonic sensor using the phased array method, and ultrasonic waves with a waveform centered on a specific frequency are sent and received from the ultrasonic probe to the metal material. A reception unit is used, and the received waveform resulting from the reception is subjected to waveform synthesis processing by a computer, and waveform processing is performed to extract a harmonic waveform of a multiple component of a specific frequency by performing time-frequency analysis on the synthesized reception waveform. Creep damage is performed by a computer and image data of the flaw detection image is generated by the computer based on the extracted harmonic waveform, and the flaw detection image is visualized and displayed in a two-dimensional section on the display unit based on the image data. Utilizing the harmonic wave of the multiple components of the specific frequencies that characteristically appears in the presence of a phase of the gap the flaw detection image visualized recognizes the presence of the air gap.

  Furthermore, in the present embodiment, it is preferable that the extracted harmonic waveform is a harmonic component of a specific frequency.

  Furthermore, when constructing a flaw detection image from the extracted harmonic waveform, it is preferable to change the time window pitch of the time-frequency analysis in accordance with the refraction angle from the ultrasonic probe.

  In the following, as an embodiment of the present invention, a material deterioration detection method and apparatus using ultrasonic waves will be described in detail with reference to the drawings.

  As shown in FIG. 1, an inspection object 10 for detecting material deterioration is a welded structure including a base material part 10A of the inspection object 10 material and a welded part 10B welded to the base material part 10A. The inspection site is a portion including the welded portion 10B and the surrounding weld heat affected zone.

  FIG. 1 is a block diagram of a material deterioration detection apparatus according to an embodiment of the present invention. As shown in FIG. 1, a material deterioration detection apparatus according to an embodiment of the present invention includes an inspection object 10 made of a metal material, an array type ultrasonic sensor 11 that makes an ultrasonic wave incident on the inspection object 10, and an array type ultrasonic sensor 11. A transmission / reception unit 12 that transmits sound waves, receives reflected waves, and processes information about the received information, and includes a display unit 13 that visualizes and displays the received signals and flaw detection results obtained by information processing as flaw detection images. Has been.

  As shown in FIG. 1, the array type ultrasonic sensor 11 is basically composed of a plurality of piezoelectric vibration elements 14 that generate and receive ultrasonic waves. The ultrasonic wave 15 is generated by the drive signal supplied from the pulsar 12C of the receiving unit 12, this is propagated in the inspection object 10, the reflected wave that appears is converted into an electrical signal, and sent as a received signal It functions to input to the receiver 12D of the receiving unit 12.

  As described above, the transmission / reception unit 12 of the material deterioration detection apparatus performs transmission and reception of ultrasonic waves by the array type ultrasonic sensor 11 and also performs reception signal processing, analysis of received information, and display of images on the display unit 13. It generates image information and controls each unit. For this purpose, it includes a computer 12A, a delay time control unit 12B, a pulsar 12C, a receiver 12D, and a data recording unit 12E.

  The pulser 12C supplies a drive signal to the array type ultrasonic sensor 11, and the receiver 12D receives the reception signal input from the array type ultrasonic sensor 11.

  The computer 12A reads the required external data from the data recording unit 12E, performs arithmetic processing, and outputs the processed data to the data recording unit 12E as necessary. The computer 12A controls the delay time control unit 12B, the pulsar 12C, and the receiver 12D so that necessary operations can be obtained.

  First, the delay time control unit 12B controls both the timing of the drive signal output from the pulsar 12C and the input timing of the received signal by the receiver 12D, thereby obtaining the operation of the arrayed ultrasonic sensor 11 by the phased array method. Like that.

  The operation of the array-type ultrasonic sensor 11 based on the phased array system here refers to an operation of transmitting and receiving an ultrasonic wave by controlling the focal position of the ultrasonic wave 15 and the incident angle 16, and thereby receiving from the receiver 12D. A reception signal is supplied to the data recording unit 12E.

  Therefore, the data recording unit 12E processes the supplied reception signal and records it as recorded data, and simultaneously sends the data to the computer 12A. As a result, the computer 12A synthesizes the waveform obtained by each piezoelectric vibration element 14 according to the delay time, applies an appropriate interpolation process to the waveform for each incident angle of each ultrasonic wave, and produces a two-dimensional square called a pixel. Two-dimensional flaw detection data in a pixel format with a grid as a unit is created (this operation will be described later as a material deterioration detection method), which is generated in the image data of the flaw detection image as data that can be imaged on the display unit 13. The control operation to be supplied and displayed is executed.

  The display unit 13 can display the two-dimensional display screen 13B in response to the computer 12A generating the two-dimensional flaw detection data as image data that can be displayed by the display unit, and the waveform display for displaying the waveform signal of each piezoelectric vibrator. A function capable of displaying the screen 13A is provided.

  In addition, FIG. 1 shows that two screens are displayed on one display unit 13, but the waveform display screen 13A and the two-dimensional display screen 13B are visualized and displayed separately on a plurality of display units. Also good.

  Next, the material deterioration detection method in this embodiment is demonstrated using the flowchart of FIG. 2, and explanatory drawing of FIG.

  First, ultrasonic waves having a waveform centered on a specific frequency are transmitted from the array-type ultrasonic sensor 11 into the inspection object 10 and propagated into the inspection object 10 (step S101). Here, the specific frequency is determined in advance by using a specimen that has been subjected to creep damage in advance or a material that is actually damaged in an actual plant, and that can cope with the degree of damage in advance.

  Next, a received waveform from a specific direction is synthesized (step S102). The synthesizing process is the same as the principle of normal phased array ultrasound, and thus the description thereof is omitted.

  Next, time-frequency analysis is performed on the synthesized received waveform to extract a harmonic waveform of a multiple component of the specific frequency (step S103). In this step, the computer 12A can obtain discrete waveform data of a specific frequency by performing a short-time Fourier transform process on the received waveform, for example. When the incident angle 16 is θ = 0 °, the time window pitch of the short-time Fourier transform processing is made to correspond to twice the length of one side of the pixel, and when the incident angle 16 is other than θ = 0 °. Corresponds to a length obtained by dividing twice the length of one side of the pixel by cos θ. As a result, the amplitude value of the harmonic component corresponding to the position of each pixel can be obtained.

  In this step, the computer 12A can use a digital frequency filter instead of the short-time Fourier transform. When a digital frequency filter is used, a frequency band including a necessary harmonic component is selectively filtered, and an effective amplitude within a time window having the obtained waveform is assigned to each pixel. Since the pitch of the time window is the same as that when the short-time Fourier transform process is used, the description thereof is omitted.

  Next, a flaw detection image is constructed from the extracted harmonic waveform (step S104). In this step, the computer 12A generates image information (also referred to as image data) for displaying a flaw detection image corresponding to the cross section of the inspection object 10 based on the harmonic waveform extracted in step S103. The computer 12A sends the image information to the display unit 13 and displays the image information as a visualized image in the area of the two-dimensional display screen 13B.

Thus, the computer 12A is a waveform processing means, and is also a flaw detection image information generation means for generating information for constructing a flaw detection image from the waveform information extracted by the waveform processing. The display unit visualizes and displays the flaw detection image based on information for constructing the flaw detection image generated by the computer 12A, that is, the image information. FIG. 3 schematically shows a display example on the two-dimensional display screen 13B of the display unit 13. FIG. In the figure, a dark-colored pixel 41 indicates that the amplitude is high, and a light-colored pixel 42 indicates that the amplitude is low. Select the key appropriately.

There is a high possibility that the void in the closed state at the early stage of the creep damage appears remarkably in the harmonic (2f ₀ ) image. It is also possible to display a comparison with an image of a fundamental frequency (f ₀ ) that is a specific frequency, and distinguish whether the connection of the gap has progressed to a crack or the initial state in which the connection has started. It is also possible.

  Finally, deterioration is evaluated from the flaw detection image displayed on the display unit 13 (step S105). The relationship between the amplitude of each pixel of the flaw detection image and the state of deterioration is obtained in advance, and the deterioration is evaluated by referring to the relationship.

  The effect by embodiment of this invention is demonstrated using FIGS. 4-6. In FIG. 4, an array type ultrasonic sensor 11 is arranged in the vicinity of a welded portion with respect to an inspection target 10 having a welded portion that has been damaged by creep, and ultrasonic waves are emitted using a single element of the piezoelectric vibrating elements 14. It is an example of the received waveform when transmitting. The signal 21 is a reflected wave from the bottom surface of the inspection object 10, and the signal 22 is a reflected wave from a substantially central part of the thickness of the inspection object 10. Looking at these reflected waves, it can be seen that a plurality of frequency components are mixed.

  The result of frequency analysis of such a received waveform is, for example, as shown in FIG. Comparing the case of a healthy specimen before damage occurs with the case of a specimen after damage, the fundamental frequency components 31 and 32 both have large amplitudes, but the harmonic component 34 of the specimen after damage is The amplitude is large as compared with the harmonic component 33 of the healthy specimen. From this, it is possible to measure whether or not damage deterioration has progressed by extracting the amplitude of the harmonic component.

FIG. 6 shows the results of measurement on a specimen that has undergone creep damage, and extracts information on the fundamental frequency component (f ₀ ) and harmonic component (2f ₀ ) from the received signal of the array-type ultrasonic sensor. This is an example of display on the display unit 13 with the image of the result of building the flaw detection image. The dotted line display in FIG. 6 is obtained by printing a flaw detection image and entering a weld groove shape between the welded portion 10B as the inspection site and the base material portion 10A of the material to be inspected.

In the image in which the harmonic component (2f ₀ ) is extracted and displayed as the flaw detection image as shown in FIG. 6 (b), the fundamental frequency component (f ₀ ) is extracted as shown in FIG. 6 (a). Compared with the image displayed as the flaw detection image, there are more reflected waves from the welded portion and the vicinity of the welded portion, and voids due to creep damage can be detected. By referring to the flaw detection image and the relationship between the amplitude obtained in advance and the state of deterioration, the state of creep damage can be evaluated.

  INDUSTRIAL APPLICABILITY The present invention has applicability to a degradation detection method and apparatus using ultrasonic waves that non-destructively detect voids generated inside a metal material.

DESCRIPTION OF SYMBOLS 10 Inspection object 10A Base material part 10B Welding part 11 Array type ultrasonic sensor 12 Transmission / reception part 12A Computer 12B Delay time control part 12C Pulser 12D Receiver 12E Data recording part 13 Display part 13A Waveform display screen 13B Two-dimensional display screen 14 Piezoelectric Vibrating element 15 Ultrasonic wave 16 Incident angle

Claims (4)

  The array type ultrasonic sensor is driven by the phased array method in the deterioration detecting device, and a waveform centered on a specific frequency is transmitted from the array type ultrasonic sensor into the inspection target. From within the inspection target generated by the transmission The reflected ultrasonic wave is received by the array-type ultrasonic sensor, and the waveform information of the harmonic waveform higher than the specific frequency is extracted based on performing frequency analysis with a computer on the received waveform obtained by the reception, A material deterioration detection method using ultrasonic waves that generates data for constructing a flaw detection image by a computer based on the extracted waveform information and visualizes the flaw detection image by a display unit based on the data.   2. The material deterioration detection method using ultrasonic waves according to claim 1, wherein the harmonic waveform is a harmonic component of the specific frequency.   3. The data for constructing the flaw detection image according to claim 1 or 2, wherein the computer generates data for constructing the flaw detection image by changing a pitch of a time window of time-frequency analysis according to an incident angle of an ultrasonic wave to the inspection object. A material deterioration detection method using ultrasonic waves, characterized by:   A transmission / reception unit that drives an array type ultrasonic sensor by a phased array method to transmit / receive ultrasonic waves having a waveform centered on a specific frequency within the inspection target, and a frequency of the received waveform received by the transmission / reception unit Waveform processing means for performing analysis to extract waveform information of a harmonic waveform higher than the specific frequency, flaw detection image information generation means for generating information for constructing a flaw detection image from the extracted waveform information, A material deterioration detection apparatus using ultrasonic waves, comprising display means for visualizing a flaw detection image based on flaw detection image information.

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