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

Method and apparatus for material deterioration detection using ultrasonic Download PDF

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JP2012122729A
JP2012122729A JP2010271015A JP2010271015A JP2012122729A JP 2012122729 A JP2012122729 A JP 2012122729A JP 2010271015 A JP2010271015 A JP 2010271015A JP 2010271015 A JP2010271015 A JP 2010271015A JP 2012122729 A JP2012122729 A JP 2012122729A
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waveform
flaw detection
detection image
frequency
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Yoshiaki Nagashima
良昭 永島
Masao Endo
正男 遠藤
Masahiro Miki
将裕 三木
Atsushi Yamamoto
敦 山本
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Mitsubishi Power Ltd
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Babcock Hitachi KK
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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

本発明は、材料の劣化の程度を超音波を用いて検査する技術分野に属し、特に高温・応力下で使用される金属材料のクリープ損傷を検出するに好適な技術分野に属する。   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.

火力発電プラントの高経年化により、配管等の構造材料の高温・応力下での健全性(クリープ損傷の程度)を非破壊で診断できる技術が重要になってきている。一方で、運転温度が高い火力発電プラントでは、構造材料としてクロム比率の高い鉄鋼材料(以下、高クロム鋼とも言う。)を溶接して用いるようになってきている。しかし、高クロム鋼の特徴として溶接箇所における溶接熱影響部で内部から劣化が進行する点があげられる。   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.

そのため、その劣化の進行程度を検査する必要がある。構造材料を非破壊検査する方法としてレプリカ法が知られている。レプリカ法は構造材料の金属表面の組織を非破壊的に観察する方法なので、構造材料の表面の損傷状況を把握できるが、構造材料の材料内部の損傷状況を検査できない、という課題がある。   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.

その課題に答える方法として、超音波を用いて金属性の構造材料の内部を検査する方法が提案されている。この方法は、クリープによって生じた構造材料内の空隙、もしくは空隙が連結することで生じたき裂の位置で、超音波が反射・散乱・回折する性質に着目したものである。   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.

例えば、下記の特許文献1には、金属材料に超音波を入射し、超音波ノイズ信号を金属材料の深さ方向の位置に対応する時間幅で時分割し、当該時分割したノイズ信号毎に周波数スペクトルを算出し、周波数スペクトルに基づいて深さ方向に対応する欠陥の進行度を示す値を算出する方法が開示されている。   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.

また、下記の特許文献2には、超音波送信探触子と超音波受信探触子を傷を挟んで配置し、金属材料内に超音波を発信させて、傷からの回折波を受信探触子により検出し、得られた回折波の分布状態ならびにレプリカ法による空隙の有無及びその分布状態に基づき金属材料内の傷がクリープ損傷によるものなのかどうかを判定する方法が開示されている。   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.

さらに、初期の劣化状態を検出する方法として、送信する周波数の高調波成分を抽出する技術が知られている。例えば、下記の特許文献3には、超音波探触子の後方散乱波もしくは表面波の送信周波数成分と高調波成分のイメージを作成し、両者の比率から残存寿命を評価する方法が示されている。   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.

また、下記の特許文献4には、アレイ型超音波センサを使って、超音波を送信し、送信周波数の高調波成分を含む超音波を受信し、受信波に基づく画像を生成する装置が示されている。   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号公報WO2007 / 110900 Publication 特開2001−153865号公報JP 2001-153865 A 特開2005−128018号公報JP 2005-128018 A 特開平11−276478号公報Japanese Patent Laid-Open No. 11-276478

特許文献1に開示の技術は、空隙に感度の良い特定の周波数帯域を限定的に表示する方法であり、閉じた状態の比較的初期の空隙に対しては感度が低いと予想されるものである。また、特許文献2に開示の技術は、一般的には、き裂の検出や寸法測定に用いられるTOFD法(Time-of-flight Diffraction法)を応用したもので、き裂にまで進展した後期のクリープ損傷には適切な方法であるが、空隙が完全に連結していない初期のクリープ損傷では、超音波の回折が生じにくく、感度が低いと予想される。   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.

また、特許文献3では、単一の超音波探触子を用い、送信周波数成分の高調波成分の情報を用いて映像化する方法であり、特許文献1,2に比べて、閉じた状態の比較的初期の空隙に対して感度が高い可能性がある。しかしながら、検査結果を映像化するには単一の超音波探触子を機械的に走査する必要があり、また、損傷位置の分解能が十分ではない可能性がある。   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.

また、特許文献4では、アレイ型超音波センサを用いて、高調波成分の画像を生成する方法が示されているが、損傷を検出する方法に関しては記載がない。   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.

従って、本発明の目的は、金属製の構造材料内のクリープ損傷の初期段階の状態に対して感度が高く、かつ探傷センサを機械的に走査することなく高い分解能で損傷位置を映像化できる材料劣化検出方法および装置を提供することにある。   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.

上記目的を達成するための本発明方法の特徴は、劣化検出装置でアレイ型超音波センサをフェーズドアレイ方式にて駆動して前記アレイ型超音波センサから検査対象内に特定周波数を中心とする波形を送信し、前記送信によって発生した前記検査対象内からの反射波を前記アレイ型超音波センサで受信し、前記受信によって得られた受信波形について計算機で周波数分析を行うことに基づいて前記特定周波数よりも高い高調波波形の波形情報を抽出し、前記抽出した波形情報に基づいて計算機で探傷画像を構築するためのデータを生成し、前記データに基づいて前記探傷画像を表示手段で可視化する超音波を用いた材料劣化検出方法である。   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.

上記目的を達成するための本発明装置の特徴は、アレイ型超音波センサをフェーズドアレイ方式にて駆動して検査対象内に特定周波数を中心とする波形の超音波を送受信する送・受信手段と、前記送・受信手段にて受信した受信波形について周波数分析を行って、前記特定周波数よりも高い高調波波形の波形情報を抽出する波形処理手段と、前記抽出した波形情報から探傷画像を構築するための情報を生成する探傷画像情報生成手段と、前記探傷画像情報に基づいて探傷画像を可視化する表示手段とを備えた超音波を用いた材料劣化検出装置である。   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.

本発明によれば、金属材料の劣化を初期段階で検出することが可能となる。   According to the present invention, it is possible to detect deterioration of a metal material at an initial stage.

本発明の実施例による材料劣化検出装置の全体構成のブロック図である。It is a block diagram of the whole structure of the material degradation detection apparatus by the Example of this invention. 本発明の実施例による材料劣化検出方法を示すフローチャート図である。It is a flowchart figure which shows the material degradation detection method by the Example of this invention. 本発明の実施例による材料劣化検出装置による2次元表示画面内容と検査対象の溶接継手形状との関係を示す模式図である。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. 本発明の実施例による材料劣化検出装置の受信信号の波形の一例を示した図である。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. 本発明の実施例による材料劣化検出装置の受信信号の周波数を解析した結果を説明する図である。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. 本発明の実施例による材料劣化検出装置の表示画像と検査対象の溶接継手形状との関係を示す図である。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.

本発明の実施例では、超音波探触子としてアレイ型超音波センサを用いて金属材料内の損傷を検査する装置おいて、超音波探触子の各振動素子へ電子的に遅延を与えた駆動信号を与えてフェーズドアレイ方式によるアレイ型超音波センサの動作を行わせ、特定周波数を中心とする波形の超音波を超音波探触子から金属材料内に対して超音波の送受信を送・受信部を利用して行い、その受信による受信波形は計算機で波形合成処理され、合成処理された受信波形に関して時間−周波数分析を施して特定周波数の倍数成分の高調波波形を抽出する波形処理を計算機で実施し、抽出した高調波波形に基づいて探傷画像の画像データを計算機で生成して、その画像データに基づいて表示部に探傷画像を二次元断面にて可視化表示させて、クリープ損傷初期の空隙の存在下で特徴的に出現する特定周波数の倍数成分の高調波波形を利用して探傷画像を可視化しその空隙の存在を認識する。   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.

さらに、本実施例では、抽出した高調波波形が、特定周波数の倍調波成分であることが好ましい。   Furthermore, in the present embodiment, it is preferable that the extracted harmonic waveform is a harmonic component of a specific frequency.

さらに、抽出した高調波波形から探傷画像を構築する際に、超音波探触子からの屈折角に応じて、時間−周波数分析の時間窓のピッチを変化させることが好ましい。   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.

以下に本発明の実施例として、超音波を用いた材料劣化検出方法及び装置について、各図に基づいて詳細に説明する。   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.

図1のように、材料の劣化を検出する検査対象10は検査対象10材料の母材部10Aと母材部10Aを溶接した溶接部10Bとからなる溶接構造物である。検査部位は、溶接部10Bとその周辺の溶接熱影響部を含む部分である。   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.

図1には、本発明の一実施形態にかかわる材料劣化検出装置のブロック図が示されている。その図1のように、本発明の実施例による材料劣化検出装置は、金属材料製の検査対象10と、これに超音波を入射するアレイ型超音波センサ11、アレイ型超音波センサ11で超音波を送信し、その反射波を受信し、その受信情報について情報処理する送・受信部12、その受信信号及び情報処理して得られた探傷結果を探傷画像として可視化表示する表示部13で構成されている。   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.

アレイ型超音波センサ11は、図1に示すように、基本的には超音波を発生し受信する複数個の圧電振動素子14で構成され、検査対象10の探傷面に設置された後、送・受信部12のパルサー12Cから供給される駆動信号により超音波15を発生し、これを検査対象10内に伝播させ、これにより現れる反射波を受けて電気的信号に変換して受信信号として送・受信部12のレシーバ12Dに入力する働きをする。   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.

このように、材料劣化検出装置の送・受信部12はアレイ型超音波センサ11により超音波の送信と受信を行うと共に受信信号処理や受信情報の分析や表示部13へ画像を表示するための画像情報の生成や各部の制御を行うもので、このため、計算機12Aと遅延時間制御部12B,パルサー12C,レシーバ12D、それにデータ収録部12Eを備えている。   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.

パルサー12Cが駆動信号をアレイ型超音波センサ11に供給し、アレイ型超音波センサ11から入力される受信信号をレシーバ12Dが受けるようになっている。   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.

計算機12Aは、データ収録部12Eから必要とされる外部データを読込んで演算処理し、必要に応じて処理したデータをデータ収録部12Eへ出力する。また、計算機12Aは、遅延時間制御部12Bとパルサー12C,レシーバ12Dを制御し必要な動作が得られるようにするものである。   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.

まず遅延時間制御部12Bは、パルサー12Cから出力される駆動信号のタイミングとレシーバ12Dによる受信信号の入力タイミングの双方を制御し、これによりフェーズドアレイ方式によるアレイ型超音波センサ11の動作が得られるようにする。   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.

ここにいうフェーズドアレイ方式によるアレイ型超音波センサ11の動作とは、超音波15の焦点位置と入射角度16を制御して超音波を送信し受信する動作のことであり、これによりレシーバ12Dからデータ収録部12Eに受信信号が供給されることになる。   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.

そこで、データ収録部12Eは、供給された受信信号を処理し、収録データとして収録すると同時に計算機12Aにデータを送る。これにより、計算機12Aは各圧電振動素子14で得られた波形を遅延時間に応じて合成処理し、各超音波の入射角度ごとの波形に適当な内挿処理を施し、ピクセルと呼ばれる2次元正方格子を単位としたピクセル形式の2次元探傷データを作成し(この動作に関しては、材料劣化検出方法として後述する)、それを探傷画像の画像データに生成して画像化できるデータとして表示部13に供給して表示させる制御動作を実行する。   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.

その表示部13は、計算機12Aで2次元探傷データを表示部が表示できる画像データに生成したものを受けて2次元表示画面13Bを表示でき、および各圧電振動子の波形信号を表示する波形表示画面13Aを表示できる機能を備えている。   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.

また、図1には一つの表示部13に2画面を表示することを示したが、波形表示画面13Aと2次元表示画面13Bを、複数の表示部に個々に表示分担させて可視化表示してもよい。   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.

次に、本実施形態における材料劣化検出方法を、図2のフローチャート、及び図3の説明図を用いて説明する。   Next, the material deterioration detection method in this embodiment is demonstrated using the flowchart of FIG. 2, and explanatory drawing of FIG.

初めに、特定周波数を中心とする波形の超音波をアレイ型超音波センサ11から検査対象10内へ向けて送信して検査対象10内に伝播させる(ステップS101)。ここで、特定周波数は、事前にクリープ損傷を付与した試験体や実機プラントで実際に損傷した材料を用いて、その損傷程度への対応が良い周波数を事前に決定しておく。   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.

次に、特定方向からの受信波形を合成する(ステップS102)。合成の処理は、通常のフェーズドアレイ超音波の原理と同じであるため、説明は省略する。   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.

次に、合成した受信波形に時間−周波数分析をして前記特定周波数の倍数成分の高調波波形を抽出する(ステップS103)。このステップで、計算機12Aは、例えば、短時間フーリエ変換処理を受信波形に施すことにより、特定周波数の離散的な波形データを求めることができる。入射角度16がθ=0°の場合には、短時間フーリエ変換処理の時間窓のピッチを、ピクセルの一辺の2倍の長さに対応させ、入射角度16がθ=0°以外の場合には、ピクセルの一辺の2倍の長さをcosθで除した長さに対応させる。これによって、各ピクセルの位置に対応する高調波成分の振幅値を求めることができる。   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.

なお、このステップで、計算機12Aは、短時間フーリエ変換の変わりに、デジタル周波数フィルタを用いることもできる。デジタル周波数フィルタを用いる場合は、必要な高調波成分を含む周波数帯域を選択的にフィルタリングし、得られた波形のある時間窓内の実効振幅を各ピクセルに割り当てる処理をする。時間窓のピッチは、短時間フーリエ変換処理を用いた場合と同様であるので説明を省略する。   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.

次に、抽出した高調波波形から探傷画像を構築する(ステップS104)。このステップで、計算機12Aは、ステップS103で抽出した高調波波形を元に、検査対象10の断面に対応した探傷画像を表示するための画像情報(画像データとも言う。)を生成する。計算機12Aは、その画像情報を表示部13に送出して2次元表示画面13Bの領域にその画像情報を可視化画像として表示する。   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.

このように、計算機12Aは波形処理手段であり、波形処理で抽出した波形情報から探傷画像を構築するための情報を生成する探傷画像情報生成手段でもある。計算機12Aで生成された探傷画像を構築するための情報、即ち画像情報に基づいて表示部は探傷画像を可視化表示する
図3は、表示部13の2次元表示画面13Bによる表示例を模式的に示した図である。同図において、色の濃いピクセル41は振幅が高いことを示し、色の薄いピクセル42は振幅が低いことを示しており、振幅の高低で色の濃淡を制御して表示し、その濃度の階調は適切に選択する。
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.

クリープ損傷初期の閉じた状態の空隙は、高調波(2f0)の画像に顕著に現れる可能性が高い。特定周波数である基本周波数(f0)の画像と比較表示することも可能であり、空隙の連結が進展してき裂に至った状態なのか、空隙が連結を始めた初期の状態なのかを区別することも可能である。 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.

最後に、表示部13に表示された探傷画像から劣化を評価する(ステップS105)。探傷画像の各ピクセルの振幅と劣化の状態の関係を予め求めておき、その関係を参照することによって、劣化を評価する。   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.

本発明の実施形態による効果を、図4から図6を用いて説明する。図4は、クリープ損傷を与えた溶接部を有する検査対象10に対して、溶接部近傍にアレイ型超音波センサ11を配置し、圧電振動素子14のうち単一の素子を用いて超音波を送信したときの受信波形の一例である。信号21は検査対象10の底面からの反射波であり、信号22は検査対象10の厚さのほぼ中央部分からの反射波である。これらの反射波を見ると、複数の周波数成分が混在していることがわかる。   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.

このような受信波形を周波数分析した結果は、例えば、図5のようになる。損傷が生じる前の健全な試験体の場合と、損傷後の試験体の場合とを比較すると、基本周波数成分31,32はいずれも振幅が大きいが、損傷後の試験体の高調波成分34は健全な試験体の高調波成分33と比較して振幅が大きい。このことから、高調波成分の振幅を抽出することで、損傷劣化が進行した状態か否かを測定できる。   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.

図6は、クリープ損傷が進んだ試験体を対象に測定した結果に対して、アレイ型超音波センサの受信信号から、基本周波数成分(f0)と高調波成分(2f0)の情報を抽出して探傷画像を構築した結果のイメージで、表示部13での表示例である。なお、図6中の点線表示は探傷画像を印刷して検査部位である溶接部10Bと検査対象材料の母材部10Aとの間の溶接開先形状を記入したものである。 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.

図6の(b)図のように高調波成分(2f0)を抽出して探傷画像として表示した画像では、図6の(a)図のように基本周波数成分(f0)を抽出して探傷画像として表示した画像と比較して、溶接部内とその周囲近傍からの反射波が多く、クリープ損傷に伴う空隙を検出できている。この探傷画像と、予め求めてある振幅と劣化の状態の関係を参照することで、クリープ損傷の状態を評価できることになる。 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.

本発明は、金属材料の内部に生じた空隙を非破壊的に検知する超音波を用いた劣化検出方法とその装置に利用可能性がある。   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.

10 検査対象
10A 母材部
10B 溶接部
11 アレイ型超音波センサ
12 送・受信部
12A 計算機
12B 遅延時間制御部
12C パルサー
12D レシーバ
12E データ収録部
13 表示部
13A 波形表示画面
13B 2次元表示画面
14 圧電振動素子
15 超音波
16 入射角度
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)

劣化検出装置でアレイ型超音波センサをフェーズドアレイ方式にて駆動して前記アレイ型超音波センサから検査対象内に特定周波数を中心とする波形を送信し、前記送信によって発生した前記検査対象内からの反射波を前記アレイ型超音波センサで受信し、前記受信によって得られた受信波形について計算機で周波数分析を行うことに基づいて前記特定周波数よりも高い高調波波形の波形情報を抽出し、前記抽出した波形情報に基づいて計算機で探傷画像を構築するためのデータを生成し、前記データに基づいて前記探傷画像を表示手段で可視化する超音波を用いた材料劣化検出方法。   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. 請求項1において、前記高調波波形が前記特定周波数の倍調波成分であることを特徴とする超音波を用いた材料劣化検出方法。   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. 請求項1または請求項2において、前記計算機により前記検査対象への超音波の入射角度に応じて、時間−周波数分析の時間窓のピッチを変化させて前記探傷画像を構築するためのデータを生成することを特徴とする超音波を用いた材料劣化検出方法。   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: アレイ型超音波センサをフェーズドアレイ方式にて駆動して検査対象内に特定周波数を中心とする波形の超音波を送受信する送・受信手段と、前記送・受信手段にて受信した受信波形について周波数分析を行って、前記特定周波数よりも高い高調波波形の波形情報を抽出する波形処理手段と、前記抽出した波形情報から探傷画像を構築するための情報を生成する探傷画像情報生成手段と、前記探傷画像情報に基づいて探傷画像を可視化する表示手段とを備えた超音波を用いた材料劣化検出装置。   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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