JP6618374B2 - Compact nonlinear ultrasonic nondestructive inspection system - Google Patents
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Description
本発明は、材料内部の欠陥を非破壊的に検査する非線形超音波非破壊検査装置に関する。 The present invention relates to a non-linear ultrasonic nondestructive inspection apparatus that nondestructively inspects defects in a material.
材料内部の１ｍｍ以上の大きさの欠陥を非破壊的に検出・評価するための装置として、従来より、一定の体積を持つ空洞、開口き裂などの欠陥を含む材料に対しスパイク波で励起した微小振幅の超音波を入射し、音響インピーダンス差により発生する欠陥からの反射波強度、背面散乱波強度などを測定することによる非破壊的な検査が行なわれてきた。こうした超音波探傷技術は「超音波探傷法」に関する出版物（非特許文献１）などに記載されている。 As a device for nondestructive detection and evaluation of defects larger than 1 mm inside a material, a material containing a defect such as a cavity with a constant volume or an open crack has been excited by a spike wave. Nondestructive inspection has been carried out by measuring the intensity of reflected waves, backscattered waves, etc. from defects caused by the difference in acoustic impedance when ultrasonic waves with a small amplitude are incident. Such an ultrasonic flaw detection technique is described in a publication (Non-patent Document 1) relating to “ultrasonic flaw detection method”.
従来の超音波探傷法では、上記非特許文献１の第２頁の図１・１に記載のように、開口き裂やボイドのような一定の体積を持つ欠陥からの反射波強度及び受信時間から欠陥の大きさと位置を評価していた。 In the conventional ultrasonic flaw detection method, as shown in FIGS. 1 and 1 on the second page of Non-Patent Document 1, reflected wave intensity and reception time from a defect having a certain volume such as an opening crack or a void are received. The size and position of the defects were evaluated.
最近では、多数の微細な圧電素子に適切に設定した時間遅れを与えて励起することにより想定した方向に集束超音波ビームを合成するフェイズドアレイ超音波装置（例えば非特許文献２）も利用されている。 Recently, a phased array ultrasonic device (for example, Non-Patent Document 2) that synthesizes a focused ultrasonic beam in an assumed direction by applying a time delay appropriately set to a large number of fine piezoelectric elements and exciting them has been used. Yes.
しかし、上記の各方法では、音響インピーダンスの差が小さく、部分的に接触しているき裂面、金属中の微小非金属介在物など、入射超音波が部分的に透過する部分を高ＳＮ比で検出することは極めて困難である。 However, in each of the above methods, the difference in acoustic impedance is small, and a portion where incident ultrasonic waves are partially transmitted, such as a crack surface that is partially in contact and a minute non-metallic inclusion in a metal, is a high SN ratio. It is extremely difficult to detect with.
そこで、従来の微小振幅スパイク波入射に代えて、数サイクルから数十サイクルの大振幅正弦波バースト波を入射して、不完全接合面において発生する波形の歪みを高調波として検出する方法が特許文献１で提案されている。しかし、この方法は音響結合剤を介して非焦点型超音波探触子を被測定物に直接接触させる方式であるため、空間分解能が数ｍｍ程度と低く、また探触子を被測定物に対して走査して内部欠陥あるいは微視組織を可視化することができないという問題点があった。 Therefore, instead of the conventional small amplitude spike wave incidence, a method of detecting a distortion of the waveform generated on the imperfectly joined surface as a harmonic by inputting a large amplitude sine wave burst wave of several to tens of cycles is patented It is proposed in Document 1. However, this method is a method in which an unfocused ultrasonic probe is directly brought into contact with an object to be measured via an acoustic binder, so that the spatial resolution is as low as several millimeters, and the probe is attached to the object to be measured. On the other hand, there is a problem that the internal defect or microscopic tissue cannot be visualized by scanning.
上記の問題点を解決するため、測定室内に設置された水槽内に被測定物を全没させ、水浸焦点型探触子を用い、水中に斜角入射した大振幅正弦波バースト波の固体中でのモード変換縦波あるいは横波を用いて閉口き裂や介在物からの散乱波の高調波成分を検出し、画像化する方法が特許文献２で提案されている。この方法によるときは、検出したい高次高調波を抽出するアナログハイパスフィルタを用い、閉口き裂や介在物で散乱された超音波から高調波を抽出することにより、約０．１ｍｍ以上の微小内部欠陥を検出し画像化することできる。 In order to solve the above problems, the object to be measured is completely immersed in a water tank installed in the measurement chamber, and a solid of a large amplitude sine wave burst wave obliquely incident on the water using an immersion focus type probe. Patent Document 2 proposes a method of detecting and imaging a harmonic component of a scattered wave from a closed crack or inclusion using a mode-converted longitudinal wave or transverse wave. When this method is used, an analog high-pass filter that extracts high-order harmonics to be detected is used, and harmonics are extracted from ultrasonic waves scattered by closed cracks and inclusions. Defects can be detected and imaged.
しかし、上記の従来の水浸高調波画像化法では、正弦波からの受信波形の歪みを高次高調波振幅だけを用いて評価しており、それ以外の波形の歪みに関する情報は無視されることになるため、波形の歪みに含まれる内部欠陥に関する多くの情報が利用されないままになり、例えば、金属内の非金属介在物とボイドの識別、さらに拡散接合面の不完全接合部と不均一元素拡散状況とを区別できないなどの問題があった。 However, in the conventional water immersion harmonic imaging method described above, distortion of the received waveform from the sine wave is evaluated using only the higher-order harmonic amplitude, and information on the distortion of the other waveforms is ignored. As a result, a lot of information about internal defects included in the waveform distortion remains unavailable, for example, identification of non-metallic inclusions and voids in the metal, and incomplete joints and non-uniformity of diffusion bonding surfaces There were problems such as indistinguishable from the element diffusion situation.
さらに、上記の従来の水浸高調波画像化法では、大振幅正弦波バースト波励起用送受信器の容積が０．６ｍ×０．５ｍ×０．２５ｍなどと大きいため、プラントなどの定期点検現場への持ち込みが容易でない、可搬型の大振幅正弦波バースト波励起用送受信器により最大２５６サイクルまでの長いバースト波を励起するようにしているため、大容量の蓄電器が必要となり、充電に要する時間が長くなってしまう、１秒あたりの超音波送信回数が１０００回程度に制限されてしまい非破壊検査を高速で行うことができない、などの問題点があった。 Furthermore, in the conventional water immersion harmonic imaging method described above, the volume of the transmitter / receiver for exciting a large-amplitude sine wave burst wave is as large as 0.6 m × 0.5 m × 0.25 m. Since a long burst wave of up to 256 cycles is excited by a portable large-amplitude sine wave burst wave excitation transmitter / receiver that is not easy to bring in, a large-capacity capacitor is required and the time required for charging The number of ultrasonic transmissions per second is limited to about 1000 times, which makes it difficult to perform nondestructive inspection at high speed.
さらに、上記の従来の水浸高調波画像化法では、送信する大振幅バースト波を励起するサイクル数が長いためその継続時間が長くなり、また被測定物表面における反射波の残響継続時間も長いため表面不感帯が大きくなり、その結果、表面直下に存在する微小欠陥を検出できないという問題点があった。 Furthermore, in the conventional water immersion harmonic imaging method described above, since the number of cycles for exciting a large amplitude burst wave to be transmitted is long, the duration is long, and the reverberation duration of the reflected wave on the surface of the object to be measured is also long. Therefore, the surface dead zone becomes large, and as a result, there is a problem in that minute defects existing immediately below the surface cannot be detected.
本発明では、上記の事情に鑑み、１サイクル大振幅正弦波を用いて、被測定物内部及び表面直下の微小欠陥を非破壊的に高速で検出・可視化し、当該欠陥の寸法を評価するとともにその種類を大まかに区分することのできる小型非線形超音波非破壊検査装置を提供することを目的とする。 In the present invention, in consideration of the above circumstances, a single cycle large amplitude sine wave is used to non-destructively detect and visualize a minute defect inside the object to be measured and immediately below the surface, and evaluate the dimension of the defect. An object of the present invention is to provide a small non-linear ultrasonic non-destructive inspection apparatus capable of roughly classifying the types.
上記課題を解決するための本発明による小型非線形超音波非破壊検査装置は、少なくとも１サイクルの大振幅正弦波（閾値を超える入射電圧に対応する大振幅の正弦波）を発生させる正弦波発生器と、前記正弦波発生器からの電気信号（少なくとも１サイクルの大振幅正弦波）に基づいて大振幅の正弦波の超音波を被測定物の内部に送信する焦点型送信超音波探触子と、前記大振幅超音波が被測定物の内部で反射した超音波を受信する焦点型受信超音波探触子と、前記焦点型受信超音波探触子で受信した超音波中の最初の１〜２サイクル分から、高調波成分の振幅又は波形の歪み、又は、前記の振幅又は波形の歪み及びそれ以外の他の超音波特性、例えば、引張側と圧縮側の最大振幅値及びそれらの比、参照時間からの引張側と圧縮側の最大振幅受信時間差及びそれらの比、周波数スペクトル、若しくは上記特性の入射電圧依存性などの超音波特性を、取得し、これらの取得した超音波特性を処理する処理手段と、を備えたものである。 A small non-linear ultrasonic nondestructive inspection apparatus according to the present invention for solving the above-described problems is a sine wave generator for generating a large amplitude sine wave of at least one cycle (a large amplitude sine wave corresponding to an incident voltage exceeding a threshold value). And a focus-type transmission ultrasonic probe that transmits ultrasonic waves of a large amplitude sine wave to the inside of the object to be measured based on an electric signal (at least one cycle of a large amplitude sine wave) from the sine wave generator; , A focus-type reception ultrasonic probe that receives the ultrasonic wave reflected by the large-amplitude ultrasonic wave inside the object to be measured, and the first to first ultrasonic waves received by the focus-type reception ultrasonic probe From two cycles onwards, harmonic component amplitude or waveform distortion, or said amplitude or waveform distortion and other ultrasonic properties, eg maximum tension and compression side amplitude values and ratios thereof, see Maximum of tension side and compression side from time Width reception time difference and their ratio, frequency spectrum, or the ultrasound characteristics such as the incident voltage dependence of the properties, acquired, those having a processing means for processing these acquired ultrasound characteristics, a.
また、本発明による小型非線形超音波非破壊検査装置は、少なくとも１サイクルの大振幅正弦波（閾値を超える入射電圧に対応する大振幅の正弦波）を発生させる正弦波発生器と、該正弦波発生器によって発生させた電気信号（少なくとも１サイクルの大振幅正弦波）を超音波として送信する焦点型送信超音波探触子と、前記焦点型送信超音波探触子を被測定物に対して相対的に移動させる可搬式走査機構と、前記大振幅正弦波発生器で発生された電気信号に同期して前記走査機構を駆動する同期操作部と、前記焦点型送信超音波探触子で発生させた超音波を水又は樹脂製楔などの媒体を通して斜め入射したとき励起されるモード変換縦波あるいは横波を被測定物の内部に伝搬させ被測定物内部の欠陥で散乱された前記モード変換横波を受信する焦点型受信超音波探触子と、前記焦点型受信超音波探触子で受信した前記モード変換縦波及び横波を増幅する増幅器と、前記増幅器で増幅した波形をＡＤ変換し記憶する波形記憶部と、前記波形記憶部で記憶した波形をデジタル処理する波形処理部と、前記波形記憶手段で記憶した波形に対し、最大振幅絶対値、引張側と圧縮側の最大振幅値及びそれらの比、参照時間からの引張側と圧縮側の最大振幅受信時間差及びそれらの比、周波数スペクトル、並びに上記特性の入射電圧依存性などの超音波特性を演算し、その演算された超音波特性を画像処理する画像化処理手段と、前記画像化処理手段で処理された画像を表示する表示手段と、前記走査機構の駆動と前記正弦波発生器の信号を同期させる同期走査手段と、を備えたものである。 In addition, a small nonlinear ultrasonic nondestructive inspection apparatus according to the present invention includes a sine wave generator that generates at least one cycle of a large amplitude sine wave (a large amplitude sine wave corresponding to an incident voltage exceeding a threshold), and the sine wave. A focus-type transmission ultrasonic probe that transmits an electric signal (a large-amplitude sine wave of at least one cycle) generated by a generator as an ultrasonic wave, and the focus-type transmission ultrasonic probe with respect to an object to be measured Generated by a portable scanning mechanism that moves relatively, a synchronous operation unit that drives the scanning mechanism in synchronization with an electric signal generated by the large-amplitude sine wave generator, and the focus-type transmission ultrasonic probe Mode-converted longitudinal waves or transverse waves that are excited when the incident ultrasonic waves are obliquely incident through a medium such as water or a resin wedge and propagated inside the object to be measured and scattered by defects inside the object to be measured. Receive A focus-type receiving ultrasonic probe, an amplifier that amplifies the mode-converted longitudinal and transverse waves received by the focus-type receiving ultrasonic probe, and a waveform memory that AD-converts and stores the waveform amplified by the amplifier A waveform processing unit that digitally processes the waveform stored in the waveform storage unit, and the waveform stored in the waveform storage unit, the maximum amplitude absolute value, the maximum amplitude value on the tension side and the compression side and the ratio thereof, Calculates the ultrasonic characteristics such as the difference between the maximum amplitude reception time on the tension side and the compression side from the reference time and their ratio, frequency spectrum, and incident voltage dependence of the above characteristics, and performs image processing on the calculated ultrasonic characteristics. An imaging processing unit; a display unit that displays an image processed by the imaging processing unit; and a synchronous scanning unit that synchronizes the driving of the scanning mechanism and the signal of the sine wave generator. .
また、本発明による小型非線形超音波非破壊検査装置においては、前記焦点型送信超音波探触子は、固定焦点の超音波探触子あるいは複数の微小圧電素子を１次元配列した１次元アレイ探触子、複数の微小圧電素子を同心円環状に配置したアニュラーアレイ探触子、又は複数の圧電素子を２次元平面に配列した２次元アレイ探触子に時間遅れパルスを与えることにより焦点型超音波探触子として機能するものであってもよい。 In the small nonlinear ultrasonic nondestructive inspection apparatus according to the present invention, the focus type transmission ultrasonic probe is a one-dimensional array probe in which a fixed focus ultrasonic probe or a plurality of micro piezoelectric elements are arranged one-dimensionally. Focused ultrasound by applying a time-delay pulse to a probe, an annular array probe in which a plurality of micro piezoelectric elements are arranged concentrically, or a two-dimensional array probe in which a plurality of piezoelectric elements are arranged in a two-dimensional plane It may function as a probe.
また、本発明による小型非線形超音波非破壊検査装置においては、前記走査機構は、（ａ）単一素子の焦点型送信超音波探触子を試験体に対し機械的に走査すること、（ｂ）１次元アレイ探触子、アニュラーアレイ探触子もしくは２次元アレイ探触子を用いて超音波ビームを電子的に走査すること、又は（ｃ）広い範囲ではアレイ探触子を機械的に走査し狭い範囲ではアレイ探触子を電子的に走査するものであってもよい。 Further, in the small nonlinear ultrasonic nondestructive inspection apparatus according to the present invention, the scanning mechanism (a) mechanically scans the specimen with a single-element focused transmission ultrasonic probe, (b ) Electronically scanning the ultrasound beam using a one-dimensional array probe, an annular array probe or a two-dimensional array probe; or (c) mechanically scanning the array probe over a wide area. However, in a narrow range, the array probe may be electronically scanned.
また、本発明による小型非線形超音波非破壊検査装置においては、前記焦点型送信超音波探触子と被測定物との間で超音波を送受信するために、（ａ）前記焦点型送信超音波探触子の少なくとも一部と被測定物を水槽に全没させる、（ｂ）前記焦点型送信超音波探触子を被測定物の検査領域を覆う部分的水槽に搭載する、又は（ｃ）前記焦点型送信超音波探触子の先端周辺から水を流して超音波が伝搬可能な水柱を形成するようにしてもよい。 In the small nonlinear ultrasonic nondestructive inspection apparatus according to the present invention, in order to transmit / receive an ultrasonic wave between the focused transmission ultrasonic probe and the object to be measured, (a) the focused transmission ultrasonic wave At least part of the probe and the object to be measured are fully immersed in the water tank; (b) the focus-type transmission ultrasonic probe is mounted in a partial water tank covering the inspection area of the object to be measured; or (c). A water column capable of propagating ultrasonic waves may be formed by flowing water from the periphery of the tip of the focus type transmission ultrasonic probe.
また、本発明による小型非線形超音波非破壊検査装置においては、前記画像化処理手段は、前記受信した波形について、最大振幅絶対値、引張側と圧縮側の最大振幅値及びそれらの比、参照時間からの引張側と圧縮側の最大振幅受信時間差及びそれらの比、周波数スペクトル、及び上記特性の入射電圧依存性などの個別超音波特性、並びにそれらを組み合わせて得られる特性値を演算又は算出するものであってもよい。 Further, in the small nonlinear ultrasonic nondestructive inspection apparatus according to the present invention, the imaging processing means, for the received waveform, the maximum amplitude absolute value, the maximum amplitude value on the tension side and the compression side and the ratio thereof, the reference time Calculates or calculates the maximum amplitude reception time difference between the tension side and the compression side from the above and their ratio, frequency spectrum, and individual ultrasonic characteristics such as dependence of the above characteristics on incident voltage, and characteristic values obtained by combining them It may be.
さらに、本発明による小型非線形超音波非破壊検査装置においては、前記大振幅正弦波発生器は、発生させる正弦波のサイクル数として１、２、又は３のいずれかを選択可能なものであってもよい。 Furthermore, in the small nonlinear ultrasonic nondestructive inspection apparatus according to the present invention, the large amplitude sine wave generator is capable of selecting any one of 1, 2, or 3 as the number of sine wave cycles to be generated. Also good.
本発明の１つの特徴は、本発明者が行った実験から得られた、大振幅正弦波超音波を試験体（被測定物）に入射しその閉口き裂部からの受信波形に含まれる正弦波からの波形の歪みの検出を行った結果、受信波の最初の１〜２サイクルに入射周波数の数倍の高調波成分が含まれていたことなどの新たな知見に基づいて、試験体の閉口き裂部からの受信波形中の高調波を抽出又は計測するためには１サイクル（少なくとも１サイクル）の大振幅正弦波を被測定物に入射すればよく、そのような１サイクル（少なくとも１サイクル）の大振幅正弦波を入射できるだけの小型で軽量かつ比較的安価な大振幅正弦波送信器を用意するだけで、高調波を利用したプラント配管などの劣化・損傷検査が可能になる点にある。よって、このような本発明によれば、連続固体の非線形超音波（高調波）計測と同様に部分接触部を伴う閉口き裂状欠陥に対しても数〜数十サイクルの大振幅バースト波の入射を行える大型（大容量の蓄電器が必要）かつ高価な大振幅正弦波送信器を使用している従来の非線形超音波非破壊検査法と比較して、高調波を利用したプラント配管などの劣化・損傷検査を、従来よりも大幅に安価に高速に且つ効率的に行えるようになる。すなわち、本発明によれば、１サイクルの大振幅正弦波入射だけで被測定物の閉口き裂面で発生する高調波を検出できるようになるので、大振幅正弦波送信器を従来より大幅に小型化・低コスト化する（例えば従来の装置では必要とされていた大容量の蓄電器を不要とする）ことが可能となり、その結果、プラント類の劣化・損傷評価などへの高調波法の適用を極めて容易かつ低コストに行えるようになる。 One feature of the present invention is that a large-amplitude sine wave ultrasonic wave obtained from an experiment conducted by the present inventor is incident on a test body (object to be measured) and is included in a received waveform from the closed crack portion. As a result of detecting the waveform distortion from the wave, based on new findings such as the presence of harmonic components several times the incident frequency in the first 1 to 2 cycles of the received wave, In order to extract or measure the harmonics in the received waveform from the closed crack portion, one cycle (at least one cycle) of a large amplitude sine wave may be incident on the object to be measured. Cycle) Large amplitude sine wave that can enter a small, lightweight, and relatively inexpensive large amplitude sine wave transmitter can be used to inspect deterioration and damage of plant piping using harmonics. is there. Therefore, according to the present invention, a large-amplitude burst wave of several to several tens of cycles can be applied to a closed crack-like defect having a partial contact portion as in the case of continuous solid nonlinear ultrasonic (harmonic) measurement. Degradation of plant piping using harmonics compared to conventional nonlinear ultrasonic nondestructive inspection methods that use large-sized (capacitance capacitors with large capacity) capable of incidence and expensive large-amplitude sine wave transmitters・ Damage inspection can be performed at high speed and efficiency at a much lower cost than before. That is, according to the present invention, harmonics generated at the closed crack surface of the object to be measured can be detected only by one cycle of large-amplitude sine wave incidence. It is possible to reduce the size and cost (for example, eliminating the need for large-capacity capacitors that were required in conventional equipment), and as a result, applying the harmonic method to plant degradation and damage assessment Can be performed very easily and at low cost.
また、本発明において、前記受信波形についてＦＦＴ（高速フーリエ変換）により得られた、高調波振幅以外の波形の歪みを表す複数の超音波特徴量を非線形超音波非破壊検査のために用いるようにしたときは、波形の歪みを発生させる実体の分類が可能になり、より高精度な非線形超音波非破壊検査が可能となる。 Further, in the present invention, a plurality of ultrasonic feature amounts representing waveform distortion other than the harmonic amplitude obtained by FFT (Fast Fourier Transform) on the received waveform are used for nonlinear ultrasonic nondestructive inspection. In this case, it is possible to classify entities that generate waveform distortion, and to perform more accurate nonlinear ultrasonic nondestructive inspection.
本発明で用いる１サイクル大振幅正弦波発生器は、例えばその容積が約０．２ｍ×０．１ｍ×０．１ｍと小型であるため、石油化学プラントなどの狭い現場において配管及びその他機器内の微小欠陥を検出する非線形超音波非破壊検査手段が確立される。 The one-cycle large-amplitude sine wave generator used in the present invention has a small volume of about 0.2 m × 0.1 m × 0.1 m, for example, so that it can be used in piping and other equipment in a narrow field such as a petrochemical plant. Non-linear ultrasonic nondestructive inspection means for detecting minute defects is established.
本発明で用いる小型１サイクル大振幅正弦波発生器は、その駆動のために必要な蓄電器容量が少ないため、１秒間に約５、０００回まで大振幅正弦波を送信できる。よって、本発明においては、約毎秒５００ｍｍの速度で移動する被測定物内の０．１ｍｍ程度の内部欠陥を検出する非線形超音波非破壊検査手段が確立される。 Since the small one-cycle large-amplitude sine wave generator used in the present invention requires a small capacity for driving, it can transmit a large-amplitude sine wave up to about 5,000 times per second. Therefore, in the present invention, a non-linear ultrasonic nondestructive inspection means for detecting an internal defect of about 0.1 mm in an object to be measured moving at a speed of about 500 mm per second is established.
本発明で用いる１サイクル大振幅正弦波発生器は、その超音波パルス幅が短いため、表面反射波の残響を短くすることができ、表面不感帯を小さくできる。よって、本発明においては、表面直下に存在する介在物、ボイド等の微小欠陥を高速に検出できるようになる。 Since the one-cycle large-amplitude sine wave generator used in the present invention has a short ultrasonic pulse width, the reverberation of the surface reflected wave can be shortened and the surface dead zone can be reduced. Therefore, in the present invention, minute defects such as inclusions and voids existing immediately below the surface can be detected at high speed.
本発明においては、１サイクル大振幅正弦波を送信し、高速・高分解能のＡ／Ｄ変換ボードで収録した波形の正弦波からの歪みを複数の特徴を用いて定量化するようにしている。よって本発明によれば、従来の最大振幅絶対値以外の、引張側と圧縮側の最大振幅、それらの比、引張側と圧縮側の最大振幅の受信時刻、周波数スペクトル、及び上記特性の入射電圧依存性など、さらに個々の特性を組み合わせた特徴量を用いることにより、被測定物内部の隙間部、部分接触部、金属中非金属介在物などを非破壊的に識別する手段が確立される。 In the present invention, a one-cycle large-amplitude sine wave is transmitted, and distortion from the sine wave of the waveform recorded by the high-speed, high-resolution A / D conversion board is quantified using a plurality of features. Therefore, according to the present invention, the maximum amplitude on the tension side and the compression side, the ratio thereof, the reception time of the maximum amplitude on the tension side and the compression side, the frequency spectrum, and the incident voltage of the above characteristics other than the conventional maximum amplitude absolute value By using a feature amount that is a combination of individual characteristics such as dependency, a means for nondestructively identifying a gap portion, a partial contact portion, a non-metallic inclusion in a metal, and the like is established.
本発明において、平面以外の表面形状を持つ被測定物に対して、請求項３に記載のアレイ探触子を用いるときは、測定物内の所望の点に超音波ビームを集束させることができるので、平面以外の表面形状を持つ被測定物内の微小なマイクロクラックからの散乱波を受信できる利点を持つ。 In the present invention, when the array probe according to claim 3 is used for a measurement object having a surface shape other than a flat surface, the ultrasonic beam can be focused at a desired point in the measurement object. Therefore, it has an advantage of being able to receive scattered waves from minute microcracks in the object to be measured having a surface shape other than a flat surface.
請求項４に係る発明によるときは、広い検査領域に対する機械的走査と狭い測定領域に対する電子走査を併用し使い分けることができるので、フェイズドアレイ探触子による電子走査範囲を超える広い範囲をも効率的に検査できるようになる。 According to the invention of claim 4, since mechanical scanning with respect to a wide inspection area and electronic scanning with respect to a narrow measurement area can be used together, it is possible to efficiently use a wide range exceeding the electronic scanning range by the phased array probe. Will be able to inspect.
請求項５に係る発明によるときは、例えば、可搬式小型水槽を設置できる配管箇所にはその水槽内で超音波探触子を走査し、可搬式小型水槽を設置できない箇所については水柱走査方式を用いることにより、検査不可能領域を減少させることができる。 When the invention according to claim 5 is used, for example, an ultrasonic probe is scanned in a piping place where a portable small water tank can be installed, and a water column scanning method is used for a place where a portable small water tank cannot be installed. By using it, the area that cannot be inspected can be reduced.
請求項６に係る発明によるときは、受信波形から得られる個々の特徴だけでなく、複数の特徴を組み合わせた評価指標を設け、その分布を可視化することにより、欠陥の種類を容易に区別できるようになる。 According to the sixth aspect of the invention, not only the individual features obtained from the received waveform but also an evaluation index combining a plurality of features is provided, and the type of defects can be easily distinguished by visualizing the distribution. become.
請求項７に係る発明によるときは、例えば、高速走査を必要とする場合には１サイクル大振幅正弦波を送信し、大エネルギーによる励起を必要とする場合には３サイクルまでの大振幅正弦波を送信することにより、幅広い非破壊検査に対応できるようになる。 According to the invention of claim 7, for example, when a high-speed scanning is required, a one-cycle large-amplitude sine wave is transmitted, and when excitation with a large energy is required, a large-amplitude sine wave of up to three cycles is transmitted. By transmitting, it becomes possible to deal with a wide range of non-destructive inspections.
〔第１実施形態〕
以下本発明の測定原理を説明した後、本発明に関わる装置の構成、作用、実験結果等を説明する。
[First Embodiment]
Hereinafter, after explaining the measurement principle of the present invention, the configuration, operation, experimental results and the like of the apparatus according to the present invention will be described.
［測定原理］
非特許文献１に記載されているように、通常の超音波探傷法は、微小振幅のスパイク波を被測定物に入射し、音響インピーダンス差を持つ界面で励起される反射波を検出し、欠陥の大きさと深さを推定する。鉄鋼内部の約１ｍｍの長さを越える開口き裂部の音響インピーダンス差は大きいので、その検出は容易である。しかし、閉口き裂面や微小非金属介在物は微細な部分接触部を伴うため局部的に超音波が透過し、音響インピーダンス差が小さくなり、その検出が困難である。
[Measurement principle]
As described in Non-Patent Document 1, a normal ultrasonic flaw detection method detects a reflected wave excited at an interface having an acoustic impedance difference by entering a spike wave having a small amplitude into a measurement object, Estimate the size and depth of. Since the difference in acoustic impedance of the opening crack portion exceeding the length of about 1 mm inside the steel is large, the detection is easy. However, since the closed crack surface and the minute non-metallic inclusion are accompanied by a minute partial contact portion, the ultrasonic wave is locally transmitted, the acoustic impedance difference becomes small, and the detection is difficult.
これに対し、部分接触部を伴う欠陥に対する従来非線形超音波法は、図１に示すように、大振幅正弦波バースト波を入射すると引張相の超音波は閉口き裂面をほとんど透過できないため頂部が裁断された波形になるが、圧縮相の超音波はほぼ正弦波形を保って透過するので、周波数域では入射周波数の整数倍周波数を持つ高調波として表示されるというモデルに基づいている。このモデルでは、き裂面が平行平面であると仮定し、引張相の頂部が裁断された波形に起因する高調波成分を適切な遮断周波数を持つハイパスフィルタあるいは適切な透過帯域のバンドパスフィルタを用いて、適切な高調波成分を抽出しその振幅を用いて、閉口き裂部を検出する。ただし、高調波振幅だけを用いるため欠陥種類の区別ができず、また数ないし数十サイクルのバースト波を送信するため検査時間が長くなる。 On the other hand, in the conventional nonlinear ultrasonic method for a defect with a partial contact portion, as shown in FIG. 1, when a large-amplitude sine wave burst wave is incident, the ultrasonic wave in the tensile phase hardly transmits the closed crack surface. However, it is based on a model in which the compressed phase ultrasonic wave is transmitted while maintaining a substantially sinusoidal waveform, and is therefore displayed as a harmonic having an integral multiple of the incident frequency in the frequency range. In this model, it is assumed that the crack plane is a parallel plane, and a high-pass filter with an appropriate cutoff frequency or a band-pass filter with an appropriate transmission band is applied to the harmonic components caused by the waveform where the top of the tensile phase is cut. Use to extract an appropriate harmonic component and use its amplitude to detect a closed crack. However, the defect type cannot be distinguished because only the harmonic amplitude is used, and the inspection time becomes long because burst waves of several to several tens of cycles are transmitted.
本発明では、図２に示すような現実の微細な凹凸を持つ数十ナノメートルの隙間を持つ閉口き裂部に大振幅正弦波を入射したとき、入射超音波により励起される圧縮応力により微細な凹凸部の接触面積が次第に増加するため、図３に示すように圧縮側の剛性が非線形的に変化するモデルを利用する。新しい接触部が生ずる際の衝撃により、図４に示すような入射周波数の高次高調波が励起される。高次高調波の発生例として、風力発電所の翼が発する非可聴域の大エネルギー低周波音波により、近くの家屋内の家具、食器などが振動して２０Ｈｚ以上の可聴音を発することが挙げられる。 In the present invention, when a large-amplitude sine wave is incident on a closed crack having a gap of several tens of nanometers with actual fine unevenness as shown in FIG. 2, it is fine due to the compressive stress excited by the incident ultrasonic wave. Since the contact area of the uneven portion gradually increases, a model in which the compression-side rigidity changes nonlinearly as shown in FIG. 3 is used. The high-order harmonics of the incident frequency as shown in FIG. As an example of the generation of higher harmonics, the high-frequency, low-frequency sound waves in the non-audible range emitted by the wings of wind power plants vibrate nearby household furniture and tableware and emit audible sounds of 20 Hz or higher. It is done.
本発明では、図３及び図４に示す事実に基づき、ハイパスフィルタを用いずに、１サイクルの大振幅正弦波入射により励起される正弦波波形からの歪みを収録し、その波形の歪みを複数の特性によって定量化し、その量の分布を可視化することにより、部分接触域を伴う閉口き裂状欠陥の検出・寸法評価及び欠陥の性質を大まかに推定する。 In the present invention, based on the facts shown in FIG. 3 and FIG. 4, a distortion from a sinusoidal waveform excited by one cycle of large amplitude sinusoidal incidence is recorded without using a high-pass filter, and a plurality of distortions of the waveform are recorded. By quantifying according to the characteristics of the material and visualizing the distribution of the amount, the detection and size evaluation of the closed crack-like defect with the partial contact area and the nature of the defect are roughly estimated.
［装置］
上記の測定原理を応用した非線形超音波非破壊検査装置について説明する。図５は、可搬式小型水槽に走査機構を搭載し、１個の超音波探触子で超音波の送信と受信を行う測定装置の実施形態を示すものである。図５において、１は金属製配管などの被測定物、１ａは被測定物１の内部の検査対象領域（微小な欠陥などが存在する領域）、２は被測定物１の表面に当接・載置される可搬型の小型水槽、３は焦点型超音波探触子（送信超音波探触子と受信超音波探触子とを兼ねる）、４は焦点型超音波探触子３を走査させる可搬型の走査機構、５は１サイクルの大振幅正弦波を発生させる１サイクル大振幅正弦波発生器である。図５の装置では、被測定物１の表面に小型水槽２が配置され、この小型水槽２に超音波探触子３走査機構４が搭載され、小型水槽２中の水中に水没された焦点型超音波探触子３と被測定物１との間で、小型水槽２中の水を媒体として超音波が伝搬され送受信される。また、焦点型超音波探触子３からの超音波は、小型水槽２中の水中及び被測定物１の内部（材料中）で集束され、検査対象領域１ａに達する。走査機構４は焦点型超音波探触子３及び小型水槽２を被測定物１上で物理的に移動させる。
[apparatus]
A nonlinear ultrasonic nondestructive inspection apparatus applying the above measurement principle will be described. FIG. 5 shows an embodiment of a measuring apparatus in which a scanning mechanism is mounted on a portable small water tank and ultrasonic waves are transmitted and received by a single ultrasonic probe. In FIG. 5, reference numeral 1 denotes an object to be measured such as a metal pipe, 1 a denotes an inspection target area inside the object to be measured 1 (area where a minute defect exists), and 2 denotes a surface of the object to be measured 1. Mounted portable small water tank, 3 is a focus type ultrasonic probe (which serves as both a transmission ultrasonic probe and a reception ultrasonic probe), and 4 is a scan of the focus type ultrasonic probe 3 A portable scanning mechanism 5 is a one-cycle large-amplitude sine wave generator that generates one-cycle large-amplitude sine wave. In the apparatus of FIG. 5, a small water tank 2 is disposed on the surface of the object to be measured 1, and an ultrasonic probe 3 scanning mechanism 4 is mounted on the small water tank 2, and the focal type is submerged in water in the small water tank 2. Ultrasonic waves are transmitted and received between the ultrasonic probe 3 and the DUT 1 using water in the small water tank 2 as a medium. Further, the ultrasonic waves from the focal-type ultrasonic probe 3 are focused in water in the small water tank 2 and inside the object to be measured 1 (in the material) and reach the inspection target region 1a. The scanning mechanism 4 physically moves the focus type ultrasonic probe 3 and the small water tank 2 on the object to be measured 1.
また図５において、６は焦点型超音波探触子３からの正弦波の発生動作と走査機構４の動作を同期させる同期走査部、７は焦点型超音波探触子３が受信した被測定物１及びその内部の検査対象領域１ａからの反射超音波を増幅する受信信号増幅部、８は受信信号増幅部７からの信号を受信してデジタル記録する波形記録部、９は前記記録された受信波形に対して最大振幅、時間差などの特徴量を計算し取得する波形処理部、１０は波形処理部９で計算された結果をグレイスケール階調あるいはカラー色調の画像に変換する画像化処理部、１１は画像化処理部１０で得られた画像などを表示する画像表示部（ディスプレイ）である。なお、本実施形態では、上記の同期走査部６、受信信号増幅部７、波形記録部８、波形処理部９、画像化処理部１０、及び画像表示部１１は、パソコンなどのコンピュータ１２により構成されている。 In FIG. 5, reference numeral 6 denotes a synchronous scanning unit that synchronizes the generation operation of the sine wave from the focal ultrasonic probe 3 and the operation of the scanning mechanism 4, and reference numeral 7 denotes a measurement target received by the focal ultrasonic probe 3. A reception signal amplification unit for amplifying the reflected ultrasonic waves from the object 1 and the inspection target region 1a therein; 8 a waveform recording unit for receiving and digitally recording a signal from the reception signal amplification unit 7; A waveform processing unit that calculates and obtains feature quantities such as maximum amplitude and time difference with respect to the received waveform, and 10 is an imaging processing unit that converts the result calculated by the waveform processing unit 9 into a grayscale tone or color tone image. , 11 is an image display unit (display) for displaying an image obtained by the imaging processing unit 10. In the present embodiment, the synchronous scanning unit 6, the received signal amplification unit 7, the waveform recording unit 8, the waveform processing unit 9, the imaging processing unit 10, and the image display unit 11 are configured by a computer 12 such as a personal computer. Has been.
前述のように、図５の装置では、被測定物１の上部に可搬式小型水槽２を置き、送信超音波探触子３を機械的に移動させる走査機構４を制御する同期走査部６からのトリガ信号に同期して、１サイクル大振幅正弦波発生器５により電気信号を送信超音波探触子３に送信し、電気信号を超音波振動に変換する。これにより発生した超音波は水中及び材料中で集束され、被測定物１の検査対象領域１ａに達する。検査対象領域１ａ内に図２に示す閉口き裂状欠陥あるいは介在物が存在するとき、前述の理由により正弦波からの波形の歪みが生ずる。この歪みを伴う散乱波が送信経路と同一の経路を通って受信超音波探触子３で受信されて電気信号に変換される。この信号を受信増幅器７で増幅し、高垂直軸分解能と高時間分解能を持つ波形記録部８にデジタル収録する。収録された波形に対して、従来の最大振幅絶対値以外に加えて、引張側あるいは圧縮側の最大振幅、それらの比、引張側と圧縮側の最大振幅の受信時刻、周波数スペクトル、及び上記特性の入射電圧依存性など、さらに個々の特性を組み合わせた特徴量を波形処理部９で計算し、その結果を画像化処理部１０でグレイスケール階調あるいはカラー色調に変換し、画像表示部１１で２次元画像として表示する。 As described above, in the apparatus of FIG. 5, the portable small water tank 2 is placed on the upper part of the object to be measured 1, and the synchronous scanning unit 6 that controls the scanning mechanism 4 that mechanically moves the transmission ultrasonic probe 3 is used. In synchronization with this trigger signal, the one-cycle large amplitude sine wave generator 5 transmits an electric signal to the transmission ultrasonic probe 3 to convert the electric signal into ultrasonic vibration. The ultrasonic waves generated thereby are focused in water and in the material, and reach the inspection target region 1a of the object 1 to be measured. When the closed crack-like defect or inclusion shown in FIG. 2 exists in the inspection target region 1a, the waveform distortion from the sine wave occurs for the above-mentioned reason. The scattered wave with the distortion is received by the reception ultrasonic probe 3 through the same path as the transmission path and converted into an electric signal. This signal is amplified by the receiving amplifier 7 and digitally recorded in the waveform recording unit 8 having high vertical axis resolution and high time resolution. For recorded waveforms, in addition to the conventional maximum amplitude absolute value, the maximum amplitude on the tension side or compression side, their ratio, the reception time of the maximum amplitude on the tension side and compression side, the frequency spectrum, and the above characteristics Further, a characteristic amount obtained by combining individual characteristics such as incident voltage dependency of the image is calculated by the waveform processing unit 9, and the result is converted into a gray scale gradation or a color tone by the imaging processing unit 10. Display as a two-dimensional image.
本実施形態のに係る装置では、１サイクル大振幅正弦波送受信器５の容積が例えば約０．２ｍ×０．１ｍ×０．１ｍという小型のものであり、可搬式の小型水槽２をも使用するので、各種プラントの狭隘な配管部の閉口き裂状欠陥の非破壊検査に有効である。 In the apparatus according to the present embodiment, the volume of the one-cycle large-amplitude sine wave transmitter / receiver 5 is small, for example, about 0.2 m × 0.1 m × 0.1 m, and a portable small water tank 2 is also used. Therefore, it is effective for nondestructive inspection of closed crack-like defects in narrow piping parts of various plants.
また、本実施形態のに係る装置では、可搬式小型水槽を置けない検査領域には水柱式の探触子走査方式を用いるようにしたので、検査不可能領域を少なくすることができる。 Further, in the apparatus according to the present embodiment, since the water column type probe scanning method is used for the inspection region where the portable small water tank cannot be placed, the region where the inspection is impossible can be reduced.
また、本実施形態のに係る装置では、１サイクル大振幅正弦波送受信器５のパルス送信回数が毎秒５０００回程度であるので、最大毎秒５００ｍｍ／ｓの高速の速度で約０．１ｍｍの大きさの欠陥を可視化することができる。 In the apparatus according to the present embodiment, the number of pulses transmitted by the one-cycle large-amplitude sine wave transceiver 5 is about 5000 times per second, so that the maximum size is about 0.1 mm at a high speed of 500 mm / s. The defects can be visualized.
［画面例１］
１サイクル大振幅正弦波発生器により、水浸法で周波数８ＭＨｚ、繰返数１の正弦波を送信し、１２ビット、２５０ＭＳ／ｓのＡＤ変換ボードを用いて収録した、サブミクロンの隙間を持つステンレス鋼の拡散接合面からの最大振幅絶対値の画像と受信波形を図６に示す。図６では、画像中心部の赤色部分では波束の前半部分（白破線枠内）に正弦波からの顕著な歪みが観察されるが、後半部分は正弦波に近い。これに対し中心からはずれた緑色部分の波形はほぼ正弦波状である。この結果から、１サイクル大振幅正弦波を送信することだけで、部分接触域で発生する高調波を検出できることが確認できた。
[Screen example 1]
A 1-cycle large-amplitude sine wave generator transmits a sine wave with a frequency of 8 MHz and a repetition rate of 1 by the water immersion method, and has a submicron gap recorded using a 12-bit, 250 MS / s AD conversion board. FIG. 6 shows an image of a maximum amplitude absolute value and a received waveform from the diffusion joining surface of stainless steel. In FIG. 6, remarkable distortion from the sine wave is observed in the first half of the wave packet (within the white broken line frame) in the red part of the center of the image, but the latter half is close to the sine wave. On the other hand, the waveform of the green part deviated from the center is almost sinusoidal. From this result, it was confirmed that the harmonics generated in the partial contact area could be detected only by transmitting one cycle large amplitude sine wave.
［画面例２］
図６と同一の拡散接合面に対し、受信波形の入射電圧（入射波振幅にほぼ比例）依存性を、図７に示す。図７では、電圧２１０Ｖでは正弦波状波形を、２９０Ｖ以上では白破線枠内に正弦波波形からの顕著な歪みを伴う波形を、観察できる。この結果から、高調波を伴う波形の歪みを発生させるためには、閾値を越える入射電圧で超音波探触子を励起する必要があることが確認できた。
[Screen example 2]
FIG. 7 shows the dependence of the received waveform on the incident voltage (substantially proportional to the incident wave amplitude) with respect to the same diffusion bonding surface as in FIG. In FIG. 7, a sinusoidal waveform can be observed at a voltage of 210V, and a waveform with significant distortion from the sinusoidal waveform within a white broken line frame at 290V or more. From this result, it was confirmed that it is necessary to excite the ultrasonic probe with an incident voltage exceeding a threshold value in order to generate waveform distortion accompanied by harmonics.
［画面例３］
図６と異なる拡散接合試験体に対する最大振幅絶対値の画像と受信波形を図８に示す。図８では、中心部では波束の前半部に、やや中心部から離れた位置では立ち上がり部とそれに続く立ち上がり部に、周辺部では立下り部だけに、正弦波からの顕著な波形の歪みが確認できた。
[Screen example 3]
FIG. 8 shows an image of a maximum amplitude absolute value and a received waveform for a diffusion bonding test specimen different from FIG. In FIG. 8, significant waveform distortion from the sine wave is confirmed in the first half of the wave packet at the center, at the rising part and the subsequent rising part at a position slightly away from the central part, and only at the falling part at the peripheral part. did it.
［画面例４］
拡散接合円柱試験体の接合界面の最大振幅絶対値の画像と受信波形を図９に示す。図示左側が８ＭＨｚ、１サイクル大振幅正弦波入射、同右側がスパイク波入射による画像と画像中の特定位置の受信波形である。両者の画像は大きな差異が見られないが、大振幅正弦波入射による赤四角位置の受信波形は正弦波からの顕著な歪みが観察される。他方、スパイク波入射による同一位置の波形は正弦波状である。
[Screen example 4]
FIG. 9 shows an image of the maximum amplitude absolute value and the reception waveform of the bonded interface of the diffusion bonded cylindrical specimen. The left side of the figure is an image of 8 MHz, one-cycle large-amplitude sine wave incident, and the right side is a spiked wave incident image and a received waveform at a specific position in the image. Although there is no significant difference between the two images, a significant distortion from the sine wave is observed in the received waveform at the red square position due to the large amplitude sine wave incidence. On the other hand, the waveform at the same position by spike wave incidence is sinusoidal.
図９に示すように、大振幅正弦波入射の最大振幅絶対値が同程度の２点について、四角枠内の位置では顕著な波形の歪みが観察されるが、丸枠内の位置では波形の歪みがわずかである。これらから、最大振幅絶対値が同程度のこの２点の散乱源の特性が異なることが分かる。 As shown in FIG. 9, remarkable distortion of the waveform is observed at the position within the square frame at two points where the maximum amplitude absolute value of the large amplitude sine wave incidence is about the same, but at the position within the round frame, Slight distortion. From these, it can be seen that the characteristics of the two scattering sources having the same maximum absolute magnitude are different.
［画面例５］
図８の最下段に示す周辺部波形は立下り部の振幅が大きいので、−側の最大振幅分布を可視化した結果を図１０に示す。図１０の下部及び右側の曲線は、図中の矢印を付けた横線及び縦線に沿う振幅分布を表す。この図１０により拡散接合境界部を明瞭に表示できる。
[Screen example 5]
Since the peripheral waveform shown at the bottom of FIG. 8 has a large amplitude at the falling portion, the result of visualizing the maximum amplitude distribution on the negative side is shown in FIG. The lower and right curves in FIG. 10 represent the amplitude distribution along the horizontal and vertical lines with arrows in the figure. With this FIG. 10, the diffusion junction boundary can be clearly displayed.
［画面例６］
図８に示した拡散接合試験体に対する、基準時間から＋側の最大振幅に達すまでの時間差分布を図１１に示す。波形図の灰色ゲート内の４４．２６４μｓから＋側最大振幅までの時間差は楕円状散乱源の中央やや上側で最も短いことが示される。拡散接合内面の凹凸部形状を反映していると考えられる。
[Screen Example 6]
FIG. 11 shows a time difference distribution from the reference time until the maximum amplitude on the + side is reached with respect to the diffusion bonding test specimen shown in FIG. It is shown that the time difference from 44.264 μs in the gray gate of the waveform diagram to the maximum amplitude on the + side is the shortest at the center and slightly above the elliptical scattering source. It is thought that the uneven | corrugated | grooved part shape of the diffusion bonding inner surface is reflected.
〔第２実施形態〕
１．従来の高調波画像化法では、部分接触域を伴う不連続部に大振幅正弦波バースト波を入射し、受信波のＡＤ変換前にアナログハイパスフィルタ（ＨＰＦ）を用いて抽出して高次高調波の振幅をマッピングすることにより、従来の音響インピーダンス差を利用する超音波探傷法によっては検出・画像化が困難な、閉口き裂、粗大粒ステンレス鋳鋼中の疲労き裂、石油化学プラントの水素侵食などの検出・可視化を、可能としていた。そこでは、ＦＦＴ（高速フーリエ変換）により抽出した高調波振幅を用いるので、受信波形の歪みに含まれる多数の情報のうち、特定周波数の高調波振幅以外の情報を無視することになっていた。
[Second Embodiment]
1. In the conventional harmonic imaging method, a large-amplitude sine wave burst wave is incident on a discontinuous part with a partial contact area, extracted using an analog high-pass filter (HPF) before AD conversion of the received wave, and higher-order harmonics. By mapping wave amplitudes, closed cracks, fatigue cracks in coarse-grained stainless steel castings, hydrogen in petrochemical plants, which are difficult to detect and image by conventional ultrasonic flaw detection methods using acoustic impedance differences It was possible to detect and visualize erosion. In this case, since the harmonic amplitude extracted by FFT (Fast Fourier Transform) is used, information other than the harmonic amplitude of a specific frequency is to be ignored among many pieces of information included in the distortion of the received waveform.
短バースト波を用いる非線形超音波法においては、部分接触域からの散乱波の最初の部分に接触域に関する情報が含まれるはずである。そこで、ＨＰＦを使用せずに散乱波波形を収録し、波形の歪みを複数の特徴量（Ｆｅａｔｕｒｅ）を用いて定量化すれば、従来より多元的な評価が可能になると考えられる。かつて超音波画像化装置が開発された頃には、受信波形に含まれる複数の特徴量を可視化するＦｅａｔｕｒｅ ｍａｐｐｉｎｇ（例えば、ＡＳＮＴ、 Ｎｏｎｄｅｓｔｒｕｃｔｉｖｅ Ｈａｎｄｂｏｏｋ、 Ｖｏ． ７ Ｕｌｔｒａｓｏｎｉｃ Ｔｅｓｔｉｎｇ、 ｐｐ．７９９−８０１、 （１９９１））のアイデアが提案された。しかし、受信振幅と伝搬時間以外の特徴量を用いる市販の超音波画像化装置は極めて少ない。 In the nonlinear ultrasonic method using a short burst wave, information on the contact area should be included in the first part of the scattered wave from the partial contact area. Therefore, if a scattered wave waveform is recorded without using an HPF, and the distortion of the waveform is quantified using a plurality of feature quantities (Features), it is considered that multiple evaluation can be performed. At the time when an ultrasonic imaging apparatus was developed, a feature mapping (for example, ASNT, Nondestructive Handbook, Vo. 7 Ultrasonic Testing, pp. 799-801, which visualizes a plurality of feature amounts included in a received waveform). )) Idea was proposed. However, there are very few commercially available ultrasonic imaging apparatuses that use feature quantities other than the reception amplitude and propagation time.
本発明者による実験では、散乱波波形の歪みを複数の特徴量を用いて表現し、それら特徴量あるいは複数の特徴量のノルム分布を画像化する、新しい非線形特徴量画像化法を構築するための最初の段階として、拡散接合により制作した模擬閉口き裂試験体（石田仁志・川嶋紘一郎、日本非破壊検査協会平成２５年度秋季講演大会概要集、 ｐｐ．６９−７３、 （２０１３））に対して、１サイクルの大振幅正弦波を入射し、ＨＰＦを使用せず、閉口き裂面からの散乱波波形を収録し、観察した。その結果、波形の歪みが受信波形の最初の部分で顕著であり、後半部ではそれが少ないことが、明らかとなった。 In the experiment by the present inventor, in order to construct a new non-linear feature value imaging method that expresses the distortion of the scattered wave waveform using a plurality of feature values and images the norm distribution of these feature values or a plurality of feature values. As the first stage of the test, for the simulated closed crack specimen produced by diffusion bonding (Hitoshi Ishida, Shinichiro Kawashima, Annual Meeting of the 2013 Non-Destructive Inspection Association, pp. 69-73, (2013)) Then, a large-amplitude sine wave of one cycle was incident, and the scattered wave waveform from the closed crack surface was recorded and observed without using HPF. As a result, it has been clarified that the waveform distortion is remarkable in the first part of the received waveform and is small in the second half part.
２．複数特徴量を用いて受信波形の歪みを表す非線形超音波法の基本的イメージ
閉口き裂（図１２参照）を例として、新しい非線形超音波評価法の基本的イメージを説明する。閉口き裂部では、図１２の左側に示すように大振幅入射波の一部が透過し一部が反射される。ＰｅｃｏｒａｒｉとＳｏｌｏｄｏｖ（Ｃ． Ｐｅｃｏｒａｒｉ ａｎｄ Ｉ． Ｓｏｌｏｄｏｖ、 ｉｎ Ｕｎｉｖｅｒｓａｌｉｔｙ ｏｆ ｎｏｎｃｌａｓｓｉｃａｌ ｎｏｎｌｉｎｅａｒｉｔｙ． Ａｐｐｌｉｃａｔｉｏｎｓ ｔｏ ｎｏｎ−ｄｅｓｔｒｕｃｔｉｖｅ ｅｖａｌｕａｔｉｏｎ ａｎｄ ｕｌｔｒａｓｏｎｉｃｓ． ｐｐ．３０９−３２６、 （２００７））は、閉口き裂の圧縮剛性が連続体と同一であると仮定した図１３に示す非線形応答モデルに基づき、閉口き裂部における波形の歪みが顕著であることを説明した。しかし、現実の閉口き裂部にはナノメートル台の隙間が存在するので、図１４に示すように、大振幅入射波による応力を受けてき裂面が接触するまでに多少の時間遅れが発生し、さらに閉口き裂部に存在する微細な凹凸部が圧縮応力を受けてつぶれ、実接触面積が増大する過程で圧縮剛性が変化する。これらの現象は圧縮波が閉口き裂面に作用する初期段階において顕著であるので、例えば図１５に示すように、正弦波からの波形の歪みは受信波形の最初の段階に顕著に現われると推測される。
2. A basic image of a new nonlinear ultrasonic evaluation method will be described by taking a closed image crack (see FIG. 12) of a nonlinear ultrasonic method representing distortion of a received waveform using a plurality of feature amounts as an example. At the closed crack portion, as shown on the left side of FIG. 12, a part of the large amplitude incident wave is transmitted and a part thereof is reflected. Pecorari and Solodov (C. Pecorari and I. Solodov, in Universality of nonclassical nonlinearity. Based on the non-linear response model shown in FIG. 13 that is assumed to be, it has been explained that the waveform distortion in the closed crack portion is significant. However, since there are gaps in the nanometer range in the actual closed crack portion, as shown in FIG. 14, a slight time delay occurs until the crack surface comes into contact with the stress due to the large amplitude incident wave. In addition, the fine irregularities present in the closed crack portion are crushed by the compressive stress, and the compression rigidity changes in the process of increasing the actual contact area. Since these phenomena are remarkable at the initial stage when the compression wave acts on the closed crack surface, it is assumed that the waveform distortion from the sine wave appears remarkably at the first stage of the received waveform as shown in FIG. Is done.
従来の高調波法では、Ａ／Ｄ変換前にアナログハイパスフィルタ（ＨＰＦ）を用いて抽出した高調波受信波形に対して、受信波が周期性を持つと想定し、ＦＦＴ（高速フーリエ変換）により高調波振幅比を求める。しかし、この方法では、局部的な波形の歪みを検出することは不可能であり、また位相情報を利用できない。 In the conventional harmonic method, it is assumed that the received wave has periodicity with respect to the harmonic received waveform extracted using an analog high-pass filter (HPF) before A / D conversion, and FFT (Fast Fourier Transform) is used. Determine the harmonic amplitude ratio. However, this method cannot detect local waveform distortion and cannot use phase information.
３．受信波形の歪み計測の実験
３．１ 試験体
端面に傾いたφ１０の穴（最大深さ１３μｍ）を加工したＳＵＳ３０４角柱（口２０ｍｍ×４０ｍｍ）に穴のない角柱を拡散接合し、隙間が直径方向に変化する模擬閉口き裂を含む試験体（石田仁志・川嶋紘一郎、日本非破壊検査協会平成２５年度秋季講演大会概要集ｐ．６９−７３（２０１３））を用いた。上記閉口き裂部のＳＥＭ（走査型電子顕微鏡）写真の例を図１６に示す。
3. 3.1 Measurement of received waveform distortion 3.1 Specimen Diffusion bonding of a square column without a hole to a SUS304 square column (mouth 20 mm x 40 mm) with a φ10 hole (maximum depth 13 μm) inclined on the end face, and the gap is in the diameter direction Specimens containing simulated closed cracks (Hitoshi Ishida and Shinichiro Kawashima, Japan Non-Destructive Inspection Association 2013 Autumn Lecture Meeting Summary Collection p. 69-73 (2013)) were used. An example of an SEM (scanning electron microscope) photograph of the closed crack portion is shown in FIG.
３．２ 測定装置
水浸高調波画像化装置を用いて、閉口き裂部を可視化後、幾つかの点の受信波形を１２ビット、５００ＭＳ／ｓのＡＤ変換ボードを用いて収録した。大振幅正弦波送受信器としてＲＩＴＥＣ ＲＰＲ−４０００を用いた。
3.2 Measuring Device After visualizing the closed crack using an immersion harmonic imaging device, the received waveforms at several points were recorded using a 12-bit, 500 MS / s AD conversion board. RITEC RPR-4000 was used as a large amplitude sine wave transceiver.
３．３ 測定方法
公称周波数１０ＭＨｚ、素子径９．６ｍｍ、焦点距離１２７ｍｍの点集束探触子を用いて、８ＭＨｚ−１サイクルの正弦波を垂直入射し、ＨＰＦを用いずに模擬閉口き裂を可視化した後、幾つかの位置における波形を収録した。送信電圧を数段階変化させ波形の歪みの差を検討した。
3.3 Measurement method Using a point focusing probe with a nominal frequency of 10 MHz, element diameter of 9.6 mm, and focal length of 127 mm, a 8 MHz-1 cycle sine wave is perpendicularly incident, and a simulated closed crack is created without using HPF. After visualization, waveforms at several locations were recorded. The difference in waveform distortion was examined by changing the transmission voltage in several steps.
４．受信波形の歪みの観察
４．１ 試験体Ａ
図１７に閉口き裂面の幾つかの点からの散乱波波形を示す。最上段のき裂中心部では受信波形の最初の立上り及びそれに続く半サイクルに顕著な波形の歪みが見られるが、第２及び３サイクルの波形は正弦波に近い。中段に示すき裂中心から幾分外れた位置の受信波形では１サイクル目のマイナス側のピーク部が尖っているが、それ以外は正弦波状である。最下段は穴外側の接合部からの波形であり、ノイズに近い。水中焦点距離１２７ｍｍの探触子を用いたため、穴部が過大表示されている。しかし、図１７から閉口き裂部で受信波形の最初の部分に大きな歪みが現われることが確認できる。
4). Observation of received waveform distortion 4.1 Specimen A
FIG. 17 shows scattered wave waveforms from several points on the closed crack surface. At the center of the crack at the uppermost stage, significant waveform distortion is observed at the first rise of the received waveform and the subsequent half cycle, but the waveforms of the second and third cycles are close to sine waves. In the received waveform at a position slightly deviated from the center of the crack shown in the middle stage, the negative peak portion of the first cycle is pointed, but the rest is sinusoidal. The bottom row is a waveform from the joint outside the hole and is close to noise. Since a probe with an underwater focal length of 127 mm is used, the hole portion is excessively displayed. However, it can be confirmed from FIG. 17 that a large distortion appears in the first part of the received waveform at the closed crack.
閉口き裂中心部において入射電圧を変化させた際の波形の歪みの差異を図１８に示す。上段（２１０Ｖ）の波形は正弦波状に近く、波形の歪みは見られない。中段（２９０Ｖ）では、最初の下側ピーク部の尖りが生ずるが、第２と３サイクルの波形は正弦波状である。下段（３２０Ｖ）の第１サイクルの波形の歪みは著しいが第２と３サイクルの波形は正弦波状である。波形の歪みの特徴は、最初のサイクルだけにおける高調波の出現である。
またこの結果から、波形の歪みを発生させる入射電圧には明らかに閾値が存在する。ちなみに、以上に対し、Ｓｏｌｏｄｏｖらは、従来の高調波法及び和差周波数法には入射波振幅の閾値が存在せず、分調波法においてそれが存在すると述べていた。
FIG. 18 shows the difference in waveform distortion when the incident voltage is changed at the center of the closed crack. The waveform of the upper stage (210V) is close to a sine wave, and no waveform distortion is observed. In the middle stage (290 V), the first lower peak is sharpened, but the waveforms of the second and third cycles are sinusoidal. The waveform of the first cycle of the lower stage (320V) is significantly distorted, but the waveforms of the second and third cycles are sinusoidal. A characteristic of waveform distortion is the appearance of harmonics only in the first cycle.
Also, from this result, there is clearly a threshold for the incident voltage that causes waveform distortion. Incidentally, Solodv et al. Stated that the conventional harmonic method and the sum-and-difference frequency method do not have a threshold of incident wave amplitude, and that they exist in the subharmonic method.
４．２ 試験体Ｂ
試験体Ａと同様に製作された試験体Ｂに対する模擬き裂部の画像と中心を含む３箇所の波形を図１９に示す。入射電圧は３２０Ｖである。図１９において、中心部では、白枠内に示すように、最初の１〜２サイクルに高次高調波が見られる。しかし、周辺部の波形は正弦波状であり歪みはない。閾値を越えた入射電圧を３２０Ｖから４２５Ｖに増大させた際の中央部の受信波形を図２０に示す。波形が飽和しないようにゲインを調整した。図から明らかなように、波形の歪みに大きな差は見られない。
4.2 Specimen B
FIG. 19 shows three simulated waveforms including the image and the center of the simulated crack for the specimen B manufactured in the same manner as the specimen A. The incident voltage is 320V. In FIG. 19, high-order harmonics are seen in the first 1-2 cycles as shown in the white frame at the center. However, the peripheral waveform is sinusoidal and has no distortion. FIG. 20 shows a reception waveform at the center when the incident voltage exceeding the threshold is increased from 320 V to 425 V. The gain was adjusted so that the waveform was not saturated. As is clear from the figure, there is no significant difference in waveform distortion.
５．検討
図１７及び図１９に示すように、拡散接合により製作したサブミクロン台の隙間を伴う模擬閉口き裂部に１サイクルの大振幅正弦波を入射し、ハイパスフィルタを使用しないで１２ビットでＡ／Ｄ変換した受信波形には、１〜２サイクル目に入射周波数の数倍の高次高調波として顕著な波形の歪みが現われる。この波形の歪みを発生させる入射電圧には、図１８に示すように、閾値が存在する。閾値を超えた電圧を３０％程度増大させても、波形の歪みの変化は少ない。
5). Study As shown in FIGS. 17 and 19, one cycle of a large-amplitude sine wave is incident on a simulated closed crack portion with a submicron gap manufactured by diffusion bonding, and 12 bits A are used without using a high-pass filter. In the received waveform subjected to the / D conversion, remarkable waveform distortion appears as high-order harmonics several times the incident frequency in the first and second cycles. As shown in FIG. 18, there is a threshold value for the incident voltage that causes distortion of this waveform. Even if the voltage exceeding the threshold is increased by about 30%, the change in waveform distortion is small.
連続固体の非線形超音波（高調波）計測と同様に、部分接触部を伴う閉口き裂状欠陥に対しても、数〜数十サイクルの大振幅バースト波入射が用いられてきた。しかし、上記の結果から、非線形超音波計測のうち高調波計測については、１サイクルの大振幅正弦波入射で良いことが明らかとなった。これにより、小型・軽量の大振幅正弦波送信器が開発されれば、プラントの劣化・損傷評価に高調波を適用することが容易になる。 Similar to continuous-state nonlinear ultrasonic (harmonic) measurement, large-amplitude burst wave incidence of several to several tens of cycles has been used for closed crack-like defects with partial contact portions. However, from the above results, it has been clarified that one cycle of large-amplitude sine wave incidence is sufficient for harmonic measurement among nonlinear ultrasonic measurements. As a result, if a small and lightweight large-amplitude sine wave transmitter is developed, it will be easy to apply harmonics to plant degradation / damage evaluation.
さらに、前記受信波形についてＦＦＴ（高速フーリエ変換）による高調波振幅以外の波形の歪みを表す複数の超音波特徴量を超音波非破壊検査のために用いるようにすれば、波形の歪みを発生させる欠陥の実体的な分類が可能になる。 Furthermore, if a plurality of ultrasonic feature quantities representing waveform distortion other than the harmonic amplitude by FFT (Fast Fourier Transform) are used for the received waveform for ultrasonic nondestructive inspection, waveform distortion is generated. Substantive classification of defects is possible.
６．まとめ
本発明者らは、１サイクルの大振幅正弦波を部分接触域を伴う閉口き裂部に入射し、最初に受信されるき裂面からの散乱波波形の詳細な解析に基づく新たな非線形超音波法を構築することを目的とし、サブミクロン台で隙間が変化する拡散接合により製作した模擬閉口き裂試験体に対して、受信波形に含まれる正弦波からの波形の歪みの検出を行った。８ＭＨｚ−１サイクルの大振幅正弦波縦波を垂直入射し、受信波の最初の１〜２サイクルに入射周波数の数倍の高調波成分が含まれ、後半の３〜４サイクルは正弦波に近いことが明らかとなった。１サイクルの大振幅正弦波入射により閉口き裂面で発生する高調波を検出できるので、大振幅正弦波送信器を従来より小型化することが可能となり、プラント類の劣化・損傷評価への高調波法の適用が容易になると考えられる。
6). Summary The present inventors have introduced a new nonlinear sine wave based on a detailed analysis of a scattered wave waveform from a crack surface that is incident on a closed crack with a partial contact area by entering a large-amplitude sine wave of one cycle. For the purpose of constructing the ultrasonic method, the distortion of the waveform from the sine wave included in the received waveform is detected for the simulated closed crack specimen manufactured by diffusion bonding where the gap changes on the submicron range. It was. Vertically incident large amplitude sine wave longitudinal wave of 8 MHz-1 cycle, the first 1-2 cycles of the received wave contain harmonic components several times the incident frequency, and the latter 3-4 cycles are close to sine wave It became clear. Since harmonics generated at the closed crack surface can be detected by one-cycle large-amplitude sine wave incidence, it is possible to make a large-amplitude sine wave transmitter more compact than before, and to improve the degradation and damage of plants. It seems that the wave method can be easily applied.
本発明は、小型の正弦波発生器から発生される大振幅の１サイクル正弦波を焦点型探触子により集束させた超音波を材料内に入射し、材料内部の欠陥で散乱された波形の歪みを検出し、非破壊的にそれらを可視化する非線形超音波非破壊装置である。本発明は、疲労き裂面、粒界応力腐食割れ部、水素割れ部などの開口き裂以外に、材料内介在物、不完全接合部、表面の微小閉口き裂等の検査にも利用することができる。 In the present invention, an ultrasonic wave obtained by focusing a one-cycle sine wave having a large amplitude generated from a small sine wave generator by a focusing probe is incident on the material, and the waveform of the waveform scattered by defects inside the material is obtained. It is a non-linear ultrasonic non-destructive device that detects distortions and visualizes them non-destructively. In addition to opening cracks such as fatigue crack surfaces, intergranular stress corrosion cracked parts, and hydrogen cracked parts, the present invention is also used for inspection of inclusions in materials, imperfect joints, surface micro-closed cracks, etc. be able to.
１ 被測定物
１ａ 検査対象領域
２ 小型水槽
３ 焦点型超音波探触子（送信超音波探触子，受信超音波探触子）
４ 走査機構
５ １サイクル大振幅正弦波発生器
６ 同期走査部
７ 受信信号増幅部
７ 受信増幅器
８ 波形記録部
９ 波形処理部
１０ 画像化処理部
１１ 画像表示部
１２ コンピュータ
1 Object to be measured 1a Inspection target area 2 Small water tank 3 Focused ultrasound probe (transmitting ultrasound probe, receiving ultrasound probe)
4 Scanning Mechanism 5 1-cycle Large Amplitude Sine Wave Generator 6 Synchronous Scanning Unit 7 Reception Signal Amplifying Unit 7 Reception Amplifier 8 Waveform Recording Unit 9 Waveform Processing Unit 10 Imaging Processing Unit 11 Image Display Unit 12 Computer
Claims (7)
前記正弦波発生器からの少なくとも１サイクルの大振幅正弦波に基づいて大振幅超音波を被測定物の内部に送信する焦点型送信超音波探触子と、
前記大振幅超音波が被測定物の内部で反射又は散乱された超音波を受信する焦点型受信超音波探触子と、
前記焦点型受信超音波探触子で受信した超音波中の最初の１〜２サイクル分から、高調波成分の振幅又は波形の歪み、並びに前記振幅又は波形の歪みから得られる複数の特性、すなわち、引張側と圧縮側の最大振幅値及びそれらの比、引張側と圧縮側の最大振幅受信時間差、周波数スペクトル、及び上記特性の入射電圧依存性を含む超音波特性を、取得し、これらの取得した超音波特性を処理する処理手段と、
を備えたことを特徴とする小型非線形超音波非破壊検査装置。 A sine wave generator for generating at least one cycle of a large amplitude sine wave;
A focus-type transmitting ultrasonic probe for transmitting large-amplitude ultrasonic waves to the inside of the object to be measured based on at least one cycle of large-amplitude sine waves from the sine wave generator;
A focus-type receiving ultrasonic probe that receives ultrasonic waves reflected or scattered inside the object to be measured;
From the first one to two cycles in the ultrasonic wave received by the focused receiving ultrasonic probe, the amplitude or waveform distortion of the harmonic component, and a plurality of characteristics obtained from the amplitude or waveform distortion, Acquired and acquired the ultrasonic characteristics including the maximum amplitude value of the tension side and the compression side and their ratio, the maximum amplitude reception time difference between the tension side and the compression side, the frequency spectrum, and the incident voltage dependence of the above characteristics. Processing means for processing the ultrasonic properties;
A compact non-linear ultrasonic non-destructive inspection apparatus characterized by comprising:
該正弦波発生器によって発生させた少なくとも１サイクルの大振幅正弦波を超音波として送信する焦点型送信超音波探触子と、
前記焦点型送信超音波探触子を被測定物に対して相対的に移動させる可搬式走査機構と、
前記大振幅正弦波発生器で発生された電気信号に同期して前記走査機構を駆動する同期操作部と、
前記焦点型送信超音波探触子で発生させた超音波を媒体を通して斜め入射したとき励起されるモード変換縦波あるいは横波を被測定物の内部に伝搬させ被測定物内部の欠陥で散乱された前記モード変換横波を受信する焦点型受信超音波探触子と、
前記焦点型受信超音波探触子で受信した前記モード変換縦波及び横波を増幅する増幅器と、
前記増幅器で増幅した波形をＡＤ変換し記憶する波形記憶部と、
前記波形記憶部で記憶した波形をデジタル処理する波形処理部と、
前記波形記憶手段で記憶した波形に対し、最大振幅絶対値、引張側と圧縮側の最大振幅値及びそれらの比、参照時間からの引張側と圧縮側の最大振幅受信時間差、周波数スペクトル、並びに上記特性の入射電圧依存性を演算又は算出し、その演算又は算出された超音波特性を画像処理する画像化処理手段と、
前記画像化処理手段で処理された画像を表示する表示手段と、
前記走査機構の駆動と前記正弦波発生器の信号を同期させる同期走査手段と、
を備えたことを特徴とする小型非線形超音波非破壊検査装置。 A sine wave generator for generating at least one cycle of a large amplitude sine wave;
A focus-type transmitting ultrasonic probe that transmits at least one cycle of a large-amplitude sine wave generated by the sine wave generator as an ultrasonic wave;
A portable scanning mechanism for moving the focused transmission ultrasonic probe relative to the object to be measured;
A synchronization operation unit that drives the scanning mechanism in synchronization with an electrical signal generated by the large amplitude sine wave generator;
A mode-converted longitudinal or transverse wave that is excited when the ultrasonic wave generated by the focus-type transmitting ultrasonic probe is obliquely incident through the medium is propagated inside the object to be measured and scattered by defects inside the object to be measured. A focus-type receiving ultrasonic probe for receiving the mode-converted shear wave;
An amplifier that amplifies the mode-converted longitudinal and transverse waves received by the focus-type receiving ultrasonic probe;
A waveform storage unit for AD-converting and storing the waveform amplified by the amplifier;
A waveform processing unit for digitally processing the waveform stored in the waveform storage unit;
For the waveform stored in the waveform storage means, the maximum amplitude absolute value, the maximum amplitude value on the tension side and the compression side and the ratio thereof, the difference between the maximum amplitude reception time on the tension side and the compression side from the reference time, the frequency spectrum, and the above An imaging processing means for calculating or calculating the incident voltage dependence of the characteristics, and performing image processing on the calculated or calculated ultrasonic characteristics;
Display means for displaying the image processed by the imaging processing means;
Synchronous scanning means for synchronizing the driving of the scanning mechanism and the signal of the sine wave generator;
A compact non-linear ultrasonic non-destructive inspection apparatus characterized by comprising:
The small-sized nonlinear ultrasonic nondestructive inspection according to any one of claims 1 to 6, wherein the large-amplitude sine wave generator can select any one of 1, 2, or 3 as the number of cycles of the sine wave to be generated. apparatus.
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