JP3730429B2 - Ultrasonic flaw detection result display method and ultrasonic flaw detection apparatus - Google Patents

Description

【００４３】
【数２】

【００４４】
次に、片道伝播時間△ｔ_ij,m と検査体１０２中の伝播速度Ｖから、ｍ番目のエコーに対する送受信位置（ｘ_i，ｙ_j）の表面から反射源１０３までの片道伝播距離Ｚ_ij,m を数３で計算し、Ｂスコープ図形の１点のデータを求める。なお、ｍ番目のエコーとは、ピーク検出処理演算部２０５によって選択される時間領域内に存在するエコーの順番である。受信されるエコーの数は、反射源の数や超音波の屈折角によって変わる。
【００４５】
【数３】

【００４６】
ここで、探傷に使用する音速Ｖは縦波音速Ｖ_L及び横波音速Ｖ_Tとする。この点データを走査経路の１ライン（ｙ_j を一定として、ｘ_i のｉ＝始点〜終点まで走査）について集積すると、反射源１０３に対し縦波音速Ｖ_Lを用いた演算結果である図形１１５と、横波音速Ｖ_Tによる図形１１６が表示される。
【００４７】
次に、画像データ演算（２）の処理（Ｓ７０）を、ホログラム再生領域の計算（Ｓ７０１）、ホログラム作成（Ｓ７０２）、ホログラム再生演算（Ｓ７０３）、音速毎の画像表示データの作成（Ｓ７０４）の順で説明する。本実施例では、まず縦波音速Ｖ_L、ついで横波速度Ｖ_Tで演算処理する。
【００４８】
図１３に、ホログラム再生領域作成の説明図を示す。数３によって得たＢスコープ図形データは、ＸＺ座標における点の集合（図形１１５，１１６）として表現される。この１点１点に対して、その点をＸ軸に射影した点を中心として、超音波の屈折角θに等しい角度で回転変換を行う。
【００４９】
超音波の屈折角θにより、Ｂスコープ図形１１５，１１６の各点を回転させ、ＸＺ断面におけるホログラム再生領域１１７，１１１８を数４により求める。さらに、走査軸Ｙの値ｙ_j を変え、各ｙに対してＸＺ断面におけるホログラム再生領域を作成する。ホログラム再生領域のデータは、図形データメモリ２０３に一時記憶される。
【００５０】
【数４】

【００５１】
これによれば、Ｂスコープ図形全体を同時に回転するのではなく、各点は各々と送受信位置（ｘ_i，ｙ_j）を結ぶ線からθだけ回転されるので、回転後の図形１１７及び１１８はそれぞれ回転前の図形１１５、１１６よりも、その占める領域が小さくなり、実際の反射源に対する図形（インジケーション）の誤差が、この回転処理によって小さくできる。
【００５２】
図１４に、ホログラム作成の説明図を示す。本実施例はパルス波を用いた超音波ホログラフィ法を採用している。従来の方法は、送信波にパルス波を用い、受信されるパルス波の受信時間と、参照波に相当するクロックパルスとの一致或は不一致を記録することで、ホログラムを作成している。これに対し、本実施例では、参照波に相当するものとしてクロックパルスを用いず、例えばcos関数のような振動関数を用い、受信パルス波の受信時間をcos関数の引数とすることで、参照波と受信波を干渉させる効果を数値的に与え、ホログラムを作成する。
【００５３】
本実施例によるホログラムＨは、数５の演算によって作成される。すなわち、受信時間に比例する量である片道伝播距離（Ｚ_ij）を基に、処理開始位置１２１から処理終了位置１２２で定められる探傷領域の間の各送受信位置（ｘ_i，ｙ_j）において、数値的に参照波と干渉させたホログラムＨ（ｘ_i,ｙ_j）を数５により作成する。
【００５４】
【数５】

【００５５】
数５において、数値的な干渉に用いる参照波（cos関数）の波数ｋとして、ｋ＝ｎ×２πｆ／Ｖを用いる。ただし、Ｖは鋼中を伝播するモードの超音波音速、ｆは探傷に使用する超音波の周波数、ｎは自然数である。ｎ＝１の場合、送信される超音波の周波数と計算上の参照波の周波数が同じになり、ｋ＝２π／λとなる。ｎの値を大きくすることで、より高い周波数を持つ参照波との干渉を数値的に計算することができる。
【００５６】
ここで、数５の導出過程を数６〜数９により説明する。被検査体１０２に数６に示す角振動数ω（＝２π／ｆ）の超音波を送信すると、反射源１０３により数７に示すエコーが受信される。ここで、ｒは受信間での伝播距離である。この受信エコーの位相情報を取り出すために、角振動数ω（＝２π／ｆ）を持つ参照波（cos波）を数値的に与えると、干渉波の強度分布は数９により計算できる。数９で、位相情報を持つ干渉項（cos関数部）が数５の関数部に相当し、この干渉項を計算してホログラムとする。
【００５７】
【数６】

【００５８】
【数７】

【００５９】
【数８】

【００６０】
【数９】

【００６１】
数５で、参照波数ｋを変えるｎの値を大きくすると、より高い周波数を持つ参照波との干渉を数値的に計算することができ、送信超音波の波長λよりも高い空間分解能を持つホログラムＨ（ｘ_i,ｙ_j）を作成することができる。分解能調整のためのｎは、ユーザが入力装置２１０からデータ記憶部２０６の波数倍数設定部２６０２に入力し、画像表示データ演算装置２０２が参照する。
【００６２】
図１５に、ホログラム再生における波数ｋの影響をイメージで示す。２つのピンホールによるホログラムとその再生像で、（ａ）は波数ｋが小さい場合、（ｂ）は波数ｋが大きい場合である。波数ｋが大きい場合は空間分解能が高く、ピンホールの存在に合致したシャープな再生像が得られている。
【００６３】
数５から求まるホログラムＨ（ｘ_i,ｙ_j）は、送受信位置ｘ_i,ｙ_jにおける１点、１点の値である。この各点の値を集積して、１次元ホログラム１２７，１２８が再生される。
【００６４】
ホログラムの再生方法は２通りあり、第１の方法は簡易な再生方法である。すなわち、１ライン走査の探傷の度に、１次元ホログラム１２７及び１２８を、ＸＺ断面におけるホログラム再生領域１１７，１１８上で像再生する。像再生はホログラム上の全点から、再生領域上の１点に対して、ホログラムの重みを付けた平面波を加算（積分）する。この操作を再生領域の全点に対して行う。再生領域の中で、反射源に近い部分では、ホログラムからの平面波の位相が揃い、積分値が大きくなり再生像が結像する。
【００６５】
この再生像を２次元表示すると、図１（ｆ）の画面が得られる。さらに、ＸＺ断面での再生像をＹ軸方向に重ね合わせて、３次元的な再生像Ｇを作成すれば、３次元の表示も可能である。この方法によれば、像再生に必要な計算時間及びメモリを大幅に削減できるので、探傷結果表示の簡易な方法として採用される。
【００６６】
第２の再生方法は、より高精度な再生方法である。ＸＺ断面におけるホログラム再生領域（面）１１７，１１８及びホログラム１２７、１２８を、探傷が終了するまでデータ記憶部２０６に記憶し、探傷終了後に再生領域を２次元的に再構成し、ＸＹ平面上の探傷領域に割り付けられた２次元ホログラムを再生する。
【００６７】
第２の方法によるホログラム再生の計算式を数１０に示す。第１の再生方法の場合と同様、ホログラム上の全点から、再生領域上の１点に対して、ホログラムＨで重み付けた球面波（ｅの関数）を加算（積分）する。この操作を再生領域の全点に対して行う。ただし、積分領域は２次元である。再生領域の中で、反射源に近い部分では、ホログラムからの平面波の位相が揃い、積分値が大きくなり再生像Ｇが結像する。
【００６８】
【数１０】

【００６９】
数１０の演算を計算機上で行うため、離散化して数値積分、或は式を変形して高速フーリエ変換などの計算手法を用いる。また、ホログラム再生計算に用いる再生参照波の波数ｋの値として、ホログラム作成に用いる参照波に対して使用した波数ｋと同様の値を使用する。ｋ＝ｎ×２πｆ／Ｖとして、ｎの値を大きくすることで、より高い周波数を持つ参照波との干渉によるホログラムを数値的に再生計算できる。この方法は、第１の再生方法と異なり、２次元的に再生処理を行うことになるため、必要となる時間及びメモリは大きくなるが、より精度の高い再生像を得ることができる。
【００７０】
縦波音速Ｖ_L を用いたホログラム再生の演算結果は、反射源１０３に対し横波で入射して横波で反射、或いは縦波で入射し横波で反射した横波エコーによる再生像１３０、１３１は消去され、反射源１０３に対し縦波で入射し縦波で反射した図形１１５の再生像１２９のみが結像される。
【００７１】
一方、横波音速Ｖ_T を用いたホログラム再生の結果は、縦波エコーによる図形１１５や反射時の横波変換による再生像は消去され、反射源１０３に対し横波で入射し、横波で反射した図形１１６に対する再生像１３０のみが得られる。これは、ホログラム作成処理と再生処理で使用される伝播音速が異なると、実際の反射源が存在する位置付近で再生波の位相が揃わず、互いに打ち消し合う結果となるためである。
【００７２】
本実施例では、再生像のデータを表示データとして、一旦、画像データメモリ２０３に記憶し（Ｓ７０４）、縦波及び横波の各再生像を重ね合わせて２次元または３次元による画像の表示を行う（Ｓ８０）。図１１に、記憶される再生像データの形式を示す。
【００７３】
２次元画像の重畳表示では、図１（ｆ）のように、一致あるいは近接した再生像１２９、１３０を同色とし、他の再生像と識別して画像表示装置２０１に出力する。或いは、再生像が一致した場合のみ画像表示装置２０１に出力する。これにより、実際の反射源に対する映像を正確に表示することができ、傷の数や位置を誤認することがなくなる。
【００７４】
図１６に、再生像として表示させたい画像を選択するメニュー画面の例を示す。表示画像をユーザに選択させる入力画面で、縦波音速として処理した場合に得られる画像データの表示、横波音速として処理した場合に得られる画像データの表示、縦波から横波にモード変換した音速で処理した場合に得られる画像データの表示などを選択でき、複数入力の場合は重畳表示となる。
【００７５】
最後に、ホログラム再生像の計算結果を３次元的な映像として表示する方法を説明する。図１７に３次元的表示のフローチャートを示す。予め、スレッシュホールドレベルＨmin を設定し、数１０で求めた再生像に対して、スレッシュホールドレベルＨmin を越えたか判定し（Ｓ7031）、越えた座標を再生像として採用する（Ｓ7032）。
【００７６】
図１８に、再生像Ｈ（ｘｙｚ）のスレッシュホールドレベルＨmin を３次元的に示す。Ｈmin を越えた斜線部の再生像が表示される。これにより、参照波にcos波を用いたときの干渉効果をＨmin で２値化しているので、反射源１０３の位置に、再生像１２９（１３０）を正しく表示することができる。
【００７７】
再生像の３次元表示は、例えば再生像データをＶＲＭＬ形式で記述し、ＶＲＭＬブラウザで表示する。図１９にＶＲＭＬ形式によるデータの一例、図２０にＶＲＭＬブラウザで表示した画面の一例を示す。ＸＹＺ座標上で、被検査体１０２内の反射源１０３が３次元表示される。なお、入力装置２１０からの指示ポインタ２２０１で表示図形をドラッグし、ユーザの望む方向に表示画面を回転して、任意の方向からの射影像を得ることもできる。
【００７８】
以上、実施例１によれば、縦波音速と横波音速をそれぞれ用いてホログラムを作成、再生するので、再生演算に用いた音速と異なる伝播速度によるインジケーションに対しては、ホログラム再生参照波の位相がそろわず、ホログラム再生像が結像しない。このため、本来の反射源と異なる位置に現れる反射源のインジケーション（虚像）が消去され、実際の反射源のある位置に対応して、反射源の映像（実像）を表示できる。また、縦波及び横波で計算した各々の再生像を重ね合わせて表示することで、その重なりの程度から実在する反射源を高信頼に確認することができる。さらに、Ｂスコープデータを屈折角で回転補正してホログラム再生領域を求めているので、超音波の広がりの影響を低減し、位置精度よく反射源の映像を表示できる。
【００７９】
上述で、被検査体表面と反射源の間の超音波の片道伝播時間△ｔ_ijを計算する数２は、超音波送信時間Ｔ₀から被検査体表面までの伝播時間Ｔ_sを考慮している。この伝播時間Ｔ_sは探触子と被検査体間に介在する水などの媒質を伝播する時間である。従って、探触子を直接、被検査体に接触する場合は、Ｔ_s＝０となる。
【００８０】
次に、実施例１による他の適用例を説明する。この適用例は被検体中に複数個の反射源があるケースで、各反射源からの複数のエコーが受信される。この場合、複数のエコーからホログラムを作成、再生し、複数個の反射源をそれぞれ正しい位置に再生して表示する。
【００８１】
図２１は、本適用例による超音波ホログラフィ法を示す説明図で、図１の（ａ）〜（ｆ）に相応する。図２１（ａ）のように、被検査体１０２に複数の反射源４０３、４０４がある場合、（ｂ）のように反射源Ａからのエコー４０５と反射源Ｂからのエコー４０６によるＡスコープ表示データが得られる。上述のように、個々の反射源からは縦波と横波によるエコーが生じ、実際には３個以上のエコーとなることも多いので、受信エコーの数と反射源の数は１対１に対応しない。以下では説明を簡単にするために、１つの反射源から１つの音速のみによるエコーが得られるものとする。
【００８２】
送受信位置（ｘ_i,ｙ_j）における反射源Ａ、Ｂからのエコーを１ラインについて集積し、（ｃ）のＸＺ断面についてのＢスコープ図形が作成される。Ｂスコープによるインジケーション４０７、４０８は、（ｄ）のように屈折角θだけ回転してホログラム再生領域４０９、４１０を求める。
【００８３】
次に、数５を用いて、処理開始位置１２１から処理終了位置１２２で定められる探傷領域に、（ｅ）のようにホログラム４１３及び４１４を作成する。ここでは、超音波信号の受信時間を、例えばcos関数のような振動関数の引数とすることで、参照波と受信波の干渉項を数値的に計算し、ホログラムを作成する。数値的な干渉に用いる参照波の波数ｋの値として、ｋ＝ｎ×２πｆ／Ｖを用いる。用いるＶの値は所定モード、例えば縦波音速である。このように、本実施例のホログラム作成は、探傷により得られた複数のエコーが、複数の反射源によるか、単一の反射源によるかを考慮することなくホログラムを作成する。
【００８４】
次に、数１０によりホログラムの再生像を作成する。再生計算に用いる再生参照波の波数ｋの値は、ホログラム作成に用いる参照波に対して使用したものと同様の値である。所定モード、例えば縦波音速によるホログラム再生の結果、２つの再生像が得られれば、それらは異なる反射源Ａ，Ｂに対応している。つまり、縦波音速によらないホログラムは像再生の過程で消去される。さらに、横波音速を用いて、上記処理を繰り返せば同様の結果が得られるので、複数の反射源の位置を縦波と横波の両方から求め、信頼性の高い探傷を行うことが可能になる。
【００８５】
〔実施例２〕
次に、本発明の実施例２を説明する。実施例１との相違は、縦波から横波へのモード変換によるエコーが受信されるケースを考慮し、超音波ホログラフィ法に用いる音速Ｖとして、縦波音速、横波音速の外に、縦波と横波の平均音速を用いる点にある。
【００８６】
図２２に、実施例２の適用ケースをイメージで示す。被検査体の内部に反射源３０１を有しており、送受信位置の探触子１０１から縦波往復径路３０２によるエコーと、縦波から横波へモード変換した径路３０３によるエコーと、横波往復径路３０４によるエコーが受信されるケースである。図２３に、パラメータ入力画面を示す。ここでは、SUS304を被検査体とし、使用する音速として縦波音速、横波音速及び平均音速を用いる。平均音速は調和平均値Ｖ_ave で数１１による。
【００８７】
【数１１】

【００８８】
図２４に、Ａスコープ図形を示す。図９の場合に比べ、１番目の縦波エコーと３番目の横波エコーの間に、縦波からモード変換した横波による２番目のエコーが表われている。図２５はＢスコープ図形で、１番目、２番目及び３番目のエコーを、それぞれ１ライン分集積した３つの図形３０５、３０６、３０７が得られる。
【００８９】
図２６に、ホログラム再生領域を示す。ここでは、Ｂスコープ図形の図形３０５〜３０７の各点を屈折角θだけ回転させ、再生領域３０８〜３１０を求める。同図では、図形３０６に対する再生領域３０９のみを示している。
【００９０】
図２７はホログラム作成方法を示す。送受信位置（ｘ_i,ｙ_j）における片道伝播距離Ｚ_ijから数５により演算し、処理開始位置から処理終了位置で定められる探傷領域に、ホログラム３１０１、３１０２及び３１０３を作成する。このとき、数値的な干渉に用いる参照波の波数ｋ＝ｎ×２πｆ／Ｖを用いる。この音速Ｖとして、縦波音速、横波音速、及び平均音速の３種を用いる。数１０によるホログラムの像再生も、縦波音速、横波音速、及び平均音速の３種を用いる。その計算結果を映像として表示する方法は、実施例１の場合と同様である。
【００９１】
実施例２によれば、被検体中の縦波、横波、及び縦波と横波の平均音速の３種を用いてホログラムを作成し、再生するので、被検査体内部で縦波と横波のモード変換が生じている場合でも、本来反射源のない位置に現れる虚像のインジケーションを自動的に消去できる。
【００９２】
また、被検査体に複数の反射源が存在し、かつ、被検体への超音波入射時のモード変換（例えば、縦波から横波）、反射源からの反射時のモード変換（縦波から横波、横波から縦波）が発生する場合にも、本実施例のように縦波、横波、及び縦波と横波の平均音速の３種を用いてホログラムを作成し、再生すれば、１つの反射源に対する各波音速の演算結果が同一ないしは近似位置を示すので、実際の反射源を正確に表示でき、信頼性の高い探傷が可能になる。
【００９３】
【発明の効果】
本発明によれば、Ｂスコープ表示データからホログラムを作成し再生する場合に、演算に用いる超音波音速を縦波または横波のモードに特定し、音速の一致する伝播経路のホログラムのみが像再生されるので、超音波のモード変換によって実在とは異なる位置に表われる虚像を消去でき、被検査体内部の傷の数と位置が正確に表示できる。
【００９４】
また、演算に用いる超音波音速を縦波及び横波、さらには縦波と横波の平均音速として、各音速に対応した像再生が行われる場合、それらを重畳表示することで１つの反射源に対する複数の演算結果を反映することができ、より高信頼な探傷結果の図形表示を実現できる。
【００９５】
また、Ｂスコープ表示データから再生領域を求めるに際し、超音波の屈折角に応じて各点を回転するので、超音波の広がりの影響を低減でき、反射源のより正確な位置と形状を再現できる。
【図面の簡単な説明】
【図１】本発明の超音波ホログラフィ法の処理イメージを示す説明図。
【図２】本発明の一実施例による超音波探傷システムの構成を示すブロック図。
【図３】一実施例による超音波探傷システムのハード構成図。
【図４】実施例１における音速データの入力画面図。
【図５】一実施例による超音波探傷システムの概略の処理手順を示すフロー図。
【図６】本発明の超音波ホログラフィ法による処理の一実施例を示すフロー図。
【図７】初期パラメータの一例を示したデータフォーマット図。
【図８】探傷データの一例を示したデータフォーマット図。
【図９】探傷結果として得られるＡスコープ図形の説明図。
【図１０】Ｂスコープ図形データの一例を示したデータフォーマット図。
【図１１】ホログラム作成の一例を示したデータフォーマット図。
【図１２】探傷結果として得られるＢスコープ図形の説明図。
【図１３】ホログラムの再生領域を示す説明図。
【図１４】ホログラムの作成を示す説明図。
【図１５】参照波の波数の影響をイメージで示す概念図。
【図１６】実施例１のホログラフィ演算に使用する音速選択のメニュー画面図。
【図１７】ホログラム再生計算の結果から３次元画像データを作成する処理のフロー図。
【図１８】スレッシュホールドレベルの説明図。
【図１９】ＶＲＭＬ形式による３次元映像データの一例を示した説明図。
【図２０】ＶＲＭＬブラウザによる３次元映像の模式図。
【図２１】実施例１の他の適用例での処理イメージを示す説明図。
【図２２】本発明の実施例２による適用例の説明図。
【図２３】実施例２における音速データの入力画面図。
【図２４】実施例２の探傷結果として得られるＡスコープ図形の説明図。
【図２５】実施例２のＢスコープ図形の説明図。
【図２６】実施例２のホログラム再生領域の説明図。
【図２７】実施例２のホログラム作成の説明図。
【符号の説明】
１０…計算機、１１…ディスプレイ装置、１２…インターフェース装置、１０１…超音波探触子、１０２…被検査体、１０３…反射源、１０４…反射径路、１０５…反射径路、１０６…送信パルス、１０７…表面からのエコー、１０８…反射源からのエコー（縦波）、１０９…反射源からのエコー（横波）、１１０…底面からのエコー、１１１…表面からのエコー、１１２…底面からのエコー、１１３…探傷開始位置、１１４…探傷終了位置、１１５…図形（縦波）、１１６…図形（横波）、１１７……回転後データ（縦波）、１１８……回転後データ（横波）、１２１…処理開始位置、１２２…処理終了位置、１２３…片道伝播距離、１２４…再生領域、１２５…片道伝播距離、１２６…再生領域、１２７…ホログラム、１２８…ホログラム、１２９…再生像（縦波による縦波再生像）、１３０…再生像（横波による横波再生像）、１３１…再生像（縦波による横波再生像）、２００…探傷図形表示処理機構、２０１…画像表示装置、２０２…画像表示データ演算装置、２０３…画像データメモリ、２０４…制御装置、２０５…ピーク検出処理演算部、２０６…データ記憶部、２０６１…音速データ記憶部、２０７…探傷データメモリ、２０８…Ａ／Ｄ変換器、２０９…受信器、１１０…探触子移動機構、１２０…超音波探傷器。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a display technique for ultrasonic flaw detection results, and more particularly, to a display method using an ultrasonic holography method and an ultrasonic flaw detection apparatus.
[0002]
[Prior art]
Conventionally, the A scope method (A scan graphic), the B scope method (B scan graphic), and the C scope method (C scan graphic) are used for displaying ultrasonic flaw detection results. In the B-scope method, the A-scope figure is intensity-modulated and represented as a line, the position on the object to be inspected and the sound wave propagation time are displayed in rectangular coordinates (X and Z axes), and the flaw detection result is expressed as a cross-sectional view of the object can do. In the C scope method, the flaw detection result is expressed in the form of a plan view (X, Y axes) viewed from above the object to be inspected. The flaw detection results displayed by the B scope and the C scope can be displayed only in two dimensions by projecting the flaw detection results of the inspected object, which is originally a three dimensional shape, onto a certain plane.
[0003]
In order to realize the three-dimensional display of the flaw detection result, it is necessary to perform a flaw detection method and a display method that pay attention to not only the intensity of the received ultrasonic wave but also the phase information of the ultrasonic wave. An applied ultrasonic holography method is known.
[0004]
The principle of the optical holography method is that light with a uniform phase such as laser light is incident on an object, phase information of light scattered from the object is recorded on the film as an interference pattern of incident light and scattered light, and then By irradiating the film with light, the phase information of the scattered light is reproduced again. In general, refer to the recording of interference pattern of scattered light from an object and incident wave (three-dimensional geometric information of the object) on a hologram, light that interferes with the reflected wave from the object (incident wave in this example) Calling a wave, reproducing the interference information by applying light to the hologram is called reproduction of the hologram, and light applied to the hologram for reproducing the hologram is called a reproduction reference wave.
[0005]
In the early ultrasonic holography method, similarly to optical holography, a received wave and a reference wave are made to interfere with each other to create a hologram. By displaying the flaw detection result using this method, a three-dimensional image can be obtained. However, since an ultrasonic wave (sin wave) having a pulse width of several μs to several tens of μs is used to cause interference with the reference wave, an oscillator and a power amplifier for transmitting the sin wave are necessary, and the apparatus is Increase in size. In addition, since the transmission wave spread in time is used, the time resolution of the received wave is reduced compared to the case of using a normal sharp pulse wave, making it difficult to distinguish waves from different reflection positions, and measuring flaw detection results. Accuracy is reduced.
[0006]
As a method for solving the problems of the initial ultrasonic holography method, there is a digital ultrasonic holography flaw detection method (Japanese Patent Laid-Open No. 54-8584). In the digital ultrasonic holography flaw detection method, a spike-like pulse echo is used for a transmission wave, and a hologram is created by coincidence of a reception wave and a clock pulse instead of interference with a reference wave. For this reason, it is possible to reduce the size of the apparatus and improve the measurement accuracy of the flaw detection result by increasing the time resolution of the received wave.
[0007]
[Problems to be solved by the invention]
In the conventional technique for displaying ultrasonic flaw detection results, there is a problem of false recognition of flaw detection results caused by ultrasonic mode conversion, in addition to the two-dimensional and three-dimensional representation formats described above. For example, when a longitudinal wave ultrasonic wave is incident on steel from the water, the ultrasonic wave transmitted to the object to be inspected propagates not only the longitudinal wave but also the transverse wave ultrasonic wave that has undergone mode conversion in the steel. If this mode conversion is used, a position that cannot be reached by a longitudinal wave can be inspected by a transverse wave. However, even if the number of reflection sources (scratches, etc.) inside the object to be inspected is one, both the echo by the ultrasonic mode used for transmission and the echo generated by the mode conversion are received by the probe, Indications (figures) appear as if there are multiple reflection sources.
[0008]
This problem cannot be solved even by the digital ultrasonic holography flaw detection method described above. In other words, when multiple echoes are received from the reflection source, the echo in the mode (for example, longitudinal wave) used for flaw detection and the echo in the mode (for example, transverse wave) generated by mode conversion are identified from among those echoes. Can not. Therefore, the position and the number of the reflection sources based on the flaw detection result cannot be correctly displayed, and an error is easily caused in the diagnosis of the ultrasonic flaw detection result, and the inspector is required to have a high degree of skill.
[0009]
The object of the present invention is to overcome the problems of the conventional ultrasonic holography method described above, identify the actual reflection source (flaw) from the ultrasonic flaw detection results in a plurality of modes, and perform the correct flaw detection in accordance with the actual flaw detection. An object of the present invention is to provide a highly reliable image display method for ultrasonic flaw detection results and an ultrasonic flaw detection apparatus that display figures in two dimensions or three dimensions.
[0010]
[Means for Solving the Problems]
The present invention that achieves the above object transmits ultrasonic waves of a predetermined mode to an object to be inspected, receives echoes reflected from a reflection source due to internal scratches, etc., and determines the position of the reflection source from the reception time of the echoes. In the method for displaying the ultrasonic flaw detection result by displaying the reflection source figure, the flaw detection data including the reception time of the echo is collected for each transmission / reception position by repeating transmission / reception while scanning the probe, and flaw detection by one line scanning B-scope graphic data is created from the data, the B-scope graphic is used as a reproduction area, a hologram is created by numerically interfering with the flaw detection data with a reference wave having a wavenumber k, and a designated mode is set in the reproduction area. Hologram reproduction is performed using the speed of sound of ultrasonic waves, and a reproduction image is displayed on the screen. The screen display is two-dimensional or three-dimensional. The flaw detection data may include the signal strength of the echo.
[0011]
According to this, only when the actual sound speed of each echo coincides with the sound speed of hologram reproduction by the ultrasonic wave of the designated mode, the hologram reproduction image is formed with the phase of the hologram reference wave aligned, and the sound speed does not match. In this case, since a reproduced image cannot be obtained, the indication of the reflection source that originally appears at the position where there is no reflection source is automatically deleted, and the image of the reflection source that actually exists is displayed at the correct position.
[0012]
The ultrasonic waves in the predetermined mode are usually longitudinal waves, and transverse waves obtained by mode conversion of incident longitudinal waves are also used. On the other hand, the ultrasonic velocity of the designated mode is set to a longitudinal wave and / or a transverse wave value, or the ultrasonic velocity of the designated mode is set to an average value of the longitudinal wave and the transverse wave in addition to the longitudinal wave and the transverse wave. In addition, reproduced images in a plurality of designated modes are displayed in a superimposed manner. In this case, the reproduced images from the same reflection source are coincident or close to each other.
[0013]
The reproduction area is obtained by rotating each point of the B scope graphic data by the refraction angle θ of the ultrasonic wave. Thereby, the influence of the spread of ultrasonic waves is reduced.
[0014]
Further, a cos function is used for the reference wave, its phase is determined from the wave number k and the propagation distance of the echo, and the wave number k determined as the reciprocal of the propagation speed of the ultrasonic wave is variably set by an integral multiple. It is characterized by that. According to this, since the cos function of the vibration wave is used as the reference wave, it is easy to obtain a numerical interference effect with the reflected wave data. Also, the wave number k can be varied by multiplying by n, and the reproduced image can be adjusted to an appropriate resolution.
[0015]
An apparatus for realizing the above-described method of the present invention includes an ultrasonic probe that transmits ultrasonic waves in a predetermined mode to an object to be inspected and receives echoes reflected from a reflection source due to internal flaws, and the like. A probe moving mechanism that scans the child according to a predetermined scanning path on the object to be inspected, and a flaw detection graphic display processing mechanism that creates the graphic data of the reflection source by determining the position of the reflection source from the reception time of the echo, An ultrasonic flaw detection apparatus comprising a display device for displaying the created graphic data on the screen, wherein the flaw detection graphic display processing mechanism is configured to transmit the echo for each transmission / reception position from the probe scanned by the probe moving mechanism. Flaw detection data including the reception time of the image, B-scope graphic data is created from the flaw detection data of one-line scanning, the B-scope graphic is used as a reproduction area, and an ultrasonic holography method using the sound velocity of ultrasonic waves in a designated mode Performs reproduction of the hologram image caused, characterized by the screen display of the reproduced image in two or three dimensions.
[0016]
The display device includes an input screen for arbitrarily selecting the sound velocity of the ultrasonic wave in the inspection mode in the designated mode, and can arbitrarily select one or a plurality of reproduced images to be displayed. . Further, the flaw detection graphic display processing mechanism is provided with means for variably setting the wave number k of the reference wave by an integer (n) so that the resolution of the reproduced image can be arbitrarily adjusted.
[0017]
In addition, when a plurality of ultrasonic sound velocities in the designated mode are designated, when the reproduced images at the respective sound velocities are coincident or close to each other, the display device displays the matched reproduced images in colors different from the reproduced images that do not coincide with each other. Use to display. Alternatively, the reproduced image is displayed only when the reproduced images at the respective sound velocities match or approach each other. As a result, the indication of the reflection source that originally appears at the position where there is no reflection source and the indication of the reflection source that actually appears at the position where the reflection source exists can be clearly distinguished, and the image of the reflection source can be displayed with high positional accuracy. it can.
[0018]
With reference to FIG. 1, an outline procedure of an image display method for ultrasonic flaw detection results according to the present invention will be described. (A) is a schematic diagram of flaw detection, in which an ultrasonic wave is obliquely incident from the probe 101 to the inspection object 102 and the echo signals of the longitudinal wave 104 and the transverse wave 105 received from the reflection source 3 are received by the probe 101. To do. (B) is an A scope figure of the flaw detection result. The horizontal axis is time t, the vertical axis is amplitude A which is signal intensity, the ultrasonic transmission pulse 106, the surface echo 107 of the object 102, the bottom echo 110 and the reflection. A longitudinal wave echo 108 and a transverse wave echo 109 from the source 103 are shown. When there is a transverse wave echo that has been mode-converted from a longitudinal wave by the reflection source 103, it is located between the echo 108 and the echo 109.
[0019]
(C) is a B scope figure, the horizontal axis X is the scanning position of the probe 101, the vertical axis Z is the ultrasonic propagation distance from the probe 101 to the reflection source 103, and the X axis is two-dimensional for one line. Show. Sources of longitudinal and transverse echoes are shown as indications 115 and 116, respectively. (D) is a calculation result of the hologram reproduction area, and the indications 115 and 116 by the B scope are rotated by the ultrasonic refraction angle θ for each point to become reproduction areas 117 and 118.
[0020]
(E) shows the creation of a hologram. A reference wave (cos function) is numerically interfered with the echo signal data at each point, and a coincidence or non-coincidence is recorded to produce a hologram. That is, the one-way propagation distance (Z _ij ), Each transmission / reception position (x) between the flaw detection areas determined from the processing start position 121 to the processing end position 122 _i , Y _j ), The hologram H (x _i , y _j ) Are integrated for one line (one dimension), holograms 127 and 128 are obtained.
[0021]
(F) is the creation and display of a reconstructed image, and the image is reconstructed from the hologram H to the reconstructed area at every sound speed in the designated mode. For example, a reproduction image 129 with a longitudinal mode and a reproduction image 130 with a transverse wave are displayed. On the other hand, the echo reproduction image 131 by the reflected wave mode-converted from the longitudinal wave to the transverse wave by the reflection source 103 is not selected as the designated mode and is erased.
[0022]
In this way, the virtual image that does not match the sound velocity of the actual echo due to ultrasonic mode conversion or the like is erased, and the reproduced image by the longitudinal wave and / or the transverse wave echo that has actually acted on the flaw detection can be reproduced at the correct position, with the same reflection. Since the sources are displayed at the same or approximate positions, misidentification of the number and position of the reflection sources can be prevented.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
A plurality of embodiments of the present invention will be described in detail with reference to the drawings. Below, the example of the figure display correct | amended by the ultrasonic holography method of this invention for B scope figure data is demonstrated. The B-scope graphic displays the position on the inspection object and the one-way sound wave propagation distance in rectangular coordinates.
[0024]
[Example 1]
FIG. 2 is a functional block diagram of the ultrasonic flaw detection system according to the first embodiment. This system is roughly divided into a flaw detection mechanism having a probe 101, a probe moving mechanism 110, and an ultrasonic flaw detector 120, and a flaw detection graphic display processing mechanism 200 that performs graphic display by an ultrasonic holography method. The flaw detection graphic display processing mechanism 200 includes an image display device 201, an image display data calculation device 202, a storage medium 203, a control device 204, a peak detection processing calculation unit 205, a data storage unit 206, a flaw detection data memory 207, and an A / D converter 208. And a receiver 209.
[0025]
The ultrasonic probe 101 is scanned along the scanning path on the XY plane of the pair to be inspected 102 by the probe moving mechanism 110. The ultrasonic flaw detector 120 generates a ultrasonic wave by transmitting a pulse signal having an appropriate frequency to the material of the inspection object 102 or the size of the reflection source 103 to be imaged to excite the probe 101. . For example, when the inspected object 102 is stainless steel and the reflection source 103 to be imaged is about several millimeters, a frequency of 5 MHz is used as a transmission signal.
[0026]
For example, a stepping motor is used as the probe moving mechanism 110. The control device 204 controls the probe moving mechanism 110 in accordance with the flaw detection conditions input from the input device 208 to the data storage unit 206, for example, flaw detection start position, flaw detection end position, probe movement pitch, scanning path, and the like. To do. Further, the probe position is stored in the data storage unit 206 while moving the probe 101.
[0027]
The ultrasonic wave from the probe 101 is incident on the object 102 to be inspected, and the echo signal propagated and reflected (or transmitted) through the inside is received again by the probe 101 and converted into an electric signal. The signal received by the probe 101 is converted into a digital signal by the A / D converter 208 via the receiver 209, and the transmission / reception time, peak value, etc. are stored in the flaw detection data memory 207.
[0028]
The A / D converter 208 appropriately selects the sampling frequency and the number of sampling points with respect to the frequency of the ultrasonic wave and the propagation speed of sound in the subject. For example, when an ultrasonic wave of 5 MHz is used and a longitudinal wave ultrasonic wave is incident on stainless steel for inspection, the sampling frequency is set to 25 M to 100 MHz, and the number of sampling points is set to 1024 to 4096. The digitized ultrasonic signal is temporarily stored in the flaw detection data memory 207, and the peak detection processing calculation unit 205 has a threshold value in a predetermined time region (a time difference region between the surface and the bottom surface of the inspection object 102). The peak of the received waveform is detected, the reception time is obtained for each waveform, and is sent to the image display data arithmetic unit 202.
[0029]
Parameters used for flaw detection conditions and image display processing are set in the data storage unit 206 by the input device 208. The parameters include sound speed data 2061 essential for characteristic processing of image display processing described later, and a multiple n2062 of wave number k for adjusting the resolution of the reproduced image. The data storage unit 206 also includes a probe position (x, y) sent from the control device 204 and an ultrasonic transmission time T. ₀ Is stored and used in the image display data arithmetic unit 202.
[0030]
The image display data calculation device 202 performs image data calculation processing based on the collected flaw detection data, and displays the image data for one-line scanning flaw detection on the B scope. Then, while the probe 101 continues scanning in the flaw detection area, the calculation processing of the collected flaw detection data and the flaw detection result display are repeated. After the scanning of one line or the entire flaw detection area is completed, image data by the ultrasonic holography method of the present invention is created from the flaw detection result in the scanning path, and the flaw detection result is displayed by a two-dimensional or three-dimensional figure.
[0031]
FIG. 3 is an external view showing a hardware configuration of the ultrasonic flaw detection system. The flaw detection graphic display processing mechanism 200 includes a computer 10, a display device 11, and an interface device 13 connected to the computer main body by a bus. The interface device 13 passes the ultrasonic signal digitally converted by the A / D converter 208 to the calculation unit of the calculation device 202. Further, the probe moving mechanism 110 is controlled by the control device 204, and the position data of the probe 101 is recorded and transferred to the data storage unit 206.
[0032]
As an input device 210 for the flaw detection graphic display processing mechanism 200, a keyboard or a pointing device is used. FIG. 4 shows an example of the parameter input screen. On this screen, the material and sound speed of the object to be inspected and the medium are set. For example, if the object to be inspected is SUS304, its longitudinal wave velocity V _L = 6000m / s, shear wave velocity V _T = 3000 m / s. When the medium is water, the longitudinal wave velocity V _L = 1500 m / s.
[0033]
FIG. 5 shows a schematic flow of online processing of the ultrasonic flaw detection system of the present embodiment. First, initial parameters are read (S10). The flaw detection graphic display processing mechanism 200 takes in the initial parameters from the input device 208 and stores them in the data storage unit 206. Also, parameters including sound speed used by the image display data calculation device 202 for processing are read from the data storage unit 206. Then, the probe 101 is set at the flaw detection start position, flaw detection is started (S20), and on-line processing of the image display data calculation device 202 is executed along with this.
[0034]
FIG. 7 shows data relating to the initial setting of ultrasonic flaw detection. The frequency f of the ultrasonic wave used for flaw detection, the longitudinal and transverse wave velocities V of the inspected object 102, the refraction angle θ of the ultrasonic wave, the A / D converter 208 Sampling frequency f _sample , X-axis and Y-axis probe scanning pitches δx, δy, XY plane flaw detection start position x ₀ , Y ₀ , End position x _e , Y _e Etc.
[0035]
The image display data arithmetic unit 202 detects flaw detection data including the probe position issued by the control unit 204, in this example, the transmission / reception position, the transmission time of the ultrasonic transmission pulse, and the reception time of the ultrasonic reception data that has undergone the peak detection process. The data is collected (S30), and the calculation process (1) is performed on the sampling points and one line of image data (S40). Here, the B scope graphic data is created and stored in the image data memory 203, and the B scope is displayed on the screen display device 201 (S50). This processing is repeated until the end of flaw detection is notified from the control device 204 (S60), that is, until the probe 101 reaches the flaw detection end position.
[0036]
FIG. 8 shows data related to the flaw detection result, and includes probe position signals Xi and Yi, and transmission time T. ₀ The reception time T of the peak waveform detected by the peak detection processing calculation unit 205 among the received waveforms. _ij , m and received signal strength I _ij , m.
[0037]
FIG. 9 shows a detection waveform of the peak detection processing calculation unit. The peak detection processing calculation unit 205 detects a peak waveform in the time domain from the surface echo to the bottom echo when the signal intensity is greater than or equal to the threshold value. In the example shown in the figure, received signals from the longitudinal wave and the transverse wave from the reflection source 103 are detected. The reception time of the longitudinal wave peak is T _ij 1 、 Reception time of shear wave peak is T _ij 2.
[0038]
When the flaw detection is completed, the image display data calculation device 202 takes out the B scope graphic data from the image data memory 203, performs the calculation process (2) by the ultrasonic holography method (S70), and performs the two-dimensional reflection source graphic by the holographic reproduction image. Alternatively, three-dimensional display is performed (S80).
[0039]
FIG. 6 shows a detailed flow of image data calculation processing. First, as the image data calculation (1) in S40, the propagation speed of the object to be inspected is read (S401). In this embodiment, the longitudinal wave velocity V _L And shear wave velocity V _T These are two. Next, B-scope graphic data is created from the flaw detection data with the peak detected and stored in the graphic data memory 203 (S402).
[0040]
FIG. 10 shows an example of B scope graphic data. An index (i, j, m) indicating the number of data points (i, j) in A / D conversion, and the number (m) of echoes in peak detection, a signal transmission / reception position (xi, yi), Transmission time (T ₀ ) And the reception time of the peak detected echo (T _ij m). The probe 101 of this example is in direct contact with the inspected object 102 without using a medium (water).
[0041]
A method of creating a B scope graphic will be described with reference to FIG. Position signal (X of the probe 101) from the probe moving mechanism 110 _ij , Y _ij ) And the X and Y axis movement pitches (δx, δy) _i , Y _j ) Is calculated by Equation 1 and the transmission time T ₀ And reception time T _ij , 1, T _ij , 2 and A / D converter 208 sampling frequency (f _sample ) To send / receive position (x _i , Y _j ) One-way propagation time Δt from the probe 101 to the reflection source 103 _ij , 1, △ t _ij , 2 is calculated by Equation 2.
[0042]
[Expression 1]

[0043]
[Expression 2]

[0044]
Next, one-way propagation time Δt _ij , m and the propagation velocity V in the test object 102, the transmission / reception position (x _i , Y _j ) One-way propagation distance Z from the surface to the reflection source 103 _ij , m is calculated by Equation 3 to obtain one point data of the B scope graphic. The m-th echo is the order of echoes existing in the time domain selected by the peak detection processing calculation unit 205. The number of echoes received depends on the number of reflection sources and the refraction angle of the ultrasonic wave.
[0045]
[Equation 3]

[0046]
Here, the sound velocity V used for flaw detection is the longitudinal wave velocity V. _L And shear wave velocity V _T And This point data is converted into one line (y _j X _i For i = scanning from the start point to the end point), the longitudinal wave velocity V _L Figure 115 which is the calculation result using, and shear wave velocity V _T A graphic 116 is displayed.
[0047]
Next, the processing (S70) of the image data calculation (2) includes the calculation of the hologram reproduction area (S701), the hologram creation (S702), the hologram reproduction calculation (S703), and the creation of image display data for each sound speed (S704). It explains in order. In this embodiment, first, longitudinal wave velocity V _L Next, the transverse wave velocity V _T The arithmetic processing is performed with.
[0048]
FIG. 13 is an explanatory diagram for creating a hologram reproduction area. The B-scope graphic data obtained by Equation 3 is expressed as a set of points (graphics 115 and 116) in XZ coordinates. With respect to each point, rotation conversion is performed at an angle equal to the refraction angle θ of the ultrasonic wave with the point projected on the X axis as the center.
[0049]
Each point of the B-scope figures 115 and 116 is rotated by the refraction angle θ of the ultrasonic wave, and the hologram reproduction regions 117 and 1118 in the XZ cross section are obtained by Equation 4. Further, the value y of the scanning axis Y _j And a hologram reproduction area in the XZ section is created for each y. The hologram reproduction area data is temporarily stored in the graphic data memory 203.
[0050]
[Expression 4]

[0051]
According to this, instead of rotating the entire B scope graphic at the same time, each point is connected to the transmission / reception position (x _i , Y _j ) Are rotated by θ from the line connecting them), the rotated figures 117 and 118 are smaller in area occupied by the figures 115 and 116 before the rotation, respectively, and the figure (indication) error relative to the actual reflection source is reduced. However, it can be reduced by this rotation process.
[0052]
FIG. 14 is an explanatory diagram for creating a hologram. In this embodiment, an ultrasonic holography method using a pulse wave is employed. The conventional method uses a pulse wave as a transmission wave, and records a coincidence or mismatch between a reception time of a received pulse wave and a clock pulse corresponding to a reference wave, thereby creating a hologram. On the other hand, in this embodiment, a clock pulse is not used as an equivalent to the reference wave, but a vibration function such as a cos function is used, and the reception time of the received pulse wave is used as an argument of the cos function. A hologram is created by giving numerically the effect of causing the wave and the received wave to interfere.
[0053]
The hologram H according to the present embodiment is created by the calculation of Equation 5. That is, the one-way propagation distance (Z _ij ), Each transmission / reception position (x) between the flaw detection areas determined from the processing start position 121 to the processing end position 122 _i , Y _j ), The hologram H (x _i , y _j ) Is created by Equation 5.
[0054]
[Equation 5]

[0055]
In Equation 5, k = n × 2πf / V is used as the wave number k of the reference wave (cos function) used for numerical interference. However, V is the ultrasonic sound velocity of the mode which propagates in steel, f is the frequency of the ultrasonic wave used for a flaw detection, and n is a natural number. When n = 1, the frequency of the transmitted ultrasonic wave is the same as the calculated reference wave frequency, and k = 2π / λ. By increasing the value of n, it is possible to numerically calculate interference with a reference wave having a higher frequency.
[0056]
Here, the derivation process of Equation 5 will be described using Equation 6 to Equation 9. When an ultrasonic wave having an angular frequency ω (= 2π / f) shown in Equation 6 is transmitted to the inspection object 102, an echo shown in Equation 7 is received by the reflection source 103. Here, r is a propagation distance between receptions. If a reference wave (cos wave) having an angular frequency ω (= 2π / f) is numerically given in order to extract phase information of the received echo, the intensity distribution of the interference wave can be calculated by Equation 9. In Equation 9, the interference term (cos function part) having phase information corresponds to the function part of Equation 5, and this interference term is calculated to form a hologram.
[0057]
[Formula 6]

[0058]
[Expression 7]

[0059]
[Equation 8]

[0060]
[Equation 9]

[0061]
In Equation 5, when the value of n that changes the reference wave number k is increased, interference with a reference wave having a higher frequency can be calculated numerically, and a hologram having a spatial resolution higher than the wavelength λ of the transmitted ultrasonic wave H (x _i , y _j ) Can be created. N for resolution adjustment is input from the input device 210 to the wave number multiple setting unit 2602 of the data storage unit 206 by the user, and is referred to by the image display data calculation device 202.
[0062]
FIG. 15 shows an image of the influence of the wave number k in hologram reproduction. A hologram with two pinholes and a reproduced image thereof, (a) shows a case where the wave number k is small, and (b) shows a case where the wave number k is large. When the wave number k is large, the spatial resolution is high, and a sharp reproduced image that matches the presence of the pinhole is obtained.
[0063]
Hologram H (x _i , y _j ) Is the transmission / reception position x _i , y _j 1 point and 1 point value. By accumulating the values of these points, the one-dimensional holograms 127 and 128 are reproduced.
[0064]
There are two hologram reproduction methods, and the first method is a simple reproduction method. That is, the image of the one-dimensional holograms 127 and 128 is reproduced on the hologram reproduction regions 117 and 118 in the XZ section every time one line scanning flaw detection is performed. Image reproduction is performed by adding (integrating) a plane wave with a weight of the hologram from all points on the hologram to one point on the reproduction area. This operation is performed for all points in the reproduction area. In the reproduction region, in the portion close to the reflection source, the phases of the plane waves from the hologram are aligned, the integral value is increased, and a reproduction image is formed.
[0065]
When this reproduced image is displayed two-dimensionally, the screen shown in FIG. 1F is obtained. Furthermore, if a three-dimensional reproduction image G is created by superimposing the reproduction images in the XZ section in the Y-axis direction, three-dimensional display is possible. According to this method, the calculation time and memory required for image reproduction can be greatly reduced, so that it is adopted as a simple method for displaying flaw detection results.
[0066]
The second reproduction method is a more accurate reproduction method. The hologram reproduction areas (surfaces) 117 and 118 and the holograms 127 and 128 in the XZ section are stored in the data storage unit 206 until the flaw detection is completed, and the reproduction area is two-dimensionally reconstructed after the flaw detection is completed. A two-dimensional hologram assigned to the flaw detection area is reproduced.
[0067]
Formula 10 for reproducing the hologram by the second method is shown in equation (10). As in the case of the first reproduction method, a spherical wave (function of e) weighted by the hologram H is added (integrated) from all points on the hologram to one point on the reproduction region. This operation is performed for all points in the reproduction area. However, the integration region is two-dimensional. In the reproduction area, in the portion close to the reflection source, the phases of the plane waves from the hologram are aligned, the integral value is increased, and the reproduction image G is formed.
[0068]
[Expression 10]

[0069]
In order to perform the calculation of Formula 10 on a computer, a calculation method such as discrete Fourierization and numerical integration, or transformation of a formula and Fast Fourier Transform is used. Further, as the value of the wave number k of the reproduction reference wave used for the hologram reproduction calculation, the same value as the wave number k used for the reference wave used for hologram creation is used. By setting k = n × 2πf / V and increasing the value of n, a hologram due to interference with a reference wave having a higher frequency can be numerically reproduced and calculated. This method differs from the first reproduction method in that the reproduction process is performed two-dimensionally. Therefore, the required time and memory are increased, but a reproduced image with higher accuracy can be obtained.
[0070]
Longitudinal wave velocity V _L As a result of the calculation of the hologram reproduction using, the reproduction images 130 and 131 by the transverse wave echo incident on the reflection source 103 and reflected by the transverse wave or incident by the longitudinal wave and reflected by the transverse wave are erased and On the other hand, only the reconstructed image 129 of the figure 115 incident by the longitudinal wave and reflected by the longitudinal wave is formed.
[0071]
On the other hand, shear wave velocity V _T As a result of the hologram reproduction using, the figure 115 by the longitudinal wave echo and the reproduction image by the transverse wave conversion at the time of reflection are erased, and only the reproduction image 130 for the figure 116 incident on the reflection source 103 by the transverse wave and reflected by the transverse wave is obtained. can get. This is because if the propagation sound speed used in the hologram creation process and the reproduction process is different, the phases of the reproduced waves are not aligned near the position where the actual reflection source exists, and cancel each other.
[0072]
In this embodiment, reproduced image data is temporarily stored in the image data memory 203 as display data (S704), and the two-dimensional or three-dimensional image is displayed by superimposing the longitudinal and transverse wave reproduced images. (S80). FIG. 11 shows the format of the stored reproduced image data.
[0073]
In the superimposed display of the two-dimensional image, as shown in FIG. 1 (f), the reproduced images 129 and 130 that are coincident or close to each other have the same color, are distinguished from other reproduced images, and are output to the image display device 201. Alternatively, it is output to the image display device 201 only when the reproduced images match. As a result, an image for the actual reflection source can be accurately displayed, and the number and position of flaws are not misidentified.
[0074]
FIG. 16 shows an example of a menu screen for selecting an image to be displayed as a reproduced image. In the input screen that allows the user to select a display image, display of image data obtained when processed as longitudinal wave sound speed, display of image data obtained when processed as shear wave sound speed, sound speed converted from longitudinal wave to shear wave mode It is possible to select display of image data obtained when processing is performed, and in the case of a plurality of inputs, the display is superimposed.
[0075]
Finally, a method for displaying the calculation result of the hologram reproduction image as a three-dimensional image will be described. FIG. 17 shows a flowchart of three-dimensional display. A threshold level Hmin is set in advance, and it is determined whether or not the threshold level Hmin is exceeded with respect to the reproduced image obtained by Equation 10 (S7031), and the coordinates exceeding are adopted as the reproduced image (S7032).
[0076]
FIG. 18 three-dimensionally shows the threshold level Hmin of the reproduced image H (xyz). A reproduced image of the shaded area exceeding Hmin is displayed. Thereby, since the interference effect when the cos wave is used as the reference wave is binarized with Hmin, the reproduced image 129 (130) can be correctly displayed at the position of the reflection source 103.
[0077]
In the three-dimensional display of the reproduced image, for example, the reproduced image data is described in the VRML format and displayed by the VRML browser. FIG. 19 shows an example of data in the VRML format, and FIG. 20 shows an example of a screen displayed on the VRML browser. On the XYZ coordinates, the reflection source 103 in the inspection object 102 is three-dimensionally displayed. It is also possible to obtain a projected image from an arbitrary direction by dragging the display figure with the instruction pointer 2201 from the input device 210 and rotating the display screen in the direction desired by the user.
[0078]
As described above, according to the first embodiment, since the hologram is created and reproduced using the longitudinal wave velocity and the transverse wave velocity, respectively, the indication of the hologram reproduction reference wave is used for the indication by the propagation velocity different from the sound velocity used for the reproduction calculation. The phases are not aligned and the hologram reproduction image is not formed. Therefore, the indication (virtual image) of the reflection source that appears at a position different from the original reflection source is erased, and the image (real image) of the reflection source can be displayed corresponding to the position where the actual reflection source is. Further, by displaying the reproduced images calculated by the longitudinal wave and the transverse wave in an overlapping manner, it is possible to confirm the existing reflection source with high reliability from the degree of the overlapping. Further, since the hologram reproduction area is obtained by correcting the rotation of the B scope data with the refraction angle, the influence of the spread of the ultrasonic wave can be reduced and the image of the reflection source can be displayed with high positional accuracy.
[0079]
As described above, the one-way propagation time Δt of the ultrasonic wave between the surface of the inspection object and the reflection source _ij Equation 2 for calculating the ultrasonic transmission time T ₀ Propagation time T from test object surface _s Is considered. This propagation time T _s Is the time for propagation through a medium such as water interposed between the probe and the object to be inspected. Therefore, when the probe is in direct contact with the object to be inspected, T _s = 0.
[0080]
Next, another application example according to the first embodiment will be described. In this application example, there are a plurality of reflection sources in the subject, and a plurality of echoes from each reflection source are received. In this case, a hologram is created and reproduced from a plurality of echoes, and the plurality of reflection sources are reproduced and displayed at the correct positions.
[0081]
FIG. 21 is an explanatory diagram showing the ultrasonic holography method according to this application example, and corresponds to (a) to (f) of FIG. When there are a plurality of reflection sources 403 and 404 on the inspected object 102 as shown in FIG. 21A, A scope display by echoes 405 from the reflection source A and echoes 406 from the reflection source B as shown in FIG. Data is obtained. As described above, longitudinal and transverse echoes are generated from individual reflection sources, and in reality, there are many cases where there are three or more echoes. Therefore, the number of reception echoes and the number of reflection sources correspond one-to-one. do not do. In the following, for simplicity of explanation, it is assumed that an echo based on only one sound velocity is obtained from one reflection source.
[0082]
Send / receive position (x _i , y _j Echoes from the reflection sources A and B in (1) are accumulated for one line, and a B scope graphic for the XZ cross section in (c) is created. The indications 407 and 408 by the B scope are rotated by the refraction angle θ as shown in FIG.
[0083]
Next, using Equation 5, holograms 413 and 414 are created as shown in (e) in the flaw detection area determined from the processing start position 121 to the processing end position 122. Here, by using the reception time of the ultrasonic signal as an argument of a vibration function such as a cos function, the interference term between the reference wave and the reception wave is numerically calculated to create a hologram. As a value of the wave number k of the reference wave used for numerical interference, k = n × 2πf / V is used. The value of V used is a predetermined mode, for example, longitudinal wave sound velocity. As described above, the hologram creation of this embodiment creates a hologram without considering whether a plurality of echoes obtained by flaw detection are caused by a plurality of reflection sources or a single reflection source.
[0084]
Next, a reproduced image of the hologram is created by Equation 10. The value of the wave number k of the reproduction reference wave used for the reproduction calculation is the same value as that used for the reference wave used for creating the hologram. If two reproduced images are obtained as a result of hologram reproduction in a predetermined mode, for example, longitudinal wave sound velocity, they correspond to different reflection sources A and B. That is, the hologram that does not depend on the longitudinal wave sound velocity is erased in the process of image reproduction. Furthermore, since the same result can be obtained by repeating the above-described processing using the shear wave velocity, it is possible to obtain the position of a plurality of reflection sources from both the longitudinal wave and the transverse wave and perform highly reliable flaw detection.
[0085]
[Example 2]
Next, a second embodiment of the present invention will be described. The difference from the first embodiment is that, in consideration of the case where an echo is received by mode conversion from a longitudinal wave to a transverse wave, as the sound velocity V used in the ultrasonic holography method, in addition to the longitudinal wave sound velocity and the transverse wave sound velocity, The average sound speed of the shear wave is used.
[0086]
In FIG. 22, the application case of Example 2 is shown with an image. A reflection source 301 is provided inside the object to be inspected, and echoes from the probe 101 at the transmission / reception position by the longitudinal wave reciprocating path 302, echoes by the path 303 mode-converted from the longitudinal wave to the transverse wave, and a transverse wave reciprocating path 304. This is a case where an echo is received. FIG. 23 shows a parameter input screen. Here, SUS304 is used as an object to be inspected, and longitudinal wave velocity, transverse wave velocity, and average velocity are used as sound velocity to be used. Average sound speed is harmonic mean V _ave In accordance with Equation 11.
[0087]
## EQU11 ##

[0088]
FIG. 24 shows an A scope graphic. Compared to the case of FIG. 9, a second echo due to a transverse wave mode-converted from a longitudinal wave appears between the first longitudinal wave echo and the third transverse wave echo. FIG. 25 is a B scope graphic, and three graphics 305, 306, and 307 in which the first, second, and third echoes are accumulated for one line are obtained.
[0089]
FIG. 26 shows the hologram reproduction area. Here, the reproduction scopes 308 to 310 are obtained by rotating the points of the B scope graphics 305 to 307 by the refraction angle θ. In the figure, only the reproduction area 309 for the graphic 306 is shown.
[0090]
FIG. 27 shows a hologram creation method. Send / receive position (x _i , y _j ) One-way propagation distance Z _ij The holograms 3101, 3102, and 3103 are created in the flaw detection area determined from the process start position to the process end position. At this time, the wave number k = n × 2πf / V of the reference wave used for numerical interference is used. As the sound velocity V, three types of longitudinal wave velocity, transverse wave velocity, and average sound velocity are used. The hologram image reproduction according to Equation 10 also uses three types of longitudinal wave velocity, transverse wave velocity, and average velocity. The method of displaying the calculation result as a video is the same as in the first embodiment.
[0091]
According to the second embodiment, the hologram is created and reproduced using the longitudinal wave, the transverse wave, and the average sound velocity of the longitudinal wave and the transverse wave in the subject. Even when conversion has occurred, the indication of a virtual image that originally appears at a position without a reflection source can be automatically erased.
[0092]
In addition, there are a plurality of reflection sources on the object to be inspected, and mode conversion at the time of incidence of ultrasonic waves on the subject (for example, longitudinal wave to transverse wave), mode conversion at the time of reflection from the reflection source (longitudinal wave to transverse wave) When a hologram is generated and reproduced using three kinds of longitudinal waves, a transverse wave, and an average sound velocity of the longitudinal wave and the transverse wave as in the present embodiment, even when a transverse wave and a longitudinal wave are generated, one reflection is obtained. Since the calculation result of each wave sound velocity with respect to the source indicates the same or approximate position, the actual reflection source can be accurately displayed, and highly reliable flaw detection is possible.
[0093]
【The invention's effect】
According to the present invention, when a hologram is created and reproduced from B-scope display data, the ultrasonic sound velocity used for the calculation is specified as the longitudinal wave mode or the transverse wave mode, and only the hologram of the propagation path having the same sound velocity is reproduced. Therefore, a virtual image appearing at a position different from the actual position can be erased by ultrasonic mode conversion, and the number and positions of scratches inside the object to be inspected can be accurately displayed.
[0094]
Further, when image reproduction corresponding to each sound speed is performed with the ultrasonic sound speed used for calculation as longitudinal and transverse waves, and further with the average sound speed of the longitudinal and transverse waves, a plurality of them can be displayed for one reflection source by superimposing them. The calculation result can be reflected, and a more reliable graphic display of the flaw detection result can be realized.
[0095]
Further, when the reproduction area is obtained from the B scope display data, each point is rotated according to the refraction angle of the ultrasonic wave, so that the influence of the spread of the ultrasonic wave can be reduced, and the more accurate position and shape of the reflection source can be reproduced. .
[Brief description of the drawings]
FIG. 1 is an explanatory view showing a processing image of an ultrasonic holography method of the present invention.
FIG. 2 is a block diagram showing the configuration of an ultrasonic flaw detection system according to an embodiment of the present invention.
FIG. 3 is a hardware configuration diagram of an ultrasonic flaw detection system according to an embodiment.
FIG. 4 is a diagram of an input screen for sound speed data according to the first embodiment.
FIG. 5 is a flowchart showing a schematic processing procedure of an ultrasonic flaw detection system according to one embodiment.
FIG. 6 is a flowchart showing an example of processing by the ultrasonic holography method of the present invention.
FIG. 7 is a data format diagram showing an example of initial parameters.
FIG. 8 is a data format diagram showing an example of flaw detection data.
FIG. 9 is an explanatory diagram of an A scope figure obtained as a result of flaw detection.
FIG. 10 is a data format diagram showing an example of B-scope graphic data.
FIG. 11 is a data format diagram showing an example of hologram creation.
FIG. 12 is an explanatory diagram of a B scope graphic obtained as a result of flaw detection.
FIG. 13 is an explanatory diagram showing a reproduction area of a hologram.
FIG. 14 is an explanatory diagram showing creation of a hologram.
FIG. 15 is a conceptual diagram illustrating the influence of the wave number of a reference wave as an image.
FIG. 16 is a menu screen diagram of sound speed selection used for the holographic calculation of the first embodiment.
FIG. 17 is a flowchart of processing for creating three-dimensional image data from the result of hologram reproduction calculation.
FIG. 18 is an explanatory diagram of a threshold level.
FIG. 19 is an explanatory diagram showing an example of 3D video data in the VRML format.
FIG. 20 is a schematic diagram of 3D video by a VRML browser.
21 is an explanatory diagram showing a processing image in another application example of Embodiment 1. FIG.
FIG. 22 is an explanatory diagram of an application example according to the second embodiment of the present invention.
FIG. 23 is a diagram of an input screen for sound velocity data in the second embodiment.
FIG. 24 is an explanatory diagram of an A scope graphic obtained as a result of flaw detection according to the second embodiment.
FIG. 25 is an explanatory diagram of a B scope graphic according to the second embodiment.
FIG. 26 is an explanatory diagram of a hologram reproduction area according to the second embodiment.
FIG. 27 is an explanatory diagram of hologram creation according to the second embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Computer, 11 ... Display apparatus, 12 ... Interface apparatus, 101 ... Ultrasonic probe, 102 ... Inspected object, 103 ... Reflection source, 104 ... Reflection path, 105 ... Reflection path, 106 ... Transmission pulse, 107 ... Echo from the surface, 108 ... Echo from the reflection source (longitudinal wave), 109 ... Echo from the reflection source (transverse wave), 110 ... Echo from the bottom surface, 111 ... Echo from the surface, 112 ... Echo from the bottom surface, 113 ... flaw detection start position, 114 ... flaw detection end position, 115 ... figure (longitudinal wave), 116 ... figure (lateral wave), 117 ... data after rotation (longitudinal wave), 118 ... data after rotation (lateral wave), 121 ... processing Start position, 122 ... Processing end position, 123 ... One-way propagation distance, 124 ... Reproduction area, 125 ... One-way propagation distance, 126 ... Reproduction area, 127 ... Hologram, 128 ... Hologram 129... Reconstructed image (longitudinal wave reconstructed image by longitudinal wave) 130... Reconstructed image (reconstructed image by transverse wave by transverse wave) 131. Image display device 202... Image display data calculation device 203. Image data memory 204... Control device 205. Peak detection processing calculation unit 206 ... Data storage unit 2061 Sound speed data storage unit 207 Flaw detection data memory 208 ... A / D converter, 209 ... Receiver, 110 ... Probe moving mechanism, 120 ... Ultrasonic flaw detector.

Claims (10)

An ultrasonic wave that transmits ultrasonic waves in a predetermined mode to the object to be inspected, receives an echo reflected from a reflection source due to internal flaws, etc., obtains the position of the reflection source from the reception time of the echo, and displays a reflection source figure In the display method of the ultrasonic flaw detection result,
By repeating transmission and reception while scanning the probe, flaw detection data including the reception time of the echo is collected at each transmission and reception position, B scope graphic data is created from flaw detection data of one line scan, and based on the B scope graphic data. The wave number obtained as k = n × 2πf / V (n is a natural number) from the sound velocity V of the ultrasonic wave in the designated mode propagating through the inspected object and the frequency f of the ultrasonic wave used for flaw detection. When a hologram is created by numerically interfering the reference wave of k with the flaw detection data, and the speed of sound in the designated mode matches the speed of sound of the flaw detection data using the same wave number k used for the creation of the hologram And displaying the reproduced image on the screen by performing hologram reproduction in the reproduction area. According to claim 1, ultrasonic sound speed of the specified mode set the value of the longitudinal wave and the transverse wave, the display method of the ultrasonic flaw detection result, characterized in that superimposed on the reproduced image obtained by each speed of sound.   2. The ultrasonic flaw detection according to claim 1, wherein the ultrasonic velocity of the ultrasonic wave in the designated mode is set to an average value of the longitudinal wave and the transverse wave in addition to the longitudinal wave and the transverse wave, and a reproduced image at each sound velocity is superimposed and displayed. How to display the results.   4. The ultrasonic flaw detection result display method according to claim 1, wherein the reproduction area is obtained by rotating each point of the B-scope graphic data by an ultrasonic refraction angle θ.   5. The wave number according to claim 1, 2, 3 or 4, wherein a cos function is used for the reference wave, a phase thereof is determined from the wave number k and a propagation distance of the echo, and the wave number is determined as an inverse of the propagation speed of the ultrasonic wave. A method for displaying an ultrasonic flaw detection result, wherein k is an integer multiple and is variably set. An ultrasonic probe that transmits ultrasonic waves in a predetermined mode to an object to be inspected and receives echoes reflected from a reflection source due to internal scratches, etc., and the probe according to a predetermined scanning path on the object to be inspected A probe moving mechanism for scanning; a flaw detection graphic display processing mechanism for determining the position of the reflection source from the reception time of the echo to generate graphic data of the reflection source; and a display device for displaying the generated graphic data on the screen. In the ultrasonic flaw detector provided,
The flaw detection graphic display processing mechanism collects flaw detection data including the reception time of the echo for each transmission / reception position from the probe scanned by the probe movement mechanism, and from the flaw detection data of one line scan, the B scope graphic The data is created, the reproduction area is obtained based on the B-scope graphic data, and k = n × from the sound velocity V of the ultrasonic wave in the designated mode propagating through the inspection object and the frequency f of the ultrasonic wave used for flaw detection. A reference wave having a wave number k obtained as 2πf / V (n is a natural number) is numerically interfered with the flaw detection data to create a hologram, and the designated mode is used using the same wave number k used for creating the hologram. An ultrasonic flaw detector which reproduces a hologram in the reproduction area and displays a reproduced image on the screen when the sound velocity of the sound coincides with the sound velocity of the flaw detection data.   The ultrasonic flaw detection apparatus according to claim 6, wherein the display device includes an input screen for arbitrarily selecting a speed of sound in the inspection target ultrasonic wave in the designated mode. According to claim 6 or 7, wherein the testing graphic display processing mechanism, ultrasonic flaw detection apparatus characterized by being provided with means for variably setting to an integer multiple of the wave number k of the reference wave.   9. The display device according to claim 6, 7 or 8, wherein when a plurality of ultrasonic sound velocities in the specified mode are specified, the display device matches the reproduced images that coincide with each other when the reproduced images at the respective sound velocities match or approach each other. An ultrasonic flaw detector characterized by displaying using a color different from that of a reproduced image not to be reproduced.   9. The display device according to claim 6, 7 or 8, wherein when a plurality of ultrasonic sound velocities in the designated mode are designated, the display device displays the reproduced images only when the reproduced images at the respective sound velocities match or are close to each other. An ultrasonic flaw detector characterized by that.

Images