JP2004239692A

JP2004239692A - Ultrasonic testing method and its system

Info

Publication number: JP2004239692A
Application number: JP2003027474A
Authority: JP
Inventors: Koji Dojo; 康二道場; Hideyuki Hirasawa; 英幸平澤; Mitsuhiro Kamioka; 光浩神岡
Original assignee: Kawasaki Heavy Industries Ltd
Current assignee: Kawasaki Heavy Industries Ltd
Priority date: 2003-02-04
Filing date: 2003-02-04
Publication date: 2004-08-26
Anticipated expiration: 2023-02-04
Also published as: JP3725126B2

Abstract

<P>PROBLEM TO BE SOLVED: To overcome a difficulty in carrying out an ultrasonic test while disposing an ultrasonic probe at an appropriate position in accordance with a body to be tested, and to solve such problems that rapid works are difficult in the ultrasonic test, and evaluation precision is decreased. <P>SOLUTION: In the method, the ultrasonic test is carried out by using an ultrasonic wave having a prescribed intensity H generated by the ultrasonic probe 5 being disposed at a plurality of prescribed positions in relation to a defect 4 disposed at a prescribed position of the body to be tested 1 having a prescribed thickness. Then, a relation between depth values of the ultrasonic axis crossover points and the ultrasonic intensity H is obtained from the ultrasonic intensity H at each position where the ultrasonic probe carries out the ultrasonic test. The relation between the depth of ultrasonic axis crossover point and the ultrasonic intensity H is converted into a relative positional relation between a defect depth v and the ultrasonic axis crossover point 3, and a positional arrangement of the ultrasonic probe 5 suitable for the ultrasonic test of the body to be tested 1 is selected based on the relative positional relation between the defect depth v and the ultrasonic axis crossover point 3, thereby obtaining an effective probe arrangement and carrying out the ultrasonic test stably. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本願発明は、溶接継手部等の内部欠陥を非破壊で検査する超音波探傷方法及びその装置に関するものである。
【０００２】
【従来の技術】
従来より、溶接継手部等の内部欠陥を非破壊で検査する手段として、超音波探傷検査（ＵＴ）が知られている。この超音波探傷検査は、被検査体の表面に探触子を密着させ、この探触子から被検査体に入射させた超音波の反射によって欠陥を検出する非破壊検査であり、入射させた超音波の反射を検出するまでの時間によって欠陥の位置を知ることができる。
【０００３】
図１２は超音波探傷方法の一例を示す図であり、（ａ）は超音波探傷方法の模式図、（ｂ）はその探傷波形の模式図である。この超音波探傷方法は、一般にＴＯＦＤ（ＴｉｍｅｏｆＦｒｉｇｈｔＤｉｆｆｒａｃｔｉｏｎ）法と呼ばれている。図示する例は、このＴＯＦＤ法によって溶接継手部１０１（探傷部）を超音波探傷検査する例であり、溶接継手部１０１の両側部に超音波探触子１０２Ａ，１０２Ｂを設け、一方の超音波探触子１０２Ａから溶接継手部１０１の溶接線方向と直交する方向に超音波を入射し、その反射を他方の超音波探触子１０２Ｂで受けて超音波探傷検査を行っている。
【０００４】
この例の場合、溶接継手部１０１から所定距離離れた位置から発信した超音波によって、被検査体１００の全板厚方向を検査するように構成されている。図示する左側が送信探触子１０２Ａであり、右側が受信探触子１０２Ｂである。送信探触子１０２Ａから発した超音波が被検査体１００の表面を伝わって受信探触子１０２Ｂで検出されるラテラル波ａと、被検査体１００の底面で反射した底面波ｂと、これらの間で欠陥１０３に反射した回折波の上端波ｃと下端波ｄとを受信探触子１０２Ｂで検知し、この信号によって、欠陥１０３の存在と欠陥１０３の位置を検出している。また、この例の場合、溶接継手部１０１に沿って超音波探触子１０２Ａ，１０２Ｂを移動させることにより、全線の超音波探傷を行う例を示している。
【０００５】
また、超音波探傷する被検査体の厚みが大きい場合、超音波探触子の探傷可能な超音波強度の範囲で全厚みを測定できないため、超音波探触子の間隔を変化させることによって超音波の交軸点（ビーム中心）を幅方向に変化させ、探傷可能な超音波強度の範囲を厚み方向に変化させて走査することによって被検査体の全厚みを測定している。この場合、超音波探触子を溶接継手部の幅方向に移動させて異なる位置で複数回の測定を行うことになる。
【０００６】
この種の従来技術として、ＴＯＦＤ法で得た被検査体断面層のＤスコープ画像を記憶装置に記憶し、その記憶装置に記憶された複数のＤスコープ画像の欠陥縞のすべてについて欠陥評価を行おうとするものがある。この従来技術では、被検査体の肉厚が大きい場合には、一対の探触子の間隔を変化させて複数回測定することによって全厚みを測定している（例えば、特許文献１参照。）。
【０００７】
また、他の従来技術として、複数の振動子を連続的に配列した一体構造のアレイ型超音波探触子のうち１又は２以上の探触子を利用し、機械操作が不要な電子走査によって、被検査対象部位全体の欠陥検出を高速かつ高精度で行えるようにしたものがある（例えば、特許文献２参照。）。
【０００８】
【特許文献１】
特開２００２−１６２３９０号公報（段落［００２７］、図３）
【特許文献２】
特開２００１−３２４４８４号公報（第２頁、図５）
【０００９】
【発明が解決しようとする課題】
しかしながら、前記したＴＯＦＤ法の場合、探傷条件を決定する既存の規格等、定型の方法はなく、一般的に板厚の１／２より大きい位置に交軸点を合わせるか、詳細な試験を行った後に交軸点を決めている。そのため、毎回、検査者毎に設定する検査条件には個人差が生じる。つまり、細部の検査条件は検査者毎に異なる設定となっている。しかも、板厚や材質の異なる種々の被検査体に対して、同じ検査者であっても同じ検査条件を設定するとは限らない。
【００１０】
また、前記したように、被検査体の厚みが大きくなって超音波探触子を幅方向に移動させるとしても、一対の超音波探触子の間隔を変化させる量が検査者によって異なるため、板厚によっては十分な感度で探傷できない領域が板厚方向に存在したり、両者が重なっている領域が存在する可能性があり、これらによって欠陥を見落とす可能性もある。このことは、板厚上下方向に交軸点を合わせた２組の探触子を配置して探傷した場合でも同様である。そのため、熟練検査者の経験に頼られている場合が多く、迅速な探傷作業を困難にしている。しかも、検査者の違いによって検査結果に差が生じ、安定した超音波探傷が困難になって、評価の精度を低下させる場合がある。
【００１１】
さらに、被検査体には高減衰材やノイズの高い材料がありこの場合には、熟練検査者であっても適切な位置に超音波探触子を配置して超音波探傷することが難しく、より迅速な探傷作業を困難にしている。
【００１２】
なお、前記特許文献１の場合でも、被検査体の肉厚が大きい場合に探触子の間隔を変化させる量の決定は困難であり、検査者の違いによって検査結果に差が生じ、安定した超音波探傷は困難である。
【００１３】
また、前記特許文献２の場合、利用する振動子の選択や、被検査対象部位の板厚方向に超音波ビームの交点を結ぶように複雑な制御を行う必要があり、複雑な制御を行う制御機が必要になるとともに、被検査体に応じた制御を行うように調整しなければならない。そのため、多くの費用と時間を要してしまう。
【００１４】
【課題を解決するための手段】
そこで、前記課題を解決するために、本願発明の超音波探傷方法は、所定厚の被検査体の所定位置に設けた欠陥に対し、複数の所定位置に配置した超音波探触子により所定の超音波強度で超音波探傷し、該超音波探傷したそれぞれの超音波探触子配置における超音波強度から超音波交軸点深さと超音波強度との関係を求め、該超音波交軸点深さと超音波強度との関係を超音波交軸点深さと欠陥深さとの相対位置関係に置き換え、該超音波交軸点深さと欠陥深さとの関係を欠陥深さと超音波交軸点との相対位置関係に置き換え、該欠陥深さと超音波交軸点との相対位置関係から被検査体の超音波探傷する位置に適した超音波探触子の配置を選択するようにしている。これにより、被検査体の厚み方向を超音波探傷する場合に、検査する被検査体に応じて、超音波探傷する位置に適した超音波交軸点となる超音波探触子の配置を容易に選択することができるので、効率的な探触子配置で安定した超音波探傷を行うことができる。
【００１５】
前記超音波探傷方法において、欠陥深さと超音波交軸点との相対位置関係に、所定のしきい値を設定することにより欠陥検出の範囲を設定し、該しきい値を設定した欠陥深さと超音波交軸点との相対位置関係から、被検査体の超音波探傷する位置に適した超音波探触子の配置を選択するようにすれば、しきい値の設定条件によってより欠陥の検出精度を向上させることができる。
【００１６】
また、この超音波探傷方法において、しきい値として、超音波強度の絶対値または無欠陥被検査体におけるノイズと超音波強度とのＳＮ比を使用して検査するようにすれば、種々の被検査体において安定したしきい値の設定ができる。
【００１７】
さらに、前記超音波探傷方法において、欠陥深さと超音波交軸点との相対位置関係を、超音波が被検査体内を伝搬する際に該被検査体に応じた補正要素で補正することにより該欠陥深さと超音波交軸点との相対位置関係の基本データを作成し、該基本データを検査する被検査体に応じた補正要素で補正することにより該被検査体の欠陥深さと超音波交軸点との相対位置関係を作成し、該欠陥深さと超音波交軸点との相対位置関係から被検査体の超音波探傷する位置に適した超音波探触子の配置を選択するようにすれば、作成した基本データを異なる被検査体に応じた補正要素で補正することにより、その被検査体の欠陥深さと超音波交軸点との相対位置関係を作成することができるので、この欠陥深さと超音波交軸点との相対位置関係から被検査体の超音波探傷する位置に適した超音波探触子の配置を容易に選択することができる。
【００１８】
また、この超音波探傷方法において、補正要素として、被検査体の材料に応じた減衰特性を使用して前記基本データを作成し、該基本データを検査する被検査体に応じた減衰特性で補正するようにすれば、補正要素の入手が容易な減衰特性によって基本データを容易に補正することができ、検査する被検査体に応じた欠陥深さと超音波交軸点との相対位置関係を迅速に得ることができる。
【００１９】
その上、この超音波探傷方法において、前記補正要素に加え、欠陥をとらえたビームとビーム中心とのずれの補正、および、欠陥先端部への超音波の入射角の差による補正を行って前記基本データを作成するようにすれば、より多くの要素で補正して正確なデータを得ることができる。
【００２０】
一方、本願発明の超音波探傷装置は、所定厚の被検査体の所定位置に設けた欠陥に対し、複数の所定位置に配置した超音波探触子により所定の超音波強度で超音波探傷し、該超音波探傷したそれぞれの超音波探触子配置における超音波強度から超音波交軸点深さと超音波強度との関係を求める検出部と、該超音波交軸点深さと超音波強度との関係を超音波交軸点深さと欠陥深さとの相対位置関係に置き換えると共に、該超音波交軸点深さと欠陥深さとの関係を欠陥深さと超音波交軸点との相対位置関係に置き換える演算部と、該演算部で演算した結果を記憶する記憶部と、被検査体の超音波探傷する位置に応じて該記憶部に記憶された欠陥深さと超音波交軸点との相対位置関係から適した超音波探触子の配置を選択する選択部とを備えるようにしている。このようにすれば、被検査体の厚み方向を超音波探傷する場合に、検査する被検査体の超音波探傷する位置に適した超音波探触子の配置を容易に選択することができるので、効率的な探触子配置で安定した超音波探傷を行うことができる。
【００２１】
また、この超音波探傷装置において、前記記憶部に、種々の被検査体内を超音波が伝搬する際に該被検査体に応じた補正要素を記憶させ、前記演算部に、該種々の被検査体から検査する被検査体を選択することにより、前記記憶部に記憶した補正要素で該選択した被検査体に応じた欠陥深さと超音波交軸点との相対位置関係を演算する機能を具備させ、前記選択部に、該演算した欠陥深さと超音波交軸点との相対位置関係から被検査体の超音波探傷する位置に適した超音波探触子の配置を選択する機能を具備させれば、演算部で得られた欠陥深さと超音波交軸点との相対位置関係を、記憶部に記憶された補正要素で検査する被検査体に応じて補正することができるので、種々の被検査体に適した超音波探触子の配置を容易に得ることができる。
【００２２】
さらに、前記超音波探傷装置において、前記演算部に、前記欠陥深さと超音波交軸点との相対位置関係を、超音波が種々の被検査体内を伝搬する際に該被検査体に応じた補正要素で補正して基本データを作成する機能と、検査する被検査体に応じた補正要素で前記基本データを補正して該被検査体の欠陥深さと超音波交軸点との相対位置関係演算する機能を具備させ、前記選択部に、該補正した欠陥深さと超音波交軸点との相対位置関係から被検査体の超音波探傷する位置に適した超音波探触子の配置を選択する機能を具備させれば、作成した基本データを異なる被検査体に応じた補正要素で補正することにより、その被検査体の欠陥深さと超音波交軸点との相対位置関係を作成することができるので、この欠陥深さと超音波交軸点との相対位置関係から被検査体の超音波探傷する位置に適した超音波探触子の配置を容易に選択することができる。
【００２３】
【発明の実施の形態】
以下、本願発明の一実施形態を図面に基づいて説明する。図１は本願発明の一実施形態における超音波探傷方法の交軸点深さと超音波強度との関係を示す説明図であり、図２は同超音波探傷方法におけるフローチャート、図３は同フローチャートにおける交軸点深さと欠陥深さとの関係を示すグラフ、図４は同フローチャートにおける欠陥深さと交軸点深さとの関係を示すグラフ、図５は同フローチャートにおいて、交軸点深さを固定し欠陥深さが変化した場合の欠陥深さと超音波強度との関係を示すグラフ、図６は同フローチャートにおける補正要因の説明図、図７は同フローチャートにおいて、計画している交軸点位置を設定した場合の超音波強度変化を示すグラフである。図１，図６では、被検査体１の厚み方向を横向きに表示している。
【００２４】
図１に示すように、超音波２の焦点位置が超音波交軸点３であり、この交軸点３の位置と欠陥４の位置と超音波２との関係を、以下のようにして予め実験的に求めるている。この欠陥４は人工的なもので、予め所定位置（深さ方向位置）に準備されており、表面からの欠陥深さｖや大きさはデータとして設定されている。一方、交軸点３は、超音波探触子５の種類によって決まり、超音波探触子５が決まれば、超音波周波数や探触子寸法、屈折角等が決まる。
【００２５】
この実施形態では、超音波探触子５の配置によって変化する交軸点３が深さ方向に３位置となるような配置を例示している。
【００２６】
このような構成により、図２のフローチャート（ａ）のように、欠陥深さを固定し、交軸点深さ（探触子間隔）を変化させて、交軸点深さと超音波強度の関係を求める、ことによって、図１の下部に示すように、欠陥深さｖに設けられた欠陥４と交軸点深さと超音波強度Ｈとの関係のグラフが得られる。このグラフは、超音波探触子５で検出されたデータに基づいてコンピュータ等の演算装置によって作成されており、この場合、コンピュータ等が検出部となる。
【００２７】
そして、図２のフローチャート（ｂ）のように、交軸点深さと超音波強度の関係を交軸点深さに対する欠陥深さの相対位置関係（交軸点深さ−欠陥深さ）に置き換える、ことによって、図３に示すような関係のグラフが得られる。このグラフも前記コンピュータ等の演算部によって演算された結果から作成される。このグラフによれば、交軸点３と欠陥４の深さとが一致した点よりも交軸点３が深い位置の時に、超音波強度Ｈが最も強くなることがわかる。
【００２８】
また、この関係から、図２のフローチャート（ｃ）のように、交軸点深さと超音波強度の関係を欠陥深さに対する交軸点の相対位置関係（欠陥深さ−交軸点深さ）に置き換える、ことにより、図４に示すような関係のグラフが得られる。このグラフも前記コンピュータ等の演算部によって演算された結果から作成され、演算された結果はコンピュータ等の記憶部に記憶される。このグラフよれば、交軸点３と欠陥４の深さとが一致した点よりも欠陥４が浅い側（図のマイナス側）の時に、超音波強度Ｈが最も強くなることがわかる。
【００２９】
その後、このようにして得られたデータから、図２のフローチャート（ｄ）のように、交軸点深さを固定し、欠陥深さが変化した場合の超音波強度の変化が計算で求められる。このデータは計算で求めることができ、例えば、コンピュータ等の演算装置によって計算され、その結果は記憶部に記憶される。しかし、前記図４に示す関係のグラフには、被検査体１の材料によって異なる内部の減衰要素等の影響が含まれている。
【００３０】
そこで、図５に示すように、図４に示した曲線（図５では破線１０で示す。）を材料に応じた補正要素で補正することにより、実線で示すように、被検査体１の厚み方向の位置が異なる場合の補正要素が除かれた曲線１１を得ることができる。この曲線１１によれば、被検査体１の厚み方向の浅い位置では補正要素が小さいので超音波強度Ｈは大きく、被検査体１の厚み方向の深い位置では補正要素が大きくなるので超音波強度Ｈが小さくなることがわかる。この実線で示された曲線が、一般的な、欠陥深さｖと超音波強度Ｈとの関係を示すグラフである。
【００３１】
この時の補正要素としては、図６に示すように、被検査体１の表面と直交する軸に対し、超音波２が欠陥４をとらえた超音波伝播経路６が交わる角度をω、超音波探触子５の交軸点３に向けた超音波２のビーム中心７と前記超音波伝播経路６との角度をφ、伝播する距離をＷｍｍ、材料の減衰係数をα、とすると、
ビーム路程が変化することによる超音波強度の補正（距離特性）：ｆ（Ｗ）、
ビーム路程が変化することによる超音波強度の変化（減衰特性）：ｇ（α，Ｗ）、
欠陥をとらえた超音波ビームと超音波ビーム中心のずれの補正：ｐ（Δφ）、
欠陥先端部への超音波の入射角の差による補正：ｑ（Δω）、
等によって補正される。
【００３２】
これにより、交軸点３と欠陥位置（深さ）の差と超音波強度の関係で表されるグラフは、超音波が材料内を伝達する際に生じる減衰量を加味した値で表される。なお、このように複数の補正要素によって補正することにより正確なデータを得ることができるが、必要に応じた補正要素で補正すればよい。例えば、被検査体１の材料によって異なる距離減衰により補正する場合、材料の減衰係数をαｄＢ／ｍｍ、距離減衰をｇ（Δｄ）とすると、各点における減衰量は、αＷ＋ｇ（Δｄ）ｄＢ、で表される。この減衰量と実験によって求めた交軸点と欠陥位置とのずれと超音波強度の関係式を利用して、欠陥位置が任意に変化する際の交軸点と超音波強度の関係を導き出してもよい。
【００３３】
そして、このようにして得られた、欠陥深さｖと超音波強度Ｈとの関係から、図２のフローチャート（ｅ）のように、計画している交軸点３の位置を設定し、順次、超音波強度の変化を求める。この時の交軸点３は複数でもよい。この時の補正要素としても、前記した補正要素と同様に、
ビーム路程が変化することによる超音波強度の補正（距離特性）：ｆ（Ｗ）、
ビーム路程が変化することによる超音波強度の変化（減衰特性）：ｇ（α，Ｗ）、
欠陥をとらえたビームとビーム中心のずれの補正：ｐ（Δφ）、
欠陥先端部への超音波の入射角の差による補正：ｑ（Δω）、
を利用して補正すればよい。
【００３４】
この実施形態では、図７に示すように、各交軸点３の位置（この実施形態では、交軸点１〜交軸点４）における欠陥深さｖと超音波強度Ｈとの関係のグラフが得られる。なお、この場合も、被検査体１に応じた補正要素として、前記複数の補正要素によって補正しているので、正確なデータを得ることができるが、前記被検査体１の材料によって異なる距離減衰等の必要に応じた補正要素のみで補正してもよい。
【００３５】
このように、この実施形態では、超音波探傷（ＴＯＦＤ法）において、探触子５の配置をずらすことで、板厚方向に交軸点位置をずらせた数通りの超音波（ＴＯＦＤの場合、回析波）強度分布をあらかじめ計測するために、所定位置の欠陥４に対して超音波探触子５の距離を変えることによって交軸点３の位置を変化させて、この交軸点３と超音波強度Ｈとの関係から、被検査体１の厚み方向における欠陥検出が可能な範囲での超音波探触子配置を選択するようにしている。この選択は、上述したコンピュータ等に記憶された計測データに基づいて、コンピュータ等の選択部（ＣＰＵ等）によって行われる。
【００３６】
そして、前記したような実験を行うことにより、超音波探触子５の位置と欠陥４の位置との関係において、超音波探傷が可能な範囲を予め掴むことができ、被検査体１の厚み方向のどの範囲を検査するには、どの位置に超音波探触子５を配置すればよいかを導くことができるようにしている。具体的には、探触子配置（交軸点の位置）と欠陥４の深さが変化したときの欠陥４からの超音波強度Ｈの関係を求め、この関係に基づいて、被検査体１の板厚に応じて、回析波の強度が十分に得られる探触子５の配置の組み合わせを決定できるようにしている。
【００３７】
ところで、上述した方法で求められた欠陥深さｖと超音波強度Ｈとの関係は、実験結果を得た材料における内部の減衰等を考慮しているため、同じ材料であれば適用できるが、他の材料に適用する場合には、実験した材料の特性と、新たに検査する材料との特性とから、新たな材料の特性に応じたデータに変換しなければ利用できない。
【００３８】
そこで、図８に示す図４のグラフから作成した基本データを示すグラフのように、ある材料の実験結果から材料特有の補正要素を取除いた基本データ（以下「マスターデータ」という。）を作成する。そして、このマスターデータに検査する材料の特性を加味することにより、その材料に応じたデータを得ることができるようにする。つまり、ある特性の材料で実験した結果からどのような材料にでも適用できるようなデータを得るようにする。
【００３９】
このマスターデータとしては、超音波２の距離減衰を補正することによって得ることができる。例えば、前記した図６に示すように、交軸点３と欠陥４との間に距離差Δｄがあるとすると、超音波強度Ｈは、Ｈ＝ｆ（Δｄ）で示されるが、欠陥までの伝播距離Ｗｍｍと減衰との関係の減衰係数αとで超音波強度を補正する必要があり、欠陥までの距離Ｗによる減衰を含む補正要素αＷで補正した超音波強度Ｈｓは、Ｈｓ＝ｆ（Δｄ）＋αＷ、で求めることができる。この補正要素には、被検査体１の材質に応じた減衰係数が用いられるため、補正された超音波強度Ｈｓは、その材料の距離減衰が取除かれたデータとなる。
【００４０】
このように、ある材料の所定位置に設けた欠陥４に対して、複数の探触子配置で超音波強度を求め、そのデータから、探触子配置を固定して欠陥４が移動した場合のデータを作成し（上述した図４）、そのデータから被検査体１の材料に応じた減衰因子を取除くことにより、純粋な欠陥深さｖと交軸点３との位置ずれと超音波強度との関係のデータを導き出しておけば、このデータをマスターデータ１２（図８）として前記コンピュータ等の記憶部に記憶させておくことにより、材料が異なっても、その材料の特性で補正すれば、その材料に応じたデータを容易に作成することができ、実験することなく材料に応じたデータを容易に作成することができる。
【００４１】
また、このようなマスターデータ１２を用意しておくことにより、任意の欠陥位置と交軸点３の超音波強度曲線を容易に得ることが可能となる。
【００４２】
さらに、このようにして実験結果のデータからマスターデータ１２を作成することにより、このマスターデータ１２を被検査体１の材料に応じて補正すれば、例えば、被検査体１が高減衰材やノイズの高い材料等であっても、それらの材料等について探触子５の配置と欠陥４からの超音波強度との関係を計算で求めることができ、迅速に最小数の超音波探触子５で効果的な超音波探傷を行うことが可能となる。
【００４３】
なお、ある欠陥４に対して実験を行う際にノイズの強度も求めておき、回析波の強度の代わりにＳＮ比を用いてもよい。
【００４４】
また、探触子５および被検査体１の材料毎に探触子５の配置と超音波強度Ｈとの関係を求め、それらのデータをデータベースとして事前に準備しておくことで、被検査体１が決定した段階で、その被検査体１に応じた補正処理を行うことで容易に最適探触子配置が決定できる。また、この手順にしたがって最適探触子配置を導く自動計算プログラムを作成し、装置に組み込むことも容易にできる。これらはオフラインで計算しても良く、コンピュータ等の装置を用いることによって達成することができる。
【００４５】
図９は本願発明の超音波探傷方法による探傷結果の画像を模式的に表現した説明図であり、図１０は同超音波探傷結果に基づいて図７のグラフにしきい値を設定する例を示すグラフである。図１１は図１０に示すしきい値を設定したグラフを平面的に示す棒グラフである。
【００４６】
図９に示すように、前記したようにして超音波探傷した結果はモニタ画面８等に表示されるが、この探傷結果には、欠陥４と欠陥以外のノイズを含んだ状態で表示される。そこで、図１０に示すように、ノイズを除いて欠陥４を検出できる程度の超音波強度にしきい値９を設定し、このしきい値９を越えている範囲での超音波強度Ｈの変化を検出したら欠陥４であると認識するようにしている。このしきい値９としては、超音波強度の絶対値を用いる他、無欠陥材料のノイズと超音波強度のＳＮ比で設定することも可能である。この場合、ノイズ計測はＴＯＦＤ画像エリア指定の強度分布状況を計測することによって行うと有効である。
【００４７】
そして、図１１に示すように、前記しきい値９によって設定された欠陥検出が可能な範囲をそれぞれ棒グラフ１３で表すことにより、被検査体１の厚み方向に、超音波探触子５の配置とその配置によって超音波探傷可能な範囲とが平面的に表される。このように表された超音波探傷可能な範囲から、目的とする超音波探傷する範囲を設定すれば、その交軸点３と欠陥検出可能範囲から、最低限、どの交軸点の配置の組み合わせを選択すればよいかを判断することができる。この例の場合、図の下側から交軸点１、交軸点２、交軸点３、交軸点４が表示されており、全板厚を検査するためには、交軸点１と交軸点４とを選択すれば最小数の超音波探触子５で検査することができる（右矢印で示す）。これにより、最小の超音波探触子５の数で、被検査体１の超音波探傷しようとする範囲（板厚全体等）の欠陥検出を安定して行うことが可能となる。なお、棒グラフで表すか否かは、検査者が視覚で探傷する厚みに応じて棒グラフから検出に最適な配置を選択する場合に有効であり、コンピュータ等の演算装置で自動的に検出する構成の場合には、図９のデータから検出してもよい。
【００４８】
以上のように、この実施形態では、超音波２の交軸点３位置を中心に計測して、超音波強度が交軸点位置から離れて弱くなったら、隣接する超音波探触子５によって欠陥４を検出することができるようにしており、その手順として、欠陥位置固定で探触子位置を変化させた実験データから超音波強度の変化を取得し、このデータを、交軸点深さと欠陥深さの相対位置関係に置き換え、このデータを、欠陥深さと交軸点深さの相対位置関係に置き換え、このデータから探触子を固定して欠陥位置が変化した場合のデータを作成し、計画している交軸点位置を設定し、超音波強度の変化を求め、このデータのしきい値以上から棒グラフを作成し、探傷する板厚に応じて棒グラフから探触子配置を選択する、ようにしている。
【００４９】
この超音波探触子の配置を自動的に選択する場合、被検査体１の板厚を全てカバーする条件を抽出して最適条件を求めるとすると、各交軸点３のしきい値をまたぐ範囲を検出可能範囲として求める。この時、探触子チャンネル数は可能な限り少ない方がよいので、最初に全板厚をカバーするチャンネルがないかを探す。すなわち、全板厚にわたって検出しきい値を越える超音波強度を与えるグラフを探す。これを満足しなければ、次に２つのチャンネルで全板厚にわたって検出しきい値を越える超音波強度を与えるグラフを探す。そして、２つの超音波探触子５でこれを繰り返し、無ければ３つの超音波探触子５で探す。その後、同様にして順次探触子５を増やして探し、最小数で検出可能な超音波探触子５の配置を探す。
【００５０】
以上のように、被検査体１が決定した場合、板厚全域にわたって回析波強度を最適にする探触子配置あるいはチャンネル数を合理的に決定することができるので、例えば、裏面近くの欠陥や板厚中央部の欠陥を重点的に検査する場合、その重点部分の超音波強度（又はＳＮ比）が高くなるような探触子配置を決定することができ、欠陥の見落としを防ぐことができる。
【００５１】
また、被検査体１の種類と探触子５の種類毎に、板厚全域にわたって超音波強度を最適にする探触子配置あるいはチャンネル数を合理的に決定することができる。
【００５２】
さらに、被検査体１と探触子５が決定した場合、最適な探傷条件（回析波強度を最適にする探触子配置あるいはチャンネル数）を即時に決定することができ、自動化装置としての機能を増すこともできる。
【００５３】
なお、前記実施の形態では、欠陥深さが変化した場合の超音波強度の変化を求めるために、複数の補正要素によって補正しているが、減衰係数による補正のみを行った場合でも可能であり、本願発明における補正要素は上述した実施形態に限定されるものではない。
【００５４】
また、上述した実施形態は一実施形態であり、本願発明の要旨を損なわない範囲での種々の変更は可能であり、本願発明は上述した実施形態に限定されるものではない。
【００５５】
【発明の効果】
本願発明は、以上説明したような形態で実施され、以下に記載するような効果を奏する。
【００５６】
被検査体の厚み方向の所定範囲を効果的に検査することができるので、被検査体の厚み方向の正確な評価結果が得られる超音波探傷を効率良く行うことが可能となる。
【図面の簡単な説明】
【図１】本願発明の一実施形態における超音波探傷方法の交軸点深さと超音波強度との関係を示す説明図である。
【図２】図１に示す超音波探傷方法におけるフローチャートである。
【図３】図２のフローチャートにおける交軸点深さと欠陥深さとの関係を示すグラフである。
【図４】図２のフローチャートにおける欠陥深さと交軸点深さとの関係を示すグラフである。
【図５】図２のフローチャートにおいて、交軸点深さを固定し欠陥深さが変化した場合の欠陥深さと超音波強度との関係を示すグラフである。
【図６】図２のフローチャートにおける補正要因の説明図である。
【図７】図２のフローチャートにおいて、計画している交軸点位置を設定した場合の超音波強度変化を示すグラフである。
【図８】図４のグラフから作成したマスターデータを示すグラフである。
【図９】本願発明の超音波探傷方法による探傷結果の画像を模式的に表現した説明図である。
【図１０】図９の超音波探傷結果に基づいて図７のグラフにしきい値を設定する例を示すグラフである。
【図１１】図１０に示すしきい値を設定したグラフを平面的に示す棒グラフである。
【図１２】（ａ）は超音波探傷方法の一例を示す模式図であり、（ｂ）はその探傷波形の模式図である。
【符号の説明】
１…被検査体
２…超音波
３…交軸点
４…欠陥
５…超音波探触子
６…超音波伝播経路
７…超音波ビーム中心
８…モニタ画面
９…しきい値
１０，１１…曲線
１２…マスターデータ
ｖ…欠陥深さ
Ｈ…超音波強度[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an ultrasonic flaw detection method for non-destructively inspecting internal defects such as welded joints and a device therefor.
[0002]
[Prior art]
Conventionally, ultrasonic inspection (UT) has been known as a means for non-destructively inspecting internal defects such as welded joints. This ultrasonic flaw detection inspection is a nondestructive inspection in which a probe is brought into close contact with the surface of an object to be inspected, and a defect is detected by reflection of ultrasonic waves incident from the probe onto the object to be inspected. The position of the defect can be known from the time until the reflection of the ultrasonic wave is detected.
[0003]
12A and 12B are diagrams illustrating an example of the ultrasonic flaw detection method. FIG. 12A is a schematic diagram of the ultrasonic flaw detection method, and FIG. 12B is a schematic diagram of the flaw detection waveform. This ultrasonic flaw detection method is generally called a TOFD (Time of Flight Diffraction) method. The illustrated example is an example in which the welding joint part 101 (flaw detection part) is subjected to ultrasonic inspection by the TOFD method. Ultrasonic probes 102A and 102B are provided on both sides of the welding joint part 101, and one ultrasonic wave is provided. Ultrasonic waves are incident from the probe 102A in a direction orthogonal to the direction of the welding line of the weld joint portion 101, and the reflected ultrasonic waves are received by the other ultrasonic probe 102B to perform ultrasonic inspection.
[0004]
In the case of this example, the apparatus is configured to inspect the object 100 to be inspected in the entire thickness direction by ultrasonic waves transmitted from a position separated from the weld joint part 101 by a predetermined distance. The illustrated left side is the transmitting probe 102A, and the right side is the receiving probe 102B. The ultrasonic wave emitted from the transmitting probe 102A travels along the surface of the device under test 100 and is detected by the receiving probe 102B. The lateral wave a is reflected by the bottom surface of the device under test 100. The upper probe c and the lower probe d of the diffracted wave reflected by the defect 103 are detected by the receiving probe 102B, and the presence of the defect 103 and the position of the defect 103 are detected by this signal. Further, in this example, an example is shown in which ultrasonic probes 102A and 102B are moved along the welded joint portion 101 to perform ultrasonic inspection of the entire line.
[0005]
In addition, when the thickness of the inspection object to be subjected to ultrasonic inspection is large, the entire thickness cannot be measured within the range of the ultrasonic intensity that can be detected by the ultrasonic probe. The total thickness of the object to be inspected is measured by changing the cross axis point (beam center) of the sound wave in the width direction and scanning while changing the range of the detectable ultrasonic intensity in the thickness direction. In this case, the ultrasonic probe is moved in the width direction of the welded joint to perform a plurality of measurements at different positions.
[0006]
As a conventional technique of this kind, a D-scope image of a cross-section layer of an object to be inspected obtained by the TOFD method is stored in a storage device, and defect evaluation is performed on all the defect fringes of the plurality of D-scope images stored in the storage device. There is something to try. In this conventional technique, when the thickness of an object to be inspected is large, the total thickness is measured by changing the distance between a pair of probes and performing measurement a plurality of times (for example, see Patent Document 1). .
[0007]
Further, as another conventional technique, one or two or more probes of an integrated array type ultrasonic probe in which a plurality of transducers are continuously arranged are used, and electronic scanning is performed without mechanical operation. There is a technique in which defect detection of the entire inspection target portion can be performed at high speed and with high accuracy (for example, see Patent Document 2).
[0008]
[Patent Document 1]
JP-A-2002-162390 (paragraph [0027], FIG. 3)
[Patent Document 2]
JP 2001-324484 A (page 2, FIG. 5)
[0009]
[Problems to be solved by the invention]
However, in the case of the above-mentioned TOFD method, there is no standard method such as an existing standard for determining flaw detection conditions, and in general, an intersection point is set to a position larger than 1/2 of the plate thickness or a detailed test is performed. After determining the intersection point. Therefore, each time, there is an individual difference in the inspection condition set for each inspector. That is, the detailed inspection conditions are different for each inspector. In addition, the same inspection conditions are not always set for the same inspector with respect to various inspection objects having different plate thicknesses and materials.
[0010]
Further, as described above, even if the thickness of the test object is increased and the ultrasonic probe is moved in the width direction, since the amount of change in the interval between the pair of ultrasonic probes differs depending on the inspector, Depending on the plate thickness, there is a possibility that a region where flaw detection cannot be performed with sufficient sensitivity exists in the plate thickness direction, or a region where the both overlap exists, and a defect may be overlooked by these. This is the same even when flaw detection is performed by arranging two sets of probes whose intersection points are aligned vertically in the thickness direction. Therefore, it often depends on the experience of a skilled inspector, making it difficult to perform a quick flaw detection operation. In addition, there is a case where a difference occurs between the test results depending on a different inspector, which makes it difficult to perform stable ultrasonic flaw detection and lowers the accuracy of the evaluation.
[0011]
Furthermore, there are high-attenuation materials and high-noise materials in the test object.In this case, it is difficult for even a skilled inspector to arrange the ultrasonic probe at an appropriate position and perform ultrasonic inspection. It has made it more difficult to conduct quick inspection work.
[0012]
Note that, even in the case of Patent Document 1, it is difficult to determine the amount by which the distance between the probes is changed when the thickness of the object to be inspected is large. Ultrasonic testing is difficult.
[0013]
Further, in the case of Patent Document 2, it is necessary to select a transducer to be used and to perform complicated control so as to connect intersections of ultrasonic beams in the thickness direction of a portion to be inspected. In addition to the need for a machine, adjustments must be made to perform control according to the test object. Therefore, much cost and time are required.
[0014]
[Means for Solving the Problems]
Therefore, in order to solve the above-described problem, the ultrasonic flaw detection method of the present invention uses a predetermined number of ultrasonic probes arranged at a plurality of predetermined positions for a defect provided at a predetermined position of a test object having a predetermined thickness. Ultrasonic flaw detection at the ultrasonic intensity, the relationship between the ultrasonic intensity and the ultrasonic intensity at the ultrasonic probe arrangement of each ultrasonic probe was obtained, the ultrasonic intersection depth. And the ultrasonic intensity are replaced by the relative positional relationship between the ultrasonic intersection axis depth and the defect depth, and the relationship between the ultrasonic intersection axis depth and the defect depth is expressed by the relative position between the defect depth and the ultrasonic intersection axis. The position is replaced with a positional relationship, and an ultrasonic probe arrangement suitable for the ultrasonic inspection position of the inspected object is selected from the relative positional relationship between the defect depth and the ultrasonic intersection point. Thereby, when ultrasonic inspection is performed in the thickness direction of the object to be inspected, it is easy to arrange the ultrasonic probe, which is an ultrasonic intersection point suitable for the position to be subjected to ultrasonic inspection, according to the object to be inspected. Therefore, stable ultrasonic testing can be performed with an efficient probe arrangement.
[0015]
In the ultrasonic flaw detection method, the relative position relationship between the defect depth and the ultrasonic intersection point, the range of defect detection is set by setting a predetermined threshold, and the threshold depth and the set defect depth By selecting an ultrasonic probe arrangement suitable for the position where ultrasonic inspection is to be performed on the inspection object based on the relative positional relationship with the ultrasonic intersection point, it is possible to detect more defects depending on the threshold setting conditions. Accuracy can be improved.
[0016]
Further, in this ultrasonic flaw detection method, if the inspection is performed using the absolute value of the ultrasonic intensity or the SN ratio of the noise and the ultrasonic intensity in the defect-free inspection object as the threshold, various inspections can be performed. A stable threshold value can be set in the inspection object.
[0017]
Further, in the ultrasonic flaw detection method, the relative positional relationship between the defect depth and the ultrasonic intersection point is corrected by a correction element corresponding to the inspection object when the ultrasonic wave propagates through the inspection object. Basic data of the relative positional relationship between the defect depth and the ultrasonic intersection point is created, and the basic data is corrected by a correction element corresponding to the inspection object to be inspected, thereby obtaining the defect depth of the inspection object and the ultrasonic intersection. A relative positional relationship with the axial point is created, and an ultrasonic probe arrangement suitable for the ultrasonic inspection position of the inspected object is selected from the relative positional relationship between the defect depth and the ultrasonic intersecting point. Then, by correcting the created basic data with a correction element corresponding to a different inspection object, it is possible to create a relative positional relationship between the defect depth of the inspection object and the ultrasonic intersecting point. Based on the relative positional relationship between the defect depth and the ultrasonic intersection point, The arrangement of the ultrasonic probe suitable position ultrasonic testing of 査体 can be easily selected.
[0018]
In this ultrasonic flaw detection method, the basic data is created using an attenuation characteristic according to the material of the inspection object as a correction element, and the basic data is corrected with an attenuation characteristic according to the inspection object to be inspected. This makes it possible to easily correct the basic data with the attenuation characteristics for which correction elements are easily available, and to quickly determine the relative positional relationship between the defect depth and the ultrasonic intersection point according to the inspection object to be inspected. Can be obtained.
[0019]
In addition, in this ultrasonic flaw detection method, in addition to the correction element, correction of the deviation between the beam capturing the defect and the beam center, and correction by the difference in the incident angle of the ultrasonic wave to the tip of the defect are performed. If the basic data is created, accurate data can be obtained by correcting with more elements.
[0020]
On the other hand, the ultrasonic flaw detector of the present invention performs ultrasonic flaw detection at a predetermined ultrasonic intensity with ultrasonic probes arranged at a plurality of predetermined positions for a defect provided at a predetermined position of a test object having a predetermined thickness. A detecting unit that determines the relationship between the ultrasonic intensity at the ultrasonic probe position and the ultrasonic intensity at the ultrasonic probe arrangement, and the ultrasonic intensity at the ultrasonic axis depth and the ultrasonic intensity. Is replaced with the relative positional relationship between the ultrasonic intersection axis depth and the defect depth, and the relationship between the ultrasonic intersection axis depth and the defect depth is replaced with the relative positional relationship between the defect depth and the ultrasonic intersection point. An arithmetic unit, a storage unit for storing a result calculated by the arithmetic unit, and a relative positional relationship between an ultrasonic intersection axis point and a defect depth stored in the storage unit according to a position of the object to be inspected by ultrasonic inspection. A selection unit for selecting a suitable ultrasonic probe arrangement from the It is. With this configuration, when ultrasonic inspection is performed in the thickness direction of the inspection object, it is possible to easily select the arrangement of the ultrasonic probe suitable for the ultrasonic inspection position of the inspection object to be inspected. In addition, stable ultrasonic testing can be performed with an efficient probe arrangement.
[0021]
Further, in this ultrasonic flaw detector, when the ultrasonic wave propagates through the various inspected objects in the storage unit, the correction element corresponding to the inspected object is stored in the storage unit. A function of calculating a relative positional relationship between a defect depth corresponding to the selected test object and an ultrasonic axis by selecting a test object to be inspected from the body, using a correction element stored in the storage unit; The selection unit is provided with a function of selecting an ultrasonic probe arrangement suitable for the ultrasonic inspection position of the inspected object from the relative positional relationship between the calculated defect depth and the ultrasonic intersection point. Then, the relative positional relationship between the defect depth obtained by the calculation unit and the ultrasonic axis point can be corrected in accordance with the inspected object to be inspected by the correction element stored in the storage unit. Easy placement of the ultrasonic probe suitable for the test object
[0022]
Further, in the ultrasonic flaw detector, the arithmetic unit determines a relative positional relationship between the defect depth and an ultrasonic axis, according to the object to be inspected when ultrasonic waves propagate through various objects to be inspected. A function of creating basic data by correcting with a correction element, and a relative positional relationship between a defect depth of the object to be inspected and an ultrasonic intersection point by correcting the basic data with a correction element corresponding to the object to be inspected. An arithmetic function, and the selection unit selects an ultrasonic probe arrangement suitable for the ultrasonic inspection position of the inspection object from the relative positional relationship between the corrected defect depth and the ultrasonic intersection point. By providing the function to perform the correction, the created basic data is corrected by a correction element corresponding to a different test object, thereby creating a relative positional relationship between the defect depth of the test object and the ultrasonic intersection point. The relative depth between this defect depth and the ultrasonic intersection point It is possible to easily select the placement of the ultrasonic probe suitable position ultrasonic testing of the inspection object from the location relation.
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory diagram showing the relationship between the intersection point depth and the ultrasonic intensity in the ultrasonic inspection method according to one embodiment of the present invention, FIG. 2 is a flowchart in the ultrasonic inspection method, and FIG. FIG. 4 is a graph showing the relationship between the depth of the intersection and the depth of the defect, FIG. 4 is a graph showing the relationship between the depth of the defect and the depth of the intersection in the same flowchart, and FIG. FIG. 6 is a graph showing the relationship between the defect depth and the ultrasonic intensity when the depth changes, FIG. 6 is an explanatory diagram of the correction factor in the flowchart, and FIG. 7 sets the planned intersection point position in the flowchart. 6 is a graph showing a change in ultrasonic intensity in the case. 1 and 6, the thickness direction of the test object 1 is displayed horizontally.
[0024]
As shown in FIG. 1, the focal position of the ultrasonic wave 2 is the ultrasonic intersecting point 3, and the relationship between the position of the intersecting point 3, the position of the defect 4, and the ultrasonic wave 2 is determined in advance as follows. Experimentally seeking. The defect 4 is artificial and is prepared at a predetermined position (depth direction position) in advance, and the depth v and the size of the defect from the surface are set as data. On the other hand, the intersection point 3 is determined by the type of the ultrasonic probe 5, and when the ultrasonic probe 5 is determined, the ultrasonic frequency, the probe size, the refraction angle, and the like are determined.
[0025]
This embodiment exemplifies an arrangement in which the intersection point 3 that changes depending on the arrangement of the ultrasonic probe 5 is located at three positions in the depth direction.
[0026]
With such a configuration, as shown in the flow chart (a) of FIG. 2, the depth of the defect is fixed, the depth of the intersecting point (probe interval) is changed, and the relationship between the intersecting point depth and the ultrasonic intensity is obtained. As a result, as shown in the lower part of FIG. 1, a graph of the relationship between the defect 4 provided at the defect depth v, the intersection point depth, and the ultrasonic intensity H is obtained. This graph is created by an arithmetic device such as a computer based on data detected by the ultrasonic probe 5, and in this case, the computer or the like serves as a detection unit.
[0027]
Then, as shown in the flowchart (b) of FIG. 2, the relationship between the intersection axis depth and the ultrasonic intensity is replaced by the relative positional relationship between the intersection axis depth and the defect depth (intersection point depth−defect depth). Thus, a graph of the relationship as shown in FIG. 3 is obtained. This graph is also created from the result calculated by the calculation unit such as the computer. According to this graph, it can be seen that the ultrasonic intensity H is highest when the intersection axis 3 is at a position deeper than the point where the intersection 3 and the depth of the defect 4 match.
[0028]
Also, from this relationship, as shown in the flowchart (c) of FIG. 2, the relationship between the intersection point depth and the ultrasonic intensity is represented by the relative positional relationship of the intersection point to the defect depth (defect depth−intersection point depth). To obtain a graph of the relationship as shown in FIG. This graph is also created from the result calculated by the calculation unit such as the computer, and the calculated result is stored in the storage unit such as the computer. According to this graph, it can be seen that when the defect 4 is on the shallower side (minus side in the figure) than the point where the intersection point 3 coincides with the depth of the defect 4, the ultrasonic intensity H is highest.
[0029]
Thereafter, from the data obtained in this way, as shown in the flowchart (d) of FIG. 2, the depth of the intersection point is fixed, and the change in ultrasonic intensity when the defect depth changes is calculated. . This data can be obtained by calculation, for example, calculated by an arithmetic device such as a computer, and the result is stored in the storage unit. However, the graph of the relationship shown in FIG. 4 includes the influence of an internal attenuation element or the like that varies depending on the material of the test object 1.
[0030]
Therefore, as shown in FIG. 5, the curve shown in FIG. 4 (indicated by a broken line 10 in FIG. 5) is corrected by a correction element corresponding to the material, and as shown by a solid line, the thickness of the object 1 is measured. It is possible to obtain the curve 11 from which the correction element when the position in the direction is different is removed. According to the curve 11, the ultrasonic intensity H is large at a shallow position in the thickness direction of the test object 1 because the correction element is small, and the ultrasonic intensity is large at a deep position in the thickness direction of the test object 1 in the thickness direction. It turns out that H becomes small. The curve shown by the solid line is a general graph showing the relationship between the defect depth v and the ultrasonic intensity H.
[0031]
As the correction element at this time, as shown in FIG. 6, the angle at which the ultrasonic wave 2 intersects with the axis orthogonal to the surface of the test object 1 and the ultrasonic wave propagation path 6 where the ultrasonic Assuming that the angle between the beam center 7 of the ultrasonic wave 2 toward the intersection axis 3 of the probe 5 and the ultrasonic wave propagation path 6 is φ, the propagation distance is Wmm, and the attenuation coefficient of the material is α,
Correction of ultrasonic intensity due to change in beam path (distance characteristic): f (W),
Change in ultrasonic intensity due to change in beam path (attenuation characteristic): g (α, W),
Correction of the deviation between the ultrasonic beam capturing the defect and the ultrasonic beam center: p (Δφ),
Correction based on the difference in the incident angle of the ultrasonic wave to the defect tip: q (Δω),
And so on.
[0032]
Thus, the graph represented by the relationship between the intersection point 3 and the difference between the defect position (depth) and the ultrasonic intensity is represented by a value that takes into account the amount of attenuation generated when the ultrasonic wave is transmitted through the material. . Note that accurate data can be obtained by performing correction using a plurality of correction elements as described above, but correction may be performed using correction elements as needed. For example, when correction is performed by different distance attenuation depending on the material of the test object 1, assuming that the attenuation coefficient of the material is α dB / mm and the distance attenuation is g (Δd), the attenuation at each point is αW + g (Δd) dB. expressed. Using the relationship between the attenuation and the deviation between the intersection point and the defect position obtained by the experiment and the ultrasonic intensity, the relationship between the intersection point and the ultrasonic intensity when the defect position changes arbitrarily is derived. Is also good.
[0033]
Then, based on the relationship between the defect depth v and the ultrasonic intensity H obtained as described above, the planned position of the intersection 3 is set as shown in the flowchart (e) of FIG. , And the change in ultrasonic intensity. At this time, a plurality of intersection points 3 may be provided. As the correction element at this time, similarly to the correction element described above,
Correction of ultrasonic intensity due to change in beam path (distance characteristic): f (W),
Change in ultrasonic intensity due to change in beam path (attenuation characteristic): g (α, W),
Correction of the deviation between the beam capturing the defect and the beam center: p (Δφ),
Correction based on the difference in the incident angle of the ultrasonic wave to the defect tip: q (Δω),
The correction may be made by using.
[0034]
In this embodiment, as shown in FIG. 7, a graph of the relationship between the defect depth v and the ultrasonic intensity H at the positions of the respective intersection points 3 (in this embodiment, the intersection points 1 to 4). Is obtained. In this case as well, accurate data can be obtained because correction is performed by the plurality of correction elements as a correction element corresponding to the test object 1. However, different distance attenuations depend on the material of the test object 1. The correction may be performed only with a correction element such as necessary.
[0035]
As described above, in this embodiment, in the ultrasonic flaw detection (TOFD method), by displacing the probe 5, several kinds of ultrasonic waves (in the case of TOFD, In order to measure the intensity distribution in advance, the position of the intersection 3 is changed by changing the distance of the ultrasonic probe 5 with respect to the defect 4 at a predetermined position. From the relationship with the ultrasonic intensity H, the ultrasonic probe arrangement within a range in which a defect can be detected in the thickness direction of the inspection object 1 is selected. This selection is performed by a selection unit (CPU or the like) of the computer or the like based on the measurement data stored in the computer or the like described above.
[0036]
Then, by performing the above-described experiment, it is possible to grasp in advance the range in which the ultrasonic flaw can be detected in the relationship between the position of the ultrasonic probe 5 and the position of the defect 4, and the thickness of the object 1 to be inspected. In order to inspect which range in the direction, it is possible to guide at which position the ultrasonic probe 5 should be arranged. Specifically, the relationship between the probe arrangement (position of the intersection point) and the ultrasonic intensity H from the defect 4 when the depth of the defect 4 changes is determined, and based on this relationship, the inspection object 1 is determined. In accordance with the plate thickness of the probe 5, it is possible to determine the combination of the arrangement of the probes 5 that can sufficiently obtain the intensity of the diffraction wave.
[0037]
By the way, the relationship between the defect depth v and the ultrasonic intensity H obtained by the above-described method can be applied to the same material because the internal attenuation and the like in the material obtained from the experimental results are considered. When applied to other materials, it cannot be used unless the characteristics of the tested material and the characteristics of the material to be newly tested are converted into data corresponding to the characteristics of the new material.
[0038]
Therefore, as shown in a graph showing basic data created from the graph of FIG. 4 shown in FIG. 8, basic data (hereinafter, referred to as “master data”) in which a correction element specific to a material is removed from an experimental result of a material. I do. By adding the characteristics of the material to be inspected to the master data, data corresponding to the material can be obtained. That is, data that can be applied to any material is obtained from the result of an experiment performed on a material having a certain characteristic.
[0039]
This master data can be obtained by correcting the distance attenuation of the ultrasonic wave 2. For example, as shown in FIG. 6 described above, if there is a distance difference Δd between the intersection point 3 and the defect 4, the ultrasonic intensity H is represented by H = f (Δd). It is necessary to correct the ultrasonic intensity with the attenuation coefficient α of the relationship between the propagation distance Wmm and the attenuation, and the ultrasonic intensity Hs corrected by the correction element αW including the attenuation by the distance W to the defect is Hs = f (Δd ) + ΑW. Since an attenuation coefficient corresponding to the material of the test object 1 is used as the correction element, the corrected ultrasonic intensity Hs is data from which the distance attenuation of the material has been removed.
[0040]
As described above, for the defect 4 provided at a predetermined position of a certain material, the ultrasonic intensity is obtained by a plurality of probe arrangements, and based on the data, the probe arrangement is fixed and the defect 4 moves. By creating data (FIG. 4 described above) and removing the attenuation factor corresponding to the material of the inspection object 1 from the data, the pure defect depth v, the displacement between the intersection 3 and the ultrasonic intensity If the data of the relationship is derived, the data is stored as the master data 12 (FIG. 8) in the storage unit of the computer or the like so that even if the material is different, it can be corrected by the characteristic of the material. Thus, data according to the material can be easily created, and data according to the material can be easily created without performing experiments.
[0041]
In addition, by preparing such master data 12, it is possible to easily obtain an ultrasonic intensity curve at an arbitrary defect position and the intersection point 3.
[0042]
Further, by creating the master data 12 from the data of the experimental results in this way, if the master data 12 is corrected in accordance with the material of the test object 1, for example, the test object 1 Even if the materials are of high quality, the relationship between the arrangement of the probes 5 and the ultrasonic intensity from the defect 4 can be obtained by calculation for those materials and the like, and the minimum number of ultrasonic probes 5 can be quickly obtained. Thus, effective ultrasonic flaw detection can be performed.
[0043]
Note that the noise intensity may be obtained when an experiment is performed on a certain defect 4, and the SN ratio may be used instead of the diffraction wave intensity.
[0044]
In addition, the relationship between the arrangement of the probe 5 and the ultrasonic intensity H is determined for each material of the probe 5 and the inspection object 1, and those data are prepared in advance as a database, so that the inspection object At the stage where 1 has been determined, the optimum probe arrangement can be easily determined by performing a correction process according to the test object 1. In addition, an automatic calculation program for guiding the optimal probe arrangement can be created according to this procedure, and can be easily incorporated into the apparatus. These may be calculated off-line and can be achieved by using a device such as a computer.
[0045]
FIG. 9 is an explanatory view schematically showing an image of a flaw detection result by the ultrasonic flaw detection method of the present invention, and FIG. 10 shows an example of setting a threshold value in the graph of FIG. 7 based on the ultrasonic flaw detection result. It is a graph. FIG. 11 is a bar graph showing in a plane a graph in which the threshold values shown in FIG. 10 are set.
[0046]
As shown in FIG. 9, the result of the ultrasonic flaw detection as described above is displayed on the monitor screen 8 or the like, and the flaw detection result is displayed with the defect 4 and noise other than the defect. Therefore, as shown in FIG. 10, a threshold value 9 is set to an ultrasonic intensity enough to detect the defect 4 excluding noise, and a change in the ultrasonic intensity H in a range exceeding the threshold value 9 is determined. If detected, it is recognized as a defect 4. As the threshold value 9, it is possible to use the absolute value of the ultrasonic intensity, or to set the SN ratio of the noise of the defect-free material and the ultrasonic intensity. In this case, it is effective to measure the noise by measuring the intensity distribution status specified in the TOFD image area.
[0047]
Then, as shown in FIG. 11, the range in which the defect can be detected set by the threshold value 9 is represented by a bar graph 13 so that the arrangement of the ultrasonic probe 5 in the thickness direction of the inspection object 1 is performed. The range in which the ultrasonic inspection can be performed is represented in a plane by the arrangement. By setting the target ultrasonic flaw detection range from the ultrasonic flaw detectable range expressed as described above, the minimum combination of the arrangement of any of the cross axis points can be determined from the intersection axis 3 and the defect detectable range. Can be determined. In this example, the intersection point 1, the intersection point 2, the intersection point 3, and the intersection point 4 are displayed from the lower side of the figure. If the intersection point 4 is selected, the inspection can be performed with the minimum number of ultrasonic probes 5 (indicated by the right arrow). Accordingly, it is possible to stably detect a defect in the range (for example, the entire thickness) of the object 1 to be subjected to ultrasonic flaw detection with the minimum number of the ultrasonic probes 5. It should be noted that whether or not to represent a bar graph is effective when the inspector selects an optimal arrangement for detection from the bar graph according to the thickness to be visually inspected, and is configured to be automatically detected by an arithmetic device such as a computer. In this case, it may be detected from the data in FIG.
[0048]
As described above, in this embodiment, measurement is performed centering on the position of the cross axis 3 of the ultrasonic wave 2, and when the ultrasonic intensity becomes weaker away from the position of the cross axis, the adjacent ultrasonic probe 5 uses The defect 4 can be detected, and as a procedure, a change in the ultrasonic intensity is obtained from experimental data in which the probe position is changed while the defect position is fixed, and this data is used as the intersection axis depth and Replace the data with the relative positional relationship between the defect depths, replace this data with the relative positional relationship between the defect depth and the intersection axis depth, and fix the probe from this data to create data when the defect position changes. , Set the planned intersection point position, find the change in ultrasonic intensity, create a bar graph from the threshold value of this data or more, and select the probe arrangement from the bar graph according to the thickness to be flawed And so on.
[0049]
When automatically selecting the arrangement of the ultrasonic probe, if conditions for covering the entire thickness of the test object 1 are extracted and optimum conditions are determined, the threshold value of each intersection point 3 is straddled. The range is determined as a detectable range. At this time, since it is better that the number of probe channels is as small as possible, a search is first made for a channel that covers the entire thickness. That is, a graph that gives an ultrasonic intensity exceeding the detection threshold value over the entire thickness is searched. If not, then look for a graph that gives an ultrasonic intensity exceeding the detection threshold over the entire thickness in the two channels. Then, this operation is repeated by the two ultrasonic probes 5, and if not, the search is performed by the three ultrasonic probes 5. Thereafter, similarly, the number of the probes 5 is sequentially increased and searched, and the arrangement of the ultrasonic probes 5 which can be detected with the minimum number is searched.
[0050]
As described above, when the test object 1 is determined, it is possible to rationally determine the probe arrangement or the number of channels that optimizes the diffraction wave intensity over the entire plate thickness. In the case of mainly inspecting defects in the central part of the sheet or thickness, it is possible to determine the probe arrangement such that the ultrasonic intensity (or S / N ratio) of the important part becomes high, and it is possible to prevent oversight of defects. it can.
[0051]
Further, for each type of the test object 1 and each type of the probe 5, it is possible to rationally determine the probe arrangement or the number of channels for optimizing the ultrasonic intensity over the entire thickness.
[0052]
Further, when the test object 1 and the probe 5 are determined, the optimum flaw detection conditions (probe arrangement or the number of channels for optimizing the diffraction wave intensity) can be immediately determined. You can add more features.
[0053]
In the above-described embodiment, the correction is performed using a plurality of correction elements in order to obtain a change in the ultrasonic intensity when the defect depth changes. However, the correction may be performed only when the correction is performed using the attenuation coefficient. However, the correction element in the present invention is not limited to the above-described embodiment.
[0054]
In addition, the above-described embodiment is one embodiment, and various changes can be made without departing from the spirit of the present invention, and the present invention is not limited to the above-described embodiment.
[0055]
【The invention's effect】
The present invention is implemented in the form described above, and has the following effects.
[0056]
Since a predetermined range in the thickness direction of the object to be inspected can be effectively inspected, it is possible to efficiently perform ultrasonic flaw detection in which an accurate evaluation result in the thickness direction of the object to be inspected is obtained.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a relationship between an intersection point depth and ultrasonic intensity in an ultrasonic flaw detection method according to an embodiment of the present invention.
FIG. 2 is a flowchart in the ultrasonic flaw detection method shown in FIG.
FIG. 3 is a graph showing a relationship between an intersection point depth and a defect depth in the flowchart of FIG. 2;
FIG. 4 is a graph showing a relationship between a defect depth and an intersection point depth in the flowchart of FIG. 2;
FIG. 5 is a graph showing a relationship between a defect depth and an ultrasonic intensity when the depth of the defect changes while the depth of the intersection point is fixed in the flowchart of FIG. 2;
FIG. 6 is an explanatory diagram of correction factors in the flowchart of FIG. 2;
FIG. 7 is a graph showing changes in ultrasonic intensity when a planned intersection point position is set in the flowchart of FIG. 2;
FIG. 8 is a graph showing master data created from the graph of FIG.
FIG. 9 is an explanatory diagram schematically showing an image of a flaw detection result by the ultrasonic flaw detection method of the present invention.
FIG. 10 is a graph showing an example in which a threshold is set in the graph of FIG. 7 based on the ultrasonic flaw detection results of FIG. 9;
FIG. 11 is a bar graph showing in a plane a graph in which the threshold values shown in FIG. 10 are set.
12A is a schematic diagram illustrating an example of an ultrasonic flaw detection method, and FIG. 12B is a schematic diagram of the flaw detection waveform.
[Explanation of symbols]
1. Inspection object
2. Ultrasonic
3: Intersecting point
4: Defect
5 Ultrasonic probe
6 Ultrasonic propagation path
7 ... Ultrasonic beam center
8: Monitor screen
9 ... Threshold
10,11 ... curve
12… Master data
v: Defect depth
H: Ultrasonic intensity

Claims

For a defect provided at a predetermined position of a test object having a predetermined thickness, ultrasonic inspection is performed at a predetermined ultrasonic intensity by ultrasonic probes arranged at a plurality of predetermined positions, and each of the ultrasonic inspections is performed. The relationship between the ultrasonic intersection axis depth and the ultrasonic intensity is determined from the ultrasonic intensity in the stylus arrangement, and the relationship between the ultrasonic intersection axis depth and the ultrasonic intensity is determined by comparing the ultrasonic intersection axis depth and the defect depth. Relative positional relationship, the relationship between the ultrasonic intersection point depth and the defect depth is replaced with the relative positional relationship between the defect depth and the ultrasonic intersection point, and the relative positional relationship between the defect depth and the ultrasonic intersection point. An ultrasonic flaw detection method for selecting an arrangement of an ultrasonic probe suitable for an ultrasonic flaw detection position of an object to be inspected.

2. The ultrasonic flaw detection method according to claim 1, wherein a predetermined threshold value is set for a relative positional relationship between the defect depth and the ultrasonic intersection point to set a defect detection range, and the threshold value is set. An ultrasonic flaw detection method for selecting an ultrasonic probe arrangement suitable for a position where an ultrasonic flaw is to be detected on an object to be inspected, based on a relative positional relationship between a detected defect depth and an ultrasonic intersection point.

3. The ultrasonic inspection method according to claim 2, wherein the inspection is performed using the absolute value of the ultrasonic intensity or the SN ratio of noise and ultrasonic intensity in the defect-free inspection object as the threshold value. Method.

2. The ultrasonic flaw detection method according to claim 1, wherein the relative positional relationship between the defect depth and the ultrasonic intersection point is corrected by a correction element according to the inspection object when the ultrasonic wave propagates through the inspection object. By creating basic data of the relative positional relationship between the defect depth and the ultrasonic intersection point, the basic data is corrected by a correction element corresponding to the inspected object to be inspected, whereby the defect depth and the ultrasonic depth of the inspected object are corrected. A relative positional relationship between the ultrasonic wave intersection point is created, and an ultrasonic probe arrangement suitable for the ultrasonic inspection position of the inspected object is selected based on the relative positional relationship between the defect depth and the ultrasonic intersection point. Ultrasonic flaw detection method.

5. The ultrasonic inspection method according to claim 4, wherein the basic data is created using an attenuation characteristic according to a material of the inspection object as a correction element, and an attenuation characteristic according to the inspection object to inspect the basic data. Ultrasonic flaw detection method corrected by.

6. The ultrasonic flaw detection method according to claim 5, wherein in addition to the correction element, correction of a deviation between a beam capturing a defect and a beam center and correction by a difference in an incident angle of an ultrasonic wave to a defect tip portion are performed. An ultrasonic flaw detection method for creating the basic data.

For a defect provided at a predetermined position of a test object having a predetermined thickness, ultrasonic inspection is performed at a predetermined ultrasonic intensity by ultrasonic probes arranged at a plurality of predetermined positions, and each of the ultrasonic inspections is performed. A detection unit that obtains a relationship between the ultrasonic cross-axis point depth and the ultrasonic intensity from the ultrasonic intensity in the stylus arrangement,
The relationship between the ultrasonic axis depth and the ultrasonic intensity is replaced with the relative positional relationship between the ultrasonic axis depth and the defect depth, and the relationship between the ultrasonic axis depth and the defect depth is referred to as the defect depth. An arithmetic unit for replacing the relative positional relationship with the ultrasonic intersection point,
A storage unit for storing a result calculated by the calculation unit;
A selection unit that selects an appropriate ultrasonic probe arrangement based on a relative positional relationship between a defect depth and an ultrasonic intersection point stored in the storage unit in accordance with the ultrasonic inspection position of the inspection object. Ultrasonic flaw detector.

The ultrasonic flaw detector according to claim 7,
In the storage unit, when the ultrasonic wave propagates through various inspected objects, the correction element corresponding to the inspected object is stored,
In the arithmetic unit, by selecting the inspected object to be inspected from the various inspected objects, the correction element stored in the storage unit, the defect depth and ultrasonic intersection point corresponding to the selected inspected object, and The function of calculating the relative positional relationship of
The selecting unit includes an ultrasonic probe having a function of selecting an arrangement of an ultrasonic probe suitable for a position where an ultrasonic inspection is performed on an object to be inspected based on a relative positional relationship between the calculated defect depth and an ultrasonic intersection point. Sonic flaw detector.

The ultrasonic flaw detector according to claim 7,
The arithmetic unit corrects basic data by correcting the relative positional relationship between the defect depth and the ultrasonic intersection axis point with a correction element corresponding to the inspection object when the ultrasonic wave propagates through various inspection objects. A function to create and a function to correct the basic data with a correction element corresponding to the inspected object to be inspected and to calculate a relative positional relationship between a defect depth of the inspected object and an ultrasonic axis point,
The selecting unit includes an ultrasonic probe having a function of selecting an arrangement of an ultrasonic probe suitable for an ultrasonic inspection position of the inspection object from a relative positional relationship between the corrected defect depth and the ultrasonic intersection point. Sonic flaw detector.