JP3573967B2 - Plate wave ultrasonic inspection method - Google Patents
Plate wave ultrasonic inspection method Download PDFInfo
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- JP3573967B2 JP3573967B2 JP19011898A JP19011898A JP3573967B2 JP 3573967 B2 JP3573967 B2 JP 3573967B2 JP 19011898 A JP19011898 A JP 19011898A JP 19011898 A JP19011898 A JP 19011898A JP 3573967 B2 JP3573967 B2 JP 3573967B2
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/04—Analysing solids
- G01N29/11—Analysing solids by measuring attenuation of acoustic waves
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2291/00—Indexing codes associated with group G01N29/00
- G01N2291/02—Indexing codes associated with the analysed material
- G01N2291/023—Solids
- G01N2291/0234—Metals, e.g. steel
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2291/00—Indexing codes associated with group G01N29/00
- G01N2291/04—Wave modes and trajectories
- G01N2291/042—Wave modes
- G01N2291/0427—Flexural waves, plate waves, e.g. Lamb waves, tuning fork, cantilever
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2291/00—Indexing codes associated with group G01N29/00
- G01N2291/04—Wave modes and trajectories
- G01N2291/044—Internal reflections (echoes), e.g. on walls or defects
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Description
【0001】
【発明の属する技術分野】
本発明は、超音波探触子から鋼板等の被探傷材に板波超音波を発生させ、その反射波を受信して被探傷材に生じた欠陥を検出する板波超音波探傷方法に関するものである。
【0002】
【従来の技術】
熱延鋼板や冷延鋼板等、その厚みが比較的薄い被探傷材の表面および内部に生じた欠陥をオンラインで非破壊検査する場合、タイヤ型探触子を用いて被探傷材内に後述するような板波超音波を伝播させ、その反射波を探触子で受信し、その反射波の中に欠陥に基づく信号が含まれているか否かによって、被探傷材に生じた欠陥を探傷する板波超音波探傷が行われている。
【0003】
図5は、タイヤ型探触子10の使用態様を示す模式的断面図である。薄板等の被探傷材Sはその長手方向(紙面と直交する方向)に搬送され、被探傷材Sの表面には接触媒質19が塗布され、この上にタイヤ型探触子が接触状態で設置される。タイヤ型探触子10は、被探傷材Sの幅方向に位置調整移動可能な装置架台から鉛直に垂下する支持棒12の下端近傍から固定軸13を被探傷材Sの幅方向に延在するように水平に突設し、この固定軸13に探触部14を回転自在に取り付けて構成されている。
【0004】
探触部14は、固定軸13に図示しない軸受を介して回転可能に取り付けられた左右一対のホイール15と、この一対のホイール15の外周縁部に形成された溝16に端部が取り付けられ一対のホイール15の外周を覆う形状のゴム等からなるタイヤ部17とからなり、固定軸13には、所定周期毎に超音波を送受信する振動子18が被探傷材Sの幅方向に対して所定の角度で傾斜して取り付けられている。また、探触部14内には充填液11が充填されている。
以上のような構成のタイヤ型探触子10を被探傷材Sのエッジ部eに配置し、振動子18から超音波を発信すると、超音波はタイヤ部17内の充填液11・タイヤ部17・被探傷材S表面の接触媒質19を介して被探傷材Sに被探傷材の幅方向と平行に所定の入射角で入射され、そこで超音波の入射角・被探傷材Sの板厚・超音波の周波数に応じた振動モードの板波超音波に変換されて被探傷材S中を伝播する。
【0005】
被探傷材S中を伝播した板波超音波は、被探傷材Sの表面・内部に生じた欠陥および被探傷材Sの端面で反射され、その反射波は、被探傷材S表面の接触媒質19・タイヤ部17・タイヤ部17内の充填液11を介して振動子18に受信されて探傷信号が得られる。
【0006】
ここで、この板波探傷に関する欠陥検出能力は、タイヤ型探触子10内の振動子18の入射角θと探傷周波数fの選定が大きく影響を与える。被探傷材S内に発生する板波は、通常の垂直探傷や斜角探傷における縦波や横波と異なり、被探傷材Sの板厚tと超音波の周波数fとの積が所定の条件を満たす時に発生する共振現象とみなすことができる。
【0007】
図6は、板波モード表の例であり、横軸が板厚tと探傷周波数fの積、縦軸が入射角θである。この図において、a0 、a1 、a2 、…(Aモード)、s0 、s1 、s2 、…(Sモード)の曲線部分で板波が発生する。つまり、被探傷材Sの板厚tはその被探傷材固有のため、変更することができないため、入射角θもしくは探傷周波数fを変更することにより、各板厚毎(被探傷材毎)に板波を発生させる必要がある。
【0008】
このため、特開昭61−91567号公報では、ストリップの内部欠陥を板波で探傷するに際し、タイヤ型探触子の水平角および入射角を端面エコー(バックエコー)の強度が最大となるようにマイクロコンピュータにより自動設定し、その最大となった端面エコー強度をCRT表示画面上で100%となるように感度調整器で感度調整し、予め設定したレベル以上の欠陥エコーを検出することにより、欠陥検出を自動的に行うようにした自動板波探傷装置が提案されている。
【0009】
【発明が解決しようとする課題】
しかし、前述の従来の自動板波探傷装置では、次のような問題点がある。
(1) タイヤ型探触子の入射角の選定に際し、所定の設定値を設定後、端面エコー強度を読み取り、記憶装置にその端面エコー強度を記憶する。次に、入射角を所定角度だけ変更した後、再度端面エコー強度を読み取り、前回記憶した端面エコー強度と比較し、それを越えている場合はその強度を最大とし、その時の入射角を設定する。また、越えていない場合には、所定角度を今とは逆方向に変更し、前回記憶した端面エコー強度となる入射角に設定する。従って、初期の所定設定値に比べ、端面エコー強度を越えたかどうかを判断しているため、入射角を初期設定値から最大端面エコー強度より離れる方向に変更していく場合には、本来の最大の端面エコー強度が得られる入射角に設定できない問題がある。
(2) 所定の角度に設定後、ある方向に角度を変更し、最大エコー強度が更新されない場合には、再度逆方向に角度を変更するため、時間を要してしまう。被探傷材走行中にこの処理を実施すると、処理中は探傷できないことになり、時間がかかればそれだけ探傷できない長さが長くなり、問題となる。
(3) 入射角の設定後に感度を調整し、端面エコーがCRT表示画面上100%になるように設定しているが、前述の通り入射角が適当な角度に設定されない場合が多く、むやみに感度を上げることになる。これにより、ノイズを検出しやすくなり、ある設定レベル以上で検出した信号が欠陥によるものか欠陥によらないものか判別できない問題もある。
【0010】
本発明は、前述のような問題点を解消すべくなされたもので、その目的は、板波超音波探傷に際し、最大端面エコー強度が得られる入射角を正確に高速で自動設定することができ、板波超音波が最大に発生している状態で欠陥検出することが可能となり、また被探傷材の走行中においても最適な入射角の設定が可能となる板波超音波探傷方法を提供することにある。
【0011】
【課題を解決するための手段】
本発明の板波超音波探傷方法は、被探傷材に対して相対移動可能に対向配置した超音波探触子から超音波を所定の入射角および探傷周波数で送信することにより、板波超音波を被探傷材内に前記相対移動方向と直交する方向に伝播させ、被探傷材の欠陥からの反射波を前記超音波探触子で受信し、その信号レベルに応じて被探傷材の欠陥を検出する方法において、予め試験片で調査した被探傷材の材質、板厚毎の静止状態の入射角を用いて初期入射角を決定し、走行状態や静止状態の被探傷材に対して、前記初期入射角で端面エコー高さを観測し、この検出された端面エコー高さが設定値以上の場合、前記初期入射角で探傷を行い、前記端面エコー高さが設定値以下の場合、前記初期入射角を所定の範囲内を所定のピッチで変更して端面エコー高さが最大となる入射角を決定し、この入射角で探傷を行うことを特徴とする(請求項1)。
【0014】
通常、走行中の被探傷材を板波超音波で欠陥検出するには、検出したい欠陥を検出するための探傷感度、被探傷材の材質毎の超音波減衰による感度補正曲線、被探傷材の板厚毎の入射角、探傷周波数が必要となる。そこで、先ず、これらの探傷感度、感度補正曲線、入射角、探傷周波数は、被探傷材から切り出した試験片により、静的状態で調査し、被探傷材の材質、板厚毎にコンピュータに記憶させておく。
【0015】
ここで、経験的に被探傷材の静止状態と走行状態では、被探傷材の平坦度、走行ラインの状態、走行ラインとタイヤ型探触子の位置関係により、異なり、静的状態で調査した結果を設定しても、走行状態においては被探傷材の幅方向の端面からのエコー強度が最大とはならない。
【0016】
そこで、本発明では、前述の静止状態の試験片等により調査した結果を用いて初期入射角θ0 を設定し、この初期値で探傷を行い、被探傷材の板幅長さを用いて端面からの反射エコーの高さE0 を認識する。この端面エコー高さE0 がある設定値A0 以上の時は、板波超音波が十分発生していると判断し、後述する自動角度変更を実施することなく、初期入射角θ0 で探傷を行う。
【0017】
端面エコー高さE0 がある設定値A0 以下の時は、初期入射角θ0 から、初期入射角θ0 を中心とする所定の範囲±Δθだけ所定のピッチpで角度を1方向に変更し、順次その角度での端面エコー高さを読み取る。例えば、初期入射角θ0 =30deg で変更範囲±Δθ=±2deg 、ピッチp=0.1deg の場合、一旦28deg に設定後、32deg まで0.1deg ピッチで角度を変更し、あるいは一旦32deg に設定後、28deg まで0.1deg ピッチで角度を変更する。この角度ピッチ毎に端面エコー高さを読み取り、所定の範囲±Δθの角度変更が終了した時点で、所定の範囲±Δθの中で最大の端面エコー高さが得られた時の角度に入射角を設定する。これら一連の動作終了後、探傷を開始する。
【0018】
以上のように、静止状態の試験片から調査した結果を初期値として用い、端面エコー高さが設定値以上の場合は、そのまま探傷を行い、設定値以下の場合は初期設定値を中心とする所定範囲を1方向に角度を変更して最大の端面エコー高さを求め、この最大端面エコー高さの入射角で探傷を行うため、最大端面エコー強度が得られる最適な入射角を正確に高速で自動設定することができ、板波超音波が最大に発生している状態で欠陥検出することが可能となる。また、最適な入射角の設定を高速で行うことができるため、被探傷材の走行中にも最適な入射角の設定を行うことが可能となる。なお、連続処理ラインでは、操業のための作業時における低速走行状態で前記設定を行うのが好ましい。
【0019】
【発明の実施の形態】
以下、本発明を図示する一実施形態に基づいて詳細に説明する。これは、タイヤ型探触子から発信される超音波の被探傷材への入射角θを自動調整する場合の例である。図1は本発明に係る板波超音波探傷装置の構成を示すブロック図である。
【0020】
図1において、本発明に係る板波超音波探傷装置1は、マイクロコンピュータ2と、超音波の発信・受信の制御および探傷信号の処理等を行う超音波探傷器3と、タイヤ型探触子の振動子の角度を調整する変角操作盤4と、タイヤ型探触子5を備えており、マイクロコンピュータ2には上位コンピュータ6からデータが送信される。タイヤ型探触子5は、従来と同様の構造であり(図5参照)、固定軸13に取り付けられた振動子18の被探傷材の幅方向に対する傾斜角度が変角操作盤4により調整され、入射角θが自動調整される。
【0021】
マイクロコンピュータ2には、予め試験片等で調査した被探傷材の材質・板厚毎の探傷感度・感度補正曲線・入射角・探傷周波数を記憶させておく。また、上位コンピュータ6より被探傷材の寸法(板幅・板厚)および材質情報を受信し、この情報に基づいて、予めマイクロコンピュータ2に記憶した探傷感度および感度補正曲線と、板幅長さに基づく端面反射エコーゲート位置を超音波探傷器3に設定し、入射角θを変角操作盤4に設定する。変角操作盤4によりタイヤ型探触子5内部の振動子18の傾斜角度が前記入射角θとなるように調整される。
【0022】
次に、被探傷材の走行ライン情報より被探傷材の走行位置を把握し、被探傷材の先端部が通過後、先に設定した条件で被探傷材の反射信号の受信を開始する。そこで、端面エコー高さを読み取りながら、振動子18の傾斜角度を端面エコー高さが最大となる入射角に自動的に設定する(以下、自動角度制御という)。その処理フローの1例を図2に示す。この処理フローは、第1になるべく高速に処理を行う、第2に正確に行うことを重視した処理フローである。次に示すような順序で自動角度制御がなされる。
(1) 先ず、前述した調査結果における入射角を初期値として設定し、この初期入射角θ0 での端面エコー高さを観測する。
(2) 観測された端面エコー高さE0 がある設定値A0 以上の時は、板波超音波が十分発生していると判断し、自動角度制御を実施せず、ステップの(8) へ移行し、探傷ゲートを被探傷材の板幅情報に基づいて設定し、探傷を開始する。
(3) 一方、観測された端面エコー高さE0 がある設定値A0 以下の時は、次に示す自動角度制御を実施する。即ち、初期入射角θ0 から、角度制御範囲±Δθの−方向下限の角度(θ0 −Δθ)に設定し、角度制御ピッチpで角度を変更し、各ピッチ毎に端面エコー高さを読み取り、これを角度制御範囲±Δθの+方向上限の角度(θ0 +Δθ)まで角度制御ピッチpで連続的に実施する。なお、この角度変更は前記とは逆に+側から−側へと行うようにしてもよい。
(4) 次に、その角度制御範囲(−Δθ〜+Δθ)において、最大の端面エコー高さE1maxを求め、この最大端面エコー高さE1maxが得られた入射角θ1 を設定する。
(5) 最大端面エコー高さEmax がある設定値A1 以上の時は、この角度制御により十分に板波超音波が発生していると判断し、ステップ(7) へ移行し、探傷ゲートを被探傷材の板幅情報に基づいて設定すると共に、最大端面エコー高さE1maxの入射角θ1 で探傷を開始する。
(6) 一方、最大端面エコー高さE1maxがある設定値A1 以下の時は、探傷感度も不足していると判断し、その端面エコー高さが100%になるように探傷感度を上げた後、ステップ(7) へ移行し、探傷ゲートを被探傷材の板幅情報に基づいて設定すると共に、最大端面エコー高さEmax の入射角θ1 で探傷を開始する。
【0023】
以上のような処理により、角度制御不要な場合は自動角度制御を実施せず、角度制御が必要な場合には連続的に自動角度変更を実施して所定の範囲内での最大の端面エコー強度が得られる角度に設定するため、板波超音波が最大に発生している最適な入射角の設定を高速で行うことができる。なお、前記角度変更範囲は予め調査した初期設定値を中心に適宜設定しているため、最大の端面エコー強度が得られる角度を確実に検出することができる。
【0024】
また、この入射角の制御を正確に行うためには、理想的には被探傷材が静止している状態が望ましいが、連続処理ラインの被探傷材は常に走行し続けているため、静止状態での自動角度制御は困難である。一方、被探傷材の走行ラインは、図3に示すように、被探傷材の先端部ではライン速度を減速して低速走行の被探傷材に対して所定の操業のための作業を実施し、この作業が終了すると、ライン速度を加速しており、この高速走行状態においては、端面エコーは接触媒質の塗布状態により角度を変更せずとも大きく変動するため、この状態で角度制御を実施すると、角度により端面エコー高さが変動しているのか、接触媒質の塗布状態により変動しているのか判別しにくい。さらに、自動角度制御を実施している間は、被探傷材を探傷することができないため、高速で走行中はその長さが長くなってしまう。
【0025】
そこで、本発明では、被探傷材の走行ラインからライン速度情報を受信し、低速状態で自動角度制御を行い、ライン速度が加速されると、自動角度制御はその時点で終了し、その終了までの間で最大の端面エコー高さが得られた角度に設定するという処理とすることにより、正確な自動角度制御を実施することができる。
【0026】
図4は、初期入射角θ0 =17.5deg 、角度制御範囲±Δθ=±2deg 、角度制御ピッチp=0.1deg で自動角度制御を実施した時の端面エコー高さの推移を示すグラフである。この図から明らかなように、初期入射角θ0 の設定時における端面エコー高さ50%に対して100%端面エコー高さの最適な入射角16.7deg を得ることができた。また、50%に対して100%の端面エコー高さが得られることにより、感度的には2倍に増大した結果が得られた。また、このような角度制御で1000本の被探傷材を評価した結果、最大で3倍の感度が増大する結果が得られた。
【0027】
なお、以上は、入射角を自動調整する例について説明したが、これに限らず、探傷周波数を自動調整する場合、入射角と探傷周波数の両方を自動調整する場合にも、前記と同様に実施できることはいうまでもない。
【0028】
【発明の効果】
前述の通り、本発明は、所定の入射角の超音波による板波超音波探傷において、予め試験片で調査した被探傷材の材質、板厚毎の静止状態の入射角を用いて初期入射角を決定し、走行状態や静止状態の被探傷材に対して、前記初期入射角で端面エコー高さを観測し、検出された端面エコー高さが設定値以上の場合、初期入射角で探傷を行い、検出された端面エコー高さが設定値以下の場合、前記初期入射角を所定の範囲内を所定のピッチで変更して端面エコー高さが最大となる入射角を決定し、この入射角で探傷を行うようにしたため、次のような効果を得ることができる。
(1) 最大端面エコー強度が得られる最適な入射角を正確に高速で自動設定することができ、板波超音波が最大に発生している状態で欠陥検出することが可能となり、被探傷材の欠陥を確実に自動検出することができる。
(2) また、最適な入射角の設定を高速で行うことができるため、被探傷材の走行中にも最適な入射角の設定を行うことが可能となり、走行する被探傷材全体の欠陥検出が可能となる。
【図面の簡単な説明】
【図1】本発明の板波超音波探傷方法を実施するための装置のブロック図である。
【図2】本発明の板波超音波探傷方法の処理フローをフローチャートである。
【図3】本発明の板波超音波探傷方法を行う走行ラインの例とタイミングを示すグラフである。
【図4】本発明の板波超音波探傷方法の自動角度制御の結果を示すグラフである。
【図5】本発明で用いるタイヤ型探触子の概要を示す断面図である。
【図6】本発明で用いる板波超音波の板波モード表の例を示すグラフである。
【符号の説明】
1…板波超音波探傷装置
2…マイクロコンピュータ
3…超音波探傷装置
4…変角操作盤
5…タイヤ型探触子
6…上位コンピュータ
11…充填液
12…支持棒
13…固定軸
14…探触部
15…ホイール
16…溝
17…タイヤ部
18…振動子
19…接触媒質[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a plate wave ultrasonic flaw detection method for generating a plate wave ultrasonic wave from an ultrasonic probe on a material to be detected such as a steel plate and receiving a reflected wave to detect a defect generated in the material to be detected. It is.
[0002]
[Prior art]
When conducting non-destructive online inspection of defects generated on the surface and inside of a material to be inspected, such as hot-rolled steel sheet and cold-rolled steel sheet, whose thickness is relatively small, a tire-type probe is used in the material to be inspected as described later. Such a plate wave ultrasonic wave is propagated, the reflected wave is received by the probe, and a defect generated in the material to be inspected is detected based on whether or not a signal based on the defect is included in the reflected wave. Plate wave ultrasonic testing is being performed.
[0003]
FIG. 5 is a schematic cross-sectional view showing a usage mode of the tire-
[0004]
The
When the tire-
[0005]
The plate wave ultrasonic wave propagated in the material to be inspected S is reflected by a defect generated on the surface and inside of the material to be inspected S and an end face of the material to be inspected S, and the reflected wave is a couplant on the surface of the material to be inspected S. 19, the
[0006]
Here, the selection of the incident angle θ of the
[0007]
FIG. 6 is an example of the plate wave mode table, in which the horizontal axis represents the product of the plate thickness t and the flaw detection frequency f, and the vertical axis represents the incident angle θ. In this figure, a 0, a 1, a 2, ... (A mode), s 0, s 1,
[0008]
For this reason, in Japanese Patent Application Laid-Open No. 61-91567, when detecting an internal defect of a strip with a plate wave, the horizontal angle and the incident angle of the tire type probe are adjusted so that the intensity of the end face echo (back echo) becomes maximum. The sensitivity is adjusted by a sensitivity adjuster so that the maximum intensity of the end face echo becomes 100% on the CRT display screen, and a defect echo equal to or higher than a preset level is detected. There has been proposed an automatic plate wave flaw detector which automatically performs defect detection.
[0009]
[Problems to be solved by the invention]
However, the above-mentioned conventional automatic plate wave flaw detector has the following problems.
(1) When selecting the incident angle of the tire-type probe, after setting a predetermined set value, the end face echo intensity is read, and the end face echo intensity is stored in the storage device. Next, after changing the incident angle by a predetermined angle, the end face echo intensity is read again, compared with the previously stored end face echo intensity, and when it exceeds, the intensity is maximized, and the incident angle at that time is set. . If it does not exceed the predetermined angle, the predetermined angle is changed to the opposite direction, and the incident angle is set to the previously stored end face echo intensity. Therefore, since it is determined whether or not the end face echo intensity has exceeded the initial predetermined setting value, when the incident angle is changed from the initial setting value to a direction away from the maximum end face echo intensity, the original maximum value is obtained. There is a problem that it is not possible to set the incident angle to obtain the end face echo intensity of
(2) After setting the predetermined angle, if the angle is changed in a certain direction and the maximum echo intensity is not updated, the angle is changed again in the reverse direction, which takes time. If this processing is performed while the material to be detected is running, flaw detection cannot be performed during the processing, and if it takes time, the length of time during which flaw detection cannot be performed becomes longer, which is a problem.
(3) The sensitivity is adjusted after setting the incident angle so that the end face echo becomes 100% on the CRT display screen. However, as described above, the incident angle is often not set to an appropriate angle. This will increase the sensitivity. This makes it easy to detect noise, and there is also a problem that it is impossible to determine whether a signal detected at a certain level or higher is due to a defect or not.
[0010]
The present invention has been made in order to solve the above-mentioned problems, and an object of the present invention is to accurately and quickly set an incident angle at which a maximum end face echo intensity is obtained at the time of plate wave ultrasonic flaw detection. To provide a plate wave ultrasonic flaw detection method capable of detecting a defect in a state where a plate wave ultrasonic wave is generated at a maximum and setting an optimum incident angle even while the material to be detected is running. It is in.
[0011]
[Means for Solving the Problems]
Lamb wave ultrasonic testing method of the present invention, by transmitting ultrasonic waves from an ultrasonic probe placed opposite to be movable relative to test object material at a predetermined incident angle and flaw detection frequency Lamb wave ultrasonic Is propagated in the material to be inspected in a direction orthogonal to the relative movement direction, a reflected wave from a defect in the material to be inspected is received by the ultrasonic probe, and a defect in the material to be inspected is detected in accordance with the signal level. In the method of detecting, the initial incident angle is determined using the material of the material to be inspected previously inspected with the test piece, the incident angle in the stationary state for each plate thickness, and for the material to be inspected in the running state and the stationary state, The end face echo height is observed at the initial incident angle, and if the detected end face echo height is equal to or more than a set value , flaw detection is performed at the initial incident angle.If the end face echo height is equal to or less than the set value , the initial Change the angle of incidence within a specified range at a specified pitch to make the end face eco-friendly. The height determines the angle of incidence becomes maximum, and performs the flaw in this angle of incidence (claim 1).
[0014]
Normally, to detect a defect in a traveling flaw detection material using a plate wave ultrasonic wave, flaw detection sensitivity for detecting a defect to be detected, a sensitivity correction curve by ultrasonic attenuation for each flaw detection material material, An incident angle and a flaw detection frequency for each plate thickness are required. Therefore, first, the flaw detection sensitivity, the sensitivity correction curve, the incident angle, and the flaw detection frequency are investigated in a static state using a test piece cut out from the flaw detection material, and stored in a computer for each flaw detection material material and plate thickness. Let it be.
[0015]
Here, empirically, the static state and the running state of the material to be inspected differ depending on the flatness of the material to be inspected, the state of the running line, and the positional relationship between the running line and the tire-type probe, and were investigated in a static state. Even if the result is set, the echo intensity from the end face in the width direction of the material to be inspected does not become maximum in the running state.
[0016]
Therefore, in the present invention, the initial incident angle θ 0 is set using the result of the investigation using the above-mentioned test piece in a stationary state, the flaw detection is performed with this initial value, and the end face is determined using the plate width length of the flaw-detected material. The height E 0 of the reflected echo from the object is recognized. When the end face echo height E 0 is equal to or larger than a certain set value A 0, it is determined that the plate wave ultrasonic wave is sufficiently generated , and the flaw detection is performed at the initial incident angle θ 0 without performing the automatic angle change described later. I do.
[0017]
When the set value A 0 or less with the end face echo height E 0 is the initial angle of incidence theta 0 or et predetermined range ± [Delta] [theta] around the initial incident angle theta 0 at a predetermined pitch p with angle in one direction Change and read the end face echo height at that angle sequentially. For example, if the initial incident angle θ 0 = 30 deg and the change range ± Δθ = ± 2 deg and the pitch p = 0.1 deg, set the angle once to 28 deg, then change the angle at 0.1 deg pitch to 32 deg, or set it once to 32 deg Then, the angle is changed at a pitch of 0.1 deg to 28 deg. The end face echo height is read for each angle pitch, and when the angle change of the predetermined range ± Δθ is completed, the incident angle is set to the angle at which the maximum end face echo height is obtained in the predetermined range ± Δθ. Set. After a series of these operations, flaw detection is started.
[0018]
As described above, the result of the investigation from the test piece in the stationary state is used as an initial value. When the end face echo height is equal to or more than the set value, the flaw detection is performed as it is, and when the echo height is equal to or less than the set value, the initial set value is centered. By changing the angle of the predetermined range in one direction to find the maximum end face echo height and performing flaw detection at the incident angle of this maximum end face echo height, the optimum incident angle that can obtain the maximum end face echo intensity is accurately and quickly Can be automatically set, and the defect can be detected in a state where the plate wave ultrasonic waves are generated at the maximum. Further, since it is possible to set the optimal incident angle at high speed, it is possible to set the optimal incident angle even during running of the test object material. In the continuous processing line, it is preferable that the setting be performed in a low-speed running state during the operation for operation.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail based on an embodiment illustrated. This is an example in which the incident angle θ of the ultrasonic wave transmitted from the tire-type probe to the material to be detected is automatically adjusted. FIG. 1 is a block diagram showing a configuration of a plate wave ultrasonic flaw detector according to the present invention.
[0020]
In FIG. 1, a plate wave
[0021]
The
[0022]
Next, the traveling position of the flaw detection material is grasped from the traveling line information of the flaw detection material, and after the tip of the flaw detection material passes, reception of the reflection signal of the flaw detection material is started under the previously set conditions. Therefore, while reading the end face echo height, the inclination angle of the
(1) First, set the angle of incidence findings described above as an initial value, to observe the end surface echo height in the initial angle of incidence theta 0.
(2) When the observed end face echo height E 0 is equal to or greater than a certain set value A 0, it is determined that the plate wave ultrasonic wave is sufficiently generated, and the automatic angle control is not performed. Then, the flaw detection gate is set based on the board width information of the flaw-detected material, and flaw detection is started.
(3) On the other hand, when the observed end face echo height E 0 is equal to or less than a certain set value A 0, the following automatic angle control is performed. That is, from the initial incident angle θ 0 , the angle is set to the lower limit angle (θ 0 −Δθ) of the angle control range ± Δθ, the angle is changed by the angle control pitch p, and the end face echo height is read for each pitch. This is continuously performed at the angle control pitch p up to the upper limit angle (θ 0 + Δθ) of the angle control range ± Δθ in the + direction. Note that this angle change may be performed from the + side to the − side in reverse to the above.
(4) In the angle control range (-Δθ~ + Δθ), determine the maximum end surface echo height E 1max, setting the incident angle theta 1 which the maximum edge surface echo height E 1max is obtained.
(5) when the set value A 1 or there is a maximum edge echo height E max is determined that sufficient plate wave ultrasound is generated by the angle control, the flow advances to step (7), flaw detection gate Is set based on the board width information of the material to be detected , and the flaw detection is started at an incident angle θ 1 of the maximum end face echo height E 1max .
(6) On the other hand, when the set value A 1 below there is a maximum edge echo height E 1max is testing sensitivity is determined to be insufficient, increasing the flaw detection sensitivity so that its end surface echo height is 100% after, the flow advances to step (7), the flaw detection gate with set based on the plate width information of the flaw material starts to flaw detection at an incident angle theta 1 of the largest end surface echo height E max.
[0023]
With the above processing, if the angle control is not required, the automatic angle control is not performed, and if the angle control is required, the automatic angle change is continuously performed, and the maximum end face echo intensity within a predetermined range is performed. Is set at an angle that can obtain the optimum angle of incidence at which the plate wave ultrasonic wave is generated to the maximum. Since the angle change range is appropriately set centered on the initial setting value checked in advance, it is possible to reliably detect the angle at which the maximum end face echo intensity is obtained.
[0024]
In addition, in order to accurately control the incident angle, it is ideally desirable that the material to be inspected is stationary. However, since the material to be inspected in the continuous processing line is always running, the stationary state is desired. It is difficult to control the angle automatically. On the other hand, as shown in FIG. 3, the traveling line of the material to be inspected performs a predetermined operation on the material to be inspected traveling at a low speed by reducing the line speed at the tip end of the material to be inspected. When this work is completed, the line speed is accelerated, and in this high-speed running state, the end face echo fluctuates greatly without changing the angle depending on the coating state of the couplant, so if angle control is performed in this state, It is difficult to determine whether the end face echo height varies depending on the angle or the application state of the couplant. Furthermore, while the automatic angle control is being performed, the flaw-detected material cannot be flaw-detected, so that the length thereof becomes longer during high-speed running.
[0025]
Therefore, in the present invention, line speed information is received from the traveling line of the material to be inspected, automatic angle control is performed in a low speed state, and when the line speed is accelerated, the automatic angle control ends at that point, and until that end. By setting the angle at which the maximum end-face echo height is obtained between the two, accurate automatic angle control can be performed.
[0026]
FIG. 4 is a graph showing the transition of the end face echo height when the automatic angle control is performed with the initial incident angle θ 0 = 17.5 deg, the angle control range ± Δθ = ± 2 deg, and the angle control pitch p = 0.1 deg. is there. FIG As is apparent from, it was possible to obtain an optimum incident angle 16.7deg 100% end surface echo height with respect to the end face echo height of 50% at the time of setting the initial angle of incidence theta 0. Further, by obtaining an end face echo height of 100% with respect to 50%, a result was obtained that sensitivity was doubled. Moreover, as a result of evaluating 1000 flaw-detected materials by such angle control, a result was obtained in which sensitivity was increased by a factor of up to three times.
[0027]
In the above, an example in which the incident angle is automatically adjusted has been described. However, the present invention is not limited to this, and in the case where the flaw detection frequency is automatically adjusted, both the incidence angle and the flaw detection frequency are automatically adjusted in the same manner as described above. It goes without saying that you can do it.
[0028]
【The invention's effect】
As described above, the present invention provides a Lamb wave ultrasonic inspection by ultrasonic predetermined incident angle, the material of the test object material examined in advance specimens, the initial incident angle using the angle of incidence of quiescent per thickness Is determined , the end surface echo height is observed at the initial incident angle with respect to the material to be inspected in a running state or a stationary state, and if the detected end surface echo height is equal to or more than a set value , the flaw detection is performed at the initial incident angle. When the detected end face echo height is equal to or less than the set value, the initial incident angle is changed within a predetermined range at a predetermined pitch to determine an incident angle at which the end face echo height is maximized, and this incident angle is determined. The following effects can be obtained because the flaw detection is performed by using
(1) The optimal angle of incidence for obtaining the maximum end-face echo intensity can be accurately and automatically set at high speed, and it is possible to detect defects while plate wave ultrasonic waves are being generated at the maximum. Can reliably be automatically detected.
(2) Since it is possible to set the optimal incident angle at high speed, it is possible to set the optimal incident angle even during running of the test object material, traveling test object material entire defect detection Becomes possible.
[Brief description of the drawings]
FIG. 1 is a block diagram of an apparatus for carrying out a plate wave ultrasonic flaw detection method of the present invention.
FIG. 2 is a flowchart showing a processing flow of the plate wave ultrasonic flaw detection method of the present invention.
FIG. 3 is a graph showing examples and timings of running lines for performing the plate wave ultrasonic flaw detection method of the present invention.
FIG. 4 is a graph showing the results of automatic angle control of the plate wave ultrasonic flaw detection method of the present invention.
FIG. 5 is a sectional view showing an outline of a tire-type probe used in the present invention.
FIG. 6 is a graph showing an example of a plate wave mode table of plate wave ultrasonic waves used in the present invention.
[Explanation of symbols]
DESCRIPTION OF
Claims (1)
予め試験片で調査した被探傷材の材質、板厚毎の静止状態の入射角を用いて初期入射角を決定し、走行状態や静止状態の被探傷材に対して、前記初期入射角で端面エコー高さを観測し、この検出された端面エコー高さが設定値以上の場合、前記初期入射角で探傷を行い、前記端面エコー高さが設定値以下の場合、前記初期入射角を所定の範囲内を所定のピッチで変更して端面エコー高さが最大となる入射角を決定し、この入射角で探傷を行うことを特徴とする板波超音波探傷方法。By transmitting an ultrasonic wave at a predetermined incident angle and a flaw detection frequency from an ultrasonic probe that is disposed so as to be relatively movable with respect to the flaw detection material, the plate wave ultrasonic wave is transmitted into the flaw detection material with the relative movement direction. Propagating in the orthogonal direction, receiving the reflected wave from the defect of the material to be inspected by the ultrasonic probe, in the method of detecting the defect of the material to be inspected according to the signal level,
The material of the test object material examined in advance specimens for using the incident angle of the stationary state of each thickness determines the initial angle of incidence, test object material traveling state or still state, the end face at the initial angle of incidence Observe the echo height, if the detected end face echo height is equal to or greater than a set value , perform flaw detection at the initial incident angle, if the end face echo height is equal to or less than a set value , the initial incident angle is set to a predetermined value A plate wave ultrasonic flaw detection method characterized by determining an incident angle at which the end face echo height is maximized by changing the range at a predetermined pitch, and performing flaw detection at this incident angle.
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