JPS61292546A - Detection for shape of surface crack - Google Patents
Detection for shape of surface crackInfo
- Publication number
- JPS61292546A JPS61292546A JP13409385A JP13409385A JPS61292546A JP S61292546 A JPS61292546 A JP S61292546A JP 13409385 A JP13409385 A JP 13409385A JP 13409385 A JP13409385 A JP 13409385A JP S61292546 A JPS61292546 A JP S61292546A
- Authority
- JP
- Japan
- Prior art keywords
- crack
- potential difference
- ratio
- aspect ratio
- depth
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Landscapes
- Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)
Abstract
Description
【発明の詳細な説明】
〔発明の利用分野〕
本発明は金属構造部材に発生したき裂を検出するき裂検
出方法に係り、特に表面き裂の形状を精度よく検出する
のに好適な方法に関する。[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a crack detection method for detecting cracks generated in metal structural members, and is particularly suitable for detecting the shape of surface cracks with high accuracy. Regarding.
従来のポテンシャル法によるき裂検出方法としてはいわ
ゆる４端子法と呼ばれるものがある・それは一対の給電
端子とその内側に一対の測定端子を一列に配列した探触
子を構造部材の表面を走査して、電位差分布の変化から
き裂を検出するものである。き裂の判定はき裂がないと
思われる領域における電位差を基準電位差とし、それよ
りも大きい電位差となったところにき裂があるとするも
のである。従って４端子法においてはき裂の有無及びき
裂のある程度の形状は判定できても、き裂の形状を精度
よく求めることはできないという欠点があった。A conventional crack detection method using the potential method is the so-called four-terminal method.It scans the surface of a structural member with a probe that has a pair of power supply terminals and a pair of measurement terminals arranged in a row inside the probe. This method detects cracks from changes in potential difference distribution. A crack is determined by using a potential difference in a region where no crack is expected to be present as a reference potential difference, and determining that a crack exists where the potential difference is larger than that. Therefore, although the four-terminal method can determine the presence or absence of a crack and the shape of the crack to some extent, it has the disadvantage that the shape of the crack cannot be determined with high accuracy.
本発明の目的は構造部材に生じた欠陥または表面き裂の
形状を簡易的ではあるが、小型コンピュータにより精度
よく検出可能な方法を提供することにある。An object of the present invention is to provide a method that is simple but capable of accurately detecting the shape of defects or surface cracks occurring in structural members using a small computer.
種々のアスペクト比の表面欠陥を有する試験片を用いて
、欠陥に直交する方向に直流電流を印加し、欠陥周辺の
電位分布或いは電位差分布を測定した結果、表面欠陥近
傍での欠陥をはさんだ位置での電位差は欠陥の先端で大
きく変化し、欠陥の最深点で最大値を示した。表面欠陥
の各位置での欠陥深さと電位差との間には一意的な関係
があったが、両者の関係は欠陥のアスペクト比によって
異なった。但し、アスペクト比が０．２５ よりも小さ
くなると両者の関係はアスペクト比には依存しなくなる
傾向にあることが分かった。また有限要素法を用いて表
面欠陥を有する部材の電場を解析し、試験片での測定結
果と比較した結果１両者はよく一致することが分かった
。従って、数種類のアスペクト比、深さを有する欠陥の
要素を作成しておき１部材表面の欠陥周辺での電位差分
布を測定して、電位差分布によく対応するアスペクト比
の要素を抽出して電位差分布を比較し、電位差分布に相
違があれば要素の接点位置を部分的に修正して電場を解
析し、一致したときの欠陥形状を実際の欠陥形状とすれ
ば精度よく欠陥形状を求められることが分かった。しか
しこの方法では精度は非常に良いけれども、形状決定に
時間がかかるし、有限要素法の計算が可能な比較的大型
のコンピュータを必要とする。そこで疲労により形成さ
れた種々の板厚のステンレス鋼管内面のき裂の形状を電
位差測定結果から判定するに当たり、大型のコンピュー
タで解析した種々のアスペクト比のき裂に対する電位分
布を基に電位差測定端子間距離の板厚に対する比から電
位差比とき裂深さ、或いはアスペクト比とき裂深さのマ
スターカーブを作成することによりき裂形状を簡易的に
求めた結果、比較的精度良くき裂形状を判定できること
が判った。Using test pieces with surface defects of various aspect ratios, we applied a direct current in a direction perpendicular to the defects and measured the potential distribution or potential difference distribution around the defects. The potential difference at the tip of the defect changed significantly and reached its maximum value at the deepest point of the defect. Although there was a unique relationship between the defect depth and the potential difference at each location of the surface defect, the relationship between the two differed depending on the aspect ratio of the defect. However, it has been found that when the aspect ratio becomes smaller than 0.25, the relationship between the two tends to become independent of the aspect ratio. In addition, we analyzed the electric field of a member with surface defects using the finite element method and compared it with the results measured on a test piece.1 It was found that the two coincided well. Therefore, by creating defect elements with several types of aspect ratios and depths, measuring the potential difference distribution around the defect on the surface of one member, and extracting elements with aspect ratios that closely correspond to the potential difference distribution, the potential difference distribution can be calculated. If there is a difference in the potential difference distribution, the contact position of the element is partially corrected, the electric field is analyzed, and the defect shape when they match is taken as the actual defect shape.The defect shape can be determined with high accuracy. Do you get it. However, although this method has very high accuracy, it takes time to determine the shape and requires a relatively large computer capable of calculation using the finite element method. Therefore, in order to determine the shape of cracks formed on the inner surface of stainless steel pipes of various thicknesses due to fatigue from the potential difference measurement results, we determined the potential difference measurement terminal based on the potential distribution for cracks with various aspect ratios analyzed using a large computer By creating a master curve of potential difference ratio and crack depth, or aspect ratio and crack depth from the ratio of the gap distance to the plate thickness, the crack shape can be determined with relatively high accuracy. It turns out it can be done.
゛〔発明の実施例〕
以下、本発明の実施例を図により説明する。第１図は直
流電流を印加したときの表面き裂近傍での電位分布を示
す等電位線図である。これは厚さ２０ｍｍの平板に表面
厚さ３０ｍｍ、深さ１５ｎｍの半円き裂がある場合につ
いて有限要素法により解析して求めた結果である。き表
面の電位分布に注目すると、等電位線はき表面にもぐり
込む。き表面にもぐり込む等電位線の数はき裂深さに応
じて変化する。また電位分布はき表面に対して対称な分
布を示すことが分かる。即ち、き裂をはさんで電位は逆
の分布を示すことから、き袋位置を判定することは容易
である。勿論、き裂をはさんで電位差を測定するとき裂
のあるところでは電位差は大きくなるため検出できる。[Embodiments of the Invention] Examples of the present invention will be described below with reference to the drawings. FIG. 1 is an equipotential diagram showing the potential distribution near a surface crack when a direct current is applied. This is the result of analysis using the finite element method for a case where a flat plate with a thickness of 20 mm has a semicircular crack with a surface thickness of 30 mm and a depth of 15 nm. If we pay attention to the potential distribution on the surface of the wafer, the equipotential lines sink into the surface of the wafer. The number of equipotential lines that penetrate into the crack surface changes depending on the crack depth. It can also be seen that the potential distribution shows a symmetrical distribution with respect to the surface. That is, since the potential shows an opposite distribution across the crack, it is easy to determine the position of the crack. Of course, when measuring the potential difference across a crack, the potential difference becomes larger where there is a crack, so it can be detected.
次に、き裂周辺の電位分布を計算した結果を第２図に示
す、これは第１図に示したき裂について求めたもので、
き裂から１．２，３，４，５゜１０ｍ５＋離れた位置に
おけるき表面を基準にした電位差分布であ−る。第２図
から分かるようにき裂からＬｏｗ離れた位置でもき裂形
状はある程度判定することが可能である。しかし、き裂
形状の精度よい検出は困難である。特に表面のき裂先端
を特定するのは困難である。ところが測定位置をき裂に
近付けると表面のき裂先端において特異点が現れるので
、表面のき裂先端を決定することは容易となる。また電
位はき裂深さに比例することが分かる。従って、き裂に
沿ってき裂の極近傍でき裂先端の前方から電位分布を測
定するか、き裂をはさんで電位差を測定すればき裂形状
を決定できる。Next, Figure 2 shows the results of calculating the potential distribution around the crack, which was obtained for the crack shown in Figure 1.
This is the potential difference distribution based on the crack surface at positions 1.2, 3, 4, 5 degrees 10 m5+ away from the crack. As can be seen from FIG. 2, it is possible to determine the shape of the crack to some extent even at a low distance from the crack. However, accurate detection of the crack shape is difficult. In particular, it is difficult to identify the crack tip on the surface. However, when the measurement position is brought closer to the crack, a singular point appears at the tip of the crack on the surface, making it easier to determine the tip of the crack on the surface. It can also be seen that the potential is proportional to the crack depth. Therefore, the crack shape can be determined by measuring the potential distribution along the crack in the very vicinity of the crack and from in front of the crack tip, or by measuring the potential difference across the crack.
ところがき裂のアスペクト比ａ／ｃ（ａ：最大き裂深さ
２ｃ：表面におけるき裂長さ）を種々変えてき裂深さ
と電位差との関係を詳細に調べた結果、き裂深さと電位
差との関係はアスペクト比の影響を受けて、それぞれ異
なる。従ってき裂形状を電位差測定結果から精度良く判
定するためには有限要素法により電場を解析し、測定値
と比較演算して両者が一致したときの有限要素法で入力
したき裂形状を実際のき裂形状とすることが必要である
。しかし、この方法は精度は良いけれども、電場を解析
するために有限要素法が適用可能なある程度大型コンピ
ュータが必要であるので、複雑なき裂形状を精度良く求
めなければならないときに好適な方法である。However, as a result of a detailed investigation of the relationship between crack depth and potential difference by varying the crack aspect ratio a/c (a: maximum crack depth, 2c: crack length at the surface), we found that the relationship between crack depth and potential difference was The relationships vary depending on the aspect ratio. Therefore, in order to accurately determine the crack shape from the potential difference measurement results, the electric field is analyzed using the finite element method, the measured value is compared with the calculated value, and when the two match, the crack shape input using the finite element method is determined as the actual It is necessary to have a crack shape. However, although this method has good accuracy, it requires a fairly large computer capable of applying the finite element method to analyze the electric field, so it is suitable when complex crack shapes must be determined with high precision. .
第３図は本発明に係わる欠陥検出装置の外観図である。FIG. 3 is an external view of the defect detection device according to the present invention.
第３図では探傷ヘッドの駆動装置１はほぼ平板に近い構
造物表面のき裂または欠陥を検出できる構造となってい
る。直流ポテンシャル法による探傷ヘッド２０には直流
電流供給用の給電端子５と電位差測定用の測定端子１０
がそれぞれ２列設けである。探傷ヘッド２０はステッピ
ングモータ２５により表面に重直な軸（Ｚ軸）まわりに
回転可能とし、測定及び給電端子を部材表面に押し付け
るための空気シリンダー３０を具備している。更に、探
傷ヘッド２０を２次元子面上を移動可能とするため、Ｘ
軸５１及びＹ軸５６の駆動機構を持ち、おのおのの座標
軸はステッピングモータ５２．５７によって駆動される
。Ｙ軸５６は側板６０に固定され、側板６０にはコンプ
レッサ６１から供給される圧縮空気で作動する吸盤６２
が取り付けてあり、部材表面に駆動装置１を固定する機
能を持つ、従って壁面状の欠陥のみならず天井面の欠陥
の検出も可能である。座標軸駆動用モータ５２，５７は
駆動制御装置６５に接続されており、駆動制御装置６５
はコンピュータ１００によって制御される。In FIG. 3, the flaw detection head driving device 1 has a structure that can detect cracks or defects on the surface of a structure that is almost flat. The flaw detection head 20 using the DC potential method has a power supply terminal 5 for supplying DC current and a measurement terminal 10 for measuring potential difference.
There are two rows of each. The flaw detection head 20 is rotatable around an axis (Z axis) perpendicular to the surface by a stepping motor 25, and is equipped with an air cylinder 30 for pressing measurement and power supply terminals against the surface of the member. Furthermore, in order to make the flaw detection head 20 movable on the two-dimensional surface,
It has a drive mechanism for an axis 51 and a Y-axis 56, and each coordinate axis is driven by a stepping motor 52, 57. The Y-axis 56 is fixed to a side plate 60, and a suction cup 62 operated by compressed air supplied from a compressor 61 is mounted on the side plate 60.
is attached and has the function of fixing the drive device 1 to the surface of the member. Therefore, it is possible to detect not only defects on the wall surface but also defects on the ceiling surface. The coordinate axis drive motors 52 and 57 are connected to a drive control device 65.
is controlled by computer 100.
第４図に電位差測定用の探傷ヘッド２０の構造を示す。FIG. 4 shows the structure of a flaw detection head 20 for potential difference measurement.
探傷ヘッド２０の基板２１はベークライトまたはアクリ
ルのような不導体で作られている。The substrate 21 of the flaw detection head 20 is made of a nonconductor such as Bakelite or acrylic.
直流電流供給用の給電端子５は等間隔に多数配列したも
のを２刺子行に、且つ、端子同士が向かいあうように配
置する。２列の測定端子１ｏはその中央が２列の給電端
子５の中央に、且つそれぞれが隣りあう給電端子の中間
にくるように等間隔で設ける。また、それぞれの給電端
子対に独立して直流電源６６を設けると共に、スイッチ
ング装置６７を設ける。スイッチング装置６７は構造物
に印加する直流電流の極性を一定時間毎に切り換えるこ
とにより測定端子１０と構造物との間に生じる熱起電力
を相殺するためのものである。この場合電位差の測定は
直流電流が安定した後でなければならず、極性を切り換
える直前が最適である。A large number of power supply terminals 5 for supplying direct current are arranged at equal intervals in two sashiko rows, with the terminals facing each other. The two rows of measurement terminals 1o are provided at equal intervals so that their centers are located at the center of the two rows of power supply terminals 5 and are located between adjacent power supply terminals. Furthermore, a DC power supply 66 and a switching device 67 are provided independently for each pair of power supply terminals. The switching device 67 is for canceling the thermoelectromotive force generated between the measurement terminal 10 and the structure by switching the polarity of the direct current applied to the structure at regular intervals. In this case, the potential difference must be measured after the DC current has stabilized, and the best time is just before switching the polarity.
次に、第５図に給電端子５と測定端子１０の基板２１へ
の取付は構造を示す。第５図では端子の数を６個とした
場合の１列の端子のみについて示した６測定端子１０及
び給電端子５は構造物との間に接触抵抗が生じない程度
まで押し付けることが必要であるし、構造物に多少の凹
凸や湾曲があっても全部が同じように接触していなけれ
ばならない。また欠陥形状を精度よく求めようとすれば
第２図に示したように欠陥から１〜２ｍ以内のところで
電位分布を測定しなければならない。そのため測定端子
１ｏの先端は円錐形とし、その後方にフランジを設け、
フランジと基板２１との間にコイルバネを入れ、探傷ヘ
ッド２０を構造物に押し付けたとき、バネにより端子が
均一に構造物に押し付けられるようにし、また、測定端
子距離は正確であることが重要であるから、基板２１に
あける穴は長くし、また案内面としての仕上げを施さな
ければならない。Next, FIG. 5 shows the structure for attaching the power supply terminal 5 and the measurement terminal 10 to the substrate 21. In Figure 5, only one row of terminals is shown when the number of terminals is six, and the six measurement terminals 10 and power supply terminals 5 need to be pressed together to the extent that contact resistance does not occur between them and the structure. However, even if the structure has some unevenness or curvature, it must all be in contact with each other in the same way. Furthermore, in order to accurately determine the shape of a defect, it is necessary to measure the potential distribution within 1 to 2 meters from the defect, as shown in FIG. Therefore, the tip of the measurement terminal 1o is made conical, and a flange is provided behind it.
A coil spring is inserted between the flange and the board 21, and when the flaw detection head 20 is pressed against a structure, it is important that the spring presses the terminals uniformly against the structure, and that the distance between the measurement terminals is accurate. Therefore, the holes drilled in the substrate 21 must be made long and finished to serve as guide surfaces.
以下、電位分布測定方法及び欠陥形状の決定法について
述べる。第１図において複数の直流電源６６からスイッ
チング装置６７を介して探傷ヘッド２０に設けた給電端
子５のそれぞれに等しく直流電流を印加して、構造部材
に均一な電場を形成する。多数の測定端子対１０の間ｌ
こ生じる電位差はスキャナー７０を介して微小電位差計
７１に取り込んで測定され、インターフェース７２を通
してコンピュータ１００に入力され、駆動装置制御装置
６５からの位置情報と合わせて電位差分布としてコンピ
ュータ１００に接続された記録装置１０３に記憶される
。記録された電位差分布からにコンピュータ１００によ
りき裂位置を判定し。Below, a method for measuring potential distribution and a method for determining defect shape will be described. In FIG. 1, DC current is equally applied from a plurality of DC power supplies 66 to each of the power supply terminals 5 provided on the flaw detection head 20 via a switching device 67 to form a uniform electric field in the structural member. between a large number of measurement terminal pairs 10
This generated potential difference is taken in and measured by a micropotentiometer 71 via a scanner 70, inputted to a computer 100 through an interface 72, and recorded as a potential difference distribution along with position information from a drive device control device 65. It is stored in the device 103. The crack position is determined by the computer 100 from the recorded potential difference distribution.
き裂周辺の詳細な電位分布を測定する０次に、電場記憶
装置１０２に記憶されている大型のコンピュータにより
種々のアスペクト比のき裂に対して解析された電場のう
ち、き裂中央でき装面に直角な方向の電位分布を基に電
位差測定端子間距離と被測定構造部材の板厚との比に対
応したき裂中央のき裂深さと電位差比との関係を作成し
、それらからき裂中央のき裂深さを決定し、ひいては全
体のき裂形状を決定するものである。Detailed potential distribution around the crack is measured.Next, among the electric fields analyzed for cracks with various aspect ratios by a large computer stored in the electric field storage device 102, the electrical potential distribution at the crack center is measured. Based on the potential distribution in the direction perpendicular to the surface, we create a relationship between the crack depth at the crack center and the potential difference ratio, which corresponds to the ratio between the distance between the potential difference measurement terminals and the thickness of the structural member to be measured, and from this we create a relationship between the crack depth at the crack center and the potential difference ratio. This determines the central crack depth and, in turn, the overall crack shape.
第６図に直流ポテンシャル法によるき製形状判定の流れ
図を示す。初めに第１図に示した駆動装置１で探傷ヘッ
ド２０を駆動装置内の全域を粗く走査して電位分布を調
べる。このときき裂の発生する方向は構造部材で大体法
っているので、き装面に直交して直流電流が流れるよう
に探傷ヘッド２０の向きをステッピングモータ２５で設
定する。FIG. 6 shows a flowchart for determining the forged shape using the DC potential method. First, using the drive device 1 shown in FIG. 1, the flaw detection head 20 is roughly scanned over the entire area within the drive device to examine the potential distribution. At this time, since the direction in which cracks occur is generally oriented in the structural member, the direction of the flaw detection head 20 is set by the stepping motor 25 so that a direct current flows orthogonally to the surface to be cracked.
もしき裂があれば第３図に示したような電位差分布が生
じるので容易に検出できる。き裂から１０■離れていて
も十分検出可能であるが、浅いき裂の場合は見落とす恐
れもある。５ｍｍ離れた位置で測定するのが安全である
ので、測定端子の間隔は１０ｍ１以下にすれば十分であ
る。き裂形状の測定精度を上げようとすれば測定端子間
距離は２ｒｍが最上であるが、逆に測定時間が増大する
ので、４ｍ程度にするにが良い。実際の測定に当っては
測定端子と同じ測定間隔で電位差分布を測定してき裂の
大体の位置を判定する。第３図に示したように電位差分
布がき裂の周辺に生じるので、き裂がない場合の基準電
位よりも大きい電位差が測定された付近にあると判定さ
れる。き裂形状を精度よく出すためには測定端子間の中
央にき裂が来るよウニ設定しなければならないので、電
位差分布が最大となった位置付近で、測定ヘッド２０を
き表面に直角な方向に細かく走査して電位重分を測定す
る。電位差が最大となったとき測定端子間の中央にき裂
はある。次にその位置でき表面に沿って電位差分布を詳
細に測定する。If there is a crack, it can be easily detected because a potential difference distribution as shown in FIG. 3 will occur. Although it is possible to detect the crack even if it is 10 cm away from the crack, there is a risk that it may be overlooked if the crack is shallow. Since it is safe to measure at a distance of 5 mm, it is sufficient to set the distance between the measurement terminals to 10 m1 or less. If you want to improve the measurement accuracy of the crack shape, the best distance between the measurement terminals is 2rm, but since this increases the measurement time, it is better to set it to about 4m. In actual measurement, the potential difference distribution is measured at the same measurement interval as the measurement terminal, and the approximate location of the crack is determined. As shown in FIG. 3, a potential difference distribution occurs around the crack, so it is determined that the potential difference is near where a potential difference larger than the reference potential when there is no crack is measured. In order to accurately determine the crack shape, it is necessary to set the crack so that it is located in the center between the measurement terminals, so the measurement head 20 is moved in the direction perpendicular to the surface near the position where the potential difference distribution is maximum. The voltage distribution is measured by scanning in detail. When the potential difference is maximum, there is a crack in the center between the measurement terminals. Next, the potential difference distribution along the surface at that location is measured in detail.
次に、電場記憶装置１０２に記憶されている各種のアス
ペクト比を有するき裂のき表面に直角な方向の電位差分
布を基に、測定端子間距離の板厚に対する比に対応する
位置における電位差比とき裂深さの関係をコンピュータ
１００により求める。Next, based on the potential difference distribution in the direction perpendicular to the crack surface having various aspect ratios stored in the electric field storage device 102, the potential difference ratio at the position corresponding to the ratio of the distance between the measurement terminals to the plate thickness is determined. The relationship between the crack depth and the crack depth is determined by the computer 100.
ここで予め大型コンピュータではアスペクト比が例えば
、１，０，０．５，０．２５，０．１２５（７）！裂に
対して電場を求めておく。この電位差比とき裂深さの関
係より各き裂深さに対する電位差比とアスペクト比の関
係をコンピュータ１００により求める。この場合両者の
関係は最もフィッティングが良くなるようにｎ次近似、
例えば５次近似すると良い。次に、この各き裂深さに対
する電位差比とアスペクト比の関係を用いて各アスペク
ト比に対するき裂深さと電位差の関係のマスターカーブ
を例えばアスペクト比が０．１２５から１．０まで０．
０１毎に求める。次に、測定された電位差分布から表面
におけるき裂長さ２ｃ：を決定する。き裂の最深点に対
応する最大の電位差比Ｖ ／ Ｖ 、 ｗａｘを適当な
アスペクト比ａ ／ ｃのマスターカーブに代入してき
裂深さａ傘を求め、ａ傘／ｃ申を計算する。Here, in advance, the aspect ratio of a large computer is, for example, 1, 0, 0.5, 0.25, 0.125 (7)! Find the electric field for the crack. From this relationship between the potential difference ratio and the crack depth, the computer 100 determines the relationship between the potential difference ratio and the aspect ratio for each crack depth. In this case, the relationship between the two is approximated to the nth order for the best fitting.
For example, a fifth-order approximation is recommended. Next, using this relationship between the potential difference ratio and aspect ratio for each crack depth, a master curve of the relationship between the crack depth and potential difference for each aspect ratio is created, for example, from 0.125 to 1.0.
Obtain every 01. Next, the crack length 2c on the surface is determined from the measured potential difference distribution. By substituting the maximum potential difference ratio V/V, wax corresponding to the deepest point of the crack into the master curve of an appropriate aspect ratio a/c, the crack depth a-umbrella is obtained, and the a-umbrella/c ratio is calculated.
ａ傘／Ｃ傘＝ ａ ／ ｃとなるまでマスターカーブを
変え、一致したときのマスターカーブを用いて電位差分
布から全体のき製形状を決定するものである。このとき
、き裂深さａ傘、表面におけるき裂長さ２ｃ傘ともに板
厚の補正をしなければならない。具体的な方法について
次に示す。The master curve is changed until A umbrella/C umbrella = a/c, and the master curve when they match is used to determine the overall molded shape from the potential difference distribution. At this time, the plate thickness must be corrected for both the crack depth a and the surface crack length 2c. The specific method is shown below.
第７図、第８回、第９図、第１０図はそれぞれアスペク
ト比ａ ／ ｃが１．０，０．５，０．２５ および０
．１２５の表面き裂を有する板厚２０ｍｍの板材につい
て有限要素法により電場を解析して得られたき裂の中央
でき表面に垂直な方向の電位分布である。板厚で基準化
したき裂の深さａ ／ ｔはき裂中央の最深点０ 、０
．１２５．０．２５ 、０．３７５．０．５ 。Figures 7, 8, 9, and 10 have aspect ratios a/c of 1.0, 0.5, 0.25, and 0, respectively.
．． This is the potential distribution in the direction perpendicular to the surface at the center of the crack, obtained by analyzing the electric field using the finite element method for a plate material with a thickness of 20 mm and having 125 surface cracks. The crack depth a/t standardized by plate thickness is the deepest point at the center of the crack 0, 0
．． 125.0.25, 0.375.0.5.
０．６２５および０．７５である。き裂が無ければ電位
差はき裂からの距離に比例して増加するが、き裂があれ
ば、き裂の周辺の電場が乱れ、き裂が深い場合にはき裂
から相当前れたところでも電場は乱れる。また、アスペ
クト比が小さいほど電場の乱れが激しく、き裂をはさん
で測定される電位差は大きくなる。通常第１図に示した
ような電位差分布測定装置の測定端子間距離ａは一定で
ある。ところが、測定される部材の板厚は様々である。0.625 and 0.75. If there is no crack, the potential difference will increase in proportion to the distance from the crack, but if there is a crack, the electric field around the crack will be disturbed, and if the crack is deep, the potential difference will increase in proportion to the distance from the crack. The electric field is also disturbed. Furthermore, the smaller the aspect ratio, the more severe the disturbance of the electric field, and the larger the potential difference measured across the crack. Usually, the distance a between the measurement terminals of a potential difference distribution measuring device as shown in FIG. 1 is constant. However, the thickness of the member to be measured varies.
第３図に示したように測定位置によって電位差あるいは
電位差比とき裂深さとの関係は異なるので、測定位置に
対応する電位差比とき裂深さとの関係を予め求めておく
ことが必要である。しかし、それは多大な労力と費用を
要する。それよりは第７図、第８図、第９図、第１０図
のような基本電位差分布を電場記憶装置１０２に記憶さ
せておき、電位差測定の都度、測定位置に対応する電位
差比とき裂深さとの関係をコンピュータ１００で求める
方が合理的である。第７図、第８図、第９図。As shown in FIG. 3, the relationship between the potential difference or the potential difference ratio and the crack depth varies depending on the measurement position, so it is necessary to obtain the relationship between the potential difference ratio and the crack depth corresponding to the measurement position in advance. However, it requires a lot of effort and cost. Rather, basic potential difference distributions such as those shown in FIGS. 7, 8, 9, and 10 are stored in the electric field storage device 102, and each time the potential difference is measured, the potential difference ratio and crack depth corresponding to the measurement position are stored. It is more reasonable to use the computer 100 to find the relationship between Figures 7, 8, and 9.
第１０図の測定位置に対応する位置の電位差から第１１
図に示すような電位差比Ｖ／Ｖ、とき裂のアスペクト比
ａ ／ ｃの関係を各き裂深さａ ／ ｔについて作成
する。次に、両者の関係をｎ次近似、例えば次式のよう
に５次近似する。11 from the potential difference at the position corresponding to the measurement position in Figure 10.
The relationship between the potential difference ratio V/V and the crack aspect ratio a/c as shown in the figure is created for each crack depth a/t. Next, the relationship between the two is approximated to the nth order, for example, to the fifth order as shown in the following equation.
Ｖ ／ Ｖ 、、＝Ａ ｏ ＋ Ａ １ ａ ／ ｃ
＋ Ａ２ ａ ／ ｃ２＋ Ａ ３ ａ ／ ｃ３＋
Ａ ４ ａ ／ ｃ’ ＋ Ａ ｓ ａ ／ ｃ’これ
を用いてアスペクト比ａ／ｃ＝ｏ、ｏｌ きざみで各
き裂深さに対する電位差を求め、最終的には第１２図の
ように各アスペクト比に対する電位差比Ｖ／Ｖ、とき裂
深さａ ／ ｔのマスターカーブを作成する。この場合
にも電位差Ｖ／Ｖ、とき裂深さａ ／ ｔのマスターカ
ーブはｎ次近似、例えば次式のように５次近似する。V / V,, = A o + A 1 a / c
+ A2 a / c2+ A 3 a / c3+
A 4 a/c' + A sa/c' Using this, calculate the potential difference for each crack depth in steps of aspect ratio a/c=o, ol, and finally calculate each aspect ratio as shown in Figure 12. Create a master curve of the potential difference ratio V/V and the crack depth a/t. In this case as well, the master curve of the potential difference V/V and the crack depth a/t is approximated to the nth order, for example, to the fifth order as shown in the following equation.
Ｖ／Ｖ、＝Ｒ０＋Ｂ１ａ／ｌ＋Ｂ、ａ／ｌ”＋Ｂ、ａ／
１３＋ Ｂ ４ａ／ｌ’ ＋ Ｂ 、ａ／１５ここでは
アスペクト比がａ ／ ｃ ＝０．１２５からａ／ ｃ
＝ １ 、０ までのき裂について電場を解析した
ので電位差比Ｖ／Ｖ、とき裂深さａ ／ ｔのマスター
カーブはａ ／ ｃ ＝ ０．１２５からａ ／ ｃ
＝ １ 、０ までの間について作成するものとする
。ただし、第１２図ではａ ／ ｃ ＝ ０ 、０１
毎のカーブを全て描くと繁雑で分かり難くなるのでａ
／ ｃ ＝０．１２５゜０．２５，０．５および１．０
の４本だけ描いた。V/V,=R0+B1a/l+B,a/l"+B,a/
13+ B 4a/l' + B , a/15 where the aspect ratio is a/c = 0.125 to a/c
Since we analyzed the electric field for cracks up to = 1 and 0, the master curve for potential difference ratio V/V and crack depth a/t is from a/c = 0.125 to a/c
= 1 to 0. However, in Figure 12, a/c = 0, 01
If you draw all the curves for each curve, it will be complicated and difficult to understand, so a
/ c = 0.125° 0.25, 0.5 and 1.0
I drew only 4 of them.
次に、測定された電位差分布からのき製形状の決定法で
ある０表面き裂の近傍で電位差を測定すれば、第３図の
ような電位差分布が得られ、部材の表面におけるき裂長
さ２０傘は電位差が急激な変化をする箇所として捉えら
れ、容易に決定される。Next, by measuring the potential difference in the vicinity of the zero surface crack, which is a method for determining the forged shape from the measured potential difference distribution, the potential difference distribution as shown in Figure 3 is obtained, and the crack length on the surface of the member is determined. 20 umbrellas can be seen as a location where the potential difference changes rapidly and can be easily determined.
き裂の深さについては、まず、き裂の最深点に相当する
と思われる電位差の最大値を用いてき裂のアスペクト比
を決定する。即ち、電位差比の最大値Ｖ ／ Ｖ 、
ｗａｘを第１２図に示したような適当なｎ次近似された
電位差比Ｖ ／ Ｖ ｏ とき裂深さａ ／ ｔのマス
ターカーブに代入して最深き裂深さａ傘を、次いでａ串
／Ｃ傘を求め、これを″マスターカーブのアスペクト比
ａ ／ ｃと比較する。両者が一致していなければ、改
めてＢ 傘／ ｃ申のマスターカーブにより最深き裂深
さａ・−を求め、更にＢ＊＊／Ｃ傘を求めてマスターカ
ーブのアスペクト比ａ／Ｃと比較する。この作業が両者
が一致するまで繰り返して一致したとき裂深さを最深き
裂深さとする。そしてこの一致したときのマスターカー
ブに各測定位置における電位差比を代入することにより
き裂全体の形状を決定するものである。以下、具体例を
用いて説明する。Regarding the depth of the crack, first, the aspect ratio of the crack is determined using the maximum value of the potential difference that is thought to correspond to the deepest point of the crack. That is, the maximum value of the potential difference ratio V/V,
wax to the appropriate n-th approximated master curve of potential difference ratio V / Vo and crack depth a / t as shown in Fig. 12 to find the deepest crack depth a, then a skewer / Find the C umbrella and compare it with the aspect ratio a/c of the master curve. If the two do not match, find the deepest crack depth a・- again using the master curve of the B umbrella/c, and then Find the B**/C umbrella and compare it with the aspect ratio a/C of the master curve.This process is repeated until the two match, and when they match, the crack depth is set as the deepest crack depth.And when this matches, The shape of the entire crack is determined by substituting the potential difference ratio at each measurement position into the master curve.A specific example will be used below to explain.
第１３図は内面にスリットを有する直径１２インチのス
テンレス鋼管を疲労試験したき裂を発生させ、スリット
を旋削により除去した後、き裂周辺で得られた電位差分
布である。横軸はき裂中央に相当すると思われる位置を
原点とした表面方向の測定位置Ｘ（■）、縦軸は電位差
Ｖ（μＶ）である、ここでｖｏはき裂がないところでの
電位差であり、第１３図で分かるようにき裂がないとこ
ろではｖｏはほぼ一定である。き裂があるところでは第
３図と同様に電位差は大きくなる。第３図と同様に表面
でのき裂の先端で電位差分布に特異点が現れるので、表
面のき裂長さ２Ｇは容易に決定される６表面のき裂長さ
２Ｇの決定法としては種々考えられる。ここで電位差比
が急激に立ち上がる前の箇所と立ち上がった後の箇所と
を直線で結び、それが電位差比Ｖ／Ｖ、＝１．０２
と交差する地点、電位差比が急激に立ち上がった後の数
箇所の電位差分布をｎ次近似して、それと基準電位差Ｖ
。どの交点、あるいはき裂に相当する位置の全体の電位
差分布ｎ次近似して、それと基準電位差ｖ０との交点で
決定する方法の３案を採用した。き裂の先端付近を細か
く測定していれば、どの方法でも表面き裂長さは精度良
く決定される。FIG. 13 shows the potential difference distribution obtained around the crack after a fatigue test was performed on a 12-inch diameter stainless steel pipe with a slit on the inner surface, and the slit was removed by turning. The horizontal axis is the measurement position X (■) in the surface direction with the origin at a position thought to correspond to the center of the crack, and the vertical axis is the potential difference V (μV), where vo is the potential difference where there is no crack. , as seen in FIG. 13, vo is almost constant where there is no crack. Where there is a crack, the potential difference increases as in FIG. 3. As shown in Figure 3, a singular point appears in the potential difference distribution at the tip of the crack on the surface, so the surface crack length 2G can be easily determined. 6 There are various ways to determine the surface crack length 2G. . Here, connect the point before the potential difference ratio suddenly rises and the point after it rises with a straight line, and it becomes the potential difference ratio V/V, = 1.02
The n-th approximation is made to the potential difference distribution at several points after the potential difference ratio suddenly rises, and the potential difference between it and the reference potential difference V is calculated.
. Three methods were adopted: which intersection point or the n-th order approximation of the entire potential difference distribution at a position corresponding to a crack is determined by the intersection point between this and the reference potential difference v0. Regardless of the method, the surface crack length can be determined with high accuracy as long as the vicinity of the crack tip is precisely measured.
第１３図ではき裂に相当する位置の電位差分布を５次近
似して、それと基準電位差ｖ０ との交点で決定する方
法を採用した結果、２ｃ＝２２．５ ｍである６次に、
き裂の７スペクト比ａ ／ ｃ、言い換えれば最大き裂
深さの推定である。電位差比が最大となるところがき裂
の最深点に対応する。最深点の電位差比はＶ／ Ｖ、璽
ａｘ＝３８．０／２４．７５＝１．５３５である１次に
、電位差測定位置に対応する０、０１毎のアスペクト比
に対する電位差比とき裂深さの関係のマスターカーブの
作成である。いま測定端子間距離はｆｌ＝５ｍｍで、配
管の板厚はｔ＝１５．７ｍである。有限要素法で得られ
たマスターカーブの対応する位置はｎ’ ＝５／１５．
７ ｘ２０＝６．４ ｍとなる。前述した第１１図と
第１２図は測定端子間距離Ｑ’＝６．４ｍにおける電位
差から得られたマスターカーブである。このマスターカ
ーブの中最初にどれか１つの関係を用いて最大き裂深さ
を計算する０例えば、ａ ／ ｃ ＝０．８のマスター
カーブに最深点の電位差比Ｖ／Ｖ、ｍａｘ＝１．５３５
を代入すると、き裂深さはａ拳＝６．３２ ｍとなる。In Fig. 13, the potential difference distribution at the position corresponding to the crack is approximated to the fifth order, and the method is determined by the intersection of this and the reference potential difference v0. As a result, the sixth order, where 2c = 22.5 m, is obtained.
7 spectral ratio a/c of the crack, in other words an estimate of the maximum crack depth. The point where the potential difference ratio is maximum corresponds to the deepest point of the crack. The potential difference ratio at the deepest point is V / V, ax = 38.0 / 24.75 = 1.535. First order, the potential difference ratio and crack depth for the aspect ratio of 0, 01 corresponding to the potential difference measurement position This is the creation of a master curve for the relationship. Now, the distance between the measurement terminals is fl = 5 mm, and the thickness of the pipe is t = 15.7 m. The corresponding position of the master curve obtained by the finite element method is n' = 5/15.
7 x 20 = 6.4 m. The above-mentioned FIGS. 11 and 12 are master curves obtained from the potential difference at the distance between the measurement terminals Q'=6.4 m. First, calculate the maximum crack depth using any one of the relationships in this master curve. 535
Substituting , the crack depth becomes a = 6.32 m.
ａ傘＝６．３２ を板厚補正するとａ傘＝４．９９ｍ
ｍとなり、ａ傘／Ｃ傘＝４．９９／１１．２５＝０．４
４である。これはマスターカーブのａ／ ｃ ＝ ０
、８ とは異なるので、改めてａ ／ ｃ ＝０．４
４のマスターカーブにＶ／Ｖ。ｍａｘ＝１．５３５を代
入すると、き裂深さはａ＊＊＝５．１７ｍｍ 、板厚補
正して＠＊＊＝４．Ｑ８ ｍとなり、ａｌｌｌｌ ／
ｃ傘＝０．３６ である、これを繰り返して最終的には
ａ ／ ｃ ＝ ０ 、３４ でａ＝３．８９ ｍと
なり、収束した。When a-umbrella = 6.32 is corrected for plate thickness, a-umbrella = 4.99m
m, and a umbrella/C umbrella = 4.99/11.25 = 0.4
It is 4. This is the master curve a/c = 0
, 8, so a/c = 0.4 again.
V/V on the master curve of 4. By substituting max=1.535, the crack depth is a**=5.17mm, and after correcting the plate thickness, @**=4. Q8 m, allll /
c umbrella = 0.36. This was repeated until finally a/c = 0, 34 and a = 3.89 m, converging.
次に、配管の内表面を旋盤により更に旋削して板厚をｔ
＝１４．４ ｒｍと薄くした後に、再び同じき裂につい
て電位差分布を測定した。その結果を第１４図に示す。Next, the inner surface of the pipe is further turned using a lathe to reduce the plate thickness to t.
After reducing the thickness to 14.4 rm, the potential difference distribution was again measured for the same crack. The results are shown in FIG.
第１３図と同じようにして表面き裂長さ２ｃ＝＝２２．
５ｍｍ、最大の電位差比Ｖ／Ｖ、ｍａｘ＝１．２８２が
求まる。有限要素法で得られたマスターカーブの対応す
る位置はΩ’ ＝５／１４．４Ｘ２０＝７．０ ｍとな
る。第７図、第８図、第９図、第１０図よりＱ＝７．０
ｍにおける電位差から第１５図の電位差比Ｖ／Ｖ、とア
スペクト比ａ／Ｃの関係が得られ、第１５図よりａ ／
ｃ ＝０．０１ きざみで電位差Ｖ／Ｖ、とき裂深
さａ／ｌの関係が第１６図のように得られる。最大の電
位差比Ｖ／ Ｖ、ｍａｘ＝１．２８２を第１６図のａ
／ ｃ ＝０．８ のｎ次近似式に代入してａ傘＝５．
０５ ｍｍ、板厚補正とてａ傘＝３．６４ ｍとなり、
ａ串／Ｃ申＝０．３２ である＊ ａ ／ ｃ ＝Ｏ−
３２のｎ次近似式に代入してａ・拳＝３．８８ ｍで、
補正してａ＊＊＝２．７９ ｍ、ａｓｓ／ｃ傘＝０．
２５ 、ａ／ｃ ＝ ０ 、２４ のｎ次近似式に代
入してａｌｌｌｌ・＝３．７１ｍｍで、補正してａ＊拳
＊＝２．６７ｍでａ＊＊申／ Ｃ傘＝０．２４となり、
収束した。１回目の旋盤加工のときのき裂深さａ＝＝３
．８９ ｍｍから２回目の旋盤加工の削り代１５．８
−１４．４＝１．４ ｒｍを差し引くとａ＝２．４９
ｒｍとなり、ａ＝２．６７ 通と良く一致する。The surface crack length 2c==22.
5 mm, the maximum potential difference ratio V/V, max=1.282, is found. The corresponding position of the master curve obtained by the finite element method is Ω' = 5/14.4X20 = 7.0 m. From Figures 7, 8, 9, and 10, Q = 7.0
From the potential difference at m, the relationship between the potential difference ratio V/V and the aspect ratio a/C in Fig. 15 can be obtained, and from Fig. 15, a /
c = 0.01 The relationship between the potential difference V/V and the crack depth a/l is obtained as shown in FIG. 16. The maximum potential difference ratio V/V, max=1.282, is expressed as a in Figure 16.
/ c = 0.8 by substituting it into the n-th approximation formula, a umbrella = 5.
05 mm, plate thickness correction becomes a umbrella = 3.64 m,
a/c=0.32* a/c=O-
Substituting into the n-th approximation formula of 32, a・fist=3.88 m,
Corrected a**=2.79 m, ass/c umbrella=0.
25, a/c = 0, 24 Substituting into the n-th approximation formula, allll・=3.71mm, correcting a*fist*=2.67m, a**monkey/C umbrella=0.24. ,
Converged. Crack depth a==3 during the first lathe machining
．． Cutting allowance for second lathe machining from 89 mm: 15.8
−14.4=1.4 Subtracting rm a=2.49
rm, which agrees well with a=2.67 letters.
次に、き裂の最深点から表面のき裂先端までのき裂深さ
は最終的に最深点のき裂を求めたときの電位差比とき裂
深さの関係を用いて各測定点における電位差から決定し
た。その結果を第１７図に示す０図中、実線は電位差分
布を測定したステンレス鋼管と同じ形状のスリットを入
れたものを応力条件を多少変えて疲労試験して得られた
破面のビーチマークである。斜線部は放電加工によるス
リットを示す、２本の破線は前述の旋盤加工前後の電位
差分布測定によるき裂形状である。２本の破線はお互い
に良く一致すると共に、５番目のビーチマークとも良く
一致する０表面のき裂先端付近の一致がやや悪いが、こ
れは電位差測定開隔が粗かったためであり、細かく測定
すれば更に良く一致すると思われる。Next, the crack depth from the deepest point of the crack to the crack tip on the surface is calculated by using the relationship between the potential difference ratio and the crack depth when finally determining the crack at the deepest point. It was decided from. The results are shown in Figure 17. In Figure 17, the solid line is a beach mark on the fracture surface obtained by fatigue testing a stainless steel tube with a slit of the same shape as the one in which the potential difference distribution was measured under slightly different stress conditions. be. The shaded area indicates a slit formed by electric discharge machining, and the two broken lines indicate the shape of a crack obtained by measuring the potential difference distribution before and after lathe processing. The two broken lines match each other well, and the match near the crack tip on the 0 surface, which also matches well with the 5th beach mark, is a little poor, but this is because the potential difference measurement gap was rough, and the fine measurement was performed. I think this would result in an even better match.
このようにこの方法によれば大型コンピュータがなくて
も小型コンピュータで十分精度良く表面き裂形状を検出
することが可能である。In this way, according to this method, it is possible to detect the surface crack shape with sufficient accuracy using a small computer even without a large computer.
以上説明したように本発明によれば電位差分布測定によ
り板状のあるいはパイプ状の部材に発生した表面き裂の
形状を大型のコンピュータでなくとも小型のコンピュー
タで十分精度良く検出することができるという効果があ
る。As explained above, according to the present invention, the shape of a surface crack that has occurred in a plate-shaped or pipe-shaped member can be detected with sufficient accuracy using a small computer rather than a large computer by measuring the potential difference distribution. effective.
第１図は解析によって
求めた表面き裂周辺の電位分布、第２図は第１図に示し
た電位分布のき裂近傍でのき裂に平行な電位差分布、第
３図は本発明に係わる欠陥検出装置の外観図、第４図は
電位差分布測定用の探傷ヘッドの構造を示す図、第５図
は端子形状及び基板への取付は状況、第６図は簡易き製
形状判定の流れ図、第７図から第１０図は種々のアスペ
クト比のき裂を有する部材を有限要素法により解析して
得られた表面に垂直な方向の電位分布、第１１図は測定
端子間距離６．４ ｍｍに対する電位差比とアスペクト
比の関係、第１２図は第１１図より得られた電位差比と
き裂深さの関係、第１３図と第１４図はステンレス鋼管
の表面き裂周辺で測定された電位差分布、第１５図は測
定端子間距離７．０ ｍに対する電位差比とアスペクト
比の関係、第１６図は第１５図より得られた電位差比と
き裂深さの関係、第１７図は破断されたステンレス鋼管
の破面のビーチマークと電位差分布測定によるき裂形状
の比較を示す図である。
１・・・駆動装置、５・・・給電端子、１０・・・測定
端子。
２０・・・探傷ヘッド、２１・・・基板、２５・・・ス
テッピングモータ、３０・・・空気シリンダ、５１・・
・Ｘ軸、５２・・・ステッピングモータ、５３・・・減
速機、５６・・・Ｙ軸、５７・・・ステッピングモータ
、５８・・・減速機、６０・・・側板、６１・・・コン
プレッサ、６２・・・吸盤、６５・・・駆動制御装置、
６６・・・直流電源、６７・・・スイッチング装置、７
０・・・スキャナー、７１・・・微小電圧計、７２・・
・インターフェース、１００・・・コンピュータ、１０
２・・・電位分布記憶装置。
第１０
療２目
き裂もめ
セ釈？火カ゛らの絶島ＬＸ ｏＶ九ノ”！１−３０
／Ｑ３
竿ら凹Figure 1 shows the potential distribution around the surface crack determined by analysis, Figure 2 shows the potential difference distribution near the crack in the potential distribution shown in Figure 1 and parallel to the crack, and Figure 3 relates to the present invention. An external view of the defect detection device, Fig. 4 shows the structure of the flaw detection head for measuring potential difference distribution, Fig. 5 shows the terminal shape and mounting status on the board, Fig. 6 shows a flowchart of simple manufacturing shape determination, Figures 7 to 10 show the potential distribution in the direction perpendicular to the surface obtained by analyzing members with cracks of various aspect ratios using the finite element method, and Figure 11 shows the distance between measurement terminals of 6.4 mm. Figure 12 shows the relationship between the potential difference ratio and the aspect ratio obtained from Figure 11. Figures 13 and 14 show the potential difference distribution measured around the surface crack of a stainless steel pipe. , Figure 15 shows the relationship between the potential difference ratio and aspect ratio for a distance of 7.0 m between the measurement terminals, Figure 16 shows the relationship between the potential difference ratio and the crack depth obtained from Figure 15, and Figure 17 shows the relationship between the fractured stainless steel. FIG. 2 is a diagram showing a comparison of beach marks on the fracture surface of a steel pipe and crack shapes obtained by potential difference distribution measurement. 1... Drive device, 5... Power supply terminal, 10... Measurement terminal. 20... Flaw detection head, 21... Board, 25... Stepping motor, 30... Air cylinder, 51...
・X axis, 52...Stepping motor, 53...Reducer, 56...Y axis, 57...Stepping motor, 58...Reducer, 60...Side plate, 61...Compressor , 62... Suction cup, 65... Drive control device,
66... DC power supply, 67... Switching device, 7
0...Scanner, 71...Microvoltmeter, 72...
・Interface, 100... Computer, 10
2... Potential distribution storage device. 10th therapy 2nd eye rift trouble sesaku? The Island of Fire LX oV Nine"! 1-30 /Q3 Pole concave
Claims (1)
端子対により直流電流を印加し、該給電端子対の間にお
いて電位差測定端子対を走査させて電位分布を測定し、
該電位分布から欠陥の形状を検出する方法において、電
位差分布を測定するための測定端子を走査する装置と該
装置を駆動する制御装置と共に、記憶回路の中にアスペ
クト比の種々異なるき裂形状についてき裂深さが異なる
場合の電位分布の解析結果を記憶させた演算装置により
、測定された電位差分布から表面におけるき裂長さを決
定し、前記測定された電位差の中最大の電位差を用いて
記憶回路の中に記憶された種々のアスペクト比のき裂に
対する電位差とき裂深さとの関係の中特定のアスペクト
比に対するマスターカーブを用いてき裂深さを決定し、
該き裂深さと表面のき裂長さの比からアスペクト比を求
め、該アスペクト比を前記のマスターカーブのアスペク
ト比と比較して、異なっていれば両者が一致するまで使
用するマスターカーブのアスペクト比を変えて計算し、
一致したときのき裂深さを表面き裂の最大き裂深さとし
、該最大き裂深さから表面のき裂先端までのき裂深さは
各測定位置における電位差から前記一致したときのマス
ターカーブを用いて求めて、全体のき裂形状を決定する
ことを特徴とする表面き裂形状検出方法。 ２、特許請求の範囲第１項記載の方法において、記憶回
路の中に記憶させるき裂のアスペクト比として１．０、
０．５、０．２５、０．１２５としたことを特徴とする
表面き裂形状検出方法。 ３、特許請求の範囲第１項記載の方法において、アスペ
クト比が種々異なるき裂のき裂深さが種種異なる場合の
き裂中央のき裂面に直交する方向の表面の電位差分布を
記憶回路の中に記憶させておき、電位差測定端子間の距
離を部材の板厚で基準化した測定位置における電位差か
ら各き裂深さに対するアスペクト比と電位差比の関係を
演算回路で求め、該関係から任意のアスペクト比に対す
る電位差比とき裂深さの関係を求め、該関係を用いて最
大電位差から最大き裂深さを決定し、各測定位置におけ
る電位差比から各測定位置におけるき裂深さを決定する
ことによりき裂形状を求めることを特徴とする表面き裂
形状検出方法。 ４、特許請求の範囲第３項記載の方法において、各き裂
深さに対するアスペクト比と電位差比の関係から電位差
比とき裂深さの関係のマスターカーブをアスペクト比が
０．０１きざみで求め、測定された最大の電位差比を用
いて任意の第一のアスペクト比に対するマスターカーブ
を用いて第一のき裂深さを決定し、該き裂深さと表面の
き裂長さの比から第二のアスペクト比を求め、該アスソ
ヘクト比を前記マスターカーブのアスペクト比と比較し
て異なっていれば第二のアスペクト比のマスターカーブ
を用いて第二のき裂深さを求め、再び第二のき裂深さと
表面のき裂長さの比から第三のアスペクト比を求め、該
アスペクト比マスターカーブのアスペクト比と比較する
、これを繰り返して両者が一致したときのき裂深さを表
面き裂の最大深さとし、各測定位置におけるき裂深さは
各測定位置における電位差比を前記のアスペクト比が一
致したマスターカーブに代入することによりき裂形状を
求めることを特徴とする表面き裂形状検出方法。 ５、特許請求の範囲第１項、第３項又は第４項のいずれ
かに記載の方法においてき裂に沿って測定された電位差
比分布において電位差比が１．０２となるところを表面
におけるき裂先端と判定することを特徴とする表面き裂
形状検出方法。 ６、特許請求の範囲第１図、第３項又は第４項のいずれ
かに記載の方法においてき裂に沿って測定された電位差
比分布においてき裂付近の電位差比分布をｎ次近似して
得られた曲線と基準電位差との交点を表面におけるき裂
先端と判定することを特徴とする表面き裂形状検出方法
。[Claims] 1. Direct current is applied to the surface of the member through one or more power supply terminal pairs spaced apart from each other, and a potential difference measuring terminal pair is scanned between the power supply terminal pairs to measure the potential distribution. death,
In the method of detecting the shape of a defect from the potential distribution, a device for scanning a measurement terminal for measuring the potential difference distribution and a control device for driving the device are used to detect crack shapes with various aspect ratios in a memory circuit. The crack length at the surface is determined from the measured potential difference distribution by a calculation device that stores the analysis results of the potential distribution when the crack depths are different, and the maximum potential difference among the measured potential differences is used to store the result. Determining the crack depth using a master curve for a specific aspect ratio among the relationships between potential difference and crack depth for cracks with various aspect ratios stored in the circuit,
Determine the aspect ratio from the ratio of the crack depth to the surface crack length, compare this aspect ratio with the aspect ratio of the master curve, and if they are different, use the aspect ratio of the master curve to be used until the two match. Calculate by changing
The crack depth when they match is the maximum crack depth of the surface crack, and the crack depth from the maximum crack depth to the surface crack tip is determined from the potential difference at each measurement position as the master when they match. A surface crack shape detection method characterized by determining the overall crack shape by determining the shape using a curve. 2. In the method according to claim 1, the aspect ratio of the crack to be stored in the storage circuit is 1.0;
0.5, 0.25, and 0.125. 3. In the method described in claim 1, the circuit stores the potential difference distribution on the surface in the direction perpendicular to the crack surface at the center of the crack when the crack depths of the cracks have different aspect ratios. The relationship between the aspect ratio and the potential difference ratio for each crack depth is determined by an arithmetic circuit from the potential difference at the measurement position where the distance between the potential difference measurement terminals is standardized by the plate thickness of the member, and from this relationship. Find the relationship between the potential difference ratio and crack depth for a given aspect ratio, use the relationship to determine the maximum crack depth from the maximum potential difference, and determine the crack depth at each measurement position from the potential difference ratio at each measurement position. A surface crack shape detection method characterized by determining the crack shape by 4. In the method described in claim 3, a master curve of the relationship between the potential difference ratio and the crack depth is determined from the relationship between the aspect ratio and the potential difference ratio for each crack depth in steps of 0.01 aspect ratio, Determine the first crack depth using a master curve for any first aspect ratio using the maximum potential difference ratio measured, and determine the second crack depth from the ratio of the crack depth to the surface crack length. The aspect ratio is determined, and the aspect ratio is compared with the aspect ratio of the master curve. If the aspect ratio is different, the second crack depth is determined using the master curve of the second aspect ratio, and the second crack depth is determined again. Find the third aspect ratio from the ratio of the depth and surface crack length, and compare it with the aspect ratio of the aspect ratio master curve. Repeat this process, and when the two match, the crack depth is determined as the maximum of the surface crack. A surface crack shape detection method characterized in that the crack depth at each measurement position is determined by substituting the potential difference ratio at each measurement position into the master curve with the same aspect ratio. 5. A crack on the surface where the potential difference ratio is 1.02 in the potential difference ratio distribution measured along the crack in the method according to any one of claims 1, 3, or 4. A surface crack shape detection method characterized by determining a crack tip. 6. Scope of Claims In the potential difference ratio distribution measured along the crack in the method according to any one of the claims 1, 3, or 4, the potential difference ratio distribution near the crack is approximated to the A surface crack shape detection method characterized by determining the intersection of the obtained curve and a reference potential difference as the crack tip on the surface.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP13409385A JPS61292546A (en) | 1985-06-21 | 1985-06-21 | Detection for shape of surface crack |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP13409385A JPS61292546A (en) | 1985-06-21 | 1985-06-21 | Detection for shape of surface crack |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS61292546A true JPS61292546A (en) | 1986-12-23 |
| JPH0364830B2 JPH0364830B2 (en) | 1991-10-08 |
Family
ID=15120268
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP13409385A Granted JPS61292546A (en) | 1985-06-21 | 1985-06-21 | Detection for shape of surface crack |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS61292546A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2007205801A (en) * | 2006-01-31 | 2007-08-16 | Okayama Univ | Damage detector and damage detection method |
| JP2019174314A (en) * | 2018-03-29 | 2019-10-10 | 三菱日立パワーシステムズ株式会社 | Dense crack depth measuring device using electric resistance method |
-
1985
- 1985-06-21 JP JP13409385A patent/JPS61292546A/en active Granted
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2007205801A (en) * | 2006-01-31 | 2007-08-16 | Okayama Univ | Damage detector and damage detection method |
| US8374803B2 (en) | 2006-01-31 | 2013-02-12 | National University Corporation Okayama University | Damage detection apparatus, damage detection method and recording medium |
| JP2019174314A (en) * | 2018-03-29 | 2019-10-10 | 三菱日立パワーシステムズ株式会社 | Dense crack depth measuring device using electric resistance method |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0364830B2 (en) | 1991-10-08 |
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