JP2004205212A - Eddy current flaw detecting probe for magnetic material and eddy current flaw detector - Google Patents
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【０００１】
【発明の属する技術分野】
本願発明は、一様な渦電流と漏洩磁束により磁性材料のキズを検出する渦電流探傷プローブとそのプローブを備えた渦電流探傷装置に関する。
【０００２】
【従来の技術】
【非特許文献１】平成１４年５月２８日 社団法人日本非破壊検査協会発行の平成１４年度春季大会講演概要集（第２０９，２１０頁）
図９〜図１１を参照して従来の渦電流探傷プローブを説明する。なお各図に共通の部分は、同じ符号を使用している。
【０００３】
図９は、従来の渦電流探傷プローブの斜視図（図９(ａ)）と渦電流を示す図（図９（ｂ））である。図９の渦電流探傷プローブは、例えば
【非特許文献１】を参照。
磁性材料の検査体Ｔには、パンケーキ状の励磁コイルＥ０と矩形状の縦置き型の検出コイルＤ０とからなる渦電流探傷プローブを設置してある。励磁コイルＥ０に励磁電流を流すと、検査体Ｔには、図９（ｂ）のように励磁コイルＥ０の巻線方向の渦電流Iｅが発生する。この場合、渦電流Iｅは、検出コイルＤ０の巻線方向に流れる成分を有しないから、電磁誘導により検出コイルＤ０に起電力が誘導されることはない。したがって検出コイルＤ０には、電流が発生しない。
【０００４】
図１０は、検査体Ｔのキズの方向と検出コイルＤ０の配置関係を示す図で、図１０(ａ)は、キズＦ０が検出コイルＤ０のコイル面と平行する方向（コイルの軸と直交する方向）にある場合を、図１０（ｂ）は、キズＦ０が検出コイルＤ０のコイル面と直交する方向（コイルの軸方向）にある場合を示す。
【０００５】
まず図１０(ａ)の場合、渦電流Iｅは、検査体Ｔにおいて乱れて変化し、キズＦ０に沿って流れる成分が生じるため、検出コイルＤ０には、起電力が誘導され、いわゆるキズ信号が発生する。したがって検出コイルＤ０に発生するキズ信号によりキズＦ０を検出できる。他方図１０(ｂ)の場合、検出コイルＤ０の巻線方向に流れる成分はほとんどないため、検出コイルＤ０には、キズ信号はほとんど発生しない。したがって図１０(ｂ)の場合には、キズＦ０の検出が難しくなる。
【０００６】
そこで図１０(ａ)と図１０（ｂ）のキズＦ０を検出する方法として、図１１のように、励磁コイルＥ０内に２つの検出コイルＤ１，Ｄ２を直交させて配置した
渦電流探傷プローブが提案されている（
【非特許文献１】参照）。
【０００７】
【発明が解決しようとする課題】
図１１の従来の渦電流探傷プローブは、励磁コイルＥ０内に２つの検出コイルＤ１，Ｄ２を直交させて配置しなければならないが、２つのコイルを交差させて組み立てることは、構造的に難しく、かつ渦電流探傷プローの構造が複雑になるためその組立て作業が困難であった。
本願発明は、これらの問題点に鑑み、キズの方向に関係なく、１個の検出コイルにより図１０(ａ)のキズも、図１０（ｂ）のキズも検出できる渦電流探傷プローブを提供することを目的とする。
【０００８】
【課題を解決するための手段】
本願発明の磁性材料の渦電流探傷用プローブは、励磁コイルと検出コイルを備えた渦電流探傷プローブにおいて、励磁コイルは磁性材料の検査体に一様な渦電流と一様な磁束を発生し、検出コイルは前記検査体のキズによって発生する渦電流の変化と漏洩磁束を検出することを特徴とする。
本願発明の磁性材料の渦電流探傷用プローブは、励磁コイルと検出コイルを備えた渦電流探傷プローブにおいて、励磁コイルは磁性材料の検査体に一様な渦電流と一様な磁束を発生し、検出コイルは前記検査体のキズに沿って流れる渦電流と前記キズにおいて発生する漏洩磁束を検出することを特徴とする。
本願発明の磁性材料の渦電流探傷用プローブは、前記１番目又は前記２番目に記載の磁性材料の渦電流探傷プローブにおいて、前記励磁コイルは矩形状の縦置き型であり、前記検出コイルはパンケーキ状であることを特徴とする。
【０００９】
本願発明の磁性材料の渦電流探傷装置は、磁性材料の検査体に一様な渦電流及び一様な磁束を発生する励磁コイルと前記検査体のキズによって発生する渦電流の変化及び漏洩磁束を検出する検出コイルとからなる渦電流探傷プローブ、前記励磁コイルに励磁電流を供給する励磁電流供給器、前記検出コイルに誘導されるキズ信号を検出するキズ信号検出器、キズ信号検出器が検出したキズ信号に基づいてキズを評価するキズ評価器、及び前記渦電流探傷プローブを前記励磁コイルのコイル面と垂直な方向に走査するプローブ駆動装置を備えていることを特徴とする。
本願発明の磁性材料の渦電流探傷装置は、前記の磁性材料の渦電流探傷装置において、前記励磁コイルは矩形状の縦置き型であり、前記検出コイルはパンケーキ状であることを特徴とする。
【００１０】
【発明の実施の形態】
図１〜図７により、本願発明の実施の形態に係る渦電流探傷プローブを説明する。なお各図に共通の部分は、同じ符号を使用している。
【００１１】
図１は、本願発明の実施の形態に係る渦電流探傷プローブの構成を示す図で、図１（ａ）は、渦電流探傷プローブを検査体Ｔに設置したときの平面図、図１（ｂ）は、図１（ａ）のＹ１−Ｙ１部分の断面図である。
図１において、Ｔは、磁性材料の検査体、Ｅは、コイル面が矩形状の縦置き型の励磁コイル、Ｄは、パンケーキ状の検出コイル、Ｅｃは、励磁コイルＥの巻線である。ｔ１〜ｔ４は、検査体Ｔの端部を示す。渦電流探傷プローブは、検出コイルＤが励磁コイルＥと検査体Ｔの間に位置するように設置してある。
【００１２】
図２は、図１の励磁コイルＥに励磁電流を流したとき、検査体Ｔに発生する渦電流と磁束を説明する図で、図２（ａ）は、平面図、図２（ｂ）は、図１（ａ）のＹ２−Ｙ２部分の断面図である。
励磁コイルＥに励磁電流を流すと、図２（ａ）のように励磁コイルＥの巻線方向に一様に同じ方向に流れる渦電流、いわゆる一様な渦電流Ｉｅ１が発生する。検出コイルＤには、渦電流Ｉｅ１により起電力Ｅｄ１，Ｅｄ２が誘導されるが、起電力Ｅｄ１，Ｅｄ２は、検出コイルＤの巻線方向に関して逆方向となり、互いに打消し合う。その結果検出コイルＤには、起電力が発生しない。したがって検出コイルＤには、電流が発生しない。
【００１３】
また励磁コイルＥに励磁電流を流すと、図２（ｂ）のように、励磁コイルＥのコイル面と垂直な方向（励磁コイルＥの巻線方向と直交する方向或いは励磁コイルＥの軸方向）に一様な磁束Ｍｆ１が発生する。磁束Ｍｆ１は、検査体Ｔ中に発生し、検査体Ｔの外へ出ないから、磁束Ｍｆ１により検出コイルＤに起電力が誘導されことはない。したがって検出コイルＤには、電流が発生しない。
【００１４】
図３は、検査体Ｔにキズがある場合の渦電流と磁束の変化を説明する図である。
まず図３（ａ）のように、検査体Ｔに渦電流Ｉｅ１と直交（或いは交差）する方向のスリット状のキズＦ１があるときは、キズＦ１付近で渦電流Ｉｅ１が乱れて変化し、キズＦ１に沿って流れる渦電流Ｉｅ２が生じる。
また図３（ｂ）のように、検査体Ｔに渦電流Ｉｅ１と平行する方向（キズＦ１と直交（或いは交差）する方向）のスリット状のキズＦ２があるときは、磁束Ｍｆ１の一部は、キズＦ２において検査体Ｔの外へ漏れ、いわゆる漏洩磁束Ｍｆ２が生じる。
【００１５】
図４、図５は、渦電流探傷プローブを励磁コイルＥのコイル面と垂直な方向に走査したときに発生するキズ信号を説明する図である。
図４は、キズＦ１に起因して発生する渦電流Ｉｅ２とキズ信号の関係を説明する図である。
【００１６】
図４（ａ）において、検出コイルＤを矢印Ｓ方向に走査した場合、検出コイルＤには、渦電流Ｉｅ２により起電力が誘導され、キズ信号は、図４（ｂ）のようになる。キズ信号は、検出コイルＤがキズＦ１に対して位置イにあるとき最大になり、位置ロにあるとき０になる。検出コイルＤが位置ロにあるときは、渦電流Ｉｅ２は、キズＦ１の長さ方向と垂直な軸に関して対称になるから、検出コイルＤの起電力は打消し合い、キズ信号は発生しない。検出コイルＤが位置ロを過ぎると、キズ信号は極性が反転し、位置ハで最大になる。
【００１７】
図５は、キズＦ２に起因して発生する漏洩磁束Ｍｆ２とキズ信号の関係を説明する図である。
図５（ａ）において、検出コイルＤを矢印Ｓ方向に走査した場合、検出コイルＤには、漏洩磁束Ｍｆ２により起電力が誘導され、キズ信号は、図５（ｂ）のようになる。キズ信号は、検出コイルＤがキズＦ２に対して位置ニにあるとき最大になり、位置ホにあるとき０になる。検出コイルＤが位置ホにあるときは、キズＦ２が検出コイルＤの中心を貫いているため、検出コイルＤの起電力が打消し合い、キズ信号は発生しない。検出コイルＤが位置ホを過ぎると、キズ信号は極性が反転し、位置ヘで最大になる。
【００１８】
図４、図５から分かるように、本願発明の渦電流探傷プローブは、そのプローブを励磁コイルＥのコイル面と垂直な方向に走査した場合、検査体Ｔのキズが渦電流Ｉｅ１と垂直な方向にあるときは渦電流によってキズを検出し、また検査体Ｔのキズが渦電流Ｉｅ１と平行な方向にあるときは漏洩磁束によってキズを検出することができる。したがって本願発明の渦電流探傷プローブは、キズの方向に関係なく検査体Ｔのキズを検出することができる。
【００１９】
図６は、本願発明の渦電流探傷プローブを用いて測定したキズ信号パターンを示す図で、図６（ａ）は、検査体が磁性材料の場合を、図６（ｂ）は、検査体が非磁性材料の場合を示す。
図６において、横軸は、励磁信号と同相のキズ信号成分を表し、縦軸は、励磁９０度進相したキズ信号成分を表している。またキズの角度０度は、励磁コイルのコイル面と直交する方向のキズ（図４（ａ）に相当）を、キズの角度９０度は、励磁コイルの巻線方向と平行な方向のキズ（図５（ａ）に相当）を示す。なお図６は、正規化してある。
【００２０】
測定に用いた渦電流探傷プローブ等の寸法は、次の通りである。
励磁コイルは、幅３０ｍｍ、長さ４０ｍｍ、高さ３０ｍｍ、検出コイルは、巻線断面積１×１ｍｍ2、外径６ｍｍである。検査体は、１６０×１６０×１５ｍｍ3のＳＭ鋼材板（磁性材料）と１６０×１６０×１．５ｍｍ3の黄銅板（非磁性材料）を用い、ＳＭ鋼材板には、深さ１．５ｍｍ、長さ１５ｍｍ、幅０．２ｍｍのスリット状キズを形成し、黄銅板には、深さ１．２ｍｍ、長さ１５ｍｍ、幅０．５ｍｍのスリット状キズを形成した。励磁コイルには、２０ｋＨｚの励磁電流を流した。
【００２１】
渦電流探傷プローブを用いると、検査体が磁性材料の場合には、図６（ａ）のようにキズ角度が０度のときも、９０度のときもともに大きなキズ信号を検出することができる。他方検査体が非磁性材料の場合には、図６（ｂ）のようにキズ角度が０度のときのキズ信号は大きいが、９０度のときのキズ信号は小さくなってしまう。
【００２２】
図６から、検査体が磁性材料の場合には、漏洩磁束を検出することにより渦電流を検出する場合と同程度にキズ信号を検出できることが分かる。本願発明の渦電流探傷プローブは、漏洩磁束を利用することにより、１個の検出コイルを用いるのみで従来の２個の検出コイルを用いた場合と同様に直交（交差）する２方向のキズを検出することができる。
【００２３】
図７は、本願発明の渦電流探傷プローブを用い、磁性材料の検査体について、キズの深さを変えて測定したキズ信号とリフトオフ雑音を示す。図７は、検出された信号の振幅の最大値のみをプロットしてある。
測定は、キズの角度が０度と９０度で、キズの深さが、１．５ｍｍ、１．０ｍｍ、０．５ｍｍ、０．２５ｍｍの４種類のキズについて、渦電流探傷プローブのリフトオフ（渦電流探傷プローブと検査体Ｔの距離）の変化が０．１〜２．０ｍｍの範囲で行った。
【００２４】
図７から、本願発明の渦電流探傷プローブは、キズの角度が０度、９０度いずれの場合にも、広い範囲の深さのキズを検出することができ、深さ０．２５ｍｍの程度の浅いキズも検出できることがわかる。また本願発明の渦電流探傷プローブは、リフトオフの変化に起因して発生する雑音、いわゆるリフトオフ雑音が非常に小さくなるから、リフトオフの変化の影響を受けずにキズを検出することができる。
なお検出されたキズ信号の振幅は、キズの深さによって異なるから、この振幅の違いからキズの深さを判別することもできる。
【００２５】
前記実施の形態の渦電流探傷プローブは、矩形状の励磁コイルとパンケーキ状検出コイルについて説明したが、励磁コイルは、一様な渦電流と一様な磁束を発生するコイルであれば矩形状に限らず、例えば三角形状等他の形状であってもよい。また検出コイルは、パンケーキ状に限らず矩形状、三角形状等他の形状であってもよい。
【００２６】
図８は、本発明の渦電流探傷プローブを用いた渦電流探傷装置の構成図である。励磁コイルＥと検出コイルＤからなる渦電流探傷プローブＰは、渦電流探傷プローブ駆動装置１１によって、磁性材料の検査体Ｔ上を励磁コイルＥのコイル面と垂直な方向（矢印Ｓ）へ走査する。渦電流探傷プローブＰの励磁コイルＥは、励磁電流供給器１２から供給される励磁電流によって、検査体Ｔに一様な渦電流と一様な磁束を発生する。検査体Ｔのキズによって発生する渦電流の変化と漏洩磁束によって、プローブＰの検出コイルＤに誘導されるキズ信号をキズ信号検出器１３によって検出し、キズ評価器１４より検査体Ｔのキズの有無、キズの深さ等を評価する。
【００２７】
【発明の効果】
本願の発明者は、一様な渦電流を発生する励磁コイルは、一様な磁束を発生し、検査体にキズがある場合には、そのキズの部分において漏洩磁束を発生することを突き止めた。そしてその漏洩磁束は、キズの検出に利用できることを実験により確認した。
【００２８】
本願発明の渦電流探傷プローブは、そのプローブを励磁コイルのコイル面と垂直な方向に走査した場合、検査体のキズが励磁コイルのコイル面と垂直（走査方向と平行）なキズは渦電流によって検出し、また検査体のキズが励磁コイルのコイル面と平行（走査方向と直交）なキズは漏洩磁束によって検出することができる。したがって本願発明の渦電流探傷プローブは、検査体のキズの方向に関係なくそのキズを検出することができる。
【００２９】
本願発明の渦電流探傷プローブは、１個の検出コイルを用いるのみでよく、従来のように２つのコイルを交差させる必要がないから、構造が簡単になり、組立て作業が容易になる。その結果本願発明は、渦電流探傷プローブのコストを低減することもできる。
本願発明の渦電流探傷プローブは、一様な渦電流と一様な磁束を利用するから、リフトオフ雑音がほとんど発生しない。したがって本願発明の渦電流探傷プローブは、リフトオフ変動の影響を受けることなく高いＳＮ比でキズ信号を検出することができる。
【図面の簡単な説明】
【図１】本願発明の実施の形態に係る渦電流探傷プローブの構成を示す図である。
【図２】本願発明の実施の形態に係る渦電流探傷プローブにより、キズのない検査体に発生する渦電流と磁束を説明する図である。
【図３】本願発明の実施の形態に係る渦電流探傷プローブにより、キズのある検査体に発生する渦電流と磁束の変化を説明する図である。
【図４】図３（ａ）の渦電流Ｉｅ２とキズ信号の関係を説明する図である。
【図５】図３（ｂ）の漏洩磁束Ｍｆ２とキズ信号の関係を説明する図である。
【図６】本願発明の実施の形態に係る渦電流探傷プローブにより、磁性材料と非磁性材料の検査体について検出した信号パターンを示す図である。
【図７】本願発明の実施の形態に係る渦電流探傷プローブにより、磁性材料の検査体の深さが異なるキズについて検出した信号パターンを示す図である。
【図８】本発明の渦電流探傷プローブを用いた渦電流探傷装置の構成図である。
【図９】従来の渦電流探傷プローブの斜視図と渦電流を説明する図である。
【図１０】従来の渦電流探傷プローブの検出コイルによる検査体のキズの検出を説明する図である。
【図１１】従来の検出コイルを２個備えた渦電流探傷プローブの平面図である。
【符号の説明】
Ｄ 検出コイル
Ｅ 励磁コイル
Ｅｃ 励磁コイルの巻線
Ｆ１，Ｆ２ 検査体のキズ
Ｅｄ１，Ｅｄ２ 起電力
Ｉｅ１，Ｉｅ２ 渦電流
Ｍｆ１，Ｍｆ２ 磁束
Ｐ 渦電流探傷プローブ
Ｔ 検査体
ｔ１〜ｔ４ 検査体Ｔの端部[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an eddy current flaw detection probe for detecting a flaw in a magnetic material by a uniform eddy current and leakage magnetic flux, and an eddy current flaw detection apparatus including the probe.
[0002]
[Prior art]
[Non-Patent Document 1] Summary of the lectures of the spring meeting of 2002 issued by the Japan Non-Destructive Inspection Association on May 28, 2002 (pp. 209, 210)
A conventional eddy current testing probe will be described with reference to FIGS. Note that the same reference numerals are used for the parts common to the drawings.
[0003]
FIG. 9 is a perspective view of a conventional eddy current flaw detection probe (FIG. 9A) and a diagram showing eddy currents (FIG. 9B). For example, see [Non-Patent Document 1] for the eddy current flaw detection probe in FIG.
An eddy-current flaw detection probe including a pancake-shaped excitation coil E0 and a rectangular vertically-placed detection coil D0 is installed on the magnetic material inspection object T. When an exciting current is supplied to the exciting coil E0, an eddy current Ie in the winding direction of the exciting coil E0 is generated in the test object T as shown in FIG. 9B. In this case, since the eddy current Ie does not have a component flowing in the winding direction of the detection coil D0, no electromotive force is induced in the detection coil D0 by electromagnetic induction. Therefore, no current is generated in the detection coil D0.
[0004]
FIG. 10 is a diagram showing the relationship between the direction of the flaw of the test object T and the arrangement of the detection coil D0. FIG. 10A shows the direction in which the flaw F0 is parallel to the coil surface of the detection coil D0 (perpendicular to the axis of the coil). 10B), and FIG. 10B shows a case where the flaw F0 is in a direction (axial direction of the coil) orthogonal to the coil surface of the detection coil D0.
[0005]
First, in the case of FIG. 10A, the eddy current Ie is disturbed and changes in the test object T, and a component flowing along the flaw F0 is generated. Therefore, an electromotive force is induced in the detection coil D0, and a so-called flaw signal is generated. appear. Therefore, the flaw F0 can be detected by the flaw signal generated in the detection coil D0. On the other hand, in the case of FIG. 10B, since almost no component flows in the winding direction of the detection coil D0, almost no flaw signal is generated in the detection coil D0. Therefore, in the case of FIG. 10B, it is difficult to detect the flaw F0.
[0006]
Therefore, as a method of detecting the flaw F0 in FIGS. 10A and 10B, an eddy current flaw detection probe in which two detection coils D1 and D2 are arranged orthogonally in an excitation coil E0 as shown in FIG. Proposed(
[See Non-Patent Document 1].
[0007]
[Problems to be solved by the invention]
In the conventional eddy current inspection probe shown in FIG. 11, two detection coils D1 and D2 must be arranged orthogonally in the excitation coil E0, but it is structurally difficult to assemble the two coils crossing each other. In addition, since the structure of the eddy current inspection probe is complicated, the assembling work is difficult.
In view of these problems, the present invention provides an eddy current flaw detection probe that can detect the flaw in FIG. 10A and the flaw in FIG. 10B with one detection coil regardless of the direction of the flaw. The purpose is to:
[0008]
[Means for Solving the Problems]
The magnetic material eddy current flaw detection probe of the present invention is an eddy current flaw detection probe provided with an excitation coil and a detection coil, wherein the excitation coil generates a uniform eddy current and a uniform magnetic flux on the test object of the magnetic material, The detection coil detects a change in an eddy current and a leakage magnetic flux generated by a flaw of the inspection object.
The magnetic material eddy current flaw detection probe of the present invention is an eddy current flaw detection probe provided with an excitation coil and a detection coil, wherein the excitation coil generates a uniform eddy current and a uniform magnetic flux on the test object of the magnetic material, The detection coil detects an eddy current flowing along a flaw of the test object and a leakage magnetic flux generated at the flaw.
The magnetic material eddy current inspection probe according to the present invention is the magnetic material eddy current inspection probe according to the first or second aspect, wherein the excitation coil is a rectangular vertical type, and the detection coil is a pan. It is characterized by a cake shape.
[0009]
The magnetic material eddy current flaw detector of the present invention uses an exciting coil that generates a uniform eddy current and a uniform magnetic flux in a magnetic material test object, and a change in eddy current and a leakage magnetic flux generated by a scratch of the test object. An eddy current flaw detection probe comprising a detection coil for detection, an excitation current supply device for supplying an excitation current to the excitation coil, a flaw signal detector for detecting a flaw signal induced in the detection coil, and a flaw signal detector. A flaw evaluator that evaluates flaws based on flaw signals and a probe drive device that scans the eddy current flaw detection probe in a direction perpendicular to the coil surface of the exciting coil are provided.
The magnetic material eddy current flaw detector of the present invention is characterized in that, in the magnetic material eddy current flaw detector, the exciting coil is a rectangular vertical type and the detection coil is a pancake shape. .
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
An eddy current testing probe according to an embodiment of the present invention will be described with reference to FIGS. Note that the same reference numerals are used for the parts common to the drawings.
[0011]
FIG. 1 is a diagram showing a configuration of an eddy current flaw detection probe according to an embodiment of the present invention. FIG. 1A is a plan view when the eddy current flaw detection probe is installed on a test object T, and FIG. 1) is a cross-sectional view taken along the line Y1-Y1 in FIG.
In FIG. 1, T is a test piece of a magnetic material, E is a vertical excitation coil having a rectangular coil surface, D is a pancake detection coil, and Ec is a winding of the excitation coil E. . t1 to t4 indicate end portions of the test object T. The eddy current flaw detection probe is installed so that the detection coil D is located between the excitation coil E and the test object T.
[0012]
2A and 2B are diagrams for explaining an eddy current and a magnetic flux generated in the test object T when an exciting current is applied to the exciting coil E in FIG. 1. FIG. 2A is a plan view, and FIG. FIG. 2 is a sectional view taken along line Y2-Y2 of FIG.
When an exciting current flows through the exciting coil E, an eddy current that flows in the same direction in the winding direction of the exciting coil E, that is, a so-called uniform eddy current Ie1 is generated as shown in FIG. Electromotive forces Ed1 and Ed2 are induced in the detection coil D by the eddy current Ie1, but the electromotive forces Ed1 and Ed2 are in opposite directions with respect to the winding direction of the detection coil D and cancel each other. As a result, no electromotive force is generated in the detection coil D. Therefore, no current is generated in the detection coil D.
[0013]
When an exciting current is applied to the exciting coil E, a direction perpendicular to the coil surface of the exciting coil E (a direction orthogonal to the winding direction of the exciting coil E or an axial direction of the exciting coil E) is applied as shown in FIG. , A uniform magnetic flux Mf1 is generated. Since the magnetic flux Mf1 is generated in the test object T and does not go out of the test object T, no electromotive force is induced in the detection coil D by the magnetic flux Mf1. Therefore, no current is generated in the detection coil D.
[0014]
FIG. 3 is a diagram illustrating changes in eddy current and magnetic flux when the inspection object T has a flaw.
First, as shown in FIG. 3A, when there is a slit-shaped flaw F1 in a direction orthogonal (or intersecting) with the eddy current Ie1 in the test object T, the eddy current Ie1 is disturbed and changes near the flaw F1, and the flaw is changed. An eddy current Ie2 flowing along F1 is generated.
Further, as shown in FIG. 3B, when the inspection object T has a slit-shaped flaw F2 in a direction parallel to the eddy current Ie1 (a direction orthogonal (or crossing) with the flaw F1), a part of the magnetic flux Mf1 is partially removed. , F2 leaks out of the test object T, so-called leakage magnetic flux Mf2 is generated.
[0015]
4 and 5 are diagrams illustrating a flaw signal generated when the eddy current flaw detection probe is scanned in a direction perpendicular to the coil surface of the exciting coil E.
FIG. 4 is a diagram illustrating the relationship between the eddy current Ie2 generated due to the flaw F1 and the flaw signal.
[0016]
In FIG. 4A, when the detection coil D is scanned in the direction of the arrow S, an electromotive force is induced in the detection coil D by the eddy current Ie2, and the flaw signal becomes as shown in FIG. 4B. The flaw signal becomes maximum when the detection coil D is at the position A with respect to the flaw F1, and becomes 0 when the detection coil D is at the position B. When the detection coil D is at the position B, the eddy current Ie2 is symmetric with respect to an axis perpendicular to the length direction of the flaw F1, so that the electromotive force of the detection coil D cancels out and no flaw signal is generated. When the detection coil D passes the position B, the polarity of the flaw signal is inverted and becomes maximum at the position C.
[0017]
FIG. 5 is a diagram illustrating the relationship between the leakage magnetic flux Mf2 generated due to the flaw F2 and the flaw signal.
In FIG. 5A, when the detection coil D is scanned in the direction of arrow S, an electromotive force is induced in the detection coil D by the leakage magnetic flux Mf2, and the flaw signal becomes as shown in FIG. 5B. The flaw signal becomes maximum when the detection coil D is at the position d with respect to the flaw F2, and becomes 0 when it is at the position e. When the detection coil D is at the position E, the flaw F2 penetrates the center of the detection coil D, so that the electromotive forces of the detection coil D cancel each other and no flaw signal is generated. When the detection coil D passes the position E, the polarity of the flaw signal is inverted and becomes maximum at the position.
[0018]
As can be seen from FIGS. 4 and 5, in the eddy current flaw detection probe of the present invention, when the probe is scanned in a direction perpendicular to the coil surface of the exciting coil E, the flaw of the test object T is directed in a direction perpendicular to the eddy current Ie1. In the case of (1), the flaw can be detected by the eddy current, and when the flaw of the test object T is in the direction parallel to the eddy current Ie1, the flaw can be detected by the leakage magnetic flux. Therefore, the eddy current inspection probe of the present invention can detect a flaw of the test object T regardless of the direction of the flaw.
[0019]
FIG. 6 is a diagram showing a flaw signal pattern measured by using the eddy current flaw detection probe of the present invention. FIG. 6A shows a case where the test object is a magnetic material, and FIG. The case of a non-magnetic material is shown.
In FIG. 6, the horizontal axis represents a flaw signal component in phase with the excitation signal, and the vertical axis represents a flaw signal component advanced by 90 degrees in excitation. A scratch angle of 0 degree refers to a scratch in a direction orthogonal to the coil surface of the exciting coil (corresponding to FIG. 4A), and a 90 ° scratch angle refers to a scratch in a direction parallel to the winding direction of the exciting coil. FIG. 5 (a) is shown. FIG. 6 is normalized.
[0020]
The dimensions of the eddy current probe used for the measurement are as follows.
The excitation coil has a width of 30 mm, a length of 40 mm, and a height of 30 mm. The detection coil has a winding cross-sectional area of 1 × 1 mm 2 and an outer diameter of 6 mm. The test body uses a 160 × 160 × 15 mm 3 SM steel plate (magnetic material) and a 160 × 160 × 1.5 mm 3 brass plate (non-magnetic material). The SM steel plate has a depth of 1.5 mm. A slit flaw having a length of 15 mm and a width of 0.2 mm was formed, and a slit flaw having a depth of 1.2 mm, a length of 15 mm and a width of 0.5 mm was formed on the brass plate. An excitation current of 20 kHz was passed through the excitation coil.
[0021]
When the test object is a magnetic material, a large flaw signal can be detected both when the flaw angle is 0 degree and when the flaw angle is 90 degrees as shown in FIG. . On the other hand, when the test object is a non-magnetic material, the flaw signal is large when the flaw angle is 0 degrees as shown in FIG. 6B, but becomes small when the flaw angle is 90 degrees.
[0022]
FIG. 6 shows that when the test object is a magnetic material, the flaw signal can be detected by detecting the leakage magnetic flux to the same extent as when detecting the eddy current. The eddy current flaw detection probe of the present invention utilizes a leakage magnetic flux to remove scratches in two orthogonal (intersecting) directions in the same manner as in the case of using two conventional detection coils by using only one detection coil. Can be detected.
[0023]
FIG. 7 shows a flaw signal and a lift-off noise measured by using the eddy current flaw detection probe of the present invention and changing the flaw depth of a test piece of a magnetic material. FIG. 7 plots only the maximum value of the amplitude of the detected signal.
The measurement was carried out by measuring the lift-off (eddy) of the eddy current probe for four types of flaws with a flaw angle of 0 degree and 90 degrees and a flaw depth of 1.5 mm, 1.0 mm, 0.5 mm, and 0.25 mm. The change of the current flaw detection probe and the test object T) was performed in the range of 0.1 to 2.0 mm.
[0024]
From FIG. 7, it can be seen that the eddy current flaw detection probe of the present invention can detect a flaw having a wide range of depths regardless of whether the flaw angle is 0 ° or 90 °, and the flaw angle is about 0.25 mm. It can be seen that shallow scratches can be detected. Further, the eddy current flaw detection probe of the present invention can detect a flaw without being affected by a change in lift-off because noise generated due to a change in lift-off, that is, a so-called lift-off noise is extremely small.
Since the amplitude of the detected flaw signal varies depending on the depth of the flaw, the depth of the flaw can be determined from the difference in the amplitude.
[0025]
Although the eddy current flaw detection probe of the embodiment has been described with respect to the rectangular excitation coil and the pancake detection coil, the excitation coil may be rectangular if it generates a uniform eddy current and a uniform magnetic flux. However, other shapes such as a triangular shape may be used. Further, the detection coil is not limited to the pancake shape, and may have another shape such as a rectangular shape, a triangular shape, or the like.
[0026]
FIG. 8 is a configuration diagram of an eddy current inspection device using the eddy current inspection probe of the present invention. The eddy current flaw detection probe P composed of the excitation coil E and the detection coil D is scanned by the eddy current flaw detection probe driving device 11 on the test object T of the magnetic material in a direction (arrow S) perpendicular to the coil surface of the excitation coil E. . The exciting coil E of the eddy current flaw detection probe P generates a uniform eddy current and a uniform magnetic flux in the test object T by the exciting current supplied from the exciting
[0027]
【The invention's effect】
The inventor of the present application has found that an exciting coil that generates a uniform eddy current generates a uniform magnetic flux, and if a test piece has a flaw, generates a leakage magnetic flux at the flaw. . Experiments have confirmed that the leakage magnetic flux can be used for detecting flaws.
[0028]
In the eddy current flaw detection probe of the present invention, when the probe is scanned in a direction perpendicular to the coil surface of the exciting coil, the flaw of the inspection object is perpendicular to the coil surface of the exciting coil (parallel to the scanning direction). Flaws detected and flaws in the inspection object parallel to the coil surface of the exciting coil (perpendicular to the scanning direction) can be detected by leakage magnetic flux. Therefore, the eddy current inspection probe of the present invention can detect a flaw regardless of the direction of the flaw of the inspection object.
[0029]
The eddy current flaw detection probe of the present invention only needs to use one detection coil, and it is not necessary to cross two coils as in the prior art, so that the structure is simplified and the assembling work is facilitated. As a result, the present invention can also reduce the cost of the eddy current inspection probe.
Since the eddy current inspection probe of the present invention utilizes a uniform eddy current and a uniform magnetic flux, almost no lift-off noise is generated. Therefore, the eddy current flaw detection probe of the present invention can detect a flaw signal with a high SN ratio without being affected by lift-off fluctuation.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of an eddy current inspection probe according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating an eddy current and a magnetic flux generated in a defect-free inspection object by the eddy current inspection probe according to the embodiment of the present invention.
FIG. 3 is a diagram illustrating changes in eddy current and magnetic flux generated in a flawed inspection object by the eddy current flaw detection probe according to the embodiment of the present invention.
FIG. 4 is a diagram illustrating a relationship between an eddy current Ie2 and a flaw signal in FIG.
FIG. 5 is a diagram illustrating a relationship between a leakage magnetic flux Mf2 and a flaw signal in FIG. 3B.
FIG. 6 is a diagram showing a signal pattern detected by the eddy current flaw detection probe according to the embodiment of the present invention for an inspection object made of a magnetic material and a non-magnetic material.
FIG. 7 is a diagram showing a signal pattern detected by the eddy current flaw detection probe according to the embodiment of the present invention for a flaw having a different depth of an inspection object of a magnetic material.
FIG. 8 is a configuration diagram of an eddy current inspection device using the eddy current inspection probe of the present invention.
FIG. 9 is a perspective view of a conventional eddy current flaw detection probe and a diagram for explaining eddy currents.
FIG. 10 is a diagram illustrating detection of a flaw of an inspection object by a detection coil of a conventional eddy current detection probe.
FIG. 11 is a plan view of an eddy current flaw detection probe provided with two conventional detection coils.
[Explanation of symbols]
D Detector coil E Excitation coil Ec Windings F1, F2 of excitation coil Scratches Ed1, Ed2 Electromotive force Ie1, Ie2 Eddy currents Mf1, Mf2 Magnetic flux P Eddy current flaw detection probe T Inspection body t1 to t4
Claims (5)
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| JP2002370917A JP4117645B2 (en) | 2002-12-20 | 2002-12-20 | Eddy current testing probe and eddy current testing equipment for magnetic materials |
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| JP2002370917A JP4117645B2 (en) | 2002-12-20 | 2002-12-20 | Eddy current testing probe and eddy current testing equipment for magnetic materials |
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Cited By (9)
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| JP2006189347A (en) * | 2005-01-06 | 2006-07-20 | Tatsuo Hiroshima | Flaw detection probe and flaw detector |
| JP2006220630A (en) * | 2005-02-14 | 2006-08-24 | Marktec Corp | Probe for eddy current flaw detection |
| JP2006322860A (en) * | 2005-05-20 | 2006-11-30 | Marktec Corp | Eddy current flaw detection probe |
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| JP2011191324A (en) * | 2011-07-04 | 2011-09-29 | Tatsuo Hiroshima | Flaw detection probe |
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| JP2006189347A (en) * | 2005-01-06 | 2006-07-20 | Tatsuo Hiroshima | Flaw detection probe and flaw detector |
| JP2006220630A (en) * | 2005-02-14 | 2006-08-24 | Marktec Corp | Probe for eddy current flaw detection |
| JP4484723B2 (en) * | 2005-02-14 | 2010-06-16 | マークテック株式会社 | Eddy current testing probe |
| JP2006322860A (en) * | 2005-05-20 | 2006-11-30 | Marktec Corp | Eddy current flaw detection probe |
| JP2007183197A (en) * | 2006-01-10 | 2007-07-19 | Hitachi Ltd | Eddy current flaw sensor |
| JP4627499B2 (en) * | 2006-01-10 | 2011-02-09 | 株式会社日立製作所 | Eddy current flaw detection sensor |
| JP2009287981A (en) * | 2008-05-27 | 2009-12-10 | Marktec Corp | Eddy-current flaw detector and eddy-current flaw detecting method |
| JP2012002705A (en) * | 2010-06-17 | 2012-01-05 | Toyota Motor Corp | Eddy current measuring sensor and eddy current measuring method |
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| JP2011191324A (en) * | 2011-07-04 | 2011-09-29 | Tatsuo Hiroshima | Flaw detection probe |
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