JP3785577B1 - Crack detection system and crack detection method - Google Patents
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Abstract
【課題】被検出体の表面のひび割れ発生箇所を、簡単に感度よく検出する。
【解決手段】
被検出体表面の測定範囲１０に設けられた複数の標点２の少なくとも３点を結んで一つの要素３（仮想領域）を形成して、測定範囲１０を複数の要素３の集まりに離散化し、各要素３の最大主ひずみを算出し、これら各最大主ひずみを差分処理して各要素３の差分ひずみを算出する演算手段と、任意のしきい値より大きな差分ひずみを有する要素を被検出体のひび割れ発生箇所として検出するひび割れ検知手段とを備えている。
【選択図】図２An object of the present invention is to easily detect the occurrence of a crack on the surface of an object to be detected with high sensitivity.
[Solution]
The element 3 (virtual region) is formed by connecting at least three points of the plurality of reference points 2 provided in the measurement range 10 on the surface of the detection object, and the measurement range 10 is discretized into a group of the plurality of elements 3. , Calculating the maximum principal strain of each element 3, calculating the difference strain of each element 3 by differentially processing each maximum principal strain, and detecting an element having a difference strain larger than an arbitrary threshold value And a crack detection means for detecting the occurrence of a crack in the body.
[Selection] Figure 2
Description
本発明は、コンクリート構造物等のひび割れによる損傷状態を検出するための、新規な方式のひび割れ検出システム及びひび割れ検出方法に関するものである。 The present invention relates to a novel crack detection system and crack detection method for detecting a damage state due to a crack in a concrete structure or the like.
トンネルやビル等のコンクリート構造物等のひび割れ状況を把握することにより、その構造物の劣化度を評価することができる。この評価により、コンクリート構造物の剥落事故を防止したり、構造物の補修や補強、解体等の対処方法を判断することができる。そのため、構造物のひび割れを検出するものとして、種々の装置や方法が提案されている。
ひび割れを検出する装置等として、電気抵抗体をコンクリートに埋設してこの抵抗体の測定値をデータ解析するもの（特許文献１参照）や、構造物に弾性振動を印加してその伝搬振動からデータを解析するもの（特許文献２参照）等が開発されている。
As a device for detecting cracks, an electrical resistor is embedded in concrete and the measured value of this resistor is analyzed (see Patent Document 1), or elastic vibration is applied to the structure and data from its propagation vibration is used. Have been developed (see Patent Document 2).
しかしながら、コンクリートに電気抵抗体を埋設する装置は、準備や手間が厄介で、測定対象の寸法構成に限度があるため、マイクロデバイス等の微小体を測定することは非常に難しい。そして、構造物に振動を印加する方法は、振動の伝搬距離が短く、測定範囲が狭いという問題がある。又、測定したデータは、構造物の表面と内部の反射波が混在しているので、解析精度に問題もある。
そこで、本発明が解決する課題は、コンクリート構造物等を複数の要素に離散化して、各要素の最大主ひずみを差分処理することにより、簡単に感度良くひび割れ発生箇所を検出できる、ひび割れ検出システム及び方法を提供することである。
However, since an apparatus for embedding an electric resistor in concrete is troublesome to prepare and troublesome, and there is a limit to the dimensional configuration of an object to be measured, it is very difficult to measure a micro object such as a micro device. And the method of applying a vibration to a structure has the problem that the propagation distance of a vibration is short and a measurement range is narrow. In addition, the measured data has a problem in the analysis accuracy because the surface of the structure and the internal reflected wave are mixed.
Therefore, the problem to be solved by the present invention is that a crack detection system can easily detect a crack occurrence location with high sensitivity by discretizing a concrete structure or the like into a plurality of elements and differentially processing the maximum principal strain of each element. And providing a method.
前記した課題を解決するため、本発明に係るひび割れ検出システムは、被検出体表面の測定範囲に設けられた複数の標点を撮像する撮像装置と、この撮像装置で撮像した標点を測定して各標点の座標を求める画像処理及び演算装置と、各標点の少なくとも３点を結んで一つの要素（仮想領域）を形成して前記測定範囲を複数の要素の集まりに離散化し、被検出体へ付与される任意荷重によって発生する被検出体表面のひずみと画像処理及び演算装置で求められる荷重付与前後の各標点の座標とから各要素の最大主ひずみを算出すると共に、これら各最大主ひずみを差分処理して前記各要素の差分ひずみを算出する演算手段と、任意のしきい値より大きな差分ひずみを有する要素を被検出体のひび割れ発生箇所として検出するひび割れ検知手段とを備えている。 In order to solve the above-described problem, a crack detection system according to the present invention measures an image pickup device that picks up a plurality of marks provided in a measurement range on the surface of a detected object, and the marks picked up by the image pickup device. An image processing and computing device for determining the coordinates of each target point, and connecting at least three points of each target point to form one element (virtual region) to discretize the measurement range into a group of a plurality of elements, The maximum principal strain of each element is calculated from the distortion of the surface of the detection object caused by the arbitrary load applied to the detection body and the coordinates of each gauge point before and after the load application obtained by the image processing and calculation device, and A calculating means for calculating the differential strain of each element by differential processing the maximum principal strain, and a crack detecting means for detecting an element having a differential strain larger than an arbitrary threshold as a crack occurrence location of the detected object It is equipped with a.
又、本発明に係るひび割れ検出方法は、連続する被検出体表面の測定範囲に存する複数の標点を撮像するステップと、この撮像した標点を測定して各標点の座標を求めるステップと、各標点の少なくとも３点を結んで一つの要素（仮想領域）を形成して測定範囲を複数の要素（仮想領域）の集まりに離散化するステップと、被検出体へ付与される任意荷重によって発生する被検出体表面のひずみと被検出体への荷重付与前後の各標点の座標とから各要素の最大主ひずみを算出するステップと、これら各最大主ひずみを差分処理して各要素の差分ひずみを算出するステップと、この差分ひずみと予め設定したしきい値を比較し、このしきい値より大きな差分ひずみを有する要素を被検出体のひび割れ発生箇所として検出するステップとを含む。 Further, the crack detection method according to the present invention includes a step of imaging a plurality of target points existing in the measurement range of the surface of the continuous object to be detected, and a step of obtaining the coordinates of each target point by measuring the acquired target points. , A step of connecting at least three points of each mark to form one element (virtual area) and discretizing the measurement range into a collection of a plurality of elements (virtual areas), and an arbitrary load applied to the detected object Calculating the maximum principal strain of each element from the distortion of the surface of the object to be detected generated by the coordinates of the target points before and after the load is applied to the object to be detected; And a step of comparing the differential strain with a preset threshold value and detecting an element having a differential strain larger than the threshold value as a crack occurrence location of the detected object.
好ましくは、三角形状に前記各要素を離散化し、任意の中心要素の最大主ひずみとこの中心要素の一の頂点を共有する３つの周辺要素の最大主ひずみを比較して差分処理する。 Preferably, each element is discretized in a triangular shape, and the differential processing is performed by comparing the maximum principal strain of an arbitrary central element with the maximum principal strains of three peripheral elements sharing one vertex of the central element.
更に好ましくは、各要素を略同一形状の直角二等辺三角形に構成し、各要素を複数の異なる配列とし、これら各配列に基づく差分ひずみからひび割れの方向性を検出する。 More preferably, each element is formed into a right isosceles triangle having substantially the same shape, each element is made into a plurality of different arrays, and the direction of cracking is detected from the differential strain based on each array.
又、各要素が略同一形状の正三角形となるよう構成しても良い。 Moreover, you may comprise so that each element may become a regular triangle of substantially the same shape.
本発明のひび割れ検出システム及び方法は、コンクリート構造物等の被検出体表面を複数の要素に離散化して、各要素の最大主ひずみを差分処理して、この差分ひずみと予め設定したしきい値を比較してひび割れ発生箇所を検出するので、コンクリートにセンサーを埋設したり振動を印加する必要がなく、簡単にひび割れを検出することができる。又、しきい値を任意に設定することで、被検出体の種類等に応じたひび割れ幅等を検出できるので、構造物の劣化度等を的確に把握することができる。 The crack detection system and method according to the present invention discretizes the surface of an object to be detected such as a concrete structure into a plurality of elements, performs differential processing on the maximum principal strain of each element, and sets this differential strain and a preset threshold value. Therefore, it is not necessary to embed a sensor or apply vibration to the concrete, so that cracks can be detected easily. Moreover, since the crack width etc. according to the kind etc. of a to-be-detected body etc. can be detected by setting a threshold value arbitrarily, the deterioration degree of a structure, etc. can be grasped | ascertained accurately.
又、各要素を三角形状に離散化し、任意の中心要素とこの中心要素の一の頂点を共有する３つの周辺要素を比較して差分処理することで、中心要素に対する周辺要素の最大主ひずみの影響を減少させることができるので、ひび割れ検出の感度が著しく向上する。 In addition, each element is discretized into a triangular shape, and the maximum principal strain of the peripheral element with respect to the central element is calculated by performing a difference process by comparing an arbitrary central element with three peripheral elements sharing one vertex of the central element. Since the influence can be reduced, the sensitivity of crack detection is significantly improved.
そして、各要素を略同一形状の直角二等辺三角形に構成して、配列の異なる各要素から差分処理することで、ひび割れの方向性を把握することができる。すなわち、各要素が直角二等辺三角形の場合、ひび割れが直角を挟む２辺を通過する際の最大主ひずみが著しく大きくなるので、任意要素においてひび割れが直角を挟む２辺を通過していることがわかり、ひび割れの方向性を把握できる。 Then, by configuring each element into a right isosceles triangle having substantially the same shape and performing differential processing from each element having a different arrangement, the directionality of the crack can be grasped. That is, when each element is a right-angled isosceles triangle, the maximum principal strain when the crack passes through two sides sandwiching a right angle is remarkably increased. You can understand and understand the direction of cracks.
更に、各要素を略同一形状の正三角形とすることで、ひび割れの方向性に関係なく、差分ひずみの値が略一定の範囲内となるので、ひび割れ検出の感度を安定させることができる。 Furthermore, by making each element an equilateral triangle having substantially the same shape, the value of the differential strain falls within a substantially constant range regardless of the directionality of the crack, so that the crack detection sensitivity can be stabilized.
以下、添付図面に基づき、本発明に係るひび割れ検出システム及び方法について詳細に説明する。
図１は、ひび割れ検出システムを説明するための図であって、図１（ａ）は、被検出体に荷重を与える状態を示す側面図、図１（ｂ）は、ひび割れ検出システムの全体を示す概略図である。図１の如く、本実施例の被検出体（１）は、下面にＣＦＲＰ（炭素繊維強化プラスチック）シートを接着して、曲げ補強がなされたコンクリート梁で、単純梁の状態にある。この被検出体（１）の寸法は、幅１００ｍｍ、高さ１００ｍｍの正方形断面で、長さ４００ｍｍで構成されている。そして、この被検出体（１）の表面中央における１００ｍｍ×１００ｍｍの測定範囲（１０）に、１０ｍｍ間隔の複数の標点（２，２，・・・）を付した。なお本例においては、被検出体（１）の表面に、手書きで黒丸の標点（２，２，・・・）を添付したが、この標点（２，２，・・・）は中心位置が明確なものであれば予め設けられた既存のものでもよい。例えば、ビルの表面に設けられたタイルの目地や、飛行機等に設けられた複数のリベット、或いは顕微鏡で可視化された金属の組織パターン等を用いることができる。
Hereinafter, a crack detection system and method according to the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a diagram for explaining a crack detection system. FIG. 1 (a) is a side view showing a state in which a load is applied to a detection target, and FIG. 1 (b) is an overall view of the crack detection system. FIG. As shown in FIG. 1, the detected object (1) of the present embodiment is a concrete beam in which a CFRP (carbon fiber reinforced plastic) sheet is bonded to the lower surface and bent and reinforced, and is in a simple beam state. The dimension of the detection object (1) is a square section having a width of 100 mm and a height of 100 mm, and a length of 400 mm. Then, a plurality of marks (2, 2,...) At intervals of 10 mm were attached to a measurement range (10) of 100 mm × 100 mm at the center of the surface of the detection object (1). In this example, a black circle mark (2, 2,...) Is attached to the surface of the detection object (1) by hand, but the mark (2, 2,...) Is the center. As long as the position is clear, an existing one provided in advance may be used. For example, tile joints provided on the surface of a building, a plurality of rivets provided on an airplane or the like, or a metal tissue pattern visualized with a microscope can be used.
この状態で、被検出体（１）の測定範囲（１０）をＣＣＤカメラ等の撮像装置（２０）で撮像する。そして、画像処理装置（２１）を用いて、この撮像した画像の各標点（２，２，・・・）の中心を節点（２’，２’，・・・）とし、この複数の節点（２’，２’，・・・）のうちの３点（２’，２’，２’）を結んで形成した仮想領域を、一つの要素（３）とする。そして、測定範囲（１０）を、互いに干渉することのない複数の要素（３，３，・・・）の集まりに分割して離散化する。即ち、測定範囲（１０）を、各節点（２’，２，・・・）から複数の三角形状の仮想領域（３，３，・・・）に分割する。図２は、測定範囲（１０）を複数の要素（３，３，・・・）に離散化した状態を示す図である。 In this state, the measurement range (10) of the detection target (1) is imaged by an imaging device (20) such as a CCD camera. Then, using the image processing device (21), the center of each target point (2, 2,...) Of the captured image is set as a node (2 ′, 2 ′,...), And the plurality of nodes. A virtual region formed by connecting three points (2 ′, 2 ′, 2 ′) of (2 ′, 2 ′,...) Is defined as one element (3). Then, the measurement range (10) is divided into a group of a plurality of elements (3, 3,...) That do not interfere with each other and discretized. That is, the measurement range (10) is divided from each node (2 ', 2, ...) into a plurality of triangular virtual areas (3, 3, ...). FIG. 2 is a diagram showing a state in which the measurement range (10) is discretized into a plurality of elements (3, 3,...).
この状態で、各節点（２’，２’，・・・）の座標を測定する。更に、図１のように、被検出体（１）の中央上面から任意荷重（Ｐ）を付与し、これによって変形した後の被検出体（１）の測定範囲（１０）における各節点（２’，２’・・・）の座標も測定する。
そして、画像処理装置（２１）に接続された演算装置（２２）を用いて、変形前後における各節点（２’，２’，・・・）の座標から、測定範囲（１０）の各仮想領域、すなわち各要素（３，３，・・・）の最大主ひずみを算出する。その後、これら最大主ひずみを差分処理し、各要素（３，３，・・・）の差分ひずみを算出する。そして、コンピュータ等のひび割れ検知装置（２３）を用いて、この差分ひずみと予め設定したしきい値を比較して、ひび割れが発生した要素（３）の検出を行う。以下、この算出方法について詳細に説明する。
In this state, the coordinates of each node (2 ′, 2 ′,...) Are measured. Further, as shown in FIG. 1, an arbitrary load (P) is applied from the center upper surface of the detected object (1), and each node (2) in the measurement range (10) of the detected object (1) after being deformed thereby. Also measure the coordinates of ', 2' ...).
Then, using the arithmetic device (22) connected to the image processing device (21), each virtual region of the measurement range (10) is calculated from the coordinates of the nodes (2 ′, 2 ′,...) Before and after the deformation. That is, the maximum principal strain of each element (3, 3,...) Is calculated. Thereafter, the maximum principal strain is subjected to differential processing, and the differential strain of each element (3, 3,...) Is calculated. Then, using a crack detection device (23) such as a computer, the differential distortion is compared with a preset threshold value to detect the cracked element (3). Hereinafter, this calculation method will be described in detail.
図３は、算出方法を説明するための一の任意要素を示す拡大図である。この任意要素（３）は、各要素ごとの最大主ひずみの算出方法を説明するために、要素（３）の番号を（ｅ）、各節点（２’）の番号を（ｉ，ｊ，ｋ）として一般化した。そして、要素番号（ｅ）における、変形前の各節点（ｉ，ｊ，ｋ）の座標を｛Ｘ０ ｅ｝、変形後の各節点（ｉ，ｊ，ｋ）の座標を｛Ｘ１ ｅ｝として後記（式１）に示す。これら座標｛Ｘ０ ｅ｝、｛Ｘ１ ｅ｝は一般化されているが、実際には任意点を原点（０，０）として、各節点（ｉ，ｊ，ｋ）を測定した座標の値である。 FIG. 3 is an enlarged view showing one arbitrary element for explaining the calculation method. In order to explain the calculation method of the maximum principal strain for each element, the arbitrary element (3) is assigned the element (3) number (e) and the node (2 ′) number (i, j, k). ). Then, in the element number (e), the coordinates of each node (i, j, k) before deformation are {X 0 e }, and the coordinates of each node (i, j, k) after deformation are {X 1 e }. As shown below (Formula 1). These coordinates {X 0 e } and {X 1 e } are generalized, but in actuality, values of coordinates obtained by measuring each node (i, j, k) with an arbitrary point as the origin (0, 0). It is.
変形前後の各節点の座標｛Ｘ０ ｅ｝、｛Ｘ１ ｅ｝を用いて、後記（式２）から変形前後の節点座標の節点変位ベクトル｛Ｕ０｝を算出する。 Using the coordinates {X 0 e } and {X 1 e } of the nodes before and after the deformation, a node displacement vector {U 0 } of the node coordinates before and after the deformation is calculated from the following expression (Formula 2).
そして、節点変位ベクトル｛Ｕ０｝から回転成分を除去するため、後記（式３）及び（式４）から得た座標変換マトリクス［Ｔ］、並びに前記｛Ｕ０｝を、後記（式５）に代入して、真の節点変位ベクトル｛Ｕｅ｝を算出する。 Then, in order to remove the rotational component from the nodal displacement vector {U 0 }, the coordinate transformation matrix [T] obtained from the following expressions (Expression 3) and (Expression 4), and the {U 0 } are expressed as follows (Expression 5). To calculate the true nodal displacement vector {U e }.
更に、後記（式６）から得たひずみ変位マトリクス［Ｂｅ］、並びに前記の真の節点変位ベクトル｛Ｕｅ｝を、後記するひずみ変位関係式（式７）に代入して、要素番号ｅのひずみ｛εｅ｝を算出する。 Further, the strain displacement matrix [B e ] obtained from the later expression (Expression 6) and the true nodal displacement vector {U e } are substituted into the strain displacement relational expression (Expression 7) described later, and the element number e The strain {ε e } is calculated.
そして、前記のひずみ｛εｅ｝及び後記（式８）から、要素番号ｅの最大主ひずみεｅを算出する。更に、この要素番号ｅの最大主ひずみεｅ、及び前記と同様の方法で算出した要素番号（ｅ）の周りの３つの任意の周辺要素（ａ，ｂ，ｃ）のそれぞれの最大主ひずみεａ，εｂ，εｃから、差分処理を行い、要素番号（ｅ）の差分ひずみΔεを得る。この差分ひずみΔεは、後記（式９）に前記のεｅ，εａ，εｂ，εｃを代入して算出する。 Then, the maximum principal strain ε e of the element number e is calculated from the strain {ε e } and the postscript (Equation 8). Furthermore, the maximum principal strain epsilon e of the element number e, and three optional peripheral element around said and calculated element number in a similar manner (e) (a, b, c) strain each maximum principal of epsilon Difference processing is performed from a 1 , ε b , and ε c to obtain a differential strain Δε of element number (e). This differential strain Δε is calculated by substituting ε e , ε a , ε b , and ε c into the following (Equation 9).
ここで、中心要素（ｅ）の差分処理を行うための周辺要素（ａ，ｂ，ｃ）の検討を行う。図４は、周辺要素を検討するための図である。図４（ａ）は、中心要素（ｅ）の一辺を共有する要素を周辺要素（ａ，ｂ，ｃ）とする場合を示し、図４（ｂ）は、中心要素（ｅ）の一つ頂点を共有する３つの要素を周辺要素（ａ，ｂ，ｃ）とする場合を示す。
図４において、ひび割れ（Ｃ１）は、図４（ａ）では要素番号（ｃ，ｅ，ａ）を通過し、図４（ｂ）では要素番号（ｅ）のみを通過する。ひび割れ（Ｃ２）は、図４（ａ）では要素番号（ａ，ｅ，ｂ）を通過し、図４（ｂ）では要素番号（ａ，ｅ）を通過する。従って、ひび割れ（Ｃ１）及び（Ｃ２）のいずれにおいても、要素番号（ｅ）の差分ひずみΔεは図４（ｂ）の場合が大きくなる（前記（式９）参照）。ここで、後述するように、差分ひずみΔεが大きい方が、ひび割れ発生箇所を検出しやすいので、図４（ｂ）の如く、中心要素（ｅ）の一つの頂点を共有する３つの要素を周辺要素（ａ，ｂ，ｃ）として、前記（式９）より要素番号（ｅ）の差分ひずみΔεを算出する。
Here, the peripheral elements (a, b, c) for performing the differential processing of the central element (e) are examined. FIG. 4 is a diagram for examining peripheral elements. 4A shows a case where an element sharing one side of the central element (e) is a peripheral element (a, b, c), and FIG. 4B shows one vertex of the central element (e). The case where the three elements sharing the symbol are the peripheral elements (a, b, c) is shown.
In FIG. 4, the crack (C 1 ) passes through the element number (c, e, a) in FIG. 4 (a), and passes only the element number (e) in FIG. 4 (b). The crack (C 2 ) passes through the element numbers (a, e, b) in FIG. 4 (a) and passes through the element numbers (a, e) in FIG. 4 (b). Therefore, in both the cracks (C 1 ) and (C 2 ), the differential strain Δε of the element number (e) is large in the case of FIG. 4B (see (Formula 9)). Here, as will be described later, the larger the differential strain Δε is, the easier it is to detect a crack occurrence location, and therefore, as shown in FIG. 4B, three elements sharing one vertex of the central element (e) As the element (a, b, c), the differential strain Δε of the element number (e) is calculated from the above (Formula 9).
そして、この差分ひずみΔεを離散化した全ての要素について算出し、予め設定したしきい値より大きな差分ひずみΔεを有する要素を、ひび割れ検知装置（２３）を用いて抽出する。このしきい値は、被検出体のひび割れが発生する差分ひずみの値を予め設定する。従って、しきい値より大きな差分ひずみΔεを有する要素に、ひび割れが発生したことになる。このしきい値は、被検出体の種類やひび割れの幅等に応じて決定することができる。そして、ひび割れ検知装置（２３）と画像処理装置（２１）とが接続され、図５の如く、ひび割れ検知装置（２３）からの信号を基にして、しきい値を超えた差分ひずみを有する要素を黒色に、それ以外の要素を白色に着色して画像処理装置（２１）に表示することにより、測定範囲（１０）におけるひび割れ発生箇所を可視化できる。この画像処理装置（２１）、演算装置（２２）、及びひび割れ検知装置（２３）は、一体のハードウェアとして構成することもできる。 Then, the differential strain Δε is calculated for all the discrete elements, and the elements having the differential strain Δε larger than a preset threshold value are extracted using the crack detection device (23). This threshold value is set in advance as a value of the differential strain at which cracks of the detected object occur. Therefore, a crack has occurred in an element having a differential strain Δε larger than the threshold value. This threshold value can be determined according to the type of object to be detected, the width of cracks, and the like. Then, the crack detection device (23) and the image processing device (21) are connected, and as shown in FIG. 5, an element having differential distortion exceeding a threshold value based on the signal from the crack detection device (23). Is black and other elements are colored white and displayed on the image processing device (21), the crack occurrence location in the measurement range (10) can be visualized. The image processing device (21), the calculation device (22), and the crack detection device (23) can also be configured as integrated hardware.
次に、要素の形状及び配列について検討する。図６は、要素形状を検討するための図であり、図６（ａ）は要素形状が正三角形の場合を示し、図６（ｂ）は要素形状が直角二等辺三角形の場合を示す。
図６の如く、ひび割れ（Ｃ）は、幅寸法をδ、ｘ軸方向のベースライン（ＢＬ）に対する角度をθ（０°〜３６０°）とする。そして、各要素（３）の図に示す辺の長さを（Ｌ）とする。この場合における、δ、θ、Ｌ、及び要素番号（ｅ）の最大主ひずみεｅの関係式は後述の（式１０）〜（式１２）となる。ここで、（式１０）は要素（３）の形状が正三角形の場合の関係式、（式１１）及び（式１２）は要素（３）の形状が直角二等辺三角形の場合の関係式を示す。
Next, the shape and arrangement of elements will be examined. 6A and 6B are diagrams for examining the element shape. FIG. 6A shows a case where the element shape is an equilateral triangle, and FIG. 6B shows a case where the element shape is a right-angled isosceles triangle.
As shown in FIG. 6, the crack (C) has a width dimension of δ and an angle with respect to the base line (BL) in the x-axis direction of θ (0 ° to 360 °). And let the length of the side shown to the figure of each element (3) be (L). In this case, the relational expressions of δ, θ, L and the maximum principal strain ε e of the element number (e) are (Expression 10) to (Expression 12) described later. Here, (Expression 10) is a relational expression when the shape of the element (3) is an equilateral triangle, and (Expression 11) and (Expression 12) are relational expressions when the shape of the element (3) is a right isosceles triangle. Show.
図７は、θとεｅの関係を示すグラフである。図７において、曲線（Ｉ）は、要素（３）の形状が正三角形の場合の変化を示し、曲線（ＩＩ）は、要素（３）の形状が直角二等辺三角形の場合の変化を示す。ここで、δ及びＬは任意の一定値である。図７の曲線（Ｉ）が示すように、要素形状が正三角形の場合、要素番号（ｅ）の最大主ひずみεｅは、いずれの角度θ（０°≦θ≦３６０°）においても、一定の範囲内で周期的に変化する値である。従って、要素（３）の形状を正三角形とし、検出したい最小のひび割れ幅δ（例えば、０．０５ｍｍ）における最小の最大主ひずみεｅをしきい値とすることで、しきい値よりも大きな値の差分ひずみΔεをほぼ安定して判別でき、ひび割れ検出の感度も安定する。 Figure 7 is a graph showing the relationship between θ and epsilon e. In FIG. 7, a curve (I) shows a change when the shape of the element (3) is an equilateral triangle, and a curve (II) shows a change when the shape of the element (3) is a right isosceles triangle. Here, δ and L are arbitrary constant values. As shown by curve (I) in FIG. 7, when the element shape is an equilateral triangle, the maximum principal strain ε e of the element number (e) is constant at any angle θ (0 ° ≦ θ ≦ 360 °). It is a value that periodically changes within the range. Big Accordingly, the shape of the element (3) is an equilateral triangle, the minimum crack width to be detected [delta] (e.g., 0.05 mm) by the smallest maximum threshold the principal strain epsilon e in, than the threshold The differential strain Δε of the value can be determined almost stably, and the sensitivity of crack detection is also stable.
そして、要素形状が直角二等辺三角形の場合には、最大主ひずみεｅは、角度θによって著しく異なる値となる。即ち、図７の曲線（ＩＩ）が示すように、最大主ひずみεｅは、ひび割れ（Ｃ）が底辺を通過する際（０°≦θ≦１１０°，１６０°≦θ≦２９０°，３４０°≦θ≦３６０°）小さな値となり、ひび割れ（Ｃ）が直角を挟む２辺を通過する際（１１０°≦θ≦１６０°，２９０°≦θ≦３４０°）大きな値となる。
このように、ひび割れ（Ｃ）が要素（３）の直角を挟む２辺を通過するときに、最大主ひずみεｅの値が大きくなる性質を利用することにより、ひび割れの方向性を把握することができる。これについて、詳細に説明する。
When the element shape is a right-angled isosceles triangle, the maximum principal strain ε e has a significantly different value depending on the angle θ. That is, as shown by curve (II) in FIG. 7, the maximum principal strain ε e is obtained when the crack (C) passes through the bottom (0 ° ≦ θ ≦ 110 °, 160 ° ≦ θ ≦ 290 °, 340 °). ≦ θ ≦ 360 °), a small value, and when the crack (C) passes through two sides sandwiching a right angle (110 ° ≦ θ ≦ 160 °, 290 ° ≦ θ ≦ 340 °), a large value.
Thus, by using the property that the value of the maximum principal strain ε e increases when the crack (C) passes through two sides sandwiching the right angle of the element (3), the direction of the crack is grasped. Can do. This will be described in detail.
図８は、ひび割れの方向性を検討するための図である。図８の（ａ）及び（ｂ）は、同一の節点（２’１，２’２，２’３，２’４）、同一方向のひび割れ（Ｃ３）で、どちらも要素（３，３’）の形状が直角二等辺三角形であるが、図８（ａ）は、節点（２’１，２’２，２’３）で要素（３）を構成した場合、図８（ｂ）は、節点（２’１，２’２，２’４）で要素（３’）を構成した場合を示す。
図８（ａ）の場合、ひび割れ（Ｃ３）は番号（３）の底辺を通過しているので、前記したように、最大主ひずみεｅが小さくなる。それに対し、図８（ｂ）の場合は、ひび割れ（Ｃ３）が要素（３’）の直角を挟む２辺を通過しているので、最大主ひずみεｅが大きくなる。このように、要素（３，３’）の形状を直角二等辺三角形とした場合に、ひび割れ（Ｃ３）に対して、要素（３，３’）の配置を変更し、差分ひずみΔεが大きく変化すれば、ひび割れ（Ｃ３）が直角を挟む２辺を通過していることがわかり、ひび割れ（Ｃ３）の方向性を把握することができる。
FIG. 8 is a diagram for examining the directionality of cracks. (A) and (b) of FIG. 8 are the same nodes (2 ′ 1 , 2 ′ 2 , 2 ′ 3 , 2 ′ 4 ) and cracks (C 3 ) in the same direction, both of which are elements (3, 3 The shape of ') is a right-angled isosceles triangle, but Fig. 8 (a) shows that when the element (3) is composed of nodes (2' 1 , 2 ' 2 , 2' 3 ), Fig. 8 (b) The case where the element (3 ′) is configured by the nodes (2 ′ 1 , 2 ′ 2 , 2 ′ 4 ) is shown.
In the case of FIG. 8A, since the crack (C 3 ) passes through the bottom of the number (3), the maximum principal strain ε e becomes small as described above. On the other hand, in the case of FIG. 8B, since the crack (C 3 ) passes through two sides sandwiching the right angle of the element (3 ′), the maximum principal strain ε e increases. Thus, when the shape of the element (3, 3 ′) is a right-angled isosceles triangle, the arrangement of the element (3, 3 ′) is changed with respect to the crack (C 3 ), and the differential strain Δε is large. if the change, notice that the crack (C 3) is passing through two sides sandwiching a right angle, it is possible to grasp the direction of crack (C 3).
本発明のひび割れ検出システム及び方法によれば、被検出体に標点を付すことで、トンネルや橋梁等の大規模なコンクリート構造物の外、管路等の小規模構造物や、マイクロチップ等の微小体等においても、ひび割れ発生箇所を簡単に検出することができる。ひび割れは、荷重を直接的に与えて生じるだけでなく、温度変化によるひずみや圧力変化等によっても生じるので、本発明は様々な技術分野において適用されるものであり、非常に有用である。 According to the crack detection system and method of the present invention, by attaching a mark to the object to be detected, outside of large-scale concrete structures such as tunnels and bridges, small-scale structures such as pipes, microchips, etc. Even in the case of microscopic objects, it is possible to easily detect the occurrence of cracks. Cracks are generated not only by directly applying a load, but also by strain and pressure changes due to temperature changes, and the present invention is applied in various technical fields and is very useful.
１・・・被検出体、１０・・・測定対象
２・・・標点、２’・・・節点
３・・・要素
Ｃ・・・ひび割れ
ｅ・・・一般化した要素番号
ｉ，ｊ，ｋ・・・一般化した節点番号
２０・・・撮像装置
２１・・・画像処理装置
２２・・・演算装置
２３・・・ひび割れ検知装置
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