JP4262609B2 - Magnetostrictive sensitivity calibration method and apparatus - Google Patents
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Description
本発明は、鋼管などの管に生ずる応力を測定する磁歪応力測定法に必要な磁歪感度の較正方法及び装置に関し、特に曲管の磁歪感度を簡便に較正する方法及び装置に関する。 The present invention relates to a magnetostriction sensitivity calibration method and apparatus necessary for a magnetostrictive stress measurement method for measuring stress generated in a pipe such as a steel pipe, and more particularly to a method and apparatus for easily calibrating magnetostriction sensitivity of a curved pipe.
ガスパイプラインなど地中に埋設されて用いられる鋼管は、地盤沈下や地表を走行する車両などからの荷重によって、鋼管に曲げ応力が発生する。大きな曲げ応力が発生した状態が継続されると、鋼管は破損するおそれがある。そこで、鋼管の破損予防のために鋼管に作用している曲げ応力（負荷応力）を測定する必要がある。
そして、パイプライン等の構造物において最も危険な部位は、応力集中が生じやすく応力分布も複雑な曲管部である。
したがって、曲管部の応力測定をして安全性を評価することが最も直接的かつ効果的である。応力測定の手法としてはひずみゲージ法が一般的であるが、パイプラインの応力を年単位の長期間でひずみゲージ法で測定することは不可能であるため、磁歪応力測定法の利用が有効である。ところが、一方、磁歪応力測定法で測定できる応力は残留応力と負荷応力が重畳したものであるが、通常安全性の評価基準となるのは残留応力を除いた負荷応力である。そのため、安全性評価のためには測定された応力から残留応力を除いて負荷応力を求める必要がある。ところが、曲管部における残留応力分布は極めて複雑であり、測定応力から残留応力を除去する理論が構築されておらず、曲管の応力測定を行っても安全性の評価に必要となる負荷応力を求めることができない。そこで、従来は直管部について応力測定を行い、その結果を境界条件として有限要素法などの計算によって曲管部の応力を推定し、安全性の評価を行っていた。
In steel pipes that are buried in the ground such as gas pipelines, bending stress is generated in the steel pipes due to ground subsidence or loads from vehicles traveling on the ground surface. If the state in which a large bending stress is generated continues, the steel pipe may be damaged. Therefore, it is necessary to measure the bending stress (load stress) acting on the steel pipe in order to prevent damage to the steel pipe.
The most dangerous part in a structure such as a pipeline is a curved pipe portion in which stress concentration is likely to occur and the stress distribution is complicated.
Therefore, it is most direct and effective to evaluate the safety by measuring the stress of the bent pipe portion. The strain gauge method is generally used as a stress measurement method, but it is impossible to measure the stress in the pipeline by the strain gauge method over a long period of a year, so it is effective to use the magnetostrictive stress measurement method. is there. On the other hand, the stress that can be measured by the magnetostrictive stress measurement method is a superposition of the residual stress and the load stress, but it is the load stress excluding the residual stress that is usually used as an evaluation criterion for safety. Therefore, for the safety evaluation, it is necessary to obtain the load stress by removing the residual stress from the measured stress. However, the residual stress distribution in the curved pipe is extremely complex, and no theory has been established to remove the residual stress from the measured stress, and the load stress required for safety evaluation even if the curved pipe stress is measured. Cannot be asked. Therefore, in the past, stress measurement was performed on a straight pipe part, and the stress of the bent pipe part was estimated by calculation such as a finite element method using the result as a boundary condition to evaluate safety.
磁歪応力測定法は強磁性材料である鋼管などの材料に荷重が作用すると材料の透磁率が応力に比例して変化することを利用するものである。磁歪応力測定法においては、鋼管の主応力差に比例した電圧値が測定されるが、この電圧値を応力に換算するための比例定数を磁歪感度という。この磁歪感度は鋼管の材質や製造方法によって固有の値を示す。そのため、磁歪応力測定法で測定しようとする鋼管については、測定前に同等の鋼管について負荷試験を行い、ひずみゲージによって実際の応力値を検出することで当該鋼管の磁歪感度を求める必要があり、この磁歪感度を求めることを磁歪感度の較正という。 The magnetostrictive stress measurement method utilizes the fact that when a load is applied to a material such as a steel pipe that is a ferromagnetic material, the magnetic permeability of the material changes in proportion to the stress. In the magnetostrictive stress measurement method, a voltage value proportional to the main stress difference of the steel pipe is measured. A proportional constant for converting this voltage value into stress is called magnetostrictive sensitivity. This magnetostrictive sensitivity shows a specific value depending on the material and manufacturing method of the steel pipe. Therefore, for steel pipes to be measured by the magnetostrictive stress measurement method, it is necessary to perform a load test on the equivalent steel pipe before measurement, and to determine the magnetostriction sensitivity of the steel pipe by detecting the actual stress value with a strain gauge, Obtaining this magnetostrictive sensitivity is called magnetostrictive sensitivity calibration.
このような磁歪感度の較正方法として、磁歪応力が測定されるべき管を、その管軸に沿って切出して細長い試験片を作成し、この試験片に前記管軸に平行な平面内で曲げモーメントを作用させ、試験片の外表面に設けた応力測定手段で真の応力を測定するとともに、磁歪センサで真の応力に対応した出力を測定し、応力測定手段によって測定された応力と、磁歪センサの出力とから、磁歪センサの磁歪感度を求めるものが知られている（特許文献１参照）。 As a method for calibrating the magnetostrictive sensitivity, a tube to be measured for magnetostrictive stress is cut out along the tube axis to create an elongated test piece, and a bending moment is formed on the test piece in a plane parallel to the tube axis. The true stress is measured by the stress measuring means provided on the outer surface of the test piece, the output corresponding to the true stress is measured by the magnetostrictive sensor, the stress measured by the stress measuring means, and the magnetostrictive sensor It is known that the magnetostrictive sensitivity of a magnetostrictive sensor is obtained from the output of the above (see Patent Document 1).
また、実際の現場にて磁歪感度を求め、鋼管の応力測定をする方法としては以下のものがある。
被検査物体の表面にひずみゲージを固定し、かつその近傍に材料の透磁率に対応した電気的出力を導出する磁歪センサを設け、被検査物体に加える力を変化させて、ひずみゲージの出力を応力に換算し、応力変化に対する磁歪センサの出力の傾きから比例定数としての磁歪感度を求め、求められた磁歪感度の値を用いて、磁歪センサの出力から被検査物体に作用する応力を測定する（特許文献２参照）。
Further, methods for obtaining magnetostrictive sensitivity at an actual site and measuring the stress of a steel pipe include the following.
A strain gauge is fixed on the surface of the object to be inspected, and a magnetostrictive sensor for deriving an electrical output corresponding to the magnetic permeability of the material is provided in the vicinity thereof, and the force applied to the object to be inspected is changed to change the output of the strain gauge. Convert to stress, obtain magnetostrictive sensitivity as a proportional constant from the slope of the magnetostrictive sensor output with respect to the stress change, and measure the stress acting on the object to be inspected from the magnetostrictive sensor output using the obtained magnetostrictive sensitivity value (See Patent Document 2).
前述のように、パイプライン等の構造物においては最も危険となる曲管部の応力測定を行いその測定結果に基づいて安全性の評価をすることが直接的かつ効果的である。しかし従来においては測定応力から残留応力を除去する理論構築がなされていなかったために、次善の手段として直管部について応力測定を行い、その結果を境界条件として有限要素法などの計算によって曲管部の応力を推定して安全性の評価を行っていたのである。
しかしながら、発明者は、鋭意研究の結果、曲管について測定応力から残留応力を除去するための理論構築を完成し、本願に先立って特許出願を行った。この理論を用いれば曲管についても測定応力から残留応力を除去することができ、曲管部について応力測定を行って安全性の評価をすることが可能となる。そこで、現場での応力測定に先立って曲管についての磁歪感度の較正方法が求められることになった。
As described above, in a structure such as a pipeline, it is direct and effective to measure the stress of the bent pipe portion, which is the most dangerous, and to evaluate the safety based on the measurement result. However, since no theoretical construction has been made to remove the residual stress from the measured stress in the past, as a suboptimal measure, stress measurement is performed on the straight pipe, and the result is used as a boundary condition to calculate the curved pipe by calculation such as the finite element method. The stress of the part was estimated and safety was evaluated.
However, as a result of earnest research, the inventor completed the theoretical construction for removing the residual stress from the measured stress for the bent pipe, and filed a patent application prior to the present application. If this theory is used, residual stress can be removed from the measured stress even for the curved pipe, and the safety can be evaluated by measuring the stress on the curved pipe portion. Therefore, prior to the on-site stress measurement, a method for calibrating magnetostrictive sensitivity for bent pipes has been required.
ところが、従来の磁歪感度の較正方法は全て直管に関するものであり、このような直管に関する磁歪感度の較正方法をそのまま曲管に適用しようとすると、以下のような問題がある。
特許文献１の方法は、鋼管の一部を短冊状に加工して試験片にするものであるが、曲管の場合には短冊状への加工が困難である。
また、曲管はその製法によって複雑かつ高い残留応力をもっているが、短冊状に加工するとこの残留応力が解放され、試験片と実管の応力状態が変わってしまう。そのため、仮に短冊状、あるいは類似の形状に加工できたとしても、そのような短冊状の試験片に基づいて磁歪感度を較正しても、実管のものとは異なったものとなってしまう。
However, the conventional magnetostrictive sensitivity calibration methods are all related to straight pipes, and if the magnetostrictive sensitivity calibration method related to straight pipes is applied to a curved pipe as it is, there are the following problems.
Although the method of patent document 1 processes a part of steel pipe into a strip shape, and makes it a test piece, in the case of a curved pipe, the process to a strip shape is difficult.
In addition, the curved pipe has a complicated and high residual stress due to its manufacturing method, but when it is processed into a strip shape, the residual stress is released, and the stress state between the test piece and the actual pipe changes. Therefore, even if it can be processed into a strip shape or a similar shape, even if the magnetostriction sensitivity is calibrated based on such a strip-shaped test piece, it is different from the actual tube.
特許文献２の方法は、実際の現場において被測定対象管を利用して磁歪感度の較正を行うものであり、短冊状の加工をしないので、少なくとも特許文献１に対して指摘したような問題はない。
しかしながら、実際の現場において荷重を付加して磁歪感度の較正することから以下のような問題がある。
現場で曲管に段階的な荷重を付加するためにはその作業が非常に煩雑となる。また、供用状態にある鋼管に対して強制的に外力を付加して応力を発生させることになるため、安全性の観点から十分な配慮をする必要があり、そのため十分な応力を与えることができず、較正試験として十分な精度を得ることが難しい。
The method of Patent Document 2 is for calibrating magnetostriction sensitivity using a measurement target tube in an actual site, and does not perform strip-shaped processing. Absent.
However, since the magnetostriction sensitivity is calibrated by adding a load at an actual site, there are the following problems.
In order to apply a stepwise load to the curved pipe at the site, the work becomes very complicated. In addition, stress is generated by forcibly applying an external force to the steel pipe in service, so it is necessary to give sufficient consideration from the viewpoint of safety, so that sufficient stress can be applied. Therefore, it is difficult to obtain sufficient accuracy as a calibration test.
以上要するに、従来においては曲管について磁歪応力測定したとしても安全性の評価をすることができないことから、磁歪感度の較正方法は全て直管を対象とするものであった。ところが、発明者の努力により曲管についての応力測定結果を用いて安全性の評価をすることが可能となったことから、その前提となる曲管についての磁歪感度の較正方法が求められるようになった。ところが、従来の磁歪感度の較正方法は全て直管を対象としていることからこれを曲管に適用することができない。このような背景から曲管についての磁歪感度の較正方法及び装置が望まれていたのである。 In short, all the conventional magnetostrictive sensitivity calibration methods are intended for straight pipes because safety evaluation cannot be performed even if magnetostrictive stress measurement is performed on a curved pipe. However, since it has become possible to evaluate the safety using the stress measurement result of the bent pipe by the inventor's efforts, a calibration method of magnetostrictive sensitivity for the bent pipe, which is the prerequisite, is required. became. However, since all conventional magnetostrictive sensitivity calibration methods are intended for straight pipes, this cannot be applied to curved pipes. From such a background, a calibration method and apparatus for magnetostrictive sensitivity of a curved pipe has been desired.
本発明はかかる課題を解決するためになされたものであり、曲管に対しても適切かつ簡易に磁歪感度を求めることができる磁歪感度の較正方法及び装置を得ることを目的としている。 The present invention has been made to solve such a problem, and an object of the present invention is to obtain a magnetostriction sensitivity calibration method and apparatus capable of obtaining magnetostriction sensitivity appropriately and easily even for a curved pipe.
（１）本発明に係る磁歪感度較正方法は、曲管に段階的な荷重を作用させて前記曲管の屈曲部に生ずる応力を応力測定手段によって測定すると共に、前記応力に対応して出力される磁歪センサの電気信号を検出し、前記測定された応力と前記磁歪センサから出力される電気信号とから前記曲管に対する磁歪センサの磁歪感度を求める磁歪感度の較正方法であって、前記荷重を、前記曲管の屈曲部に対して前記屈曲部を押し潰すように管軸直交方向に付加することを特徴とするものである。 (1) In the magnetostrictive sensitivity calibration method according to the present invention, a stepwise load is applied to a curved pipe to measure the stress generated in the bent portion of the curved pipe by a stress measuring means and output corresponding to the stress. A magnetostrictive sensitivity calibration method for detecting a magnetostrictive sensitivity of the magnetostrictive sensor with respect to the curved pipe from the measured stress and the electrical signal output from the magnetostrictive sensor. The bending portion of the bent pipe is added in a direction perpendicular to the tube axis so as to crush the bent portion .
（２）また、上記（１）のものにおいて、前記応力測定手段と前記磁歪センサを管内面に設置したことを特徴とするものである。 (2) In the above (1), the stress measuring means and the magnetostrictive sensor are installed on the inner surface of the tube .
（３）また、上記（１）または（２）のものにおいて、前記荷重は、管軸が作る平面に対して直交方向に付加する圧縮荷重とし、前記磁歪センサと応力測定手段を、荷重作用線上であって前記曲管の管中心点に対して対称位置に設置したことを特徴とするものである。
なお、荷重作用線とは荷重作用方向を示す仮想線をいう。
(3) In the above (1) or (2) , the load is a compressive load applied in a direction orthogonal to the plane formed by the tube axis, and the magnetostrictive sensor and the stress measuring means are placed on the load action line. And it installed in the symmetrical position with respect to the pipe | tube center point of the said curved pipe.
In addition, a load action line means the virtual line which shows a load action direction.
（４）また、上記（１）または（２）のものにおいて、前記磁歪センサと応力測定手段を、荷重作用点に対して管軸方向対称位置に設置したことを特徴とするものである。 (4) Further, in the above (1) or (2) , the magnetostrictive sensor and the stress measuring means are installed at symmetrical positions in the tube axis direction with respect to the load acting point.
（５）本発明に係る磁歪感度較正装置は、磁歪感度が測定される曲管に対して段階的な荷重を作用させる荷重付加手段と、前記曲管に設置されて前記荷重付加手段によって荷重が付加されたときに前記曲管の屈曲部に生ずる応力を検出する応力検出手段と、前記曲管に設置されて前記応力に対応する電気信号を出力する磁歪センサと、前記応力検出手段の検出値と前記磁歪センサの出力値とから前記曲管に対する磁歪センサの磁歪感度を演算する演算手段とを有し、
前記荷重付加手段は、前記曲管の屈曲部外周面に当接する当接部と、該当接部を前記曲管側に押し付けて圧縮荷重を付加するジャッキを備え、
前記磁歪センサと前記応力検出手段は、前記曲管の屈曲部の管内面に設置されることを特徴とするものである。
(5) The magnetostrictive sensitivity calibration apparatus according to the present invention includes a load adding means for applying a stepwise load to the curved pipe whose magnetostrictive sensitivity is measured, and a load applied by the load adding means installed in the curved pipe. A stress detecting means for detecting a stress generated in a bent portion of the bent pipe when added; a magnetostrictive sensor installed in the bent pipe for outputting an electric signal corresponding to the stress; and a detected value of the stress detecting means. And a calculation means for calculating the magnetostrictive sensitivity of the magnetostrictive sensor with respect to the curved pipe from the output value of the magnetostrictive sensor,
The load applying means includes a contact portion that contacts the outer peripheral surface of the bent portion of the bent tube, and a jack that applies a compressive load by pressing the contact portion toward the bent tube side,
The magnetostrictive sensor and the stress detecting means are installed on the inner surface of the bent portion of the bent tube .
本発明においては、曲管に段階的な荷重を作用させて前記曲管の屈曲部に生ずる応力を応力測定手段によって測定すると共に、前記応力に対応して出力される磁歪センサの電気信号を検出し、前記測定された応力と前記磁歪センサから出力される電気信号とから前記曲管に対する磁歪センサの磁歪感度を求める磁歪感度の較正方法であって、前記荷重を、前記曲管の屈曲部に対して前記屈曲部を押し潰すように管軸直交方向に付加するようにしたので、曲管に対する荷重の付加が容易にでき、簡易に高精度の磁歪感度の較正が実現できる。 In the present invention, a stepwise load is applied to the bent pipe to measure the stress generated in the bent portion of the bent pipe by the stress measuring means, and an electric signal of the magnetostrictive sensor output corresponding to the stress is detected. A magnetostrictive sensitivity calibration method for obtaining magnetostrictive sensitivity of the magnetostrictive sensor with respect to the curved pipe from the measured stress and an electric signal output from the magnetostrictive sensor, wherein the load is applied to a bent portion of the curved pipe. On the other hand, since the bending portion is applied in the direction perpendicular to the tube axis so as to be crushed, it is possible to easily apply a load to the bent tube, and to easily calibrate the magnetostriction sensitivity with high accuracy.
図６は本発明において使用される磁歪センサの動作原理を示す説明図であり、図６（ａ）が原理説明図、図６（ｂ）が磁歪センサの説明図である。
図６において、１は励磁コア、１ａは励磁コイル、２は励磁コア１と互いに直交状態に配設された磁気異方性検出コア、２ａは磁気異方性検出コイル、３は交流定電流電源、４は電圧計、５は測定対象物である。
6A and 6B are explanatory views showing the operation principle of the magnetostrictive sensor used in the present invention. FIG. 6A is an explanatory view of the principle, and FIG. 6B is an explanatory view of the magnetostrictive sensor.
In FIG. 6, 1 is an excitation core, 1a is an excitation coil, 2 is a magnetic anisotropy detection core disposed orthogonal to the excitation core 1, 2a is a magnetic anisotropy detection coil, and 3 is an AC constant current power source. Reference numeral 4 denotes a voltmeter, and 5 denotes an object to be measured.
上記のように構成された磁歪センサの動作原理を説明する。測定対象物５にひずみ（応力）が作用すると、透磁率μに異方性が生じる。例えば、測定対象物５が図６（ａ）に示すような応力状態にある場合、引張応力方向であるＸ方向の透磁率μｘがＹ方向の透磁率μｙに比べて相対的に大きくなる。
このとき、励磁コイル１ａに電流を流すと、励磁コア１の片方の足Ｅ1の先端から出た磁束の大部分は最短距離で直接他方の足Ｅ2に向かうが、Ｅ1Ｄ1間及びＤ2Ｅ2間はＥ1Ｄ2間及びＤ1Ｅ2間に比べて透磁率がμｘ―μｙだけ大きいために、一部は図中の矢印で示すように磁気異方性検出コア２の中を経由して、励磁コア１の他方の足Ｅ2に向かう。
以上の動作を交流磁界で考えると、磁気異方性検出コイル２ａには誘導電流が流れ、電圧計４に電圧が検出される。この電圧は透磁率の異方性が大きい程より大きなものとなる。また、このとき磁歪センサを測定対象上で回転させると、磁歪センサの出力Ｖは（１）式で表現される様な周期１８０°の余弦関数となる。
Ｖ＝Ａ＋Ｂ・cos(θ−Ｃ) ------（１）
但し、Ａ：オフセット、Ｂ：変動振幅量、Ｃ：位相角
The operation principle of the magnetostrictive sensor configured as described above will be described. When strain (stress) acts on the measuring object 5, anisotropy occurs in the magnetic permeability μ. For example, when the measuring object 5 is in a stress state as shown in FIG. 6A, the magnetic permeability μx in the X direction, which is the tensile stress direction, is relatively larger than the magnetic permeability μy in the Y direction.
At this time, when a current is passed through the exciting coil 1a, most of the magnetic flux emitted from the tip of one leg E1 of the exciting core 1 goes directly to the other leg E2 at the shortest distance, but between E1D1 and D2E2 is between E1D2 Since the permeability is larger by [mu] x- [mu] than that between D1E2 and a part thereof, the other leg E2 of the exciting core 1 passes through the magnetic anisotropy detection core 2 as shown by arrows in the figure. Head for.
Considering the above operation with an alternating magnetic field, an induced current flows through the magnetic anisotropy detection coil 2 a and a voltage is detected by the voltmeter 4. This voltage becomes larger as the magnetic permeability anisotropy is larger. At this time, when the magnetostrictive sensor is rotated on the object to be measured, the output V of the magnetostrictive sensor becomes a cosine function having a period of 180 ° as expressed by the equation (1).
V = A + B ・ cos (θ-C) ------ (1)
A: Offset, B: Fluctuation amplitude, C: Phase angle
センサ出力Ｖは励磁コア１または磁気異方性検出コア２と主応力の方向が４５°のときに最大出力となり、このときセンサ出力は、Ｘ方向の透磁率μｘとＹ方向の透磁率μｙの差、すなわちμｘ―μｙに比例する。
Ｖ＝Ｍ０・（μｘ―μｙ） ----------（２）
但し、Ｍ０は比例定数
The sensor output V becomes the maximum output when the direction of the principal stress is 45 ° with the excitation core 1 or the magnetic anisotropy detection core 2, and the sensor output at this time is the permeability μx in the X direction and the permeability μy in the Y direction. It is proportional to the difference, that is, μx−μy.
V = M0 ・ (μx-μy) ---------- (2)
However, M0 is a proportional constant
透磁率μは被測定物のひずみ（応力）と比例関係にあるため、結果的に下記の（３）式となる。
Ｖ＝Ｍ１・（σｘ―σｙ） -----------（３）
但し、Ｍ１は比例定数
この比例定数Ｍ１が磁歪感度であり、測定対象に応じて較正試験を実施して求められるものである。
Since the magnetic permeability μ is proportional to the strain (stress) of the object to be measured, the following equation (3) is obtained.
V = M1 · (σx-σy) ----------- (3)
However, M1 is a proportionality constant. This proportionality constant M1 is magnetostriction sensitivity, and is obtained by performing a calibration test in accordance with the measurement object.
次に、上記の原理に基づく本発明の一実施形態である磁歪感度較正装置を説明する。図１は本発明の一実施形態に係る磁歪感度較正装置の模式図であり、図１（ａ）が正面図、図１（ｂ）が側面図である。
測定対象となる曲管６は平面かつ水平で剛な定盤７に横置きされている。つまり、曲管６の軸線がつくる平面が水平になるように定盤７上に置かれている。曲管６を跨ぐようにして門型の反力架台８が配置され、反力架台８の横架部には荷重付加用のジャッキ９が取り付けられている。ジャッキ９の下端側には曲管６の周面形状に対応した当接部を有する治具１０が取り付けられている。したがって、曲管６にはジャッキ９に取り付けられた治具１０を介して曲管６の軸線が作る平面に直交方向に押しつぶされるような荷重が段階的に付加できるように構成されている。
Next, a magnetostriction sensitivity calibration apparatus according to an embodiment of the present invention based on the above principle will be described. FIG. 1 is a schematic diagram of a magnetostrictive sensitivity calibration apparatus according to an embodiment of the present invention, in which FIG. 1 (a) is a front view and FIG. 1 (b) is a side view.
The curved pipe 6 to be measured is placed horizontally on a flat, horizontal and rigid surface plate 7. That is, it is placed on the surface plate 7 so that the plane formed by the axis of the curved pipe 6 is horizontal. A gate-type reaction force frame 8 is disposed so as to straddle the curved tube 6, and a load-adding jack 9 is attached to the horizontal portion of the reaction force frame 8. A jig 10 having a contact portion corresponding to the shape of the peripheral surface of the curved pipe 6 is attached to the lower end side of the jack 9. Therefore, the bending tube 6 is configured so that a load that is crushed in a direction orthogonal to a plane formed by the axis of the bending tube 6 can be applied in a stepwise manner via the jig 10 attached to the jack 9.
また、曲管６の内面には応力検出手段としてのひずみゲージ１１と磁歪センサ１２が設置されている。ひずみゲージ１１は荷重作用線２１（図１参照）上で治具１０が当接する部位の内面に配置され、磁歪センサ１２はひずみゲージ１１設置位置と曲管の径方向における中心点の対称位置に配置されている。
ひずみゲージ１１と磁歪センサ１２は荷重が作用したときに同一の歪が生ずる箇所に設置する必要があるが、本実施形態のように、曲管６の軸線が作る平面に直交方向に荷重を付加するようにしたことで、ひずみゲージ１１と磁歪センサ１２の設置すべき箇所を容易に設定できる。
A strain gauge 11 and a magnetostrictive sensor 12 are installed on the inner surface of the bent tube 6 as stress detecting means. The strain gauge 11 is disposed on the inner surface of the portion where the jig 10 abuts on the load acting line 21 (see FIG. 1), and the magnetostrictive sensor 12 is located at a symmetrical position between the strain gauge 11 installation position and the central point in the radial direction of the curved pipe. Has been placed.
Although the strain gauge 11 and the magnetostrictive sensor 12 need to be installed at a location where the same strain is generated when a load is applied, the load is applied in a direction orthogonal to the plane formed by the axis of the curved pipe 6 as in this embodiment. By doing so, the location where the strain gauge 11 and the magnetostrictive sensor 12 should be installed can be easily set.
以上のように構成された本実施の形態の装置を用いた磁歪感度の較正方法を以下に説明する。
なお、この実施形態で用いた曲管６は高圧ガス導管に使用されるマンドレルエルボ材で、JISのPT370-sch40
材、呼び径300A である。
ジャッキ９を下降させて曲管６に段階的な荷重を付加してゆき、ひずみゲージ１１から検出される応力と、磁歪センサ１２から出力される電圧を求める。
図２はこの結果をグラフに整理したものであり、横軸（Ｘ軸）がひずみゲージ１１から検出された応力を示し、縦軸（Ｙ軸）が磁歪センサ１２から出力される電圧を示している。また、図２のグラフ中にはＸ-Ｙの関係を最小二乗法で直線に回帰した結果を併記してある。この回帰結果の傾きが本較正試験方法で求められた磁歪感度であり、この例では1.9665(mV/MPa)である。
なお、図１では、ひずみゲージ１１によって検出される応力と磁歪センサ１２から出力される電圧から磁歪感度を演算する手段については図示していないが、このような演算手段はコンピュータによって実現できる。
A magnetostrictive sensitivity calibration method using the apparatus of the present embodiment configured as described above will be described below.
The bent pipe 6 used in this embodiment is a mandrel elbow material used for a high-pressure gas conduit, and is JIS PT370-sch40.
The material has a nominal diameter of 300A.
The jack 9 is lowered and a stepwise load is applied to the bent tube 6 to obtain the stress detected from the strain gauge 11 and the voltage output from the magnetostrictive sensor 12.
FIG. 2 is a graph of the results. The horizontal axis (X axis) indicates the stress detected from the strain gauge 11, and the vertical axis (Y axis) indicates the voltage output from the magnetostrictive sensor 12. Yes. The graph of FIG. 2 also shows the results of regression of the XY relationship to a straight line using the least square method. The slope of this regression result is the magnetostriction sensitivity obtained by this calibration test method, which is 1.9665 (mV / MPa) in this example.
In FIG. 1, means for calculating the magnetostriction sensitivity from the stress detected by the strain gauge 11 and the voltage output from the magnetostrictive sensor 12 is not shown, but such calculation means can be realized by a computer.
次に、上述した図１に示した方法で求めた磁歪感度が、実際の現場における付加荷重によって発生する応力測定の磁歪感度として適用できるかどうかの検証を行った。
図３はこの検証に用いた装置の説明図である。この検証用装置は、図１で用いたものと同様の曲管１３の両端に袖管１４ａ、１４ｂを溶接している。この袖管１４ａ、１４ｂは端部にフランジ１５ａ、１５ｂを有している。片側の袖管１４ａのフランジ１５ａを定盤１６に固定し、他方の袖管１４ｂのフランジ１５ｂを油圧ジャッキ１７のロッドにピンを介して取り付けられている。また、曲管１３の外面にひずみゲージ１８と磁歪センサ１９を設置している。
Next, it was verified whether the magnetostrictive sensitivity obtained by the method shown in FIG. 1 described above can be applied as the magnetostrictive sensitivity of the stress measurement generated by the applied load in the actual site.
FIG. 3 is an explanatory diagram of the apparatus used for this verification. In this verification apparatus, sleeve tubes 14a and 14b are welded to both ends of a bent tube 13 similar to that used in FIG. The sleeves 14a and 14b have flanges 15a and 15b at their ends. The flange 15a of the sleeve tube 14a on one side is fixed to the surface plate 16, and the flange 15b of the other sleeve tube 14b is attached to the rod of the hydraulic jack 17 via a pin. Further, a strain gauge 18 and a magnetostrictive sensor 19 are installed on the outer surface of the bent tube 13.
図３に示した検証用の装置において、ジャッキ１７のロッドを段階的に伸ばすことで曲管に段階的に曲げモーメントを付加し、曲管外面に発生した応力をひずみゲージ１８で求め、ひずみゲージの至近に設定した磁歪センサ１９の出力と共に計測した。
図４は図３の方法で求めた結果をグラフに整理したものであり、横軸（Ｘ軸）がひずみゲージ１８から検出された応力を示し、縦軸（Ｙ軸）が磁歪センサ１９から出力される電圧を示している。また、図４にはＸ-Ｙの関係を最小二乗法で直線に回帰した結果を併記してある。この回帰結果の傾きが本較正試験方法で求められた磁歪感度である。
図１に示した本発明による方法によって得られた結果と、図３に示した検証用装置で得られた結果を表１に示す。
In the verification apparatus shown in FIG. 3, a bending moment is applied to the curved pipe stepwise by extending the rod of the jack 17 stepwise, and the stress generated on the outer surface of the curved pipe is obtained by the strain gauge 18, and the strain gauge Was measured together with the output of the magnetostrictive sensor 19 set in the vicinity.
FIG. 4 is a graph in which the results obtained by the method of FIG. 3 are arranged. The horizontal axis (X axis) indicates the stress detected from the strain gauge 18, and the vertical axis (Y axis) is output from the magnetostrictive sensor 19. The voltage to be shown. FIG. 4 also shows the result of regressing the XY relationship to a straight line by the method of least squares. The slope of this regression result is the magnetostriction sensitivity obtained by this calibration test method.
Table 1 shows the results obtained by the method according to the present invention shown in FIG. 1 and the results obtained by the verification apparatus shown in FIG.
表１から明らかなように、両者の結果は実用的な誤差範囲内にあり、非常によく一致している。このことから、図１の様な簡易な磁歪感度の較正試験方法によっても図３に示すような実際の荷重状態と同様の結果が得られることが実証された。 As is clear from Table 1, both results are within a practical error range and are in good agreement. From this, it was proved that the same result as the actual load state as shown in FIG. 3 can be obtained by the simple magnetostriction sensitivity calibration test method as shown in FIG.
以上のように、本実施の形態によれば、図３に示すような袖管を設けた大掛かりな装置を用いることなく極めて簡便な装置及び方法によって、実際の現場に適用できる磁歪感度の較正が可能となる。 As described above, according to the present embodiment, the magnetostriction sensitivity that can be applied to an actual site can be calibrated by a very simple device and method without using a large-scale device provided with a sleeve as shown in FIG. It becomes.
また、本実施の形態では磁歪センサ１２を荷重作用線上に設置していることから、管周方向と管軸方向の透磁率の差が大きく小さい荷重で大きな応力差及び出力電圧が得られるので磁歪感度の精度が高い。
この点を実証するために、水平方向内面（図１において（ア）（イ）で示す部位）に磁歪センサ１２を設置した場合の負荷応力と出力電圧の関係を求めたので、これを図５及び表２に示す。
In the present embodiment, since the magnetostrictive sensor 12 is installed on the load action line, a large stress difference and output voltage can be obtained with a large load and a small difference in permeability between the tube circumferential direction and the tube axis direction. High sensitivity accuracy.
In order to verify this point, the relationship between the load stress and the output voltage when the magnetostrictive sensor 12 is installed on the inner surface in the horizontal direction (the part indicated by (a) and (b) in FIG. 1) was obtained. And in Table 2.
図５及び表２から分かるように、水平位置（ア）（イ）で測定したものは付加する荷重に対して応力及び電圧のふれが小さいために、相関係数も0.9以下と低く高精度の磁歪感度が得られていない。
これに対して、上下位置の本実施形態では、応力及び電圧のふれが大きく相関係数も0.9938と大きく高精度の結果が得られていることが実証された。
As can be seen from FIG. 5 and Table 2, the stress measured at the horizontal position (A) (B) is small in stress and voltage with respect to the applied load. Magnetostrictive sensitivity is not obtained.
On the other hand, in this embodiment in the vertical position, it was proved that stress and voltage fluctuations were large and the correlation coefficient was as large as 0.9938, and a highly accurate result was obtained.
また、本実施の形態においては、ひずみゲージ及び磁歪センサを曲管の内面に設置するようにしたので、これらを外面に設置する場合に必要となる塗装や被覆材の剥離作業が不要である。また、袖管の溶接が不要なことから磁歪感度較正に使用した曲管を実工事に供用できるという効果もある。 Further, in the present embodiment, since the strain gauge and the magnetostrictive sensor are installed on the inner surface of the curved pipe, it is not necessary to perform the painting or the covering material peeling work required when installing them on the outer surface. Further, since there is no need to weld the sleeve tube, there is also an effect that the bent tube used for magnetostriction sensitivity calibration can be used for actual construction.
なお、上記の実施の形態においては、曲管の屈曲部に対して管軸がつくる面に直交する方向から曲管に段階的な圧縮荷重を作用させた例を示した。
しかし、本発明はこれに限られるものではなく、曲管の屈曲部に対して管軸直交方向に段階的な圧縮荷重を作用させるものを広く含む。例えば、図１に示したのと同様に曲管を定盤７上に置き、曲管の屈曲部内側に反力壁を設け、屈曲部の外側からジャッキ等で曲管屈曲部に水平方向の圧縮荷重を段階的に付加するようにしてもよい。
In the above-described embodiment, an example in which a stepwise compressive load is applied to the bent pipe from the direction perpendicular to the surface formed by the pipe axis with respect to the bent portion of the bent pipe is shown.
However, the present invention is not limited to this, and widely includes those in which a stepwise compressive load is applied in the direction perpendicular to the tube axis to the bent portion of the bent tube. For example, a curved pipe is placed on the surface plate 7 in the same manner as shown in FIG. 1, a reaction wall is provided inside the bent portion of the bent tube, and a horizontal direction is placed on the bent pipe bent portion with a jack or the like from the outside of the bent portion. You may make it add a compressive load in steps.
また、図１に示した本実施形態では荷重を付加するジャッキ側にのみ治具１０を取り付けたが、曲管の管径などに応じて適宜定盤７側にも同様の治具を設けてもよい。
さらに、図１に示した例では定盤７上に曲管を水平に横置きした例を示したが、適当な反力壁を用いることにより曲管を立てた状態にして水平方向に荷重を付加するようにしてもよい。
さらに、図１では曲管の内面上側（ジャッキ側）にひずみゲージ１１を設置し、内面下側（定盤側）に磁歪センサ１２を設置したが、上下逆にしてもよい。
また、ひずみゲージ１１と磁歪センサ１２を、荷重作用点に対して管軸方向対称位置に設置してもよい。
Further, in the present embodiment shown in FIG. 1, the jig 10 is attached only to the jack side to which the load is applied, but a similar jig is also provided on the surface plate 7 side as appropriate according to the tube diameter of the curved pipe. Also good.
Further, in the example shown in FIG. 1, an example in which the curved pipe is horizontally placed on the surface plate 7 is shown. However, a load is applied in the horizontal direction in a state where the curved pipe is erected by using an appropriate reaction force wall. You may make it add.
Furthermore, in FIG. 1, the strain gauge 11 is installed on the inner surface upper side (jack side) of the curved pipe, and the magnetostrictive sensor 12 is installed on the lower inner surface side (surface plate side).
Further, the strain gauge 11 and the magnetostrictive sensor 12 may be installed at positions symmetrical with respect to the load acting point in the tube axis direction.
６…曲管、８…反力架台、９…ジャッキ、１０…治具、１１…ひずみゲージ、１２…磁歪センサ 6 ... curved pipe, 8 ... reaction force mount, 9 ... jack, 10 ... jig, 11 ... strain gauge, 12 ... magnetostrictive sensor
Claims (5)
前記荷重を、前記曲管の屈曲部に対して前記屈曲部を押し潰すように管軸直交方向に付加することを特徴とする磁歪感度較正方法。 The magnetostrictive sensitivity calibration method according to claim 1, wherein the load is applied in a direction perpendicular to the tube axis so as to crush the bent portion with respect to the bent portion of the bent tube.
前記荷重付加手段は、前記曲管の屈曲部外周面に当接する当接部と、該当接部を前記曲管側に押し付けて圧縮荷重を付加するジャッキを備え、
前記磁歪センサと前記応力検出手段は、前記曲管の屈曲部の管内面に設置されることを特徴とする磁歪感度較正装置。 A load applying means for applying a stepwise load to the bent pipe whose magnetostriction sensitivity is measured, and a bent portion of the bent pipe when the load is applied by the load adding means installed on the bent pipe Stress detecting means for detecting stress, a magnetostrictive sensor that is installed in the bent pipe and outputs an electrical signal corresponding to the stress, a detected value of the stress detecting means, and an output value of the magnetostrictive sensor, with respect to the bent pipe An arithmetic means for calculating the magnetostrictive sensitivity of the magnetostrictive sensor,
The load applying means includes a contact portion that contacts the outer peripheral surface of the bent portion of the bent tube, and a jack that applies a compressive load by pressing the contact portion toward the bent tube side,
The magnetostrictive sensitivity calibration apparatus, wherein the magnetostrictive sensor and the stress detecting means are installed on an inner surface of a bent portion of the bent tube .
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