JP4691279B2

JP4691279B2 - Stress measuring method and stress measuring apparatus

Info

Publication number: JP4691279B2
Application number: JP2001209800A
Authority: JP
Inventors: 精一安福; 誠池田; 敬松岡; 亮介村井; 俊蔵岡; 壽男勝野
Original assignee: 中電技術コンサルタント株式会社
Priority date: 2001-07-10
Filing date: 2001-07-10
Publication date: 2011-06-01
Anticipated expiration: 2021-07-10
Also published as: JP2003028734A

Description

【０００１】
【発明の属する技術分野】
本発明は、橋梁等の構造物を構成する鋼材にどの程度の応力が作用しているかを現場において測定する方法および装置に関する。
【０００２】
【従来の技術】
例えば、橋梁等の構造物を構成している鋼材について、その鋼材にどの程度の内在応力が作用しているかを定量的に測定することは、該構造物の安全性を評価するうえで重要なことである。
【０００３】
内在応力を測定する方法のひとつに磁歪による応力の測定方法が挙げられる。この応力測定方法は、例えば特開平5-231961号公報に開示されているように、強磁性体である鋼材に荷重が作用すると磁化特性に異方向性が生じる（荷重の作用方向に磁化されやすくなり、荷重の作用方向に垂直な方向に磁化されにくくなる）という現象を利用し、両方向の磁化特性の差を磁歪センサによって検出して、鋼材に作用する内在応力の方向とその大きさとを測定するというものである。
【０００４】
上記のような応力測定方法を高精度に実施するためには、鋼材の応力感度を可能な限り正確に承知しておくことが重要であるが、既設の構造物、つまり実構造物の鋼材については応力感度が不明である場合がほとんどである。
【０００５】
応力感度は、被測定物である鋼材と磁歪センサとの間隔（これを"リフトオフ"という）に影響を受けて変化する。一般に、実構造物には防錆、防蝕のために塗装が施されるが、この塗膜の厚さは一定ではなくばらつきを生じている。そのため応力感度を正確に認知しようとすれば、測定個所の塗膜を剥がしてリフトオフを測定するか、塗膜の上から膜厚を計測できる膜厚計を使用する必要がある。
【０００６】
しかしながら、塗膜を剥がしてリフトオフを測定する場合は塗膜の除去作業を手作業で行わなければならず、作業量が増大する。応力測定を複数箇所にわたって実施する場合はなおさらである（複数箇所に実施する場合、１箇所の塗膜だけ除去してリフトオフを測定し、他の測定個所については除去作業を行わずに当該リフトオフ量を流用したとしても、上記のように膜厚は一定ではないため、正確ではない）。
【０００７】
また、膜厚計（例えば超音波パルス式距離計）を使用する場合は塗膜を除去する必要はないが、この場合も膜厚計を使って測定作業を行わなければならず、作業量は少なからず増大する。
【０００８】
このような、塗膜のばらつきに起因してリフトオフを確定し難いという事情を考慮して、リフトオフによる影響を受けることなく被測定物に作用する応力を測定する方法が特開平05-231960号、特開平06-307948号、特願2000-02600号の各公報に開示されている。この応力測定方法においては、あらかじめ被測定物について、リフトオフに対するリフトオフ電圧（励磁によって誘起される起電力）の関係、ならびにリフトオフと磁歪感度との関係を求め、さらにこれらの関係からリフトオフ電圧と磁歪感度との関係を求めておく。
【０００９】
被測定物に作用している応力の測定時には、磁歪センサによってリフトオフ電圧を測定し、あらかじめ求めておいたリフトオフ電圧と磁歪感度との関係をもとに測定電圧値に対応する磁歪感度を求める。そして、測定電圧値および磁歪感度をもとに応力を算出するというものである。
【００１０】
【発明が解決しようとする課題】
ところで、上記の応力測定方法においては、励磁用コイルを巻いたコの字型の励磁用ヨークと、検出用コイルを巻いたコの字型の検出用ヨークとを互いにヨーク鞍部の中央で直交するように接合した構造の磁歪センサを使用している。
【００１１】
この磁歪センサにおいては、励磁用ヨークと検出用ヨークとを別体に構成して両者を接合する構造を採用しているため、励磁用ヨークの先端と検出用ヨークの先端との配置が狂い易い。当該の配置が少しでも狂うと、励磁によって誘起される起電力が大きく変化してしまい、正確な応力測定を行うことができなくなる。
【００１２】
本発明は上記の事情に鑑みてなされたものであり、磁歪センサにおける測定誤差を少なくして正確に応力測定を行うことができる応力測定方法および応力測定装置を提供することを目的としている。
【００１３】
【課題を解決するための手段】
上記の課題を解決するための手段として、次のような構成の応力の測定方法および応力測定装置を採用する。すなわち本発明に係る請求項１記載の応力の測定方法は、一対の軸部からなる第１のコア、および該第１のコアの配列方向に直交して配置された同じく一対の軸部からなる第２のコアを一体化したセンサ本体に、前記第１のコアに第１の導線を巻回して励磁用コイルを構成し、前記第２のコアには第２の導線を巻回して検出用コイルを構成した磁歪センサを使って被測定物に作用する応力を測定する応力の測定方法であって、応力が作用している前記被測定物に前記磁歪センサを近接させ、前記励磁用コイルに通電して前記被測定物を励磁し、通電によって前記励磁用コイルに発生する電圧、および励磁によって前記検出用コイルに誘起される出力電圧を検出し、前記磁歪センサに前記被測定物を励磁するべく通電した励磁電流と前記励磁用コイルに発生した電圧とからインピーダンスを算出し、被測定物またはこれと同材質の試料を励磁するべく前記磁歪用コイルに通電した励磁電流および前記励磁用コイルに発生した電圧から算出されるインピーダンスと、励磁によって前記検出用コイルに誘起される出力電圧および前記被測定物またはこれと同材質の試料に作用させた応力から算出される応力感度と、に基づいてあらかじめ求められた、前記被測定物に関するインピーダンスと応力感度との関係を参照して、前記算出されたインピーダンスに対応する応力感度を推定し、該推定された応力感度と前記出力電圧とをもとに前記被測定物に作用する応力の大きさを算出することを特徴とする。
【００１４】
請求項２記載の応力の測定方法は、請求項１記載の応力の測定方法において、前記被測定物またはこれと同材質の試料を対象として、該対象に任意の応力を作用させながら前記磁歪センサと前記被測定物との間隔を段階的に変化させ、各段階において前記励磁用コイルに通電して前記被測定物を励磁し、前記励磁用コイルに発生する電圧を検出し、前記被測定物を励磁するべく通電した励磁電流と前記励磁用コイルに発生した電圧とから各段階におけるインピーダンスを算出し、各段階におけるインピーダンスと前記間隔との関係、ならびに該間隔と応力感度との関係を求め、さらにこれらの関係から前記被測定物に関する前記インピーダンスと前記応力感度との関係をあらかじめ求めておくことを特徴とする。
【００１５】
請求項３記載の応力測定装置は、一対の軸部からなる第１のコア、および該第１のコアの配列方向に直交して配置された同じく一対の軸部からなる第２のコアを一体化したセンサ本体に、前記第１のコアに第１の導線を巻回して励磁用コイルを構成し、前記第２のコアには第２の導線を巻回して検出用コイルを構成した磁歪センサと、被測定物またはこれと同材質の試料を励磁するべく前記磁歪用コイルに通電した励磁電流および前記励磁用コイルに発生した電圧から算出されるインピーダンスと、励磁によって前記検出用コイルに誘起される出力電圧および前記被測定物またはこれと同材質の試料に作用させた応力から算出される応力感度と、に基づいてあらかじめ求められた、前記被測定物に関するインピーダンスと応力感度との関係を記憶する記憶手段と、前記磁歪センサに前記被測定物を励磁するべく通電した励磁電流と通電によって前記励磁用コイルに発生した電圧とからインピーダンスを算出し、該算出されたインピーダンスに対応する応力感度を、前記記憶手段に記憶されたインピーダンスと応力感度との関係を参照して推定し、該推定された応力感度と励磁によって前記検出用コイルに誘起された出力電圧とをもとに前記被測定物に作用する応力の大きさを算出する演算手段とを備えることを特徴とする。
【００１６】
請求項４記載の応力測定装置は、請求項３記載の応力測定装置において、前記被測定物またはこれと同材質の試料を対象として、該対象に任意の応力を作用させながら前記磁歪センサと前記被測定物との間隔を段階的に変化させ、各段階において前記励磁用コイルに通電して前記被測定物を励磁し、前記励磁用コイルに発生する電圧を検出し、前記被測定物を励磁するべく通電した励磁電流と前記励磁用コイルに発生した電圧とから各段階におけるインピーダンスを算出し、各段階におけるインピーダンスと前記間隔との関係、ならびに該間隔と応力感度との関係を求め、さらにこれらの関係から前記被測定物に関する前記インピーダンスと前記応力感度との関係をあらかじめ求め、該関係を前記記憶手段に記憶させておくことを特徴とする。
【００１７】
請求項５記載の応力測定装置は、請求項３または４記載の応力測定装置において、前記第１のコアに、前記励磁に際して通電される第３の導線が巻回されていることを特徴とする。
【００１８】
本発明においては、被測定物またはこれと同材質の試料を使って被測定物に関するインピーダンスと応力感度との関係を事前に取得しておき、実際の測定に際してこの関係を利用して被測定物の応力感度を特定することにより、リフトオフが不明のままでも、被測定物に実際に作用している応力を測定することが可能である。
【００１９】
さらに、磁歪センサに、励磁用コイルのコアと検出用コイルのコアとを一体化した構造を採用したことにより、励磁用コイルを構成する一対の軸部と検出用コイルを構成する一対の軸部との配置が狂うことがない。
【００２０】
【発明の実施の形態】
本発明に係る応力の測定方法および応力測定装置の実施形態を図１ないし図６に示して説明する。
図１には本発明に係る応力測定装置を示しており、符号１は既設の橋梁を構成している鋼材（被測定物）、２は磁歪センサ、３は出力信号を処理する解析用コンピュータである。磁歪センサ２は鋼材１に近接して配置されている。
【００２１】
磁歪センサ２は、図２に示すように、一対の軸部２１ａ，２１ｂからなるコア（第１のコア）２１、およびコア２１の配列方向に直交して配置された同じく一対の軸部２２ａ，２２ｂからなるコア（第２のコア）２２を一体化したセンサ本体２３に、コア２１に導線（第１の導線）２４を巻回して励磁用コイルを構成し、コア２２には導線（第２の導線）２５を巻回して検出用コイルを構成したものである。
【００２２】
センサ本体２３には、円柱状の基部２６に、軸部２１ａ，２２ａ，２１ｂ，２２ｂが基部２６の中心軸線を取り囲むように立設されている。センサ本体２３は、円柱状の基体の一方の端面に中心軸線方向から十字に切り込みを入れることによって形成される。
【００２３】
励磁用コイルを構成するコア２１の一方の軸部２１ａには、導線２４とは独立して導線（第３の導線）２７が巻回されてリフトオフ検出用コイルが構成されている。磁歪センサ２を被測定物に近接させて励磁用コイルに通電すると、被測定物が磁化されることによって検出用コイルにはリフトオフと励磁電流とに見合った起電力が発生するが、これと同時にリフトオフ検出用コイルにもリフトオフと励磁電流とに見合った起電力（これを"リフトオフ電圧"という）が発生するようになっている。
【００２４】
解析用コンピュータ３には、あらかじめ求めておいた鋼材１に関するインピーダンスと応力感度との関係を記憶する記憶手段３１と、鋼材１を励磁するべく磁歪センサ２に通電した励磁電流と電圧値、励磁によって誘起される出力電圧値、ならびに記憶手段３１に記憶された情報をもとに鋼材１に作用する応力の大きさを算出する演算手段３２とが設けられている。
【００２５】
記憶手段３１に記憶される情報、すなわち鋼材１に関するインピーダンスと応力感度との関係はあらかじめ次のようにして求められる。
まず、鋼材１またはこれと同材質の試料を対象として、該対象に任意の応力を作用させながら磁歪センサ２と鋼材１とのリフトオフを段階的に変化させ、各段階において励磁用コイルに通電し、通電によって励磁用コイルに発生する励磁電圧と電流、および励磁によって検出用コイルに誘起される出力電圧を検出する。これをもとに、まず、リフトオフの各段階における出力電圧と応力との関係を求める。図３はリフトオフを２．０３ｍｍ(◆)、０．６７ｍｍ(△)、０．２５ｍｍ(□)、０．０５ｍｍ(●)の４段階に変化させたときの出力電圧と応力との関係を示すグラフである。
【００２６】
次に、図３に示す出力電圧と応力との関係から、リフトオフの各段階におけるインピーダンスとリフトオフとの関係、ならびにリフトオフと応力感度との関係を求める。図４、図５はこれらの関係を示すグラフである。なお、この場合のインピーダンスとは、励磁コイルにかけられた励磁電圧を励磁電流で除した値であり、応力感度とは出力電圧を対象物に作用させた応力で除した値である。
【００２７】
さらに、図４に示すインピーダンスとリフトオフとの関係、ならびに図５に示すリフトオフと応力感度との関係から、鋼材１に関するインピーダンスと応力感度との関係を求める。図６はこれらの関係を示すグラフであり、記憶手段３１には、図６のようなインピーダンスと応力感度との対応関係を表す情報が記憶されている。
【００２８】
続いて、上記のように構成された応力検出装置を用い、既設の橋梁を構成する鋼材１に実際に作用している内在応力を測定する方法について説明する。
まず、鋼材１の測定個所に、磁歪センサ２をリフトオフ不明のままで近接させ、励磁用コイルに通電して鋼材１を励磁し、通電した励磁電流(Ｉ)と通電によって励磁用コイルに発生する励磁電圧(Ｖ_c)、および励磁によって検出用コイルに誘起される出力電圧(Ｖ)を検出する。
次に、磁歪センサ２に通電した励磁電流値(Ｉ)と通電によって発生する励磁電圧とからインピーダンス値(Ｒ＝Ｖ_c／Ｉ)を算出する。
続いて、記憶手段３１に記憶させたインピーダンスと応力感度との関係を参照してインピーダンス値に対応する応力感度(Ｓ_e)を抽出し、これをもとに鋼材１に作用する内在応力の大きさを算出する。鋼材１に作用する内在応力は出力電圧(Ｖ)を応力感度で除した値として与えられるから、実際に鋼材１に作用している内在応力の大きさは(Ｖ／Ｓ_e)ということになる。
【００２９】
上記のような応力の測定方法においては、鋼材１またはこれと同材質の試料を使って鋼材１に関するインピーダンスと応力感度との関係を事前に取得しておき、実際の測定に際してこの関係を利用して応力感度を特定することにより、リフトオフが不明のままでも、既設の橋梁を構成する鋼材１に実際に作用している内在応力を測定することができる。
【００３０】
また、上記応力測定に使用する磁歪センサ２は、励磁用コイルのコア２１と検出用コイルのコア２２とを一体化した構造を備えるから、励磁用コイルを構成する一対の軸部２１ａ，２１ｂと検出用コイルを構成する一対の軸部２２ａ，２２ｂとの配置が狂うことがない。これにより、磁歪センサ２における測定誤差を少なくして正確に応力測定を行うことができる。
【００３１】
なお、本実施形態においては励磁用コイルに別個にリフトオフ検出用コイルを設けた構成としたが、励磁電流の通電によって励磁用コイルに発生する電圧値が検出可能である場合、例えば励磁電流の周波数を極端に早くすることによって励磁用コイルにより大きな電圧が発生する場合等には、特にリフトオフ検出用コイルを設ける必要はない。
【００３２】
【発明の効果】
以上説明したように、本発明に係る応力の測定方法および応力測定装置によれば、被測定物またはこれと同材質の試料を使って被測定物に関するインピーダンスと応力感度との関係を事前に取得しておき、実際の測定に際してこの関係を利用して被測定物の応力感度を特定することにより、リフトオフが不明のままでも、被測定物に実際に作用している応力を測定することができる。
【００３３】
さらに、磁歪センサに、励磁用コイルのコアと検出用コイルのコアとを一体化した構造を採用したことにより、励磁用コイルを構成する一対の軸部と検出用コイルを構成する一対の軸部との配置が狂うことがない。これにより、磁歪センサにおける測定誤差を少なくして正確に応力測定を行うことができる。
【図面の簡単な説明】
【図１】本発明に係る応力測定装置の構成を示す概略図である。
【図２】応力測定装置を構成する磁歪センサの構造を示す斜視図である。
【図３】リフトオフの各段階におけるリフトオフ電圧と応力との関係を示すグラフである。
【図４】インピーダンスとリフトオフとの関係を示すグラフである。
【図５】リフトオフと応力感度との関係との関係を示すグラフである。
【図６】インピーダンスと応力感度との関係を示すグラフである。
【符号の説明】
１鋼材（被測定物）
２磁歪センサ
３解析用コンピュータ
２１コア（第１のコア）
２２コア（第２のコア）
２３センサ本体
２４導線（第１の導線）
２５導線（第２の導線）
２７導線（第３の導線）
３１記憶手段
３２演算手段[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for measuring on the site how much stress is acting on a steel material constituting a structure such as a bridge.
[0002]
[Prior art]
For example, quantitatively measuring how much internal stress is acting on a steel material constituting a structure such as a bridge is important in evaluating the safety of the structure. That is.
[0003]
One method of measuring the intrinsic stress is a method of measuring stress due to magnetostriction. In this stress measurement method, for example, as disclosed in Japanese Patent Application Laid-Open No. H5-231961, when a load is applied to a steel material that is a ferromagnetic material, anisotropy occurs in the magnetization characteristics (easily magnetized in the direction in which the load is applied). , And the direction of the internal stress acting on the steel is measured by detecting the difference in the magnetization characteristics in both directions with a magnetostrictive sensor. It is to do.
[0004]
In order to carry out the stress measurement method as described above with high accuracy, it is important to be aware of the stress sensitivity of steel as accurately as possible. In most cases, the stress sensitivity is unknown.
[0005]
The stress sensitivity changes under the influence of the distance between the steel material to be measured and the magnetostrictive sensor (this is referred to as “lift-off”). In general, the actual structure is painted for rust prevention and corrosion prevention, but the thickness of the coating film is not constant but varies. Therefore, in order to accurately recognize the stress sensitivity, it is necessary to peel off the coating film at the measurement site and measure the lift-off, or to use a film thickness meter that can measure the film thickness from above the coating film.
[0006]
However, when peeling off the coating film and measuring lift-off, the coating film must be removed manually, which increases the amount of work. This is especially true when stress measurement is performed at multiple locations. (When it is performed at multiple locations, lift-off is measured without removing the coating film at one location and removing the other measurement locations.) Is not accurate because the film thickness is not constant as described above.
[0007]
In addition, when using a film thickness meter (for example, an ultrasonic pulse distance meter), it is not necessary to remove the coating film, but in this case as well, measurement work must be performed using the film thickness meter, and the amount of work is Increases not a little.
[0008]
In consideration of such a situation that lift-off is difficult to be determined due to variations in the coating film, a method for measuring stress acting on the object to be measured without being affected by lift-off is disclosed in Japanese Patent Application Laid-Open No. 05-231960, This is disclosed in Japanese Patent Application Laid-Open No. 06-307948 and Japanese Patent Application No. 2000-02600. In this stress measurement method, the relationship between lift-off voltage (electromotive force induced by excitation) with respect to lift-off and the relationship between lift-off and magnetostriction sensitivity is obtained in advance, and the lift-off voltage and magnetostriction sensitivity are obtained from these relationships. Seeking a relationship with
[0009]
When measuring the stress acting on the object to be measured, the lift-off voltage is measured by a magnetostrictive sensor, and the magnetostrictive sensitivity corresponding to the measured voltage value is obtained based on the relationship between the lift-off voltage and the magnetostrictive sensitivity obtained in advance. Then, the stress is calculated based on the measured voltage value and the magnetostrictive sensitivity.
[0010]
[Problems to be solved by the invention]
By the way, in the stress measurement method described above, the U-shaped excitation yoke wound with the excitation coil and the U-shaped detection yoke wound with the detection coil are orthogonal to each other at the center of the yoke collar. A magnetostrictive sensor having such a joined structure is used.
[0011]
This magnetostrictive sensor employs a structure in which the excitation yoke and the detection yoke are configured separately and joined to each other, and therefore, the arrangement of the tip of the excitation yoke and the tip of the detection yoke tends to be out of order. . If the arrangement is a little out of order, the electromotive force induced by excitation changes greatly, and accurate stress measurement cannot be performed.
[0012]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a stress measurement method and a stress measurement apparatus that can accurately perform stress measurement while reducing measurement errors in a magnetostrictive sensor.
[0013]
[Means for Solving the Problems]
As means for solving the above problems, a stress measuring method and stress measuring apparatus having the following configuration are employed. That is, the stress measuring method according to claim 1 of the present invention includes a first core composed of a pair of shaft portions, and a pair of shaft portions arranged perpendicular to the arrangement direction of the first cores. An excitation coil is formed by winding the first conductor around the first core around the sensor body integrated with the second core, and the second conductor is wound around the second core for detection. A stress measuring method for measuring a stress acting on an object to be measured using a magnetostrictive sensor comprising a coil, wherein the magnetostrictive sensor is brought close to the object to be measured on which the stress is applied, and Energize the object to be measured by energization, detect a voltage generated in the excitation coil by energization and an output voltage induced in the detection coil by excitation, and excite the object to be measured in the magnetostrictive sensor Excitation current and the excitation current Calculating the impedance from the voltage generated in the yl, and the impedance calculated from the voltage generated in the excitation current and the exciting coil is energized to the magnetostrictive coil so as to excite the sample to be measured or which the same material The measured object obtained in advance based on the output voltage induced in the detection coil by excitation and the stress sensitivity calculated from the stress applied to the measured object or a sample of the same material. Referring to the relationship between the impedance and the stress sensitivity for, and estimate the stress sensitivity corresponding to the calculated impedance, acting on the object to be measured on the basis of said output voltage and said estimated stress sensitivity The magnitude of the stress is calculated.
[0014]
The stress measurement method according to claim 2 is the stress measurement method according to claim 1, wherein the magnetostrictive sensor is applied to the object to be measured or a sample of the same material as the object while applying an arbitrary stress to the object. And in steps, the excitation coil is energized in each stage to excite the measurement object, and the voltage generated in the excitation coil is detected, and the measurement object The impedance at each stage is calculated from the excitation current energized to excite the current and the voltage generated in the excitation coil, and the relationship between the impedance at each stage and the interval, as well as the relationship between the interval and stress sensitivity, Furthermore, the relationship between the impedance and the stress sensitivity relating to the object to be measured is obtained in advance from these relationships.
[0015]
The stress measuring apparatus according to claim 3, wherein the first core composed of a pair of shaft portions and the second core composed of the same pair of shaft portions arranged orthogonal to the arrangement direction of the first cores are integrated. A magnetostrictive sensor in which a first conducting wire is wound around the first core to form an exciting coil around the sensor body, and a detecting coil is constructed by winding the second conducting wire around the second core. And the impedance calculated from the excitation current energized in the magnetostrictive coil and the voltage generated in the excitation coil to excite the object to be measured or the sample of the same material, and the detection coil induced by the excitation. and the stress sensitivity is calculated from the output voltage and the allowed to act on a sample of the object or this same material stress that was determined in advance based on, the relationship between the impedance and the stress sensitivity for the object to be measured An impedance is calculated from a memory means for storing, an excitation current energized to excite the object to be measured in the magnetostrictive sensor, and a voltage generated in the excitation coil by energization, and a stress sensitivity corresponding to the calculated impedance Is estimated with reference to the relationship between the impedance stored in the storage means and the stress sensitivity, and based on the estimated stress sensitivity and the output voltage induced in the detection coil by excitation, And an arithmetic means for calculating the magnitude of the stress acting on the object.
[0016]
The stress measuring device according to claim 4 is the stress measuring device according to claim 3, wherein the magnetostrictive sensor and the sample are measured while applying an arbitrary stress to the object to be measured or a sample of the same material as the object. The distance from the object to be measured is changed stepwise, and the excitation coil is energized in each stage to excite the object to be measured, and the voltage generated in the excitation coil is detected, and the object to be measured is excited. Impedance at each stage is calculated from the excitation current energized as much as possible and the voltage generated in the exciting coil, and the relationship between the impedance and the interval at each stage and the relationship between the interval and the stress sensitivity are obtained. The relationship between the impedance and the stress sensitivity related to the object to be measured is obtained in advance from the relationship, and the relationship is stored in the storage means.
[0017]
The stress measuring device according to claim 5 is the stress measuring device according to claim 3 or 4, wherein a third conducting wire to be energized during the excitation is wound around the first core. .
[0018]
In the present invention, the relationship between the impedance and the stress sensitivity relating to the object to be measured is obtained in advance using the object to be measured or a sample of the same material, and the object to be measured is utilized in actual measurement. By specifying the stress sensitivity, it is possible to measure the stress actually acting on the object to be measured even if the lift-off remains unknown.
[0019]
Further, by adopting a structure in which the excitation coil core and the detection coil core are integrated in the magnetostrictive sensor, a pair of shaft portions constituting the excitation coil and a pair of shaft portions constituting the detection coil. And the placement will not go crazy.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of a stress measuring method and a stress measuring apparatus according to the present invention will be described with reference to FIGS.
FIG. 1 shows a stress measuring apparatus according to the present invention. Reference numeral 1 denotes a steel material (object to be measured) constituting an existing bridge, 2 denotes a magnetostrictive sensor, and 3 denotes an analysis computer for processing an output signal. is there. The magnetostrictive sensor 2 is disposed close to the steel material 1.
[0021]
As shown in FIG. 2, the magnetostrictive sensor 2 includes a core (first core) 21 including a pair of shaft portions 21 a and 21 b, and a pair of shaft portions 22 a and 22 a that are arranged orthogonal to the arrangement direction of the cores 21. An excitation coil is formed by winding a conducting wire (first conducting wire) 24 around a core 21 around a sensor body 23 in which a core (second core) 22 made of 22b is integrated. ) 25 is wound to constitute a detection coil.
[0022]
In the sensor body 23, shaft portions 21 a, 22 a, 21 b, and 22 b are erected on a columnar base portion 26 so as to surround the central axis of the base portion 26. The sensor body 23 is formed by making a cross incision from the central axis direction on one end face of a cylindrical base.
[0023]
A conductive wire (third conductive wire) 27 is wound around one shaft portion 21a of the core 21 constituting the exciting coil independently of the conductive wire 24 to form a lift-off detection coil. When the magnetostrictive sensor 2 is brought close to the object to be measured and the excitation coil is energized, the object to be measured is magnetized, and an electromotive force corresponding to the lift-off and excitation current is generated in the detection coil. An electromotive force (referred to as “lift-off voltage”) corresponding to the lift-off and excitation current is also generated in the lift-off detection coil.
[0024]
The analysis computer 3 stores the storage means 31 for storing the relationship between the impedance and the stress sensitivity relating to the steel material 1 obtained in advance, and the excitation current, voltage value, and excitation applied to the magnetostrictive sensor 2 to excite the steel material 1. Calculation means 32 for calculating the magnitude of the stress acting on the steel material 1 based on the induced output voltage value and the information stored in the storage means 31 is provided.
[0025]
Information stored in the storage means 31, that is, the relationship between the impedance and the stress sensitivity related to the steel material 1 is obtained in advance as follows.
First, for the steel material 1 or a sample of the same material, the lift-off between the magnetostrictive sensor 2 and the steel material 1 is changed in stages while applying an arbitrary stress to the object, and the exciting coil is energized in each stage. The excitation voltage and current generated in the excitation coil by energization and the output voltage induced in the detection coil by excitation are detected. Based on this, first, the relationship between output voltage and stress at each stage of lift-off is obtained. FIG. 3 shows the relationship between the output voltage and the stress when the lift-off is changed in four stages of 2.03 mm (♦), 0.67 mm (Δ), 0.25 mm (□), and 0.05 mm (●). It is a graph.
[0026]
Next, from the relationship between the output voltage and stress shown in FIG. 3, the relationship between impedance and lift-off at each stage of lift-off and the relationship between lift-off and stress sensitivity are obtained. 4 and 5 are graphs showing these relationships. The impedance in this case is a value obtained by dividing the exciting voltage applied to the exciting coil by the exciting current, and the stress sensitivity is a value obtained by dividing the output voltage by the stress applied to the object.
[0027]
Furthermore, from the relationship between the impedance and the lift-off shown in FIG. 4 and the relationship between the lift-off and the stress sensitivity shown in FIG. FIG. 6 is a graph showing these relationships, and the storage means 31 stores information representing the correspondence between impedance and stress sensitivity as shown in FIG.
[0028]
Next, a method for measuring the inherent stress actually acting on the steel material 1 constituting the existing bridge using the stress detection device configured as described above will be described.
First, the magnetostrictive sensor 2 is brought close to the measurement location of the steel material 1 without knowing the lift-off, and the excitation coil is energized to excite the steel material 1 and is generated in the excitation coil by the energized excitation current (I) and energization. An excitation voltage (V _c ) and an output voltage (V) induced in the detection coil by excitation are detected.
Next, an impedance value (R = V _c / I) is calculated from the excitation current value (I) energized in the magnetostrictive sensor 2 and the excitation voltage generated by the energization.
Subsequently, the stress sensitivity (S _e ) corresponding to the impedance value is extracted with reference to the relationship between the impedance stored in the storage means 31 and the stress sensitivity, and based on this, the magnitude of the internal stress acting on the steel material 1 is extracted. Is calculated. Since the internal stress acting on the steel material 1 is given as a value obtained by dividing the output voltage (V) by the stress sensitivity, the magnitude of the internal stress actually acting on the steel material 1 is (V / S _e ). .
[0029]
In the stress measurement method as described above, the relationship between the impedance and the stress sensitivity related to the steel material 1 is obtained in advance using the steel material 1 or a sample of the same material, and this relationship is used for actual measurement. By specifying the stress sensitivity, it is possible to measure the internal stress actually acting on the steel material 1 constituting the existing bridge even if the lift-off remains unknown.
[0030]
The magnetostrictive sensor 2 used for the stress measurement has a structure in which the excitation coil core 21 and the detection coil core 22 are integrated, and therefore a pair of shaft portions 21a and 21b constituting the excitation coil, and Arrangement with a pair of axial part 22a, 22b which comprises the coil for a detection does not go out of order. Thereby, the measurement error in the magnetostrictive sensor 2 can be reduced and the stress can be measured accurately.
[0031]
In the present embodiment, a lift-off detection coil is separately provided in the excitation coil. However, when the voltage value generated in the excitation coil can be detected by energization of the excitation current, for example, the frequency of the excitation current When a large voltage is generated by the exciting coil by making the speed extremely fast, it is not particularly necessary to provide a lift-off detecting coil.
[0032]
【The invention's effect】
As described above, according to the stress measuring method and the stress measuring apparatus according to the present invention, the relationship between the impedance and the stress sensitivity relating to the object to be measured is obtained in advance using the object to be measured or a sample of the same material. In addition, the stress actually acting on the object to be measured can be measured even if the lift-off remains unknown by specifying the stress sensitivity of the object to be measured by utilizing this relationship in actual measurement. .
[0033]
Further, by adopting a structure in which the excitation coil core and the detection coil core are integrated in the magnetostrictive sensor, a pair of shaft portions constituting the excitation coil and a pair of shaft portions constituting the detection coil. And the placement will not go crazy. Thereby, the measurement error in the magnetostrictive sensor can be reduced and the stress can be measured accurately.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing the configuration of a stress measuring apparatus according to the present invention.
FIG. 2 is a perspective view showing a structure of a magnetostrictive sensor constituting the stress measuring device.
FIG. 3 is a graph showing the relationship between lift-off voltage and stress at each stage of lift-off.
FIG. 4 is a graph showing the relationship between impedance and lift-off.
FIG. 5 is a graph showing the relationship between lift-off and stress sensitivity.
FIG. 6 is a graph showing the relationship between impedance and stress sensitivity.
[Explanation of symbols]
1 Steel (measurement object)
2 magnetostrictive sensor 3 analysis computer 21 core (first core)
22 core (second core)
23 Sensor body 24 Conductor (first conductor)
25 Conductor (second conductor)
27 Conductor (third conductor)
31 Storage means 32 Calculation means

Claims

A sensor main body in which a first core composed of a pair of shaft portions and a second core composed of a pair of shaft portions arranged perpendicular to the arrangement direction of the first cores are integrated with the first core A stress acting on the object to be measured using a magnetostrictive sensor in which a first conducting wire is wound around a core to constitute an exciting coil, and a second conducting wire is wound around the second core to constitute a detecting coil. Measuring method of stress,
Bringing the magnetostrictive sensor close to the object to be measured in which stress is applied;
Energize the excitation coil by energizing the excitation coil,
Detecting the voltage generated in the excitation coil by energization and the output voltage induced in the detection coil by excitation,
Impedance is calculated from the exciting current energized to excite the object to be measured in the magnetostrictive sensor and the voltage generated in the exciting coil,
Impedance calculated from the excitation current energized in the magnetostrictive coil and the voltage generated in the excitation coil to excite the object to be measured or a sample of the same material, and the output induced in the detection coil by excitation Refer to the relationship between the impedance and stress sensitivity relating to the object to be measured, which is obtained in advance based on the voltage and the stress sensitivity calculated from the stress applied to the object to be measured or the sample of the same material. , stress sensitivity corresponding to the calculated impedance to estimate,
A stress measurement method, comprising: calculating a magnitude of a stress acting on the object to be measured based on the estimated stress sensitivity and the output voltage.

Targeting the object to be measured or a sample of the same material as the object, an interval between the magnetostrictive sensor and the object to be measured is changed stepwise while applying an arbitrary stress to the object, and the exciting coil is changed at each step. The excitation current is excited to detect the voltage generated in the excitation coil, and the excitation current supplied to excite the measurement object and the voltage generated in the excitation coil are detected at each stage. Impedance is calculated, and the relationship between the impedance and the interval at each stage and the relationship between the interval and the stress sensitivity are obtained. Further, the relationship between the impedance and the stress sensitivity relating to the object to be measured is obtained in advance from these relationships. The stress measurement method according to claim 1, wherein:

A sensor main body in which a first core composed of a pair of shaft portions and a second core composed of a pair of shaft portions arranged perpendicular to the arrangement direction of the first cores are integrated with the first core A magnetostrictive sensor in which a first conducting wire is wound around a core to constitute an exciting coil, and a second conducting wire is wound around the second core to constitute a detection coil;
Impedance calculated from the excitation current energized in the magnetostrictive coil and the voltage generated in the excitation coil to excite the object to be measured or a sample of the same material, and the output induced in the detection coil by excitation A memory for storing the relationship between the impedance and the stress sensitivity relating to the object to be measured, which is obtained in advance based on the voltage and the stress sensitivity calculated from the stress applied to the object to be measured or the sample of the same material. Means,
Impedance is calculated from an excitation current energized to excite the object to be measured in the magnetostrictive sensor and a voltage generated in the excitation coil by energization, and stress sensitivity corresponding to the calculated impedance is stored in the storage means. Estimating with reference to the relationship between the stored impedance and stress sensitivity, the stress acting on the object to be measured based on the estimated stress sensitivity and the output voltage induced in the detection coil by excitation A stress measuring device comprising: a calculating means for calculating a size.

Targeting the object to be measured or a sample of the same material as the object, an interval between the magnetostrictive sensor and the object to be measured is changed stepwise while applying an arbitrary stress to the object, and the exciting coil is changed at each step. The excitation current is excited to detect the voltage generated in the excitation coil, and the excitation current supplied to excite the measurement object and the voltage generated in the excitation coil are detected at each stage. Impedance is calculated, and the relationship between the impedance and the interval at each stage and the relationship between the interval and the stress sensitivity are obtained. Further, the relationship between the impedance and the stress sensitivity relating to the object to be measured is obtained in advance from these relationships. 4. The stress measuring apparatus according to claim 3, wherein the relationship is stored in the storage means.

5. The stress measuring device according to claim 3, wherein a third conductive wire that is energized during the excitation is wound around the first core. 6.