JP3653545B2 - Linearity measuring method and measuring apparatus for dynamic response characteristics of strain gauge - Google Patents

Description

の積の２倍の加速度（ａ(t)）が発生する。
【数２】

ここで、ε(t)は端面に入射する弾性波パルスの歪であり、・は時間微分項を表す。
（１）式より、端面の運動速度をｖ(t)、端面の動的変位をｄ(t)とすると（１）式より以下の（２）、（３）式が成立する。
【数３】

【数４】

【００３５】
実際に、測定対象となる歪ゲージを金像棒の端面と側面の境界面に貼ることは不可能なので、飛翔体との衝突端面から
Ｌ_Ｂ
だけ離れた位置に歪ゲージを貼ったとすると、ゲージで観測される歪と端面の運動加速度、運動速度、動的変位との関係について、（４）、（５）、（６）式が成立する。式中の・は時間微分を表す。
【数５】

【数６】

【数７】

【００３６】
前記（４）式から計算される端面の運動加速度が、加速度センサへの入力信号となる。（５）式で計算される運動速度が、レーザ干渉計への入力信号となる。（６）式で計算される動的変位が非接触変位センサへの入力信号となる。
【００３７】
動的線形性を計測する歪ゲージで観測される過渡的信号は図３で示される。時間区間[t_c − t_d]の波形は、弾性波パルスが棒端面で反射してできる引張り応力波パルスであり、飛翔体が衝突する端面の方向に伝播するので、レーザ干渉計、加速度センサ、非接触変位センサへの入力信号となる加速度、速度、動的変位を発生させることには寄与しない。（４）式によって加速度センサへの入力信号となる加速度信号を発生させる歪、（５）式によってレーザ干渉計（振動計）への入力信号となる速度信号を発生させる歪、（６）式によって非接触変位計への入力信号となる動的変位信号を発生させる歪は、すべて図３の中の時間区間[t_a − t_b]に現れる歪信号である。
【００３８】
前記（１）式より加速度センサの出力信号から求められる端面に入射する弾性波パルスの歪（ε_Ａ(t)）は下記の（７）式で、（２）式より干渉計の出力信号から求められる端面に入射する弾性波パルスの歪（ε_Ｖ(t)）は（８）式で、（３）式より非接触変位センサ、変位測定装置から求められる端面に入射する弾性波パルスの歪（ε_Ｄ(t)）は（９）式で表される。（９）式における・は時間微分を表す。
【数８】

【数９】

【数１０】

【００３９】
また、金属丸棒中における波動の伝播は、以下の（１０）式で表される。
【数１１】

ただしここで、
t：時刻
l_p：飛翔体の長さ
Ｃ_ｐ：飛翔体の中の縦波弾性波の伝播速度
ε_ｔ(t,z)：スカラクの解析解の一次の項
【数１２】

【数１３】

【数１４】

ただしここで、
Ｖ_１：飛翔体の衝突速度
t：衝突後の経過時間
ν：ポアソン比
Ｄ_ａ：金属棒の直径
ｚ：金属棒の軸方向の座標
【００４０】
前記（７）式と（１０）式から棒端面の運動加速度を加速度センサで計測した結果を用いての歪ゲージへの入力信号としての歪信号（ε^ｉ _Ａ(t)）が得られる。（８）式と（１０）式とから棒端面の運動速度をレーザ干渉計で計測した結果を用いての歪ゲージへの入力信号としての歪信号（ε^ｉ _ｖ(t)）が得られる。（９）式と（１０）式とから棒端面の動的変位を非接触変位センサなどで計測した結果を用いての歪ゲージへの入力信号としての歪信号（ε^ｉ _Ｄ(t)）が得られる。
【００４１】
第１の飛翔体１、第２の飛翔体２について、以下の表のように記号を定義する。
表１：

【００４２】
上記のような理論に基づく計測技術を用いて実際に計測を行う際には、第１の飛翔体と第２の飛翔体の衝突時間差を考慮しない場合と、それを考慮する場合により、またそれらの各場合において、時間領域における比較に際して加速度センサで計測する場合とレーザ干渉計で計測する場合と非接触変位センサで計測する場合とに応じて下記の評価関数を用いて計算し、更にそれらの各場合において、周波数領域における比較を下記の計算式を用いて計算を行うことにより実施することができる。以下、これらについて順に説明する。
【００４３】
１．衝突時間差を考慮しない場合。
１）時間領域における比較
１−１）加速度センサで計測する場合の評価関数の一例：
【数１５】

（信号の存在する区間［t_１，t_２］で積分する）
【００４４】
１−２）レーザ干渉計で計測する場合の評価関数の一例：
【数１６】

（信号の存在する区間［t_１，t_２］で積分する）
【００４５】
１−３）非接触変位センサで計測する場合の評価関数の一例：
【数１７】

（信号の存在する区間［t_１，t_２］で積分する）
【００４６】
２）周波数領域における比較
２−１）加速度センサで計測する場合は、一例として、
【数１８】

を計算し、絶対値が１の許容値から外れた周波数を、ゲインに関する動的線形性の成立限界周波数とする。また位相に関しては、計算結果の位相がゼロの許容値から外れた周波数と、位相に関する動的線形性の成立限界周波数とする。
【００４７】
２−２）レーザ干渉計で計測する場合は、一例として、
【数１９】

を計算し、絶対値が１の許容値から外れた周波数を、ゲインに関する動的線形性の成立限界周波数とする。また位相に関しては、計算結果の位相がゼロの許容値から外れた周波数と、位相に関する動的線形性の成立限界周波数とする。
【００４８】
２−３）非接触変位センサで計測する場合は、一例として、
【数２０】

を計算し、絶対値が１の許容値から外れた周波数を、ゲインに関する動的線形性の成立限界周波数とする。また位相に関しては、計算結果の位相がゼロの許容値から外れた周波数と、位相に関する動的線形性の成立限界周波数とする。
【００４９】
２．衝突時間差を考慮する場合
第１の飛翔体１、第２の飛翔体２が金属棒に厳密に同時に衝突するような制御が簡単ではない場合には、時間差をΔtとし、加速度センサを用いて端面の運動加速度からゲージの入力過渡歪信号を求める場合には、ε^ｉ１ _Ａ(t)＋ε^ｉ２ _Ａ(t−Δt)がε^ｉ１２ _Ａ(t)にもっとも良く一致するようにΔtをパラメータとして求める。レーザ干渉計から端面の運動加速度からゲージの入力過渡歪信号を求める場合には、ε^ｉ１ _Ｖ(t)＋ε^ｉ２ _Ｖ(t−Δt)がε^ｉ１２ _Ｖ(t)に最も良く一致するようにΔtをパラメータとして求める。非接触動的変位センサから端面の運動加速度からゲージの入力過渡歪信号を求める場合には、ε^ｉ１ _Ｄ(t)＋ε^ｉ２ _Ｄ(t−Δt)がε^ｉ１２ _Ｄ(t)にもっとも良く一致するようにΔtをパラメータとして求める。このようにして求められたΔtを上記「１．衝突時間差を考慮する場合」における１）の各式及び２）の各式に適用することによって得られる。
【００５０】
本発明は更に種々の態様で実施することができ、例えば、先端部に高分子材料、プラスティックスなどを取り付けることにより、飛翔体本体部が金属、高分子材料、あるいはプラスティックスなど、各種異なる材料との積層構造を備えた飛翔体を用い、この飛翔体の衝突による金属棒内部に発生する弾性波パルスの周波数帯域を適宜調整することもできる。
【００５１】
また、前記実施例においては内外二重管型の発射により第１の飛翔体と第２の飛翔体を発射する例を示したが、例えば１本の管によって内側面で第１の飛翔体を案内し、外側面で第２の飛翔体を案内することも可能である。また、内側発射管、外側発射管を多重にし、多重内側発射管、多重外側発射管各々から発射される複数の飛翔体の発射の位相を制御することによって、金属棒内部に発生する弾性波の周波数帯域を狭帯域化する手法を採用しても良い。
【００５２】
更に、弾性波伝播の理論であるスカラクの解析解によって端面に入射する弾性波パルスの歪から、歪ゲージへの入力となる過渡歪信号を求める際に、スカラクの解析解の少なくとも１次の項、さらに精度をあげるためにはスカラクの解析解の高次の項までをも用いるような、歪ゲージの動的応答特性の線形性計測方法及びそれを実施する装置としてもよい。
【００５３】
また、上記手法で明らかになった歪ゲージのゲインおよび位相に関する動的線形性が成立する周波数領域において、金属棒端面の運動加速度計測、運動速度計測、動的変位計測結果と波動伝播理論から導かれるゲージ入力過渡歪信号と歪ゲージの出力信号（増幅器を含む場合、含まない場合の両方）を周波数領域で比較することにより、歪ゲージの周波数応答特性を求めても良い。
【００５４】
【発明の効果】
本発明は上記のように構成したので、動的線形性が保証された信頼性の高い歪ゲージを得ることができ、この歪ゲージを用いるすべての計測の信頼性を向上させることがででる。したがって、この歪ゲージを使用する、例えば構造物の静的強度の計測、構造物の動的強度の計測の信頼性が向上し、更にこのような計測の信頼性の向上により建築構造物、橋梁、道路、車両、センサなどあらゆる製品の動的歪計測の信頼性が向上する。
【図面の簡単な説明】
【図１】 本発明において、干渉計を用いて歪ゲージの動的線形性を計測する装置の実施例を示す図である。
【図２】本発明において、加速度センサを用いて歪ゲージの動的線形性を計測する装置の実施例を示す図である。
【図３】本発明において歪ゲージで観測される波形の例を示す図である。
【符号の説明】
１ 第１の飛翔体
２ 第２の飛翔体
３ 金属棒
４ 歪ゲージ
６ 第１端面
７ 内側発射管
８ 第２端面
９ 外側発射管
１０ 干渉計
１１ 計算機[0001]
BACKGROUND OF THE INVENTION
The present invention implements a method for measuring linearity of dynamic response characteristics of strain gauges widely used in the field of industrial measurement, such as vibration analysis of structures, dynamic stress analysis experiments, or main components inside sensors. It is related with the measuring device for this.
[0002]
[Prior art]
Strain gauges are used in an extremely wide range of industrial measurement fields. Specifically, dynamic stress analysis experiments on structures, vibration analysis experiments, vehicle collision experiments, or acceleration sensors with built-in strain gauges.
[0003]
[Problems to be solved by the invention]
In such measurement of vibration and impact, reliable measurement is impossible unless the linearity of the dynamic response characteristics of the strain gauge is guaranteed, but there was no appropriate method in the past. Measurements were made on the assumption that the gauge gave the correct results, and there was almost no theoretical study on how to attach the gauge or the linearity of the dynamic response characteristics.
[0004]
Regarding the method for measuring the dynamic characteristics of the strain gauge, a patent application has already been filed by the present inventor regarding the method for measuring the frequency characteristics, and the patent has already been granted, although linearity is assumed in the derivation of the frequency characteristics. However, the dynamic linearity measurement method and apparatus have not been sufficiently studied.
[0005]
Therefore, the present invention proposes a measurement method for evaluating the linearity of the dynamic response characteristic of a strain gauge and a device for carrying out the method, and aims to improve the reliability of the measurement technique using the strain gauge. To do.
[0006]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the invention according to claim 1 is characterized in that a strain gauge to be measured is attached to a metal rod, only the first flying object, only the second flying object, and the first and second objects. with simultaneous or small time difference of both flying object, said metal by respectively collide with the first end surface of the rod is respectively generating acoustic wave pulse inside metal bar, the first end surface of the elastic wave pulse metal rod generated by the collision Measure the velocity of the second end face that occurs when it reaches the second end face on the opposite side, and input to the strain gauge using the theory of propagation of elastic wave pulses and the signal of the measured speed in each measurement. By obtaining a transient strain signal acting as a signal, simultaneously obtaining an output signal of a strain gauge obtained at the time of each collision, and comparing the transient strain signal and the output signal of the strain gauge in the time domain or the frequency domain , It is obtained by the linearity measuring method of the dynamic response characteristics of the strain gauge, characterized in that to measure the dynamic linearity of the gauge dynamics.
[0007]
The invention according to claim 2 is the linearity measuring method of the dynamic response characteristic of the strain gauge according to claim 1, wherein the speed of the second end face is measured by a measuring means using laser light. It is.
[0008]
The invention according to claim 3 is the linearity measuring method of the dynamic response characteristic of the strain gauge according to claim 2, wherein the measuring means using the laser beam is a laser interferometer.
[0009]
According to a fourth aspect of the present invention, a strain gauge as a measurement object is attached to a metal rod, and only the first flying object, only the second flying object, and both the first and second flying objects are simultaneously attached. or with a small time difference, the first end surface of the metal bar by each collision is respectively generating acoustic wave pulse inside metal bar, the said elastic wave pulses generated by each collision opposite the first end surface of the metal bar Measure the acceleration of the second end face that occurs when the two end faces are reached, and in each measurement, use the theory of propagation of elastic wave pulses and the signal of the measured acceleration to act as an input signal to the strain gauge. By obtaining a strain signal, simultaneously obtaining a strain gauge output signal obtained at the time of each collision, and comparing the transient strain signal and the output signal of the strain gauge in the time domain or the frequency domain. It is obtained by the linearity measuring method of the dynamic response characteristics of the strain gauge, characterized in that to measure the dynamic linearity.
[0010]
Further, in the invention according to claim 5, a strain gauge to be measured is attached to a metal rod, and only the first flying object, only the second flying object, and both the first and second flying objects are simultaneously attached. or with a small time difference, the first end surface of the metal bar by each collision is respectively generating acoustic wave pulse inside metal bar, the said elastic wave pulses generated by each collision opposite the first end surface of the metal bar each measured dynamic displacement of the second end surface that occurs when it reaches the second end face, acting as an input signal to the strain gauge by using the propagation theory of Sukaraku acoustic wave pulses, the speed of the signal measured at each measurement The strain gauge output signal obtained at the time of each collision is obtained, and the strain gauge output signal is obtained by comparing the transient strain signal with the strain gauge output signal in the time domain or the frequency domain. Dynamic characteristics It is obtained by the linearity measuring method of the dynamic response characteristics of the strain gauge, characterized in that to measure the dynamic linearity.
[0011]
The invention according to claim 6 is the linearity measuring method of the dynamic response characteristic of the strain gauge according to claim 5, wherein the dynamic displacement of the second end face is measured by a non-contact displacement sensor. Is.
[0012]
The invention according to claim 7 provides an elastic wave pulse generated in a metal rod where the flying body collides by providing a member made of a material different from that of the flying body at the tip of the flying body to form a flying structure. The frequency band is adjusted, and the linearity measuring method of the dynamic response characteristic of the strain gauge according to any one of claims 1 to 6 is provided.
[0013]
The invention according to claim 8 is characterized in that the first flying object and the second flying object are slidably disposed in a central space of the flying object launch tube and the periphery thereof. It is set as the linearity measuring method of the dynamic response characteristic of the strain gauge as described in any one of Claim 6.
[0014]
The first flying object and the second flying object are multiplexed to be able to be fired from multiple launch tubes , and the time difference between the firing of the first flying object and the second flying object is controlled to control the inside of the metal rod. 7. The method of measuring linearity of dynamic response characteristics of a strain gauge according to claim 1, wherein the frequency band of the elastic wave generated in the strain gauge is narrowed. .
[0015]
In the invention according to claim 10, when a transient strain signal to be input to the strain gauge is obtained from the strain of the elastic wave pulse incident on the end face by the analytical solution of scalar which is the theory of acoustic wave propagation, The dynamic response characteristic of a strain gauge according to any one of claims 1 to 6, wherein at least a first-order term of the analytical solution and a higher-order term are used for further improving accuracy. This is a linearity measurement method.
[0016]
According to an eleventh aspect of the present invention , a time difference that is a difference in collision time between the first flying object and the second flying object with respect to the metal rod is generated when the first flying object collides with the metal rod. The input transient strain signal to the strain gauge and the input transient strain signal to the strain gauge generated when the second projectile collides with the metal rod are simultaneously transmitted by the first projectile and the second projectile. calculated as best fit time difference input transients distortion signal to the strain gauges that occurred when fired, taking into account the best fit time difference, when the first projectile and a second projectile fired singly The dynamic linearity of the strain gauge is measured from the strain gauge output signal and the strain gauge output signal obtained when the first and second projectiles are fired almost simultaneously with a small time difference. Any one of claims 1 to 6 It is obtained by the linearity measuring method of the dynamic response characteristics of the strain gage according to One.
[0017]
According to a twelfth aspect of the present invention, the dynamic linearity related to the gain and phase of the strain gauge, which is clarified by the linearity measuring method of the dynamic response characteristic of the strain gauge of any one of the first to eleventh aspects. In the frequency domain where the characteristics are established, one of the measurement results of motion velocity, motion acceleration of the metal rod end face, dynamic displacement measurement , strain gauge input transient strain signal and strain gauge output signal derived from wave propagation theory This is a linearity measurement method for the dynamic response characteristic of a strain gauge, characterized in that the frequency response characteristic of the strain gauge is obtained by comparison in the frequency domain.
[0018]
In the invention according to claim 13, the metal rod with the strain gauge attached thereto, only the first flying object, only the second flying object, and both the first and second flying objects can be used simultaneously or with a minute time difference. have, opposite the first end surface of the first and projectile launching means by each collision to each generate an elastic wave pulse inside the metal rod on the end face, the elastic wave pulses generated by each collision metal bar of the metal bar Measure the velocity of the second end face that occurs when the second end face is reached, and act as an input signal to the strain gauge using the propagation theory of elastic wave pulses and the measured speed signal in each measurement. The strain gauge output signal obtained at the time of each collision is obtained, and the strain gauge output signal is obtained by comparing the transient strain signal with the strain gauge output signal in the time domain or the frequency domain. Movement It is obtained by the linearity measuring apparatus of the dynamic response characteristics of the strain gauge, characterized in that a dynamic linearity estimation means for measuring the dynamic linearity of sex.
[0019]
The invention according to claim 14 is the linearity measuring apparatus for dynamic response characteristics of a strain gauge according to claim 13, wherein the speed of the second end face is measured by a measuring apparatus using laser light. It is.
[0020]
The invention according to claim 15 is the linearity measuring apparatus for dynamic response characteristics of a strain gauge according to claim 14, wherein the measuring means using the laser beam is a laser interferometer.
[0021]
According to the sixteenth aspect of the present invention, there is provided a metal rod having a strain gauge attached thereto, only the first flying object, only the second flying object, and both the first and second flying objects simultaneously or with a minute time difference. have, opposite the first end surface of the first and projectile launching means by each collision to each generate an elastic wave pulse inside the metal rod on the end face, the elastic wave pulses generated by each collision metal bar of the metal bar Measure the acceleration of the second end face that occurs when the second end face is reached, and act as an input signal to the strain gauge using the propagation theory of elastic wave pulses and the measured acceleration signal in each measurement. to determine the transient distortion signal, determined simultaneously output signals of the strain gauges obtained the at each collision, the transient distortion signal and an output signal of the strain gauge, by comparing the time domain or frequency domain, distortion gate It is obtained by the linearity measuring apparatus of the dynamic response characteristics of the strain gauge, characterized in that a dynamic linearity estimation means for measuring the dynamic linearity of the dynamic characteristics.
[0022]
In the invention according to claim 17, the metal rod with the strain gauge attached thereto, only the first flying object, only the second flying object, and both the first and second flying objects may be simultaneously or with a minute time difference. have, opposite the first end surface of the first and projectile launching means by each collision to each generate an elastic wave pulse inside the metal rod on the end face, the elastic wave pulses generated by each collision metal bar of the metal bar The dynamic displacement of the second end face that occurs when the second end face is measured is measured, and the input signal to the strain gauge is measured using the elastic wave pulse theory of propagation and the measured velocity signal in each measurement. By obtaining the transient strain signal that acted as , and simultaneously obtaining the output signal of the strain gauge obtained at the time of each collision, by comparing the transient strain signal and the output signal of the strain gauge in the time domain or frequency domain, Distortion game It is obtained by the linearity measuring apparatus of the dynamic response characteristics of the strain gauge, characterized in that a dynamic linearity estimation means for measuring the dynamic linearity of the dynamic characteristics.
[0023]
The invention according to claim 18 is the linearity measuring apparatus for dynamic response characteristics of a strain gauge according to claim 17, wherein the dynamic displacement of the second end face is measured by a non-contact displacement sensor. Is.
[0024]
According to a nineteenth aspect of the present invention, there is provided an elastic wave pulse generated in a metal rod where the flying object collides by providing a member made of a material different from that of the flying object body at the tip of the flying object to form a laminated structure. The frequency band of the strain gauge according to any one of claims 13 to 18 is adjusted.
[0025]
The invention according to claim 20 is provided with a flying object launching tube that slidably arranges the first flying object and the second flying object in and around the central space. The strain gage dynamic response characteristic linearity measuring apparatus according to any one of claims 13 to 18.
[0026]
The invention according to claim 21 is characterized in that the flying object launch tube is formed by a double tube of a central tube and a surrounding tube, and the first flying object and the second flying object are arranged at the center of the central tube. 21. The linearity measuring apparatus for dynamic response characteristics of a strain gauge according to claim 20, wherein the linear measuring apparatus is slidably disposed in the space and the space between the central tube and the surrounding tube.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
If linearity does not hold in various measurements, accurate measurement is difficult. Linearity is important in dynamic measurement, but it is generally not easy to verify dynamic linearity with respect to gain and phase.
[0028]
In this regard, as a general definition, the dynamic linearity is such that the output signal for the input signal x (t) is X (t) and the output signal for the input signal y (t) is Y (t). If the output signal for the input signal a · x (t) + b · y (t) is a · X (t) + b · Y (t) using the arbitrary constants a and b, the dynamic linearity is established. It can be said that
[0029]
Based on this concept, as shown in FIG. 1, a strain gauge 4 to be measured is attached to the metal rod 3, and the first flight fired from the inner launch tube 7 on the first end face 6 of the metal rod 3. The movement speed of the second end face 8 generated when the elastic wave pulse generated by the collision of the body 1 reaches the second end face 8 opposite to the first end face is measured. Using the elastic wave propagation theory, a dynamic strain ε ₁ (t) and an output ε _{out, 1} (t) of the gauge which acted as an input signal to the strain gauge 4 by the first flying object 1 are obtained.
[0030]
When measuring the motion speed of the second end face 8 of the metal rod 3, the interferometer 10 shown in FIG. 1 irradiates the second end face 8 with a laser beam from the interferometer 10 and detects the reflected light. Is measured as a speed change of the second end face 8, and the measurement data is output to a computer 11 such as a personal computer, and is compared with a signal from the strain gauge 4 to calculate the movement of the strain gauge 4 using a calculation formula as will be described later. The linear characteristic of the dynamic response characteristic is calculated. In the embodiment of FIG. 2 (a), the acceleration sensor 12 is used to measure the change in acceleration of the second end face 8, and in the embodiment of FIG. 2 (b), the non-contact displacement sensor 13 is used. The example which measures the displacement of a 2nd end surface is shown, and also in these, the calculator 11 as shown in FIG. 1 is used, and the linear characteristic of the dynamic responsiveness of the strain gauge 4 is calculated using the calculation formula as mentioned later To do.
[0031]
Next, the second wave generated when the elastic wave pulse generated by causing the second projectile 2 launched from the outer launch tube 9 to collide with the first end face 6 of the metal rod 3 reaches the second end face 8. The dynamic velocity ε ₂ (t) and the gauge acting as an input signal to the gauge by the second flying object 2 are measured using the strain and elastic wave propagation theory derived from the result of measuring the movement speed of the end face 8. Output ε _{out, 2} (t) is obtained.
[0032]
Finally, when the first flying object 1 and the second flying object 2 are simultaneously collided with the first end face 6 of the metal rod 3, the strain signal acting as an input signal to the strain gauge 4 is the linearity of the elastic wave. Therefore, ε ₁ (t) + ε ₂ (t). At this time, the output signal of the gauge is ε _out (t). If linearity holds, the output signal should be ε _{out, 1} (t) + ε _{out, 2} (t), so this signal and ε _out (t) can be By comparing, the dynamic linearity of the strain gauge is measured with respect to gain and phase.
[0033]
The present invention can be implemented by the basic idea as described above and the apparatus as described above, and the theory for applying the basic idea in the present invention to actual measurement will be described below. Will be described in order. That is, the present invention can be implemented by the following theoretical analysis, and this theory supports the implementation of the measuring method and measuring apparatus according to the present invention.
[0034]
When an impact is applied to the end face of a metal rod that is sufficiently long with respect to the diameter, such as by causing a flying object (regardless of material or structure) to collide, an elastic wave pulse is generated inside the metal rod. When this elastic wave pulse reaches the other end face, it becomes a plane elastic wave pulse, and in the process of reflection at the end face, longitudinal elastic wave (C) inside the rod and strain rate

Acceleration (a (t)) twice as large as the product of.
[Expression 2]

Here, ε (t) is the distortion of the elastic wave pulse incident on the end face, and · represents a time differential term.
From the equation (1), if the end surface motion velocity is v (t) and the end surface dynamic displacement is d (t), the following equations (2) and (3) are established from the equation (1).
[Equation 3]

[Expression 4]

[0035]
Actually, since it is impossible to attach the strain gauge to be measured to the boundary surface between the end face and the side face of the metal rod, L _B from the collision end face with the flying object
Assuming that a strain gauge is attached at a position far away from each other, equations (4), (5), and (6) are established for the relationship between the strain observed by the gauge and the motion acceleration, motion speed, and dynamic displacement of the end face. . In the formula, represents a time derivative.
[Equation 5]

[Formula 6]

[Expression 7]

[0036]
The motion acceleration of the end face calculated from the equation (4) becomes an input signal to the acceleration sensor. The motion speed calculated by the equation (5) becomes an input signal to the laser interferometer. The dynamic displacement calculated by the equation (6) becomes an input signal to the non-contact displacement sensor.
[0037]
The transient signal observed with a strain gauge that measures dynamic linearity is shown in FIG. The waveform of the time interval [t _c − t _d ] is a tensile stress wave pulse formed by reflecting the elastic wave pulse at the rod end face, and propagates in the direction of the end face where the flying object collides. It does not contribute to the generation of acceleration, speed, and dynamic displacement that are input signals to the non-contact displacement sensor. Distortion that generates an acceleration signal that is an input signal to the acceleration sensor by equation (4), distortion that generates a velocity signal that is an input signal to the laser interferometer (vibrometer) by equation (5), and by equation (6) All distortions that generate a dynamic displacement signal that is an input signal to the non-contact displacement meter are distortion signals that appear in the time interval [t _a −t _b ] in FIG.
[0038]
The distortion (ε _A (t)) of the elastic wave pulse incident on the end face obtained from the output signal of the acceleration sensor from the equation (1) is the following equation (7), and from the output signal of the interferometer from the equation (2). The distortion (ε _V (t)) of the elastic wave pulse incident on the required end face is the equation (8), and the distortion of the elastic wave pulse incident on the end face obtained from the non-contact displacement sensor and the displacement measuring device from the expression (3). (Ε _D (t)) is expressed by equation (9). In the formula (9), * represents time differentiation.
[Equation 8]

[Equation 9]

[Expression 10]

[0039]
Moreover, the propagation of the wave in a metal round bar is represented by the following (10) Formula.
[Expression 11]

Where
t: Time
l _p : Length of flying object C _p : Propagation speed of longitudinal elastic wave in flying object ε _t (t, z): First term of Scalak's analytical solution

[Formula 13]

[Expression 14]

Where
V ₁ : Colliding speed of flying object
t: elapsed time after collision ν: Poisson's ratio D _a : diameter of metal bar z: coordinate in the axial direction of the metal bar
From the equations (7) and (10), a strain signal (ε ⁱ _A (t)) is obtained as an input signal to the strain gauge using the result of measuring the motion acceleration of the rod end surface with an acceleration sensor. From the equations (8) and (10), a strain signal (ε ⁱ _v (t)) is obtained as an input signal to the strain gauge using the result of measuring the motion speed of the rod end surface with a laser interferometer. A strain signal (ε ⁱ _D (t)) as an input signal to the strain gauge using the result of measuring the dynamic displacement of the rod end surface by a non-contact displacement sensor or the like from the equations (9) and (10) is can get.
[0041]
Symbols are defined for the first flying object 1 and the second flying object 2 as shown in the following table.
Table 1:

[0042]
When actually measuring using the measurement technique based on the theory as described above, the case where the collision time difference between the first flying object and the second flying object is not taken into consideration, and the case where it is taken into account, and In each of the cases, the following evaluation function is used for the calculation in the time domain for the comparison with the acceleration sensor, the measurement with the laser interferometer, and the measurement with the non-contact displacement sensor. In each case, the comparison in the frequency domain can be performed by calculating using the following calculation formula. Hereinafter, these will be described in order.
[0043]
1. When the collision time difference is not considered.
1) Comparison in the time domain 1-1) An example of an evaluation function when measuring with an acceleration sensor:
[Expression 15]

(Integrate over the interval [t ₁ , t ₂ ] where the signal exists)
[0044]
1-2) An example of an evaluation function when measuring with a laser interferometer:
[Expression 16]

(Integrate over the interval [t ₁ , t ₂ ] where the signal exists)
[0045]
1-3) An example of an evaluation function when measuring with a non-contact displacement sensor:
[Expression 17]

(Integrate over the interval [t ₁ , t ₂ ] where the signal exists)
[0046]
2) Comparison in the frequency domain 2-1) When measuring with an acceleration sensor,
[Expression 18]

And the frequency that deviates from the allowable value having an absolute value of 1 is defined as the critical frequency of the dynamic linearity related to the gain. Further, regarding the phase, it is assumed that the phase of the calculation result is out of the allowable value of zero, and the dynamic linearity establishment limit frequency regarding the phase.
[0047]
2-2) When measuring with a laser interferometer,
[Equation 19]

And the frequency that deviates from the allowable value having an absolute value of 1 is defined as the critical frequency of the dynamic linearity related to the gain. Further, regarding the phase, it is assumed that the phase of the calculation result is out of the allowable value of zero, and the dynamic linearity establishment limit frequency regarding the phase.
[0048]
2-3) When measuring with a non-contact displacement sensor,
[Expression 20]

And the frequency that deviates from the allowable value having an absolute value of 1 is defined as the critical frequency of the dynamic linearity related to the gain. Further, regarding the phase, it is assumed that the phase of the calculation result is out of the allowable value of zero, and the dynamic linearity establishment limit frequency regarding the phase.
[0049]
2. When the collision time difference is taken into consideration, if it is not easy to control the first projecting object 1 and the second projecting object 2 to collide with the metal rod at the same time, the time difference is set to Δt, and an end face using an acceleration sensor is used. When ^obtaining the input transient strain signal of the gauge from the motion acceleration of ε ⁱ¹ _A (t) + ε ⁱ² _A (t−Δt), Δt is obtained as a parameter so that ε ⁱ¹² _A (t) best matches ε ⁱ¹² _A (t). When ^obtaining the input transient strain signal of the gauge from the motion acceleration of the end face from the laser interferometer, Δt so that ε ⁱ¹ _V (t) + ε ⁱ² _V (t−Δt) best matches ε ⁱ¹² _V (t). As a parameter. When ^obtaining the input transient strain signal of the gauge from the motion acceleration of the end face from the non-contact dynamic displacement sensor, ε ⁱ¹ _D (t) + ε ⁱ² _D (t−Δt) best matches ε ⁱ¹² _D (t). Thus, Δt is obtained as a parameter. The Δt obtained in this way is obtained by applying it to the respective equations 1) and 2) in the above “1. Considering the collision time difference”.
[0050]
The present invention can be further implemented in various modes. For example, by attaching a polymer material, plastic or the like to the tip portion, the flying body body is made of various materials such as metal, polymer material, or plastic. The frequency band of the elastic wave pulse generated inside the metal rod due to the collision of the flying object can be appropriately adjusted.
[0051]
Moreover, in the said Example, although the example which launches the 1st flying body and the 2nd flying body by the inside / outside double tube type launch was shown, for example, the 1st flying body is formed on the inner surface by one pipe. It is also possible to guide and guide the second flying object on the outer surface. Also, by multiplying the inner launch tube and the outer launch tube, and controlling the phase of the launch of multiple projectiles launched from each of the multiple inner launch tube and the multiple outer launch tube, the elastic wave generated inside the metal rod A technique for narrowing the frequency band may be adopted.
[0052]
Furthermore, when obtaining a transient strain signal to be input to the strain gauge from the distortion of the elastic wave pulse incident on the end face by the analytical solution of scalac, which is the theory of elastic wave propagation, at least a first-order term of the sparse analytical solution. In order to further improve the accuracy, a method for measuring the linearity of the dynamic response characteristic of the strain gauge and the apparatus for implementing the same can be used, such as using even higher-order terms of the analytical solution of Scalak.
[0053]
In addition, in the frequency domain where the dynamic linearity related to the gain and phase of the strain gauge revealed by the above method is established, it is derived from the motion acceleration measurement, motion speed measurement, dynamic displacement measurement results and wave propagation theory of the metal rod end face. The frequency response characteristic of the strain gauge may be obtained by comparing the gauge input transient strain signal and the strain gauge output signal (both including and not including the amplifier) in the frequency domain.
[0054]
【The invention's effect】
Since the present invention is configured as described above, a highly reliable strain gauge with guaranteed dynamic linearity can be obtained, and the reliability of all measurements using the strain gauge can be improved. Therefore, the reliability of the measurement of static strength of structures, for example, the measurement of dynamic strength of structures using this strain gauge is improved, and further, the reliability of such measurements is improved to improve the reliability of building structures and bridges. This improves the reliability of dynamic strain measurement for all products such as roads, vehicles and sensors.
[Brief description of the drawings]
FIG. 1 is a diagram showing an embodiment of an apparatus for measuring the dynamic linearity of a strain gauge using an interferometer in the present invention.
FIG. 2 is a diagram showing an embodiment of an apparatus for measuring dynamic linearity of a strain gauge using an acceleration sensor in the present invention.
FIG. 3 is a diagram showing an example of a waveform observed with a strain gauge in the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 1st projectile body 2 2nd projectile body 3 Metal rod 4 Strain gauge 6 First end surface 7 Inner launch tube 8 Second end surface 9 Outer launch tube 10 Interferometer 11 Computer

Claims (21)

Affix the strain gauge to be measured to a metal bar,
Only the first projectile, and only the second projectile, and the first and second with the same time or a very small time difference of both the projectile, each internal metal rod by respectively collide with the first end surface of the metal rod Generate an elastic wave pulse,
Measuring the velocity of the second end face generated when the elastic wave pulse generated by each collision reaches the second end face opposite to the first end face of the metal rod;
In each of the above measurements, the propagation theory of the elastic wave pulse and the signal of the measured velocity are used to obtain a transient strain signal that acts as an input signal to the strain gauge,
At the same time, obtain the output signal of the strain gauge obtained at the time of each collision,
The dynamic response characteristic of the gauge is characterized by measuring the dynamic linearity of the strain gauge dynamic characteristic by comparing the transient strain signal and the output signal of the strain gauge in the time domain or the frequency domain. Linearity measurement method.  2. The method of measuring linearity of dynamic response characteristics of a strain gauge according to claim 1, wherein the speed of the second end face is measured by a measuring means using laser light.  3. The method for measuring linearity of dynamic response characteristics of a strain gauge according to claim 2, wherein said laser beam measuring means is a laser interferometer. Affix the strain gauge to be measured to a metal bar,
Only the first projectile, and only the second projectile, and the first and second with the same time or a very small time difference of both the projectile, each internal metal rod by respectively collide with the first end surface of the metal rod Generate an elastic wave pulse,
Measuring the acceleration of the second end face generated when the elastic wave pulse generated by each collision reaches the second end face opposite to the first end face of the metal bar,
In each of the above measurements, the elastic wave pulse sparse propagation theory and the measured acceleration signal are used to obtain a transient strain signal that acts as an input signal to the strain gauge,
At the same time, obtain the output signal of the strain gauge obtained at the time of each collision,
A dynamic response characteristic of a strain gauge, characterized by measuring dynamic linearity of a strain gauge dynamic characteristic by comparing the transient strain signal and an output signal of the strain gauge in a time domain or a frequency domain. Linearity measurement method. Affix the strain gauge to be measured to a metal bar,
Only the first projectile, and only the second projectile, and the first and second with the same time or a very small time difference of both the projectile, each internal metal rod by respectively collide with the first end surface of the metal rod Generate an elastic wave pulse,
Measuring the dynamic displacement of the second end face that occurs when the elastic wave pulse generated by each collision reaches the second end face opposite to the first end face of the metal rod;
In each of the above measurements, the propagation theory of the elastic wave pulse and the signal of the measured velocity are used to obtain a transient strain signal that acts as an input signal to the strain gauge,
At the same time, obtain the output signal of the strain gauge obtained at the time of each collision,
A dynamic response characteristic of a strain gauge, characterized by measuring dynamic linearity of a strain gauge dynamic characteristic by comparing the transient strain signal and an output signal of the strain gauge in a time domain or a frequency domain. Linearity measurement method.  6. The method for measuring linearity of dynamic response characteristics of a strain gauge according to claim 5, wherein the dynamic displacement of the second end face is measured by a non-contact displacement sensor.  A member of a material different from that of the flying body is provided at the tip of the flying body to make the flying body a laminated structure, and a frequency band of an elastic wave pulse generated inside the metal rod with which the flying body collides is adjusted. The linearity measurement method for dynamic response characteristics of a strain gauge according to any one of claims 1 to 6.  The said 1st flying body and the 2nd flying body are arrange | positioned so that sliding is possible in the center space of a flying body launcher tube, and its circumference | surroundings. To measure the linearity of dynamic response characteristics of strain gauges. The first flying object and the second flying object are multiplexed to be able to be fired from multiple launch tubes , and the time difference between the firing of the first flying object and the second flying object is controlled to control the inside of the metal rod. 7. The method of measuring linearity of dynamic response characteristics of a strain gauge according to claim 1, wherein the frequency band of the elastic wave generated in the strain gauge is narrowed.  When obtaining a transient strain signal to be input to the strain gauge from the distortion of the elastic wave pulse incident on the end face by the analytical solution of scalac, which is the theory of elastic wave propagation, at least a first-order term of the sparse analytical solution, 7. The method for measuring linearity of dynamic response characteristics of a strain gauge according to claim 1, wherein even higher-order terms are used to increase accuracy. A time difference which is a difference in collision time of the first flying object and the second flying object with respect to the metal rod, and an input transient strain signal to the strain gauge generated when the first flying object collides with the metal rod; An input transient strain signal to the strain gauge generated when the second flying object collides with the metal rod is used to output the strain gauge generated when the first flying object and the second flying object are simultaneously fired. Find the input transient distortion signal as the most suitable time difference ,
In consideration of the most suitable time difference , the first flying object and the second flying object are output with a strain gauge output signal obtained when each of the first flying object and the second flying object is fired independently, and a minute time difference. The strain gage dynamic according to any one of claims 1 to 6, wherein the dynamic linearity of the strain gage is measured from an output signal of the strain gage obtained when the bodies are launched almost simultaneously. Response characteristic linearity measurement method. In the frequency domain where the dynamic linearity regarding the gain and the phase of the strain gauge revealed by the linearity measuring method of the dynamic response characteristic of the strain gauge according to any one of claims 1 to 11 is established, Strain gauge by comparing one of measurement results, motion acceleration measurement of metal rod end face, dynamic displacement measurement result , strain gauge input transient strain signal derived from wave propagation theory and strain gauge output signal in frequency domain A method for measuring the linearity of a dynamic response characteristic of a strain gauge, characterized by obtaining a frequency response characteristic of a strain gauge. A metal rod which put a strain gauge, a first projectile only, and a second projectile only, and have at the same time or a very small time difference the first and second two projectile, the first end surface of the metal rod a projectile firing means each colliding with generating each elastic wave pulse inside the metal rod caused the when acoustic wave pulses generated by each collision has reached the second end surface opposite the first end surface of the metal bar Each of the speeds of the second end face is measured, and in each measurement, a transient propagation signal acting as an input signal to the strain gauge is obtained by using the propagation theory of elastic wave pulses and a signal of the measured speed. The strain gauge output signal obtained at the time of collision is obtained, and the dynamic strain linearity of the strain gauge is measured by comparing the transient strain signal and the strain gauge output signal in the time domain or the frequency domain. dynamic Linearity measuring apparatus of the dynamic response characteristics of the strain gauge, characterized in that a shape estimating means.  The linearity measuring apparatus for dynamic response characteristics of a strain gauge according to claim 13, wherein the speed of the second end face is measured by a measuring apparatus using laser light.  15. The linearity measuring apparatus for dynamic response characteristics of a strain gauge according to claim 14, wherein the measuring means using laser light is a laser interferometer. A metal rod which put a strain gauge, a first projectile only, and a second projectile only, and have at the same time or a very small time difference the first and second two projectile, the first end surface of the metal rod a projectile firing means, respectively collide with to each generate an elastic wave pulse inside the metal rod,
The acceleration of the second end surface generated when the elastic wave pulse generated by each collision reaches the second end surface opposite to the first end surface of the metal rod is measured, and in each of the measurements, the propagation of the elastic wave pulse is sparse. The transient strain signal that acts as an input signal to the strain gauge using the theory and the measured acceleration signal is obtained, and at the same time, the output signal of the strain gauge obtained at the time of each collision is obtained, the transient strain signal, and the strain gauge The dynamic response of the strain gauge is characterized by comprising a dynamic linearity estimating means for measuring the dynamic linearity of the strain gauge dynamic characteristics by comparing the output signal of the strain gauge in the time domain or the frequency domain Characteristic linearity measuring device. A metal bar with a strain gauge,
Only the first projectile, and only the second projectile, and the first and second with the same time or a very small time difference of both the projectile, each internal metal rod by respectively collide with the first end surface of the metal rod A flying object launching means for generating an elastic wave pulse;
The respectively measured dynamic displacement of the second end surface that occurs when it reaches the second end surface opposite the first end surface of the elastic wave pulses generated by each collision metal rod, said Sukaraku acoustic wave pulse in each measurement A transient strain signal that acts as an input signal to the strain gauge using the propagation velocity signal and the measured velocity signal, and simultaneously obtains an output signal of the strain gauge obtained at the time of each collision, the transient strain signal, Dynamic strain linearity estimation means for measuring the dynamic linearity of the strain gauge dynamic characteristics by comparing the output signal of the strain gauge in the time domain or the frequency domain. Response characteristic linearity measurement device.  18. The apparatus for measuring linearity of dynamic response characteristics of a strain gauge according to claim 17, wherein the dynamic displacement of the second end face is measured by a non-contact displacement sensor.  A member of a material different from that of the flying body is provided at the tip of the flying body to make the flying body a laminated structure, and a frequency band of an elastic wave pulse generated inside the metal rod with which the flying body collides is adjusted. The linearity measuring apparatus for dynamic response characteristics of a strain gauge according to any one of claims 13 to 18.  19. A projectile launcher tube comprising the first projectile and the second projectile slidably disposed in a central space and the periphery thereof. The linearity measuring device of the dynamic response characteristic of the strain gauge described in 1. The flying object launch tube is formed by a double tube of a central tube and its surrounding tube,
The strain according to claim 20, wherein the first flying body and the second flying body are slidably disposed in a central space of a central tube and a space between the central tube and a surrounding tube. A linearity measuring device for dynamic response characteristics of gauges.

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