JP2012189352A - Sonic velocity measuring apparatus and method for ultrasonic waves propagated on surface - Google Patents
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Abstract
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本発明は、表面を伝播する超音波の音速を測定する装置と方法に関する。 The present invention relates to an apparatus and method for measuring the speed of sound of ultrasonic waves propagating on a surface.
材料は、材料組成や加工方法、熱処理方法や材料の使用環境（負荷応力や熱履歴など）で音速が変化することが知られている。従って、材料の音速変化を監視することで材料特性の変化を監視することができる。具体的には材料に加わる応力の変化、材質の劣化の監視あるいは表面改質（浸炭処理など）などの加工の監視などができる。 It is known that the speed of sound of a material changes depending on the material composition, processing method, heat treatment method, and material usage environment (load stress, thermal history, etc.). Therefore, a change in material properties can be monitored by monitoring a change in sound velocity of the material. Specifically, it is possible to monitor changes in stress applied to the material, deterioration of the material, or processing such as surface modification (such as carburization).
また例えば、溶射、メッキ、浸炭などの表面処理が施されている材料では、母材と表面改質部の音速は異なってくる。例えば、より波長の長い低い周波数成分では、超音波はより深い層までの表層部を伝播することで、母材の音速の影響をより大きく受ける。一方、短い波長の高い周波数の超音波は、より表層部を伝播するために表面改質部の音速の影響を大きく受ける。このために、音速の周波数依存性を評価することにより、表面改質部の膜厚などの把握が可能になる。 Further, for example, in a material that has been subjected to a surface treatment such as thermal spraying, plating, or carburizing, the sound speed of the base material and the surface modified portion is different. For example, in a low-frequency component having a longer wavelength, the ultrasonic wave is more greatly affected by the sound velocity of the base material by propagating through the surface layer portion up to a deeper layer. On the other hand, high-frequency ultrasonic waves having a short wavelength are greatly affected by the sound velocity of the surface modification portion in order to propagate through the surface layer portion. For this reason, it is possible to grasp the film thickness of the surface modification portion by evaluating the frequency dependence of the sound velocity.
上述した目的のため、表面を伝播する表面波の音速測定手段が、既に提案されている（例えば、特許文献１）。 For the above-mentioned purpose, a sound velocity measuring means for surface waves propagating on the surface has already been proposed (for example, Patent Document 1).
音速の変化量は、１％未満の極微量であることがほとんどであり、上述の目的のためには高精度な音速計測が必要となる。また、高精度な音速計測のためには、超音波の正確な伝播時間の計測と共に、超音波の伝播距離を正確に求める必要がある。 The amount of change in sound speed is almost an extremely small amount of less than 1%, and high-accuracy sound speed measurement is required for the above-described purpose. In addition, for high-accuracy sound speed measurement, it is necessary to accurately determine the ultrasonic propagation distance as well as the measurement of the ultrasonic propagation time.
図１は従来の測定法を示す模式図である。この図において、１は材料表面、２は表面波用探触子、３は振動子、４はくさび形部材である。
従来の測定法では、この図に示すように２つの表面波用探触子２を対向させ、超音波５の伝播時間を測定する。測定した超音波５の伝播時間には、くさび形部材４内を伝播する時間も含まれるので、表面波用探触子２内での超音波伝播時間を予め求めておき、補正する必要がある。この補正した伝播時間と、表面波用探触子２の入射点間距離から表面波（超音波５）の音速を求めることができる。
FIG. 1 is a schematic diagram showing a conventional measurement method. In this figure, 1 is a material surface, 2 is a surface wave probe, 3 is a vibrator, and 4 is a wedge-shaped member.
In the conventional measuring method, as shown in this figure, two surface wave probes 2 are opposed to each other, and the propagation time of the ultrasonic wave 5 is measured. Since the measured propagation time of the ultrasonic wave 5 includes the propagation time in the wedge-shaped member 4, the ultrasonic wave propagation time in the surface wave probe 2 needs to be obtained in advance and corrected. . The sound velocity of the surface wave (ultrasonic wave 5) can be obtained from the corrected propagation time and the distance between the incident points of the surface wave probe 2.
図２は、表面波用探触子内での伝播時間の測定法を示す模式図である。
従来の測定法で測定する伝播時間は図１に示すｔ１＋ｔ２＋ｔ３であり、表面波用探触子２内での伝播時間ｔ１＋ｔ３は例えば、図２に示すように表面波用探触子２を反対向きに重ね合わせて伝播時間を測定することで求める。このときの超音波５の入射点位置は、振動子３が置かれている面の法線上であり、振動子３の中心線上として求められる。
FIG. 2 is a schematic diagram showing a method for measuring the propagation time in the surface wave probe.
The propagation time measured by the conventional measuring method is t1 + t2 + t3 shown in FIG. 1, and the propagation time t1 + t3 in the surface wave probe 2 is, for example, the surface wave probe 2 facing in the opposite direction as shown in FIG. It is obtained by measuring the propagation time by superimposing on. The incident point position of the ultrasonic wave 5 at this time is on the normal line of the surface on which the transducer 3 is placed, and is obtained as the center line of the transducer 3.
しかし、この方法にはいくつかの問題点があり、測定精度の限界がある。例えば、実際に探傷するときの超音波５の入射点位置は、くさび形部材４の振動子３が置かれている面の傾きから幾何学的に求められる位置とは異なる位置にずれる。実際の超音波５の屈折はスネルの法則に従うので、試験体の表面波の音速によって異なる位置となり、振動子３の中心線上に必ずしも位置しない。従って、この入射点位置のずれに伴う誤差が必然的に発生する。 However, this method has some problems and has a limit of measurement accuracy. For example, the position of the incident point of the ultrasonic wave 5 when the flaw detection is actually performed deviates from a position geometrically determined from the inclination of the surface on which the transducer 3 of the wedge-shaped member 4 is placed. Since the actual refraction of the ultrasonic wave 5 follows Snell's law, the position varies depending on the speed of sound of the surface wave of the specimen, and is not necessarily located on the center line of the vibrator 3. Therefore, an error accompanying the deviation of the incident point position inevitably occurs.
図３は、超音波波形の立ち上がり位置とノイズを示す模式図である。
また超音波の伝播時間の測定に関しても誤差が発生する。正確な伝播時間は、図３（Ａ）に示すように波形６の立ち上がり位置で定義される。しかし超音波の伝播にはノイズの発生が必然的にあり、ノイズを伴う場合には、図３（Ｂ）に示すように波形６の立ち上がり位置を正確に読み取ることが不可能になる。従って、従来の測定方法には、誤差が含まれる。
FIG. 3 is a schematic diagram showing the rising position of the ultrasonic waveform and noise.
An error also occurs with respect to the measurement of ultrasonic propagation time. The exact propagation time is defined by the rising position of the waveform 6 as shown in FIG. However, noise is inevitably generated in the propagation of ultrasonic waves, and when the noise is accompanied, it is impossible to accurately read the rising position of the waveform 6 as shown in FIG. Therefore, the conventional measurement method includes an error.
本発明は、上述した問題点を解決するために創案されたものである。すなわち、本発明の目的は、入射点位置と波形の立ち上がり位置の影響を受けることなく、表面を伝播する音速を高い精度で計測することができる超音波の音速測定装置と方法を提供することにある。 The present invention has been developed to solve the above-described problems. That is, an object of the present invention is to provide an ultrasonic sound velocity measuring apparatus and method capable of measuring the sound velocity propagating on the surface with high accuracy without being affected by the position of the incident point and the rising position of the waveform. is there.
本発明によれば、対象物の表面に沿って配置された超音波送信部及び超音波受信部と、
超音波受信部で検出した超音波波形から超音波の音速を算出する超音波演算部とを備え、
前記超音波送信部又は超音波受信部は、対象物の表面に沿って正確に測定された間隔で配置された複数の超音波素子からなり、
各超音波素子により超音波を送信又は受信し、超音波受信部で受信した超音波波形の伝播時間差を波形相関により求め、これから音速を測定する、ことを特徴とする表面を伝播する超音波の音速測定装置が提供される。
According to the present invention, an ultrasonic transmission unit and an ultrasonic reception unit arranged along the surface of the object,
An ultrasonic calculation unit that calculates the sound velocity of the ultrasonic wave from the ultrasonic waveform detected by the ultrasonic receiving unit,
The ultrasonic transmission unit or the ultrasonic reception unit is composed of a plurality of ultrasonic elements arranged at intervals accurately measured along the surface of the object,
Transmitting or receiving ultrasonic waves by each ultrasonic element, obtaining a propagation time difference of ultrasonic waveforms received by the ultrasonic receiving unit by waveform correlation, and measuring the speed of sound from this, and measuring ultrasonic velocity propagating on the surface A sound speed measuring device is provided.
また本発明によれば、対象物の表面に沿って配置された超音波送信部及び超音波受信部と、
超音波受信部で検出した超音波波形から超音波の音速を算出する超音波演算部とを備え、
前記超音波送信部又は超音波受信部は、対象物の表面に沿って正確に測定された間隔で配置された複数の超音波素子からなり、
各超音波素子により超音波を送信又は受信し、超音波受信部で受信した超音波波形の伝播時間差を波形相関により求め、これから音速を測定する、ことを特徴とする表面を伝播する超音波の音速測定方法が提供される。
Moreover, according to the present invention, an ultrasonic transmitter and an ultrasonic receiver arranged along the surface of the object,
An ultrasonic calculation unit that calculates the sound velocity of the ultrasonic wave from the ultrasonic waveform detected by the ultrasonic receiving unit,
The ultrasonic transmission unit or the ultrasonic reception unit is composed of a plurality of ultrasonic elements arranged at intervals accurately measured along the surface of the object,
Transmitting or receiving ultrasonic waves by each ultrasonic element, obtaining a propagation time difference of ultrasonic waveforms received by the ultrasonic receiving unit by waveform correlation, and measuring the speed of sound from this, and measuring ultrasonic velocity propagating on the surface A method of measuring the speed of sound is provided.
上記本発明の装置及び方法によれば、超音波送信部又は超音波受信部が、対象物の表面に沿って正確に測定された間隔で配置された複数の超音波素子からなるので、超音波の送信又は受信の条件は全ての超音波素子間で同一であり、各超音波素子で送信又は受信する超音波の伝播時間差は、唯一超音波素子間の距離に依存する。
また、受信した超音波波形の重ね合わせによる相関処理を行うので、超音波の立ち上がり時間を測定することなく伝播時間差を正確に求めることができ、ノイズの発生に対しても正確に伝播時間差を測定することができる。
従って、超音波の入射点位置と波形の立ち上がり位置の影響を受けることなく、表面を伝播する音速を高い精度で計測することができる
According to the apparatus and method of the present invention, since the ultrasonic transmission unit or the ultrasonic reception unit is composed of a plurality of ultrasonic elements arranged at intervals accurately measured along the surface of the object, The transmission / reception conditions are the same for all ultrasonic elements, and the difference in the propagation time of ultrasonic waves transmitted or received by each ultrasonic element depends solely on the distance between the ultrasonic elements.
In addition, since correlation processing is performed by superimposing received ultrasonic waveforms, it is possible to accurately determine the propagation time difference without measuring the rise time of the ultrasonic wave, and accurately measure the propagation time difference even when noise is generated. can do.
Therefore, the speed of sound propagating on the surface can be measured with high accuracy without being affected by the position of the ultrasonic incident point and the rising position of the waveform.
以下、本発明の好ましい実施形態を、図面を参照して説明する。なお各図において、共通する部分には同一の符号を付し、重複した説明は省略する。 Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In each figure, common portions are denoted by the same reference numerals, and redundant description is omitted.
図４は、本発明による音速測定装置の第１実施形態図である。
この図において、本発明の音速測定装置１０は、超音波送信部１２、超音波受信部１４及び超音波演算部１６を備える。
FIG. 4 is a diagram showing a first embodiment of a sound velocity measuring device according to the present invention.
In this figure, the sound velocity measuring apparatus 10 of the present invention includes an ultrasonic transmission unit 12, an ultrasonic reception unit 14, and an ultrasonic calculation unit 16.
超音波送信部１２及び超音波受信部１４は、対象物の表面１に沿って配置されている。対象物の表面１は、この例では平面であるが、曲面であってもよい。 The ultrasonic transmitter 12 and the ultrasonic receiver 14 are disposed along the surface 1 of the object. The surface 1 of the object is a flat surface in this example, but may be a curved surface.
この例において、超音波送信部１２は、表面波用探触子であるが、本発明はこれに限定されず、微小平板の振動子であってもよい。微小平板の振動子は、例えば圧電素子からなる。
表面波用探触子を超音波送信部１２として送信に用いることで、より強い表面波を送信できる。一方、微小平板の振動子を用いた場合、垂直方法にも縦波が送信され、板厚が薄い場合には底面の多重反射を受信して計測の妨害になるおそれがある。
In this example, the ultrasonic transmission unit 12 is a surface wave probe, but the present invention is not limited to this and may be a micro-plate vibrator. The fine flat plate vibrator is made of, for example, a piezoelectric element.
By using the surface wave probe as the ultrasonic transmitter 12 for transmission, a stronger surface wave can be transmitted. On the other hand, when a micro flat plate vibrator is used, a longitudinal wave is transmitted also in the vertical method, and when the plate thickness is thin, there is a possibility that measurement may be disturbed by receiving multiple reflections on the bottom surface.
この例において、超音波受信部１４は、対象物の表面１に沿って同一の間隔（ピッチ）ΔＸで配置された複数（この例で１２）の超音波素子１５からなる。各超音波素子１５は、この例では微小平板の振動子からなる。超音波素子１５の間隔ΔＸは、正確に距離が求められることが好ましい。以下、超音波素子１５の間隔（ピッチ）を「素子間距離」と呼ぶ。
このような複数の超音波素子１５は、単一の超音波素子を精密機械加工で微小な超音波素子に分割することで、素子間距離ΔＸを均一に精度よく加工が可能である。また予め、素子間距離ΔＸを正確に測定し、測定結果に反映させてもよい。
In this example, the ultrasonic receiving unit 14 includes a plurality (12 in this example) of ultrasonic elements 15 arranged at the same interval (pitch) ΔX along the surface 1 of the object. In this example, each ultrasonic element 15 is composed of a fine flat plate vibrator. The distance ΔX between the ultrasonic elements 15 is preferably determined accurately. Hereinafter, the interval (pitch) between the ultrasonic elements 15 is referred to as “inter-element distance”.
Such a plurality of ultrasonic elements 15 can be processed with a uniform and accurate inter-element distance ΔX by dividing a single ultrasonic element into fine ultrasonic elements by precision machining. In addition, the inter-element distance ΔX may be accurately measured in advance and reflected in the measurement result.
超音波演算部１６は、記憶装置、出力装置を備えたコンピュータ（ＰＣ）であり、超音波受信部１４で検出した超音波波形から超音波の音速ｖを算出する。 The ultrasonic calculation unit 16 is a computer (PC) having a storage device and an output device, and calculates the ultrasonic velocity v from the ultrasonic waveform detected by the ultrasonic reception unit 14.
上述した音速測定装置１０を用い、本発明の方法では、超音波送信部１２により対象物の表面１に超音波５を送信し、対象物の表面１を伝播する超音波５を超音波受信部１４の複数の超音波素子１５により順次受信し、受信した超音波波形６から超音波演算部１６によりその伝播時間差Δｔを波形相関により求め、これから音速ｖを測定するようになっている。 In the method of the present invention using the above-described sound velocity measuring apparatus 10, the ultrasonic wave transmitting unit 12 transmits the ultrasonic wave 5 to the surface 1 of the object, and the ultrasonic wave receiving unit transmits the ultrasonic wave 5 propagating through the surface 1 of the object. The ultrasonic wave is sequentially received by a plurality of ultrasonic elements 15, and the propagation time difference Δt is obtained from the received ultrasonic waveform 6 by the ultrasonic calculation unit 16 by waveform correlation, and the sound velocity v is measured therefrom.
なお、本発明は上述した構成に限定されず、超音波受信部１４の代わりに、超音波送信部１２を対象物の表面１に沿って同一の間隔ΔＸで配置された複数の超音波素子で構成してもよい。
この場合、本発明の方法では、超音波送信部１２の複数の超音波素子から対象物の表面１に超音波を同時に送信し、対象物の表面１を伝播する超音波５を１又は複数の超音波受信部１４により順次受信し、受信した超音波波形６から超音波演算部１６によりその伝播時間差Δｔを波形相関により求め、これから音速ｖを測定する。
In addition, this invention is not limited to the structure mentioned above, Instead of the ultrasonic receiver 14, the ultrasonic transmitter 12 is a plurality of ultrasonic elements arranged at the same interval ΔX along the surface 1 of the object. It may be configured.
In this case, in the method of the present invention, ultrasonic waves are simultaneously transmitted from the plurality of ultrasonic elements of the ultrasonic transmission unit 12 to the surface 1 of the object, and one or more ultrasonic waves 5 that propagate through the surface 1 of the object are transmitted. The ultrasonic wave receiving unit 14 sequentially receives the ultrasonic wave 6, the ultrasonic wave calculating unit 16 obtains the propagation time difference Δt by the waveform correlation, and the sound velocity v is measured therefrom.
図５は、本発明による音速測定装置の第２実施形態図である。
この図に示すように、各超音波素子１５をフレキシブルな台座に取り付けておくことで、対象物の表面１が曲面であっても精度よい音速ｖの測定が可能になる。
その他の構成は、第１実施形態と同様である。
FIG. 5 is a diagram showing a second embodiment of the sound velocity measuring device according to the present invention.
As shown in this figure, by attaching each ultrasonic element 15 to a flexible pedestal, even if the surface 1 of the object is a curved surface, it is possible to accurately measure the sound velocity v.
Other configurations are the same as those of the first embodiment.
図６は、本発明による音速測定の概念図である。
この図は、図４の装置に対応しており、複数（この例では１２）の超音波素子１５の位置をからＸ１，Ｘ２，Ｘ３，Ｘ４，Ｘ５・・・Ｘｎ、各超音波素子１５が超音波波形６を検出した時間を最初の時点からｔ１，ｔ２，ｔ３，ｔ４，ｔ５・・・ｔｎで示している。
位置Ｘ１，Ｘ２，Ｘ３，Ｘ４，Ｘ５・・・Ｘｎは、予め測定することができる既知の距離であり、時間ｔ１，ｔ２，ｔ３，ｔ４，ｔ５・・・ｔｎは、超音波受信部１４により検出され、超音波演算部１６により記憶される。また、素子間距離ΔＸは、位置Ｘ１，Ｘ２，Ｘ３，Ｘ４，Ｘ５・・・Ｘｎの間隔であり、超音波の伝播時間差Δｔは、時間ｔ１，ｔ２，ｔ３，ｔ４，ｔ５・・・ｔｎの間隔である。
FIG. 6 is a conceptual diagram of sound speed measurement according to the present invention.
This figure corresponds to the apparatus of FIG. 4, and the positions of a plurality of (in this example, 12) ultrasonic elements 15 are X1, X2, X3, X4, X5. The time when the ultrasonic waveform 6 is detected is indicated by t1, t2, t3, t4, t5.
The positions X1, X2, X3, X4, X5,... Xn are known distances that can be measured in advance, and the times t1, t2, t3, t4, t5,. Detected and stored by the ultrasonic calculator 16. The inter-element distance ΔX is an interval between the positions X1, X2, X3, X4, X5... Xn, and the ultrasonic wave propagation time difference Δt is the time t1, t2, t3, t4, t5. It is an interval.
図７は、本発明による測定結果の整理方法を示す概念図である。
この図において、横軸は時間ｔ、縦軸は距離Ｘであり、図中の各点（○印）は、図６における計測データである。超音波の音速ｖは、距離Ｘ／ｔで表される。
すなわち、図４の装置で得られた計測データから、伝播時間差Δｔと素子間の間隔（素子間距離ΔＸ）との関係を最小二乗法により求め、その勾配より音速ｖを求める。
また、受信した超音波波形６からウェーブレット解析により複数の異なる周波数における波形を抽出し、次いでそれぞれの周波数における音速を求め、音速の周波数依存性を求めることが好ましい。
FIG. 7 is a conceptual diagram showing a method for organizing measurement results according to the present invention.
In this figure, the horizontal axis is time t, the vertical axis is distance X, and each point (circle mark) in the figure is measurement data in FIG. The sound velocity v of the ultrasonic wave is represented by a distance X / t.
That is, the relationship between the propagation time difference Δt and the distance between elements (interelement distance ΔX) is obtained from the measurement data obtained by the apparatus of FIG. 4 by the least square method, and the sound velocity v is obtained from the gradient.
Further, it is preferable to extract waveforms at a plurality of different frequencies from the received ultrasonic waveform 6 by wavelet analysis, then obtain the sound speed at each frequency, and obtain the frequency dependence of the sound speed.
以下、本発明の実施例を説明する。
図４に示した装置において、幅０．５５ｍｍの超音波素子１５をピッチ０．６ｍｍの素子間距離ΔＸで並べた探触子（超音波受信部１４）を用いて測定を行った。超音波素子１５の幅は用いた探傷周波数５ＭＨｚの波長に比べて小さく、指向性の鈍いものであり、超音波素子１５を試験片に平行に配置しても、表面波や縦波成分のラテラル波を送受信（送信及び受信）することができる。
Examples of the present invention will be described below.
In the apparatus shown in FIG. 4, measurement was performed using a probe (ultrasonic receiving unit 14) in which ultrasonic elements 15 having a width of 0.55 mm were arranged at an element distance ΔX having a pitch of 0.6 mm. The width of the ultrasonic element 15 is smaller than the wavelength of the flaw detection frequency of 5 MHz used, and the directivity is dull. Even if the ultrasonic element 15 is arranged in parallel to the test piece, the lateral of the surface wave and the longitudinal wave component is obtained. Waves can be transmitted and received (transmitted and received).
この実施例では、超音波素子１５と同一形状の超音波素子を送信用に用いた。また、板厚５０ｍｍの軟鋼製試験片の表面１に、送信用の超音波素子から３．６ｍｍ離れた位置に１番目の超音波素子１５を配置し、０．６ｍｍ間隔で合計２６個の超音波素子１５を配置して計測した。 In this embodiment, an ultrasonic element having the same shape as the ultrasonic element 15 is used for transmission. Further, the first ultrasonic element 15 is arranged at a position 3.6 mm away from the transmitting ultrasonic element on the surface 1 of the test piece made of mild steel having a thickness of 50 mm, and a total of 26 ultrasonic elements are arranged at intervals of 0.6 mm. The sound wave element 15 was arranged and measured.
図８は、各超音波素子１５で受信した波形を示す図である。この図において、横軸は超音波伝播時間（μｓｅｃ）であり、縦軸は２６個の超音波素子１５の波形を送信用素子に近い順に上から分離して示している。
この図から、表面波７の伝播によるエコー群に加えて、縦波成分のラテラル波８の伝播によるエコー群が観察されていることがわかる。なお、ここでのサンプリングピッチは１００ＭＨｚとしたが、更に高いサンプリングピッチを用いることでデータの読み取り精度を改善できる。
FIG. 8 is a diagram showing a waveform received by each ultrasonic element 15. In this figure, the horizontal axis represents the ultrasonic wave propagation time (μsec), and the vertical axis represents the waveforms of the 26 ultrasonic elements 15 separated from the top in the order of proximity to the transmitting elements.
From this figure, it can be seen that in addition to the echo group due to the propagation of the surface wave 7, an echo group due to the propagation of the lateral wave 8 of the longitudinal wave component is observed. Although the sampling pitch here is 100 MHz, the data reading accuracy can be improved by using a higher sampling pitch.
ほぼ中央にある超音波素子の受信波Ａを基準波形とし、表面波７及びラテラル波８のエコーの伝播時間差を求めた。このとき波形相関を用いた。
用いた波形相関は、基準の波形をｆ０（ｔ）とし、伝播時間差Δｔを求める波形のｆ（ｔ＋Δｔ）を掛け合わせて関数ｆ（Δｔ）を求め、これが最大値を示すときのΔｔを求めるものである。
この実施例では、掛け合わせる時間範囲を０．４μｓｅｃの範囲とし、図８の基準波形Ａに対象とした時間範囲を両矢印で示した。
Using the received wave A of the ultrasonic element at approximately the center as a reference waveform, the propagation time difference between echoes of the surface wave 7 and the lateral wave 8 was obtained. At this time, waveform correlation was used.
The waveform correlation used is that the reference waveform is f 0 (t), and the function f (Δt) is obtained by multiplying f (t + Δt) of the waveform for obtaining the propagation time difference Δt, and Δt when this shows the maximum value is obtained. Is.
In this embodiment, the time range to be multiplied is set to a range of 0.4 μsec, and the time range targeted for the reference waveform A in FIG. 8 is indicated by a double arrow.
図９は、図８の表面波７に対して求めた関数ｆ（Δｔ）を示す図である。この図において、横軸は伝播時間差Δｔ（μｓｅｃ）、縦軸は関数ｆ（Δｔ）である。また、図中の各曲線は、２６個の超音波素子１５の波形に対する関数ｆ（Δｔ）を送信用素子に近い順で左から示している。
各曲線において、最大値を示すときのΔｔが基準波形Ａとの伝播時間差に相当する。
FIG. 9 is a diagram showing a function f (Δt) obtained for the surface wave 7 of FIG. In this figure, the horizontal axis represents the propagation time difference Δt (μsec), and the vertical axis represents the function f (Δt). Each curve in the figure shows the function f (Δt) with respect to the waveforms of the 26 ultrasonic elements 15 from the left in the order closer to the transmitting element.
In each curve, Δt corresponding to the maximum value corresponds to the propagation time difference from the reference waveform A.
図１０は、図９から求めた伝播時間差Δｔと伝播距離Ｘの関係図である。
相関係数は、表面波に対してｒ２＝１．００００で、ラテラル波に対してｒ２＝０．９９９９であり、いずれも極めて精度よく測定ができているのがわかる。この直線の勾配より音速を求めると、表面波で３０３５ｍ／ｓｅｃ、ラテラル波で５８０８ｍ／ｓｅｃが得られている。
FIG. 10 is a relationship diagram of the propagation time difference Δt and the propagation distance X obtained from FIG.
Correlation coefficient, with r 2 = 1.0000 with respect to the surface wave is r 2 = 0.9999 against lateral wave, either it can be seen that are made very accurate measurement. When the sound speed is obtained from the gradient of this straight line, 3035 m / sec is obtained for the surface wave and 5808 m / sec is obtained for the lateral wave.
上述したように、本発明は、従来の測定法の課題を克服して、精度よく表面を伝播する超音波の音速ｖを測定するものである。
本発明では、微小に分割した超音波素子１５を等間隔に並べて表面１を伝播する超音波５を受信する。次いで、各超音波素子１５での超音波５の受信時間差Δｔを、超音波５の波形相関を用いることで正確に求める。得られた伝播時間差Δｔと素子間距離ΔＸとの相関を求めて、この相関曲線より音速ｖを正確に測定する。
As described above, the present invention overcomes the problems of the conventional measurement method and measures the sound velocity v of the ultrasonic wave propagating on the surface with high accuracy.
In the present invention, the ultrasonic waves 15 propagating through the surface 1 are received by arranging the ultrasonic elements 15 that are finely divided at equal intervals. Next, the reception time difference Δt of the ultrasonic wave 5 at each ultrasonic element 15 is accurately obtained by using the waveform correlation of the ultrasonic wave 5. The correlation between the obtained propagation time difference Δt and the inter-element distance ΔX is obtained, and the sound velocity v is accurately measured from this correlation curve.
本発明の計測方法では、超音波５の受信条件は全ての超音波素子１５間で同一であり、各超音波素子１５で受信する超音波５の伝播時間差Δｔは、唯一素子間の距離ΔＸに依存する。また、受信した波形６の重ね合わせによる相関処理を行うので、超音波５の立ち上がり時間を測定することなく伝播時間差Δｔを正確に求めることができ、ノイズの発生に対しても正確に伝播時間差Δｔを測定することができる。 In the measurement method of the present invention, the reception condition of the ultrasonic wave 5 is the same among all the ultrasonic elements 15, and the propagation time difference Δt of the ultrasonic wave 5 received by each ultrasonic element 15 is only the distance ΔX between the elements. Dependent. Further, since the correlation process is performed by superimposing the received waveform 6, the propagation time difference Δt can be accurately obtained without measuring the rise time of the ultrasonic wave 5, and the propagation time difference Δt can be accurately detected even when noise is generated. Can be measured.
なお、超音波５が伝播する過程で、より高い周波数成分の方が減衰が大きく、超音波の周波数成分に変化が生じる。この場合には、受信波形のウェーブレット変換を行い、同一周波数の波形を抽出して波形相関をすることで、正確な伝播時間差を求めることができる。 In the process of propagation of the ultrasonic wave 5, the higher frequency component is more attenuated and changes in the ultrasonic frequency component. In this case, an accurate propagation time difference can be obtained by performing wavelet transform of the received waveform, extracting a waveform of the same frequency, and performing waveform correlation.
なお、本発明は、上述した実施形態に限定されず、本発明の要旨を逸脱しない範囲で種々に変更することができることは勿論である。
例えば、ここでは同一の間隔に配置された素子での伝播時間差より音速を求める方法について述べたが、素子間の距離を予め正確に測定してあれば、同一の間隔でなくても素子間距離と超音波の伝播時間差より同様に音速を正確に求めることができる。
また、各素子間での送受信時のエコー高さと超音波の伝播距離の関係より、音速と同時に超音波の減衰率を求めることもできる。
In addition, this invention is not limited to embodiment mentioned above, Of course, it can change variously in the range which does not deviate from the summary of this invention.
For example, the method for obtaining the sound speed from the propagation time difference between the elements arranged at the same interval has been described here. However, if the distance between the elements is accurately measured in advance, the distance between the elements is not necessarily the same interval. Similarly, the speed of sound can be accurately obtained from the difference in propagation time between the ultrasonic wave and the ultrasonic wave.
Also, the ultrasonic attenuation rate can be obtained simultaneously with the sound velocity from the relationship between the echo height during transmission / reception between the elements and the propagation distance of the ultrasonic wave.
１ 表面、２ 表面波用探触子、３ 振動子、４ くさび形部材、
５ 超音波、６ 波形、７ 表面波、８ ラテラル波、
１０ 音速測定装置、１２ 超音波送信部、
１４ 超音波受信部、１５ 超音波素子、１６ 超音波演算部
1 surface, 2 surface wave probe, 3 transducers, 4 wedge-shaped member,
5 ultrasonic waves, 6 waveforms, 7 surface waves, 8 lateral waves,
10 sound velocity measuring device, 12 ultrasonic transmitter,
14 Ultrasonic receiver, 15 Ultrasonic element, 16 Ultrasonic calculator
Claims (4)
超音波受信部で検出した超音波波形から超音波の音速を算出する超音波演算部とを備え、
前記超音波送信部又は超音波受信部は、対象物の表面に沿って正確に測定された間隔で配置された複数の超音波素子からなり、
各超音波素子により超音波を送信又は受信し、超音波受信部で受信した超音波波形の伝播時間差を波形相関により求め、これから音速を測定する、ことを特徴とする表面を伝播する超音波の音速測定装置。 An ultrasonic transmitter and an ultrasonic receiver disposed along the surface of the object;
An ultrasonic calculation unit that calculates the sound velocity of the ultrasonic wave from the ultrasonic waveform detected by the ultrasonic receiving unit,
The ultrasonic transmission unit or the ultrasonic reception unit is composed of a plurality of ultrasonic elements arranged at intervals accurately measured along the surface of the object,
Transmitting or receiving ultrasonic waves by each ultrasonic element, obtaining a propagation time difference of ultrasonic waveforms received by the ultrasonic receiving unit by waveform correlation, and measuring the speed of sound from this, and measuring ultrasonic velocity propagating on the surface Sound velocity measuring device.
超音波受信部で検出した超音波波形から超音波の音速を算出する超音波演算部とを備え、
前記超音波送信部又は超音波受信部は、対象物の表面に沿って正確に測定された間隔で配置された複数の超音波素子からなり、
各超音波素子により超音波を送信又は受信し、超音波受信部で受信した超音波波形の伝播時間差を波形相関により求め、これから音速を測定する、ことを特徴とする表面を伝播する超音波の音速測定方法。 An ultrasonic transmitter and an ultrasonic receiver disposed along the surface of the object;
An ultrasonic calculation unit that calculates the sound velocity of the ultrasonic wave from the ultrasonic waveform detected by the ultrasonic receiving unit,
The ultrasonic transmission unit or the ultrasonic reception unit is composed of a plurality of ultrasonic elements arranged at intervals accurately measured along the surface of the object,
Transmitting or receiving ultrasonic waves by each ultrasonic element, obtaining a propagation time difference of ultrasonic waveforms received by the ultrasonic receiving unit by waveform correlation, and measuring the speed of sound from this, and measuring ultrasonic velocity propagating on the surface Sound speed measurement method.
The sound speed measurement method according to claim 2, wherein waveforms at a plurality of different frequencies are extracted from the ultrasonic waveform by wavelet analysis, sound speeds at the respective frequencies are obtained, and frequency dependence of the sound speed is obtained.
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