JPS58160865A - Method and device for measuring ultrasonic wave attenuation in material - Google Patents

Abstract

PURPOSE:To measure the real extent of attenuation of an ultrasonic wave by combining multiple information extracted from analysis in frequency of an ultrasonic wave output signal, and applying resulted information with arithmetic processing. CONSTITUTION:An ultrasonic wave generated by an ultrasonic wave transmitter and receiver 3 using laser light include a wide range spectrum up to tens MHz and is transmitted to intrude into a material. Then, a detected ultrasonic wave pulse echo signal while drawn on an oscilloscope 8 through an amplifier 4 is digitized by a high-speed wave memory 5 and read. On the basis of this read data, a computer 6 calculates the thickness of the material from a preset velocity of the ultrasonic wave and time intervals of the pulse train. Further, the high-speed Fourier transform of each pulse echo waveform is carried out to calculate the attenuation of each ultrasonic wave of preset frequencies f1-f3. Then, information variables increased by the frequency analysis are used in combination to find the real attenuation accompanying the propagation of the ultrasonic wave, reflection loss, and diffraction loss repsectively and separately, and reliable information for estimating the crystal particle size of the material and other various constants of the physical properties are obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention transmits and receives ultrasonic pulses, performs frequency analysis of the output, and converts the output into multiple information.

The present invention relates to a method and apparatus for measuring true ultrasonic attenuation due to propagation.

The ultrasonic attenuation characteristics in a material are closely linked to the physical or material properties of that material, and by knowing the true attenuation of ultrasonic waves transmitted through the material, it is possible to It becomes possible to measure crystal grain size, etc.
Due to its extremely important industrial importance, many researchers have recently attempted to measure it.

However, in most measurements, the reflection loss and diffraction loss of ultrasonic pulses are measured without separating them, and there is also a lack of consideration of the surface properties of the reflecting surface, which greatly affect ultrasonic attenuation. Furthermore, the amount of ultrasonic attenuation changes depending on its frequency, but the frequency of the ultrasonic pulse sent out by the ultrasonic probe includes sideband components at the resonant frequency of the probe. Measuring the attenuation characteristics of an ideal single-frequency ultrasound wave has been difficult.

FIG. 1 is an explanatory diagram of a conventional ultrasonic attenuation characteristic measuring device and a graph showing the measurement results.

As shown in Figure (b), the ultrasonic pulse-echo train exhibits exponential attenuation with respect to the propagation distance It simply shows a damping characteristic that is a mixture of all of the factors.

By the way, electromagnetic ultrasound technology, technology using laser light, etc.
A method for transmitting and receiving ultrasonic waves without contact has been proposed.
Although this eliminates the need to consider the acoustic impedance mismatch at the ultrasound transmitting and receiving points, the above-mentioned problem still exists as long as only the peak value attenuation of the pulse echo train is measured.

The present invention aims to solve the above-mentioned problems and to measure the true amount of ultrasonic attenuation by combining and processing multiplexed information extracted by frequency analysis of an ultrasonic output signal.

In other words, the present invention detects ultrasonic echoes obtained by sending ultrasonic waves into a material, performs frequency analysis on the detected echoes, and extracts multiple frequency information in the frequency domain to determine whether the ultrasonic waves are A material in which the true attenuation of ultrasonic waves in the material is output by calculating the attenuation other than the true attenuation due to reflection loss, diffraction loss, etc. when propagating through the material. The method for measuring ultrasonic attenuation is the first invention. Further, an ultrasonic transmitter/receiver device transmits ultrasonic waves into the material and detects one reflected echo, a frequency analyzer frequency-analyzes the output signal from the ultrasonic transmitter-receiver device, and a frequency analyzer output from the frequency analyzer. Based on multi-frequency information in the frequency domain, calculate the amount of attenuation other than the true attenuation due to reflection loss, diffraction loss, etc. when ultrasonic waves propagate through the material. A second invention provides an apparatus for measuring ultrasonic attenuation in a material, characterized in that it is provided with an arithmetic device that outputs the true attenuation amount of ultrasonic waves in a material.

The details of the present invention will be explained below.

What is the attenuation of ultrasonic waves that undergo multiple reflections between interfaces?

It is classified into reflection loss at the interface, diffraction loss, and attenuation due to propagation. Therefore, if the attenuation constant when transmitting and receiving ultrasonic pulses is α(f)CdB), then 1,
This is given by equation (1).

α(f)=αrtf)/2d+αa(f) ten αt(f)
...(1) Here, αr(f)(ds)
, αa (f) (d B/cm ), αt
(f) (d\"cm"J represents the sum of reflection loss, diffraction loss and true page reduction constant at the upper and lower boundary surfaces of ultrasonic waves, respectively, and is a function of frequency f. Also, dCCrn]
represents the thickness of the ultrasonic propagation material in the propagation direction. The present inventors conducted an experiment to measure reflection loss and diffraction loss and obtained the following findings. Reflection loss αr (
f) varies depending on the surface properties of the ultrasonic reflecting surface, but in general, the frequency f and the reflection loss αr (dB) are:

There is a linear relationship on the logarithmic axis, and it is expressed by equation (2).

αr(f) −to −fq ・・
(2) Here, is a constant that changes depending on the surface properties, and q is approximately 0.5. Next, the diffraction loss αa (f) hardly depends on the material of the ultrasonic propagation material, and as in the case of reflection loss, there is a difference between one frequency f and the diffraction loss αa (dB/cm) on the logarithmic axis. A linear relationship holds true and is given by equation (3).

αa(f)=r-f” ------
−−・−(3) Here, r and e are constants, and θ is approximately −
It is l.

Next, the true attenuation constant αt['dB/6++''J of ultrasonic waves is the average crystal grain size of the ultrasonic propagation material.If the wavelength of ultrasonic waves is λ, then the following is generally given for the frequency f: will be given to you.

Here, tI*t2 is a constant determined by the crystal grain size.

Based on the above results, the reduction constant α(f) is given (the equation 1 can be rewritten as equation (5)).

α(f) = kf'/2d +rf' +tfu(q
:: 0.5. s::-1, u:; 2or 4
) ...<5) In equation (5), the unknown quantity is r
, t, and d, where d is obtained by multiplying the time interval of the measured pulse-echo train by the ultrasound propagation speed.

Next, the pulse echo train PI+P2 shown in FIG. 2(a)
1... is frequency analyzed l, and among the results obtained as shown in the same figure (b), an appropriate frequency fl * f2 + f3
We will focus on As shown in the same figure (C), p, r, and t are the attenuation constant α(fi) for each frequency.
(i = 1.2.3) and by solving the three-dimensional simultaneous equations obtained from equation (5), it is given as equation (6).

By performing multiplex information quantification using single frequency analysis using the above method, it becomes possible to separate the ultrasonic attenuation into reflection loss, diffraction loss, and true propagation attenuation.

Next, an example of implementing the above method of the present invention will be described. FIG. 3 is a block diagram showing one embodiment of the present invention.

The ultrasonic transmitting/receiving device 3 in FIG.
This is an ultrasonic wave transmitting/receiving device using a laser beam as shown in No. 188987. The reason for using a laser beam is that in addition to the advantage of being non-contact, the ultrasonic waves generated by the Q-switched pulsed laser beam include a broadband spectrum up to several tens of MHz.

The ultrasonic noknosis echo signal generated and detected by this is amplified by the amplifier 4 and then drawn on the oscilloscope 8, and at the same time, the high-speed wave memory 5
It is then digitized and read in.

Based on this read data, the calculator 6 calculates the thickness d from the preset ultrasonic sound velocity and the time interval of the pulse train.
Calculate. moreover.

A fast Fourier transform is applied to each pulse echo waveform, and each ultrasonic attenuation amount α(f) defined by Equation 1 (1) is calculated for a preset frequency fIIf21f.

Thereafter, calculations of r and t are performed on the unknown numbers according to equation (6), and the results of each calculation are output to the display device 7.

As described above, according to the present invention, by combining the information increased by frequency analysis, the true attenuation, reflection loss, and diffraction loss accompanying the propagation of ultrasonic waves are separately determined. Is it possible to obtain reliable information for estimating various physical property constants such as the grain size of the material? It has the advantage of being able to provide

In addition, in the above embodiment, the ultrasonic transmitting and receiving device is
Although the device was shown in Japanese Patent Application No. 188987/1987,
Other types of devices using laser light may be used, or a device using a normal ultrasonic flaw detection device or an electromagnetic ultrasonic technique may be used.

Furthermore, a combination of these may be used.

Furthermore, in the above embodiment, the parameters r, θ, and U in equation (5) were treated as known values.

If we accept that the calculation time of the computer will be longer, more accurate measurements can be made by treating these as unknowns and increasing the frequencies used for calculation from 3 frequencies to 6 frequencies.

Also, in one embodiment.

During frequency analysis, the waveform was digitized using a high-speed wave memory and then subjected to fast Fourier transformation, but the analog waveform may also be directly frequency-analyzed using an analog spectrum analyzer.

[Brief explanation of the drawing]

FIG. 1(a) is an explanatory diagram of a conventional ultrasonic attenuation characteristic measuring device, FIG. 1(b) is a graph showing the measurement results, and FIG. 2 is an explanatory diagram of the implementation method of the present invention. (a) is a graph showing the measured pulse echo train, (b) is a graph showing the result of frequency analysis of the pulse echo train, and (C
) is an explanatory diagram of the method for determining the number of reduced settings from the result of (b), and FIG. 3 is a block diagram showing an embodiment of the present invention. 1... Ultrasonic propagation material 2... Ultrasonic probe 3.
・・Ultrasonic transmitting/receiving device 4・・Amplifier 5・・High speed wave memo 6・・Computer 7・・
・Display device 8... Oscilloscope Hayabusa/Diagram (b) Iyun 41 Toku G-11χ → GS expense 1 Rod 3 figure procedural amendment (voluntary) 1981 Part 49 Japanese Patent Office Commissioner Shima 1) Haruki 1. Indication of the incident Patent Application No. 42519 of 1982 2 Title of the invention Method and apparatus for measuring ultrasonic attenuation in materials 3
, person making the amendment or correction Relationship to the case Address of the patent applicant
2-6-3 Otemachi, Chiyoda-ku, Tokyo Name (6)
65) Nippon Steel Corporation Representative Takeshi 1)
Toyoichi 4th generation Osamu Address: 3-3-3-5 Nihonbashi, Chuo-ku, Tokyo Date of amendment order: Showa 1920 Month/Day (shipment date) 6 Number of inventions increased by amendment 8 Contents of amendment Amend the claims in a separate document. 2. "Diffraction" on page 2, lines 18, 4, lines 8 and 17, page 5, lines 4, 11 and 14, page 6, lines 1 and 3, page 8, line 2, page 9, line 11 are corrected to "diffraction". 3. On page 7, line 4, "Analysis 1" is corrected to "Analysis-". 4 Correct page 7, line 6 rPJ to rkJ. )! The scope of claims is amended as follows. l Ultrasonic echo obtained by rapidly injecting ultrasonic waves into the material (
The detected echoes are frequency-analyzed, and from the extracted multi-frequency information in the frequency domain, the amount of attenuation other than the true attenuation due to reflection loss, diffraction loss, etc. when the ultrasonic wave propagates through the material is determined. A method for measuring ultrasonic attenuation in a material, characterized by calculating the amount of attenuation and outputting the true amount of attenuation of ultrasonic waves in the material. 2. An ultrasonic transmitter/receiver that rapidly injects ultrasonic waves into a material and detects reflected echoes, a frequency analyzer that analyzes the frequency V of the output signal from the ultrasonic transmitter/receiver, and an output from the frequency analyzer. Based on multiple frequency information in the frequency domain, f-Reflection loss when ultrasonic waves propagate 1 A calculation device is provided which calculates the amount of attenuation other than the true attenuation due to mass sales loss, etc., and outputs the true amount of attenuation of the ultrasonic waves in the material. A method for measuring ultrasonic attenuation in a material, characterized by:

Claims (1)

[Claims] ■ Detecting ultrasonic echoes obtained by rapidly injecting ultrasonic waves into a material, frequency-analyzing the detected echoes, and extracting multiple pigeon wave number information in the extracted frequency domain. When a sound wave propagates through a material, the amount of attenuation other than the true attenuation sound due to reflection loss, diffraction loss, etc. of the ticket is calculated, and the true amount of attenuation of the ultrasonic wave in the material is output. Method for measuring ultrasonic attenuation in materials. 2. An ultrasonic transmitter/receiver that quickly injects ultrasonic waves into a material and detects one reflected echo; a frequency analyzer that frequency-analyzes the output signal from the ultrasonic transmitter/receiver; and a frequency analyzer output from the frequency analyzer. Based on the multi-frequency information in the frequency domain, the amount of attenuation other than the true attenuation due to reflection loss, diffraction loss, etc. when the ultrasonic wave propagates through the material is calculated, and the true attenuation of the ultrasonic wave in the material is calculated. 1. An apparatus for measuring ultrasonic attenuation in a material, comprising: an arithmetic device that outputs an amount of attenuation.