JPS58184507A - Device for measuring thickness of surface layer - Google Patents

Abstract

PURPOSE:To make it possible to measure a thickness which is shorter than the wavelength of an operating ultrasonic wave, by inputting the ultrasonic wave into a thin surface layer through a shoe, converting the wave into a surface wave (rubbing wave), performing computation based on an ultrasonic wave propagation speed and an incident angle. CONSTITUTION:The transmission and reception of ultrasonic waves are performed by a probe 8, herein a transmitting part and a receiving part are separated, by using a semicircular shoe 7. A critical incident angle thetain, at which the incident ultrasonic wave is converted into a rubbing wave, is obtained by Snell's law. By measuring the critical incident angle, the propagating speed of the rubbing wave is obtained by using a continuous wave. Then, a thickness t1 of the surface layer to be measured is further obtained.

Description

[Detailed description of the invention] The present invention relates to a thickness measurement method using ultra-f modification,
It is sometimes suitable for measuring the thickness of a zirconium layer in a fuel receiving tube.

Conventional ultrasonic surface layer thickness measurement methods include a reflection method and a resonance method. (Ultrasonic Technology Handbook) However, these methods require a reflective surface and are limited by the distance resolution of ultrasonic waves. The drawback was that it could not be used to measure the thickness of orders.

The purpose of the present invention is to develop a new method that eliminates the need for an ultrasonic reflecting surface in the conventional method of measuring surface layer thickness using ultrasonic waves, and which solves the drawback that measurement becomes difficult as the surface layer to be measured becomes thinner. An object of the present invention is to provide a surface layer thickness measuring device.

The principle of the present invention will be explained using figures. In the layered structure shown in FIG.
cm), and if the modification λ of the surface wave (-)p wave), the thickness tl of one surface layer, and the thickness i of the lower layer satisfy the conditions t, 4λ × t, then the thickness 1, It is known that the following relationship holds true between the propagation encounter of a surface wave propagating through the surface layer l and [C].

However, in equation (1), f is the frequency of the incident MAt wave,
μm and μm are the rigidity modulus of the material of the surface layer 1 and the lower layer 2, respectively.

For convenience, the thickness tl of the surface layer can be determined by measuring the propagation velocity C of the Love waves. However, Equation (1) (II'i) is for a continuous wave with a constant wave number, which is 69, and is not suitable for measuring the propagation velocity using a pulse wave that has many frequency components.

Therefore, as a method of measuring the propagation velocity using continuous waves, as shown in Fig. 1, ultra-f waves are transmitted and received by a transceiver split type probe 8 using a semicircular shoe 7, and the incident ultrasonic wave is converted into a love wave. Critical incidence to be transformed 01. Adopt a method to find out.

It is known that the following equation holds true according to Snell's law.

Friends, C? is determined by the inside of the shoe and the ultrasonic propagation speed. Therefore, by measuring this critical angle of incidence, the propagation speed of the Love wave [C using a continuous wave can be calculated as (from equation 4, puddle, and (
The surface layer thickness 1 of the object to be measured is determined by the formula 1).

In order to measure the critical incidence angle θ1, a shoe 7 and a transmitter/receiver type III probe 8 are used as shown in FIG. The incident wave and the reflected wave are displayed on the CRT with the incident angle of the ultrasonic wave being 11 and the critical incident angle being 81.

In the case of #(#, , the incident ultrasonic wave is reflected at the 0 point of the surface 3, the P point of the shoe 7, and then again at the 0 point and returns to the probe 8, so the incident wave and the reflected wave are A phase delay occurs.Next, when the condition of 9, θ; #龜, where - is large is satisfied, the ultrasonic wave is converted into a Love wave, and a part of it is reflected at the Q point of shoe 7 and returns. However, the position between the incident wave and the reflected wave is θ
It can be seen that the width is larger than that of #-1, and the width of the pregnancy is also smaller. θ, >6. In this case, since the ultrasonic waves travel in eight directions within the surface layer 1, almost no reflected waves return. The CRT display of the incident wave 9 reflected waves in the above three cases is shown in (il), OH) in Fig. 2.

Therefore, by scanning the outer edge of the probe 8t and the shoe 7, the critical angle '1m for conversion into a Love wave can be found.

Hereinafter, one embodiment of the present invention will be described using FIG. 3.

In this embodiment, the above-described surface layer thickness measurement method is applied to the temporary fuel stack tube 22.
This was difficult for the measurement of the zirconium inner layer 21.

Ultrasonic waves are transmitted from the transmitting/receiving split type probe 8 to the zirconium inner layer 21 via the shoe 7t by nine continuous frequencies generated by the ultrasonic transmitter gN device 32. The probe 8 scans the outer edge of the shoe 7 with the probe scanning device 18 which is capped by the probe control device 33. The shoe 7 is fixed to the scanning device by the guide 11. Next, the received ultrasonic waves by the probe 8 are transmitted by the ultrasonic transmitter 32 and the CI
The signal is sent to the LT display device [31 and becomes a signal for measuring the critical angle of incidence for Love rIIL conversion. The incident angle data 0 when the Nyoshirabu wave change is observed on the CRT display I&d31 is sent from the probe control device i33 to the arithmetic device 35.

Further, frequency data f is transmitted from the ultrasonic transmitter 32 to ultrasonic propagation velocities C, , C, in Zircaloy and zirconicum.
The data of ν, the rigidity μm, μ, and the sound velocity data C7 at the shoe 7 are sent from the input device 34 to the calculation f7c Kasumi 35. The arithmetic unit 35 calculates the above critical incident angle #11, sound velocity C1 in the shoe, frequency f1 of the incident ultrasonic wave, Zircaloy,
Data of sound velocity and rigidity in zirconium 9m C,,C,
, μm.

Based on μmt, calculations are performed using Equation 1) and Equation (1), and the obtained zirconium inner layer thickness t is displayed on the display device 36. FIG. 4 shows the calculation contents of the calculation device 35.

According to the above embodiment, the thickness (~70 μm) of the zirconium inner layer of the fuel storage tube can be easily measured, which has been difficult to measure using conventional ultrasonic measurement methods.

When measuring the surface layer using conventional ultrasound, it is impossible to measure when the thickness of the surface layer to be measured is less than the thickness of the ultrasound wave used. However, according to the present invention, it is possible to measure the thickness of the ultrasonic wave and the thickness of the ultrasonic wave, thereby greatly improving the quality control of products where surface layer thickness control is important.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the shoe and the transmitting/receiving split type probe arranged on the surface of the layered structure material, and Figure t42 is a diagram showing the direction of propagation of the ultrasonic wave when the incident angle of the ultrasonic wave is changed, as well as the incident wave. Figure #g3 is a diagram showing the overall configuration of the FC implementation applied to the thickness measurement of the zirconium inner layer of a full fuel cladding tube according to the present invention, and Figure 4 is a flowchart of calculations in the arithmetic unit. It is. 1...Surface layer, 2...Lower layer, 6...Love wave, 7
...Shoe that touches the circular outer edge, 8.Transmission/reception part wJI type probe, 12..Probe travel f, f device, 31..C
RT display device, 32...Ultrasonic transmission g! Vessel, 33...
Probe control device, 34... Input device, 35... Arithmetic device, 36... Display W & position. Kaya hard

Claims (1)

[Claims] 1. In a layered structure consisting of a lower layer and a thin surface layer composed of two materials having different ultrasonic propagation velocities t-M, the step of measuring the ultrasonic velocity in each substance and storing the value; An ultrasonic wave is made incident on a thin one-sided layer through a shoe and converted into a surface wave (two-wave wave), and the step of measuring and storing the incident angle and the propagation velocity within the shoe;
A surface layer thickness measuring device comprising the step of performing a calculation using the ultrasonic propagation velocity and incident angle stored in the step and displaying the thickness of the surface layer.