JPH07260651A - Cracking developing rate measuring apparatus for film - Google Patents

Abstract

PURPOSE:To provide an apparatus for measuring the cracking developing rate of a thin film accurately and automatically through a simple structure. CONSTITUTION:A first AE sensor 1 is disposed obliquely forward of a fixed point F in the spreading direction of a crack 5 made in a thin film 4. A second AE sensor 2 is disposed obliquely rearward of the fixed point F in the spreading direction of crack. Electric signals from the first and second AE sensors 1, 2 are fed to a signal operating section 3 where high and low frequencies f1, f2 are determined by a frequency analyzer 11 and crack spreading rate Vc is operated automatically by an operating unit 12 according to a specific theoretical formula.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a measuring device for evaluating a thin film, and more particularly to a film cracking speed measuring device for evaluating the strength of a thin film by obtaining a speed of film cracking.

[0002]

2. Description of the Related Art There are various parameters for evaluating the strength of a thin film. As one of the parameters, for example, a method of pulling a thin film to generate a crack and evaluating the hardness and strength of the thin film from the progress speed of the crack can be considered. However, in the prior art, there was no measuring device having a simple structure suitable for measuring the film crack velocity.

[0003]

When the strength of the thin film is high, when the thin film is pulled, a crack is generated with an acoustic wave (AE wave), and the progress speed of the crack is relatively high. On the other hand, when a thin film having low strength is pulled by the same force, it is observed that the crack also progresses at a relatively slow speed with the AE wave.
When the sound generation point is the fixed point F, a sound higher than the actual sound at the fixed point F is observed at a position in front of the fixed point F. On the contrary, at a position behind the fixed point F, a sound lower than the actual sound at the fixed point F is observed. This phenomenon is a known fact as the Doppler shift phenomenon.

The present invention utilizes Doppler shift to simultaneously measure the sound emitted from a fixed point F with a pair of AE sensors to accurately and automatically measure the speed of progress of a film crack trying to pass through the fixed point F. An object of the present invention is to provide a film crack velocity measuring device that enables strength evaluation of a thin film.

[0005]

In order to achieve the above-mentioned object, the present invention comprises a pair of AE sensors and a signal calculator, and a film crack passing through a given fixed point along a predetermined traveling direction. Of the AE of one of the
The sensor directs the fixed point obliquely forward along the traveling direction, detects an AE wave generated with a positive Doppler shift when the film crack passes through the fixed point, and outputs a first electric signal. The other AE sensor points the fixed point from obliquely rearward along the traveling direction and detects the AE wave generated with a negative Doppler shift when the film crack passes through the fixed point. Of the film, the signal calculator processes the first and second electric signals, and calculates the progress speed of the film crack based on the frequency change corresponding to the positive and negative Doppler shifts. It constitutes a crack velocity measuring device.

[0006]

[Function] A pair of AEs are provided in front of and behind the crack in the traveling direction.
A sensor is provided, the sound at the fixed point F is simultaneously measured by the AE sensor, and the frequency-intensity distribution is obtained. A pair of A
When the AE waves measured by the E sensor are emitted from the same sound source, the AE sensor in the front in the traveling direction of the crack receives a higher frequency sound due to the Doppler shift than the AE sensor in the rear. By calculating the frequency change in the pair of AE sensors, the progress rate of the film crack can be calculated by a theoretical formula. The measuring device of the present invention is a relatively simple device in which a pair of AE sensors are arranged.
It can be carried out easily, and the progress rate of the film crack can be accurately obtained.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the overall structure of this embodiment, FIG. 2 is a spectrum diagram showing the frequency-intensity distribution by a pair of AE sensors, and FIG. 3 is an explanatory plan view for explaining the crack generation state of the thin film in this embodiment. Is.

As shown in FIG. 1, the film crack velocity measuring apparatus of this embodiment is roughly divided into a pair of AE sensors and a signal calculating section 3. The AE sensors are a first AE sensor 1 and a second AE sensor 2. As shown in FIG. 3, the thin film 4 is pulled up and down by the pulling force P to generate a crack 5. The crack 5 progresses along a fixed direction, but a fixed point F on the way is taken into consideration. The first AE sensor 1 is arranged along the traveling direction of the crack 5 with the fixed point F oriented obliquely from the front. Further, the second AE sensor 2 is arranged along the traveling direction of the crack 5 with the fixed point F oriented obliquely from the rear. First and second AE
The structures of the sensors 1 and 2 are not particularly limited, but a structure for directing the fixed point F is required, and therefore an ultrasonic microscope concave spherical lens having the shape shown in the drawing is adopted in this embodiment. The first and second AE sensors 1 and 2 are composed of glass-like delay materials 6 and 6 and transducers 7 and 7 fixed to them.
And concave spherical surfaces 8 are formed on the lower surfaces of the delay members 6 and 6. As shown in the figure, the AE signal from the fixed point F enters the delay members 6 and 6 as a divergent spherical wave, and the transducer 7 and
Received at 7. As shown in FIG. 1, the first AE sensor 1 is disposed obliquely in front of the thin film 4, and its axis is inclined with respect to the surface of the thin film 4 by an angle θ ₁ . In addition, the second AE sensor 2
Is arranged obliquely behind the thin film 4, and its axis is inclined with respect to the surface of the thin film 4 by an angle θ ₂ . In the case of the first and second AE sensors 1 and 2, water 9 is used as a transmission medium (coupler).

On the other hand, the signal calculation unit 3 processes a first electric signal and a second electric signal input from the first and second AE sensors 1 and 2 through the preamplifiers 10 and 10, respectively. 11 (or the difference detector 11), and an arithmetic unit 12 and the like for obtaining the progress velocity Vc of the film crack from the frequencies f ₁ and f ₂ obtained by the device 11.

When a crack 5 is generated in the thin film 4, the crack 5 propagates along a certain direction as shown in FIG. 3, and the first and second AE sensors 1 and 2 have the frequency-intensity distribution shown in FIG. A
The E waveform is measured. That is, as shown in FIG. 2, the AE waveform measured by the first AE sensor 1 and the volume waveform measured by the second AE sensor 2 have the same shape,
Maximum peak frequency f ₁ and f ₂ which acoustic intensity occurs of different and the frequency f ₁ of the first AE sensor 1 due to the Doppler shift is higher than the frequency f ₂ of the second AE sensor 2. The detection results obtained by the first and second AE sensors 1 and 2 are the preamplifiers 10 and 1 as the first and second electric signals.
It is input to the signal calculation unit 3 via 0.

Next, the contents of the frequency analysis and the calculation of the traveling speed Vc in the signal calculation unit 3 will be described. The crack progress velocity Vc is theoretically obtained by the following equation based on the Doppler shift effect. Vc = Vw · {(1-f ₁ / f ₂ ) / cos θ ₁ + (f ₁ /
f ₂ ) cos θ ₂ } Here, Vc: moving speed of film crack Vw: sound velocity of water (constant) f ₁ / f ₂ : ratio of frequencies at peak intensity by the first and second AE sensors θ ₁ , θ ₂ : Inclination angle of the first and second AE sensors With the above, the crack sound at the moment of passing the fixed point F is measured, the peak frequencies f ₁ and f ₂ are obtained from the frequency-intensity distribution, and the arithmetic unit 12 is calculated by the theoretical formula. The traveling speed Vc is obtained by performing a predetermined calculation.

In the above description, the first and second A
An ultrasonic microscope concave spherical lens is adopted as the E sensors 1 and 2, but the present invention is not limited to the above as long as it has the property of directing to the fixed point F of the sound generation point.

[0013]

According to the present invention, the following remarkable effects are obtained. 1) Since the AE sensors are arranged before and after the fixed point F and the structure for measuring the crack sound using the Doppler shift is adopted, the peak frequencies f ₁ and f ₂ can be clearly obtained. As a result, the speed Vc of progress of the film crack can be accurately obtained. 2) Since the first and second electric signals are input to the signal calculation unit and the crack progress speed is automatically calculated by the calculation device based on the theoretical formula, an accurate progress speed can be obtained regardless of the shape and material of the thin film. It can be calculated automatically and instantaneously. As a result, various thin film strength evaluations are performed. 3) A relatively simple structure in which a pair of AE sensors having directivity with respect to the fixed point F are arranged in front of and behind the fixed point F can be implemented easily and inexpensively. 4) The crack progress rate is a new and useful parameter for the strength evaluation of thin films.

[Brief description of drawings]

FIG. 1 is a block diagram showing the overall structure of an embodiment of the present invention.

FIG. 2 is a diagram of frequency-intensity distribution of sound waves measured by the AE sensor of this embodiment.

FIG. 3 is a plan view showing a crack progressing state of the thin film of this example.

[Explanation of symbols]

 1 1st AE sensor 2 2nd AE sensor 3 Signal calculation part 4 Thin film 5 Crack 6 Delay material 7 Transducer 8 Concave spherical surface 9 Water 10 Preamplifier 11 Frequency analysis device 12 Calculation device

Claims (1)

[Claims] 1. An apparatus comprising a pair of AE sensors and a signal calculator, for measuring a moving speed of a film crack passing through a given fixed point along a predetermined moving direction, wherein one AE is used.
The sensor directs the fixed point obliquely forward along the traveling direction, detects an AE wave generated with a positive Doppler shift when the film crack passes through the fixed point, and outputs a first electric signal. The other AE sensor points the fixed point from obliquely rearward along the traveling direction and detects the AE wave generated with a negative Doppler shift when the film crack passes through the fixed point. The signal calculator processes the first and second electric signals, and calculates the progress speed of the film crack based on the frequency change corresponding to the positive and negative Doppler shifts. A film crack velocity measuring device characterized by.