JP2002195987A - Measuring method and device for inner defect size - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a measuring method for inner defect size enabling measurement of a flaked defect size on an even flat plate or a laminated flat plate by using a flexuously-vibrating ultrasonic excited in a measuring body (RAM wave). SOLUTION: The characteristic of this measuring method is to excite a flexuously-vibrating ultrasonic (RAM wave) in a measuring body, measure the time difference of a repetitive wave caused by an inner defect extending in a flexuous vibration propagating direction parallel to the measuring body surface to measure the size of the inner defect on the measuring body using both the time difference and the flexuous vibration sound wave velocity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring the size of an internal defect which can measure the size of a peeled defect of a uniform flat plate or a laminated flat plate by using an ultrasonic wave (lamb wave) having a bending vibration excited in an object to be measured. A method and an apparatus therefor.

[0002]

2. Description of the Related Art In a material or the like having a laminated structure, the adhesion between layers is reduced due to heat or the like in a manufacturing process or the like, and internal defects such as peeling as shown in FIG. . Such internal defects are a serious problem concerning the reliability of the material, and it is important to detect such internal defects beforehand.

Conventionally, the following two methods are well known as methods for detecting such internal defects (peeling defects) in a material. In the first method, in FIG. 6, ultrasonic waves are vertically incident on the plate surface from the ultrasonic oscillator A, and the ultrasonic oscillation / receiver A is scanned over the whole plate D which is the object to be measured. Is received by the ultrasonic oscillation / receiver A, or the transmitted waveform is received by the receiver E on the opposite side to obtain an image of the peeling defect. In this method, not only the presence or absence of peeling but also the size information can be obtained, but it takes time to scan the whole. In the second method, in FIG. 6, an ultrasonic wave B is applied to a wedge W (the sound speed corresponds to the solid sound speed used; generally, acryl 2700 m / s to aluminum 6000 m / s) or water (1500 m / s) as a medium. By obliquely entering the object D to be measured, the sound speed is approximately 5000 m / s to 60
Exciting the vibration mode S propagating in the plate D at 00 m / s,
This is a method of detecting a defect in a propagation path. Scanning may be performed in only one direction. However, when this vibration mode is used, only the presence / absence of a peeling-like defect can be known, but defect size information cannot be obtained.

[0004]

The vibration mode when the ultrasonic wave is obliquely incident on the object to be measured (ultrasonic wave (lamb wave) that bends and vibrates) has a sound speed of about 5000 m / s to 6000 m / s.
(Academic S0 mode) and slow sound speed 500m / s ~
There are two types of 1500 m / s mode (A0 mode).
When the vibration mode having a low sound speed is used, repeated reflection occurs at the peeled portion, and the peel length can be measured. However, when wedges or water are used, this vibration mode cannot be excited. The reason is as follows. The angle of incidence obeys the following Snell's law (Fig. 2
reference). sin θ = cw / c, θ is the incident angle, c is the vibration speed in the vibration mode of the plate, and in the case of the vibration mode with a large sound speed (cw
= 5000 m / s to 6000 m / s), acrylic (cw
= 2700 m / s) or water (cw = 1500 m / s) has sufficient θ, but the vibration mode with low sound speed (cw = 50 m / s)
At 0 m / s to 1500 m / s), there is no incident angle. However, as shown in FIG. 2B, when a gas (for example, cw = 340 m / s in the case of air) is used as a medium, an incident angle of a vibration mode having a low sound velocity exists, and excitation is possible.

[0005] The present invention has been made based on the above findings, and the present invention uses a gas such as air instead of the water or wedge described above as a medium, propagates ultrasonic waves in the gas, and generates ultrasonic waves obliquely. A different vibration mode (mode with slow sound speed: bending-oscillating ultrasonic wave (Lamb wave)) that enters the plate and has no incident angle in the case of wedge or water propagates through the plate and separates The present invention provides a novel method and apparatus for measuring the size of a defect inside a flat plate, which causes repeated reflection at a portion and uses the time interval of the repetitive wave packet of the received waveform to measure a peeling defect in the plate. This aims to solve the above problem.

[0006]

For this reason, the technical solution adopted by the present invention is to excite an ultrasonic wave (lamb wave) which bends and vibrates in the object to be measured, and propagates the bending vibration in parallel with the surface of the object to be measured. A method for measuring the size of an internal defect, comprising measuring a time difference between repetitive waves caused by an internal defect extending in a direction, and measuring a size of the internal defect in the object to be measured from the time difference and a bending vibration propagation velocity. In addition, there is provided a method for measuring an internal defect size, wherein the object to be measured is a uniform flat plate or a laminated flat plate. Further, the apparatus includes a gas-propagating ultrasonic oscillator, a receiver, and a control device, and the gas-propagating ultrasonic oscillator is an ultrasonic oscillator that can excite an ultrasonic wave (lamb wave) that bends and vibrates in an object to be measured. An apparatus for measuring the size of an internal defect. Further, the ultrasonic wave generated from the ultrasonic wave propagating in the gas has a product fd of 0.1 MHz mm to 1.2 when the frequency is f and the plate thickness of the measured object is d.
The internal defect size measuring device according to claim 3, wherein the internal defect size is set between MHz mm.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method and an apparatus for measuring the size of an internal defect in a flat plate according to the present invention will be described below. FIG. 1 shows a schematic configuration of a defect measuring device according to the present invention, and FIG. FIG. 3 is an explanatory diagram of a repetitive wave, and FIG. 4 is a flowchart in the control device.

In FIG. 1, reference numeral 1 denotes a gas-propagating ultrasonic oscillator, 2 denotes a receiver, 3 denotes control means, 4 denotes a display means, 5 denotes an object to be measured, and 6 denotes an internal defect. 1 and each receiver 2 are connected to a device 3 as control means, and the device 3 is connected to a display means 4 as needed. It should be noted that, as necessary, a gas-propagating ultrasonic oscillator 1 having a receiving function may be used.

The ultrasonic transducer 1 in a gas is installed obliquely (at an incident angle θ) on the surface of a flat plate as an object to be measured, and the receiver 2 is placed at a position distant from the ultrasonic oscillator 1 in a gas in accordance with the incident angle. Install at the same reception angle θ. Ultrasonic oscillator for propagation in gas 1
The frequency of the generated ultrasonic wave is f and the thickness of the measured object is d.
When the product fd is 0.1 MHzmm to 1.2 MHzm
Set between m. As a result, two types of vibration modes, a high-speed vibration mode and a low-speed vibration mode, can be obtained as the vibration modes propagating in the body to be measured by the ultrasonic waves generated from the gas-propagating ultrasonic oscillator 1. Also, receiver 2
Although three are arranged in the drawing, the number can be increased or decreased as appropriate.

A method for measuring a defect (exfoliated portion) inside an object to be measured by using the above-described apparatus will be described with reference to FIG. In FIG. 2, first, ultrasonic waves are emitted obliquely from the gas-propagating ultrasonic oscillator 1 toward the object 5 to be measured.
A vibration mode having a low sound speed [A0 mode: an ultrasonic wave (lamb wave) that bends and vibrates] is excited in the inside. When the A0 mode vibration propagates through the object 5 to be measured, waves propagating at both ends of the peeled part defect 6 area are reflected as shown in FIG. 2, and a repetitive wave as shown in FIG. 3 is generated. The repetitive wave is received by the receiver, and the size of the defect area is measured based on the time interval t of the repetitive wave and the speed of the wave propagating in the body to be measured.
Display on display means.

A measurement flow performed in the control device will be described.
In step S1, an ultrasonic wave is oscillated from the gas-propagating ultrasonic oscillator 1. In step S2, the arrival time of the first repetition wave and the arrival time of the second repetition wave are measured by the receiver, and the time difference is calculated in step S3. Then, in step S4, step S3
Is multiplied by the propagation speed of the vibration mode from the time difference obtained in step S5 and the propagation speed of the object (material) taken in from step S6 to determine the size of the defect region, and the result is displayed in step S5 if necessary. I do. Note that the propagation speed of the measured object is specific to the material, and the speed is determined if the material is determined. That is, since the longitudinal wave velocity and the transverse wave velocity are basically measured as the material-specific values, it is possible to obtain the sound velocity in the S0 mode or the A0 mode by performing calculation by applying these values to a known theoretical formula. it can. In the above flowchart, step S3
The propagation speed is captured between step S4 and step S4. The propagation speed may be captured anywhere before step S4. For example, the propagation speed may be automatically captured from the map by specifying the material of the measured object at the start of the program. Is also possible.

Although the embodiment of the present invention has been described above, the means for installing the ultrasonic transducer in gas and the receiver on the object to be measured can be appropriately selected, and the control means can be a personal computer or a personal computer. Dedicated equipment can be used. Furthermore, the present invention may be embodied in any other form without departing from the spirit or main characteristics thereof, and thus the above embodiments are merely illustrative in all respects and should not be construed as limiting.

[0013]

As described in detail above, the present invention provides:
Using an ultrasonic oscillator that propagates ultrasonic waves in a gas, a vibration mode having a low sound speed is excited at an incident angle according to Snell's law, and a vibration mode having a low sound speed is propagated through the plate. Then, reflection is repeatedly caused at a peeled portion in the plate, and a peeling defect in the plate is measured by using a time interval of the repetitive wave packet. Therefore, according to the present invention, it is possible to efficiently measure the size of the peeling defect in the object to be measured without the need for sensor scanning of the entire plate.

[Brief description of the drawings]

FIG. 1 is a schematic configuration of a defect measurement device according to the present invention.

FIG. 2 is an explanatory view of a method for measuring the size of a defect inside the flat plate.

FIG. 3 is a diagram of a repetitive wave generated in a measured object.

FIG. 4 is a flowchart in the present control device.

FIG. 5 is a diagram showing an internal defect in a measured object.

FIG. 6 is an explanatory diagram of a conventional internal defect measurement method.

FIG. 7 is a diagram illustrating a vibration mode propagation state when a wedge is used as a medium and when a gas is used.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ultrasonic oscillator propagated in gas 2 Receiver 3 Control means 4 Display means 5 Object to be measured 6 Internal defect

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[Procedure amendment]

[Submission date] January 9, 2001 (2001.1.9)

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] All figures

[Correction method] Change

[Correction contents]

FIG.

FIG. 3

FIG. 5

FIG. 2

FIG. 4

FIG. 6

FIG. 7

Claims (4)

[Claims] An ultrasonic wave (lamb wave) that bends and vibrates in an object to be measured is excited, and a time difference of a repetitive wave caused by an internal defect parallel to a surface of the object and extending in a propagation direction of the bending vibration is measured. A method for measuring the size of an internal defect, comprising: measuring a size of an internal defect in the object to be measured from the bending vibration propagation velocity. 2. The method according to claim 1, wherein the object to be measured is a uniform flat plate or a laminated flat plate. 3. A gas-propagating ultrasonic oscillator, a receiver, and a control device, wherein the gas-propagating ultrasonic oscillator is capable of exciting an ultrasonic wave (lamb wave) that bends and vibrates in a measured object. An apparatus for measuring the size of an internal defect, which is an ultrasonic oscillator. 4. An ultrasonic wave generated from a gas-propagating ultrasonic oscillator has a product fd when a frequency is f and a plate thickness of an object to be measured is d.
4. The apparatus according to claim 3, wherein is set between 0.1 MHz mm and 1.2 MHz mm.