JPH01229925A - Ultrasonic applied stress measuring probe - Google Patents

Abstract

PURPOSE:To enhance receiving sensitivity and to prevent the generation of a measuring error, by providing the first and second transversal wave vibrators, the first and second shield plates and a longitudinal wave vibrator and setting the thickness of each of the first and second shield plates to 1/4-1/10 the wavelength of a transversal wave. CONSTITUTION:A probe is fixed on an object to be measured and, at first, the first transversal wave vibrator 2 is excited and, subsequently, the second transversal wave vibrator 3 is excited to generate two kinds of transversal waves. Next, a longitudinal wave vibrator 5 is excited to generate a longitudinal wave and the respective propagation times of said waves are measured and, from the measured result, the stress of the object to be measured is measured. At this time, the first and second shield plates 4, 6 suppress the transmission of the mechanical vibrations generated in the vibrators 2, 3 to the rear. However, an ultrasonic wave is propagated. Further, the thickness of each of the first and second shield plates 4, 6 is set to a condition stopping vibration but propagating an ultrasonic wave and the practical thickness range satisfying this condition is 1/4-1/10 the wavelength of the transversal wave.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ultrasonic stress measurement probe used when measuring stress in a C steel structural member using ultrasonic waves.

[Prior Art] As shown in Fig. 3, the basic principle of ultrasonic stress measurement is to generate longitudinal waves and principal stress (1!) at the same spot to be measured.
The propagation time ('r
t,: Longitudinal wave 'r,: Transverse wave vibrating in the σ direction) is measured. At this time, the following relational expression holds between each propagation time and principal stress.

TS2 TSI σ1−σ:=i, □ −α electric T“ TSl”TS□ σ1+σ, =42−−α2 T-T.

μ2, β2, α1, α2: Material constants Therefore, conventionally, for this measurement, TL was first measured using a longitudinal wave probe, and then TSL, Tj2 were measured using a shear wave probe, changing to the vibration directions σ1 and σ2. are being measured.

[Problems with Prior Art] Normally, when measuring propagation time, a liquid called a couplant is inserted between the sample and the probe in order to effectively propagate the ultrasonic waves.

For this reason, with conventional methods, the thickness of the couplant film changes as the probe needs to be changed each time, making highly accurate measurement impossible.
There is a problem with reaching 2.

The present invention has been proposed in view of these points, and an object thereof is to propose an ultrasonic stress measuring probe whose measurement error is smaller than that of the conventional example.

[Means for Solving the Problems] As a means for solving the above problems, the present invention provides a protection plate, a first shear wave vibrator, a first shielding plate, a second shear wave vibrator, a second shear wave vibrator, and a second shear wave vibrator. A shielding plate, a longitudinal wave oscillator, and a damper are arranged, and the thickness of the first and second g closing plates is set to 18 to 18 of the transverse wave wavelength.
We propose an ultrasonic stress measurement probe that is set at 1/1o.

[Effect] In the above probe, it is placed on the object to be measured.

First, the first transverse wave oscillator is excited, first the second transverse wave oscillator is excited to generate two types of transverse waves, and then the longitudinal wave oscillator is excited to generate longitudinal waves, and each propagation The time is measured, and the stress of the wave meter i!11 is measured using the above-mentioned relational expression based on the result.゛C Suppresses the generated mechanical vibrations from being transmitted to the rear (in both directions). (11L, , Ultrasonic waves propagate.

In addition, 1. The thickness of the second shielding plate is set to stop vibration, a'Lf
The condition is that the waves propagate, and the optimum value that satisfies this condition is 1/4 to 1/10 of the transverse wave wavelength in the practical range C1, preferably about 1 μm.

This data is shown in FIG.

[Example] FIG. 1 shows the structure of the probe according to the present invention,
No. 0, 1 is a front protection plate that protects the vibrator and comes into direct contact with the surface of the object to be measured.

2 is a first transverse wave oscillator for measuring SI of the above relational expression.

3 is a second transverse wave oscillator for measuring 82 of the above relational expression; 4 is a transverse wave oscillator located between the first and second transverse wave oscillators 2.3, which suppresses the reverberation of the vibration of the first transverse wave oscillator 2 and provides electrical insulation. This is the first shielding plate that guarantees the following.

5 is a longitudinal wave oscillator, 6 is a second transverse wave oscillator 3 and a longitudinal wave oscillator 5
A second shielding plate is provided between the first and second transverse wave transducers 3 to suppress reverberation of the second transverse wave transducer 3 and to ensure electrical insulation. The thickness of the second shielding plate 4.6 is the WJ wave wavelength (Sl, S2)
It is 1/8 of that.

7 is a damper that suppresses the reverberation of the longitudinal wave oscillator 5;

Reference numeral 8 denotes an electrode attached to both sides of the first and second transverse wave vibrators 2.3 and the longitudinal wave vibrator 5, and an electric signal is transmitted from the electrode 8 to each vibrator, and the vibration of the vibrator is can be extracted as an electrical signal.

Table 1 shows the ultrasonic reception sensitivity based on the arrangement example of each transducer. The best example is where the second transverse wave vibrator is placed, followed by the longitudinal wave vibrator.

<Margin below> Table ■ An example of measuring stress acting on a steel structural member using the above probe will be described next.

First, a probe is placed on the surface of a steel structural member. In this case,
Care must be taken to ensure that there are no objects between the probe and the front protection plate 1. Next, an electrical signal is sent to the first transverse wave transducer 2 to excite the transducer 2 to generate ultrasonic waves, and the vibration reflected from the bottom surface of the steel structural member is sent as an electrical signal from the electrode 8. “Take in C.

When the second transverse wave oscillator 3 is excited to rotate, JJ: iron!
The reflected vibration from the t1 structure is captured as an electrical signal.

Next, the -i signal is input from the electrode 8 to the longitudinal wave transducer 5, and this is excited to generate an ultrasonic wave. The stress acting on the steel structural member is determined using the above-mentioned relational expression based on this data.

[Effects of the present invention] As described below, the present invention provides a probe in which a second transverse transducer is disposed next to the first transverse transducer, and a longitudinal transducer is disposed next to the first transverse transducer. A first and second shielding plate was placed between the transducers to suppress vibration reverberation and prevent ultrasonic waves from passing through.

As a result, when each oscillator is excited, other oscillators are affected and excited, and two or three types of waves are generated. Therefore, the probe has a three-layer structure, and the same point Since At11 can be determined at all times, the reception sensitivity will be high and there will be no measurement error Xi.

Also, 311 can be determined at the same point.

From this point, J
There is no risk of incurring a constant error.

4. Explanation of inside of the cylinder on page 1. Figure 1 is an explanatory diagram of the probe according to the present invention. Figure 213 is an explanatory diagram of the reception sensitivity with respect to the plate thickness and wavelength ratio of the e-closing plate. Figure 3 is an illustration of the ultrasonic wave. It is a diagram explaining the principle of stress measurement.

■...Front protection plate 2...First shear wave vibrator 3...Second shear wave vibrator 4...First shielding plate 5... . . . Longitudinal wave oscillator 6 . . . Second shielding plate 7 . . . Tamper 8 . . . '/81/6', /4', 72 plate thickness and wavelength ratio

Claims (1)

[Claims] 1. In order from the side of the object to be measured: a protection plate, a first transverse wave vibrator, a first
A shielding plate, a second transverse wave vibrator, a second shielding plate, a longitudinal wave vibrator, and a damper are arranged, and the thickness of the first and second shielding plates is set to 1/4 to 1/10 of the transverse wave wavelength. Ultrasonic stress measurement probe consisting of 2. The ultrasonic stress measurement probe according to claim 1, wherein the first and second shielding plates are made of a material that suppresses vibration reverberation and ensures electrical insulation.