JPS5926898B2 - Ultrasonic transducer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic transducer for water immersion flaw detection that can focus an ultrasonic beam into a line and make the focused beam long.

Recently, when performing ultrasonic flaw detection, there is a strong demand to further improve the accuracy of defect evaluation by quantitatively measuring the size, directionality, etc. of detected defects, and at the same time to further shorten the inspection time.

Therefore, 1) it is necessary to focus the beam in order to accurately determine the defect position; 2) it is desirable to focus the beam on a line rather than a point in order to shorten the inspection time; 3) and When ultrasonic waves are emitted onto a material to be inspected, it is necessary to avoid the influence of reflected waves (S echoes) from the surface of the material. However, in conventional water immersion vertical probes, the ultrasonic beam depends on the frequency and diameter of the transducer, so it has not been possible to narrow it down beyond a certain limit.

In addition, the focus type probe that focused the ultrasonic beam narrowly had a short focusing band, which was equivalent to a point. In addition, in split type probes to avoid the influence of s-echo, a two-piece type is usually used, so due to the probe structure, if a transducer with strong directionality and the same area is used for both transmission and reception. This meant that transmission and reception were performed using a transducer with half the area, resulting in a loss in sensitivity.

The present invention was made to solve the above-mentioned problems, and the ultrasonic beam emitted from the transducer is focused linearly on the material to be inspected, and the length of the focused line is equal to the thickness of the material to be inspected. It is an object of the present invention to provide an ultrasonic receiver capable of equalization.

Next, the present invention will be described with reference to an illustrated embodiment. 1st
The figure shows an ultrasonic transducer with a hole in the center. FIG. 2 is a cross-sectional view of the ultrasonic transducer according to the present invention, in which 1 is an ultrasonic vibrator made of piezoelectric ceramic or single crystal, and 2 has a hole for the ultrasonic vibrator and a large hole in the center. 3 is a sound absorbing material made of epoxy elastomer, butyl rubber, phenol resin, etc. mixed with a filler having a sound absorbing effect, and 4 is tungsten, epoxy. A damper made of composite material, 5 a connector for electrical connection, 6 a connector 5 from the ultrasonic transducer 1
The lead wire 8 is a case, and a circular wedge 2 made of plastic material is tightly attached to the annular vibrator 1 with the center hole aligned with the hole in the vibrator 1 and the wedge 2. A cylindrical sound absorbing body 3 is fitted, and these are loaded into a case 8 with a damper 4. Figure 3 shows a cross section of the state in which such an ultrasonic transducer is placed perpendicularly to a material to be inspected, such as a steel plate 11, underwater, and an ultrasonic beam is emitted from an ultrasonic vibrator. ing.

Now, an ultrasonic wave 13 is emitted from the ultrasonic transducer 1 into the water from the outermost side of the inclined surface 7 of a circular wedge made of plastic material, and an echo (S echo) 13' generated from the surface of the steel plate 11 is transmitted to the wedge 2 and the ultrasonic wave 13. The sound absorber 3 passes through the outermost hole of the sound wave vibrator 1.
A part of the ultrasonic wave 13 enters the steel plate, is reflected at the bottom surface 15 (B echo), and proceeds from the steel plate into the water to the outside of the circular wedge 2'. Ultrasonic waves 1 emitted into the water from the innermost side of the inclined surface 7 of the circular wedge
4 is reflected as an S echo through the dead zone of the steel plate,
The ultrasonic wave 14' is incident on the innermost absorber of the inclined surface of the wedge on the opposite side of the wedge and is absorbed as it is by adjusting the angle of the inclined surface of the circular wedge and the wedge 2. If the size of the central hole of the ultrasonic transducer 1 is selected, all the S echoes will be incident on the sound absorber 3 and the influence thereof can be avoided. This makes it possible to extremely reduce the dead zone where flaw detection is not possible. Also, no B echo is received. As an example, in Fig. 4, the thickness of the steel plate T=
10m77! , diameter of the vibrator 2R = 20v1t1 sound velocity in water Cw = 1500m/s1 Ca in organic glass = 274
The inclination angle φ3 of the wedge is determined by setting Cs=3200 m/s in 0 m/s1 steel (transverse wave). Therefore, when a transverse wave with a short wavelength is used to increase the resolution so that even the smallest flaws can be detected, the conversion efficiency of the transverse wave that enters the steel plate from water and becomes a transverse wave is generally at its maximum when the incident angle φ is 17 degrees. Therefore, when calculating with φ = 17°, it becomes.

As shown in Figure 3, when an ultrasonic beam is emitted from an underwater ultrasonic transducer at a certain distance to a material to be inspected of a certain thickness, the ultrasonic beam that has entered the material to be inspected will
They are focused on a line 16 and further advance.

Therefore, if there is a flaw on the line 16, the focused ultrasonic beam makes the flaw detection point extremely clear, and the resolution of the position can be significantly improved, as well as the flaw detection sensitivity. Therefore, it is possible to detect flaws in a range from the surface to the bottom of the inspected material at once, which is not possible with a point-focused probe, so when inspecting the entire steel plate, the probe can be scanned over the entire surface only once. Bye. Therefore, the inspection time can be further shortened.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of an annular ultrasonic transducer, Fig. 2 is a sectional view showing the structure of an ultrasonic transducer according to the present invention, and Fig. 3 is a perspective view of an annular ultrasonic transducer according to the present invention. A cross-sectional view of the ultrasonic beam emitted into the material to be inspected.
FIG. 4 is an explanatory diagram of a specific example. DESCRIPTION OF SYMBOLS 1... Annular ultrasonic transducer, 2... Circular wedge, 3... Sound absorber, 7... Inclined surface of circular wedge, 11 ... Material to be inspected, 12...
...Vacancies in the ultrasonic vibrator.

Claims (1)

[Claims] 1. A circular wedge of plastic material having a hole of the same size as the hole in the center is placed over and close to the hole in the annular ultrasonic transducer having a hole in the center, and placed at the position of the hole. An ultrasonic transducer characterized in that a cylindrical ultrasonic absorber is provided to linearly focus an ultrasonic beam emitted from the vibrator into a material to be inspected through a liquid.