JP3233816B2 - Peeled defect detection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a peeling defect which is applied to the detection of a peeling defect occurring in a stellite silver brazing portion of a turbine blade or the like.

[0002]

2. Description of the Related Art As shown in FIG. 3, a stellite 12 is joined to a surface of a turbine blade by means of a silver brazing portion 11, and defects generated in the silver brazing portion 11 are void-like defects 13 and peeling defects. There are defects 14.

[0003] In the conventional defect detection by nondestructive inspection of a stellite silver brazed portion of a turbine blade, a radiation transmission test has been applied. Since there is a large difference in the transmittance of the defect, it can be detected with high sensitivity. However, the peeling defect 14 having almost no difference in the transmittance with the healthy part cannot be detected.

[0004]

As described above, in the conventional defect detection of a stellite silver brazed portion of a turbine blade, a radiation transmission test is applied, and good detection of void-like defects is possible. However, it was impossible to detect a peeling defect because there was no difference in radiation transmittance between a healthy part and a peeling defect.

As a countermeasure, it is conceivable to detect a peeling defect using ultrasonic waves. In the case of defect detection using ultrasonic waves, as shown in FIG. 4, an ultrasonic beam 4 is incident on the subject 3 from its surface. The probe 1 has a dead zone 6 for a certain time after the transducer 1a transmits the ultrasonic beam 4,
During that time, no echo can be detected.

On the other hand, for the subject 3, the gap between the stellite and the silver solder is very small, about 0.002 mm, and the thickness of the stellite is as thin as 1.6 mm. For this reason, the defect echo 8 from the peeling defect 14 is hidden in the dead zone 6 by the ordinary ultrasonic inspection method, and it is impossible to determine the defect echo 8. The present invention seeks to solve the above problems.

[0007]

According to the present invention, there is provided a method for detecting a spalled defect, comprising the steps of:
Surface by disposing an ultrasonic probe through the delay material, ultrasonic
The ultrasonic beam entering from the wave probe to stellite, terpolymers
Receives <br/> defect echo reflected by the defect of the bottle blades and stellite boundaries before Symbol ultrasonic probe, counts the number of reflections, a case where the number of reflections is more than 4 times the release form missing
If less than 4 times, peeling defects have occurred.
It is characterized by determining that there is no.

[0008]

In the above, the ultrasonic beam transmitted by the ultrasonic probe is incident on the subject through the delay member, and reaches the defect when the brazing portion of the thin metal plate has a defect.

[0009] The ultrasound beam reaches the defect and delayed by the delay member, because received by the ultrasonic probe, defect echo by the defect immediately after the ultrasonic beam transmission of the ultrasonic probe The dead zone that is formed can be avoided, and the ultrasonic probe can reliably receive the defect echo and detect the defect.

[0010] Further, among the defects formed in the brazed portion, the peel-like defects are planar with a certain dimension or more.
Since the ultrasonic beam incident on the subject repeatedly reflects a predetermined number of times or more due to the defect, when a defect echo is repeatedly received four times or more, it can be determined that a peeling defect exists.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for detecting a peeling defect according to one embodiment of the present invention will be described with reference to FIG. In this embodiment,
This is applied to the defect detection of the stellite silver brazed part of the turbine blade as the test object.

In the defect detection method of this embodiment shown in FIG. 1, the ultrasonic probe 1 is connected to the object 3 via the delay member 2.
After transmitting the ultrasonic beam 4 from the ultrasonic probe 1, the number of reflections of the defect echo 8 from the defect 5 is counted. The defects 14 and those less than four times are determined to be void defects 13.

In the above description, since the ultrasonic beam 4 transmitted from the probe 1 enters the subject 3 via the delay member 2 made of acrylic resin, the surface 3a, the defect 5, and the bottom surface 3b of the subject 3 1, the surface echo 7, the defect echo 8, and the bottom surface echo 9 can be received by the probe 1 after passing through the dead zone 6 as shown in FIG.

Therefore, it is possible to avoid a situation in which the reception time of the defect echo 8 by the probe 1 is within the dead zone 6 and the defect 5 cannot be detected as in the conventional method.

In the case of defect detection by the ultrasonic probe 1, if the area of the defect 5 is large, the ultrasonic beam 4 repeatedly reflects according to the size of the defect 5, as shown in FIG. but when the small area of the defect 5, does not cause almost repeated as shown in Figure 2 (c).

On the other hand, the defect 5 is formed at the interface between the stellite and the silver brazing portion. In the case of the void defect 13, the diameter is 2 mm or less, and the reflection surface of the ultrasonic beam 4 is spherical. On the other hand, in the case of the detachment defect 14, the length is 3 mm or more. Therefore, in the case of the separation defect 14, the ultrasonic beam 4 is repeatedly reflected by the defect 14.

An ultrasonic inspection test was performed to confirm the number of times of reflection of the ultrasonic beam depending on the size of the reflection surface of the defect 5, and the results shown in the following Table 1 were obtained. That is, when the diameter of the defect 5 is 3 mm or more, the reflection is repeated clearly four times or more, whereas when the diameter of the defect 5 is 2 mm or less, the maximum number of reflections is two times.

[0018]

[Table 1]

Therefore, in this embodiment, if the number of reflections of the ultrasonic beam 4 by the defect is less than four, it is determined to be a void defect 13, and if it is four or more, the peeling defect 1 is determined.
4 was determined. The void defect 13 can be detected more accurately by using a radiation transmission test together.

[0020]

According to the peeling defect detecting method of the present invention, an ultrasonic beam emitted by an ultrasonic probe is incident on a subject through a delay member, and a defect echo caused by a defect in the subject is detected. Since the ultrasonic probe receives and counts the number of reflections, the ultrasonic beam is delayed by the delay material and reaches the defect, and the echo of the defect can avoid the dead zone. In addition, the defect-like defect has a larger ultrasonic beam receiving area than other defects and reflects the ultrasonic beam multiple times, so the number of reflection echoes is counted and the number of reflections is reduced.
By determining whether the number is four or more, it is possible to identify the peeling defect.

[Brief description of the drawings]

FIG. 1 is an explanatory view of an embodiment of the present invention, wherein (a) is an ultrasonic probe according to the embodiment, (b) is an echo received by the probe, and (c) is a defect having a void. An ultrasonic beam in the case of a shape defect, (d) is a defect echo in the case of (c), (e) is an ultrasonic beam in the case where the defect is a peeling defect, and (f) is a defect echo in the case of (e). FIG.

FIGS. 2A and 2B are operation explanatory diagrams according to the embodiment, in which FIG. 2A shows an ultrasonic beam when a defect is large, FIG. 2B shows a defect echo in the case of FIG. FIG. 7D is an explanatory diagram of a defect echo in the case of FIG.

FIG. 3 is an explanatory diagram of a subject.

FIG. 4 is an explanatory diagram of a conventional defect detection method using ultrasonic waves;
(A) is an ultrasonic probe according to a conventional method, (b) is an echo received by the probe, and (c) is an explanatory diagram of a defect echo when a defect is close to the surface of a subject.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ultrasonic probe 2 Delay material 3 Subject 4 Ultrasonic beam 5 Defect 6 Dead zone 8 Defect echo 11 Silver brazing part 12 Stellite 13 Void defect 14 Peeling defect

Claims (1)

(57) [Claims] 1. A stella brazed to a turbine blade.
An ultrasonic probe is arranged on the surface of the
The incident ultrasound beam from the ultrasound probe to stellite receives the previous SL ultrasonic probe a defect echo due to defects in a turbine blade and Stellite boundary counts the number of reflections, the number of reflections 4 If more than one time, peeling off
If less than 4 times, peeling defects have occurred.
A method for detecting a peeling defect, the method comprising: determining that no defect exists.