JPS5890165A - Ultrasonic inspection method and its device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates generally to non-destructive inspection of structures for defects, and more particularly to ultrasonic inspection methods and apparatus.

Inspection of steam and water transport pipes of steam and water pressure generators is necessary to ensure safe and reliable operation of such power systems. Many non-destructive techniques are known for inspecting transport pipes for defects such as cracks, dents, and holes that can result in structural failure under long-term operating loads.

In ultrasonic inspection systems, waves are launched into the structure being inspected and waves reflected or attenuated from structural defects are detected. Analysis of these waves determines the size and location of the defect.

The accuracy and reliability of an ultrasound inspection system depends on the sensitivity of the reflected ultrasound waves. Traditionally, many defects that could be detected under optimal conditions are rendered undetectable by noise in the received signal.

It is therefore an object of the present invention to provide an improved method and apparatus for ultrasonically inspecting bodies for defects.

Another object of the invention is to provide a method of ultrasound transmission, reception and processing that improves the signal to noise ratio.

Yet another object of the invention is to provide an apparatus for processing a signal thereby improving the information content and reducing the noise content.

Yet another object of the invention is to provide a method for detecting and analyzing unidirectional ultrasound signals. It is to provide.

Briefly, according to the invention, ultrasound waves are emitted into a structure by a transducer means while the transducer means moves relative to the structure. During an interval of time after each emission of ultrasonic waves, the ultrasonic waves are received by one Herance transducer means, and the time reference of the received waves is adjusted to compensate for the displacement of the transducer means. The conditioned waves are then summed to improve the signal to noise ratio of the composite signal.

More specifically, the displacement of the transducer means during the launch of the wave into the body where the signal of the wave reflected from a defect in the structure located in the direction of the movement of the transducer means is divided by the velocity of the ultrasonic wave. is increased by decreasing the delay of the received wave's time reference by a time interval equal to twice .

Furthermore, the wave received from the defective part of the body located in the direction in which the transducer means was moved is equal to twice the displacement of the transducer means during the firing of the wave into the body divided by the velocity of the ultrasonic wave. The time is increased by increasing the delay of the time reference of the received wave. The same method is used if separate transducer means are used to emit and receive ultrasound and it is desired that the waves reflected from the defect be detected.

If waves propagating directly from the transmitting means to the receiving means are to be detected, the signals are summed without adjustment of the time reference.

If digital signal processing is used, the displacement of the transducer means between wave pulses is selected to be a multiple of the product of 1/2 the received wave combing time interval and the ultrasound velocity. It is useful to have This ensures that an equal number of points on each waveform are digitized in successive repetitions of the measurement, thus ensuring that the summation is coherent.

Furthermore, cancellation of undesired signals can be achieved by 1 % of the wavelength of the ultrasound signal
is increased by selecting the displacement of the transuser means during periodic signal firing to be an odd multiple of /8.

Although the method and apparatus may be implemented using either analog or digital signal processing, in the preferred embodiment the received signals are digitized to facilitate processing accuracy and flexibility.

The invention and its objects and features will become more readily apparent from the following detailed description taken in conjunction with the drawings and the appended claims.

Referring to the drawings, FIG. 1 is a functional block diagram illustrating a portion of a body, such as tube 6-10, with segments 12 inspected for defects and shown partially in cross-section. In inspecting a tube 10, an ultrasonic transmitter 14 emits ultrasonic waves into the body of the tube 10, and an ultrasonic receiver 16 emits ultrasonic waves within the tube during a time interval simulating the emission of ultrasonic waves by the transmitter 14. receive. Therefore, with proper timing of the receiver 16, the reflected wave from the defect in the segment 12 is transmitted to the receiver 16.
received by.

To inspect the entire length of the tube, the transmitter J3 and receiver are pulled through the tube, and the receiver 16 may receive reflected waves from a defect in the tube 10 located in front of the receiver 16. .

Conversely, when the transmitter and receiver are at positions 15 and 17, respectively, the light reflected from the defect in segment 12 is received from the direction opposite to the movement of the transmitter and receiver.

Therefore, when emitting signals periodically and collecting the received signals for coherent summation, consideration must be given to the speed of movement of the transmitter and receiver and the direction in which the reflected waves are received. Therefore, it should be evaluated.

Assuming that the i~lummitter 14 and receiver 16 are stopped, the l~lancemitter 14 is pulsed and the reflected wave is received and recorded by the receiver 16. Since the transmitter and receiver are not moving, the received waves can be summed directly by triggering the transmitter in normal relation to its received wave. Assuming that the noise sources are random, coherent summation of the signals reinforces the reflected signal and minimizes the noise content, thereby improving the signal to noise ratio of the summed signal.

However, in inspecting a tube, it is desirable that the transmitter J3 and receiver move linearly through the tube so that the entire length of the tube is inspected.

By a linear displacement of the transducer between the signals and an appropriate selection of the sample time interval, the time reference of the received signal can be adjusted, so that only the signals that differ from the direction of movement of the receiver can be adjusted. are added coherently. Alternatively, the time reference can be adjusted so that the reflected signals in the direction in which the transmitter and receiver moved are coherently summed.

Additionally, the received signals can be summed without time adjustment, such that only signals transmitted in one direction and received from the other direction are coherently summed.

Assuming that the transmitter and receiver combination moves a distance Δ× during the transmitted pulse, the signal from the defect in front of the transducer will be transmitted over time T−2Δ
It arrives X/C earlier and the signal from behind the transmitter and receiver arrives a time T=2ΔX/C later, where C is the speed of the ultrasound. - Signals sent in the force direction and received from the other direction will have a fixed time reference.

9- 1 of the time to compensate for slow, constant or early arrival of waves
3 different buffers with 1 quasi-displacement 20122 OJ
: and 24 by adding each received signal.
Thus, the three composite waves are achieved by summing the time-adjusted signals, where only the desired signals are summed and all other signals and noise are substantially eliminated by the summing process. reduced to

In order to sum the signals to be coherent, the displacement Δ× of the lance transmitter during signal transmission must be a multiple of the product of 1/2 the time interval of the sample period and the ultrasonic velocity, i.e. ΔX - MCΔt/2 Furthermore, for more effective cancellation of undesired signals, the displacement Δ× is preferably an odd multiple of 1/8 of the wavelength of the ultrasound signal applied to the tube. ΔX −Nλ/8 FIG. 2 is a functional block diagram of an apparatus for implementing ultrasound examination according to the invention. Position 10 - Monitor 30 is a conventional rotary transducer that forms part of a receiver or transmitter probe and converts the motion of that probe into a train of digital pulses (e.g., 1.000 pulses per revolution of the shaft). It's okay. The pulses are used to condition the transmitter's firing and provide a reference point for digital processing of the received signal.

In one embodiment of control box 32, this sequence of pulses corresponds to approximately 0.134 inches of probe movement.
11) is provided with a counting circuitry that converts each signal into a trigger signal. Additionally, the control box provides a 342 KHz center frequency tone burst to the transmitter 36 and digitizer circuits 1-3.
912 KHz clock which is applied to 4. These values are M-2, N-3, and C-0,,122
Choosing an angle of about 0.31 cm/μsec satisfies the above equation. The transmitter and receiver may consist of w1 magnetic transducers of the type disclosed in U.S. Pat. No. 4.127.035 or co-pending GT No. Δ35185. The digitizer is a conventional one (7) Tekatsu B I
omatlon 8100 Trans+ent
It should be RecO1'dor.

By digitizing the received signals, computer 40 stores the signals for additive storage in memory 712! I! can be programmed to do so. Additionally, display 44 may be configured for displaying stored signals. Memory/I2 may be a floppy disk and display/1/I2 may be a floppy disk.
I am T etronlx 4006 display terminal%
N'll and the computer is M 1Qr
A microcomputer such as oIIOVa;
bJ: Yes.

In the embodiment described above, the transmitter and receiver pass through the Hnconel tube at a rate of 12 inches per second.
It was pulled at a speed of about 3 (LCIII). Signal pulses were generated every 378 wavelengths (0.134 inches) using a center frequency of 34.2 K Hl for the 1-lanced dicosa signal. When digitizing the received signal, 912KH2 or more than twice the highest frequency in the ultrasonic pulse.
Bling rate was used to satisfy the Nyquist condition for signal sampling. Thus, 90 samples were taken for each foot of the tube, and a sample spacing corresponding to 4 feet (about 120 cm) was used for each 4 foot (about 120 cm) of the tube.
20 cIm) were examined and 360 wave trains were averaged, yielding an improved theoretical signal to noise ratio of 25.6 db to random noise.

The method and apparatus for ultrasonic inspection of bodies according to the present invention is particularly useful for inspection of tubes such as those used in steam-powered power generation equipment.

However, the invention can be applied to inspecting other structures where the transmitter and receiver can be moved during inspection.

Therefore, although the invention has been described with reference to specific embodiments, the description is illustrative of the invention and should not be construed as limiting the invention.

Various modifications and applications will occur to those skilled in the art without departing from the true spirit and scope of this invention, which is limited by the following claims.

[Brief explanation of the drawing]

FIG. 1 is a functional block diagram illustrating one embodiment of the ultrasonic testing method according to the present invention. FIG. 2 is a functional block diagram of an embodiment of an apparatus for ultrasonic inspection according to the present invention. In the figure J3, 10 is a tube, 12 is a segment, 14.1
5.36 is a transmitter, 16.17°38 is a receiver, 20.22.24 is a buffer, 30 is a position monitor,
32 is a barb box, 34 is a digitizer, 40 is a combicoater, 42 is a memory, and 44 is a display. 14- 14M of drawings (no changes to the contents) FIG, -I FIG, -2 Procedural amendment I (method) % formula % 1. Indication of the case Patent application No. 191673 of 1988 2. Name of the invention Ultrasonic examination Method and device 3, relationship with the case of the person making the amendment Patent applicant address El., California, United States of America
Segundo East Imberial Highway, 223
0 Name Rockwell International Corporation Representative John J.D. Dinken 4
, Agent address: Yachiyo Daiichi Building, 2-3-9 Tenjinbashi, Kita-ku, Osaka City Voluntary amendment 6, Drawing subject to amendment 7, Contents of amendment S A drawing with a cat in ink is attached to the attached sheet a-+. There are no changes to the content. More than 2-399

Claims (5)

[Claims] (1) A method of inspecting a structure for defects using a transducer that moves relative to the structure.
R periodically generate ultrasound within the structure, detect said waves during time intervals, adjust the time reference of each detected wave to compensate for the displacement of said transducer, and adjust the time reference of each detected wave to compensate for the displacement of said transducer. A method comprising the steps of: summing the detected waves after adjusting a reference; and analyzing the summed waves. (2) The step of adjusting the time reference includes the step of adjusting the time reference between successive wave occurrences separated by the wave speed.
2. The method of claim 1, further comprising: delaying each detected wave by a time equal to twice the displacement of the lance deflector. 3. The method of claim 2, wherein the transducer moves at a speed that is many times the product of -1 the speed of the ultrasound and 172 of the sample time interval of the received waves. (4) The above-mentioned 1 to 1-range users are 1 of the wavelength of ultrasonic waves.
4. The method of claim 3, wherein the moving speed is an odd multiple of /8. (5) An apparatus for inspecting defects in a structure, comprising: a first transducer that periodically generates ultrasonic waves within the structure; and a transducer that moves the first transducer with respect to the structure. a second transducer for detecting MI ultrasound within a structure; and a second transducer for detecting MI ultrasound within a structure; and a time of each detected wave to compensate for movement of the first transducer. and means for summing a plurality of said detected waves with an adjusted time reference.