This paper presents an application of numerical simulation for ultrasonic guided wave in piping with elbow. A displacement field of torsion al guided waves in elbow and piping beyond elbow was computed using three-dimensional finite element models. We tried to utilize the predic ted displacement field to optimize the measurement condition or estimation of defect detectability. Experimental validation was carried our using artificial defects in elbow and beyond elbow region. Good agreement was obtained bet...
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Optimum measurements for pipe wall thinning in an elbow using torsional guided waves

Health monitoring of piping is one of the important issues to maintain its integrity.The guided wave monitoring is one of the promising methods r the health monitoring of piping．In this report，the optimum conditions of the guided wave method for both the flow-accelerated corrosion (FAC) and erosion of liquid droplet impingement (LDI) at around the elbow part of the piping were proposed and evaluated．The reason of the optimum con ditions was first explained and the experimental verifications were shown．Nume...
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On optimum detections of both LDI and FAC on an elbow part of piping by guided waves

In this paper, axial locations of defects in elbow pipes were estimated by the T(0,1) mode guided waves. 50A Schedule 40 aluminum pipes with the JIS short- and long elbows and a 100A Schedule 40 aluminum pipe with the JIS long elbow were prepared and evaluated, respectively. The T(0,1) mode guided wa ves (30, 40 and 50 kHz) were generated and detected by the piezoelectric ring-shaped sensor system. In the straight regions of the elbow pipes, estimates were good agreement with the real locations of the ...
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On estimation errors of defect locations using guided wave

The authors have previously been reported a novel method of an efficient transduction method for guided waves using the wave reflector just located near the sensor. The sensitivity of the method with the reflector has been 2.0-2.5 times larger than that without the reflector. This paper describes a much more efficient method for defect detection using guided waves with two reflectors. The novel method called Multireflecting Guided wave Energy Trapping (MGET) method is evolved from the above-described effi...
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Highly sensitive defect detection using Multireflecting Guided wave Energy Trapping (MGET) method.

Piezoelectric ring-shaped sensor (PeRS) has been widely used for guided wave inspection of piping. The PeRS i s normally consisted of plural transducer elements located along circumference at regular interval. Due to th e structure, in addition to the axially propagating torsional mode guided waves, circumferential (C-) Lamb wa ves have also been generated as spurious waves at the same time. Especially in the resonant conditions determ ined by both the specific frequencies and locations of sensor elements,...
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Wall-thickness measurement by resonant phenomena of the circumferential Lamb waves generated and detected by eight transducer-elements located evenly on circumference of pipe.

In this paper, a method of accurately measuring the pipe wall thickness by using noncontact air-coupled ultrasonic transducer (NAUT) was presented. In this method, accurate measurement of angular wave number (AWN) is a key technique because the AWN is changes minutely with the wall thickness. An autointerference of the circumferential (C- ) Lamb wave was used for accurate measurements of the AWN. Principle of the method was first explained. Modified method for measuring the wall thickness near a butt wel...
英字タイトル:
Accurate wall thickness measurement using autointerference of C ircumferential Lamb wave.