This study reports the results of nondestructive testing and evaluation of artificial thermal fati gue cracks using direct current potential drop method. ?ix artificial thermal fatigue cracks, intro duced into type 304L austenitic stainless steel plates with a thickness of 25mm, are prepared; and potential drops across the cracks are measured using a direct current source of approximately 80A. The specimens are then served to destructive tests to reveal the true profiles of the cracks. Fini te element simu...
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Nondestructive Testing and Evaluation of Artificial Thermal Fatigue Cracksusing Direct Current Potential Drop Method

This study evaluates the distribution of electrical contact across the surface of thermal fatigue cracks by four- terminal direct current potential drop method. This study prepared seven artificial thermal fatigue cracks, artificially introduced into Inconel or type 316L stainless steel plates with a thickness of 25 mm. Columnar specimens embedded into a resin were fabricated from the plate s to measure the electrical resistance across the cracks directly. The results indicated th at thermal fatigue crac...
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Evaluation of the electrical contacts of thermal fatigue cracks across their surfaces 東北大院・工学研究科

In a process of hot and cold fluid mixing, temperature fluctuation in the fluid can occur. When this fluctuation is caused by unstable fluid mixing process, the surrounding structure would be damaged by high-cycle thermal fatigue. This phenomenon is observed in various nuclear power plants, which means it is important to investigate the relation between the fluid mixing process and the thermal fatigue. When there exists a 90-degree bend i n the upstream of the mixing area, the fluid mixing process becomes ...
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Estimation on the thermal hydraulic characteristics in a non-isothermal fluid mixing

The evaluation method for maintenance optimization in long-term operation of nuclear power plant (NPP) has been proposed by using Probabilistic Safety Assessment (PSA) in general. Possible troubles in the maintenance activities of NPP are modeled and simulated by using Fault Tree with failure rates of components estimated by operating experiences in Japan. The Monte-Carlo simulation has been performed to compare the maintenance strategies such as cycle extension of periodic inspection and overhaul for...
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Development of an Evaluation Method for Maintenance Optimization in Long-term Operation of Nuclear Power Plant with Probabilistic Safety Assessment

This study develops a low frequency magnetic flux leakage testing method for monitoring a wall thinning appearing on the inner surface of a magnetic pipe. We conducted the numerical simulations to evaluate how the presence of wall thinning perturbates electromagnetic fields induced by an encircling coil. The result of the simulations shows measuring the axial component of magnetic flux density enables to detect and evaluate wall thinning. ...
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Development of low frequency magnetic flux leakage testing method aimed at monitoring a wall thinning appearing in a magnetic pipe

This work addresses LDI (Liquid Droplet Impingement) accompanied with pipe wall thinning in nuclear and thermal power plant s. In order to clarify the factors that affect the wall thinning, the structure of supersonic two-phase flow after an orifi ce is visualized with a digital video camera. The visualization experiment proves that the droplets impinges the pipe wall shortly after the orifice and that the amount of water droplets that passes through the orifice is the important parameter....
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Evaluation of Liquid Droplets Impact Erosion in downstream areas of an orificecaused by supersonic two-phase flow

This paper reports research activities in the authors’ group to develop a novel non-destructive testing method using a microwave to quickly inspect the inner surface of a pipe. The method propagates a microwave inside a pipe to detect anomalies appearing the inner surface on the basis of the reflection of the microwave due to the anomalies. Because the method does not require probe scanning unlike conventional non-destructive testing methods such as eddy current testing, it can inspect a long pipe quit...
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Development of a non-destructive testing method for a long-range inspection of the inner surface of a long pipe

Abstract The NDT method using electromagnetic waves has the possibility to detect widely and quickly inner surface crack existin g in large pipes. The purpose of this study is to demonstrate validity of the method to detect the thin crack introduced by pla sma discharge fabrication. Through this study, it has been shown that both reflected and transmitted waves carry a lot of inform ation on existence of the crack. Experimental results indicate that there exists attractive possibility in this new NDT metho...
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Development of crack detection method by using electromagnetic wave

A circular electromagnetic TE11-mode is used for detection of longitudinal crack in a stainless steel pipe. To show the capability of microwave nondestructive t esting for detection of crack in large and complex piping systems such as steam generator (SG) tube, inspected pipe including U-bend are examined in this study....
英字タイトル:
Microwave Nondestructive Detection of Longitudinal Crack in Pipe with U-bend