We are developing remote filed eddy current testing (RFECT) method using pancake coils for evaluating local wall thinn ing of large diameter pipes. This paper shows a study to improve the detectability and sizing capability of this RFECT method. The study was performed by numerical calculations and laboratory experiments. The results show that introduci ng differential pick-up coils makes detection signals more stable and improves the detectability of our RFECT method....
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Improvement of remote field eddy current testing using pancake coils

This study proposes a novel nondestructive evaluation method of chill contents in gray cast irons by means of AC magnetization method. For the purpose, magnetic properties of cast irons w ith different chill contents were evaluated by B-H loop analyzer. Results were discussed in view of matrices and graphite, and it was found that some magnetic parameters, especially B-H l oop area, correlate well with ratio of cementite area to graphite one. Focusing on the fact, AC magnetic method was applied to evaluati...
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Evaluation of Chill Contents in Flaky Cast Irons Based on AC Magnetization Method

This paper shows phase characteristics of crack indications obtained with a multi-coil ECT probe, and proposes a method to reduce noise and extract crack indications from the detection signals of this multi-coil ECT p robe based on these phase characteristics. Because this multi-coil ECT probe performs two kinds of scanning patterns: U-scan and T-scan, and obtains two sets of signal distributions for one scanning area simultaneousl y, the proposed method uses a two-stage process that includes so-called a m...
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Extraction of crack indications from ECT signals by using signal phase characteristics

Electromagnetic acoustic resonance (EMAR) method is useful for measuring thickness of pipe. But in the case of thickness changing complicatedly in part of pipe wall thinning for various factor, accurate thickness measurement is difficult. In this study, thickness of specimens of pipe corroded under various conditions is evaluated by EMAR. The error of thickness evaluation is investigated in view of maximum value of spectrum and roughness and curvature of pipe. As a result, it is suggested that signal streng...
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Evaluation of pipe wall thinning with electromagnetic acoustic resonance method considering effects of roughness and curvature of inner surface.

The authors have proposed a novel eddy current testing(ECT) probe for thick-walled plates. A basic concept of the probe is that a couple of differential pick-up coils is arranged between two exciting coils carrying currents opposite to each other. This arrangement allows strong eddy currents opposite to scan surfaces and the weak decay of eddy currents in the thickness direction. In this study, the present probe was applied to ECT of welding area. For the purpose, experiments were carried out u...
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Weld Inspection Using Eddy Current Testing Probe for Thick-walled Plates

This study proposes a method to fabricate an artificial defect that is almost identical to stress corrosion cracking from the viewpoint of electromagnetic nondestructive evaluations. The key idea is to realize a region having electrical resistance embedded inside a conductive materials using solid state bonding. A rough region is introduced into the surface of the materials to be bonded so that the region is partially bonded to realize electrical resistance. Experimental demonstrations are carried out...
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Fabrication of imitative stress corrosion cracking specimens suitable for electromagnetic nondestructive evaluations using solid state bonding

This study proposes a method to fabricate artificial defects that is almost identical to stress corrosion cracking from the viewpoint of electromagnetic nondestructive evalua tions. The key idea is to realize a region having electrical resistance embedded inside a conductive materials using solid state bonding. A rough region is introduced into th e surface of the materials so that the region is partially bonded to realize electrical resistance The validity of the method is demonstrated using type 316L aus...
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Fabrication of imitative stress corrosion cracking specimens suitable for electromagnetic nondestructive evaluations using solid state bonding

This paper proposes a methodology of lift-off measurement using optical system embedded in Eddy Current Testing (ECT) system. Firstly, the influence of lift-off on ECT signal was evaluated. Secondly, both ECT signal with lift-off shifting and the lift-off signal were acquired by means of an ECT probe with an optical displacement sensor. Then two cases of the crack shapes reconstructions were carried out using inverse analysis code. One was computed with taking the measured lift-off into account and t...
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Methodology of Lift-off Measurement Using Optical System in Eddy Current Testing

This study discusses the stress corrosion cracking (SCC) model which improves accuracy of depth sizing of SCCs with eddy current testing (ECT). For this purpose, the factors that influence ECT for SCCs are evaluated. In this study, the crack morpholog y and oxide fillings in SCCs are evaluated. As a first step, SCCs introduced at room temperature and fatigue cracks with oxide fillings are evaluated. To discuss the EC signals of SCCs, SCCs are artificially introduced and their ECT signals are obtain ed. The...
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Evaluation of the influence of crack branching structure and oxide fillings of stress corrosion cracking for depth sizing based on eddy current testing

This paper proposes a neural network to achieve automated data analysis target. A neural network, which is commonly used as an artificial intelligence technology, possesses excellent feature recognition and logistic regression ability, which are very important to implement automated data analysis. In this paper, the principle and characteristics of the neural network are presented. A neural network is established to discern the depth and length of slits automatically, and it is verified whether the ANN can ...
英字タイトル:
Feasibility study of neural network technology applied to advanced eddy current testing -Depth and length sizing of defects using neural networks-