Showing papers by "Tetsuya Uchimoto published in 2010"
TL;DR: In this paper, a comprehensive magnetic investigation of structural low-carbon steel subjected to uniaxial plastic tension was carried out and the applied applicability of the examined techniques for the non-destructive characterization of steel degradation was discussed.
Abstract: Macroscopic hysteresis and local Barkhausen noise techniques were used for the comprehensive magnetic investigation of structural low-carbon steel subjected to uniaxial plastic tension. Scattering of the measured magnetic parameters was substantial within the Luders band region with stabilization at higher strains. Compressive residual stresses in the deformation direction formed a hard magnetization axis with intriguing two-phase remagnetization. The magnetic parameters had the highest sensitivity to strain in this direction. They changed as cos2 with rotation to the perpendicular easy magnetization axis, where the magnetic sensitivity was the lowest. The relation between the deformed steel microstructure (dislocation and residual stress patterns) and the obtained magnetic behaviour is interpreted. The applicability of the examined techniques for the non-destructive characterization of steel degradation is discussed.
38 citations
TL;DR: In this paper, a dual probe with simple structure combining an electromagnetic acoustic transducer (EMAT) and Eddy current probe was proposed for monitoring of piping wall thinning in a high temperature environment.
Abstract: Eddy current testing (ECT) and ultrasonic testing (UT) have been widely used for the non-destructive testing of metal structures ECT has a high capability of sizing surface breaking cracks and UT is suitable for sizing sub-surface breaking cracks in thick-wall structures Based on this background, the authors have proposed a novel dual probe with simple structure combining an electromagnetic acoustic transducer (EMAT) and Eddy current probe The performance of the probe was verifi ed at room temperature However, the operating temperature of boiling-water nuclear reactors is 300 degrees C In this paper, the above dual probe is applied to monitoring of piping wall thinning in a high temperature environment For this purpose, the structure and components of the probe are discussed so that the present probe should withstand 300 degrees C Finally, the basic performance of the probe at high temperatures is investigated through an experiment using an electric furnace
22 citations
TL;DR: The applicability of magnetic techniques (hysteresis and Barkhausen noise) in the detection of plastic deformation was comprehensively studied in this paper, where structural low carbon steel subjected to uniaxial plastic tension was accurately measured for a wide range of residual strains and at different magnetization angles with respect to the stress direction.
Abstract: The applicability of magnetic techniques (hysteresis and Barkhausen noise) in the detection of plastic deformation was comprehensively studied. Structural low-carbon steel subjected to uniaxial plastic tension was accurately measured for a wide range of residual strains and at different magnetization angles with respect to the stress direction. In addition to classical magnetic parameters, new quantities with better sensitivity-stability ratios were introduced on the basis of two-phase remagnetization caused by compressive residual stress. The magnetic methods had highest sensitivity in the deformation direction (hard magnetization axis). The parameters changed as cos 2 with rotation to the perpendicular easy magnetization axis, where the magnetic sensitivity was lowest. In this direction, only the root mean square value of Barkhausen noise considerably changed with the strain. The extremes of the Barkhausen parameters with respect to the magnetization angle did not exactly correspond to the hysteresis extremes (real easy and hard magnetization axes) in that there was a shift of about ±10°.
18 citations
TL;DR: In this article, the authors reported correlation of magnetic descriptors with Brinell hardness and conductivity of ductile cast iron, aiming to develop a novel nondestructive method by magnetic adaptive testing.
15 citations
TL;DR: In this paper, the Magnetic Adaptive Testing (MAT) method was applied for investigation of ductile cast iron samples having matrix and graphite structure, and linear, sensitive correlation with low scatter of values was found between the magnetic and the mechanical characteristics.
Abstract: The method of Magnetic Adaptive Testing (MAT) was applied for investigation of ductile cast iron samples having matrix and graphite structure. This method is typical by its low required magnetization of samples, because it is based on the measurement of minor magnetic hysteresis loops and calculates magnetic descriptors for characterization of the sample. Results of the non-destructive magnetic tests were compared with the results of destructive mechanical measurements of Brinell hardness and also with the results of non-destructive eddy current measurements. Linear, sensitive correlation with low scatter of values was found between the magnetic and the mechanical characteristics. If the parameters of MAT measurement are properly chosen, then they do not depend on temperature in the T = 20-180°C range, in contrast to the results of eddy current measurements. Based on these results, MAT is suggested as a highly promising non-destructive alternative of destructive tests for monitoring structural changes in cast iron and in other ferromagnetic objects.
9 citations
09 May 2010
TL;DR: In this paper, the magnetic hysteresis curves were simulated by the Monte Carlo method to study magnetic property changes under the sensitization of Ni base alloy Alloy 600 (Inconel), which is well used as structural materials in nuclear power plants.
Abstract: Magnetic hysteresis curves were simulated by the Monte Carlo method to study magnetic property changes under the sensitization of Ni base alloy, Alloy 600 (Inconel), which is well used as structural materials in nuclear power plants. Different distributions of spin concentration depending on heating duration time in cubic clusters caused to change the hysteresis curve. The calculation results agree with the experimental ones, and it suggests that the magnetic dynamic process can tell the degree of sensitization due to fatigue for Alloy 600 .
6 citations
TL;DR: In this article, the shape and size of graphite in flake graphite cast iron was analyzed based on electromagnetic non-destructive methods and the conductivity and relative permeability of the graphite was evaluated.
Abstract: This paper discusses the feasibility of characterizing the shape and size of graphite in flake graphite cast iron based on electromagnetic nondestructive methods. Several flake graphite cast iron specimens containing graphite of various shapes and sizes were prepared and their electromagnetic properties such as conductivity and relative permeability were evaluated systematically. Both the conductivity and the relative permeability were found to mainly depend on the shape and size of graphite. The conductivity was specifically found to have a good correlation with the shape and size of graphite and this was independent of the pearlite area fraction of matrix. The conductivity also correlates well to the ultrasonic velocity which indicates the amount and size of the graphite. The DC potential drop method was used to evaluate the structure of graphite and its capability was evaluated.
6 citations
TL;DR: In this article, a dual probe with simple structure combining an electromagnetic acoustic transducer (EMAT) and Eddy current probe was proposed for monitoring of piping wall thinning in a high temperature environment.
Abstract: Eddy current testing (ECT) and ultrasonic testing (UT) have been widely used for the non-destructive testing of metal structures. ECT has a high capability of sizing surface breaking cracks and UT is suitable for sizing sub-surface breaking cracks in thick-wall structures. Based on this background, the authors have proposed a novel dual probe with simple structure combining an electromagnetic acoustic transducer (EMAT) and Eddy current probe. The performance of the probe was verifi ed at room temperature. However, the operating temperature of boiling-water nuclear reactors is 300 degrees C. In this paper, the above dual probe is applied to monitoring of piping wall thinning in a high temperature environment. For this purpose, the structure and components of the probe are discussed so that the present probe should withstand 300 degrees C. Finally, the basic performance of the probe at high temperatures is investigated through an experiment using an electric furnace.
6 citations
4 citations
TL;DR: In this article, an EMAT/EC dual probe was proposed for the material characterization of cast irons, which can obtain ultrasonic and EC signals with a single probe structure.
Abstract: Mechanical properties of cast irons strongly depend on the graphite morphology and the matrix structure, thus both of them should be evaluated for their characterization. The former can be evaluated by ultrasonic testing (UT), and the latter can be evaluated by eddy current testing (ECT). Considering the background above, this study proposes a novel method for the material characterization of cast irons with an EMAT/EC dual probe. For this purpose, we conducted UT and ECT for cast irons with different graphite morphology and matrix structures with the present probe. As a result, correlations betwe en the nodularity of graphite and ultrasonic velocity, and between one the pearlite ratio and EC signals were obtained. These results imply that the EMAT/EC dual probe is effective for the material characterization of cast irons. Cast iron is an Fe-C base alloy that contains iron as the princ ipal ingredient and carbon more than 2%. It is useful engineering material due to its excellent mecha nical properties, such as strength, ductility, free cutting, and productivity. Accordingly, it is widely used f or the parts of automobiles, industrial machinery and so forth. However, the manufacturing process of casting is complex, and the microstructure control is difficult. Therefore, nondestructive characterization of mechanical properties of cast irons is necessary and one of key issues in the foundry industry. The structure of cast irons consists of graphite and a steel matrix. Mechanical properties of cast irons depend on the graphite morphology and the matrix structure, thus both of them should be evaluated for their characterization. The nodularity of cast irons is estimated by measuring the ultrasonic velocity, and the method is established (1). The matrix structure and hardness of cast iron are estimated by measuring the EC signals of ductile cast irons (2). Therefore, the graphite morphology and matrix structure can be evaluated by ultrasonic testing (UT) and eddy current testing (ECT), respectively. We have proposed an EMAT/EC dual probe (3) that can obtain ultrasonic and EC signals with a single probe structure. This probe was applied to the evaluation of wall thinning of pipes, and the feasibility of the nondestructive evaluation based on the complementarity between ECT and UT was verified. This paper proposes a new method for the material characterization of cast irons with an EMAT/EC dual probe. The material properties of cast irons are not uniform and should be characterized with respect to each point. The dual probe with a single and compact structure can acquire UT and EC signals
3 citations
01 Jan 2010
TL;DR: The Magnetic Adaptive Testing (MAT) as mentioned in this paper is a non-destructive method for monitoring structural changes in different types of ferromagnetic materials, which uses sensitive correlations between the varied microstructure of the magnetized material and the corresponding, highly sensitive modifications of some minor hysteresis loops.
Abstract: Systematic measurement of minor magnetic hysteresis loops of traditional hysteresis tests requires substantially lower magnetization of samples and offers higher sensitivity of detection of changes in the ferromagnetic materials’ microstructure. The keynote idea of this method, called Magnetic Adaptive Testing (MAT) is utilization of sensitive correlations between the varied microstructure of the magnetized material and the corresponding, highly sensitive modifications of some of the minor hysteresis loops. The paper presents some of the recent results of the MAT measurement performed on specially prepared series of cast iron samples. Results of the non-destructive magnetic tests were compared with the destructive mechanical measurements of Brinell hardness and linear correlation was found between them. A very good correlation was also found between magnetic descriptors and conductivity and chill/ferrite area fraction. Based on these results, Magnetic Adaptive Testing is suggested as a highly promising non-destructive method for monitoring structural changes in different types of ferromagnetic materials.
TL;DR: In this article, the authors proposed a method to reduce noise and extract crack indications from detection signals of a 48-channel ECT system based on its signal phase characteristics, which uses a two-stage process that includes so-called main filter and sub filter.
Abstract: This paper proposes a method to reduce noise and extract crack indications from detection signals of a 48-channel ECT system based on its signal phase characteristics. Because this 48-channel ECT system performs two kinds of scanning patterns: U-scan and T-scan, and obtains two sets of signal distributions for one scanning area simultaneously, the pro posed method uses a two-stage process that includes so-called main filter and sub filter. Using these two filters imposes more str ict conditions on extracting crack indications so as to reduce more noise. The experimental results show that the proposed fi ltering method is effective to extract only crack indications from detection signals including complicated noises.
TL;DR: In this paper, an EMAT/EC dual probe was proposed for the material characterization of cast irons, which can obtain ultrasonic and EC signals with a single probe structure.
Abstract: Mechanical properties of cast irons strongly depend on the graphite morphology and the matrix structure, thus both of them should be evaluated for their characterization. The former can be evaluated by ultrasonic testing (UT), and the latter can be evaluated by eddy current testing (ECT). Considering the background above, this study proposes a novel method for the material characterization of cast irons with an EMAT/EC dual probe. For this purpose, we conducted UT and ECT for cast irons with different graphite morphology and matrix structures with the present probe. As a result, correlations betwe en the nodularity of graphite and ultrasonic velocity, and between one the pearlite ratio and EC signals were obtained. These results imply that the EMAT/EC dual probe is effective for the material characterization of cast irons. Cast iron is an Fe-C base alloy that contains iron as the princ ipal ingredient and carbon more than 2%. It is useful engineering material due to its excellent mecha nical properties, such as strength, ductility, free cutting, and productivity. Accordingly, it is widely used f or the parts of automobiles, industrial machinery and so forth. However, the manufacturing process of casting is complex, and the microstructure control is difficult. Therefore, nondestructive characterization of mechanical properties of cast irons is necessary and one of key issues in the foundry industry. The structure of cast irons consists of graphite and a steel matrix. Mechanical properties of cast irons depend on the graphite morphology and the matrix structure, thus both of them should be evaluated for their characterization. The nodularity of cast irons is estimated by measuring the ultrasonic velocity, and the method is established (1). The matrix structure and hardness of cast iron are estimated by measuring the EC signals of ductile cast irons (2). Therefore, the graphite morphology and matrix structure can be evaluated by ultrasonic testing (UT) and eddy current testing (ECT), respectively. We have proposed an EMAT/EC dual probe (3) that can obtain ultrasonic and EC signals with a single probe structure. This probe was applied to the evaluation of wall thinning of pipes, and the feasibility of the nondestructive evaluation based on the complementarity between ECT and UT was verified. This paper proposes a new method for the material characterization of cast irons with an EMAT/EC dual probe. The material properties of cast irons are not uniform and should be characterized with respect to each point. The dual probe with a single and compact structure can acquire UT and EC signals