This study aims at proposing a novel magnetic testing method, eddy current magnetic signature method for evaluation of residual strain in carbon steels. This method characterize the eddy current magnetic signatures that is eddy current signals in an impedance plain during magnetization process. In order to discuss the feasibility of this method, eddy current magnetic signatures of a set of tensile test specimens are investigated. The relationship between eddy current signature and plastic deformation is di...
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Nondestructive Evaluation of Residual Strain in Carbon Steels by Eddy Current Magnetic Signature Method

Laser peening is a surface enhancement process that introduces compressive residual stress on materials by irradiating laser pulses under aqueous environment. The process utilizes the impulsive effect of high-pressure plasma generated by ablative interaction of each laser pulse. It is very beneficial to shorten ou tage period if laser peening is available during refueling work. It is confirmed that laser peening can be available in the situation by experiment and analys is. This report describes detail of ...
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Study on availability of laser peening during refueling work- Preventive maintenance to shorten outage period

In welds of steel structure of nuclear power plants, stress corrosion cracking and fatigue cracking occur, and the residual stress due to welding becomes one of the main factors causing them. Therefore, it is necessary to understand the residual stress distribution of a welded region, and residual stress analysis performed by the finite element method (FEM) has been become an effective tool. Previously, in order to shorten computation time, the analyses are carried out in a two-dimensional model and th...
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Residual stress analysis of multi-pass welded joint in nuclear power plant using idealized explicit FEM.

In this study, a residual stress distribution in a dissimilar plate butt-welded joint was simulated by a thermo-elastic finite element method. The base metal was the austenitic stainless steel SUS316L. The other base metal was nickel super-alloy NCF600, and the weld metal was the alloy 82 (YNiCr-3). The dimensions of the plate butt-welded joint were a width of 200 mm, a length of 250 mm and a thickness of 25 mm. The welding joint was fabricated by TIG welding with 22 passes. For comparison, the residu...
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Residual Stresses in Dissimilar Metal Joint by Multi-pass Welds

Magnetic NDE technique for an estimation of degradation distribution in tensile-tested structural steel has been developed. In order to scan magnetic properties of steel promptly , magnetic yoke-probe having primary and secondary coils wounded around the yoke was adopted. To simplify the detection procedure, the principle same as the transformer was emplo yed. The voltage induced at secondary coil decreases with the increase in the applied tensile stress. As for spatial distribution of output voltage, the ...
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NDE of degradation distribution in tensile-tested specimen using magnetic sensing

Special attentions have been increasingly paid for the diagnosis of social infrastructures after the collapse of ceiling of Sasago tunnel of Chuo Expressway. It is reported that the main cause was due to the age-related degradation of chemical anchors. Chemical anchors are also frequently used in nuclear power stations. Here we have been trying to apply PFM (Probabilistic Fracture Mechanics) to the diagnosis of social infrastructures using Dr. Mainte, an integrated simulator to optimize maintenance activi...
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A Study of Application of PFM (Probabilistic Fracture Mechanics) to the Diagnosis of Social Infrastructures ]

Abstract Magnetic NDE of ferromagnetic steel using spectrum analysis of induced voltage at pick-up coil and magnetic induction has been studied. Magnetic yoke, having an excitation coil and a pick-up coil, was located on a specimen, and a sinusoidal current was applied to the excitation coil for magnetizing the specimen. A voltage induced at the pick-up coil was measured, and the corresponding magnetic in duction was calculated. Then, their frequency spectrums were obtained thorough Fourier analysis. For ...
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NDE of ferromagnetic steel using spectrum analysis of changes in inducedvoltage and magnetic flux density

Toshiba have developed a method of reactor internals replacement and also applied some of methods to improve the residual stress for internals that can't be replaced easily. Ultrasonic shot peening (USP) is a stress improvement method that improves the surface residual stress of heat affected zone by using the vibration of Ultrasonic wave. As th e system of USP is simpler and more compact than the other methods, USP is applicable to welds on the bottom of reactor vessel during reactor internals replacemen...
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Application of Ultrasonic Shot Peening for Internals of Boiled Water ReactorPower Plants

Dr. Mainte, an integrated simulator for maintenance optimization of LWRs (Light Water Reactors) has been developed based on PFM (Probabilistic Fracture Mechanics) analyses in terms of safety, availability and economic efficiency, environmental impact and social acceptance. For the further improvement of maintenance activities, the importance of reducing human errors is often pointed out. Human errors are well recognized to be affected by mental stress conditions. Due to the amendment of Industrial Safe...
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Effects of Human Error and its Reduction Analyzed by Dr. Mainte, Integrated Simulator of Maintenance Optimization of LWRs 2

Dr. Mainte, an integrated simulator for maintenance optimization of LWRs (Light Water Reactors) has been developed based on PFM (Probabilistic Fracture Mechanics) analyses. The concept of the simulator is to provide a decision-making system to optimize maintenance activities for representative components and piping systems in nuclear power plants totally and quantitatively in terms of safety, availability and economic efficiency, environmental impact and social acceptance. For the further improvement ...
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Effects of Human Error and its Reduction Analyzed by Dr. Mainte, Integrated Simulator of Maintenance Optimization of LWRs