This study proposes numerical analysis model considering grain boundary slip and microscopic h eterogeneity in order to estimate stress distribution which effect crack initiation and propaga tion. The FEM-MD combined method for considering grain boundary slip is discussed. The estimat ion of mechanical properties for taking account of microscopic heterogeneity is also discussed....
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Development of Numerical Analysis Model considering Grain Boundary Slip and Microscopic Heterogeneity for the Evaluation of Crack Initiation and Propagation

Temper bead welding (TBW) is one effective repair welding method for the large-scale nuclear power plants instead of post weld heat treatment (PWHT). Consistent Layer (CSL) technique is the theoretically most authoritative method among the five temper bead welding techniques. For TBW, toughness is the key criteria to evaluate the tempering effect. A neural network-based method for toughness prediction in heat affected zone (HAZ) of low-alloy steel has been investigated to evaluate the tempering effect...
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Prediction of Toughness in HAZ produced by Temper Bead Welding of Consistent Layer Technique

In this study, a predictive simulation model coupling weld bead formation and thermal conduction was developed for construction of the method of predicting or evaluating the temperature distribution during temper bead welding. Welding parameters used in the analysis were estimated from experimental welding conditions based on the thermal conduction theory and numerical simulations of previous works. The simulation results were compared with the experimental results under the same welding conditions to ...
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Predictive Simulation Model of Bead Shape and Temperature Distribution during Temper Bead Welding

Even when a macroscopically uniform deformation is applied to a polycrystalline material, the generated microscopic strain distribution will not be uniform due to factors such as the non-uniform grain orientation distribution and grain boundaries. Despite the strong need to accurately measure strain distributions, suitable method is limited. This study proposes an experimental method for estimating strain distributions in polycrystalline materials considering multiple slip systems. Firstly, a polycryst...
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Estimation of Microscopic Deformation Behavior by Digital Image Correlation Method Considering Multiple Slip Systems in Polycrystalline Materials

The SCC susceptibility of the weld metal was evaluated from the maximum depth and number of cracks occurring during the CBB (Creviced Bent Beam) test in high temperature pressurized water using plate specimens cut from shielded metal arc weld metals. When the specimen received a heat treatment consisting of stress relief annealing (SR) for 72 ks at 893 K and subsequent ageing (LTA) for 720 ks at 673 K, however, the significant influences of the increases in C and Nb contents on the SCC susceptibility were...
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Effects of C and Nb Contents on Stress Corrosion Cracking of Shielded Metal Arc Weld Metalfor 600 Type Alloy in High Temperature Pressurized Pure Water

Weld residual stress and distortion affect to fatigue, SCC, static tensile strength, brittle fracture, or other failures in various components. Computational method is useful for evaluating weld residual stress and distortion as well as direct measuring method. Re cently developed methods by the authors for innovative numerical simulation of weld residual stress in various scales and fields are introduced. A lot of applications of the computational approach to weld residual stress evaluation are expected ...
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Innovative Computational Simulation of Weld Residual Stress from Mega- to Micro-Structures

Abstract For the last couple of years, issue of defects in Alloy 600 weld lowered the capacity factor of nuclear power plants. To apply newly developed repair technique, like temper-bead welding that has not been prescribed in technical standards, it is necessary to evaluate its technical applicability to the requirement. In the previous cases, this process has been completed by issuance of no action letter for specific area and condition, utilizing implementation process, such as confirm testing by J...
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Study on implementing newly developed repair welding technique within a limited time frame for nuclear power plant

In this study, a semi-nondestructive procedure for stress strain curve estimation was developed using instrumented indentation technique. Additionally, to estimate local stress ? strain curve in the welds with mechanical heterogeneity, a relation between spherical indentation size and measuring range of mechanical property was quantified by using finite element analysis of spherical indentation technique. The developed technique was applied to estimate mechanical properties of low alloy steel and its weld...
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Study on Mechanical Characterization of Steel and Its Welds through Instrumented Indentation Technique

The Deep hole drilling (DHD) technique has received much attention as a measurement method for through-thickness residual stress. In the past, however, the traditional DHD technique has ignored the effects of plastic deformation around a reference hole, which has been occurred in the DHD procedure. Therefore, the evaluation results obtained by the traditional DHD technique can have accuracy problem. When residual stress is large, the problem is serious because the area which deform plastically. In this...
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A highly accurate residual stress measurement method by the deep hole drilling technique considering the effect of plastic deformation

In order to reutilize nuclear power generation and maintain their presence, it is important to take actions based on assumptions beyond "safety myth". For example, in the field of SCC, long term reliability may be further assured based on evaluation under severer condition than the usual operating environment. Since such severe conditions cannot be reasonably simulated by the experiment in the laboratory, it is effective to utilize numerical simulation as reported in the previous paper. This paper rep...
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Development of an evaluation method utilizing numerical simulation to assure long-term reliability of residual stress improvement by surface treatment