Open Access
ABSTRACT
A.Toshimitsu Yokobori Jr1,*, Go. Ozeki1, Toshihito OHMI1,2, Tadashi Kasuya3, Nobuyuki Ishikawa4, Manabu Enoki3, Satoshi Minamoto5
The International Conference on Computational & Experimental Engineering and Sciences, Vol.22, No.2, pp. 119-119, 2019, DOI:10.32604/icces.2019.05177
Abstract Authors have been founded that hydrogen diffusion and concentration behavior for notched specimens of multi-materials with space distribution of various material properties were dominated not only by the space gradient of hydrostatic stress caused by the notch tip, ∇σp but also by that of diffusion coefficient, ∇D(T, HV, εp) caused by space distributions of temperature, hardness and plastic strain due to multi-materials. In this research, on the basis of our proposed coupled analysis of heat transfer induced thermal stress driven hydrogen diffusion, the effect of ∇D(T, HV, εp) ) on hydrogen concentration behavior was clarified by solving the problem of… More >
Open Access
ABSTRACT
Tadashi Kasuya1,*, A. Toshimitsu Yokobori Jr2, Nobuyuki Ishikawa3, Manabu Enoki1, Satoshi Minamoto4
The International Conference on Computational & Experimental Engineering and Sciences, Vol.22, No.2, pp. 120-120, 2019, DOI:10.32604/icces.2019.05227
Abstract Weld cold cracking is categorized as hydrogen cracking. To assess cold cracking susceptibility of steel HAZ (heat affected zone), it is necessary to estimate local hydrogen content and residual stress at a weld root that are in general numerically calculated by FEM and/or FDM. To conduct numerical calculations, physical and mechanical properties such as diffusion coefficient of hydrogen in steel are necessary. In this work, we have developed empirical formulae to calculate HAZ hardness, hydrogen diffusion coefficient and tensile properties. The present empirical formula of HAZ hardness is expressed using chemical compositions of a welded steel and weld thermal history.… More >
Open Access
ABSTRACT
Hitoshi Izuno1, Masahiko Demura1,*, Masaaki Tabuchi2, Yohichi Mototake3, Masato Okada1,3
The International Conference on Computational & Experimental Engineering and Sciences, Vol.22, No.2, pp. 121-121, 2019, DOI:10.32604/icces.2019.05270
Abstract An accurate creep deformation model is needed for detailed description of creep behavior of high temperature structural materials, e.g., Grade 91 steels used in boiler tubes of thermal power plants. Two types of creep constitutive equations are known, as follows: the one, e.g., modified theta method, assumes the existence of a steady state; and the other, e.g., theta method, does not. So far, both types have been selected on a case by case basis and there is no consensus on whether or not the steady state should be assumed even if limited in the Grade 91 steels. In this study,… More >
Open Access
ABSTRACT
Dmitry S. Bulgarevich1,*, Susumu Tsukamoto1, Tadashi Kasuya2, Masahiko Demura1, Makoto Watanabe1,3
The International Conference on Computational & Experimental Engineering and Sciences, Vol.22, No.2, pp. 122-122, 2019, DOI:10.32604/icces.2019.05271
Abstract The microstructure of steel greatly determines its mechanical properties/performance and holds information on chemical composition and processing history. Therefore, quantitative analysis of optical or SEM images on formed microstructure phases is one of the primary interests for metallurgy. So far, such analyses in laboratories are done manually by experts and are very time consuming. However, with modern microscopy techniques of automated image acquisitions over the large imaging areas and even by using of sample slicing for three-dimensional imaging, the amount of image data could be overwhelming for manual examinations. In this respect, there is a possibility that machine learning (ML)… More >
Open Access
ABSTRACT
Masahiko Demura1,*, Junya Sakurai1,2, Masayoshi Yamazaki1, Junya Inoue1,2
The International Conference on Computational & Experimental Engineering and Sciences, Vol.22, No.2, pp. 123-123, 2019, DOI:10.32604/icces.2019.05303
Abstract Creep is a complicated and time-dependent phenomenon, which is affected by the initial state and the degradation of microstructures. It is thus considered that the information about the microstructure is essential to predict the creep rupture time. On the other hand, there is a strong, practical need for the prediction without the investigation of microstructures nor the disclosure of the detailed process that should control the initial microstructures. In this study, we examined how modern machine learning technique can help to predict the creep rupture time in heat-resistant ferrite-type steels without the direct information about the microstructures and the process… More >
Open Access
ABSTRACT
Takayuki Shiraiwa*, Fabien Briffod, Manabu Enoki
The International Conference on Computational & Experimental Engineering and Sciences, Vol.22, No.2, pp. 124-124, 2019, DOI:10.32604/icces.2019.05311
Abstract The purpose of this study is to evaluate fatigue performances of welded structures using numerical simulations. The fatigue life of welded joint is complicatedly affected by various factors such as geometries, defects, residual stress and microstructure. Conventional fatigue life assessments are generally based on fracture mechanics and predict the fatigue life for long crack propagation. In order to predict the total fatigue life more accurately, it is necessary to consider the lifetime for crack initiation and microstructually short crack (MSC) growth. In this study, a numerical framework to predict the fatigue life including crack initiation, MSC growth and long crack… More >
Open Access
ABSTRACT
Fabien Briffod*, Alexandre Bleuset, Takayuki Shiraiwa, Manabu Enoki
The International Conference on Computational & Experimental Engineering and Sciences, Vol.22, No.2, pp. 125-125, 2019, DOI:10.32604/icces.2019.05319
Abstract The fatigue behavior of metallic materials is a multi-scale problem (from a time and length-scale perspective) intimately influenced by microstructural features that determine the early stages of crack propagation. Prediction of fatigue life is traditionally based on the evaluation of macroscopic mechanical fields at the structure level and on the application of empirical rules. However, these structure-oriented methods are material-specific and do not consider the material variability at lower scales. Hence, reliable prediction of fatigue performances and its variability requires on one side the characterization and quantification of early damage mechanisms and on the other side the incorporation of local… More >
Open Access
ABSTRACT
Hideaki NISHIKAWA*, Yoshiyuki FURUYA
The International Conference on Computational & Experimental Engineering and Sciences, Vol.22, No.2, pp. 126-126, 2019, DOI:10.32604/icces.2019.05354
Abstract Fatigue life is determined by microscopic fatigue crack initiation and growth. Since fatigue crack is generally initiated on the slip plane of microstructure and propagated by slip deformation of the crack tip, fatigue life should depends on microstructure. To computationally simulate the effect of microstructure on fatigue property, it is necessary to understand microstructural small fatigue crack initiation and growth behavior. Although Ti-6Al-4V alloy has superior fatigue strength, fatigue strength of forged pancake, used for such as airplane engine, is normally lower than that of rolled alloy. It is possibly comes from microstructural difference, such as micro-texture. However, it is… More >
Open Access
ABSTRACT
Hiromichi Nagao1,2,*, Shin-ichi Ito1,2, Tadashi Kasuya3, Junya Inoue4,3
The International Conference on Computational & Experimental Engineering and Sciences, Vol.22, No.2, pp. 127-127, 2019, DOI:10.32604/icces.2019.05384
Abstract Data assimilation (DA) is a computational technique to integrate numerical simulation models and observational/experimental data based on Bayesian statistics. DA is accepted as an essential methodology for the modern weather forecasting, and is applied to various fields of science including structural materials science. We propose a DA methodology to evaluate unobservable parameters involved in multi-phase-field models with the aim of accurately predicting the observed grain growth, such as in metals and alloys. This approach integrates models and a set of observational image data of grain structures. Since the set of image data is not a time series, directly applying conventional… More >
Open Access
ABSTRACT
Junya Sakurai1, Junya Inoue2,3,4, Masahiko Demura4,*, Yoichi Mototake5, Masato Okada4,5, Masayoshi Yamazaki4
The International Conference on Computational & Experimental Engineering and Sciences, Vol.22, No.2, pp. 128-128, 2019, DOI:10.32604/icces.2019.05408
Abstract According to the inherent creep strength concept proposed by Kimura et al., microstructural strengthening effect is expiring after a long-term creep deformation at high temperature. In the region, the solid solution hardening effect becomes dominant so that the rupture time is expected to be a simple function of chemical composition and test conditions. In fact, they found that there was a linear relationship between logarithm rupture time and the amount of Mo for the carbon steel JIS STB410. They also found the positive correlations of Cr and Mn to the logarithmic rupture time. However, it is difficult to specify the… More >
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