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Miwa, Yukio; Kaji, Yoshiyuki; Okubo, Nariaki; Kondo, Keietsu; Tsukada, Takashi
Nihon Kikai Gakkai M&M 2007 Zairyo Rikigaku Kanfarensu Koen Rombunshu (CD-ROM), p.236 - 237, 2009/07
In core structural materials of next generation reactors, materials' degradation behavior by neutron irradiation damage and thermal (cyclic) stress should be considered with fair accuracy in design process, because the materials are used under higher temperature gradients and higher neutron flux fields than those in the present light water reactors. In the current experiential design rules, service lives of core structural components were determined by the materials degradation such as the increase of ductile-to-brittle transition temperature after post irradiation examination data. However, other materials degradations such as irradiation-assisted stress corrosion cracking (IASCC), which occurs by the degradation synergistically interacting with radiation hardening, local chemical composition change, swelling and radiation creep, should be considered reasonably in the design process of the next generation reactors, because of the anticipation of the beneficial effects by synergy of radiation damage. To predict material failure by IASCC with reasonable accuracy, in this study, each material degradation phenomenon with different dose dependence was modeled with consideration of radiation induced stress relaxation. In this paper, the models obtained by ion-irradiation experiments and compared by data from neutron irradiation experiments were presented, and the concept of our new evaluation method and the programming code for the failure simulation were outlined.
Okajima, Satoshi*; Honda, Kei*; Sakai, Shinsuke*; Izumi, Satoshi*; Oishi, Kunio*; Kasahara, Naoto
Nihon Kikai Gakkai M&M 2007 Zairyo Rikigaku Kanfarensu Koen Rombunshu (CD-ROM), p.262 - 263, 2007/10
It is well known that fatigue damage accumulates around T-junctions of piping system where two kinds of fluid with different temperatures are mixed. Kasahara et al. have proposed the thermal fatigue evaluation method based on power spectrum density (PSD). However, this method is too complex to practical use in the design stage. In this paper, a simplified damage evaluation guideline is proposed based on the Kasahara et al. method. The damage evaluation procedure from stress PSD is simplified in this guideline.
Kasahara, Naoto; Takasho, Hideki*
Nihon Kikai Gakkai M&M 2007 Zairyo Rikigaku Kanfarensu Koen Rombunshu (CD-ROM), p.421 - 422, 2007/10
For design analysis of perforated plates, axi-symmetric models with equivalent solid plates are conventionally adopted to simplify perforated geometries. ASME Sec.III Appendix A-8000 provides elastic constants for equivalent solid plates. However, no design codes give inelastic material properties of equivalent plates. This study reveals that perforated plates have their own effective stress ratio (ESR), which is a function of geometry and is independent from their materials. ESR enables the general determination method of non-linear equivalent material properties for perforated plates.
Onizawa, Kunio
Nihon Kikai Gakkai M&M 2007 Zairyo Rikigaku Kanfarensu Koen Rombunshu (CD-ROM), p.234 - 235, 2007/10
no abstracts in English
Bubphachot, B.*; Watanabe, Osamu*; Kawasaki, Nobuchika; Kasahara, Naoto
Nihon Kikai Gakkai M&M 2007 Zairyo Rikigaku Kanfarensu Koen Rombunshu (CD-ROM), p.346 - 347, 2007/10
Crack initiation and propagation were observed on perforated plates at elevated temperature by the CCD video camera. The test specimens are made of SUS304 stainless steel, and temperature is kept to be 550
C, and the geometry of the perforated plate specimens are changed by diameter size of the hole. The photographs of all cycles were recorded to obtain number of cycle of crack initiation (
). The results were compared with predictions by the stress redistribution locus (SRL) method and the Neuber's rule's method.