Progressive deformation (ratcheting) is one of the failure modes by excessive seismic loadings. These occurrence conditions seem to be similar to the conditions for thermal ratcheting which is called Bree’s diagram. After experiments for ratcheting have done, there were similar results with Bree diagram in some frequency of input waves and not in other frequency. This paper shows detail results by numerical analysis and gives three frequency regions to clarify different characteristics in dynamic load...
英字タイトル:
Progressive deformation by dynamic loadings and effects of frequency

According to the design standards of nuclear equipment, ductile fracture is assumed as the failure mode due to monotonic loading in the elastic-plastic region, but it is known that failure mode called local failure occurs at the part with high stress triaxiality. In the past, the authors have proposed a fracture surface that can uniformly evaluate transition of failure modes from ductile fracture to local failure. This research proposes the extension method of the fracture surface to creep region. ...
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Investigation on extension of local failure evaluation method in plastic region to creep region

The failure mode so called a local failure could occur at a specific structural discontinuities of pressure vessels. Local failure, which is a type of ductile fracture, generally occurs under multiaxial stress conditions. In this paper, tensile tests and elastic plastic finite element analyses for smooth and notched specimens were performed to study a mechanism of local failure. From these investigation, it was concluded that the local failure occurs under high triaxial stress conditions and this condit...
英字タイトル:
Study on Mechanism of Local Failure and Proposal of Fracture Surface Based on the Mechanism

In nuclear power plants, a lot of failure cases by high cycle thermal fatigue have been reported, which is induced by temperature fluctuation of the coolant. To ensure the safety of the nuclear power plants, the thermal fatigue failure should be prevented adequately. Thus The Japan Society of Mechanical Engineers (JSME) published the high cycle thermal fatigue evaluation guideline. In the guideline, it is proposed that the structural integrity can be judged by the location of thermal stratification, which...
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Study on the mechanism of stress generation of straight pipe and elbow pipe which has thermal stratification

The conventional purpose in the field of structural strength has been to prevent damage to design basis events (DBE). For beyond design basis events (BDBE), it is necessary to mitigate the impact on safety on the premise that damage will occur. The authors propose a mitigation method that suppresses the consequence into a fracture mode with a large impact by reducing the load due to a fracture with a small impact on safety. We will introduce the research results for individual component, extend the applicab...
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New approach to beyond design basis events in structural strength field

Experimental and analytical study was carried out with notched specimens which simulated multiaxial stress state in structural discontinuity, in order to reveal the mechanism and dominant parameters of “local failure”. Both the tensile test and finite element analyses (FEA) exhibited, notch strengthening. Furthermore, in the tensile test, failures of notched specimens were progressed from inside, where hydrostatic stress showed the maximum value in the FEM, whereas Mises stress did not show the maximum valu...
英字タイトル:
Experimental and Analytical Study on Dominant Parameters of Local Failure of Structures