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A. Kamei

Bio: A. Kamei is an academic researcher from Tohoku University. The author has contributed to research in topics: Stress intensity factor & Crack closure. The author has an hindex of 7, co-authored 12 publications receiving 197 citations.

Papers
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Journal ArticleDOI
TL;DR: In this article, a power type expression for fatigue crack growth was derived and the frequency dependence for this power function type was obtained, and reasonable agreement with experimental results from the literature was obtained.
Abstract: Dislocation group dynamics theory is used to deduce a power type expression for fatigue crack growth. In general, the results reflect only a single rate process, and thus one activation energy which is small compared to those in usual rate processes. The frequency dependence for this power function type fatigue crack growth rate was also obtained, and yield reasonable agreement with experimental results from the literature.

77 citations

Journal ArticleDOI
TL;DR: In this article, a simulation of the dynamic behavior of linear arrays of edge dislocations emitted from a source under a constant rate τ of application of stress for the case when stress τ and velocity v are related by the expression v = Mτm.
Abstract: The computer simulation is presented of the dynamic behaviour of linear arrays of edge dislocations emitted from a source under a constant rate τ of application of stress for the case when stress τ and velocity v are related by the expression v = Mτm . It is shown that the number N of dislocations emitted is controlled only by the dynamic factor: τ ≈ τ(m+1/m+2) t, where t is time. For large values of N, N is given by A0η m+1, where A0 is a material constant. The dynamic behaviour, such as the position of, the effective stress on, and the velocity of the lead dislocation is deduced. The possibility of the application of the results to the kinetic theory of fatigue crack propagation is discussed.

35 citations

Journal ArticleDOI
TL;DR: In this article, the energy unstable and critical local stress requirements for low-stress brittle fracture of notched specimens were derived based on the combined micro-and macro fracture mechanics, that is, the two requisites necessary for the crack propagation.

25 citations

Journal ArticleDOI
Takeo Yokobori1, M. Yoshida1, H. Kuroda1, A. Kamei1, S. Konosu1 
TL;DR: In this article, the basic equations for the general configuration of a crack and a slip band are obtained based on micro-and macro fracture mechanics, and the coefficients of mutual interaction in stress intensity factors are calculated for the critical configuration of them corresponding to the low stress brittle fracture.

13 citations


Cited by
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TL;DR: In this paper, various criteria and parameters have been proposed in the literature for predicting mixed-mode crack growth directions and rates, and the physical basis and limitations for each criterion are briefly reviewed, and corresponding experimental supports are discussed.

332 citations

Journal ArticleDOI
TL;DR: In this paper, the fracture mechanics stress intensity, K, measured for the cleavage strength of carbon steel by Professor Yokobori and colleagues, at Tohoku University and elsewhere, is shown to follow a Hall-Petch dependence on average grain diameter, l, in accordance with the model-based relationship K = c's 1 2 [σ 0 +kl −1 2 ] for which c' is a numerical factor, 5 is the effective length of the local plastic zone associated with unstable crack growth, σ 0 is a friction stress for appropriate dislocation movement within the poly

238 citations

Journal ArticleDOI
TL;DR: In this article, the effects of annealing and changes in stress state on the toughness of Zr-Ti-Ni-Cu-Be alloy have been determined in amorphous state, both notched and fatigue precracked specimens have been tested.
Abstract: The effects of annealing and changes in stress state on the toughness of both 4 mm thick and 7 mm thick plates of a Zr-Ti-Ni-Cu-Be alloy have been determined In the amorphous state, both notched and fatigue precracked specimens have been tested The effects of changing the notch root radius from a fatigue precrack to that of a blunt notch on the fracture toughness are dramatic The toughness increases from approximately 179 ± 18 MPa√m in the fatigue precracked specimens to in excess of 130 MPa√m in the notched specimens These results are compared to similar tests on a range of structural materials, including aluminum alloys, steels, Ti alloys, and metal matrix composites The increased toughness obtained by increasing the notch root radius in this bulk metallic glass far exceeds that typically observed in other structural materials Possible reasons for this are presented In addition, the effects of changes in loading rate and various annealing treatments on the toughness are presented and rationalized via both crack path and fracture surface observations Annealing of this bulk metallic glass at temperatures below Tg produces increases in strength/hardness, rapid decreases in toughness, and a corresponding change in the fracture morphology Changes in loading rate did not have a significant effect on the toughness for either notched or fatigue precracked specimens

107 citations