Papers by Keyword: Nanovoids

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Authors: Mark Knop, Nick Birbilis, Stan Lynch
Abstract: The processes involved in corrosion fatigue in general are briefly outlined, followed by a brief review of recent studies on the effects of cycle frequency (rise times) and electrode potential on crack-growth rates at intermediate ΔK levels for cathodically protected high-strength steels. New studies concerning the effects of fall times and hold times at maximum and minimum loads on crack-growth rates (for Kmax values below the sustained-load SCC threshold) are presented and discussed. Fractographic observations and the data indicate that corrosion-fatigue crack-growth rates in aqueous environments depend on the concentration of hydrogen adsorbed at crack tips and at tips of nanovoids ahead of cracks. Potential-dependent electrochemical reaction rates, crack-tip strain rates, and hydrogen transport to nanovoids are therefore critical parameters. The observations are best explained by an adsorption-induced dislocation-emission (AIDE) mechanism of hydrogen embrittlement.
Authors: Terry C. Lowe
Abstract: Recent research on the fatigue properties of nanostructured metals and alloys has shown that they generally possess superior high cycle fatigue performance due largely to improved resistance to crack initiation. However, this advantage is not consistent for all nanostructured metals, nor does it extend to low cycle fatigue. Since nanostructures are designed and controlled at the approximately the same size scale as the defects that influence crack initiation attention to preexisting nanoscale defects is critical for enhancing fatigue life. This paper builds on the state of knowledge of fatigue in nanostructured metals and proposes an approach to understand and improve fatigue life using existing experimental and computational methods for nanostructure design.
Authors: M. Ponga, Ignasio Romero, M. Ortiz, M.P. Ariza
Abstract: Tensile failure of metals often occurs through void nucleation, growth and coalescence. This work is concerned with the study of plastic nanovoid cavitation in face-centeredcubic (FCC) crystals at finite temperature. In particular, the Quasicontinuum (QC) method,suitably extended to finite temperatures, is taken as the basis for the analysis. We specificallyfocus on nanovoids in copper single crystals deforming in uniaxial and triaxial tension. Thecomplex structure of dislocations around the nanovoid and the evolution of stress, deformationand temperature of the sample is described in the present work.
Authors: Alexander Stronski
Abstract: Defect configuration of Ge5As37S58 chalcogenide glasses was studied by positron annihilation lifetime spectra (PALS). Size of nanovoids was determined using Liaos formula for radius of nanovoids in spherical approximation. Peculiarities of structural features were obtained from Raman spectra.
Authors: Koji Inoue, Yasuyoshi Nagai, Yuzuru Sasaki, Zheng Tang, Hideaki Ohkubo, Masuyuki Hasegawa
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