The financial investigation of charitable funds

Isaac, Sherry; Fowler, Ross

doi:10.1017/s002026810003537x

Cited by 2 publications

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Crack Nucleation in Persistent Slipbands

Hunsche

Neumann

1988

Basic Questions in Fatigue: Volume I

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The development of persistent slipband topography, crack nucleation, and crack growth in fatigued copper single crystals was studied by an new section technique, which reveals surface topographies with a resolution of 20 nm. Experiments were performed in air, oxygen, hydrogen, water vapor, high vacuum, and ultrahigh vacuum in order to study the influence of the environment on these processes. The development of persistent slipband topography, including intrusions, extrusions, and the protrusion of the whole persistent slipband, does not depend on environment. Crack nucleation and early propagation, however, do strongly depend on the environment. Intrusions can also be distinguished from crack nuclei by their finite vertex angle of approximately 30 deg. Quantitative data of the average protrusion growth as well as crack growth are presented. Chains of large voids were found in high vacuum and ultrahigh vacuum along the trace of the primary slip plane and are interpreted as remnants of rewelded Stage I cracks.

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Crack Nucleation in Persistent Slipbands

Hunsche

Neumann

1988

Basic Questions in Fatigue: Volume I

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Continuous Observations of the High-Temperature Fatigue in Pure Metals by means of the Microscopic Cine-Camera

Tanaka

Homma

1966

Trans. JIM

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In order to study the high temperature fatigue mechanism in pure metals, an apparatus containing a microscopic cine-camera combined with the fatigue machine was devised for continuous and direct observations of the specimen surface during the fatigue in vacuum at elevated temperatures. A Xenon flash tube was used for illuminating the specimen surface. It was triggered synchronizingly at the same phase of deformation of the specimen. Each cut of the fatigue process was photographed in the time-lapse sequences and also taken in motion picture if necessary.The time-lapse technique was effective in analyzing the fatigue mechanism at elevated temperatures. The results obtained in the specimens of pure aluminum and lead under reversed bending and torsional stresses (1) The grain boundaries move in a way that they are in parallel with the maximum shear stress direction of the specimen axis. Accordingly, grain boundaries of polycrystals are gradually aligned orthogonally with the maximum shear stress direction during the fatigue.(2) Subgrains generate in coarsed grains or in single crystals under reversed stress, and their grain boundaries are aligned orthogonally as in the above case.(3) The surface markings consisting of a series of sharp valleys and peaks due to the deformation band (4) These continuous observations for the fatigue process serve to support the high-temperature fatigue mechanism which has been described in the previous reports.

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The financial investigation of charitable funds

Cited by 2 publications

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Crack Nucleation in Persistent Slipbands

Crack Nucleation in Persistent Slipbands

Continuous Observations of the High-Temperature Fatigue in Pure Metals by means of the Microscopic Cine-Camera

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