1Faculty of Engineering, Kyoto University, Kyoto
The exo-electron emissions from metal surfaces subjected to repetitive stresses have been studied using an electron-multiplier counting system, and the environmental effects on fatigue strength are discussed from the viewpoint of the exo-electron emissions.
The exo-electrons from metal surfaces are extraordinarily increased by repetitive stresses and take a maximum value at a fixed number of cycles (Ne max). Thereafter the number of emitted electrons gradually decreases and becomes almost constant. The decay of emission rate after the release of stress repetitions is very fast, its half time being shorter than 1 sec. The decay behaviors at cycle numbers before and after Ne max are defferent; the decay is remarkably fast at the beginning of fatigue cycles. The decay of the emission rate from the surfaces subjected to fatigue damages is, however, smaller than that from the mechanically processed surfaces, which shows the more persistent emission characteristics caused by the former than by the latter. The pulse height distribution of emitted electrons is hardly affected by the progress of fatigue damage. However, sufficient allowances should be made for the role of exo-electrons in the environmental effects on fatigue strength, in view of the energy height of exo-electrons. The number of exo-electrons per cycle increases drastically with increasing stress cycle frequency.
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