A B S T R A C T The growth rate of main cracks at different temperatures and under the static load has been investigated in aluminum and zinc foils. The observation of the crack growth during loading has been made by means of general microfilming as well as by electron microscope. It has been shown that the growth of main cracks occurs by means of the initiation, development, and coalescence of secondary microcracks which arise at the tip of the main one. The interaction and the growth of cracks of all dimensions, from submicroscopic and up to macroscopic, takes place at constant rate, without any steps. The rate depends exponentially upon the applied stress and the reciprocal test temperature; the activation energy of the crack growth process is near to that of sublimation for the metals.

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