Local strain measurement for prediction of fatigue macrocrack initation in notched specimens

摘要

On the basis of direct measurement of the opening displacement of the notch contour the procedure of the evaluation of local elastoplastic strains range, Δε{sup}*, is developed. The experimental values of Δε{sup}* are compared with the calculational data using known equations by Neuber, Glinka, etc. It is shown that for Δε{sup}* < 2% the experimental and calculational values are in good agreement but only in the case when the gradient of strains near the notch tip is taken into account. The proposed experimental method is used for the prediction of period N{sub}i to fatigue macrocrack initiation in specimens of a complicated shape.