METHOD FOR DETERMINING CRACK GROWTH RATE DUE TO CYCLIC LOADS Russian patent published in 2012 - IPC G01N3/32 

FIELD: machine building.

SUBSTANCE: length L of crack is measured in each N loading cycle. Experimental L(N) dependence is obtained. Crack resistance coefficients C and n are calculated with possibility of further determination of crack growth rate in a part due to cyclic loads under real-time conditions of its operation. For calculation of crack resistance coefficients C and n, measurements in which crack length growth rate is less than 10^-3 mm/cycle are chosen. Maximum size of length L of the crack in the chosen measurements is accepted as maximum value that corresponds to upper boundary of section of stable crack growth. Crack resistance coefficients C_k and n_k are determined using iteration method, where k - iteration number. Relationship of C_k and n_k and the number of the rest points in k iteration is built, and a point corresponding to horizontal asymptote of the corresponding relationship is determined. Values C_k and n_k at the above point are accepted as final values of crack resistance coefficients C and n, and size of length L of crack at that point is accepted as minimum value, which corresponds to lower boundary of section of stable crack growth.

EFFECT: improvement of accurate determination of crack growth rate in parts due to cyclic loads owing to increasing the validity of determination of crack resistance coefficients C and n without any additional costs.

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