Spoluautoři LAZAROVA Tsvetelina, ANGELOVA Donka, GEORGIEV Alexander

Fatigue in Cr–Mo steel, JIS SCM435, candidate for use in fuel cell vehicles is investigated at different test frequencies in two groups of hydrogen charged and uncharged specimens under tension-compression fatigue and stress ratio R= −1. Specimens are machined in hour-glass shape with artificial hole from which initial cracks start their propagation. The obtained fatigue data of each frequency are presented in plots “Crack length, a - Number of cycles, N” and “Fatigue crack growth rate, da/dN – Crack length, a”. A mathematical model consists of double-parabolic-linear-curve is found for the data in the presentation “Fatigue crack growth rate, da/dN – Crack length, a” and a comparison made between those curves for the different frequencies. The adequacy of modelling is checked and proved by comparison between experimental fatigue lifetimes and the calculated by the model.