Abstract:

In order to comprehensively analyze the size effect of notched samples,the fatigue performance of notched samples was experimentally investigated for two kinds of materials ( 45# steel and Q235 steel) under cyclic tension. The results show that,for geometrically similar specimens,the effect of notch shape on the fatigue life can be neglected because it is too slight,and that there exists a thickness effect apart from the stress gradient,namely a critical thickness exceeding which the fatigue life may reduce. Moreover,by introducing the characteristic parameter L /G that represents the effect of geometric size on the fatigue performance,the test results of fatigue strength of geometrically similar specimens are fitted and compared with the calculated values obtained by the Peterson method,finding that the proposed fitting expression is more effective. Finally,an empirical formula of size coefficient of notched samples under tension,which well accords with the actual situation,is presented according to the equation of fatigue strength and the definition of size coefficient.

Key words: geometrically similar specimen, notched sample, size coefficient, gradient effect, thickness effect