Study on fatigue crack propagation of a through-thickness crack subjected to out-of-plane bending

In Japan, fatigue through-thickness cracks have been reported in some steel bridges. Some of the cracks originate due to the effects of out-of-plane bending. In order to perform more efficient maintenance to prevent fatigue damages, it is essential to identify the crack propagation behavior of through-thickness cracks due to stress resulting from out-of-plane bending. The stress intensity factor for through-thickness cracks resulting from bending is an important factor for the assessment crack propagation behavior and has previously been determined by making the assumption that the crack front shape is straight in the thickness direction. However, the actual crack front is curved under the stresses of out-of-plane bending. In this paper, in order to identify the propagation behavior of through-thickness cracking due to out-of-plane bending, a fatigue test on through-thickness cracked plate was carried out. Furthermore, the stress intensity factor along curved crack front was investigated via finite element analysis on a test specimen.