An experimental study of loading parameters effect on fatigue crack closure in 12NC6 steel

► Analysis of the influence of several parameters on fatigue crack closure. ► Experimental study of Pmax levels influence on crack closure and on FCG reported. ► Verify of the crack opening loads measurements influence on the crack propagation rate. ► Relationship between the opening loads and the fatigue crack length. ► Crack closure can be influenced by several factors, R, Kmax, ΔK. In this paper, the fatigue crack closure (FCC) phenomenon was experimentally revealed using the back face strain gauges technique. The effects of the loading parameters on FCC have been investigated on 12NC6 heat treated steel. Four yield stresses values have been tested. The loading conditions were chosen to have the stress intensity factor range ΔK between 17 and 30MPam with four load ratio values: 0.05–0.1–0.3 and 0.5. In this study, the closure stress intensity factor Kcl is approximately constant for all load ratio values (R). The expression describing the evolution of the closure parameter U is obtained as a function of both the R and Kmax.