Effects of a single tensile overload on fatigue crack growth in a 316L steel

Abstract

The aim of this study was to investigate the effects of a single tensile overload on subsequent fatigue crack growth in a 316L stainless steel. Fatigue tests were conducted under the plane stress condition, and further supplemented with compliance measurements and field emission scanning electron microscopy (FESEM) observations. Effects of a tensile overload, e.g. initial acceleration and subsequent retardation of fatigue crack growth, were explained and quantified by FESEM and compliance measurements. The FESEM observations suggest that the initial crack growth acceleration stems from void and quasi‐cleavage fracture within the fatigue damage zone in the vicinity of the crack tip. Systematic compliance measurements taken during fatigue crack growth suggest that the overall crack growth retardation is related to strain hardening and residual compressive stress produced by the plastic deformation associated with the tensile overload.

Development of a Novel Approach for Fatigue Life Prediction of Structural Materials

“…With further application of loading cycles the crack growth rate reaches a stable growth curve. Such behavior has been observed previously from the experiments on 316L stainless steel [20] and the crack acceleration upon application of overload was attributed to the cracking from voids within the overload plastic zone.…”

“…This is a noticeable phenomenon which distinguishes this material from other alloys discussed in present work. Short period of post-overload crack growth acceleration has been previously observed for other metallic materials [20,51], however the magnitude of such acceleration was much lower. After initial acceleration, the crack growth slows down reaching a minimum point.…”

“…The fatigue crack growth results predicted by using Eqs (14)(15), (17), (19)(20)(21) and (23)(24)(25) are shown in solid lines in Figs. 16 and 18 for the specimens subjected to the overloading and high-low sequential loading conditions.…”

“…Therefore fi=\ is used in Eqs. (19) and (20). For 7075-T651 aluminum alloy under consideration, the yield stress {cr y ) is estimated to be 420.3 MPa.…”

“…It was shown that the introduction of the hydrogen into the metastable austenitic steel decreased the rate of crack propagation. An effect of the application of a single tensile overload on crack growth rate in 316L steel was investigated by Wheatley et al [20]. A short period of crack growth rate acceleration after the application of the overload was observed.…”