Growth of very long “short cracks” initiated at holes

Effect of small defect orientation on fatigue limit of carbon steels

“…It is also noted that the length of non-propagating crack was a bit longer in JIS-S15C than in JIS-S45C, both of which are nearly independent of the tilt angle. The earlier results suggest the existence of a crack arrest such as crack closure development [32][33][34] and grain boundary barrier [35][36][37][38] irrespective of the tilt angle of defect. Figure 8 shows scanning electron microscope images of fracture surfaces observed in JIS-S45C.…”

Microstructural model for predicting high cycle fatigue strength in the presence of holes under proportional biaxial loading

“…Experimental confirmation of these facts has been presented recently by Lorenzino and Navarro [28,29]. The initiation and growth behavior of very long microstructurally short fatigue cracks formed at circular holes in specimens subjected to axial fatigue loading was extensively studied by these authors.…”

“…The results reported by them, although very interesting in themselves would only be relevant for our study in the case of very big notches compared to the microstructure, where cracks that are small with respect to R are, nonetheless, large compared to the grain size: these are ''large cracks'' and their growth is governed by linear elastic fracture mechanics. The problem we address in our paper is, however, completely different: we are analyzing the fatigue limit conditions and therefore we are studying cracks that are small in themselves and compared with the microstructure in ''normal'' materials (however see [28][29][30] for very long ''short cracks''). Their behavior, as is very well known, is definitely not well described by LEFM and thus the necessity of bringing into the picture a short crack growth model.…”

A modification of UniGrow 2‐parameter driving force model for short fatigue crack growth

“…In fact, most structures and components contain various forms of cracks or defects at smaller length scales because of material imperfection, fabrication, and assembly conditions. 15,[19][20][21][22][23][24] Those detailed investigations were aimed to shed light into the characterization of crack behaviour controlling factors associated with material and environmental, loading conditions, etc. However, the design of most structures is still based on crack initiation that do not account for such unavoidable small defects.…”

“…Although long cracks may be detected and monitored, short cracks are practically undetectable by current NDI techniques. 15,[19][20][21][22][23][24] Recently, many modelling efforts have been also made to evaluate fatigue crack behaviours of materials in the SC regime. As a result, components may be overdesigned using a high factor of safety, or their service life expectancy may become unreliable in the presence of such small defects.…”