Stress-intensity factor solutions for embedded elliptical cracks in round bars subjected to tensile load

Abstract

In this paper, stress-intensity factor solutions are presented for an embedded elliptical crack in a round bar subjected to tensile load. The stress-intensity factors (SIF) are presented in a tabulated form and were obtained from three-dimensional finite-element analyses of this crack configuration. The solutions provide the stress-intensity factor as a function of three dimensionless parameters representative of the crack size, the crack aspect ratio of the elliptical flaw and its relative position in the cross section. The dimensionless parameters cover ranges that allow most internal flaw shapes in practice to be considered. In order to validate the numerical model developed, some particular cases are compared with solutions of embedded elliptical flaws in different geometries available in the literature. Afterwards, a sequential methodology for fatigue crack growth is presented, including the conditions for the recategorization from the internal elliptical crack to a semi-elliptical surface crack. A comparison of the predicted crack paths with experimental results of fatigue crack propagation initiated from internal defects in round bars is also presented. This experimental validation shows the capability of the proposed SIF solutions for the study of the fatigue crack propagation initiated from internal defects in this geometry.