Soluciones del factor de intensidad de tensiones para fisuras elípticas internas en barras cilíndricas sometidas a esfuerzos de tracción

Resumo

There is a large number of applications in which internal defects, such as pores or inclusions, are the main cause of the fatigue cracks initiation in round bars. This paper presents a set of stress intensity factor solutions for internal elliptical cracks in round bars subjected to tensile loads. Solutions have been obtained from a 3D finite element analysis, and are presented in a tabulated form as a function of three dimensionless parameters: the crack size to the radius of the round bar, the crack aspect ratio of the elliptical flaw and its relative position in the cross area. In order to validate the numerical model developed, some extreme situations are compared with solutions of embedded elliptical flaws in different geometries available in the literature. Afterward, and in order the fatigue analysis of this geometry to be complete, the conditions for the recategorization of the internal elliptical crack to a semi-elliptical surface crack are defined, that allows the fatigue crack growth calculation to be continued as the internal defect reaches the surface of the round bar. Finally, a comparison with experimental results of the evolution of fatigue crack growth initiated from internal defects in round bars subjected to tensile loads is presented. This experimental validation allows the capacity of the solutions provided for the analysis of growth of fatigue cracks in this geometry to be evaluated.