Propagation of microcracks at stress amplitudes below the conventional fatigue limit in Ti6Al4V
Authors: Hines J.A.; Lütjering G.
Source: Fatigue & Fracture of Engineering Materials & Structures, Volume 22, Number 8, August 1999 , pp. 657-665(9)
Abstract:Fatigue crack growth below the conventional fatigue limit was examined in Ti6Al4V in two different microstructural conditions, bi-modal and fully lamellar. Tests conducted at R = -1, at room temperature and in air showed that there is a stress dependency in the da/dNK behaviour in both microstructures. The increasing crack front roughness associated with increasing crack size results in a decrease in the crack growth rate relative to the crack growth rate in a single grain. The da/dN vs. K lines were drawn for each crack size and a thresholdK was determined using the intercept of the lines with da/dN = 10-10 m cycle-1. These values were used to construct modified TakahashiKitagawa diagrams to predict microcrack growth below the fatigue limit for each microstructure. A comparison of the two microstructures indicated differences in behaviour in microcrack and macrocrack growth that were explained by differences in crack front roughness at a given crack size.
Document Type: Research article
Publication date: 1999-08-01