Study of the Stress Intensity Factor of an Unbalanced Rotating Cracked Shaft

Abstract

The components of machines very often present defects that can grow to fatigue cracks when they are submitted to the working solicitations. In the case of shaft,this is particularly important because the catastrophic failures can lead to personal injuries or economic problems. When a cracked shaft rotates, the breathing mechanism appears. The crack opens and closes passing from the open state to the close state with a transition that produces a partial opening. The shafts present additionally misalignments or/and unbalances that alter their normal function. In this paper, we present a Finite Element Method (FEM) study of the influence of the eccentricity in the breathing mechanism of a rotating cracked shaft. The classical Jeffcott rotor model has been chosen for this study. To simulate the rotation of the shaft, different angular positions have been considered. The Stress Intensity Factor (SIF) along the crack front during the rotation has been studied considering different angles of eccentricity. The work allows to know the influence of the unbalance of rotating shafts in the crack breathing mechanism, in the values of the Stress Intensity Factor and in the propagation of cracks.