Failure analysis of a locomotive turbocharger main-shaft

A failure investigation has been conducted on a locomotive turbocharger main shaft. The fracture position is located at a sharp edged groove between two journals with different cross-sectional area. Fractography investigation indicates that the rotating bending fatigue is the dominant failure mechanism of the main-shaft. Detailed metallurgical analysis indicates the root fillet region of the groove had subjected to abnormal high-temperature resulting from the intense friction between the bearing-sleeve and the assisted pushing bearing, which makes the fatigue strength of the root fillet region of the groove decrease. Over-small root fillet radius of the groove by which stress concentration is created facilitates the fatigue cracks to initiate in the root fillet region. (c) 2008 Elsevier Ltd. All rights reserved.