Prediction of fatigue crack propagation lives of turbine discs with forging-induced initial cracks Jianfu Hou ⇑ , Ron Wescott, Marco Attia Aerospace Division, Defence Science and Technology Organisation (DSTO), 506 Lorimer Street, Fishermans Bend 3207, Australia article info Article history: Received 12 December 2013 Received in revised form 15 July 2014 Accepted 30 August 2014 Available online xxxx Keywords: Turbine disc stress analysis Turbine disc cracking Forging flaw 3D crack growth prediction abstract This paper presents a study on residual life assessment of turbine discs in a military aircraft engine that were found to be susceptible to fatigue cracking failure due to forging flaws formed in the original manufacturing process. As these flaws were not considered in the original life assessment, it is important to predict the residual lives of affected turbine discs and to determine the safe inspection intervals in order to prevent possible failures during service. The examination of the cracked disc revealed that the flaw was formed during the hammer forging. A systematic analysis approach was developed to analyse all four turbine discs and to predict the fatigue crack growth (FCG) rates by using advanced finite element (FE) and numerical FCG predictions. The critical locations for these discs were found to be on the aft neck face of disc web. The predicted FCG for the cracked disc correlated reason- ably well with the striation counting from the cracked disc. The residual lives for represen- tative discs at the critical location and associated inspection intervals are determined for life management of the affected turbine discs. Crown Copyright Ó 2014 Published by Elsevier Ltd. All rights reserved. 1. Introduction Turbine discs in aircraft engines experience both cyclic and sustained centrifugal and thermal loads due to the nature of the engine operating cycles. Consequently, most turbine discs are failure-critical components and their design life limits are often determined by the accumulation of low cycle fatigue (LCF) damage during service [1,2]. Therefore, prediction of fatigue damage and the associated crack growth rates are very important in determining either the likely failure modes or the com- ponent replacement intervals to prevent failures under normal operating conditions [3,4]. In general, common failure locations for turbine discs under normal operating conditions are often at the critical design features such as bolt holes and disc firtrees [4,5] and the design stress and life limits are calculated based on these locations. There are a number of investigations devoted to both failure analyses and life assessment of turbine discs in literature. The numerical stress predictions for disc/blade attachment area were described by Meguid and Papanikos et al’s work [5,6]. The numerical crack growth prediction for disc fir-tree root cracks under spin rig testing condition was described by Claudio et al. [7]. Hou et al. [8] described the experimental and nonlinear numerical analysis approach for the investigation of a turbine blade failure at the blade fir-tree. The fatigue fracture of turbine components was also described in the work by Bhaumik [9] and Park et al. [10]. In the work by McEvily [11], the unexpected engine fatigue failures were found to be the main cause for crash of aircraft. Witeck [12] carried out a failure investigation of turbine disc at the disc/blade attachment by utilising a non- linear FE method to determine the high stress zones under operating condition in order to identify the actual failure location. http://dx.doi.org/10.1016/j.engfracmech.2014.08.015 0013-7944/Crown Copyright Ó 2014 Published by Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Engineering Fracture Mechanics xxx (2014) xxx–xxx Contents lists available at ScienceDirect Engineering Fracture Mechanics journal homepage: www.elsevier.com/locate/engfracmech Please cite this article in press as: Hou J et al. Prediction of fatigue crack propagation lives of turbine discs with forging-induced initial cracks. Engng Fract Mech (2014), http://dx.doi.org/10.1016/j.engfracmech.2014.08.015