Effect of Shot Peening on Low Cycle Fatigue Life of Compressor Disc of a Typical Fighter Class Aero-Engine

AbstractThis investigation deals with the study of a compressor disc made of α-β titanium alloy of a typical fighter aero-engine having a TBO (Time Between Overhaul) of 550hours and TTL (total technical life) of 1500hours. In general, the failure of most of compressor discs is attributed to low cycle fatigue (LCF) due to the presence of residual tensile stresses at the dovetail slots. In the present study, shot peening was carried out to introduce compressive residual stress at the dove tail slots in order to enhance fatigue life of the disc. The local stress at the longitudinal and transverse edge of the slot generally increases upto 450MPa and 230MPa, respectively, during service. In the present study, the introduced residual compressive stresses measured by XRD technique on the slot and face of the disc has been found to be of the order 650MPa & 770MPa, respectively. Stress controlled LCF tests (R=0.1, maximum stress = 85% Yield Strength, frequency = 0.33Hz) have been conducted at room temperature. The LCF life of shotpeened disc was observed to be nearly three times as compared to that of unpeened disc. Following this surface treatment, life of the disc has been revised from 800 to 1500hours, thereby eliminating the need of disc replacement at operating units. This has improved the reliability and serviceability of the fleet