Publication Date


Document Type


Committee Members

Tarun Goswami (Committee Co-chair), Ravi Penmetsa (Committee Member), Raghavan Srinivasan (Committee Member), Bor Zeng Jang (Committee Chair)

Degree Name

Master of Science in Engineering (MSEgr)


There is an economic need to extend the fatigue life of turbine engine rotor disks. The probability of failure during the operation life must be quantified as components remain in service beyond their traditional safe-life limit. Fracture mechanics based probabilistic methods are utilized to predict the probability of failure of components containing manufacturing and fatigue anomalies. Total fatigue life is defined in terms of crack initiation and propagation phases. A micromechanical initiation model uses material properties at the micro-scale to characterize the initiation phase, while short and long fatigue-crack growth models predict the crack propagation phase. A Monte Carlo simulation determines the fatigue-life variability by modeling random material properties in the fatigue models. This methodology is applied to a representative α+β alloy (Ti-6AL-4V) fan disk to quantify the probability of failure due to manufacturing and fatigue induced anomalies. It is concluded that fatigue damage increases the risk beyond the safe-life limit, but proper inspection planning can maintain the risk and enhance the life of components.

Page Count


Department or Program

Department of Mechanical and Materials Engineering

Year Degree Awarded