The paper presents the results of a probabilistic creep life study on F5001P turbine discs and demonstrates the importance of using physics based probabilistic damage modeling techniques to deal with life prediction uncertainty in forged components. In physics based modeling, the influence of individual microstructural or thermal-mechanical loading factors on metallurgical crack initiation can also be studied with relative ease. In a previous study, Life Prediction Technologies Inc.’s (LPTi’s) prognosis tool known as XactLIFE™ was successfully used to conduct deterministic analysis to establish the fracture critical location of F5001P first stage discs under steady state loads. In this paper, the variability in life is further established as a function of prior austenite grain size. The analysis used typical engine operating data from the field in terms of engine speed and average exhaust gas temperature (EGT). The primary objectives of the case study are to show how prognosis can allow a user to assess fleet reliability for engine specific operating conditions. The lower bound deterministic creep life and probabilistic creep life at 0.1% cumulative probability of failure are very close in magnitude.

The results of a prognostics case study on GE Frame 5001P first stage turbine disc are presented in this paper. Currently used and promoted practices for metallurgical analysis such as hardness testing and replica based microstructural assessment and inspection of rotors for dimensional checks and cracks are not sufficient to ensure safety and reliability of the engine. The uncertainly of all engine variables including operational environment must be considered prior to returning the engine to service. It is required to accurately predict the temperature profile of the discs that can have serious consequences on the residual life assessment of the fracture prone rotors. The safe inspection interval (SII) determination of the design life expired engines and defining non-destructive inspection (NDI) sensitivity requirements for continued safe operation of the engine are equally important.

The paper presents the results of a probabilistic creep life study on RRA 501 KB turbine blades and demonstrates the importance of using physics based probabilistic damage modeling techniques to deal with life prediction uncertainty in cast equiaxed components. It is shown that physics based damage analysis yields accurate results and considerably less mechanical properties data is needed for life prediction of cast components. In physics based damage analysis, it is also easy to quickly assess the life limiting damage modes and to establish fracture critical locations in components. In physics based modeling, the influence of individual microstructural or thermal-mechanical loading factors on metallurgical crack nucleation can also be studied with relative ease. Residual life of service exposed parts and effectiveness of life extension techniques can also be predicted because the state of microstructure due to prior service and repair can be taken into account. In this study, Life Prediction Technologies Inc.’s (LPTi’s) prognosis tool known as XactLIFE™ was successfully used to establish the fracture critical location of RRA 501KB first stage gas turbine blades under steady state loads. Deterministic analysis was first used to compute the lower bound airfoil nodal creep life of the various finite element nodes and this was followed by probabilistic creep life analysis to take into account the variability of microstructure from one blade to another. The analysis used typical engine operating data from the field in terms of engine speed and average turbine inlet temperature (TIT). The primary objectives of the case study are to show how prognosis can allow a user to predict component fracture critical locations, establish inspection intervals to avoid failures and establish fleet reliability for engine specific operating conditions.

Prognosis and health monitoring (PHM) technology needs to be developed to meet the challenges posed by aging gas and steam turbines in power plants, transportation systems, gas pipelines, and other industries. It is necessary to use physics based residual life prediction and life extension techniques to take into account the state of damage due to prior service. This paper focuses on the requirements of the technology and the state of the development to date. In this study, Life Prediction Technologies Inc.’s (LPTi’s) prognosis tool known as XactLIFE™ was successfully used to establish the fracture critical location of RRA 501KB first stage gas turbine blades under steady state loads and to compute the average life to creep crack initiation in the blade airfoils. The analysis used typical engine operating data from the field in terms of engine speed and average turbine inlet temperature (TIT). The blade is known to suffer airfoil untwist and lengthening during service and this is obviously followed by stress rupture failure. The primary objectives of the case study are to show how prognosis can allow a user to predict fracture critical locations to avoid failures.