Probabilistic Methodology for Life Prediction of Aircraft Turbine Rotors

Abstract

The presence of rare metallurgical or manufacturing anomalies in aircraft turbine rotors/disks may contribute to uncontained engine failures. A probabilistic methodology has been developed to quantify the risk of fracture and the influence of periodic inspection on overall risk, supplementing the current safe life approach. This paper summarizes the methodology and computational implementation, including a brief description of a new method for defining surface damage-related crack growth using 3D finite element results. The results can be applied to risk assessment of aerospace structures where uncertainties associated with fatigue crack growth must be quantitatively addressed.

A Probabilistic Framework for Risk Prediction of Gas Turbine Engine Components With Inherent or Induced Material Anomalies

“…Since the computation time associated with predicting the crack propagation life associated with each Monte Carlo sample may be nontrivial, a number of techniques have been developed over the past several years to improve computational efficiency. A summary of these techniques is provided in Table 1 [12]. Figure 8.…”

“…Comprehensive design systems have been developed for rotors and disks that may contain inherent material anomalies [4][5][6][7][8][9][10]. Recently, some initial strategies have been developed to address components with induced anomalies [11][12][13]. Since inherent and induced anomalies originate from entirely different manufacturing processes, risk assessment is often treated separately for these two anomaly types.…”

Development of a Physically-Based Methodology for Predicting Material Variability in Fatigue Crack Initiation and Growth Response

“…(7) can be utilized in two ways: (1) for computing the Ni distribution for a given value of crack size at initiation, ai, and (2) for computing the distribution of ai for a given number of fatigue cycles. For both cases, the general probabilistic framework described by Enright et al [15] is employed.…”

“…(1) can be used to predict Nf scatter attributed to material variability. A general probabilistic framework has been developed to address the influences of both the material-and non-material-specific variables on the probability of fatigue fracture (Enright and Wu [12], Leverant [13], Wu et al [14], Enright et al [15]). The Nf scatter results shown in this report can be directly applied to this framework, allowing the designer to quantify the influences of the fundamental micromechanics variables on overall component risk.…”

Adaptive Optimal Sampling Methodology for Zone-Based Probabilistic Life Prediction

“…The occurrence of metallurgical anomalies is relatively rare (i.e., expected value on the order of one anomaly per million pounds of disk material 2,3 ), so a probabilistic approach has been developed for the fracture mechanics-based life prediction of components which may contain the anomalies [4][5][6][7][8] . A zone-based method is used to address the location uncertainty associated with these anomalies in which a component is subdivided into a number of zones of approximately equal risk.…”