Subsurface crack nucleation and growth behavior and energy-based life prediction of a titanium alloy in high-cycle and very-high-cycle regimes

The empirical models commonly used for probabilistic life prediction do not provide adequate treatment of the physical parameters that characterize fatigue damage development. For these models, probabilistic treatment is limited to statistical analysis of strain-life regression fit parameters. In this paper, a model is proposed for life prediction that is based on separate nucleation and growth phases of total fatigue life. The model was calibrated using existing smooth specimen strain-life data, and it has been validated for other geometries. Crack nucleation scatter is estimated based on the variability associated with smooth specimen and fatigue crack growth data, including the influences of correlation among crack nucleation and growth phases. The influences of crack nucleation and growth variability on life and probability of fracture are illustrated for a representative gas turbine engine disk geometry.

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Crack FEA of the First Stage Blade of Gas Turbines

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.450.429 ◽

2010 ◽

Vol 450 ◽

pp. 429-432

Author(s):

Ping Zhao ◽

Wei Li ◽

Qing Hua He

Keyword(s):

Gas Turbines ◽

Life Prediction ◽

Crack Nucleation ◽

Creep Damage ◽

Nucleation And Growth ◽

Prediction System ◽

Edge Region ◽

Element Analysis ◽

Fatigue Crack Nucleation ◽

Crack Nucleation And Growth

To investigate the physical cause of premature blade cracking during the acceleration mission test (AMT) in a test cell environment, an in-depth finite element analysis (FEA) of the blade was conducted using a life prediction system. The results obtained showed that the blades had suffered excessive airfoil creep damage, leading to excessive blade lengthening and airfoil untwisting particularly in the trailing edge region. It is predicted that the uneven rubbing action might have contributed to the fatigue crack nucleation and growth process just below the platform in the shank region of the blade under AMT fatigue cycling conditions, and the excessive creep deformation made a significant effect on the overall crack nucleation process.

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Probabilistic Treatment of Crack Nucleation and Growth for Gas Turbine Engine Materials

Volume 5: Marine; Microturbines and Small Turbomachinery; Oil and Gas Applications; Structures and Dynamics, Parts A and B ◽

10.1115/gt2006-90813 ◽

2006 ◽

Cited By ~ 1

Author(s):

M. P. Enright ◽

R. C. McClung ◽

S. J. Hudak ◽

W. L. Francis

Keyword(s):

Gas Turbine ◽

Life Prediction ◽

Crack Nucleation ◽

Gas Turbine Engine ◽

Nucleation And Growth ◽

Smooth Specimen ◽

Growth Phases ◽

Adequate Treatment ◽

Turbine Engine ◽

Crack Nucleation And Growth

The empirical models commonly used for probabilistic life prediction do not provide adequate treatment of the physical parameters that characterize fatigue damage development. For these models, probabilistic treatment is limited to statistical analysis of strain-life regression fit parameters. In this paper, a model is proposed for life prediction that is based on separate nucleation and growth phases of total fatigue life. The model was calibrated using existing smooth specimen strain-life data, and has been validated for other geometries. Crack nucleation scatter is estimated based on the variability associated with smooth specimen and fatigue crack growth data, including the influences of correlation among crack nucleation and growth phases. The influences of crack nucleation and growth variability on life and probability of fracture is illustrated for a representative gas turbine engine disk geometry.

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