Research Papers: Gas Turbines: Manufacturing, Materials, and Metallurgy

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

[+] Author and Article Information
M. P. Enright, R. C. McClung, S. J. Hudak, W. L. Francis

 Southwest Research Institute, San Antonio, TX 78238

J. Eng. Gas Turbines Power 132(8), 082106 (May 26, 2010) (8 pages) doi:10.1115/1.4000289 History: Received May 14, 2009; Revised June 05, 2009; Published May 26, 2010; Online May 26, 2010

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.

Copyright © 2010 by American Society of Mechanical Engineers
Your Session has timed out. Please sign back in to continue.



Grahic Jump Location
Figure 1

A proposed FaNG model addresses the different phases of fatigue damage development

Grahic Jump Location
Figure 12

Influence of correlation among crack nucleation and growth portions of crack initiation life on crack nucleation life confidence intervals: (a) R=0.1 and (b) R=0.5

Grahic Jump Location
Figure 13

The FaNG model was applied to risk assessment of an aircraft gas turbine engine disk

Grahic Jump Location
Figure 14

For the gas turbine engine disk, predicted life values based on the FaNG model are generally higher than the smooth-specimen-based SWT model, particularly at relatively high stress range values: (a) R=0.1 and (b) R=0.5

Grahic Jump Location
Figure 15

A comparison of fracture probability values associated with FaNG and smooth-specimen-based SWT models indicates that FaNG predictions may be under- or overconservative depending on the stress range value and on the relationship among nucleation and growth lives

Grahic Jump Location
Figure 2

The FaNG model predicts the nucleation life portion of smooth specimen life associated with a specific initial crack size

Grahic Jump Location
Figure 3

A probabilistic framework has been developed to predict the fracture risk associated with crack nucleation and growth (19)

Grahic Jump Location
Figure 4

Predicted nucleation life for a smooth specimen at various definitions of the crack nucleation size

Grahic Jump Location
Figure 5

Predicted nucleation life fraction for a smooth specimen at various definitions of the crack nucleation size

Grahic Jump Location
Figure 6

Comparison of FaNG model (for different crack nucleation sizes) and normalized SWT predictions with R=0.1 notch fatigue test data

Grahic Jump Location
Figure 7

Comparison of FaNG model predictions (crack nucleation size=0.003 in.) with notch fatigue test data for three different stress ratios

Grahic Jump Location
Figure 8

Predicted crack nucleation life fractions based on the FaNG model for notch fatigue specimens at three different stress ratios

Grahic Jump Location
Figure 9

Crack initiation lives and associated nonlinear regression equation for Ti–6Al–4V smooth specimen data (24)

Grahic Jump Location
Figure 10

Ti–6Al–4V crack growth rate data (24-25) and associated probability densities illustrate the dependence of da/dN variability on ΔK

Grahic Jump Location
Figure 11

Crack growth lives based on data from the AGARD study (24-25) were used to estimate Ti–6Al–4V crack growth life variability: (a) crack growth life results based on individual specimens and (b) crack growth life probability density



Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In