Plasticity effects and crack-closure modeling of small fatigue cracks were used on a Ti-6Al-4V alloy to calculate fatigue lives under various constant-amplitude loading conditions (negative to positive stress ratios, R) on notched and un-notched specimens. Fatigue test data came from a high-cycle-fatigue study by the U.S. Air Force and a metallic materials properties handbook. A crack-closure model with a cyclic-plastic-zone-corrected effective stress-intensity factor range and equivalent-initial-flaw-sizes (EIFS) were used to calculate fatigue lives using only crack-growth-rate data. For un-notched specimens, EIFS values were 25-μm; while for notched specimens, the EIFS values ranged from 6 to 12 μm for positive stress ratios and 25-μm for R = −1 loading. Calculated fatigue lives under a wide-range of constant-amplitude loading conditions agreed fairly well with the test data from low- to high-cycle fatigue conditions.
Issue Section:
Gas Turbines: Structures and Dynamics
References
1.
Pearson
, S.
, 1975, “Initiation of Fatigue Cracks in Commercial Aluminum Alloys and the Subsequent Propagation of Very Short Cracks
,” Eng. Fract. Mech.
, 7
, pp. 235
–247
. 2.
Kitagawa
, H.
, and Takahashi
, S.
, 1976, “Applicability of Fracture Mechanics to Very Small Cracks or the Behaviour in the Early Stages
,” Proc. Second International Conference on Mechanical Behavior of Materials
, Boston, MA
, pp. 627
–631
.3.
Zocher
, H.
, ed., 1983, “Behaviour of Short Cracks in Airframe Components
,” AGARD Conf. Proc.
No. 328.4.
Ritchie
, R. O.
, and Lankford
, J.
, eds., 1986, Small Fatigue Cracks
, The Metallurgical Society, Inc.
, Warrendale, PA
.5.
Miller
, K. J.
, and de los Rios
, E. R.
, eds., 1986, “The Behaviour of Short Fatigue Cracks
,” European Group on Fracture
, Publication No. 1.6.
Ritchie
, R. O.
, and Lankford
, J.
, 1986, “Overview of the Small Crack Problem
,” Small Fatigue Cracks
, R. O.
Ritchie
and J.
Lankford
, eds., The Metallurgical Society, Inc., Warrendale, PA, pp. 1–5.7.
Newman
, J. C.
, Jr., 1983, “A Nonlinear Fracture Mechanics Approach to the Growth of Small Cracks
,” Behaviour of Short Cracks in Airframe Components
, Zocher
, H.
, ed., AGARD Conf. Proc. 328
, pp. 6.1
–6.26
.8.
Newman
, J. C.
, Jr., Swain
, M. H.
, and Phillips
, E. P.
, 1986, “An Assessment of the Small-Crack Effect for 2024-T3 Aluminum Alloy
,” Small Fatigue Cracks
, The Metallurgical Society, Inc., Warrendale, PA, pp. 427
–452
.9.
Newman
, J. C.
, Jr., and Edwards
, P. R.
, 1988, “Short-Crack Growth Behaviour in an Aluminum Alloy - an AGARD Cooperative Test Programme
,” AGARD Conf. Proc.
R-732
, pp. 1–96.z10.
Newman
, J. C.
, Jr., Phillips
, E. P.
, and Swain
, M. H.
, 1997, “Fatigue-Life Prediction Methodology using Small-Crack Theory
,” NASA Paper No. TM-110307.11.
Newman
, J. C.
Jr., Phillips
, E. P.
, and Everett
, R. A.
, Jr., 1999, “Fatigue Analyses Under Constant- and Variable-Amplitude Loading using Small-Crack Theory
,” NASA Paper No. TM-209329.12.
Newman
, J. C.
, Jr., Schneider
, J.
, Daniel
, A.
, and McKnight
, D.
, 2005, “Compression Pre-Cracking to Generate Near Threshold Fatigue-Crack-Growth Rates in Two Aluminum Alloys
,” Int. J. Fatigue
, 27
, pp. 1432
–1440
. 13.
Ruschau
, J. J.
, and Newman
, J. C.
, Jr., 2008, “Compression Precracking to Generate Near Threshold Fatigue-Crack-Growth Rates in an Aluminum and Titanium Alloy
,” J. ASTM International
, 5
(7
), pp. 1–11.14.
Yamada
, Y.
, and Newman
, J. C.
, Jr., 2009, “Crack Closure Under High Load-Ratio Conditions for Inconel-718 Near Threshold Conditions
,” Eng. Fract. Mech.
, 76
, pp. 209
–220
. 15.
Suresh
, S.
, 1985, “Crack Initiation in Cyclic Compression and Its Application
,” Eng. Fract. Mech.
, 21
, pp. 453
–463
. 16.
Pippan
, R.
, Plöchl
, L.
, Klanner
, F.
, and Stüwe
, H. P.
, 1994, “The Use of Fatigue Specimens Precracked in Compression for Measuring Threshold Values and Crack Growth
,” J. Test. Eval.
, 22
, p. 98
. 17.
Gallagher
, J. P.
, 2001, “Improved High-Cycle Fatigue (HCF] Life Prediction
,” AFRL-ML-WP-TR-2001-4159.18.
deLaneuville
, R. E.
, and Sheldon
, J. W.
, 2001, “Crack Growth
,” AFRL-ML-WP-TR-2001-4159, Appendix 3B, pp. 1–12.z19.
Lenets
, Y. N.
, 2001, “Nucleation and Propagation of Small Cracks
,” AFRL-ML-WP-TR-2001-4159, Appendix 3C, pp. 1–14.20.
Bellows
, R.
, 2001, “Effect of Specimen Geometry and Frequency on HCF Smooth Specimen Behavior
,” AFRL-ML-WP-TR-2001-4159, Appendix 3F, pp. 1–4.21.
deLaneuville
, R. E.
, and Sheldon
, J. W.
, 2001, “Notch Fatigue
,” AFRL-ML-WP-TR-2001-4159, Appendix 3J, pp. 1–6.22.
Metallic Materials Properties Development and Standardization, U.S. Department of Transportation, Federal Aviation Administration
, 2003, Washington, D.C., Paper No. DOT/FAA/AR-MMPDS-01.23.
Garr
, K. R.
, and Hresko
, G. C.
, 2000, “A Size Effect on the Fatigue Crack Growth Rate Threshold of Alloy 718
,” ASTM Spec. Tech. Publ.
, 1372
, pp. 155
–174
.24.
Newman
, J. C.
, Jr., 1981, “A Crack Closure Model for Predicting Fatigue Crack Growth Under Aircraft Spectrum Loading
,” ASTM Spec. Tech. Publ.
, 748
, pp. 53
–84
.25.
Elber
, W.
, 1971, “The Significance of Fatigue Crack Closure
,” ASTM Spec. Tech. Publ.
486
, pp. 230
–242
.26.
Newman
, J. C.
, Jr., 1992, “FASTRAN-II - A Fatigue Crack Growth Structural Analysis Program
,” Paper No. NASA TM 104159.27.
Newman
, J. C.
, Jr., 1992, “Effects of Constraint on Crack Growth Under Aircraft Spectrum Loading
,” Fatigue of Aircraft Materials
, A.
Beukers
ed., Delft University Press, The Netherlands, pp. 83
–109
.28.
Newman
, J. C.
Jr., Ruschau
, J. J.
, and Hill
, M. R.
, “Improved Test Method for Very Low Fatigue-Crack-Growth-Rate Data
,” Fatigue Fracture Eng. Mater. Struct
. (to be published).29.
El
Haddad
, M. H.
, Dowling
, N. E.
, Topper
, T. H.
, and Smith
, K. N.
, 1980, “J-Integral Application for Short Fatigue Cracks at Notches
,” Int. J. Fracture
, 16
, pp. 15–30. 30.
Hudak
, S. J.
, Jr., and Chan
, K. S.
, 1986, “In Search of a Driving Force to Characterize the Kinetics of Small Crack Growth
,” Small Fatigue Cracks
, R. O.
Ritchie
and J.
Lankford
, eds., Metallurgical Society
, Warrendale, PA
, pp. 379
–405
.31.
Rice
, J. R.
, 1968, “A Path Independent Integral and the Approximate Analysis of Strain Concentration by Notches and Cracks
,” J. Appl. Mech.
, 35
, pp. 379
–386
.32.
Newman
, J. C.
, Jr., 1992, “Fracture Mechanics Parameters for Small Fatigue Cracks
,” ASTM Spec. Tech. Publ.
1149
, pp. 6
–28
.33.
Lenets
, Y. N.
, Bellows
, R.
, and Merrick
, H.
, 2000, “Propagation Behavior of Naturally Initiated Cracks in Round Bars of Ti-6Al-4V
,” Proc. 5th National Turbine High Cycle Fatigue Conference
, HCF’00.34.
Lenets
, Y. N.
, Nelson
, R.
, and Merrick
, H.
, 2002,” Growth of Small Cracks at Different Stress Ratios
,” Proc. 7th National Turbine Engine High Cycle Fatigue Conference
, HCF’02.35.
Lanciotti
, A.
, and Galatolo
, R.
, “Short Crack Observations in Ti-6Al-4V under Constant Amplitude Loading
,” AGARD Conf. Proc.
, R-732
, pp. 10.1
–10.7
.Copyright © 2012
by American Society of Mechanical Engineers
You do not currently have access to this content.
