Abstract
An assessment has been made of the potential reduction in calculated fatigue-crack-growth lives when the small-crack effect is considered. The assessment was based on small-crack and large-crack grwoth-rate data of 2024-T3 aluminum alloy forR=−1 andR=0 constant-amplitude loading and for a fighter-wing spectrum loading (FALSTAFF). The potential impact of the small-crack effect was assessed by comparing lives computed using only large-crack data to those computed using a combined small- and, large-crack data based. Based on life calculations, the small-crack effect would have: (1) no impact on life analyses that assume an initial crack depth large than about 0.3 mm (such as in current airframe damage-tolerance analyses); (2) only a small impact on life analyses that assume an inital depth of 0.1 mm (such as im some current durability analyses) if the large-crack thresholds are ignored; but (3) a large impact on life analyses that assume an initial depth of about 0.01 mm (such as in a total-life analysis).
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
ASTM Standard Test Method for Measurement of Fatigue Crack Growth Rates, ASTM E647-86a.
Pearson, S., “Initiation of Fatigue Cracks in Commercial Aluminum Alloys and the Subsequent Propagation of very Short Cracks,”Eng. Fract. Mech.,7,235–247 (1975).
Kitagawa, H. and Takahashi, S., “Applicability of Fracture Mechanics to very Small Cracks or the Cracks in the Early Stage,” Proc. 2nd Int. Conf. on Mechanical Behaviour of Materials, Boston, 627–631 (1976).
El Haddad, M.H., “A Study of the Growth of Short Fatigue Cracks Based on Fracture Mechanics,” PhD Thesis, Univ., of Waterloo (1978).
Ritchie, R.O. and Lankford, J., “Overview of the Small Crack Problem,” Small Fatigue Cracks, ed. R. O. Ritchie and J. Lankford, 1–5 (1986).
Newman, J.C. Jr., “A Nonlinear Fracture Mechanics Approach to the Growth of Small Cracks,” Proc. AGARD Specialists Meeting on Behaviour of Short Cracks in Aiframe Components, AGARD-CP-328 (1983).
Leis, B.N., et al., “Critical Review of the Fatigue Growth of Short Cracks,”Eng. Fract. Mech.,23,883–898 (1986).
Van Dijk, G.M. and de Jonge, J.B., “Introduction to a Fighter Aircraft Loading Standarf for Fatigue Evaluation FALSTAFF,” NLR MP 75017U (1975).
Phillips, E.P., “The Influence of Crack Closure on Fatigue Crack Growth Thresholds in 2024-T3 Aluminum Alloys,” Mechanics of Fatigue Crack Closure, ed. J.C. Newman, Jr. and W. Elber, ASTM STP-982 (1988).
Brown, C.W. and Smith, G.C., “A Two Stage Plastic Replication Technique for Monitoring Fatigue Crack Initiation and Early Fatigue Crack Growth,” Advances in Crack Length Measuremewnt, ed. C.J. Beevers, Engineering Materials Advisory Services LTD, 41–51 (1982).
Newman, J.C., Jr., Swain, M.H. and Phillips, E.P., “An Assessment of the Small-Crack Effect for 2024-T3 Aluminum Alloys,” Small Fatigue Cracks, ed. R.O. Ritchie and J. Lankford, 427–452 (1986).
Andrade, A. andFreitas, M., “Behavior of Short Cracks in a 2024 Aluminum Alloy Sheet Teste at Several Stress Ratios,”FATIGUE '87, ed. R.O. Ritchie and E.A. Starke, Jr.,1,271–279 (1987).
Tanaka, K., Akiniwa, Y. and Matsui, E., “Propagation of Small Fatigue Cracks in 2024-T3 Aluminum Alloys,” FATIGUE '87, ed. R.O. Ritchie and E.A. Starke,1,361–370 (1987).
Swain, M.H. and Newman, J.C., Jr., “On the Use of Marker Loads and Replicas for Measuring Growth Rates for Small Cracks,” Proc. AGARD Conf. on Fatigue Crack Topography, AGARD-CP-376 (1984).
Potter, J.M. and Yee, B.G.W., “User of Small Crack Data to Bring About and Quantify Improvements to Aicrafts Structural Integrity,” Proc. AGARD Specialists Meeting on Behaviour of Short Cracks in Airframe Components, AGARD-CP-328 (1983).
Wang, D.Y., “A Study of Small Crack Growth Under Transport Spectrum Loading,” Proc. AGARD Specialists Meeting on Behaviour of Short Cracks in Airframe Components, AGARD-CP-328 (1983).
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Phillips, E.P., Newman, J.C. Impact of small-crack effects on designlife calculations. Experimental Mechanics 29, 221–225 (1989). https://doi.org/10.1007/BF02321379
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF02321379