The merging of fatigue and fracture mechanics concepts: A historical perspective
- NASA Langley Research Center, Hampton, VA (United States)
The seventh Jerry L. Swedlow Memorial Lecture presents a review of some of the technical developments, that have occurred during the past 40 years, which have led to the merger of fatigue and fracture mechanics concepts. This review is made from the viewpoint of crack propagation. As methods to observe the fatigue process have improved, the formation of fatigue micro-cracks have been observed earlier in life and the measured crack sizes have become smaller. These observations suggest that fatigue damage can now be characterized by crack size. In parallel, the crack-growth analysis methods, using stress-intensity factors, have also improved. But the effects of material inhomogeneities, crack-fracture mechanisms, and nonlinear behavior must now be included in these analyses. The discovery of crack-closure mechanisms, such as plasticity, roughness, and oxide/corrosion/fretting product debris, and the use of the effective stress-intensity factor range, has provided an engineering tool to predict small- and large-crack-growth rate behavior under service loading conditions. These mechanisms have also provided a rationale for developing new, damage-tolerant materials. This review suggests that small-crack growth behavior should be viewed as typical behavior, whereas large-crack threshold behavior should be viewed as the anomaly. Small-crack theory has unified fatigue and fracture mechanics concepts; and has bridged the gap between safe-life and durability/damage-tolerance design concepts. 192 refs.
- OSTI ID:
- 566570
- Report Number(s):
- CONF-9606178-; TRN: IM9805%%196
- Resource Relation:
- Conference: 28. ASTM national symposium on fatigue and fracture mechanics, Saratoga Springs, NY (United States), 25-27 Jun 1996; Other Information: PBD: 1997; Related Information: Is Part Of Fatigue and fracture mechanics: 28. volume; Underwood, J.H.; Macdonald, B.D.; Mitchell, M.R. [eds.]; PB: 704 p.; ASTM special technical publication, 1321
- Country of Publication:
- United States
- Language:
- English
Similar Records
Fatigue-crack propagation in advanced aerospace materials: Aluminum-lithium alloys
On the fatigue behavior of {gamma}-based titanium aluminides: Role of small cracks