Introducing the K{sub max} sensitivity concept for correlating fatigue crack growth data

Book · Wed Dec 31 04:00:00 EST 1997

OSTI ID:293061

Donald, J K ^[1]; Bray, G H; Bush, R W ^[2]

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1. Fracture Technology Associates, Bethlehem, PA (United States)
2. Alcoa Technical Center, Alcoa Center, PA (United States)

Previous attempts to correlate stress ratio effects in fatigue crack growth rate data have often emphasized one important contribution, such as crack closure, without considering other mitigating factors such as K{sub max}. In the past, correlating stress ratio effects using closure have been hampered by non-repeatable measurements of closure and contradictory results. A new analysis technique for determining {Delta}KJ{sub eff} is based on an interpretation of crack closure as a stress redistribution (or load transfer) on a relatively compliant crack wake and is able to account for the contribution of cyclic crack-tip strain below the opening load. This results in the observation that the fatigue crack growth rate is not determined solely by {Delta}K{sub eff} but also depends on K{sub max}. It was observed that this K{sub max} dependence takes the form of a power-law with the magnitude of the exponent being a measure of K{sub max} sensitivity. A procedure for determining the intrinsic crack growth rate curve without the measurement or modeling of crack closure will be described. The implications for fatigue-life prediction are profound.

• OSTI ID: 293061
• Report Number(s): CONF-970980--; ISBN 0-87339-382-1
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM BASE ALLOYS
CRACK PROPAGATION
CRACKS
ELONGATION
EXPERIMENTAL DATA
FATIGUE
SERVICE LIFE
STRESS INTENSITY FACTORS
ULTIMATE STRENGTH
YIELD STRENGTH