Effect of water vapor pressure on fatigue crack growth in Al–Zn–Cu–Mg over wide-range stress intensity factor loading
2014; Elsevier BV; Volume: 137; Linguagem: Inglês
10.1016/j.engfracmech.2014.11.009
ISSN1873-7315
AutoresJames T. Burns, Ralph Bush, Jiahe Ai, Jennifer Jones, Sangha Lee, Richard P. Gangloff,
Tópico(s)Non-Destructive Testing Techniques
ResumoInvestigation of the deleterious effect of high purity water vapor on fatigue crack growth rate (da/dN) in 7075-T651 shows that growth rate declines with decreasing water vapor pressure (PH2O) over a wide range of stress intensity range (ΔK). Decreasing ΔK experiments exhibit a novel minimum in da/dN for intermediate PH2O and low ΔK. This minimum and testing protocol dependent environmental-fatigue behavior are explained by crack wake fracture morphology and R-dependent crack opening displacement effects on molecular flow to the crack tip. This environmentally-based mechanism leads to the onset and reversal of a non-conservative and false high threshold stress intensity range.
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