Incorporating Small Fatigue Crack Growth in Probabilistic Life Prediction: Effect of Stress Ratio in Ti-6Al-2Sn-4Zr-6-Mo (Preprint)
Journal article preprint
AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH STRUCTURAL MATERIALS DIV
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The effect of stress ratio on the statistical aspects of small fatigue crack growth behavior was studied in a duplex microstructure of Ti-6Al-2Sn-4Zr-6Mo Ti-6-2-4-6 at 260 degrees C with particular emphasis on incorporating small-crack data into probabilistic life prediction and the influence of stress ratio on probabilistic lifetime limits. A Focused Ion Beam FIB was used to machine micro-notches in test specimens, which served as crack-initiation sites and enabled the acquisition of multiple small-crack growth data sets from single experiment. Stress ratios of -0.5, 0.05, and 0.5 were employed, and small-crack growth was monitored by the acetate replication method. Qualitatively, change in the stress ratio produced almost negligible influence on the small-crack growth behavior when plotted as crack growth rate dadN versus applied stress intensity factor range delta K. A probabilistic method was employed to represent the variability in the small-crack growth behavior and the statistical differences with respect to stress ratio.
- Metallurgy and Metallography