Microstructure and Temperature Effects on the Fatigue Variability Behavior of AN alpha+beta Titanium Alloy and Implications for Life Prediction (Postprint)

摘要

We have studied the effects of microstructure and temperature on the fatigue variability behavior of the alpha+beta titanium alloy, Ti-6Al2Zr-4Sn- 6Mo (Ti-6-2-4-6). These variables had separate influence on the minimum, and the mean behavior. This was related to perhaps a fundamental aspect of fatigue variability which dictates that at any stress level, the mean is dominated by a mechanism different from the one controlling the lower-tail behavior. As a result in this material, while the mean response was increasingly dominated by the crack initiation regime with decreasing stress level (which is the conventionally expected behavior), at the same time the life-limiting behavior was controlled by the crack growth regime. This produced a very systematic effect of microstructure and temperature on total uncertainty in lifetime depending on the sensitivity of crack initiation and growth regimes to these variables. We suggest a new paradigm to treat the fatigue variability behavior and show that, this can have significant implications for life management especially, with respect to reducing the uncertainty with life prediction and improving the reliability of design life.