| Abstract Scope |
Cyclic fatigue is the root cause of many catastrophic failures in advanced engineering systems. The physical origins of fatigue strength in a large set of face centered cubic, hexagonal close packed, and body centered cubic metallic materials have been studied by probing the cyclic deformation processes at nanometer resolution over large volumes of material. Recent advances in accelerated fatigue testing, in-situ electron microscopy, digital image correlation and multimodal data analysis have been integrated to quantitatively analyze slip events and their reversibility. Quantitative relations between the yield and ultimate tensile strength, fatigue strength and the physical characteristics of early slip localization events are identified. Interestingly, the fatigue strength at 109 cycles of metallic alloys can be predicted by the amplitude of slip localization during the first cycle of loading. These observations provide a physical basis for well-known empirical fatigue laws. The implications for design of fatigue-resistant materials will be discussed. |