Subsurface Crack Initiation in High Cycle Fatigue at Cryogenic Temperatures.

Fatigue-induced thick oxide formation and its role on fatigue crack initiation in Ni thin films at low temperatures

This study highlights an oxidation-assisted fatigue crack initiation mechanism in 20 lm thick electroplated Ni films under loading conditions relevant for a wide range of microelectromechanical systems, such as extreme stress gradients at the surface (50% decrease over the first micrometer from the surface). Microresonators subjected to in-plane bending at 8 kHz were fatigued for billions of cy...

Side Effects of Shot Peening on Fatigue Crack Initiation Life

Shot peening beneficial effects on fatigue life of mechanical components are well known. However, there are some reports in the literature that indicate inappropriate shot peening parameters tend to reduce the fatigue life. It is therefore, the purpose of this study to find a logical quantitative justification for these observations. Using finite element method, a dynamic elastic-plastic simula...

Ultra-high-Q phononic resonators on-chip at cryogenic temperatures

Long-lived, high frequency phonons are valuable for applications ranging from optomechanics to emerging quantum systems. For scientific as well as technological impact, we seek high-performance oscillators that offer a path towards chip-scale integration. Confocal bulk acoustic wave resonators have demonstrated an immense potential to support long-lived phonon modes in crystalline media at cryo...

Measurement of Subsurface Fatigue Crack Size Using Nonlinear Adaptive Learning

Hold-time Effects on Low-cycle-fatigue Behavior of Hastelloy® X Superalloy at High Temperatures

Total strain-controlled low-cycle-fatigue tests with and without hold times were performed at temperatures ranging from 816°C to 982°C in a laboratory air on a nickel-based superalloy, HASTELLOY X. The influence of hold times on the cyclicstress response and fatigue life was studied. At the temperatures considered, the alloy exhibited initial cyclic hardening, followed by a saturated cyclic-str...