Cyclic Magnetic Actuation for Potential Characterization of Interfacial Fatigue Fracture

Interfacial Cyclic Fatigue of Atomic-Layer-Deposited Alumina Coatings on Silicon Thin Films

“…Another observed trend is an increase in dλ / dN with G a , with roughly 3 orders of magnitude increase in dλ / dN for an order of magnitude increase in G a . A power fit was applied for each environment, because such relationships are typically employed to model fatigue crack growth rates (refs − ). The power exponent is approximately 1.7 for the mild environment and about 1.4 for the harsh environment.…”

“…The magnetically actuated peel test (MAPT) is a promising technique to determine G c as well as both subcritical and fatigue delamination properties. 14,15 However, the MAPT technique has so far been only demonstrated for thin films on flat substrates. In contrast, the microresonator technique allows calculation of the fatigue delamination rates of ALD coatings on the rough sidewalls of DRIE silicon films, under fully reversed loading conditions, which is a configuration relevant for a large range of silicon MEMS devices.…”

“…The four-point bending (4PB) testing technique, while very adequate to measure the interfacial fracture energies ( G c ) of thin films (including ultrathin films), and subcritical delamination, is not well suited to study fatigue properties, especially in the very high cycle fatigue regime. The magnetically actuated peel test (MAPT) is a promising technique to determine G c as well as both subcritical and fatigue delamination properties. , However, the MAPT technique has so far been only demonstrated for thin films on flat substrates. In contrast, the microresonator technique allows calculation of the fatigue delamination rates of ALD coatings on the rough sidewalls of DRIE silicon films, under fully reversed loading conditions, which is a configuration relevant for a large range of silicon MEMS devices.…”

“…Interfacial fracture in thin films has been the subject of numerous studies, − some of which reported time-dependent delamination growth. ,, Fewer studies also investigated interfacial fatigue (possibly because of the experimental difficulties mentioned above), most prominently of metal/ceramic systems. ,,,, Classical metal fatigue was found to drive the observed interfacial fatigue , and interfacial fatigue crack growth was found to occur at lower strain energy release rates than interfacial fracture under static loading . Some studies also reported that the interfacial strength is reduced in harsher environments, both under static loading or displacement ,, and cyclic loading. , With respect to ALD coatings, many investigations have so far focused on the monotonic − and thermomechanical properties of ALD coatings, but little is known about their cyclic degradation properties , even though MEMS are inherently subjected to cyclic loading.…”