The role of debris‐induced cantilever effects in cyclic fatigue of micron‐scale silicon films

The presence of debris, surface roughness, or other asperities on crack faces creates a geometry that is reminiscent of a lever (the crack face) on a fulcrum (the debris or surface asperity). This ‘cantilever effect’ is intuitive and is routinely forwarded as a mechanism for crack advance when compressive loads are applied. Recently this cantilever effect has also been linked to fatigue of micron‐scale silicon films. Finite‐element modelling was used in this study to evaluate different wedging configurations that would be likely to occur within micromachined silicon thin films. The results of the model clearly show that wedges or other asperities in the wake of a crack do not increase the magnitude of the stress intensity factor during compression.