ABSTRACTMEMS devices may experience significant alternating loads during service, associated with both applied and vibrational loading. Long-term reliability and lifetime predictions require understanding of possible fatigue mechanisms in these structures. Although silicon is not generally considered susceptible to fatigue crack growth, recent studies suggest that there may be fatigue processes in silicon MEMS structures. The phenomenon, however, has still not been extensively studied. In this work, we used a compressive double cantilever beam geometry to examine stable crack growth. Crack length and loads were carefully monitored throughout the test in order to distinguish between the apparent role of environmentally assisted crack growth (stress corrosion) and mechanically induced fatigue. Results revealed similar step-like crack extension versus time for the cyclic and monotonic tests. The fatigue crack-growth curve extracted from the crack extension data exhibited a nearly vertical slope with no evidence of fatigue crack-growth. Fracture surfaces for the monotonic and cyclic tests were similar, further suggesting that a true mechanical fatigue crack-growth mechanism did not occur.
The application of strain energy density criterion to fatigue crack growth behavior of cracked components
