An interface edge is the likeliest site of fracture initiation because

of the stress singularity due to modulus mismatch. As illustrated

in Fig. 6.1, the singular stress (stress-concentrated) region near the

interface edge proportionally scales down (Becker et al., 1997) in

a continuum media as the size of a component becomes small. In

a component with single-micrometer or nanometer size, the region

governed by the singular field is confined in the nanoscale (Kiramura

et al., 2002, 2003). In such a case, the applicability of fracture

mechanics to the crack initiation from the edge is questionable

because the concept is built on continuummechanics.