Recall from lecture notes that the max stress at the tip of an elliptic hole under uniaxial Mode-I (opening mode) loading can be described by the equation and graph presented in the Figure. As the shape of the elliptic hole approaches that of a crack (p0), the stress concentration becomes very large, and 2 VP >1. s fe Therefore: Max oy~ 2S sia 8- P is tip radius SO 2 oy 9 Ox 2c 2 S Max dy = S -s (1+2 ) 5 x/p The leading edge of a 2 m (0.002 mm) long crack in glass is found to experience a stress concentration factor of 200 under uniaxial Mode-I loading. a. Estimate the radius of curvature at the crack tip. Provide your answer in nm (106 nm = 1 mm). b. Compare this answer with the average atomic spacing in glass (look up a reasonable value on the internet) and comment on whether this radius is indicative of significant crack-tip blunting due to plastic deformation at the crack tip.