An infinite steel plate, 30 mm thick, is subjected to a tensile stress. It contains a through thickness crack perpendicular to the stress direction.

(a) Calculate the fracture stress (σc) for a crack length (2a) of 50 mm, assuming plane strain conditions. (b) If conditions were plane stress instead, what would be the failure condition, and at what expected stress level? (c) What microstructure would you expect such a steel to possess?

Given

KIC = 80 MPa m^-1; yield stress (Sy ) = 1000 MPa.

Assume Y = 1 for an infinite plate.