A manufacturer of pressure vessels is worried about his steel fracturing abruptly as the chambers are loaded to high pressures because the steel is heavily cold-rolled with a very high yield strength (σy > 1 GPa). He decides to measure the fracture toughness of his steel using a thick-compact tension sample (Y = 1.12). He puts a 100 µm crack in the specimen, loads it in tension, and measures a fracture toughness of 10 MPa m^1/2.
a. What was the fracture stress during this experiment?