Consider a beam made of 7075-t6 aluminum with h = 1 in, and thickness t. the plane strain fracture toughness for the material is 26 and yield strength is 75 ksi. find the nominal bending moment m to fracture the beam for crack lengths a = 0.10, 0.20 and 0.30 in, and plate thicknesses of t = 0.10, 0.20 and 0.30 in. find the plastic zone radius and ratio for all cases at the point of fracture. can you justify linear elastic fracture mechanics assumption at the crack tip based on