In a plate (width w = 220 mm) of D6ac steel, there is an initial edge crack of size 10 mm. The material data are as follows: Yield point = 1345 MPa, ultimate limit = 1572 MPa, the Paris law constants...

In a plate (width w = 220 mm) of D6ac steel, there is an initial edge crack of size 10 mm. The material data are as follows: Yield point = 1345 MPa, ultimate limit = 1572 MPa, the Paris law constants C = 4.3937 × 10⁻¹¹
(in MPa, m units) and m = 2.55, and Wheeler retardation constant p = 1.43. Assume plane strain. The plate is subjected to a constant amplitude fatigue loading ∆σ = 120 MPa for 10, 000 cycles. This is followed by an overload cycle of amplitude 360 MPa. Subsequently, a constant amplitude loading of 220 MPa is applied for 12, 000 cycles. Find the crack sizes at different stages.