On the same material as in the above problem, a fatigue loading is applied and the fatigue life is 1000 cycles. in each loading cycle, the material is first fully loaded and then fully unloaded. (a) what are the maximum stress, the minimum stress, the mean stress, the stress range (∆σ), the stress amplitude (s), and the r-raito? (b) we know that the fracture toughness of the material is 40 mpam1/2. what is the final fatigue crack length in the last loading-unloading cycle, cf? assume that the geometric factor y = 1.2.