Assume that the fatigue striations just before final fracture on the part in Example Problem 11.7 had increased to 1×10-5 meters per cycle when the internal crack length had grown to 2a = 0.03 m. Assume that the data in Figure 11.27 is for a minimum stress of 0.
(a) Determine the stress intensity range that created these striations, and compare the value of Kmax to the value of KIc.
(b) Predict the stress range applied to this part just before failure.
(c) Did the part fail by fatigue fracture due to propagation of a crack to a critical size, or by an overload exceeding the ultimate tensile strength?
(c) This stress range is significantly below the yield stress, thus the material was not overloaded to exceed the tensile strength. It had to fail by fatigue fracture to a critical sized crack.
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