The manufacturer of a product that is subjected to repetitive cycles has specified that the product should be removed from service when any crack reaches 15% of the critical crack length required to cause fracture. consider a crack that is initially 0.02 mm long in a material with a fracture toughness of 55 mpa √m . the product is continuously cycled between compressive and tensile stresses of 300 mpa at a constant frequency. assume external cracks for which f = 1.12. the materials constants for these units are n = 3.4 and c = 2 × 10-11.
(a) what is the critical crack length required to cause fracture?
(b) how many cycles will it take for the product to be removed from service as specified by the manufacturer,
(c) assuming the specifications were not followed, how many cycles will it take for product to fail? (2+3+3 = 8 points)