(Solved): 1. (a) Sketch the S-N curves (stress amplitude vs number of cycles to failure) of materials with a ...

1. (a) Sketch the S-N curves (stress amplitude vs number of cycles to failure) of materials with and without fatigue limits. (4 marks) (b) State the laws determining low cycle fatigue (Coffin-Manson's law) and high cycle fatigue (Basquin's law). (5 marks) (c) Describe the conditions that lead to linear creep. How does temperature affect the mechanism of linear creep? How does grain size affect the creep rate of linear creep? (6 marks) (d) One steel sheet is under cyclic loading. The tensile stress is equal to \( 80 \mathrm{MPa} \) and the compressive stress is equal to \( 40 \mathrm{MPa} \). Prior to testing, the steel sheet has an internal crack of \( 10 \mathrm{~mm} \) in length. Calculate the stress intensity factor. (6 marks) (Hints: \( K=C \sigma \sqrt{a \pi} \), where \( C \) is a sample geometry dependent constant and it can be assumed to be \( 1 ; \sigma \) is the applied stress; \( a \) is the half crack length.) (e) Briefly explain why cold-worked metals are more susceptible to corrosion than noncold-worked metals. (4 marks)