A lifting shackle in a glass-making factory is made from a special high-temperature stainless steel. It is expected that the shackle will experience a tensile load of 5kN and the design allows for a maximum creep strain of 1% over the design life of 10,000 operating hours.
The supplier of the alloy has measured the stress exponent, n, to be 4.5, the activation energy, QC , to be 110,000 J/mol and the pre-exponential constant, K_{2} , to be 2 ×10^{-8}(the constants K_{2} and n are in MPa, % and hour units).
(a) Calculate the minimum required cross-sectional area of the shackle if operating at 800^{o}C.
(b) If the temperature were to be increased to 900^{o}C and the load and cross-sectional area kept the same, what would be the time to 1% strain what would the creep strain be after 10,000 hours?