Failure Mechanisms

· In steady state creep (secondary creep) the strain rate is related to the applied stress, temperature, and material properties by the Dorn-Weertman relationship:

where B = Constant, n ~ 5, E = Young's Modulus, E_D = self diffusion energy, D₀ = Temperature independent diffusion coefficient.
· The strong stress dependence comes from dislocation recovery processes involving cross-slip (screw dislocations) and climb (edge dislocations).
· The exponential temperature dependence of the creep rate indicates that diffusion processes are important in both deformation and recovery.