The effects of sub-zero(-22Co) cyclic rotating bending on the S-N behavior and cumulative damage are reported for 207-T4 aluminum alloy .Experimental characterization of fatigue behavior showed that the S-N curves behavior may described by the following Basquin's formulas:
σ_f=1230〖(N_f)〗^(-0.15) At room temperature (RT)
σ_f=1563〖(N_f)〗^(-0.17) At sub-zero temperature (-22Co)
From the above equation, the fatigue behavior can be change at σ_f=204 MPa and N_f=159475 cycles .
Slightly increase in fatigue life results above 204 MPa and slightly decrease in fatigue below the 204 MPa stress level. A non-linear experimental law is introduced for the accumulation of damage at sub-zero temperature variable fatigue. This law gave conservative and safe fatigue life time prediction when applying to the data of variable fatigue at low temperature (-22 Co).