Impact fatigue strength and behavior of plastic deformation due to cyclic creep in the fatigue process were experimentally studied for the annealed oxygen-free copper. The impact fatigue properties were analyzed in consideration of the duration time as well as the magnitude of impact stress.
The impact fatigue strength was well represented by a linear relation between stress σ and cumulative duration time NfT. The behavior of cyclic creep plastic deformation was clearly divided into three regions of i) primary creep, ii) minimum creep rate and iii) accelerative creep, and it was expressible by a formula with the terms of plastic strain εp and, normalized number of cycles N/Nf but without σ and T.
The minimum creep rate region occupys about 90% of the total impact fatigue life and governs the life to failure Nf due to impact fatigue damage. The property parameters (m0, D0) of impact fatigue strength and the material constants (a1, a2) in the cyclic creep plastic deformation's formula are related to the static tensile property values i.e. tensile strength σB, reduction of area ψ, elongation δ, including the cases of various other copper materials as well as the annealed oxygen-free copper. The impact fatigue strength and the cyclic creep plastic deformation in the fatigue process can be well estimated from the static tensile property by use of these relations.