Influences of Secondary Stress Fluctuations of Small Amplitude on Low Cycle Corrosion Fatigue

Abstract

Low cycle corrosion fatigue tests of a high strength steel were carried out in 1 % NaCl under the primary trapezoidal stress wave form superimposed with the secondary stress fluctuations of small amplitude during a holding period at maximum load, and the following results have been obtained. The influences of small secondary stress fluctuations during a holding time in primary trapezoidal wave forms are far more dangerous in corrosive environment than presumed in air, and the corrosion fatigue life remarkably decreases when the secondary stress waves are applied However, balance between mechanical damaging action and corrosive action is reached at the total amplitude of secondary waves Δσ= 0.15 σ_max, which increases the fatigue life owing to the suppression of crack initiation. Though the propagation rate of corrosion fatigue is insensible to secondary stress fluctuations of small amplitude, the rate increases monotonously with an increase of Δσ over a limiting value (ΔK₁ = 10 kg·mm^(-3)/2.The secondary stress fluctuations increase also the thinning due to corrsion and fatigue deformation of materials.