Cumulative Damage in the Low Cycle Fatigue

Abstract

The authors proposed a hypothesis of cumulative damage due to the low cycle fatigue and gave the following formula for fatigue fracture criterion for the multi-stage loading test; Σ^^p__(i=1)(n_iΔW_ci)(σ_maxi)^α=C(σ_maxp)^β where n_i and ΔW_ci are number of cycles and plastic strain energy per cycle in the i-th stage, respectively; σ_maxi and σ_maxp denote maximum tensile stresses in the i-th and final stages, respectively; α, β and C are material constants. Experimental data on stainless steel show that the above formula approximately holds good. The above formula is transformed into Σ^^p__(i=1)a_i(n_i/N_fi)=1 for multi-stage constant strain cycling test. Deviations in the experimental value of Σ(n_i/N_fi) from Miner's damage rule may be explained by this formula.