A B S T R A C T Stepped-isothermal fatigue failure is the main failure mechanism of modern engine pistons under bench reliability test condition. This paper presents a methodology for stepped-isothermal fatigue analysis of engine pistons, which consists of a fatigue criterion, evaluation of temperature and stress distribution by finite element analysis and the final life prediction. The major character of the methodology is the fatigue definition of engine pistons with respect to engine load change cycle and a damage-based fatigue criterion accounting for the nonlinear creep-fatigue damage. Taking as an example, the fatigue life of an engine piston was predicted by the proposed analysis procedures.The analysis results showed that the most critical area was located in the throat edge. Moreover, the proposed methodology can give a relatively accurate and reasonable life prediction for an engine piston under the loading condition of bench reliability test, with a benefit of decreasing the needed component's reliability tests and design time.Keywords creep-fatigue damage interaction; engine pistons; life prediction; steppedisothermal fatigue.
N O M E N C L A T U R Eα = heat transfer coefficient A, r, m = material constants of creep damage evolution model D c = creep damage D f = fatigue damage D = total damage h g = average heat transfer coefficient K′ = cyclic strength coefficient m, M = material constants of fatigue damage evolution model N = number of cycles to failure N p = stepped-isothermal fatigue life n′ = cyclic strain-hardening exponent t = creep time t 1 , t 2 = times in stepped-isothermal block loading T = temperature T max = maximal temperature T min = minimal temperature T = gas temperature T g = average gas temperature R p0.2 = yield strength ϕ = crank angle σ a = stress amplitude σ (t) = function of time per cycle ε pa = plastic strain amplitude τ 0 = duration of each operating cycle Correspondence: J. Liu,