Stepped‐isothermal fatigue analysis of engine piston

Abstract

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,

Differences in Dry Sliding Wear Behavior between Al–12Si–CuNiMg Alloy and Its Composite Reinforced with Al2O3 Fibers

“…The generated oxidation on the counterface can act as solid lubricant film or peeling-off layer, depending on the magnitude of sliding distance and normal load [20]. Generally, in actual operating conditions for many components, such as engine pistons, applied load and sliding velocity significantly vary during the operating cycle [24].…”

Low Cycle Fatigue Behavior of Heat‐Resistant Austenitic Cast Steels at 950 °C

“…The positive influence of lowering the SDAS on fatigue lifetime has also been reported in high cycle fatigue of other cast materials. [24,25] Particularly, Zhang et al found that the fatigue life varied slightly with SDAS when it was below 30 μm, but dropped quickly with the SDAS increasing above 30 μm, especially at low strain ranges. [24] In this study, the average SDAS of alloy 1.4826 was just below 30 μm, while the average SDAS of alloys 1W6C4N and 3C2N was above 30 μm.…”

“…[24,25] Particularly, Zhang et al found that the fatigue life varied slightly with SDAS when it was below 30 μm, but dropped quickly with the SDAS increasing above 30 μm, especially at low strain ranges. [24] In this study, the average SDAS of alloy 1.4826 was just below 30 μm, while the average SDAS of alloys 1W6C4N and 3C2N was above 30 μm. Comparing the LCF lifetime and the SDAS in the three investigated alloys, it is suggested that the critical SDAS for affecting LCF lifetime at the low strain range was also around 30 μm in austenitic cast steels.…”

Effect of intermetallic particles and grain boundaries on short fatigue crack growth behaviour in a cast Al–4Cu–3Ni–0.7Si piston alloy

“…10 This has necessitated intensive research and development of new piston designs and materials that can withstand the increasingly harsh combination of thermo-mechanical fatigue and highcycle fatigue loads. 2, [10][11][12][13][14] Recent investigations are looking at increasing the performance of piston alloys by further increasing the Cu and Ni contents and increasing the Si level above the eutectic although there are concerns about reductions in castability. 5 The aim of these developments has been to achieve maximum performance at high temperatures of 350 °C and above.…”

“…There has been a steady increase in engine performance accompanied with requirements for increased system efficiency, minimum weight and more stringent emission legislation . This has necessitated intensive research and development of new piston designs and materials that can withstand the increasingly harsh combination of thermo‐mechanical fatigue and high‐cycle fatigue loads . Recent investigations are looking at increasing the performance of piston alloys by further increasing the Cu and Ni contents and increasing the Si level above the eutectic although there are concerns about reductions in castability .…”