Evaluation of Non Conservatism of Combined Rainflow Counting and Miner's Rulefor Damage Cumulation in Strain Controlled Fatigue

摘要

One of the aims of this paper is to show the difference between strain and stress control in uniaxial and nonrnproportional constant amplitude loading and in uniaxial variable amplitude loading. An experimental program has beenrnrealised on two stainless steel 304L and 316L and a ferritic A42 steel. For uniaxial constant amplitude loading we show thatrnfor 316L and 304L stainless steel, cyclic overloading has a positive effect on lifetime in stress control and a negative effect inrnstrain control, while these effects are negligible for the ferritic steel. Tests performed on 316 stainless steel show that stressrncontrolled constant amplitude out of phase tension-torsion loadings are less damaging than uniaxial equivalent ones, inrncontrast with strain controlled tests.rnIn variable amplitude loading we show that a rainflow counting procedure combined to Miner's damage cumulation rulernis conservative for stress controlled tests but not for strain controlled tests.rnFor uniaxial constant amplitude loading a new linear damage cumulation rule is proposed. It takes into account thernmemory effect in terms of cyclic behaviour and is in accordance with experimental results. Moreover a conservative damagerncumulation is proposed for the case of strain control. The modelling is extended to the case of non proportional loading andrnagrees with experimental data.rnAn attempt has been done to extend this model to the case of variable amplitude loading but the results are notrnconclusive.