某型高镍铸铁排气歧管热疲劳寿命预测

摘要

In view of the low accuracy of the thermal fatigue life prediction formula for exhaust manifold made of high-nickel cast iron D5S, high temperature tensile tests on D5S material are conducted to estimate the pa-rameters in Manson-Coffin formula for life prediction. By utilizing the fluid-solid coupling function of STARCCM+and ABAQUS,the thermal fatigue life of D5S exhaust manifold is predicted. The results show that the highest surface temperature of manifold is located at the converging zone of exhaust gas flow from four cylinders and the averageΔPEEQ value in this dangerous zone reaches 0. 548％ after 5 cycles. The strain-life curve is obtained based on ten-sile test data, the predictive life is calculated to be 1,678 cycles, and according to engine verification bench test the real fatigue life of two sample manifolds is 2,217 and 2,014 cycles respectively, judged by pressure drop caused by cracking, demonstrating that the fatigue life predicted by corrected formula is closer to that by test, compared with that predicted by empirical formula ( 625 cycles) .%针对目前D5S高镍铸铁排气歧管热疲劳寿命预测公式精度不高的缺陷,对D5S材料进行高温拉伸试验,以估计Manson-Coffin公式寿命预测参数,结合STARCCM+与ABAQUS流固耦合功能,对D5S排气歧管热疲劳寿命进行预测.结果表明,排气歧管表面温度最高位置出现在四缸排气流汇合处,5个循环后危险位置平均ΔPEEQ值达到0.548％;根据高温拉伸试验数据获得材料的应变寿命曲线,并计算出危险位置预测寿命为1678个循环;发动机台架验证试验的结果,两根歧管的寿命分别为2217个循环和2014个循环.与经验公式预测结果(625次循环)相比,修正公式所得结果与试验结果更为接近.研究成果可为D5S材料排气歧管寿命预测提供依据.