汽车发动机曲轴疲劳性能分析研究

Investigation of Fatigue Performance of Automobile Engine Crankshaft

目的汽车发动机曲轴在疲劳实验的过程中,经常会出现非正常疲劳裂纹,裂纹从轴颈末端的油孔槽开始起源,造成曲轴轴颈的扭转强度达不到要求。有必要对汽车发动机曲轴的疲劳性能进行研究。方法通过疲劳、拉伸、金相实验以及疲劳断口SEM手段,对曲轴疲劳试样进行了分析。结果汽车曲轴疲劳实验在循环基数为1×107次下,弯矩的疲劳极限为607.5 Nm;曲轴轴颈的中部所受到的疲劳极限压力为96.7 MPa;该40Cr曲轴断口为典型的韧窝和台阶混合断裂。结论曲轴的钻油孔在轴颈内壁造成的应力集中,比较容易产生缺陷;曲轴轴颈在交变应力的作用下,很容易产生疲劳裂纹并扩展,导致曲轴的早期断裂。

During fatigue testing of the automobile engine crankshaft, abnormal fatigue cracks often occur. The cracks originate from the oil hole slot at the end of the crankshaft journal, which leads to the unqualified torsional strength of the shaft journal. It is necessary to have a research on the fatigue performance of automobile engine crankshaft. The crankshaft fatigue sample was analyzed by fatigue test, tensile test, OM, and fatigue fracture SEM. The fatigue limit of the lower mo- ment was 607.5 Nm at the circulation base of 1 x 107 times in the fatigue test of automotive crankshaft. The fatigue limit pressure was 96.7 MPa at the middle of crankshaft journal. The fracture of the 40Cr crank was the typical dimple and step mixed fracture. Due to the stress concentration in the inner wall of the shaft journal caused by the drill hole of crankshaft, the defects occurred easily. On the other hand, under alternating stress, fatigue cracks occurred easily in the crankshaft journal and expanded, causing early break of the crankshaft.