The changing behavior of temperature and stress for a cast iron cylinder head was investigated.Then the loading characteristics under thermal and mechanical loads were determined, which can provide the reference for building the life prediction model of cylinder head.The head finite element model was first built and calibrated with temperature and stress data and was further used for predicting the temperature and stress varying characteristics under steady working condition and altering condition between idle and rated speed.The simulation results show that the maximum temperature and thermal stress locate near the exhaust valve bridge region on the firing deck.The amplitude of temperature fluctuation in the firing deck region is less than 30℃, but it will still lead to thermal stress.The produced thermal stress is negligible compared with the steady thermal stress, but important to have to be considered in high cycle fatigue evaluation compared with high frequency gas stress.The load varies obviously in firing deck region under the altering condition between idle and rated speed.The temperature and stress are in out of phase, the stress amplitude is very high, and therefore the firing deck region generates the low cycle fatigue easily.%研究了某柴油机铸铁缸盖结构温度和应力随时间的变化行为,明确热-机械载荷作用下缸盖的承载规律,为缸盖寿命预测模型建立提供依据.首先建立了缸盖有限元分析模型,利用实测温度和应力数据对模型进行了标定,进而基于该模型计算了标定工况及怠速与标定工况交替变化条件下缸盖温度和应力的变化规律.仿真结果表明:缸盖最高温度和最大热应力出现在鼻梁区域;在工作循环内,缸盖火力面温度波动幅值在30 ℃以内,由此引起的波动热应力相对定常热应力较小,但相对高频气体应力较大,故在火力面高周疲劳校核过程中必须考虑其带来的影响;在怠速和标定转速交替变化工况下,鼻梁区载荷变化最明显,温度与应力呈现反相状态,应力幅值较高,该区域易发生低周疲劳损伤.
展开▼
