铝合金气缸盖低周热疲劳寿命计算评估

Low-Cycle Thermal Fatigue Life Calculation of an Aluminum Alloy Cylinder Head

在应用有限元方法对内燃机受热件的低周热疲劳寿命进行计算评估时,材料的力学循环响应迟滞回线所表征的能量被认为是最合理的损伤参量,因而采用能量法则对气缸盖低周热疲劳寿命进行评估将使结果更加准确.对气缸盖铝合金材料进行高温下等幅值恒应变负荷低周疲劳试验,得到材料高温下基于能量法则的低周疲劳寿命预测模型及其参数.对气缸盖在其典型低周热疲劳负荷-启停循环下的寿命进行计算评估,得到气缸盖火力面低周热疲劳寿命及其分布规律.结果表明:爆发压力与热负荷相比,对火力面应力负荷的贡献相对较小,并且各缸火力面疲劳寿命最低区域位于排气门边缘区域,此外各缸排气门鼻梁区、气门与喷油孔鼻梁区和进/排气门鼻梁区的寿命相对较小.

When calculating the low-cycle thermal fatigue life of the heated components by applying the finite element method, the energy featured by the cyclic response of material was considered to be the most reasonable damage parameter. Therefore, the use of the energy method to assess the low-cycle thermal fatigue life of the cylinder head can obtain more accurate results. The low-cycle fatigue test at high temperature condition was conducted on the aluminum alloy material of a cylinder head, which employed the alternating load with equal amplitude and constant strain. The tested results revealed the low-cycle fatigue life prediction model and the parameters were also obtained based on the energy law. The low-cycle thermal fatigue life and its distribution on the firepower surface of the cylinder head were also obtained. The results show that the combustion pressure contributes less to the stress load on the firepower surface than the thermal load does. The regions with the lowest fatigue life on the firepower surface of each cylinder are lo- cated at the edge of the exhaust valves, Besides, in each cylinder, the fatigue life is shorter at the nose area of the exhaust valves, the nose area between the valves and the injection hole, and the regions near the nose area of the exhaust valves.