涡轮增压器叶片高低周疲劳寿命特性

转子是涡轮增压器高速旋转部件,在运行中承受高低周疲劳载荷,其安全运行尤为重要。为获得涡轮增压器叶片的高低周疲劳寿命,通过改变高低周疲劳中高周应力比和单个复合疲劳载荷块中的高周频率,分析疲劳寿命特征,建立了基于Miner理论的寿命评估模型,利用此模型分析得出160000 r/min转速下涡轮叶片的高低周复合疲劳寿命。通过有限元分析软件对相同转速下涡轮叶片进行应力分析,得到低周应力、高周应力的最大值及其关键部位,并对涡轮叶片进行模态分析与谐响应分析,结合Ncode商用软件得出叶片关键部位高低周复合疲劳寿命。对基于Miner理论的寿命评估模型和Ncode软件所预测的叶片高低周寿命结果比较发现,随着高低周载荷谱中高周应力、高周循环数逐渐增加,修正后的模型所得寿命与Ncode软件所得寿命均呈递减趋势,寿命误差在两倍范围之内,两种方法均能较为可靠地预测高低周复合疲劳工况下的叶片疲劳寿命,而基于Miner理论的寿命修正模型的使用相对较为方便,所求寿命较为可靠,易于在工程中推广应用。

金属基复合材料低压涡轮轴结构高周疲劳寿命估算

研究基于名义应力法的连续纤维增强复合材料轴结构疲劳寿命的估算方法,并通过与实验寿命值对比,验证寿命预测方法的有效性。针对某型低压涡轮轴,模拟其实际受载情况,设计并建立了连续纤维增强复合材料低压涡轮轴结构有限元分析模型,经计算获得轴结构的名义应力,结合修正后的复合材料S-N曲线,估算出复合材料轴结构高周疲劳寿命。通过比较不同铺层方案复合材料轴结构高周疲劳寿命,总结出铺层方案对结构疲劳寿命的影响规律。

Effect of microvoids on microplasticity behavior of dual-phase titanium alloy under high cyclic loading(Ⅰ):Crystal plasticity analysis

A crystal plasticity finite element(CPFE)model was established and 2D simulations were carried out to study the relationship between microvoids and the microplasticity deformation behavior of the dual-phase titanium alloy under high cyclic loading.Results show that geometrically necessary dislocations(GND)tend to accumulate around the microvoids,leading to an increment of average GND density.The influence of curvature in the tip plastic zone(TPZ)on GND density is greater than that of the size of the microvoid.As the curvature in TPZ and the size of the microvoid increase,the cumulative shear strain(CSS)in the primaryα,secondaryα,andβphases increases.Shear deformation in the prismatic slip system is dominant in the primaryαphase.As the distance between the microvoids increases,the interactive influence of the microvoids on the cumulative shear strain decreases.