涡轮增压器叶片高低周疲劳寿命特性分析

转子是涡轮增压器高速旋转部件，在运行中常承受高低周疲劳载荷，它的安全运行尤为重要。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高周频率，分析疲劳寿命特征，建立基于Miner理论的寿命评估模型。利用此模型分析得出160 000 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，随高低周载荷谱中高周应力、高周作用次数逐渐增加，修正后模型所得寿命与经Ncode商用软件所得寿命均呈递减趋势，寿命误差在两倍范围之内，两种方法均可较为可靠的预测高低周复合条件下的叶片疲劳寿命，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。

Analysis of high and low cycle fatigue life characteristics

The rotor is a high-speed rotating part of turbocharger, which often bears high and low cycle fatigue load in operation. Its safe operation is particularly important. In order to obtain the high and low cycle fatigue life of turbocharger blade, the fatigue life characteristics were analyzed by changing the high and low cycle composite stress ratio and the high cycle frequency in a single composite fatigue load block, and the life evaluation model based on Miner''s theory was established. Based on this model, the combined fatigue life of turbine blade at 160000r/min is 19094 times. Finite element analysis software was used to analyze the stress of turbine blades at the same speed, and the maximum values of low and high cyclic stresses and their crucial positions were obtained. Through the modal analysis and harmonic response analysis results of turbine blades, combined with the commercial software Ncode, the high-low cycle composite fatigue life of crucial parts of blades was obtained to be 19,664 times. The difference between the life assessment model based on Miner''s theory and the prediction of high-low cycle life of blades by Ncode software is 2.89%, which can both reliably predict the fatigue life of blades under high-low cycle composite conditions. The solution process of NCODE software is weak in universality and complex in operation, while the life modification model based on Miner''s Theory is relatively convenient to use and easier to be popularized and applied in engineering.