【作者】 孙兴华；

【导师】 蔡志勤；

【作者基本信息】 大连理工大学 ， 动力学与控制， 2008， 硕士

【摘要】 镍基高温合金用于制造航空发动机的高压涡轮叶片。为了提高涡轮叶片持久寿命设计参数选取和设计方法的可靠性,从涡轮叶片代表性部位取材并设计、加工试验试件,其中包括有孔(气膜冷却孔)、直孔和斜孔试件。对无孔试件和有孔试件在不同温度和应力下分组进行持久拉伸试验,记录试件断裂时间和拉伸过程中的蠕变变形量。试验结果表明,与标准试件比较,13个无孔试件持久寿命时间大为缩短,即使同一名义应力下,不同试件试验数据也存在着一定的离散性,但是每组(三个)试件中至少有两个数据是比较接近的;6个带孔试件的断裂时间较为接近,与标准试件比较相同名义应力下,持久寿命大为降低,由于应力集中效应的影响,其降低幅度大于无孔试件,降低幅度最大约为88%。气膜孔为直孔或斜孔,其对持久寿命的影响差别不大。为了解释上述试验结果,对试件进行有限元数值模拟和断口分析。通过采用θ法和非线性回归方法得到Norton蠕变规律参数,再将Norton参数转化成ANSYS所支持的格式,进而在ANSYS下进行有限元数值模拟。求得应力集中最大节点的应力值,进而算出其持久寿命,并与标准试件进行比较。模拟结果显示,气膜冷却孔的应力集中效应将大大降低试件的持久寿命,寿命预测时应该充分考虑其影响。断口分析表明,持久寿命数据离散是因为有些试件断口处存在较大尺寸的第二相粒子,其可能成为潜在的裂纹源,导致试件寿命大为降低。本文还将测得的试件变形值,换算成蠕变应变值,再对相同应力条件下的应变取平均,用修正θ法得到模拟试件的持久寿命预测方程,并且验证其可靠性。更多还原

【Abstract】 The directionally crystal nickel-based high-temperature alloy is used for the turbine blade of some advanced engines recently. In order to enhance the reliability of design parameters and design method for the endurance life of the turbine blade, the endurance life experiments are made on the specimens cut from the typical part of the turbine blades with film cooling hole including perpendicular-hole and nonperpendicular-hole.For each specimen, its endurance life and creep deformation values at different time are recorded during the endurance life experiment, and creep strains are gained. The experimental results show that the film cooling holes have a significant influence on endurance life compared with standard specimens’ one. For 13 non-hole specimens, their endurance lives are much shorter than those of standard specimens. Their experimental results are very different even though at same nominal stress, but at least two data in every group (three specimens) are relatively close. For 6 specimens with holes, their endurance lives are very close, but all of them are even shorter than non-hole specimens, where the largest difference compared with standard specimens is up to 88%.To validate these experimental results, FEA simulation and fracture analysis is carried out. Since the number of the specimens is limited, the Norton creep law parameters which are transformed to the parameters in software ANSYS are gained usingθ-Project Concept method and nonlinear regression method. Moreover, the endurance life is obtained by computing the maximum stress value, then is compared with standard specimens’ endurance life. The numerical simulation analysis demonstrates that the endurance life has significantly been influenced by the film cooling hole’ Stress Concentration Effects, which should be adequately taken into account when predicting the turbine blade’s endurance life. Additionally, fracture analysis shows that the second-phase particles which may become the source of crack make experimental data very different and the endurance life decreases very much.In this paper, the predicting equation is also obtained using modifiedθ-Project Concept, and its reliability is proved.更多还原