【作者】 陈勇；

【导师】 高德平；

【作者基本信息】 南京航空航天大学 ， 航空宇航推进理论与工程， 2003， 博士

【摘要】 随着对航空发动机性能、可靠性、寿命等要求的不断提高，发动机涡轮盘将承受更高的温度和应力，传统高温合金已不能满足这一要求。而粉末高温合金材料具有组织均匀、晶粒细小、屈服强度高、高温疲劳性能好等优点，已成为新型涡轮盘的首选材料。由于粉末高温合金工艺的特殊性，夹杂的存在是不可避免的。因此研究夹杂对粉末高温合金涡轮盘强度与寿命的影响十分必要。本文围绕含夹杂粉末高温合金涡轮盘的裂纹扩展寿命问题，开展了以下工作： （1）用有限元法研究了夹杂裂开以及夹杂与基体界面脱开对应力强度因子的影响。结果表明，对于含Al₂O₃夹杂的FGH95粉末高温合金材料，当夹杂裂开或界面脱开时，应力强度因子均小于将夹杂视为初始裂纹时的应力强度因子。 （2）推导了远场应力、热应力耦合作用下含夹杂裂纹体的应力强度因子求解公式，改进了体积力法中的裂纹面合力平衡条件，将应力强度因子的求解归结为解一组积分方程，再将积分方程转化为线性方程组进行数值求解。算例分析结果表明方法正确、有效。含Al₂O₃夹杂的FGH95材料应力强度因子的主要影响因素为夹杂的尺寸、夹杂与裂纹之间的距离以及裂纹长度，而热应力的对其影响很小。 （3）建立了考虑裂纹面接触的有限元模型，较传统不考虑裂纹面接触的方法更适于模拟裂纹扩展和裂纹闭合效应。分析了含夹杂粉末高温合金材料在不同载荷下的张开应力，可用于对应力强度因子的修正。计算结果表明：界面脱开的夹杂使得应力强度因子幅值下降。 （4）进行了含夹杂粉末冶金涡轮盘裂纹扩展寿命研究，并计算分析了某型发动机粉末高温合金涡轮盘裂纹扩展寿命，可供其型号研制中参考。提出了含夹杂粉末高温合金涡轮盘寿命分三个阶段的概念，即：夹杂附近初始裂纹的孕育阶段、初始裂纹扩展到可见裂纹（0.78mm）阶段（裂纹扩展第一阶段）以及从可见裂纹扩展到临界裂纹阶段（裂纹扩展第二阶段）。并建议将第一阶段裂纹扩展寿命作为含Al₂O₃夹杂的FGH95粉末高温合金涡轮盘的寿命。 （5）运用自适应显式积分方法，编制了Bodner-Partom（B-P）统一粘塑性本构关系与大型通用有限元程序ANSYS的接口子程序。计算结果表明接口子程序具有在不同应变率条件下、应变率跳级拉伸条件下以及循环载荷条件下的模拟能力，程序正确、可靠，适于涡轮盘等发动机热端部件的应力分析。更多还原

【Abstract】 Turbine disks will endure higher temperature and higher stress due to increasing demanding on the performance, reliability and life of aeroengines, and traditional superalloys couldn’t meet the demand. Powder metallurgy (PM) superalloys has the advantage of homogeneous organization, superfine grain, high yield strength and high elevated temperature fatigue strength, so it becomes the first choice material for the new turbine disks. But being limited in the level of manufacturing technique, inclusions (mainly nonmetallic inclusion) is unavoidable. So it is essential to study the effect of inclusion on the strength and life of PM superalloy turbine disks. The main contents are as following:(1) Finite element method (FEM) is used to study the effects of broken inclusion and debonded interface on the stress intensity factors (SIF). In the material of FGH95 containing Al2O3 inclusions, broken inclusion and debonded interface decrease the value of SIF comparing with that of the same size crack without inclusions.(2) The interaction between a round inclusion and a crack under thermal and remote mechanical loading is analyzed based on the body force method (BFM). The traction-free condition on the crack line is mended to get more accurate results. It can be expressed by a series of integral equations which can be discretized to a set of linear equations and then it can be solved easily. Stress intensity factors (SIF) are gotten through the root of the linear equations. The calculation results in this paper is compared to that in other references to validate the method and program. The method is used to the material of FGH95 PM superalloy containing Al2O3 inclusions, and the key factors that affect the SIF are the size of the inclusion, the distance between the inclusion and the crack and the crack length. The thermal stress has little effect on SIF.(3) The finite element model, in which the contact between the crack lines is considered, is more accurate than traditional FE model to simulate the crack growth and crack closure. This model is used to calculate the opening stress of FGH95 PM superalloys. The calculating results in the case of debonded interface show that the opening stress is increased and the amplitude of SIF is decreased.(4) The crack growth life of a PM superalloy turbine disk containing inclusions is studied. Total life of PM superalloy turbine disks can be divided into three parts: the crack (nearthe inclusion) initiation life, the life from the initial crack expanding to the visible crack (0.78mm), and the life from the visible crack expanding to the critical crack. The life of the initial crack expanding to the visible crack is the majority of the life of FGH95 PM superalloy turbine disks containing AlO3 inclusions.(5) The ANSYS user subroutines for the simulation of elastic visco-plastic behavior for PM superalloys is developed by using the Bodner-Partom constitutive equations. The calculation result is compared with that of some experiments and other references, and it is satisfactory. The subroutines can be applied to the stress analysis of turbine disks in aeroengines.更多还原