镍基单晶高温合金多轴低周疲劳损伤研究

项目名称： 镍基单晶高温合金多轴低周疲劳损伤研究

项目编号： No.50875080

项目类型： 面上项目

立项/批准年度： 2009

项目学科： 生物科学

项目作者： 丁智平

作者单位： 湖南工业大学

项目金额： 31万元

中文摘要： 镍基单晶高温合金是一种新型各向异性材料，具有优越的抗蠕变、抗疲劳性能。研究它在多轴应力状态下的低周疲劳寿命分析方法，为航空发动机热端部件提供较为可靠的设计依据，具有重要的理论意义和应用价值。本项目首先研究镍基单晶合金在多轴应力状态下的低周疲劳损伤机理和演化规律，基于含内变量不可逆热力学原理，用损伤应变能释放率作为热力学广义力描述正交各向异性材料的疲劳损伤过程，导出含有三个弹性常数的立方晶体单晶材料应力/应变三轴因子；其次基于正交设计，进行680℃#21644;850℃#28201;度下的DD3镍基单晶合金薄壁圆管试样（001取向）拉/扭非比例循环加载低周疲劳试验，定量分析、研究拉/扭载荷的应变路径角、相位角、循环特性和温度诸因素对低周疲劳损伤的影响规律，第三根据镍基单晶合金的微观结构特征，建立γ#947;'双相单胞微观尺度力学模型，进行多轴非比例循环加载有限元数值模拟和多尺度分析；最后基于能量耗散理论和损伤力学原理，引入表征非比例加载效应的特征参量和表征拉/扭载荷耦合效应的立方晶体单晶材料应变三轴因子，构造循环塑性应变能作为疲劳损伤参量，导出多轴应力状态下损伤演化方程，建立镍基单晶合金多轴低周疲劳寿命预测模型。

中文关键词： 镍基单晶合金；低周疲劳损伤；多轴非比例加载；双相单胞模型；寿命预测

英文摘要： Single crystal Ni-based superalloy is an orthotropic material which has excellent performance of anti-fatigue/creep under elevated temperature. Study on analysis method of low cycle fatigue life under multiaxial stress state of the material and provide more reliable basis for design of the hot sections of aero engine has important theory significance and application value. Firstly, this project researched low cycle fatigue damage mechanism and evolution of single crystal nickel-based superalloy under multiaxial stress state. Based on the irreversible thermodynamics theory with internal variables, a damage strain energy release ratio, as generalized thermodynamic force used to describe fatigue damage process of orthotropic materials, is applied to derive a triaxiality factor for single crystal superalloy that contains three elastic constants. Secondly, tension/torsion low cycle fatigue tests of single crystal Ni-based superalloy, DD3, was carried out under non-proportional loadings based on orthogonal design at elevated temperatures, using thin-walled tube specimens with〈001〉orientation. Factors, strain range, strain path angle, tension/torsion phase angle, strain ratio and temperature, was analyzed quantitatively on low cycle fatigue damage. Thirdly, according to micro structure feature, a γ#947;' two-phase unit cell finite element model was established to generate numerical simulation and do multiscale analysis under non-proportional loadings. Finally, based on energy dissipation theory and principle of damage mechanics, a cyclic plastic strain energy as fatigue damage parameter is built by introducing the characteristic parameters of non-proportional loading effect and the triaxiality factor which characterize coupling effects of tension / torsion loading for single crystal superalloy, and then a damage evolution equation for single crystal superalloy under multiaxial stress state is derived and a low cycle fatigue life prediction model is established.

英文关键词： single crystal Ni-based superalloy;low cycle fatigue damage;multiaxial non-proportional loading;two-phase unit cell model;life prediction