一种镍基单晶合金多轴低周疲劳损伤参量

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,定义了含有3个弹性常数的镍基单晶应力三轴性因子,它不仅反映多轴载荷下的复杂应力状态,还显示正交各向异性材料偏轴受载时存在的正应力与剪应力的耦合效应,是对各向同性材料应力三轴性因子的拓展.用镍基单晶应力三轴性因子修正Mises应变范围作为疲劳损伤参量,引入损伤驱动力循环特征参数反映循环载荷的交变特性,提出了单晶合金低周疲劳损伤模型.利用DD3和CMSX-2单晶合金低周疲劳试验数据,采用多元线性回归分析方法拟合疲劳损伤模型参数,试验所得数据都落在2倍和2.5倍偏差分布带内.

A multiaxial Low Cycle Fatigue Damage Parameter for Single Crystal Nickel-Based Superalloys

Strain energy release ratio,being known as thermodynamics generalized force,was applied to describe fatigue damage course of orthotropy materials.From the definition of strain energy release ratio,a triaxiality factor for single crystal superalloy that contains three elastic constants was defined.Not only may the triaxiality factor show the multiaxial complex stress states as well as the coupling effect of the tensile and torsional stress in orthotropy material while the applied loading deflects from the principal axes directions of material coordinate system.It is a prolongation for triaxiality factor of isotropy material.By using the triaxiality factor to modify strain range as a failure parameter and introducing a cyclic characteristic parameter for damage force to take account of alternately changed characteristic of cyclic loading,a low cycle fatigue damage model for single crystal superalloy was proposed.The low cycle fatigue test data correlation to DD3 and CMSX-2 single crystal superalloy with the parameter by using multivariate linear regression analysis is good and the all test data fall into the factor of 2.0 and 2.5 scatter band respectively.