基于单胞模型镍基单晶高温合金低周疲劳寿命的预测

Low Cycle Fatigue Life Prediction for Ni-Based Single Crystal High Temperature Alloy Based on Unit Cell Model

基于镍基单晶高温合金的微观尺度结构特征,建立了γ/γ′双相单胞有限元模型,并基于能量耗散理论,引入统一表征非对称载荷循环特性和拉/扭多轴效应的k参量,以循环塑性应变能作为损伤参量,建立了镍基单晶高温合金低周疲劳寿命预测模型;分别利用宏观有限元模型和γ/γ′双相单胞微观有限元模型对[001]取向的DD3、PWA1480和CMSX-2镍基单晶高温合金的单轴、多轴低周疲劳试验过程进行数值模拟。结果表明:微观单胞有限元模型反映了试验合金的微观结构特性,其预测精度明显优于宏观有限元模型的;上述3种合金几乎所有的试验数据分别落在1.3,2.0和2.0倍偏差分布带内。

Based on the microstructure feature of Ni-based single crystal high temperature alloy, a γ/γ′ two- phase unit cell finite element model was built. Based on energy dissipation theory, a parameter k was introduced to express asymmetrical load cyclic characteristic and tension/torsion multiaxial effect, the low cycle fatigue life prediction model for nickel based single crystal high temperature alloy was proposed by using cyclic plasticity strain energy as a damage parameter. The process of uniaxial and multiaxial low cycle fatigue tests for DD3, PWA1480 and CMSX-2 Ni-based single crystal high temperature alloy along [001] orientation were simulated by using the macro finite element model and the γ/γ′ two-phase unit cell micro finite element model. The results show that the micro unit cell model not only reflected the microstructure characteristics of the tested alloys, but also was better than the macro model in prediction accuracy. Almost all test datas of three kinds alloys above-mentioned distributed in 1.3, 2. 0 and 2. 0 scatter band, respectively.