单晶高温疲劳损伤参量的选取与寿命建模

Damage parameter determination and life modeling for high temperature fatigue of single crystals

高温疲劳损伤是引起单晶涡轮叶片破坏的主要因素之一。利用不同试验条件下DD6标准试件的低周疲劳和蠕变-疲劳试验结果,结合基于滑移系的黏塑性应力-应变分析,分别研究了晶体取向、应变范围、平均应变以及保载时间等对单晶高温疲劳损伤的影响机制。进而采用滑移剪应变最大的滑移系作为临界滑移系,选取临界滑移系上的最大Schmid应力、最大滑移剪应变率、循环Schmid应力比以及滑移剪应变范围等细观参量作为损伤参量,建立了一种新的基于临界平面的循环损伤累积(CDA)模型。结果表明,该模型对于DD6高温疲劳寿命预测精度基本在3倍分散带内。

High temperature fatigue damage is a major factor causing the failure of single crystal turbine blades.The influence mechanisms of crystal orientation,strain range,mean strain and dwell time on the high temperature fatigue damage of nickel-based single crystal superalloys are studied respectively with the results of low cycle fatigue and creep-fatigue tests on DD6 standard specimens under different testing conditions and with viscoplastic stress-strain analysis based on slip systems.Furthermore,the slip system with the max slip shear strain is utilized as the critical slip system where the max Schmid stress,max slip shear strain rate,cyclic Schmid stress ratio and slip shear strain range are selected as the damage parameters,and a new cyclic damage accumulation（CDA）model based on critical plane is proposed.The results indicate that the predicted high temperature fatigue life of DD6 with the proposed CDA model based on critical plane is basically within a factor three of the experimental life.