非对称循环载荷下镍基单晶合金低周疲劳寿命预测

Low-Cycle Fatigue Life Prediction of Single Crystal Nickel-Based Superalloys under Asymmetrical Cyclic Loading

在680℃温度下进行[001]、[011]和[111]三种取向的DD3单晶合金光滑试样非对称循环载荷低周疲劳试验,结果表明,晶体取向对DD3单晶合金的应变疲劳寿命有显著的影响,[001]取向寿命最长,[111]取向寿命最短。用晶体取向函数修正总应变范围可以在很大程度上消除晶体取向对疲劳寿命的影响。引入参量k表示载荷循环特性对疲劳寿命的影响,它与循环寿命之间呈幂函数关系。根据影响单晶叶片低周疲劳寿命的主要因素,提出循环塑性应变能的计算方法,构成塑性应变能的主要因素应包括总应变范围、取向函数和载荷循环特性等影响参量,它们与塑性应变能之间呈幂函数关系。用塑性应变能作为损伤参量导出单晶合金低周疲劳寿命预测模型,利用低周疲劳试验数据进行多元线性回归分析,所有试验数据均落在2.6倍偏差的分布带内。

Low cycle fatigue experiments of DD3 single crystal superalloys along ,and orientations under asymmetrical cyclic loading at 680℃ showed that crystal orientation affected low cycle fatigue life of DD3 single crystal superalloy significantly,life along orientation was the longest,life along orientation was the shortest.By modifying strain range with orientation function,the effect to fatigue life from orientation could be eliminated.A parameter k was introduced to express the effect that characteristic of cy...