基于灰色理论镍基单晶合金多轴非比例加载低周疲劳研究

基于灰色理论研究DD3镍基单晶合金高温多轴非比例加载低周疲劳特性，对等效应变范围、温度、应变路径角、拉/扭载荷相位角和轴向应变比等影响疲劳寿命的因素进行灰色关联度分析，并引入损伤参量Q表征非对称循环特性和拉/扭多轴效应，以参量Q、等效应变范围Δεe和Mises等效应力范围Δσe构造疲劳损伤参量，建立低周疲劳寿命GM(1, N)预测模型。结果表明，各影响因素与多轴低周疲劳寿命的关联度等级依次为等效应变范围、温度和应变路径角为一级，拉/扭载荷相位角为二级，轴向应变比为三级；680 ℃和850 ℃温度下的GM(1, N)疲劳寿命模型的预测寿命与试验寿命的绝对关联度分别为0.97、0.86，平均相对误差分别为4.9%、6.0%；两种温度的试验数据几乎分别落在1.93、2.13倍偏差分布带内。

Study on Low Cycle Fatigue of Ni-based Single Crystal Alloy under Multi-axial Non-proportional Loading Based on Grey Theory

Based on grey theory, the characteristics on low cyclic fatigue of DD3 Ni-based single crystal alloy under multi-axial non-proportional loading are researched. Degree of grey incidence of factors influencing fatigue life, such as equivalent strain range, temperature, strain path angle, tension/torsion phase angle, axial strain ratio, is analyzed. A damage parameter Q is introduced to express asymmetric load cyclic characteristic and tension/torsion multi-axial effect. A low cyclic fatigue life prediction model GM(1, N) with parameter Q, equivalent strain range Δεe and Mises stress range Δσe as damage parameters is built. The results show that degree of grey incidence of influencing factors on multi-axial low cyclic fatigue life，from maximum to minimum，are equivalent strain range , temperature and strain path angle for the first level, tension/torsion phase angle for the second level, and axial strain ratio for the third level. Absolute degree of incidence of test life and predictive life for fatigue model GM(1, N) at 680 ℃ and 850 ℃ are 0.97, 0.86, respectively, and mean relative errors are 4.9%, 6.0% respectively. Almost all test data of above-mentioned two temperatures were fall into the factors of 1.93 and 2.13 scatter band, respectively.