一种基于混合硬化本构模型的汽轮机轮盘榫槽疲劳寿命预测方法

A Method for Predicting Fatigue Life of Turbine Rotor Wheel Groove Based on Mixed Hardening Constitutive Model

针对汽轮机转子轮盘的受力特点,以非对称载荷下材料的瞬态应力应变响应为基础,在内变量理论框架下,建立起某型汽轮机轮盘材料的率无关循环塑性本构模型;并结合局部应力应变法,进一步建立了基于混合硬化本构模型(N-5L1)描述平均应力松弛行为的汽轮机轮盘榫槽疲劳寿命预测方法。通过与实验结果相比较,表明混合硬化本构模型能够较好地模拟脉动加载下转子轮盘材料的循环应力应变响应及平均应力松弛行为,由此建立的寿命预测方法可对轮盘榫槽进行较为准确的疲劳寿命预测(与试验寿命误差总体落在1.5倍分散带以内),明显优于基于平均应力松弛经验公式的疲劳寿命预测值。

According to the stress characteristics of turbine rotor wheel and based on the transient stress-strain response of the material under asymmetric load,the rate-independent cyclic plastic constitutive model of the rotor wheel material of a turbine was established in theoretical framework of internal variables.Combined with the local stress and strain method,an approach for predicting the fatigue life of the turbine wheel groove was further established based on the mixed hardening constitutive model(N5L1)to describe the average stress relaxation behavior.Comparing with the experimental results,it showed that the mixed hardening constitutive model can well simulate the cyclic stress-strain response and average stress relaxation behavior of the rotor wheel material under pulsating loading.The established life prediction method can predict the fatigue life of the roulette mortisecan with good accuracy(the overall error with the test life is within 1.5 times of the dispersion zone),and it was obviously better than the predicted fatigue life based on the empirical formula of average stress relaxation.