应变能-频率分离法及其应用

 应变能-频率分离法（SEFS）为频率分离法（FS）和频率修正损伤函数法（Ostergren M）的分析、综合与修正。SEFS法提出预测高温低周疲劳寿命的自变量为非弹性应变能、拉伸进程的频率（V_t）及拉压进程的时间比（V_c/V_t）,即用Ostergren公式中的损伤函数代替FS中的非弹性应变（△in）。并用这三种方法对国产材料GH33A（700℃）、1Crl8Ni9Ti（600℃）与国外九种材料及相应工艺的现有试验数据进行验证,结果表明,SEFS比FS和Ostergren M的预测能力有所改进。

A STRAIN ENERGY-FREQUENCY SEPARATION METHOD AND ITS APPLICATION

A modified energy approach, Strain Energy-Frequency Separation （SEFS） method, is developed for predicting low cycle fatigue life at elevated temperature, since FS method fails to take the mean stress effects into account and Ostergren method is very cumbersome and complicated in dealing with wave shape effects. SEFS method combines three independent variables, inelastic strain energy （ΔεinσT）, tension-going frequency （vt） and loop-time unbalance （vc/vt）, in a power-law relation'to predict the low cycle fatigue life at high temperature （Eq. 10）. SEFS method is evaluated and compared with FS and Ostergren methods by predicting the low cycle fatigue lives of GH33A nickel base superalloy at 700℃, 1Cr18Ni9Ti stainless steel at 600℃, Rene' 95 at 650℃ and AF2-1DA at 760℃. It is shown that SEFS method is better than FS and Ostergren methods （Table 1）.