LC9材料疲劳特性的测试及其寿命预测方法探讨

On Fatigue Property Tests of LC9 Aluminum Alloy and their Analysis

对ＬＣ９－ＣＳ棒材进行轴向应变控制疲劳试验，较全面地测试出材料的应变疲劳特性，包括稳态应力应变曲线，瞬态应力应变曲线，Ｍａｎｓｏｎ－Ｃｏｆｆｉｎ公式描述的εａ－Ｎｆ曲线以及当量应变寿命（εｅｑ－Ｎｆ）曲线。并对上述特性曲线构成的不同寿命预测方法与试验进行了深入比较，结果表明，瞬态应力应变曲线和εｅｑ－Ｎｆ曲线能较好地反映材料的疲劳特性。并能兼顾应变疲劳和应力疲劳分析的需要。

LC9 aluminum alloy is but recently used in Chinese aeronautical industry. Our fatigue property tests of LC9 may very likely be the most extensive in China, numbering 192 specimens. Besides, a novel neural network method is used in analyzing test data.in this paper, a series of axial strain-controlled fatigue tests of LC9-CS bar specimenshas been conducted to get the fstigue characteristics of this material. The tests lead to a stable cyclic σ～ε curve, a number of cyclic transient σ～ε curves, a εa～Nf relationship (deduced from Manson-Coffin equation) and a εeq～Nf relationship. Especially, a set of Back Propagation Neural Network (BPNN ) is established to reflect the highly nonlinear feature of transient cyclic σ～ε curves, which is very hard to be descrigbed with traditional mathematical methods. The computation results of BPNN are satisfactory from the viewpoint of engineering application. Combining transient cyclic σ～ε curyes with εeq～Nf relationship is the best wad to describe the fatigue characteristics of material.