服役环境下材料S-N曲线的BP模型

目前常规条件下各种金属材料的S—N曲线已基本完备，但是考虑腐蚀环境影响的S—N曲线还很少见。本文研究了在加速腐蚀当量环境谱作用后，LY12-CZ铝舍金材料的S—N曲线随日历年限的变化规律。首先，将试件暴露于加速腐蚀环境中，进行0年、3年、8年和13年的腐蚀试验。其次进行常幅谱下的疲劳试验。试验结果表明：腐蚀环境作用后的疲劳寿命均值随日历年限的增加显著降低，而变异系数呈增长的趋势。鉴于腐蚀环境作用后的S—N曲线具有较强的非线性，本文采用反向传播网络对加速腐蚀后的疲劳试验结果进行训练，建立了日历腐蚀环境下材料S—N曲线的BP模型，仿真结果与试验结果吻合较好。

BP Model of S-N Curve under Service Environment

S N curves of sorts of metals under general condition have been maturity. But the S N curves considering the effect of corrosive environment are reported. This paper researches the S N curves of aluminum alloy LY12 CZ under the constant amplitude loading after the corrosion of different equivalent calendar years. First, specimens are exposed to the corrosive environment for equivalent calendar time of zero year, 3 years, 8 years and 13 years. Secondly, the fatigue tests are carried out. Finally, BP model of S N curve on the basis of experimental data is established. Experimental results show that corrosive environment observably depresses the average value of fatigue life and makes the variance of fatigue life with calendar years trend to accretion. Results also reveal that the S N curves varying with calendar years consist of intensively nonlinear characteristics and previous method which describes S N curves does not adapt the case. The BP model can reveal the inherent nonlinear relationship between input data and output data, simulational and experimental results are in good agreement.