基于微观结构的2B06铝合金全寿命概率模拟

Probabilistic Simulation Approach for Holistic Life of Aluminum Alloy 2B06 Based on Material Microstructure

通过新型铝合金2B06轧制薄板材料的金相分析和疲劳断口的扫描电镜分析知,其疲劳裂纹萌生机理与材料微观结构有着紧密的联系,该型铝合金轧制薄板光滑试件的疲劳裂纹一般倾向于尺寸较大的S相(Al2CuMg)粒子处萌生。经统计分析获得S相粒子尺寸的分布规律;将S相粒子当量假设为表面裂纹,运用概率断裂力学,建立涵盖"材料微观结构→短裂纹扩展→长裂纹扩展→断裂"失效过程的全寿命概率模拟理论模型,通过不同应力水平和不同应力比的多组疲劳试验对模型进行验证。结果表明,提出的全寿命概率模拟方法是合理的、可行的。

A quantitative metallographic analysis and fatigue fractographic analysis using respectively KH-7700 microscope and scanning electron microscope reveals that the fatigue crack initiation mechanism depends heavily on material microstruc- ture for aluminum alloy 2B06. The fatigue crack initiates generally from S-type （AI2OuMg） constituent particles for the smooth rolled sheet specimens. Through statistic analysis, the cumulative distribution functions of the width and length of Stype constituent particles are obtained. The constituent particles are assumed to be surface cracks, and a holistic life simulation approach is proposed using probabilistic fracture mechanics based on material microstructure for 2B06, which includes short crack growth life and long crack growth life. A considerable number of fatigue tests with different maximum stress levels and different stress ratios are carried out to validate the approach, which shows that this aPProach is valid and feasible.