不同应力幅比加载下2A12铝合金的多轴疲劳性能

采用SDN100/1000电液伺服拉扭复合疲劳试验机对2A12铝合金进行不同应力幅比下的多轴疲劳实验,观察试样断口形貌并结合加载过程中的疲劳循环曲线进行失效机理分析。结果表明:单级加载条件下,随应力幅比的增加合金的疲劳寿命提高,纯扭转条件下断面存在平整的光滑区域,随应力幅比的增加断面划痕减少,并能观察到疲劳条带以及鱼骨状、鳞片状和蜂窝状特殊形貌;不同应力幅比累积路径下,多轴疲劳寿命随一级加载周次变化的规律不同;高-低应力幅比累积路径下,拉压方向一级高应力幅比加载阶段出现明显的循环硬化现象,材料产生"锻炼效应"。

Multiaxial Fatigue Properties of 2A12 Aluminum Alloy Under Different Stress Amplitude Ratio Loadings

The multiaxial fatigue behavior of 2A12 aluminum alloy was studied with SDN100/1000 electro-hydraulic servo tension-torsion fatigue tester under different stress amplitude ratios, the fracture morphology and the fatigue loading curve were observed to study the failure mechanism.The results show that, under the one stage loading condition, the fatigue life prolongs with the stress amplitude ratio increasing.Under pure torsion loading, smooth and even area exists in the fracture surface.As the stress amplitude ratio increases, the number of scratch reduces, the fatigue striation and some special morphology such as the fishbone pattern, scale pattern and honeycomb pattern can be observed;under cumulative paths of different stress amplitude ratios, the variation of multiaxial fatigue life changes with first stage loading cycles;under cumulative paths of high-low stress amplitude ratio, the cycle hardening occurs obviously in the axial direction for the first stage high stress amplitude ratio loading and 2A12 alloy shows training effect.