2A12铝合金的多轴加载疲劳行为

采用SDN100/1000电液伺服拉扭复合疲劳试验机对2A12铝合金进行多关键参数的多轴疲劳性能研究,通过对断口的微观分析探究疲劳失效机理。结果表明:等效应力加载条件下,随拉扭相位差的增加疲劳寿命降低,0°相位差下断面裂纹源区能观察到轮胎状、鱼骨状以及钟乳石状的特殊形貌,裂纹扩展区存在二次裂纹和模糊的疲劳条带;分别改变拉、扭平均应力,多轴疲劳寿命均降低,裂纹源区能看到白色絮状的氧化物,瞬断区存在二次裂纹和剪切型韧窝;不同加载波形条件下,正弦波对应最长的多轴疲劳寿命,三角波次之,方波时最短且体现出最大的结构耗能。低-高两级加载条件下,材料产生"锻炼效应"。

Fatigue Behavior of 2A12 Aluminum Alloy Under Multiaxial Loading

The multiaxial fatigue behavior of 2A12 aluminum alloy was studied with SDN100/1000 electro-hydraulic servo tension-torsion fatigue tester under multiple variables,and the failure mechanism was investigated by scanning electron microscopy (SEM).The results show that under the loading condition of equivalent stress,the fatigue life decreases with the increase of phase angle.For the phase angle 0°,some special features can be observed in the crack initial zone,such as the tire pattern,fishbone pattern and stalactite pattern.There are secondary cracks and vague fatigue striations in the crack propagation zone;the multiaxial fatigue life decreases with the change of mean stress for tension or torsion.Some white flocculent oxides can be found in the crack initiation zone,and secondary crack as well as shear-type elongated dimples in the instantaneous fracture zone;facing different loading waveforms,the multiaxial life of sine wave is the longest,triangle wave in the second place,and the square wave is the shortest,under the loading condition of equivalent stress,square wave leads to the maximum structural energy dissipation.Under the low and high two step loading,2A12 shows training effect.