中文摘要：

针对非比例加载路径对金属材料的疲劳行为及疲劳寿命的影响进行了研究。对LY12CZ铝合金薄壁圆管试样进行了单轴、纯扭和90°非比例路径下的疲劳实验。结果表明单轴拉压与纯扭加载下的滞后环形状基本一致，应力与应变同时达到最大值及最小值。而90°非比例路径下，应力与应变的最大值并不同时到达，存在一定程度的滞后。材料在90°非比例路径下存在附加强化，但不明显。在相同幅值的加载应变下，90°非比例路径的VonMises等效应变的最大值比比例路径下的小，但是最大等效应变作用的时间却远远高于比例加载情况。在相同等效应变幅下，纯扭路径的疲劳寿命最高，单轴次之，90°非比例路径的疲劳寿命最低。

英文摘要：

The effect on the fatigue behavior and the fatigue life of the metal materials under nonpropotional loading path is studied. Fatigue experiments of LY12CZ allumimum alloy thin-walled tubular specimens are conducted under axial tension-compression, pure torsion and 90° out-of-phase loading. It is found that the shapes of the hysteresis loops for the uniaxial loading and the pure torsional loading are approximately identical, and the peak axial and the torsional stresses are in agreement with their respective peak strain values. But for the 90° out-of-phase path, the peak axial and torsional stresses do not coincide with their respective peak strain values. There exists a lag between the stress and the strain peaks for both axial and torsional deformation responses. A little additional hardening is found under 90° out-of-phase loading compared with the stress responses for uniaxial cyclic loading. The difference between proportional and nonproportional loading paths is explained through the Von Mises equivalent stain. When the applied axial and torsional stains amplitudes keep fixed and just the phase between them is changed. The maximum Von Mised equivalent stain for 90° out-of-phase path is smaller than that for proportional path, but the time of holding the maximum equivalent stain under 90° out-of-phase path is longer than that under proportional path. When applying the same maximum Von Mises equivalent stain loading, the fatigue life under the pure torsion loading is the longest, the fatigue life under the uniaxial cyclic loading is the next, and the fatigue life of the specimens under 90° out-of-phase loading is the shortest.