Faculty of Mechanical Engineering, Semnan University, Semnan, Iran.
PLoS One. 2023 Feb 7;18(2):e0281263. doi: 10.1371/journal.pone.0281263. eCollection 2023.
In the present article, fatigue properties (pure and fretting) of magnesium alloys (AM60) under cyclic bending loading were compared. For this objective, a rotary fatigue testing device was utilized with a fretting module on standard cylindrical samples under bending loads with zero means stress. The fretting fatigue condition decreased fatigue lifetime compared with pure fatigue but in an amazing Epsilon-shaped trend. Comparatively speaking to the state of pure fatigue, the fatigue lifetime of the fretting fatigue condition reduced by 91.0% and 44.8%, respectively, between the lowest level of stress (80 MPa) and the greatest level of stress (120 MPa). To study the fracture behavior and the fractography analysis, field-emission scanning electron microscopy (FESEM) was utilized. In general, since both quasi-cleavage and cleavage were seen; therefore, the fracture behavior for all samples was brittle. In both test conditions (fretting fatigue and pure fatigue), at higher stress levels, the average crack length was higher than at low-stress levels. In addition, the number of cracks (in high- and low-stress levels) was observed to be less in fretting fatigue conditions than in pure fatigue conditions, but the average crack length in fretting fatigue conditions in high-stress levels and low-stress levels was 212.82% and 259.47% higher than the average crack length under the pure fatigue condition, respectively.
本文比较了循环弯曲载荷下镁合金（AM60）的疲劳性能（纯疲劳和微动疲劳）。为此，利用带有微动模块的旋转疲劳试验装置，在弯曲载荷下对标准圆柱形试样进行零均值应力的微动疲劳试验。与纯疲劳相比，微动疲劳条件下的疲劳寿命降低，但呈惊人的ε形趋势。与纯疲劳状态相比，在最低应力（80 MPa）和最高应力（120 MPa）之间，微动疲劳条件下的疲劳寿命分别降低了 91.0%和 44.8%。为了研究断裂行为和断口形貌分析，采用了场发射扫描电子显微镜（FESEM）。总的来说，由于观察到准解理和解理，因此所有试样的断裂行为均为脆性。在两种试验条件（微动疲劳和纯疲劳）下，在较高的应力水平下，平均裂纹长度高于较低的应力水平。此外，在微动疲劳条件下，高、低应力水平的裂纹数量均少于纯疲劳条件，但高、低应力水平下的微动疲劳条件下的平均裂纹长度分别比纯疲劳条件下的平均裂纹长度高 212.82%和 259.47%。
