一种用于金属薄板轴向拉压疲劳试验的防弯夹具

在金属薄板的轴向疲劳S-N曲线测试中,研究将一种侧向防弯曲夹具应用于存在压向载荷的试验。通过粘贴应变片方法测量试样的表面应力,对试样的受力情况做了定量的分析。测量结果表明试样安装防弯曲夹具后,基本消除了由压缩失稳产生的弯曲应力。且通过对不同拧紧方式的测量,表明一定的夹紧力下不对试验力产生影响。试验夹具设计成对试样中心轴线的支撑而让边缘疲劳敏感部位处在非接触状态,试样断口表明疲劳起源在这些并没有与试样接解的部位。用钛和铝两种材料的薄板在不同试验机上进行了不同寿命和频率的试验,试验结果与正应力比试验同时给出以对比,各种研究表明本试验有效解决了薄板疲劳受压时的失稳问题。

A Research for Thin Metal Sheet Fatigue Test under Tension-Compression Loading

A research was performed on thin metal sheet fatigue test under tension-compression loading. A restraint was applied to the fatigue test in order to prevent the occurrence of unsteady compression. To determine the effects of the restraint on the stress in a specimen, the specimen surface strain was measured by an adhesive strain gage. The measured stress in specimen shows that the simple fixture is efficient to prevent the occurring of bending stress in the compression load condition. The stress measurements were performed under different fix forces. The results show that the fix force has no obvious effects on the applied axis tension or compression stresses of the tests. The restraint is designed to clip the center part of specimen and let the fatigue sensitive part free. The configurations of the fracture surfaces show that the fatigue failure started from the edge of the sheet specimen. That place is far from the fixture. Two kinds of metal sheets, aluminum and titanium, were used to perform the fatigue test with different machines for various lives or frequencies. The results were plot together with those of positive ratios for comparing. It is shown that the proposed fixture is efficient for fatigue test.