Low-Cycle-Fatigue Characteristics of Short Glass Fiber Reinforced Polybuthyleneterephthalate
Low-Cycle-Fatigue Characteristics of Short Glass Fiber Reinforced Polybuthyleneterephthalate
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短玻纤增强聚对苯二甲酸丁二醇酯的低周疲劳特性
DOI：
10.2472/jsms.56.406
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发表时间：
2007
期刊：
影响因子：
--
通讯作者：
Keisuke Tanaka
中科院分区：
文献类型：
--
作者：
H. Oka;Ryoichi Narita;Y. Akiniwa;Keisuke Tanaka
两种短玻璃纤维增强聚对苯二甲酸丁二醇酯 (PBT) 圆柱形试样，一种是熔接线位于中心的试样（W 试样），另一种是成型方向平行于试样轴线的试样（MD 试样），在轴向总应变控制条件下进行疲劳试验。在相同总应变范围内比较，W试件的疲劳寿命略短于MD试件，但差异很小。当根据应力幅值或非弹性应变能绘制曲线时，W 样品的疲劳寿命要短得多。应力-应变磁滞回线中的拉伸峰值应力随着循环次数的增加而降低。 MD 试样在峰值应力减少 30% 至 40% 时发生不稳定断裂，而 MD 试样在拉伸峰值应力减少 40% 时峰值应力急剧下降，非弹性能达到最大值。 W试件未发生不稳定断裂。使用同步加速器 X 射线的计算机断层扫描 (CT) 用于无损观察疲劳试样中的裂纹扩展行为。在W试样中，裂纹从表面开始向内延伸，形成连续的长裂纹，而在MD试样中，仅在试样的中心区域观察到许多小裂纹，直到不稳定断裂。
Two kinds of cylindrical specimens of short-glass-fiber reinforced polybuthyleneterephthalate (PBT), the one with weld line at the center (W specimens) and the other with molding direction parallel to the specimen axis (MD specimens), were fatigued under axial total-strain-controlled conditions. The fatigue life of W specimens was slightly shorter than that of MD specimens when compared at the same range of total strain, although the difference was very small. When plotted against the stress amplitude or inelastic strain energy, the fatigue life was much shorter for W specimens. The tensile peak stress in stress-strain hysteresis loops decreased with the number of cycles. Unstable fracture took place at 30 to 40% reduction of peak stress in MD specimen, while in MD specimens a sharp decrease in the peak stress and the maximum in inelastic energy took place at the 40% reduction of the tensile peak stress. Unstable fracture did not occur in W specimens. The computerized tomography (CT) using synchrotron X-rays was applied to observe nondestructively the crack growth behavior in fatigued specimens. In W specimens, crack started from the surface and extended inward as a continuous long crack, while only many small cracks observed at the central region of the specimens until unstable fracture in MD specimen.