Evaluation of dynamic fracture-initiation toughness using a novel impact bend test procedure.
Evaluation of dynamic fracture-initiation toughness using a novel impact bend test procedure.
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使用新型冲击弯曲测试程序评估动态断裂起始韧性。
DOI：
10.2472/jsms.39.1637
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发表时间：
1990
期刊：
影响因子：
--
通讯作者：
M. Nakano
中科院分区：
文献类型：
--
作者：
T. Yokoyama;K. Kishida;M. Nakano
描述了一种新颖的冲击弯曲测试程序，用于确定加载速率 KI 为 106MPa√m/s 量级时的动态断裂起始韧性 KId。分体式霍普金森压力棒技术用于测量施加到疲劳预裂弯曲试样上的动态载荷。弯曲样本的动态应力强度因子历史通过动态有限元代码进行评估。使用裂纹尖端附近的应变计检测裂纹萌生的开始。 KId 值由裂纹萌生时的临界动态应力强度因子确定。对 Ti-6246 合金和 7075-T6 铝合金进行了一系列动态断裂试验。将两种合金获得的 KId 值与准静态加载条件下获得的相应值进行比较。借助扫描电子显微镜检查断裂表面形态，以合理化所测量的断裂起始韧性随加载速率变化的明显差异。此外，基于显微硬度测试，通过测量断裂试样内部的裂纹尖端塑性区尺寸，证实了 KId 测定的有效性。
A novel impact bend test procedure is described for determining the dynamic fracture-initiation toughness, KId, at a loading rate KI of the order of 106MPa√m/s. The split Hopkinson pressure bar technique was used to measure dynamic loads applied to a fatigue-precracked bend specimen. The dynamic stress intensity factor history for the bend specimen was evaluated by means of a dynamic finite element code. The onset of crack initiation was detected using a strain gage near a crack tip. The KId value was determined from the critical dynamic stress intensity factor at crack initiation. A series of dynamic fracture tests were performed for a Ti-6246 alloy and a 7075-T6 aluminum alloy. The KId values obtained for both the alloys were compared with the corresponding values obtained under quasi-static loading conditions. The fracture surface morphology was examined with the help of a scanning electron microscope to rationalize the apparent differences in the measured fracture-initiation toughness in response to the change in loading rate. Furthermore, the validity of the KId determination was confirmed by measurements of the crack tip plastic zone size in the interior of the fracture specimens based on the microhardness tests.