Velocity of propagation of cleavage cracks in Tungsten
Velocity of propagation of cleavage cracks in Tungsten
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DOI：
10.1007/bf00183824
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发表时间：
1966-06
期刊：
影响因子：
--
通讯作者：
Derek Hull;P. Beardmore
中科院分区：
文献类型：
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作者：
Derek Hull;P. Beardmore
断裂表面的研究已经在200和3000 K之间的温度下在[010]中拉出的预裂纹钨单晶上进行。裂纹是由火花技术引入的，并且是原子级尖锐的。解理面的形貌随裂纹扩展应力和温度的变化而变化。在低应力和低温下，表面的大部分是“镜面”光滑的。使用倾斜照明的光滑表面被发现被覆盖的Wallner线开始在晶体的边缘或在小的分裂步骤。随着应力和温度的增加，光滑表面的面积逐渐变小，并最终限制在一个狭窄的尖峰沿着[001]。河流的密度也增加了。观察到从断裂面一侧向外扩展的不同河线密度的区域分离的边界数，并归因于裂纹尖端的应力场和横向弹性应力波之间的相互作用。解理裂纹的速度估计从形状的沃尔纳线和河流线边界的形状。在77°和20°K时，极限裂纹速度分别接近横向弹性波速度的0.60和0.82。在较高的温度下，在河流线的存在下，速度是0.20和0.55之间的横向弹性波速度。
Fracture surface studies have been made on pre-cracked tungsten single crystals pulled in [010] at temperatures between 200 and 3000K. The cracks were introduced by a spark technique and were atomically sharp. The appearance of the cleavage face varied with crack propagation stress and temperature. At low stresses and low temperatures a large proportion of the surface was ‘mirror’ smooth. Using oblique illumination the smooth surface was found to be covered with Wallner lines which started either at the edge of the crystal or at small cleavage steps. As the stress and temperature increased the area of smooth surface became progressively smaller and was restricted eventually to a narrow spike along [001]. The density of river lines also increased. A number of boundaries separating regions of different river line density were observed which spread out from the side of the fracture surfaces and were attributed to interaction between the stress field at the tip of the crack and a transverse elastic stress wave. The velocity of the cleavage cracks was estimated from the shape of the Wallner lines and from the shape of the river line boundaries. The limiting crack velocity approached 0.60 and 0.82 of the velocity of transverse elastic waves at 77° and 20°K respectively. At higher temperatures, in the presence of river lines, the velocity was between 0.20 and 0.55 of the transverse elastic wave velocity.