摘要
应用电子拉伸机、扫描电镜和Ｘ光衍射仪对高密度聚乙烯和聚丙烯材料的拉伸形变断裂行为进行了实验研究。结果表明，高分子材料小拉形变量是在缩颈扩展阶段发生局部集中形变的累积量；拉伸取向主要是由局集形变贡献的，冷拉阶段的时间长短对取向度影响不大，并用Ｘ光衍射仪测定取向函数值进行了验证；材料在屈服阶段断裂时，其断裂部分一般总是发生在由弹性形变向塑性形变的转变处；一旦发生了塑变，沿外力方向产生了取向，则对裂纹萌生及扩展起抑制作用。
In this paper, the fracture behaviors of high-density polyethylene and polypropylene in the times of tension deformation have been investigated submicroscopically with Instron tester, scanning electron microscope and X-ray diffractometer. The experimental results have showed that the deformation of polymer in macro cold tension stage is the accumulation and concentration of local deformation in the step of necking down and propagation. The concentrated behavior of local deformation is obviously the main contributory to the orientation of polymer in cold tension stage. The length of time of cold tension has little effect on the orientation degree in the position where plastic deformation occurred and it has been tested and verified with X-ray diffractometer through measuring the functional value of tension orientation. When the elastoplastic fracture of polymer is produced in tension tests, its fracture always occurrs in the position where the elastic deformation is changed to the plastic one. Once the polymer has been completed the change of elastic deformation to the plastic one, the macromolecular chains in deformation position orientate along with the direction of tension. So that the propagation of crack is resisted to a certain extent, and the fracture resistance increase to stop the fracture even at the low speed of tension.
出处
《机械工程材料》
CAS
CSCD
1996年第3期15-17,共3页
Materials For Mechanical Engineering
基金
国家自然科学基金
