Fatigue crack propagation in high-density polyethylene
Fatigue crack propagation in high-density polyethylene
复制标题
高密度聚乙烯中的疲劳裂纹扩展
DOI：
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发表时间：
1991
期刊：
影响因子：
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通讯作者：
J. Runt
中科院分区：
文献类型：
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作者：
J. Yeh;J. Runt
研究了高密度聚乙烯（HDPE）结晶微结构对疲劳裂纹扩展的影响。不同的热历史被用来产生样品具有相同的结晶度和超分子结构的三种不同分子量的HDPE。从脆性断裂应力的测量和预测的聚合物的估计链尺寸使用的方法最初采取的黄和布朗的修改后的版本，获得了估计的连接链密度。随着分子量的降低，FCP抗性显著降低，并且观察到向更脆的断裂表面的明显过渡。详细的研究破坏区之前的增长裂纹显示过渡到一个更高度分支的裂纹结构与较高的FCP电阻的样品。这些结果强烈表明，分支损伤区结构通过扩大和钝化裂纹尖端，从而在疲劳裂纹扩展过程中消耗更多的能量，提高了FCP抗性。另外还努力制备具有相同结晶度和连接链密度但不同超分子结构的样品。然而，在文献中的报告相反，没有显着差异FCP电阻观察到不同的平均球晶尺寸的标本。这可能是因为扩展的裂纹前缘之前是一个明显的塑性变形区，预计不会直接遇到球晶。
An investigation of the influence of crystalline microstructure on fatigue crack propagation (FCP) in high-density polyethylene (HDPE) is reported. Various thermal histories were used to generate samples with the same crystallinity and supermolecular structure for three different molecular weight HDPEs. Estimation of tie chain densities were obtained from measurements of brittle fracture stress and predicted from the estimated chain dimensions of the polymers using the modified version of the approach originally taken by Huang and Brown. A significant decrease in FCP resistance and a clear transition to a more brittle fracture surface was observed with decreasing molecular weight. Detailed studies of damaged zones preceding the growing crack show a transition to a more highly branched crack structure for those samples associated with a higher FCP resistance. These results strongly suggest that the branched damaged zone structure improves the FCP resistance by enlarging and blunting the crack tip and, therefore, consuming more energy during the fatigue crack propagation. Additional efforts were made to prepare samples with the same crystallinity and tie chain density, but different supermolecular structure. However, in contrast to reports in the literature, no significant difference in FCP resistance was observed for specimens with different average spherulite sizes. This is probably because the propagating crack front is preceded by a significant zone of plastic deformation and is not expected to directly encounter the spherulites.