挤出工艺对聚乙烯管材残余应力分布的影响

Effect of Extrusion Processing on Residual Stress Distribution of Polyethylene Pipe

通过调整冷却速度制备出具有不同残余应力分布的高密度聚乙烯(PE-HD)管材,考察了挤出工艺对PE-HD管材内外层残余应力和常规物理性能的影响。结果表明,随着冷却速度的增加,管材纵向回缩率逐步增大,且其静液压破坏时间和管材耐慢速裂纹增长(SCG)破坏时间也随之降低;同时管材外层的残余应力随着冷却速度和钻孔深度的增加逐步提高,呈现非均匀分布的情况,而管材内层的残余应力较小,均匀性差异不显著,并通过分层拉伸试验验证了盲孔法测量管材内外层残余应力的适用性。

The high density polyethylene(PE-HD) pipes with different residual stress were extruded under different cooling conditions, and the effect of extrusion processing on the physical properties and residual stress in the inner and outer layers of PE pipes were investigated. The results indicated that the longitudinal reversion rate of PE-HD pipes increased gradually with an increase of cooling rate, but their hydrostatic failure time and failure time of resistance to slow crack growth decreased simultaneously. On the other hand, the residual stress of outer layer increased gradually with increasing the cooling rate and enlarging the hole depth, which presented a non-uniform distribution. However, the residual stress of inner layer was relatively smaller and the non-uniform distribution was undistinguishable. The validity of the hole-drilling method for the residual stress test of PE-HD pipes was also confirmed by the tensile test results on the different layers of PE-HD pipes.