Sun Jin, Hua Ye, Wei Ruo-qi
Papers # 2016 Berlin
Nowadays large diameter HDPE pipes have been widely used in water supply, municipal gas, mines, nuclear service and other fields, while residual stress of large diameter thick-walled pipes in the extrusion processing have resulted in lots of engineering failure cases. In this paper residual stress and mechanical property of HDPE pipes (250mm diameter and SDR11) have been studied. It is shown that the SCG failure time increases and the longitudinal reversion rates decrease along with the reduced difference value between melt temperature and cooling temperature. Then residual stresses of HDPE pipe are analyzed by the hole-drilling strain gage method and non-uniform distribution model. It is found that the residual stress of pipe also decrease gradually with the reduced temperature difference. And the mechanical behavior on outer, middle and inner regions of pipe wall have been studied through tensile experiment. The samples from the outer regions show the lowest tensile yield strength and the highest residual stress. Therefore the validity of the hole-drilling method on residual stress of HDPE pipes is confirmed by the same variation tendency of residual stresses and physical properties.