Barreling at cut ends of PE pipe: numerical and experimental investigation [PE]

When a thermoplastic pipe is cut to length, residual stresses are released causing local bending, reducing the diameter of the pipe at the cut end. Moving back inwards from the cut end, the measured pipe diameter does not simply increase to its initial value but locally overshoots to a new maximum : “pipe barreling”. This paper studies the development of the barreled shape in terms of residual stresses frozen in during post-extrusion pipe cooling. A non-linear heat transfer analysis determines the thermal history of the material during solidification, considering temperature dependant material properties and the kinetics and effects of crystallisation. Residual strains in the cooled pipe are determined using a thermoelastic model and compared with experimental data obtained using the layer removal method. A shell-theory solution for barreling is coupled to the numerical analysis to determine the deflection of the pipe wall near the cut end. Barreling is simulated for PE pipe of various dimensions and processing conditions. Finally, the model is validated by comparing the results to experimental data and the effect of barreling on electrofusion joints is discussed.