Photoelastic Method Revisited for Residual Stress Measurement in High Density Polyethylene Pipes

Residual stresses, also called “frozenin”
stresses in highdensity
polyethylene (HDPE)
pipes, result from uneven cooling that occurs between the inner and outer surfaces during the
extrusion process in manufacture. Most known methods of measurements involve intrusive testing to
determine the magnitude and profile of the residual stresses in the pipe wall thickness. The
Photoelastic Coating Technique (Photostress Method TM ) described in this paper involves capturing the
locked in stresses with minimal interference and local disturbance as the residual stress is released.
The existing methods used intrusive testing to determine the residual stress profile whereas the test
recommended to WIS 43203
gives a single residual stress value at the bore. The Photostress
Method permits stress measurements to be made directly at different points in the pipe wall and a
welldefined
residual stress profile was consequently obtained. An idealised equation for the residual
stress profile was found it was postulated that the residual stress profile in the pipe wall can be
determined once the residual stress at the pipe bore was obtained using either the WIS method or the
Photostress Method.

Citation:
Choollun, V.K. et al (2009) ‘Photoelastic Method Revisited for Residual Stress Measurement in High Density Polyethylene Pipes’ Proceedings of the AC&T, pp. 86-94..