Development of notched ring test for measuring slow cracking resistance in plastics pipes and fittings

Abstract

A novel Notched Ring Test (NRT) method for measuring slow cracking resistance (SCR) in plastics pipes and fittings has been developed and applied to determine its applicability as the standard test method. The NRT specimen in the form of a notched full ring, directly obtained from an extruded pipe or injection moulded fitting, was subjected to three-point bend loading and has demonstrated its effectiveness in generating slow cracking in a time frame of order of magnitude shorter than the currently available SCR measurement methods. Performance comparison between the NRT method and other methods was achieved by utilising the stress intensity factor concept and showed NRT generating slow cracking at intensity levels where ductile yielding occurred with other methods. Details of the NRT method in terms of test implementation, its SCR performance and the stress intensity factor approach to SCR evaluation are presented.