MULTILAYER POLYMER PIPES – THE INFLUENCE OF RESIDUAL STRESS ON FATIGUE LIFETIME
Lukas Travnicek, Pavel Hutar, Jan Poduska, Andreas Frank, Florian Arbeiter, Jaroslav Kucera, Jiri Sadilek, Gerald Pinter, Lubos Nahlik
# 2021 Amsterdam
The application of recycled material in pressure piping systems has been considered lately – it was suggested, that the recycled polyethylene could be used as a part of a multilayer pipe together with virgin material. This type of pressure pipes is not availableon the market yet, so their properties can be only estimated. Multilayer pipes made of virgin materials, where one of the layers is made of a slightly worse grade of polyethylene can give an idea about some of the properties. In this paper, the residual stress in a multilayer polyethylene pipe with the middle layer made of polyethylene with slightly lower mechanical properties is investigated. Lifetime estimation including the influence of residual stress is then carried out. The applied lifetime estimation procedure takes advantage of the fact, that the stress field around a crack tip in polyethylene can be described by the stress intensity factor. The lifetime of the pipe is then estimated by integration of the power law, which describes the crack growth rate. Eventually, the results are compared with lifetime estimations of the same pipe, where the residual stress was not considered. The comparison shows that the residual stress should not be neglected in lifetime estimations due to its significant influence.
article source https://www.pe100plus.com/PPCA/MULTILAYER-POLYMER-PIPES-THE-INFLUENCE-OF-RESIDUAL-STRESS-ON-FATIGUE-LIFETIME-p1788.html