Dario Sinnone, Francesca Tisi, Mario Vitali
Papers # 2012 Barcelona
Polypropylene is widely used for double-wall structured pipes for sewage applications due to the superior performance it demonstrates versus traditional materials such as high density polyethylene, concrete and metals. Its outstanding balance of mechanical properties enable optimized designs and reduced weight per unit length of the pipe without affecting or increasing pipe stiffness and strength. To evaluate the improvement of pipe radial compressive behavior and potential weight savings, Finite Element Method was used. Radial static compression was simulated according to pipe standards to evaluate pipe rigidity and strength under various combinations of profile shape, thickness, diameter and material type. The simulation methodology was first validated by comparing predicted compression force versus displacement curves to the corresponding curves measured in a real-life test. Good correlation between predicted and real behavior is observed, providing that the nonlinear material behavior and the accurate thickness distribution along the profile section are correctly taken into account. For this purpose, specific tensile tests on specimens cut from structured pipes were performed on various materials to measure true stress-strain curves by using LyondellBasell methods for Optical Strain measurement. In parallel, a methodology was developed to predict the thickness distribution resulting from the extrusion and forming of a structured double-wall pipe using simulation. By using the values of the extruded pipe’s wall thickness, final inner and outer diameters, and profile of the corrugation, simulation estimates the thickness distribution of the final profile, which can be subsequently used to simulate the compression of the pipe. The study confirmed that better results are obtainable with polypropylene versus high density polyethylene in sewage pipes. It also demonstrated the improved performance of high modulus polypropylene used in this application.