Polypropylene for structured sewage pipes. comparative study of materials in use through computer simulation of radial compression
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.
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