A new engineering approach to predict the hydrostatic strength of uPVC


Visser, H.A. and Engels, T.A.P. and Govaert, L.E. and Bor, T.C. (2007) A new engineering approach to predict the hydrostatic strength of uPVC
In: PPS E/A, 2007, Göteborg, Sweden.

open access
Abstract:Extruded unplasticised Poly(Vinyl Chloride) (uPVC) pipes are certified using pressurised pipe tests.
During these tests the pipes are subjected to a certain temperature and internal pressure, while the
time-to-failure, the time at which the internal pressure drops due to rupture or fracture, is measured.
These tests are time consuming and are therefore costly. To circumvent these costs a model-based
approach is proposed where the time-to-failure is predicted. The input parameters for this approach
can be determined using short term measurements. The approach uses the observation that the timeto-
failure kinetics of uPVC pipes subjected to an internal pressure is independent of the type of failure
mode (ductile, semi-ductile or brittle). This supports our statement that the underlying mechanism
that initiates failure is similar for these types of failure. Local deformation of the material up to a
critical value of the anelastic strain is believed to determine the start of failure of the material. This
critical strain appears to be constant for the testing conditions used during this study. A pressure
modified Eyring expression is employed to calculate the strain rate resulting from the applied stress
at a certain temperature. The time-to-failure follows from the calculated strain rate and the critical
strain of the material. This approach has been verified against literature data and shown to hold
quantitatively. Furthermore, the model seems to hold for different processing conditions.
Item Type:Conference or Workshop Item
Engineering Technology (CTW)
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Link to this item:http://purl.utwente.nl/publications/70502
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