The Role of Crazing in the Impact Fracture Toughness of PE Pipe Grades [PE]
# 1995 Edinburgh
A new method based on the Dugdale zone solution for finite geometries is
presented to analyse the case of craze growth at the notch tip in Charpy impact
experiments. It is believed that correct values of initiation toughness are
calculated via this method, leading to greater confidence in the extrapolation
technique used to derive the plane strain fracture toughness for polyethylene at
high impact speeds. An extensive comparison of the fracture performance of a
PEE0 and a PE100 resin has been performed using this approach. There is no
difference in minimum plane strain fracture toughness between the grades, but
the PE100 resin has far superior resistance to crack initiation by virtue of higher
energy absorption through crazing.
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Design of pipe systems for lifetimes in excess of 100 years depends on accelerated testing of pipe at
different temperatures, and standard extrapolation methods for assessment of the minimum required
strength. However resistance to slow crack growth is an essential parameter to take into account for
the development of...
Design of pipe systems for 50 year lifetimes depends on accelerated testing of pipe at
different temperatures and standard extrapolation methods for assessment of whether the
minimum required strength is achieved. Further acceleration is used in the notched pipe
test (NPT), which is a medium term (up to 1000 hour)...
The development of pipe grades requires the careful balance of several mechanical properties, of which two of the most important are the resistance to slow crack growth (SCG) and rapid crack propagation (RCP). In this paper, we present small-scale tests which enable the rapid assessment of these properties. These...
A series of PE 80 and PE 100 materials have been investigated to determine
whether there exists a link between resistance to slow crack growth as
measured by notched pipe test and creep of macroscopic oriented samples.
Preliminary results suggests that there is a correlation between a single
creep parameter and...
A critical appraisal has been carried out of the creep
fracture of the fibrils in the pre-crack damage zone
(craze) of polyethylene homo and copolymers. It has been
shown that by assuming that the fibrils are drawn to the
natural draw ratio of the material, a clear correlation
can be established between the creep rate...
Two novel techniques have been applied to the problem of determining the fracture toughness of polyethylene appropriate to the situation of rapid crack propagation in pipe systems.Agreement is found between the data from the two methods used for evaluating four grades of polyethylene of widely different toughness. By...