Publication detail
Multilayer polymer pipes failure assessment based on a fracture mechanics approach
HUTAŘ, P. ZOUHAR, M. NÁHLÍK, L. ŠEVČÍK, M. MÁŠA, B.
Czech title
Hodnocení porušení vícevrstvého polymerního potrubí pomocí postupů lomové mechaniky
English title
Multilayer polymer pipes failure assessment based on a fracture mechanics approach
Type
journal article - other
Language
en
Original abstract
It is widely recognised that quasi-brittle fracture (through initiation and subsequent crack propagation mechanism) at low stresses is the most common mode of failure for high-density polyethylene pressure pipes. Slow crack growth in such pipes usually starts at a small defect at or near the inner pipe surface. Knowledge of a stress intensity factor is a key point for establishing the maximum load that a cracked pipe can withstand without failure, for description of the crack kinetic, and consequently for assessment of the pipe lifetime. To this aim a finite element stress analysis is used to calculate the stress intensity factor for internal and external cracks in a three layer composite plastic pipe consisting of two protective layers and the main pipe. The polyethylene pressure pipe is loaded by internal pressure. In kontrast to homogeneous pipes the estimations of KI for multilayer (composite) pipes are numerically more elaborated and the fracture mechanics approach is complicated by the existence of interfaces between single layers, where material parameters are changed by a step. Special attention is paid to the configuration of a crack growing close to the interface and the effective values of stress intensity factor are estimated for a crack with its tip at the interface. It is shown that under special conditions (depending mainly on the elastic mismatch of materials) the crack can be arrested at the interface and significantly influence the lifetime of the pipe.
Czech abstract
It is widely recognised that quasi-brittle fracture (through initiation and subsequent crack propagation mechanism) at low stresses is the most common mode of failure for high-density polyethylene pressure pipes. Slow crack growth in such pipes usually starts at a small defect at or near the inner pipe surface. Knowledge of a stress intensity factor is a key point for establishing the maximum load that a cracked pipe can withstand without failure, for description of the crack kinetic, and consequently for assessment of the pipe lifetime. To this aim a finite element stress analysis is used to calculate the stress intensity factor for internal and external cracks in a three layer composite plastic pipe consisting of two protective layers and the main pipe. The polyethylene pressure pipe is loaded by internal pressure. In kontrast to homogeneous pipes the estimations of KI for multilayer (composite) pipes are numerically more elaborated and the fracture mechanics approach is complicated by the existence of interfaces between single layers, where material parameters are changed by a step. Special attention is paid to the configuration of a crack growing close to the interface and the effective values of stress intensity factor are estimated for a crack with its tip at the interface. It is shown that under special conditions (depending mainly on the elastic mismatch of materials) the crack can be arrested at the interface and significantly influence the lifetime of the pipe.
English abstract
It is widely recognised that quasi-brittle fracture (through initiation and subsequent crack propagation mechanism) at low stresses is the most common mode of failure for high-density polyethylene pressure pipes. Slow crack growth in such pipes usually starts at a small defect at or near the inner pipe surface. Knowledge of a stress intensity factor is a key point for establishing the maximum load that a cracked pipe can withstand without failure, for description of the crack kinetic, and consequently for assessment of the pipe lifetime. To this aim a finite element stress analysis is used to calculate the stress intensity factor for internal and external cracks in a three layer composite plastic pipe consisting of two protective layers and the main pipe. The polyethylene pressure pipe is loaded by internal pressure. In kontrast to homogeneous pipes the estimations of KI for multilayer (composite) pipes are numerically more elaborated and the fracture mechanics approach is complicated by the existence of interfaces between single layers, where material parameters are changed by a step. Special attention is paid to the configuration of a crack growing close to the interface and the effective values of stress intensity factor are estimated for a crack with its tip at the interface. It is shown that under special conditions (depending mainly on the elastic mismatch of materials) the crack can be arrested at the interface and significantly influence the lifetime of the pipe.
Keywords in Czech
Vícevrstvé trubky, zobecněný součinitel intenzity napětí, materiálové rozhraní, pomalý růst trhliny, polymerní potrubí
Keywords in English
Multilayer pipes, generalised stress intensity factor, material interface, slow crack growth, polyolefin pipes
RIV year
2013
Released
09.05.2013
ISSN
1350-6307
Volume
33
Number
1
Pages from–to
151–162
Pages count
12
BIBTEX
@article{BUT100909,
author="Pavel {Hutař} and Michal {Zouhar} and Luboš {Náhlík} and Martin {Ševčík} and Bohuslav {Máša},
title="Multilayer polymer pipes failure assessment based on a fracture mechanics approach",
year="2013",
volume="33",
number="1",
month="May",
pages="151--162",
issn="1350-6307"
}