Moore, Prediger, Stephenson
Materials and Their Characteristics # 1985 York
Fracture mechanics techniques are applied to UPVC pipe compositions in order to obtain quantitative and credible toughness results. The influence of polymer molecular weight and pipe age-in-service is then examined.
The techniques are also applied to considerations of material toughness and pipe toughness.
Plastics pipes, particularly those manufactured from PVC and polyethylene, have been in service successfully for many years. The continuing interest and activity in predicting the service life of pipe indicate that a full understanding of the numerous factors influencing pipe lifetimes has not yet been achieved. Whilst it would seem reasonable to expect that pipe toughness could be easily measured and directly related to service performance this has proven not to be the case. Nevertheless significant advances in testing techniques and prediction methods have been made in recent years. A sound basis for the consideration of toughness is essential if further progress is to be made. In this paper we consider four aspects of toughness.
- what to measure
- how to measure it
- what might influence it
- how to use it
Fracture mechanics concepts have been established as quantitative methods for measuring toughness (1). They have been applied to a range of materials with considerable success.
Despite the marriage of a linear elastic theory to non-linear viscoelastic materials, fracture mechanics may usefully be applied to thermoplastics. There has been recent progress in the identification of appropriate geometry and size factors in order to achieve objective and valid measurements of fracture mechanics parameters. These ideas are documented in the literature (2,3 ), but because they are an important consideration in this work, it seems appropriate to define the main steps in the argument.
Author(s) : David Becerril García, Jacinto Cortés-Pérez, Ian D. Moore
Joint performance of joints in gravity flow buried pipelines is very important since joint failure could produce structural or service limits to the system. Standards have been developed to evaluate that joints have the necessary structural and leakage capacities which specify test methods that are not clear and do...
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The robustness of PVC-U pipes can be increased by blending PVC with chlorinated polyethylene (CPE). By varying the level of incorporation a spectrum of properties can be achieved. Data are presented which indicate that the tensile yield stress decreases with increasing amounts of CPE, whilst the fracture toughness,...
Author(s) : Wood, Moore
The erosion of pipe materials in slurry flow streams occurs through a variety of wear processes. As a result, the comparative wear resistance of materials is extremely difficult to predict from a knowledge of basic physical and engineering properties. Design and selection criteria must hence be based on empirical...
Author(s) : Moore, Stephenson
A model is established for the calculation of flexural rigidity (EII of pipe sections that contain a solid skin - foamed core - solid skin structure. Stiffness of t h e pipe can be calculated from (EII. The model accommodates different and similar materials in the skin and the core, a range of section dimensions...
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A number of UPVC pressure pipes .of different sizes and classes, have been characterised in materials. Long term testing was performed on specimens under a range of loading regimes, including hydrostatic burst testing, long term fracture toughness testing and dynamic fatigue. In all instances the behaviour...
Author(s) : Moore, Stephenson, Whale
Short term tests For the evaluation of the toughness of UPVC pipe materials have been examined. A combination of fracture toughness (a fracture mechanics parameter) and tensile yield stress provide an assessment of toughness. These tests have been applied to commercial pipe samples and to laboratory extruded strip. A...
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Power engineers have an urgent need for the extreme corrosion resistance which GRP can provide. Engineers in the power industry are finding that GRP materials have the properties needed to meet the new requirements - and that they can do so at reasonable cost. We believe that the power industry will continue to be a...