Applicability of Linear Elastic Fracture Mechanics to Rigid PVC Pipe Materials.
MASSACHUSETTS INST OF TECH CAMBRIDGE
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Pressurized plastic pipes for water and natural gas distribution are a prominent example of the increasing use of plastics in engineered structural applications. As such, they require careful design for properties such as stiffness and strength. Designs are typically limited by the stress-rupture curve, which defines the stress level the material can withstand for long time periods without a creep-rupture type of ductile failure 1. Under certain conditions, most plastics can also fail in a brittle mode, and this is well known for the PVC polyvinylchloride pipes investigated in this study 2. As will be shown, brittle failures are more likely to occur in the presence of large flaws, and under low temperature or high rate conditions. The brittle fracture of PVC and other plastics has received increasing attention 3-7. Although difficult to use as a design parameter in all but the most sophisticated cases, brittle fracture properties of plastics may be of practical importance in choosing between different materials, and in formulating improved plastics. Many of the techniques of brittle fracture study have been adopted from metals technology. Consideration of the particular yield phenomena and viscoelastic characteristics of plastics has also been developing 3-6. Among the topics which have not been given sufficient attention for plastics is the validity of fracture toughness test results. The theoretical basis of most brittle fracture studies is linear elastic fracture mechanics LEFM 8. The central assumption of LEFM is that the failure process at the crack tip occurs under the control of the stress intensity factor, K1, which char acterizes the intensity of the stress field very close to a sharp crack tip. MM
- Pumps, Filters, Pipes, Tubing, Fittings and Valves