| Since nowadays polymers are being used increasingly for load bearing industrial applications, understanding the fatigue process in these materials is very necessary and essential. For application of linear elastic fracture mechanics (LEFM) to polymers, it is necessary to recognize potential pitfalls caused by their viscoelastic behavior, i.e. stress-strain dependence on time (or frequency) and temperature. Due to their viscoelastic nature, the fatigue crack propagation (FCP) behavior of most polymers is sensitive to test variables such as cyclic frequency and temperature. In this study, Fatigue crack propagation in chlorinated polyvinyl chloride (CPVC) pipefittings and high density polyethylene (HDPE) pipes are investigated over the frequency and temperature ranges of 0.1--10Hz and -10--70°C, respectively. Monotonic tests are also performed on both materials for different temperatures, and their result shows decrease in yield stress with increase in temperature. (Abstract shortened by UMI.)... |
