A comprehensive evaluation of transient-test-based approaches for determining creep function in heterogeneous polymer pipes

Determining the creep function of polymer pipes is the primary problem in predicting their reaction to abrupt loads, such as transient flow. This study analyzes transient pressure data’s time and frequency domains to evaluate the pipe wall creep function. First, the methodologies currently used in the literature are assessed. A numerical example and four experimental tests using various pipe system topologies, such as simple reservoir-pipe-valve (R-P-V) and heterogeneous viscoelastic pipelines, are then conducted using the suggested methodology. The Kelvin-Voigt (K-V) mechanical model with three elements is used in the study to compute the creep function, and the coefficients of retardation times, creep compliance coefficients, and pressure wave speed are the decision variables. The findings of this study indicate that attempting to determine the creep function solely based on leakage-dependent parameters such as resonant frequencies and zero-crossing times does not yield satisfactory results, even in the case of a simple R-P-V pipeline. By selecting an appropriate signal segment from both the time and frequency domains of the pressure signal, the creep function can be determined with satisfactory accuracy. Lastly, the accuracy of the suggested approach was validated by applying the methodology to experimental data of different topologies.