The widespread use of plastic pipes in different fluid conveyance systems has greatly driven the recent development and application of transient-based methods (TBMs) for leak detection in viscoelastic/polymeric pipelines. Current TBMs for viscoelastic pipe leak detection are usually achieved by a two-step procedure, namely viscoelastic parameters identification and leak detection, which requires the pre-knowledge of intact system states (i.e., non-leak) for comparative analysis. This paper presents an efficient single-step frequency domain inverse transient analysis (FDITA) method for simultaneous identifications of viscoelastic parameters and leaks in plastic pipes, so as to enhance the applicability and accuracy of TBMs. Both the single and branched polymeric pipe systems are applied for the method development and application. To this end, analytical solutions of single and branched systems from the transfer matrix method are firstly derived to represent the transient frequency responses of viscoelastic pipelines with leaks. A global optimized nonlinear curve fitting method is then employed to identify both viscoelastic parameters and potential leaks by knowing/measuring other system and flow conditions. Extensive experimental validations and numerical applications of both single and branched pipe systems demonstrate the very good efficiency and accuracy of the developed method for leak detection in different viscoelastic pipe systems. Furthermore, the mechanism of transient wave-leak-viscoelasticity is analysed based on these application results and theoretical evidence. Finally, a sensitivity analysis is performed to quantify and discuss the advantages and potential limitations of the developed method in the paper.

塑料管道在不同流体输送系统中的广泛使用极大地推动了基于瞬态方法 (TBM) 的粘弹性/聚合物管道泄漏检测的最新发展和应用。当前用于粘弹性管道泄漏检测的 TBM 通常通过两步程序实现，即粘弹性参数识别和泄漏检测，这需要预先了解完整系统状态（即非泄漏）以进行比较分析。本文提出了一种高效的单步频域逆瞬态分析（FDITA）方法，用于同时识别塑料管道中的粘弹性参数和泄漏，以提高TBM的适用性和准确性。单管和支管聚合物管系统均适用于方法开发和应用。为此，首先从传递矩阵法推导出单系统和分支系统的解析解来表示存在泄漏的粘弹性管道的瞬态频率响应。然后采用全局优化的非线性曲线拟合方法通过了解/测量其他系统和流动条件来识别粘弹性参数和潜在泄漏。单管和支管系统的大量实验验证和数值应用证明了所开发的方法在不同粘弹性管道系统中进行泄漏检测的非常好的效率和准确性。此外，基于这些应用结果和理论证据，分析了瞬态波泄漏粘弹性的机理。最后，