The analysis of ultrasonic wave propagation in an axisymmetric viscoelastic cylindrical waveguide under time-dependent preload is presented. It requires investigation of the transient response for understanding the dynamics of a multi-wire structure for non-destructive evaluation and health monitoring applications. The purpose of this research is to establish a platform for calculating the time-transient response of waveguides for propagating acoustic emission (AE) signals using a semi-analytical finite element (SAFE) method. The time-transient response analysis is carried out in the frequency domain, which combines the Fourier transform and Cauchy residue theorem. The fundamental idea is to use the modal superposition method to calculate the frequency response at each point and then utilize the inverse Fourier transform to convert the response to the time domain. For the numerical investigation, an axisymmetric SAFE method is utilized to simulate the AE signal for propagating in an infinitely long, high-strength steel wire with a diameter of 5 mm. The time-dependent loads used in the numerical investigation for analyzing time-transient responses are narrowband and broadband excitations. A nonlinear model for transient response analysis is developed to consider the contact state and friction effects of the surrounding steel wires in the multi-wire environment. A nonlinear device consisting of contact springs and friction-type dampers is considered to account for the contact state and friction effects of the surrounding steel wires. The investigations are carried out with a single set and two sets of nonlinear devices under various stiffness values and preload conditions to understand the response characteristics. The estimated value of the contact spring stiffness is based on calculating the Hertz semi-width between the steel wires when the seven-wire steel strands are under tension. From observation, the standard nonlinear features input high-frequency fluctuation components into the original ideal linear system and cause extended high-frequency fluctuation at the tail of the waveform. The proposed nonlinear model for analyzing the preload condition in the axisymmetric viscoelastic waveguide showed a possible way for guided wave propagation-based health monitoring applications for prestressed cables.

提出了随时间变化的预载下超声波在轴对称粘弹性圆柱形波导中传播的分析。它需要研究瞬态响应，以了解多线结构的动力学，以进行无损评估和健康监测应用。本研究的目的是建立一个平台，使用半解析有限元（SAFE）方法计算传播声发射（AE）信号的波导的时间瞬态响应。瞬态响应分析是在频域进行的，结合了傅里叶变换和柯西剩余定理。其基本思想是利用模态叠加方法计算各点的频率响应，然后利用傅里叶逆变换将响应转换到时域。在数值研究中，采用轴对称 SAFE 方法来模拟 AE 信号在直径为 5 mm 的无限长高强度钢丝中传播。用于分析瞬态响应的数值研究中使用的瞬态载荷是窄带和宽带激励。开发了用于瞬态响应分析的非线性模型，以考虑多线环境中周围钢丝的接触状态和摩擦效应。考虑由接触弹簧和摩擦型阻尼器组成的非线性装置来解释周围钢丝的接触状态和摩擦效应。研究使用单组和两组非线性装置在不同刚度值和预载条件下进行，以了解响应特性。 接触弹簧刚度的估计值是基于计算七根钢绞线受拉时钢丝之间的赫兹半宽度。从观察来看，标准的非线性特征将高频波动分量输入到原来的理想线性系统中，导致波形尾部出现扩展的高频波动。所提出的用于分析轴对称粘弹性波导中预载条件的非线性模型为基于导波传播的预应力电缆健康监测应用提供了一种可能的方法。