Efficient and accurate predictions of wave propagation are a vital component of wave-based nondestructive interrogation techniques. Although a variety of models are available in the literature, most of them are suited to a particular wave type or a specific frequency regime. In this paper we present a multi-wave model for wave propagation in axisymmetric fluid-filled waveguides, either buried or submerged in a fluid, based on the semi-analytical finite elements. The cross-section is discretised with high-order spectral elements to achieve high efficiency, and the singularities resulting from adopting a Lobatto scheme at the axis of symmetry are handled appropriately. The surrounding medium is modelled with a perfectly matched layer, and a practical rule of choice of its parameters, based only on the material properties and the geometry of the waveguide, is derived. To represent the fluid and the solidfluid coupling, an acoustic SAFE element and appropriate coupling relationships are formulated. The model is validated against both numerical results from the literature and experiments and the comparisons show very good agreement. Finally, an implementation of the method in Python is made available with this publication.
Waves that propagate at low frequencies in buried pipes are of considerable interest in a variety of practical scenarios, for example leak detection, remote pipe detection, and pipeline condition assessment and monitoring. Whilst there has been considerable research and commercial attention on the accurate location of pipe leakage for many years, the various causes of pipe failures and their identification, have not been well documented; moreover, there are still a number of gaps in the existing knowledge. Previous work has focused on two of the three axisymmetric wavetypes that can propagate: the s=1, fluid-dominated wave; and the s=2, shell-dominated wave. In this paper, the third axisymmetric wavetype, the s=0 torsional wave, is investigated. The effects of the surrounding soil on the characteristics of wave propagation and attenuation are analysed for a compact pipe/soil interface for which there is no relative motion between the pipe wall and the surrounding soil. An analytical dispersion relationship is derived for the torsional wavenumber from which both the wavespeed and wave attenuation can be obtained. How torsional waves can subsequently radiate to the ground surface is then investigated. Analytical expressions are derived for the ground surface displacement above the pipe resulting from torsional wave motion within the pipe wall. A numerical model is also included, primarily in order to validate some of the assumptions made whilst developing the analytical solutions, but also so that some comparison in the results may be made. Example results are presented for both a cast iron pipe and an MDPE pipe buried in two typical soil types
Unwanted accretions on structures are a common machinery maintenance problem, which can pose a serious safety threat if not treated effectively and punctually. In this paper we investigate the capability of piezoexcited structural waves for invoking delamination of accreted material from waveguides. We apply a wavebased technique for modelling piezoelectric excitation based on semi-analytical finite elements to model the interface shear stress associated with piezo-actuated structural waves. As a proof of concept, we present a demonstration experiment in which patches of material are removed from a beam-like waveguide with emulated anechoic terminations using ultrasonic excitation.
In this paper we present a wave-based technique for modelling waveguides equipped with piezoelectric actuators in which there is no need for common simplifications regarding their dynamic behaviour, the interaction with the waveguide or the bonding conditions. The proposed approach is based on the semianalytical finite element (SAFE) method. We developed a new piezoelectric element and employed the analytical wave approach to model the distributed electrical excitation and scattering of the waves at discontinuities. The model was successfully verified numerically and validated against an experiment on a beam-like waveguide with emulated anechoic terminations.
Unwanted accretions on structures, such as aircraft and wind turbine icing or deposits in pipes, are a common problem, which can pose a serious safety threat if not treated effectively and punctually. In this paper we investigate the capability of piezo-excited structural waves for delaminating accreted material. The core of the concept is to utilise the stress distribution associated with waves propagating through the structure to detach unwanted build-up.We apply a wave-based technique for modelling piezoelectric excitation based on semi-analytical finite elements to calculate the shear stress at the interface between the host structure and the accretion generated by piezoactuated waves. Our analyses include the effects of the actuator's dynamics and allow for comparing different types of actuators, identifying the most effective frequency of excitation and formulating realistic power requirements. For the dual purpose of proof of concept and validation of the model, we present a demonstration experiment in which patches of accreted material are removed from a beam-like waveguide with emulated anechoic terminations using ultrasonic excitation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.