Investigation of guided wave propagation in pipes fully and partially embedded in concrete

Abstract

The application of long-range guided-wave testing to pipes embedded in concrete results in unpredictable test-ranges. The influence of the circumferential extent of the embedding-concrete around a steel pipe on the guided wave propagation is investigated. An analytical model is used to study the axisymmetric fully embedded pipe case, while explicit finite-element and semi-analytical finite-element simulations are utilised to investigate a partially embedded pipe. Model predictions and simulations are compared with full-scale guided-wave tests. The transmission-loss of the T(0,1)-mode in an 8 in. steel pipe fully embedded over an axial length of 0.4 m is found to be in the range of 32–36 dB while it reduces by a factor of 5 when only 50% of the circumference is embedded. The transmission-loss in a fully embedded pipe is mainly due to attenuation in the embedded section while in a partially embedded pipe it depend strongly on the extent of mode-conversion at entry to the embedded-section; low loss modes with energy concentrated in the region of the circumference not-covered with concrete have been identified. The results show that in a fully embedded pipe, inspection beyond a short distance will not be possible, whereas when the concrete is debonded over a fraction of the pipe circumference, inspection of substantially longer lengths may be possible.

Novel method for true guided waves spectral characteristics estimation using a logistic function fit and nonlinear least square algorithm

“…The positive (negative) values of RE correspond to the overestimation (underestimation) of wavenumber or frequency for the investigated approaches, respectively. The REs for LFN curves were computed for differentmodel discretizations, that is, (12,14,16,18,20), Set No. 1; (14,16,18,20,24), Set No.…”

“…1; (14,16,18,20,24), Set No. 2; and (16,18,20,24,28), Set No. 3, respectively,where the numbers indicate the number of elements through the plate thickness.…”

“…The out-of-plane excitability curves error for the logistic function (LFN) and EXC-LISA techniques computed for (a) A 0 , (b) S 0 , and (c) A 1 Lamb wave modes for 18-ply carbon fiber-reinforced plastic of 2-mm-thick anisotropic plate. The LFN curves were computed for different sets of discretization, that is, , continues line; , dashed line; and (16,18,20,24,28), dash-dotted line. Consequently, the EXC-LISA results were computed for the highest discretization used for LFN approach, that is, 20, 24, and 28 elements, respectively…”

On the scattering of torsional waves from axisymmetric defects in buried pipelines

“…This is a different challenge, as one must move from the analysis of an infinite waveguide to a finite, or more usually semi-infinite, guide. This is especially problematic in the analysis of large structures such as pipelines, where under favourable conditions the inspection range can extend to well over 10 m. For example, in a recent study Leinov et al 5 required 21.13 million hexahedral elements to study a partially embedded pipe that was 4 m long. This is likely to deliver over 100 million degrees of freedom for this pipe, and even with such a large number, the upper centre frequency was restricted to 35 kHz.…”

“…For this reason there are very few articles that address scattering in buried, or embedded, cylindrical structures of finite or semi-finite length. The recent work of Leinov et al 5 examined a partially buried pipe, whereas for fully buried systems that avoid a full FE discretisation, previous work has generally been restricted to viscometers, where guided waves are used to infer the properties of a surrounding medium. Relevant examples for viscometers include the use of longitudinal modes to measure the viscosity of different fluids, 16 as well as the measurement of density 17,18 and the dependence of properties on temperature 19 .…”