Depth-resolved elastic property tomography using higher-order shear-horizontal modes
Abstract
Early material degradation can produce weak, local changes in elastic stiffness before a crack or void forms, but conventional ultrasonic measurements dilute these changes through path and thickness averaging. This paper introduces DEPTH (Depth-resolved Elastic Property Tomography using Higher-order modes), which uses mode-to-mode scattering among higher-order guided waves to reconstruct elastic-property variations as a function of axial position and depth through a plate. The formulation is developed using shear-horizontal (SH) modes, for which the reconstructed property is shear modulus. A Born formulation shows that each incident-received mode pair contains at most two cosine depth orders, allowing the through-thickness field to be recovered from diverse modal mixtures across mode pairs and frequency. The matrix-free regularised inverse is evaluated using direct two-dimensional modal data, practical single-surface excitation and reception, and full three-dimensional finite-element data. In a 10 mm plate, the ideal two-dimensional case gives a through-thickness point-spread FWHM of 0.84-1.03 mm, while the single-surface configuration recovers four compact targets at the correct depths. This provides the first demonstration of depth-resolved elastic-property tomography from multimode guided-wave transmission with excitation and reception confined to a single physical plate surface. With full three-dimensional propagation and finite-width transduction, the reconstruction retains the compact-target positions with a whole-image correlation of 0.899 against a matched acquisition-limited reconstruction. These simulation results demonstrate that higher-order guided-wave mode conversion can provide local depth-resolved elastic-property tomography from surface-access measurements, with potential for characterising early-stage damage such as fatigue.
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BibTeX
@misc{huthwaite2026depthresolved,
title = {{Depth-resolved elastic property tomography using higher-order shear-horizontal modes}},
author = {Peter Huthwaite},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.31455},
eprint = {2609.31455},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.31455},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Depth-resolved elastic property tomography using higher-order shear-horizontal modes
AU - Peter Huthwaite
PY - 2026
DA - 2026/09/25
PB - arXiv
DO - 10.48550/arxiv.2609.31455
UR - https://arxiv.org/abs/2609.31455
AB - Early material degradation can produce weak, local changes in elastic stiffness before a crack or void forms, but conventional ultrasonic measurements dilute these changes through path and thickness averaging. This paper introduces DEPTH (Depth-resolved Elastic Property Tomography using Higher-order modes), which uses mode-to-mode scattering among higher-order guided waves to reconstruct elastic-property variations as a function of axial position and depth through a plate. The formulation is developed using shear-horizontal (SH) modes, for which the reconstructed property is shear modulus. A Born formulation shows that each incident-received mode pair contains at most two cosine depth orders, allowing the through-thickness field to be recovered from diverse modal mixtures across mode pairs and frequency. The matrix-free regularised inverse is evaluated using direct two-dimensional modal data, practical single-surface excitation and reception, and full three-dimensional finite-element data. In a 10 mm plate, the ideal two-dimensional case gives a through-thickness point-spread FWHM of 0.84-1.03 mm, while the single-surface configuration recovers four compact targets at the correct depths. This provides the first demonstration of depth-resolved elastic-property tomography from multimode guided-wave transmission with excitation and reception confined to a single physical plate surface. With full three-dimensional propagation and finite-width transduction, the reconstruction retains the compact-target positions with a whole-image correlation of 0.899 against a matched acquisition-limited reconstruction. These simulation results demonstrate that higher-order guided-wave mode conversion can provide local depth-resolved elastic-property tomography from surface-access measurements, with potential for characterising early-stage damage such as fatigue.
ER -