Open Access

ARTICLE

Suppression of Dry-Coupled Rubber Layer Interference in Ultrasonic Thickness Measurement: A Comparative Study of Empirical Mode Decomposition Variants

Weichen Wang¹, Shaofeng Wang¹, Wenjing Liu^1,*, Luncai Zhou², Erqing Zhang¹, Ting Gao³, Grigory Petrishin⁴

1 Inner Mongolia Key Laboratory of Intelligent Diagnosis and Control of Mechatronic Systems, Inner Mongolia University of Science and Technology, Baotou, 014000, China
2 Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, 730000, China
3 Inner Mongolia institute of Special Equipment Inspection and Research, Baotou, 014000, China
4 Mechanical Engineering Faculty, Sukhoi State Technical University of Gomel, Gomel, 246000, Belarus

* Corresponding Author: Wenjing Liu. Email:

Structural Durability & Health Monitoring 2026, 20(1), . https://doi.org/10.32604/sdhm.2025.071278

Received 04 August 2025; Accepted 26 September 2025; Issue published 08 January 2026

Abstract

In dry-coupled ultrasonic thickness measurement, thick rubber layers introduce high-amplitude parasitic echoes that obscure defect signals and degrade thickness accuracy. Existing methods struggle to resolve overlap-ping echoes under variable coupling conditions and non-stationary noise. This study proposes a novel dual-criterion framework integrating energy contribution and statistical impulsivity metrics to isolate specimen re-flections from coupling-layer interference. By decomposing A-scan signals into Intrinsic Mode Functions (IMFs), the framework employs energy contribution thresholds (>85%) and kurtosis indices (>3) to autonomously select IMFs containing valid specimen echoes. Hybrid time-frequency thresholding further suppresses interference through amplitude filtering and spectral focusing. Experimental results demonstrate the framework’s robustness, achieving 92.3% thickness accuracy for 5 mm steel specimens with 5 mm rubber coupling, outperforming conventional methods by up to 18.7%. The dual-criterion approach reduces operator dependency by 37% and maintains ΔT < 0.03 mm under surface roughness up to 6.3 μm, offering a practical solution for industrial nondestructive testing with thick dry-coupled interfaces.

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Keywords

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