Performance of Damage Identification Based on Directional Wavelet Transforms and Entopic Weights Using Experimental Shearographic Testing Results.

Andrzej Katunin

doi:10.3390/s21030714

Abstract

The paper aims to analyze the performance of the damage identification algorithms using the directional wavelet transforms, which reveal higher sensitivity for various orientations of spatial damage together with lower susceptibility to noise. In this study, the algorithms based on the dual-tree, the double-density, and the dual-tree double-density wavelet transforms were considered and compared to the algorithm based on the discrete wavelet transform. The performed analyses are based on shearographic experimental tests of a composite plate with artificially introduced damage at various orientations. It was shown that the directional wavelet transforms are characterized by better performance in damage identification problems than the basic discrete wavelet transform. Moreover, the proposed approach based on entropic weights applicable to the resulting sets of the detail coefficients after decomposition of mode shapes can be effectively used for automatic selection and emphasizing those sets of the detail coefficients, which contain relevant diagnostic information about damage. The proposed processing method allows raw experimental results from shearography to be significantly enhanced. The developed algorithms can be successfully implemented in a shearographic testing for enhancement of a sensitivity to damage during routine inspections in various industrial sectors.

Highlights

The proposed approach based on entropic weights applicable to the resulting sets of the detail coefficients after decomposition of mode shapes can be effectively used for automatic selection and emphasizing those sets of the detail coefficients, which contain relevant diagnostic information about damage
The aim of this paper is to evaluate the performance of the mentioned directional wavelet transforms accompanied with the new technique of an automated selection of sets of wavelet coefficients after decomposition of mode shapes based on entropic weights
The performance of the directional wavelet transforms (WTs) in structural damage identification (SDI) problems was evaluated based on the experimental shearographic testing results of the composite plate with the artificially introduced damage sites

Summary

Introduction

The structural damage identification (SDI), in the light of the maintenance philosophies applied nowadays, like damage tolerance and condition-based maintenance, becomes of strategic importance, especially in the aircraft, aerospace, automotive and civil infrastructure industrial branches. Among the non-destructive testing (NDT) techniques applied for SDI in numerous problems, a class of vibration-based techniques is one of the well-established and effective approaches mainly due to their testing simplicity and costeffectiveness as well as relatively high sensitivity to damage [1]. This class of techniques involves all testing approaches based on modal analysis, including traditional testing with vibration sensors, like accelerometers or microelectromechanical system (MEMS)

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Conclusion