Guided Wave Damage Characterization via Minimum Variance Imaging with a Distributed Array of Ultrasonic Sensors

Abstract

ABSTRACT. Guided wave imaging with a distributed array of inexpensive transducers offers a fast and cost-efficient means for damage detection and localization in plate-like structures such as aircraft and spacecraft skins. As such, this technology is a natural choice for inclusion in condition-based maintenance and integrated structural health management programs. One of the implementation challenges results from the complex interaction of propagating ultrasonic waves with both the interrogation structure and potential defects or damage. For example, a guided ultrasonic wave interacts with a surface or sub-surface defect differently depending on the angle of incidence, defect size and orientation, excitation frequency, and guided wave mode. However, this complex interaction also provides a mechanism for guided wave imaging algorithms to perform damage characterization in addition to damage detection and localization. Damage characterization provides a mechanism to help discriminate actual damage (e.g. fatigue cracks) from benign changes, and can be used with crack propagation models to estimate remaining life.This work proposes the use of minimum variance imaging to perform damage detection, localization, and characterization.Scattering assumptions used to perform damage characterization are obtained through both analytical and finite element models. Experimental data from an in situ distributed array are used to demonstrate feasibility of this approach using a through-hole and two through-thickness notches of different orientations to simulate damage in an aluminum plate.

Lamb wave (A0 mode) scattering directionality at defects

“…Taking the scattering pattern into account for the signal processing, e.g. minimum variance imaging for distributed sensors, has been shown to improve the sensitivity for crack-like defects and to allow for the estimation of the defect orientation [12].…”

Lamb wave-based BVID imaging for a curved composite sandwich panel

“…The need for rapid nondestructive evaluation (NDE) techniques for composites is growing rapidly as the complexity and dimensions of the structures are increasing significantly [1]. Lamb waves were intensely studied and applied for large-area NDE and structural health monitoring (SHM) due to their superior capabilities in longdistance propagation and through-thickness interrogation [2]. BVID in particular was detected using guided waves in [3].…”

Profile imaging of actual defects in steel plate based on electromagnetic ultrasonic SH guided wave scattering

“…Levine exploited block-sparse technique to reconstruct positions of defects based on a multidimensional linear scattering mode l of Lamb waves [2 1-22]. The minimum variance imaging method was applied in Hall ' s work to detect and locali ze a through-ho le and two thro ugh-thickness notches according to scattering assumptions in an aluminum plate [23]. Besides, the scattering 3 http://mc.manuscriptcentral.com/insi Insight mechanism and related theoretical models were studi ed by simulation computation and experiments [24][25][26][27].…”