Yiming Deng

Pulsed Eddy-Current Based Giant Magnetoresistive System for the Inspection of Aircraft Structures

Research in nondestructive evaluation is constantly increasing the sensitivity of detection of small cracks embedded deep in layered aircraft structures. Pulsed eddy-current (PEC) techniques using coil probes have shown considerable promise in detection and characterization of buried cracks in multilayered structures. In this paper, we describe the design and development of a nondestructive inspection system that uses pulse excitation of a planar multiline coil to generate a transient field that is detected via a giant magnetoresistive (GMR) field sensor. An analysis algorithm using features in time and frequency domain processes the experimentally measured signals for automatic detection of small cracks under fasteners in multilayered structures at a depth of up to 10 mm.

A GMR-Based Eddy Current System for NDE of Aircraft Structures

Onsite real-time nondestructive evaluation of aircraft using eddy current techniques has gained significance in the past few years. In this paper, emphasis is placed on developing a flexible and a fast real-time inspection system using giant magnetoresistive (GMR) field sensors. Experimental signals are compared with finite-element model (FEM) model simulations and signals acquired using traditional data acquisition methods. Several advantages of the improved design are discussed

Electromagnetic Imaging Methods for Nondestructive Evaluation Applications

Electromagnetic nondestructive tests are important and widely used within the field of nondestructive evaluation (NDE). The recent advances in sensing technology, hardware and software development dedicated to imaging and image processing, and material sciences have greatly expanded the application fields, sophisticated the systems design and made the potential of electromagnetic NDE imaging seemingly unlimited. This review provides a comprehensive summary of research works on electromagnetic imaging methods for NDE applications, followed by the summary and discussions on future directions.

EC-GMR Data Analysis for Inspection of Multilayer Airframe Structures

Eddy-current testing (ECT) is widely used in inspection of multilayer aircraft skin structures for the detection of cracks under fasteners (CUF). Detection of deep hidden CUF poses a major challenge in traditional ECT techniques largely because the weak eddy-current signal due to a subsurface crack is dominated by the strong signal from the aluminum or steel fastener. Giant magnetoresistive (GMR) sensors are finding increasing applications in directly measuring weak magnetic fields associated with induced eddy currents. The measured flux image at a fastener site is in general symmetric and an asymmetry is introduced by the presence of a subsurface crack, which is used for defect detection. This paper presents novel methods that employ the resident phase information, for improving detection probability of GMR signal analysis. Using computational model, the effectiveness of the proposed methods for enhancing detection of CUF is investigated. Results demonstrating the potential of these techniques for detection of second layer CUF are presented.

Model-Based Inversion Technique Using Element-Free Galerkin Method and State Space Search

This paper presents a signal inversion technique in nondestructive evaluation (NDE) application for defect profile reconstruction using the element-free Galerkin (EFG) method and state space search. The advantage of EFG method is that it relies only on a set of nodes, instead of a complex mesh to discretize the solution domain. In the inversion procedure, remeshing is avoided to increase the efficiency and accuracy of the solution, which is a major advantage over the traditional finite-element method (FEM). The iterative state space search method using the tree structure is developed for implementing the defect updating scheme. Preliminary results are presented for validation. The robustness of the technique has been shown on noisy signals.

Enhanced Laser-Based Magneto-Optic Imaging System for Nondestructive Evaluation Applications

An enhanced and innovative laser-based magneto-optic (MO) imaging (LMOI) system is presented in this paper to detect buried subsurface flaws in metallic structures for structural nondestructive evaluation. Several key improvements for the new imaging device have been discussed, including the following: the optimization of the MO sensor, the design of the magnetic excitation device, and the development of the image processing approaches, which result in the enhanced MO image quality comparing to the first generation of LMOI. Experimental data have also been obtained that clearly demonstrated the improvement in imaging results.

Magneto-Optic Imaging for Aircraft Skins Inspection: A Probability of Detection Study of Simulated and Experimental Image Data

The increasing fleet of aging aircrafts has resulted in an increasing demand for cost effective nondestructive evaluation (NDE) techniques that are accurate, reliable, and easy to use. Magneto-Optic Imaging (MOI) is such a technique, which has gained wide acceptance for detection of both surface and subsurface defects in multi-layer aircraft structures. The main advantage of MOI is rapid inspection and ease of interpreting image data in contrast to complex impedance signals from conventional eddy current instruments. One missing piece of the puzzle for advanced MOI systems is how to quantitatively analyse the MO images, and understand the detectability limits when image data are acquired under varying operational conditions. This paper presents a probability of detection (POD) study that is conducted using both simulation model-predicted and experimental MO image data. Simulated panels from a 3-D FEM model and experimental panels with machined defects are used to generate data for interpretation by human inspectors or automated systems, and subsequently for POD studies. The POD curves demonstrate the merits in optimizing inspection parameters that maximized the performance of current MOI systems. Parameters quantifying the detectability of MO image data using skewness functions are also presented and discussed.

Glottic configuration in patients with exercise‐induced stridor: A new paradigm

Paradoxical vocal fold motion and exercise‐induced paradoxical vocal fold motion (EIPVFM) are two related conditions that do not have definitive diagnostic criteria. Much of the EIPVFM literature describes patients with characteristic physiologic findings of severe upper airway obstruction or obvious airflow limitation in the clinical context of exertional dyspnea with audible stridor. The objective of this study was to highlight a group of patients who demonstrate important clinical findings of EIPVFM (exertional dyspnea with audible stridor) without simultaneously definitive physiologic findings (mild glottic adduction and normal flow volume loops).

Mass Spectrometric Collisional Activation and Product Ion Mobility of Human Serum Neutral Lipid Extracts

A novel method for lipid analysis called CTS (collisional activation and traveling wave mass spectrometry), involving tandem mass spectrometry of all precursor ions with ion mobility determinations of all product ions, was applied to a sample of human serum. The resulting four-dimensional data set (precursor ion, product ion, ion mobility value, and intensity) was found to be useful for characterization of lipids as classes as well as for identification of specific species. Utilization of ion mobility measurements of the product ions is a novel approach for lipid analysis. The trends and patterns of product mobility values when visually displayed yield information on lipid classes and specific species independent of mass determination. Collection of a comprehensive set of data that incorporates all precursor-product relationships, combined with ion mobility measurements of all products, enables data analysis where different molecular properties can be juxtaposed and analyzed to assist with class and species identification. Overall, CTS is a powerful, specific, and comprehensive method for lipid analysis.

Multi-Wave and Hybrid Imaging Techniques: A New Direction for Nondestructive Testing and Structural Health Monitoring

In this article, the state-of-the-art multi-wave and hybrid imaging techniques in the field of nondestructive evaluation and structural health monitoring were comprehensively reviewed. A new direction for assessment and health monitoring of various structures by capitalizing the advantages of those imaging methods was discussed. Although sharing similar system configurations, the imaging physics and principles of multi-wave phenomena and hybrid imaging methods are inherently different. After a brief introduction of nondestructive evaluation (NDE), structure health monitoring (SHM) and their related challenges, several recent advances that have significantly extended imaging methods from laboratory development into practical applications were summarized, followed by conclusions and discussion on future directions.