Search

Comprehensive and accurate inspections of welded components have become of increasing importance as NASA develops new hardware such as Ares rocket segments for future exploration missions. Simulation and modeling will play an increasing role in the future for nondestructive evaluation in order to better understand the physics of the inspection process, to prove or disprove the feasibility for an inspection method or inspection scenario, for inspection optimization, for better understanding of experimental results, and for assessment of probability of detection. This study presents simulation and experimental results for an ultrasonic phased array inspection of a critical welded structure important for NASA future exploration vehicles. [ABSTRACT FROM AUTHOR]

US Air Force aircraft are managed by Damage Tolerance Assessment (DTA) and Nondestructive Evaluation (NDE) plays a critical role in insuring their flight safety. This paper provides an overview of current NDE capabilities for aircraft structures. The potential migration to Condition-Based Maintenance (CBM) will require NDE to evolve from detection of defects to characterization of their location and size. This represents multiple significant challenges as aircraft have many material and geometry factors that complicate this analysis. This paper provides a strategy to resolve these factors. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

Previous work on the detection of cracks around fastener holes in multi-layer structures using eddy current NDE has met with some success; however, challenges remain in detecting smaller corner cracks while minimizing false call rates. To address this issue, a 3D model was developed for this problem and successfully validated with experimental data. Using this model, a series of numerical studies were performed to identify potential features for defect classification. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

This paper presents a study of crack detection methods for holes in structures with limited accessibility containing fasteners with variable interface conditions. For far crack detection, a method was first designed using models, and refined using a signal processing parameter optimization scheme and an iterative neural network training process. For near crack detection, a method incorporating the spatial variation of the principal components was developed. Using these methods, improvements in crack detection performance were achieved. © 2003 American Institute of Physics [ABSTRACT FROM AUTHOR]

This paper presents a study of ultrasonic NDE models for a cylindrical hole containing an elastic layer and a fluid-filled hole. For the elastic layer case, both dispersion relations and analytical solutions were solved to assess the sensitivity of leaky Rayleigh waves to annulus properties. A BEM model was formulated for the scattering of shear waves by a fluid-filled hole with a notch. Through simulated studies, a viable inspection technique was derived and validated experimentally. © 2003 American Institute of Physics [ABSTRACT FROM AUTHOR]

This paper investigates the possibility of crack detection for holes containing elastic inserts. A BEM model was formulated for the scattering response of an incident shear wave transducer signal by a cylindrical hole with a radial notch, an elastic insert, and a stiffness interface between the hole and the insert. Through simulated and experimental studies, certain interface conditions were identified for which significant interface waves can be generated and subsequently used for inspection purposes. [ABSTRACT FROM AUTHOR]

In earlier work, an automated protocol was considered to detect bottom cracks in weep holes. During experimentation, this protocol was found to produce some false calls and miss certain small cracks. In this paper, a technique is presented which examines the variation in the A-scan signals as the transducer is incrementally moved along the wing surface. The advantage of this B-scan classification technique is its ability to detect superimposed signals independently from the shape of the pulse. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]