Showing papers by "William H. Prosser published in 2002"

Structural Health Monitoring Sensor Development at NASA Langley Research Center

Abstract: NASA is applying considerable effort on the development of sensor technology for structural health monitoring (SHM). This research is targeted toward increasing the safety and reliability of aerospace vehicles, while reducing operating and maintenance costs. Research programs are focused on applications to both aircraft and space vehicles. Sensor technologies under development span a wide range including fiber-optic sensing, active and passive acoustic sensors, electromagnetic sensors, wireless sensing systems, MEMS, and nanosensors. Because of their numerous advantages for aerospace applications, fiber-optic sensors are one of the leading candidates and are the major focus of this presentation. In addition, recent advances in active and passive acoustic sensing will also be discussed.

Wave propagation sensing for damage detection in plates

Abstract: Health monitoring of aerospace structures can be done passively by listening for acoustic waves generated by cracks, impact damage and delaminations, or actively by propagating diagnostic stress waves and interpreting the parameters that characterize the wave travel. This paper investigates modeling of flexural wave propagation in a plate and the design of sensors to detect damage in plates based on stress wave parameters. To increase understanding of the actual physical process of wave propagation, a simple model is developed to simulate wave propagation in a plate with boundaries. The waves can be simulated by applied forces and moments in the model either to represent passive damage growth or active wave generation using piezoceramic actuators. For active wave generation, the model considers a piezoceramic patch bonded perfectly to a quasi-isotropic glass-epoxy composite plate. Distributed sensors are used on the plate and are modeled as being constructed using active fiber composite and piezoceramic materials. For active wave generation, a moment impulse is generated by the actuation of a piezoceramic patch. The waves generated from the patch are detected by the distributed sensor. For passive sensing of acoustic waves, a step function is used to simulate an acoustic emission from a propagating damage. The resulting acoustic wave is measured by the distributed sensor and produces micro-strains in the sensor nodes. The strains produce a single voltage signal output from the distributed sensor. Computational simulations and animations of acoustic wave propagation in a plate are discussed in the paper. A new method to locate the source of an acoustic emission using the time history of the dominant lower frequency components of the flexural wave mode detected by continuous sensors is also presented.

Editorial: Letter of Introduction from the Editors of Structural Health Monitoring

Abstract: Dear Readers, Welcome to Structural Health Monitoring: An International Journal. Structural Health Monitoring (SHM) is the continuous or regular monitoring of the condition of a structure or system using built-in or autonomous sensory systems, and any resultant intervention to preserve structural integrity. SHM is a broad multidisciplinary field both in terms of the diverse science and technology involved as well as in its varied applications. The technological developments necessary to enable practical structural health monitoring are originating from scientists and engineers in many fields including physics, chemistry, materials science, biology, and mechanical, aerospace, civil and electrical engineering. SHM is being implemented on diverse systems and structures such as aircraft, spacecraft, ships, helicopters, automobiles, bridges, buildings, civil infrastructure, power generating plants, pipelines, electronic systems, manufacturing and processing facilities, biological systems, and for the protection of the environment, and for defense. The motivation for this new journal is to better facilitate a widespread dissemination and understanding of these rapidly progressing new SHM technological advances and their applications. The SHM journal will also serve as a primary repository and reference source for the crosscutting science and new technology of structural health monitoring. As a result, we anticipate that this journal will lead to new applications and transfer of SHM technology into other fields, particularly in the broad areas of sensing, smart materials, signal processing, modeling, and integration. The journal will contain basic and applied research papers, review and position papers from government and industry, announcements for conferences, reviews, and other information pertaining to SHM. The scope of the journal will be broad, interdisciplinary, and international. In the first issues, a number of papers in the journal will discuss recent research progress, new research directions, and strategic research areas that are needed. These include integration and scaling for global coverage using large numbers of sensors, ultra-reliable sensors, damage mitigation, intervention, new materials, biological materials, algorithms, and applications. The journal will also publish expanded papers from conferences and papers that deal with interdisciplinary research and education. The journal is expected to be of significant benefit to the economies of the world, because SHM can increase the life, performance, safety, and reduce maintenance actions for all types and levels of structures, from nanostructure, to microstructure, to infrastructure. One imperative of the journal is to continuously integrate new technology and ideas into SHM and, conversely, to integrate SHM technology into new applications and other fields. As an example, Bio-Nanotechnology (integrating biological function with nanoscale precision) seems very promising for producing major advances in the field of SHM. Perhaps in this century, the integration of Biomimetics, Nanotechnology, SHM and Smart Structures will deliver vastly improved communication architectures, material systems, sensors, and actuators. The result of this could be superelastic lightweight structures that can self-assemble, monitor their own health and performance, react and adapt to their environ-