Showing papers by "Christoph Schaal published in 2015"
TL;DR: Some of the useful properties of guided Lamb type waves are investigated, using analytical, numerical and experimental methods, in an effort to provide the knowledge base required for the development of viable structural health monitoring systems for composite structures.
65 citations
TL;DR: In this paper, a detailed study of the interaction of Rayleigh surface waves with defects in a thick aluminum plate is carried out using numerical simulations and laboratory experiments, which are shown to partially result in Lamb wave conversion.
51 citations
TL;DR: In this paper, the authors proposed wave-based Structural Health Monitoring (SHM) to detect damages in civil and mechanical structures, in order to apply SHM to multi-wire cables, in which ultrasonic wave propagation in coupled waveguides is studied theoretically, numerically and experimentally.
18 citations
TL;DR: In this article, a pitch-catch method was used to induce and detect guided Lamb waves for damage detection in composite structures, including an aluminum plate and an aluminum honeycomb sandwich panel with woven composite face sheets.
Abstract: In composite structures, damages are often invisible from the surface and can grow to reach a critical size, potentially causing catastrophic failure of the entire structure. Thus safe operation of these structures requires careful monitoring of the initiation and growth of such defects. Ultrasonic methods using guided waves offer a reliable and cost-effective method for structural health monitoring in advanced structures. Guided waves allow for long monitoring ranges and are very sensitive to defects within their propagation path. In this work, the relevant properties of guided Lamb waves for damage detection in composite structures are investigated. An efficient numerical approach is used to determine their dispersion characteristics, and these results are compared to those from laboratory experiments. The experiments are based on a pitch-catch method, in which a pair of movable transducers is placed on one surface of the structure to induce and detect guided Lamb waves. The specific cases considered include an aluminum plate and an aluminum honeycomb sandwich panel with woven composite face sheets. In addition, a disbond of the interface between one of the face sheets and the honeycomb core of the sandwich panel is also considered, and the dispersion characteristics of the two resultant waveguides are determined. Good agreement between numerical and experimental dispersion results is found, and suggestions on the applicability of the pitch-catch system for structural health monitoring are made.
7 citations
TL;DR: In this paper, an experimental and numeri-cal studies are conducted, in an effort to understand the interaction of guided ultrasonic waves with simple models of the stiffener, in order to improve the reliability of ultrasonic damage detection in stiffened plate structures.
Abstract: Stiffeners are important structural components in modern composite and honey-comb structures. The safe operation of such composite structures, which are com-monly used in aeronautical applications, requires careful monitoring as hidden de-fects may compromise the structural safety. In order to improve the reliability of ultrasonic damage detection in stiffened plate structures, experimental and numeri-cal studies are conducted, in this paper, in an effort to understand the interaction of guided ultrasonic waves with simple models of the stiffener. Through a series of measurements in different positions, the amplitudes of scattered waves for various configurations of the stiffener are determined. Moreover, the group velocity of the waves in the stiffened structure is analyzed. The experimental findings are compared with results from numerical simulations. doi: 10.12783/SHM2015/248
4 citations