Learn More
Diffuse ultrasonic waves for structural health monitoring offer the advantages of simplicity of signal generation and reception, sensitivity to damage, and large area coverage; however, there are the serious disadvantages of no accepted methodology for analyzing the complex recorded signals and sensitivity to environmental changes such as temperature and(More)
A spatially sparse array of conventional piezoelectric transducers is attached to a part surface to monitor its structural health. Artificial flaws are incrementally added to simulate damage progression. The structure is flooded with ultrasonic energy by transmitting on a single transducer, and waveforms are recorded from other transducers in the array.(More)
The application of temperature compensation strategies is important when using a guided wave structural health monitoring system. It has been shown by different authors that the influence of changing environmental and operational conditions, especially temperature, limits performance. This paper quantitatively describes two different methods to compensate(More)
A number of tomographic and phased-array methods have been proposed for generating two dimensional images of plate-like structures using sparse arrays of spatially distributed ultrasonic transducers. The phased array differential approach is considered here whereby pulse echo and through transmission signals are recorded before and after localized damaged(More)
Guided wave structural health monitoring is a challenging problem, in part because of the complexity of signals received in a real structure containing geometrical features and boundaries. Signals scattered from damage can be one or two orders of magnitude smaller in amplitude than the direct arrival. Detection of these small, scattered signals is often(More)
Permanently attached piezoelectric sensors arranged in a spatially distributed array are under consideration for structural health monitoring systems incorporating active ultrasonic methods. Most damage detection and localization methods that have been proposed are based upon comparing monitored signals to baselines recorded from the structure prior to(More)
The level of post-subtraction noise due to benign structural features limits the sensitivity that guided wave structural health monitoring systems can achieve. Subtraction of reference signals without compensation leads to unacceptably high post-subtraction noise in the presence of modest environmental changes, and in particular temperature. Hence some form(More)
A full scale wing panel fatigue test was undertaken in 2007 as a part of the DARPA Structural Integrity Prognosis System (SIPS) program. Both local and global ultrasonic sensors were installed on the wing panel and data were recorded periodically over a period of about seven weeks. The local ultrasonic sensors interrogated a small number of selected(More)
The sensitivity to damage achievable by guided wave structural health monitoring systems is limited by the repeatability of recorded signals under normal operating conditions. Direct subtraction of reference signals leads to unacceptably high post-subtraction noise in the presence of modest temperature changes due to variations in reflections from benign(More)
Several imaging algorithms are being considered for localizing damage in plate-like structures by analyzing changes in signals recorded from permanently mounted guided wave sensor arrays. Delay-and-sum type algorithms have been shown to be effective for damage localization, but exhibit side lobes that significantly reduce the signal-to-noise ratio. Adaptive(More)