Jennifer E. Michaels

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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 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)
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)
Permanently mounted ultrasonic transducers have the potential to interrogate large areas of a structure, and thus be effective global sensors for structural health monitoring. Recorded signals, although very sensitive to damage, are long, complex, and difficult to interpret compared to pulse echo and through transmission signals customary for nondestructive(More)
Attached ultrasonic sensors can detect changes caused by crack initiation and growth if the wave path is directed through the area of critical crack formation. Dynamics of cracks opening and closing under load cause nonlinear modulation of received ultrasonic signals, enabling small cracks to be detected by stationary sensors. A methodology is presented(More)
−This paper presents a set of inexpensive signal processing experiments that can be used as projects or hands-on demos to supplement signals and systems courses. Signals and systems concepts tend to be very mathematical and abstract, and students who prefer more practical material are at a disadvantage in these courses. The experiments are performed on the(More)
A methodology is presented for health monitoring and subsequent inspection of critical structures. Algorithms have been developed to detect and approximately locate damaged regions by analyzing signals recorded from a permanently mounted, sparse array of transducers. Followup inspections of suspected flaw locations are performed using a dual transducer(More)
Ultrasonic guided wave imaging with a sparse, or spatially distributed, array can detect and localize damage over large areas. Conventional delay-and-sum images from such an array typically have a relatively high noise floor, however, and contain artifacts that often cannot be discriminated from damage. Considered here is minimum variance distortionless(More)