Accepted Manuscripts

John N. Wertz, Laura Homa, John Welter, Daniel Sparkman and John Aldrin
ASME J Nondestructive Evaluation   doi: 10.1115/1.4040233
The US Air Force seeks to improve lifecycle management of composite structures. Nondestructive characterization of damage is a key input to this framework. One approach to characterization is model-based inversion of ultrasound inspection data; however, the computational expense of simulating the response from damage represents a major hurdle for practicality. A surrogate forward model with greater computational efficiency and sufficient accuracy is therefore critical to enabling damage characterization via model-based inversion. In this work, a surrogate model based on Gaussian process regression is developed on the chirplet decomposition of the simulated quasi-shear scatter from delamination-like features that form a shadowed region within a representative composite layup. The surrogate model is called in the solution of the inverse problem for the position of the hidden delamination, which is achieved with <0.5% error in <20 minutes on a workstation computer for two unique test cases. These results demonstrate that solving the inverse problem from the ultrasonic response is tractable for composite impact damage with hidden delaminations.
TOPICS: Nondestructive evaluation, Composite materials, Damage, Delamination, Inverse problems, Air Force, Inspection, Shear (Mechanics), Ultrasound, Electromagnetic scattering, Life cycle management, Computers, Errors
Shyh-shiuh Lih, Hyeong Jae Lee, Yoseph Bar-cohen and Mircea Badescu
ASME J Nondestructive Evaluation   doi: 10.1115/1.4040112
A system consisting of a multiplexer and multiple ultrasonic probes was developed for in-situ monitoring of the water condensation height in steam pipes under steady-state and turbulent flow conditions. The measurement method, the signal processing techniques, the experimental setup, and the test results are presented in this paper. The feasibility and efficiency of the developed multi transducers and signal processing algorithms were demonstrated. The measured water height and wave pattern in dynamic surface conditions inside the pipe were verified through the snapshot of the recorded video images. The developed methodology built the framework for the use of multiple transducers array ultrasonic system for practical application to in-situ monitor the water height in steam pipes.
TOPICS: Turbulence, Nondestructive evaluation, Pipes, Testing, Transducers, Steady state, Steam, Water, Signal processing, Probes, Waves, Algorithms, Condensation

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