<p>This paper investigates the potential of an attenuation measurement for assessing the ultrasonic inspectability of coarse-grained components using qualified procedures in a practical setting. Our focus is on a reliable estimation of a representative grain size which can potentially be done in situ. To gain deep insight into the effect of the parameters of a grain size distribution on the attenuation we conducted an extensive parametric study. We generated a large number of numerical microstructures with different parameters of a lognormal distribution and simulating the propagation of ultrasound using grain-scale time-domain finite element simulations. Demonstrating the known non-uniqueness of the relationship between the attenuation and the lognormal distribution parameters, we suggested that the correlation length calculated from a single exponential fit to the two-point correlation function could be used in practice as a more robust descriptor of grain statistics similarity between components. The experimental part of the study focused on an industrial Inconel 600 mock-up with spatially varying attenuation measured across the whole sample. We compared the measured attenuation with that coming from a grain-scale FE modal based on examination. We also estimated correlation lengths from measured signals using the second-order approximation model for three zones with distinctly different attenuation, achieving good agreement with the material examination. We concluded that correlation length could replace the average grain size metric in practical settings, as it retains more statistical information than the mean grain size and allows for linking measurements to the established theoretical attenuation models which this paper demonstrates.</p>

Characterising Grain Statistics in Castings Using Ultrasonic Measurements

Paper Proceedings: https://asmedigitalcollection.asme.org/qnde/QNDE2021/volume/85529

ASME 2021 48th Annual Review of Progress in Quantitative Nondestructive Evaluation (QNDE2021)

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