Vibrothermography, or sonic IR, is a nondestructive evaluation technique used to find surface and near surface defects-such as cracks and delaminations-through observations of vibration-induced heat generation. This method has significant interest as an industrial inspection method, however, a lack of understanding of the fundamental physics governing the heat generation process has limited its application despite extensive theoretical, numerical simulation, and experimental work. Significant theoretical and numerical simulation work has been performed, but has yet to be rigorously verified experimentally. This paper presents experimental verification of the sources of heat generation in vibrothermography; specifically friction, plasticity, and viscoelasticity. Specific experimental evidence is presented that verifies each of these heat-generating mechanisms.
A method is described to measure crack opening stresses and closure stress profiles of a surface-breaking crack. Vibration is used to generate frictional heat by rubbing crack face asperities. Heat is generated at regions of contacting crack asperities under low, but nonzero, closure stress. Increasing force is applied to incrementally open the crack and measure the locations of crack heating as a function of applied load. Surface crack closure stresses are approximated from the heating locations as the load is varied and the crack opening stress is measured from the load required to fully open the crack and terminate heat generation.
Thermal imaging with an infrared camera can be used to view the location and intensity of heat sources in space and time. In a thermal conductor, thermal diffusion blurs out those heat sources. Knowledge of the physics of thermal diffusion can be used to enhance the spatial and temporal resolution of thermal images. In two dimensions, quantitative reconstruction of the heat source intensity is possible. The same algorithm applied to three-dimensional heat flows provides dramatic improvements in temporal and spatial resolution of the thermal images. Performance is illustrated both in theory and by experiment. An application example demonstrates utility to nondestructive evaluation.
AbstractThermal imaging with an infrared camera can be used to view the location and intensity of heat sources in space and time. In a thermal conductor, thermal diffusion blurs out those heat sources. Knowledge of the physics of thermal diffusion can be used to enhance the spatial and temporal resolution of thermal images. In two dimensions, quantitative reconstruction of the heat source intensity is possible. The same algorithm applied to three-dimensional heat flows provides dramatic improvements in temporal and spatial resolution of the thermal images. Performance is illustrated both in theory and by experiment. An application example demonstrates utility to nondestructive evaluation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.