Parametric study of heat diffusion in vibrothermography using analytical and numerical methods
Trundnowski, Anthony James.
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The development of precise and accurate non-destructive examination (NDE) techniques is an essential element in preventing failures and increasing reliability in engineering materials. In particular, few present day composite material NDE techniques give the desired precision and cost-effectiveness required for many high-reliability applications such as on airplane wings or wind turbine blades. This study contributes to the development of a NDE technique known as vibrothermography. Vibrothermography is performed by measuring frictional heating of internal flaws that occur as a result of inducing specimen vibrations via an ultrasonic transducer. This frictional heat conducts itself to the surface, where it can be detected by an infared camera. Vibrothermography is a potential cost-effective alternative to detecting a wide variety of flaws in composite materials. This study models the heat generation that occurs during a vibrothermography test; and it simulates the manner at which this heat would conduct to the specimen's surface. Once the models were developed, they were used to simulate the influence of the following potential test parameters: specimen thickness, flaw generation amount, flaw size, flaw depth, and flaw orientation. The results provide an initial insight of which of these parameters could most greatly influence a vibrothermography test, and which ones may or may not be able to be detectable from a vibrothermograhy test. Lastly, in conjunction with Kyle Spaulding, an initial thermal-mechanical combined analysis was developed that includes specimen vibration, heat generation, and heat conduction to create a start to finish vibrothermography simulation. This model is soon to be compared with experimental data. If the model results match experimental data, then the models will be implemented as a useful tool in determining the overall feasibility, accuracy, reliability, and optimal test procedures for vibrothermography.