Investigation of Ultrasonic Heating by Infrared Imaging and Finite Element Simulation

摘要

We presented a measurement technique of ultrasonic heating utilizing a thermo camera. Due to properties of the instrument the position of the measurement is the specimen-air-interface, which can be easily geometrically identified in simulation results. Measurement results were compared to simulations based on the Finite Element Method. The differences are in the same range as the accuracy of the thermo camera, but are expected to be reduced, if the measurement of the normal velocity distribution of the transducer can be improved. Particular emphasis deserves the special coupling scheme of the acoustic and heat conduction simulation. In our case we couple a continuous wave acoustic simulation with a transient simulation of heat conduction. Only in that case a numerical simulation of the ultrasonic heating process becomes practical, since the insonation over 150 seconds correspond to a duration of more than 10~8 periods of the acoustic signal. Hence in transient mode, where a multiple of the number of periods would have to be used as number of time steps, an acoustic simulation would not be possible in reasonable time.