Final Thesis

Transfer path analysis for vibro-acoustic quality control

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Ultrasonic Metal Welding (USMW) is a way to weld pieces of metal together. The concept is simple: two metal sheets are placed on the anvil, and pressed against each other by thesonotrode. The sonotrode then vibrates at 20 kHz, causing the sheets to rub against each other and creates the weld. However, the quality of the weld fluctuates between different welds, even with the same welding parameters, and the fluctuations are still not understood. During welding, the vibrations of the sonotrode are passed down through the metal sheets and into the anvil. The amount of vibrations passed to the anvil therefore depends on howstrong the weld is, and could therefore indicate how good the weld is. How the vibrations of the sonotrode transfer to the anvil is called the transfer path, and is described by the transfer function. The goal of this project is to study this transfer function, based on measurements of the vibrations of the sonotrode and anvil. We will try to find different transfer functions for different stages of welding, and better understand how welding exactlyhappens. This will mainly be done using a Matlab toolbox. If time permits, we will also try to draw an equivalent mechanical circuit of the system.