Final Thesis

Evaluation of the validity of a theoretical model in USMW

Master Thesis of Gomez Belmonte, Jose Maria

Ultrasonic metal welding (USMW) is a technique of welding small-area materials by means of high-frequency vibration friction welding. Despite its wide use, it is still hard to monitor the welding process, and optimize the strengths of the welds it produces. The objective of this work is to offer a simple characterization of the state of the welding process over time. This would allow quality control of all welds in an industrial process. Furthermore, the analysis of the model and the available data will provide a better understanding of the physical behaviour of the weld over time. This study will focus specifically on the USMW of two copper parts, analysing different measurements made with laser Doppler vibrometers and a high-speed camera. First, whether the motion transfer process between the horn and the anvil fulfils the properties of linearity and time invariance (LTI system), and can therefore be described by a transfer function, is checked. Then, the different phases of the welding process are studied. After this analysis and evaluation, with the data obtained from the measurements, the validity of a simple equivalent model will be studied by trying to fit it to the results of the measurements.