Ultrasonic metal welding is a solid-state bonding process in which metal workpieces are
\nexposed to high-frequency vibrations. It is an effective joining technology with a wide range
\nof industrial applications with its unique advantages. The vibrations of mechanical parts in
\nthe machine cause fluctuations in the air pressure, thus causing sound waves to radiate. The
\nradiating sound may be directly related to the component vibrations. As a result, changes
\nin the process can be monitored by detecting changes in the airborne sound. This thesis
\naims to study the airborne sound radiated during ultrasonic metal welding and estimate the
\nrelation between the sound and the process stages. Several features are examined to achieve
\nthis goal, starting with frequency analysis. The spectrogram of the airborne sound shows
\nthat the sound emitted has a mostly constant amplitude and contains many frequencies,
\nmost notably the fundamental frequency and its harmonics. These frequencies are examined
\nin relation to time in order to define transitions between different stages. Additionally, a
\nrelationship between the welding strength and the welding frequency is investigated but no
\ncorrelation was discovered. Two ratios are derived to measure nonlinearity, one comparing
\nthe fundamental frequency with all other frequencies, and the other with its harmonics. The
\nanalysis presents comprehensive tables showing the relationship between welding stages and
\nthe studied features. It is evident from the tables that there is a correlation between the
\nfrequency behaviors and the stages of the process.<\/p>\n
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