For fulfilling the demand of durable yet lightweight electrical connections in transportation industries, ultrasonic metal welding (USMW) sees widespread use in these branches. As the ultrasound oscillations utilized in the welding procedure occur at a range of only a few micrometers at frequencies of 20–100 kHz for an overall duration of only 50–1500 ms, it is not possible to observe the compaction behavior with the bare eye. This paper focusses on investigating the oscillation behavior of the horn, the anvil, and the joining partners during the welding procedure by utilizing an array of synchronized laser vibrometers and performing welds with incrementing time stages. The oscillation data is correlated with temperature measurements in the welding zone as well as tensile testing results. Inter alia the formation of sidebands at the fundamental frequency as well as 2nd- and 3rd-order harmonics has been observed for the anvil, terminal, and wire front face when exceeding optimal weld time which would lead to maximum joint strength. Following the assumption of other research groups, the cause of these sidebands could be a change in relative motion of these components. As the terminal is slipping with increasing weld time, it could be assumed that the reason for the sidebands is low-frequency movement of the anvil, modulated onto the fundamental frequency, additionally indicating successful bonding of the stranded wire and the terminal. Furthermore, this slipping of the terminal on the anvil could lead to increased wear of the anvil knurls.

Friction stir welding (FSW) is an innovative solid-state joining process, which is suitable for joining dissimilar materials with strongly differing physical and chemical properties such as aluminum and steel. Where other joining methods such as fusion welding struggle to achieve appropriate joint strengths due to the excessive formation of brittle aluminum-rich intermetallic phases (IMP), FSW joints of aluminum and steel only show small layers of IMP, thus, sufficient tensile strengths in proximity to the maximum tensile strength of the weaker aluminum base material can be reached. With the aim to optimize the mechanical and microstructural properties of such dissimilar joints for widening the field for possible industrial applications, several hybrid friction stir welding methods have been developed which include an additional energy input, whereas the ultrasound enhancement (USE-FSW) is one of the most promising. The current work was carried out on AA6061/DC04 joints which were successfully friction stir welded with and without ultrasound support, in respect to the influence of varying the ultrasound transmission side. The functionality of the USE-FSW setup could be verified by multi point laser vibrometer measurements. Additionally, a higher proportion of transversal oscillation for the transmission of power ultrasound into aluminum could be detected using a scanning vibrometer. In comparison to the conventionally friction stir welded joints the ultrasound enhancement led to an avoidance of weld defects and an increase of the steel particle volume in the stir zone. The joint produced with power ultrasound transmission via aluminum resulted in a more uniform interface.

Ultrasonic metal welding is a solid-state joining technique widely used in electrical and electronics manufacturing, including aluminum wire connections for modern vehicles. Throughout production, transport, and storage, aluminum stranded wires are exposed to possible contamination and progressive surface oxidation, both of which can adversely affect the wire quality and, consequently, the quality of the welds. This study focuses on the influence of surface impurities and oxide-layer characteristics on the USMW performance of aluminum stranded wires. To isolate key variables, the wires were subjected to controlled storage environments with varying temperature, relative humidity, and storage duration. Despite differences in these storage parameters, all joints after USMW met the mechanical performance requirements specified in the relevant DIN standard. However, weldability and the magnitude of property degradation still varied markedly depending on the storage environment. The results of welding combined with advanced XPS surface analysis and laser vibrometry investigations show that storage humidity is the primary factor governing the surface state of the wires as well as post-weld properties, underscoring the need for strict environmental control prior to welding. A further key parameter is the condition of the native oxide film on each strand’s surface immediately after wire production.

The new QTec Scanning Vibrometer is employed to analyze wave propagation resulting from corrosion. At a distance of d = 1.66 m, Lamb wave characteristics were recorded using an AE sensor and compared to a simulated corrosion event signal. The vibrometer's signal correlation enabled wave path reconstruction, ultimately facilitating the localization of the corrosion source by considering reflections and constructive interference effects in the AE sensor time signal.

As part of a joint research project between the Institute of Fluid Mechanics (LSTM) and the Institute of Fundamentals and Theory of Electrical Engineering (IGTE), an international benchmark case for fluid–structure–acoustic interaction was developed. The research focused on an enclosed centrifugal fan, and its aerodynamic, aeroacoustic and structure–acoustic properties were characterised through experimental measurements. This paper provides an overview of the centrifugal fan, its enclosure and the test rig used for the experimental investigations. Rather than interpreting the results, the focus is on presenting the benchmark case and providing an overview of the available data. The entire benchmark dataset is listed and freely accessible via the Zenodo European platform in the EAA benchmark data collection.