Analysis of the oscillation behavior during ultrasonic welding of EN AW-1070 wire strands and EN CW004A terminals

Abstract

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.

Application of electrical power measurements for process monitoring in ultrasonic metal welding

“…The prediction quality of all models is limited for joints with higher strength, which is at least partially attributed to the quality of the peel test conducted. Compared to other machine learning models of the literature, the prediction quality is at least of similar quality as models presented in [25], while inferior to the random forest model presented in [17]. Both other models require sensor equipment in vicinity of the welding to measure vibration of horn and anvil, and both models used a shear strength as reference quality data.…”

“…This relates to over-welding [6]. Further power and depth curves are listed in the Appendix Figs 17,18,19,20,21,22,23,24,25,26,27 and 28. All graphs use a uniform color scheme indicating the strength of the associated weld; the color bar shows the strength in N.…”

“…Various researchers proposed that internal monitoring solutions are not feasible to allow precise monitoring [6,7] leading to further investigations using external measurement equipment. Very often laser-dopplervibrometers are used for process monitoring [6,[24][25][26][27][28][29]. Elisabeth B. S. et al used the relationships between tensile shear strength of Cu-sheet welds and process curves from welding machine and additional vibration sensors at horn and anvil to build a prediction model.…”

“…Different features are extracted from the dataset and used for prediction of tensile shear strength using linear regression as well as multi-layer perceptron regression. [24] Gester et al used the vibrometers for describing a wire-terminal application [25].…”

Assessment of the Structural State of Dissimilar Welded Joints by the Acoustic Emission Method

“…The most sensitive method is ultrasonic testing. The use of ultrasonic testing for dissimilar welded joints of reactor equipment is noted in several works [7,8].Essentially, testing is carried out using special equipment and techniques that take into account the design features of each welded joint [9,10]. However, the coarse-grained structure leads to a high attenuation of ultrasonic vibrations in the austenitic steels, and the complex structure of a dissimilar welded joint displays a high level of interference [11].…”