Ultrasonic weld strength and weld microstructure characteristics in multi-strand aluminum cables (EN AW-1370) - Effect of process parameters

摘要

Analysis of the joint strength between multiple thin aluminum strands in multi-strand single core cables after ultrasonic welding was carried out by performing T-peel tests. Herewith, the effect of two process parameters, namely the sonotrode pressure and the amplitude of sonotrode vibrations on the joint strength was studied. It was found that a larger applied pressure resulted in a larger maximum T-peel force, while large magnitudes of pressure and amplitude at the same time decreased the fracture energy of the weld and resulted in a weak joint. Furthermore, 3D reconstruction of the images captured by computer tomography of the joint revealed that for a high pressure value and a low value of vibration amplitude, the structure of the weld under the sonotrode was much more compact compared to a high value of vibration amplitude and a low value of pressure. To this end, volume fraction of the gaps between the aluminum strands inside the microstructure of the weldment was quantified and compared between specimens with different process parameters. Finally, a correlation between the joint strength and the microstructure porosity (voids) of the weldment has been presented and discussed.