Cable length affected vibration-related joint degradation

What the study found: Cable length strongly affected whether ultrasonically welded cable-arrester joints stayed intact or degraded during welding. The study also found that vibration propagation, especially unsynchronized vibration transmission reflected in relative phase shifts, was linked to joint failure.
Why the authors say this matters: The authors say a mechanistic understanding of vibration propagation during ultrasonic metal welding is needed to ensure process reliability, because ultrasonic vibrations can interfere with previously welded joints. The study suggests this is relevant for lightweight electrical connections in transportation, including electric-vehicle cable-arrester joints.
What the researchers tested: The researchers studied stranded aluminum wire cables welded to copper terminals at both ends by linear ultrasonic metal welding. They combined laser vibrometry, high-speed videography, and tensile shear testing with a scaled finite element model in ANSYS Workbench that was validated against the experimental data.
What worked and what didn't: Mechanical testing showed robust joints at 300 mm cable length, non-weldable behavior at 225 mm, and isolated failures at 150 mm and 375 mm, while longer cables showed no signs of joint degradation. Laser vibrometry showed vibration amplitudes decreased with increasing length because of damping, but critical lengths showed pronounced amplitude and phase shifts associated with degradation. The simulations reproduced these effects and indicated elevated weld-zone stresses of about 130 MPa at critical lengths.
What to keep in mind: The abstract does not describe limitations beyond the tested material pair, cable lengths, and welding setup. The findings are specific to EN AW-1370 aluminum stranded wires, CW004A copper terminals, and the conditions studied.

Key points

• Cable length strongly affected whether welded cable-arrester joints degraded during ultrasonic metal welding.
• Robust joints were reported at 300 mm, while 225 mm showed non-weldable behavior.
• Laser vibrometry found lower vibration amplitudes at longer lengths, with critical lengths showing amplitude and phase shifts.
• Finite element simulations reproduced the experimental vibration effects and indicated weld-zone stresses of about 130 MPa at critical lengths.
• The authors identified unsynchronized vibration transmission, expressed as relative phase shifts, as the main cause of failure.