Microstructural characterization of aluminum cables and ultrasonically welded terminals for electric/hybrid electric vehicles

Abstract

Aluminum cables are much more cost effective and lightweight when compared to standard copper wiring. Without sacrificing conductivity, aluminum wiring can offer up to a 48% weight reduction versus copper wiring. This is particularly important in vehicle wiring, since any reduction in weight will improve fuel economy which will result in reduced carbon dioxide emissions. Although replacing copper wiring with aluminum wiring offers such advantages, it does come with its own set of challenges. One such challenge is creating successful terminal connections. Connecting aluminum cables to terminals by mechanical crimping is not nearly as effective as crimping copper cables to terminals. While crimping aluminum to terminals may work for smaller cables and wires, to connect larger aluminum cables, such as battery cables in vehicles, another method of connection should be used. A potentially effective connection alternative method is through ultrasonically welding the cables to the terminals. Ultrasonic welding is a process of joining two overlapping metal pieces by applying pressure and high frequency vibrations to them, causing dynamic shear stresses high enough for plastic deformation to occur and bond the pieces. Aluminum and aluminum alloys are one of the most easily welded structural metals by this method. Since no electrical current actually passes through the aluminum being welded, the heat of the weld is not high enough to affect the mechanical properties of the welded sample. Ultrasonic welding does have some drawbacks, such as thickness limitations, but for the cables in this project, this limitation should not be a problem. An area of particular interest in this project is the ultrasonic welding of aluminum and brass for aluminum cables/brass terminals applications in electric/hybrid electric cars. The purpose of this project is to understand the materials characteristics involved in the successful ultrasonic welding of aluminum cables to brass terminals used in electric/hybrid electric cars. In order to ach