Investigation on Interface Failure and Shear Strength of CMT Brazed Lap Joint of Dissimilar Materials

In order to save fuel consumption by reducing the weight of automobile body, the use of aluminum alloys has a great advantage. However, how to join aluminum alloys with steels becomes a big problem in the assembly lines. Cold metal transfer (CMT) is a promising joining process for steel/Al dissimilar materials. To evaluate the shear strength and to investigate the failure modes of CMT brazed lap joints of dissimilar materials, both experimental observation and numerical simulation are performed. A numerical model for the failure criteria of the interface layer failure between steel and aluminum is developed. The interface layer of CMT brazed lap joint can be modeled by the interface element. The failure stress and failure energy at the interface element are proposed as the failure criteria for the prediction of shear strength of CMT lap joints. If steel sheet thickness becomes thicker, stress distribution and concentration at interface layer elements have some change and shear strength at the interface layer can be improved. Then the failure occurring at the interface element may transfer to the fusion line at the side of the aluminum alloy sheet.