Fracture strength of welded aluminium joints in commercial road vehicles

This work presents a study of the failure of a commercial vehicle structure based on welded aluminium plates using metallographic techniques to analyze the microstructure of the weld fillet, the plates and the joints. A hardness study evaluates the differences between the fillet and the aluminium plates. To measure the mechanical strength of the joints, an experimental testing program was designed to reveal the maximum stresses that the structure can support. The results reveals brittle failure initiated at flaws localized near the joints acting as stress concentrators. To reproduce the behaviour of the joints including the weakness due to the presence of defects, a maximum stress failure model was derived, from the data obtained from the mechanical tests. The failure of the structure was simulated numerically using a finite difference code. The results show that the vehicle does not fail in the absence of flaws. However, failure occurs when the weakening introduced by the presence of flaws is included.