Residual stresses in AA7108 aluminium alloy sheets joined by friction stir welding

Friction stir welding is a revolutionary joining process which has seen remarkable growth in research, development and application in recent years. In order to better characterise the welding, it is becoming necessary to evaluate the residual stresses, because these can modify as well the structure as the initial properties of material. In the current work, we will focus particularly in the method of measurements based on ultrasonic waves. This method has the advantage of being nondestructive, easy, inexpensive and fast to use in situ. The experimental results obtained on AA7108-T79 aluminium alloy joined by friction stir welding (FSW), showed small compressive residual stresses in the base material and high tensile residual stresses in the heat affected zone. Advantages bound to this method were proved and results remain very promising.