Numerical prediction of temperature and residual stress fields in LFSW

In recent years important innovations have been introduced in FSW technology such as, for example, the Laser assisted friction stir welding (LFSW). In this technique the FSW process is assisted, during the weld, by the pre-heating of a de-focalized laser that allows an easier advancement of the tool. This technique should lead higher welding speeds, lower clamping forces and lower residual stress. Moreover, the prediction of residual stress is a relevant, complex and still open issue for welding process design. In this work an uncoupled thermo-mechanical finite element model has been developed to predict the temperature and residual stress fields in LFSW. Both the thermal and mechanical parts of the model have been validated on the base of experimental data. The temperature field has been recorded by an infrared camera, while residual stress field has been measured by X-ray diffraction analysis. The LFSW test was conducted on 6 mm thick 5754 H111 aluminium alloy plates.