FATIGUE CRACK RESISTANCE OF FRICTION STIR WELDED PMMC BUTT JOINTS

摘要

In this work the fatigue crack growth behaviour of an alumina particle-reinforced aluminum alloy friction stir welded (FSW) butt joint is characterized. Tests are conducted both in Stage I (near-threshold) and Stage II (Paris) regimes at two different Rratios. Two crack position in the welded zone are considered, along the weld line and at the weld side, respectively. The increase of fatigue crack growth (FCG) rates with R-ratio has been evaluated in terms of crack closure, that in particulate metal matrix composites is generated mainly by crack surface roughness, crack deflection or trapping mechanisms, and in FSW joints is enhanced by residual stresses. Results are presented in a direct comparison with the parent material behavior. The specimen halves have been examined at the scanning electro microscope after fracture in order to highlight crack path features.