Evaluation of fatigue life in laser peened thin aluminum panels

Editor's Note: This article by Enrico Troiani and Sara Taddia on laser shock peening of thin aluminum panels briefly describes the laser shock peening process as it applies to enhancing the fatigue life of the thin aluminum panels, obviously used on aircraft but no doubt generally applicable. Unlike laser applications in welding aluminum alloys, laser shock peening does not fuse the aluminum surface, rather the laser energy pu lses a re absorbed by the coa ting placed on the alu min u m surface and the localized explosion is directed by flowing water into the surface of the materialI, thus introducing compression in the surface layers. As the authors show in Figure 2, unlike conventional shot peening, laser shock peening introduces a gentler form of compression with minimal cold working. But laser shock peening has its own set of process parameters, which must be controlled to optimize its effects. As the University of Bologna is famous for its application of finite element modeling and computer simulation to alumin um processing, Troiani and Taddia show how to apply the laser shock peening process to limit crack propagation in thin aluminum panels. As our focus in the International Patent Calendar in this issue is on Aerospace Aluminum, readers should take note of U.S. patent 9,150,941 assigned to Airbus, which involves the use of laser shock peening to prevent and slow down crack advancement in metal aircraft structures. Enrico informs us that he is working with some of the inventors at Airbus on numerical simulation of laser shock peenin