Experimental investigation into the comparison between shot peening and laser shock peening on AA 6056-T4 aluminium alloy

Currently, within the aviation industry there has been a large focus on enhancing the fatigue life of thin-walled aircraft structures, such as the fuselage. In the past decades, shot peening was seen to aid in accomplishing this goal. In more modern and recent times, laser shock peening techniques were said to provide a more substantial improvement to the treated material, in comparison to shot peening. Laser shock peening relies on a more focused and precise peening process, whereas shot peening utilised a multitude of shots (small spherical metal/plastic/glass beads) which are projected towards a material surface (via a high pressure), which randomly impacts the material surface to create compressive residual stresses and thus improve fatigue life. Samples of AA6056-T4 Aluminium alloy used for integral structures, with a thickness of 3.2mm were used to represent a thin-walled component. These were used for comparative testing of material properties after Laser Shock Peening and Shot peening had been executed on the test pieces. The material properties investigated were material deflection, surface roughness, micro-hardness and residual stresses at various laser intensities and shot peening pressures. Laser shock peening had shown the best results, with higher deflections between 2.12 to 3 times higher than shot peening, a smoother surface finish (roughness values 2-2.5 times less than shot peening), deeper hardness penetration and deeper residual stress into the aluminum alloy test pieces.