ADVANCED MATERIALS & PROCESSES | APRIL 2025 19 Laser shock peening (LSP) is a novel surface engineering method that improves component performance through the introduction of deep compressive residual stress. The first reported investigation on the effect of stress waves created by lasers and their effect on metals was by White in 1963 and the first patent for application of LSP was in 1974[1,2]. Initial applications of LSP were limited due to the expense of the required laser systems and the slow repetition rates of lasers of the time. However, over the last few decades its application has increased significantly as more suitable laser systems were developed. LSP has been used widely in aero engine manufacture for the prevention of fretting fatigue. It has also been used for foreign-object damage mitigation. In aerospace manufacture, the method has been used as a forming technique for shaping components, such as the wing of the Boeing 747-8. In parallel with the developments in laser peening in the 1990s for aerospace components, predominantly in the United States, the method was also used in Japan in nuclear power applications: specifically, the peening of welds in the pressure vessels of boiling- water reactors that were found to be potentially susceptible to stress- corrosion cracking. This led to the existence of two similar approaches to laser peening: DEVELOPMENTS IN LASER SHOCK PEENING FOR AEROSPACE APPLICATIONS An innovative method to add residual stress has demonstrated significant impact in safety-critical applications such as aero engines, while additional research focuses on lowering the cost and increasing equipment flexibility. Niall A. Smyth and Michael E. Fitzpatrick Coventry University, United Kingdom of global locations where laser peening can be conducted. As a result, there has been much effort into evolving laser peening to use lower-cost, more flexible equipment, particularly the lasers and delivery system from the laser to the component, and also in broadening the range of applications of the method. RESIDUAL STRESS The primary reason for most applications of laser peening is to introduce surface compressive residual stress, to prevent the initiation and/or propagation of cracks. The residual stress induced by laser peening can extend several millimeters below the surface, depending on the material being peened. Higher strength materials such as steel and titanium can one with relatively large laser spots (several mm in dimension) and high power density (>2 GW/cm2), and one using smaller spots (sub-mm) and lower power density but with higher repeat coverage of shocks on the surface. The primary application for domain, in terms of number of products peened, remains aerospace, and aero engines in particular. There have been numerous trial and bespoke solutions for specific problems, but laser peening has not progressed to have the ubiquity and ease of application of shot peening. The reasons for this are: 1) the relative inflexibility of the laser peen system, with the need for the laser and a robotic positioner for either it or the component being peened; 2) the time and resources needed for the set-up and operation of the process; and 3) the relative scarcity Fig. 1 — Illustration of typical laser shock peening process.
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