Laser Shock Peening of Airframe Structures: Process Mechanics & Influence of Process Parameters

Laser Shock Peening (LSP) is an emerging technique that has been successfully used to introduce compressive residual stresses into metallic structures with a wide range of possible applications such as aircraft engine components, panel forming, nuclear power reactors, steel bridges, and medical implants. In contrast there is limited information available on airframe applications, despite the fact that the aeronautical industry is strongly interested on the possible application of the LSP method at different stages of aircraft life, i.e. in production as a cost and time effective solution to introduce compressive residual stresses in critical areas; or during maintenance as an on-site repair solution for unexpected fatigue issues arising at an early stage; or for ageing aircraft skin structures susceptible to different forms of in-service damage. The present research programme thus investigates LSP without an ablative coat (LSPwC), with the primary objective of optimizing the LSP process for improving fatigue life of thin‐walled airframe aluminum structures, by introducing controlled compressive residual stresses.

The programme designed accordingly included the following key elements:

1. Establishment of a versatile experimental configuration, and LSP of thin, dog-bone specimens of standard airframe aluminum alloys using various parameter combinations.

2. Investigation into the physics and mechanics of the LSP process, through high-speed imaging and several diagnostic tools, for a greater understanding of the process.

3. Experimental assessment of process performance for different parameter combinations through residual stress measurements, surface analyses, and fatigue tests of treated samples.

The integrated experimental approach used and the ensuing results will considerably advance the understanding of the process parameters leading to a robust, quality controlled LSP process. Consequently, this would allow for the achievement of engineered residual stress profiles, thus potentially extending the LSP application from an uncontrolled repair solution to a controlled design solution for conventional and innovative airframe structures.