AN IMPROVED METHODOLOGY FOR MODELLING AND SIMULATION OF LASER SHOCK PEENING
Abstract - The evolution of laser shock peening as a surface treatment and processing technique has opened several vistas for providing preventive and condition-based maintenance solutions for the prevention of downtimes from in-service failure of power plant components, such as aircraft engine turbine blades. Advancements in computational power with the development of supercomputers has also progressively sparked intensive research in the development of laser shock peening (LSP) models, capable of modelling and simulating the induction of compressive layers around and beneath the surface of turbine blades, utilizing the conventionally well-known Johnson-Cook plasticity/damage models. However, founded upon a phenomenological yet a fully physics-based constitutive model, this study presents a unique experimentally validated computational modelling approach of the LSP process employing a mechanical threshold stress (MTS) damage model for compressive residual stress induction irrespective of increasing laser shock intensities. Encouragingly, the results revealed better accuracy and predictive capabilities when compared to conventional empirical LSP models. Furthermore and hitherto overlooked previously by researchers, the technique described in this study shows considerable promise when benchmarked against experimental results, with surface residual stresses of about 700 MPa being induced on the X12Cr material to an affected depth threshold of 0.6mm. Based on the results achieved, it may be stated with confidence that the proposed modelling approach can render reliable guidance for practical control of the LSP process operation in the overall quest to mitigate crack initiation and growth especially at the surface of the turbine blades, as well as to prevent catastrophic failure of the aircraft turbine engine while in service.
Keywords - Laser shock peening, Mechanical threshold stress, Finite Element Analysis.