Depth of Compressive Residual Stress Enhancement In Laser Shock Peening of Power Generation Turbine blades

Arresting the susceptibility to catastrophic failure of critical components like turbine blades has become essential and now drives research and innovation in condition-based maintenance and failure prevention in power generation turbines. Laser shock peening (LSP) is one technique which is now employed by engineers, to mitigate failure and strategically ensure the health of plant components. Over the years, research has been focused more on achieving compressive residual stress induction, with ways of enhancing the depth of penetration yet scarcely investigated. This study thus applied numerical methods to define how the various inputs affect the depth of compressive residual stress (CRS) penetration in X12Cr steel and the hierarchy of influence of the input parameters when achieving maximum depths possible, of compressive stresses, are prioritized. Commercial finite elements (FE) code was used to model LSP on X12Cr steel, a common material used in manufacturing turbine blades. Validated with experimental results, the FE code was transformed to an empirical function by data fitting and optimized using a gradient-based maximization objective algorithm. Results reveal the combination of less than 50% degree of overlaps, mid-range shot diameters, 4-6 GW/cm(2) shot intensity and prolonged peak exposure time produces enhanced penetration of compressive stresses. Furthermore, the hierarchy of influence of the five input parameters investigated, on penetration depth maximization, revealed that the degree of shot overlaps is the most influential input in this regard, followed by shot size, shot intensity, shot angle and exposure time in descending order.