1 American Institute of Aeronautics and Astronautics Sensitivity Analysis of Laser Peening, a Fatigue Life Enhancement Process Gulshan Singh * , Miguel Cortina # , and Harry Millwater † University of Texas at San Antonio, TX 78249, USA Fatigue failure is a common type of problem for airframe structures especially with the growth in the number of aging aircrafts. Laser peening (LP) is a surface enhancement technique that improves surface fatigue properties by inducing compressive stresses on the peened surface and has been applied to many aerospace components such as turbine blades, lugs, and boltholes. Experiments- and/or simulation-based parametric studies or deterministic optimization methods have been applied in the literature to determine the LP parameters for an application. However, LP is a very high-speed (nano seconds) process that involves uncertainties in the component, material, and laser peening process. Therefore, parametric studies and a deterministic approach are not sufficient and it is valuable to compute the probabilistic and localized sensitivities for the fatigue life with respect to the laser peening variables. An in-depth sensitivity analysis can provide a better understanding of the process, reduce the number of experiments and simulations, and make the LP process a cost-affective surface treatment for aerospace applications. A probabilistic sensitivity analysis using several different methods was conducted in order to determine the importance and relative ranking of the laser peening random variables for a crack growing from a bolthole. Nomenclature E . [] = expected value operator over entire sample space f = PDF F = CDF g = limit state function I = indicator function (I=1 in failure region, I=0 otherwise) n = number of random variables N = number of Monte Carlo samples P f = probability-of-failure x = random variable X = vector random variable κ θ = kernel function with respect to an arbitrary distribution parameter θ z = response function µ = mean σ = standard deviation θ = arbitrary PDF parameter p = pressure pulse magnitude of laser peening process * Post-Doctoral Researcher, Department of Mechanical Engineering, UTSA and AIAA member. # Graduate Student, Department of Mechanical Engineering, UTSA and AIAA student member. † Professor, Department of Mechanical Engineering, UTSA and AIAA member. 52nd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference<BR> 19th 4 - 7 April 2011, Denver, Colorado AIAA 2011-2145 Copyright © 2011 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.