The research objective of this award is to investigate an innovative hybrid process combining laser shock peening with creation of nanostructures to minimize the relaxation of compressive residual stresses and work hardening. This project will discover the fundamental process mechanisms of the nanoparticle integrated laser shock peening process, and understand how this process produces the unique micro/nanostructures, which results in stabilized residual stresses and work hardening. Experiments and simulations will be conducted to investigate the effects of the type, size and distribution of the nanoparticles on the resulting microstructure and residual stress distribution. The stability of residual stress and dislocation structure under different temperatures and cyclic loadings will be studied using transmission electron microscopy and X-ray diffraction. Dislocation-pinning mechanisms will be investigated to explain the stabilizing effects. In order to study the mechanism of fatigue life enhancement, we will build a fatigue life model to predict the improved fatigue life considering the time variant residual stresses and hardness under real service conditions. Fatigue testing experiments will be designed to validate this model.
The successful completion of this work will make an improvement to laser shock peening that produces compressive residual stress and a work hardening layer. This work can ensure the benefit of integrating a pre-stressing concept into component design with minimum risk for improved fatigue life, increased reliability and reduced weight. The impact can be transferred to the majority of load-carrying and structural components. This project will meet the challenges of education in materials science, engineering and manufacturing by (a) enhancing interdisciplinary and nontraditional manufacturing for research and education in Purdue University, (b) providing a multidisciplinary research opportunity for students to advance discovery and understanding of cutting edge manufacturing processes and (c) outreach to undergraduate and graduate students to retain them in science and engineering, especially underrepresented and minority students.
