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Prediction of Stable Fatigue Crack Growth in Laser Peened 316L SS with Variable Beam Diameter and Pre-crack Length Using Artificial Neural Network

Ariyanfar, Alireza | 2022

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 54913 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Farrahi, Gholamhossein
  7. Abstract:
  8. Processing an alloy can enhance its mechanical properties. Based on repeated radiation of high-power pulsed laser beam, laser shock peening (LSP) is one way to impart favorable residual stress in an alloy and to enhance its damage tolerance property. Study of overlapping LSP is possible through the simulation of limited laser shots. Still, its computational cost is higher than that of a single shot. This research, primarily, is aimed at improving a methodology for reduction of computations in the study of an overlapping LSP and its impacts on fatigue crack growth. Addressing research gaps by utilizing the methodology is the secondary goal. The methodology consists of plastic strain prediction by FE simulations and neural networks, experimental characterization of material, and fatigue crack analysis. It is shown that change of pulse width and beam diameter in a constant energy influences plastic strain insignificantly and significantly, respectively. A proper diameter encourages crack closure and stability of fatigue crack growth rate except in periphery of the coverage area, where destructive field of residual stress accelerates the growth. Application of LSP to a specimen after further growth of its pre-crack suppresses this adverse effect and results in a higher total life of pre-crack and crack growth
  9. Keywords:
  10. Plastic Strain ; Residual Stress ; Finite Element Method ; Artificial Neural Network ; Crack Growth ; Fatigue Crack ; Fatigue Crack Growth Rate ; Laser Shock Peening

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