Optimization of Residual Stress Field and Improvement of Fatigue Properties of Thin-Walled Pipes by Filling Laser Shock Peening

In the present work, a filling and laser shock peening (LSP) method is put forward and applied to a thin-walled pipe. Specimens were experimentally and numerically investigated to identify the residual stress field and fatigue properties of a pipe with and without LSP treatment. The numerical simulation indicated that the residual compressive stress first increased and subsequently dropped as the laser power density increased, and the extent of influence of the stretching wave, reflected from the lower surface on the unloaded area, increased with the spot diameter, causing surface tensile stress in the unloaded area. By filling the pipe with the guided-wave material, the residual stress field of the pipe that was treated with LSP was optimized, and the influence of the stress wave reflection on the residual stress field was effectively decreased. The surface residual stress of the filled guided wave material was -326 MPa, improving it by 57.6% compared with the pipe not filled with guided wave materials. The fatigue life of the pipe with the filled waveguide material that was treated by LSP was extended by 48.9%, compared with the untreated pipe.