Optimizing of compressive stress region by local treatment technologies on Francis runner

The existing of residual compressive stress increases the fatigue resistance of welding structures.The local compressive stress was realized around the fusion boundary in the Francis turbine runner by optimizing the welding process, where fracture could easily occur.And the influence of local heating and peening on the stress field in the fracture-easily-occurred region of runner was simulated and measured based on the real runner.The results indicate that the stress field in the fracture-easily-occurred region of runner can be regulated and controlled by local heating and peening processes.And the local compressive stress region was optimized.The value of residual compressive stress in the fracture-easily-occurred region of runner was further improved, and high compressive stress region was formed, especially, the compressive stress region was expanded.These processes can promote the realization of local compressive stress in the fracture-easily-occurred region of Francis runner and effectively enhance the fatigue resistance of the runner.