Abstract: Structural optimization and high-steady machining of region of high stress play key roles for hydraulic performance of pelton turbine. Finite element model of bucket is established, and reasonable boundary condition are determined. Based on operation characteristics of pelton turbine, load cases and stress evaluation criteria of bucket are determined. Meanwhile, the manufacturability of the root of pelton is considered fully based on the requirements of the hydraulic performance and strength of pelton. The results of study shows that curvature uniformity of bucket root, depth of bucket root and thickness of bucket root are main factors influencing the stress level of bucket. By the structural optimization of bucket root, the compound stress, amplitude of alternating stress and average value of alternating stress are reduced by 16%, 13.3% and 15.5% respectively. The stress level and fatigue safety factor of the final bucket structure meet the design requirements. The size of inside hole of tool holder with larger aspect ratio (20: 1) is optimized through the finite element model and experiment, of which result demonstrate the lowest amplitude can be obtained when the diameter is 8 mm. The performance and machining accuracy of pelton turbine can be certified through the optimization strategy, which is validated by the experimental machining and the practical application.

Key words: bucket, cutting vibration, damping tool holder, finite element, structural optimization, pelton turbine