Lightweight design with weld fatigue constraints for a three-axle bogie frame using sequential approximation optimisation method

A lightweight optimisation model with static strength and weld fatigue constraints is constructed for the welded frame of a three-axle bogie, and it is solved by an adaptive sequential approximation optimisation (SAO) method based on kriging models. To improve the accuracy of approximate functions on the basis of a small sample set, seven kriging models are used to construct the relationships between weld fatigue damage and plate thickness. The Master S-N Curve Approach is adopted for weld fatigue assessment considering its mesh-insensitivity and reliability. The weight of the bogie frame is reduced by 9.2% after optimisation. The optimisation results give a recommended design for the welded bogie frame and demonstrate the validity of the proposed optimisation method. The robustness analysis results for the recommended engineering design shows that the weld fatigue failure will not happen when the deviations of variables are considered.