Random vibration fatigue life assessment and optimization of a train buffer beam considering welding residual stress

Abstract

The traditional fatigue design of accessories attached to a train body does not consider welding residual stress for fatigue life prediction of welded structures during the design stage, thereby resulting in insufficient fatigue strength for local welded parts. The power spectral density of random excitation caused by rail irregularity from American six-level spectrums was obtained in this paper. Through welding thermal elastoplastic theory combined with ellipsoid heat source model, a numerical simulation for welding residual stress production and distribution of a train buffer beam was conducted. In accordance with the coupling stress component, the fatigue performance of a train buffer beam under random loads was evaluated by the AA6082 welded joint S-N curve, whose lifetime did not satisfy design requirements. Then, the surrogate model of a train buffer beam for anti-fatigue optimization design was constructed based on the response surface method. The fatigue life of the optimized train buffer beam increased by two orders with the use of the genetic algorithm to find the optimal solution in global variables.