Prediction of rate-dependent residual strength of aluminum alloy of car body for in-service high-speed trains
The structure and materials of high-speed trains will gradually deteriorate under the influence of complex boundary conditions during long-term service,posing potential safety risks.The commonly used aluminum alloy 6005A-T6 for high-speed trains was focused in this study.Firstly,the mesostructure of the material was decoupled into matrix phase and void phase,and a damage evolution equation that conforms to the Weibull distribution characteristics of mesostructure continuity was derived.Secondly,an experimental-numerical method considering strain rate was proposed to identify the accelerated damage evolution behavior after material necking.The damage evolution equation covering the entire process of void nucleation,growth,and aggregation was deduced.The undamaged constitutive of the matrix phase was obtained.Finally,a damage sequence interaction model was proposed based on the mesoscopic physical mechanism,which achieved the damage evolution equation of materials containing previous service damage in subsequent ductile deformation by measuring only the apparent elastic modulus.The rate-dependent residual strength of materials containing service damage was accurately predicted.The results show that the average relative error between the predicted and the experimental values is less than 1%.The damage changes from positive sensitivity to negative sensitivity in strain rate as the damage develops.For the fatigue-ductility mechanism,voids continue to grow based on the voids developed from the previous fatigue damage.