Block braked railway wheels are subjected to thermal and rolling contact loading.The thermal loading results in high temperatures and thermal stresses which cause slow time dependent processes such as creep,relaxation...Block braked railway wheels are subjected to thermal and rolling contact loading.The thermal loading results in high temperatures and thermal stresses which cause slow time dependent processes such as creep,relaxation and static recovery of the wheel material.At the same time,the rolling contact loading implies a very fast mechanical load application.This paper is focused on material modeling of pearlitic steel for a wide range of loading rates at elevated temperatures.The starting point is a viscoplasticity model including nonlinear isotropic and kinematic hardening.The Delobelle overstress function is employed to capture strain rate dependent response of the material.The model also includes static recovery of the hardening to capture slower viscous(diffusion dominated)behaviour of the material.Experiments for the pearlitic wheel steel ER7 in terms of cyclic strain-controlled uniaxial tests with hold-time,uniaxial ratchetting tests including rapid cycles and biaxial cyclic tests with tension/compression and torsion are used to calibrate the material model.These experiments were performed under isothermal conditions at different temperatures.In the ratchetting tests,higher loading rates are obtained and these have been used to calibrate the high strain rate response of the viscoplasticity model.The paper is concluded with a numerical example of a block braked wheel where the importance of accounting for the viscoplasticity in modelling is highlighted.展开更多
基金The current study is part of the ongoing activities in CHARMEC-Chalmers Railway Mechanics(www.chalmers.se/charmec).Parts of the study have been funded from the European Union’s Horizon 2020 research and innovation programme in the projects In2Track,In2Track2 and In2Track3 under Grant Agreements Nos.826255 and 101012456The simulations were performed using resources at Chalmers Centre for Computational Science and Engineering(C3SE)provided by the Swedish National Infrastructure for Computing(SNIC).
文摘Block braked railway wheels are subjected to thermal and rolling contact loading.The thermal loading results in high temperatures and thermal stresses which cause slow time dependent processes such as creep,relaxation and static recovery of the wheel material.At the same time,the rolling contact loading implies a very fast mechanical load application.This paper is focused on material modeling of pearlitic steel for a wide range of loading rates at elevated temperatures.The starting point is a viscoplasticity model including nonlinear isotropic and kinematic hardening.The Delobelle overstress function is employed to capture strain rate dependent response of the material.The model also includes static recovery of the hardening to capture slower viscous(diffusion dominated)behaviour of the material.Experiments for the pearlitic wheel steel ER7 in terms of cyclic strain-controlled uniaxial tests with hold-time,uniaxial ratchetting tests including rapid cycles and biaxial cyclic tests with tension/compression and torsion are used to calibrate the material model.These experiments were performed under isothermal conditions at different temperatures.In the ratchetting tests,higher loading rates are obtained and these have been used to calibrate the high strain rate response of the viscoplasticity model.The paper is concluded with a numerical example of a block braked wheel where the importance of accounting for the viscoplasticity in modelling is highlighted.
