Modelling of temperature and strain rate dependent behaviour of pearlitic steel in block braked rail

• 作 者: Ali Esmaeili Johan Ahlstr?m Magnus Ekh Dimitrios Nikas Tore Vernersson
• 机 构: CHARMEC/Department of Industrial and Materials Science,Chalmers University of Technology,Gothenburg,
• 出 处: 铁道工程科学（英文版）
• 发表日期: 2021年4期
• 关键词: Block braking High temperatures Pearlitic steel Railway wheels Viscoplasticity

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 uni-axial tests with hold-time, uniaxial ratchetting tests including rapid cycles and biaxial cyclic tests with ten-sion/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 con-cluded with a numerical example of a block braked wheel where the importance of accounting for the viscoplasticity in modelling is highlighted.