Constitutive Modeling of Large Ratcheting Strains in Carbon Steel

Licentiate thesis, 2004

A thermodynamically consistent constitutive material model for describing the large strain response of polycrystalline metals during cyclic loading is proposed. In particular, it is proposed to model experimentally observed large ratcheting strains in rail steel by the classical Armstrong-Frederick evolution rule and several back-stresses. In addition, it is suggested that the multi-axial ratcheting rate depends on the Hessian of the yield function. In order to predict a physically realistic response, the model parameters are calibrated (via optimization algorithms) against different sets of experimental data for railway steel.