Viscoelastic plastic continuous physical model of a magnetorheological damper applied in the high speed train

In the preliminary design stage of high-speed train smart suspension,a simple,yet accurate magnetorheological(MR)damper model whose parameters have clear physical meaning is needed.Based on the working mechanism analysis and the dynamic behavior study of the MR damper,a new consecutive viscoelastic plastics(VEP)model is proposed.A methodology to find the parameters of the proposed model directly has been proposed.The comparison with experimental results indicates that the proposed model could adequately characterize the intrinsic nonlinear behavior of the MR damper,including the hysteretic behavior,roll-off phenomenon,and the variation of the hysteresis width in terms of the frequency and magnitude of excitation.The results of experimental testing prove that the accuracy of the proposed model is higher than that of the phenomenological model while only containing four undetermined parameters with clear physical meaning.Moreover,based on the proposed VEP model,a nonlinear stiffness VEP(nkVEP)model is developed with higher precision in the hysteretic region.The nkVEP model,which can reproduce the behavior of the damper with fluctuating input current,is developed.The proposed model could predict accurately the response of the MR damper in a wide range of frequency and displacement.

Influences of soil hydraulic and mechanical parameters on land subsidence and ground fissures caused by groundwater exploitation

In order to study the influences of hydraulic and mechanical parameters on land subsidence and ground fissure caused by groundwater exploitation, based on the Biot＇s consolidation theory and combined with the nonlinear rheological theory of soil, the constitutive relation in Biot＇s consolidation theory is extended to include the viscoelastic plasticity, and the dynamic relationship among the porosity, the hydraulic conductivity, the parameters of soil deformation and effective stress is also considered, a three-dimensional full coupling mathematical model is established and applied to the study of land subsidence and ground fissures of Cangzhou in Hebei Province, through the analysis of parameter sensitivity, the influences of soil hydraulic and mechanical parame-ters on land subsidence and ground fissure are revealed. It is shown that the elastic modulus E , the Poisson ratio, the specific yield m and the soil cohesion c have a great influence on the land subsidence and the ground fissures. In addition, the vertical hydraulic conductivity zk and the horizontal hydraulic conductivity ks also have a great influence on the land subsidence and the ground fissures.