磁流变液动态屈服行为的随机多尺度建模

根据能量保守原理,将微观粒子运动的动能等效成宏观动态屈服的应变能,建立内秉悬浮粒子运动涨落的磁流变液剪切应力的随机多尺度模型.分析表明,悬浮粒子初始随机条件和Brownian运动,以及剪切应变加载过程中,链簇反复断裂、重组的先后次序和数目不均匀,导致系统宏观屈服性态的非线性涨落和随机涨落;同时,微观运动涨落在体积平均过程中被严重弱化,宏观随机涨落相对不明显.拟合Bingham剪变率本构模型则进一步表明,外加场强对宏观屈服性态的变异性有一定程度的影响,磁流变液装置设计中应该考虑物理参数的随机性.

Stochastic Multiscale Model for Dynamic Yield Behavior of Magnetorheological Fluids

Dynamic yield behavior of magnetorheological fluids is investigated by upscaling information of microscale interaction between particles,employing a large-scale molecular dynamical simulation technique,to macroscale bulk behavior.We conduct a stochastic multiscale model for dynamic yield of magnetorheological fluids based on equivalence of system energy at different scales.It is revealed that the dynamic yield exhibits nonlinear and stochastic fluctuations due to heterogeneity of sequence and number of cluster-sheet reconstructions under shear fields loading,as well as Brownian motion of suspensions with initial random conditions.Meanwhile,we investigate fluctuation of microscale particle motions,relationship between stress and strain,and constitutive relationship of shear rate.It is noted that the microscale thermal fluctuation is far more than macroscale variations since the upscaling from microscale to macroscale results in degradation of fluctuations.Besides,the macroscale variations relies on external magnetic field as in the constitutive relationship of shear rate,i.e.Bingham model,which is supposed to be considered in the design and optimization of magnetorheological devices.