磁流变液剪切特性的分子动力学模拟

磁流变液是一种高效可控的新型材料,研究其磁流变机理有着广阔的应用前景.目前学者对磁流变剪切特性的多因素分析研究较少.采用LAMMPS分子动力学的方法建立了磁流变液微观模型,分析了磁性颗粒间的相互作用,对磁流变液的剪切过程进行了二维状态下的微观数值模拟,并综合分析了影响剪切屈服应力的主要因素.模拟结果表明,磁性颗粒会沿着磁场方向形成若干条长链状结构,颗粒链受到剪切作用发生变形、倾斜甚至断裂;剪切速率较低时,剪切屈服应力保持稳定;随着颗粒体积百分率的增加,剪切屈服应力呈线性增加的趋势;低磁场强度时,剪切屈服应力随磁场强度增加而增长较快,较高磁场强度时,剪切屈服应力随磁场强度增加的增速放缓;在一定范围内颗粒半径越大,粒径分布越集中,剪切屈服应力越大;随着模拟温度的增加,剪切屈服强度先保持稳定,后下降逐渐明显.

Molecular dynamics simulation of shear properties of magnetorheological fluids

Magnetorheological fluid (MRF) is a new type of material with high efficiency and controllability.It has a broad application prospect to study the mechanism of MRF.At present,there are few studies on the multifactor analysis of magnetorheological shear properties.In this paper,the LAMMPS molecular dynamics method was used to establish the micro-model of magnetorheological fluids (MRF),and the interaction between magnetic particles was analyzed.The two-dimensional numerical simulation of the shear process of MRF was carried out,and the main factors affecting the shear yield stress were analyzed comprehensively.The simulation results show that magnetic particles would form several long chain structures along the direction of the magnetic field,and the chains would deform,tilt or even break under the shear action.When the particle volume fraction increased,the shear yield stress increased linearly.When the magnetic field strength was low,the shear yield stress increased rapidly with the increase of the magnetic field strength.When the magnetic field strength was high,the shear yield stress increased slowly with the increase of the magnetic field strength.In a certain range,the larger the radius of particles or the concentration of particle size distribution,the greater the shear yield stress.With the increase of simulated temperature,the shear yield strength first kept stable,and then decreased gradually.