High-velocity micromorphological observation and simulation of magnetorheological gel using programmable magneto-controlled microfluidics system and micro-tube dynamic models

Application of magnetorheological gel (MRG) is a promising tool for high performance mitigation due to its outstanding energy absorption and dissipation properties. However, the lack of recognition on micromorphological variation for MRG and its magneto-mechanical coupling mechanism limits its extensive application. Herein, combined with the magnetic sensitivity nature of MRG, we develop a magneto-controlled microfluidic system for flexible simulation toward ms-level impact conditions. Microstructural changes of MRG, prepared with solid-liquid composite method, are characterized from variable magnet-field setups and gradual velocities. Experiments reveal that the increasing magnetic flux density can effectively enhance the stability of chains in as-fabricated MRG, while the chains can support excessive velocities up to 4.5 m s-1 before breaking. Meanwhile, under the preset velocity range, the maximum change rates of the average and standard deviation for inclinations are 183.71% and 40.06%, respectively. Successively, an experiment-conducted microdynamic model is developed for numerical simulation of the MRG mechanical behaviors. During that, high-velocity MRG behaviors are explored with a tubular rather than regular flat-structure boundary condition setups, to pursue more trustable results. Simulation readouts meet nicely with those from experiments in revealing the magneto-mechanical coupling mechanism of MRG under multiphysics. The interaction between magnetic force, repulsive force and viscous resistance is mainly illustrated. This work provides a reliable observation basis for micromorphological variation of MRG, also suggests a new method for the mechanism of magneto-mechanical coupling at extreme velocities.