The chain-like structure and motion of the magnetic particles (MPs) in magnetorheological fluid (MRF) determine the rheological properties of MRF. In order to investigate the appearance and motion state of the chain-like structure of MPs under both static and flowing states of MRF, the formation process of MP chains in a stationary MRF under the action of an external magnetic field was observed by microscope. And the length of MP chains was measured by an objective micrometer to reveal the key factors affecting the length of formed chain. The MP chains broke after the magnet rotated by 90 degrees. The MRF was injected into a microchannel to observe the motion of MP chains. The speeds of the MP chains were measured by micrometer under different magnetic field strengths and inflow rates. The static test results show that the particle diameter has the greatest influence on the length of chain. The maximum length of the MP chains is 978.2 μm with a magnetic field strength of 130.31 mT; the diameter and mass fraction of the MPs are 2 μm and 3%. The MP chains will break from a long chain into short chains and rotate at a certain angle due to the rotation of magnetic field. The test results at different inflow rates show that the moving speed of MP chains in the microchannel increases with the increase of inflow rate and the decrease of magnetic field strength. In addition, the MP chains can withstand a carrier fluid flow rate of up to 0.32 m/s.

磁流变流体（MRF）中磁性颗粒（MPs）的链状结构和运动决定了MRF的流变特性。为了研究MRF静态和流动状态下MP链状结构的出现和运动状态，通过显微镜观察了固定MRF在外部磁场作用下MP链的形成过程。用物镜千分尺测量MP链的长度，以揭示影响形成链长度的关键因素。磁铁旋转90度后，MP链断裂。将MRF注入微通道以观察MP链的运动。MP链的速度通过千分尺在不同的磁场强度和流入速率下测量。静态测试结果表明，粒径对链长的影响最大。MP链的最大长度为978.2μm，磁场强度为130.31 mT；MP的直径和质量分数分别为2μm和3％。MP链将从长链断裂成短链，并由于磁场的旋转而以一定角度旋转。在不同流入速率下的测试结果表明，MP链在微通道中的移动速度随着流入速率的增加和磁场强度的降低而增加。此外，MP链可以承受高达0.32 m / s的载液流速。MP的直径和质量分数分别为2μm和3％。MP链将从长链断裂成短链，并由于磁场的旋转而以一定角度旋转。在不同流入速率下的测试结果表明，MP链在微通道中的移动速度随着流入速率的增加和磁场强度的降低而增加。此外，MP链可承受高达0.32 m / s的载液流速。MP的直径和质量分数分别为2μm和3％。MP链将从长链断裂成短链，并由于磁场的旋转而以一定角度旋转。在不同流入速率下的测试结果表明，MP链在微通道中的移动速度随着流入速率的增加和磁场强度的降低而增加。此外，MP链可以承受高达0.32 m / s的载液流速。