数字显微全息应用于磁流变液微观结构与机理的三维可视化研究

Three-Dimensional Visualization of the Micro-Structure and Mechanism of Magnetorheological Fluids Using Digital Micro-Holography

将数字显微全息(DMH)技术应用于磁流变液微观结构与机理的观测,提出了全局灰度梯度法(OS)和最小二乘方滤波器(CLS)技术来提高铁磁性微粒子的焦平面定位精度,利用校准靶面置于磁流变液测量域中方式获得铁磁性微粒子的真实放大倍率。搭建了用于测试磁流变液特性的数字显微全息测量系统,同时利用以上处理方法,得到了磁流变液在无磁场下其铁磁性微粒子和有磁场下其微观结构的三维空间分布,实时观测了磁流变液微观结构的变换过程,获得了磁流变液在外加磁场下的成链结构、链化速度和响应时间,验证了磁流变液的响应时间为毫秒量级,与电子显微镜观测实验结果进行对比,证明了数字显微全息可以高效、简便、实时地测量磁流变液的流变特性。

A digital micro-holographic （DMH） system is designed for the observation of the micro-structure and mechanism of magneto rhedogical （MR） fluids. To obtain the actual magnification of ferromagnetism micro-particles in the MR fluids, the experimental method using calibration target is employed. The overall-sharpness （OS） method and the constrained least squares （CLS） filter are introduced to enhance the precision of focal plane of ferromagnetism micro-particles determination in digital holography. Based on the digital holography system and these numerical methods, the three-dimensional （3D） distribution of ferromagnetism micro-particles in MR fluids without an applied magnetic field and the micro-structure of MR fluids with an applied magnetic field are investigated. The transformation process of micro-structure of MR fluids under an applied magnetic field is monitored in real-time, the chaining structure, chaining speed and responding time of MR effect are obtained, and the responding time of MR fluids to be millisecond level is verified. The experimental results of MR fluids measured by DMH are contrasted with electron microscope, which indicates DMH is a high-efficiency, simple and real-time measuring system for measurement of behaviors of MR fluids.