Applications Of Digital Holographic Microscopy (DHM) On Measurement The Micro-structure Of Magnetorheological Fluids

Digital holographic microscopy (DHM) is combined with digital holography (DH)and microtechnique which can be used for capture the micro-spatial informations ofmeasurement domains in real-time. The dynamic3D imaging of measuring targets isobtained by hologram reconstruction. It is widely applied for a variety of microscalecomplex flow field and medicine testing fields, etc. and has wide-developing prospects.Magnetorheological fluids (MRF) is a newly-developing intelligent materials. Therheological properties of MR Fluids is controlled continuously by applied magnetic fieldand the mechanical property of MR Fluids is changed. The macro-scopic mechanicalproperties of MR Fluids depends on its micro-scopic structure, and the mechanicalproperties of MR Fluids is influenced by the size of ferromagnetic particles and volumefraction is deserved to exploring. Currently, the micro-structure and magnetic rheologicalmechanism of MR Fluids is observed with ordinary microscopy by2D or static3D form,it unabled to reflect the three-dimensional microcosmic transformation process andrheological properties of MR Fluids under additional magnetic field effectively.A DHM measuring system is designed and optimized for the observation of themicro-structure and mechanism of MR Fluids. To obtain the actual magnification offerromagnetism micro-particles in the MR Fluids, the experimental method usingcalibration target is employed. The holograms of MR Fluids is reconstructed byconvolution method. The overall-sharpness (OS) method and the constrained leastsquares (CLS) filter are introduced to enhance the precision of focal plane offerromagnetism micro-particles determination in digital holography. And ferromagnetismmicro-particles is extracted by laplacian of gaussian (LoG) operator method.Based on the DHM system and these numerical methods, the size informations offerromagnetism micro-particles is acquired and the3D distribution of ferromagnetismmicro-particles in MR Fluids without an applied magnetic field and the micro-structure ofMR Fluids with an applied magnetic field are investigated. The transformation process ofmicro-structure of MR Fluids under a constant applied magnetic field is monitored inreal-time, the chaining structure, chaining speed, responding time, acceleration and forceof MR Fluids is obtained, the responding time is millisecond level of MR Fluids isverified. The experimental results of MR Fluids measured by DHM is contrasted with microscope. And indicated DHM is a high-efficiency, simple, real-time and accuracymeasuring system for measurement of behaviors of MR Fluids.