Study On Testing Device For Rheological Properties Of Magnetorheological Glue

As a smart material, magnetorheological material has been studied and used widely because of its advantages such as simple controllability and large shear yield stress. With the development of its engineering applications, the demands of high sedimentation stability, temperature stability and dynamic range are receiving more and more attentions. Magnetorheological glue(MRG) that satisfies the demands above should be given investigations on its preparation and rheological properties. Currently the rheology test for liquid magnetorheological materials by general commercial rheometers with configuration of parallel disk is limited at low shear rate, due to the centrifugal effect that MR sample can be thrown out of the test gap at a high shear rate. Hence, a testing device for rheology at high shear rate is designed based on a coaxial cylinder configuration which has an upper and a lower buffer. Considering that there is little study in the aspect of microscopic analysis for MRG, a microscopic kinetic model is established to guide the design, preparation and application of MRG. Details of this study are summarized as follows:(1) Since the microscopic mechanism of the MRG is not yet clear, a microscopic kinetic model for magneto-induced rheology behavior of MRG was established in order to study shear stress as a function of particle concentration in mass fraction, particle diameter and viscosity of elastic glue. Under the guidance of this theoretical model, 9 different samples were made. Rheological tests were done by means of an Anton Paar rheometer and the results showed that the model was effective for design and preparation of MRG.(2) The theoretical design of testing device for rheological properties of MRG(MRG testing device) was analyzed. Magnetic circuit was studied based on the magnetism theory and simulative analysis by ANSYS, in order to optimize the design for maximum flux,minimum of core material and flux leakage. In addition, using shear flow mode and the related theory, the coaxial cylinder testing chamber structure was carried out in order to decrease the measurement invalid caused by centrifugal effect at high shear rate, as well as use of a buffer chamber to eliminate the effects of plane interference and centrifugal force. The test gap was 0.2mm. The MRG testing device can be used to test liquid magnetorheological materials.(3) The MRG testing device was designed, fabricated, assembled and debugged. The major challenges of concentricity, seal and positioning of the mechanical structures were solved. The torque sensor, data acquisition card, servo motor and other hardware were selected according to the specific requirements. Then, a prototype was made. At last, computer programs for control algorithm, communications between the hardware components, data storage, data process, and user interface were carried out. Further, the testing system was debugged and calibrated.(4) The MRG testing device was used to measure the shear stress of MRG at high and low shear rate. Also, an Anton Paar rheometer was used for rheology test at low shear rate in order for verification of the MRG testing device. The comparison showed that the data had a good agreement and the effectiveness of the MRG testing device at low shear rate was verified.