Research On Wall Slip Characteristics Of Magnetorheological Fluid Under Rotating Shear

Magnetorheological fluid is a new type of intelligent magnetosensitive material formed by ferromagnetic particles dispersed in a carrier fluid.Due to its unique magnetorheological effect,it has been widely used in practical engineering.However,the magnetorheological fluid is often accompanied by the wall slip effect during the shear rheology,which affects the mechanical output efficiency of magnetorheological device,which is not conducive to the precise control and development of the magnetorheological fluid and the magnetorheological device.In order to study the internal slip law of magnetorheological fluid under the rotating shear,and improve the effective transmission capacity of magnetorheological fluid,based on the analysis of the shear rheological characteristics and constitutive equations of magnetorheological fluid,a theoretical method for effectively detecting the slip velocity and the slip layer of the magnetorheological fluid was proposed.Four types of shear walls were analyzed based on rotating shear,the influence of the physical properties of the shear wall on the magnetic field distribution was analyzed using Maxwell simulation software.From the microscopic level,the magnetic particles on the shear wall were subjected to force and motion state analysis,and the magnetorheological fluid wall slip test bench was independently developed.The influencing factors of slip of magnetorheological fluid were investigated systematically,and the experimental study and analysis of the wall slip of magnetorheological fluid were conducted.The research work of the thesis is divided into the following aspects:(1)The characteristics and deficiencies of the four typical constitutive equations of magnetorheological fluids are analyzed and summarized,and the Bingham model is selected as the theoretical basis for rotational shear slip of magnetorheological fluid.The rheological characteristics of the magnetorheological fluid under rotating shear are analyzed,and a method for effectively measuring the slip velocity and thickness of the slip layer of the magnetorheological fluid is proposed.A magnetorheological fluid mechanics model based on the slip conditions is established.(2)In order to study the slip evolution of magnetorheological fluid,combined with the shear mode commonly used in practical engineering,the rotating shear structure and its magnetic circuit were analyzed and optimized.Based on the analysis and comparison of existing researches at home and abroad,four types of shear walls were designed: semicircular groove bottom,triangular groove bottom,rectangular groove bottom and smooth non-groove bottom.The influence of the shear wall material and shape on the magnetic field distribution was analyzed using the Maxwell simulation software.As a result,the steel semicircular groove bottom shear wall surface is optimal.(3)From a microscopic perspective,the slip mechanism of magnetorheological fluid is analyzed,and a two-dimensional microscopic model of magnetic particles in a magnetic field was established,and analyze the force and moment of a single magnetic particle.Further analyzed the force relationship between the magnetic particle cluster and the shear walls,and explored its movement trend on different shear wall surfaces.(4)A self-developed magneto-rheological fluid slip test bench was used to systematically study the influence of wall slip influencing factors on the shear yield stress of the magnetorheological fluid.The effect of shear wall shape on the temperature rise of magnetorheological fluid was analyzed.The parameters of the wall surface morphology,magnetic field strength and shear speed with significant effect were selected for the experimental study of the slip velocity and slip layer of the magnetorheological fluid.The internal variation law of the shear slip on the wall of magnetorheological fluid was revealed.