Dynamics Of Magnetorheological Fluid Sandwich Beam Structure

Smart material structure is a new structure developed to meet the high requirement in the fields of modern aeronautics, astronautics, electronics and mechanics. Magnetorheological fluid (MRF) is a kind of inteligent material. The devices made by using magnetorheological effect have a lot of advantages such as continuous controll ability, less noise, fast response, simplicity of structure, low power consumption and so on. Therefore MRF has a great potential application in engineering.The properties of MRF, such as viscosity, shear modulus and damping can be changed quickly, controllably and reversibly under the varying magnetic field. The MRF can be compounded with other elastic materials to form the MRF sandwich beams and plates. The stiffness and damping properties of such structures can be controlled through the different levels of applied magnetic field, which is great worthy to control the working performance of aerospacecraft, vehicle and mechanical structures. The dynamics of MRF sandwich beam structures has been investigated theoretically and experimentally in this thesis. The main research includes as follows.1. The MRF was supposed to be the linear viscoelastic materials. The stress–strain relationship of MRF was expressed by using the complex shear modulus. The flexural vibration model of the MRF sandwich beam structures has been developed. The vibration characteristics of beam structures with the simply supported and cantilevered conditions were analyzed.2. A kind of beam structure with non-continously distributed MRF and its design method have been presented. The relationships of the natural frequencies, loss factors, mode shapes, and transverse vibration response with the excitation frequencies and applied magnetic field levels have been obtained.3. A finite element model of a simply supported MRF sandwich beam has been developed. The element matrices of up and down elastic material layers and internal MRF layer were formed to derive the dynamic equations of the MRF sandwich beam. The vibration properties and the responses under the harmonic excitation of the simply supported MRF sandwich beam with up and down Aluminium layers were analyzed. The effects of the magnetic field level and height of MRF on the dynamic response were also analyzed.4. The experimental investigation of dynamics of the MRF sandwich beam structures with the simply supported and cantilevered boundary conditions was conducted, under the different magnetic field levels. The effects of MRF on the vibration suppression of the beam structures were analyzed.The theoretical results agreed with the experimental results. The natural frequencies and loss factors of the MRF sandwich beam structures increased with the increment of the applied magnetic field levels, and the vibration response of the beam structures decreased obviously, which indicated that MRF had an effective vibration suppression of the sandwich beam structures under the applied magnetic field.