Research On Acoustic Performance And Optimization Of Sandwich Panel With Magnetorheological Fluid

As an intelligent fluid,magnetorheological fluid(MRF)has attracted the attention of scientific researchers and engineers in the field of vibration reduction because of its good controllability and rapid response.It has been applied to a certain range of vibration reduction fields.In order to expand the application fields of MRF and discuss the feasibility of its application in the fields of transportation vehicles,the research on the acoustic performance and the optimization of the sandwich panel structure cored with MRF was carried out.The main contents and conclusions are stated as follows:(1)Experimental research on the acoustic performance of MRF unit.In order to discuss the influence of the magnetic field strength and the direction on its acoustic performance,two MRF units were designed and fabricated.During the test in the standing wave tube,the field strength direction is vertical and parallel to the direction of the sound wave emitted by the speaker,respectively.The magnetic field strength of the MRF is provided by rare earth permanent magnets in different thicknesses.The field strength distribution of the MRF unit is simulated by the magnetic field analysis module of COMSOL software.The tube measured the sound transmission loss(STL)of the two MRF unit bodies under different magnetic field strength and direction,compared with the STL of the unit body whose core layer are air layer and water.Studies have shown that the direction of the magnetic field has a significant effect on the sound insulation performance of the MRF unit.When the sound propagation direction is parallel to the direction of the magnetic field,the MRF unit can obtain a larger STL in the middle and low frequency bands,and the adjustability of the sound insulation amount in the entire frequency band is also better.(2)Theoretical study on the acoustic performance of MRF sandwich panels.First,based on the energy method and sound propagation theory,the mathematical model on the STL of the sandwich panel is established.Second,the storage modulus and the loss modulus of the MRF in the sandwich panel were discussed.Finally,based on the established theoretical model on the STL of sandwich panel,the effects of the magnetic field strength,the thickness of the surface layer and the core layer on the STL of the MRF sandwich panel were analyzed.Studies have shown that with the increase of the magnetic field strength,the frequency corresponding to the valley of the STL of the sandwich panel increases significantly,which means that the sound insulation of the MRF sandwich panel in the mid-low frequency region increases.The influence of the thickness of the surface layer and the core layer on the STL of the sandwich panel were basically the same,but the effect of the thickness of the core layer is more obvious.As the thickness increased,the STL of the MRF sandwich panel increased overall,but the frequency that corresponds to the valley of the STL became lower,which means that the increased thickness would reduce the STL value in some frequency bands.Therefore,the thickness of the core layer and surface layer should be selected reasonably.(3)Simulation study on the acoustic performance of the MRF sandwich panel.In order to further verify the reliability of the theoretical analysis results of the STL of the MRF sandwich panel,the acoustic finite element models of the MRF unit and the MRF sandwich panel were constructed using COMSOL software.Simulation analysis of its STL and the distribution of sound pressure level in the sound field.Based on the modal shapes and natural frequencies of the sandwich panel obtained by simulation,the STL curve of the sandwich panel was explained.The research shown that the finite element analysis results of the STL of the MRF unit were in good agreement with the experimental results,which proved that the finite element model and analysis method of the MRF unit established by COMSOL software was reliable.The finite element analysis results of the MRF sandwich panel established by COMSOL software were also in good agreement with the theoretical analysis results.This also indirectly proved that the theoretical analysis results of the STL of the MRF sandwich panel are credible.(4)Multi-objective optimization research on the structure of the MRF sandwich panel.In order to get the rationally designed MRF sandwich panel,a compromised design scheme was obtained between the sound insulation performance of the panel and the panel mass.The areal density and the STL of the MRF sandwich panel were taken as the optimization objective functions.The thickness of the aluminum alloy surface layer and the MRF core layer were used as optimization design variables,and the deformation constraints of the plate were also considered.The NSGA-II genetic algorithm was used to carry out the dual-objective optimization study of the MRF sandwich panel.The research obtained the Pareto frontier optimized for the MRF sandwich panel,and the solution corresponding to the knee point is the best design that takes both account the weight goal and the acoustic goal into consideration.This research has laid a theoretical foundation for the application of MRF sandwich panel in automobiles,and its good sound insulation and adjustable performance in a wide frequency band provide innovative ideas for the design of automotive front wall or roof panel.