Optimization Design Of Mechanical/Acoustic Metamaterials Based On Full-Cycle Interactive Progressive Method

Vibration and noise are important factors affecting the operating efficiency,service life and human experience of confined transport equipment such as high-speed railways,ships,aircrafts,and diving instruments.Conventional materials and structures have long design cycles,weak control capabilities,and unsatisfactory effects for vibration/noise reduction performances.It is challenging to meet the rapidly developing application requirements of confined transport equipment.Metamaterials break through the functional limits of conventional structures by designing novel geometric shapes,which is of great significance to improve the vibration/noise reduction performance of confined transport equipment.Therefore,the improvement of vibration/noise reduction performance of confined transport equipment were selected as the optimization object,and a full-cycle interactive progressive(FIP)design method was proposed in this paper.Four typical mechanical and acoustic metamaterials(gradual stiffer mechanical metamaterials,chiral mechanical metamaterials,pressure modulation acoustic metamaterials and frequency modulation acoustic metamaterials)were studied to realize the FIP design of mechanical and acoustic metamaterials oriented to vibration/noise reduction performance.The main research contents of this paper are as following:Firstly,a FIP design method based on the surrogate model was proposed.In order to solve the complex problem in designing the unconventional physical properties of metamaterials with traditional optimization methods,the FIP design method that integrates topology optimization,parametric optimization,experimental analysis and feedback adjustment was proposed.Among them,the topology optimization innovated the initial structure,the parametric optimization determined the parameters combination scheme of the initial structure,the experimental analysis verified the design effect of the optimized structure,and the feedback adjustment enhanced the interactive design capabilities of the FIP method.Secondly,FIP design of the gradual stiffer property of the mechanical metamaterials was studied.In order to meet the demand for vibration reduction and stability maintenance of the confined transport equipment in this research,the mechanical model of the structural gradual stiffer property of the mechanical metamaterials was proposed at first.Then,an explicit-implicit hybrid iterative method was proposed to solve the problem that the stability and convergence cannot be balanced in the process of nonlinear finite element analysis.Finally,the FIP method was used to design the gradual stiffer mechanical metamaterial,which maintained the stability of the overall configuration of the mechanical structure under gentle loads.Among them,a combination scheme of gentle compression experiment and microscopic morphology monitoring is designed,the performance-parameters influence law and effective application conditions of the gradual stiffer mechanical metamaterials were studied,and the effectiveness of the FIP design method was verified.Thirdly,FIP design of the energy absorption property of the mechanical metamaterials was studied.In order to enhance the vibration reduction and impact resistance performance of the enclosed carrier equipment of the confined transport equipment in this research,the couple stress analysis model of the chiral structure was established at first.Then,the FIP method was used to design the chiral mechanical metamaterial that meet the design requirements of energy absorption property,which improved its cushioning and vibration damping ability under impact load.Among them,the shock compression experiments using some custom-made fiber grating sensors were designed,and the influence of boundary conditions on the energy absorption properties of the chiral mechanical metamaterial was studied.Moreover,the feedback adjustment was carried out to reduce the deviation between the experimental and simulation results,and the accuracy of the FIP design method was improved.Fourthly,FIP design of the surficial acoustic pressure level of the acoustic metamaterials was studied.In order to improve the acoustic absorption and noise reduction performance of the acoustic structures in the confined transport equipment in this research,the acoustic pressure distribution model in the acoustic-structural interaction system was established at first.Then,a singular integral processing method based on compactly supported radial basis function was proposed,which solved the singular integrals that accompany the nonlinear boundary element analysis of acoustic metamaterials.Finally,the FIP method was used to design the pressure modulation acoustic metamaterial with better acoustic absorption and noise reduction performance,which realized the simultaneous adjustment of the acoustic insulation and absorption function.Among them,a test platform for acoustic properties based on impedance tubes was built to verify the effect of the FIP design method for improving the acoustic absorption and noise reduction performance of the pressure modulation acoustic metamaterial.Fifthly,FIP design of the structural fundamental frequency of the acoustic metamaterial structure was studied.In order to avoid the resonant noise that is likely to be generated by the confined transport equipment in the medium-low frequency environment in this research,the frequency response model of the solid structure in the acoustic-structural interaction system was established at first.Then,the FIP method was used to design the frequency modulation acoustic metamaterial with better vibration and noise reduction performance,which solved the problem of raising the structural fundamental frequency of under the excitation of medium-low frequency noise.Among them,a feedback adjustment model that strengthened the effects of parametric optimization was established to reduce the deviation between the results of parameter optimization and the actual demand.The frequency response experiments based on a closed acoustic box were designed to verify the effectiveness of the FIP method in designing frequency modulation acoustic metamaterial.Lastly,the main research work and innovation points of this thesis were summarized,and the future feasibility work was prospected.