Research On High-precision Crack Detection Of Two-dimensional Acoustic Metamaterials

Acoustic metamaterial(AM)is a kind of man-made periodic composite material.As it has the ability to block the propagation of elastic waves in a specific frequency range,it has received extensive attention in the field of sound absorption and noise reduction in the recent years.Currently,the research on AM is mainly based on the premise that the structure is intact and uncracked.However,in the practical mechanical working environment,the appearance of crack is inevitable in AM due to various complex factors,such as severe vibration or corrosion,therefore,it is ve ry urgent to develop an effective high-accuracy crack estimation method to detect the location and size of crack in AM to avoid the potential lo ss of structure life.The current crack detection research is mostly based on the single-mode-wavelet analysis results.However,because the crack-induced modal signal changes are not significant at specific orders,the traditional single-mode-wavelet detection strategy isn't robust enough.In this paper,an ES-FEM coupled weighted modal-wavelet analysis strategy coupled is proposed for the crack prediction research of AM.Firstly,the multi-order mode shapes of cracked AM are computed by ES-FEM,and the obtained mode shape data is further interpolated and extended.Then,the detail coefficients of multi-order smoothed mode shapes are calculated through the discrete wavelet transform(DWT).Finally,the damage index and crack width estimator are established from the weighted multi-order detail coefficients to locate crack and predict crack width,respectively.The main highlights of this paper can be summarized as:(1)The edge-based smooth finite element method(ES-FEM)is applied to the modal analysis of cracked AM.Compared with the numerical results obtained from the traditional finite element method,the simulation accuracy and convergence rate of the results from ES-FEM are significantly improved.(2)An ES-FEM coupled weighted modal-wavelet analysis strategy is established in this paper.The proposed damage index obtained by this strategy is employed to the crack location of AM,which significantly ove rcomes the disadvantages of ambiguity and weak robustness in traditional modal-wavelet based crack detection methods.(3)A crack width estimator is presented based on the ES-FEM coupled weighted modal-wavelet analysis strategy.By combining the crack width estimator with the corresponding damage index,a reasonable prediction of crack width can be obtained in AM.