Study On Defect Mode And Local Resonance In Periodic Corrugated Elastic Plates

Acoustic waves in the ocean play an important role in the acquisition of ocean information.In some cases,the low frequency radiated noise of the hull is easy to propagate through the sea water to the bottom,forming the acoustic signal.However,the acoustic signal attenuation is large and changes with the sea state,which makes the stability and characteristics easy to be affected and difficult to detect.In order to solve this problem,a new method of constructing elastic wave resonance structure is proposed in this paper,and an experimental system based on laser vibrometer is built to verify the theoretical prediction.Through the optimization of structural parameters,the effective enhancement and accurate extraction of specific acoustic signals are realized,and the detection performance of acoustic sensors is greatly improved.These works provide theoretical guidance and key technology reserve for new ocean information exploration technology and ocean data acquisition.This paper focuses on the propagation and regulation of elastic waves in periodic undulating structures,including the following innovations:(1)Firstly,we not only construct the control model of elastic wave propagation in the periodic undulating structure,and carry out theoretical study on the resonance mechanism of elastic wave in the undulating structure,but also derive the unique dispersion relationship of elastic wave in the surface of solid sidewall periodic undulating structure.This special dispersion relationship provides a new way for us to better understand the propagation of elastic waves in undulating structures.(2)Secondly,we designed a laser ultrasonic detection system based on laser Doppler vibration,and carried out an in-depth study on the propagation law of elastic waves in periodic undulating structures by using the scanning experiment scheme.Compared with the traditional fixed position detection,this method is more flexible and comprehensive,and can accurately detect the propagation law of elastic wave in the structure.(3)Finally,we change the phase difference above and below the periodic undulating structure,and introduce a rectangular defect in the center of the periodic undulating structure.Through theoretical analysis and experimental results,we reveal the special spectral characteristics and local resonance mechanism of the single defect corrugated structure.By further using the bandgap relationship between phase shift and elastic wave,we successfully filter the noise frequency band of acoustic signals selectively,and realize the effective enhancement of acoustic signals by changing the geometric parameters of defects.In conclusion,through theoretical analysis,numerical simulation and experimental methods,the resonance mechanism of elastic wave in periodic undulation structure is deeply studied in this paper,and the regulation of elastic wave mode is successfully realized.These research results provide a solid theoretical basis and experimental verification for the design of wave control devices and the high precision detection of acoustic signals.