Reasearch On Mechanism And Key Technology Of Intense Acoustic Emission Cluster Wave Generator Based On Box Detection

With the prosperous development of international trade,countries all over the world pay particular attention to security problem,the current commonly used container detection technology such as mechanical hammer,X-ray detection,infrared wave detection has some defect of high cost and low efficiency,it is important how to use a simple,rapid,efficient and low cost method to detect whether there is any residual object problem after the container unloading.Sound waves detection is a new nondestructive detection technology developed in recent years,it has the characteristics of spread is far,harmless to the human body,test speedly and low cost,cluster wave generator is a kind of acoustic emission device using the lorentz force mechanism to achieve,it is key components in acoustic detection technology,so the study of its mechanism and key technology have great significance.This paper's project from the shenzhen customs,aims to develop a device that can emit high intensity pulse wave generator for container detection,the generator is mainly used for judging if container is empty after unloading,the test method is that use the cluster wave generator to excite container,then collecting signal to analysis the characteristics of the container is empty or not,so as to determine whether the container is empty,in view of the strong demand,the mechanism of cluster wave generator,prolong the service life of cluster wave generator,the effective acoustic vibration frequencies of container,the following work has been done in this paper.(1)This paper firstly investigates and analyzes the status quo of the subject at home and abroad,compares and summarizes the current container inspection technology,and expounds the advantages of acoustic detection technology and the importance of generator research.(2)Through static analysis,confirming where cluster wave generator's the largest stress deformation position is,and impose a blocking ring on the cluster wave generator.(3)Around the requirement of strong sound,the influence of different outer diameters,inner diameters and thicknesses on the maximum stress of the diaphragm is analyzed to determine the optimal size parameters of the diaphragm.(4)Analyze the influence of the dynamic inductance of the cluster wave generator on the loop current,deduce the analytical formula of the coil's spatial magnetic field intensity,revealing the cluster wave's emission mechanism of the cluster wave generator by conducting electromagnetic field simulation of the cluster wave generator,(5)Multi-physic's field coupling simulation analysis is carried out for cluster wave generator,and the directivity distribution of cluster wave generator's diagram is obtained,and the effective frequency band of container excitation is analyzed.(6)Experimental test of sound pressure level is carried out for the cluster wave generator manufactured in the previous optimal design,and experimental study is conducted on whether the diaphragm with central hole of the cluster wave generator has the effect of reducing the frequency.After the above researching,the following conclusions are drawn:(1)Under the impact of pulse sound wave,the stress deformation of the diaphragm with blocking ring is smaller than that without retaining ring,so it is not easily tore for the diaphragm,which can prolong the service life of the cluster wave generator.(2)After the optimization analysis of the diaphragm and combining with the actual assembly size,the size of diaphragm is optimal when the outer diameter is 72 mm and the thickness is 2mm and the diameter of the center hole is 28 mm.(3)Due to the influence of dynamic inductance,the amplitude and attenuation time of the current in the loop are decrease.Because the current is an alternating current,the final output diaphragm deformation is different at different time,and the vibration amplitude of the diaphragm at different positions at the same time is also different,resulting in the outward radiation of sound waves of different frequencies.(4)Cluster wave generator has no directivity in the low frequency part,good directivity in the medium frequency part and poor directivity in the high frequency part.The effective vibration frequency band of container is the medium frequency part.(5)Through experimental test,it is verified that when the voltage value of the cluster wave generator charging power supply is 2000 V,the loudest pressure level can reach 159 dB,which meets the strong sound requirements of the container detection.Opening a central hole for the diaphragm can reduce the frequency.