Experimental Research On Vibration And Acoustic Intensite Responses Of Thin Plate With All-through Crack

The thin plate is a significant part in mechanical equipment,and the all-through crack is an important structure defect feature of the thin plate.In order to ensure the safety and durability of the mechanical equipment,lots of researches have been studied on the detection of the thin plate all-through crack.The structure with an all-through crack leads to vibration intensifying and noise increasing.The traditional methods focused on detecting single vibration response or single acoustic response,thus they can not solve the vibration and noise problems simultaneously.In this thesis,the vibration,noise and radiate sound intensity information was adopted as measurement data,to research and compare the sound-vibration characteristics of the thin plate in different all-through crack cases,and find the similarities and connections of the sound-vibration characteristics,so as to identify and predict whether a protential defection exists in the thin plate or not and provide the position of the defection.In this thesis,the vibration response and acoutic response of the thin plate with all-through crack are research theoretically and experimentally,and the results were analyzed.Firstly,the purpose,background and significance of the study was summarized.Secondly,the theory of the vibration of the thin plate and the theory of sound intensity were deduced.The natural frequencies and mode shapes of the thin plate with 4 kinds of all-through cracks are obtained by ANSYS software;then the simulations results of the thin plate with and without all-through crack are compared,and the influence of crack on the plate was investigated.It shows that the frequency of plate with crack is lower than the one of plate without crack in the same mode,and the mode shape of the plate with crack is changed in different degree.Thirdly,the experiment of vibration and sound intensity responses of the 4 kinds of plates was made by Polytec Laser Doppler Vibrometer and B&K2260 device.The experiment results of sound intensity of the plate and the ones of vibration response of the plate were compared,and the connection between vibration response to sound intensity was investigated.It shows that the sound intensity related to the mode shape of the thin plate;the distribution of sound intensity magnitude is in agreement with the amplitude of vibration of the same plate;eventually the location of all-through crack can be recognized by the sound intensity on the surface plate.Finally,researches in this thesis have been summarized,and the topics for further study have been proposed.