Investigation Of Vibro-acoustic Response Of Thin Plate With Cracks

Cracking is an important feature of structure defects of thin plate.It has serious impact on the safety and durability of the structure.So the research on the method of obtaining the cracking characteristics of thin plate by vibro-acoustic has great significance.Focusing on rectangular thin plate structure,the structure mode analysis,experimental modal analysis and vibro-acoustic response measurement on the thin plate with no cracking characteristics and the thin plate with three different cracking characteristics has been done.Then study on the effect of cracking characteristics on the mode,natural frequency and vibro-acoustic response of the thin plate.Firstly,the paper elaborated the background and significance of the study,and describing the vibration theory of thin plate briefly.Then some of the vibration modes and natural frequencies are obtained by mode simulation analysis of the thin plate with no cracking characteristics and the thin plate with different cracking characteristics with Ansys.Comparing the simulation results of the thin plate with cracks and the thin plate without cracks,the influence rule of cracking characteristics on thin plate mode has been researched.The simulations reveal that the natural frequencies of the thin plate with cracking characteristics are lower than the thin plate with no cracking characteristics,the vibrational modes of the thin plate changed when the cracking was in the node line position.In chapter three,the experimental modal analysis of on the thin plate with no cracking and the thin plate with three different crackings has been done by the Polytec,and compared the the simulation results,analyzed the influence of cracking characteristic on the natural frequency and vibrational modes of the thin plate with crackings.The research results show that the experiment results agree well with simulation results.Chapter four describes the method of NAH(Near field acoustic holography),the numerical simulating of single sound source field is presented by MATLAB.Referencing the simulation results of MATLAB,The Measuring point distance and measuring distance of microphone array which is used to measure the acoustic response of the thin plate have been designed,and rectangular microphone array have been made.Chapter five measures and calculates the vibra-acoustic response of the thin plate with no crackings and the thin plate with three different cracking characteristics by the homemade rectangular microphone array,comparing the calculations with the vibrational modes of the thin plate with crackings,and analyzing the influence of cracking characteristic on the acoustic response of the thin plate.The research results show that the acoustic response of the thin plate related to the vibrational modes of the thin plate,the distribution of acoustic pressure magnitude were in agreement with the the amplitude location of vibration mode.And the acoustic response can recognize the location of crackings.Finally,summarizing the entire work of this paper and making conclusions and suggestions for future research.