Rescarch On Optimization And Application Of Acoustic Characteristics Of Damping Reinforced Thin Plates

Thin plate structure is a common structural form in modern industrial production.Because of its light quality,simple structure and excellent heat dissipation,it has been widely used in various fields and products.Small to a variety of mechanical components of the shell,large to the aircraft,submarines,ships fuselage have used a large number of such structures.However,due to the low rigidity,easy deformation,low damping,large radiation surface,and high radiation efficiency of the thin plate structure,it is easy to become a vibroacoustic radiation source in the structure,and it becomes an adverse influence on the stability and safety of the structure and product.In this thesis,starting from the study of the stiffness characteristics of the structure,the stiffness characteristics,vibration response characteristics and acoustic radiation characteristics of rectangular plates,stiffened plates and damping stiffened plates are systematically studied.Summarized the optimized design scheme for vibration and noise reduction of plate and shell structure based on the combination of reinforced and damped materials,and passed experimental verification.Finally,the topology design and optimization scheme of vibration reduction and noise reduction structure were applied to the vibration damping design of the fan housing,and good results were obtained.The main work of this thesis are as follows:Study on structural stiffness characteristics: Starting from the rectangular plate,using the first six modes of the structure as the evaluation index,the finite element analysis software Workbench was used to analyze the influence of the constraints,thickness,aspect ratio,etc.on the structural stiffness;The effects of the number of stiffened plates and the distribution pattern of stiffened upper plates on the stiffness of stiffened plates are studied;For damping stiffened plates,the influence of the thickness and distribution of the damping layer on the stiffness of the structure is studied.Finally,the fitting curves of structural modal frequencies varying with various topological parameters are formed,and their changing trends and rules are summarized.Research and optimization of structural vibration and acoustic radiation characteristics: In this thesis,the finite element analysis software Workbench and the acoustic analysis software Virtual.Lab Acoustics are used for the joint simulation.The vibration response and acoustic response of the structure are analyzed and studied.The thickness of the rectangular plate,the position of the excitation point of the stiffened plate,the number and distribution of the ribs,the thickness of the damping layer of the damping stiffened plate,and the distribution form,the impact of the above factors on structural vibration response and acoustic radiation was analyzed.The vibration acceleration level curve and the sound power level curve of the structure were plotted using Matlab,and the influence trends of structural vibration and acoustic radiation characteristics of different topological structures were analyzed and summarized.The variation curves of vibration acceleration level and sound radiation power level with factors such as plate thickness,number of reinforcements,and thickness of damping layer were formed.Based on the comparison and analysis of the effect of damping layer distribution on structural vibration and acoustic radiation,the use of different dampings was concluded.The layer distribution form optimizes the design of vibration reduction and noise reduction.The simulation analysis results show that the optimization design scheme reduces the vibration acceleration level at the peak point to more than 3dB.The optimized design scheme reduces the power level of the peak point sound radiation above 4dB,and the total sound radiation power level also reduces 2.6dB.Structural sound and vibration characteristics experimental verification: In this thesis,the sound and vibration test and analysis system was set up using sound and vibration test and analysis software LMS Test.Lab and PULSE,the experimental models of rectangular plates,stiffened plates and damping stiffened plates are designed.The experimental scheme is formulated.The experimental results are verified by the experimental modality of the stiffened plates.The experimental boundary conditions and the rationality of the reinforced bars are proved.The vibration response comparison test and acoustic contrast test were performed on the rectangular plate,stiffened plate and damping stiffened plate.The effect of reinforcement and damping on the structural vibration and vibration characteristics was verified.Structural vibration and vibration characteristics optimization design project application: In this thesis,the obtained laws and optimization design schemes are applied to the optimization design of vibration damping and noise reduction of the fan housing.Based on the method of combining stiffeners with damping,a set of system optimization design methods for vibration and noise reduction of plate and shell structures are proposed,the analysis result show that compared with the fan casing before optimization,the vibra acclelration level of the fan casing after optimization can be reduced by more than 10 dB.The optimized design of this article provides theoretical and practical guidance for the design of vibration reduction and noise reduction of similar structures.