Topology Optimization Of Acoustic Radiation For Constrained Layer Damping Structures

Damping material can restrain the vibration and acoustic radiation of plate structureeffectively. The acoustical models of passive constrained layer damping(PCLD)structures are established based on the finite element method(FEM) and boundaryelement method(BEM), and their acoustic characteristics are studied. A topologyoptimization model is set up, with structures’ acoustic parameters defined as theobjective function and volume fraction of damping material defined as the constraintcondition. The research proves to be a theoretical reference with engineering practicalvalue for noise suppression and light weight design of structures. The contents of thisthesis are expressed as follows:①To begin with, the finite element dynamical model of PCLD structure isestablished. An example is given to calculate the first ten modal frequencies of a PCLDplate, then results using finite element method and analytical method are compared andanalyzed, which verified the validity of the finite element model. In addition, thevelocity response of vibrating PCLD structure is analyzed by transfer function, whichprovides the boundary condition for acoustic radiation analysis.②According to the acoustic radiation theory, Helmholtz boundary integralfunction and Rayleigh integral function are deduced. A simply supported PCLD platemodel and the model of cubic box with PCLD surface are built, and their field pointpressure and acoustic power under harmonic excitation are calculated respectively,which lays the foundation of acoustic optimization.③A topology optimization to minimize the field point pressure and acousticpower of a PCLD plate is conducted with the volume fraction of damping materialdefined as the constraint condition. Using the evolutionary structural optimization(ESO)method, the topology optimization process is calculated and the optimal configurationof damping material is achieved. It is concluded that the optimal structures can restrainthe acoustic radiation effectively with less damping material.④A topology optimization to minimize the field point pressure and acousticpower of a PCLD box is conducted with the existence of damping material elementdefined as the design variable. The sensitivity of objective function to design variable isdeduced and the optimal layout of damping material on the plastic surface is achievedusing ESO method. It is concluded that the optimal structures can produce less acoustic radiation with less damping material.⑤An experiment platform for the field point pressure of PCLD box is established.The comparison of tested results of box without damping material, box withfull-covered damping material and optimized box verifies the validity of theoreticalanalysis and topology optimization, which proves to be the theoretical basis for practicalengineering application.