To predict sound-absorbing performance of anechoic materials,the acoustic reflection problem of a viscoelastic layer backed with periodically rib-stiffened infinite double plates is studied in this paper.The reason wh...To predict sound-absorbing performance of anechoic materials,the acoustic reflection problem of a viscoelastic layer backed with periodically rib-stiffened infinite double plates is studied in this paper.The reason why structural theories of plates are not applicable to viscoelastic plates is explained through comparing dispersion and attenuation curves of flexural waves with those of Lamb waves.As a result,（visco-）elastic theory is adopted to deal with（visco-）elastic plates,and ribs are treated by structural theories of plates.The coupling between ribs and plates are solved by Hull＇s method,and solution of the reflected field is obtained.The accuracy of present method is validated by comparing with the results by the structural theories of plates.The influence of a backing on the acoustic reflection of the viscoelatic layer is analyzed by computing reflection coefficients.Performances of different viscoelastic materials are evaluated by the average reflection coefficients.The computational results show that,influence of a backing on the acoustic reflection cannot be suppressed by the viscoelastic materials in low frequencies.The resonance is determined by the coupling of the fluid layer and the double plates.And ribs,which are coupled with the double plates,mainly reduce the acoustic reflection.展开更多
The vibroacoustic response and sound absorption performance of a structure composed of multilayer plates and one rigid back wall are theoretically analyzed. In this structure, all plates are two-dimensional, microperf...The vibroacoustic response and sound absorption performance of a structure composed of multilayer plates and one rigid back wall are theoretically analyzed. In this structure, all plates are two-dimensional, microperforated, and periodically rib-stiffened. To investigate such a structural system, semianalytical models of one-layer and multilayer plate structures considering the vibration effects are first developed. Then approaches of the space harmonic method and Fourier transforms are applied to a one-layer plate, and finally the cascade connection method is utilized for a multilayer plate structure. Based on fundamental acoustic formulas, the vibroacoustic responses of microperforated stiffened plates are expressed as functions of a series of harmonic amplitudes of plate displacement, which are then solved by employing the numerical truncation method. Applying the inverse Fourier transform, wave propagation, and linear addition properties, the equations of the sound pressures and absorption coefficients for the one-layer and multilayer stiffened plates in physical space are finally derived. Using numerical examples, the effects of the most important physical parameters-for example, the perforation ratio of the plate, sound incident angles, and periodical rib spacing-on sound absorption performance are examined. Numerical results indicate that the sound absorption performance of the studied structure is effectively enhanced by the flexural vibration of the plate in water. Finally, the proposed approaches are validated by comparing the results of stiffened plates of the present work with solutions from previous studies.展开更多
In order to theoretically predict and analyze the vibration response and acoustic radiation characteristics of a periodical orthogonally rib-stiffened plate,its vibro-acoustic equations of an underwater infinite model...In order to theoretically predict and analyze the vibration response and acoustic radiation characteristics of a periodical orthogonally rib-stiffened plate,its vibro-acoustic equations of an underwater infinite model are established.The rib-stiffened plate is stimulated by a harmonic plane pressure.By using the Fourier transforms,Poisson’s summation formula and space harmonic method,the structural vibration response and acoustic radiation pressure are expressed as functions of displacement harmonic components.Efficient semi-analytical methods are proposed in this work,and then approximate solutions for finite terms of the harmonic components are obtained by employing the truncation technique.Effects of the vibration response,rib spacing and torsional moment of the ribs on the radiation pressure are examined,and the validity of the present methods is also verified.Theoretical results show that the torsional moment of the ribs affects the modal frequencies of the stiffened plate,which should not be neglected in engineering applications with high precision requirement.With attachment of the ribs to the thin plate,its far field radiation pressure can be reduced in the low frequency range by adjusting rib spacing and cross sectional size of the ribs.展开更多
统计能量分析(statistical energy analysis,SEA)是复杂耦合系统中、高频动力学特性计算的有力工具.本文以波传播理论和SEA的基本原理为基础,研究周期加筋板中弯曲波传播特性.分析了周期结构的频率带隙特性和加强筋对板上弯曲波的滤波...统计能量分析(statistical energy analysis,SEA)是复杂耦合系统中、高频动力学特性计算的有力工具.本文以波传播理论和SEA的基本原理为基础,研究周期加筋板中弯曲波传播特性.分析了周期结构的频率带隙特性和加强筋对板上弯曲波的滤波特性对SEA计算结果的影响规律,发现经典SEA由于忽视了加筋板中物理上不相邻子系统间存在的能量隧穿效应,而导致响应预测结果产生最高近40 d B的误差.为了解决这一问题,本文应用高级统计能量分析(advanced statistical energy analysis,ASEA)方法,考虑能量在不相邻子系统间的传递、转移和转化的物理过程,从而大幅提高子系统响应的预测精度,将误差在大部分频段降低至小于5 d B.设计了模拟简支边界条件的加筋板振动测试实验装置,实验测试结果与有限元结果符合较好,对理论模型进行了验证.展开更多
基金supported by the Research Funds(9140A10040813CB04001)the Natural Science Foundation of Shandong Province(2013ZRF01039)
文摘To predict sound-absorbing performance of anechoic materials,the acoustic reflection problem of a viscoelastic layer backed with periodically rib-stiffened infinite double plates is studied in this paper.The reason why structural theories of plates are not applicable to viscoelastic plates is explained through comparing dispersion and attenuation curves of flexural waves with those of Lamb waves.As a result,（visco-）elastic theory is adopted to deal with（visco-）elastic plates,and ribs are treated by structural theories of plates.The coupling between ribs and plates are solved by Hull＇s method,and solution of the reflected field is obtained.The accuracy of present method is validated by comparing with the results by the structural theories of plates.The influence of a backing on the acoustic reflection of the viscoelatic layer is analyzed by computing reflection coefficients.Performances of different viscoelastic materials are evaluated by the average reflection coefficients.The computational results show that,influence of a backing on the acoustic reflection cannot be suppressed by the viscoelastic materials in low frequencies.The resonance is determined by the coupling of the fluid layer and the double plates.And ribs,which are coupled with the double plates,mainly reduce the acoustic reflection.
基金supported by the National Natural Science Foundation of China (Grants 51405276, 51505261, and 50875030)the Natural Science Foundation of Shandong Province, China (Grants ZR2014EEQ019 and ZR2014EEP025)the Foundation for Young Teacher Development of the Shandong University of Technology
文摘The vibroacoustic response and sound absorption performance of a structure composed of multilayer plates and one rigid back wall are theoretically analyzed. In this structure, all plates are two-dimensional, microperforated, and periodically rib-stiffened. To investigate such a structural system, semianalytical models of one-layer and multilayer plate structures considering the vibration effects are first developed. Then approaches of the space harmonic method and Fourier transforms are applied to a one-layer plate, and finally the cascade connection method is utilized for a multilayer plate structure. Based on fundamental acoustic formulas, the vibroacoustic responses of microperforated stiffened plates are expressed as functions of a series of harmonic amplitudes of plate displacement, which are then solved by employing the numerical truncation method. Applying the inverse Fourier transform, wave propagation, and linear addition properties, the equations of the sound pressures and absorption coefficients for the one-layer and multilayer stiffened plates in physical space are finally derived. Using numerical examples, the effects of the most important physical parameters-for example, the perforation ratio of the plate, sound incident angles, and periodical rib spacing-on sound absorption performance are examined. Numerical results indicate that the sound absorption performance of the studied structure is effectively enhanced by the flexural vibration of the plate in water. Finally, the proposed approaches are validated by comparing the results of stiffened plates of the present work with solutions from previous studies.
基金supported by the National Natural Science Foundation of China(51405276,51505261,50875030)the Natural Science Foundation of Shandong Province,China(ZR2014EEQ019)the Foundation for Young Teacher Development Program of Shandong University of Technology
文摘In order to theoretically predict and analyze the vibration response and acoustic radiation characteristics of a periodical orthogonally rib-stiffened plate,its vibro-acoustic equations of an underwater infinite model are established.The rib-stiffened plate is stimulated by a harmonic plane pressure.By using the Fourier transforms,Poisson’s summation formula and space harmonic method,the structural vibration response and acoustic radiation pressure are expressed as functions of displacement harmonic components.Efficient semi-analytical methods are proposed in this work,and then approximate solutions for finite terms of the harmonic components are obtained by employing the truncation technique.Effects of the vibration response,rib spacing and torsional moment of the ribs on the radiation pressure are examined,and the validity of the present methods is also verified.Theoretical results show that the torsional moment of the ribs affects the modal frequencies of the stiffened plate,which should not be neglected in engineering applications with high precision requirement.With attachment of the ribs to the thin plate,its far field radiation pressure can be reduced in the low frequency range by adjusting rib spacing and cross sectional size of the ribs.
文摘统计能量分析(statistical energy analysis,SEA)是复杂耦合系统中、高频动力学特性计算的有力工具.本文以波传播理论和SEA的基本原理为基础,研究周期加筋板中弯曲波传播特性.分析了周期结构的频率带隙特性和加强筋对板上弯曲波的滤波特性对SEA计算结果的影响规律,发现经典SEA由于忽视了加筋板中物理上不相邻子系统间存在的能量隧穿效应,而导致响应预测结果产生最高近40 d B的误差.为了解决这一问题,本文应用高级统计能量分析(advanced statistical energy analysis,ASEA)方法,考虑能量在不相邻子系统间的传递、转移和转化的物理过程,从而大幅提高子系统响应的预测精度,将误差在大部分频段降低至小于5 d B.设计了模拟简支边界条件的加筋板振动测试实验装置,实验测试结果与有限元结果符合较好,对理论模型进行了验证.
