چكيده به لاتين
Structures vibrate and generate acoustic waves when exposed to time-varying loads. The characteristics of these acoustic waves depend on the vibrational behavior of the structure, which itself depend on various factors such as the mechanical properties of the structure, load type and position, boundary conditions, and structure geometry. Today, the vibroacoustic control of structures has become an important problem in the aerospace, marine, construction, and military industries. In this research, an analytical model for the active/semi-active vibroacoustic control of hybrid intelligent double-walled structures incorporating piezoelectric and electrorheological actuators under the impact of sound waves is presented. The double-walled structures are considered in standard geometric shapes such as rectangular plate, cylindrical shell, and spherical shell. Also, hybrid configurations of piezoelectric materials (as active actuators) and electrorheological fluid (as semi-active actuators) are implemented in the double-walled sandwich structures. The dynamic equations of the structures are derived assuming the classical displacement field, Maxwell's electrodynamic equations, Kelvin-Voigt viscoelastic relations, and Hamilton’s principle, leading to the final coupled equations when combined with the fluid-structure boundary conditions to form the final coupled equations. Using the Fourier series expansions of the incoming, reflected and outgoing acoustic pressures, the structural displacement field, and the Galerkin method, the dynamic equations are discretized and transformed into the state-space matrix. Vibroacoustic phenomena such as sound transmission loss from double-walled rectangular plates and double-walled cylindrical shells and sound scattering from hybrid intelligent double-walled spherical shells are investigated. Subsequently, the multi-input-multi-output sliding mode control strategy is used to provide the ability to improve the vibroacoustic behavior of hybrid intelligent double-walled structures based on the collaborative active/semi-active performance of operating elements. Numerical simulations show that the hybrid active/semi-active piezoelectric/electrorheological and electrorheological/piezoelectric double-walled cases (which exhibit a high performance, accuracy, reliability and low energy consumption) can improve the sound transmission loss from the rectangular plate and cylindrical shell compared with the fully active piezoelectric/piezoelectric case using less energy consumption. Also, the effectiveness and capabilities of the proposed intelligent hybrid system for acoustic cloaking in the double-walled spherical shell with respect to the impinging sound field at selected frequencies are investigated. In particular, the superior acoustic attenuation capabilities in piezoelectric/electrorheological and electrorheological/electrorheological configurations are demonstrated considering the advantage of low activation energy in elements using electrorheological fluid. In addition, the accuracy of the obtained equation for the models of double-walled structures are demonstrated through a set of comparisons with the available data and comprehensive simulations in COMSOL Multiphysics.
