Effects of general structural stress on vibrational power flow

Vibrational power flow contains two types of information, namely, vibration velocity and structural internal force, and is an important parameter for measuring vibration level and transmission. Structures are often under stress because of the working environment. This stress changes the vibration velocity and internal force of the structure. As a result, this stress affects the power flow. In practical engineering, structural stress often has a complex distribution. However, earlier studies mainly focused on the overall uniformly distributed stress, which cannot be applied to practical engineering vibration problems. The finite element method can handle this problem, but has several shortcomings, such as the lack of a clear explanation of the essential relationship between structural stress and vibration, the complicated process of applying specific stress, and the large number of calculations. This study considers the effect of general structural stress and determines the dynamic equation of a structure undergoing stress. By utilizing the orthogonality of specific order modes to decouple, we obtain the power flow analytical solution, which can be applied to structures with arbitrary distributed stress. Finally, we calculate and analyze the effect of structural stress on a welding plate. Results show that structural stress has a more significant effect on power flow than velocity and inner force and should be taken into account when considering vibration prediction and reduction in practical engineering.

Study on Vibrational Power Flow Propagation Characteristics in a Laminated Composite Cylindrical Shell Filled with Fluid

The characteristics of vibrational power flow in an infinite laminated composite cylindrical shell filled with fluid excited by a circumferential line cosine harmonic force are investigated using wave propagation approach. The harmonic motions of the shell and the fluid filled in the shell are described by Love shell theory and acoustic wave equation, respectively. Under the driving force, the vibrational power flow input into the coupled system and the transmission of the power flow carried by different internal forces (moments) of the shell in the axial direction are established. Numerical computations are implemented to investigate the vibrational power flow input and its propagation. It is found that characteristics of the vibrational power flow vary with different circumferential mode orders and frequencies, and the presence of fluid in the shell significantly affects the vibration of the shell structure. Additionally, parametric investigations are carried out to study the effects of the fiber orientation, modulus ratio E11/E22, and thickness-to-radius parameter h/R on input power into the coupled system and propagation power along the shell axial direction. This work will provide some guidance for the vibration control of the laminated composite cylindrical shell.

An Investigation of Vibrational Power Flow in One-Dimensional Dissipative Phononic Structures

Owing to their ability to block propagating waves at certain frequencies, phononic materials of self-repeating cells are widely appealing for acoustic mitigation and vibration suppression applications. The stop band behavior achieved via Bragg scattering in phononic media is most commonly evaluated using wave propagation models which predict gaps in the dispersion relations of the individual unit cells for a given frequency range. These models are in many ways limited when analyzing phononic structures with dissipative constituents and need further adjustments to account for viscous damping given by complex elastic moduli and frequency-dependent loss factors. A new approach is presented which relies on evaluating structural intensity parameters, such as the active vibrational power flow in finite phononic structures. It is shown that the steady-state spatial propagation of vibrational power flow initiated by an external disturbance reflects the wave propagation pattern in the phononic medium and can thus be reverse engineered to numerically predict the stop band frequencies for different degrees of damping via a stop band index (SBI). The treatment is shown to be very effective for phononic structures with viscoelastic components and provides a clear distinction between Bragg scattering effects and wave attenuation due to material damping. Since the approach is integrated with finite element methods, the presented analysis can be extended to two-dimensional lattices with complex geometries and multiple material constituents.

Optimization Method of the Rubber Elastic Element Structure Based on the Vibrational Power Flow

The isolation design of the ship must be considered based on flexibility, usually using vibration power flow analysis theory. The proposed vibration power flow based on finite element method aims the optimization to minimize the vibration power flow. The rubber elastic element structural optimization method has been study as follows.

The Vibro-Acoustic Characteristics of the Cylindrical Shell Partially Submerged in the Fluid

The characteristics of the sound radiation and vibrational power flow of the partially submerged cylindrical shell under a harmonic excitation are studied. The approximate acoustic boundary of the free surface is used to solve the fluid domain. The structure-fluid coupling equation is established based on the Flügge and Helmholtz theories. The far-field sound pressure is calculated and compared with that in infinite field. It is found that the far-field sound pressure presents large gap in different immersion status in the presence of the free surface while the results of the input power flow in these cases have less differences.