Laboratory experimental study of contact interaction between cut shells and resilient bodies

The study presented herein describes promising designs of shell vibration isolators. The feature of the proposed designs is the cut thin-walled shell usage as the main bearing link. These resilient elements have high load capacity and, on the other hand, can provide the desired level of damping. From the point of view of mechanics, shell resilient elements are considered as the deformable systems with dry friction. When simulating these systems, structurally nonlinear non-conservative mixed contact issues of cut shell – resilient body frictional interaction arise. In order to take into account all essential options of the aforementioned issues and specify shell resilient element peculiarities of behavior under operational loads, the authors used the method of laboratory experiments for research. We considered two different contact systems. The first one is a cylindrical shell cut along its generatrix, which contacts a deformable filler. The second system is a cylindrical shell with several incomplete slots interacting with the elastic filler. The stress state and radial displacements of the shells, pliability of the resilient elements, and energy dissipation in the contact systems were time-tracked. As a result, we obtained relations for monitored options of the contact bodies and deformation diagrams for different physical-mechanical and geometrical options of the systems It was found that for a fixed cycle asymmetry coefficient with an increase in the friction coefficient between the shell and the filler, the amount of energy dissipated per cycle gradually decreases. The idea of optimizing shell vibration protection devices according to the criterion of maximum absorption of energy from external influences by determining the required tribological properties of contacting pairs is declared.

Cylindrical Shell Vibration Gyroscope Excited and Detected by High-Temperature-Sintered Piezoelectric Ceramic Electrodes

A cylindrical shell piezoelectric vibration gyroscope is a kind of Coriolis vibration gyroscope. Its core components are the cylindrical quartz resonator (CQR) and the piezoelectric ceramic electrodes (PCEs). In order to develop a high-precision Cylindrical shell piezoelectric vibration gyroscope, it is very important to reduce the influence of the PCEs and obtain a high-quality-factor CQR. To achieve this goal, a novel high-temperature sintering method is proposed to combine the CQR and the PCEs, and the corresponding sintered resonators are fabricated. After sintering, results of the acoustic excitation experiment and piezoelectric excitation experiment are tested, and the influence of the sintered PCEs on the CQR is determined. A complete gyroscope is obtained by vacuum packaging the sintered resonator. Through the open-loop and closed-loop tests, the performance parameters of gyroscope are obtained. The feasibility of the high-temperature sintering method is proved by experiments.

Vibro-acoustic and sound transmission loss analysis of truncated conical shell subjected to incident sound wave

A combination of analytical method for shell vibration, boundary element method (BEM) for acoustic media of shell outer space, and finite element method (FEM) for shell inner space was used to study the vibro-acoustic behavior and extract sound transmission loss factor (STL) of a coupled vibro-acoustic system. The equation of motion of the shell is extracted based on the Donnell–Mushtari hypothesis and using Hamilton principles. The acoustic pressure on the outer and inner space is obtained using BEM on the defined nodes on the surface and these localized nodal pressures are converted to nodal concentrated forces. Finally, vibration of the coupled vibro-acoustic model is solved in frequency domain and vibration response of shell and acoustic pressure at any point in the media (outer, on the surface, and inner of shell) are obtained. Also, the STL of the shell is extracted based on the ratio of total acoustic energy received by the shell to that transferred to inner space.

Study on the Mechanism of Fatigue Failure at Branch Connections Caused by Shell Mode Vibration

Acoustically induced vibration (AIV) is a vibration of piping systems caused by the acoustic loading generated mainly from pressure reducing devices. Recently, the capacities of the pressure reducing systems have been increased and some of the piping systems which are susceptible to acoustic fatigue, such as in flare and depressuring system. Demands on the development of reasonable design method for AIV is increasing. In this paper, the mechanisms of the fatigue failure of branch connection due to AIV were intensively studied. Firstly, the mechanism of the stress concentration was discussed. branch vibration caused by the shell mode vibration was assessed using several branch connection models, massless rigid model, fixed rigid model, and beam model. Next, the relationship between shell-vibration and stress concentrations is studied and re-organized based on acoustic vibration theories. Finally, the risk of the fatigue failure of the branch connection due to acoustic loading was discussed.

Application of Vectorial Wave Method in Free Vibration Analysis of Cylindrical Shells

The vectorial form of the Wave Propagation Method (VWM), regarding the dispersion of harmonic plain (elasto-dynamic) waves within certain wave-guides, is developed for the vibration analysis of circular cylindrical shells. To obtain this goal, all plain waves are divided into positive-negative going wave vectors along with the shell axis. Based on the Flügge thin shell theory, the shell continuity as well as boundary conditions are well satisfied by introducing the propagation and reflection matrices. Furthermore, all elements of the reflection matrix are derived for certain classical supports. As an example, for demonstrating the feasibility of VWM in the shell vibration analysis, a circular cylindrical shell with two ended flexible support is adopted. The natural frequencies of the systemaswell asmode shapes are obtained using VWM. The aquired results are compared with those of the previous works and found in excellent agreement. It is also found that VWM could mathematically provide a reduced dimensional matrix (dominant matrix) to calculate the natural frequencies of the system. Accordingly, the proposed method can provide high computational efficiency and remarkable accuracy, simultaneously.