Vibration Characteristics Analysis And Testing Of Bellows

Bellows, which is an important part of industrial piping systems,has a very wide range of applications in the chemical industry, energy, marine engineering, aerospace and other fields. Because its structure is made up of expansion joints, bellows is palying an important role for the piping systems to reduce noise and vibration. However, due to the flow of the fluid, it will inevitably lead to pipeline oscillation, reduction of the reliability of the system, and even the occurrence of major accident.The main contents of this article include: 1) for the calculating formulation of natural frequencies of the bellows’ vibration in the National Standard, the axial stiffness is computed using ANSYS instead of the axial stiffness formulation in the National Standard. It greatly improves the calculation accuracy of the axial natural frequencies of the bellows; 2) using the simplified finite element algorithm and experimental data of the natural frequencies of the dry mode of the bellows’ vibration in [16], the shell finite element model in this article is validated for the dry mode calculation; 3) this thesis takes advantage of Pro / E and ICEM CFD to establish finite element model, and gives the rapid establishment of high-quality finite element mesh approach, and gets the vibration response of fluid-structure coupling in the action of a fluid situation; 4) the wet modes of the liquid-filled bellows are calculated using the new ACT module in ANSYS Workbench 14.5 or later Version; 5) the transient responses of the bellows under the steady flow and both ends clamped boundary conditions are simulated, meanwhile, the bellows’ displacement, velocity and acceleration responses are obtained; 6) an experimental piping system is designed to observe the actual vibration response of the bellows, and the results are collected and analyzed by Data Acquisition and Signal Processing analyzer.Conclusions:1) For the calculation of the axial frequency of the nonstandard bellow,the axial stiffness coefficient of the bellows is calculated using the finite element method, and the results are more accurate than the calculation results of the National Standard.2) the dry mode of the bellows using shell element to calculate is more accurate than that of the solid element.3) using the Acoustic Extension method for solving the bellows wet mode is feasible.At the same time, the fluid coupling reduces the natural frequency of bellow.4) the flow of the fluid make the bellows have obvious vibration, but due to the low velocity of fluid, the amplitude of vibration is on the micro-scale. 5) the actual vibration response of the bellows is verified by the testing devices.