Papers by Keyword: Random Vibration

Abstract: Based on the random vibration theory and numerical analysis method, the paper presents a process of carrying out the fatigue life prediction for pipeline of a rocket engine under random excitation. The numerical analysis adopt the power spectrum density of acceleration as random loads. The material parameters of the simulation contains two straight lines in double logarithmic coordinate. The location of danger points is found and the root mean square stress, fatigue life of it is acquired in different excitation directions. The results show that the root of the ball head is the location of danger points, whose fatigue life is 3763 seconds. Furthermore, the location of danger points and its fatigue life obtained from numerical analysis are consistent with the test.

Abstract: Traction transformers areheavy and suffering dynamic load all the time when the train is starting,stopping and moving. These load cases make it necessary to design tractiontransformers in fatigue resistance view. In this paper, random vibrationsimulation is done for traction transformer with finite element method. ThisFEM result is used for fatigue analysis. Several methods of damage accumulationfor random vibration are discussed and compared with test result. Result showssingle moment method is a better choice for traction transformers.

Abstract: In order to provide precise guidance for the landing of carrier-based aircrafts, the phased array antenna and the principle of time reference scanning beam are used in the shipborne MLS. The phased array antenna is installed under the flight deck of the ship stern, so the vibration could change the relative position of antenna elements, which will cause the navigation error. In this paper, through the establishment of antenna array pattern and phased array antenna vibration error model, an error calibration algorithm is proposed after the simulation of phased array antenna’s random vibration effects on the guiding performance of shipborne MLS in three axes. Computer simulations show that the calibration algorithm could improve the guiding performance of shipborne MLS.

Abstract: To assess the structural strength of spherical cylinder, the finite element model was constructed by the NX NASTRAN software. Firstly,the basic principle of random vibration response analysis was introduced, then the random vibration response analysis of the cylinder assembly was analyzed. The simulation result shows that the stress of the joint between spherical cylinder clamp and the base is larger than other areas in conditions of a given random vibration load. The spherical cylinder structure is safe and that the maximum RMS stress is about 20 MPa.

Abstract: This work aims to predict fatigue life of hybrid integrated circuit (HIC) hermetical metal sealing structure mounted on PCB under random vibration loading. The prediction method consists of following steps. Firstly, finite-element model was developed to obtain model parameters (including natural frequencies and mode shapes) and power spectral density (PSD) of the critical part of sealing structure by ANSYS workbench. Secondly, modal test and random vibration test were conducted to verify the results of simulation. Thirdly, the Von Mises stress PSD was transformed into time-history data through inverse Fourier transform with Matlab program after calculating from the FEA results. The rainflow-counting algorithm was employed to evaluate cumulative damages of the critical part. The material’s S-N curve, Palmgren-Miner’s damage accumulation rule and rainflow-counting algorithm were used to predict fatigue life. A specially designed fixture and board with heat sink were used in the experiment to verify the first five mode shapes and response spectrum of the six critical points with hammer excitation. The calculation result of in this study is 70.3 hours which could be a reference for structural design of hybrid integrated circuit hermetical metal sealing under vibration conditions.

Abstract: In this paper, the magneto-elastic nonlinear random vibration of a clamped rectangular thin plate in magnetic field is studied. According to the magneto-elastic theory of plates and shells and the theory of structural random vibration, the magneto-elastic nonlinear random vibration equation of a clamped rectangular thin plate in a magnetic field is derived. Then the nonlinear random vibration equation is transferred into the Ito differential equation, and the Ito differential equation is solved using FPK equation method. Thus the numerical characteristics of displacement response and velocity response of the rectangular thin plate are obtained. Finally, through a numerical example, the influences of magnetic field parameters on the numerical characteristics are discussed, and some methods which can be used to effectively control the random vibration responses of the plate are given.

Abstract: This document conducts simulation analysis on spherical anti-seismic bearing employing the Finite Element Methods and PSD analysis of random vibration based on modal analysis, from which results as statistical parameters of random vibration of structure and demonstrates: this specific anti-seismic spherical bearing satisfies industry security demands related.

Abstract: For the fracture failure phenomena occurred in random vibration experiment of the isolation clamp cylinder on the aerospace vehicles, the NX NASTRAN was used to make the finite element modeling for the overall structure of cylinder and analyze the random vibration response. The simulation results show that the maximum RMS stress of the clamp was 96 MPa at the test load conditions. The position of the maximum RMS stress is consistent with the one where fracture happens during vibration test. According to finite element analysis results, the original structure has been modified. The maximum RMS stress of modified structure is only 21.8 MPa.

Abstract: A numerical procedure to compute the mean and covariance matrix of the random response of stochastic structures modeled by FE models is presented. With the help of Gegenbauer polynomial approximation, the calculation of dynamic response of random parameter system is transformed into an equivalent certainty expansion order system's response calculation. Non-stationary, non-white, non-zero means, Gaussian distributed excitation is represented by the well-known Karhunen-Loeve (K-L) expansion. The Precise Integration Method is employed to obtain the K-L decomposition of the non-stationary filtered white noise random excitation. A very accurate result is obtained by a small amount of K-L vectors with the vector characteristic of energy concentration, especially for the small band-width excitation. Correctness of the method is verified by the simulations.

Abstract: Common solution for energy harvester device is project design according harmonic excitation around natural frequency matching excitation source. Environment vibration is random and wide band causing short time of resonance in disagreement of project objectives. Control driven of energy harvesting to take advantage of the higher vibration range can results in greater energy converted. This study investigates a non-ideal excitation behavior and their efficiency in convert electricity via piezoelectric direct effect from the available system energy compared to harmonic excitation source. Numeric evaluation was performed based in bimorph piezoelectric beam in dimensionless consideration. Chaos behavior and harvest energy capability were compared from non-ideal to harmonic excitation. Results demonstrate considerable higher quantity of energy available for non-ideal approach compared to harmonic resonant design and encourages advance study to control and enhance energy from random and wide band vibration source.