Advanced Materials Research Vols. 291-294

Abstract: This paper concerns the determination of qualitative properties of linear vibrational systems, in particular for a single branch structure consisting of a pinned beam-rod system. First, we establish the characteristic equations satisfied by the Green’s function for this structure. The Green’s functions corresponding to support conditions where the left end of the beam was pinned-end are deduced by adopting the direct integral method. Using the theory of oscillation kernels established by Gantmakher and Krein, oscillatory properties of the Green's function for the beam-rod system are proved. Furthermore, four oscillation properties associated with frequencies and mode functions for the system are given.

Abstract: This paper discusses four types of piezoelectric basic equations, and there are two piezoelectric sensors which are composed of piezoelectric ceramics tightly pasting in the thin-walled structure. They can respectively measure structure of strain and strain rate changes. Based on the description of two kinds of piezoelectric sensors formation, The output display solution and their frequency domain forms are furtherly presented, and the advantages of the sensor are discussed. This conclusion can provide theoretical guidance for structural vibration active control.

Abstract: Combining Self-organizing Feature Map (SOM) and Factorial hidden Markov model (FHMM), a new FHMM fault recognition method based on multi-sensor vibration information fusion is proposed. In the proposed method, the SOM neural network is used to reduce the information redundancy in feature vectors extracted from the multi-sensor’s vibration measurements, FHMM as a classifier. The fault recognition in the speed-up and speed-down process of rotating machinery was successfully completed. The experiment result shows that the proposed method is very effective.

Abstract: This paper sets up a dynamic analysis model for cylinder-seal system. A new identification method for fluid-induced force and stiffness coefficients in eccentric seal is presented. The study shows that the system stability decreases with increasing cross-coupled stiffness in a certain range. Beyond this range, the system will be destabilized. Influences of rotating speed, inlet pressure, eccentricity and clearance on fluid-induced force were tested in the rig. It was found that a large tangential fluid-induced force was produced in the direction perpendicular to the eccentric displacement of rotor. The difference between the tangential and radial fluid-induced force became larger and larger with the increasing rotating speeds. Under the action of the seal force, the logarithmic decrement descended with increasing rotating speeds, and the stability of the system decreased. These effects became more and more serious for higher inlet pressure and tighter clearance.

Abstract: The failure of civil engineering structure will lead to heavy losses. So, identifying structural damage is necessary as early as possible. The excellent localization performance of lifting wavelet transform will facilitate significantly damage diagnosis. On the base of wavelet energy distribution of structural acceleration response, taking advantage of characteristics of lifting wavelet and entropy, the structural damage identification method based on lifting wavelet entropy is proposed in this paper. And the lifting wavelet time entropy index and the relative lifting wavelet entropy index are established. The new method and damage indexes are verified in numerical simulation and laboratory test of simple beam. The analysis results show that lifting wavelet time entropy can identify structural damage moment and the relative lifting wavelet entropy can identify structural damage location. The feasibility of method proposed is instructed.

Abstract: The accurate calculation of transmission line modes is very important for power line design, the dynamic properties, anti-vibration, anti-galloping analysis. However, the existing simplified theories and models will Cause large calculation error. Based on the strain - displacement relationship of spatial curved beam theory, a three-node curved beam power line element was realized, which was used to take a modal analysis. The results show that the curved beam element used to calculate modes of power line is accurate. The results of the analysis were compared with results of only considering translation of power line, results of considering axial deformation and bending. The results of parametric analysis show that the bending cross-section modulus of the transmission lines has a greater impact on the translation and rotation frequency. The iced conductor eccentricity can slightly reduce the frequency of wire.

Abstract: Based on the experimental study, this paper analyzes the stress given by series of Structured Infilling-walls reducing vibration multi-functionally in the help of the finite element analysis software, ANSYS. It is a comprehensive comparative analysis that different structures, thickness of walls, storeys, and spans are included. The conclusion is drawn that filling-wall can improve the mechanical properties of multi-functional vibration-reducing structure of infilling-wall, which provides theoretical evidence for infilling wall multi-functional vibration-reducing structure under different circumstances that the infill wall stand the proportion provides certain theoretical basis. The appropriate brittle anti-pressure pieces can be fixed according to the comparative finding which also contributes a lot to the achievement of the purpose of this project.

Abstract: The main sound source of motorcycle noise is engine exhaust noise in the paper. Installing muffler can effectively reduce the exhaust noise, in the other word, if the acoustic performance of muffler can be improved, exhaust noise of engine will effectively be suppressed. Based on the FEM, establishing the acoustic simulation model, the performance of muffler relates to acoustic is studied. Based on muffling theory, the optimal projects of the interior structure for muffler are proposed. Through doing experiments of insertion loss for muffler and the pass-by noise for motorcycle, these confirmed that the improved muffler can reduce the motorcycle’s noise.

Abstract: Displacement fundamental equations of the moderately thick cylindrical shallow shells concerning five independent variables, i.e. five middle surface displacements are established based on the displacement fundamental equations of the moderately thick shells by transverse shearing deformation and basic hypothesis on shallow shells. Three assistant displacement functions are introduced to solve the equations, which are tenth-order differential equations with variable coefficient; and then five second-order differential equations are converted into a second-order differential equation and two fourth-order transition differential equations using the Cauchy-Riemann condition, afterwards another assistant displacement function is introduced to build its decoupled governing differential equations, finally five displacement components through four assistant displacement functions are obtained.

Abstract: Displacement fundamental equations of moderately thick shallow spherical shells in polar coordinates concerning five independent variables, i.e. five middle surface displacements are established, based on the displacement fundamental equations of the moderately thick shells by transverse shearing deformation and basic hypothesis on shallow shells. Four assistant displacement functions are introduced to solve displacement fundamental equations of circular moderately thick shallow spherical shells , which are tenth-order differential equations with variable coefficient, then the decoupled governing differential equations are built up, and five displacement components through four assistant displacement functions are obtained.