Abstract: Based upon the Reissner-Naghdi-Berry’s shell theory, a domain decomposition method (DDM) is utilized to investigate the vibration characteristics of the combined cylindrical-spherical shell with different boundary conditions. The combined shell was first apart from prescribed-displacement boundary and then divided into some cylindrical and spherical shell subdomains, respectively. The boundary equations were introduced into the energy functional of the combined shell as well as the constraint equations derived from interface continuity conditions between two adjacent shell subdomains. Fourier series and Chebyshev orthogonal polynomials were employed as the admissible displacement functions for each shell subdomain in the circumferential direction and axial direction in order to obtain the discretization equations of motion of the combined shell. Exact free vibration solutions of the combined shell has been performed via the DDM and were compared with those obtained by the finite element software ANSYS to confirm the reliability and accuracy.
Abstract: Marine risers are key apparatus in connecting the subsea wells to the oil production platform. When the ocean current flow past a riser, the vortex shedding behind riser may induce vibration. If the frequency of vortex shedding is approaching or equal to the natural frequency of riser, the resonance will be generated. Such phenomenon leads to the potential fatigue damage of riser. Therefore, the safety and assurance of marine risers are widely arousing the interest of offshore engineering. In present paper, previous apparatus or methods in suppressing vortex-induced vibration (VIV) of risers used in marine engineering are firstly analyzed, and correspondingly the conditions in design of VIV suppressors are proposed. Based on the Bernoulli equation, the disturbance in flow around a bluff body and the relationship of vortex shedding in span-wise direction, a new method of VIV suppression is proposed. The numerical results have shown that the vibration of risers could be reduced by such disturbance.
Abstract: In order to study the flow-induced vibration of the spillway tunnel working gate of one reservoir, hydraulic model test with scale 1:20 was conducted to obtain the dynamic pressure characteristics on the working gate. Experiment modal analysis method was employed to identify the structure dynamic characteristics through the 1:10 working gate mode test. The 3D FEM model of the gate was built to simulate the vibration response of the structure. The research showed the low order modal frequencies of the working gate were not fully breaking away from the high energy zone of the dynamic water, which would induce severe vibration. The vibration response of the gate became the biggest when it was operating at 0.5 partial opening.
Abstract: The simulated prediction of the structural vibration of diesel engine has been made in this paper. The displacement maps on different frequencies were obtained by using finite element model. The FFT (Fast Fourier Transform Algorithm) was used to the displacement data of the parts where the vibration is strong. So, the displacement spectrum was obtained on those points. The study shows that response displacements between 60~500Hz are bigger than others. This is due to the rigid displacement of the diesel engine. There are some other big response displacements around 800Hz, 1400Hz and 1800Hz.This is the result of local vibration of the oil pan, flywheel shell and gear room cover. Improve the three parts structure can effectively reduce vibration of the diesel engine.
Abstract: Ultrasonic vibration system is the chief component of USM machine tool. Whether products are precisely machined is lie on the performance of the system. To design good performance of ultrasonic vibration system, finite element method is used to analyse the dynamic performance of the system based on theoretic calculation. The dynamic performance of transformer and transformer with tool is analysed respectively, including natural vibration characteristic and harmonic characteristic. The result of FEA is compared with theoretic calculation. The parametric optimization design technique of the finite element analysis package ANSYS is applied to optimize the structure dimension of the piezoelectric transducer and transformer with tool. Then amplitude of the optimized system and the previous system is compared based on laser-CCD sensor for micro-displacement. The optimized system is more superior and has larger amplitude. Last some round holes are machined on kentanium YG8, monocrystalline silicon, PZT. And machining effect of single Micro-USM is got by the test.
Abstract: It is necessary and valuable to build the transferring relationship between test bed datum and ship datum for satisfying the boundary requirements of exciting forces in ship’s vibration-acoustic analysis. Principle of the force transferring technique for machineries with multiple supporting points is introduced first, and then the measurement method for free velocities of machineries is given. A method for transferring test bed datum to ship datum of machinery force characteristics is discussed and applied to deal with a practical problem, in which the numerical simulation is used for predicting admittance of ship mounting seat absenting reality. Experimental results show that the proposed method is valid.
Abstract: In order to attain the purpose of anti-galloping, a simplified model for iced quad bundle conductors of three degrees of freedom in vertical, horizontal and torsional directions is established by means of the Hamilton principle, in which the effect of spacers stiffness and damping is considered. Based on the model, the influence of related parameters such as fluid density, damping ratio on conductor galloping amplitude and critical wind velocity is analyzed. Simultaneously, the relation curve between elastic property of spacers and conductor galloping is obtained. The results indicate that the conductor galloping can be weakened to some degree with the proper enlargement of damping ratio, the reasonable setting of spring stiffness on spacers and the avoidance of areas such as the wind outlet and windward as much as possible when choosing the line path and so on.
Abstract: With high-rise construction increasing in city, it demands more and higher-performance tower cranes. Damages by wind to the tall and towering structures are usually very serious, but these dangers are often hidden.The paper uses the finite element software ANSYS to set up the overall modeling of the TC6010 tower crane which is produced by a company, and carry on the FEM analysis effected by wind based on it . The paper obtains the data of the displacement response of the complete machine after exerting the wind wave, and has the preliminary analysis to the result. The results show that the tower crane is a low-frequency vibrating system and easy to cause the structure resonance, the crane tower may damage in the boom firstly under the action of wind load.
Abstract: Bending vibration of helicopter driveshaft is a main source causing damage of bearing supports and noise of transmission system. Firstly, we get driveshaft element stiffness matrices and mass matrices based on the finite element theory. Then, we get calculate matrix eigenvalue of the entire system. Finally, we get natural frequencies and natural modes of different bearing system. Mass eccentricity is one of the main excitation sources of the transmission system vibration and noise. This excitation is transmitted to base by bending vibration of drive shaft, causing body vibration and noise. As transmission rate changes with different bearing stiffness of supports, it can be employed to reflect influence from bearing stiffness of supports on bending vibration of axis. Transmission rate can be used as input parameters (motivation) or goal parameters to reflect the performance of driveshaft vibration.