柱壳隔振系统动力学特性的研究

对柱壳隔振系统动力学特性进行的研究 ,以往常建立在刚体模型的基础上 ,这是导致振动预报与实测间存在较大误差的主要原因。从基于有限元分析的弹性体模型出发 ,本文对涉及柱壳隔振系统动力学特性的结构与材料方案进行了模拟激励下的响应分析与灵敏度分析 ,讨论了其中的各种影响因素。通过实物模型试验 ,验证了已建立的动力学模型 。

一种熔模精密铸件免振壳抛丸机的研究

熔模精密铸件免振壳抛丸机改变了传统的工艺,将原来的振壳机用抛丸的工艺加以替代,同时将铸件和冒口浇铸系统进行粗抛,抛落下来的制壳材料根据颗粒大小加以分离、储存、再次利用。该设备既极大的提高了工作效率,改善了大气环境,又避免了工件的二次周转及原材料的浪费。

透平轮运行异常的原因分析及处理

本文利用DCS系统、离线监测系统分析某厂输出功率为1987KW蒸汽轮机径向瓦振动值突发波动及轮室压力低的原因。根据设备的历史运行趋势及现场振动监测排除转子硬碰硬摩擦的原因,通过对工艺操作的调整排除工艺原因。然后结合汽轮机运行机理,查看设备现场运行环境,对比同类设备的运行状态,最终准确判断透平径向振动间歇性波动及轮室压力低的原因并解决引起该故障现象的根本问题。

蜡油加氢C-1001汽轮机振动分析及解决措施

机组发生故障后,利用"壳振+轴振""在线+离线"监测模式,结合轴心轨迹分析、波形频谱分析等各种手段,对设备振动信号进行全方位捕捉,对设备故障部位进行快速定位、定性和定量分析,并采取针对性措施,以求最大化地缩小故障范围,做到精密检修。

A unified prediction solution for vibro-acoustic analysis of composite laminated elliptical shells immersed in air

A semi-analytical method to conduct vibro-acoustic analysis of a composite laminated elliptical shell immersed in air is proposed.A variational method and multi-segment technique are used to formulate the dynamic model.The sound radiation of the exterior fluid field is calculated by a spectral Kirchhoff–Helmholtz integral formulation.The variables containing displacements and sound pressure are expanded by the combination of Fourier series and Chebyshev orthogonal polynomials.The collocation points are introduced to construct an algebraic system of acoustic integral equations,where these points are distributed on the roots of Chebyshev polynomials,and the non-uniqueness solution of system is eliminated by a combined Helmholtz integral.Numerical examples for sound radiation problems of composite laminated elliptical shells are presented and individual contributions of the circumferential modes to the acoustical results of composite laminated elliptical shells are also given.The effects of geometric and material parameters on sound radiation of composite laminated elliptical shells are also investigated.

Microstructure and properties of novel polarization maintaining fiber

An improved type of elliptical jacket polarization maintaining fiber was developed by using a modified chemical vapor deposition method with special treatment. Different from conventional elliptical jacket, the shape of the stress jacket was transmuted. The cross-section of fiber consists of 5 layers: substrate, outer cladding, stress jacket, inner cladding and core. The cross sectional component distribution was investigated by electron probe microscopy and energy dispersive spectrum. The finite element method was used to calculate the stress birefringence. Based on the analyses of the microstructure, the technological process is improved. The temperature cycling test of the fiber wound into gyroscope coils was performed. The results show that the fiber possesses superior performance at high and low temperatures compared with other fibers. The high homogeneity is achieved by well-controlled modified chemical vapor deposition process. A homogeneous length of 8 km fiber is obtained. With advantages in homogeneity and length, the fiber has great potential in applications such as fiber gyroscopes, fiber hydrophone and other optical fiber sensors.

Vibration and Instability of Third⁃Order Shear Deformable FGM Sandwich Cylindrical Shells Conveying Fluid

The vibration and instability of functionally graded material(FGM)sandwich cylindrical shells conveying fluid are investigated.The Navier-Stokes relation is used to describe the fluid pressure acting on the FGM sandwich shells.Based on the third-order shear deformation shell theory,the governing equations of the system are derived by using the Hamilton’s principle.To check the validity of the present analysis,the results are compared with those in previous studies for the special cases.Results manifest that the natural frequency of the fluid-conveying FGM sandwich shells increases with the rise of the core-to-thickness ratio and power-law exponent,while decreases with the rise of fluid density,radius-to-thickness ratio and length-to-radius ratio.The fluid-conveying FGM sandwich shells lose stability when the non-dimensional flow velocity falls in 2.1-2.5,which should be avoided in engineering application.

Vibrations of revolution shells in turning-point range and applications in loudspeakers

An overview of the research conducted in the area of linear and nonlinear vibrations of loudspeakers and revolution shells was given in the turning-point frequency range in Chapter 1. It shows that some problems concerning vibrations of shells in the turning-point range have to be further studied. The linear vibrations of truncated revolution shells with the first-order turningpoint were systematically investigated in the turningpoint range from Chapter 2 to Chapter 6, including the general solutions for the free vibration, the eigenvalues under various boundary conditions, the forced vibrations driven by an edge force or an edge displacement and some related special effects, and the applications in loudspeaker vibrations. The nonlinear autoparametric vibration was examined in Chapter 7. Main results are listed as follows.

Research on cylindrical shell vibration reduction systems

Longitudinal and horizontal vibration must both be reduced in an effective vibration isolation system. We present a cylindrical shell vibration isolator as a dynamic system composed of four springs and dampers. Vibration is directly produced by the motion of machinery, and more is subsequently generated by harmonic frequencies within their structure. To test the effectiveness of our isolator, we first determined equations for the transmission of vibration from the machine to its cylindrical shell. Damping effects produced by the vibration parameters of our system are then analyzed.

Modeling and optimal vibration control of conical shell with piezoelectric actuators

In this paper numerical simulations of active vibration control for conical shell structure with dis-tributed piezoelectric actuators is presented.The dynamic equations of conical shell structure are derivedusing the finite element model (FEM) based on Mindlin's plate theory.The results of modal calculationswith FEM model are accurate enough for engineering applications in comparison with experiment results.The Electromechanical influence of distributed piezoelectric actuators is treated as a boundary conditionfor estimating the control force.The independent modal space control (IMSC) method is adopted and theoptimal linear quadratic state feedback control is implemented so that the best control performance withthe least control cost can be achieved.Optimal control effects are compared with controlled responses withother non-optimal control parameters.Numerical simulation results are given to demonstrate the effective-ness of the control scheme.

The Coupling Effect of Spatial Reticulated Shell Structure with Cables

The spatial reticulated shell structure with cables (RSC) is a kind of coupling working system, which consists of flexible cables, reticulated shell structure (RS) and tower columns. The dynamic analysis of RSC based on the coupling model was carried out. Three kinds of elements such as the spatial bar element, cable element and beam element were introduced to analyze the reticulated shell, cable and tower column respectively. Furthermore, such parameter influences as structural boundary conditions, grid configuration, the span-to-depth ratio and the arrangement of cable system upon structural dynamics were analyzed. The structural vibration modes can be divided into four groups based on some numerical examples. And the frequencies in the same group are very close while the frequencies in different groups are different from each other obviously. It is clear that the sequence of the appearance of the each mode group heavily depends on the comparative stiffness of the tower column system, RS and cables.

A Smoothed Finite Element Method for the Static and Free Vibration Analysis of Shells

A four-node quadrilateral shell element with smoothed membrane-bending based on Mindlin-Reissner theory is proposed. The element is a combination of a plate bending and membrane element. It is based on mixed interpolation where the bending and membrane stiffness matrices are calculated on the boundaries of the smoothing cells while the shear terms are approximated by independent interpolation functions in natural coordinates. The proposed element is robust, computationally inexpensive and free of locking. Since the integration is done on the element boundaries for the bending and membrane terms, the element is more accurate than the MITC4 element for distorted meshes. This will be demonstrated for several numerical examples.

CFD Simulation of Pulsation Noise in a Small Centrifugal Compressor with Volute and Resonance Tube

The rotational frequency tone noise emitted from the automobile turbocharger is called the pulsation noise. The cause of the pulsation noise is not fully understood, but is considered to be due to some manufacturing errors, which is called the mistuning. The effects of the mistuning of the impeller blade on the noise field inside the flow passage of the compressor are numerically investigated. Here, the flow passage includes the volute and duct located downstream of the compressor impeller. Our numerical approach is found to successfully capture the wavelength of the pulsation noise at given rotational speeds by the comparison with the experiments. One of the significant findings is that the noise field of the pulsation noise in the duct is highly one-dimensional although the flow fields are highly three-dimensional.

Exact free vibration analysis of open circular cylindrical shells by the method of reverberation-ray matrix

This paper is concerned with the free vibration analysis of open circular cylindrical shells with either the two straight edges or the two curved edges simply supported and the remaining two edges supported by arbitrary classical boundary conditions. Based on the Donnell-Mushtari-Vlasov thin shell theory, an analytical solution of the traveling wave form along the simply supported edges and the modal wave form along the remaining two edges is obtained. With such a unidirectional traveling wave form solution, the method of the reverberation-ray matrix is introduced to derive the equation of natural frequencies of the shell with different classical boundary conditions. The exact solutions for natural frequencies of the open circular cylindrical shell are obtained with the employment of a golden section search algorithm. The calculation results are compared with those obtained by the finite element method and the methods in the available literature. The influence of length, thickness, radius, included angle, and the boundary conditions of the open circular cylindrical shell on the natural frequencies is investigated. The exact calculation results can be used as benchmark values for researchers to check their numerical methods and for engineers to design structures with thin shell components.

Determination of the ^(25)Mg(p,γ)^(26)Al resonance strength at E_(c.m.)=58 keV via shell model calculation

The observation of 26Al is an useful tool for γ-ray astronomy and in studies of galactic chemical evolution. The most likely mechanism for 26Al nucleosynthesis is in the hydrogen burning MgAI cycle, and the 26Al production reaction 25Mg（p, γ）26Al at the important temperature range below T = 0.2 GK is still not well known. The spectroscopic factor of 58 keV resonance level in 26Al is determined with shell model calculation and then used to deduce the resonance strength of the 25Mg（p, γ）26Al reaction. The result provides a reference for the future 25Mg（p, γ）26Al direct measurement at Jinping underground laboratory.

Influence of structural defects on the optical properties of strongly coupled Au nanoshell arrays

The effects of different defects on optical properties and plasmon resonances properties of Au nanoshell arrays were investigated by using the finite-difference time-domain(FDTD) theory.It is found that the optical properties of the nanoshell arrays are strongly influenced by different defects.We show that when the hollow Au nanoshell arrays are placed in air,there is a wide photonic band gap(PBG) in the infrared region,but the band gap becomes narrower as we introduced different defects.Based on the distributions of electric field component E z and the total energy distribution of the electric and the magnetic field,we show that there exhibit dipoles field distributions for the plasmon mode at the long-wavelength edge of the band gap,but composite higher order modes are excited at the short-wavelength edge of the band gap.The plasmon resonant modes also can be controlled by introducing defects.

Axisymmetric 3:1 internal resonance of thin-walled hyperelastic cylindrical shells under both axial and radial excitations

Nonlinear vibration with axisymmetric 3:1 internal resonance is investigated for an incompressible neo-Hookean hyperelastic cylindrical shell under both axial and radial harmonic excitations.A full nonlinear strain-displacement relation is derived from the large deflection theory of thin-walled shells.A set of nonlinear differential equations describing the large deflection vibration are formulated by the Lagrange equation and the assumption of small strains.Steady-state responses of the system are predicted via the harmonic balance method with the arc length continuation,and their stabilities are determined via the modified sorting method.The effects of excitations on the steady-state responses are analyzed.The results reveal a crucial role played by the phase difference in the structural response,and the phase difference can effectively control the amplitude of vibration.

Synthesis of monodispersed Fe3O4@C core/shell nanoparticles

We report a facile method to synthesize dispersed Fe304@C nanoparticles （NPs）. Fe304 NPs were firstly prepared via the high temperature diol thermal decomposition method. Fe304@C NPs were fabricated using glucose as a carbon source by hydro- thermal process. The obtained products were characterized by X-ray diffraction （XRD）, transmission electron microscopy （TEM）, vibrating sample magnetometer （VSM） and Raman spectra. The results indicate that the original shapes and magnetic property of Fe304 NPs can be well preserved. The magnetic particles are well dispersed in the carbon matrix. This strategy would provide an efficient approach for existing applications in Li-ion batteries and drug delivery. Meanwhile, it offers the raw materials to assemble future functional nanometer and micrometer superstructures.

Upper mantle anisotropy and crust-mantle deformation pattern beneath the Chinese mainland

Over the past 10 years, the number of broadband seismic stations in China has increased significantly. The broadband seismic records contain information about shear-wave splitting which plays an important role in revealing the upper mantle anisotropy in the Chinese mainland. Based on teleseismic SKS and SKKS phases recorded in the seismic stations, we used the analytical method of minimum transverse energy to determine the fast wave polarization direction and delay time of shear-wave splitting. We also collected results of shear-wave splitting in China and the surrounding regions from previously published papers. From the combined dataset we formed a shear-wave splitting dataset containing 1020 parameter pairs. These splitting parameters re- veal the complexity of the upper mantle anisotropy image. Our statistical analysis indicates stronger upper mantle anisotropy in the Chinese mainland, with an average shear-wave time delay of 0,95 s; the anisotropy in the western region is slightly larger （1.01 s） than in the eastern region （0.92 s）. On a larger scale, the SKS splitting and surface deformation data in the Tibetan Plateau and the Tianshan region jointly support the lithospheric deformation mode, i.e. the crust-lithospheric mantle coherent deformation. In eastern China, the average fast-wave direction is approximately parallel to the direction of the absolute plate motion; thus, the upper mantle anisotropy can be attributed to the asthenospheric flow. The area from the Ordos block to the Sichuan Basin in central China is the transition zone of deformation modes between the east and the west regions, where the anisotropy images are more complicated, exhibiting ＂fossil＂ anisotropy and/or two-layer anis^3trc^py. The c^llisi（3n between the Indian Plate and the Eurasian Plate is the main factor of upper mantle anisotropy in the western region of the Chinese mainland, while the upper mantle anisotropy in the eastern region is related to the subduction of the Pacific Plate and the Philippine Sea Plate beneath the Eurasian Plate.