Surface Topography of Fine-grained ZrO_2 Ceramic by Two-dimensional Ultrasonic Vibration Grinding

The surface quality of fine-grained ZrO2 engineering ceramic were researched using 270# diamond wheel both with and without work-piece two-dimension ultrasonic vibration grinding（WTDUVG）. By AFM images, the surface topography and the micro structure of the two-dimensional ultrasonic vibration grinding ceramics were especially analyzed. The experimental results indicate that the surface roughness is related to grinding vibration mode and the material removal mechanism. Surface quality of WTDUVG is superior to that of conventional grinding, and it is easy for two-dimensional ultrasonic vibration grinding that material removal mechanism is ductile mode grinding.

Trispectrum and correlation dimension analysis of magnetorheological damper in vibration screen

In order to improve the screening efficiency of vibrating screen and make vibration process smooth,a new type of magnetorheological (MR) damper was proposed. The signals of displacement in the vibration process during the test were collected. The trispectrum model of autoregressive (AR) time series was built and the correlation dimension was used to quantify the fractal characteristics during the vibration process. The result shows that,in different working conditions,trispectrum slices are applied to obtaining the information of non-Gaussian,nonlinear amplitude?frequency characteristics of the signal. Besides,there is correlation between the correlation dimension of vibration signal and trispectrum slices,which is very important to select the optimum working parameters of the MR damper and vibrating screen. And in the experimental conditions,it is found that when the working current of MR damper is 2 A and the rotation speed of vibration motor is 800 r/min,the vibration screen reaches its maximum screening efficiency.

Investigation into rail corrugation in high-speed railway tracks from the viewpoint of the frictional self-excited vibration of a wheel–rail system

A finite element vibration model of a multiple wheel-rail system which consists of four wheels, one rail, and a series of sleepers is established to address the problem of rail corrugation in high-speed tracks. In the model, the creep forces between the wheels and rail are considered to be saturated and equal to the normal contact forces times the friction coefficient. The oscillation of the rail is coupled with that of wheels in the action of the saturated creep forces. When the coupling is strong, self- excited oscillation of the wheel-rail system occurs. The self-excited vibration propensity of the model is analyzed using the complex eigenvalue method. Results show that there are strong propensities of unstable self-excited vibrations whose frequencies are less than 1,200 Hz under some conditions. Preventing wheels from slipping on rails is an effective method for suppressing rail corrugation in high-speed tracks.

Coupled extension and thickness-twist vibrations of lateral field excited AT-cut quartz plates

In this paper, the coupled extension and thickness- twist vibrations are studied for AT-cut quartz plates under Lateral Field Excitation （LFE） with variations along the x1- direction. Mindlin＇s two-dimensional equations are used for anisotropic crystal plates. Both free and electrically forced vibrations are considered. Important vibration characteristics are obtained, including dispersion relations, frequency spectra, and motional capacitances. It is shown that, to avoid the effects of the couplings between extension and thickness-twist vibrations, a series of discrete values of the length/thickness ratio of the crystal plate need to be excluded. The results are of fundamental significance for the design of LFE resonators and sensors.

Nanoscale mass sensing based on vibration of single-layered graphene sheet in thermal environments

Based on vibration analysis, single-layered graphene sheet （SLGS） with multiple attached nanoparticles is developed as nanoscale mass sensor in thermal environments. Graphene sensors are assumed to be in simplysupported configuration. Based on the nonlocal plate the- ory which incorporates size effects into the classical theory, closed-form expressions lot the frequencies and relative fre- quency shills of SLGS-based mass sensor are derived using the Galerkin method. The suggested model is justified by a good agreement between the results given by the present model and available data in literature. The effects of tem- perature difference, nonlocal parameter, the location of the nanoparticle and the number of nanoparticles on the relative frequency shift of the mass sensor are also elucidated. The obtained results show that the sensitivity of the SLGS- based mass sensor increases with increasing temperature difference.

NMR Parameters and Vibrational Investigation of 2-Dicyanovinyl-5-(4-ethoxyphenyl) thiophene by ab initio HF and DFT Calculations

Optimized geometry and harmonic vibrational frequency of 2-dicyanovinyl-5-（4- ethoxyphenyl）thiophene （C16Hj2N2OS） are calculated at the HF/6-31＋＋G（d,p） and B3LYP/6- 311 ＋＋G（d,p） levels. Mulliken charges in the ground state are also calculated. The research shows the presence of intermolecular interaction in the title compound. The scaled harmonic vibrational frequencies have been compared with experimental FT-IR spectra. A detailed interpretation of the infrared spectra of the title compound is reported. The theoretical spectrograms for IR spectra of the title compound have been constructed, The isotropic chemical shift computed by 13C and 1H NMR analyses also shows good agreement with the experimental observations.

Structural and Vibrational Study of 2-（Quinolin-8-yloxy）-Acetic Acid based on FT-IR-Raman Spectroscopy and DFT Calculations

We have prepared the 2-（quinolin-8-yloxy）-acetic acid and characterized it by infrared and Raman spectroscopies in the solid phase. The Density Functional Theory （DFT） method, together with the 6-31G^＊ and 6-311＋＋ G^＊＊ basis sets, show that three stable molecules, for the anhydrous and monohydrated compounds were theoretically determined in the gas phase, and that probably the two more stable conformations are present in the solid phase of the monohydrated compound. The harmonic vibrational wavenumbers for the optimized geometries were calculated at B3LYP/6-31G^＊and B3LYP/6-311＋＋G^＊＊ levels. For a complete assignment of all the observed bands in the vibrational spectra the DFT calculations were combined with Pulay＇s scaled quantum mechanical force field （SQMFF） methodology in order to fit the theoretical Wavenumber values to the experimental ones. The characteristics of the electronic delocalization of all structures of both forms were performed by using natural bond orbital （NBO）, while the corresponding topological properties of electronic charge density are analysed by employing Bader＇s atoms in molecules theory （AIM）.

Seismic Sequence in Carbonate Rocks By Vibrational Liquefaction

On the basis of the records of strong seismic events taking place in soft carbonate sediments, a new seismic sequence system of vibrational liquefaction is established, which consists of a series of units, such as escaped structure of micrite veins and liquefied deformation formed in the period of seismic liquefaction, land subsidence structure after liquefaction, tsunamic hummocky and turbidite produced by seismic events, This sequence is a generalization and summation of field observation in vast areas, which shows the whole process of a strong seismic event and provides an unified theoretical explanation. The pattern of the seismic sequence by vibrational liquefaction provides one of correlation standards for geologists in the field to discriminate events in carbonate sequences. Based on the pattern of seismic sequence, the authors first advance a new conception of the Palaeo-Tanlu (Tancheng-Lujiang) Zone and discuss primarily its geological significations.

Synchronization of three homodromy coupled exciters in a non-resonant vibrating system of plane motion

In this paper, the synchronization problem of three homodromy coupled exciters in a non-resonant vibrating system of plane motion is studied. By introducing the average method of modified small parameters, we deduced dimensionless coupling equation of three exciters, which converted the problem of synchronization into that of the existence and stability of zero solutions for the average differential equations of the small parameters. Based on the dimensionless coupling torques and characteristics of the cor- responding limited functions, the synchronization criterion for three exciters was derived as the absolute value of dimensionless residual torque difference between arbitrary two motors being less than the maximum of their dimensionless coupling torques. The stability criterion of its synchronous state lies in the double-condition that the inertia coupling matrix is positive definite and all its elements are positive as well. The synchronization determinants are the coefficients of synchronization ability, also called as the general dynamical symmetry coefficients. The double-equilibrium state of the vibrating system is manifested by numeric method, and the numeric and simulation results derived thereof indicate the indispensable and crucial role the structural parameters of the vibrating system play in the stability criterion of synchronous operation. Besides, by adjusting its structural parameters, the elliptical motion of the vibrating system successfully met the requirements in engineering applications.

Vibration analysis of axisymmetric functionally graded viscothermoelastic spheres

The present study focuses on the analysis of free vibrations of axisymmetric functionally graded hollow spheres. The material is assumed to be graded in radial di- rection with a simple power law. Matrix Frrbenious method of extended power series is employed to derive the analytical solutions for displacement, temperature, and stresses. The dispersion relations for the existence of various types of pos- sible modes of vibrations in the considered hollow sphere are derived in a compact form. In order to explore the character- istics of vibrations, the secular equations are further solved by using fixed point iteration numerical technique with the help of MATLAB software. The numerical results have been presented graphically for polymethyl methecrylate materials in respect of natural frequencies, frequency shift, inverse quality factor, displacement, temperature change, and radial stress.

Evaluating performance of cutting machines during sawing dimension stones

The performance of cutting machines in terms of energy consumption and vibration directly affects the production costs. In this work, our aim was to evaluate the performance of cutting machines using hybrid intelligent models. For this purpose, a systematic experimental work was performed. A database of the carbonate and granite rocks was established, in which the physical and mechanical properties of these rocks (i.e., UCS, elastic modulus, Mohs hardness, and Schmiazek abrasivity factor) and the operational parameters (i.e., depth of cut and feed rate) were considered as the input parameters. The predictive models were developed incorporating a combination of the multi-layered perceptron artificial neural networks and genetic algorithm (GANN-BP) and the support vector regression method and Cuckoo optimization algorithm (COA-SVR). The results obtained indicated that the performance of the developed GANN-BP and COA-SVR models was close to each other and that these models had good agreements with the measured values. These results also showed that these proposed models were suitable tools in evaluating the performance of cutting machines.

Effect of Base Width and Stiffness of the Structure on Period of Vibration of RC Framed Buildings in Seismic Analysis

Fundamental natural period of vibration T of the building is an important parameter for evaluation of seismic base shear. Empirical equations given in the Indian seismic code for the calculation of the fundamental period of a framed structure, primarily as a function of height, do not consider the effect of stiffness of the structure, base dimensions of the structure, number of panels in both the directions, amount of infill and properties of the infill. The fundamental period can be evaluated using simplified expressions found in codes, which are based on earthquake recordings in existing buildings, laboratory tests, numerical or analytical computations. These technical codes provide expressions which depend on basic parameters such as building height or number of stories. Building periods predicted by these expressions are widely used in practice although it has been observed that there is scope for further improvement in these equations since the height alone is inadequate to explain period variability. It is also known that the period of a RC frame structure differs depending on whether the longitudinal or transverse direction of the structure is considered. The aim of this study is to find the effects of building base width in both the directions, stiffness of the structure etc. and to predict the fundamental period of vibration of reinforced concrete buildings with moment resisting frames (MRF). A few examples of dynamic analysis are presented in this study to show the effect of base dimensions and stiffness of the structure in calculating the time period of the structure. And it is recommended to be incorporated in the formula for evaluating the natural period of vibration of structures.

花岗岩劈裂破坏电磁-震动有效信号重构与混沌特征

电磁辐射、震动监测技术广泛应用于地下工程动力灾害的监测预警,对地下工程的安全高效开发具重要意义。深入研究电磁-震动信号有助于推动岩体监测预警技术的发展,然而当前电磁辐射和震动信号(电磁-震动)分析主要集中于信号的相关性和时频特征,对于花岗岩破裂电磁-震动信号的非线性动力特征研究较少,相关特征尚未明确。基于此,利用经验模态信号(EMD)重构和分形理论相结合的方法,分析了花岗岩劈裂破坏电磁-震动信号的混沌特征,揭示了电磁-震动信号非线性动力特征。研究结果表明:花岗岩劈裂破坏产生的电磁辐射与震动信号在时间上具有较好的一致性,劈裂破坏产生的电磁-震动信号频谱集中在中低频段;花岗岩破坏有效电磁辐射信号的盒维数D_(E)=1.600 6,有效震动信号的盒维数D_(A)=1.594 8,两者频率结构特征高度相似;利用EMD分解重构方法可以获得花岗岩破裂有效电磁辐射与震动信号,使用EMD分解重构去除了高频存在的干扰对花岗岩破裂电磁-震动信号中的混沌特征描述更为精准。有效电磁辐射与震动信号包含的低频、大能量信号比原始信号更多,更能表征微小裂纹扩展;重构后电磁-震动信号的不均匀度相较于初始信号整体有明显的上升,不同能量信号出现的频率关系整体出现下降,重构后的有效电磁-震动信号以低频、大能量信号为主,但震动信号的不均匀程度大于电磁辐射。

磁流变阻尼器振动信号的三谱-关联维研究

研发一种新型的磁流变阻尼器,用专门设计的测试平台测试其动力学特性,通过采集振动过程中的位移信号,建立时间序列的AR三谱模型,采用关联维数定量刻画振动过程中不同工作状态的分形特征。结果表明,在不同工作状态下,三谱切片可以获得信号的非高斯、非线性幅频特性信息,且与振动信号的关联维数存在相关性,对选取磁流变阻尼器最优工作参数有重要的意义。

车辆-轨道-桥梁空间耦合振动引起的环境振动

首先建立了车辆-无碴轨道-桥梁系统空间耦合振动模型,通过随机振动分析得到桥墩墩底反力,然后建立了土体-建筑物的三维有限元模型,并将以上得到的墩底反力作为土体-建筑物三维有限元模型的外部激励。分析结果表明,周围土体振动强度随距离的增加而减小,且都存在反弹区;周围建筑物的振动强度随桥墩距离的增大而减小,且在建筑物低层横向和竖向振动相差不大,但是到了高层处横向振动明显大于竖向振动。

轴向运动体系非线性振动分析的多元L-P方法

采用多元L-P方法分析轴向运动体系的非线性振动。根据哈密顿原理建立梁的横向运动微分方程,利用Galerkin方法离散运动方程。研究了轴向运动梁在强迫力作用下的内部共振问题,获得了反映内部共振复杂的频率—振幅响应曲线。算例表明推广的多元L-P法是一个适合于轴向运动体系非线性振动分析的好的定量方法。

基于关联维数G-P算法的齿轮故障诊断

基于关联维数的齿轮故障诊断方法,通过研究关联维数的G-P算法,确定嵌入维数这一重要参数,由此计算齿轮在不同状态下的振动信号的关联维数。最后发现嵌入维数逐渐增大时,关联维数趋于稳定,而且不同状态下的关联维数明显不同。

热-机载荷作用下弹性梁大振幅振动的混沌响应

考虑几何非线性和外阻尼效应,导出弹性梁大振幅振动的动力学控制方程,研究两端不可移简支梁在横向周期载荷和非均匀热载荷共同作用下的混沌运动.采用Galerkin变分原理将问题的非线性偏微分方程转化为二自由度的Hamilton系统,由Melnikov方法解析给出系统发生混沌运动的临界条件;数值计算出Lyapunov指数和分形维数,并绘制出反映系统运动特征的相平面图、位移波形图以及功率谱图,分析梁的非线性动力学行为.结果表明,在热轴力大于临界值后梁的运动会呈现混沌性态.

新型InSb-In薄膜磁阻式振动传感器的设计

介绍了一种用InSbIn共晶体薄膜磁敏元件制成的准全方位振动传感器。它由两对对称轴方向互相垂直的InSbIn磁敏元件构成,可将检测方位范围由一维扩展到现在的二维平面,并用单片机P87LPC760对传感器信号进行处理,应用中可提高检测信号的准确性。经实测,在机械振动的中低频率检测范围内,传感器的有效频带不窄于4～760Hz,其通频带内信噪比为30～32dB,经换算得灵敏度为16mV/gn。同时,得到传感器振动强度大小与磁敏电阻器输出信号关系曲线。

缸套-活塞间隙与振动信号关联维数的关系评价

利用发动机气缸套振动信号特征评价气缸套-活塞组件磨损状态,建立了发动机气缸套、活塞、曲柄和连杆机构的动力学模型并进行了动力学仿真.然后又进行了气缸套表面振动分析,并对所得到的振动模拟信号进行了基于关联维数的信号特征评价.结果表明,随气缸套-活塞组件磨损间隙的增加,振动信号幅值增大,气缸套表面振动加速度信号的自相关程度变大,气缸套表面振动信号的关联维数有下降的趋势,这些关联性可以作为发动机气缸套-活塞组件磨损状态评价的特征量.