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分析滤波器；线性预测；窄带语音水印；通带激励替代；能量规范化；谱包络成形；合成滤波器 1

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Stability and dynamics of rotor system with 45° slant crack on shaft

Yanli LIN, Xiaohui SI, Fulei CHU

《机械工程前沿（英文）》 2011年第6卷第2期页码 203-213 doi: 10.1007/s11465-011-0131-4

摘要：

Crack on a shaft is one of the common damages in a rotor system. In this paper, transverse vibrations are calculated to compare the influences of transverse crack and slant crack on the rotor system. Results show that the vibration amplitude of the rotor system with a 45° slant crack on the shaft is larger than that with a transverse crack when the two types of crack have the same depth and the rotor system runs in the same condition. Stability and dynamic characteristics of the rotor system with a 45° slant crack on the shaft under torsional excitation are analyzed by considering opening and closing of the crack. It is shown that the instability of the transverse vibration of the rotor system increases with increasing difference between the bending stiffness in two main directions, and the vibration is stable when the two bending stiffness are identical. The spectrum analysis of the steady-state response reveals that the gravity and the eccentricity produce different frequency components, and when the two bending stiffness are identical, the multiple frequency components of the torsional excitation disappear. Further investigation shows that the vibration amplitudes in combined frequencies increase rapidly in transversal, torsional, and axial vibration with increasing slant crack depth. The results are helpful for the understanding the dynamic behavior of a rotor system with a slant crack on a shaft and can be used for the detection of the slant crack on a shaft.

关键词： rotor dynamics slant crack stability torsional excitation open and close

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Mechanism of self-excited torsional vibration of locomotive driving system

Jianxin LIU, Huaiyun ZHAO, Wanming ZHAI

《机械工程前沿（英文）》 2010年第5卷第4期页码 465-469 doi: 10.1007/s11465-010-0115-9

摘要： A single wheelset drive model and 2-DOFs torsional vibration model were established to investigate the self-excited torsional vibration of a locomotive driving system. The simulation results indicate that the self-excited torsional vibration occurs when the steady slip velocity is located at the descending slope of the adhesion coefficient curve. The principle of energy conservation was used to analyze the mechanism of the self-excited vibration. The factors affecting on the amplitude of the self-excited vibration are studied.

关键词： locomotive driving system self-excited torsional vibration mechanism influence factor

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Approximation of structural damping and input excitation force

Mohammad SALAVATI

《结构与土木工程前沿（英文）》 2017年第11卷第2期页码 244-254 doi: 10.1007/s11709-016-0371-9

摘要： Structural dynamic characteristics are the most significant parameters that play a decisive role in structural damage assessment. The more sensitive parameter to the damage is the damping behavior of the structure. The complexity of structural damping mechanisms has made this parameter to be one of the ongoing research topics. Despite all the difficulties in the modeling of damping, there are some approaches like as linear and nonlinear models which are described as the energy dissipation throughout viscous, material or structural hysteretic and frictional damping mechanisms. In the presence of a mathematical model of the damping mechanisms, it is possible to estimate the damping ratio from the theoretical comparison of the damped and un-damped systems. On the other hand, solving the inverse problem of the input force estimation and its distribution to each SDOFs, from the measured structural responses plays an important role in structural identification process. In this paper model-based damping approximation method and a model-less structural input estimation are considered. The effectiveness of proposed methods has been carried out through analytical and numerical simulation of the lumped mass system and the results are compared with reference data. Consequently, high convergence of the comparison results illustrates the satisfactory of proposed approximation methods.

关键词： structural modal parameters damping identification method input excitation force identification Inverse problem

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Flexural-torsional buckling behavior of aluminum alloy beams

Xiaonong GUO,Zhe XIONG,Zuyan SHEN

《结构与土木工程前沿（英文）》 2015年第9卷第2期页码 163-175 doi: 10.1007/s11709-014-0272-8

摘要： This paper presents an investigation on the flexural-torsional buckling behavior of aluminum alloy beams (AAB). First, based on the tests of 14 aluminum alloy beams under concentrated loads, the failure pattern, load-deformation curves, bearing capacity and flexural-torsional buckling factor are studied. It is found that all the beam specimens collapsed in the flexural-torsional buckling with excessive deformation pattern. Moreover, the span, loading location and slenderness ratio influence the flexural-torsional buckling capacity of beams significantly. Secondly, besides the experiments, a finite element method (FEM) analysis on the flexural-torsional buckling behavior of AAB is also conducted. The main parameters in the FEM analysis are initial imperfection, material property, cross-section and loading scheme. According to the analytical results, it is indicated that the FEM is reasonable to capture mechanical behavior of AAB. Finally, on the basis of the experimental and analytical results, theoretical formulae to estimate the flexural-torsional buckling capacity of AAB are proposed, which could improve the application of present codes for AAB.

关键词： flexural-torsional buckling aluminum alloy beams (AAB) finite element method (FEM) theoretical formula

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A novel structural modification to eliminate the early coupling between bending and torsional mode shapes

Nazim Abdul NARIMAN

《结构与土木工程前沿（英文）》 2017年第11卷第2期页码 131-142 doi: 10.1007/s11709-016-0376-4

摘要： In this paper, a novel structural modification approach has been adopted to eliminate the early coupling between the bending and torsional mode shapes of vibrations for a cable stayed bridge model generated using ABAQUS software. Two lateral steel beams are added to the middle span of the structure. Frequency analysis is dedicated to obtain the natural frequencies of the first eight mode shapes of vibrations before and after the structural modification approach. Numerical simulations of wind excitations are conducted for the 3D model of the cable stayed bridge with duration of 30 s supporting on real data of a strong wind from the literature. Both vertical and torsional displacements are calculated at the mid span of the deck to analyze both the bending and the torsional stiffness of the system before and after the structural modification. The results of the frequency analysis after applying lateral steel beams declared a safer structure against vertical and torsional vibrations and rarely expected flutter wind speed. Furthermore, the coupling between the vertical and torsional mode shapes has been removed to larger natural frequencies magnitudes with a high factor of safety. The novel structural approach manifested great efficiency in increasing vertical and torsional stiffness of the structure.

关键词： aeroelastic instability structural damping flutter wind speed bending stiffness torsional stiffness

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An analytical method for calculating torsional constants for arbitrary complicated thin-walled cross-sections

DU Baisong, GE Yaojun, ZHOU Zheng

《结构与土木工程前沿（英文）》 2007年第1卷第3期页码 293-297 doi: 10.1007/s11709-007-0038-7

摘要： In this paper, an analytical method is proposed for calculating torsional constants for complicated thin-walled cross-sections with arbitrary closed or open rib stiffeners. This method uses the free torsional theory and the principle of virtual work to build governing equilibrium equations involving unknown shear flows and twisting rate. After changing the form of the equations and combining these two unknowns into one, torsional function, which is a function of shear flow, shear modulus, and twisting rate, is included in the governing equations as only one of the unknowns. All the torsional functions can be easily obtained from these homogeneous linear equations, and torsional constants can be easily obtained from the torsional functions. The advantage of this method is that we can easily and directly obtain torsional constants from the torsional functions, rather than the more sophisticated shear flow and twisting rate calculations. Finally, a complicated thin-walled cross-section is given as a valid numerical example to verify the analytical method, which is much more accurate and simpler than the traditional finite element method.

关键词： homogeneous complicated thin-walled numerical example advantage torsional function

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Lateral-torsional buckling capacity assessment of web opening steel girders by artificial neural networks

Yasser SHARIFI,Sajjad TOHIDI

《结构与土木工程前沿（英文）》 2014年第8卷第2期页码 167-177 doi: 10.1007/s11709-014-0236-z

摘要： Bridge girders exposed to aggressive environmental conditions are subject to time-variant changes in resistance. There is therefore a need for evaluation procedures that produce accurate predictions of the load-carrying capacity and reliability of bridge structures to allow rational decisions to be made about repair, rehabilitation and expected life-cycle costs. This study deals with the stability of damaged steel I-beams with web opening subjected to bending loads. A three-dimensional (3D) finite element (FE) model using ABAQUS for the elastic flexural torsional analysis of I-beams has been used to assess the effect of web opening on the lateral buckling moment capacity. Artificial neural network (ANN) approach has been also employed to derive empirical formulae for predicting the lateral-torsional buckling moment capacity of deteriorated steel I-beams with different sizes of rectangular web opening using obtained FE results. It is found out that the proposed formulae can accurately predict residual lateral buckling capacities of doubly-symmetric steel I-beams with rectangular web opening. Hence, the results of this study can be used for better prediction of buckling life of web opening of steel beams by practice engineers.

关键词： steel I-beams lateral-torsional buckling finite element (FE) method artificial neural network (ANN) approach

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Proposing two new methods to decrease lateral-torsional buckling in reduced beam section connections

Samira EBRAHIMI; Nasrin BAKHSHAYESH EGHBALI; Mohammad Mehdi AHMADI

《结构与土木工程前沿（英文）》 2022年第16卷第12期页码 1581-1598 doi: 10.1007/s11709-022-0886-1

摘要： Reduced web section (RWS) connections can prevent lateral-torsional buckling and web local buckling experienced by reduced beam section (RBS) connections. In RWS connections, removing a large portion of web can result in shear demand intolerance induced to plastic hinge region. The present study aims to resolve the problems of RBS and RWS connections by proposing two new connections: (1) RBS with stiffener (RBS-ST) and (2) RBS with reduced web (RW-RBS) connections. In the first connection (RBS-ST), a series of stiffeners is connected to the beam in the reduced flange region, while the second connection (RW-RBS) considers both a reduction in flanges and a reduction in web. Five beam-to-column joints with three different connections, including RBS, RBS-ST, and RW-RBS connections were considered and simulated in ABAQUS. According to the results, RBS-ST and RW-RBS connections can decrease or even eliminate lateral-torsional buckling and web local buckling in RBS connection. It is important to note that RW-RBS connection is more effective in long beams with smaller shear demands in the plastic hinge region. Moreover, results showed that RBS and RW-RBS connections experienced strength degradation at 4% to 5% drift, while no strength degradation was observed in RBS-ST connection until 8% drift.

关键词： RBS RBS-ST RW-RBS lateral-torsional buckling cyclic performance

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Hole quality in longitudinal–torsional coupled ultrasonic vibration assisted drilling of carbon fiber

Guofeng MA, Renke KANG, Zhigang DONG, Sen YIN, Yan BAO, Dongming GUO

《机械工程前沿（英文）》 2020年第15卷第4期页码 538-546 doi: 10.1007/s11465-020-0598-y

摘要： Carbon fiber reinforced plastic (CFRP) composites are extremely attractive in the manufacturing of structural and functional components in the aircraft manufacturing field due to their outstanding properties, such as good fatigue resistance, high specific stiffness/strength, and good shock absorption. However, because of their inherent anisotropy, low interlamination strength, and abrasive characteristics, CFRP composites are considered difficult-to-cut materials and are prone to generating serious hole defects, such as delamination, tearing, and burrs. The advanced longitudinal–torsional coupled ultrasonic vibration assisted drilling (LTC-UAD) method has a potential application for drilling CFRP composites. At present, LTC-UAD is mainly adopted for drilling metal materials and rarely for CFRP. Therefore, this study analyzes the kinematic characteristics and the influence of feed rate on the drilling performance of LTC-UAD. Experimental results indicate that LTC-UAD can reduce the thrust force by 39% compared to conventional drilling. Furthermore, LTC-UAD can decrease the delamination and burr factors and improve the surface quality of the hole wall. Thus, LTC-UAD is an applicable process method for drilling components made with CFRP composites.

关键词： longitudinal–torsional coupled ultrasonically drilling CFRP thrust force hole quality

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Torsional vibrations of a cylindrical foundation embedded in a saturated poroelastic half-space

Dazhi WU,Lu YU

《结构与土木工程前沿（英文）》 2015年第9卷第2期页码 194-202 doi: 10.1007/s11709-015-0292-z

摘要： Considering the interactions between an embedded foundation and saturated soil, the torsional vibrations of a cylindrical foundation embedded in a saturated poroelastic medium are analyzed in this paper. Both a rigid foundation and an elastic foundation are considered. Assuming both the side surface and the bottom surface of the foundation are perfectly bonded to soil, the reaction torques that the side soil and bottom soil acting on the foundation can be gained from basic dynamic equations of the poroelastic medium. According to the dynamic equilibrium equations of a foundation under harmonic torque, the torsional vibrations of an embedded cylindrical foundation are presented. Besides, the angular amplitude of the foundation, the equivalent stiffness and damping coefficients of the soil are expressed explicitly. Selected examples are presented to investigate the influence of relevant parameters on the torsional vibrations.

关键词： embedded foundation saturated soil rigid foundation elastic foundation torsional vibration

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同步发电机励磁系统中PWM控制的仿真研究

贾贵玺,徐伟,郭宝钥,张臣堂

《中国工程科学》 2005年第7卷第6期页码 50-53

摘要：

优良的励磁控制系统不仅可以保证发电机运行的可靠性和稳定性，而且可有效地提髙发电机和电力系统技术指标。同步发电机励磁系统采用了PWM整流技术，实现励磁电流低谐波和励磁功率单元高功率因数转换，提高了发电机供电质量，并用MATLAB对设计系统做出仿真验证，证明该设计对改善发电机输出电压、提高功率单元电能利用率有明显效果。

关键词： PWM 高功率因数励磁系统 Matlab仿真

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Sensitivity analysis of torsional vibration behavior of the shafting of a turbo generator set to changes

XIE Danmei, ZHANG Hengliang, DONG Chuan, LIU Zhanhui, YANG Changzhu

《能源前沿（英文）》 2007年第1卷第4期页码 483-486 doi: 10.1007/s11708-007-0072-4

摘要： Aiming at a 300 MW turbo-generator model, the sensitivity of natural torsional frequencies and modes of torsional vibration (TV) to the rotational inertia and stiffness of the turbo-generator were analyzed. Calculation results show

关键词： Calculation MW turbo-generator sensitivity stiffness

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一种基于子带激励替换的窄带语音水印算法 Article

Wei LIU, Ai-qun HU

《信息与电子工程前沿（英文）》 2017年第18卷第5期页码 627-643 doi: 10.1631/FITEE.1601503

摘要：本文建议了一种新的窄带语音水印算法，该算法将部分语音信号替换为一个经过幅度调节和频谱成形的隐蔽信号。文中从理论上证明了若仅对一小部分载体语音作修改，则不但可以建立一个用于隐蔽通信的理想信道模型，而且还能确保隐藏信号的不可感知性和带水印信号的可懂度。在此基础上，文中建议了一个实际的系统模型。在嵌入器中，使用了能量规范化准则，使得通带水印信号的能量与原始通带语音激励信号的能量相等，然后使用合成滤波器来对该水印信号进行频谱成形。在提取器中，先用带通滤波器去除带外信号，然后用分析滤波器对失真进行补偿。实验结果显示，本文建议算法的数据速率可达400 bits/s，具有更佳的带宽效率，且有良好的不可感知性。此外，该算法对实际应用中的各种攻击也是顽健的。

关键词：分析滤波器；线性预测；窄带语音水印；通带激励替代；能量规范化；谱包络成形；合成滤波器

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Control of wind-induced vibration of long-span bridges and tall buildings

GU Ming

《结构与土木工程前沿（英文）》 2007年第1卷第1期页码 51-62 doi: 10.1007/s11709-007-0005-3

摘要： With the rapid increase in scales of structures, research on controlling wind-induced vibration of large-scale structures, such as long-span bridges and super-tall buildings, has been an issue of great concern. For wind-induced vibration of large-scale structures, vibration frequencies and damping modes vary with wind speed. Passive, semiactive, and active control strategies are developed to improve the wind-resistance performance of the structures in this paper. The multiple tuned mass damper (MTMD) system is applied to control vertical bending buffeting response. A new semiactive lever-type tuned mass damper (TMD) with an adjustable frequency is proposed to control vertical bending buffeting and torsional buffeting and flutter in the whole velocity range of bridge decks. A control strategy named sinusoidal reference strategy is developed for adaptive control of wind-induced vibration of super-tall buildings. Multiple degrees of freedom general building aeroelastic model with a square cross-section is tested in a wind tunnel. The results demonstrate that the proposed strategies can reduce vibration effectively, and can adapt to wind-induced vibration control of large-scale structures in the uncertain dynamic circumstance.

关键词： torsional buffeting large-scale semiactive adjustable frequency building aeroelastic

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Excitation-emission matrix (EEM) fluorescence spectroscopy for characterization of organic matter in

Jinlan Yu, Kang Xiao, Wenchao Xue, Yue-xiao Shen, Jihua Tan, Shuai Liang, Yanfen Wang, Xia Huang

《环境科学与工程前沿（英文）》 2020年第14卷第2期 doi: 10.1007/s11783-019-1210-8

摘要： • Principles and methods for fluorescence EEM are systematically outlined. • Fluorophore peak/region/component and energy information can be extracted from EEM. • EEM can fingerprint the physical/chemical/biological properties of DOM in MBRs. • EEM is useful for tracking pollutant transformation and membrane retention/fouling. • Improvements are still needed to overcome limitations for further studies. The membrane bioreactor (MBR) technology is a rising star for wastewater treatment. The pollutant elimination and membrane fouling performances of MBRs are essentially related to the dissolved organic matter (DOM) in the system. Three-dimensional excitation-emission matrix (3D-EEM) fluorescence spectroscopy, a powerful tool for the rapid and sensitive characterization of DOM, has been extensively applied in MBR studies; however, only a limited portion of the EEM fingerprinting information was utilized. This paper revisits the principles and methods of fluorescence EEM, and reviews the recent progress in applying EEM to characterize DOM in MBR studies. We systematically introduced the information extracted from EEM by considering the fluorescence peak location/intensity, wavelength regional distribution, and spectral deconvolution (giving fluorescent component loadings/scores), and discussed how to use the information to interpret the chemical compositions, physiochemical properties, biological activities, membrane retention/fouling behaviors, and migration/transformation fates of DOM in MBR systems. In addition to conventional EEM indicators, novel fluorescent parameters are summarized for potential use, including quantum yield, Stokes shift, excited energy state, and fluorescence lifetime. The current limitations of EEM-based DOM characterization are also discussed, with possible measures proposed to improve applications in MBR monitoring.

关键词： excitation-emission matrix (EEM) dissolved organic matter (DOM) membrane bioreactor (MBR) fluorescence indicator characterization method