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非线性 2

RLC网络；谐振性质；振荡特性；幅频特性 1

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圆柱 1

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Investigation of vortical flows over oscillating body using fast Lagrangian vortex method

Baoshan ZHU ,

《能源前沿（英文）》 2009年第3卷第3期页码 297-306 doi: 10.1007/s11708-009-0010-4

摘要： A computational method facilitating long-time and high-resolution unsteady vortical flows is developed with the advantages of the discrete vortex methods. Both the velocity and pressure distribution of the flow field are calculated by integral formulations in combination with a fast summation algorithm. The vorticity field is described by Lagrangian representation, which is well suited to the moving boundary. Viscosity diffusion of the vorticity is considered with the core spreading model corrected by an adaptive splitting and merging algorithm. The effectiveness of the present method is examined by comparing the numerical results of unsteady separated flows which pass a cylinder and a thin cambered blade undergoing rotational oscillations with available experimental results. Interesting results about vortex shedding patterns and lock-in characteristics are provided for the thin cambered blade.

关键词： unsteady vortical flows fast vortex method vortex shedding rotational oscillation thin cambered blade

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Bending and rotational behaviour of semi-continuous composite beams

WANG Jingfeng, LI Guoqiang

《结构与土木工程前沿（英文）》 2008年第2卷第2期页码 116-122 doi: 10.1007/s11709-008-0015-9

摘要： Stresses and deflections were measured in various semi-continuous composite beams. The bending and rotational capacities of the composite connections were measured in terms of beam curvatures and deflections by using two full-scale semi-rigid composite frames with monotonic loadings. The effect of semi-rigid connections on the performance of composite beams with various loadings was compared with predictions and codes. The tests show that the semi-continuous composite beams are more economic and effective than the simple or continuous composite beams. The semi-rigid connections affect the bending capacities and beam deflections, so the connection behavior should be considered in the design of composite beams. Yielding analysis of the steel beam bottom flange has some influence on the deflection calculation of composite beams.

关键词： rotational effective deflection calculation semi-continuous composite full-scale semi-rigid

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properties of friction stir welded aluminum alloy joints based on axial force, traverse speed, and rotational

Biranchi PANDA,A. GARG,Zhang JIAN,Akbar HEIDARZADEH,Liang GAO

《机械工程前沿（英文）》 2016年第11卷第3期页码 289-298 doi: 10.1007/s11465-016-0393-y

摘要：

Friction stir welding (FSW) process has gained attention in recent years because of its advantages over the conventional fusion welding process. These advantages include the absence of heat formation in the affected zone and the absence of large distortion, porosity, oxidation, and cracking. Experimental investigations are necessary to understand the physical behavior that causes the high tensile strength of welded joints of different metals and alloys. Existing literature indicates that tensile properties exhibit strong dependence on the rotational speed, traverse speed, and axial force of the tool that was used. Therefore, this study introduces the experimental procedure for measuring tensile properties, namely, ultimate tensile strength (UTS) and tensile elongation of the welded AA 7020 Al alloy. Experimental findings suggest that a welded part with high UTS can be achieved at a lower heat input compared with the high heat input condition. A numerical approach based on genetic programming is employed to produce the functional relationships between tensile properties and the three inputs (rotational speed, traverse speed, and axial force) of the FSW process. The formulated models were validated based on the experimental data, using the statistical metrics. The effect of the three inputs on the tensile properties was investigated using 2D and 3D analyses. A high UTS was achieved, including a rotational speed of 1050 r/min and traverse speed of 95 mm/min. The results also indicate that 8 kN axial force should be set prior to the FSW process.

关键词： tensile properties ultimate tensile strength tensile elongation friction stir welding tool rotational speed genetic programming welding speed

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Numerical analysis of strongly nonlinear oscillation systems using He’s max-min method

H. BABAZADEH, G. DOMAIRRY, A. BARARI, R. AZAMI, A. G. DAVODI

《机械工程前沿（英文）》 2011年第6卷第4期页码 435-441 doi: 10.1007/s11465-011-0243-x

摘要：

Nonlinear functions are crucial points and terms in engineering problems. Actual and physical problems can be solved by solving and processing such functions. Thus, most scientists and engineers focus on solving these equations. This paper presents a novel method called the max-min method for presenting an accurate approximate analytical solution to strong nonlinear oscillators. It can solve many linear or nonlinear differential equations without the tangible restriction of sensitivity to the degree of the nonlinear term. It is also quite convenient due to the reduction in the size of calculations. The algorithm suggests a promising approach and is systematically illustrated step by step.

关键词： min-max method nonlinear oscillation duffing equation mathematical pendulum He’s energy balance method

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Parametric oscillation of cables and aerodynamic effect

Yong XIA, Jing ZHANG, Youlin XU, Yozo FUJINO,

《结构与土木工程前沿（英文）》 2010年第4卷第3期页码 321-325 doi: 10.1007/s11709-010-0028-z

摘要： This paper addresses the aerodynamic effect on the nonlinear oscillation, particularly parametric vibration of cables in cable-stayed bridges. A simplified 2-DOF model, including a beam and a stayed cable, is formulated first. Response of the cable under global harmonic excitation which is associated with wind speed is obtained using the multiple scales method. Via numerical analysis, the stability condition of the cable in terms of wind speed is derived. The method is applied to a numerical example and a long-span bridge to analyze its all stay cables. It is demonstrated that very large vibration at one of the longest cables in the middle span of the bridge can be parametrically excited when the wind speed is over around 210 km/h (58.5 m/s).

关键词： parametric vibration cables cable-stayed bridge nonlinear vibration

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Evaluation of the influence of El Niño–Southern Oscillation on air quality in southern China from long-term

《环境科学与工程前沿（英文）》 2022年第16卷第2期 doi: 10.1007/s11783-021-1460-0

摘要：

•Strong ENSO influence on AOD is found in southern China region.

关键词： El Niño–Southern Oscillation Aerosol concentration Aerosol particle size Contribution separation Decadal trend Southern China

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Design and analysis of a class of redundant collaborative manipulators with 2-dimension large rotational

Xiaodong JIN, Yuefa FANG, Dan ZHANG, Xueling LUO

《机械工程前沿（英文）》 2020年第15卷第1期页码 66-80 doi: 10.1007/s11465-019-0570-x

摘要： The parallel spindle heads with high rotational capability are demanded in the area of multi-axis machine tools and 3D printers. This paper focuses on designing a class of 2R1T (R: Rotation; T: Translation) parallel spindle heads and the corresponding collaborative 5-axis manipulators with 2-dimension (2D) large rotational angles. In order to construct 2D rotational degrees of freedom (DOF), a platform with 2-dimension revolute joints is proposed first. Based on the constraint screw theory, the feasible limbs that can be connected in the platform are synthesized. In order to provide constant rotational axis for the platform, a class of redundant limbs are designed. A class of redundant 2R1T parallel spindle heads is obtained by connecting the redundant limbs with the platform and the redundant characteristics are verified by the modified Grübler-Kutzbach criterion. The corresponding 5-axis collaborative manipulators are presented by constructing a 2-DOF series translational bottom moving platform. The inverse kinematics and the orientation workspace as well as the decoupling characteristics of this type of 2R1T parallel spindle heads are analyzed. The results show that these manipulators have large 2D rotational angles than the traditional A3/Z3 heads and can be potentially used in the application of multi-axis machine tools and the 3D printers.

关键词： parallel mechanism redundant mechanism large rotational angles machine tools 2R1T spindle head collaborative manipulator

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Soft curvature sensors for measuring the rotational angles of mechanical fingers

Haixiao LIU, Li LI, Zhikang OUYANG, Wei SUN

《机械工程前沿（英文）》 2020年第15卷第4期页码 610-621 doi: 10.1007/s11465-020-0596-0

摘要： The design, fabrication, and testing of soft sensors that measure elastomer curvature and mechanical finger bending are described in this study. The base of the soft sensors is polydimethylsiloxane (PDMS), which is a translucent elastomer. The main body of the soft sensors consists of three layers of silicone rubber plate, and the sensing element is a microchannel filled with gallium-indium-tin (Ga-In-Sn) alloy, which is embedded in the elastomer. First, the working principle of soft sensors is investigated, and their structure is designed. Second, the relationship between curvature and resistance is determined. Third, several sensors with different specifications are built in accordance with the structural design. Experiments show that the sensors exhibit high accuracy when the curvature changes within a certain range. Lastly, the soft sensors are applied to the measurement of mechanical finger bending. Experiments show that soft curvature sensors can effectively reflect mechanical finger bending and can be used to measure the bending of mechanical fingers with high sensitivity within a certain working range.

关键词： soft sensor Ga-In-Sn alloy strain sensing curvature sensing mechanical finger bending

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混沌工程学

龙运佳

《中国工程科学》 2001年第3卷第2期页码 10-15

摘要：

世界是非线性的，线性只是其近似描述，混沌的发现表明：某些确定性非线性系统具有内在的随机行为。事实上，以往20年，无所不在的混沌现象几乎在每个学科都有所报道，如数学、物理学、化学，甚至社会科学。但理论研究学者的主要兴趣在于探究混沌的本质。与此同时，混沌的实际利用在许多工程领域受到重视，如信息工程、系统工程、医药工程、农业工程、电气工程、生物工程、机械工程、土木工程等。混沌工程学是一门新的研究混沌实际利用及其基本理论的非线性工程科学。文章对现代混沌工程学的定义、对象、概念、方法、理论与应用加以总结，并介绍其近来的进展及作者的工作。混沌工程学在国民经济与国防建设中研究的热点是：混沌分析技术，混沌控制技术与混沌生成技术。

关键词：非线性混沌振荡振动波

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一种新型转子式陀螺的分辨率为0.47″的转子微偏转角度检测方法 Article

Hai LI, Xiao-wei LIU, Rui WENG, Hai-feng ZHANG

《信息与电子工程前沿（英文）》 2017年第18卷第5期页码 591-598 doi: 10.1631/FITEE.1500454

摘要：差分电容检测被广泛应用于振动陀螺仪质量块的位移测量，然而由于结构、理论以及接口电路等因素的限制其在转子式陀螺所需的转子偏转角度检测方面还尚未取得较高分辨率。本文提出了一种差分电容检测结构，用以测量一种新型转子式陀螺转子的偏转角度。本文建立了结构电容与转子偏转角度之间关系的数学模型，分析了差分电容与结构参数之间的关系，并获得了初步优化的尺寸参数。设计了一款低噪声读出接口电路将差分电容的变化转换为电压信号。对陀螺仪的转台测试结果表明，该角度检测结构的最小可分辨的偏转角度小于0.47″（0.00013°），三次多项式补偿后检测结构的非线性可达0.33%，并可进一步提高。结果表明该检测结构和电路有助于实现该陀螺仪的高精度。

关键词：微角度检测；差分电容结构；转子式陀螺

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Development of an analytical model to estimate the churning losses in high-speed axial piston pumps

《机械工程前沿（英文）》 2022年第17卷第2期 doi: 10.1007/s11465-021-0671-1

摘要： The axial piston pumps in aerospace applications are often characterized by high-speed rotation to achieve great power density. However, their internal rotating parts are fully immersed in the casing oil during operation, leading to considerable churning losses (more than 10% of total power losses) at high rotational speeds. The churning losses deserve much attention at the design stage of high-speed axial piston pumps, but accurate analytical models are not available to estimate the drag torque associated with the churning losses. In this paper, we derive the analytical expressions of the drag torque acting on the key rotating parts immersed in oil, including the cylinder block and the multiple pistons in a circular array. The calculated drag torque agrees well with the experimental data over a wide range of rotational speeds from 1500 to 12000 r/min. The presented analytical model provides practical guidelines for reducing the churning losses in high-speed axial piston pumps or motors.

关键词： axial piston pump rotating parts high rotational speed churning losses drag torque

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Scrutiny of non-linear differential equations Euler-Bernoulli beam with large rotational deviation by

M. R. AKBARI,M. NIMAFAR,D. D. GANJI,M. M. AKBARZADE

《机械工程前沿（英文）》 2014年第9卷第4期页码 402-408 doi: 10.1007/s11465-014-0316-8

摘要：

The kinematic assumptions upon which the Euler-Bernoulli beam theory is founded allow it to be extended to more advanced analysis. Simple superposition allows for three-dimensional transverse loading. Using alternative constitutive equations can allow for viscoelastic or plastic beam deformation. Euler-Bernoulli beam theory can also be extended to the analysis of curved beams, beam buckling, composite beams and geometrically nonlinear beam deflection. In this study, solving the nonlinear differential equation governing the calculation of the large rotation deviation of the beam (or column) has been discussed. Previously to calculate the rotational deviation of the beam, the assumption is made that the angular deviation of the beam is small. By considering the small slope in the linearization of the governing differential equation, the solving is easy. The result of this simplification in some cases will lead to an excessive error. In this paper nonlinear differential equations governing on this system are solved analytically by Akbari-Ganji’s method (AGM). Moreover, in AGM by solving a set of algebraic equations, complicated nonlinear equations can easily be solved and without any mathematical operations such as integration solving. The solution of the problem can be obtained very simply and easily. Furthermore, to enhance the accuracy of the results, the Taylor expansion is not needed in most cases via AGM manner. Also, comparisons are made between AGM and numerical method (Runge-Kutta 4th). The results reveal that this method is very effective and simple, and can be applied for other nonlinear problems.

关键词： AGM critical load of columns large deformations of beam nonlinear differential equation

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Vibratory behaviors of Jeffcott system on cylindrical roller bearings

Hao WU, Jianwen WANG, Qi AN

《机械工程前沿（英文）》 2009年第4卷第3期页码 305-309 doi: 10.1007/s11465-009-0036-7

摘要： A Jeffcott rotor system of cylindrical roller bearings is studied in detail. Its critical speed is calculated by a new calculation method with roller bearing stiffness and damping. The influences of bearing parameters, such as the roller length, rotor mass, distance between the bearings and the kinematics viscosity of oil on the system critical speed are numerically studied, and the influences of an oil film and damping on the critical speed are also studied. Regular curves of the relationship between the geometric parameters and the system critical speed are obtained. The results show that with increasing roller length and radial load, the critical speed increases; and with increasing rotor mass and the distance between the bearings and the kinematics viscosity, the critical speed decreases. This means that an oil film will decrease the critical rotational speed of the rotor system.

关键词： roller bearing bearing-rotor system design value critical rotational speed

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Depth of cut models for multipass abrasive waterjet cutting of alumina ceramics with nozzle oscillation

Jun WANG

《机械工程前沿（英文）》 2010年第5卷第1期页码 19-32 doi: 10.1007/s11465-009-0082-1

摘要： An experimental study of the depth of cut in multipass abrasive waterjet (AWJ) cutting of alumina ceramics with controlled nozzle oscillation is presented. It is found that this cutting technique can significantly increase the depth of cut by an average of 50.8% as compared to single pass cutting without nozzle oscillation under the corresponding cutting conditions and within the same cutting time. Predictive models for the depth of cut are then developed. The modelling process starts with single pass cutting using a dimensional analysis technique and the particle erosion theories applied to alumina ceramics, before progressing to the development of the models for multipass cutting. The models are finally assessed both qualitatively and quantitatively with experimental data. It is shown that the model predictions are in good agreement with the experimental data with the average deviations of about 1%.

关键词： abrasive waterjet engineering ceramics depth of cut cutting performance nozzle oscillation machining

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Oscillation frequency of simplified arterial tubes

Hui AN, Fan HE, Lingxia XING, Xiaoyang LI

《机械工程前沿（英文）》 2009年第4卷第3期页码 300-304 doi: 10.1007/s11465-009-0038-5

摘要： To construct the spatial kinetic equation of an arterial tube and obtain its radial natural frequency, a linear-elastic and small deformation condition is assumed. The theoretical analysis is first presented and the finite element method is then used to numerically simulate the spatial kinematics. The results show that the first-order frequency is 15.8 Hz and the obtained exact analytical solutions agree well with numerical solutions, which proves that the theoretical analysis and numerical simulation are both correct.

关键词： spatial kinematics natural frequency finite element method