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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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Stability analysis of large diameter thin-walled tube beam-columns

PAN Hanming, GUO Yanlin, LIANG Shuo, PEI Shengxing, LIANG Weisheng, WANG Lewen

《结构与土木工程前沿（英文）》 2008年第2卷第2期页码 123-132 doi: 10.1007/s11709-008-0017-7

摘要： Based on a blind spot in the current design standard of steel structures, the large diameter thin-walled tube beam-columns are analyzed using nonlinear finite element method in this paper. The influence of several factors on stability capacity of the large diameter thin-walled tube beam-columns is taken into account. Thus, according to the correlative design standard of steel structures, and on the basis of the numerical analytical results by the finite element methods, the calculation formulas of the stability bearing capacity are presented for beam-column members of the large diameter thin-walled tubes. Three tests of thin-walled steel tube beam-columns were reported. Test results for deformations and ultimate strength are found to be in a good agreement with the corresponding values predicted by the calculation formulas, and the proposed methods can be used in design practice.

关键词： ultimate strength nonlinear numerical analytical diameter thin-walled practice

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Laser interference fabrication of large-area functional periodic structure surface

Lei WANG, Zi-Han WANG, Yan-Hao YU, Hong-Bo SUN

《机械工程前沿（英文）》 2018年第13卷第4期页码 493-503 doi: 10.1007/s11465-018-0507-9

摘要：

Functional periodic structures have attracted significant interest due to their natural capabilities in regulating surface energy, surface effective refractive index, and diffraction. Several technologies are used for the fabrication of these functional structures. The laser interference technique in particular has received attention because of its simplicity, low cost, and high-efficiency fabrication of large-area, micro/nanometer-scale, and periodically patterned structures in air conditions. Here, we reviewed the work on laser interference fabrication of large-area functional periodic structures for antireflection, self-cleaning, and superhydrophobicity based on our past and current research. For the common cases, four-beam interference and multi-exposure of two-beam interference were emphasized for their setup, structure diversity, and various applications for antireflection, self-cleaning, and superhydrophobicity. The relations between multi-beam interference and multi-exposure of two-beam interference were compared theoretically and experimentally. Nanostructures as a template for growing nanocrystals were also shown to present future possible applications in surface chemical control. Perspectives on future directions and applications for laser interference were presented.

关键词： laser interference four-beam interference multi-exposure of two-beam interference additive fabrication

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大孔径光纤过渡器中光波特性分析

王云明,孙小菡,张明德

《中国工程科学》 2002年第4卷第10期页码 52-56

摘要：

提出了基于束传输法（BPM）的大孔径光纤锥形过渡器理论分析模型。讨论了过渡器在纵向边界线性和非线性情况下（包括类似正弦型和余弦型变化），分别以大小端作为输入端口，耦合角度以及耦合长度对过渡器的损耗和耦合效率的影响，得出了过渡器最佳纵向边界、耦合角度和耦合长度。

关键词：束传输法（BPM）大孔径光纤锥形过渡器插入损耗

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步行激励下大跨度钢-混凝土空心板组合梁振动舒适度研究 Article

刘界鹏, 黄鉥, 李江, Y. Frank Chen

《工程（英文）》 2022年第19卷第12期页码 93-104 doi: 10.1016/j.eng.2021.04.025

摘要：

大跨度预制钢-混凝土空心板组合梁（CBHCS）是一种新型的楼板结构，可用于各种大跨度结构。然而，人为引起的振动会对此类结构的使用产生影响。为了减轻振动，需要探究由人引起的步行力与楼板状态之间的关系。本文首先使用测力板获取了25 名测试者的150 个步行力，确定了单步行走的傅里叶级数中的动态载荷系数和相位角。其次，对7 个CBHCS试样进行了行走测试，获取了模态振型、固有频率、阻尼比和加速度等基本动态特性。CBHCS楼板系统通常表现出高频（>10 Hz）和低阻尼（阻尼比低于2%）的特性。本文还使用有限元方法进行了灵敏度研究，以研究CBHCS楼板系统的振动性能，考虑了楼板厚度、
钢梁类型、接触时间和人体重量。最后，本文推导了基频和峰值加速度的解析表达式，与实验结果吻合较好，具有实际的应用价值。

关键词：组合梁空心板步行力楼板振动模态振型

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Scaling up of cluster beam deposition technology for catalysis application

《化学科学与工程前沿（英文）》 2021年第15卷第6期页码 1360-1379 doi: 10.1007/s11705-021-2101-7

摘要： Many research works have demonstrated that the combination of atomically precise cluster deposition and theoretical calculations is able to address fundamental aspects of size-effects, cluster-support interactions, and reaction mechanisms of cluster materials. Although the wet chemistry method has been widely used to synthesize nanoparticles, the gas-phase synthesis and size-selected strategy was the only method to prepare supported metal clusters with precise numbers of atoms for a long time. However, the low throughput of the physical synthesis method has severely constrained its wider adoption for catalysis applications. In this review, we introduce the latest progress on three types of cluster source which have the most promising potential for scale-up, including sputtering gas aggregation source, pulsed microplasma cluster source, and matrix assembly cluster source. While the sputtering gas aggregation source is leading ahead with a production rate of ~20 mg·h^–1, the pulsed microplasma source has the smallest physical dimensions which makes it possible to compact multiple such devices into a small volume for multiplied production rate. The matrix assembly source has the shortest development history, but already show an impressive deposition rate of ~10 mg·h^–1. At the end of the review, the possible routes for further throughput scale-up are envisaged.

关键词： nanoparticle cluster cluster beam deposition magnetron sputtering heterogeneous catalysis

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面向精密增材制造的大范围柔性伺服系统

Zhen Zhang, Peng Yan, Guangbo Hao

《工程（英文）》 2017年第3卷第5期页码 708-715 doi: 10.1016/J.ENG.2017.05.020

摘要：

本文主要介绍可用于微立体光固化（MSL）工艺的基于分布柔度簧片的大范围柔性纳米伺服系统的设计、开发和控制。作为这一高精度工艺的使能技术，本文设计了一种兼具毫米级运动行程和纳米级运动精度的紧凑型台式柔性纳米运动系统。由于在运行中无需装配和维护，这种柔性运动系统非常适合苛刻的操作条件。从机械设计的角度来看，镜像对称布局和适当的冗余约束对于抑制寄生运动至关重要。本文对此系统进行了详细的有限元分析（FEA），分析结果表面系统具有满意的机械特征。通过纳米运动系统的动力学模型辨识，本文设计了实时控制策略，并将其应用在一体加工的原型系统中。实验验证了面向MSL 工艺过程的轨迹跟踪性能。所提出的纳米伺服运动系统具有毫米级的工作范围，圆轨迹跟踪误差约为80 nm（均方根值）。

关键词：精密增材制造微立体光固化纳米定位分布柔度簧片

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Processing parameter optimization of fiber laser beam welding using an ensemble of metamodels and MOABC

《机械工程前沿（英文）》 2022年第17卷第4期 doi: 10.1007/s11465-022-0703-5

摘要： In fiber laser beam welding (LBW), the selection of optimal processing parameters is challenging and plays a key role in improving the bead geometry and welding quality. This study proposes a multi-objective optimization framework by combining an ensemble of metamodels (EMs) with the multi-objective artificial bee colony algorithm (MOABC) to identify the optimal welding parameters. An inverse proportional weighting method that considers the leave-one-out prediction error is presented to construct EM, which incorporates the competitive strengths of three metamodels. EM constructs the correlation between processing parameters (laser power, welding speed, and distance defocus) and bead geometries (bead width, depth of penetration, neck width, and neck depth) with average errors of 10.95%, 7.04%, 7.63%, and 8.62%, respectively. On the basis of EM, MOABC is employed to approximate the Pareto front, and verification experiments show that the relative errors are less than 14.67%. Furthermore, the main effect and the interaction effect of processing parameters on bead geometries are studied. Results demonstrate that the proposed EM-MOABC is effective in guiding actual fiber LBW applications.

关键词： laser beam welding parameter optimization metamodel multi-objective

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Application of consistent geometric decomposition theorem to dynamic finite element of 3D composite beam

Iman FATTAHI, Hamid Reza MIRDAMADI, Hamid ABDOLLAHI

《结构与土木工程前沿（英文）》 2020年第14卷第3期页码 675-689 doi: 10.1007/s11709-020-0625-4

摘要： Analyzing static and dynamic problems including composite structures has been of high significance in research efforts and industrial applications. In this article, equivalent single layer approach is utilized for dynamic finite element procedures of 3D composite beam as the building block of numerous composite structures. In this model, both displacement and strain fields are decomposed into cross-sectional and longitudinal components, called consistent geometric decomposition theorem. Then, the model is discretized using finite element procedures. Two local coordinate systems and a global one are defined to decouple mechanical degrees of freedom. Furthermore, from the viewpoint of consistent geometric decomposition theorem, the transformation and element mass matrices for those systems are introduced here for the first time. The same decomposition idea can be used for developing element stiffness matrix. Finally, comprehensive validations are conducted for the theory against experimental and numerical results in two case studies and for various conditions.

关键词： composite beam dynamic finite element degrees of freedom coupling experimental validation numerical validation

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卫星通信大型双极化中国版图赋形微带反射阵天线的优化设计 Research Articles

Gang ZHAO, Yong-chang JIAO, Guan-tao CHEN

《信息与电子工程前沿（英文）》 2020年第21卷第1期页码 159-173 doi: 10.1631/FITEE.1900496

摘要：设计了一款具有中国版图赋形的大型双频双极化微带反射阵天线。为充分补偿两个频段范围内的空间相位延迟差，采用一种适用于大型双极化反射阵的3层矩形贴片单元。由于赋形区域形状复杂、赋形增益要求很高，该反射阵天线单元数量超过25 000个，优化变量数超过150 000个，导致其设计非常困难。本文首先通过离散快速傅里叶变换及其逆变换建立口径场和远场的一一对应关系，为赋形反射阵天线的优化奠定基础。进而采用基于交替投影的交集方法，优化获得多个典型频率下所有单元的目标反射相位。为避免优化过程陷入局部极值点，采用一种产生合适初始解的新方法。为验证设计方法的有效性，制作了一个7569单元的双极化反射阵天线并进行实验测试。测试与仿真结果吻合良好。为使宽带工作的大型反射阵天线带宽范围的空间相位延迟极小化，提出一种确定馈源最佳位置的方法。为在两个相互正交方向上同时找到单元的最优尺寸，建立一种新的优化模型，通过正多面体优化方法进行优化计算。最后，设计了一款覆盖中国陆地版图的单元数为25 305的双频双极化微带反射阵天线。仿真结果表明，该反射阵天线在两个工作频带范围内均可满足中国版图覆盖要求，证明所提出的复杂赋形波束大型反射阵天线优化设计方法可靠和有效。

关键词：反射阵；双极化；赋形波束；限相位综合

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Experimental and numerical analysis of beam to column joints in steel structures

Gholamreza ABDOLLAHZADEH, Seyed Mostafa SHABANIAN

《结构与土木工程前沿（英文）》 2018年第12卷第4期页码 642-661 doi: 10.1007/s11709-017-0457-z

摘要： The behaviors such as extreme non-elastic response, constant changes in roughness and resistance, as well as formability under extreme loads such as earthquakes are the primary challenges in the modeling of beam-to-column connections. In this research, two modeling methods including mechanical and neural network methods have been presented in order to model the complex hysteresis behavior of beam-to-column connections with flange plate. First, the component-based mechanical model will be introduced in which every source of transformation has been shown only with geometrical and material properties. This is followed by the investigation of a neural network method for direct extraction of information out of experimental data. For the validation of behavioral curves as well as training of the neural network, the experiments were carried out on samples with real dimensions of beam-to-column connections with flange plate in the laboratory. At the end, the combinational modeling framework is presented. The comparisons reveal that the combinational modeling is able to display the complex narrowed hysteresis behavior of the beam-to-column connections with flange plate. This model has also been successfully employed for the prediction of the behavior of a newly designed connection.

关键词： beam to column connections experiments component method neural network model combinational modeling

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disrupting chemicals from water through urethane functionalization of microfiltration membranes via electron beam

《环境科学与工程前沿（英文）》 2023年第18卷第4期 doi: 10.1007/s11783-024-1805-6

摘要：

● Urethane functionalities created on PES membranes via electron beam irradiation.

关键词： Surface functionalization Electron beam irradiation Microfiltration Endocrine disrupting chemicals

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软夹芯夹层梁最大弯曲正应力的计算

郝景新,刘文金,吴新凤

《中国工程科学》 2014年第16卷第4期页码 92-95

摘要：

最大弯曲正应力是衡量夹层梁弯曲性能的重要参数之一，本文推导出了将软夹芯夹层梁等效成等截面均质单层梁计算最大弯曲正应力的方法，并在此基础上进行三点弯曲试验的算例研究。结果表明：修正单层梁理论与层合梁理论计算的结果是一致的。当破坏载荷与夹层梁横截面的尺寸一定时，随着芯层与总厚度比的增加，修正单层梁理论计算的最大正应力值逐渐增加，而单层梁理论计算的结果为一恒定值。最大弯曲正应力修正公式的建立为夹层梁的工程应用提供理论基础。

关键词：夹层梁弯曲正应力单层梁理论弯曲特性

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Bending and vibration of a discontinuous beam with a curvic coupling under different axial forces

Heng LIU, Jie HONG, Dayi ZHANG

《机械工程前沿（英文）》 2020年第15卷第3期页码 417-429 doi: 10.1007/s11465-019-0584-4

摘要： The transverse stiffness and vibration characteristics of discontinuous beams can significantly differ from those of continuous beams given that an abrupt change in stiffness may occur at the interface of the former. In this study, the equations for the deflection curve and vibration frequencies of a simply supported discontinuous beam under axial loads are derived analytically on the basis of boundary, continuity, and deformation compatibility conditions by using equivalent spring models. The equation for the deflection curve is solved using undetermined coefficient methods. The normal function of the transverse vibration equation is obtained by separating variables. The differential equations for the beam that consider moments of inertia, shearing effects, and gyroscopic moments are investigated using the transfer matrix method. The deflection and vibration frequencies of the discontinuous beam are studied under different axial loads and connection spring stiffness. Results show that deflection decreases and vibration frequencies increase exponentially with increasing connection spring stiffness. Moreover, both variables remain steady when connection spring stiffness reaches a considerable value. Lastly, an experimental study is conducted to investigate the vibration characteristics of a discontinuous beam with a curvic coupling, and the results exhibit a good match with the proposed model.

关键词： discontinuous beam bending stiffness transverse vibration axial loads gyroscopic moments

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Dynamic analysis of composite beam subjected to harmonic moving load based on the third-order shear deformation

Mohammad Javad REZVANIL, Mohammad Hossein KARGARNOVIN, Davood YOUNESIAN

《机械工程前沿（英文）》 2011年第6卷第4期页码 409-418 doi: 10.1007/s11465-011-0245-8

摘要：

The response of an infinite Timoshenko beam subjected to a harmonic moving load based on the third-order shear deformation theory (TSDT) is studied. The beam is made of laminated composite, and located on a Pasternak viscoelastic foundation. By using the principle of total minimum potential energy, the governing partial differential equations of motion are obtained. The solution is directed to compute the deflection and bending moment distribution along the length of the beam. Also, the effects of two types of composite materials, stiffness and shear layer viscosity coefficients of foundation, velocity and frequency of the moving load over the beam response are studied. In order to demonstrate the accuracy of the present method, the results TSDT are compared with the previously obtained results based on first-order shear deformation theory, with which good agreements are observed.

关键词： timoshenko composite beam pasternak viscoelastic foundation third-order shear deformation theory (TSDT) harmonic moving load