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Experimental study of modal parameter identification in a simulated ambient-excited structure

JI Xiaodong, QIAN Jiaru, XU Longhe

《结构与土木工程前沿（英文）》 2007年第1卷第3期页码 281-285 doi: 10.1007/s11709-007-0036-9

摘要： Structure modal parameter online identification was used to monitor the structural health as evidenced by changes in the vibration characteristics. The natural excitation technique and the eigensystem realization algorithm were combined to identify the modal parameters in the time domain of a structure excited by simulated ambient vibrations. The mass-normalized mode shapes were obtained from the eigen-sensitivity analysis. The experimental modal analysis was performed on a two-story steel braced frame model excited by simulated ambient vibrations and hammer impacts. The mass-normalized mode shapes were acquired by changing the structural mass and by eigen-sensitivity analy sis. From finite element analysis results and the experimental data, it is shown that this method is effective.

关键词： eigensystem realization eigen-sensitivity analysis realization algorithm vibration effective

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Parameter studies on impact in a lap joint

Amir M. RAHMANI,Elizabeth K. ERVIN

《机械工程前沿（英文）》 2015年第10卷第1期页码 64-77 doi: 10.1007/s11465-014-0322-x

摘要：

To represent a loose lap joint, a beam impacting four springs with gaps is modeled. Modal analysis with base excitation is solved, and time histories of contact points are closely monitored. Using the impulse during steady state response, six influential parameters are studied: damping ratio, contact stiffness, intermediate contact position, gap, excitation amplitude and beam height. For all parameters, the system response is highly controlled by modes with two contacting springs. Each parameter’s effect on system response is presented including unstable regions, unique trend behaviours result. Recommendations for structural designers are also noted.

关键词： impact mechanics contact joint behaviour modal analysis parameter study

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移动式颗粒床除尘器的设计研究

吕保和

《中国工程科学》 2007年第9卷第10期页码 45-48

摘要：

分析了移动式颗粒床除尘器的特点，并与传统除尘器进行了比较。结合理论计算与实际运行试验，提出了移动式颗粒床除尘器主要结构参数及主要性能参数的设计计算方法，证明了该方法具有较好的实际应用价值。

关键词：移动式颗粒床除尘器结构参数性能参数

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Experimental study on velocity characteristics of recirculation zone in humid air non-premixed flame

GU Xin, ZANG Shusheng, GE Bing

《能源前沿（英文）》 2008年第2卷第2期页码 140-144 doi: 10.1007/s11708-008-0037-y

摘要： To examine the effect of the flow field within the recirculation zone on flame structure, the characteristic velocity fields of methane/humid air flame in non-premixed combustion behind a disc bluff-body burner were experimentally studied by particle image velocimeter (PIV).The results show that two stagnation points exist on the centerline in the recirculation zone flame. However, the distance of the two stagnation points in humid air combustion shortens, and the minimal dimensionless velocity increases compared with the conventional non-humid air combustion. In addition, the positional curves of the minimal velocities can be partitioned into three phases representing three different flame patterns. The analysis of axial minimal velocities on the centerline and their positions under different co-flow air velocity conditions reveals that fuel-to-air velocity ratio is the crucial parameter that governs humid air combustion flame characteristics.

关键词： distance bluff-body fuel-to-air velocity stagnation parameter

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Parametric study on damage control design of SMA dampers in frame-typed steel piers

Xiaoqun LUO, Hanbin GE, Tsutomu USAMI,

《结构与土木工程前沿（英文）》 2009年第3卷第4期页码 384-394 doi: 10.1007/s11709-009-0065-7

摘要： This paper focuses on damage control design of SMA dampers in steel frame piers. A parametric study based on time history analyses is carried out on frame-typed bridge piers with axial-type SMA damping device. The parameters examined are design parameters of strength ratio and stiffness ratio . Seismic performance indexes on displacement and strain are investigated under three JRA recommended Level 2 Ground Type П strong earthquake motions. Design recommendations are suggested following the results of the parametric study.

关键词： damage control design shape memory alloy parameter study displacement-based verification strain-based verification time history analysis

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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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Determination of effective stress parameter of unsaturated soils: A Gaussian process regression approach

Pijush Samui, Jagan J

《结构与土木工程前沿（英文）》 2013年第7卷第2期页码 133-136 doi: 10.1007/s11709-013-0202-1

摘要： This article examines the capability of Gaussian process regression (GPR) for prediction of effective stress parameter ( ) of unsaturated soil. GPR method proceeds by parameterising a covariance function, and then infers the parameters given the data set. Input variables of GPR are net confining pressure ( ), saturated volumetric water content ( ), residual water content ( ), bubbling pressure ( ), suction ( ) and fitting parameter ( ). A comparative study has been carried out between the developed GPR and Artificial Neural Network (ANN) models. A sensitivity analysis has been done to determine the effect of each input parameter on . The developed GPR gives the variance of predicted . The results show that the developed GPR is reliable model for prediction of of unsaturated soil.

关键词： unsaturated soil effective stress parameter Gaussian process regression (GPR) artificial neural network (ANN) variance

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1000 MW ultra-supercritical turbine steam parameter optimization

FENG Weizhong

《能源前沿（英文）》 2008年第2卷第2期页码 187-193 doi: 10.1007/s11708-008-0030-5

摘要： The 2 × 1000 MW ultra-supercritical steam turbine of Shanghai Waigaoqiao Phase III project, which uses grid frequency regulation and overload control through an overload valve, is manufactured by Shanghai Turbine Company using Siemens technology. Through optimization, the steam pressure is regarded as the criterion between constant pressure and sliding pressure operation. At high circulating water temperature, the turbine overload valve is kept closed when the unit load is lower than 1000 MW while at other circulating water temperatures the turbine can run in sliding pressure operation when the unit load is higher than 1000 MW and the pressure is lower than 27 MPa This increases the unit operation efficiency. The 3D bending technology in the critical piping helps to reduce the project investment and minimize the reheat system pressure drop which improves the unit operation efficiency and safety. By choosing lower circulating water design temperature and by setting the individual Boiler Feedwater Turbine condenser to reduce the exhaust steam flow and the heat load to the main condenser, the unit average back pressure and the terminal temperature difference are minimized. Therefore, the unit heat efficiency is increased.

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Structural parameter design method for a fast-steering mirror based on a closed-loop bandwidth

Guozhen CHEN, Pinkuan LIU, Han DING

《机械工程前沿（英文）》 2020年第15卷第1期页码 55-65 doi: 10.1007/s11465-019-0545-y

摘要： When a fast-steering mirror (FSM) system is designed, satisfying the performance requirements before fabrication and assembly is vital. This study proposes a structural parameter design approach for an FSM system based on the quantitative analysis of the required closed-loop bandwidth. First, the open-loop transfer function of the FSM system is derived. In accordance with the transfer function, the notch filter and proportional-integral (PI) feedback controller are designed as a closed-loop controller. The gains of the PI controller are determined by maximizing the closed-loop bandwidth while ensuring the robustness of the system. Then, the two unknown variables of rotational radius and stiffness in the open-loop transfer function are optimized, considering the bandwidth as a constraint condition. Finally, the structural parameters of the stage are determined on the basis of the optimized results of rotational radius and stiffness. Simulations are conducted to verify the theoretical analysis. A prototype of the FSM system is fabricated, and corresponding experimental tests are conducted. Experimental results indicate that the bandwidth of the proposed FSM system is 117.6 Hz, which satisfies the minimum bandwidth requirement of 100 Hz.

关键词： fast-steering mirror structural parameter PI controller bandwidth notch filter

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Energy efficient cutting parameter optimization

Xingzheng CHEN, Congbo LI, Ying TANG, Li LI, Hongcheng LI

《机械工程前沿（英文）》 2021年第16卷第2期页码 221-248 doi: 10.1007/s11465-020-0627-x

摘要： Mechanical manufacturing industry consumes substantial energy with low energy efficiency. Increasing pressures from energy price and environmental directive force mechanical manufacturing industries to implement energy efficient technologies for reducing energy consumption and improving energy efficiency of their machining processes. In a practical machining process, cutting parameters are vital variables set by manufacturers in accordance with machining requirements of workpiece and machining condition. Proper selection of cutting parameters with energy consideration can effectively reduce energy consumption and improve energy efficiency of the machining process. Over the past 10 years, many researchers have been engaged in energy efficient cutting parameter optimization, and a large amount of literature have been published. This paper conducts a comprehensive literature review of current studies on energy efficient cutting parameter optimization to fully understand the recent advances in this research area. The energy consumption characteristics of machining process are analyzed by decomposing total energy consumption into electrical energy consumption of machine tool and embodied energy of cutting tool and cutting fluid. Current studies on energy efficient cutting parameter optimization by using experimental design method and energy models are reviewed in a comprehensive manner. Combined with the current status, future research directions of energy efficient cutting parameter optimization are presented.

关键词： energy efficiency cutting parameter optimization machining process

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Hierarchical parameter estimation of DFIG and drive train system in a wind turbine generator

Xueping PAN, Ping JU, Feng WU, Yuqing JIN

《机械工程前沿（英文）》 2017年第12卷第3期页码 367-376 doi: 10.1007/s11465-017-0429-y

摘要：

A new hierarchical parameter estimation method for doubly fed induction generator (DFIG) and drive train system in a wind turbine generator (WTG) is proposed in this paper. Firstly, the parameters of the DFIG and the drive train are estimated locally under different types of disturbances. Secondly, a coordination estimation method is further applied to identify the parameters of the DFIG and the drive train simultaneously with the purpose of attaining the global optimal estimation results. The main benefit of the proposed scheme is the improved estimation accuracy. Estimation results confirm the applicability of the proposed estimation technique.

关键词： wind turbine generator DFIG drive train system hierarchical parameter estimation method trajectory sensitivity technique

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Variational mode decomposition based modal parameter identification in civil engineering

Mingjie ZHANG, Fuyou XU

《结构与土木工程前沿（英文）》 2019年第13卷第5期页码 1082-1094 doi: 10.1007/s11709-019-0537-3

摘要： An out-put only modal parameter identification method based on variational mode decomposition (VMD) is developed for civil structure identifications. The recently developed VMD technique is utilized to decompose the free decay response (FDR) of a structure into to modal responses. A novel procedure is developed to calculate the instantaneous modal frequencies and instantaneous modal damping ratios. The proposed identification method can straightforwardly extract the mode shape vectors using the modal responses extracted from the FDRs at all available sensors on the structure. A series of numerical and experimental case studies are conducted to demonstrate the efficiency and highlight the superiority of the proposed method in modal parameter identification using both free vibration and ambient vibration data. The results of the present method are compared with those of the empirical mode decomposition-based method, and the superiorities of the present method are verified. The proposed method is proved to be efficient and accurate in modal parameter identification for both linear and nonlinear civil structures, including structures with closely spaced modes, sudden modal parameter variation, and amplitude-dependent modal parameters, etc.

关键词： modal parameter identification variational mode decomposition civil structure nonlinear system closely spaced modes

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单缝桥梁在温度作用下的结构受力计算

赵怡彬,邵旭东

《中国工程科学》 2012年第14卷第10期页码 103-112

摘要：

桥台处伸缩缝问题是长期困扰工程界的难题，它会带来跳车、桥梁局部损坏、伸缩缝装置经常更换等各种问题。为有效解决这一问题，提出了一种适用于大中型桥梁的新型结构体系——单伸缩缝桥梁（单缝桥）。在考虑接线路面裂缝开展的情况下，建立了温度作用下单缝桥的简化计算模型，推导了单缝桥受力、变形的理论公式，用Fortran90编制程序，进行计算。以一座总长280 m的单缝梁桥为例，温度降低20 ℃时，接线路面钢筋最大应力为148 MPa，最大裂缝宽度为0.185 mm，符合规范要求；台后结构对主梁产生的附加应力仅为0.105 MPa，影响很小。通过对影响单缝桥性能的因素：支座类型、配筋率、接线路面长度、摩擦系数、土体刚度、桥长、温差等进行分析，绘制图表，得到以下主要结论：温降时，接线路面受拉，混凝土开裂，是较不利的状况；30 m长的接线路面可以满足结构受力和变形的需要；选择摩擦系数较小的支座和减少接线路面与垫层的摩擦力可以减少结构内力，在接线路面与垫层间推荐加铺土工格栅。

关键词：单缝桥梁温度作用受力与变形理论公式参数分析

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Shallow foundation response variability due to soil and model parameter uncertainty

Prishati RAYCHOWDHURY,Sumit JINDAL

《结构与土木工程前沿（英文）》 2014年第8卷第3期页码 237-251 doi: 10.1007/s11709-014-0242-1

摘要： Geotechnical uncertainties may play crucial role in response prediction of a structure with substantial soil-foundation-structure-interaction (SFSI) effects. Since the behavior of a soil-foundation system may significantly alter the response of the structure supported by it, and consequently several design decisions, it is extremely important to identify and characterize the relevant parameters. Moreover, the modeling approach and the parameters required for the modeling are also critically important for the response prediction. The present work intends to investigate the effect of soil and model parameter uncertainty on the response of shallow foundation-structure systems resting on dry dense sand. The SFSI is modeled using a beam-on-nonlinear-winkler-foundation (BNWF) concept, where soil beneath the foundation is assumed to be an assembly of discrete, nonlinear elements composed of springs, dashpots and gap elements. The sensitivity of both soil and model input parameters on shallow foundation responses are investigated using first-order second-moment (FOSM) analysis and Monte Carlo simulation through Latin hypercube sampling technique. It has been observed that the degree of accuracy in predicting the responses of the shallow foundation is highly sensitive soil parameters, such as friction angle, Poisson’s ratio and shear modulus, rather than model parameters, such as stiffness intensity ratio and spring spacing; indicating the importance of proper characterization of soil parameters for reliable soil-foundation response analysis.

关键词： shallow foun dation sensitivity analysis centrifuge data first-order-second-moment (FOSM) method parameter uncertainty

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苏通大桥主桥结构体系研究

张喜刚,裴岷山,袁洪,徐利平,朱斌

《中国工程科学》 2009年第11卷第3期页码 20-25

摘要：

苏通大桥主跨1 088m，是目前世界上最大跨径的斜拉桥。大桥桥位处建筑条件复杂，抗震和抗风要求高，选择合理的桥梁结构体系是保证结构安全和功能的关键。介绍了苏通大桥结构体系的比选过程，比较了全漂浮、黏滞阻尼器、液压缓冲器和塔梁固接4种体系，重点分析对比了不同参数下黏滞阻尼器和液压缓冲器的结构响应，首次提出了用于桥梁的带有附加限位功能的特大型液体黏滞阻尼器，对阻尼器的设计参数进行了分析研究，并在苏通大桥上实现了这一新型装置。

关键词：苏通大桥斜拉桥结构体系阻尼器阻尼参数限位