基于颗粒阻尼吸振的波纹辊轧机非线性垂振控制

轧机振动理论的研究一直是轧制成形领域的前沿科学问题，对板材的质量和设备的稳定运行至关重要。随着轧制复合成形技术的快速发展，波纹辊轧机作为一种具有特殊辊型的设备，在复合板制备上具有细化晶粒、改善板形、提高结合强度等突出优点，逐渐成为当前的研究热点，但是复杂辊型曲线所诱发的轧制力动态变化对轧机的稳定性控制提出了新的挑战。为了对波纹辊轧机的非线性垂振进行合理的控制，建立了考虑波平辊系之间的非线性刚度、波纹界面非线性阻尼和轧制力动态波动的非线性垂振方程，通过分岔图、最大Lyapunov指数、相轨迹和Poincare截面分析了轧制力的动态变化对系统稳定性的影响，发现轧制力的动态变化诱发系统产生了复杂的动力学行为。设计了一种颗粒阻尼吸振器对波纹辊轧机非线性垂振进行控制，运用多尺度法求解得到了安装颗粒阻尼吸振器系统的幅频特性曲线方程，分析了钢珠颗粒群质量、吸振器刚度系数、阻尼系数以及质量比对幅频特性曲线的影响，通过数值仿真研究了颗粒阻尼吸振器对非线性垂振的控制效果。最后，通过试验验证了颗粒阻尼吸振器设计的正确性和可行性，缩短动态过程调整时间的同时也减小了系统的振幅，为波纹辊轧机非线性动力学分析及稳定...     

现代连轧机耦合振动抑制重要进展

阐述五十多年以来连轧机振动问题提出、研究内容、研究进展和研究展望。通过现场测试发现连轧机存在垂扭耦合振动、液机耦合振动、弯扭耦合振动和机电耦合振动现象;然后通过理论研究、仿真分析也证明了连轧机耦合振动的存在及特征规律;最终确定了连轧机振动性质为机电液界多态耦合振动。据此开发了抑制连轧机耦合振动的通用技术,发明了"连轧机耦合振动解耦抑振器"并在某连轧机组上成功应用,取得了良好的抑振效果。     

数值仿真处理机械振动课程若干教学难点

针对单自由度受迫振动中的自由伴随振动和拍振、两自由度受迫振动中的动力吸振以及多自由度自由振动中主振型和振型叠加等若干不易理解的难点问题,采用数值仿真与解析推导相结合的教学思路设计,使得抽象问题形象化,理论问题趣味化,促进学生对振动现象和规律的深入理解与应用,强化学生在工程实践中分析问题和解决问题的能力。     

连轧机振动控制重要进展综述

阐述连轧机振动控制的新思路和对策。提出了轧机存在垂扭耦合振动、液机耦合振动、弯扭耦合振动和机电耦合振动现象。确定了轧机振动性质为机电液界多态耦合振动,找到了抑制轧机振动的通用技术,发明了“轧机耦合振动解耦抑振器”并在某连轧机组上成功应用,取得了良好的抑振效果。     

填充床鼓泡电化学反应器行为特性：II.丙烯阳极直接氧化强非线性模 …

利用逆算符方法（ＩＯＭ）对所建立的填充床鼓泡电化学反应器的强非线性微分方程组进行了近似解析求解。利用该近似解析解，一方面可以直观地分析有关参数对反应器行为特性的影响；另一方面，与测量电极反应伏安特性曲线的实验方法相结合，可较方便地回归出非线性模型的参数值，并对模拟结果加以验证。     

高炉煤气布袋除尘内外反吹技术的性能分析

通过 对高炉 煤气外滤 式脉冲 反吹除尘 器与内滤 式加压 反吹除尘 器进行 性能 分析 ， 找 出外滤式脉 冲反吹 除尘器的 优越性， 证明 其值得推 广．     

硅合金电炉两种不同除尘工艺的应用

阐述了负压长袋及吹风脉冲式除尘器与正压反吸大布袋防尘器的应用及特点，通过技改，达到了预期效果。     

动力法计算振冲碎石桩桩体压缩模量

振冲碎石桩为散体结构,所形成的复合地基受垂直荷载后的变形较刚性桩复合地基要大,为研究振冲碎石桩复合地基的沉降规律,建立振冲器动力性能指标与碎石桩桩体强度的关系.根据压缩模量概念,结合振冲桩制桩工艺,建立桩体压缩模量与振冲器激振力、施工中的加密段长、加密电流及留振时间的关系式--动力法.采用动力法和载荷试验法所得的压缩模量在沉降量计算中进行对比,结果与按实际观测推算值的偏差均小于10%.     

高转速汽轮鼓风机框架式基础动力模态及结构动反应分析

通过对一汽轮鼓风机框架式基础的动力分析计算，对高转速动力机器框架式基础设计的资料获取，力学模型的选择，计算结果进行了探索和研究，对高转速动力机器框架式基础的设计具有参考价值。     

干吸塔分酸装置的改造实践

介绍了韶关冶炼厂制酸系统干吸塔分酸装置的改造实践。改造时将分酸装置由分酸槽挂爪式改为管式分酸器，有效地延长了干吸塔的寿命。     

Acceleration Feedback-Based Active and Passive Vibration Control of Landing Gear Components

In this paper, a novel methodology is developed to absorb the vibrations of relatively large-scale aircraft structures such as landing gear components. This is accomplished using a combination of active and passive controls. A system equivalent to a Boeing 747 landing gear break rod is selected as a test bed. The expected goal of this study is to dissipate the fundamental vibration mode of the tube. A beam-type dynamic absorber and a constrained layer damping treatment are used for passive vibration control. Simulations and experimental results are provided for the dynamic absorber case. In addition, full-state feedback along with state estimation based on the “reciprocal state space” method is presented. The plant responses and estimates for both the open loop and closed loop systems are shown in simulations. An optimal controller based on acceleration measurements using piezoelectric actuators is implemented using a hardware in the loop protocol for the active vibration control of the system. The integrated controller with passive and active components absorbs the fundamental mode of the system, according to the experimental results.     

Dynamic Field Test, System Identification, and Modal Validation of an RC Minaret: Preprocessing and Postprocessing the Wind-Induced Ambient Vibration Data

The investigation of dynamic response for civil engineering structures largely depends on a detailed understanding of their dynamic characteristics, such as the natural frequencies, mode shapes, and modal damping ratios. Dynamic characteristics of structures may be obtained numerically and experimentally. The finite-element method is widely used to model structural systems numerically. However, there are some uncertainties in numerical models. Material properties and boundary conditions may not be modeled correctly. There may be some microcracks in the structures, and these cracks may directly affect the modeling parameters. Modal testing gives correct uncertain modeling parameters that lead to better predictions of the dynamic behavior of a target structure. Therefore, dynamic behavior of special structures, such as minarets, should be determined with ambient vibration tests. The vibration test results may be used to update numerical models and to detect microcracks distributed along the structure. The operational modal analysis procedure consists of several phases. First, vibration tests are carried out, spectral functions are produced from raw measured acceleration records, dynamic characteristics are determined by analyzing processed spectral functions, and finally analytical models are calibrated or updated depending on experimental analysis results. In this study, an ambient vibration test is conducted on the minaret under natural excitations, such as wind effects and human movement. The dynamic response of the minaret is measured through an array of four trixial force-balanced accelerometers deployed along the whole length of the minaret. The raw measured data obtained from ambient vibration testing are analyzed with the SignalCAD program, which was developed in MATLAB. The employed system identification procedures are based on output-only measurements because the forcing functions are not available during ambient vibration tests. The ModalCAD program developed in MATLAB is used for dynamic characteristic identification. A three-dimensional model of the minaret is constructed, and its modal analysis is performed to obtain analytical frequencies and mode shapes by using the ANSYS finite-element program. The obtained system identification results have very good agreement, thus providing a reliable set of identified modal properties (natural frequencies, damping ratios, and mode shapes) of the structure, which can be used to calibrate finite-element models and as a baseline in health monitoring studies.     

Output-Only System Identification of Posttensioned Segmental Concrete Highway Bridges

This paper discusses the application of system identification of a highway bridge using finite-element method and ambient-vibration testing. The posttensioned Gülburnu Highway Bridge located on the Giresun-Espiye state highway was selected as a case study. A finite-element model of the bridge was developed using SAP2000 software, and dynamic characteristics were obtained analytically. During the test, sources of ambient excitations were provided by the traffic effects over the bridge. Ambient-vibration tests were applied to the bridge to identify dynamic characteristics. The selection of measurement time, frequency span, and effective mode number was considered from similar studies in the literature. Two output-only system identification methods, enhanced frequency domain decomposition and stochastic subspace identification, were used to estimate the dynamic characteristics of the bridge experimentally. The accuracy and efficiency of both methods were investigated and compared with finite-element results. Results suggest that ambient-vibration measurements are sufficient to identify structural modes with a low range of natural frequencies. In addition, the dynamic characteristics obtained from the finite-element model of the bridge have a good correlation with experimental frequencies and mode shapes.     

Manufacture of Zn-Co Substituted Y-Type Barium Hexagonal Ferrites by Citrate Precursor Route and Their Microwave Properties

Ba2ZnxCo2-xFe12O22 hexaferrites with x=0.0, 0.4, 0.8, 1.2, 1.6 and 2.0 were prepared by citrate sol-gel process. The complex dielectric constant and complex permeability of hexaferrites were studied as functions of the measuring frequency，composition and sintering temperature in the range 100MHz～6GHz. The natural resonance phenomenon is observed in μ″ spectrum for all Y-type hexaferrites, which resonance frequency is dependent on zinc content and firing temperature. The natural resonance frequencies of Co2Y hexaferrite were calculated, which is in agreement with the measuring results. The reflection loss of those ferrites is measuring frequency as well as absorber thickness dependent, and the higher the frequency and the thickness are, the higher the reflection loss is.     

An inverse computational method for determining the constitutive parameters using the hot torsion test results

Recently a number of inverse computational methods were presented for determining constitutive parameters from the results of mechanical tests. These are based on minimization of the least square errors of the measured and calculated load-displacement results of the given test. Uniqueness of the minimum obtained from these methods has not been investigated properly. This paper presents an approximate solution for the minimum error in the inverse computational determination of constitutive parameters using the hot torsion test. The approximation is based on an analytical solution for the torsion test. It shows that for the hot torsion test, the existing inverse computational methods based on a load-displacement objective function fail to predict a unique set of constitutive parameters for an assumed rigid-viscoplastic constitutive relationship. A new objective function was developed to ensure the uniqueness of the solution for the constitutive parameters. An algorithm is presented for applying the new method to the hot torsion test results.     

Characterization of Spectral Analysis of Surface Waves Shear Wave Velocity Measurement Uncertainty

The spectral analysis of surface waves (SASW) method is a nondestructive test for characterization of the variation with depth of the shear modulus of soils. While the testing procedure is well developed, only one preliminary study has investigated measurement uncertainty associated with SASW, and the methods utilized to quantify measurement uncertainty were prohibitive to routine assessment. Knowledge of this uncertainty, and ability to include its assessment in routine testing, would allow for inclusion of SASW results in reliability-based design and in assessment of the spatial variability of shear modulus. In this study, a large sample of test data was collected from two test sites. Characteristic statistics, statistical distribution, and measurement uncertainty were determined for each phase of SASW. Using the empirical statistical properties and measurement uncertainty results as validation criteria, an analytically based uncertainty assessment system was developed. Phase angle, inverse phase angle, and phase velocity data typically display a coefficient of variation (COV) of 2%, and the COV for combined phase velocity data is typically 1.5%. The COV for shear wave velocity is typically between 5 and 10%, and thus the inversion appears to magnify measurement uncertainty. Phase angle, inverse phase angle, phase velocity, and combined phase velocity data are normally distributed. Shear wave velocity samples at a given depth are generally normally distributed. Using a small sample of experimental data and the analytically based process developed in this study, the measurement uncertainty of SASW test results can be assessed as part of routine testing.     

Quantification of Uncertainty in Structural Dynamic Models

Structural dynamic models are used to simulate the performance of structures in a dynamic environment. The predictive accuracy of a model has been defined as the accuracy of predicted structural response under conditions for which the structure has not been tested. This paper addresses the quantification of modeling uncertainty, not including the additional uncertainties that may be introduced by the dynamic environment itself. Uncertainty is quantified relative to measured quantities (i.e., experimentally derived modal frequencies and displacements). Although these “measurements” are known to be uncertain themselves, they are taken as the “truth” reference, so modeling uncertainty by definition includes experimental uncertainty as well as parametric uncertainty and the uncertainty of model form (the equations of motion). This paper shows how this modeling uncertainty can be derived by comparing analysis and test modes of generically similar structures and thereafter be used to evaluate the accuracy of numerical simulations based on prior analysis and test experience. Practical examples are given.     

Vibration Characteristics of K?mürhan Highway Bridge Constructed with Balanced Cantilever Method

K?mürhan Highway Bridge is a reinforced concrete box girder bridge located on the 51st km of Elaz??–Malatya Highway over the F?rat River. Because of the fact that the K?mürhan Bridge is the only bridge in this part of F?rat, it has major logistical importance. So, this paper aims to determine dynamic characteristics such as natural frequencies, mode shapes, and damping ratios of the bridge using experimental measurements and finite-element analyses to evaluate current behavior. The experimental measurements are carried out by ambient vibration tests under traffic loads. Due to the expansion joint in the middle of the bridge, special measurement points are selected and experimental test setups are constituted. Vibration data are gathered from the both box girder and bridge deck. Measurement time, frequency span, and effective mode number are determined by considering similar studies and literature. The peak picking method in the frequency domain is used for the output-only modal identification. An analytical modal analysis is performed on the developed two- and three-dimensional finite-element model of the bridge using SAP2000 software to provide the analytical frequencies and mode shapes. At the end of the study, dynamic characteristics of the Elaz?? and Malatya parts of the bridge obtained from the experimental measurements are compared with each other and transverse effects on the bridge are determined. Also, experimental and analytical dynamic characteristics are compared. Good agreement is found between dynamic characteristics in the all measurement test setups performed on the box girder and bridge deck and analytical modal analyses.     

Modal Testing, Finite-Element Model Updating, and Dynamic Analysis of an Arch Type Steel Footbridge

This paper describes an arch type steel footbridge, its analytical modeling, modal testing, finite-element model updating, and dynamic analysis. A modern steel footbridge which has an arch type structural system and is located on the Karadeniz coast road in Trabzon, Turkey is selected as an application. An analytical modal analysis is performed on the developed three-dimensional finite-element model of footbridge to provide analytical frequencies and mode shapes. Field ambient vibration tests on the footbridge deck under natural excitation such as human walking and traffic loads are conducted. The output-only modal parameter identification is carried out by using peak picking of the average normalized power spectral densities in the frequency domain and stochastic subspace identification in the time domain, and dynamic characteristics such as natural frequencies, mode shapes, and damping ratios are determined. The finite-element model of the footbridge is updated to minimize the differences between analytically and experimentally estimated modal properties by changing some uncertain modeling parameters such as material properties. Dynamic analyses of the footbridge before and after finite-element model updating are performed using the 1992 Erzincan earthquake record. At the end of the study, maximum differences in the natural frequencies are reduced from 22 to only 5% and good agreement is found between analytical and experimental dynamic characteristics such as natural frequencies and mode shapes by model updating. Also, maximum displacements and principal stresses before and after model updating are compared with each other.