【作者】 冯辉荣；

【导师】 陈立群；

【作者基本信息】 上海大学 ， 一般力学与力学基础， 2016， 博士

【摘要】 工程索道已被广泛应用于各类工程领域,各种新型索道的设计与技术创新也越来越多,这对悬索理论的研究提出了更高的要求。工程索道系统不仅有静力设计的要求,更存在着复杂的动力学理论与控制机理。索道系统动力学的研究关系着索道工程的安全、经济与正常运行。因此,工程索道的应用与理论研究是当今世界研究的热点问题之一。尤其在工程索道动力学理论与控制方面的研究,已引起越来越多研究人员的广泛兴趣。值得特别关注的是,林业架空索道的悬索系统是最复杂的索道系统之一,其操作运行过程复杂,具有研究的复杂性、挑战性、与实践性。因此,对林业架空索道系统的动力学研究具有普遍意义。介绍了悬索动力学理论的国内外研究现状、国内外林业架空索道的研究现状、设计理论、存在的问题与研究局限,并分析了工程索道的发展趋势。明确了承载索状态控制是索道安装架设过程中的核心问题。在弹性假设条件下,为揭示悬索线长与张力状态受到各类工况中的温度变化、弹性伸长、支座位移、风荷载等因素的影响规律,基于索单元的张力和索长的状态,提出了悬索状态可分为自然态、施工态和工作态三种状态,并以自然态线长相等为桥梁,建立基本状态协调方程。阐明基本状态方程是不同悬索理论建立状态协调方程的理论基础,提出了悬索单位长度的重量与刚度的比值(重刚比)是影响悬索静态位形的主要参数,并以埃特金加速迭代法为例推荐状态方程的有效解法。针对悬索斜抛物线状态方程,引入埃特金加速迭代解法,阐述其基本原理和计算步骤。结合工程索道案例,通过比较分析普通迭代法、牛顿迭代法和埃特金加速迭代法的求解过程,得到不同温度下无荷的悬索跨中张力、索长、中央挠度及中挠系数的变化规律,以及温度效应对悬索参数的响应规律,结果表明埃特金加速迭代法实用且简便。以单跨全悬增力式架空林业集材索道为例,研究在货物脱钩等突发情况下,承载索因积蓄的弹性能瞬间释放而产生自由振动。基于弦振动理论,建立了在指定位置脱钩的悬索振动方程,分析了脱钩工况下悬索振动固有频率、周期、波长等特征参数及主振动、自由振动、总能量等响应变化规律,并以三维图形进行直观表征与分析。说明了脱钩振动分析对林业架空索道的安装设计、技术改进与使用安全规程的指导意义,为工程中设置自动卸货、自动装载等最佳作业位置提供动力学理论依据。基于Euler梁假设,以实际工程索道为研究对象,考虑索道系统中跑车与悬索结构表面的非线性接触问题,关注悬索表面螺旋式不平度对跑车运行的影响,引入赫兹接触模型,得到了钢索与跑车的非线性接触模型。通过建立跑车-钢索耦合动力学振动控制方程,探索了悬索表面不平度对钢索的振动位移的响应;得到了跑车速度对钢索振动位移、振动频率和钢索最大张力等因素的影响,明确了跑车速度、钢索不平度、悬索重量刚度比、跑车重量及挂物重等参数对悬索系统强迫振动的影响与稳态响应机理,并结合工程案例进行了数值仿真。仿真结果表明当跑车通过跨中时,悬索具有最大位移与最大张力。重点分析了在跨中及距跨支座两端为1/4与3/4位置时,在跑车不同特定速度下,承载索的垂向位移时间历程,进行了相应的静态和动态悬索轴向力对比分析。同时分析了在不同跑车速度下,跑车与挂重的垂向位移时间历程,及其对承载索静态和动态轴向力的影响。明确了轴向力随车轮位置变化的静力学特性。明确了接触力对系统的影响。明确了悬索-跑车耦合振动的最不利速度与最优速度,为工程索道设计提供了理论储备与参考。进一步基于Euler梁假设,结合实际工程索道,考虑悬索表面的不平度参数,引入赫兹接触模型,建立跑车-钢索耦合振动控制方程。以里兹法进行数值仿真,通过振动响应曲线揭示了钢索不平度对钢索位移、跑车位移与挂重物位移的不同响应结果。仿真结果与解析分析可为工程索道设计提供理论储备与参考。明确了钢索表面不平度对轴向力的影响,明确了车轮直径与钢索不平度幅值对索道系统的振动特性的影响。为工程索道设计中跑车行走轮直径与钢索不平度的优化配合,提供了动力学理论参考。最后,对本论文工作给予了总结,并对未来的研究进行了讨论与展望。本文主要创新性工作包括下列几个方面:1.对悬索状态进行了分类,并应用新的加速迭代法求解悬索状态方程,提高了悬索状态方程求解的收敛速度。提出了悬索单位长度的重量与刚度的比值是影响悬索静态位形的主要参数。2.引入赫兹接触模型来考察跑车与悬索的接触模型,研究了考虑悬索与跑车接触参数对索道系统耦合振动力学模型及动力学性能的影响,并通过数值模拟验证了研究的必要性与可行性。3.考虑了钢索表面的不平度对跑车-钢索耦合振动模型的影响,建立了钢索-跑车耦合振动力学模型,并对横向振动参数进行了分析。4.针对实际工程应用来建立数学与力学模型,让理论研究更加切合生产实际,让理论研究成果能直接指导生产实践。更多还原

【Abstract】 Engineering cables have been widely used in many engineering fields.There are increasingly many designs and technical innovation of various new types of cables.For this reason,there are higher demands and requirements for the study of suspension theory not only static designs,but also the complex dynamics theory and control mechanism.The study on the dynamics of cable systems is related to the safety,economy and normal operation of the designs.Therefore,their applications and theoretical research in engineering are among the focused issues in the relevant fields.In particular,the research on dynamics and control of engineering cable has attracted very much research attention.It is noteworthy that the suspension system of forestry aerial cable is one of the most complicated cable systems.Not only its operation process is complex,but its research involves much complexity,challenges and engineering practicality.Therefore,the research on dynamics of forestry aerial cableway system is of universal and general implications.Contemporary research on the theory of cable dynamics and on research of domestic and global forestry aerial cableway are introduced in this dissertation.In addition,the design theory,standing problems and limitations,and development trends of engineering cableway are also analyzed.Cable control is the core issue during cableway installation process.Within the assumption of elasticity,the effects of various parameters on cable length and tension in various working conditions are investigated,including temperature changes,elastic elongation,bearing displacement and wind load.It is proposed in this project that suspended cable can be recognized as one of the three states: natural state,construction state and work state based on unit cable tension and cable length.The basic state compatibility equation is established by referring to natural state cable length.This work has also shown that the state compatibility equation is the theoretical basis for establishing different flexible cable theories.The ratio of suspension weight per unit length to stiffness(the ratio of cable weight to stiffness)is the main parameter that affects the static configuration of cableway suspension.Effective solution method of the state compatibility equation by using the Aitken fast iteration algorithm is also presented.The Aitken fast iteration algorithm is introduced for the inclined parabolic state equation of a flexible cable.The basic principle and calculation procedure are also presented.By taking engineering cableway as an example,the common iteration method,Newton iteration method and Aitken fast iteration algorithm are analyzed and compared.The span tension,cable length,center deflection and center deflection coefficient of an unloading flexible cable for different temperatures are obtained.The response pattern of flexible cable parameter to temperature is also solved.The result shows that the Aitken fast iteration algorithm is both practical and simple.The free vibration due to instantaneous elastic energy release during cargo unhooking is analyzed based on the theory of string(rope)vibration.The overhead skidding single span cableway with full suspension reinforcement is used as an example.The unhooking vibration model is established with illustrated 3D graphics and the natural angular frequency,period,wavelength,vibration mode,and the total energy are discussed.The results can be used in installation design,technology advancement and the safety code of practice for forestry aerial ropeways.This dissertation considers the actual engineering cableways as research targets.Based on the Euler beam assumptions,the nonlinear contact problems of cableway systems for carriage and suspension structure surface are considered.The effects of suspension helical surface roughness on carriage running are of particular concern.By using the Hertz contact model,the nonlinear contact models of cable and carriage are obtained.By establishing the carriage and cable coupling dynamics vibration control equation,the response of surface roughness on cable suspension vibration displacement is investigated.The effects of velocity on cable vibration displacement,frequency,maximum cable tension and other factors are obtained.It is clear that the influence of carriage speed,cable roughness,suspension weight stiffness ratio,carriage weight,hanging weight and other parameters influence significantly forced vibration of the suspension system and the steady state response.By combining the engineering cases,a numerical simulation is carried out.The simulation results show that when the carriage passes through the span,the suspension is at maximum displacement and maximum tension.The most unfavourable speed and optimum speed for the coupled vibration of suspension and carriage are determined.The analytical database and design reference for engineering ropeway are presented.The Euler beam assumptions are adopted and the surface roughness parameters of suspension cable are considered in this project.Using a practical engineering cableway as the research target and by introducing the Hertz contact model,the governing equation for coupled vibration of a carriage and skyline is presented.Vibration response is analyzed by numerical analysis using the Ritz method.Numerical simulation examples show that the responses of cable displacement,carriage and hanging goods do significantly depend on cable roughness.The analysis and simulation results provide theoretical comparison and reference for engineering ropeway design.Finally,a summary of the present work is presented in this dissertation.Possible future research and recommendations for the project are also discussed.The main innovations of this project are described as follows:1.Classification of cable suspension state is presented.A new fast iteration algorithm is used to solve the suspension state equation,and the solution convergence rate for the suspension state equation is improved.The ratio of cable weight per unit length to stiffness is the main parameter that affects the static configuration of cableway suspension.2.By using the Hertz contact model,nonlinear contact models of cable and carriage are established.The influence of contact parameters for cable and carriage on the mechanical model and the coupled cable dynamic vibration performance is investigated.The necessity and feasibility of research are verified by numerical simulation.3.The influence of surface irregularities on suspended cable and carriage is considered.The governing equation of the coupled vibration of a carriage and skyline is presented.The transverse vibration parameters are analyzed.4.With practical engineering applications in mind,a mathematical and mechanical model is developed such that this theoretical study will become more practical.The theoretical research results can also be directly applied in practical production.更多还原