Modeling And Analysis Of Transverse Vibration Of Forestry Aerial Ropeway

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.