【作者】 李皓玉；

【导师】 杨绍普；

【作者基本信息】 北京交通大学 ， 车辆工程， 2011， 博士

【摘要】 摘要：随着国民经济和公路交通运输业的快速发展,高速重载成为了道路交通的发展趋势,重型车辆对路面的动荷载是造成路面早期破坏的一个主要原因,高速公路的静力法设计越来越难以满足要求。研究车辆荷载作用下路面的动力学行为,揭示路面的破坏机理,推动路面结构设计从静态向动态转化已成为目前道路界研究的热点问题之一。目前道路工作者在求解路面的动力响应时,由于理论分析和数值计算上的复杂性,一般将车辆荷载简化为冲击荷载、移动的恒载或移动的简谐荷载,而忽略掉其“移动随机荷载”的本质特性。车辆动荷载引起路面的早期破坏,而路面的破坏反过来又会引起车辆振动加剧,严重影响行车的安全性、舒适性,并进一步增加车辆对路面的动荷载,车辆与路面是一个相互作用相互耦合的系统,要研究路面在车辆荷载作用下的动力学行为,应把车辆与路面作为一个系统来研究。本文通过动荷载将车辆模型和路基路面模型相连接,建立车辆一路面一路基相互作用系统,基于此系统对移动随机荷载作用下路面的动力学特性进行了理论分析和仿真计算,系统分析了车路系统参数对路面的动力响应和疲劳寿命的影响。主要研究内容包括：(1)建立了八自由度整车模型,对行驶于不平整路面上的车辆动荷载进行了频域仿真分析,探讨了路面不平度、行车速度、车辆悬架刚度和阻尼、轮胎刚度和阻尼等参数对动荷载的影响规律。综合考虑行驶平顺性和道路友好性两方面的因素对车辆悬架进行了优化。结果表明,重型车辆作用于路面的动荷载以低频振动为主,通过适当减小前后悬架的刚度和增大前后悬架的阻尼,可有效地提高车辆的行驶平顺性和道路友好性。(2)以Kelvin地基和弹性半空间地基上的无限大双层板模型模拟路基路面结构,通过积分变换法得到单位脉冲荷载作用下路面响应的Green函数,然后根据线性系统的叠加原理,利用广义Duhamel积分推导出了移动荷载作用下路面动力响应的解析解。通过算例对移动恒载和移动简谐荷载作用下路面的振动特性进行了分析和研究,明确了振动在路面结构中的传播规律。(3)通过动荷载将车辆模型和Kelvin地基上的无限大双层板模型相连接,建立车辆一路面一路基相互作用系统,基于此系统对移动随机荷载作用下路面的动力响应进行了数值仿真,讨论了各类参数对路面动力响应的影响,形成了一套重型车辆对路面破坏性研究的系统化方法。(4)以粘弹性本构关系模拟沥青面层,建立了层状粘弹性体系模型,利用积分变换和传递矩阵法,推导出了单位脉冲荷载作用下层状粘弹性体系表面位移的Green函数,结合广义Duhamel积分,对层状粘弹性体系表面位移的Green函数进行积分逆变换,给出了移动荷载作用下表面位移的解析解。利用样条插值函数开发了计算奇异、振荡函数多重无穷积分的计算程序,完成了表面位移从积分变换域到时间一空间域的转化,结合算例分析了移动恒载和移动简谐荷载作用下层状粘弹性体系表面位移的振动特性。结果表明,粘弹性解大于弹性解,且粘弹性材料能反映路面变形的滞后现象,符合路面材料的受力特点。(5)以粘弹性本构关系模拟沥青面层,依据层状体系理论,建立了路面结构的粘弹性三维ANSYS有限元模型,考虑车辆和路面的相互作用,对移动随机荷载作用下路面结构中的位移、应力和应变进行了仿真计算。将沥青面层底部的拉应变与已有的路面疲劳破坏评价指标相联系,分析讨论了路面等级、载重、行车速度和车辆参数对路面疲劳寿命的影响规律,揭示了路面结构在车辆荷载作用下的疲劳损伤破坏规律和机理。图85幅,表4个,参考文献208篇。更多还原

【Abstract】 With the continuous development of national economy and highway transportation industry, the high speed and heavy duty phenomenon has become extraordinary common. The early pavement damage caused by dynamic load of heavy duty vehicle is becoming more and more serious and receives widespread attention. The static method to design highway has found difficult to meet the demand. It is a prevailing subject to study the dynamics of pavement structure, reveal the pavement damage mechanism, and promote the changing of pavement design criterion from static to dynamic. Although many studies have recently been conducted to find the dynamic responses of the pavement to moving load, most of them have used moving load of constant and harmonic amplitude, and have not considered the stochastic variations in load amplitude with time.Pavement damage makes vehicle’s vibration increase, which can seriously reduce the vehicle’s driving safety and riding comfort. As a result, vehicle dynamic load increase greatly. Vehicle and pavement are interacted and coupled. When analyzing the dynamic responses of the pavement, the interaction between vehicle and pavement must be considered. In this dissertation, the vehicle model, pavement model and subgrade model are linked to a vehicle-pavement-subgrade interaction system by the vehicle dynamic load. Based on this interaction system, the dynamic responses of the pavement under moving stochastic load are systemically researched by employing the methods of theoretical analysis and simulation. The effects of vehicle and pavement parameters on the dynamic responses and the fatigue failure of the pavement structure are discussed in detail. The main contents include:(1)A whole-vehicle model with eight degrees of freedom subjected to pavement surface roughness is built to simulate the vehicle dynamic load in frequency domains. The effects of vehicle parameters, vehicle moving speed and pavement surface roughness on the power spectral density (PSD) of the dynamic load are investigated. A two-objective optimum concept to design vehicle suspension with the recognition of ride performance and road friendliness as the objective functions is presented and illustrated. The results show that the dynamic load generated by the heavy duty vehicle is primarily distributed in the low frequency region, and decreasing suspension stiffness and increasing suspension damping can not only improve the ride performance but also reduce the pavement damage.(2) An infinite two-layer plate resting on Kelvin foundation and elastic half-space is put forward to model the subgrade and pavement structure. The Fourier transform is used to derive the Green’s function of the pavement under the unit impulse load. Based on the superposition principle of linear system, the analytical solutions of the dynamic responses are then derived using the generalized Duhamel integral. The vibration characteristics of the pavement under moving constant and harmonic load are analyzed through some examples, and the regularities of vibration propagation in subgrade and pavement are clarified.(3) A vehicle-pavement-subgrade interaction system is established by linking the vehicle model and the infinite two-layer thin plate resting on Kelvin foundation through the vehicle dynamic load. Based on this interaction system, the dynamic responses of the pavement under moving stochastic load are simulated. The effects of the model parameters on the dynamic responses of the pavement are discussed in detail. Some helpful conclusions and suggestions about vehicle and pavement design are given. A full systematic method as this to study the dynamics of the pavement structure is made.(4) A multilayered viscoelastic system is established by modelling the asphalt surface as viscoelastic constitutive relation. By means of integral transforms and transfer matrix, the Green’s function of the multilayered viscoelastic system under the unit impulse load is obtained. The analytical solution of the steady-state displacement is then derived by combining the generalized Duhamel integral with the Green’s function. The spline interpolation numerical algorithm is successfully used to calculate the multiple integral of singular and oscillatory function, and transfers the solution from the integral transform domain to the time-space domain. The vibration characteristics of the multilayered viscoelastic system under moving constant and harmonic load are analyzed through some examples. Viscoelastic material can reflect the delaying of the pavement deformation, which is in good agreement with the situation of pavement material and mechanics.(5) Based on the layered theory, a 3-D viscoelastic ANSYS model of the pavement structure is established by modelling the asphalt surface as viscoelastic constitutive relation. The time-dependent deflection, stress and strain of the pavement are obtained by linking together the pavement surface roughness, a moving heavy duty vehicle, and a multilayered pavement structure. The fatigue life of pavement structure is calculated by taking the tensile strain at the bottom of asphalt surface as the evaluation index. A parametric study then follows to show the effects of road grade, loading capacity, vehicle moving speed and vehicle parameters on the fatigue life of the pavement. The fatigue-induced failure regularity and mechanism of the pavement under moving stochastic load is elucidated.更多还原