【作者】 罗辉；

【导师】 朱宏平；

【作者基本信息】 华中科技大学 ， 结构工程， 2007， 博士

【摘要】 沥青路面的力学行为机理和各种裂纹是沥青路面理论与实践研究前沿之一。开展沥青路面力学行为及裂纹产生机理、裂纹扩展行为的研究可以更加全面地描述路面的力学行为,进一步理解路面损伤与早期破坏的原因,并为沥青路面的设计与养护提供指导。本文对沥青路面力学行为和疲劳裂纹的扩展作了数值与试验研究。主要内容如下(1)利用沥青混合料的热粘弹本构关系,考虑沥青路面各层之间的接触状态,对降温条件下的沥青路面的温度应力响应进行了有限元分析。研究了初始温度、降温幅度、降温速率、面层厚度、基层模量、基层与面层温缩系数等对温度应力响应的影响。(2)对沥青路面在移动行车荷载下的动力响应进行了有限元分析。引入无反射边界条件,消除了有限元方法由于模型尺寸的有界给动力分析结果带来的不良影响,考虑了面层材料的粘弹属性;分析了基层模量、基层厚度、层间接触状态、材料阻尼、行车速度、轮胎接地压力等因素的影响。(3)提出了一种无单元伽辽金方法同有限元方法的耦合方法——过渡单元耦合方法。介绍了无单元伽辽金同有限元常用的耦合方法,并对其中两种常用的耦合方法:过渡单元法和配点法作了重点阐述,讨论了其理论基础和其耦合方法的线性一致性问题。在过渡单元耦合法的基础上,提出了简化的过渡单元耦合方法,并通过数值算例证明了简化的过渡单元耦合方法的有效性。(4)对无单元伽辽金方法在裂纹扩展中的应用进行了研究,介绍了无单元法求取裂纹尖端应力强度因子的围线积分法和面积积分方法,并对其实现过程作了说明。对基于无单元伽辽金方法的裂纹扩展模拟的实现进行了重点研究,具体说明了其扩展准则,扩展增量的选取,几何形状更新方法。并通过数值算例验证了无单元伽辽金方法在断裂力学和裂纹扩展方面的应用。(5)通过预切口沥青混凝土小梁的三点弯曲疲劳实验,研究了预切口沥青混凝土小梁的疲劳破坏特征,研究了预切口三点弯曲小梁的疲劳寿命和裂纹扩展路径。并通过自编的无单元伽辽金/有限元耦合裂纹扩展模拟程序对预切口小梁疲劳实验进行了数值模拟,验证了程序的有效性。结果表明,随着预切口裂纹偏离加载中点距离的增加,相同集中作用力下,裂纹的起裂角增大,小梁的疲劳寿命增大。随着应力水平的增大,疲劳寿命下降。试验结果表明,由于沥青混凝土材料颗粒的不均匀性,裂纹扩展路径通常沿着集料颗粒边界扩展而很少切断颗粒。(6)通过无单元伽辽金/有限元耦合方法模拟了沥青路面结构中裂纹的扩展路径。在开裂路面的综合参数研究中详细评价了不同的路面结构组合、超载和荷载相对裂纹的位置的影响。荷载的位置连同沥青面层和基层刚度对裂纹的扩展有很大的影响,计算出了裂纹增长的方向,且表明随着裂纹长度的增加其扩展方向会发生改变。路面结构(厚度和刚度)的不同组合对沥青路面表面裂纹的扩展行为有较大的影响。更多还原

【Abstract】 The study on the asphalt pavement mechanics behavior in service and the asphalt overlay’s crack propagation is a popular and advanced topic in the asphalt pavement researches. The exploring on the mechanics behavior and crake expanding performance of asphalt pavement will contribute to a better understand on working state of the asphalt pavement, which is the base for further discovery on the causes of the immature damage, and can guide the asphalt pavement design and rehabilitation. The thesis makes the numerical and test study on the asphalt pavement’s mechanics behavior and the crack propagation. The main works in the thesis are as following:(1)Based on the visco-elasticity of the asphalt concrete, the thermal stress responses of the pavement are studied considering the contact mechanics of the interface by the finite element method. Further, the influence of the initial temperature, the cooling range, the cooling rate, the overlay’s thickness and the base module on the temperature stress response is analyzed.(2)The dynamic response of the asphalt pavement under the moving wheel loads is analyzed using the finite element method. The non-reflective boundary is introduced to avoid the disturbance for the limit size of the finite element model’s domain which would reflect the wave at the model’s boundary, and the visco-elasticity of the asphalt concrete is taken into account too. The influence of the base module, the base’s thickness, the contact condition of the interface, the damping, the velocity of the wheel loads is studied.(3)The coupling method combining the element free Galerkin method (EFGM) and the finite element method (FEM) is discussed. The usual coupling methods are addressed, while two widely used methods-interface elements approach and collocation approach-are presented in detail on its theory bases and the linear consistency. A simplified transition element method is represent based on traditional transition element method, which is proved valid by the numerical sample.(4)The application of EFGM on the crack propagation is addressed. Two methods-contour integral and area integral- are introduced to calculate the stress intensity factor (SIF) of the crack tip, and their implements are explained. And the crack propagation modeling attracts much attention, especially on the crack criterion, the selection of the crack increment, the refreshment of the geometry. Some samples on the crack propagation simulation work have been offered. The application of EFGM in the field of Crack Mechanics and Crack Propagation is proved to be available by numerical case studies.(5)The fatigue characteristic, fatigue life and crack propagation path of the pre-sawed asphalt concrete beam have been studied by the three-point bending fatigue test. Furthermore, the test has been numerical simulated with the program based on the coupling of EFGM and FEM. The result of the test and simulation shows that, the fatigue life ascends with the increase of the distance between the loading point and the sawed crack. And the fatigue life descends with the increase of the stress level. The crack propagation path abides certain rule in general. And the test demonstrates that the path propagates along the boundary of the aggregate nearly not splits the particles.(6)The crack propagation path of asphalt pavement under wheel loads is firstly simulated by the coupling of EFGM and FEM method interiorly. The influences of the overlay thickness, the base modules, the overloads, the loading positions are evaluated in detail by parameter analysis. The loading position and the module of overlay and base heavily influence the crack propagation path. The SIFs are calculated along with the crack propagating. The crack angles are also analyzed, and the results show that the crack angle will change with the crack propagating. The various combinations of depth and rigidity will make different crack propagation behavior of asphalt pavement.更多还原