沥青路面自上向下裂缝传播的模拟外文翻译Word下载.docx

1、 Top-down crack in asphalt pavements has been reported as a widespread mode of failure. A solid understanding of themechanisms of crack growth is essential to predict pavement performance in the context of thickness design, as well as in the design and optimization of mixtures. Using the coupled ele

2、ment free Galerkin （EFG） and finite element （FE） method, top-down crack propagation in asphalt pavements is numerically simulated on the basis of fracture mechanics. A parametric study is conducted to isolate the effects of overlay thickness and stiffness, base thickness and stiffness on top-down cr

3、ack propagation in asphalt pavements. The results show that longitudinal wheel loads are disadvantageous to top-down crack because it increases the compound stress intensity factor （SIF） at the tip of top-down crack and shortens the crack path, and thus the fatigue life descends.The SIF experiences

4、a process “sharply ascendingslowly descendingslowly ascendingsharply ascending again” with the crack propagating. The thicker the overlay or the base, the lower the SIF; the greater the overlay stiffness, the higher the SIF. The crack path is hardly affected by stiffness of the overlay and base.Key

5、words: Road engineering; Top-down crack; Coupled element free Galerkin （EFG） and finite element （FE） method; Stress intensity factor （SIF）; Crack propagating path1 Introduction Cracking is one of the most influential distressesthat govern the service life of asphalt concrete pavements. Since crackin

6、g leads to water penetration,thereby weakening the foundation of the pavement structure and contributing to increased roughness, a number of studies have been conducted to obtain a better understanding of cracking mechanisms in asphalt concrete pavements . A solid understanding of the mechanisms of

7、crack growth is essential to predict pavement performance in the context of thickness design, as well as in the design and optimization of mixtures. Top-down crack in asphalt pavements has been reported as a widespread mode of failure. Recently,most studies on top-down crack of asphalt pavements hav

8、e focused on the initiation （Svasdisant et al., 2002; Wang et al., 2003）, but the mechanisms for top-down crack propagation have not been completely explained, only little literature involved（Sangpetngam et al., 2004; Mao et al., 2004）.The theory of fracture mechanics has been used as a basis for pr

9、edicting crack growth in asphalt mixtures. But the complexity of the problem and the lack of simple-to-use analysis tools have been obstacles to a better understanding of hot-mix asphalt fracture mechanics. Until today, the well-known finite element （FE） method has been the primary tool used for mod

10、eling cracks and their effects in mixtures and pavements （Song et al., 2006）. Unfortunately, it is both complex and numerically intensive for fracture mechanics applications. Some researchers predicted crack growth in asphalt mixtures with the boundary element method （BEM） （Sangpetngam et al., 2004）

11、, but the BEM is not capable of dealing with the multi-medium issues and complicated nonlinear problems.The element free Galerkin （EFG） method is advantageous in solving moving boundary problems,such as modeling of growing cracks. Fundamentally in EFG, a structured mesh is not used, since only a sca

12、ttered set of nodal points is required in the domain of interest. This feature presents significant implications for modeling fracture propagation, because the domain of interest is completely discretized by a set of nodes. Since no element connectivity data are needed, the burdensome remeshing requ

13、ired by the FE method can be avoided.Although EFG is attractive for simulating crack propagation, it costs more computational time than a regular FE, and the imposition of the essential boundary conditions is complicated. Furthermore,due to the level of maturity and comprehensive capabilities of FE,

14、 it is often advantageous to use EFG only in the sub-domains where its capabilities can be exploited efficiently.In this work, a combination of coupled EFG and FE modeling and fracture mechanics was selected for physical representation and analysis of a pavement with a growing top-down crack, and th

15、e effect on the crack propagation of structural parameters was analyzed.2 Numerical theories2.1 Element free Galerkin method The EFG method adopts the moving least-squares （MLS） to construct the approximate function （Belytschko et al., 1994; 1995; 1996） （1） where is the approximate function, is the

16、parameter vector about nodes, and （x） is the MLS shape function which could be written as （x）,（x） （2） （3） （4）The matrices P（x） and W（x） are defined as （5） （6） where p（x）=p1（x）, p2（x）, , pm（x） is the basis function,and m is the order of the basis function; w（xxi）is the weight function associated with node i. In this study, a linear basic function and cubic spl