A methodology was presented relating the microstructure of asphalt mixtures to their damage behavior. Digital image techniques were used to capture the asphalt mixture microstructure, and the finite element method was...A methodology was presented relating the microstructure of asphalt mixtures to their damage behavior. Digital image techniques were used to capture the asphalt mixture microstructure, and the finite element method was used to simulate the damage evolution of asphalt mixture through splitting test. Aggregates were modeled to be linearly elastic, and the mastics were modeled to be plastically damaged. The splitting test simulation results show that the material heterogeneity, the properties of aggregates and air voids have significant effects on the damage evolution approach. The damage behavior of asphalt mixture considering material heterogeneity is quite different from that of the conventional hypothesis of homogeneous material. The results indicate that the proposed method can be extended to the numerical analysis for the other micromechanical behaviors of asphalt concrete.展开更多
Stresses, particularly those at geometric discontinuities, can influence structural integrity of engineering components. Motivated by the prevalence of cutouts in components, the objective of this paper is to demonstr...Stresses, particularly those at geometric discontinuities, can influence structural integrity of engineering components. Motivated by the prevalence of cutouts in components, the objective of this paper is to demonstrate ability to stress analyze finite, circularly-perforated orthotropic composites whose external loading may be unknown. Recognizing difficulties in obtaining purely theoretical or numerical solutions, the paper presents a hybrid means of stress analyzing such structures. Individual stresses, including those on the edge of the hole, are obtained in a loaded finite graphite/epoxy composite tensile plate containing a round hole by processing measured values of a single displacement field with an Airy stress function in complex variables. Displacements are recorded by digital image correlation. Traction-free conditions are satisfied analytically at the edge of the hole using conformal mapping and analytic continuation. Stresses satisfy equilibrium and strains satisfy compatibility. Significant features of the technique include its wide applicability, it smooths the measured information, does not require knowing the applied loading, and the rigorous mechanics foundation by which strains are determined from measured displacements.展开更多
Efficient large-scale nondestructive quality assessment of graphene on Pt is essential to the in-depth growth research and practical applications of graphene.Here,we present a very simple method for directly observing...Efficient large-scale nondestructive quality assessment of graphene on Pt is essential to the in-depth growth research and practical applications of graphene.Here,we present a very simple method for directly observing the domains and defects in graphene on Pt using an ordinary optical microscope.This was achieved by modifying graphene on Pt using methylene blue(MB).Because the chemical activities of graphene and Pt surface differ significantly,the adsorption and reaction of MB on graphene and platinum surface differ.We can determine the distribution of graphene crystal domains and defects by comparing the colors in the optical images.In addition,this characterization method causes no obvious damage to the Pt substrate and graphene.Moreover,it does not affect the recycling of the substrate or the subsequent characterization or application of graphene.Our study provides a nondestructive method for measuring the quality of graphene on Pt on a large scale,as well as a reference for the characterization and doping of other two-dimensional materials.展开更多
基金Project(50808086) supported by the National Natural Science Foundation of China
文摘A methodology was presented relating the microstructure of asphalt mixtures to their damage behavior. Digital image techniques were used to capture the asphalt mixture microstructure, and the finite element method was used to simulate the damage evolution of asphalt mixture through splitting test. Aggregates were modeled to be linearly elastic, and the mastics were modeled to be plastically damaged. The splitting test simulation results show that the material heterogeneity, the properties of aggregates and air voids have significant effects on the damage evolution approach. The damage behavior of asphalt mixture considering material heterogeneity is quite different from that of the conventional hypothesis of homogeneous material. The results indicate that the proposed method can be extended to the numerical analysis for the other micromechanical behaviors of asphalt concrete.
文摘Stresses, particularly those at geometric discontinuities, can influence structural integrity of engineering components. Motivated by the prevalence of cutouts in components, the objective of this paper is to demonstrate ability to stress analyze finite, circularly-perforated orthotropic composites whose external loading may be unknown. Recognizing difficulties in obtaining purely theoretical or numerical solutions, the paper presents a hybrid means of stress analyzing such structures. Individual stresses, including those on the edge of the hole, are obtained in a loaded finite graphite/epoxy composite tensile plate containing a round hole by processing measured values of a single displacement field with an Airy stress function in complex variables. Displacements are recorded by digital image correlation. Traction-free conditions are satisfied analytically at the edge of the hole using conformal mapping and analytic continuation. Stresses satisfy equilibrium and strains satisfy compatibility. Significant features of the technique include its wide applicability, it smooths the measured information, does not require knowing the applied loading, and the rigorous mechanics foundation by which strains are determined from measured displacements.
基金financially supported by the National Defense Technology Innovation Special Zone Project, the National Natural Science Foundation of China (51402342)the Science and Technology Commission of Shanghai Municipality (20501130200)。
文摘Efficient large-scale nondestructive quality assessment of graphene on Pt is essential to the in-depth growth research and practical applications of graphene.Here,we present a very simple method for directly observing the domains and defects in graphene on Pt using an ordinary optical microscope.This was achieved by modifying graphene on Pt using methylene blue(MB).Because the chemical activities of graphene and Pt surface differ significantly,the adsorption and reaction of MB on graphene and platinum surface differ.We can determine the distribution of graphene crystal domains and defects by comparing the colors in the optical images.In addition,this characterization method causes no obvious damage to the Pt substrate and graphene.Moreover,it does not affect the recycling of the substrate or the subsequent characterization or application of graphene.Our study provides a nondestructive method for measuring the quality of graphene on Pt on a large scale,as well as a reference for the characterization and doping of other two-dimensional materials.
