Computational multiscale methods for granular materials

The fine-scale heterogeneity of granular material is characterized by its polydisperse microstructure with randomness and no periodicity. To predict the mechanical response of the material as the microstructure evolves, it is demonstrated to develop computational multiscale methods using discrete particle assembly-Cosserat continuum modeling in micro- and macro- scales,respectively. The computational homogenization method and the bridge scale method along the concurrent scale linking approach are briefly introduced. Based on the weak form of the Hu-Washizu variational principle, the mixed finite element procedure of gradient Cosserat continuum in the frame of the second-order homogenization scheme is developed. The meso-mechanically informed anisotropic damage of effective Cosserat continuum is characterized and identified and the microscopic mechanisms of macroscopic damage phenomenon are revealed. c 2013 The Chinese Society of Theoretical and Applied Mechanics. [doi： 10.1063/2.1301101]

Engineering phonon thermal transport in few-layer PdSe_(2)

Engineering phonon transport in low-dimensional materials has great significance not only for fundamental research,but also for thermal management applications of electric devices.However,due to the difficulties of micro and nano processing and characterization techniques,the work on tuning phonon transport at nanoscale are scarce.In this work,by introducing Ar+plasma,we probed the phonon transport in two-dimensional(2D)layered semiconductor PdSe_(2)under different defect concentrations.By using thermal bridge method,the thermal conductivity was measured to decrease by 50%after a certain Ar+irradiation,which implied a possible phase transition.Moreover,Raman characterizations were performed to show that the Raman sensitive peaks of PdSe_(2)was red-shifted and finally became disappeared with the increase of defect concentration.“Defect engineering”proves be a practical strategy in tuning the phonon thermal transport in low-dimensional materials,thus providing guidance for potential application in designing thermoelectric devices with various emerging materials.

Liquid bridge force between two unequal-sized spheres or a sphere and a plane

Liquid bridge force acting between wet particles is an important property in particle characterization. This paper deals with liquid bridge force between either two unequal-sized spherical particles or a sphere and a flat plate under conditions where gravitational effect arising from bridge distortion is negligible. In order to calculate the force of the liquid bridge efficiently and accurately, expressions of liquid configuration and liquid bridge force were derived by building a mechanical model, which assumes the liquid bridge to be circular in shape between either two unequal-sized spheres or a sphere and a plane. To assess the accuracy of the numerical results of the calculated liquid bridge forces, they were compared to the nuhlished experimental data.

SHM-based F-AHP bridge rating system with application to Tsing Ma Bridge

This paper aims at developing a structural health monitoring(SHM)-based bridge rating method for bridge inspection of long-span cable-supported bridges.The fuzzy based analytic hierarchy approach is employed,and the hierarchical structure for synthetic rating of each structural component of the bridge is proposed.The criticality and vulnerability analyses are performed largely based on the field measurement data from the SHM system installed in the bridge to offer relatively accurate condition evaluation of the bridge and to reduce uncertainties involved in the existing rating method.The procedures for determining relative weighs and fuzzy synthetic ratings for both criticality and vulnerability are then suggested.The fuzzy synthetic decisions for inspection are made in consideration of the synthetic ratings of all structural components.The SHM-based bridge rating method is finally applied to the Tsing Ma suspension bridge in Hong Kong as a case study.The results show that the proposed method is feasible and it can be used in practice for longspan cable-supported bridges with SHM system.