Molecular dynamics simulations are carried out to study atomic diffusion in the explosive welding process of Ni 50 Ti 50 -Cu (at.%). By using a hybrid method which combines molecular dynamics simulation and classical diffusion theory, the thickness of the diffusion layer and the atomic concentration distribution across the welding interface are obtained.The results indicate that the concentration distribution curves at different times have a geometric similarity. According to the geometric similarity, the atomic concentration distribution at any time in explosive welding can be calculated. Ni 50 Ti 50 -Cu explosive welding and scanning electron microscope experiments are done to verify the results. The simulation results and the experimental results are in good agreement.

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Different types of carbon coated iron (Fe) based nanoparticles were controllably synthesized by detonation decomposition of urea nitrate metal complex explosive precursors. In order to control the detonation synthesis of the Fe-based composite nanoparticles, the main components of the urea nitrate metal complex explosive precursors were optimally designed. The components, morphologies, structures and various Fe-based phase composition of the as-obtained composite nanoparticles were further investigated by x-ray diffraction, transmission electron microscopy, electron diffraction spectroscopy and energy dispersive x-ray spectroscopy. The results show that discrete, spherical, uniformly sized (~55 nm) iron oxide nanocrystals and core-shell structural composite nanoparticles (graphite coated Fe) were effectively synthesized by adjusting the densities, oxygen balances and mole ratios of C:Fe of these compound explosive precursors. The formation mechanism of these carbon coated Fe-based composites during the instantaneous detonation reaction process is further discussed.

Two 3-D numerical models of the discrete element method (DEM) for impact problems are proposed. The models can calculate not only the impact problems of continuum and non-continuum, but also the transient process from continuum to non-continuum. The stress wave propagation in a concrete block and a dynamic splitting process of a marble disc under impact loading are numerically simulated with the proposed models. By comparing the numerical results with the corresponding results obtained by the finite element method (FEM) and the experiments, it is proved that the models are reliable for three-dimensional impact problems.