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Jing Zhang - One of the best experts on this subject based on the ideXlab platform.

  • sintering phenomena and mechanical strength of nickel based materials in direct metal laser sintering process a molecular dynamics study
    Journal of Materials Research, 2016
    Co-Authors: Yi Zhang, Jing Zhang
    Abstract:

    This paper presents an atomistic scale model on sintering of nickel Particles in direct metal laser sintering process. Both sintering phenomena and mechanical strength of sintered Particles are simulated using molecular dynamics method. A two-Particle atomistic model is developed to investigate the Diffusion of atoms during nickel sintering. The Diffusion of Particle surface is higher than the Particle core, with calculated activation energy of nickel Particle Diffusion 6.10 kJ/mol in the Particle core, and 6.24 kJ/mol on the Particle surface, which are reasonably in agreement with the experimental data of 7.89 kJ/mol. The sintered model shows a 5-fold twinning structure at 1200 K, and two parallel twin boundaries at 1300 K. The mechanical properties of nickel nanoParticles sintered at various heating rates are investigated using uniaxial tensile test simulations. The results show that higher heating rate during sintering increases the mechanical strength of the sintered material. Deformation mechanism of sintered structures is illustrated from the correlation between stress and dislocation evolution.

Yi Zhang - One of the best experts on this subject based on the ideXlab platform.

  • sintering phenomena and mechanical strength of nickel based materials in direct metal laser sintering process a molecular dynamics study
    Journal of Materials Research, 2016
    Co-Authors: Yi Zhang, Jing Zhang
    Abstract:

    This paper presents an atomistic scale model on sintering of nickel Particles in direct metal laser sintering process. Both sintering phenomena and mechanical strength of sintered Particles are simulated using molecular dynamics method. A two-Particle atomistic model is developed to investigate the Diffusion of atoms during nickel sintering. The Diffusion of Particle surface is higher than the Particle core, with calculated activation energy of nickel Particle Diffusion 6.10 kJ/mol in the Particle core, and 6.24 kJ/mol on the Particle surface, which are reasonably in agreement with the experimental data of 7.89 kJ/mol. The sintered model shows a 5-fold twinning structure at 1200 K, and two parallel twin boundaries at 1300 K. The mechanical properties of nickel nanoParticles sintered at various heating rates are investigated using uniaxial tensile test simulations. The results show that higher heating rate during sintering increases the mechanical strength of the sintered material. Deformation mechanism of sintered structures is illustrated from the correlation between stress and dislocation evolution.

Jakob Mann - One of the best experts on this subject based on the ideXlab platform.

  • an experimental investigation of the relative Diffusion of Particle pairs in three dimensional turbulent flow
    Journal of Fluid Mechanics, 2000
    Co-Authors: Jakob Mann
    Abstract:

    The Particle tracking (PT) technique is used to study turbulent Diffusion of Particle pairs in a three-dimensional turbulent flow generated by two oscillating grids. The experimental data show a range where the Richardson–Obukhov law 〈 r 2 〉 = C e t 3 is satisfied, and the Richardson–Obukhov constant is found to be C = 0.5. A number of models predict much larger values. Furthermore, the distance–neighbour function is studied in detail in order to determine its general shape. The results are compared with the predictions of three models: Richardson (1926), Batchelor (1952) and Kraichnan (1966 a ). These three models predict different behaviours of the distance–neighbour function, and of the three, only Richardson's model is found to be consistent with the measurements. We have corrected a minor error in Kraichnan's (1996 a ) Lagrangian history direct interaction calculations with the result that we had to increase his theoretical value from C = 2.42 to C = 5.5.