923 research outputs found
Thermal Modeling of Metal Powder-Based Selective Laser Sintering
In order to get a better understanding of Selective Laser Sintering (SLS) process of the metal
powders, three-dimensional modeling of laser sintering of a metal powder mixture that contains
two kinds of metal powder with significantly different melting points under a moving Gaussian
laser beam is investigated numerically. Laser induced melting and resolidification accompanied
by shrinkage are modeled using a temperature transforming model. The liquid flow of the melted
low melting point metal driven by capillary and gravity forces is also included in the physical
model. Both complete and partial shrinkages are considered in the model. Simulations are
performed for both single line laser scanning and multiple-line laser scanning. The numerical
results are compared with experimental results and a detailed parametric study is performed. The
effects of the moving heat source intensity, the scanning velocity, the thickness of the powder
layer and the number of existing sintered layers underneath on the sintering depth, the shape of
the heat affected zone (HAZ) and the temperature distribution are discussed. The optimized
dimensionless moving heat source intensity increases with increasing scanning velocity in order
to achieve the desired sintering depth and bond the newly sintered layer to the previously
sintered layers.Mechanical Engineerin
Numerical Investigation of Evaporation Induced Self-Assembly of Sub-Micron Particles Suspended in Water
Self-assembly of sub-micron particles suspended in a water film is
investigated numerically. The liquid medium is allowed to evaporate leaving
only the sub-micron particles. A coupled CFD-DEM approach is used for the
simulation of fluid-particle interaction. Momentum exchange and heat transfer
between particles and fluid and among particles are considered. A history
dependent contact model is used to compute the contact force among sub-micron
particles. Simulation is done using the open source software package CFDEM
which basically comprises of two other open source packages OpenFOAM and
LIGGGHTS. OpenFOAM is a widely used solver for CFD related problems. LIGGGHTS,
a modification of LAMMPS, is used for DEM simulation of granular materials. The
final packing structure of the sub-micron particles is discussed in terms of
distribution of coordination number and radial distribution function (RDF). The
final packing structure shows that particles form clusters and exhibit a
definite pattern as water evaporates away
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