Numerical simulation of the laser-induced formation of shapes from polymer powders is achieved using an extension of a previously developed model of nonisothermal powder sintering. The extended model mimics the Selective Laser Sintering process which is used to produce a multiple layer part via laser irradiation. Model predictions of the physical features and effective thermophysical properties (porosity and thermal conductivity) of the object demonstrate sensitivity to several thermal processing parameters. Predicted values of the effective thermal conductivity and average porosity of the processed item are reported and correlated. [S1087-1357(00)00904-7]

Sintering of powders occurs in a wide array of manufacturing technologies and geophysical phenomena. Despite the prevalence of powder sintering, little attention has been paid to sintering of macroscopic shapes under non-isothermal conditions. In this paper (1) features of a representative, experimentally grown solid shape produced by non-isothermal sintering are discussed, (2) prediction of the solid shape evolution is achieved using a hybrid heat transfer, sintering, and consolidation model, (3) comparison of the actual and predicted solid shapes is made, (4) parametric simulation of solid part growth in conjunction with void expansion is attained, and (5) analytical predictions of the void space evolution are developed and discussed.

Laser-induced sintering of powders has become prevalent in a number of Solid Freeform Fabrication technologies such as Selective Laser Sintering (SLS), which is used to produce nearly solid parts from initially-porous powder via laser irradiation. In this paper, a model is presented which can be used to predict the shape and general features of consolidated heat affected zones produced by laser-induced, non-isothermal sintering of polymer powder. Comparisons between experimental results and predictions are made, and the model is used to investigate the influence of various thermal processing parameters on the sintering operation. The model is then extended to simulate the manufacture of a simple multiple layer part which is produced in a manner similar to SLS.

Naphthalene sublimation experiments have been conducted to examine the effect of rotation on the regional heat]mass transfer distribution for turbulent air flow in a rotating smooth two-pass square channel that has a 180 turn with sharp corners. The Reynolds number ranges from 5,500 to 14,500 and the rotation number goes up to 0.24. The test channel models the first two passes of serpentine internal cooling passages of gas turbine blades.Flow around a sharp turn causes larger heat]mass transfer increase in the turn and in the second pass than flow around a smooth turn. In the first pass with radially outward flow, rotation increases the heat]mass transfer on the trailing wall and decreases the heat]mass transfer on the leading wall. The reversed trend in the second pass with radially inward flow is evident only after four hydraulic diameters downstream of the turn exit. With rotation, there is an abrupt increase of the regional heat]mass transfer in the upstream portion of the turn on the leading wall. The regional heat]mass transfer on the trailing wall, however, increases along the streamwise direction in the turn, as in the stationary channel case. In the turn and immediately downstream of the turn, the shape of the heat]mass transfer distribution in a rotating channel is invariant over the range of rotation number studied. In a rotating channel, decreasing the Reynolds number increases the heat]mass transfer on the trailing wall and decreases that on the leading wall in the first pass, and increases the heat] mass transfer on both walls in the turn and immediately downstream of the turn.

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