Reduced-dimensional material geometries

Table 5.3-1 Examples of reduced-dimensional material geometries, and definitions of their dimensionality and of the associated type of confinement...

Consider the equation of heat conduction in a solid with the laser energy absorbed on the irradiated surface as a heat source. By judiciously selecting the beam geometry, dwell time, and sample configuration, the problem may be reduced to solvable one- and two-dimensional heat flow analyses. Phase transitions can be included and the temperature distributions that are produced can be calculated. Examples will be selected to provide specific guidance in the choice of lasers and materials. The result of all this will be an idea of the effects that one may produce by laser heating of solids. 

The layflat was a representation of the part under consideration that reduced the problem of flow in a three-dimensional geometry to flow in a plane. For example, consider an open box with a thickened lip at the open end. If the box is to be injected at the center of its base, a potential problem could arise from polymer flowing aroimd the rim of the box and forming an airtrap (Fig. 7.56). The layflat of the box is shown in Fig. 7.57. As can be seen, the box has been folded out to form the layflat. Analysis could now be done on the various flow paths on the layflat. For example, the results of such analysis could be used to thicken the sections shown to promote flow and so prevent the flow of material around the thickened rim. While this type of analysis was undoubtedly useful, it did require considerable skill on the part of the user to produce the layflat and optimize the various flow paths. 

Furthermore, it can be possible to obtain the sintered part with its exact dimensions net shape), without the need for a machine finishing in applications that require high dimensional accuracy. The other side of the coin is the technical complexity of the process and the high costs incurred, as well as the limitations on the geometry of the parts, which can only have simple forms and a rather reduced size. We must have pressurization devices manufactured in materials that resist the temperatures required by sintering - and even if these temperatures are lower... 

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