Three-Dimensional Plastic Model

A method for the automatic fabrication of a three-dimensional plastic model has been described (11). 

The solid model is fabricated by exposing a liquid photocurable polymer of 2 mm thickness to UV radiation, and subsequently stacking the cross-sectional solidified layers. 

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Kodama H (1981) Automatic method for fabricating a three-dimensional plastic model with photohardening polymer. Rev Sci Instrum 52 1770-1773... 

Tsardaka and co-workers [102,141,142] presented the Heckel plot with dependence on time and analyzed deformation in combination with elastic recovery. Additional areas to describe plasticity were determined from two-dimensional (2D) plots [129], Finally, the three-dimensional (3D) model [143, 144] was developed by fitting a plane to a 3D data plot on the basis of normalized time, pressure, and porosity according to Heckel. 

In this subsection, a special case of experience traces will be addressed. In contrast to the structural models described in the last subsection, multimedia information usually does not provide any possibility of extracting meaningful semantic information. As a concrete application scenario, the visualizations resulting from three-dimensional plastics engineering simulations can be stored as short video clips, and then structured and annotated according to an appropriate domain model. This allows the retrieval and thus the reuse of these complex simulation results, together with the domain experts interpretations. 

Figure 5.21 A probable three dimensional structural model for a PAN based HM carbon fiber. Source Reprinted with permission from Barnett FR, Norr MK, Proceedings of the International Conference on Carbon Fibres, their Composites and Applications, London (Plastics Institute), 32, 1974. Copyright 1974, Maney Publishing (who administers the copyright on behalf of lOM Communications Ltd., a wholly owned subsidiary of the Institute of Materials, Minerals Mining).

In papers published in 1947 and 1948, Oldroyd [47] developed a three-dimensional of Eq. 2.15 that could predict non-Newtonian viscosity and three-dimensional plastic yielding based on a von Mises stress criterion. Subsequently, SHbar and Pasley [48] developed a similar three-dimensional model, which accounted for thixotropy. 

A tensorial formulation of a Bingham plastic fluid was first introduced by Hohenemser and Prager (1932) and later by Oldroyd (1947). On the other hand, the experimental data presented above show that particulate-filled molten thermoplastics and elastomers exhibit both non-Newtonian viscosity and normal stress effects at large strain rates or large shear stresses, while exhibiting yield values at small strain rates or small shear stresses. Therefore, it is desirable to develop a three-dimensional rheological model that can describe such experimental observations. 

Note that different perfectly plastic models for three dimensional case are considered in (Mosolov, Myasnikov, 1971). 

Years ago plastic scale models were fabricated for each plant under construction, providing excellent three-dimensional representations of the actual facilities. Today, in the age of the microcomputer, it is quicker, easier, and much cheaper to generate models by means of computer graphics. 

This process uses a moving laser beam, directed by a computer, to prepare the model. The model is made up of layers having thicknesses about 0.005-0.020 in. (0.012-0.50 mm) that are polymerized into a solid product. Advanced techniques also provides fast manufacturing of precision molds (152). An example is the MIT three-dimensional printing (3DP) in which a 3-D metal mold (die, etc.) is created layer by layer using powdered metal (300- or 400-series stainless steel, tool steel, bronze, nickel alloys, titanium, etc.). Each layer is inkjet-printed with a plastic binder. The print head generates and deposits micron-sized droplets of a proprietary water-based plastic that binds the powder together. 

Molecular modeling helps students understand physical and chemical properties by providing a way to visualize the three-dimensional arrangement of atoms. This model set uses polyhedra to represent atoms, and plastic connectors to represent bonds (scaled to correct bond length). Plastic plates representing orbital lobes are included for indicating lone pairs of electrons, radicals, and multiple bonds—a feature unique to this set. 

While there are many choices and options for engaging in rapid prototyping, we ll cover the basic steps involved in stereolithography—an additive technique by which plastic models are built thin layer upon thin layer, resulting in a three-dimensional prototype created by a machine with very little human involvement. 

There have been many efforts for combining the atomistic and continuum levels, as mentioned in Sect. 1. Recently, Santos et al. [11] proposed an atomistic-continuum model. In this model, the three-dimensional system is composed of a matrix, described as a continuum and an inclusion, embedded in the continuum, where the inclusion is described by an atomistic model. The model is validated for homogeneous materials (an fee argon crystal and an amorphous polymer). Yang et al. [96] have applied the atomistic-continuum model to the plastic deformation of Bisphenol-A polycarbonate where an inclusion deforms plastically in an elastic medium under uniaxial extension and pure shear. Here the atomistic-continuum model is validated for a heterogeneous material and elastic constant of semi crystalline poly( trimethylene terephthalate) (PTT) is predicted. 

Fivel M. C., Robertson, C. F., Canova, G. R. and Boulanger, L., Three-Dimensional Modeling of Indent-Induced Plastic Zone at a Mesoscale, Acta Mater. 46, 6183 (1998). 

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