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The objective of this paper is to present the development of simulation and design optimization capabilities, for polymer forming processes, in the context of addressing industrial needs. Accomplishments generated from close to twenty years of research in this field, at the National Research Council (NRC), are presented. Polymer forming processes such as extrusion blow moulding, stretch blow moulding and thermoforming have been the focus of the work, yet the research is extendable to similar polymer forming operations such as micro-blow moulding, sheet blow moulding and composites stamping. The research considers material models, process sequence integration and design optimization, derivative processes and 3D finite elements with multi-body contact. [ABSTRACT FROM AUTHOR]

We present a detailed study of inelastic collisions at low temperature in several supersonic jets of N2, H2, and H2+He mixtures using different nozzles and stagnation conditions. Absolute number density and rotational population data of unprecedented accuracy are measured along the jet axis by Raman spectroscopy with high spatial resolution (<5 μm) and high-sensitivity (<1 photon/sec). The experimental data are interpreted by means of a master equation describing the time evolution of the rotational populations in terms of the state-to-state rate coefficients derived from high-level quantum calculations. This combination of experimental and calculated data leads to a detailed understanding of the underlying physics, consistent with the assumed isentropic behaviour. The breakdown of rotational-translational thermal equilibrium, and its space-time evolution along the jet axis are accounted for by the microscopic (state-to-state rate coefficients) and macroscopic (flow velocity, number density, temperatures) physical quantities. A highly consistent picture, free from any additional parameters, bridges this way the microsopic and macroscopic approaches to fluid dynamics along the jet axis. [ABSTRACT FROM AUTHOR]

The use of polyethylene terephthalate (PET) in the stretch blow molding process presents several challenging issues due to various processing parameters and complex behavior of the material, which is both temperature and strain-rate dependent. In this paper, we generalize the G’Sell-Jonas law in 3D to model and simulate the elasto-visco-plastic (EVP) behavior of PET, taking into account strain-hardening and strain-softening. It is observed that the internal pressure (inside the preform) is significantly different from the nominal pressure (imposed in the blowing device upstream) since the internal pressure and the enclosed volume of the preform are fully coupled. In order to accurately simulate this phenomenon, a thermodynamic model was used to characterize the pressure-volume relationship (PVR). The predicted pressure evolution is thus more realistic when imposing only the machine power of the blowing device (air compressor or vacuum pump). Mechanical and temperature equilibrium equations are fully nonlinear and solved separately with implicit schemes on the current deformed configuration, which is updated at each time step. Biaxial characterization tests were used to determine the model parameters in order to simulate the stretch blow molding process using the pressure-volume thermodynamic relationship. To validate this model, thickness predictions for three industrial cases will be presented and compared to experimental measurements. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

New line shape calculations for CO buffered by Ar are compared to high-resolution measurements from a difference-frequency laser spectrometer, over a range of thermodynamic conditions relevant to the atmosphere. The calculations are based on solving the quantum kinetic (i.e. transport/relaxation) equation for the molecules within the impact approximation, and rely on the commonly used MOLSCAT and MOLCOL codes to determine the speed-dependent collisional relaxation rate. Velocity-changing effects are treated classically using a rigid sphere potential. The comparison initially reveals that the experimental profiles exhibit only 10% to 30% of the expected Dicke narrowing, which leads us to reevaluate our understanding of the narrowing process. A more subtle aspect of the disagreement between theory and experiment draws our attention to an assumption implicit in the calculation of the collisional relaxation rate: the assumption of a Maxwellian form for the velocity dependence of the off-diagonal elements of the density matrix (i.e. the optical coherences). This assumption allows for an analytical simplification of the problem, but eliminates velocity-changing effects (so that they must be added back in using a supplementary classical calculation, which is based here on a rigid sphere interaction). We find that the removal of the above-mentioned assumption should allow for accurate and fully quantum mechanical (but numerical) line shape calculations for systems like CO-Ar on existing computers. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

A practical matrix-based formalism for solving the master equation for a spectral line is applied to the P(2) transition in the fundamental band of carbon monoxide perturbed by argon. The method assumes that the effect of intermolecular collisions on the internal relaxation of the molecules is uncorrelated with the effect of those collisions on the translational motion of the molecules. Comparison with high-resolution line shape measurements reveals that at low pressures, the omission of statistical correlation leads to a miscalculation of the shape of the line. [ABSTRACT FROM AUTHOR]

Pressure shifts of CO fundamental lines perturbed by He and Ar have been measured at 296 K with a laser frequency difference spectrometer. The results are compared with close coupling calculations based on recent potential energy surfaces with an analysis on the parts of the shifts that are symmetric and antisymmetric with respect to a change in the sign of the line number m. [ABSTRACT FROM AUTHOR]