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Experiments to populate and validate a processing model for polyurethane foam. BKC 44306 PMDI-10

Mondy, Lisa A.; Bauer, Stephen; Hileman, Michael B.; Thompson, Kyle R.; Smith, David; Rao, Rekha R.; Shelden, Bion; Soehnel, Melissa; O'Hern, Timothy J.; Grillet, Anne M.; Celina, Mathew C.; Wyatt, Nicholas B.; Russick, Edward M.

We are developing computational models to elucidate the expansion and dynamic filling process of a polyurethane foam, PMDI. The polyurethane of interest is chemically blown, where carbon dioxide is produced via the reaction of water, the blowing agent, and isocyanate. The isocyanate also reacts with polyol in a competing reaction, which produces the polymer. Here we detail the experiments needed to populate a processing model and provide parameters for the model based on these experiments. The model entails solving the conservation equations, including the equations of motion, an energy balance, and two rate equations for the polymerization and foaming reactions, following a simplified mathematical formalism that decouples these two reactions. Parameters for the polymerization kinetics model are reported based on infrared spectrophotometry. Parameters describing the gas generating reaction are reported based on measurements of volume, temperature and pressure evolution with time. A foam rheology model is proposed and parameters determined through steady-shear and oscillatory tests. Heat of reaction and heat capacity are determined through differential scanning calorimetry. Thermal conductivity of the foam as a function of density is measured using a transient method based on the theory of the transient plane source technique. Finally, density variations of the resulting solid foam in several simple geometries are directly measured by sectioning and sampling mass, as well as through x-ray computed tomography. These density measurements will be useful for model validation once the complete model is implemented in an engineering code.

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TYPE SAND Report YEAR 2014
DOIOSTI

Exploring mediated reality to approximate X-ray attenuation coefficients from radiographs

Proceedings of SPIE - The International Society for Optical Engineering

Jimenez, Edward S.; Orr, Laurel J.; Morgan, Megan L.; Thompson, Kyle R.

Estimation of the x-ray attenuation properties of an object with respect to the energy emitted from the source is a challenging task for traditional Bremsstrahlung sources. This exploratory work attempts to estimate the x-ray attenuation profile for the energy range of a given Bremsstrahlung profile. Previous work has shown that calculating a single effective attenuation value for a polychromatic source is not accurate due to the non-linearities associated with the image formation process. Instead, we completely characterize the imaging system virtually and utilize an iterative search method/constrained optimization technique to approximate the attenuation profile of the object of interest. This work presents preliminary results from various approaches that were investigated. The early results illustrate the challenges associated with these techniques and the potential for obtaining an accurate estimate of the attenuation profile for objects composed of homogeneous materials.

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TYPE Conference Poster YEAR 2014
OSTIScopus

Irregular large-scale computed tomography on multiple graphics processors improves energy-efficiency metrics for industrial applications

Proceedings of SPIE - The International Society for Optical Engineering

Jimenez, Edward S.; Goodman, Eric; Park, Ryeojin; Orr, Laurel J.; Thompson, Kyle R.

This paper will investigate energy-efficiency for various real-world industrial computed-tomography reconstruction algorithms, both CPU- and GPU-based implementations. This work shows that the energy required for a given reconstruction is based on performance and problem size. There are many ways to describe performance and energy efficiency, thus this work will investigate multiple metrics including performance-per-watt, energy-delay product, and energy consumption. This work found that irregular GPU-based approaches1 realized tremendous savings in energy consumption when compared to CPU implementations while also significantly improving the performanceper- watt and energy-delay product metrics. Additional energy savings and other metric improvement was realized on the GPU-based reconstructions by improving storage I/O by implementing a parallel MIMD-like modularization of the compute and I/O tasks.

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TYPE Conference Poster YEAR 2014
OSTIScopus
Results 51–75 of 105
Results 51–75 of 105
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