A graph-spectral approach to shape-from-shading

In this paper, we explore how graph-spectral methods can be used to develop a new shape-from-shading algorithm. We characterize the field of surface normals using a weight matrix whose elements are computed from the sectional curvature between different image locations and penalize large changes in surface normal direction. Modeling the blocks of the weight matrix as distinct surface patches, we use a graph seriation method to find a surface integration path that maximizes the sum of curvature-dependent weights and that can be used for the purposes of height reconstruction. To smooth the reconstructed surface, we fit quadrics to the height data for each patch. The smoothed surface normal directions are updated ensuring compliance with Lambert's law. The processes of height recovery and surface normal adjustment are interleaved and iterated until a stable surface is obtained. We provide results on synthetic and real-world imagery

Development of the in situ forming of a liquid infused preform (ISFLIP) process : a new manufacturing technique for high performance fibre reinforced polymer (FRP) components

A problem is not a problem anymore if no solution exists; therefore, in the present dissertation, a novel manufacturing technique, the In Situ Forming of a Liquid Infused Preform (ISFLIP), is proposed as a solution to some typical problems that manufacturing of Fibre Reinforced Polymer (FRP) parts through Vacuum Infusion (VI) involves, such as not taking advantage of the full potential of FRPs, long processing times and lack of reproducibility. ISFLIP is a hybrid process between VI and diaphragm forming in which a flat preform of a stack of reinforcement fabrics is firstly impregnated with a low viscosity matrix and, then, formed over a mould while the matrix is still in the low viscosity state. Being focused on high performance FRPs and shell components, from simple to complex double curvature shapes, a number of trade-offs between VI and diaphragm forming were overcome to lay the foundations from which ISFLIP ability to manufacture FRP components has been proven. In order to adopt a VI manufacturing methodology that fitted ISFLIP targets, important contributions to more general VI have also been made in terms of part quality optimization, addressing the major concern that void content is in VI, with competitive manufacturing times. An effective vacuum degassing procedure in which bubble formation is enhanced through high speed stirring, and a non-conventional filling and post-filling strategy are proposed for this purpose. Eventually, void content was virtually eliminated and post-filling time minimized without affecting fibre content. In ISFLIP, textile preforms are formed together with a series of auxiliary materials (plastic films and sheets, textile fabrics and knitted meshes), most of them showing different in-plane deformation mechanisms. Forming performance of preforms, as well as final part quality, are severely affected by interactions between all these materials different in nature. Uncertainties on this respect and an initial evaluation of attainable shapes were also addressed to define a more focused research plan to the final goal, still distant, of implementing ISFLIP in a real production environment. Results obtained throughout the research project give cause for reasonable optimism in ISFLIP potential and future prospects.Un problema deja de ser un problema si no existe solución; por lo tanto, en esta disertación, una novedosa técnica de fabricación, el Conformado In Situ de una Preforma Infusionada con resina Líquida (ISFLIP, por sus siglas en inglés), se propone como solución a algunos problemas típicos relacionados con la fabricación de piezas de Polímero Reforzado con Fibra (FRP) a través de la Infusión por Vacío (VI), problemas tales como el desaprovechamiento de todo el potencial de los FRPs, largos tiempos de procesado y falta de reproducibilidad. ISFLIP es un proceso híbrido entre la VI y el conformado por membrana elástica en el que una preforma plana formada a partir de un apilado de tejidos de refuerzo es en primera instancia impregnada con una resina de baja viscosidad y, entonces, conformada sobre un molde mientras que la matriz permanece todavía en el estado de baja viscosidad. Estando centrado en los FRPs de altas prestaciones y en componentes con formas tipo concha, desde curvaturas simples hasta formas con doble curvatura complejas, un número importante de compensaciones entre la VI y el conformado por membrana se han ido superando para asentar las bases a partir de las cuales se ha probado la capacidad de ISFLIP para fabricas componentes de FRP. Con la vista puesta en implementar una metodología de fabricación por VI que cumpliese los objetivos definidos para ISFLIP, también se han realizado importantes contribuciones de carácter más general relacionadas con la VI en términos de optimización de parámetros de calidad de las piezas, abordando la gran preocupación que la porosidad final supone en la VI, y consiguiendo unos tiempos de fabricación competitivos. Con este propósito se han propuesto un proceso de desgasificación por vacío muy efectivo en el que se favorece la nucleación de burbujas mediante la agitación a alta velocidad, y una prometedora y no convencional estrategia de llenado y post-llenado de la preforma. Finalmente, se consiguió virtualmente eliminar la porosidad atrapada en las piezas, minimizando el tiempo de post-llenado sin afectar la fracción de fibra contenida. En ISFLIP las preformas textiles se conforman junto con una serie de materiales auxiliares (films y hojas plásticas, mallas y tejidos textiles), que muestran diferentes mecanismos de deformación en plano. El conformado de las preformas y el acabado final de las piezas se ve severamente afectado por todas las interacciones entre todos estos materiales diferentes en naturaleza. También se han abordado las incertidumbres que surgen al respecto y una evaluación inicial de las geometrías abarcables para definir un plan de investigación más concreto con el que poder afrontar la meta final, todavía distante, de implementar ISFLIP en un entorno productivo real. Los resultados obtenidos a lo largo de este proyecto de investigación permiten ser razonablemente optimistas en cuanto al potencial de ISFLIP y sus expectativas

The Minimized Power Geometric model: An analytical mixing model for calculating polyphase rock viscosities consistent with experimental data

International audienceHere we introduce the Minimized Power Geometric (MPG) model which predicts the viscosity of any polyphase rocks deformed during ductile flow. The volumetric fractions and power law parameters of the constituting phases are the only model inputs required. The model is based on a minimization of the mechanical power dissipated in the rock during deformation. In contrast to existing mixing models based on minimization, we use the Lagrange multipliers method and constraints of strain rate and stress geometric averaging. This allows us to determine analytical expressions for the polyphase rock viscosity, its power law parameters, and the partitioning of strain rate and stress between the phases. The power law bulk behavior is a consequence of our model and not an assumption. Comparison of model results with 15 published experimental data sets on two-phase aggregates shows that the MPG model reproduces accurately both experimental viscosities and creep parameters, even where large viscosity contrasts are present. In detail, the ratio between experimental and MPG-predicted viscosities averages 1.6. Deviations from the experimental values are likely to be due to microstructural processes (strain localization and coeval other deformation mechanisms) that are neglected by the model. Existing models that are not based on geometric averaging show a poorer fit with the experimental data. As long as the limitations of the mixing models are kept in mind, the MPG model offers great potential for applications in structural geology and numerical modeling

IMPROVED RESERVOIR CHARACTERIZATION AND SIMULATION OF A MATURE FIELD USING AN INTEGRATED APPROACH

Reservoir characterization involves various studies which comprises assimilation and interpretation of representative reservoir rock and fluid data for a simulation model under varying recovery mechanisms. The main challenge in reservoir simulation is the task of simplifying complex reservoir situations while ensuring a high level of data utilization to obtain a unique solution for history matching. Retaining geologic continuity in the simulation model is necessary to ensure the predictive capability of the reservoir model. In this study, the systematic assignment of reservoir properties with optimal utilization of very limited data has ensured that the fluid movement through the heterogeneous reservoir rock in a mature field is appropriately established. The key towards such a systematic assignment is classification of pore attributes. Pore attributes, which occur due to variations in depositional environments and diagenetic processes in a reservoir, have been identified through interpretation of the petrophysical data and the development of core- well log relationships in a consistent manner. Electrofacies along with petrophysical classification methods have been applied to quantify heterogeneity found in carbonate and sandstone reservoirs. It is observed that the electrofacies derived from well logs represent lithofacies found in the core measurements. The characterization approach has been shown to provide reliable accuracy of petrophysical property prediction when comparison was made with core measurements. These optimum correlation models were extended to uncored wells to describe the reservoir simulation model. A reservoir simulation model, built using this approach, provides a rapid means for history matching between the simulated results and the observed productions at the field while retaining the geological continuity. The integrated approach and structured methodology developed in this study resulted in a reservoir simulation model with adequate resolution of data that simulated the production history with sufficient realism, without necessity for alternations in petrophysical properties

DUAL-MODALITY (NEUTRON AND X-RAY) IMAGING FOR CHARACTERIZATION OF PARTIALLY SATURATED GRANULAR MATERIALS AND FLOW THROUGH POROUS MEDIA

Problems involving mechanics of partially saturated soil and physics of flow through porous media are complex and largely unresolved based on using continuum approach. Recent advances in radiation based imaging techniques provide unique access to simultaneously observe continuum scale response while probing corresponding microstructure for developing predictive science and engineering tools in place of phenomenological approach used to date. Recent developments with X-ray/Synchrotron and neutron imaging techniques provided tools to visualize the interior of soil specimen at pore/grain level. X-ray and neutron radiation often presents complementary contrast for given condensed matter in the images due to different fundamental interaction mechanisms. While X-rays mainly interact with the electron clouds, neutrons directly interact with the nucleus of an atom. The dual-modal contrasts are well suited for probing the three phases (silica, air and water) of partially saturated sand since neutrons provide high penetration through large sample size and are very sensitive to water and X-rays of high energy can penetrate moderate sample sizes and clearly show the particle and void phases. Both neutron and X-ray imaging techniques are used to study microstructure of partially saturated compacted sand and water flow behavior through sand with different initial structures. Water distribution in compacted sand with different water contents for different grain shapes of sand was visualized with relatively coarse resolution neutron radiographs and tomograms. Dual-modal contrast of partially saturated sand was presented by using high spatial resolution neutron and X-ray imaging. Advanced image registration technique was used to combine the dual modality data for a more complete quantitative analysis. Quantitative analysis such as grain size distribution, pore size distribution, coordination number, and water saturation along the height were obtained from the image data. Predictive simulations were performed to obtain capillary pressure – saturation curves and simulated two fluid phase (water and air) distribution based image data. In-situ water flow experiments were performed to investigate the effect of initial microstructure. Flow patterns for dense and loose states of Ottawa sand specimens were compared. Flow patterns and water distribution of dense Ottawa and Q-ROK sand specimens was visualized with high resolution neutron and X-ray image data

Sound Absorption Properties of Perforated Recycled Polyurethane Foams Reinforced with Woven Fabric

[EN] The acoustic properties of recycled polyurethane foams are well known. Such foams are used as a part of acoustic solutions in different fields such as building or transport. This paper aims to seek improvements in the sound absorption of these recycled foams when they are combined with fabrics. For this aim, foams have been drilled with cylindrical perforations, and also combined with different fabrics. The effect on the sound absorption is evaluated based on the following key parameters: perforation rate (5% and 20%), aperture size (4 mm and 6 mm), and a complete perforation depth. Experimental measurements were performed by using an impedance tube for the characterization of its acoustic behavior. Sound absorption of perforated samples is also studied¿numerically by finite element simulations, where the viscothermal losses were considered; and analytically by using models for the perforated foam and the fabric. Two textile fabrics were used in combination with perforated polyurethane samples. Results evidence a modification of the sound absorption at mid frequencies employing fabrics that have a membrane-type acoustic response.This research was financially supported by the Ministry of Economy and Innovation (MINECO) and the European Union FEDER through project FIS2015-65998-C2-2 and by projects AICO/2016/060 and ACIF/2017/073 by Regional Ministry of Education, Culture and Sport of the Generalitat Valenciana and with the support of European Structural Investment Funds (ESIF-European Union).Atiénzar-Navarro, R.; Rey Tormos, RMD.; Alba, J.; Sánchez Morcillo, VJ.; Picó Vila, R. (2020). Sound Absorption Properties of Perforated Recycled Polyurethane Foams Reinforced with Woven Fabric. Polymers. 12(2):1-18. https://doi.org/10.3390/polym12020401S118122Hamernik, R. P., & Ahroon, W. A. (1998). Interrupted noise exposures: Threshold shift dynamics and permanent effects. The Journal of the Acoustical Society of America, 103(6), 3478-3488. doi:10.1121/1.423056Ramis, J., Alba, J., Del Rey, R., Escuder, E., & Sanchís, V. J. (2010). Nuevos materiales absorbentes acústicos basados en fibra de kenaf. Materiales de Construcción, 60(299), 133-143. doi:10.3989/mc.2010.50809Ramis, J., Del Rey, R., Alba, J., Godinho, L., & Carbajo, J. (2014). A model for acoustic absorbent materials derived from coconut fiber. Materiales de Construcción, 64(313), e008. doi:10.3989/mc.2014.00513Yang, W., Dong, Q., Liu, S., Xie, H., Liu, L., & Li, J. (2012). Recycling and Disposal Methods for Polyurethane Foam Wastes. Procedia Environmental Sciences, 16, 167-175. doi:10.1016/j.proenv.2012.10.023Gama, N., Silva, R., Carvalho, A. P. O., Ferreira, A., & Barros-Timmons, A. (2017). Sound absorption properties of polyurethane foams derived from crude glycerol and liquefied coffee grounds polyol. Polymer Testing, 62, 13-22. doi:10.1016/j.polymertesting.2017.05.042Rey, R. del, Alba, J., Arenas, J. P., & Sanchis, V. J. (2012). An empirical modelling of porous sound absorbing materials made of recycled foam. Applied Acoustics, 73(6-7), 604-609. doi:10.1016/j.apacoust.2011.12.009Chen, S., & Jiang, Y. (2016). The acoustic property study of polyurethane foam with addition of bamboo leaves particles. Polymer Composites, 39(4), 1370-1381. doi:10.1002/pc.24078Delany, M. E., & Bazley, E. N. (1970). Acoustical properties of fibrous absorbent materials. Applied Acoustics, 3(2), 105-116. doi:10.1016/0003-682x(70)90031-9Johnson, D. L., Koplik, J., & Dashen, R. (1987). Theory of dynamic permeability and tortuosity in fluid-saturated porous media. Journal of Fluid Mechanics, 176(-1), 379. doi:10.1017/s0022112087000727Allard, J., & Champoux, Y. (1992). New empirical equations for sound propagation in rigid frame fibrous materials. The Journal of the Acoustical Society of America, 91(6), 3346-3353. doi:10.1121/1.402824Voronina, N. (1994). Acoustic properties of fibrous materials. Applied Acoustics, 42(2), 165-174. doi:10.1016/0003-682x(94)90005-1Umnova, O., Attenborough, K., Shin, H.-C., & Cummings, A. (2005). Deduction of tortuosity and porosity from acoustic reflection and transmission measurements on thick samples of rigid-porous materials. Applied Acoustics, 66(6), 607-624. doi:10.1016/j.apacoust.2004.02.005Zhang, C., Li, J., Hu, Z., Zhu, F., & Huang, Y. (2012). Correlation between the acoustic and porous cell morphology of polyurethane foam: Effect of interconnected porosity. Materials & Design, 41, 319-325. doi:10.1016/j.matdes.2012.04.031Chevillotte, F. (2012). Controlling sound absorption by an upstream resistive layer. Applied Acoustics, 73(1), 56-60. doi:10.1016/j.apacoust.2011.07.005Lou, C.-W., Huang, S.-Y., Huang, C.-H., Pan, Y.-J., Yan, R., Hsieh, C.-T., & Lin, J.-H. (2015). Effects of structure design on resilience and acoustic absorption properties of porous flexible-foam based perforated composites. Fibers and Polymers, 16(12), 2652-2662. doi:10.1007/s12221-015-5164-6Lin, J.-H., Chuang, Y.-C., Li, T.-T., Huang, C.-H., Huang, C.-L., Chen, Y.-S., & Lou, C.-W. (2016). Effects of Perforation on Rigid PU Foam Plates: Acoustic and Mechanical Properties. Materials, 9(12), 1000. doi:10.3390/ma9121000Xia, X., Zhang, Z., Zhao, W., Li, C., Ding, J., Liu, C., & Liu, Y. (2017). Acoustic properties of closed-cell aluminum foams with different macrostructures. Journal of Materials Science & Technology, 33(11), 1227-1234. doi:10.1016/j.jmst.2017.07.012ATALLA, N., PANNETON, R., SGARD, F. C., & OLNY, X. (2001). ACOUSTIC ABSORPTION OF MACRO-PERFORATED POROUS MATERIALS. Journal of Sound and Vibration, 243(4), 659-678. doi:10.1006/jsvi.2000.3435Olny, X., & Boutin, C. (2003). Acoustic wave propagation in double porosity media. The Journal of the Acoustical Society of America, 114(1), 73-89. doi:10.1121/1.1534607Sgard, F. C., Olny, X., Atalla, N., & Castel, F. (2005). On the use of perforations to improve the sound absorption of porous materials. Applied Acoustics, 66(6), 625-651. doi:10.1016/j.apacoust.2004.09.008Carbajo, J., Prieto, A., Ramis, J., & Río-Martín, L. (2019). A non-parametric fluid-equivalent approach for the acoustic characterization of rigid porous materials. Applied Mathematical Modelling, 76, 330-347. doi:10.1016/j.apm.2019.05.046Ekici, B., Kentli, A., & Küçük, H. (2012). Improving Sound Absorption Property of Polyurethane Foams by Adding Tea-Leaf Fibers. Archives of Acoustics, 37(4), 515-520. doi:10.2478/v10168-012-0052-1Segura Alcaraz, M. P., Bonet-Aracil, M., Segura Alcaraz, J. G., & Montava Seguí, I. (2017). Sound absorption of textile material using a microfibres resistive layer. IOP Conference Series: Materials Science and Engineering, 254, 072022. doi:10.1088/1757-899x/254/7/072022Pieren, R. (2012). Sound absorption modeling of thin woven fabrics backed by an air cavity. Textile Research Journal, 82(9), 864-874. doi:10.1177/0040517511429604Romero-García, V., Theocharis, G., Richoux, O., & Pagneux, V. (2016). Use of complex frequency plane to design broadband and sub-wavelength absorbers. The Journal of the Acoustical Society of America, 139(6), 3395-3403. doi:10.1121/1.4950708Ingard, K. U., & Dear, T. A. (1985). Measurement of acoustic flow resistance. Journal of Sound and Vibration, 103(4), 567-572. doi:10.1016/s0022-460x(85)80024-9Jayabal, S., & Natarajan, U. (2011). Drilling analysis of coir-fibre-reinforced polyester composites. Bulletin of Materials Science, 34(7), 1563-1567. doi:10.1007/s12034-011-0359-yDel Rey, R., Alba, J., Blanes, M., & Marco, B. (2013). Absorción acústica de cortinas textiles en función del vuelo. Materiales de Construcción, 63(312), 569-580. doi:10.3989/mc.2013.0551

Composite Materials in Design Processes

The use of composite materials in the design process allows one to tailer a component’s mechanical properties, thus reducing its overall weight. On the one hand, the possible combinations of matrices, reinforcements, and technologies provides more options to the designer. On the other hand, it increases the fields that need to be investigated in order to obtain all the information requested for a safe design. This Applied Sciences Special Issue, “Composite Materials in Design Processes”, collects recent advances in the design methods for components made of composites and composite material properties at a laminate level or using a multi-scale approach