Numerical Modeling of the Medium-Density Fiberboard Hot Pressing Process, Part 2: Mechanical and Heat and Mass Transfer Models
Keywords:
Mathematical model, hot pressing, coupled mechanical and heat and mass transfer models, coupling, moving domain, finite element method, resin cure dynamics, nonhomogeneous density profileAbstract
In this study, coupled mechanical and heat and mass transfer models describing mat compression and heat and moisture transfer occurring during hot pressing of medium-density fiberboard mats are presented. The mat is considered an aging linear elastic material and is described by a mechanical model in three dimensions. Rheological properties of the mat depended on time, space, temperature, moisture content, and resin cure. Hardening and softening phases of the material behavior were accounted for and treated with separate constitutive laws. Press closing was taken into account, and a coupling procedure between mechanical and heat and mass transfer models was elaborated. Development of the vertical density profile was dynamically predicted by the model. Both mechanical and heat and mass transfer models were discretized in space by the finite element method. An implicit second-order backward finite difference scheme was used for time discretization. All calculations were carried out on a moving geometry whose deformation (compression) was a function of a press closing schedule. Model results exhibited good agreement with experimental results. Under various press closing schedules, the model gave information on variables such as density profile, total gas pressure, air and vapor pressure, temperature, moisture content, RH, and degree of resin cure.References
Bathe KJ (1982) Finite element procedures in engineering analysis. Prentice-Hall, New York, NY. 735 pp.nBazant ZP (1979) Thermodynamics of solidifying or melting viscoelastic material. J Eng Mech Div 105(EM6):933-955.nBelley D (2009) Détermination des propriétés de transfert de chaleur et de masse des panneaux de fibres de bois MDF. MSc thesis, Université Laval, Québec, Canada. 70 pp.nBeuth L, Benz T, Vermeer PA, Wieckowski Z (2008) Large deformation analysis unsing a quasi-static material point method. J Theor Appl Mech 38(1):45-60.nBolton AJ, Humphrey PE (1988) The hot pressing of dryformed wood-based composites. Part I. A review of the literature identifying the primary physical process and the nature of their interaction. Holzforschung 42(6): 403-406.nBolton AJ, Humphrey PE, Kavvouras PK (1989) The hot pressing of dry-formed wood-based composites. Part VI. The importance of stresses in the pressed mattress and their relevance to the minimisation of pressing time and the variability of board properties. Holzforschung 43(6): 406-410.nCarvalho LM, Costa CAV (1998) Modeling and simulation of the hot-pressing process in the production of medium density fiberboard (MDF). Chem Eng Commun 170:1-21.nCarvalho LMH, Costa MRN, Costa CAV (2001) Modeling rheology in the hot-pressing of MDF: Comparison of mechanical models. Wood Fiber Sci 33(3):395-411.nCarvalho LMH, Costa MRN, Costa CAV (2003) A global model for the hot-pressing of MDF. Wood Sci Technol 37:241-258.nDai C (2001) Viscoelasticity of wood composite mats during consolidation. Wood Fiber Sci 33(3):353-363.nDai C, Yu C (2004) Heat and mass transfer in wood composite panels during hot-pressing. Part 1. A physical-mathematical model. Wood Fiber Sci 36(4):585-597.nDubois F, Randriambololona H, Petit C (2005) Creep in wood under variable climate conditions: Numerical modelling and experiment validation. Mech Time-Depend Mater 9:173-202.nGanev S, Gendron G, Cloutier A, Beauregard R (2005) Mechanical properties of MDF as a function of density and moisture content. Wood Fiber Sci 37(2): 314-326.nGarrigues J (2007) Fondements de la mécanique des milieux continus. Hermès-Lavoisier. Paris. 250 pp.nGhazlan G, Caperaa S, Petit C (1995) An incremental formulation for the linear analysis of thin viscoelastic structures using generalized variables. Int J Numer Methods Eng 38:3315-3333.nHumphrey PE (1982) Physical aspects of wood particleboard manufacture. PhD thesis, University of Wales, Wales, UK.nHumphrey PE, Bolton AJ (1989) The hot pressing of dryformed wood-based composites. Part II. A simulation model for heat and moisture transfer and typical results. Holzforschung 43(3):199-206.nKamke FA, Wolcott MP (1991) Fundamentals of flakeboard manufacture: Wood-moisture relationships. Wood Sci Technol 25:57-71.nKavazović Z (2011) Modélisation mathématique du pressage à chaud des panneaux MDF: Couplage du modèle mécanique avec le modèle couplé de transfert de chaleur et de masse. PhD thesis, Université Laval, Québec, Canada. 145 pp. http://www.giref.ulaval.ca/publications/memoireset-theses.html'>http://www.giref.ulaval.ca/publications/memoireset-theses.htmlnKavazović Z, Deteix J, Cloutier A, Fortin A (2010) Sensitivity study of a numerical model of heat and mass transfer involved during the MDF hot pressing process. Wood Fiber Sci 42(2):130-149.nKavvouras PK (1977) Fundamental process variables in particleboard manufacture. PhD thesis, University of Wales, Wales, UK. 156 pp.nLee JN, Kamke FA, Watson LT (2007) Simulation of the hot-pressing of a multi-layered wood strand composite. J Composite Mater 41(7):879-904.nNigro N, Storti M (2001) Hot-pressing process modeling for medium density fiberboard (MDF). Int J Math 26(12):713-729.nPereira C, Carvalho LMH, Costa CAV (2006) Modeling the continuous hot-pressing of MDF. Wood Sci Technol 40:308-326.nReddy JN (2006) An introduction to the finite element method. 3rd ed. McGraw Hill, Higher Education, New York, NY. 766 pp.nSiau J (1984) Transport processes in wood. Springer-Verlag. New York. 245 pp.nThömen H (2000) Modeling the physical process in natural fiber composites during batch and continuous pressing. PhD thesis, Oregon State University, Corvallis, OR. 187 pp.nThömen H, Haselein CR, Humphrey PE (2006) Modeling the physical process relevant during hot pressing of wood-based composites. Part 2. Rheology. Holz Roh Werkst 64:125-133.nThömen H, Humphrey PE (2003) Modeling the continuous pressing process for wood-based composites. Wood Fiber Sci 35(3):456-468.nThömen H, Humphrey PE (2006) Modeling the physical process relevant during hot pressing of wood-based composites. Part 1. Heat and mass transfer. Holz Roh Werkst 64:1-10.nThömen H, Ruf C (2008) Measuring and simulating the effects of the pressing schedule on the density profile development in wood-based composites. Wood Fiber Sci 40(3):325-338.nvon Haas G (1998) Untersuchungen zur Heißpressung von Holzwerkstoffmatten unter besonderer Berücksichtigung des Verdichtungsverhaltens der Permeabilität der Temperatur-leitfähigkeit und der Sorptionsgeschwindigkeit. PhD thesis, Hamburg University, Germany. 264 pp.nvon Haas G, Frühwald A (2000) Untersuchungen zur Verdichtungsverhalten von Faser- Span- und OSB-Matten. Holz Roh Werkst 58:317-323.nWang S, Winistorfer PM (2000a) Consolidation of flakeboard mats under theoretical laboratory pressing and simulated industrial pressing. Wood Fiber Sci 32(4):527-538.nWang S, Winistorfer PM (2000b) Fundamentals of vertical density profile formation in wood composites. Part 2. Methodology of vertical density formation under dynamic conditions. Wood Fiber Sci 32(2):220-238.nWang S, Winistorfer PM, Young TM (2004) Fundamentals of vertical density profile formation in wood composites. Part 3. MDF density formation during hot-pressing. Wood Fiber Sci 36(1):17-25.nWang S, Winistorfer PM, Young TM, Helton C (2001a) Step-closing pressing on medium density fiberboard. Part 1. Influences on the vertical density profile. Holz Roh Werkst 59:19-26.nWang S, Winistorfer PM, Young TM, Helton C (2001b) Step-closing pressing on medium density fiberboard. Part 2. Influences on panel performance and layer characteristics. Holz Roh Werkst 59:311-318.nWinistorfer PM, Moschler WW Jr., Wang S, DePaula E, Bledsoe BL (2000) Fundamentals of vertical density profile formation in wood composites. Part 1. In-situ density measurement of the consolidation process. Wood Fiber Sci 32(2):209-219.nWinistorfer PM, Young TM, Walker E (1996) Modeling and comparing vertical density profiles. Wood Fiber Sci 28(1):133-141.nWolcott MP, Kamke FA, Dillard DA (1990) Fundamentals of flakeboard manufacture: Viscoelastic behavior of the wood component. Wood Fiber Sci 22(4):345-361.nYu C, Dai C, Wang BJ (2007) Heat and mass transfer in wood composite panels during hot pressing. Part 3. Predicted variations and interactions of the pressing variables. Holzforschung 61:74-82.nZombori BG, Kamke FA, Watson LT (2003) Simulation of the internal conditions during the hot-pressing process. Wood Fiber Sci 35(1):2-23.nZombori BG, Kamke FA, Watson LT (2004) Sensitivity analysis of internal mat environment during hot pressing. Wood Fiber Sci 36(2):195-209.n
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