## Conférences

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Conférence externe
Coupled Mechanical and Heat and Mass Transfer Numerical Model For MDF Hot Pressing Process
Zanin Kavazovic, (A. Cloutier, A. Fortin)
GIREF
The hot pressing process of medium density fiberboard involves complex interactions between mechanical and heat and mass transfer (H&MT) properties of the fiber mat. We propose combined mechanical and H&MT numerical models  based on the finite element method. Press closing was imposed and the development of a non homogeneous time and space-dependent vertical density profile was numerically predicted at each time step by a mechanical model  (incremental formulation). The constitutive law is based on the generalized Maxwell model where ageing, hardening and softening phases of the material are taken into account. The mechanical model was combined to the heat and mass transfer model. The H&MT model is based on conservation principles leading to three governing equations  (conservation of energy, air mass and water vapor mass) which are expressed as functions of the state variables:  temperature, air pressure, and vapor pressure. This results in a 3D unsteady-state mathematical model in which the fiber mat’s properties and state variables vary in time and space. We achieved the full coupling of the three non linear and strongly coupled conservation equations by solving them as a fully coupled system. The non linear system is solved by Newton’s method and all material properties are updated at each iteration. The full Lagrangian formulation of all equations was used and calculations were performed on a moving geometry. Since the mesh grid moves, it is updated after each time step. The numerically predicted results are in good concordance with laboratory measurements.
Date: 2011-06-20 à 19:00
Endroit: 65th International Convention of the Forest Products Society, Portland, Oregon, USA