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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)
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
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,
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
 (conservation of energy, air mass and water vapor mass)
which are expressed as functions of the state variables:
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
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