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The hot pressing process of oriented strand board: Dr. Azzeddine OUDJEHANE Review of the modeling.

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Presentation on theme: "The hot pressing process of oriented strand board: Dr. Azzeddine OUDJEHANE Review of the modeling."— Presentation transcript:

1 The hot pressing process of oriented strand board: Dr. Azzeddine OUDJEHANE Review of the modeling.

2  "Everything should be as simple as possible, but not simpler."

3 Manufacturing process 1. Logs are flaked 2. Flakes are dried Adhesive applied 5. Panels are trimmed to the final sizes 4. Mats are hot-pressed T=200 o C 3. Mats are formed

4 Hot pressing of wood mats Continuous press Multiple openings platen press

5 Continuous press Cross section of a continuous press (H Thoemen 2000)

6 Hot-pressing mechanisms Rheology and mechanics Rheology and mechanics Deformation under applied pressure Thermodynamics Thermodynamics Heat and mass transfer Adhesion Adhesion Resin cure

7 Background review (1) Modeling the continuous pressing process for wood based composites, by H. Thomen et OSU Modeling the continuous pressing process for wood based composites, by H. Thomen et OSU

8 Burger-Humphrey model used by H. Thomen et al for the continuous hot- pressing

9 Background review (2) A global model for the hot pressing of MDF, by Costa et Porto U. A global model for the hot pressing of MDF, by Costa et Porto U.

10 Background review (3) Viscoelastic behavior of wood fibers during the hot pressing of MDF, by J. Van Houts et Auckland U. Viscoelastic behavior of wood fibers during the hot pressing of MDF, by J. Van Houts et Auckland U.

11 Background review (4) Effect of panel moisture content and density on moisture movement, by A.Cloutier et Laval U. Effect of panel moisture content and density on moisture movement, by A.Cloutier et Laval U.

12 Background review (5) OSB preparation technology at high moisture content: Transfer mechanisms and pressing parameters, by A. Pizzi et al ENSTIB-HH U.- Siempelkamp OSB preparation technology at high moisture content: Transfer mechanisms and pressing parameters, by A. Pizzi et al ENSTIB-HH U.- Siempelkamp

13 Background review (6) Hot pressing of OSB by step closure, by S.Wang, P.Winnistorfer et UTK Hot pressing of OSB by step closure, by S.Wang, P.Winnistorfer et UTK

14 Density profile and consolidation during pressing by Siqun Wang et al

15 Background review (7) Simulation of the internal conditions during the hot pressing process, by Z. Ballazs, F. Kamke et VTU Simulation of the internal conditions during the hot pressing process, by Z. Ballazs, F. Kamke et VTU

16 Background review (8) Mat formation and pressing models, by P.Hubert, C.Dai et FORINTEK Mat formation and pressing models, by P.Hubert, C.Dai et FORINTEK

17 Flow chart for the model component with FEM solver, by P.Hubert et al Forintek Flow chart for the model component with FEM solver, by P.Hubert et al Forintek

18 Background review (9) 3D heat and mass transfer during OSB hot pressing, by P. Garcia et UBC 3D heat and mass transfer during OSB hot pressing, by P. Garcia et UBC

19 Background review (10) A continuum model of the interaction between manufacturing variables and consolidation of wood composite mats, by A. Oudjehane et UBC A continuum model of the interaction between manufacturing variables and consolidation of wood composite mats, by A. Oudjehane et UBC

20 Framework of Analysis Structure model Consolidation model Mechanical model Loose mat analysis End-product analysis

21  accounts for the deformation process = consolidation of the mat into a panel C Consolidation tensor C such that : hoho a hphp History of Deformation in any location of the mat / panel. in the mat / panel.

22 Properties of composite panels Raw material properties Forming process variables Hot-pressing parameters Density = F Strands’ thickness and density Panel density Number of deposited strands Panel thickness, mass transfer flux tr C = F Strands’ thickness and density Panel consolidation Number of deposited strands Panel thickness, mass transfer flux

23 Properties of composite panels Stiffness - Compliance MOE = F (trC,  ) oriented layout F (trC) randomly oriented layout Strength MOR= F (trC,  ) oriented layout F (trC) randomly oriented layout Internal bond IB (internal Bond) = F (trC) Dimensional stability TS (thickness swell) = F (trC)

24 Consolidation Model  define the history of deformation induced by the manufacturing process. tptp hoho a

25 Consolidation Model hoho a a h1h1 h 1 =N f.  f a tptp t p = panel thickness Consolidation = Elimination of voids + Compression of flakes With heat and mass transfer CR= compression ratio=panel thickness/strand thickness m(z)=mass transfer flux = function of moisture content  define the deformation induced by the manufacturing process in any location of the mat.

26 Consolidation Model Position control press Time Platen position t1t1 Press closing mat initial thickness panel thickness t2t2 Press relaxation t3t3 Press opening

27 Consolidation Model Strain Time t1t1 Pressuret1t1 Hot-Press Closing Time t1t1 Strain rate Constitutive Equation  t  = K. t (U(t) Stress = F (strain, strain rate)  (t) =  v +  c

28 Rheological Model Non-linear viscoelastic and viscoplastic Non-linear viscoelastic and viscoplastic   E  Viscoelastic strain  v ss    Viscoplastic strain  c

29 Model vs. Experience Visco-elastic plastic with creep consolidation model by A.Oudjehane et al 1998

30 Consolidation Model Constitutive Equation Hot-Press Relaxation Time Strain t1t1 t2t2 Pressure Time t1t1 t2t2 Strain = cte. Stress = F(Strain, Strain rate)

31 Next step Implement the heat and mass transfer into the consolidation model Implement the heat and mass transfer into the consolidation model

32 Flaking Drying Blending Forming process On-line measurement Hot-pressing On-line measurement Strands properties Moisture content Resin content Mat layout Mat thickness Software Panel thickness Pressing conditions MOE, MOR, Density TS, IB Towards on-line evaluation of OSB

33 I believe what I see, I see what I look at, I look at what I want.  Je crois ce que je vois, Je vois ce que je regarde, et je regarde ce que je veux. Blaise Pascal


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