Drying shrinkage of sawn timber of Norway spruce (Picea abies): Industrial measurements and finite element simulations

Abstract

Industrial measurements of green and dry cross-section dimensions were performed for 189 Norway spruce (Picea abies) centre-yield boards with dry dimensions 51 × 149 mm. Two, three or four boards were sawn from each log, depending on log size. Different approaches were used for simulations of cross-section shrinkage during drying. An analytical model, an elastic, an elastic– mechanosorptive and an elastic– plastic finite element simulation model were tested. Thickness and width shrinkage and deformation were simulated. Shrinkage results were compared with each other and with the experimental results. All simulation models gave roughly the same degree of agreement with experimental results except for the centre board from the three-board sawing pattern. For the other boards, the analytical model was not generally better or worse than the results from the finite element models. Shrinkage deformations in finite element models that included mechanosorption or plasticity were nearly the same as for the elastic finite element model except for the centre board of the three-board sawing pattern. The mechanosorptive model was the best model for the shrinkage of the centre board of this sawing pattern except for mid-thickness shrinkage. Comparison between the different finite element simulation models of stresses in the centre board revealed large differences.

Keywords:

• Drying
• elastic–plastic
• finite element
• mechanosorption
• Norway spruce
• Picea abies
• shrinkage
• wood

Acknowledgements

The authors thank The Swedish Governmental Agency for Innovation Systems (Vinnova) and the project ‘More Wood - Less Sawdust’ for funding this work.