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Licensed Unlicensed Requires Authentication Published by De Gruyter February 15, 2013

A numerical and experimental study regarding the influence of some process parameters on the damage state in wood chips

Per Isaksson , Per A. Gradin and Lisbeth M. Hellström EMAIL logo
From the journal Holzforschung


The specific energy consumption during mechanical refining operation can be reduced by choosing the optimal process parameters in the wood chipping process such that a beneficial pretreatment is obtained. In the case of the utilization of a larger knife-edge angle, which is one such process parameter, the energy reduction is presumably due to the increased compressive loading parallel to the wood fibers. In the present article, a chip damage parameter D of spruce is in focus, which is relevant for cracking parallel to the fibers. D is defined and its dependence on the chip length and edge angle of the chipping knife is analyzed numerically by means of finite element analyses (FEA). The cutting force was measured in a pilot wood chipper for a number of knife-edge angles. There is a good correlation between the experimental results and those of FEA.

Corresponding author: Lisbeth M. Hellström, Mid Sweden University, FSCN, SE-851 70 Sundsvall, Sweden

The Swedish Foundation for Knowledge and Competence Development (KK-Foundation) is greatly acknowledged for their financial support.


Adina R&D, Inc. Theory and Modelling Guide. Watertown, MA, 1995.Search in Google Scholar

Bathe, K.J. Finite Element Procedures. Prentice-Hall, USA, 1996.Search in Google Scholar

Berg, J-E., Gradin, P.A. (2000) Effect of temperature on fracture of spruce in compression, investigation by use of acoustic emission monitoring. J. Pulp Paper Sci. 26:294–299.Search in Google Scholar

Crisfield, M.A. Non-Linear Finite Element Analysis of Solids and Structures. Advanced Topics. John Wiley and Sons, UK, 1997.Search in Google Scholar

Dinwoodie, J.M. (1968) Failure in timber. Part 1: microscopic changes in cell wall structure associated with compression failure. J. Int. Wood Sci. 21:37–53.Search in Google Scholar

Dinwoodie, J.M. (1974) Failure in timber. Part 2: the angle of shear through the cell wall during longitudinal compression stressing. J. Int. Wood Sci. Technol. 8:56–67.Search in Google Scholar

Dourado, N.M.M., de Moura, M.F.S.F., Morais, J.J.L., Silva, M.A.L. (2010) Estimate of resistance-curve in wood through the double cantilever beam test. Holzforschung 64:119–126.10.1515/hf.2010.010Search in Google Scholar

Dunne, F., Petrinic, N. Introduction to Computational Plasticity. Oxford University Press, UK, 2005.Search in Google Scholar

Frazier, W.C., Williams, G.J. (1982) Reduction of specific energy in mechanical pulping by axial precompression of wood. Pulp Paper Canada 83:T162–T167.Search in Google Scholar

Frühmann, K., Burgert, I., Stanzl-Tschegg, S.E., Tschegg, E.K. (2003) Mode I fracture behaviour on the growth ring scale and cellular level of spruce (Picea abies [L.] Karst.) and beech (Fagus sylvatica L.) loaded in the TR crack propagation system. Holzforschung 57:653–660.10.1515/HF.2003.098Search in Google Scholar

Hellström, L.M., Gradin, P.A., Engstrand, P., Gregersen, Ø. (2011) Properties of wood chips for thermomechanical pulp (TMP) production as a function of spout angle. Holzforschung 65:805–809.10.1515/HF.2011.087Search in Google Scholar

Hill, R. The Mathematical Theory of Plasticity. Clarendon Press, Oxford, UK, 1950.Search in Google Scholar

Karlebo Handbok. Liber AB, Stockholm, Sweden, 2000 (in Swedish).Search in Google Scholar

Keunecke, D., Stanzl-Tschegg, S., Niemz, P. (2007) Fracture characterisation of yew (Taxus baccata L.) and spruce (Picea abies [L.] Karst.) in the radial-tangential and tangential-radial crack propagation system by a micro wedge splitting test. Holzforschung 61:582–588.10.1515/HF.2007.089Search in Google Scholar

Kivimaa, E., Murto, J.O. Investigations on factors affecting chipping of pulp wood. Statens Tekniska Forskningsanstalt, Finland Publ. 9, 1949.Search in Google Scholar

Landis, E.N., Navi, P. (2009) Modeling crack propagation in wood and wood composites. A review COST Action E35 2004–2008: wood machining – —micromechanics and fracture. Holzforschung 63:150–156.10.1515/HF.2009.010Search in Google Scholar

Matlab. The MathWorks, Inc., Natick, MA, 2010.Search in Google Scholar

Navi, P., Stanzl-Tschegg, S.E. (2009) Micromechanics of creep and relaxation of wood. A review COST Action E35 2004–2008: wood machining—micromechanics and fracture. Holzforschung 63:186–195.10.1515/HF.2009.013Search in Google Scholar

Smith, I., Snow, M., Asiz, A., Vasic, S. (2007) Failure mechanisms in wood-based materials: a review of discrete, continuum, and hybrid finite-element representations. Holzforschung 61:352–359.10.1515/HF.2007.055Search in Google Scholar

Stanzl-Tschegg, S.E., Navi, P. (2009) Fracture behaviour of wood and its composites. A review COST Action E35 2004–2008: wood machining—micromechanics and fracture. Holzforschung 63:139–149.10.1515/HF.2009.012Search in Google Scholar

Svensson, B.A. Frictional studies and high rate testing of wood under refining conditions. Doctorial thesis. Mid Sweden University, Department of Natural Science, Sundsvall, 2007.Search in Google Scholar

Uhmeier, A., Persson, K. (1997) Numerical analysis of wood chipping. Holzforschung 51:83–90.10.1515/hfsg.1997.51.1.83Search in Google Scholar

Vasic, S., Stanzl-Tschegg, S. (2007) Experimental and numerical investigation of wood fracture mechanisms at different humidity levels. Holzforschung 61:367–374.10.1515/HF.2007.056Search in Google Scholar

Zienkiewicz, O.C., Taylor, R.L. The Finite Element Method, vol. 2: Solid Mechanics. Butterworth-Heinemann, UK, 2000.Search in Google Scholar

Received: 2012-9-7
Accepted: 2013-1-14
Published Online: 2013-02-15
Published in Print: 2013-08-01

©2013 by Walter de Gruyter Berlin Boston

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