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Fracture processes in wood chipping

<p>In both the chemical and mechanical pulping process, the logs are cut into wood chips by a disc chipper before fibre separation. To make the wood chipping process more efficient, one have to investigate in detail the coupling between theprocess parameters and the quality of the chips. The objective of this thesis is to obtain an understanding of the fundamental mechanisms behind the creation of wood chips. Both experimental and analytical/numerical approaches have been taken inthis work. The experimental investigations were performed with an in‐house developed equipment and a digital speckle photography equipment. The results from the experimental investigation showed that the friction between the log and chipping tool is probably one crucal factor for the chip formation. Further more it was found that the indentation process is approximately self‐similar, and that the stress field over the entire crack‐plane is critical for chip creation. The developed analytical model predicts the normal and shear strain distribution. The analytical distributions are in reasonable agreement with the corresponding distributions obtained from a finite element analysis.</p>

Identiferoai:union.ndltd.org:UPSALLA/oai:DiVA.org:miun-7827
Date January 2008
CreatorsHellström, Lisbeth
PublisherMid Sweden University, Department of Natural Sciences, Engineering and Mathematics, Sundsvall : Mid Sweden University
Source SetsDiVA Archive at Upsalla University
LanguageEnglish
Detected LanguageEnglish
TypeLicentiate thesis, comprehensive summary, text
RelationMid Sweden University licentiate thesis, 1652-8948 ; 32

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