engleski

Welding of modified beech wood

Wood welding is a mechanical, physical and chemical process during which melt is produced, which then turns into a solid joint after cooling. The paper shows current world-wide knowledge on welding of modified wood while the results of wood welding were received from the Faculty of Forestry in Zagreb. Research was made on the effect that the modification (thermal and chemical) has on the strength of the rotationally welded joint. Research results show that dowels welded in the direction of wood fibres have greater embedded force than the dowels welded vertically onto the direction of fibres with modified as well as non-modified wood. Modification of wood increases the brashness and some mechanical properties of wood are reduced which in turn has causes reduction of the strength of welded joint. One of the main factors of reduction of joint strength is the inability to use the optimal tightness which is in the span from 2 to 2.6 mm and duration of the welding process (depending on the frequency of spin and the shift of dowel along the transversal axle). By comparing the welding of dowel into non-modified beech wood and thermally treated beech wood (160 °C) in the direction of fibres, reduction of embedded force of 25% was noted. If the samples are also chemically treated, the embedded force i.e. the strength of joint will reduce for additional 7% (total of 32%). When welding the dowels vertically on fibres, the difference in the strength of joint (reducing of embedded force) of non-modified and thermally modified samples is 36%. If these comparisons were made at optimal tightness for welding of non-modified wood, the percentage differences would be much greater.

welding; modification; beech wood; dowel; joint strength; embedded force

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