Influence of biological pretreatment of wooden dowels on strength of rotary welded joints

Abstract

Welding wood achieves joints whose strength is comparable with the strength of glued joints. When welding, the top of the dowel is not welded because of the lack of melted lignin. To achieve satisfactory strength of a welded joint, it is necessary to optimize the main welding factors such as interference fit, frequency of dowel rotation, welding depth, welding duration, etc. There are also other ideas to increase the strength of welded joints. One of these ideas involves pre-treatment of dowels with wood decaying fungi to increase the proportion of lignin on the surface of the dowels and thus in the melt. This paper presents the results of the impact of pretreatment of beech wood dowels with the brown-rot fungus Gloeophyllum trabeum. Results showed that biological pretreatment of the dowels had a significant impact on the pull-out force of the joint. Pretreatment for 4 weeks caused a substantial increase in pull-out force, while pretreatment for 2 weeks did not have a positive effect on the strength of the welded joint. Grooved dowels exhibited an increase in pull-out force of 26.9%, while smooth dowels had an increase of 21.1% of pull-out force. Research also determined additional vibrations during welding.

Influence of the depth of friction-welded dowels on the strength of rotary welded joints

“…Cellulose fibers are intertwined in the melt thus formed. The smoke that appears as a result of welding consists of water vapor, CO2, and degradation compounds from wood polymeric carbohydrates and from amorphous lignin (Pizzi et al 2004;Kanazawa et al 2005;Leban et al 2008;Župčić 2010;Belleville et al 2013;Župčić et al 2023). The proportion of CO2 emitted is very low, and neither CO nor methane is emitted due to the relatively low temperature of dowel welding (Omrani et al 2008).…”

“…The proportion of CO2 emitted is very low, and neither CO nor methane is emitted due to the relatively low temperature of dowel welding (Omrani et al 2008). During the welding process, the properties of welded joints could be influenced by insertion speed, density, welded depth, welding time, rotational frequency, wood species, direction of welding (parallel or perpendicular to the wood grain direction), width of growth rings, moisture content, welding temperature, interference fit, and pretreatments (Pizzi et al 2004;Ganne-Chedeville et al 2005;Bocquet et al 2007;Leban et al 2008;Rodriguez et al 2010;Župčić et al 2011;Auchet et al 2012;Belleville et al 2016;Župčić et al 2022;Župčić et al 2023). Welding effectiveness is directly associated with the properties of the original wood constituents, primarily lignin and carbohydrates (Belleville et al 2013).…”