Benoit Belleville

Determination of optimal wood-dowel welding parameters for two North American hardwood species

Rotational wood-dowel welding has been shown to rapidly produce wood joints of considerable strength without any adhesive. The technique offers an opportunity to increase productivity and reduce costs in the furniture industry. The objective of the study was to define optimal wood-dowel welding parameters for two North American hardwood species frequently used for indoor appearance products: sugar maple (Acer saccharum) and yellow birch (Betula alleghaniensis). Optimized parameters for individually studied species were determined using a rotational wood-dowel welding machine designed for the technique. A comparative analysis of wood-dowel welding parameters was performed. The investigated parameters for both species were grain orientation, rotational speed, and insertion speed. Temperature profile measurements at the interface during rotational wood-dowel welding were also carried out. Optimal welding mechanical properties were determined from the dowel withdrawal strength using a standard tensile strength test. Results revealed a significant interaction between species, rotational speed, and insertion speed. Sugar maple produced wood joints with higher withdrawal strength than yellow birch. The best results for sugar maple and yellow birch were obtained with a rotational speed of 1000 rpm. A 25 mm s−1 insertion speed produced significantly stronger welded joints in sugar maple than at 12.5 mm s−1. For yellow birch, a 16.7 mm s−1 insertion speed provided the best results. Both species and rotational speed had a significant effect on peak temperature at the interface during welding. Peak welding temperatures with optimal parameters were 244 and 282 °C for sugar maple and yellow birch, respectively.

Wood Blockboards Fabricated by Rotational Dowel Welding

Holding wood pieces together by rotationally welded dowels can be used to make blockboard panels with the dowels inserted in the side of the wood substrate slats. The average results for both tensile and three-point bending tests indicate that a 20° dowel insertion angle yields strength results better than 10° and 0° insertion angles. Applied load vs deformation in the two types of tests showed that blockboard panel stiffness was greater for the panels with 20° dowel insertion angle.Holding wood pieces together by rotationally welded dowels can be used to make blockboard panels with the dowels inserted in the side of the wood substrate slats. The average results for both tensile and three-point bending tests indicate that a 20° dowel insertion angle yields strength results better than 10° and 0° insertion angles. Applied load vs deformation in the two types of tests showed that blockboard panel stiffness was greater for the panels with 20° dowel insertion angle.

An investigation of thermochemical changes in Canadian hardwood species during wood welding

Thermochemical changes during wood-dowel welding were investigated in two Canadian hardwood species commonly used for indoor appearance applications: sugar maple (Acer saccharum) and yellow birch (Betula alleghaniensis). The original reference wood sample and the welded interface between two bonded wood pieces, a dowel and a substrate, were compared to explain differences in mechanical properties between species. Pyrolysis gas chromatography–mass spectrometry (Py-GC/MS), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), and X-ray photoelectron spectroscopy (XPS) were used. The gases emitted during wood welding were determined by Py-GC/MS and gas chromatography coupled with a thermal conductivity detector and a flame ionization detector (GC-TCD/FID). Results showed that thermal welding of birch and maple woods degrades hemicelluloses and affects lignin polymer through depolymerisation. Welding effectiveness is therefore directly associated with the properties of the original wood constituents, primarily lignin and carbohydrates. The lignin-related changes at the welded interface were greater for sugar maple than for yellow birch, corroborating mechanical property differences observed between the two species. The gases proportions were similar for both species and no harmful gases were detected in the smoke released during welding process.ZusammenfassungUntersucht wurden die thermochemischen Veränderungen, die beim Einbringen von Dübeln mittels Reibschweißen in zwei in Kanada für Innenanwendungen häufig verwendeten Laubholzarten Zuckerahorn (Acer saccharum) und Gelbbirke (Betula alleghaniensis) auftreten. Die Schweißfläche zwischen den zwei verbundenen Holzteilen, einem Dübel und einem Holz, und dem nicht betroffenen Holz wurden verglichen, um unterschiedliche mechanische Eigenschaften beider Holzarten anhand von Pyrolyse-Gaschromatographie–Massenspektrometrie (Py-GC/MS), Fourier-Transformations-Infrarot-Spektroskopie in abgeschwächter Totalreflexion (ATR-FTIR) und Röntgen-Photoelektronenspektroskopie zu bestimmen. Die beim Reibschweißen emittierten Gase wurden bestimmt mittels Py-GC/MS und Gaschromatographie gekoppelt mit einem Wärmeleitfähigkeitsmesser und einem Flammenionisationsdetektor (GC-TCD/FID). Die Ergebnisse zeigten, dass beim Reibschweißen von Birken- und Ahornholz Hemicellulosen abgebaut werden und auch das Ligninpolymer depolimerisiert wird. Die Güte der Verschweißung hängt deswegen direkt von den Eigenschaften der zu verschweißenden Holzbestandteile ab, insbesondere dem Lignin und der Kohlenhydrate. Veränderungen des Lignins an der Schweißfläche waren bei Zuckerahorn größer als bei Gelbbirke und bestätigen damit die unterschiedlichen mechanischen Eigenschaften beider Holzarten. Die Gasanteile waren bei beiden Holzarten vergleichbar und im Rauch, der beim Schweißen entsteht, wurden keine schädlichen Gase festgestellt.

Assessing the potential of wood welding for Australian eucalypts and tropical species

The wood welding potential of Australian and tropical species has been investigated. Optimized parameters for Eucalyptus saligna, Eucalyptus pilularis, Corymbia maculata, Ochroma pyramidale, and Tectona grandis were determined using a standard tensile strength test. The results confirmed the importance of density in the optimisation process. The grain direction also proved to have a significant impact on the welded joint strength of species featuring large wood rays or vessels in diagonal and/or radial pattern. Wood welding could therefore be an alternative for such species where gluing is required.

Comparing two intermittent drying schedules for timber drying quality

ABSTRACT Intermittent drying techniques for drying timber may provide various benefits by improving timber quality and addressing energy efficiency through saving in energy consumption. The purpose of this study was to compare two intermittent drying schedules applied in the treatment of Eucalyptus delegatensis boards, through assessing surface and internal check development, moisture content (MC) profiles during drying, and timber distortions at the end of drying. The study used identical conditions during the heating phase at 45°C/60% relative humidity (RH), except for RH during the nonheating phase (80 and 90%). The results, discussed in this paper, analyzed the timber quality during and at the end of drying. The different RH during the nonheating phase did not generate a significant difference in MC at the case boards between the two drying schedules. The assessed quality of timber at the end of drying was based on AS/NZS 4787:2001. MC gradient, drying stress residual, internal checking and collapse were graded as class “A” (class A is the highest grade and D is the lowest). Bow, cupping, and spring were under the permissible levels based on grading standard AS 2082–2007. Measured data were validated using Drytek® simulation software showing MC movement in case boards.

Drying timber in a solar kiln using an intermittent drying schedule of conventional laboratory kiln

Abstract The purpose of this study was to apply an intermittent drying schedule developed from a conventional kiln to a solar kiln. Implementing this experiment could help better understand the oscillation of the temperature inside a solar kiln and timber quality during drying progress. The theoretical recharge and discharge curves were used to predict the temperature inside the solar kiln using experimental data obtained previously using a solar kiln. The surface and internal checks were measured using ImageJ freeware, and the development of the Moisture Content (MC) profile was assessed by coring and slicing method for the Eucalyptus delegatensis boards during drying. The results showed that the recharge and discharge model can predict the temperature with less than 2 °C error from the experimental data in the solar kiln. The total drying time to 12% MC was 87 days for the solar kiln. The drying rate was equivalent to the conventional kiln decreasing at an average rate of 0.2% per day. The surface check formation was found when the MC gradient between the core and the case of the board was greater than 42% at 9 days of drying in the solar kiln and conventional laboratory kiln. The applied drying schedule used in the solar kiln was successful and offered similar drying time. However, the oscillation of temperature in the intermittent drying will require further improvement to get closer conditions in a solar kiln.

Water resistance of natural joint of spruce produced by linear friction welding without any treatment

ABSTRACT This research work showed that spruce wood can be butt welded in a short time end-grain to-end-grain without any treatment. Wood welding has already been shown to be well adapted to the manufacture of wood structures of larger dimensions. When pressure increased, the welded material formed is of higher density and consequently the water resistance improved. The welded spruce samples present a much improved water resistance when the welding pressure was increased from 2.75 MPa to 3.75 MPa for the same welding time of 6 s. The welded interphase in end-grain-to-end-grain butt welding of spruce appears to occur by the formation of an interphase having the appearance of finger-joints. This is due to the different behaviours of the late and early wood rings of spruce during welding. This, by increasing the surface of contact, is shown to improve the water resistance of the original butt joint.

Wood machining properties of Australian plantation-grown Eucalypts

This study assessed the moulding, drilling, turning, sanding, and routing properties of seven plantation-grown hardwood species from southeast Australia to evaluate their potential as a resource for the manufacture of high quality furniture and furnishings. Eucalyptus grandis, Eucalyptus saligna, Corymbia maculata, Eucalyptus camaldulensis, Eucalyptus sideroxylon, Eucalyptus cladocalyx, and Eucalyptus globulus were machined using different tools, and the surface quality obtained was visually graded. A sanding sequence of 100-150 grit produced satisfactory surfaces for furniture manufacturing for most studied species. Usually, a feeding direction against the rotational direction of the tool showed best results and reduced incidence of corner breakout when routing. Overall, high-density plantationgrown Australian hardwood species performed well during machining trials with the use of appropriate parameters and cutting tools allowing overcoming some typical processing difficulties for some species. The data obtained within this study will allow optimising the machining process of plantation-grown wood in Australia and increase value from the current plantation resource.