Moisture Sensitivity of Scots Pine Joints Produced by Linear Frictional Welding

Vaziri, Mojgan; Lindgren, Owe; Pizzi, A.; Mansouri, Hamid

doi:10.1163/016942410x501098

Cited by 25 publications

(21 citation statements)

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“…As found previously [7,10], combination of 1.3 MPa welding pressure and 1.5 s welding time was the best factors combination which generated the most heat and improved water resistance of the weldline. Figure 3 shows that the densification degree of the weldline varies between 164-190% of the untreated wood density and degrees of densification for sapwood specimens are higher than for heartwood specimens.…”

Section: Discussionsupporting

confidence: 76%

“…1. Previous investigations [7,10] showed that this factors combination (0.75 MPa welding pressure, 2.5 s welding time and sapwood) led to a long crack in the middle of weldline and short crack time. Figure 2 indicates that there is no definite relationship between density and crack time of the speci- mens.…”

Section: Resultsmentioning

confidence: 87%

“…As described in earlier work [7] 80 specimens of dimensions 200 mm × 20 mm × 20 mm were cut from heartwood and sapwood of Scots pine in longitudinal direction of wood grain (40 specimens from heartwood and 40 specimens from sapwood). The specimens were conditioned for one week at standard conditions (RH 65%, 20 • C) before testing.…”

Section: Methodsmentioning

confidence: 99%

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Influence of Weldling Parameters on Weldline Density and Its Relation to Crack Formation in Welded Scots Pine Joints

Vaziri

Lindgren

Pizzi³

2011

Journal of Adhesion Science and Technology

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Exterior use of welded wood laminates without further treatment is not recommended. Frictional welded joints have poor resistance to moisture variation, especially to drying. Therefore, application of welded woods is limited to interior use without exposure to highly variable air humidity. Influences of some welding and wood parameters such as welding pressure, welding time and heartwood/sapwood on weldline density of Scots pine (Pinus sylvestris) joints were investigated. Interdependence between density and water resistance of weldline (in terms of crack time) was also studied by comparing the results of this investigation with those of the earlier studies. Specimens composed of two wood pieces, each measuring 20 mm × 20 mm × 200 mm, were welded together to form a specimen measuring 40 mm × 20 mm × 200 mm by a vibration movement of one wood surface against another at a frequency of 150 Hz. An X-ray Computerized Tomography scanner was used to measure weldline density. Weldlines of sapwood produced by 1.3 MPa welding pressure and 1.5 s welding time showed the highest density. No correlation between weldline density and crack time was evident.

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Section: Discussionsupporting

confidence: 76%

Section: Resultsmentioning

confidence: 87%

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Influence of Weldling Parameters on Weldline Density and Its Relation to Crack Formation in Welded Scots Pine Joints

Vaziri

Lindgren

Pizzi³

2011

Journal of Adhesion Science and Technology

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“…A certain temperature is necessary to reach the "melting" state. Welding pressure has a greater influence on heat generation in the interphase than does welding time (Vaziri et al 2010). When the welding pressure is increased, the frictional force and the amount of energy supplied to the interphase rises; thus, welding time can be reduced as welding pressure is increased.…”

Section: Introductionmentioning

confidence: 99%

“…With the same welding parameters, but maintaining A = 3 mm in all cases, Leban et al (2004) obtained tensile-shear strengths of 8.7, 5.4, and 4.2 MPa on average for beech, oak (Quercus robur L.), and spruce wood, respectively. Since then, several researchers Omrani et al 2009;Vaziri et al 2010) have found that a WT of 1.5 s leads to greater, yet not necessarily long-term, water resistance than a WT of 2.5 s. Mansouri et al (2009) reported results on the strength of welded (WT = 1.5 s, WF = 150 Hz, and A = 2 mm) beech wood joints, finding that in dry conditions, values of around 13.4 MPa were obtained, but after 4 h of immersion in water, the strength decreased markedly. In further studies conducted by Mansouri et al (2011), welded joints in high-quality Scots pine (Pinus sylvestris L.) wood had an average strength value of about 4.1 MPa for heartwood and 3.5 MPa for sapwood.…”

Section: Introductionmentioning

confidence: 99%

Influence of Welding Time on Tensile-Shear Strength of Linear Friction Welded Birch (Betula pendula L.) Wood

Ruponen¹,

Čermák²,

Rhême³

et al. 2015

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aThe purpose of this work was to determine the optimal welding time for linear friction welding of birch (Betula pendula L.) wood while keeping the other parameters constant and at similar levels compared to other species in a similar density range. Specimens with dimensions of 20 × 5 × 150 mm 3 were welded together, and the influence of welding time (2.5, 3.0, 3.5, and 4.0 s) on the mechanical properties of the specimens was determined. The studies included a tensile-shear strength test as well as visual estimation of wood failure percentage (WFP). Additionally, X-ray microtomographic imaging was used to investigate and characterise the bond line properties as a non-destructive testing method. The highest mean tensile-shear strength, 7.9 MPa, was reached with a welding time of 3.5 s. Generally, all four result groups showed high, yet decreasing proportional standard deviations as the welding time increased. X-ray microtomographic images and analysis express the heterogeneity of the weld line clearly as well. According to the averaged group-wise results, WFP and tensile-shear strength correlated positively with an R 2 of 0.93. An extrapolation of WFP to 65% totals a tensile-shear strength of 10.6 MPa, corresponding to four common adhesive bonds determined for beech.

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The role of lignin in wood working processes using elevated temperatures: an abbreviated literature survey

Börcsök

Pásztory

2020

Eur. J. Wood Prod.

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The lignin, cellulose and hemicelluloses in wood are polymers that behave similarly to the artificial polymers and are bonded together in wood. Lignin differs from the other two substances by its highly branched, amorphous, three-dimensional structure. Under appropriate conditions, the moist lignin incorporated in the wood softens at about 100 °C and allows the molecules of it to deform in the cell walls. There are many advantages and disadvantages to this phenomenon. If we know this process accurately and the industrial areas where it matters, we may be able to improve these industrial processes. This article provides a brief theoretical summary of lignin softening and the woodworking processes where it plays a role: wood welding, pellet manufacturing, manufacturing binderless boards, solid wood bending, veneer manufacturing, and solid wood surface densification.

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Moisture Sensitivity of Scots Pine Joints Produced by Linear Frictional Welding

Cited by 25 publications

References 5 publications

Influence of Weldling Parameters on Weldline Density and Its Relation to Crack Formation in Welded Scots Pine Joints

Influence of Weldling Parameters on Weldline Density and Its Relation to Crack Formation in Welded Scots Pine Joints

Influence of Welding Time on Tensile-Shear Strength of Linear Friction Welded Birch (Betula pendula L.) Wood

The role of lignin in wood working processes using elevated temperatures: an abbreviated literature survey

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