This article aims to investigate the contact characteristics of mortise and tenon (M&T) joints in the traditional timber structures. In particular, the normal embedded compressive contact between ...contact surfaces of M&T joint was investigated. Based on basic contact theory and contact characteristics between mortise and tenon, a normal elasto-plastic contact model, which can reflect the real normal contact behavior of M&T joints in traditional wooden structures, was proposed. Coulomb friction contact was utilized to describe the tangential slipping characteristics of the contact surfaces. Micro-morphology scanning tests of wood samples with different roughness were carried out to determine the parameters involved in the normal contact model. The normal contact model subroutine of M&T joint was compiled by FORTRAN language, implemented into ABAQUS through user-defined interface (UINTER). Then the proposed model was verified by shear tests of wood contact surfaces considering different normal pressures. Finally, a finite element model (FEM) of straight tenon joint subjected to cyclic reversed loading, based on the proposed normal elasto-plastic contact model, was developed, and a FEM considering normal “hard contact” between the contact surfaces, was also performed. The simulation results were validated by the experimental results. Results showed that the user-defined normal elasto-plastic contact FEM was more in line with the actual force state and mechanical behavior of M&T joints, which can more accurately predict the failure modes and simulate the hysteretic behavior of M&T joints, compared to the FEM considering normal “hard contact” of the contact surfaces.
In this study, 2
5
(five factors at two-level factorial design) design of experiment was applied to investigate a set of optimal machining parameters to achieve a minimum surface roughness value for
...Abies nordmanniana.
Wood specimens were prepared using different values of spindle speed, feed rate, depth of cut, tool radius, and cutting directions. Average surface roughness
R
z
values were applied using a stylus. The objectives were to: (1) obtain the effective variables of wood surface roughness; (2) analyze which of these factors had an impact on variability in the CNC machining process; (3) evaluate the optimal cutting values within the range of different cutting levels of machining parameters. The results indicate that the design of experiment (DOE) based on the desirability function approach determined the optimal machining parameters successfully, leading to minimum
R
a
compared to the observed value. Minimum surface roughness values of tangential and radial cutting directions were 3.58 and 3.21 µm, respectively.
Water-based antimicrobial agents, used in environmentally friendly applications, are widely used in wood protection industries. Furthermore, nanomaterials as antimicrobial agents, because of their ...biocidal component, huge specific surface area, and unique nanoscale effect, have attracted attention in the field of biodurability. We employed aqueous dispersed nano-silver with a diameter of 10 nm~20 nm to treat poplar wood and evaluated its leaching resistance and anti-mold effect on the wood surface. The results revealed that the higher the retention of the nano-silver, the stronger the protection efficiency of the wood surface against three molds (
Tiegh,
Thom, and
ex Fr); and the leachability of the nano-silver presented a slowly growing trend with the increase in the retention. When the wood surface attained a silver retention of 0.324 g·m
, its anti-mold efficiency against
Tiegh,
Thom, and
ex Fr reached 80, 75, and 80%, respectively, which achieved or even exceeded the required standard value of effective mold inhibition (75%). Notably, the nano-silver leaching rate at this retention attained merely 4.75 %. The nanoparticle, well distributed on a wood surface, may promote sufficient contact with fungi as well as strong interaction with wood cell wall components, which probably contributed to the effective anti-mold efficiency and the leaching resistance. This study provided positive evidence for the anti-mold effect of nano-silver on wood surface.
The demand for engineered wood products (EWPs) continues to rise internationally. However, for some important Australian commercial timbers such as plantation grown southern pine and native forest ...sourced spotted gum, a major impediment to achieving commercially viable EWP production is difficulties experienced in gluing – particularly for sawn laminate based EWPs such as glulam. Wettability and permeability have a major influence on wood adhesion. This study investigated the efficacy of different surface machining preparations on the wettability and permeability of southern pine and spotted gum. For both species, planing resulted in poor wettability, whereas face milling and sanding treatments post-planing improved wettability. Wettability increased in southern pine earlywood compared to latewood; and wettability decreased for both species with increased time post-surface machining. Planing resulted in the highest permeability for southern pine but the lowest permeability for spotted gum. Face milling resulted in higher permeability compared to sanding treatments.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
•Surface finishing of thermally modified wood to extend protection in outdoor uses.•Application of waterborne and UV-curable coatings on industrially modified samples.•Tracking changes caused by ...thermal modification that affects coating performance.•The modified wood improves adherence when compared with unmodified wood.•The thermal modification did not affect the elastic properties of the coated surface.
Thermally modified wood has been developed as an industrial method to improve durability and dimensional stability of wood and thus extends the range of uses and service life of wood-based products. Despite the improvements gained by treatment, surface finishing using coatings prevents esthetical changes such as color degradation or occasional growth of mold adding protection in outdoor use and extending the service life of products. The wood finishing process was carried out with commercially available waterborne and UV-curable coatings on industrially modified at 192, 200, 212°C and unmodified European ash (Fraxinus excelsior L.) wood, using an industrial rollers system and a laboratory brushing system. Changes caused by thermal treatment which could affect the surface finish were measured and compared with control samples, such as water uptake, wettability and acidity. Following the wood finishing, surface properties and esthetic changes were evaluated; as well as the coatings performance. Thermally modified wood presented improved adherence compared with unmodified wood with a significant improvement in samples modified at 212°C, which also present the highest hardness when UV-cured. Finishes with UV-curing maintain the hydrophobic effect of thermally modified wood, whereas waterborne finishes increase the surface wettability. Thermal modification did not negatively influence on the elastic properties of the coated substrate and thus allows this material to be finished with different coating systems in the same conditions as unmodified wood.
One of the most significant limitations for a wider utilisation of the renewable and CO
-storing resource wood is its low ultraviolet (UV) light stability. The protection of the wood surface without ...altering its aesthetic appeal requires an optically transparent but UV protective coating which should be strongly attached to the rough and inhomogeneous substrate. For this purpose, ZnO nanostructures were deposited onto the wood surface via a chemical bath deposition process. The morphology of crystalline ZnO was controlled by aluminium nitrate or ammonium citrate in the growth step resulting in nanorod arrays or platelet structures, respectively. Detailed structural, chemical and mechanical characterisations as well as accelerated weathering exposure revealed the effective performance of the platelet structure, which formed a dense and thin ZnO coating on spruce. The total colour change (Δ
in the CIE system) was calculated to be 20.5 for unmodified wood, while it was about three for the modified samples after 4 weeks accelerated weathering test. Moreover, the ZnO coating also suppressed crack initiation and propagation indicating a substantial increase in durability.
• Key message
Visual perception of the appearances of different wood surfaces is greatly influenced by their features, such as color, grain, and gloss. Among these features, human visual perception ...of wood grain type occurs through a later and higher-ordered cognitive process than the perception of color or gloss. Dark wood was subjectively preferred to light- or medium-colored wood, and both matte and glossy wood were preferred to semigloss wood.
•
Context
Understanding how the appearance of wood is processed in visual perception is critical for wood product design and will help improve consumer satisfaction. Unlike traditional subjective evaluation, neuroscientific methods enable a quantitative understanding of the process and are sensitive to the human visual perceptual response to the appearance of wood surfaces.
•
Aims
The objectives of this study were to quantify the visual perception process and to explore the human neural activity elicited by different wood surface appearances.
•
Methods
Three types of wood differing in color (light, medium, and dark) were cut to expose two different grain types (radial and tangential) and finished to three different gloss values (matte, semigloss, and glossy); digital images of these stimuli were shown to the subjects on a screen. A subjective emotion scale was constructed to measure their subjective evaluation, and neural ERP (event-related potential) data reflecting subjects’ early visual perception were recorded. Finally, all the data underwent analysis of variance as well as correlation analysis.
•
Results
Regarding early visual perception, the measurements of relevant ERP components showed that subjects perceived the color and gloss of wood more quickly than the grain type, and their perception of wood grain involved a higher-order cognitive process. The match or mismatch between a given stimulus and a subject’s visual memory of wood surface appearance could enhance different ERP components, respectively. In addition, subjects had significantly greater appreciation for dark wood than for other colors, and semigloss wood was less favored than matte or glossy wood.
•
Conclusion
This study provides an objective method to measure the visual perceptual processing of wood appearance; this method may help improve the efficiency of material selection for wood product design. Furthermore, the quantification method can be used by designers in measuring their wood products, and the results can be treated as indicators by which to evaluate the appearance of wood.
본 총설에서는 외부에 사용되는 목재를 풍화인자로부터 보호하기 위해 실행되고 있는 최근의 연구동향에 대해 조사분석하였다. 주요 기상열화 인자로부터 목재의 표면 보호를 위한 연구 동향에 대하여 조사한 결과 다음과 같은 결론을 얻었다. 목재보존제로 사용된 크롬, 구리 등의 무기화합물이 목재를 기상열화로부터 보호할 수 있는 것으로 보고되었다. 또한 ACQ처리 ...목재의 표면에 wax나 oil같은 소수성물질과 UV 흡수제, HALS(Hindered Amine Light Stabilizers) 등을 방부목재 표면에 precoating하면 기상열화 저항성을 강화할 수 있다고 보고되었다. 또한 방부목재 표면에 불투명 도막형성의 페인트/스테인 및 반투명스테인등이 기상열화방지에 대한 시너지 효과가 높힐수 있다는 보고들이 다수 있었다. 또한 방부목재의 표면보호를 위한 재도장 처리의 필요성이 시사되었다. 투명성의 도막에 UV방지를 위한 첨가물로서 미세입자의 ZnO 또는 TiO 2 , Co, Cr, Fe, Mn, Ni과 Ti 등의 금속이온, Tris-resorcinol triazine derivatives, triazine 및 Benzotriazole과 같은 UV흡수제 등이 소개되었다. Methylation, acetylation 또는 alkylation 등과 같이 화학적으로 개질된 경우에는 이로 인한 중량증가가 높은 경우 기상열화 방지효과가 상승된다는 연구들이 소개되었다, 열처리목재의 기상열화 저항성에 대해서는 여러 가지 상반되는 연구보고 들이 있었고, UV저항성을 지닌 도장의 필요성이 강조된 보고가 있어 보다 심도 있는 연구의 필요성이 시사되었다.
A review of research trends on wood surface protection for exterior use obtained the following conclusions: It has been reported that inorganic compounds such as chrome and copper used as wood preservatives can protect wood from weathering. It has been shown that precoating with hydrophobic substances such as wax and oil, UV absorbers, and HALS (Hindered Amine Light Stabilizers) enhances weathering resistance on the surface of ACQ-treated wood. Opaque coatings of paint/stains and semitransparent stains on the surface of preservative treated wood can increase the synergistic effects on prevention of weathering deterioration. Also the need for repainting periodically for the protection of the preservative treated wood surface has also been suggested. ZnO or TiO 2 of fine particles, metal ions such as Co, Cr, Fe, Mn, Ni and Ti, and UV absorbers such as tris-resorcinol triazine derivatives, triazine and benzotriazole were introduced as additives for preventing UV in the transparent coating on wood. Several reports showed that chemical modification such as methylation, acetylation, or alkylations have made some increases the effects of preventing weathering with the increasing weight gain of chemical formulas. In heat-treated wood, there were various contradictory reports on the resistance of weathering, and there were some other reports emphasizing the necessity of painting with UV resistance, which leads to the necessity of more advanced studies.
Research was done to develop the optimal method of wood surface preparation for scanning electron microscopy (SEM). Since 2018, environmental scanning electron microscope (ESEM™) FEI Quanta 250 has ...been installed at the Department of Wood Science and Technology in Ljubljana. We tested several methods for the pre-preparation and cutting of wood surfaces for SEM analyses. The samples had been either dried, soaked in water and frozen, impregnated with paraffin or simply moistened before cutting. We analysed wood surfaces obtained by splitting, sawing, planing, sanding and cutting on a sliding microtome with different blades. The effect of gold coating on the SEM image quality was also evaluated. Best results were obtained by cutting a pre-moistened surface on a sliding microtome with a low profile replaceable blade and gold coated afterwards. Determined methodology is technically less demanding, not time consuming and obtains results that satisfy needs for wood anatomy research at magnifications up to 12.000x. Guidelines for the optimal preparation of samples were prepared, and theoretical and practical basis for investigations of wood anatomy using SEM were provided. The method was afterwards used in analyses of invasive alien plant species – investigating their anatomical structure in the framework of the AlienPLAntSpEcies - APPLAUSE project (Urban Innovative Actions initiative). It was demonstrated that the use of the SEM opened new scope in detailed investigations of the wood structure and properties.
Istraživanje je provedeno kako bi se razvila optimalna metoda pripreme drvne površine za pretražnu elektronsku mikroskopiju (SEM). Od 2018. na Odsjeku za znanost i tehnologiju o drvu u Ljubljani instaliran je uređaj za pretražnu elektronsku mikroskopiju u uvjetima okoliša (ESEMTM) FEI Quanta 250. Proučavali smo nekoliko metoda za pripremu i rezanje površine drva za SEM analizu. Uzorci su sušeni, potapani u vodi i smrzavani te prije rezanja impregnirani parafi nom ili samo navlaženi. Analizirali smo površine drva dobivene cijepanjem, piljenjem, blanjanjem, brušenjem i rezanjem na mikrotomu različitim oštricama. Također je proučavan utjecaj zlatnog premaza na kvalitetu SEM fotografi ja. Najbolji rezultati dobiveni su rezanjem prethodno navlažene površine na mikrotomu, i to zamjenjivim noževima niskog profi la, nakon čega je površina drva pozlaćena. Primijenjena je metodologija tehnički manje zahtjevna, ne oduzima mnogo vremena, a dobiveni rezultati zadovoljavaju potrebe istraživanja anatomije drva pri povećanju i do 12 000 puta. Sastavljene su smjernice za optimalnu pripremu uzoraka te je postavljena teorijska i praktična osnova za istraživanje anatomije drva primjenom SEM-a. Metoda je potom primijenjena za istraživanje invazivnih biljnih vrsta – za ispitivanje njihove anatomske strukture u sklopu projekta AlienPLAntSpEcies – APPLAUSE (Urban Innovative Actions). Potvrđeno je da je upotreba SEM-a otvorila novo područje u detaljnim istraživanjima strukture i svojstava drva.
When utilizing microspheres to construct structural color layers on wood surfaces, the cellular structure of wood can influence the self-assembly of microspheres and the resulting structural color ...layers. To investigate this influence, seven types of wood were selected in this study, and structural color layers were constructed on their surfaces. A comparative analysis was conducted on the color production and macro and micro morphologies of the structural color layers on different wood surfaces, along with an examination of the types and causes of surface defects. The study found that when a microsphere-containing emulsion was applied to a wood surface, the emulsion tended to flow along the vessels of hardwood and the tracheids of softwood. Overflow or seepage of the emulsion could lead to a reduction in the number of microspheres per unit area, resulting in uneven thickness and uneven color generation of the structural color layers. Although the structural color layers on different wood exhibited the same color, there were variations in their tones, appearance, and morphology. Defects such as minor bumps and pits were present on the structural color layers. Bump defects might originate from microsphere encapsulation of fiber bundles or the displacement of air within vessel lumens by emulsion, while pits were mainly caused by the inflow of emulsion into the vessel lumens. This study clarified the influence of wood surface cells, particularly vessels and tracheids, on the construction and color production of structural color layers, providing support for the controllable modification of wood surfaces using structural colors.
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