Influence of wood wall panels on physiological and psychological responses

The effect of visual stimulation from wood on the body was examined in a comparative study using full-sized hinoki wall panels and a white steel wall panel. Continuous blood pressure measurements were used as the physiological indicator. Sensory evaluation by the semantic differential (SD) method and the profile of mood states (POMS) test were performed to determine changes in psychological impression. Results showed that visual stimulation from hinoki wall panels had an emotional and natural impression upon humans. Blood pressure decreased significantly in subjects who liked them, and there was no significant increase in blood pressure in subjects who disliked them. Visual stimulation from the white steel wall panel made an unhealthy and closed impression and increased the sense of depression. In addition, there was stress and a significant increase in blood pressure in subjects who disliked them. Consequently, visual stimulation from hinoki and white steel wall panels had different physiological and psychological effects. Results also showed that the same visual stimulation induced different physiological responses depending on the values of the individuals.Part of this paper was presented at the 48th Annual Meeting of the Japan Wood Research Society in Shizuoka, April 1998     

Reducing eye fatigue through the use of wood

To clarify if eye fatigue is lessened when looking at wood, we carried out objective examinations using a near-point ruler and also performed sensory evaluations. Visual contact target materials were a white plastic panel, a black plastic panel or a wood panel which had Japanese ash flat grain surface. Each size of the materials was 140 × 280 mm. Test subjects were 30 undergraduate and graduate students. Each subject’s visual distance to a panel was 40–50 cm. The results showed that subjects suffered from more eye fatigue when looking at white and black plastic panels compared to looking at the wood panel in objective examinations. In sensory evaluations, almost all subjective symptom items for eyes and head progressed when subjects looked at white plastic panel or black plastic panel. However, almost no progression of subjective symptoms was noted when subjects looked at the wood panel. In both objective examinations and sensory evaluations, eye fatigue was most highly associated with the black plastic panel, followed by the white plastic panel and, finally, the wood panel.     

Strain fields around knots in Norway spruce specimens exposed to tensile forces

Two-dimensional strain fields around knots in two Norway spruce specimens subjected to tension loading were detected using a contact-free measuring technique based on white-light digital image correlation. The first specimen included a traversing Edge knot, and the second one, a Centric knot. The development of strain fields as a function of load level was measured by consecutive cyclic load tests where one side of the specimen was studied during each test. The objectives were to examine to what extent the strain fields could be detected, to investigate the correlation between strain fields measured on different sides of a specimen and to analyse the strain distributions around the knots. The results show that the applied technique is useful for catching both overall and detailed information about the behaviour of knots in wood members exposed to loading. Clear wood defects that could not have been detected by neither visual inspection nor scanning were observed, and conclusions could be drawn regarding the release of internal stresses. The correlations between strain fields on different sides of the specimens were excellent, and the correspondence between measurement results and comparative finite element calculations was surprisingly good considering the fact that the employed FE models were fairly simple.     

The analytical influence of all types of knots on bending

The influence of different types of knots and fiber deviations on the bending of wood, as managed using visual grading standards, was analytically discussed in this research by means of the finite element method. The effect of each geometrical variable on the strength and stress distribution has been studied individually. This was accomplished after validating a previously presented finite element model that accounted for the three-dimensional shape of the knots and fiber deviations. The simulated sizes and positions were those commonly managed by the standards for strength grading. The research presents the effect of: (1) the size and position of cylindrical face knots; (2) size and position of truncated conical face knots; (3) size and position of shallow conical face knots; (4) size and position of conical edge knots; (5) inclination of face knots. In each case, the analytical predictions of the modulus of rupture and stress distribution are detailed. Seven characteristic positions with distinct mechanical behavior were found, which should be accounted for in order to improve the wood grading efficiency.     

基于物联网大数据的人造板企业改扩建策略

随着我国经济的持续健康发展,我国木材供需矛盾日益加大。发展人造板产业,是缓解我国木材供需矛盾的重要举措。近年来,我国人造板产量持续增长,这得益于人造板企业的改扩建,也得益于物联网大数据技术在人造板企业改扩建中的应用。简要分析了人造板企业改扩建必要性,阐述了物联网大数据对人造板企业改扩建的作用,提出了基于物联网大数据的人造板企业改扩建措施。     

Production and properties of wood-welded panels made from two Canadian hardwoods

This study examines the suitability of wood welding technology for producing composite panels for furniture applications with two Canadian hardwood species, sugar maple (Acer saccharum) and yellow birch (Betula alleghaniensis). For each species, twelve 30 × 225 × 300 mm³ panels were manufactured using a panelling machine specifically designed for rotational wood-dowel welding with optimized parameters obtained from a previous study. Six edge-glued panels of the same size were manufactured from each species using a non-structural polyvinyl acetate adhesive and tested for comparative purposes. The experimental programme included three-point bending at 255-mm span and visual inspection of the panels to assess performance at standard moisture conditions and after an ageing cycle with variable relative humidity. Average breaking load of 1.79 and 1.70 kN was obtained at standard moisture conditions for welded panels of yellow birch and sugar maple, respectively. Fractures consistently occurred in the dowel’s cross section, whereas no slippage was observed along the welded interface. Delamination between wood slats occurred after the ageing cycle, but did not affect the bending properties. Results confirm the suitability of wood-dowel welding for producing furniture panelling with Canadian hardwood species. Further research is needed to design panels with a more efficient position and use of welded dowels and with panel product properties that are comparable or superior to those of glued counterparts.     

Microscopic observation of wood-based composites exposed to fungal deterioration

This study was conducted to investigate the susceptibility of various wood composite panels exposed to wood-deteriorating fungi. Five wood-attacking fungi (three mold fungi, one brown rot fungus, one white rot fungus) were inoculated into four types of commercial wood composite panels (plywood, oriented strand board, particleboard, and medium-density fiberboard). One solid wood sample was included as a control. The attacking patterns of the fungi in each panel was observed by scanning electron microscopy. The weight losses due to the exposure were compared. All wood composites were more or less susceptible to all fungi inoculated. The attacking mode of the fungi was highly dependent on the types of wood composite, which had inherently different shapes of voids owing to different shapes and characteristics of the raw furnish materials used. Plywood and medium-density fiberboard showed a large weight loss after an 8-week exposure to decay fungi. Plywood is the most susceptible to white and brown rot fungi. This study indicates that all wood composite panels should undergo careful consideration to prevent fungal deterioration when they are used for exterior and humid interior applications.     

Effect of image characteristics of edge-grain patterns on visual impressions

To demonstrate the psychophysical effect of edge-grain patterns on visual impressions received by human observers, printed images of the edge-grain patterns of 16 species were prepared as well-regulated visual stimuli, and impressions of the patterns on 32 subjects were evaluated using six categories. Image characteristics of the patterns were expressed numerically using contrast values that were derived by multi-resolution contrast analysis (MRCA) proposed by the authors, and relationships between the image characteristics and the visual impressions were examined. The difference in lightness between local areas with a certain size in the image was used as the contrast value, which could be used to detect the change in lightness due to the particular feature in the edge-grain pattern. While some impressions were almost independent of the contrast values, other impressions showed highly positive or negative linear relationships to the contrast values, derived at the optimal filter size in MRCA. Moreover, these optimal sizes were rarely affected by color information. The contrast value proposed in this paper would be a good numerical index that could be used not only to describe image characteristics of the edge-grain patterns but also to estimate some of their visual impressions.     

Estimation of demand for wood panels in Iran by the year of 2012

Considering increasing rate of Iran population and consumption of wood panels, the authors investigated the per capita consumption of wood panels during the years from 1997 to 2007. The exponential smoothing method was used to obtain a per capita consumption pattern of wood panels in Iran for estimating demand of wood panels by the year of 2012. Results show that the consumption of particleboard, fiberboard, and medium density fiberboard in Iran will increase by 33%, 72% and 107 %, respectively, by the year of 2012; however, the consumption of plywood will increase only by 7% by 2012. The deficient amount of wood panels in Iran is estimated over 1400000 m3. The results of this study provide the technique reference for planners of wood panel industries in Iran in capital investment decisions.     

Knots detection in wood using microwaves

This work describes a microwave technique used to generate and process data on knots in wood prior to processing. The experimental design was a simple system composed of a microwave emitter and receiver used to scan the wood samples with knots. Signals were calibrated and amplified, and then a data storage and graphic visualization were performed. A PCL-711 data acquisition card was used in conjunction with data acquisition software. The preliminary results obtained for the studied wood samples were viewed in 2- and 3-dimensional graphics, showing a strong relation with the visual inspection of the samples.     

基于Faster R-CNN的实木板材缺陷检测识别系统

我国木材资源有限,为了提高木材的利用率,采用机器视觉来实现木材缺陷快速而稳定的检测,不仅可以克服人工检测的低效率和木材缺陷识别的低准确率,而且对提高木材加工企业的智能化水平具有重要意义。为了高效、快速、准确地进行无损检测,采用深度学习方法,建立了一种基于快速深度神经网络的实木板材缺陷识别模型。首先采用Resnet V2结构对采集到的实木板材缺陷图像进行特征提取,然后应用该模型对节子、孔洞等实木板材缺陷进行训练学习,最后构建了Faster R-CNN检测框架,并使用tensorflow开发平台对节子、孔洞等实木板材缺陷进行预测输出。具体选取了2 000块杉木样本,通过旋转对原始的实木板材图像进行数据扩充,扩充后图像的80%作为训练集,20%作为验证集来进行仿真。仿真结果表明,该模型对实木板材节子缺陷检测正确率为98%,对实木板材孔洞缺陷检测正确率为95%,验证了将深度学习算法应用于实木板材缺陷检测中的有效性。     

应力波技术在古建筑木构件腐朽探测中的应用

采用应力波测定仪对西藏古建筑上的腐朽与虫蛀木构件进行无损检测和目测腐朽观察,并将两种结果进行比较.结果表明:应力波无损检测技术可以准确的判定木构件的内部腐朽与虫蛀;表层腐朽分级与无损检测结果基本一致;在古建筑维护中,可在目测基础上,再采用应力波技术检测确认,为准确更换木构件提供定量评价依据.     

Defect detection in lumber including knots using bending deflection curve: comparison between experimental analysis and finite element modeling

A new method has been developed for detecting localized defects such as edge knots using a bending deflection curve. The coordinates of a bottom edge (edgeline) of an unloaded piece of lumber are extracted from a digital image, and a bending deflection curve is obtained from the displacement of the edgeline of the lumber using a digital image correlation (DIC) technique. Depending on the knots within the beam, the bending deflection curve is shifted from the curve of a defect-free beam. The measured bending deflection curve is regressed to a theoretical curve by elementary beam theory. A finite element method (FEM) model of the beams including defects as simplified knot structure has been performed. Comparison between the bending experiment and FEM analysis shows that cross-sectional reductions cause characteristic variations in the bending deflection curves depending on the position of encased knots, and local grain distortions cause variations in the curves depending on the direction of spike knots. Using the residual variance between the measured deflection curve and a polynomial regression curve, it is possible to detect knots at which failures initiate. Part of this article was presented at the 57th Annual Meeting of the Japan Wood Research Society, Hiroshima, Japan, August 2007     

Shear behavior of cross-laminated timber wall consisting of small panels

A cross-laminated timber (CLT) wall plays the role of resisting shear stress induced by lateral forces as well as vertical load. Due to the press size, CLT panels have a limitation in size. To minimize the initial investment, some glulam manufactures wanted to make a shear wall element with small-size CLT panels and panel-to-panel connections and wanted to know whether the shear wall would have equivalent shear performance with the wall made of a single CLT panel. In this study, this was investigated by experiments and kinematic model analysis. Two shear walls made of small CLT panels were tested. The model showed a good agreement with test results in the envelope curve. Even though the shear walls were made of small panels, the global peak load did not decrease significantly compared with the wall made of a single CLT panel, but the global displacement showed a large increase. From this analysis, it was concluded that the shear wall can be designed with small CLT panels, but displacement should be designed carefully.     

我国果木人造板生产现状及发展概述

我国是世界果木经济林种植大国之一,每年约可产生4 175万t枝桠材,近10年来,我国已经开始以果木为原料生产人造板.笔者对我国果木人造板生产现状、企业运行情况、应用及市场情况、存在的问题等方面进行了调研和总结,并在此基础上给出了发展建议,以期对果木人造板生产健康有序发展提供支持.     

废弃纺织物/木刨花复合板制备工艺

采用常规热压法对废弃纺织物和木刨花制备复合人造板相关工艺进行了试验,并讨论了各因素对板性能的影响。结果表明:利用废弃纺织物和木刨花制备人造板在工艺上是可行的。制造复合板的较优参数:纺织纤维形态为碎布条或絮状纤维、刨花/碎布条配比为7∶3、施胶量为12%、密度0.7 g/cm3,最优配比制备的板材其物理力学性能都已达到GB/T4897.2-2003要求。     

Identification of moisture-induced stresses in cross-laminated wood panels from beech wood (Fagus sylvatica L.)

The crosswise bonding of the layers in laminated solid wood panels results in internal stresses when the humidity varies. The layers hinder one another as a result of the anisotropy of wood. The purpose of this study was to determine the internal stress state in free and constrained swelling. The expansion properties in the three panel directions were measured. Furthermore, the swelling of samples was constrained while the resulting forces were recorded. Hygroscopic warping experiments were carried out inducing a climate gradient within the panels. Afterwards the stresses were calculated from released deformations and non-destructive measurements of the Young’s modulus. The materials used were untreated and heat-treated beech wood, the latter modified in two levels. In addition to homogenously structured panels, treated top layers were combined with an untreated middle layer. Swelling, swelling pressure, warping and internal stresses considerably decreased from untreated to treated wood. If layers from treated and untreated material were combined, stresses and deformations increased as compared to the variants produced only from treated wood. It was concluded that the lower equilibrium moisture content of heat-treated beech wood improves its dimensional stability, which results in smaller deformation differences between the layers. Hence, the stresses were less distinctive.     

Effects of fire-retardant treatment and wood grain on three-dimensional changes of sandwich panels made from bubinga decorative veneer

ABSTRACT

The effects of a fire-retardant treatment (FRT) and wood grain on three-dimensional changes of aircraft sandwich panels were evaluated. Unvarnished and varnished panels having the outer decorative layer made with bubinga (Guibourtia spp.) were studied. Half of the samples from each type of panel received an FRT (phosphate-based) on all three layers of the decorative plywood. The other half had the two inner layers treated and the outer layer untreated. Three different figures formed by the rotary cutting and grain orientation were identified and separately studied on veneer surfaces. Samples pre-conditioned to 20°C and 40% relative humidity (RH) underwent an adsorption (25°C, 90% RH) and then a desorption (25°C, 40% RH) treatments. Changes in moisture content (MC), swelling, shrinkage, roughness, and waviness were measured after each moisture exposure condition. The results showed that the FRT increased significantly MC, swelling, and shrinkage of unvarnished and varnished panels. This treatment as well as the type of wood figure affected roughness and waviness variations of unvarnished panels. However, the effects of these two factors were not noticeable once panels were varnished.     

Utilization of pine (Pinus pinea L.) cone in manufacture of wood based composite

Physical and mechanical properties of medium density fiberboards (MDF) made from various mixtures of wood fibers and stone pine (Pinus pinea L.) cones were evaluated using European standards. MDF panels were manufactured using standardized procedures that simulated industrial production at the laboratory. Six panel types were made from mixtures of wood fiber/cone flour, 100/0, 90/10, 80/20, 70/30, 60/40, and 50/50 percents, respectively. Addition of the cone flour into the MDF significantly reduced formaldehyde emission from the panel. In addition, the addition of 10% cone flour also improved water resistance of the MDF panels made using urea–formaldehyde (UF) resin. However, further addition of the cone flour into the panel negatively influenced their water resistance. Flexural properties and internal bond strength decreased with the increase of cone flour content in the panel. The UF resin is the main source of formaldehyde emission from the UF-bonded wood-based panels. Depending on addition of the cone flour in the panels, the formaldehyde emission values ranged from 2.6% to 55.3% lower than the panels made from 100% wood fiber. Based on the findings obtained from this study, pine cone can be used as a renewable biological formaldehyde catcher as an alternative to the traditional formaldehyde catchers for E1 Class MDF manufacture.