Wood Grain Research Articles

RELATIONSHIP BETWEEN WOOD ANATOMICAL FEATURES AND SURFACE ROUGHNESS CHARACTERISTICS

This study aimed to investigate the relationship between surface roughness and anatomical features of wood in 15 different species of boards. Surface roughness was measured parallel and perpendicular to the wood grain using a surface profilometer, and anatomical features such as pore size and distribution were analyzed using microscopic techniques. The results showed that surface roughness perpendicular to the grain direction was consistently higher than that parallel to the grain direction for all wood samples. This difference in roughness was correlated with pore size and density. It shows that the larger pores and lower density lead to higher roughness perpendicular to the grain. The study also found that traditional hand planning methods (push and pull) produced a smooth surface finish, with no statistical differences in roughness.

Evaluation of CNC routed surface quality of maple (Acer pseudoplatanus) and oak (Quercus robur L.) with different milling angles as function of grain orientation

The study assessed CNC routing quality on maple and oak samples, using 90º V-Grooving router bits at various milling angles as function of grain orientation: 0°, 15°, 30°, 45°, 60°, 75°, 90°, and feed speeds of 3 and 6 m/min at spindle speed of 15,000 rpm. The routing quality was evaluated by roughness parameters for the V flank surfaces and by visual examination for the flanks’ edges. The change in the feed speed had no significant effect for the flanks surface quality of both species, but roughness values were considerable higher for maple samples at 90º and u=3 m/min (Rk = 23.7 µm compared to along the grain, Rk=9.83 µm for u=6 m/min) due to possible processing vibrations. The milling angle as function of grain orientation was significant in the case of oak, as the processing roughness increased with the cutting angle from 0° (Rk=11 to 13 µm) to 60°(Rk =28 to 30 µm). Fuzziness around the earlywood pores of oak was higher for the 6 m/min feed speed. A substantial increase in waviness coinciding with the annual growth areas was measured for crosscut oak samples (Wa = 34.0 µm, compared with Wa =7 .39 µm along the grain). The surface waviness of maple was not sensitive to the variation in the cutting angle or feed speed (Wa was around 3 to 4 µm). For the flank edges, the best visual option was found for cutting along the wood grain and the worst was for 60º, which caused biggest ruptures and especially for the 3 m/min feed speed, for both species.

Highly Anisotropic Carbonized Wood as Electronic Materials for Electromagnetic Interference Shielding and Thermal Management

AbstractLightweight carbonized wood has a hierarchically 3D porous framework and orthotropic channels along the growth direction, which demonstrate great potential for multifunctional electronic materials. Herein, carbonized wood with outstanding electromagnetic interference (EMI) shielding effectiveness (SE), high thermal conductivity, and excellent Joule heating property is fabricated. It also exhibits a highly anisotropic EMI shielding performance in the cross‐ and tangential‐sections. In the tangential‐section, the shielding performance of carbonized wood is tuned by monitoring the angle between the wood grain and the electric field vibration direction of the electromagnetic waves, and the SE value ranges from 29 to 77 dB when the angle changes from 90° to 0°. Benefiting from the high SE obtained from structural optimization and the low density, carbonized balsa wood displays a high SSE (the ratio of SE to density) and SSE/t (the ratio of SSE to thickness) of 1069 dB cm3 g−1 and 3263 dB cm2 g−1, respectively. The thermal conductivity of carbonized wood is also angle‐dependent, which ranges from 0.865 to 1.897 W m−1 K−1. With the improvement in thermal conductivity, carbonized wood can be used as a heat sink material. Meanwhile, excellent Joule heating properties are achieved due to the effective conductive pathway in carbonized wood.

Highly anisotropic MXene@Wood composites for tunable electromagnetic interference shielding

Smart electromagnetic interference (EMI) shielding material with a dynamically adjustable electromagnetic response based on real-time requirements is attractive for future electromagnetic devices. Herein, a highly anisotropic [email protected] composite ([email protected]) with convenient shielding effectiveness (SE) regulation is fabricated by coating MXene on the natural wood surface. Benefiting from the anisotropic pore structure and abundant free radicals, the [email protected] displays a better impedance match in the tangential-section than in the cross-section. In the tangential-section, [email protected] can respond to changes in the dihedral angle between the wood grain and the electromagnetic wave electric field, and achieve the off/on switch between electromagnetic wave transmission and shielding. The SE ranges from 27.4 to 57.6 dB as the dihedral angle alters from 90° (perpendicular) to 0° (parallel). The finite element analysis simulation further reveals the tunable electromagnetic response. This sustainable EMI shielding material based on natural wood offers a novel platform for exploiting intelligent electromagnetic devices.

Hysteretic behaviors of Pingshenke Dou-Gong brackets of ancient timber buildings under different loading directions

To study the effect of loading directions on the seismic behavior of Dou-Gong bracket, numerical analysis was conducted on two Pingshenke Dou-Gong brackets under the overhanging direction (DG-1) and width direction (DG-2). The simulated hysteretic characteristic, stiffness degradation, and energy dissipation of Dou-Gong brackets were compared and validated by the test results. The horizontal displacement and relative slip of Dou-Gong components were discussed. Besides, parameter analyses considering the loading direction, wood grain direction, and material properties were performed. Results indicate that DG-2 has higher stiffness, bearing and energy dissipation capacity than DG-1, but poor deformation capacity. The positive component displacement of DG-1 is greater than DG-2, while the negative is the opposite. The relative slip between Da-Dou and Pingban-Fang is larger than other components. The overhanging and width direction are the most adverse direction for DG-1 under positive and negative load, respectively. DG-1 has the largest bearing capacity when Da-Dou is friction in the longitudinal surface under the tangential grain direction, but the grain direction has little influence on DG-2. The larger the friction coefficient and compressive strength, the greater the bearing capacity, but the initial stiffness is not improved. The elastic modulus has little effect on the initial stiffness and bearing capacity of Dou-Gong bracket.

Wood color modification with iron salts aqueous solutions: effect on wood grain contrast and surface roughness.

Wood is a biosourced material with unique aesthetic features due to its anatomy and chemical composition. White oak wood surface color can be modified with the use of iron salts, which react with wood phenolic extractives, present as free molecules in wood porous structure. The impact of modifying wood surface color with iron salts on the final appearance of wood, including its color, grain contrast and surface roughness, was evaluated in this study. Results showed that following the application of iron (III) sulphate aqueous solutions on white oak wood surface, its roughness increased, which is due to grain raising after wetting of wood surface. The color modification of wood surface with iron (III) sulphate aqueous solutions was compared with a non-reactive water based blue stain. The contrast associated to wood grain that was expressed by the standard deviation of luminance values in wood images, also increased after application of the iron (III) sulphate aqueous solution on white oak wood surface. The comparison of contrast changes showed that wood samples stained with iron (III) sulphate on their curved surface had the highest increase in grain contrast compared to iron-stained wood showing the straight grain and to wood surfaces colored by a non-reactive water-based stain for both curved and straight grains.

Application of 3D Scanning Method to Assess Mounting Holes’ Shape Instability of Pinewood

Swelling and shrinkage anisotropy affect the susceptibility to an assembly of wooden elements by changing designed clearances or interference fits. This work described the new method to measure mounting holes' moisture-induced shape instability and its verification using three sets of twin samples made of Scots pinewood. Each set of samples contained a pair with different grain patterns. All samples were conditioned under reference conditions (relative air humidity-RH = 60% and temperature 20 °C), and their moisture content (MC) reached equilibrium (10.7 ± 0.1%). On the side of each sample, the seven mounting holes of 12 mm in diameter were drilled. Immediately after drilling, Set 1 was used to measure the effective hole diameter with 15 cylindrical plug-gauges with diameters of 0.05 mm step, while Set 2 and Set 3 were separately re-seasoned by six months in two extreme conditions. Set 2 was conditioned with air at 85% RH (reached an equilibrium MC of 16.6 ± 0.5%), while Set 3 was exposed to air at 35% RH (reached an equilibrium MC of 7.6 ± 0.1%). Results of the plug gauge tests highlighted that holes in the samples subjected to swelling (Set 2) increased an effective diameter in the range of 12.2-12.3 mm (1.7-2.5%), while samples subjected to shrinking (Set 3) reduced the effective diameter to 11.9-11.95 mm (0.8-0.4%). To accurately reproduce the complex shape of the deformation, gypsum casts of holes were made. The 3D optical scanning method was used to read the gypsum casts' shape and dimensions. The 3D surface map of deviations analysis provided more detailed information than the plug-gauge test results. Both the shrinking and swelling of the samples changed the shapes and sizes of the holes, but shrinking reduced the effective diameter of the hole more than swelling increased it. The moisture-induced changes in the shape of holes are complex: the holes ovalized with a different range, depending on the wood grain pattern and hole depth, and were slightly extended in diameter at the bottom. Our study provides a new way to measure 3D hole initial shape changes in wooden elements during desorption and absorption.

Effects of wood texture and color on aesthetic pleasure: two experimental studies

The texture and color on wood are key factors that influence an individual's perception of it. However, little research has been done to confirm what kind of pattern in textures and colors are more likely to evoke individual aesthetic pleasure. Therefore, twenty-four decorative wood from northern China were selected, identified, and quantified in their colors with a CR-5 Colorimeter. We picked out eight kinds of wood with optimal texture characteristics through feature-fusion wood grain recognition (FWGR) and enhanced the texture features with photoshop in VR space. The result show that, in the color dimension, woods in the hue range of 20-25 and saturation of 65-75 were considered beautiful for individual perception of aesthetic. In the texture dimension, the size of the space affects the individual's preference for texture. When the pattern of the wood ray is continuous and clear, the individual's perception of its fluidity is enhanced; while for the fuzzy and interrupted pattern of the wood ray, the individual does not follow the fluidity of the line but focuses on the overall uniformity.

Sensory Inspection of Wood Grain by Traversing the GAN Latent Space

Sensory Inspection of Wood Grain by Traversing the GAN Latent Space

An elastic-plastic kinking layer model for parallel-to-grain wood embedment behavior considering wood drilling damage

This paper presents the results of the experimental and numerical studies on the influence of drilling damage of wood on the wood embedment behavior. Wood drilling tests were conducted to quantify the distribution of wood residual strain by use of digital image correlation technique. Parallel to wood grain repetitive compression tests were also conducted to determine the mechanical properties of wood within the kinking zone. Wood half-hole bolt embedment tests were conducted, and a wood kinking layer model was proposed and incorporated into a FEM model for the wood embedment behavior simulation. The model predictions were compared with the embedment test results and results from FEM models with different consideration of the weakened wood around the bolt holes. It was found that drilling can develop significant parallel and perpendicular to grain and shear residual strain in the surrounding wood. The distribution and magnitude of the residual strains were correlated with the hole diameter and drilling speed, and the thickness of a kinking layer can be taken as 1/13 and 1/7 of the hole diameter under the low and high drilling speeds considered in this study, respectively. It was observed from the repetitive tests of wood that during the steady-state kinking process, wood exhibited nearly constant peak stress and reloading modulus of elasticity. The FEM model with the proposed kinking layer model achieved a better agreement with the test results than FEM models based on wood foundation theory or a nonlinear contact model regarding the embedment elastic modulus, the maximum load, and the distribution of the strain in the embedment zone.

Tracking the histories of individual fuel particles in packed bed combustion

This paper introduces a simple technique for sampling individual fuel particles at various stages in overfeed packed bed combustion. A particle is secured to the end of a thin stainless steel rod, which is then used to track the motion of the particle and to remove it from the bed for sampling at the desired time. The particles so tracked provide a record of changes in mass, volume, density, and individual dimensions as combustion proceeds in the bed. Results of a number of experiments of this sort on the packed bed combustion of parallelepipedal wood particles are presented, which among other things show that particle shrinkage during pyrolysis is generally – but not always – largest along the direction of the wood grain and less in the cross-grain directions. The “tracker rod” technique has the advantage over single particle experiments in a furnace that the particles are exposed to the varying and non-uniform conditions in the actual packed bed of fuel; it is, however, only suited to fixed beds, not fluidized or moving beds.

A novel method and validation for obtaining the optimal interference fit of round-end mortise-and-tenon joint

ABSTRACT To determine the optimal interference fit of mortise-and-tenon (M&T) a novel method is proposed. To validate its effectiveness, compression tests were conducted considering the effects of wood species (beech and western hemlock), tenon widths (30, 40, 50 mm), and grain orientations (radial, diagonal, and tangential) to obtain the optimal interference fit and contact force (CF). Furthermore, the mounting force (MF) and withdrawal force capacity (WFC) of T-shaped M&T joints constructed by the control and optimal interference fit were evaluated by compression and withdrawal tests, respectively. The results indicated that (1) all three evaluated factors had significant effects on the tenon compression behavior and CF; (2) the derived optimal fits showed that the tenon with a larger width required a higher fit value based on regression equations; (3) the MF and WFC were significantly affected by the three evaluated factors and proportional to the tenon fit; (4) the maximum WFC occurred at the M&T joints made of western hemlock with 50-mm tenon width in tangential orientation with 0.99-mm interference fit, and the beech with 30-mm tenon width in diagonal orientation with 0.78-mm interference fit. The proposed method will assist the wood product manufacturers to design M&T joints rationally.

The effect of partial delignification on the stress–strain relationship in transverse compression

Due to very significant improvements in the mechanical performance of solid wood, densification after partial or full delignification has received renewed attention. While studies predominantly focus on isolated cases, e.g., one wood species densified in one anatomical direction, systematic investigations of the effect of wood structure on the densification process are seldom performed. The present study compares the deformation patterns of one representative softwood (spruce) and hardwood (poplar), respectively, in transverse compression. In terms of variables, the native and partially delignified state, wet and dry conditions, and three different orientations of wood grain are considered. It shows that the structural inhomogeneity of spruce wood, with low-density earlywood and high-density latewood, governs its densification pattern and hinders defect-free densification. Contrarily, diffuse-porous poplar is structurally more homogeneous, which together with more efficient softening by delignification leads to favorable densification behavior. Overall, delignification led to a significant softening of both wood species in transverse compression, which greatly enhanced the softening effect of high wood moisture content.

Comparative Surface Quality of Maple (Acer pseudoplatanus) Cut through by CNC Routing and by CO2 Laser at Different Angles as Related to the Wood Grain

The evaluation of surface quality is an important criterion to understand the effect of the cutting angle in relation to the grain and of the processing tool on wood. This paper examines, in a comparison, the surface quality of maple cut through by CNC and CO2 laser, for different angles with regard to the wood grain: 0°, 15°, 30°, 45°, 60°, 75°, and 90° and at different feed speeds of the CNC router: 2; 2.5; 3; 3.5 and 4 m/min. The direction of processing as related to the grain was a more significant factor in comparison with the feed speed when CNC was used, with best options for 0°, 90° and 75° and worst for 15°, where fuzzy grain was predominant, followed in order by 30°, 45°, and 60°, where pull-out material prevailed. The laser smoothed the core roughness, Rk, with no significant differences as related to the wood grain direction and enhanced an anatomical waviness earlywood-latewood, with the earlywood processed deeper. As the cutting advanced from along to across the grain, the laser uncovered more wood anatomical details and with less destruction. No significant differences in Rk between CNC cutting and laser processing were found for angles: 0°, 60°, and 75°, but surfaces processed at 15°, 30°, and 45° were significantly rougher in the case of CNC cutting. Comparative FTIR investigation of surfaces cut by laser and CNC (at 0° and 90°) clearly revealed temperature-induced chemical changes, such as hemicelluloses degradation, possibly demethylation and advanced condensation in the structure of lignin, in the case of laser processing.

Linear woodcutting of European beech: experiments and computations

Hardwood species are becoming increasingly important with the growing need for a diversity of forests that have recently been facing global temperature changes or conifer pests. This further leads to the growth of its potential as a building material that may originate from sustainable production. As hardwoods need to be properly processed, the article deals with the disintegration of European beech. The influence of wood grain direction, uncut chip thickness and cutting speed on the cutting force magnitudes was experimentally investigated using the device with a rotating arm of approximately 4 m in diameter. Then, the disintegration process was modelled using the finite element method in Abaqus/Explicit. The developed material model consisting of orthotropic elasticity and plasticity with rate-independent and rate-dependent tensile–compressive failure asymmetry was implemented through the user subroutine, while the crack initiation and propagation were realized using the element deletion technique. The computationally predicted average values of cutting forces and chip shapes were, except for a few tests, in good agreement with the experiments. It means that the model may be used for further investigation, such as the influence of tool wear.

Mode I fracture of beech-adhesive bondline at three different temperatures

ABSTRACT Single edge-notched three-point bending tests (SEN-TPB) for mode I were utilized to experimentally evaluate fracture properties of adhesive bondlines in European beech (Fagus Sylvatica L.). The bondline was examined at two anatomical planes with TR and RT orientation and at control and two elevated temperatures (70°C and 140°C). Among epoxy (EPI), melamine-urea formaldehyde (MUF), and polyurethane (PUR) adhesives, the highest average critical energy G c with 0.80 N/mm and fracture energy G f with 1079.4 N/mm were obtained for EPI in the TR plane and under standard climate conditions (20°C/65% relative humidity), followed by MUF (G c = 0.50 N/mm and G f = 620 N/mm) and PUR (G c = 0.25 N/mm and G f = 290.9 N/mm), respectively. PUR was least effected by elevated temperature, and no significant differences for G c and G f between TR and RT bondline orientations were found for MUF and PUR treated at 20°C/65% relative humidity while comparisons between other factors varied significantly. Treatment of specimens at elevated temperatures resulted in reduced fracture performance regardless of wood grain orientation or the adhesive system.

Colour sorting of red oak, yellow poplar and maple veneers using self-organizing map: comparisons between different camera genres

Colour sorting is a vital process in manufacturing of high-quality wood products. It is however a manual process in a large majority of manufacturing facilities in Malaysia. Automation is an ideal solution; however, costs are prohibitive for small and medium industries (SMI). This project aims to produce a flexible solution that can cater for manufacturers of different scales. Three cameras of different price ranges were used: (i) Hikrobot® MV-CE200-10UC (CE200), (ii) Logitech® C920 HD Pro (C920), and (iii) Sony® RX0 II (RX0 II). After setting up a veneer imaging prototype, human sorted images of American red oak (Quercus rubra), yellow poplar (Liriodendron tulipifera), and maple (Acer spp.) were acquired. After performing image preparations and calibrations, 26 features were extracted from each image. The features were based on the average and standard deviation of the wood basal colour and wood grain colour. Salient features were obtained using Sequential Forward Selection (SFS), which were then used to train a Self-Organizing Map (SOM). The results affirmed that the colour of the basal colour is highly correlated with human sorted colour groups. As expected, CE200 performed the best being of industrial grade. Interestingly, C920 exhibited comparable performance to CE200. RX0 II performed the worst due to its interface software limitations. This proposed system achieved accuracies of 89.0% for red oak, 94.3% for poplar and 96.4% for maple. This research will assist the SMI to develop affordable vision systems for colour sorting.

Extraction of plant parenchyma by computer image processing technology

People are increasingly using different kinds of plant products, such as wood, but there are many kinds of wood and it is difficult to analyze and identify them, so how to use auxiliary equipment to analyze wood and achieve the goal of accurate wood identification without damaging the product itself has become one of the important problems to be solved in the field of wood research. The axial thin-walled tissue has important wood grain information and it is one of the important features for wood identification. In this paper, we studied the microscopic images of broadleaf wood, and obtained the microstructure images of wood cross-section by photographing, and extracted the complete axial thin-walled tissue morphology of wood by using computer image processing technology and other ways about computer vision. Firstly, the axial thin-walled wood images were de-noised to eliminate some noise effects, so as to facilitate the separation of the axial thin-walled wood; then the images were processed by mathematical morphology to successfully extract the axial thin-walled wood and duct morphology from the cross-sectional images of broadleaf wood; finally, the axial thin-walled wood was separated from the duct by calculating the area of the closed area.

Packed bed combustion of binary mixtures of wood particles of different shapes and sizes

• Combustion of binary mixtures of particles of different sizes and shapes. • Experiments compared with numerical model. • Mean particle size and sphericity make model agree well with experiment. • Model must include particle overlap and wood grain orientation. This paper presents the results of experiments and numerical modelling on the quasi-steady overfeed combustion and gasification of binary mixtures of fuel particles of different sizes and shapes in a fixed bed. The particles used comprised six different parallelepipedal shapes cut from wood, which were combined to give various binary mixtures. Physically appropriate definitions of average quantities for a packed bed are the volume surface or Sauter mean diameter and a related average sphericity, and the main objective of the work was to determine whether these could be used to model bed combustion of a particle mixture. Measured gas concentration and temperature profiles in the burning bed are compared with a one-dimensional numerical model, which is shown to give good predictions using these mean quantity definitions. Samples of bed solids taken after the conclusion of each experiment give insight into the variation of particle mass, size and sphericity during combustion, and the averages of these also agreed with model predictions, with the caveat that the model can only calculate the average particle size, and is not able to reproduce the individual burning histories of different sizes of particles. The effects of different orientations of the wood fibres in the particles are evident from the experimental data. The results show the importance of including these effects as well as the reduction in bed specific surface area due to particle overlap in calculations.

Intrinsic Image Decomposition Using Paradigms.

Intrinsic image decomposition is the task of mapping image to albedo and shading. Classical approaches derive methods from spatial models. The modern literature stresses evaluation, by comparing predictions to human judgements ("lighter", "same as", "darker"). The best modern intrinsic image methods train a map from image to albedo using images rendered from computer graphics models and example human judgements. This approach yields practical methods, but obtaining rendered images can be inconvenient. Furthermore, the approach cannot explain how a one could learn to recover intrinsic images without geometric, surface and illumination models, as people and animals appear to do. This paper describes a method that learns intrinsic image decomposition without seeing human annotations, rendered data, or ground truth data. Instead, the method relies on paradigms - spatial models of albedo and of shading. Rather than finding the "best" albedo and shading for an image via optimization, our approach trains a neural network on synthetic images. The synthetic images are constructed by multiplying albedos and shading fields sampled from our models. The network is subject to a novel smoothing procedure that ensures good behavior at short scales on real images. An averaging procedure ensures that reported albedo and shading are largely equivariant - different crops and scalings of an image will report the same albedo and shading at shared points. This averaging procedure controls long scale error. The standard evaluation for an intrinsic image method is a WHDR score. Our method achieves WHDR scores competitive with those of strong recent methods allowed to see training WHDR annotations, rendered data, and ground truth data. Our method produces albedo and shading maps with attractive qualitative properties - for example, albedo fields do not suppress wood grain and represent narrow grooves in surfaces well. Because our method is unsupervised, we can compute estimates of the test/train variance of WHDR scores; these are quite large, and suggest is unsafe to rely small differences in reported WHDR.