Grade Wood Research Articles

Optimization of kraft pulping process for Sesbania aculeata (dhaincha) stems using RSM

Abstract The shortage of superior grade wood fibers is a prime problem faced by Indian pulp and paper industries. As a result, the pulp and paper industry find it difficult to withstand the competition in the market, which had grown extremely competitive. In order to increase the utilization of non-wood fibers resources in the production of high quality eco-friendly papers, dhaincha, a non-wood fiber resource has potential industrial application. In this research, pulp and paper were developed from Sesbania aculeata stem using kraft pulping followed by bleaching. Optimization of conditions for pulping was carried out by Response Surface Methodology. The relationship between three variables and three responses were studied using Box–Behnken experimental design. The developed pulp was evaluated for kappa number, brightness index, viscosity, FTIR and TGA. Then paper was developed by using optimized pulp and evaluated for physical properties. The statistical analysis (ANOVA) was carried out in order to establish the relationship between the concentration of NaOH, Na2S, treatment time and temperature with kappa number, brightness index and viscosity. The physical properties of pulp and developed handmade paper highlights the sustainable use of dhaincha plant in pulp and paper industry.

An Efficient and Accurate Surface Defect Detection Method for Wood Based on Improved YOLOv8

Accurate detection of wood surface defects plays a pivotal role in enhancing wood grade sorting precision, maintaining high standards in wood processing quality, and safeguarding forest resources. This paper introduces an efficient and precise approach to detecting wood surface defects, building upon enhancements to the YOLOv8 model, which demonstrates significant performance enhancements in handling multi-scale and small-target defects commonly found in wood. The proposed method incorporates the dilation-wise residual (DWR) module in the trunk and the deformable large kernel attention (DLKA) module in the neck of the YOLOv8 architecture to enhance the network’s capability in extracting and fusing multi-scale defective features. To further improve the detection accuracy of small-target defects, the model replaces all the detector heads of YOLOv8 with dynamic heads and adds an additional small-target dynamic detector head in the shallower layers. Additionally, to facilitate faster and more-efficient regression, the original complete intersection over union (CIoU) loss function of YOLOv8 is replaced with the IoU with minimum points distance (MPDIoU) loss function. Experimental results indicate that compared with the YOLOv8n baseline model, the proposed method improves the mean average precision (mAP) by 5.5%, with enhanced detection accuracy across all seven defect types tested. These findings suggest that the proposed model exhibits a superior ability to detect wood surface defects accurately.

Probing the complexity of wood with computer vision: from pixels to properties.

We use data produced by industrial wood grading machines to train a machine learning model for predicting strength-related properties of wood lamellae from colour images of their surfaces. The focus was on samples of Norway spruce (Picea abies) wood, which display visible fibre pattern formations on their surfaces. We used a pre-trained machine learning model based on the residual network ResNet50 that we trained with over 15 000 high-definition images labelled with the indicating properties measured by the grading machine. With the help of augmentation techniques, we were able to achieve a coefficient of determination (R2) value of just over 0.9. Considering the ever-increasing demand for construction-grade wood, we argue that computer vision should be considered a viable option for the automatic sorting and grading of wood lamellae in the future.

Assessment on Strength and Stiffness Properties of Aged Structural Timber

Despite the growing popularity of wood and wood-based products in the construction industry, there has been insufficient focus on assessing the condition, preservation, and potential reuse of existing timber. While numerous standards evaluate the quality of freshly sawn timber, there is currently no standardized system for assessing the strength properties of aged and reused timber. The lack of these guidelines is also one of the reasons the results obtained in numerous research are often fluctuating, and we cannot draw clear conclusions. The matter is further complicated by the lack of data on old in-situ wood and its exploitation, which would help to evaluate its condition. Consequently, there is a real practical need to assess the condition of old timber to avoid unnecessary demolition and the loss of valuable and structurally sound building material. What sets this study apart from others is that, in addition to destructive testing, the 4-point non-destructive (ND) bending tests were conducted on all four faces of test specimens. This provided an opportunity to assess the wood visually and then find connections to associate external characteristics with real properties. This methodology aimed to determine whether it is feasible to visually assess the most practical way to use wooden elements in construction. If this question arises, which face of the beam would be better suited for the tension side and which for the compression side? The old timber used in testing originated from an old library building located on Vaksali Street, Tartu, Estonia and is estimated to be about 120 years old. This paper investigates and compares the collected data with a Nordic standard for grading fresh-sawn timber and two established Italian standards for visually assessing aged timber. This comparison contributes to developing a standardized framework for future visual assessments. ND and destructive four-point bending tests were performed to validate and find appropriate visual characteristics to determine the strength and stiffness of the timber elements. The primary goals of this study were first to compare the results obtained from existing ND methods with actual results and secondly to provide guidelines for better visual grading of wood in the future, based on Nordic Standard INSTA 142 (2010) and Italian standards UNI 11119 (2004) and UNI 11035 (2010) Contrary to previous research conclusions, the visual assessment results yielded unexpected outcomes. The results show that the grading standards significantly underestimated the real strength of the wood, and even more, none of the visual assessments overestimated the real strength of the specimens. Therefore, based on prior research and the findings derived from this study, there is evident a substantial potential for extensive development and optimization within this field.

Economic losses caused by butt rot in Norway spruce trees in Norway

ABSTRACT Butt rot is a main defect in Norway spruce (Picea abies (L.) Karst.) trees and causes large economic losses for forest owners. However, little empirical research has been done on the effects of butt rot on harvested roundwood and the magnitude of the resulting economic losses. The main objective of this study was to characterize the direct economic losses caused by butt rot in Norway spruce trees for Norwegian forest owners. We used data obtained from seven cut-to-length harvesters, comprising ∼400,000 trees (∼140,000 m3) with corresponding stem profiles and wood grade information. We quantified the economic losses due to butt rot using bucking simulations, for which in a first case, defects caused by butt rot were included, and in a second case, all trees were assumed to be free of butt rot. 16% of trees were affected by butt rot, whereby butt rot tended to occur in larger trees. When butt rot was present in a tree, the saw log volume was reduced by 48%. Proportions of roundwood volume affected by butt rot varied considerably across harvested stands. Our results suggest that butt rot causes economic losses upwards of 7% of wood revenues, corresponding to € 18.5 million annually in Norway.

Optimization of Glulam Beams with Spatially Dependent Polymorphic Uncertainty Modeling of Structural Inhomogeneity in Virtual Boards

AbstractSeveral uncertainties are induced by the natural growth of wood. The properties of timber components are affected by naturally varying material characteristics. In addition, structural inhomogeneity has to be accounted for solid wood components. Structural inhomogeneity is dependent on, e.g., natural fissures, inclusions, and especially branches that pervade wooden boards. Those pervasions result in timber boards containing multiple scattered knots.Polymorphic uncertainty models are required to account for diverse uncertainty characteristics. Natural variability and lack of knowledge are persistent for the uncertainty modeling of natural materials, such as wood. To incorporate those aleatoric and epistemic uncertainty characteristics, uncertainty analyses are performed based on combined fuzzy and stochastic models.In this contribution, fuzzy probability based random fields are proposed as polymorphic uncertainty approach, with respect to spatial dependencies of the uncertain variables. Methods for the simulation of timber boards are introduced, where knots are established referred to the specific position of the tree trunk axis and spread over the components.Glulam beams, containing multiple slats of wooden boards, are investigated for bending load cases as numerical example. The tensile zone is simulated with knots in the timber boards. The basic deterministic solution is performed with a local‐orthotropic material formulation, with respect to the grain directions of the wood matrix and knots. Therefore, the knots are discretized separately in the FE mesh. Distinct material properties and grain directions are assigned to the discrete knots and to the surrounding wood matrix, while the grain directions are dependent on the tree trunk axis.Both, stochastic and fuzzy models are used in field formulations for the spatially dependent polymorphic uncertainties. The knottiness of timber boards – specified by parameters of knot geometry, location and incidence – is dependent on the wood grade. In this contribution, methods for decision making of glulam beam designs are suggested. For this purpose, several design variables are examined. First, the knottiness or wood grade, where a higher grade results in reduced structural inhomogeneity, and second, the thickness of the slats in the glulam beam are considered. Both aspects influence the reliability and robustness of the component, but affect the costs. The maximum endurance of the glulam beam under bending is desired. Therefore, an optimization of the glulam beam design is performed, with respect to the multiple conflicting objectives.

Characterization and Prediction of Mechanical and Chemical Properties of Luanta Fir Wood with Vacuum Hydrothermal Treatment.

Since the chemical composition of wood is closely related to its mechanical properties, chemical analysis techniques such as near-infrared (NIR) spectroscopy provide a reasonable non-destructive method for predicting wood strength. In this study, we used NIR spectra with principal component analysis (PCA) to reveal that vacuum hydrothermal (VH) treatment causes degradation of hemicellulose as well as the amorphous region of cellulose, resulting in lower hydroxyl and acetyl group content. These processes increase the crystallinity of the luanta fir wood (Cunninghamia konishii Hayata), which, in turn, effectively increases its compressive strength (σc,max), hardness, and modulus of elasticity (MOE). The PCA results also revealed that the primary factors affecting these properties are the hemicellulose content, hydroxyl groups in the cellulose amorphous region, the wood moisture content, and the relative lignin content. Moreover, the ratios of performance deviation (RPDs) for the σc,max, shear strength (σs,max), hardness, and modulus of rupture (MOR) models were 1.49, 1.24, 1.13, and 2.39, indicating that these models can be used for wood grading (1.0 < RPD < 2.5). Accordingly, NIR can serve as a useful tool for predicting the mechanical properties of VH-treated wood.

Teakwood Grade Identification with GLCM and K-NN with Adaboost Optimization

Teak is one type of tree that has many functions and uses. Teak wood has a very high quality to be used as raw material for the manufacture of home furniture such as tables, chairs, cabinets, and others. But middle testers (Perhutani staff) who test the quality of wood grade have limitations if the classification uses the five senses of sight and also there are still many furniture entrepreneurs who are often mistaken about teak wood quality assessment. This resulted in a lack of quality grade teak wood used as raw material for making home appliances or for furniture and trade needs under the Perhutani Corporation, especially the Cepu Kph. The teak wood image data is then acquired through preprocessing data ready to be processed. By using GLCM as an image feature extraction both training data and testing data. After the image characteristics are obtained, the image is classified by the K-Nearest Neighbor method with adaboost optimization. The final result is obtained in the form of wood grade quality classification namely grade A, B, C and D according to the class

Tree species-based differences vs. decay performance and mechanical properties following chemical and thermal treatments

Many thermal and chemical treatments are known to inhibit wood decay despite the wood grade processed, but their impact, e.g., chemicals’ leaching and decay resistance, may not be similar. The aim of this study was to test whether some model treatments retain their performance in different wood species. Additionally, the effects of thermal modification and linseed oil-based varnish treatments as means to mitigate water-soluble chemicals leaching were assessed. The mass loss caused by Trametes versicolor was measured after a 12-week exposure to analyze whether the different treatment approaches prevented the fungal decay after a standard leaching test. The mechanical properties before and after exposure were tested independently to determine whether the mechanical properties of different wood species were affected by the tested treatments and wood decay. The responses of the tested wood species were found to vary by treatments, but thermal and chemical fixation methods for water-soluble tannins were beneficial in all cases considering the mass loss and the degradation of modulus of rupture and modulus of elasticity of treated wood. Varnish was overall the most effective treatment against decay, but the results emphasize the need for testing potential preservation methods and chemicals on several species.

Phytochemical Screening and Characterization of Agarwood (Aquilaria malaccensis) Chips Wood Grade as Incense Headspace Volatile Compounds by GC-MS.Ms.Q.TOF, SPME

AbstractAgarwood (Aquilaria malaccensis) is an Asian tree traditionally used for many medicinal purposes, its oil constituents and inhaled vapor has sedative, antidepressant and anxiolytic activities. Gas Chromatography and quadruple time of flight –mass spectrometry (GC.MS.MS/Q.TOF) in the MS-MS mode has been used in screening and identification of multiple compounds of three different grade of agarwood chipwood, using DB-1 column which led to identification of 96 compounds while the majority of the compounds about 500 compounds remain UN knowing to the difficulties of confirming or rejecting them . The generated results were so complicated and very difficult to be interpreted for the presence of isomers with similar matched spectrums; the absence of official standard references for these compounds make the judgment of confirming the identified compounds more complicated and very hard to absolute identification to be assessed. The compounds were extracted by applying a solvent less technique; trapping incense and volatile headspace. The total Ion chromatogram detected compounds are distributed among different array over the chemical families among monoterpenes, sesquiterpenes, hydrocarbons, oxygenated monoterpenes, sesquiterpenes, norterpenoids and diterpenoids ,short chain glycols, carboxylic acids and others. The flowing compounds are the major terpene, sesquiterpene and oxygenated sesquiterpenoid found in all grades of A. malaccensis chipswood under investigation, furthermore; the study represented that the characterization of compounds from agarwood chips wood is highly possible through incense volatile sample.

Grading materials for stringed instruments soundboards: An approach considering the orthotropic elastic and damping properties

Choosing or designing materials for stringed instruments soundboards is an issue that garnered the attention of luthiers and scientists for a long time, leading to the definition of descriptors that assess the ability of materials to efficiently radiate sound. This approach often considers the material properties along one direction, neglecting their anisotropic nature or taking it into account with some approximations. The authors propose an alternative approach that considers material anisotropy, soundboard geometry and their effect on the vibration and damping. Two orthotropic descriptors are derived, which include the elastic and damping properties along different directions. These descriptors are used to compare different materials, as well as to grade wood with non destructive tests and to analyse the effect of wood grain orientation. The use of these descriptors can provide useful information to both scientists and luthiers regarding materials choice and composite materials design for the construction of stringed musical instruments.

Моделювання якісної структури стовбурів сосни звичайної за допомогою випадкового процесу

The study highlights methodological aspects of predicting stem volume of merchantable Scots pine trees by grade categories using distribution models of different quality zones along stems. The study is based on empirical data collected in the mature stand during clear-cut harvesting. In total it includes measurements of 245 tree stems for which sequence and lengths of different quality categories were evaluated. A semi-Markov model was applied to characterize a random process of height-relevant co-occurrence and length of merchantable wood, firewood, and residues. The model was determined by the following parameters: 1) input occurrence probabilities of specific grade category in the butt section of tree stems (initial state of the system); 2) distribution matrix of grade categories by lengths; 3) matrix with transition probabilities between grade classes on different stem heights. In this study, we considered the process in which the initial state of the system was associated with merchantable wood which was true for most pine stems. We used beta-function to model lengths of grade categories which parameters were fitted using relative stems height. We also used empirical data to calculate probabilities of transition between merchantable wood, firewood, and residuals along pine stems. The analysis indicates that the length distribution of merchantable wood and firewood depends on the relative height where the grade is observed, and total tree stem height. Thus, we identified four zones where the function of beta-distribution was used to model lengths of each grade category with customized parameters depending on the relative height of their location on tree stem. As a result, we developed a methodology that can be used to simulate datasets with tree stem characteristics, and further to predict the distribution of volume by grade categories depending on their diameters, heights, and merchantability. It is worth noting that our study is focused merely on merchantable pine stems, and one should expect another relationship for stems of different tree species as well as for merchantable pulpwood trees. Given the new standard for merchantable wood classification adopted in Ukraine, the developed methodology is suitable for updating existing tables of distribution of tree stem volumes by wood grade categories.

Correlation between Anatomical Grading and Acoustic–Elastic Properties of Resonant Spruce Wood Used for Musical Instruments

This paper deals with the acoustic and elastic properties of resonant wood, classified into four classes, according to the classification of wood quality by the manufacturers of musical instruments. Traditionally, the quality grades of resonant wood are determined on the basis of the visual inspections of the macroscopic characteristics of the wood (annual ring width, regularity, proportion of early and late wood, absence of defects, etc.). Therefore, in this research, we studied whether there are correlations between the acoustic and elastic properties and the anatomical characteristics of wood used for the construction of violins. The results regarding the identification of the anatomical properties of resonant spruce, the wood color, and the acoustic/elastic properties, determined by ultrasonic measurements, were statistically analyzed to highlight the connection between the determined properties. From the statistical analysis, it can be seen that the only variables with the power to separate the quality classes are (in descending order of importance) the speed of sound propagation in the radial direction, Poisson’s ratio in the longitudinal–radial direction, and the speed of propagation of sounds in the longitudinal direction.

Semi-empirical estimation of log taper using stem profile equations

In January 2019 the forest industry in Ukraine adopted European standards for measuring and grading of round wood based on mid-point diameters, which caused major discrepancies from traditionally used estimates of timber volume using top diameters. To compare methods of merchantable wood volume estimation, we investigated the stem form inside bark for two dominant tree species in Ukraine, i.e. Scots pine (Pinus sylvestris L.) and common oak (Quercus robur L.). We used tree stem measurements to fit stem profile equations, whereas simulation was applied to derive log taper. We found that Newnham's (1992) variable-exponent taper equation performed well for predicting stem taper for both tree species. Then, we simulated the structure of harvested wood, so that it replicated annual distribution of logs by their length and diameters. As a result, the average log taper was estimated at 0.836 ÷ 0.855 cm·m&lt;sup&gt;–1&lt;/sup&gt; and 1.180 ÷ 0.121 cm·m&lt;sup&gt;–1&lt;/sup&gt; for pine and oak, respectively. The study also indicated that log taper varied along stems. The higher rates of diameter decrease were found for butt logs, for which the taper was 2.5–3.5 times higher than its average for the whole stem. The results of our study ensure the stacked round wood volume conversion between estimates obtained using top and mid-point diameters.

Comparison of community structures of Phoebe chekiangensis pure forests and heterogeneous mixed forests

Taking the 13 years pure artificial forest Phoebe chekiangensis and heterogeneous mixed forests in Tiantong mountain, Zhejiang Province as the research object, the characteristics of stand development, tree competition differentiation, tree height/breast diameter ratio and dominant wood growth were compared and analyzed from the perspective of ecology. The results show that compared with pure forests, the growth advantages of heterogeneous mixed-age forests were significant. Average breast diameter growth of stand increased 1.8%; the growth of single plant wood accumulation increased 7.4%. The relationship between tree height and diameter showed that the high growth of Phoebe chekiangensis individuals in the heterogeneous mixed forest was significantly promoted, and the high growth of the tree was 8.4% higher than that of pure forest. 1–5 grade wood scale sizes Phoebe chekiangensis in heterogeneous mixed forests and pure forests are ranked grade 3 (43.7%) &gt; grade 2 (26.5%) &gt; grade 4 (15.7%) &gt; grade 1 (12.9%) &gt; grade 5 (1.2%); grade 3 (34.7%) &gt; level 2 (25.6%) &gt; level 4 (20.0%) &gt; level 1 (18.2%) &gt; level 5 (1.2%); the straight-diameter structure shows a normal distribution, and the degree of differentiation of pure forests is greater than that of heterogeneous forests. The dominant trees of Phoebe chekiangensis pure forest and heterogeneous forest accounted for 18.2% and 12.9% of the total number of plants respectively, providing a reserve of 51.1% and 35.4% respectively, reflecting the contribution of dominant trees caused by the self-thinning effect.

Elastic moduli of butt-end logs and the variable knots distribution in Scots pine from Western Poland

In studies on Polish pine wood, the parameters determining its usefulness for processing are highly variable. In contrast, international studies on the optimum utilization of coniferous sawn wood describes its visual features as those indicating the distribution of defects and their impact on the selected mechanical and physical properties of sawn wood. Knottiness is one of the qualitative properties of sawn wood that is essential for wood grading. The objective of this study was to determine a correlation between variable knots and their soundness on the one hand and their selected strength parameters on the other. One of the basic issues of this work includes structural timber optimization. For Polish sawn wood, these indicators are still relatively new. The study material involved edged butt-end log lumber from a 120-year-old forest stand. The results confirmed a correlation between knots frequency and modulus of elasticity. The correlation was strong, indicating that sound knots play a major role in the process of the strength assessments. The study did not demonstrate a significant share of rotten knots and their effect on strength.

Investigating the Optimal Location of Potential Forest Industry Clusters to Enhance Domestic Timber Utilization in South Korea

South Korea has abundant forest resources capable of supplying the domestic wood demand. Despite the extensive forest resources, there is continued uncertainty about the nature, quantity, and quality of the timber contained in any particular forested area. Additionally, some technical, logistic, and economic challenges act as barriers to the expansion of domestic timber utilization. To overcome these limitations and to enhance the domestic timber utilization in South Korea, this study investigated the optimal location of potential forest industry clusters. The potential forest availability was estimated based on localized allometric equations. The integration of the analytical hierarchy process and GIS modeling, including a supply chain that minimizes transportation costs, allowed the identification of optimal forest industry clusters locations that balanced the economic, environmental, and social dimensions within the forest industry supply chain. The study reveals that the estimated potential forest resources availability presented approximately 1 billion m3, including sawlog (474 million m3) and pulpwood grade (541 million m3). Additionally, 45 percent of the sawlogs and 48 percent of the pup grade wood were produced from the Gangwon and Gyeongsangbuk-do regions. Furthermore, the logistic analysis indicates that ten potential forest industry clusters are best aligned with the optimal socio-economic impacts with minimized timber transportation costs. To identify the optimal size and number of potential forest industry clusters, further studies that consider fixed and variable costs for maintaining the forest industry clusters are required.

ЕКСПЕРИМЕНТАЛЬНІ ДОСЛІДЖЕННЯ СУЦІЛЬНОЇ ДЕРЕВИНИ КОНСТРУКЦІЙНИХ РОЗМІРІВ З ВРАХУВАННЯМ ФАКТОРА ВОЛОГОСТІ

2National University of Water and Environmental Engineering, Rivne Materials, elements and structures made of wood can be operated in environments with different humidity. Humidity of wood directly affects its strength and deformable properties. The works of domestic and foreign authors who studied the effect of moisture on the strength and deformability of wood of different species were analyzed in detail. It turned out that there are very few such works. According to these works, it is difficult to detect the effect of moisty on the basic physical and mechanical properties of wood. And they usually concerned the testing of wood under a soft load regime, which does not fully reflect their real stress-strain state. We have developed a method of experimental studies of various deciduous (birch, alder, ash) and coniferous (larch, pine, spruce) compression along the fibers with a single short-term load under a rigid test mode (by increasing the displacement of the press plate) with different moisture (30%, 21% , 12%). The age of all wood samples was 60 years. Section of prisms 30x30x120mm and grades of wood without defects and damages. The total number of tested samples - 126 pcs. After conducting experimental research and processing the results, complete diagrams of deformation of wood σ-u deciduous (birch, alder, ash) and coniferous (larch, pine, spruce) wood species from the beginning of loading and to the point of ultimate deformation, respectively, at a moisty of 30% , 21%, 12%. For the first time, critical deformations of different wood species at the corresponding maximum stress at different moisty were obtained experimentally. It was found that with a decrease in moisty from 30% to 12%, the strength of wood of all species increases. The critical deformations herewith are reduced.

Eucalyptus globulus finger jointed solid timber and glued laminated timber with superior mechanical properties: Characterisation and application in strained gridshells

This work establishes the main guidelines to produce high-performance Eucalyptus globulus Labill finger jointed solid timber and glued laminated timber laths and analyse their potential for application in multilayer strained gridshells. To this end, a proposal for strength grading of eucalyptus solid timber is firstly provided, combining visual and mechanical criteria. The bending strength of industrially produced eucalyptus finger jointed solid timber ​​and glued laminated timber laths using different wood grades and two adhesives (1C-PUR and MUF) is investigated. The results suggest that strength classes D55 for finger jointed solid timber and GL56 for glued laminated timber could be reached by appropriately graded solid timber and adhesive. Moreover, the superior performance of eucalyptus products over those made of other species in terms of the minimum design radius of curvature, considering rheological aspects, and the stiffness of multilayer curved systems with semi-rigid connections as shown by FEM analysis, is discussed. Finally, eucalyptus products are successfully used in two full-scale strained gridshells, highlighting the promising future for this species here.

Color variance of dry coconut wood and its relationship with the density

The color variance of dry coconut wood and its relationship with the wood density was explored. Coconut trunks with two different ages of 30 and 60 years old were selected for the experiment. Wood color was measured by the CIE L*a*b* or CIELAB color system on both the transverse (longitudinal-tangential plane) and cross (tangential-radial plane) sections. The results showed that all color parameters (L*, a*, b*) tended to decrease with increasing wood density for both sections in which the value on transverse section was slightly higher. At a given density, the color value of the older trunk was lower. All color parameters appeared to be related with density in a linear relationship with relatively low R2 for both ages. The best correlation was observed for the b*-density relationship on cross sectional samples for both trunk ages, showing R2 values of 0.53 to 0.60. This implies that it might be possible to use this color parameter as input for the grading of coconut wood’s density.