WOOD RESEARCH Volume 62, Number 4, 2017
Miroslav Gašparík, Milan Gaff, and Babiak Marian

Tension stress simulations of layered wood using a finite element method

This article investigates the material thickness of the individual layer composition influence on the stresses under tension loading. The SolidWorks application was used for tension stress simulations. This simulated course of tensions was carried out for soft and hard materials as a function of their thicknesses. Hard material was represented by beech wood and soft material by aspen wood. Subsequently, the tensile stress and deformation of various two- and three-layered compositions of these materials were analyzed. Based on our results, the soft material was the weakest link; therefore, the ultimate tensile strength of the entire layered material is directly dependent on it. Hard material can withstand greater tensile stress and deformation without breaking, as soft material does.

WOOD RESEARCH Volume 62, Number 4, 2017
Dong Wang, Li Min Peng, Feng Fu, Bo Qi Song, and Mei Hong Liu

Changes of microscopic structures and sound absorption properties of decayed wood

Utilizing waste decayed wood is an effective method of conservation woodresourceand protection environment.In this paper, the sound absorption property of decayed poplar wood (Populus tomentosa) was investigated by analyzed the changes of microscopic structure, pore characteristics and sound absorption properties. Experimental results indicated that the sound absorption coefficientof decayed poplar woodwas significantly improved compared with the health wood. The components of cell wall were decomposed after decayed resulting in the pit membrane being disappeared, even the cell wall are decomposed and formed new pores. In addition, the pore size and connectivity increased, flow resistivity and sound impedance decreasing for the decayed poplar wood. Those results revealed that propagation path and internal friction between sound wave and cell wall increased, resulting in the acoustic attenuation increasing. The decayed waste woods as a sound absorption material would become possible.

WOOD RESEARCH Volume 62, Number 4, 2017
Ricardo Baettig, Jorge Guajardo, Marina Salas, Jorge Cornejo, and Jaime Tapia

Physical and chemical traits in false heartwood for two populus hybrids

A comparative analysis was performed to determine the density, moisture content, shrinkage, pH, and concentration of potassium and calcium in samples of false heartwood and sapwood from two commercial poplar hybrids. The results showed that the calcium concentration is on average three times higher in false heartwood than in sapwood. In turn, the potassium concentration is on average five times higher in false heartwood than in sapwood. The pH increased from slightly acidic in sapwood to slightly basic in false heartwood. The moisture content is markedly higher in false heartwood than in sapwood. However, density and shrinkage do not differ between the two types of wood. A chemometric model analysis was used to differentiate between the two types of wood by using near infrared reflectance spectroscopy (NIRS) with multivariate analysis. The NIRS-implemented method demonstrated efficiency to discriminate between both types of wood.

WOOD RESEARCH Volume 62, Number 4, 2017
Agnieszka Jankowska, Magdalena Reder, and Tomasz Gołofit

Comparative study of wood color stability using accelerated weathering process and infrared spectroscopy

The objective of this study was to investigate effects of artificial weathering on color stability of six tropical wood species: Apuleia leiocarpa (Vog.) Macbride, Bagassa guianensis Aubl., Dipteryx odorata (Aubl.) Wild., Hymenea courbaril/Linn., Manilkara bidentata A. Chev., Tabebuia sp. Chemical composition of weathered wood was also studied by FT-IR spectra. With the progressive artificial weathering color of wood changed gradually. Hymenea courbaril Linn. wood occurred the greatest range of the total color change. The largest changes in intensity of the wood color took place at the beginning of artificial weathering process. FT-IR analysis indicated the occurrence of lignin and hemicellulose oxidative changes resulting in formation of carbonyl and carboxyl compounds during weathering. Oxidation products are the main cause of wood surface discoloration. Additionally, changes suggesting depolymerisation of cellulose were identified as well.

WOOD RESEARCH Volume 62, Number 4, 2017
Yuanyuan Miao, Lili Qin, Fengliang Sun, Lingjing Zhu, Xinwei He, and Zhenbo Liu

Influence of the main components content of Picea jezoensis on acoustic vibration properties

The main chemical composition content of Picea jezoensis (holocellulose, lignin, and extractive content) was measured using the traditional chemical experiment method, and the vibrational parameters including of dynamic elastic modulus E, specific dynamic elastic modulus E/ρ, acoustic impedance Z(ω) and sound radiation coefficient R, of the spruce samples were measured using the multi-channel fast Fourier transform analyzer. The relationship between the different components and wood acoustic vibration properties were analyzed by simple linear regression analysis and bivariate regression models. The results showed that the holocellulose content significantly affected on the acoustic properties of the wood. The vibrational properties first increase and then decrease with the increase in holocellulose content. The best vibration properties is achieved when the holocellulose content is 62% to 65%. Lower lignin content and benzyl alcohol extractive content are beneficial in improving the acoustic properties of wood.

WOOD RESEARCH Volume 62, Number 4, 2017
Anton Osvald and Milan Gaff

Effect of thermal modification on flameless combustion of spruce wood

The paper deals with the effect of heat treatment of spruce wood (Picea abies (L) Karst.) at the temperatures of 160°C, 180°C and 210°C – on the change of properties that characterize its relation to fire and burning,in particular in the phase called flameless combustion. A test method, which is sufficiently sensitive to monitor these changes, has been used for the evaluation of these changes. The results show that thermally modified spruce wood has positive assessment even in this regard.

WOOD RESEARCH Volume 62, Number 4, 2017
Wen-Gang Hu and Hui-Yuan Guan

Experimental and numerical study on optimization design of stretcher positions

In this study, the withdrawal strength of T-shaped joint was investigated through using Finite Element Method (FEM) and Analytic Method (AM). Firstly, the mechanical properties of wood were measured by conducting the experiment. In addition, the influence of friction coefficient between wood interfaces was studied with various size of contact area, direction of grain and pressure. Then, a mathematical model of oval mortise and tenon joint withdrawal strength was established based on linear elastic mechanics. Subsequently, the withdrawal strength of T-shaped joint was analyzed on the basis of numerical method with Finite Element Method (FEM) software. Finally, with the application of the experimental method, comparison and analysis were made between numerical method and analytic method. The results demonstrated that the consistency level between the numerical method and experiment was 83 %, which is more accurate than that between analytic method and experiment 80 %. As a results, the mathematical model was applicable to calculate the withdrawal strength of mortise and tenon joint which can also meet the engineering requirements of wood construction and wooden products structure design. In addition, the FEM applied in the study was more precise than analytic method while the latter was comparatively simple and convenient. These two methods were capable of evaluating the withdrawal strength of mortise and tenon joint, which can also be applied to structure design and optimization of wood construction and wooden products in order to make the design more scientific and reasonable.

WOOD RESEARCH Volume 62, Number 4, 2017
Juraj Gigac, Monika Stankovská, and Mária Fišerová

Comparison of capillary flow porometry and mercury intrusion porosimetry in determination pore size distribution of papers

Capillary flow porometry and mercury intrusion porosimetry achieved a good agreement in determining the pore size distribution in papers for the top layers of corrugated board. Differences in the papers composition as well as structure can be easily detected by changes in the measured parameters, thus allowing a better understanding their behaviour at processing and use. Water absorption is mainly dependent on the diameter of the large pore and to a lesser extent from the diameter of medium pore, surface free energy of paper and the swelling ability of recycled and bleached pulp fibres.

WOOD RESEARCH Volume 62, Number 4, 2017
Xu Peng

Fiber in-situ synthesis of calcium silicate for usage in fine paper

This paper researches fiber in-situ synthesis of calcium silicate that is made from sodium silicate solution extracted from fly ash, lime milk and fiber and its usage in fine paper. The in-situ synthesis technique was used to prepare man-made calcium silicate loaded in paper. The paper is in line with the copy paper standards. The experiments determined the optimum conditions for papermaking as follows, the pre-processing time of fiber immersed in the silicon solution 6h, pulp freeness 42°SR, the SiO2 concentration of the silicon solution 65.5g/L, the effective calcium concentration milk of lime 175g/L, stirring speed 550r/min, the reaction temperature 95°C, the reaction time 90min. Under these conditions, the filler retention rate in fine paper can reach more than 80%. A scanning electron Microscope-Spectroscopy (SEM-EDX), X-ray diffraction (XRD), infrared spectroscopy (FT-IR) was used to analyze paper products and structure. The results showed that the calcium silicate generated within the cell lumen, cell wall, and other open spaces of the fibers, and good bonding was demonstrated between the filler and fibers.

WOOD RESEARCH Volume 62, Number 4, 2017
Vladimir Fedyukov, Ekaterina Saldaeva, and Maria Chernova

Different ways of elastic modulus comparative study to predict resonant properties of standing spruce wood

Resonant method of determining modulus of elasticity and shift and decrement of fluctuations’ operates in Russia to determine elastic-viscous properties of wood (GOST 16483.31-197474). The method is destroying and demanding much time and expenses for manufacturing pre-production models in the form of rectangular bar sized 20×20×300 mm, which requires tree cutting down, severing, sawing, etc.; as a consequence, it has not found wide implementation in the practice of research and, especially, selection of qualitative material for musical instruments manufacturing. The work objective is to conduct basic research on revealing a more effective and precise non-destructive method for identifying Young’s dynamic modulus of elasticity as a basic criterion of standing spruce-tree resonant wood quality with the aim of its selection at an early age and creation of perspective object for woodworking with reference to musical instruments manufacture.

WOOD RESEARCH Volume 62, Number 4, 2017
Mehmet Akgül, Birol Uner, Osman Çamlibel, and Ümit Ayata

Manufacture of medium density fiberboard (MDF) panels from agribased lignocellulosic biomass

Lignocellulosics fibers and commercially-manufactured-chip (Pinus sylvestris L., Fagus orientalis and Quercus robur L.) with 11% moisture conten twere used for the experiment. The mixingratios of lignocellulosics fibers was 20% which is from okra and tobaccos talks, hazelnut and walnuts hell, and pinecone for each mixture in preformed panel and commercially-manufactured-chip was 100 % for the control sample. A commercial ureaformaldehyde (UF) adhesive was used as a binder. The physical and mechanical properties such as density, thickness swelling (TS), bending strength (BS), modulus elasticity (MOE), internalbond (IB), screw holding ability (SHA) perpendicular to the plane of panel, Janka hardness perpendicular to the plane of panel properties of MDF were measured.The results indicated that all the panels met the general purpose-use requirements of TS-EN. Thus, our results suggest that biomass from different sources can be an alternative raw material for MDF manufacturing process.

WOOD RESEARCH Volume 62, Number 4, 2017
Lijie Qu, Jiali Zhang, Zhenyu Wang, Zhengbin He, and Songlin Yi

Effects of ultrasonic pretreatment on the drying characteristics of Eucalyptus grandis × Eucalyptus urophylla

In this paper, wood pretreatments were carried out at an ultrasound intensity of 300 W and a frequency of 40 kHz for 60 min, and the ensuing drying process used a temperature of 60 °C. The study analyzed the pretreated wood before and after ultrasonic pretreatment via drying dynamics, electron microscope scanning, and Fourier transform infrared spectroscopy. The results showed that ultrasonic pretreatment successfully improved the effective water diffusivity, decrease the drying time, reduce the amount of extractives on the inner wood pores, and create microchannels in the wood, resulting in improved heat and mass transfer rates. These results indicate that ultrasonic pretreatment is an effective method for the drying of eucalyptus.

WOOD RESEARCH Volume 62, Number 4, 2017
Inácio Lhate, Luís Cristóvão, and Mats Ekevad

Machining properties of lesser used wood species from Mozambique

The present study was aiming at measuring cutting forces for wood of lesser used species from Mozambique such as Acacia nigrescens Oliv (namuno), Pericopsis angolensis Meeweven (muanga), Pseudolachnostylis maprounaefolia Pax (ntholo) and Sterculia appendiculata K. Schum (metil). Another aim was to use an expeditious method to compare performance of the species when cut. A machinability index calculated using Digraph and Matrix Methods was used for ranking the performance of the species when cut. Two different cutting tools 20o and 30o rake angle were used. Main cutting force in 90°-90° and 90°-0°cutting directions were measured by piezoelectric gauge. The results of the experiments showed that cutting forces followed normal trends to increase with density and decrease with increasing rake angle. The ratio between wood density and cutting forces in cutting directions 90°-90° and 90°-0° were 7 s2m-4 and 17.3 s2m-4, respectively. The most difficult species to be machined was Namuno, whereas the easiest species to be machined was Metil.

WOOD RESEARCH Volume 62, Number 4, 2017
Yuzhi Xu, Baojin Wang, and Yi Shen

Study on laser cutting technology of bamboo

The research advances of laser cutting technology were first stated. Then to study the performance of bamboo laser cutting and obtain the optimum technological parameters, we used a laser cutting machine with 60 W power laser tube and observed the magnified kerf shape. We found laser cutting perpendicular to the fiber direction was more difficult than other cutting directions under the same conditions. The notch depth was the deepest by parallel cutting and the notch width was the widest by oblique cutting. When the thickness of laser-cut bamboos was 3 mm, we obtained moderate kerf width, thinner carburization zone and better kerf quality under laser nozzle height 20 mm, cutting speed 30 m.min-1 and laser output power 48 W, which were the optimum technological parameters of bamboo laser cutting.

WOOD RESEARCH Volume 62, Number 4, 2017
Martina Merková and Josef Drábek

Investment evaluation and business performance of manufacture companies in Slovakia

The paper is focused on area of investment measurement and management in manufacturing enterprises in Slovakia and especially analyses wood processing industry. The aim of this study was to investigate using of certain methods and groups of indicators in investment effectiveness valuation and their possible impact in better business performance. Discounted cash flow valuation is one of several ways of approaching valuation, however, it is a foundation of all other valuation approaches, so we are mainly interested in indicators such as Net Present Value or Internal Rate of Return. We used in the research two-dimensional inductive statistics between categorical variables, the dependence we examined with contingency and we also applied analysis of variance. Our research statistically confirmed that better business performance is significantly dependent on use of certain investment effectiveness valuation methods.