WOOD RESEARCH Volume 64, Number 4, 2019
SHAOXIANG CAI, Shouheng Hu, YANJUN LI, Xinzhou Wang, Lican Chen, and Jun Li

Nanomechanical behavior of wood cell walls observed by different indentation loading prerequisites

The variations of nanomechanical behavior of wood cell walls under different peak loads, loading times, and holding times were studied. Samples were separately loaded to preset peak loads of 100, 150, 200, 250 and 300 μN. Changes in the micromechanical properties were tracked in the longitudinal direction to determine change values of the elastic modulus and hardness. Moreover, the creep behavior was also analyzed under different holding times. It was found that the longer the holding time, the larger the creep ratio of all of the samples, and the creep rate decreased slowly with longer loading times. Finally, when the peak load was larger, the displacement rate and strain rate increased, but the strain rate in each test exhibited a tendency to become constant after 10 s.

WOOD RESEARCH Volume 64, Number 4, 2019
Ondřej Schönfelder, Aleš Zeidler, Vlastimil Borůvka, and Lukáš Bílek

Impact of silvicultural measures on the quality of Scots pine wood. Part I. effect of regeneration method

This study deals with the influence of the silvicultural measures on selected mechanical properties of Scots pine (Pinus sylvestris L.) wood in the Czech Republic. Sample trees were selected at two different localities that are characteristic of Scots pine growth, and they represent two different Scots pine regeneration methods, namely the clear-cutting and shelterwood regeneration method. We tested compressive strength and impact bending strength. The density of the wood was also evaluated as a factor influencing strength characteristics. The shelterwood regeneration method shows higher values in most of the investigated characteristics (49.3 MPa for the shelterwood method and 44.6 MPa for the clear-cutting method in the case of compressive strength); however, these differences are not significant for the processing industry. Another positive effect of the shelterwood regeneration method is the even distribution of the properties within the trunk in radial direction in contrast to clear-cutting method.

WOOD RESEARCH Volume 64, Number 4, 2019
Małgorzata Kajda-Szcześniak and Tomasz J. Jaworski

Analysis of the formation and primary minimization of nitrogen oxides during the combustion of nitrogen-rich post-consumer wood waste

The article presents research on mechanism of formation of nitric oxide during combustion of wood derivative wastes in grid furnace boilers including waste incineration plants. Considering their elemental composition (large amount of nitrogen) they require supervision in thermal processes for their treatment. Concentrations of the formed nitric oxides, depending on the parameters of the combustion process and the size of the combusted grains, were subject to evaluation. The source of nitrogen in tested wastes is urea-formaldehyde resin used as a joint. The tests proved that the dominant mechanism is fueling mechanism for formation of nitrogen oxides. It is possible to limit this mechanism with original methods that interfere directly into the combustion process in the chamber (following temperature regime, granulation and humidity of the waste, intensity of mixing waste on the grill, stream of original air in the amount adjusted to the combustion phase in the grill). The article specifies main recommendations for the conduction of thermal transformation of wastes minimizing fuel nitric oxides.

WOOD RESEARCH Volume 64, Number 4, 2019
Thulani Shabangu, Linda Z. Linganiso, Tshwafo E. Motaung, Motloung V. Setumo, and Lehlohonolo F. Koao

Comparison of fibre from maize stalk domains and sugar cane bagasse

The aim of this study is to investigate properties of pulverised cellulosic material from parts of maize stalks and sugar cane bagasse (SCB). Both materials were foremost subjected to a cutting mill before boiling with water. The chemical compositions and mechanical properties of the maize stalk residues and sugar cane bagasse were performed using a TAPPI standard. Optical microscope, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and Ultraviolet-visible spectroscopy (UV-Vis) were used to characterise the materials. Rind displays thinner and longer fibres, which are less unequal and almost quadrangular. In fact, it has a highest crystallinity trailed by nodes and sugar cane bagasse in sequence. Interestingly, thermal stability of SCB is dominating followed by rind and nodes.

WOOD RESEARCH Volume 64, Number 4, 2019
Mariana Neves Ferreira Ribeiro and Cláudio Henrique Soares Del Menezzi

Effect of the temperature and pressure on properties of densified medium density fiberboards

The objective of this work was to evaluate the physical and mechanical properties of thermally compressed MDF (medium density fiberboard). For this purpose, MDF boards were subjected a combination of two temperatures (150°C and 170°C) and two pressures (25% and 50% of the perpendicular compression strength). After the treatment the following properties were assessed: bending strength and stiffness, compressive parallel strength, surface hardness, thickness swelling and water absorption after 2, 24 and 72 hours of immersion in water. It was found that in general, the results did not show any significant improvements regarding physical properties. However, mechanical properties were positively affected by treatments and densified boards had higher values than untreated boards, reaching a fourfold value in the case of the surface hardness. Regarding physical properties, there were no improvements compared to the untreated board for the thickness swelling, despite all treatments have showed lower water absorption. In general, temperature was the most important factor for physical properties and the pressure was the most important factor for mechanical properties.

WOOD RESEARCH Volume 64, Number 4, 2019
Xia Lei, Yuanbo Wu, Hongchang L., Xin Guo, Ruizhi Wen, and Li Hui

Study of the discoloration behaviour of teak wood (Tectona grandis Linn. fil.) caused by simulated sunlight

To investigate the discoloration behaviour of teak (Tectona grandis Linn. fil.) during irradiation, teak veneer specimens were exposed to xenon lamp light simulating sunlight for 80 h and subsequently analysed with a colorimeter. The colour changes were explained by recording Fourier transform infrared (FTIR) and gas chromatography-mass spectrometry (GC-MS) spectra at different exposure times. Forty hours of simulated irradiation marked a key point in the colorimetric analysis. During irradiation of 40 h, the increase in the CIELAB parameters ∆a* and ∆b* originated from the generation of carbonyl derivatives that were determined by FTIR analysis. Besides that, by combining GC-MS and microscopic analyses, the decrease in ∆L* in the first 20 h resulted from extractives migrating from the interior to the surface, and that the subsequent increase in ∆L* mainly arose from volatilization of the extractives. Additionally, the decrease in ∆b* after another 40 h of irradiation was mainly due to decreasing volatile extractive contents. Our conclusion reveals the causes of photo-induced discoloration in teak.

WOOD RESEARCH Volume 64, Number 4, 2019
Andrzej Sioma

Quality control system of wooden flanges based on vision measurement system

The paper presents a design of a robotic product control system made for the wooden flange production line. The system has been designed for installation in automated production lines that allow the production of short product batches with a quick change of the type series of the manufactured products. The purpose of the work was to develop a flexible quality control system that would enable the development and adjustment of the product parameters control procedure to various product type series. The quality control station has been designed with an industrial robot and a set of 2D and 3D vision systems that take measurements of the set of parameters described for wooden flanges used in the production of cable drums. The paper presents the description of the parameters of the product subject to quality control and the premises adopted in the design process of the station. The image analysis method has been presented as developed for selected product parameters, in the scope of measurements on the image, along with the presentation of measurement results.

WOOD RESEARCH Volume 64, Number 4, 2019
Kang-Jae Kim, Ji-Ae Ryu, and Tae-Jin Eom

Characteristics of the heat treated wood packaging materials according to international standards for phytosanitary measures and verifiability of heat treatment

We aimed to develop a control method to assess compliance with International Standards for Phytosanitary Measures No.15 (ISPM 15) heat treatment wood packaging materials by physicochemical properties and chemo-metrical approach. Larix leptolepis (Siebold & Zucc.) (Gordon larch), Pseudotsuga menziesii (Douglas fir) and Picea jezoensis (spruce) as wood samples were used in this study. The ISPM 15 processing of wood did not alter the physico-chemical characteristics. By the ISPM 15 processing of wood, the core moisture content of timber was approximately 6%, regardless of the wood species, whereas that before heat treatment was 10-12%. Among the different parameters of wood, the moisture content can be classified by the PCA according to the ISPM 15 processing, which can be easily changed by mild heat treatment. Furthermore, the changes in chemical properties occurring after the ISPM 15 processing were clearly distinguished by using the ATR-PCA system.

WOOD RESEARCH Volume 64, Number 4, 2019
Radosław Mirski, Dorota Dziurka, and Aleksandra Banaszak

Effects of manufacture conditions on physical and mechanical properties of rape-polymer boards

The paper presents a method of manufacturing boards composed of lignin-cellulose chips and thermoplastic polymers (waste-based particle polymer composites, WPPC) by means of flat pressing. Rape chips, similar in size to wood chips in traditional particleboards, served as filling material, and polyethylene and polypropylene made up the outer layers. The polymers enriched only the external layers, as this allowed for considerable shortening of pressing time. The resulting boards featured satisfactory properties as compared with control, not polymer covered boards. Our study identified a temperature of 220°C and low moisture content of the polymer-containing layers as favorable for production of this type of boards. We also found out that using a sublayer with higher moisture content not only shortened the pressing time, but also improved the board properties evaluated by a bend test.

WOOD RESEARCH Volume 64, Number 4, 2019
Shuang Yan Zhang, Chuan Gui Wang, Xue Qin Fang, and Yuan Yuan Li

Characterization of lignins from the black liguor of Australian eucalyptus kraft of the nail

Lignin samples were separated from the black liquor of Australian eucalyptus kraft pulping by ethanol-acid precipitation or acid precipitation. Elemental analysis, FT-IR, and 1H NMR were conducted to compare their structural characteristics. The thermal behaviors were studied by TGA and heating value was examined with oxygen bomb calorimeter. The obtained C9 expanded formulas for acid-extraction lignin and ethanol-acid-extraction lignin were C9H9.52O2.96 and C9H9.58O3.18, respectively. According to FT-IR and 1H NMR analyses, the two lignins were similar to hardwood lignin of type GS. However, the acid-extraction lignin showed a high proportion of syringyl (S) unit. TG results showed that degradation process of the two lignins was similar, but their degradation temperatures were different. The weight loss rate reached its maximum value of 8.49 wt% / °C and 4.39 wt% / °C for ethanol-acid-extraction lignin and acidextraction lignin, whose temperature of maximum weight loss was 371°C and 356°C respectively. Results of oxygen bomb calorimeter tested showed the incendiary heat of ethanol-acid-extraction lignin was higher than that of acid-extraction lignin.

WOOD RESEARCH Volume 64, Number 4, 2019
ŽIKICA TEKIĆ, LJILJANA KOZARIĆ, MARTINA VOJNIĆ PURČAR, and Snježan Lukić

Load-bearing capacity of metal connector plates depending on location and geometry of the nail

This paper presents results of the experimental determination of the load-bearing capacity of structural timber connections realized by nail metal connector plates as a function of nail location, length and diameter. Three different diameters of the nails have been used, specifically 2.0, 2.5, and 3.1 mm. The length of the metal nails in connectors has been determined after the detailed analysis, and kept at 20 mm during the experimental research. Nails distribution over the connector plate is such that it forms the series of equilateral triangles, so that a side of the triangle equals five times the diameter of the nails used. Preceding the testing, and while using the above listed parameters certain analysis has been done. In order to experimentally determine the load-bearing capacity of the nail metal connectors, the penetration depth, i.e. the length of the nails has been kept constant, while using three different nail diameters. The testing has been done on multiple samples in the accordance with Eurocode 5.

WOOD RESEARCH Volume 64, Number 4, 2019
WAYAN DARMAWAN, Muhammad Azhari, Istie S. Rahayu, Dodi Nandika, Rumanintya L. Putri, and Satoru Nishio Malela

The chips generated during up milling and down milling of pine wood by helical router-bits

Development of new helical edge router bits (helix angle 15°, 30°, 45°, and 60°) with a cutting circle diameter of 8 mm was studied. The purpose of the research work was to investigate chips formation and surface roughness characteristics in milling the pine wood by the straight and helical edge bits. The generated chips were classified in four types by sieving into spiral chip (5 mesh), flow chip (10 mesh), thin chip (30 mesh), and granule chip (< 30 mesh). The experimental results showed that the spiral chip was generated most often (on a weight percentage basis) by the bits during down milling process. More flow and thin chips were produced by the bits during up milling process. Better surface roughness was produced by bits during down milling compared to up milling. When the helix angle of the bits increased the amount of spiral and flow chips were increased and granule chip was reduced. The machined surface was better in roughness (lower Ra values) as the helix angle of the bits increased both in up milling and down milling processes.

WOOD RESEARCH Volume 64, Number 4, 2019
B. Li and Z. Zhang

Laser shock process as new tensioning method for circular saw blade

Laser shock process for circular saw blade was proposed and analyzed in this paper. The high pressure plasma shock wave generated by strong laser beam was applied to many local areas of circular saw blade to generate local plastic deformation. Resistance strain rosette and static strain acquisition instrument were used for measuring the stress field of laser shocked circular saw blade. The natural frequency of circular saw blade after laser shock process was tested by hammer vibration test method. Based on reasonable simplification and hypothesis, laser shock process for circular saw blade was built by finite element method. The stress field obtained by experiment and theoretical calculation shows that investigated process is feasible. The natural frequencies of laser shocked circular saw blade for nodal diameters Nd = 2 and Nd = 3 are increased which means that the dynamic stability of circular saw blade is enhanced after modification.

WOOD RESEARCH Volume 64, Number 4, 2019
Paweł Czarniak, Karol Szymanowski, Jacek Wilkowski, Jarosław Górski, and Fabrice Dagrain

Machinability characterization of solid wood with scratching and drilling techniques

This paper describes the characterization of four wood species (alder, oak, jatoba and obeche) with regards to their machinability, i.e. susceptibility to mechanical processing expressed by different machinability indicators. Three types of tests were performed. Drilling tests were conducted on a computer numerical control (CNC) working center as well as on a conventional vertical drilling machine. Both machines were fully instrumented with transducers to continuously measure the torque and the thrust force while drilling. Scratching tests were performed on an instrumented shaper, allowing continuous measurement of the normal and tangential components of the total force applied on a cutter while cutting. This resulted in correlations between particular machinability indicators that were estimated with usage of different measurement benches. Moreover, machinability indicators obtained in this way were compared to the mechanical properties of the wood species. Especially strong correlations were obtained with density or strength in static bending. Those alternative techniques were to some extent coincidental. Particularly, similar results occurred with assessments on CNC machine indicators (torque and thrust force) and friction coefficients (MIε-drilling) during drilling on a conventional drilling machine or indicator C2. The necessity of some improvements in fitting the geometry of an elementary cutter regards to specific properties of solid wood proved in described below experiments should result in higher reliability and usefulness of testing method.

WOOD RESEARCH Volume 64, Number 4, 2019
Li W. G. and Zhang Z. K.

The effect of micro-pits texture on the coefficient of friction between wood and cemented carbide under different wood moisture content

Friction is an important factor during cutting of wood. Micro-texture has been proven to be an effective measure for the improvement of material friction performance. This paper investigates the effect of the cemented carbide surface micro-pits texture on the performance of wood cutting tools with the purpose to reduce the coefficient of friction on knife/workpiece contact zone. Birch (Betula spp.) and pine (Pinus sylvestris) were selected as the research object, the impacts of wood moisture content and the load used on the friction coefficient of different micropits structures were assessed and compared. We found that at a diameter of the micro-texture of 60 μm, the coefficient of friction can be effectively reduced at different wood moisture contents. The average friction coefficient between cemented carbide and wood surface increased with increasing moisture content below fiber saturation point (FSP). But the increase in free water quantity can lead to a more considerable decrease in the friction coefficient. At a higher working load, the value of the average coefficient of friction between the surfaces increases.

WOOD RESEARCH Volume 64, Number 4, 2019
Meihong Liu, Limin Peng, Zhengqiang Fan, and Dong Wang

Sound insulation and mechanical properties of wood damping composites

The sound insulation performance and mechanical properties of medium density fiberboard (MDF) and rubber multilayer panels were studied. The MDF and rubber materials were compounded under certain conditions of hot pressing, temperature and amount of glue. The weighted sound reduction was 28.0 dB for 6 mm MDF, while it was 37.4 dB for 6 mm wood composite damping material, increased by 25.1%. Compared to the monolayer MDF, the composite panels showed increased sound insulation at the resonant frequency, and the critical frequency moved to a higher frequency. The coincidence valley became shallow, effectively suppressing the anastomosis effect. As the rubber thickness increased, the multilayer composite material exhibited enhanced sound insulation efficiency and mechanical properties, and the damping properties of the composite increased, making the composite resistant to bending deformations caused by incident sound waves.

WOOD RESEARCH Volume 64, Number 4, 2019
Chenqian Pan, Wei Tan, Bifeng Kuang, Yanxiong Fang, Yintao Lin, and Xiaolan Cai

A novel glue remover for pressure sensitive tapes on aged paper

Pressure-sensitive adhesives consisting of polymer (t-butyl acrylate, PtBA) was widely used to repair aging paper. Over time, whiteness, mechanical properties and durability of paper degrade with the aging of adhesive. In this study, novel paper-friendly glue-remover (GR), consisting of organic solvents, was designed for removal of PtBA from aging paper. Dichloromethane and hexane were screened to prepare GR according the swelling degree of aged adhesive. For detail, the component of GR was adjusted to optimize removal effect and minimize the damage of GR on aged paper. Treated with GR consisting of 40% (v/v) dichloromethane/ normal hexane, the removal rate of PtBA was high to 56%. Results of mechanical and chromatism test indicates the GR will not damage the mechanical strength or handwriting on the paper. Moreover, the pH of paper increased from 3.55 to 5.75 after removal of glue, which suggested that GR help remove acid from aging paper.