WOOD RESEARCH Volume 65, Number 2, 2020
VLADIMÍR IHNÁT, HENRICH LÜBKE, Balberčák Jozef, and Kuňa Vladimír

Size reduction downcycling of waste wood. Review

The article includes research related to utilization of waste wood which is primarily size reduced due to its voluminity for next processing for lower value added products for about last twenty years. Procedures and results obtained by different authors were considered in one study. In this review a wood waste downcycling was consider as a process of transformation of large size wood products over their lifetime to the new products, where a size reduction is one of the first operations needed to achieve to. Incineration of each way was excluded from the present review, but second-generation biofuels are considered as potential products for the future. Two points of research selection according to origin and according to products made of waste wood was applied in this review. Comparison shown that the most industrially applicable implementation of treated particles obtained from waste wood is intended to the composite materials production as particleboards, fibreboards, cement-bonded and wood-plastics.

WOOD RESEARCH Volume 65, Number 2, 2020
Sinn Gerhard, Jürgen Maierhofer, Dieter Loidl, Stephan Puchegger, and Stefanie Stanzl-Tschegg

Elastic constants of six wood species measured with the resonant beam technique

The elastic properties of six wood species were determined using the resonant beam technique. By stimulation of transverse vibrations and analyzing the responding oscillations of carefully prepared rectangular beams of wood, simultaneous determination of one Young’s modulus and two shear-moduli on one specimen is possible. Using three different cutting orientations along the principal material directions all three Young’s moduli and three shear moduli can be determined. This paper presents the application of this technique to six wood species: two softwoods, two hardwoods and two tropical woods.

WOOD RESEARCH Volume 65, Number 1, 2020
Candan Kus Sahin and Busra Onay

Alternative wood species for playgrounds wood from fruit trees

A number of orchard woods have been investigated for suitability in the playgrounds, in the view of responders. In this sense, photos were taken of the specially prepared samples as stimuli, and there were three different groups of respondents. It was observed that the participants were effective in terms of age grouping and material preferences. For group A and C, majority of the participants preferred wooden elements for playground material. However, the majority of participants in group B (50.5%) preferred plastic elements, followed by wooden (31.5%), and then metal (18.0%). Moreover, it was seen that the most significant factors for selection of material for a playground should be safety for both Group A (79%), and C (76.5%), whereas it was aesthetic appearance, for group B (71%). Similar results were found for color properties of wood — the majority of participants of all three groups preferred light colored wooden elements in playgrounds. The results for the aesthetic preferences of wood species judged one-by-one and judged together received similar results. The preference scores for fig wood (Figus canica) is significantly higher than for other wood species, while “wood color” and “aesthetic appearance” are reliable positive predictors to aesthetic preferences.

WOOD RESEARCH Volume 65, Number 1, 2020
Anderson Renato Vobornik Wolenski, Rodrigo Guerra Peixoto, Veronika Fedotova, André Luis Christoforo, and Francisco Antonio Rocco Lahr

Short note: Shear strength estimation model for tropical wood species

For safety reasons, wood strength values are calculated based on their characteristic values. Brazilian national standard (NBR, in Portuguese “Norma Brasileira Regulamentadora”) 7190 (1997) establishes ratios for characteristic strength estimation and three forms of wood characterization, with an emphasis on the simplified procedure for common species, which allows obtaining the strength characteristic values through equations correlating different mechanical properties. The present work evaluates the accuracy of the relation proposed by NBR 7190 (1997) of shear strength along the grain (fv0,k) to compression strength along the grain (fc0,k) (fv0,k=0.12 fc0,k). 960 experimental measurements of shear and compression strength values were performed for 40 hardwood species, and the precision of the relation proposed by the Brazilian standard was evaluated using the analysis of variance (ANOVA) method. Linear, exponential, logarithmic, and geometric regression models were used as an alternative to the NBR relation for shear strength estimation. The statistical analysis revealed that the geometric regression is the model of best fit.

WOOD RESEARCH Volume 66, Number 3, 2021
Huijun Dong, Mohsen Bahmani, Miha Humar, and Sohrab Rahimi

Fiber morphology and physical properties of branch and stem wood of hawthorn (crataegus azarolus l.) grown in zagros forests

This study aims at investigating the effect of three altitude levels (below 1800 m, 1800-2000 m and above 2000 m) on the physical and biometric properties of stem-wood and branch-wood of hawthorn species. Moreover, the relationship between wood dry density and volumetric swelling, fiber length, fiber diameter, cell wall thickness were studied. Results indicated that altitude had significant effects on the dry density, volumetric swelling and fiber length of stem wood while did not significant effects on the density of branch wood. Additionally, some physical and biometric properties had relatively greater correlation coefficients in branch wood than in stem wood whereas others had higher coefficients in stem wood compared to branch wood. Deep understanding of properties this wood species will provide a fresh insight into the relationship between wood properties and environmental factors.

WOOD RESEARCH Volume 64, Number 3, 2019
Hung-Chi Su, Shu-Fen Tung, Chun-Ta Tzeng, and Chi-Ming Lai

Variation in the charring depth of wood studs inside wood-frame walls with time in a fire

In this study, the variation in the charring depth of wood studs inside wood-frame walls (WFWs) in a fire was investigated. First, the time variation in the surface temperature of wood studs inside WFWs was determined based on ISO 834 fire-resistance tests, and the resulting heating conditions were used in subsequent heat exposure tests. Then, wood stud specimens of four different wood species (Chinese fir, Japanese cedar, Southern pine and spruce) were each subjected to a heat exposure test in an electric furnace. The results exhibited no significant correlation between the charring depth of the wood stud specimens and the preheating density. In addition, the test data validated that the equation proposed by Sugahara can be used for predicting the charring depth of wood studs inside WFWs in a fire.

WOOD RESEARCH Volume 64, Number 3, 2019
Roman Fojtík

Moisture content analysis of wooden bridges

The article deals with assessing the impact of moisture content conditions in wood mass of the wood bridges constructions on their lifespan in Central Europe. Wood moisture content as one of main factors influencing the wooden elements mechanical properties was studied on seventeen wooden bridge constructions. The dependence of temperature and relative humidity on material moisture content was observed in summer season and also in winter season. The lifespan of historical and modern wood structures was discussed as well.

WOOD RESEARCH Volume 64, Number 2, 2019
Ngargueudedjim Kimtangar, Guersoube Tao, and Guy Edgard Ntamack

Study of the correlation between fiber and mechanical properties of wood Borassus aethiopum Mart. of chad

Palmyra palm (Borassus aethiopum Mart.) is a large palm tree whose wood is often used for its mechanical resistance and weathering in buildings in Africa. In this work, the influence of fibre characteristics on the mechanical properties of wood was studied. For this purpose, the mechanical characteristics were determined and study of the micrograph of the sapwood and Duramen which are the useful parts of this wood were carried out. The results of this study show the mechanical properties of the palmyra are very influenced by the number and the mechanical characteristics of the fibres. The proposed polynomial model of the evolution of the mechanical characteristics gives the good results because the maximum relative mistakes of the prevision are 4.43% for the breaking strength and 0.40% for the Young’s modulus.

WOOD RESEARCH Volume 64, Number 1, 2019
S. Sadiye Yasar

Effects of wood preservatives on the combustion process and combustion quality of wood

This study examines the combustion properties of Scots pine (Pinus sylvestris L.) and Oriental beech (Fagus orientalis L.) in 3 stages (CWF, SC and EC) according to ASTM E 160-50 (1975). Wood samples were impregnated with Tanalith-E (T) and Wolmanit-CB (WC) and then were varnished with Synthetic (St) and water based (wb) varnishes. When the combustion was completed, the weight loss, combustion temperatures, illuminance values, total time of combustion, and demolition time were measured. As the result, illuminance value of Oriental beech wood decreased, while the smoke density increased. Scots pine was later destroyed in the combustion process. Areas with a risk of fire are advised to use pine wood instead of beech. Wolmanit-CB and synthetic varnish reduced the temperature and illuminance values. Oriental beech, Tanalith-E, and synthetic varnish resulted in the highest temperatures for all combustion stages. This triple interaction increased total combustion time values by more than 90% when compared with the control samples.

WOOD RESEARCH Volume 66, Number 1, 2021
Minghua Wang, MING LI, TINGTING DENG, SAIYIN FANG, Xiaosong Li, and Fei Lai

Study on lamb wave propagation characteristics along the grain of thin wood sheet

Through the time-frequency analysis of the propagation waveform of the acoustic emission (AE) signal propagating in the thin sheet of Pinus sylvestris var. mongolica, the propagation characteristics of the stress wave when propagating as a lamb wave was studied. An AE source was generated on the surface of the specimen, the discrete wavelet transform method was used to achieve AE signal de-noising and reconstruct the waveform of the AE signal. On this basis, the time difference positioning method was used to calculate the propagation velocity of lamb waves, and compared with the propagation characteristics of lamb waves in the metal specimen. The results show that the high-frequency mode of lamb waves attenuated sharply as they propagate in the thin wood sheet, indicating that the microstructure of wood has a significant low-pass characteristic for lamb waves. The average attenuation rates of lamb waves in metal and thin wood sheet were 87.1% and 75.7%, and the velocity was 4447.0 m.s-1 and 1186.3 m.s-1, respectively. This shows that AE signals can travel longer distances in the thin wood sheet, but the propagation velocity is significantly reduced.