WOOD RESEARCH Volume 67, Number 3, 2022
Cuixiang Lu, Yuan Liu, HUICHUAN JIANG, and QUANJI LU

Impact of heat treatment on the surface color and glossiness of young eucalyptus wood

The study analyzed the impact of heat treatment conditions (temperature and duration) on the surface color and glossiness of young eucalyptus wood. The young eucalyptus wood samples were treated at different treatment temperatures (165°C, 185°C, 205°C) and duration (2 h, 3 h, 4 h). The color of the young eucalyptus wood was determined using CIE L*a*b* system and the gloss was measured with glossmeter at 20°, 60°, and 85° incident angle before and after the heat treatment. The total color difference (E* ), lightness (L*), red-green index (a*), and yellow-blue index (b*), were investigated at different treatment conditions. The values of L* and b* decrease continuously with the increasing temperature and duration. The results of analysis of variance (two-way ANOVA) indicate that the heat treatment temperature has a significant effect on the colorimetric properties of the heat-treated young eucalyptus wood. The gloss decreased after the heat treatment for both perpendicular and parallel directions. ANOVA analysis showed that the treatment temperature duration have a significant effect on the parallel glossiness of 85°(p＜0.05). These are probably due to differences in surface roughness between untreated and heat-treated wood. To achieve the desired color like teak wood, the preferred temperature is no more than 185°C.

WOOD RESEARCH Volume 67, Number 3, 2022
Ladislav Dzurenda and Michal Dudiak

Effect of UV radiation on change in color of steamed beech wood

The wood of the beech (Fagus Sylvatica L.) was steamed with a saturated steam-air mixture at a temperature of t = 95°C, or saturated steam at t = 115°C and t = 135°C to obtain a pale pink, red-brown and rich brown-red color. Subsequently, samples of unsteamed and steamed beech wood were irradiated with a UV lamp in a Xenotest Q-SUN Xe-3-HS after drying in order to test the color stability of steamed beech wood. The color change of the wood surface was evaluated by means of measured values on the coordinates of the color space CIE L*a*b*. The results show that the surface of unsteamed beech wood as well as steamed beech wood with a steam-air mixture at a temperature of t = 95°C and saturated steam with a temperature of t = 125°C darkened and turned brown to a brown-yellow color due to UV radiation. The deep brown-red color of the surface of beech wood steamed with saturated steam with a temperature of t = 135°C brightened to a brown-yellow color similar to the color of unsteamed beech wood. The analysis of the changes in the color space CIE L* a* b* shows that the greater the darkening and browning of the beech wood by steaming, the smaller the changes in the values of ΔL*, Δa* Δb* of the steamed beech wood caused by UV radiation. The positive effect of steaming on UV resistance is evidenced by the decrease in the overall color difference ΔE*. While the value of the total color difference of unsteamed beech wood caused by UV radiation is ΔE* = 15.3, for beech wood steamed with a saturated steam-air mixture at t = 95°C it decreased to ΔE* = 9.5, which is a decrease of 37.9%, for steamed beech wood steamed with saturated steam with temperature t= 115°C is ΔE* = 6.2 which is a decrease of 59.4% and for steamed beech wood steamed with saturated steam with temperature t = 135°C is ΔE* = 4.5 which is a decrease of 70.5%.

WOOD RESEARCH Volume 67, Number 3, 2022
EUN-SUK JANG and Chun-Won Kang

Why the sound-absorbing performance of heartwood and sapwood differs in yellow poplar (Liriodendron tulipifera) cross-sections?

In this study, we investigated why the sound-absorbing performance is different with between heartwood and sapwood of yellow poplar, which are known for their sound-absorbing properties. We performed image observation as well as gas permeability, pore size, and porosity analysis, and measured the sound absorption coefficient of all samples using an impedance tube. We determined that the pores were significantly larger, and the gas permeability and through-pore porosity much higher, in the sapwood than the heartwood. The average sound absorption coefficient of the sapwood at 2000-6400 Hz (0.61 ± 0.04) was 2.7x that of the heartwood (0.23 ± 0.03). The average NRC of the sapwood (0.23 ± 0.01) was 1.9x that of the heartwood (0.12 ± 0.01). This study ultimately determined that the sapwood, as a consequence of its larger pore size and superior through-pore porosity, which thereby improved its gas permeability, outperformed the heartwood in terms of sound-absorption. We also determined that pore size and through-pore porosity were the primary parameters that determined the sound-absorbing performance of yellow poplar cross-sections.

WOOD RESEARCH Volume 67, Number 3, 2022
Huijun Dong, Mohammad Dahmardeh Ghalehno, Leila Fathi, Elham Ghehsare Ardestani, Miha Humar, and Mohsen Bahmani

Comprehensive evaluation of hawthorn wood characteristics in relation to soil physicochemical properties

Characteristics of hawthorn wood concerning soil physicochemical properties were studied. Physical properties such as dry wood density and volumetric swelling and fiber dimension parameters like fiber length, fiber diameter, and cell wall thickness were investigated. Soil properties including clay, silt soil, sand soil, electrical conductivity, pH, nitrogen, phosphorus, potassium, and organic matter content were determined. Pearson correlation was applied to explore the relationship between soil and wood properties. The mean wood density and volumetric swelling obtained were 0.71 g.cm-3 and 18%, respectively. Moreover, the mean values of fiber length, fiber diameter, and cell wall thickness were 0.80 mm, 20.50 μm, and 5.78 μm, respectively. Pearson correlation analysis showed a significant and positive correlation between wood dry density, cell wall thickness and volumetric swelling with percentage of silt, while a negative relationship between fiber length and percentage of silt were found.

WOOD RESEARCH Volume 67, Number 3, 2022
Vinodini Raman, Kang Chiang Liew, and Rafidah Md Salim

Relationship between cell lumen area and lignin content of alkaline-treated densified timber of Paraserianthes falcataria

In this study, low-density plantation timber, Paraserianthes falcataria was pretreated with 3%, 6% and 9% NaOH before densification process. Alkaline pretreatment leads to lignin reductions and cell wall structure becomes more porous. Densification was done by crushing the cell wall with hot-press machine, resulting in reduction of thickness to about 60%. Scanning electron microscopy images were captured and processed through ImageJ software. As to support the data, lignin content determination was conducted according to TAPPI T222 and the correlation coefficient between cell lumen areas and lignin content were studied statistically.

WOOD RESEARCH Volume 67, Number 3, 2022
Kayode Olaoye, Emmanuel Adelusi, and Olayiwola Ajala

Timbre harmonic of selected hardwood species

One of the limited information about the acoustic characteristics of wood is the timbre harmony. We measure the sound harmony of selected hardwood species using a timbre harmonic model. 324 wood samples of 20 x 20 x 300 mm (R x T x L) were collected axially from 12 trees of Albizia adianthifolia, Gmelina arborea, Delonix regia and Boscia anguistifolia for the experiment. Results were subjected to descriptive statistics and analysis of variance. The timbre harmonic model prescribed a scale of 0-1, 0 being the perfect harmonic while 1 represents imperfect harmonic. G. arborea wood had the significantly lowest mean timbre harmonic of 0.078 ± 0.006, thus it had the best sound harmony. Meanwhile, A. adianthifolia wood had the highest timbre harmonic value (0.120 ± 0.008). Conclusively, this study successfully measured the timbre harmonic of sound from selected hardwood species and information provided revealed the species all performed fairly, owing to their values closer to 0.00.

WOOD RESEARCH Volume 67, Number 3, 2022
Bengang Zhang, Liping Yu, Qiaoyan Zhang, De Li, Yuan Tu, Guoming Xiao, Zhigang Wu, and Jiankun Liang

Effects of fire retardants on mechanical properties and water resistance of Pinus massoniana particleboard

Pinus massoniana Lamb. wood particleboards processed by inorganic and organic fire retardants of two densities were prepared by isocyanate and MUF resin. Variations of internal bonding strength (IB), modulus of rupture (MOR), modulus of elasticity (MOE) and thickness swelling rate (TS) of particleboard were observed. Results demonstrated decreasing of IB from 0.81 MPa to 0.42 MPa and 0.36 MPa, MOR from 17.3 MPa to 12.5 MPa and 12.3 MPa, MOE from 1840 MPa to 1328 MPa and 1117 MPa, and increasing of TS from 5.2% to 15.1% and 11.2%, respectively, for the treated MUF particleboards of density 0.65 g.cm-3. Similarly, decreasing of IB from 0.93 MPa to 0.66 MPa and 0.64 MPa, MOR from 16.2 MPa to 10.6 MPa and 12.1 MPa, MOE from 1246 MPa to 1573 MPa and 1466 MPa, and increasing of TS from 6.7% to 7.1% and 6.0%, respectively, when isocyanate adhesive was used. The similar changes were showed when the density of particleboard was 0.75 g.cm-3. Improving density of particleboard appropriately and decrease density difference between the surface to chip layers could make the profile density curve tend to be stable, which could get a relatively high mechanical strength and water resistance. Synergistic effects between isocyanate and fire retardants was confirmed. The particleboard prepared with isocyanate was obviously superior to that prepared with MUF resin in all performances.

WOOD RESEARCH Volume 67, Number 3, 2022
Kristýna Vopatová and Kamila Cábová

Modelling of steel to timber joint exposed to fire

The paper presents an investigation on a timber joint with an inserted steel plate under fire exposure. According to standard EN 1995-1-2 (2004), the fire resistance of unprotected timber joints is limited to 30 min. However, several studies have shown that these joints can achieve higher fire resistance comparing to values given in the standard. In order to verify this, a numerical model of bolted steel-timber joint at elevated temperature was created. The presented model is focused on heat transport in the joint, which is affected by the presence of the steel plate and bolts. The model was validated on experimental results taken from literature and on measurement from a fire tests conducted in a medium-sized furnace. Considering the results of validation, the model has a good ability to predict residual cross-section, temperature of steel plate and bolts and temperature of timber elements. The results of validated numerical model are also compared to the analytical model.

WOOD RESEARCH Volume 67, Number 3, 2022
Chengshuo Sun, Kang Zhou, Zirui Ren, Yutang Chen, and Bin Na

Steam-pressing mechanism of low density magnesia-bonded wood-wool panel

In this paper, wood-wool panel was prepared by steam pressing as opposed to the traditional cold-pressing and hot-pressing methods in order to eliminate the shortcomings of both methods. Cold pressed wood panels have low strength. The overall performance of heat pressed wood panel was poor. The water absorption of these two panels was too large. The steam pressing mechanism was studied by the means of X-ray diffraction and scanning electron microscope. The surface structure, moisture absorption and mechanical properties of wood-wool panel were investigated by experimental testing and numerical analysis. The surface structure of the wood-wool panel became stable, the moisture absorption was reduced, and the mechanical properties of the wood-wool panel were enhanced. The static bending strength of autoclaved wood-wool panel was 4% higher than that of cold-pressed wood-wool panel, and 7.4% higher than that of hot-pressed wood-wool panel. And the sound absorption coefficient increased by 6.3% and 5% respectively. The thermal conductivity was 2.4% lower than that of cold-pressed wood-wool panel.

WOOD RESEARCH Volume 67, Number 3, 2022
Bo Li and Yuan An

Deformation behavior of circular saw blades with different body structures after roll tensioning

A roll tensioning process for circular saw blades with four typical body structures was built with the finite element method. After roll tensioning, the elastoplastic deformation behaviors of the four blades were simulated and tested and the effects of roll reduction displacement on flatness were analyzed. The abilities of the blades to withstand cutting temperature load after the roll tensioning process were compared. The theoretical results showed that each of the four circular saw blades with unique body structures had different process parameters in an appropriate tensioning state. Circular saw blades with different body structures showed variation in improvements of their ability to withstand cutting temperature load after an appropriate tensioning process.

WOOD RESEARCH Volume 67, Number 3, 2022
Boštjan Vimpolšek, Andrej Androjna, and Andrej Lisec

Modelling of post–consumer wood sorting and manipulation: Computational conception and case study

Latest scientific findings and policy guidelines emphasize the importance of returning bio-based waste raw materials through cascading use, also including post-consumer wood (PCW). To accomplish the concept of cascading use it is crucial to properly sort PCW given by the quality of raw materials which is resource consuming process. For this purpose, we have (1) selected appropriate activities, (2) constructed a model with different sub models in time, fuel and energy consumption, and (3) defined the inputs, performed calculations and presented (mid) outputs. In the case study all sub models have been compared with each other, demonstrated on the example of Slovenia. The results show that the reuse of wood is justified and should be implemented to a greater extent. Sensitivity analysis has exposed that modifying the values of the input parameters or (mid) outputs may change the final results in time and fuel consumption among selected sub models.

WOOD RESEARCH Volume 67, Number 3, 2022
Qizhao Lin, Xin He, Jian Qiu, and Hong Wang

A micro-graph retrieval system for coniferous woods using multiple methods

Inspired by the successful application of deep convolutional neural network, a coniferous micro-graphs retrieval framework based on deep learning and image processing technology is proposed. The idea of the proposed framework is that the texture feature of representing three section surfaces can be learned and classified by a fully CNN, and the canals can be deep learned by an U-net CNN when the data labels are available. In addition, the image processing technologies are also proposed to identify whether the growth ring boundaries are distinct and whether there is a “window-like” cross-field pitting. Finally, a coniferous micro-graphs retrieval system is realized based the proposed methods. Experimental results demonstrate that this system outperforms in terms of recognition accuracy. In addition, the system can be further developed into more intelligent coniferous retrieval system that can automatically identify more coniferous microscopic features, so as to obtain more accurate retrieval results.

WOOD RESEARCH Volume 67, Number 3, 2022
Junfeng Hu, Xi Yu, and Yafeng Zhao

Bamboo defect classification based on improved transformer network

Deep learning-based methods, especially convolutional neural networks (CNNs), have shown their effectiveness for image classification. In this paper, vision transformer technology is used to classify the surface defects of processed bamboo, which can be more quick and accurate compared with the low efficiency of manual identification. In the first step, we replace the activation function from Gelu to Mish in the encoder part, but the classification performance is not satisfied. Then, to get a better classification results, we keep the original activation function and introduce the DropBlock. Compared with dropout, DropBlock can obtain better classification accuracy. Finally, compared with the results after transfer learning, it is proved that replacing dropout with DropBlock can improve the classification accuracy. The results on the bamboo chip datasets show that the accuracy of this method is 2% higher than the original transformer network whether using transfer learning.

WOOD RESEARCH Volume 67, Number 3, 2022
Xu Sheng, Xu Peng, Du Yuting, and Zhao Puqi

Short notes: A research on the application of industrial by-product calcium sulfate whiskers in paper filling

The basic properties of calcium sulfate whiskers were studied and compared with commercial ground calcium carbonate (GCC) fillers. The modified whiskers were used for paper filling and compared with a commercial precipitated calcium carbonate (PCC). As a result, it shows that when the unmodified calcium sulfate whisker is used to fill the paper, the ash content of the handmade sheet is low because of its dissolution problem. The ash content of the paper increased obviously when the modified calcium sulfate whisker was added, which reached the ash level of PCC filling. In addition, the paper strength increased greatly, but the light scattering coefficient decreased. In addition, the strength property of the modified calcium sulfate whisker filling paper is basically the same as that of the PCC filling paper with 14.99% ash content when the ash content of the modified calcium sulfate whisker filling paper is 21.95%.