WOOD RESEARCH Volume 70, Number 2, 2025
ZHIYING TIAN, SAIYIN FANG, MING LI, TINGTING DENG, ERZHUANG ZHAI, CHUMIN CHEN, and YONGCHUAN WU

THE ANISOTROPIC VELOCITY MODEL OF INTERNAL ACOUSTIC EMISSION SIGNALS IN ZELKOVA WOOD AND THE INFLUENCE OF HOLES ON THEIR PROPAGATION PROCESS

In this article, an acoustic emission (AE) source was generated through pencil-lead break (PLB). On Zelkova schneideriana specimens featuring central through-holes with diameters ranging from 8 to 16 mm, the time-difference-of-arrival (TDOA) in combination with the least squares fitting approach was utilized to establish an anisotropic model of the AE wave velocity within the wood as it varies with the detection angle. Then, a pulse signal was generated through a signal generator to analyze the influence of the holes on the peak values of AE signals at different angles. The results indicate that when the propagation angle is less than 80°, the AE wave velocity rises rapidly with the increase of the angle and eventually approximates the longitudinal wave velocity along the grain. The AE signal peak emerged in the direction approximately 30° for the specimen without holes. In the presence of holes, as the hole diameter increases, the variation trend of AE peak amplitudes within an angular range of -18° to +18° relative to the hole center becomes progressively smoother, with a concurrent reduction in their mean value. This distinct characteristic can serve as a robust indicator for identifying internal hole defects in wood

WOOD RESEARCH Volume 70, Number 1, 2025
JINGGUI WANG, MING LI, SAIYIN FANG, TINGTING DENG, ERZHUANG ZHAI, CHUMIN CHEN, and KEFEI CHEN

RESEARCH ON WOOD DAMAGE FRACTURE CHARACTERISTICS BASED ON ACOUSTIC EMISSION RA-AF VALUE AND ENERGY CONCENTRATION

To study the acoustic emission (AE) characteristics and fracture properties of wood at different stress stages, three-point bending tests and real-time AE monitoring were carried out on Zelkova schneideriana and Pinus sylvestris var. in this paper. Different stress stages were classified according to AE ringing counts-cumulative AE ringing counts-load curves, damage modes of wood at different stages were identified based on distribution characteristics of RA-AF data, and fracture behavior of wood was predicted by energy concentration k. Results show that distribution characteristics of AE RA-AF data can characterize the types of cracks generated in each stress stage of wood. The crack modes generated by both specimens during three-point bending loading are tension shear composite cracks, and the proportion of tensile cracks is significantly higher than that of shear cracks, but during the elastic-plastic stage, Zelkova schneideriana specimens will produce a large number of shear cracks, whereas Pinus sylvestris var. specimens have predominantly tensile cracks, with only a small number of shear cracks produced before and after fracture. The sudden change in the energy concentration k curve between elastic-plastic deformation stage and fracture stage can be used as a precursor of damage for both specimens under three-point bending test conditions

WOOD RESEARCH Volume 69, Number 4, 2024
KUN DU, YOULI WANG, ZHIHENG ZHANG, MING LI, and SAIYING FANG

THE ATTENUATION CHARACTERISTICS OF DIFFERENT FREQUENCY COMPONENTS OF ACOUSTIC EMISSION SIGNAL DURING PROPAGATION IN ELM AND PINE WOOD

In order to gain a deeper understanding of the attenuation characteristics of different frequency components of acoustic emission signal when propagating in wood, this research conduct pencil lead fracture experiments on the surface of elm and pine specimen. Original AE signals acquired by different sensors are decomposed using 5-level wavelet transform, the attenuation characteristics of different frequency components are studied, and the acoustic emission source is located according to the energy of different frequency components. The results indicate that the propagation distance is the main factor affecting the attenuation of AE signals. The longer the propagation distance, the greater the degree of attenuation. The attenuation characteristics of high-frequency components of acoustic emission signals deviate from the ideal attenuation model after the propagation distance greater than 10 cm. The higher the frequency components of acoustic emission signals, the faster they attenuatewhen propagation in elm and pine specimen

WOOD RESEARCH Volume 69, Number 3, 2024
ROMAN HERDA, MILOŠ SLIVANSKÝ, JÁN BRODNIANSKY, and TOMÁŠ KLAS

DETERMINATION OF FLEXURAL STRENGTH AND YOUNG’S MODULUS OF ELASTICITY OF ACTIVELY BENT WOOD

The article focuses on the experimental verification of wooden laths with a cross-section of 10 mm x 40 mm which were selected for active bending. The laths are made of pine wood and are 2 m in length. The research includes experimental measurements to determine the limit deformations achieved by bending the wood without chemical treatment, by applying compressive force to an originally straight beam, causing it to buckle and further deform. Ten bending tests of beams were performed, and from the same pieces, 21 tests were conducted using the four-point bending test to determine the flexural strength, and 30 tests to determine the global modulus of elasticity

WOOD RESEARCH Volume 69, Number 3, 2024
HILAL ULAŞAN and CEVDET SÖĞÜTLÜ

THE EFFECT OF SUPPORT LAYER MATERIAL AND ADHESIVE TYPE ON COMPRESSIVE DYNAMIC BENDING AND SHEAR STRENGTH IN LAMINATED WOOD

In this study, strength properties of wood material reinforced with carbon fiber fabric, steel wire mesh and bamboo veneer were determined. Polyvinylacetate (PVAc) and polyurethane (PUR) glues (D4)were used for the lamellas obtained from Scotch pine (Pinus sylvestris L.) and eastern beech (Fagus orientalis L.). Compressive strength according to TS EN 408+A1; dynamic bending (shock) strength according toTS ISO 13061-10 and shear strength according to ASTM D 3110 were determined on 3 and 5-layers samples. According to the results, the highest compressive strength (62.8 N/mm2) was found in 5-layerseastern beech samples reinforced with carbon fiber fabric and bonded with PUR glue. The highest dynamic bending strength value (110.8 kJ/m2) was found in 5-layerseastern beech samples reinforced with carbon fiber fabric and bonded with PUR glue and the highest shear strength value (12.3 N/mm2) in 3-layered eastern beech samples reinforced with steel wire mesh and bonded with PUR glue

WOOD RESEARCH Volume 69, Number 2, 2024
XIN ZHANG, MING LI, SAIYIN FANG, FEILONG MAO, LONGFEI YANG, YUE ZHAO, and GEZHOU QIN

EVALUATION OF WOOD DAMAGE AND FRACTURE BEHAVIOR BASED ON ENERGY ENTROPY OF ACOUSTIC EMISSION SIGNALS

In order to assess the damage and fracture behavior of wood under continuous loading, an energy entropy and b-value associated with the acoustic emission (AE) signal were defined to quantitatively describe the release of strain energy during loading. Firstly, the acoustic emission signals of the wood in the three-point bending test were collected. This paper presents the concept of energy entropy according to the definition of information entropy. In order to further evaluate the strain energy intensity released by the damage behavior of the wood specimen, the acoustic emission b-value was defined. Finally, by jointly analysing the dynamics of these two parameters, the test process can be divided into three phases. The results show that even in the elastic phase, micro-destructive behavior occur inside the wood specimen; in the plastic phase, the wood specimen is not only subjected to macroscopic damage, but also often accompanied by fine cracks inside

WOOD RESEARCH Volume 69, Number 2, 2024
JURAJ KOPÚNEK, JOZEF MARTINKA, PETER RANTUCH, TOMÁŠ ŠTEFKO, IGOR WACHTER, and FILIP MARTINKA

PRELIMINARY STUDY OF DEPENDENCE OF SMOKE AND CARBON MONOXIDE EMISSION ON HEAT RELEASE RATE FROM FAST-GROWING WOOD SPECIES

The aim of this paper is to create the model for prediction of carbon monoxide release rate (CORR) and smoke production rate (SPR) from heat release rate (HRR) of fast-growing wood species. The model is independent on wood species, thus is suitable for all fast-growing wood species. Three wood species hybrid poplar J-105 (Populus nigra × P. maximowiczii A. Henry), white willow (Salix alba L.) and black locust (Robinia pseudoacacia L.) were used for universal model creation. The heat release rate, smoke production rate and carbon monoxide release rate have been measured at three heat fluxes (25, 35 and 50 kW.m-2) by the cone calorimeter. The average values of CORR and SPR for all investigated wood species were 0.051 g.m-2.s-1 and 0.086 m2.m-2.s-1, respectively. Both dependencies of SPR and CORR on HRR have shown similar trends during the ignition phase (unstable trend) and during the intense burning phase (roughly linear increasing with HRR). The main difference was shown during the steady state phase (dependency of SPR on HRR is stable while dependency of CO on HRR is highly unstable). The results also proved a significant impact of wood density on these dependencies, thus, the neural network for prediction of SPR, CORR from HRR was applied. The coefficients of determination R2 for trained neural networks, for both SPR and CORR, were achieved in the range from 0.96 to 0.97

WOOD RESEARCH Volume 69, Number 1, 2024
RIZKI ARISANDI, AQMAL NUR JIHAD, ALMAAS HUKMA SHABIYYA PALEVA, FAJAR ARIEF KURNIAWAN, GANIS LUKMANDARU, NOOR KHOMSAH KARTIKAWATI, ANTO RIMBAWANTO, SRI SUNARTI, TONI HERAWAN, LILIEK HARYJANTO, ASRI INSIANA PUTRI, FAJAR LESTARI, and ARIF NIRSATMANTO

CHARACTERIZATION OF EXTRACTIVE COMPOSITION IN THE WOOD AND BARK OF CAJUPUTI (MELALEUCA CAJUPUTI SUBSP. CAJUPUTI POWELL.) GROWN IN GUNUNGKIDUL, INDONESIA

The aim of this study was to analyze the extractive composition of the wood and bark of cajuput (M. cajuputi subsp. cajuputi) to consider the end use material according to the characteristics of the its extractives. Results showed that the extractives properties of M. cajuputi, i.e. the contents of n-hexane, methanol, hot water extractives and total phenolic content (TPC), flavonoid content (TFC) and total polysaccharides (TSP) were 0.84 to 1.05%, 1.00 to 1.03% and 1.43 to 1.46%, and 19.2 to 38.7 and 23.2 to 27.3 mg GAE/g dried extract, 11.8 to 16.0 and 7.55 to 14.0 mg QE/g dried extract and 79.3 to 102.8 and 148.8 to 165.9 mg Glu/g dried extract, respectively. Bark had higher extractive levels than wood. In addition, TPC and TSP in the bark were greater than in the wood parts, whereas the reverse trend was found in TFC. The relatively high contents of TPC and TFC in the wood and bark suggest that their potential antioxidant properties. Based on the GC-MS analysis, the high content of sterols-steroids (31.4%) and triterpenoids (21.9%) in the bark part will have potential in the field of pharmacology

WOOD RESEARCH Volume 68, Number 4, 2023
Ladislav Dzurenda and Michal Dudiak

COLOR DIVERSITY OF BEECH WOOD WITH A FALSE HEARTWOOD IN THE COLOR SPACE CIE L*a*b*

The color of the false heartwood of Fagus sylvatica L. perceived by the human eye is in a wide range of shades from light brown-yellow to red-brown. The article analyzes the color in the color space CIE L*a*b* of dry wood of the false heartwood type: round, flame, star and marble. The color of the wood was measured with a colorimeter Color reader CR-10. The most colorful is the wood marble with a false heartwood. The results of statistical processing of the measured color values of dry beech wood, marble false heartwood on a planed surface identify it with values on the lightness coordinate L* = 65.2 ± 6.9 and on the chromatic coordinates: red color a* = 13.2 ± 2.3 and yellow b* = 19.2 ± 1.9. The most homogeneous in color is the color of the ring wood of the false heartwood with the coordinate values: L* = 63.7 ± 3.1; a* = 12.6 ± 1.7 and b* = 20.1 ± 1.6. The color diversity of the darkness and yellow-brown-red shades of the wood of the false heartwood is numerically quantified by the values of the total color difference ΔEsx* = 3.9 – 7.5. The presented values of the color of false heartwood beech complement the knowledge about the color of false heartwood and by defining the boundaries of color in the color space CIE L*a*b*, they create space for designers to model the color diversity of compositions and construction-joinery products made of sapwood and false heartwood beech

WOOD RESEARCH Volume 68, Number 4, 2023
FEILONG MAO, SAIYIN FANG, MING LI, GEZHOU QIN, YUE ZHAO, and Ning Xu

Study on Acoustic Black Hole Effect of Acoustic Emission Signals in Pinus sylvestris var. mongolica litv

The difference in density and wave velocity causes distinct wave impedance between air and wood, resulting in complex acoustic emission (AE) signals due to reflection on the wood’s surface. This study explores the suppression of AE signal reflection by modifying the structure of thin wood panels, utilizing the theory of acoustic black holes (ABH). Initially, a one-dimensional ABH structure was created by forming a wedge structure on one side of the specimen. Pencil-lead break (PLB) tests simulated sudden AE sources on the specimen’s surface. AE signals were collected using three equidistant sensors on the upper surface, with a sampling frequency of 2 MHz. The AE signal was then segmented into frequency bands using the differential method and analyzed in both time and frequency domains. Comparisons were made to understand the impact of the one-dimensional ABH on AE signal propagation. Results demonstrated that the one-dimensional ABH effectively suppressed AE signal reflection on the wood’s surface, reducing the high-frequency components by 18.31%, 20.83%, and 12.09% for each sensor, respectively. Furthermore, the experimental cut-off frequency of 0.98 kHz surpassed the theoretically calculated value of 0.39 kHz due to the disparity between the ABH structure’s thickness and the theoretical prediction.

WOOD RESEARCH Volume 68, Number 2, 2023
MARIJA TODOROVIĆ, Mathieu Koetsier, NAĐA SIMOVIĆ, IVAN GLIŠOVIĆ, and Marko Pavlović

Determination of mode I fracture properties of European spruce

In this paper an efficient procedure for obtaining a cohesive law for Mode I timber fracture (crack opening), based on the Double Cantilever Beam (DCB) tests is given. DCB tests were performed on ten European spruce specimens in order to determine the energy release rate vs crack length (R curves). Two crucial parameters – crack length during the experiment and the crack tip opening displacement were obtained using 2D Digital Image Correlation (DIC) technique. In order to determine accurate fracture resistance (R curve), procedure which includes calculating cumulative released energy was employed. The cohesive law for Mode I fracture of wood was obtained by differentiation of the strain energy release rate as a function of the crack tip opening displacement. This cohesive law is further implemented in the successful numerical modelling of failure modes in large-scale end-notched glulam beams which were experimentally tested in four-point bending configuration.

WOOD RESEARCH Volume 68, Number 1, 2023
SAIYIN FANG, MING LI, Wei Li, Chang Lin Huang, TINGTING DENG, and KUN DU

Experimental analysis of acoustic emission propagation velocities and energy attenuation law of p and s waves in wood using improved TDOA measurements

To explore the propagation law of AE signal in wood, the propagation velocity of P-wave and S-wave and the energy attenuation law of different frequency components were studied By PLB (pencil-lead break) tests. Firstly, an improved time-difference-of-arrival (TDOA) method was designed to determine the arrive time. The propagation velocities of P-wave and S-wave were calculated. Then, the Young’s modulus was estimated by P-wave velocity. Finally, on the basis of eliminating the influence of standing wave, the energy attenuation models were obtained by numerical fitting and wavelet decomposition. The results showed that the improved TDOA algorithm can calculate the propagation velocity of P-wave and S-wave at the same time through one test, and the P-wave velocity can be used to estimate the Young’s modulus. P-wave propagated faster in soft wood, while S-wave propagated faster in hard wood. The higher the frequency of AE signal, the faster the energy attenuation.

WOOD RESEARCH Volume 67, Number 6, 2022
GEZHOU QIN, MING LI, SAIYIN FANG, TINGTING DENG, Changlin Huang, Zhouling Yang, FEILONG MAO, and YUE ZHAO

Study on the dispersion characteristics of wood acoustic emission signal based on wavelet decomposition

Artificial AE sources were generated on the surfaces of Ulmus pumila, Zelkova schneideriana, Cunninghamia lanceolata, and Pinus sylvestris var. mongolica Litv. specimens. The AE transverse wave signal was decomposed into 3-layers detail signals by wavelet decomposition and reconstructed, and it was calculated based on correlation analysis. Then the longitudinal wave speed was calculated according to the time-difference-of-arrival (TDOA) method, and the wood dispersion phenomenon was studied. The results showed that the dispersion phenomenon of Ulmus pumila was obvious. The propagation speed of high-frequency signal was 2.38 times that of low-frequency signal. The ratio of high and low frequency propagation speed of soft wood was 1.72 and 1.73. The dispersion degree of Zelkova schneideriana was the weakest, and the propagation speed of the high frequency was 1.25 times of the low one. The ratios of longitudinal and transverse wave speeds of the four specimens were 4.59, 4.07, 4.24 and 4.2, respectively.

WOOD RESEARCH Volume 67, Number 5, 2022
Vasiliki Kamperidou, Izabela Ratajczak, Waldemar Perdoch, and Bartłomiej Mazela

Impact of thermal modification combined with silicon compounds treatment on wood structure

In the present study silicon containing formulations were investigated for their applicability in solid wood modification. Black pine sapwood was thermally modified at 180oC and 200oC (3, 5 and 7 hours) and afterwards, an additional chemical treatment with silicon containing systems (N-2-aminoethyl-3-aminopropyltrimethoxysilane) followed, in an attempt to invigorate hydrophobicity and durability of wood. Infrared spectroscopy (FTIR) was used to examine the formation of new bonds in the treated materials and atomic absorption spectrometry (AAS) to measure the silane concentration. The results showed a high reactivity between thermally modified wood and organosilicon compounds. The presence of bands representing vibrations of the Si–O–CH3 group in IR spectra of modified wood and after extraction confirms the stable character of the formed bonds between the hydroxyl group of wood and the methoxy groups of organosilanes. Furthermore, reactivity between wood and AE-APTMOS and alkyd resin solution was confirmed by the AAS results. Alkyd resin caused a higher concentration of silica in wood mass, which increases as the thermal treatment temperature increases. The organosilicon compounds caused a much higher resistance to water washout, revealing permanent binding of silanes to wood mass.

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 1, 2022
Khawaja Adeel Tariq, Muhammad Haroon, Abdullah Habib Mughal, and Sher Ali

Physical and mechanical characterization of structural wood used in pakistan

Six species of wood (Vachellia nilotica, Eucalyptus camaldulensis, Ziziphus mauritiana, Albizia lebbeck, Melia azedarach, Dalbergia sissoo) were tested in compression and tension parallel to the grain. The specimens were collected from different areas of Pakistan. The compressive strengths, tension parallel to grain and hardness of the wood were determined by testing rectangular shape wooden specimens (ASTM D143 2014, Janka 1906). It was observed that compressive and tensile strength of Vachllia nilotica parallel to the grain is higher than other species whereas, Eucalyptus camaldulensis hardness behaviour along radial and tangential surface is higher among the wooden samples tested.

WOOD RESEARCH Volume 66, Number 6, 2021
Petr Kuklík, Zdeněk Prošek, and Anna Gregorová

Comprehensive approach to ensure durabilty of external wooden structures

The article deals with durability of wood, durability of wooden structures and surface modification of wood. We are trying to eliminate the factors causing degradation of wood with the use of photocatalytic materials. Those materials are efficient UV absorbers and they are able to destroy biological aggressors also. The planar particles of titanium oxide TiO2 were chosen for the purpose of our research and applied on a wooden surface. In our case, we used a water solution of TiO2. The main goal of our work was to study the interaction between planar particles of TiO2 and wood matter. The samples of pine wood (Pinus sylvestris) were monitored for 255 days and subsequently evaluated using an electron microscope. The use of TiO2 was compared with reference material and a reference commercial coating.

WOOD RESEARCH Volume 61, Number 6, 2016
Alperen Kaymakci, Nadir Ayrilmis, and Huseyin Akkilic

Utilization of tinder fungus as filler in production of HDPe/wood composite

Selected physical and mechanical properties of high density polyethylene (HDPE) composites filled with various mixtures of wood flour and tinder fungus (Fomes fomentarius) were investigated. For this aim, different mixtures of tinder fungus flour and wood flour (0/40, 10/30, 20/20, and 30/10, and 40/0) (by weight) were compounded with HDPE with a coupling agent (maleic anhydride grafted polyethylene (MAPE) in a twin screw co-rotating extruder. The test specimens were produced by injection moulding machine. The thickness swelling and water absorption of the HDPE/wood composites significantly decreased with increasing content of the tinder fungus flour. The mechanical properties of the composites were negatively affected by increasing amount of tinder fungus flour but there were no significant differences up to 30 wt % tinder fungus content, except for the tensile strength. The optimum physical and mechanical properties for the filled HDPE composites were found to be a 10/30/60/3 formulation of wood flour, tinder fungus, HDPE, and MAPE, respectively.

WOOD RESEARCH Volume 61, Number 6, 2016
Onur Ülker and Erol Burdurlu

Some mechanical properties of densified and laminated Lombardy poplar (Populus nigra L.)

In this study, it was studied the effects of densification and then lamination processes on some mechanical properties of Lombardy poplar (Populus nigra L.), which is one of the low density tree species. Densification temperatures were 80, 100, 120 and 140ºC and ratios of densification were 15, 30 and 50 %. Furthermore, lamellas with a thickness of 4 mm cut from densified materials were laminated by bonding one on top of the other with urea formaldehyde (UF) and polyvinyl acetate (PVAc) adhesives. Bending, modulus of elasticity, compression and tensile tests were applied by preparing specimens from the pieces. According to test results, the most suitable temperature level was 120°C. As the ratio of densification was increased at this temperature level, increase were observed in the mechanical properties. Also, lamination provided significant increases in the mechanical values compared to laminated but undensified Lombardy poplar. Increases were observed in the mechanical properties reaching 444 % with application of densification and lamination processes.

WOOD RESEARCH Volume 61, Number 6, 2016
Jin Heon Kwon and Nadir Ayrilmis

Short note. effect of hot-pressing parameters on selected properties of flakeboard

Physical and mechanical properties of flakeboards produced from radiata pine flakes under different hot-pressing conditions were investigated in this study. The flakeboard mats were hot-pressed at 2.8 MPa with two different temperatures (170 and 190°C) and three different durations (7, 10, and 15 min). At the 170°C of hot-pressing temperature, the highest bending strength was found in the flakeboards pressed for 7 min while the highest modulus of elasticity was found in the flakeboards pressed for 15 min. The highest internal bond strength was found to be 0.13 MPa for the flakeboards pressed at 190°C for 15 min. The thickness swelling and water absorption of flakeboards pressed at 190°C were lower than those of the flakeboards pressed at 170°C. The control of hot press temperature and duration appears an effective method to enhance serviceability of flakeboard.