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.
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.
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.
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.
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.
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%.
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.
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.
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.
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.
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.
In this study, the surface quality of birch wood (Betula) test pieces planned with experimental planning tools (ET1, ET2) and influence of tool wear of quality of surface were examined. These tools were made by surfacing using a submerged arc welding (SAW) technique and a mixture of alloying elements (cromium, tungsten, fero-manganese, silicon carbide) spread on the surface under industrial flux. Surface roughness was measured along and across wood fibre. According to the results of experiments it is obviously that average roughness parameters along fibre is lower than across. Planning tool wear results revealed that 3200 m of cutting length is not significant for tools ET1 and ET2 wear. The same can be said about tool nose width change: For ET1 from 2.8 to 2.9 μm, and for ET2 from 2 to 3.4 μm – effect of negligible changes of tool edge geometry on planned surface quality is low. Feed of planning tool played more significant role – twice higher feed per insert (ET1 – 1.00 mm, ET2 – 0.5 mm) showed lower surface quality after planning. To reach necessary wood surface quality, lower feed rate and suggested experimental planning tool ET2 with higher wear resistance than commercial tool is preferable for planning of birch wood.
The article deals with research of joints with glued-in threaded rods. The introduction provides a brief presentation of the issue. The first part focuses on axially loaded glued-in threaded rods. The second part explains the behaviour of joints with glued-in rods loaded by bending moment. Theoretical analysis was performed on models based on the finite element method. Verification of theoretical results was realized by practical experiments. Tensile tests were carried out on timber blocks with glued-in bars to verify the depth of affixing. Furthermore, the resistance in bending was confirmed on actual beams with glued-in bars in the middle of the span. Results and the follow-up work are summarized in the conclusion.
Wood material is generally preferred due to its resilience against earthquakes, aesthetic properties, and its warmth as well as being natural. One of the major problems of employing this natural and breathable product is its ease of combustibility. Despite this adverse characteristic, its high resistance against burning and its ability to maintain its weight bearing characteristics until the very end does not lead to sudden collapses as is seen in steel and concrete systems. Treating wood with impregnating materials in order to improve its resistance against burning is an improved safety measure for the prevention of ignition. This study investigate seasonal effects on the ignition characteristics of chestnut wood samples impregnated using either Tanalith-E or Wolmanit-CB as detailed in ASTM–D 1413–76 and surface-treated using water-based or synthetic varnish as detailed in ASTM-D 3023- 88. The temperature of burning process was the highest in the investigated samples, in those impregnated with Wolmanit-CB and those that were treated with water-based varnish. The results of the study indicated that weight loss was lower during winter (84.59 %), for samples that were impregnated using Wolmanit-CB (84.46 %) and in those that were treated with water-based varnish (84.18 %). On the other hand, the O2 content was determined to be the highest and the CO content the lowest in winter samples that were impregnated using Wolmanit-CB and treated with synthetic varnish.
Hydrothermal carbonization (HTC) is a chemical pretreatment of wood waste for convert it in biochar by the application of high temperatures and pressures in a reaction time that do not exceed 10 hours. One of the main applications of the HTC biochar is as pellets. In this research durability against fungal decay and dimensional stability associated with relative humidity changes of HTC pellets were analyzed and evaluated. A comparison of these properties between HTC pellets and wooden EN+ pellets has been carried out. HTC pellets are significantly more durable against fungal attack, more dimensionally stable against relative humidity changes and denser than wood pellets, which confers better properties for logistics processes like storage and transport.
This paper describes the chemical and physical properties of Pinus leiophylla, P. montezumae and P. Pseudostrobus timber by-products (wood chips, bark and wood-bark). The physical features determined were the initial moisture content, bulk density and calorific value whereas the determined chemical characteristics were pH, inorganic compounds, inorganic compounds microanalysis, extractives, lignin, and holocellulose. Such by-products were collected in the industrial complex at the Indigenous Community of Nuevo San Juan Parangaricutiro, located in Michoacán, México. The initial moisture content of the samples varied from 33.6 to 56%, while their bulk density ranged from 0.19 to 0.31 g.cm-3. The calorific value for the wood residues of the three different species of pines varied from 17.95 to 18.93 MJ.kg-1. Regarding their chemical characteristics, barks were more acid than woods, and in general, the inorganic content was lower in woods than in barks. According to the X-ray microanalysis, the major inorganic compounds found in ash were calcium, magnesium, and potassium. No heavy metals were detected at all. For the three pine species, extractives levels in barks were higher than in woods. Also, barks contained a higher concentration of lignin than woods. The highest holocellulose content was found in wood residues rather than in barks. It is concluded then that the three pine species timber by-products present physic and chemical properties that make them suitable for the production of solid biofuel.
Our work on the physical properties of wood in hardwood species, Quercus robur L., Q. petraea (Matts) Liebl., and Q. pyrenaica Willd., for study its use in cooperage, began with the proportion appraisal of bark, sapwood, and heartwood, and its relationship with age, to know and assess the variation thereof in the Galician oaks. To properly perform our study, it was necessary to fell several Quercus trees within the study area (Galicia, NW Spain). In total, 45 trees were selected in 15 different stands located in the Galician provinces of Lugo and Ourense, from which we obtained 45 slices of wood at 60 cm height on the tree trunk. There are many anatomical differences between hardwood and softwood species; however wood parts of a tree system are common to both. The analysis of different proportions of bark, sapwood, and heartwood made it possible to reveal: i) the rapid growth of Quercus pyrenaica gives rise to the formation of large proportion of heartwood in a few years; ii) Quercus petraea has the largest proportion of heartwood, but the studied trees are older and their growth is slower than the other species; iii) Quercus robur has an intermediate growth between the other two species. Therefore, our aim was to carry out a complete description of these parts of the wood, later, in upcoming work estimate their physical properties for use in cooperage industry.
Studies on the content and distribution of mineral substances including calcium (Ca), potassium (K), magnesium (Mg), manganese (Mn), iron (Fe), sodium (Na), zinc (Zn), aluminum (Al), lead (Pb) and strontium (Sr) were performed. Samples of Scots pine were gained from stems with Ist degradation degree of tree (considered to grow in the area with weak environmental pollution), IInd degradation degree (strong pollution) and IIIrd degradation degree (very strong pollution). Nitrogen industrial plant was acknowledged as the source of pollution. Samples were collected from butt-end, middle- and top sections of the stem in following zones: sapwood, heartwood adjacent sapwood, heartwood and bark. Results indicate that nitrogen industrial plant causes the decrease of mineral substances content in bark from butt-end section of stems with IInd and IIIrd degradation degree in relation to stems with Ist degradation degree. Calcium content is the highest in heartwood and decreases in the direction to stem perimeter, regardless of stem section and environmental pollution degree. Very strong pollution decreases potassium content in wood in comparison to samples collected in areas with strong and weak pollution. Environmental pollution also decreases sodium content in wood, and increases content of manganese, aluminum, lead and strontium.
Chosen metals contents were analyzed in Norway maple (Acer platanoides L.) in bark, roots and wood samples collected from the polluted environment. Samples were gained from three cca. 40-year old trunks, which were grown on Krakowskie Przedmieście st., next to the St. Anna church in Warsaw, Poland. Wood of trunk and the main roots, as well as bark from butt-end section were also sampled. Contents of Ca, Mg, Mn, Zn, Fe, Al, K, Na and Sr were examined with the application of spectrometric methods. The results show that environmental pollution significantly influences the content of examined elements. The change of Na content is the most spectacular. Its content is hundred times higher, in wood and bark, as well as in the main roots, in relation tree from non-polluted environment, what is probably caused by urban environment salinity.
The development of wood use as a renewable raw material for construction caused that can be also seen as the construction of bridge structures, which have to withstand the environment. It is a modern construction using LLD or replicas of historical buildings using RD. Many of these constructions, despite impregnation, are struggling with biological pests that greatly reduce their durability. Revealing of the most dangerous ones is complex and usually cost such amount of money. Diagnostic methods and their results are different. The article deals with the comparison of the diagnosis methods of wood decaying fungi from the family of Gloeophyllaceae to the real construction.