Water distribution during ultrasound-assisted vacuum drying of wood

Wood ultrasound drying is an innovation method, it can reduce overall drying time, increase the mass transfer rate, and increase the effective water diffusivity. In this paper, poplar was taken as experimental material. The drying process was carried out under the conditions that the drying medium temperature is 60°C, the absolute pressure is 0.02 MPa, the ultrasound power is 100 W and the ultrasound frequency is 20 kHz. The moisture content distribution and water diffusion coefficient were studied, and the model among wood moisture content variation, drying time and water diffusion coefficient was established. Results indicated that the moisture gradient increases along with the increase of drying time during the drying process, free water and bound water are dried simultaneously when wood moisture content is above the fiber saturation point; Wood moisture decreased linearly when moisture is above the fiber saturation point, while the descending rate decreases when the moisture content is below the fiber saturation point. The water diffusion coefficient decreases along with the increase of drying time and increases exponentially along with the increase of moisture content. The moisture diffusion coefficient is 2.89×10-4 at the beginning stage, it is 3.02×10-6 when the moisture content is at the fiber saturation point, and it is 2.27×10-7 cm2.s-1 when the moisture content is 10 %; The equation between the water diffusion coefficient and the moisture content was established and it could be used to predict the water diffusion coefficient during ultrasound-assisted vacuum drying.

The effect of air temperature, precipitation and humidity on ring widths in the black locust (Robinia pseudoacacia L.) growing in urban conditions

This study characterizes the basic biometric traits of the black locust growing in urban conditions of the city of Wrocław (south-western Poland) and sets out the relationship between annual tree ring widths and air temperature, air humidity and precipitation. Materials consisted of 54 wooden discs taken from felled straight-trunked trees at four sampling sites at a height of 1.3 m from the ground in the area of a defunct garden established at the turn of the 20th century. Meteorological indicators were calculated based on daily data obtained from the Wroclaw meteorological station, part of the national atmospheric monitoring network. Tree ring widths were determined separately in heartwood and sapwood using LINTABTM 6 and TSAP-Win software, to an accuracy of 0.01 mm. Just over 85 % of the analyzed trees were at least 61 years old. In the heartwood layer the average tree ring width of 2.44 mm was about 1.08 mm wider than in the sapwood layer. Results confirmed the significant effect of warm winter and cool July on the ring widths of the black locust. The greatest demand for water was statistically proven in the period June to August in the year preceding the formation of the tree ring, and in the months January and September in the year of the tree ring formation.

Fire resistance performance of wood materials colored with eco-friendly pomegranate skin (Punica granatum) extracts

The main goal of this study was to determine fire resistance properties of wood treated with pomegranate extract and mordant mixes. According to that wood materials Scotch pine (Pinus sylvestris L.), Oriental beech (Fagus orientalis Lipsky) were chosen. Aluminum sulphate (KAl2(SO4)3.18H2O) copper sulphate (CuSO2.5H2O) and vinegar were used as mordant agent and a synthetic dye was used for comparison. Ultrasonic assisted method were used for extractionthe plant dyestuff from pomegranate skin (Punica granatum) and then applied to wood blocks by immersion (classic) and immersion ultrasonic assisted methods. The combustion test was realized according to ASTM-E 69-02 (2002) standard. The mass losses release of gasses (CO, O2) and the temperature differences of samples were detected for each 30 seconds during combustion. The results showed that the aluminum sulphate mixes were showed the best results on all tests. Unfortunately test performances are not enough to retard the fire effect on the wood materials. Eco-friendly natural colorant might be developed to use them as fire retardant.

Gamma process model for timber-concrete composite beam deterioration prediction

The main goal of maintenance management is to accurately predict the performance of structures over their life-cycle in order to develop the optimal maintenance programs. The aim of this paper is to present one of the prediction models of aging of timber concrete composite structures which will capture the true nature of deterioration. We focus on modelling the deterioration of deflection in the mid-span of the timber-concrete composite beam under a service load. Due to the nature of this composite beam, relative mid-span deflection is generally uncertain and non-decreasing over time, so it could be regarded as a gamma process. The progress of deterioration and estimate its service life will be presented.

Transverse loading distribution related to micro-cracks evolution on a timber-concrete slab

Numerical simulation based on a non-linear material behaviour definition of concrete being a part of a coupled timber-concrete load-bearing system is presented in this paper. The main goal of a NL material modelling performed and introduced herein is to define the influence of concrete fragility over transverse loading distribution horizontally a locally loaded slab. The gained knowledge is consequently applied in a local fire exposure problem. Numerical simulations based on both linear elastic (LE) and non-linear (NL) material behaviour are compared with the results obtained from several real-size experiments and the effects of specific phenomena are discussed further. NL material definition of concrete is also termed as a “damaged material model” in certain references. This work is a continuation of the research performed at the Department of Civil Engineering, University of Coimbra, which’s result had been analysed and further published in paper (Dias et al. 2013) and doctoral thesis (Monteiro 2015).

Influences of seasonal alterations on the burning characteristics of impregnated and surface treated chestnut (Castanea sativa Mill.) wood

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.

Resonance wood microstructure peculiarities

In researches there are contradictory conclusions about interconnection between macrostructural and acoustic characteristics of sounding timber. Unfortunately, there are only a few works of such kind and all of them are of sporadic nature, which give evidence of necessity to continue such researches both at the level of macrostructure and microstructure. The aim of the research is to reveal the peculiarities of sounding timber microstructure, thanks to which it combines two incompatible, at first sight, parameters: High modulus of elasticity (rigidity) and low density. As a result, sounding timber differs from ordinary one in its unique acoustic characteristics, especially in delicacy and timber of sounding. The research results were obtained through applying an electronic scanning microscope to 360 constant and temporary specimens. For this purpose, 800 timber cuts were made in transversal, radial and tangential directions of a tree stem. Besides, macerated material was used to define early and late tracheids length. In the course of the experiment the increment layers width, the number of tracheids in a radial row of early wood, the number of tracheids in a radial row of late wood, the radial and tangential diameters of early and late tracheids, the thickness of tracheids radial and tangential walls in early and late wood, the quantity of vertical resin ducts and their diameter, the height and number of plies in linear (single-row) rays, the height and number of plies in fusiform rays, the diameter of a horizontal resin duct, the quantity and diameter of rounded bordering pores on tracheid walls were studied. The research results revealed a number of differentiating characteristics of sounding spruce timber microstructure.

Flame retardance and antibacterial performance of wooden wallpaper treated with composite modifying agent

To improve the flame retardance and antibacterial properties of wooden wallpaper, a composite modifying agent, containing primarily a phosphorus-nitrogen flame retardant (APP/PER/GP), synergistic and smoke suppression agent (OMMT) and silver loaded with nano TiO2 (Ag-TiO2), was prepared and applied to the wooden wallpaper using an ultrasonic immersion method. The combustion performance (including smoke suppression performance), antibacterial activity and the surface micrographs of the flame retardant/antibacterial wooden wallpaper (FRAW) were investigated and characterized using a cone calorimeter test (CCT), antibacterial rate (AT) and inhibition zone, atomic force microscope (AFM), field emission scanning electron microscope (FE-SEM) and energy dispersive spectrometer (EDS). Furthermore, CIE1976 (L* a* b*) color system was used to estimate the surface color change of the FRAW. It was found that the composite modifier distributed on the surface of FRAW with a micrometer, improved the flame retardance of FRAW, but also improved its antibacterial property. In addition, the smoke release behavior of the FRAW indicated that OMMT had good smoke suppression properties. Furthermore, the result of color difference test showed that the flame retardant and antibacterial treatment had little effect on the decorative appeal of the wooden wallpaper.

The system wood chipping in disc chipper – problems of uniformity of chips length

The system wood chipping in disc chipper Carthage-Norman in industrial plant in Poland was investigation, because there were problems with obtaining homogeneous length of chips. The knife height, wedge angle of knife, clearance angle (pull-in angle), spout angle, average log diameter and construction parameters of chipper have been measured. These parameters were used to determine analytical of average length of chips in the studied disc chipper – Carthage-Norman. Model in Matlab/Simulink for the computation of the chip theoretical length was used. Also carried out the calculation and simulation to determine the maximum and minimum length of chips that can theoretically occur while cutting wood in the studied chipper. Finally, the theoretical lengths of wood chips and the actual lengths produced during cutting were compared.

The effect of heat treatment on the some physical and mechanical properties of beech (Fagus orientalis Lipsky) wood

This study describes the effect of heat treatment on the some of the physical and mechanical properties of beech (Fagus orientalis Lipsky) wood at different temperatures and times. Samples of beech wood were heat-treated at 150, 175, and 200°C for 1, 3 and 5 h. The mechanical properties of the heat-treated and untreated samples were determined by bending tests, modulus of elasticity in bending, compression strength parallel to grain, and Brinell hardness. Physical properties were determined by weight loss, density, and volumetric swelling tests. The results showed that the heat treatment increased the weight loss, density loss and dimensional stabilization. In addition, an increase was observed for compression strength parallel to grain (except for at 200°C for 5 h), while a small increase was determined in the bending strength, modulus of elasticity in bending, hardness values of heat-treated wood samples at 150°C for 1 and 3 h. However, the heat treatment at higher temperature and duration clearly decreased bending strength, modulus of elasticity in bending,and hardness.

Analysis of intensity of changes in the moisture content of wood chips in the production of wood polymer composites during drying and storage processes

The article presents the results of research on changes in humidity of wood chips intended for the of wood-polymer composites (WPC) manufacture. In the studies were used wood chips of various origin (coniferous and deciduous wood) and the various forms (from dust-meal, through small chips on big chips). Measured moisture content of chips during drying in the dryer and after that, during the natural return to hygroscopic equilibrium with the atmosphere of the storage space. After drying, the samples were stored in open and closed containers.

Producing process for veneer decorative straw particleboards

Technical parameters in different steps of birch (Betula alnoides Buch.-Ham. ex D. Don) veneered decorative straw particleboards producing process including moisture content adjustment, sanding, hot-pressing and conversation to improve the surface warp was discussed in this study. The results showed that it took at least 24 h to adjust the stable moisture content between 8 and 10 % in environment of 30ºC and 40 % relative humidity (RH). Surface warp decreased with the increase of sand thickness till 0.8 mm which indicated the complete remove of hardening layer. Modified “PVAc+GB-3+flour” bonded boards had better surface bonding strength than PVAc with a best hot-pressing parameter: unit pressure 0.7 MPa, temperature 90ºC and hot pressing time 180 s. In addition, surface warp of hot-pressed veneer decorative straw particleboards stabled when conserved for 24 h sealed with plastic films. Enterprise large scale production according to this technical process proved to decrease the surface warp from 1.05±0.3 % (normal process with sanding thickness of 0.3 mm) to 0.84±0.2 %.

The influence of chosen factors of a circular saw blade on the noise level in the process of cross cutting wood

Research was focused on evaluation of a circular saw blade tooth spacing on maximum equivalent noise level LAeq in the process of cross cutting wood. There were used circular saw blades with uniform tooth spacing and a full body and non-uniform tooth spacing with dilatation gaps. The measurements were done on the measuring device which was designed at the Department of Environmental and Forest Technology where it has been modernised. For research, testing samples of three wood species i.e. spruce (Picea abies), pine (Pinus sylvestris) and beech (Fagus sylvatica) were used. In the cutting process, two feeding speeds were set up with the same revolutions of circular saw blades and for more precise statistical significance; every measurement was repeated several times. At the research, there was found out that the circular saw blade with uniform tooth spacing has lower equivalent noise level at smaller feeding speed and cutting soft wood species. The circular saw blade with non-uniform tooth spacing has lower equivalent noise level at higher feeding speed.

Factors influencing the mechanical stability of wood pellets

One possible way to use waste materials in the wood industry (chip, dust, smaller pieces) is to transform them into pellets. Pellet making requires, however, additional energy which should be as low as possible. Present work examines the possible origins of binding forces and experimental evidences show that also the presence of water on particle surfaces plays a definite role. It also turned out that the water potential curve of timber materials can successfully be used to estimate the relation of compaction pressure to the water tension of the material.

Strength of corner and middle joints of upholstered furniture frames constructed with black locust and beech wood

Great interest is attracted lately in the utilization of Black locust (Robinia pseudoacacia L.) timber large quantities that are expected to be harvested and enter the market next years, since this species was included in the proposed and financed species for cultivation by the European Union. This study was carried out to evaluate the strength of the two most frequent joints in the upholstered furniture frames, constructed with black locust, using also beech wood (Fagus sylvatica L.) for comparative reason. In the specific research, the joints of mortise and tenon and double dowel were selected to be used and were constructed both in corner and middle joints, using two adhesives (PVAc and PUR). Bending moment capacity of the joint specimens was investigated, as well as the coefficient of elasticity of each joint.

Optical measurements of sawdust dimensions

This article deals with optical measuring of sawdust dimensions by IP camera. Optical methods of sawdust dimensions measurement are relatively extended and offer more information about measurement sample than other methods. By descripted method it is possible to specify dimensions, perimeter, area of each particle, as well as eccentricity, centroid position, segmentation of edges and other. Using IP cameras to obtain the image with samples it is possible to measure sawdust, e. g. at the manufacturing, and to evaluate the results at another location (laboratory). This eliminates need to carry a measuring system to measuring location. Compared to other methods (e. g. sieve method), descripted method is repeatable because the samples are not mechanical damaged and crumbed by jolting through the sieves.