Papers by Vlastimil Borůvka
BioResources
Joints are used to join furniture parts, and they represent a critical part of the structure of f... more Joints are used to join furniture parts, and they represent a critical part of the structure of furniture. The quality of joints is greatly affected by the accuracy of their execution. When designing furniture, it is important to carefully consider the type of joint used so that it can hold all the joined elements together. Under loading of the joined structures, internal forces develop, which can lead to failure of the joints. This study investigated the elastic stiffness of spruce (Picea abies L.) dowel joints. The effects of selected factors such as the type of loading (compressive versus tensile), the size of the dowels (one-half versus one-third of the thickness of the joined elements), the type of adhesive used (polyvinyl acetate versus polyurethane), and annual ring deflection were examined. Spruce dowel joints exhibited the highest elastic stiffness values with a higher-diameter dowel glued with PUR adhesives and subjected to compressive loading. The impact of annual rings w...
BioResources
When designing wooden structures and furniture, it is very important to consider joints that allo... more When designing wooden structures and furniture, it is very important to consider joints that allow the structure to stay together and upright. There are many different types of wood joints. The selection of a joint type and its properties are some of the most important design choices. This article was dedicated to the Domino joint, which allows for strong joints. The Domino joiner is a loose tenon and mortise manufacturing joining tool. This article discusses the effect of selected parameters, such as the type of stress (tensile and compressive), size of the Domino joiner (one-half and one-third thickness), wood species (beech (Fagus sylvatica L.) and spruce (Picea abies L.)), and adhesive type (polyvinyl acetate and polyurethane), on the joint stiffness. The influence of the annual rings was also monitored.
Industrial Crops and Products
Forests, 2021
This paper deals with the effect of heat treatment on the selected physical properties of birch w... more This paper deals with the effect of heat treatment on the selected physical properties of birch wood. Five stages of heat treatment were used, ranging from 160 °C to 200 °C, in 10 °C increments, having a peak treatment duration of 3 h for each level. Primarily, changes in thermal characteristics, namely conductivity, diffusivity, effusivity, volume heat capacity, changes in colour and gloss parameters, mass loss due to modification and different moisture content in wood under given equilibrium climatic conditions, were monitored. The ISOMET 2114 analyser was used to measure the thermal characteristics. The measurement principle of this analyser is based on the analysis of the thermal response of the analysed material to pulses of heat flow. Measurements of colour, gloss, density and moisture content were carried out according to harmonised EN standards. The aim was to experimentally verify the more or less generally known more positive perception of heat-treated wood, both by touch ...
Bioresources, May 25, 2018
Furniture must be designed to suit the intended use. Producers need to guarantee its quality and ... more Furniture must be designed to suit the intended use. Producers need to guarantee its quality and stiffness. During external loading, there are internal forces that can be transmitted and may result in a failure. This article examines the dowel joint, which is one of the most popular furniture joints. It discusses the effects of selected parameters, such as type of loading (tension and pressure), the size of the dowel (one-half or one-third of the joined parts), wood species [beech (Fagus sylvatica L.) and spruce (Picea abies L.)], and the adhesives type (polyvinyl acetate and polyurethane), on the joint stiffness. The effect of the annual rings was also monitored; however it was not determined as significant. Based on the results, the dowel joint is recommended with greater diameters and while using PVAc gluing. Article also deals with test simulation in virtual environment using the programme Solidworks.
WOOD RESEARCH 66(3) 2021, 2021
The article presents the results of a marketing survey in the area of customer preferences in the... more The article presents the results of a marketing survey in the area of customer preferences in the case of different degrees of heat-treated solid wood and birch veneer. Part of the marketing survey was a questionnaire survey, where the respondents, as potential customers, expressed their preferences for individual samples which, at first glance, differed in colour due to the different degrees of heat treatment. The result of the research is a clear preference for the heat-treated samples compared to the reference sample without heat treatment. A more detailed secondary analysis of the data from the questionnaire survey was performed with regard to the gender, age and education of the respondents. Here, too, it is possible to conclude a clear preference for heat-treated samples for these groups of respondents. The article also analyses the possibilities of the marketing strategy with a focus on marketing communication, especially in relation to wood processors and producers.
Trees, 2021
Regeneration method effects within-stem variability of mechanical wood properties but has no impa... more Regeneration method effects within-stem variability of mechanical wood properties but has no impact on overall quality of Scots pine logs. In Central Europe, group shelterwood regeneration method relying on natural regeneration is generally considered as an approach that meets the criteria of close-to-nature silviculture. We tested its effect on wood properties in contrast to the clearcutting method with subsequent artificial regeneration by planting in the case of Scots pine (Pinus sylvestris L.). Four localities were chosen in the Czech Republic, where both regeneration methods were applied. Sample trees were felled and subsequently evaluated for the impact of the applied regeneration method on wood properties. Modulus of elasticity, bending strength and wood density were used as indicators of wood quality. The impact of the regeneration method on the examined characteristics of the wood was not statistically significant, 78 MPa (megapascal) for shelterwood and 75 MPa for clearcutting method in the case of bending strength, and they are of negligible importance in terms of influencing end-product potential. Much more significant was the impact of the applied regeneration method on the distribution of the properties along trunk radius, where the shelterwood method provides even distribution. Non-destructive methods turned out to be useful tools for elastic properties estimation of wood as the close correlation to modulus of elasticity was confirmed (r = 0.66 and r = 0.82 for shelterwood and clearcutting method, respectively).
Annals of Warsaw University of Life Sciences - SGGW. Forestry and Wood Technology, 2015
The Strength Determination of Corner joints used for Wooden Windows. The work is aimed at the met... more The Strength Determination of Corner joints used for Wooden Windows. The work is aimed at the methodical procedure assessment of rectangular corner joints applied on window casement and its strength. Mechanical properties of testing samples are further evaluated by universal testing machine. For this reason a component necessary for fixing corner joints has been designed. The testing samples are loaded by bending moment with tensile and compressive forces. The values obtained in testing are further used in final equations for calculating the values of joint stiffness and bending moment capacity of which will help to decide which joint is preferable for construction applications.
This study deals with the impact of silicon-based chemicals on selected physical and mechanical p... more This study deals with the impact of silicon-based chemicals on selected physical and mechanical properties of wood. Wood of European beech and Scots pine was the testing material used for impregnation using water glass and commercial product Lukofob EVO 50. The impact of the treatment on dimensional stability, bending strength and modulus of elasticity was tested. Wood density was also evaluated. Although the modification using silicon-based staffs resulted in a statistically significant decrease in swelling for both of the tested species, the positive effect of the treatment was accompanied by a decrease in the strength and stiffness of wood. Water glass had a stronger effect on the tested properties from the chemicals we used in our research.
Polymers, 2021
In the future, we can expect increased requirements to the health and ecological integrity of bio... more In the future, we can expect increased requirements to the health and ecological integrity of biocides used for the protection of wood against bio-attacks, and it is therefore necessary to search for and thoroughly test new active substances. Caffeine has been shown to have biocidal efficacy against wood-destroying fungi, moulds and insects. The aim of the research was to determine whether the effectiveness of caffeine, as a fungicide of natural origin, is affected by a different type of treated wood. Norway spruce mature wood (Picea abies), Scots pine sapwood (Pinus sylvestris), and European beech wood (Fagus sylvatica) were tested in this work. The samples were treated using long-term dipping technology or coating (according to EN 152:2012) and then tested against selected wood-destroying brown rot fungi according to the standard EN 839:2015, wood-staining fungi according to EN 152:2012, and against mould growth according to EN 15457:2015. The penetration of caffeine solution into...
Journal of Cleaner Production, 2021
The aim of this study was to test caffeine e harmless to health and eco-friendly natural compound... more The aim of this study was to test caffeine e harmless to health and eco-friendly natural compound e as a potentially effective fungicide and insecticide for wood protection. Caffeine treatment of wood, using simple and cheap long-term dipping technology, was tested against the brown-rot fungus Rhodonia placenta and termite Reticulitermes flavipes. Fungi and insects can cause severe loss of functionality of wooden structures. The current search for of nature-friendly products is understandable in the context of the changing world environment. The experiment with caffeine-treated refractory Norway spruce (Picea abies) wood lasted for 16 weeks against the rot attack according to EN 113, and for 6 weeks against the termite attack according to EN 118. Mass losses of caffeine treated wood samples without ageing, caused by R. placenta and R. flavipes were small, only 1.4% or 0.5%, respectively. Results clearly suggested that caffeine is an alternative to commercial biocides, e.g., to the reference in wood well fixable Bochemit QB, containing boric acid and alkylbenzyldimethylammonium chloride. Caffeine was sensitive for leaching out from wood by water even in the presence of an additional hydrophobic protective layer. Based on the achieved results it is possible to recommend caffeine treatment as an environmentally friendly alternative for wood protection, but only in the interior or outdoor under roof area against termite attack and also against brown-rot fungi. Treatment with caffeine had no negative impact on the compression strength and colour of the spruce wood, while it improved surface wetting important for potentially follow-up coating or adhesive applications.
BioResources, 2017
The effects of selected factors, wood species (Fagus sylvatica L. and Picea abies L.), type of jo... more The effects of selected factors, wood species (Fagus sylvatica L. and Picea abies L.), type of joint (haunched mortise and tenon, and haunched dovetail mortise and tenon), tenon thickness (one-third and half-joint thickness), type of adhesive (polyvinyl acetate and polyurethane adhesive), loading type (compressive and tensile), and direction of the annual rings were evaluated relative to the elastic stiffness. The testing samples were loaded by bending moment with tensile and compressive forces in the angular plane. The wood species, type of joint, tenon dimension, and type of adhesive all had a statistically significant effect on the elastic stiffness. However, the interaction of those factors was statistically insignificant. The loading type and direction of the annual rings did not have a significant effect on the elastic stiffness. For spruce, the use of mortise and tenon with a toothed feather (MTTF) was found to be disadvantageous, whereas the use of a toothed feather was favo...
Journal of Forest Science, 2017
After spruce, the Scots pine (Pinus sylvestris Linnaeus) is the second most important commercial ... more After spruce, the Scots pine (Pinus sylvestris Linnaeus) is the second most important commercial coniferous tree species in the Czech Republic. However, we are finding out that awareness of the variability of properties, and possibilities to affect them, are noticeably small for this type of tree species in our conditions. The goal of this study is to primarily evaluate the importance of site conditions, silvicultural measures and other factors for the density of Scots pine wood in the Doksy locality in the Czech Republic. The Doksy locality is represented by three forest stands with different silvicultural history. Samples were taken from each stand, the basal and central parts of which were subsequently processed for test samples with dimensions of 20 × 20 × 30 mm. Wood density at 12% moisture content was ascertained in the test samples. The highest density value of 0.541 g·cm–3 was reached in a stand that is regenerated using the shelterwood method with long regeneration period, ...
Forests, 2020
This paper should primarily lead to a targeted expansion of the database dealing with bending cha... more This paper should primarily lead to a targeted expansion of the database dealing with bending characteristics, and thus help to understand the static and dynamic bending strength depending on the direction of external forces. Wood is very often used in the structural elements of buildings and wood products (e.g., furniture), in which there is both a static load, and in many cases a dynamic load, whilst the direction of loading is usually not considered. Specifically, the paper focuses on determining the bending strength and impact strength of seven economically-important wood species in the Czech Republic. The research includes not only the above-mentioned strength characteristics, but also the elastic characteristics, i.e., the static modulus of elasticity, and the dynamic modules of elasticity determined using the ultrasound and resonance methods. The procedure was methodologically in accordance with the valid harmonized standards or the usual methodological regulations. The most ...
Forests, 2020
With the gradual decline in the proportion of spruce as the most important tree species in the Cz... more With the gradual decline in the proportion of spruce as the most important tree species in the Czech Republic, the importance of pine will increase. The test material for this study was selected from two localities with important representation of pure Scots pine stands. Two stands, representing clear-cutting and shelterwood regeneration methods were selected from each locality. In the case of shelterwood method, tree samples from a lower layer were cut down and subsequently evaluated in terms of the impact of the regeneration method on the density of the wood, the density of earlywood and latewood, the proportion of latewood and the width of the annual rings. These qualitative parameters of the wood were compared before and after the release of the parent stand canopy. The clear-cutting regeneration method served as a reference. The values obtained before the release of the parent stand canopy are significantly different from values after its removal (share of latewood 47.7% and 48...
Journal of Forest Science, 2018
The Scots pine (Pinus sylvestris Linnaeus) is one of the most important commercial tree species i... more The Scots pine (Pinus sylvestris Linnaeus) is one of the most important commercial tree species in Central Europe, yet we know very little about the variability of its wood properties. The aim of this study is to primarily analyse the impact of different tree growth rates and site characteristics on the shrinkage of Scots pine wood. The investigated forest stands are located at two sites of the Czech Republic that are characteristic for Scots pine silviculture. At each site, sample trees were selected from two stands representing two variants of the silvicultural treatment, i.e. a clear-cutting and shelterwood system with long regeneration period. Wood shrinkage in radial and tangential directions and volumetric shrinkage were determined in accordance with Czech standards. Lower values of shrinkage were found out in forest stands regenerated by the shelterwood method. The wood in the central part of the trunk shows lower shrinkage values than in the basal part in both stands. The un...
Forests, 2019
This work deals with the quality of birch (Betula pendula) wood from different sites and the impa... more This work deals with the quality of birch (Betula pendula) wood from different sites and the impact of heat treatment on it. Two degrees of heat treatment were used, 170 °C and 190 °C. The resulting property values were compared with reference to untreated wood samples. These values were wood density, compressive strength, modulus of elasticity (MOE), bending strength (MOR), impact bending strength (toughness), hardness, swelling, limit of hygroscopicity, moisture content and color change. It was supposed that an increase in heat-treatment temperature could reduce strength properties and, adversely, lead to better shape and dimensional stability, which was confirmed by experiments. It was also shown that the properties of the wood before treatment affected their condition after heat treatment, and that the characteristic values and variability of birch properties from 4 sites, 8 stems totally, were reflected in the properties of the heat-treated wood. Values of static MOR were the e...
Forests, 2017
This study compares the quality of wood from two distinct sites in the Czech Republic—from former... more This study compares the quality of wood from two distinct sites in the Czech Republic—from former afforested agricultural land and forest land. We compared the properties of Norway spruce wood (Picea abies Karst.) and Scots pine wood (Pinus sylvestris L.), the most important domestic tree species, to Douglas fir (Pseudotsuga menziesii (Mirbel) Franco), a North American tree species and a potential substitute for the domestic spruce. Wood density, modulus of elasticity (MOE), modulus of rupture (MOR) and impact bending strength were the properties tested that were used for comparing tree species. Without taking into consideration the site, the highest density values from the tested tree species were obtained for Douglas fir (0.568 g·cm−3), followed by the pine (0.508 g·cm−3) and the spruce (0.463 g·cm−3). The Douglas fir also dominated in the remaining assessed properties, whilst the influence of site was not confirmed, with the exception of MOE and MOR, and only for the Douglas fir ...
Forests, 2018
This paper deals with the impact of heat treatment on the elastic and strength properties of two ... more This paper deals with the impact of heat treatment on the elastic and strength properties of two diffuse porous hardwoods, namely Fagus sylvatica and Betula pendula. Two degrees of the heat treatment were used at temperatures of 165 • C and 210 • C. The dynamic and static elasticity modulus, bending strength, impact toughness, hardness, and density were tested. It is already known that an increase in treatment temperature decreases the mechanical properties and, on the other hand, leads to a better shape and dimensional stability. Higher temperatures of the heat treatment correlated with lower elastic and strength properties. In the case of higher temperature treatments, the decline of tested properties was noticeable as a result of serious changes in the chemical composition of wood. It was confirmed that at higher temperature stages of treatment, there was a more pronounced decrease in beech properties compared to those of the birch, which was the most evident in their bending strength and hardness. Our research confirmed that there is no reason to consider birch wood to be of a lesser quality, although it is regarded by foresters as an inferior tree species. After the heat treatment, the wood properties are almost the same as in the case of beech wood.
BioResources, 2016
The effect of thermal treatment temperatures on the dynamic and static modulus of elasticity (MOE... more The effect of thermal treatment temperatures on the dynamic and static modulus of elasticity (MOE) of Norway spruce wood (Picea abies (L.) H. Karst.) was evaluated. The dynamic MOE was measured using ultrasound and resonance methods in the longitudinal and transverse directions. The static MOE was determined by the three-point bending test. The dynamic MOE values determined by the ultrasound method were higher than the static MOE values in each case. As the temperature of the thermal treatment increased, the difference between the dynamic and static MOE values decreased. The MOE increased with increasing temperature, and it was more pronounced on a tangential surface. Increasing the sensor distance had a positive effect on the correlation between the static and dynamic MOE, and the effect from the increased temperature decreased. Measurement by the resonance method showed twice as high MOE values in the transverse direction than in the longitudinal direction. The thermal treatment caused a significant decrease in the MOE only in the transverse direction, and the differences were insignificant in the longitudinal direction. The dynamic MOE values measured by the resonance method were higher than the static MOE values but slightly lower than the values measured by the ultrasound method.
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Papers by Vlastimil Borůvka