Scielo RSS <![CDATA[Maderas. Ciencia y tecnología]]> vol. num. AHEAD lang. es <![CDATA[SciELO Logo]]> <![CDATA[Nondestructive testing used on timber in Spain: A literature review]]> Abstract: Nondestructive testing (NDT) includes several highly efficient techniques for the estimation of the physical and mechanical properties of structural timber. Apart from visual grading, scientific research using Nondestructive testing on timber has been used in Spain since the 1990s. Nondestructive testing can be used for two different purposes: timber grading and the assessment of existing timber structures. The most common devices used in Spain are portable ones based on ultrasound, stress waves, vibration and probing techniques. Many statistical linear models for estimating the mechanical properties of new sawn timber and timber from existing structures have been proposed. Furthermore, several factors that affect Nondestructive testing measurements have been studied (moisture content, temperature, specimen dimensions, sensors position-grain angle, among others) and adjustment factors have also been proposed. Species have been characterized for visual grading standards from the 1980s to date. The large number of research works using different species, devices and procedures shows the need of homogenization and standardization of Nondestructive testing use. This paper presents a review of research works using Nondestructive testing on timber in Spain, in order to add to knowledge, elucidate the concepts to unify Nondestructive testing used and promote research group collaboration in the near future. <![CDATA[Thermochemical behavior of <em>Eucalyptus grandis</em> wood exposed to termite attack]]> Abstract: This study aimed to evaluate the variations in thermal and chemical characteristics of juvenile Eucalyptus grandis wood submitted to a deterioration test by Nasutitermes termites. For this purpose, a biodeterioration test with termites was conducted according to ASTM D 3345 (2008), in which, after the end of the period corresponding to the test (40 days), we evaluated the mass loss, chemical composition and thermal stability of the main components of the deteriorated wood samples and those belonging to the control group. We found that deterioration due to exposure of the samples to Nasutitermes sp. termites caused a mass loss of 66,88% for wood with a density at 12% moisture content of 412 kg/m3. The quantitative chemical composition showed a reduction in the contents of cellulose, hemicellulose and lignin. Analysis of the variations of the organic functional groups related to the chemical composition of the wood by Fourier Transform Infrared Spectroscopy and relative intensity of the spectral bands also showed reductions, demonstrating homogeneous deterioration of the main components of the deteriorated woods. The thermal stability showed an increase in deteriorated wood for most of the temperature ranges, mainly for those that corresponded to losses in moisture and volatiles (25 °C - 100 °C), hemicelluloses (240 °C - 300 °C), celluloses, and together with initial lignin degradation (310 °C to 400 °C), possibly due to the removal of cellulose and hemicellulose, as well as the deposition of substances expelled by the termites in the cell wall. From the results, we conclude that the termites do not have specificity regarding the chemical component and that the deterioration caused variations in the chemical composition of the wood, whereas the opposite was observed for thermal stability, which presented an increase in most of the temperatures ranges for the deteriorated woods compared to the control group. <![CDATA[Failure under stress of grapevine wood: The effects of the cerambycid <em>Xylotrechus arvicola</em> on the biomechanics properties of <em>Vitis vinifera</em>]]> Abstract: Xylotrechus arvicola is an insect pest on Vitis vinifera in the main wine-producing regions of Spain. X. arvicola larvae bore inside grapevine wood, which cause structural damages in the plants´ biomechanical properties. Grapevine wood affected and unaffected by larvae, were collected from vineyards. Compression and flexural tests were used to quantify biomechanical wood properties. Affected wood broke more quickly and endured a lower supported force than unaffected wood in both varieties and moisture states. Tempranillo was the most resistant variety on trunks, while Cabernet-Sauvignon was the most resistant variety on branches, where all infested varieties showed a lower rate of bending. Grapevine wood affected by X. arvicola larvae shows an important decrease in its resistance in both moisture states - dry and wet wood - and it is observed due to the faster break in time and a lower supported force. These damages give the affected wood greater sensitivity to external mechanical factors in the vineyards, such as strong winds, harvest weight and the vibration exerted by harvesting machines. The aspect of stress-time curves in all cases follow similar patterns, so in future studies might be possible to stablish relationships between both wet and dry samples and different infestation levels. <![CDATA[Possibility of using lichen and mistletoe extracts as potential natural wood preservative]]> Abstract: Increasing environmental pressures on toxic chemical wood preservatives lead to the development of natural and environmentally friendly wood preservatives. In this study, using possibilities of lichen (Usnea filipendula) and leaves of mistletoe (Viscum album) as potential natural wood preservative were researched. Impregnation procedure was applied at four different concentration levels and with two different extraction methods (hot water and methanol). The concentration levels were arranged as 3%, 5%, 10%, 15% for hot water and as 3,75%; 6,25%; 12,5%; 18,75% for methanol. The treatment procedure has been applied according to the ASTM D-1413 (1988) standard test method. The fungal decay test has been done according to the EN 113 (1996) standard test method using a brown rot fungus, Coniophora puteana for both treated test and untreated control samples. The best results were obtained at the highest concentration level of the solutions. However, the weight losses in treated test specimen have not met the standard requirements. Nevertheless, it can be assumed that both natural extracts provide promising protection performance. <![CDATA[Use of nearest neighbors (k-NN) algorithm in tool condition identification in the case of drilling in melamine faced particleboard]]> Abstract: The purpose of this study was to develop an automatic indirect (non-invasive) system to identify the condition of drill bits on the basis of the measurement of feed force, cutting torque, jig vibrations, acoustic emission and noise which were all generated during machining. The k-nearest neighbors algorithm classifier (k-NN) was used. All data analyses were carried out in MATLAB (MathWorks - USA) environment. It was assumed that the most simple (but sufficiently effective in practice) tool condition identification system should be able to recognize (in an automatic way) three different states of the tool, which were conventionally defined as “Green” (tool can still be used), “Red” (tool change is necessary) and “Yellow” (intermediate, warning state). The overall accuracy of classification was 76 % what can be considered a satisfactory result at this stage of studies.