Roundwood pre-grading with longitudinal acoustic waves for production of structural boards

The assessment of timber quality at any stage of the production chain promises to be an advantage for the forest and timber industry. This paper presents results of wood pre-grading by means of the dynamic modulus of elasticity, which was performed along the complete processing chain—from standing trees to sawn timber. The measurements were conducted on 154 forty-year-old trees of Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) from two forest experimental stands in Southern Germany. Long logs of about 13 m were bucked into short logs of 4.1 m; the dataset contained 1,820 boards cut out of 332 short logs. Pre-grading was performed at different levels: standing tree, long log, and short log. The boards were machine strength graded by a ViSCAN-COMPACT grading machine. The investigation showed high correlations between different stages in the production chain of timber. For strength classes C24 and C30 an increase in yield of about 10 percentage points by rejecting the 25 % worst logs (short or long) was observed. It did not matter if pre-grading was realized at the stage of long logs or short logs. However, methods of pre-grading at standing tree must be improved to obtain reliable prediction of dry sawn timber quality of managed forest stands (r² = 0.17).     

Estimating mechanical properties of clear wood from ten‐year‐old Melia azedarach trees using the stress wave method

The objective of this study was to examine the potential of stress wave velocity (SWV) as a rapid and non-destructive method to estimate the mechanical properties of Melia azedarach wood. The SWV, dynamic modulus of elasticity (MOE_d), modulus of elasticity (MOE), modulus of rupture (MOR, bending strength) and density were determined on ninety 20 ? 20 ? 320 mm clear wood specimens, obtained from stems of three ten-year-old M. azedarach trees, and tested at environmental equilibrium in 20°C, 60?% relative humidity (a moisture content of approximately 12?%). There was a statistically significant (0.1?% level) but weak correlation (R²?=?0.23) between the SWV and MOE, but no statistically significant correlation was found between the SWV and MOR. Much better results for prediction of static properties of M. azedarach wood were obtained when SWV and wood density (WD) were used together through calculation of MOE_d in the air-dry condition (MOE: R²?=?0.76, MOR: R²?=?0.47), although in the case of MOR a model based on WD alone is slightly better (R²?=?0.58), and WD is also almost as good as MOE_d for predicting MOE. It is concluded that SWV coupled with WD can be employed as a predicting parameter to evaluate the mechanical properties of M. azedarach wood during the manufacturing process, although WD alone is also effective. The SWV alone would not be useful due to MOE being almost directly proportional to WD at this moisture content.

     

Radially sawn timber—the Primwood Method for improved properties

A new manufacturing system, the PrimWood Method, has been proposed to improve the utilization of wood. A basic concept within this method is the sawing pattern called star-sawing, which produces timber with both rectangular and triangular cross sections. This method facilitates an efficient production of radially sawn timber with vertical annual rings, without juvenile wood. The sawn timber produced in the PrimWood Method is used to produce high quality, knot-free solid wood panels with vertical annual rings. In this process, part of the timber is finger-jointed to form knot-free lengths which are glued together into a block. This block can then be divided according to thickness into thinner panels with vertical annual rings. The PrimWood Method has been tested in an industrial plant. The manufacturing system was designed for a sawing capacity of about 30,000 m³ logs, which corresponds to 16,800 m³ of star-sawn timber per shift per annum. The production of solid wood panel was then designed to give a volume of 5,800 m³ per annum.     

Predicting the bending properties of air dried and modified <Emphasis Type="Italic">Populus tremula</Emphasis> L. wood using combined air-coupled ultrasound and electrical impedance spectroscopy

Air-coupled ultrasound and electrical impedance spectroscopy are non-destructive measurement methods, which can be used, for example for quality assessment of sawn timber. Both methods may be used in through-transmission and one-sided reflection mode to measure internal properties and detect defects in wood materials. The ultrasound method is based on mechanical waves and is mainly affected by the mechanical properties of wood. Density affects both methods, and the electrical impedance method is especially affected by moisture content and the chemical properties of wood. In this study, the relations between the methods and the bending properties of air dried and modified aspen (Populus tremula L.) specimens were examined. The modification method was a combination of compression and thermal modification. According to the study, electrical impedance spectroscopy combined with air-coupled ultrasound measured across the grain is a potential non-destructive technique for the strength estimation of aspen wood.     

Correspondences between manually estimated compression wood in Norway spruce and the warp of the sawn timber

Picea abies L.) and the warping of the sawn timber in terms of bow, spring and twist as well as further deformation after ripping of the dried products. The amount of compression wood was defined and measured on logs according to the methods of the Swedish Timber Measurement Council (Regulations for measuring of round wood) and on the sawn timber according to the Nordic Timber. The impact of two different drying schedules was also investigated. The study shows that visible compression wood in both the butt end of the log and within the sawn timber was a rather poor indicator of the warp of the dried sawn timber. In no comparison did the correlation coefficient, r, exceed 0.3. In contrast to this, the correlation between the amount of compression wood and the warp of secondary products was fair, r = 0.79. This means that it should be possible to identify sawn timber less suitable for secondary processing by the amount of compression wood. The corresponding correlation between compression wood in the butt end of the log and the warp of the secondary products was r = 0.46. No significant differences could be shown in the degree of warp, as related to compression wood, between sawn timber or secondary products, dried at a wet-bulb temperature of 55 °C/117 h, LT-schedule, and a dry-bulb temperature of 110 °C/24 h, HT-schedule, respectively.

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r  = 0,79). Es sollte also m?glich sein, weniger geeignete Schnittware anhand ihres Druckholzanteils auszusortieren. Die Korrelation zwischen Druckholzanteil am Stammende und der Verwerfung im Schnittholz betrug 0,46. Für das Ausma? der Verformungen wurde kein signifikanter Unterschied zwischen den beiden Tocknungsbedingungen (55 °C/117 h und 110 °C/24 h) gefunden.

     

Verfahren der zerstörungsfreien Holzprufung — Entwicklungstendenzen in Nordamerika and Folgerungen für die Anwendung in Mitteleuropa —

In the field of research as well as in industries the non-destructive evaluation of wood is of growing importance in Northern America, because: 1. Compared with the traditional timber ressource from old stands, logs from plantations and second-growth stands show a bigger variety of wood quality and sometimes even a lower wood quality. 2. New timber engineering technologies and new composites need a homogeneous, well defined wood quality. 3. Methods and practical solutions in the field of non-destructive testing have significantly improved within the last years. In this paper, the stand of the art and the recent developments in the fields of optical, mechanical and electrical non-destructive testing methods for Canada and the United States are described, and the possibility of their application under central european conditions are discussed. Part 11 of this publication will deal with non-destructive acoustic     

Der Import tropischer Hölzer in die Bundesrepublik Deutschland

The import of tropical round logs into the Federal Republic of Germany has decreased by about 2/3, within the last 20 years. However, the import of sawn tropical timber, as well as veneer and plywood increased in the same period. But, generally, a continuous reduction of the tropical wood consumption in our country must be stated. The main reason for that may be found in the reduced volume of house building. This results in a lower consumption of furniture and therefore also the furniture production has reduced by about 1/3 within the last 10 years. Africa was and still is the main shipper for round logs, whereas sawn timber is supplied by Southeast-Asia. There is however a continuous change with respect to the importance of the volume of tropical woods, which are shipped from overseas countries. Style and fashion influence the wood species imported. Regarding the demand of tropical wood, our sawmills nowadays show greater consumption figures than veneer and plywood manufacturing industries.     

Evaluation of density and strength of Norway spruce wood by near infrared reflectance spectroscopy

The non-destructive evaluation of wood properties by Near Infrared Reflectance Spectroscopy (NIR) has been assessed. The surfaces of specimens of clear wood (Picea abies) were NIR-scanned, and the results compared to such properties as moisture content, density, compression strength and chemical and biological degradation. In addition, the NIR-scans of clear wood specimens were compared to the bending strength of the structural timber from which it had been cut. The NIR dependency of surface roughness was investigated and found to be of minor importance. NIR calibrations for moisture content (MC<30%), density, compression strength and chemical degradation proved that the NIR technique is an excellent non-destructive method (r ²≧0.9; independent test set). Even biological degradation was determined with a most promising accuracy (r ²=0.75; independent test set). For the prediction of the bending strength of timber NIR proved less efficient. However, NIR still contributed to timber strength prediction at the same level as annual ring width, the parameter which is presently visually assessed by timber graders. It is concluded that the NIR method is very versatile in the non-destructive evaluation of wood. The results merit further investigations in order to develop proper models and instrumentation for commercial use.     

Radially sawn timber—the Primwood Method for improved properties

A new manufacturing system, the PrimWood Method, has been proposed to improve the utilization of wood. A basic concept within this method is the sawing pattern called star-sawing, which produces timber with both rectangular and triangular cross sections. This method facilitates an efficient production of radially sawn timber with vertical annual rings, without juvenile wood. The sawn timber produced in the PrimWood Method is used to produce high quality, knot-free solid wood panels with vertical annual rings. In this process, part of the timber is finger-jointed to form knot-free lengths which are glued together into a block. This block can then be divided according to thickness into thinner panels with vertical annual rings. The PrimWood Method has been tested in an industrial plant. The manufacturing system was designed for a sawing capacity of about 30,000 m³ logs, which corresponds to 16,800 m³ of star-sawn timber per shift per annum. The production of solid wood panel was then designed to give a volume of 5,800 m³ per annum.

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Radial gesägtes Holz—Die Primwood Methode zur Verbesserung seiner Eigenschaften

Zusammenfassung In der vorliegenden Arbeit wird ein neues Verarbeitungsverfahren, die sogenannte Primwood Methode, zur Verbesserung der Holznutzung vorgestellt. Ein grundlegendes Konzept dieses Verfahrens ist das Einschnittmuster, genannt Sternsägen, welches Nutzholz mit rechteckigen und dreieckigen Querschnitten liefert. Diese Methode erleichtert eine wirtschaftlich effiziente Herstellung von radial geschnittenem Nutzholz mit stehenden Jahresringen ohne Juvenilholz. Das auf diese Weise hergestellte Schnittholz wird verwendet, um astfreie, qualitativ hochwertige Vollholzplatten mit stehenden Jahresringen zu produzieren. Darüberhinaus werden diese Platten mit Keilzinkung versehen, um astfreie Abschnitte zu bilden, welche zu einem Block verleimt werden. Dieser kann dann der gewünschten Dicke entsprechend in dünnere Platten mit stehenden Jahresringen aufgeteilt werden. Die Primwoodmethode wurde im industriellen Maßstab geprüft. Der Betrieb war für eine Kapazität von ungefähr 30.000 m³ Roh- Rundholz ausgelegt, was ungefähr 16.800 m³ sterngesägtem Schnittholz pro Schicht und Jahr entspricht. Anschließend wurde die Produktion von Vollholzplatten auf ein Volumen von 5.800 m³ pro Jahr eingerichtet

     

Non-Destructive Estimation of Mechanical and Chemical Properties of Persimmons by Ultrasonic Spectroscopy

Fruit properties, including ripeness, are still being measured destructively in most countries. Recently, an increased attention has been given to non-destructive methods, such as ultrasonic techniques, for quality assessment of food commodities. The aim of this study was to evaluate the feasibility of ultrasonic spectroscopy to monitor the changes of mechanical properties (rupture force and modulus of elasticity) and chemical properties (soluble solids content) in two cultivars of persimmons (Karaj and Shomali) during 3 weeks of storage. Samples’ ultrasonic properties such as ultrasonic velocity and attenuation coefficient were analyzed with transducers, and their textural properties were obtained using destructive compression test and their refractometric properties were measured from its fresh-squeezed juice in laboratory. Mechanical and chemical properties were statistically modeled from ultrasonic parameters. The results showed that our proposed model could predict persimmons’ mechanical and chemical properties well, i.e., rupture force (R² = 0.893/0.837; RMSE = 3.683/3.849 for Shomali and Karaj cultivars, respectively), modulus of elasticity (R² = 0.826/0.861; RMSE = 0.231/0.217 for Shomali and Karaj cultivars, respectively) and soluble solids content (R² = 0.931/0.987; RMSE = 0.519/0.851 for Shomali and Karaj cultivars, respectively).     

Rahmenbedingungen,Entwicklungsmöglichkeiten und Zukunftserwartungen in der Holzwirtschaft aus der Sicht der Sägeindustrie

Sawmills are the most important customers of forest products. About 45% of the annual fellings in Europe are consumed by sawmills, in case of softwood the portion is 53%. In Austria nearly 60% of the yearly production are machined to sawn timber. During the last years the structure of sawmills in Austria and in whole Europe has changed substantially. The main reason has to be seen in the development of sawmilling technology. Another reason is the increasing demand for smaller sawn timber dimensions to be used for lamnating purposes. Also the high cutting quality of the new rotating tools did contribute to structural changes within the sawmilling industry. Based on these changes in sawing technology and markei demands, some requests for adequate forestry responses are arising.

-preserving wood quality by immediate offer and transport after felling.

-cutting logs according to customers demands

-increased supply of small dimensions

-supplying with different species according to forestry and market demands.

     

The impact of log-end splits and spring on sawn recovery of 32-year-old plantation Eucalyptus globulus Labill.

Thirty dominant or co-dominant, straight trees were selected from a 32-year-old thinned plantation of Eucalyptus globulus Labill. Growth strain at tree surface at breast height was estimated using a CIRAD-forêt method. Log-end splits in the butt logs were measured. The butt logs were quarter-sawn following a pre-determined sawing pattern. The most common dimensions of sawn boards were 28×105×3000and 28×77×3000?mm.The volume of the curved-edge off-cuts was estimated for each butt log. The end splits in the dried sawn boards were measured and the volume of the wood containing the splits in the boards calculated. The estimated reduction in sawn recovery due to removing the curved edges in the slabs was equivalent to 6% of the log volume. The estimated reduction in recovery due to end-docking log-end splits was equivalent to 1% of the log volume, or approximately 4% of the dried board volume. For a sawmill processing 40000?m³ of logs per annum, this could translate into an annual loss of $?758000 (log volume) and $?385000 (board volume). These numbers are high in the context that end splits in these logs overall were quite mild and the estimated strain at tree surface was moderate.     

Distortion and visible crack formation in green and seasoned timber: influence of annual ring orientation in the cross section

This work describes distortion (bow, crook, twist, cup) and the formation of visible cracks in green and seasoned timber of Scots pine and Norway spruce. Distortion and crack formation have been evaluated according to the original location in the cross section of the log. The purpose is to describe differences in distortion and crack formation between sawn timber taken from star sawing and from traditional sawing patterns. Bow and crook develop in the green timber immediately after sawing as a result of growth stress release. Drying and conditioning in general lead to a marginal increase in bow, but crook may show a large percentage increase depending on the location of the wood in the cross section. Twist and cup do not occur directly after sawing, but arise during seasoning of the wood. In sawn wood, the juvenile wood has a major influence on the twist. This means that timber sawn close to the pith shows a greater twist than timber sawn away from the pith. This is a consequence of the fibre orientation in this timber. Cupping increases with decreasing radius of curvature of the annual rings in the cross section of the timber. Cracks occur in timber before seasoning. The pattern of crack formation is the same in both pine and spruce; timber sawn close to the pith or with pith enclosed exhibits a considerably larger number of visible cracks than timber sawn away from the pith. Cracks occur mainly on surfaces orientated to the pith, a fact that becomes clearer when timber is observed close to the pith. Seasoned star-sawn timber with a rectangular cross section has bow and crook of the same extent as or less than that of timber sawn according to traditional sawing patterns. Seasoned star-sawn timber with a triangular cross section has high bow, but the crook is low. Star-sawn timber does not show any cup and has a good shape stability according to the geometrical shape in the cross section. It also has a very small twist and shows very few visible cracks after seasoning.     

Radially sawn timber

This work decribes deformation and crack formation in sawn timber of pine and spruce after first drying and subsequent cycles of resoaking in water and drying. The influence of annual ring orientation and the occurrence of juvenile wood was determined. In addition, the influence of compression wood, annual ring orientation at the edges of the cross section, the position of the board surface in relation to the pith, and the condition of the board surface i.e. whether wet or dry during resoaking were studied. When timber is exposed to repeated cycles of wetting and drying, warp, viz spring, bow, twist and cup, increases and is greater after the first cycle. The influence of annual ring orientation on spring, bow and twist depends on the type of deformation and on the kind of wood. Generally, the results indicated that timber with vertical and semi (half) vertical annual rings show less deformation (mean values) than plain sawn timber and timber containing pith. Cup is mainly caused by transverse anisotropy and is strongly influenced by the radius of the annual ring. Therefore, timber with vertical annual rings do not show any cup. Spring, twist and, especially bow are strongly influenced by compression wood. Large amount of compression wood in sawn timber increases such deformation. The distance between sawn timber in the log and the pith with surrounding juvenile wood is of vital significance for cracking. During moisture cycling, the amount of boards that develop cracks increased irrespective of their prior location in the cross section of the stem. Timber sawn from near the pith or distinctly containing pith has a higher relative crack length compared to timber sawn away from and lacking pith. In timber exposed to repeated cycles of wetting and drying the crack length increases irrespective of its prior location in the stem.     

In situ density estimation of timber pieces by drilling residue analysis

Density values are essential for the characterization of wood elements in existing structures. A new method for the in-situ density estimation of timber pieces is proposed based on weighting the residue generated by conventional drilling. This research includes the design and development of a residue collector device coupled to a conventional drill and testing on four Spanish coniferous species: Laricio pine, Scots pine, Radiata pine and Maritime pine (Pinus nigra Arn., Pinus sylvestris L., Pinus radiata D. Don. and Pinus pinaster Ait., respectively). For each species, 44 specimens (except Scots pine, with 42) 60?×?90 mm cross-section and 150 mm length (half radial and half tangential orientation) were tested. Specimen density was obtained by mass/volume ratio. Three 8 mm diameter 46.5 mm deep holes were drilled in each specimen using a brad point bit. The drilling residue was weighed and density was calculated as a ratio to bore volume. Although only slightly smaller, residue density statistically differs from average specimen density. But the specimen density can be inferred by the correlation, statistically significant, with residuals drilling density (R²?=?80.7%) and even better with residual drilling mass (R²?=?84.4%).     

The Application of FT-MIR Spectroscopy for the Evaluation of Energy Value,Fat Content,and Fatty Acid Composition in Selected Organic Oat Products

In this study, Fourier transform mid-infrared (FT-MIR) spectroscopy was investigated as a rapid and non-destructive method for the determination of selected quality parameters of oat flakes and cakes. The spectra of 14 commercial products were registered in the spectral range of 4,000–370 cm^?1. Chemometric approach was applied to collect spectral and reference data on fat content, fatty acid composition, and the heat of combustion, and to correlate them. Reference data were obtained with the use of Soxhlet method, gas chromatography, and bomb calorimetry. Statistically significant coefficients in the determination of spectral data and fat, linoleic acid, stearic acid, palmitic acid content, and energy value are R ²?=?0.93, R ²?=?0.93, R ²?=?0.82, R ²?=?0.92, and R ²?=?0.95, respectively. The energy value, as well as the saturated and monounsaturated fatty acid content, was statistically higher in cakes as compared to that in flakes.     

Drying of tangentially-sawn regrowth Tasmanian Eucalyptus obliqua

The Tasmanian sawmilling industry has traditionally been heavily focused on the processing of mature eucalypt timbers. However, the available log supply has contained an increasingly high proportion of younger, smaller regrowth logs. In response to this change, the Tasmanian sawmilling industry carried out an experimental program aimed at determining a means of processing regrowth Eucalyptus obliqua into high quality sawn and dried timber similar to that available from mature logs. Initial investigations revealed that application of conventional processing techniques to the production of dried machined tangentially sawn (“backsawn”) 25 mm and 19 mm thick boards did not produce commercially viable results. Two possible techniques for reducing drying degrade were investigated: storing boards for some time prior to drying and periods of zero airflow applied intermittently during drying. Neither technique proved effective. Quartersawn timber was found to undergo less surface checking and endsplit than did backsawn. Thinner boards showed no decrease in drying degrade when compared to thicker boards.     

Effect of high-temperature drying on properties of Norway spruce and larch

In timber drying, mechanical properties may be changed due to treatment temperature and treatment duration. In general, when increasing the kiln temperature, drying time is decreased and some timber properties are negatively affected. In this study, the effect of different drying temperatures (80, 120 and 170 °C) on equilibrium moisture content and sorption rate, on bending strength and stiffness was investigated for Norway spruce and larch from four proveniences and the results were compared to those obtained for heat-treated wood (Thermowood ^®). The experiments confirm earlier research that both treatment temperature and treatment duration affect the properties. High-temperature drying or treatment can be optimized for several applications, yielding strong but not so durable timber or vice versa.     

Untersuchung der Holzqualität von Traubeneichen aus unterschiedlich dicht begründeten Beständen

Logs taken from two stands of Quercus petraea Liebl. (age appr. 120 years) established in different density of stocking were comparatively investigated in view of dimension and quality. Afterwards the logs were cut into boards which were graded according to DIN 68 370. The logs of the stand with wide seeded strips showed clearly stronger dimensions and roughly better quality properties in the middle and lower part of stems. The results of the log and timber grading show a significant better quality for the wood coming from the stand which was established by wide seeded strips. Also the timber volume produced out of that stand was 18% higher compared with the narrow spaced stand which has been natural regenerated.     

Modelling of the mechanical properties of Castanea sativa Mill. structural timber by a combination of non-destructive variables and visual grading parameters

Linear regression models were constructed for chestnut beams of Spanish origin (Asturias, Galicia, Catalonia and Extremadura) using the global modulus of elasticity (MOE _g ) and bending strength (MOR), both obtained by destructive tests, as dependent variables, and the results of non-destructive measurements, visual grading parameters and density as independent variables. The variables selected were density, wave velocity, sample length, dynamic modulus of elasticity, maximum knot diameter in relation to height and concentrated knot diameter ratio. Linear regression models were constructed to indirectly estimate the mechanical properties of the beams. Ultrasonic velocity, density and sample length were the best predictors of MOE _g (R ²?=?0.740 and 0.734 SE). Regression adjustments for MOR presented low coefficients of determination and high errors. The visual grading parameters of the beams did not play a significant role in the prediction of either MOE _g or MOR.