Editorial: “Fifty years Annals of Forest Science”

International audienceKey MessageAnnals of Forest Scienceis publishing a series of review papers to celebrate 50 years of activities as a journal in forest and wood science. The reviews emphasize the extent to which forest and wood sciences changed and developed as a large array of disciplines devoted to complex objects with sometimes many conflicting issues

Influence of grain direction in vibrational wood welding

Wood grain orientation differences in the two surfaces to be bonded yield bondlines of different strength in no-adhesives wood welding. Longitudinal wood grain bonding of tangential and radial wood sections yields an approximately 10% difference in strength results of the joint. Cross-grain (±90°) bonding yields instead a much lower strength result, roughly half that observed for pieces bonded with the grain parallel to each other. These differences can be explained by the very marked effect that homogeneity of fibre orientation is known to have on fibre–matrix composites. Oak yields lower results than beech and maple and is more sensitive to welding conditions. Differences in both anatomical and wood constituent composition can account for this difference in performance. Contrary to the other wood species, oak always presents joint bondlines where little or no increase in density at the interface is noticed. This explains its somewhat lower strength results. This is based on the different mode of bonding predominant in this species, while the other species present two different modes of bonding. Thus, two types of bondlines are observed by scanning electron microscopy (SEM): (i) bondlines where entangled fibre–matrix composites are formed at the interface and (ii) bondlines in which direct welding of the cell walls occurs, just by fused intercellular material or cell surface material. In this latter case the cells remain flat, without an entangled fibre–matrix composite being formed. This is the almost exclusively predominant case for oak. Both cases and even hybrid cases between the two have also been observed in beech

Parameters of wood welding: A study with infrared thermography

Welding of wood is a well-known joining procedure that offers several advantages over traditional mechanical fasteners or gluing. During welding, extensive solid-state transformation phases occur in the so-called melting zone and the heat-affected zone. The nature and the extension of such transformations are correlated to the energy input and thus to the heat generated during the process at the wood joint interface. In the present work the influence of the welding parameters and wood grain orientation on the temperature profile and distribution and final strength of welded connections was investigated. For this purpose, the characteristics of the joints were evaluated with both destructive and non-destructive techniques. Non-destructive evaluation was performed with infrared thermography, which allowed measurement of the maximal and average peak temperature, temperature profile and distribution, and rate of temperature increase. Thus, this technique can also be used to detect welding defects and to provide information on material modification during welding

Parameters of wood welding: A study with infrared thermography

Welding of wood is a well-known joining procedure that offers several advantages over traditional mechanical fasteners or gluing. During welding, extensive solid-state transformation phases occur in the so-called melting zone and the heat-affected zone. The nature and the extension of such transformations are correlated to the energy input and thus to the heat generated during the process at the wood joint interface. In the present work the influence of the welding parameters and wood grain orientation on the temperature profile and distribution and final strength of welded connections was investigated. For this purpose, the characteristics of the joints were evaluated with both destructive and non-destructive techniques. Non-destructive evaluation was performed with infrared thermography, which allowed measurement of the maximal and average peak temperature, temperature profile and distribution, and rate of temperature increase. Thus, this technique can also be used to detect welding defects and to provide information on material modification during weldin

\u3ci\u3eAnnals of Forest Science\u3c/i\u3e Promotes Multidisciplinary Research on Forests and Wood in a Changing World and Is Now a Full Open Access Journal

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Automatic knot detection and measurements from X-ray CT images of wood: A review and validation of an improved algorithm on softwood samples

International audienceAn algorithm to automatically detect and measure knots in CT images of softwood beams was developed. The algorithm is based on the use of 3D con- nex components and a 3D distance transform constituting a new approach for knot diameter measurements. The present work was undertaken with the objective to automatically and non-destructively extract the distributions of knot characteristics within trees. These data are valuable for further studies related to tree development and tree architecture, and could even contribute to satisfying the current demand for automatic species identification on the basis of CT images. A review of the literature about automatic knot detection in X-ray CT images is provided. Relatively few references give quantitatively accurate results of knot measurements (i.e., not only knot localisation but knot size and incli- nation as well). The method was tested on a set of seven beams of Norway spruce and silver fir. The outputs were compared with manual measurements of knots performed on the same images. The results obtained are promising, with detection rates varying from 71 to 100%, depending on the beams, and no false alarms were reported. Particular attention was paid to the accuracy obtained for automatic measurements of knot size and inclination. Comparison with manual measurements led to a mean R2 of 0.86, 0.87, 0.59 and 0.86 for inclination, maximum diameter, length and volume, respectively

Quantification de la biomasse aérienne des forêts françaises

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The Modulus of Elasticity of Hybrid Larch Predicted By Density, Rings Per Centimeter, and Age

A total of 492 specimens from eighteen trees representing fast-growth larch were studied. The mean values of the modulus of elasticity (MOE), density, age, and rings per centimeter were determined for each. Mathematical models were developed to predict the MOE from the other parameters. Linear models are first presented showing the dependence of MOE on each of the three parameters, density, age, and rings per centimeter. A multivariate linear regression model is then developed for MOE as a function of all three parameters. The correlation coefficient of this model is 0.66, an improvement over each of the models for which each parameter is taken individually. A prediction of MOE by visual means alone, i.e., using only age and rings per centimeter in a linear model, is also presented. The correlation coefficient of this model is 0.58, which is superior to any of the parameters taken individually. In order to develop a model useful for extrapolation beyond the range of test data, a nonlinear model is presented. The parameters of this nonlinear model can easily be interpreted in terms of (1) the maximum attainable stiffness, (2) the ring age for maximum MOE growth rate vs. age, and (3) the shape parameter of the model. We found that the nonlinear model matched the data well and incorporated the realistic conditions of zero MOE at zero ring age and a limit on the maximum attainable MOE