Papers by jean-michel leban
HAL (Le Centre pour la Communication Scientifique Directe), 1998
Microdensitometric analysis of wood samples: data computation method used at Inra-ERQB (CERD prog... more Microdensitometric analysis of wood samples: data computation method used at Inra-ERQB (CERD program). The procedure used at Inra for computing data derived from the microdensitometric analysis of a wood sample is described and discussed. The initial data are in the form of one or several radial density profiles. The first step of the treatment, which is the most time consuming and the only one requiring manual intervention, consists in locating the annual ring limits on each profile of each ring. The intermediate data -which can be corrected using an independent measurement of density (ratio weight/volume of the whole sample)are then com- puted for each ring profile. Finally, each ring is described by several 'synthetic' values: the ring width, the mean density, the minimal and maximal density, the earlywood and latewood widths and ratios, and a set of density values (named 'quantiles') describing the shape of the ring profile.
HAL (Le Centre pour la Communication Scientifique Directe), 1998
Localization of the earlywood-latewood transition in oak rings using micro- densitometric analysi... more Localization of the earlywood-latewood transition in oak rings using micro- densitometric analysis. The ring widths and the earlywood-latewood limits in 96 annual rings of oak (Quercus petraea Liebl.) have been measured by image analysis of cross sections. A microdensitometric analysis has been performed on the same rings. The position of the earlywood-latewood transition has been estimated in each ring by searching the intersection of the den- sity profile with a threshold of density. This threshold has been computed in three ways: 1) a fixed threshold, 2) a floating threshold depending on the minimal and maximal densities in the ring and 3) a floating threshold depending on the mean density in the ring. Each method has been tested with several parameters and the estimated values of the earlywood and latewood widths and ratios have been compared with the anatomical observations. The second and third methods are more accurate than the first method. The second method is preferred because the quality of the results is less dependent on the choice of the parameters. (© Inra/Elsevier, Paris.) wood anatomy / X-ray densitomety / Quercus petraea / wood density / earlywood
Travail des matériaux - Assemblage
Cet article est consacre a la mise en œuvre d’un procede d’assemblage de pieces de bois entre ell... more Cet article est consacre a la mise en œuvre d’un procede d’assemblage de pieces de bois entre elles par friction, sans l’utilisation d’adhesifs et en quelques secondes. Deux principaux types d’assemblage ont ete elabores, possedant tous deux des proprietes mecaniques comparables a celles des memes assemblages colles. Un procede par friction lineaire, realise a l’aide d’une machine de soudage par friction, permet d’assembler selon differentes orientations du bois. Un procede de chevilles de bois, realise par friction circulaire a l’aide d’une perceuse classique, pourrait deboucher sur de larges applications dans l’industrie de l’ameublement.
HAL (Le Centre pour la Communication Scientifique Directe), Dec 10, 2018
Annals of Forest Science, 2022
We have the pleasure to announce here a new step in the already long history of Annals of Forest ... more We have the pleasure to announce here a new step in the already long history of Annals of Forest Science (formerly Annales des Sciences Forestières, founded 1964). Since January 1, 2022, Annals of Forest Science is published under a full open access model. It joins two other INRAE journals within the BMC-Springer Open Access publishing scheme: Veterinary Research and Genetics, Selection, Evolution, in the frame of a 5-year publishing contract that INRAE signed with Springer Nature (2022-2026). All papers published from now on will be fully and immediately accessible to readers and users worldwide, under pdf and xml formats. As authors, you will be free to archive and disseminate the papers you authored as you wish. You will keep all rights over the papers, which will be published under a CC-BY license (with some adjustments if required). This should enable a larger impact of the papers we publish and a faster dissemination of the research results in the rapidly expanding field of Forest and Wood Sciences. This is only one among several moves undertaken by Annals of Forest Science to become fully Open Science compliant in agreement with the Open Data policy of BMC-Springer. Indeed, Open Science is not restricted to
Wood Science and Technology, 2010
End-grain-to-end-grain welding gave butt joints of good strength with three high density Australi... more End-grain-to-end-grain welding gave butt joints of good strength with three high density Australian eucalyptus woods, namely Sidney blue gum (Eucalyptus saligna), Spotted gum (Eucalyptus maculata, Corymbia maculata spp.) and Black butt (Eucalyptus pilularis). The absence or limited tendency to defibration in end-grain-to-end-grain welding for wood densities as high as these, around 800–900 kg/m3, indicates that end-grain-to-end-grain welding is possible and yields
Trees, 2013
ABSTRACT Studying the effects of dendrometric and climatic variables on within-ring density varia... more ABSTRACT Studying the effects of dendrometric and climatic variables on within-ring density variations needs flexible and interpretable models. We described the within ring density profile using a piecewise linear regression and studied its dependence on (1) dendrometric variables such as cambial age (CA) and ring width (RW), and (2) climatic variables. Based on X-ray analysis of 5,191 Norway spruce rings, a six-parameter three-segmented model was fitted on each within-ring density profile. Each model parameter was related to dendrometric and climatic variables using multiple linear regressions. Then, these models were assembled in two models relating the within-ring density profile to (1) RW and CA (model M1), and (2) climatic variables (model M2). M1 showed an R2 of 83.4 % and a residual standard error of 68.5 kg m-3. Larger rings were associated with a decrease of latewood proportion and mean ring density. Rings with high CA were characterised by high maximum ring density. M2 showed an R2 of 60.9 % and a residual standard error of 94.9 kg m-3. Warm summers increased the maximum ring density. Years with favourable water status decreased mean ring density. The piecewise linear models allowed the classification of within-ring density profiles in three types. Considering CA and RW led to the most explicative model since RW described many processes such as silviculture or climate. Earlywood density was impacted by water status while latewood density was conditioned by both temperatures and water status. Our approach may be used for the identification of withinring density fluctuations or to assess the effects of silviculture or global change on the within-ring density profile.
Scandinavian Journal of Forest Research, 2006
This study focused on the amount of sapwood and its variation by means of computed tomographic (C... more This study focused on the amount of sapwood and its variation by means of computed tomographic (CT) imaging. Twenty-four trees were selected from four Norway spruce [ Picea abies (L.) Karst.] stands in north-eastern France, varying in age, density and fertility. In each stand, ...
Journal of Adhesion Science and Technology, 2011
Application of rosin, a wood derived, non-toxic, natural, inexpensive and easily and abundantly a... more Application of rosin, a wood derived, non-toxic, natural, inexpensive and easily and abundantly available natural material, to the wood faces to be joined by either linear vibration welding or rotational dowel welding has shown to greatly enhance the water resistance of welded wood joints. The method of application has been shown to have a marked effect on the results, with the application and drying of a diluted rosin solution to the wood surfaces before welding yielding the best results. The considerable improvement in water resistance does not still allow classification of the joints as fully exterior grade. However, dowel welding can now be used for protected exterior joints due to a combination of rosin waterproofing and joint geometry. Welded dowel joints holding together for longer than 455 days immersion in water indicate this to be the case. Rosin-treated linear vibration joints held together well in excess of 30 days but retained a measurable strength, in the best case, only up to 18 days water immersion. The wood anatomy and chemical reasons for the effect of rosin were determined by X-ray microdensitometry and CP–MAS 13C-NMR analysis.
Journal of Adhesion Science and Technology, 2006
ABSTRACT Vibration welding of wood that has been preheated according to an industrial two-step pr... more ABSTRACT Vibration welding of wood that has been preheated according to an industrial two-step process indicates that such wood can be welded and can yield welded joints of good strength. The joint strength is, however, markedly lower than obtained when welding non-heat-treated timber. In general, weld strength of the timber is poor if welding is done on hydrothermolyzed wood. The strength results are instead much better if welding is done at the end of the complete heat treatment process, i.e., after the dry heat step. The weld lines of heat-treated wood show entangled cells where there is none or very little of the molten matrix intercellular material usually observed in welded timber. Furthermore, in weldlines obtained after hydrothermolysis an increase in rigidity and brittleness of the wood cells is observed. Hence, the wood cells are not entangled at all or very little. Both observations indicate that heat treatment has affected the main melting region of the wood, namely the intercellular material. As most of this material is already either lost or heavily cross-linked during heat treatment, only little of it is now available to melt and bind the wood surfaces during vibrational wood welding.
Journal of Adhesion Science and Technology, 2007
A zig-zag pattern of rotationally welded dowels across the interface of a butt joint between two ... more A zig-zag pattern of rotationally welded dowels across the interface of a butt joint between two wood planks was shown to yield strong joints without any adhesive. Tests after 2 h in boiling water showed that the joints were able to resist both 2 h immersion in boiling water, as well as the subsequent oven drying. Some unusual densification patterns
Journal of Adhesion Science and Technology, 2008
... A model considering temperature, welding time and thermal flow was recently developed for the... more ... A model considering temperature, welding time and thermal flow was recently developed for the wood-dowel rotation welding and was verified us-ing infrared thermography [14]. ... Three couples of specimens were welded for each welding time. ...
Journal of Adhesion Science and Technology, 2009
ABSTRACT A change in linear welding conditions, namely higher vibration frequency (150 Hz) and lo... more ABSTRACT A change in linear welding conditions, namely higher vibration frequency (150 Hz) and lower displacement (2 mm) during welding, produced a quicker rise in temperature of the weldline. This allowed a much shorter welding time (1.5 s). X-ray microdensitometry mapping showed a progressive increase in broadening and average density of the weldline as the welding time lengthens. As the welding time lengthens the maximum temperature reached at the end of welding is progressively higher. This causes increasingly greater degradation. This effect was confirmed also by CP-MAS C NMR and it was found that the lower is the degree of deterioration of the weldline of the wood joint the shorter is the welding time. Monitoring of the temperature of the weldline showed that the temperature reached in wood joints during welding was inversely correlated to its water resistance. Furthermore, the increase in weldline temperature is markedly quicker at a vibration frequency of 150 Hz than at 100 Hz. Thus, the shorter is the welding time the lower is the degree of deterioration of the weldline of the wood joint. This appears to be due to welding occuring when water vapour is still present in the joint, hence providing a less damaging welding environment.
Industrial Crops and Products, 2013
hfsg, 2012
Tracheid dimensions influence the quality of wood and that of pulp and paper. Both between- and w... more Tracheid dimensions influence the quality of wood and that of pulp and paper. Both between- and within-ring variations are influenced by tree developmental stage, site, genetics, and forest management. To contribute to the knowledge in this regard, the radial and tangential tracheid dimensions on Norway spruce, defined as the lumens and double cell wall thickness, have been measured using a SilviScan device. Namely, 4947 annual rings from 35 trees from plantations in France, Norway, and Sweden were examined. Mixed-effects models were constructed concerning the radial and tangential tracheid widths for the total ring and in three within-ring compartments – earlywood (EW), transition wood (TW), and latewood (LW) – as functions of age, radius, height in the tree, and growth rate. Between-site and between-tree variations were also considered. The mean radial tracheid width was 34.2 μm (EW), 29.9 μm (TrW), and 22.1 μm (LW). The tangential tracheid width was on average 30.1 μm in all comp...
Forest Ecology and Management, 2008
We analysed crown dynamics at the stand level in three plots of an even-aged sessile oak stand (o... more We analysed crown dynamics at the stand level in three plots of an even-aged sessile oak stand (one unthinned reference plot and two plots of different thinning intensities) of a long-term experiment in Rhineland Palatinate, Germany. Crown projections and stem locations were recorded ...
Holz als Roh- und Werkstoff, 1991
... P. Triboulot, P. Kremer, and P. Martin * Laboratoire d'Automatique et de Commande Nu... more ... P. Triboulot, P. Kremer, and P. Martin * Laboratoire d'Automatique et de Commande Num6rique, ESSTIB, Universit6 de Nancy I, All6e des h~tres, F-88000 Epinal, France ... More details are ~ven in Lam-bert (1985) and Triboulot et al, (1987). ...
Holz als Roh- und Werkstoff, 2008
Computers and Electronics in Agriculture, 2012
... CRM2, UMR CNRS-UHP 7036), Henri Poincaré University, Science Faculty - BP 239, 54506 Vandoeuv... more ... CRM2, UMR CNRS-UHP 7036), Henri Poincaré University, Science Faculty - BP 239, 54506 Vandoeuvre les Nancy - France E-mail: jover.jeremy@gmail.com ... 1. Introduction More and more, with a view to increase productivity or traceability, supply chain managers mark pieces. ...
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Papers by jean-michel leban