Étude de l'effet d'un traitement ignifuge et de l'orientation du fil du bois sur la formation de la pelure d'orange des panneaux sandwich décoratifs

Le produit de finition appliqué sur la surface du mobilier des avions d’affaires tend à se détériorer avec le temps. Un défaut d’apparence appelé pelure d’orange d’aspect ondulé apparaît sur la surface décorative vernie du mobilier. À cet égard, le comportement des composants des panneaux sandwichs décoratifs face aux changements du milieu ambiant mérite d’être étudié. Ainsi, afin de comprendre la formation de ce défaut, les effets d’un traitement ignifuge, de l’orientation du fil et de la structure anatomique sur les changements tridimensionnels de la surface des panneaux sandwich, ont été étudiés. Dans un premier volet, les effets de ces variables furent étudiés sur des panneaux fabriqués avec des placages décoratifs de bubinga et la loupe de noyer. Deux groupes d’échantillons, un non vernis et un vernis, furent évalués pour ces deux espèces. Les deux groupes ont subi une adsorption (25°C et 90% HR), et une désorption (25°C et 40% HR). Les changements dimensionnels dans le plan des placages ont été étudiés par le gonflement et le retrait tandis que les changements dimensionnels hors du plan ont été évalués par la variation de la rugosité et de l’ondulation. Pour les panneaux de bubinga, les résultats ont montré que le traitement ignifuge a augmenté l’hygroscopicité et par conséquent les changements tridimensionnels des panneaux non vernis. L’orientation élevée du fil du placage externe a augmenté les changements hors du plan de ces panneaux. Chez les panneaux vernis, le traitement ignifuge a aussi augmenté la teneur en humidité provoquant seulement des changements dimensionnels significatifs dans le plan des panneaux. Cependant, les effets du traitement ignifuge et de l’orientation du fil du bois sur les changements tridimensionnels ne furent pas détectés après le vernissage. D’autre part, pour les panneaux de la loupe de noyer, le traitement ignifuge a augmenté significativement l’hygroscopicité et les changements tridimensionnels des panneaux non vernis et vernis. Ce traitement a aussi provoqué une différenciation marquée des surfaces dominées par des fibres par rapport aux surfaces dominées par le parenchyme dans les panneaux non vernis. L’effet de la structure de bois de loupe sur la topographie de surface ne fut pas perceptible une fois que les panneaux ont été vernis. Dans un deuxième volet, l’effet d’un traitement ignifuge et de la structure du bois de loupe de noyer sur la déformation des panneaux sandwich soumis à une adsorption (25°C et 90% HR) fut étudié par la méthode de corrélation d’images numériques à trois dimensions (CIN-3D). Des panneaux non vernis et vernis fabriqués avec la couche décorative de la loupe de noyer furent étudiés. Des zones de fil irrégulier (figures tourbillonnantes) et de traces de bourgeons (figures des yeux) ont été identifiées sur la surface externe décorative. Le gain en teneur en humidité a été mesuré après l’adsorption. Les changements dimensionnels dans le plan des panneaux et le déplacement hors du plan du panneau ont été mesurés pour chaque type de figure. L’application de cette méthode a confirmé que le traitement ignifuge augmente la déformation dans le plan et le déplacement hors du plan de la surface des panneaux non vernis et vernis suite à une adsorption. Il a aussi révélé que ce traitement provoque une différenciation significative des zones dominées par les fibres par rapport aux surfaces dominées par le parenchyme dans les panneaux vernis. Sur la base des résultats obtenus, la pelure d’orange apparaît suite à des modifications physiques dans la surface du bois due aux variations de la teneur en humidité. La méthode de CIN-3D s’est révélée plus adéquate pour la mesure de ce défaut.The finishing product applied to the surface of aircraft furniture tends to deteriorate with time. A defect called orange peel, with a wavy appearance, appears on the decorative surface of the finished furniture. In this regard, the behavior of the components of sandwich panels to the environmental changes deserves to be studied. Thus, in order to understand the defect formation, the effects of a fire-retardant treatment, grain orientation and wood structure on the three-dimensional changes of the surface of sandwich panels were studied. In the first part of this project, the effects of this variables were studied on sandwich panels made with decorative veneers of bubinga and the walnut burl. Two groups of samples, an unvarnished and varnish, were evaluated for these two species. Both groups underwent an adsorption (25 °C and 90% RH) and a desorption (25 °C and 40% RH) treatments. In-plane dimensional changes were studied by the swelling and shrinkage while out-of-plane dimensional changes were evaluated by the roughness and waviness. In bubinga panels, the results showed that the fire-retardant treatment increased the hygroscopicity and consequently the three-dimensional changes of unvarnished panels. The higher wood grain orientation of the outer veneer increased the out-of-plane dimensional changes of these panels. In varnished panels, the fire-retardant treatment also increased the moisture content provoking only significant in-plane dimensional changes of the panels. However, the effects of fire-retardant treatment and wood grain direction on the three-dimensional changes were not noticeable once the panels were varnished. On the other hand, in walnut burl panels, the fire-retardant treatment increased significantly the hygroscopicity and the three-dimensional change of unvarnished and varnished panels. This treatment also provoked a marked differentiation of fiber-dominated surfaces from parenchyma-dominated surfaces in unvarnished panels. The effect of burl wood structure on out-of-plane changes of varnished panels was not detected. In a second part of the study, the effect of a fire-retardant treatment and wood burl structure on the deformation of sandwich panels exposed to an adsorption was studied by the three-dimensional digital image correlation method (3D-DIC). Unvarnished and varnished panels made with walnut burl decorative veneer was studied. Swirl grain and bud trace areas were identified on the burl pattern of the veneer surface. Changes in moisture content were measured after adsorption treatment. The in-plane and out-of-plane dimensional changes of the panels were measured for each type of figure after the adsorption treatment. The application of this method has confirmed that the fire-retardant treatment increases the in-plane deformation and the out-of-plane displacements of the unvarnished and varnished panels after adsorption. The method also revealed that this treatment causes a significant differentiation of the fiber-dominated surfaces from the parenchyma-dominated surfaces in varnished panels. Based on the results, the orange peel defect appears as a result of physical changes in wood surface due to variations in moisture content. The DIC-3D method was more appropriate to measure this defect

Análisis dendrocronológico de tres especies forestales del Bosque Seco Ecuatorial Estacional

Universidad Nacional Agraria La Molina. Facultad de Ciencias Forestales. Departamento Académico de Manejo ForestalEn la presente investigación, fueron aplicadas técnicas de dendrocronología en árboles de Palo santo, Hualtaco y Sapote, en el bosque seco ecuatorial estacional BTES visando caracterizar la estructura del anillo de crecimiento, comprobar la anualidad de la formación de los anillos y determinación de la edad de los árboles y aplicar la técnica de densitometría de Rayos X. Anillos de crecimiento delimitados por zonas fibrosas con los cuales se determino la edad de las especies; Palo santo (59 años) y Hualtaco (47 años). Las tasas de crecimiento en Palo santo fue de 0,31 a 0,67 cm/año, en Hualtaco fue de 0,44 a 0,72cm/año. La variable climática determinante para el mayor crecimiento en diámetro del tronco de los árboles fue la precipitación anual acumulada de Lambayeque. Los perfiles radiales de densidad aparente por densitometría de Rayos X, posibilitan la identificación del límite exacto de los anillos. Por otro lado, la especie Capparis scabrida resulto no ser potencial para estudios dendrocronológicos debido a la estructura anatómica y a la alta variación de su perfil densitométricoTesi

EFFECT OF TOOL TIP RADIUS ON RING DEBARKER PERFORMANCE OF FROZEN AND UNFROZEN BLACK SPRUCE LOGS

The effects of the tool tip radius on debarking quality of unfrozen and frozen black spruce logs were studied. The power, energy consumption and torque on frozen conditions were also studied. A proto-type one-arm ring debarker was used. The experiment consisted of debarking logs using three tool tip radii (40, 180, and 300 µm) for each temperature (-20°C and +20°C). The rotational and feed speeds, tip overlap, and rake angle were kept constants. Debarking quality was evaluated by two criteria: the proportion of bark remaining on log surfaces and the amount of wood in bark residues (WIB). Log characteristics, used as covariates, ie dimensions, eccentricity, bark thickness, knot features, bark/wood shear strength (BWSS), basic densities and moisture contents of sapwood and bark were measured, as well as total removed material after debarking. The results showed that tool tip radius had a significant effect on debarking quality of frozen and unfrozen logs. The proportion of bark on log surfaces increased and the amount of WIB decreased as tip radius increased. At the same applied radial force, a wider tip radius showed a shallower tip penetration leaving bigger regions of bark on the log surfaces. In contrast, a narrower tip radius showed a deeper tip penetration resulting in important wood fiber tear-out. The bark thickness and inner bark MC also affected debarking quality. The mean power, mean torque, and energy consumption increased as the tip radius decreased. However, this effect will depend on the choice of the applied radial force during debarking. Motor performance was also affected by the total removed material, log diameter, and BWSS. Overall, the results highlight the importance of choosing an adequate combination of tool tip radius and applied radial force to obtain the most profitable debarking quality with an efficient energy consumption

Dendrochronology of the mahogany trees, Swietenia macrophylla King., Meliaceae, occurring in the Amazon Rainforest of the Department of Madre de Dios, Peru

Estudos sobre a fenologia e anatomia do lenho de árvores de espécies tropicais revelam um desenvolvimento e crescimento cíclicos, relacionados com as condições climáticas (temperatura e precipitação) e de sítio (competição, luz, armazenamento de água no solo, etc.). A sensibilidade a estes fatores resulta, para as árvores de algumas espécies, na sazonalidade da atividade cambial e na formação de anéis de crescimento anuais. Essa característica possibilita a determinação da idade, da taxa de crescimento em diâmetro do tronco e da reconstrução de eventos climáticos, bem como na aplicação de técnicas de manejo florestal sustentável. No presente trabalho, foram aplicadas as técnicas de dendrocronologia, em árvores de mogno, de duas populações na floresta tropical Amazônica do Peru, visando a (i) caracterização da estrutura macro e microscópica do lenho e dos anéis de crescimento, (ii) comprovação da anualidade da formação dos anéis de crescimento e determinação da idade das árvores, (iii) avaliação da biodeterioração do lenho das árvores, (iv) aplicação da densitometria de raios X no estudo do lenho e dos anéis de crescimento e (v) aplicação dos anéis de crescimento em dendroclimatologia e dendroecologia. Foram selecionadas 20 árvores de mogno em duas populações localizadas no Departamento de Madre de Dios, Peru e extraídas amostras radiais do seu lenho, com sonda de Pressler. Injúrias no tronco de árvores de mogno foram realizadas em outubro/2006 e analisadas as cicatrizes no lenho em outubro/2007, relacionando-as com a formação dos anéis de crescimento. Foi caracterizada a estrutura anatômica do lenho e dos anéis de crescimento, determinando-se o seu número, largura e aplicadas técnicas de dendrocronologia. Os anéis de crescimento foram sincronizados, utilizando os programas COFECHA, ARSTAN e RESPO, determinando-se a relação da sua largura com as variáveis climáticas e a idade das árvores. A podridão interna do lenho das árvores foi avaliada determinando-se o diâmetro do oco interno do lenho do tronco. A variação radial da densidade aparente do lenho foi determinada pela densitometria de raios X. Anéis de crescimento delimitados pelo parênquima axial marginal são comprovadamente anuais e possibilitaram a determinação da idade das árvores de mogno (80-122 anos) e a construção de cronologias. A variável climática determinante para o maior crescimento em diâmetro do tronco das árvores foi a precipitação dos meses prévios, do início e do final da estação chuvosa (junho-agosto, dezembro e março) indicando o seu potencial para as reconstruções climáticas. Os perfis radiais de densidade aparente do lenho, obtidos por densitometria de raios X, possibilitaram a identificação do limite exato dos anéis de crescimento, pelos valores mínimos de densidade da região do parênquima marginal. A análise de regressão entre a largura dos anéis obtida pela mesa de medição e por densitometria de raios X apresentou valor de r2=0.92, mostrando a potencialidade dos raios X como ferramenta para estudos de dendrocronologia. O oco do lenho do tronco foi observado em 20% das árvores de mogno, com DAP acima de 62 cm.Studies in phenology and wood anatomy show a cyclical development and growth related to climatic conditions (temperature and rainfall) and site characteristics (competence, light, water storage in the soil, etc.), the sensibility to these factors results, for some tree species, in seasonality of cambium activity and formation of annual tree-rings. This characteristic enables to estimate age, growth rate in trunk diameter and reconstruction of climatic events, as well as in application of techniques of sustainable forest management. In this study, dendrochronological techniques were applied in mahogany trees from two populations in the Amazon rainforest of Peru, with the aim of (i) characterization of macroscopic and microscopic wood structure and the tree rings, (ii) checking the annual formation of tree rings and determining tree age, (iii) evaluation of the biodeterioration in wood of trees (hollow), (iv) application the X-ray densitometry in the study of wood and tree rings and (v) application the tree rings in dendroclimatology and dendroecology. Twenty mahogany trees were selected in two populations located in the department of Madre de Dios, Peru and removed radial samples from the trunk, with increment corer (Pressler). In October, 2006 injuries in the trunk of mahogany trees were carried out and in October 2007, the scars were analyzed, associating them to the formation of the tree rings. Wood and tree rings anatomic structure was characterized determining its number, width and dendrochronology techniques applied. Tree rings have been synchronized, using COFECHA, ARSTAN and RESPO programs, determining the relation between the width with the climatic variables and the age of trees. The internal wood decay was evaluated by providing the internal diameter of hollow in the trunk. The radial variation of the apparent wood density was determined by the X ray densitometry. Tree rings delimited by a marginal axial parenchyma bands are annual and enable to determine the age of mahogany trees (80-122 years) and the construction of chronologies. The climatic determinant variable for the greatest growth in diameter of the trunk of trees was the rainfall in the previous months, beginning and final of the rainy season (June - August, December and March) indicating its potential for climatic reconstructions. The radials profiles of apparent density of wood, obtained for X ray densitometry, making possible identification of the exact limit of growth rings for minimal values of density in the region of marginal parenchyma. The regression analysis between ring width measured with Velmex (0,001) table and for X ray was r2=0.92, showing the potential of X rays as tool for dendrochronological studies. Decay in the trunk was observed in 20 % of trees over 62 cm of DBH

Variation of wood density and relationship with the tree-ring width of mahogany trees, Swietenia macrophylla, from Amazonian tropical forest of Peru

Mahogany trees, Swietenia macrophylla, occur in open rainforest, semi deciduous and deciduous and dense rainforest of Peruvian Amazonian tropical forest. They occur, preferentially, in areas with a defined dry season, with typical phenology and seasonal variation activity, forming distinct tree-rings. The present work had as aim to determine the wood density radial variation of 14 mahogany trees, of two populations of the Peruvian Amazonian tropical forest, through the X-ray densitometry and to evaluate their application as methodology, compared to the classic method of measurement table, for the determination of the treering width. The radial wood apparent density of the trees profiles rendered it possible to delimit the areas of juvenile-adult wood and of the heartwood-sapwood, relative to the anatomical structure and chemical composition differences, due to the extractives and the vessels obstruction by tyloses. The mean, minimum and maximum wood apparent density of the mahogany trees for the Populations A and B were of 0.70; 0.29; 1.01 g.cm(-3) and 0.81; 0.29; 1.19 g.cm(-3), respectively. The analysis of the variance and mean test indicate differences of mean wood density among the mahogany trees of each population, probably due to the age of the trees. There was no correlation between mean wood density of mahogany trees among the two populations, as well as, between the tree-ring width and the respective mean density. The X-ray densitometry technique is an important tool in the evaluation of the radial variation of wood apparent density and the delimitation of tree-ring boundaries, with correlations of 0.94 and 0.93 in relation to measurement table, for each sampled population

Novel Yield Model of <i>Pinus patula</i> Schltdl. & Cham. Growth near the Ecological Limit in Northwestern Peruvian Andes

Forest plantations with exotic species in the northwestern Peruvian Andes have brought different ecosystem benefits. The wood productivity in this Páramo region is directly related to the great availability of water from abundant rainfall compared to other regions of the semi-arid Andes. To address the lack of information on forest inventories of plantations in the Páramo region, this study used annual growth rings (dendrochronology) to build new models of tree growth and wood productivity and compared 22-year-old Pinus patula plots with thinning and unthinning treatments. Our results show that late thinning, removing 63% of stem density in the 15th year, does not have significant effects on the diameter increase or stand-level productivity. For these plantations, we propose a management rotation of 21 years with a first thinning treatment (35%) at 5 years and a second thinning treatment (50%) at 12 years. Production at 21 years is expected to be between 194.6 m3 ha−1 and 504.6 m3 ha−1 for stands with low and high wood productivity, respectively. Tree-ring studies are potentially useful for monitoring forest plantations and provide an alternative method for forest managers who use allometric equations to predict silvicultural treatments and to propose management guides for plantations