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Forestry companies have invested in genetic improvement to increase wood production in a shorter amount of time. Thus, studies are needed to compare the properties of clonal and seminal wood materials. The objective of this study was to analyze physical and mechanical properties of Tectona grandis from clonal (C1 and C2) and seminal (S) origin and evaluate the yield and quality of sawn wood subjected to outdoor and oven drying. Genetic material was collected from six, 15-year-old trees. Clone C2 presented the lowest amount of bark, and 51 % heartwood up to half the commercial height, while the heartwood of C1 and S went up to 25 % of the height. The three materials did not differ statistically for maximum angular deviation, pith eccentricity, basic density, Janka hardness, anisotropy, commercial income of sawn wood and the presence of knots. After the drying processes, the bowing and crooking indexes were less than 5 mm.m-1, however, the seminal material showed a higher cracking incidence after outdoor and oven drying. In conclusion, the wood properties of the three materials are similar. In addition, the oven drying process is recommended., Las empresas forestales han invertido en mejoramiento genético para aumentar la producción de madera en menos tiempo. Por tanto, se necesitan estudios para comparar las propiedades de los materiales de madera clonales y seminales. El objetivo de este estudio fue analizar las propiedades físicas y mecánicas de Tectona grandis de origen clonal (C1 y C2) y seminal (S) y evaluar el rendimiento y calidad de la madera aserrada sometida a secado al aire libre y al horno. Se recolectó material genético de seis árboles de 15 años. El clon C2 presentó la menor cantidad de corteza, y un 51 % de duramen hasta la mitad de la altura comercial, mientras que el duramen de C1 y S llegó hasta un 25 % de la altura. Los tres materiales no difirieron estadísticamente en cuanto a desviación angular máxima, excentricidad de la médula, densidad básica, dureza Janka, anisotropía, ingreso comercial de la madera aserrada y presencia de nudos. Luego de los procesos de secado, los índices de arqueamiento y torcedura fueron menores a 5 mm.m-1, sin embargo, el material seminal presentó una mayor incidencia de agrietamiento luego del secado al aire libre y al horno. En conclusión, las propiedades de la madera de los tres materiales son similares. Además, se recomienda el proceso de secado en horno

För att minska energiförbrukningen och höja kapaciteten vid virkestorkning kan adaptiv styrning användas. Adaptiv styrning är en typ av processåterkoppling som visar på hur torkningen fortskrider och kan användas för att styra torkprocessen optimalt. Adaptiv styrning har funnits till kammartorkar länge. Tvärcirkulerande kanaltorkar (TC) liknar kammartorkar och man vill nu införa adaptiv styrning på dem. Syftet med studien var att analysera förutsättningarna för att tillämpa adaptiv styrning i TC-torken. En fältstudie genomfördes där funktionen adaptiv fuktkvotsberäkning som används som styrvariabel vid adaptiv styrning kontrollerades. Klimatmätningar under torkning genomfördes för att kontrollera om temperaturgivarna ger en bra bild av klimatet vid torksatsen. Resultatet visar att funktionen adaptiv fuktkvotsberäkning stämmer överens för start- och slutfuktkvot i TC-torken. Funktionen fungerade något sämre på satser som innehöll virke med blandade dimensioner. Klimatmätningarna visar att temperaturgivarna återskapar klimatet vid virkessatsen på ett korrekt vis. Simuleringar visar att virket idag övertorkas och att en viss förkortning av torktiden hade varit möjlig. Det finns goda förutsättningar för att tillämpa adaptiv styrning i TC-torken

För att minska energiförbrukningen och höja kapaciteten vid virkestorkning kan adaptiv styrning användas. Adaptiv styrning är en typ av processåterkoppling som visar på hur torkningen fortskrider och kan användas för att styra torkprocessen optimalt. Adaptiv styrning har funnits till kammartorkar länge. Tvärcirkulerande kanaltorkar (TC) liknar kammartorkar och man vill nu införa adaptiv styrning på dem. Syftet med studien var att analysera förutsättningarna för att tillämpa adaptiv styrning i TC-torken. En fältstudie genomfördes där funktionen adaptiv fuktkvotsberäkning som används som styrvariabel vid adaptiv styrning kontrollerades. Klimatmätningar under torkning genomfördes för att kontrollera om temperaturgivarna ger en bra bild av klimatet vid torksatsen. Resultatet visar att funktionen adaptiv fuktkvotsberäkning stämmer överens för start- och slutfuktkvot i TC-torken. Funktionen fungerade något sämre på satser som innehöll virke med blandade dimensioner. Klimatmätningarna visar att temperaturgivarna återskapar klimatet vid virkessatsen på ett korrekt vis. Simuleringar visar att virket idag övertorkas och att en viss förkortning av torktiden hade varit möjlig. Det finns goda förutsättningar för att tillämpa adaptiv styrning i TC-torken

In the present work, it was demonstrated that mass transfer and mass transfer coefficients related to the wood drying process can be satisfactorily quantified using thermography. The method was based on continuous measurements of the wood's surface temperature, which were converted to a vapor pressure at the wood surface. The results showed that the values of the experimentally obtained transfer coefficients were in the same order of magnitude as values obtained with classical empirical correlations that apply in boundary layer theory. The measurements also showed that an average value of the mass transfer coefficient obtained during drying satisfactorily describes the complete process. The measurement set-up makes it possible to determine a surface potential accurately and continuously, which is useful in the assessment of wood drying processes.

In the present work, it was demonstrated that mass transfer and mass transfer coefficients related to the wood drying process can be satisfactorily quantified using thermography. The method was based on continuous measurements of the wood's surface temperature, which were converted to a vapor pressure at the wood surface. The results showed that the values of the experimentally obtained transfer coefficients were in the same order of magnitude as values obtained with classical empirical correlations that apply in boundary layer theory. The measurements also showed that an average value of the mass transfer coefficient obtained during drying satisfactorily describes the complete process. The measurement set-up makes it possible to determine a surface potential accurately and continuously, which is useful in the assessment of wood drying processes.

The surface temperature of a drying wooden board is strongly related to the drying process. However, it is relatively difficult to determine the surface temperature accurately during drying. In this paper, an experimental setup for analyzing the wood surface during drying by thermal imaging as well as dry and wet-bulb temperature reference surfaces was tested. Spruce sapwood samples were dried in various climates and evaluated with respect to both mass loss and surface temperature. The experimental setup enabled both qualitative and quantitative analysis of the wood drying process. The results showed that thermal imaging enabled a detailed view of the drying progression. The distinct correlation between surface temperature and mass change showed that an accurate determination of a basic, often considered, and difficult-to-determine drying potential is possible.

This study aimed to evaluate the spatial distribution of the air circulation speed and the final moisture content of pine lumber after kiln drying by using geostatistics. Two kilns acting on boards of 27 mm and 42 mm were evaluated. Air circulation speed and final moisture content were collected in different regions of the kilns. There was no significant difference for air circulation speed and final moisture content between the front and rear regions of the equipment. In the horizontal axis (Y-axis), air circulation speed averages did not differ statistically in both situations, but higher values for this variable were obtained from the spaces between the piles. Final moisture content tended to increase when closer to the door opening. In the vertical axis (Z-axis), the lower part tended to reach higher air circulation speed values. Thus, the spatial behavior influences the air circulation speed and final moisture content during lumber drying. Besides, the variograms presented the same tendency in comparison to the data obtained in a conventional manner, which indicates that geostatistics can be used to represent variables in kilns during the drying process

The aim of this study was to determine how varying the inputted surface area value of wood samples would affect the determination of kiln-drying schedules using the drastic drying test. For this purpose, eight individuals of two Eucalyptus clones were selected. Specimens were obtained for drastic drying tests at 100 °C, to measure the basic density and to determine the initial moisture content. The initial and final temperatures and the drying potential were calculated in 100 mm × 50 mm × 10 mm samples, considering the surface area to be 130 cm² (Updated Method), in contrast to the surface area of 100 cm² that is commonly used in the method known as the Standard Method. Based on these findings, kiln-drying schedules were set for the lumber from each clone. Although the significant differences aforementioned, it was observed that the drying schedules developed by Standard Method and Updated Method are similar

A non-linear elastic constitutive model for a swelling/shrinking orthotropic wood matrix is proposed. Themodel is thermodynamically consistent, derived based on the principles of continuum mechanics and thehybrid mixture theory. Moisture induced strains are introduced considering finite deformations by assuming amultiplicative split of the deformation gradient tensor into a swelling and an elastic part. Novel definitions ofthe Cauchy stress tensor and the moisture-dependent elastic material tangent matrix are obtained. The modelis coupled to a multi-phase transient mass and heat transport model developed in Part I of this work. Inthis part of the work 2-D and 3-D test examples are used to describe the ability of the model to simulatemoisture-induced distortions when drying wood within the hygroscopic and also from the over-hygroscopicmoisture ranges. Despite deriving the model considering wood, the obtained constitutive relations can besuitably adopted to other orthotropic porous materials displaying properties similar to that of wood.

A non-linear elastic constitutive model for a swelling/shrinking orthotropic wood matrix is proposed. Themodel is thermodynamically consistent, derived based on the principles of continuum mechanics and thehybrid mixture theory. Moisture induced strains are introduced considering finite deformations by assuming amultiplicative split of the deformation gradient tensor into a swelling and an elastic part. Novel definitions ofthe Cauchy stress tensor and the moisture-dependent elastic material tangent matrix are obtained. The modelis coupled to a multi-phase transient mass and heat transport model developed in Part I of this work. Inthis part of the work 2-D and 3-D test examples are used to describe the ability of the model to simulatemoisture-induced distortions when drying wood within the hygroscopic and also from the over-hygroscopicmoisture ranges. Despite deriving the model considering wood, the obtained constitutive relations can besuitably adopted to other orthotropic porous materials displaying properties similar to that of wood.

A non-linear elastic constitutive model for a swelling/shrinking orthotropic wood matrix is proposed. Themodel is thermodynamically consistent, derived based on the principles of continuum mechanics and thehybrid mixture theory. Moisture induced strains are introduced considering finite deformations by assuming amultiplicative split of the deformation gradient tensor into a swelling and an elastic part. Novel definitions ofthe Cauchy stress tensor and the moisture-dependent elastic material tangent matrix are obtained. The modelis coupled to a multi-phase transient mass and heat transport model developed in Part I of this work. Inthis part of the work 2-D and 3-D test examples are used to describe the ability of the model to simulatemoisture-induced distortions when drying wood within the hygroscopic and also from the over-hygroscopicmoisture ranges. Despite deriving the model considering wood, the obtained constitutive relations can besuitably adopted to other orthotropic porous materials displaying properties similar to that of wood.

A non-linear elastic constitutive model for a swelling/shrinking orthotropic wood matrix is proposed. Themodel is thermodynamically consistent, derived based on the principles of continuum mechanics and thehybrid mixture theory. Moisture induced strains are introduced considering finite deformations by assuming amultiplicative split of the deformation gradient tensor into a swelling and an elastic part. Novel definitions ofthe Cauchy stress tensor and the moisture-dependent elastic material tangent matrix are obtained. The modelis coupled to a multi-phase transient mass and heat transport model developed in Part I of this work. Inthis part of the work 2-D and 3-D test examples are used to describe the ability of the model to simulatemoisture-induced distortions when drying wood within the hygroscopic and also from the over-hygroscopicmoisture ranges. Despite deriving the model considering wood, the obtained constitutive relations can besuitably adopted to other orthotropic porous materials displaying properties similar to that of wood.

This study aimed to evaluate the spatial distribution of the air circulation speed and the final moisture content of pine lumber after kiln drying by using geostatistics. Two kilns acting on boards of 27 mm and 42 mm were evaluated. Air circulation speed and final moisture content were collected in different regions of the kilns. There was no significant difference for air circulation speed and final moisture content between the front and rear regions of the equipment. In the horizontal axis (Y-axis), air circulation speed averages did not differ statistically in both situations, but higher values for this variable were obtained from the spaces between the piles. Final moisture content tended to increase when closer to the door opening. In the vertical axis (Z-axis), the lower part tended to reach higher air circulation speed values. Thus, the spatial behavior influences the air circulation speed and final moisture content during lumber drying. Besides, the variograms presented the same tendency in comparison to the data obtained in a conventional manner, which indicates that geostatistics can be used to represent variables in kilns during the drying process

The aim of this study was to determine how varying the inputted surface area value of wood samples would affect the determination of kiln-drying schedules using the drastic drying test. For this purpose, eight individuals of two Eucalyptus clones were selected. Specimens were obtained for drastic drying tests at 100 °C, to measure the basic density and to determine the initial moisture content. The initial and final temperatures and the drying potential were calculated in 100 mm × 50 mm × 10 mm samples, considering the surface area to be 130 cm² (Updated Method), in contrast to the surface area of 100 cm² that is commonly used in the method known as the Standard Method. Based on these findings, kiln-drying schedules were set for the lumber from each clone. Although the significant differences aforementioned, it was observed that the drying schedules developed by Standard Method and Updated Method are similar

A non-linear elastic constitutive model for a swelling/shrinking orthotropic wood matrix is proposed. Themodel is thermodynamically consistent, derived based on the principles of continuum mechanics and thehybrid mixture theory. Moisture induced strains are introduced considering finite deformations by assuming amultiplicative split of the deformation gradient tensor into a swelling and an elastic part. Novel definitions ofthe Cauchy stress tensor and the moisture-dependent elastic material tangent matrix are obtained. The modelis coupled to a multi-phase transient mass and heat transport model developed in Part I of this work. Inthis part of the work 2-D and 3-D test examples are used to describe the ability of the model to simulatemoisture-induced distortions when drying wood within the hygroscopic and also from the over-hygroscopicmoisture ranges. Despite deriving the model considering wood, the obtained constitutive relations can besuitably adopted to other orthotropic porous materials displaying properties similar to that of wood.

The article considers the problem of sawn timber drying. The relevance of research is driven by the need to improve the automated process control system for drying sawn timber on the basis of modern information technologies, as well as to reduce the energy intensity of these technologies, which is enshrined in the program documents of forest industry development at the government level. The functional purpose of the automated control system is to provide a set level of the wood moisture content with the required quality of wood (zero ruptures). It is of immense complexity to obtain such functional dependency on the heating temperature in the chamber and the equilibrium air humidity by traditional statistical met-hods due to the uncertainty conditions of parameters, therefore, the apparatus of the fuzzy set theory should be used. Thus, the research purpose included generation of functional dependences of the sawn timber moisture content and drying time on the heating temperature and the equilibrium air humidity in the drying chamber based on fuzzy inference. The methodological basis of the theoretical studies was as follows: the theory of drying; the provisions of mathematical and fuzzy modeling; and, in terms of checking the adequacy of the proposed fuzzy model, the methods of mathematical statistics and experimental theory. The research results are the obtained dependences of the moisture content of sawn timber and drying time on the heating temperature and the equilibrium air humidity in the drying chamber, the synthesis of which is performed by means of Fuzzy Logic Toolbox of MATLAB application. The proposed functions of the moisture content and sawn timber drying time take into account the basic process configurations (the heating temperature and the equilibrium air humidity) and are experimentally verified for adequacy. The practical applicability of the results lies in the possibility of creating an intelligent system of automatic control of the sawn timber dr, Рассмотрена проблема сушки пиломатериалов. Актуальность исследований обусловлена необходимостью совершенствования системы автоматизированного управления технологическим процессом сушки пиломатериалов на базе современных информационных технологий, снижения энергоемкости этих технологий, что закреплено в программных документах развития лесной отрасли на правительственном уровне. Функциональным назначением системы автоматизированного управления является обеспечение заданного уровня влажности древесины при ее необходимом качестве (исключение повреждений). Получить такую функциональную зависимость от температуры нагрева в камере и равновесной влажности воздуха традиционными статистическими методами чрезвычайно сложно из-за условий неопределенности параметров, поэтому следует использовать аппарат теории нечетких множеств. Цель исследований заключалась в получении функциональных зависимостей влажности пиломатериалов и времени сушки от температуры нагрева и равновесной влажности воздуха в сушильной камере на основе нечеткого вывода. Методологическую основу теоретических исследований составили: теория сушки, положения математического и нечеткого моделирования, а в части проверки адекватности предложенной нечеткой модели – методы математической статистики и теории эксперимента. Результатами исследований являются полученные зависимости влажности пиломатериалов и времени сушки от температуры нагрева и равновесной влажности воздуха в сушильной камере, синтез которых выполнен средствами Fuzzy Logic Toolbox приложения MATLAB. Предложенные функции влажности и времени сушки пиломатериалов учитывают основные параметры процесса (температуру нагрева и равновесную влажность воздуха) и экспериментально проверены на адекватность. Практическая применимость результатов заключается в возможности создания интеллектуальной системы автоматического управления процессом сушки пиломатериалов.

Considering that drying is one of the main stages of wood used for the generation of steam, this paper presents an analysis of the drying process of wood used to feed boilers of a company located in the south of Brazil, over the period of one year. The scope of the present study is dunnii eucalyptus type. However a comparison with the saligna type was made in order to calculate the energetic gains between these two species in relation to their drying. And a comparison between the power generated by both species was made. The paper also presents a relationship between covered piles of firewood and uncovered piles, as well as their cost/benefit results. It was possible to verify that the best time of the year for the firewood cutting in the region under study is until the end of September, so the piles will have at least five months of exposure during the summer months. It has also been found that covered piles can reduce humidity up to 20%, and have a viable cost/benefit., Considerando que a secagem é uma das principais etapas da lenha quando esta é utilizada para a geração de vapor, este trabalho apresenta uma análise do comportamento da secagem de lenha ao longo de um ano utilizada para alimentar caldeiras de uma empresa localizada no sul do Brasil. O escopo do estudo é o tipo de eucalyptus dunnii, porém se fez um comparativo com o tipo saligna para que fosse possível calcular os ganhos energéticos entre estas duas espécies em relação ao tempo de secagem, assim como um comparativo entre o poder calorífico de ambas as espécies. O trabalho também apresenta uma relação entre pilhas de lenha cobertas com lona e pilhas não cobertas, assim como seus resultados de custo/benefício. Foi possível constatar que a melhor época do ano para realização do corte da lenha, para a região em estudo, é até o final do mês de setembro, pois assim as pilhas terão, no mínimo, cinco meses de exposição aos meses de verão. Constatou-se também que pilhas cobertas conseguem reduzir a umidade para até 20%, e têm seu custo/benefício viável.

Considering that drying is one of the main stages of wood used for the generation of steam, this paper presents an analysis of the drying process of wood used to feed boilers of a company located in the south of Brazil, over the period of one year. The scope of the present study is dunnii eucalyptus type. However a comparison with the saligna type was made in order to calculate the energetic gains between these two species in relation to their drying. And a comparison between the power generated by both species was made. The paper also presents a relationship between covered piles of firewood and uncovered piles, as well as their cost/benefit results. It was possible to verify that the best time of the year for the firewood cutting in the region under study is until the end of September, so the piles will have at least five months of exposure during the summer months. It has also been found that covered piles can reduce humidity up to 20%, and have a viable cost/benefit., Considerando que a secagem é uma das principais etapas da lenha quando esta é utilizada para a geração de vapor, este trabalho apresenta uma análise do comportamento da secagem de lenha ao longo de um ano utilizada para alimentar caldeiras de uma empresa localizada no sul do Brasil. O escopo do estudo é o tipo de eucalyptus dunnii, porém se fez um comparativo com o tipo saligna para que fosse possível calcular os ganhos energéticos entre estas duas espécies em relação ao tempo de secagem, assim como um comparativo entre o poder calorífico de ambas as espécies. O trabalho também apresenta uma relação entre pilhas de lenha cobertas com lona e pilhas não cobertas, assim como seus resultados de custo/benefício. Foi possível constatar que a melhor época do ano para realização do corte da lenha, para a região em estudo, é até o final do mês de setembro, pois assim as pilhas terão, no mínimo, cinco meses de exposição aos meses de verão. Constatou-se também que pilhas cobertas conseguem reduzir a umidade para até 20%, e têm seu custo/benefício viável.

The estimation of the pixel-wise distribution of the moisture content (MC) in wood using X-ray computed tomography (CT) requires two scans of the same wood specimen at different MCs, one of which is known. Image-processing algorithms are needed to compensate for the anisotropic distortion that wood undergoes as it dries. An alternative technique based on dual-energy CT (DECT) to determine MC in wood has been suggested by several authors. The purpose of the present study was to evaluate the hypothesis that DECT can be used for the determination of MC in real time. A method based on the use of the quotient between the linear attenuation coefficients (μ) at different acceleration voltages (the so-called quotient method) was used. A statistical model was created to estimate the MC in solid sapwood of Scots pine, Norway spruce and brittle willow. The results show a regression model with R2 > 0.97 that can predict the MC in these species with a RMSE of prediction of 0.07, 0.04 and 0.11 (MC in decimal format) respectively and at MC levels ranging from the green to the totally dry condition. Individual measurements of MC show an uncertainty of up to ±0.4. It is concluded that under the conditions prevailing in this study, and in studies referred to in this paper, it is not possible to measure MC with DECT., Validerad;2019;Nivå 2;2019-10-24 (johcin)

The estimation of the pixel-wise distribution of the moisture content (MC) in wood using X-ray computed tomography (CT) requires two scans of the same wood specimen at different MCs, one of which is known. Image-processing algorithms are needed to compensate for the anisotropic distortion that wood undergoes as it dries. An alternative technique based on dual-energy CT (DECT) to determine MC in wood has been suggested by several authors. The purpose of the present study was to evaluate the hypothesis that DECT can be used for the determination of MC in real time. A method based on the use of the quotient between the linear attenuation coefficients (μ) at different acceleration voltages (the so-called quotient method) was used. A statistical model was created to estimate the MC in solid sapwood of Scots pine, Norway spruce and brittle willow. The results show a regression model with R2 > 0.97 that can predict the MC in these species with a RMSE of prediction of 0.07, 0.04 and 0.11 (MC in decimal format) respectively and at MC levels ranging from the green to the totally dry condition. Individual measurements of MC show an uncertainty of up to ±0.4. It is concluded that under the conditions prevailing in this study, and in studies referred to in this paper, it is not possible to measure MC with DECT., Validerad;2019;Nivå 2;2019-10-24 (johcin)

The drying of Eucalyptus nitens is a troublesome process as the species is extremely prone to drying defects. This paper reports ongoing research toimprove the understanding of surface checking and cell collapse in Chilean grown Eucalyptus nitens during drying. Computed tomography (CT) scanning was used as a powerful tool for studying the internal changes in the wood-material during the drying process. Different levels of temperatures have been tested with the same equilibrium moisture content (EMC) conditions and low air velocity. The results confirm that a low drying temperature and a low air velocity, which results in a slow rate of drying, reduce internal cell collapse and surface checking .

[EN] The drying of Eucalyptus nitens is a troublesome process as the species is extremely prone to drying defects. This paper reports ongoing research to improve the understanding of surface checking and cell collapse in Chilean grown Eucalyptus nitens during drying. Computed tomography (CT) scanning was used as a powerful tool for studying the internal changes in the wood-material during the drying process. Different levels of temperatures have been tested with the same equilibrium moisture content (EMC) conditions and low air velocity. The results confirm that a low drying temperature and a low air velocity, which results in a slow rate of drying, reduce internal cell collapse and surface checking .

The occurrence of wetwood in balsam fir is a problem in the drying of sawn lumber: drying time increases and moisture content of dried lumber is heterogeneous. Permeability may be used as an indicator of drying rates. Longitudinal, radial, and tangential intrinsic permeability of balsam fir wet-wood and normal heartwood was measured in this study. The longitudinal intrinsic permeability was about 2,000 times and 9,000 times higher than the tangential and the radial intrinsic permeability, respectively. Wetwood had a higher longitudinal permeability than normal heartwood, but no significant difference was found between the radial and tangential directions. Sampling height in the tree, basic density, and growth ring width had no effect on the intrinsic permeability. An increase of latewood percentage in the growth rings resulted in an increase in longitudinal intrinsic permeability and a decrease in tangential intrinsic permeability. Radial flow seemed to be controlled by ray blockage in wetwood and normal heartwood, which may result in radial impermeability of wood. A poorly drained stand seemed to favor wetwood formation.

Collapse and drying stresses are currently induced during the drying of Eucalyptus nitens in solid wood products. The purpose of this study was to investigate these drying stresses by measuring hygromechanical strains during the drying of Eucalyptus nitens boards. Small samples of Eucalyptus nitens wood were oriented in the radial and tangential directions and tested to determine the hygromechanical strains during the drying process. This experimental work consisted of cantilevered bending tests conducted under variable relative humidity conditions. Tests were performed in a conditioning chamber at 30 °C with an equilibrium moisture content ranging from 22 to 12% under four levels of stress: 0, 10, 20 and 30% of the rupture load. The strains were determined using strain gauges, and the total deflection was measured with a linear variable differential transformer. The results show that in hygromechanical strains during the drying of Eucalyptus nitens, both the surface deformation and mechano-sorption strain were found to be proportional to the applied stress and reached their maximum values in the tangential direction. The total deflection increased 0,18 mm/mm with a surface deformation of 0,20 mm/mm, and the mechano-sorptive strain provides a greater contribution with a value of 0,11 mm/mm, thus corresponding to 59% of the total deformation. In attempts to improve the drying schedules of Eucalyptus nitens to develop solid wood products, mechano-sorptive behavior may be applied to relieve collapse and drying stress.

The drying of Eucalyptus nitens is a troublesome process as the species is extremely prone to drying defects. This paper reports ongoing research toimprove the understanding of surface checking and cell collapse in Chilean grown Eucalyptus nitens during drying. Computed tomography (CT) scanning was used as a powerful tool for studying the internal changes in the wood-material during the drying process. Different levels of temperatures have been tested with the same equilibrium moisture content (EMC) conditions and low air velocity. The results confirm that a low drying temperature and a low air velocity, which results in a slow rate of drying, reduce internal cell collapse and surface checking .

[EN] The drying of Eucalyptus nitens is a troublesome process as the species is extremely prone to drying defects. This paper reports ongoing research to improve the understanding of surface checking and cell collapse in Chilean grown Eucalyptus nitens during drying. Computed tomography (CT) scanning was used as a powerful tool for studying the internal changes in the wood-material during the drying process. Different levels of temperatures have been tested with the same equilibrium moisture content (EMC) conditions and low air velocity. The results confirm that a low drying temperature and a low air velocity, which results in a slow rate of drying, reduce internal cell collapse and surface checking .

[EN] The drying of Eucalyptus nitens is a troublesome process as the species is extremely prone to drying defects. This paper reports ongoing research to improve the understanding of surface checking and cell collapse in Chilean grown Eucalyptus nitens during drying. Computed tomography (CT) scanning was used as a powerful tool for studying the internal changes in the wood-material during the drying process. Different levels of temperatures have been tested with the same equilibrium moisture content (EMC) conditions and low air velocity. The results confirm that a low drying temperature and a low air velocity, which results in a slow rate of drying, reduce internal cell collapse and surface checking .

[EN] The drying of Eucalyptus nitens is a troublesome process as the species is extremely prone to drying defects. This paper reports ongoing research to improve the understanding of surface checking and cell collapse in Chilean grown Eucalyptus nitens during drying. Computed tomography (CT) scanning was used as a powerful tool for studying the internal changes in the wood-material during the drying process. Different levels of temperatures have been tested with the same equilibrium moisture content (EMC) conditions and low air velocity. The results confirm that a low drying temperature and a low air velocity, which results in a slow rate of drying, reduce internal cell collapse and surface checking .

Virkestorkning är ett mycket energikrävande men nödvändigt förädlingssteg för träindustrin. Eftersom energi- och tidsåtgången framförallt är beroende av mängden fukt som ska drivas ur virket så är kännedom om virkets initiala och slutliga fuktinnehåll avgörande för en optimerad process. Industriellt, idag, görs ofta en grov uppskattning av virkets initiala fuktmängd. Denna fuktmängd ligger sedan till grund för torkningens genomförande och dess resultat. I föreliggande arbete undersöks huruvida invägning av virkespaketen före torkning kan användas för att bestämma virkets fuktinnehåll och hur detta kan bidra till att optimera torkprocessen. 17 fullständiga torkningsförsök genomfördes på ett konventionellt sågverk i norra Sverige. I försöken vägdes virkespaketen och torkningsscheman anpassades därefter.Genom mätningar av virkets fuktkvot och jämförelse med tidigare torkning där konventionella torkningsscheman använts så kunde det konstateras att paketvägningen bidrar till en förbättrad och optimerad torkningsprocess., Drying is a very energy-intensive but important process in the wood industry. Since the amount of energy used is, more or less, proportional to the amount of water released, the measurement of the initial and final wood moisture content is crucial to optimize the process. Today, a rough estimate of the initial wood moisture content is used as dryer operation input data. The process could be improved by a more accurate determination of the initial moisture level. The present work examines if weighing the wood can be used as a method to determine the wood moisture level and how this can optimize the drying process. 17 drying trials were conducted at a sawmill in northern Sweden. The wood was weighed and new drying schedules were constructed and adjusted accordingly. The result show that weighing the wood results in more accurate drying schedules and overall an optimized drying process.

Virkestorkning är ett mycket energikrävande men nödvändigt förädlingssteg för träindustrin. Eftersom energi- och tidsåtgången framförallt är beroende av mängden fukt som ska drivas ur virket så är kännedom om virkets initiala och slutliga fuktinnehåll avgörande för en optimerad process. Industriellt, idag, görs ofta en grov uppskattning av virkets initiala fuktmängd. Denna fuktmängd ligger sedan till grund för torkningens genomförande och dess resultat. I föreliggande arbete undersöks huruvida invägning av virkespaketen före torkning kan användas för att bestämma virkets fuktinnehåll och hur detta kan bidra till att optimera torkprocessen. 17 fullständiga torkningsförsök genomfördes på ett konventionellt sågverk i norra Sverige. I försöken vägdes virkespaketen och torkningsscheman anpassades därefter.Genom mätningar av virkets fuktkvot och jämförelse med tidigare torkning där konventionella torkningsscheman använts så kunde det konstateras att paketvägningen bidrar till en förbättrad och optimerad torkningsprocess., Drying is a very energy-intensive but important process in the wood industry. Since the amount of energy used is, more or less, proportional to the amount of water released, the measurement of the initial and final wood moisture content is crucial to optimize the process. Today, a rough estimate of the initial wood moisture content is used as dryer operation input data. The process could be improved by a more accurate determination of the initial moisture level. The present work examines if weighing the wood can be used as a method to determine the wood moisture level and how this can optimize the drying process. 17 drying trials were conducted at a sawmill in northern Sweden. The wood was weighed and new drying schedules were constructed and adjusted accordingly. The result show that weighing the wood results in more accurate drying schedules and overall an optimized drying process.

In this work, a set-up with a device measuring the mass of wood packages is examined as an aid to estimate the average moisture content (MC) of wood packages. As the basic density needs to be presumed in the set-up, an estimator of the basic density as a function of log diameter is determined for Norway spruce (Picea abies (L.) Karst) and Scots pine (Pinus sylvestris). In total, 1920 specimens were collected at two different sawmills and analysed for this purpose. Specimens collected at the butt-end of pine had the greatest variation in basic density and it is recommended that they should be omitted when sawmills create their own functions for basic density estimation. Furthermore, the variation in basic density was shown to have the greatest impact on the estimated MC. A maximum error estimator of the MC became 14% at a MC of 70% and 9% at a MC of 10%. It was therefore concluded that the described method should not be used to estimate the MC of packages after drying but can serve as a valuable indicator of average green MC of a drying batch.

In this work, a set-up with a device measuring the mass of wood packages is examined as an aid to estimate the average moisture content (MC) of wood packages. As the basic density needs to be presumed in the set-up, an estimator of the basic density as a function of log diameter is determined for Norway spruce (Picea abies (L.) Karst) and Scots pine (Pinus sylvestris). In total, 1920 specimens were collected at two different sawmills and analysed for this purpose. Specimens collected at the butt-end of pine had the greatest variation in basic density and it is recommended that they should be omitted when sawmills create their own functions for basic density estimation. Furthermore, the variation in basic density was shown to have the greatest impact on the estimated MC. A maximum error estimator of the MC became 14% at a MC of 70% and 9% at a MC of 10%. It was therefore concluded that the described method should not be used to estimate the MC of packages after drying but can serve as a valuable indicator of average green MC of a drying batch.

During the drying of sawn timber, hydrostatic tension forces within the cell may exceed the compressive strength perpendicular to the grain of the thin cell wall and the cell then collapses. This phenomenon is common in hardwoods such as Sequoia sempervirens, Thuja plicata, Tsuga heterophylla, Juglans nigraand many species of eucalyptus and oak. Usually, this leads to severe surface deformation, and both surface and internal checking(honeycombing) may occur. The quality of the final product is lowered by these cracks and deformations. The aim of this study was to investigate, by CT-scanning samples throughout the drying process, whether it is possible to detect when and how cracking and deformation occurs and develops in specimens of Eucalyptus nitens. Based on this knowledge, better drying schedules can be developed to improve the yield and ensure a higher quality of the sawn timber. Three specimens, one specimen in each drying run, of Eucalyptus nitens were used for the tests. Their cross-sectional dimensions, prior to drying, were 105x23 mm2 and their length was 70 cm. A specially designed laboratory drying kiln that fits within the gantry of a Siemens Somatom Emotion medical CT-scanner was used (Fig. 1). With this equipment, it is possible to scan the inside of the kiln without interrupting the drying process.

Eucalyptus nitens has become a commercially important species in Chile and it isrepresenting one of the fastest growing wood-stock in the country. Today, it is widelyused for pulp and paper production, but the interest in using the solid wood has increasedin recent years. Before the sawn timber can be utilized, its moisture content must bereduced. Often during drying, hydrostatic tension forces within the cell exceed thecompressive strength of the thin cell wall of Eucalyptus nitens and the cell collapses. Thisphenomenon usually leads to severe surface deformation and both surface and internalcracks (honeycombing). Yield and quality of the final product, and thereby sawmills’profitability, are decreased by these cracks and deformations. The aim of this study wasto investigate, by CT-scanning samples throughout the drying process, if it is possible todetect when and how cracking and deformation occurs and develops in specimens ofEucalyptus nitens from Chile. Based on this knowledge, better drying schedules canhopefully be developed to improve the yield and provide a higher end-quality of the sawntimber.

Collapse and drying stresses are currently induced during the drying of Eucalyptus nitens in solid wood products. The purpose of this study was to investigate these drying stresses by measuring hygromechanical strains during the drying of Eucalyptus nitens boards. Small samples of Eucalyptus nitens wood were oriented in the radial and tangential directions and tested to determine the hygromechanical strains during the drying process. This experimental work consisted of cantilevered bending tests conducted under variable relative humidity conditions. Tests were performed in a conditioning chamber at 30 °C with an equilibrium moisture content ranging from 22 to 12% under four levels of stress: 0, 10, 20 and 30% of the rupture load. The strains were determined using strain gauges, and the total deflection was measured with a linear variable differential transformer. The results show that in hygromechanical strains during the drying of Eucalyptus nitens, both the surface deformation and mechano-sorption strain were found to be proportional to the applied stress and reached their maximum values in the tangential direction. The total deflection increased 0,18 mm/mm with a surface deformation of 0,20 mm/mm, and the mechano-sorptive strain provides a greater contribution with a value of 0,11 mm/mm, thus corresponding to 59% of the total deformation. In attempts to improve the drying schedules of Eucalyptus nitens to develop solid wood products, mechano-sorptive behavior may be applied to relieve collapse and drying stress.

Collapse and drying stresses are currently induced during the drying of Eucalyptus nitens in solid wood products. The purpose of this study was to investigate these drying stresses by measuring hygromechanical strains during the drying of Eucalyptus nitens boards.Small samples of Eucalyptus nitens wood were oriented in the radial and tangential directions and tested to determine the hygromechanical strains during the drying process. This experimental work consisted of cantilevered bending tests conducted under variable relative humidity conditions. Tests were performed in a conditioning chamber at 30 °C with an equilibrium moisture content ranging from 22 to 12% under four levels of stress: 0, 10, 20 and 30% of the rupture load. The strains were determined using strain gauges, and the total deflection was measured with a linear variable differential transformer.The results show that in hygromechanical strains during the drying of Eucalyptus nitens, both the surface deformation and mechano-sorption strain were found to be proportional to the applied stress and reached their maximum values in the tangential direction. The total deflection increased 0,18 mm/mm with a surface deformation of 0,20 mm/mm, and the mechano-sorptive strain provides a greater contribution with a value of 0,11 mm/mm, thus corresponding to 59% of the total deformation. In attempts to improve the drying schedules of Eucalyptus nitens to develop solid wood products, mechano-sorptive behavior may be applied to relieve collapse and drying stress.

Collapse and drying stresses are currently induced during the drying of Eucalyptus nitens in solid wood products. The purpose of this study was to investigate these drying stresses by measuring hygromechanical strains during the drying of Eucalyptus nitens boards.Small samples of Eucalyptus nitens wood were oriented in the radial and tangential directions and tested to determine the hygromechanical strains during the drying process. This experimental work consisted of cantilevered bending tests conducted under variable relative humidity conditions. Tests were performed in a conditioning chamber at 30 °C with an equilibrium moisture content ranging from 22 to 12% under four levels of stress: 0, 10, 20 and 30% of the rupture load. The strains were determined using strain gauges, and the total deflection was measured with a linear variable differential transformer.The results show that in hygromechanical strains during the drying of Eucalyptus nitens, both the surface deformation and mechano-sorption strain were found to be proportional to the applied stress and reached their maximum values in the tangential direction. The total deflection increased 0,18 mm/mm with a surface deformation of 0,20 mm/mm, and the mechano-sorptive strain provides a greater contribution with a value of 0,11 mm/mm, thus corresponding to 59% of the total deformation. In attempts to improve the drying schedules of Eucalyptus nitens to develop solid wood products, mechano-sorptive behavior may be applied to relieve collapse and drying stress.

In this work, a set-up with a device measuring the mass of wood packages is examined as an aid to estimate the average moisture content (MC) of wood packages. As the basic density needs to be presumed in the set-up, an estimator of the basic density as a function of log diameter is determined for Norway spruce (Picea abies (L.) Karst) and Scots pine (Pinus sylvestris). In total, 1920 specimens were collected at two different sawmills and analysed for this purpose. Specimens collected at the butt-end of pine had the greatest variation in basic density and it is recommended that they should be omitted when sawmills create their own functions for basic density estimation. Furthermore, the variation in basic density was shown to have the greatest impact on the estimated MC. A maximum error estimator of the MC became 14% at a MC of 70% and 9% at a MC of 10%. It was therefore concluded that the described method should not be used to estimate the MC of packages after drying but can serve as a valuable indicator of average green MC of a drying batch.

Collapse and drying stresses are currently induced during the drying of Eucalyptus nitens in solid wood products. The purpose of this study was to investigate these drying stresses by measuring hygromechanical strains during the drying of Eucalyptus nitens boards.Small samples of Eucalyptus nitens wood were oriented in the radial and tangential directions and tested to determine the hygromechanical strains during the drying process. This experimental work consisted of cantilevered bending tests conducted under variable relative humidity conditions. Tests were performed in a conditioning chamber at 30 °C with an equilibrium moisture content ranging from 22 to 12% under four levels of stress: 0, 10, 20 and 30% of the rupture load. The strains were determined using strain gauges, and the total deflection was measured with a linear variable differential transformer.The results show that in hygromechanical strains during the drying of Eucalyptus nitens, both the surface deformation and mechano-sorption strain were found to be proportional to the applied stress and reached their maximum values in the tangential direction. The total deflection increased 0,18 mm/mm with a surface deformation of 0,20 mm/mm, and the mechano-sorptive strain provides a greater contribution with a value of 0,11 mm/mm, thus corresponding to 59% of the total deformation. In attempts to improve the drying schedules of Eucalyptus nitens to develop solid wood products, mechano-sorptive behavior may be applied to relieve collapse and drying stress.

Collapse and drying stresses are currently induced during the drying of Eucalyptus nitens in solid wood products. The purpose of this study was to investigate these drying stresses by measuring hygromechanical strains during the drying of Eucalyptus nitens boards.Small samples of Eucalyptus nitens wood were oriented in the radial and tangential directions and tested to determine the hygromechanical strains during the drying process. This experimental work consisted of cantilevered bending tests conducted under variable relative humidity conditions. Tests were performed in a conditioning chamber at 30 °C with an equilibrium moisture content ranging from 22 to 12% under four levels of stress: 0, 10, 20 and 30% of the rupture load. The strains were determined using strain gauges, and the total deflection was measured with a linear variable differential transformer.The results show that in hygromechanical strains during the drying of Eucalyptus nitens, both the surface deformation and mechano-sorption strain were found to be proportional to the applied stress and reached their maximum values in the tangential direction. The total deflection increased 0,18 mm/mm with a surface deformation of 0,20 mm/mm, and the mechano-sorptive strain provides a greater contribution with a value of 0,11 mm/mm, thus corresponding to 59% of the total deformation. In attempts to improve the drying schedules of Eucalyptus nitens to develop solid wood products, mechano-sorptive behavior may be applied to relieve collapse and drying stress.

During the drying of sawn timber, hydrostatic tension forces within the cell may exceed the compressive strength perpendicular to the grain of the thin cell wall and the cell then collapses. This phenomenon is common in hardwoods such as Sequoia sempervirens, Thuja plicata, Tsuga heterophylla, Juglans nigraand many species of eucalyptus and oak. Usually, this leads to severe surface deformation, and both surface and internal checking(honeycombing) may occur. The quality of the final product is lowered by these cracks and deformations. The aim of this study was to investigate, by CT-scanning samples throughout the drying process, whether it is possible to detect when and how cracking and deformation occurs and develops in specimens of Eucalyptus nitens. Based on this knowledge, better drying schedules can be developed to improve the yield and ensure a higher quality of the sawn timber. Three specimens, one specimen in each drying run, of Eucalyptus nitens were used for the tests. Their cross-sectional dimensions, prior to drying, were 105x23 mm2 and their length was 70 cm. A specially designed laboratory drying kiln that fits within the gantry of a Siemens Somatom Emotion medical CT-scanner was used (Fig. 1). With this equipment, it is possible to scan the inside of the kiln without interrupting the drying process.

Eucalyptus nitens has become a commercially important species in Chile and it isrepresenting one of the fastest growing wood-stock in the country. Today, it is widelyused for pulp and paper production, but the interest in using the solid wood has increasedin recent years. Before the sawn timber can be utilized, its moisture content must bereduced. Often during drying, hydrostatic tension forces within the cell exceed thecompressive strength of the thin cell wall of Eucalyptus nitens and the cell collapses. Thisphenomenon usually leads to severe surface deformation and both surface and internalcracks (honeycombing). Yield and quality of the final product, and thereby sawmills’profitability, are decreased by these cracks and deformations. The aim of this study wasto investigate, by CT-scanning samples throughout the drying process, if it is possible todetect when and how cracking and deformation occurs and develops in specimens ofEucalyptus nitens from Chile. Based on this knowledge, better drying schedules canhopefully be developed to improve the yield and provide a higher end-quality of the sawntimber.

Microwave treatment can be used to increase wood permeability, speeding subsequent drying or impregnation processes with potential savings in time, energy and cost. However microwave treatment can reduce the strength of the treated timber. Treatment pressure can be used to alter the boiling point of water, which could have a significant effect on the resultant strength and permeability. Three methodologies were used to investigate the relationship between microwave treatment conditions, in particular pneumatic pressure, and the resultant strength and permeability of the timber. A device was designed and constructed with the aim of enabling the simultaneous measurement of the permeability of small cylindrical samples during microwave treatment. Testing of the individual components proved successful, however moisture vapour generated during microwave heating of the timber samples presented problems during combined testing. Permeability measurements were performed separately in the second and third methodologies and utilised larger samples. Controlled temperature and controlled power density treatments were trialled with the controlled power density treatment providing more consistent results. Bending testing and an impregnation cycle were found to be the most reliable methods of assessing strength and permeability respectively. High power microwave treatment increased the permeability and reduced the strength of the treated timber. Treating the samples under elevated pressure, followed by an immediate pressure delta minimised this strength loss. A ranking system was proposed to assess the combined strength and permeability resulting from treatment. Using this ranking system, an optimum balance between high permeability and maximum strength was obtained using a high power, Elevated Pressure Microwave treatment followed by an Immediate Pressure Delta (EPMIPD). This treatment performed better than atmospheric pressure microwave treatments conducted as part of this resear

Discoloration of birch wood during kiln drying is a considerable problem for theindustry, since any deviation from the preferred bright whitish colour reduces theusability and value of the sawn timber. This study was conducted in an effort toincrease the understanding of how MC, temperature and air humidity influence silverbirch lightness. The air humidity was represented by the equilibrium moisturecontent (EMC). Within the investigated intervals of 20-70°C and 9-20% EMC, theCIELAB colorimetric responses, were measured at the surface and at depths of 1 and5 mm below the surface. The results showed that lightness reduction was mainlycontrolled by temperature when long as the local moisture content of wood (MC)exceeded the fibre saturation point (FSP). High temperature in combination withhigh EMC levels promote lightness reduction. Transformation of naturally occurringwood constituents into coloured substances takes place within hours and does notappear to be caused by process related precursors. This study showed that visuallydetectable darkening occurred in samples with a local MC exceeding the FSP whenexposed to drying temperatures higher than 40°C in combination with EMC levelsabove 15%.

Numerical and experimental investigations were carried out on well defined log-disc samples of Norway spruce consisting of both heartwood and sapwood, with the aim of gaining more adequate knowledge of stress and fracture generation during the drying process. Use of thin discs enabled a well-controlled and simplified drying history of the samples to be obtained. Experiments supported by the numerical model showed the heartwood to dry below the fibre saturation point, much earlier than the sapwood, and thus to start shrinking at a much earlier stage.

Moisture-induced fracture and lack of shape stability in solid wood products are well known problems to the saw-milling and building industries. Cracks that initiate during the drying process may cause severe material losses and the building industry may be forced to use alternative building materials. The cracking caused by kiln-drying of solid timber (and round wood) is extremely difficult to predict due to the strong orthotropic and non-homogeneous characteristics of the material in combination with considerable amounts of microscopic defects which may act as crack initiators. An experimental study has been performed to reveal the cracking behaviour of Norway spruce during drying from green moisture content down to equilibrium moisture content (EMC) at a temperature of 22-24°C and a RH of 64%. The moisture related strains and crack widths were measured with a digital image correlation system (ARAMIS) on thin discs cut from a timber log. The history of the strain field over the entire cross section of the discs was measured throughout the drying period. The results showed that the thicker discs (30 mm) cracked very early during the drying process. They also cracked significantly more than the thinner ones (15 mm) and the crack patterns developed differently. For the thicker discs the early cracks which may partly be caused by the moisture gradient in the longitudinal direction of the log, closed and became invisible later during the drying process. This indicates that sealing of timber log ends in the green moisture state could significantly reduce the development of end-cracks. It was also recognized that the initial moisture content and the shrinkage properties vary significantly from pith to bark. Based on this experimental finding it can be concluded that modelling of crack propagation in solid wood must take the material inhomogeneities into account.

During drying, stresses and deformations develop in a wood board due to shrinkage fields which result from moisture content and temperature field variations. In spite of numerous works done in wood drying modelling in the last decades, wood drying optimisation based on modelling and simulation remains far from initial expectations. Two main reasons can explain this assessment: the huge variability of wood and the variations in drying conditions throughout the board stack in a dryer.To address these two key problems, we used a dual scale numerical tool able to compute simultaneously the stress and deformation of hundreds of boards in the stack during drying. A rigorous one-dimensional mechanical formulation, based on previous works, has been used for calculating stress and deformation during drying. The mechanical model is fitted into a module and then added to a dual scale (boardstack) model. This numerical tool has been used to improve the drying schedules recommended by the Technical Centre for Wood and Furniture in France (CTBA) for spruce. The proposed drying schedules allow the board quality to be improved. Note that the optimisation was limited to medium temperature values, so that the proposed schedule can be applied to conventional kilns.

The objective of this study was to develop an accurate and simple method for measuring the engineering coefficients of the 3D elasticity tensor of wood. A method using a semi-ring extensometer (SRE) and a compression specimen (6-specimen technique) is proposed. The SRE is made of a semi-ring stainless steel blade pin-jointed to two aluminum fixing plates, and two resistance strain gauges bonded to the top and bottom faces of the blade at mid-span position. Groups of five matched compression specimens (20 mm x 20 mm x 60 mm) from black spruce wood (Picea mariana (Mill.) B.S.P.), cut in six different orientations with respect to load axis (three orthotropic directions and three diagonal directions at an angle of 45 degrees to the load axis) were used for the calibration of the SRE. A resistance strain gauge bonded directly to the wood surface was used as a reference for both the axial and transverse measurements. The validation of the technique was made with another series of specimens cut in the same six orientations. The axial strain data of the SRE were then compared to the ones obtained from a linear displacement sensor (LVDT). For the transverse directions, the SRE results in terms of Poisson’s ratios and shear moduli were compared with corresponding data obtained from the literature. Results showed that the R2 value of the relationship between the Young’s moduli determined with the SRE and the LVDT varied from 0.88 to 0.97. The SRE technique appeared also reliable to evaluate both the Poisson’s ratios and shear moduli as the obtained values were in good agreement with the literature data. As compared to bonded strain gauges, the SRE technique is reusable, simpler and cheaper to use and its sensitivity is nearly independent of temperature.

During drying, stresses and deformations develop in a wood board due to shrinkage fields which result from moisture content and temperature field variations. In spite of numerous works done in wood drying modelling in the last decades, wood drying optimisation based on modelling and simulation remains far from initial expectations. Two main reasons can explain this assessment: the huge variability of wood and the variations in drying conditions throughout the board stack in a dryer.To address these two key problems, we used a dual scale numerical tool able to compute simultaneously the stress and deformation of hundreds of boards in the stack during drying. A rigorous one-dimensional mechanical formulation, based on previous works, has been used for calculating stress and deformation during drying. The mechanical model is fitted into a module and then added to a dual scale (boardstack) model. This numerical tool has been used to improve the drying schedules recommended by the Technical Centre for Wood and Furniture in France (CTBA) for spruce. The proposed drying schedules allow the board quality to be improved. Note that the optimisation was limited to medium temperature values, so that the proposed schedule can be applied to conventional kilns.

The objective of this study was to develop an accurate and simple method for measuring the engineering coefficients of the 3D elasticity tensor of wood. A method using a semi-ring extensometer (SRE) and a compression specimen (6-specimen technique) is proposed. The SRE is made of a semi-ring stainless steel blade pin-jointed to two aluminum fixing plates, and two resistance strain gauges bonded to the top and bottom faces of the blade at mid-span position. Groups of five matched compression specimens (20 mm x 20 mm x 60 mm) from black spruce wood (Picea mariana (Mill.) B.S.P.), cut in six different orientations with respect to load axis (three orthotropic directions and three diagonal directions at an angle of 45 degrees to the load axis) were used for the calibration of the SRE. A resistance strain gauge bonded directly to the wood surface was used as a reference for both the axial and transverse measurements. The validation of the technique was made with another series of specimens cut in the same six orientations. The axial strain data of the SRE were then compared to the ones obtained from a linear displacement sensor (LVDT). For the transverse directions, the SRE results in terms of Poisson’s ratios and shear moduli were compared with corresponding data obtained from the literature. Results showed that the R2 value of the relationship between the Young’s moduli determined with the SRE and the LVDT varied from 0.88 to 0.97. The SRE technique appeared also reliable to evaluate both the Poisson’s ratios and shear moduli as the obtained values were in good agreement with the literature data. As compared to bonded strain gauges, the SRE technique is reusable, simpler and cheaper to use and its sensitivity is nearly independent of temperature.