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Sehlstedt-Persson, M., Hansson, L., Couceiro, J. & Vikberg, T. (2019). Konditionering av virke vid olika fuktkvoter: studier i tomograf. Skellefteå
Open this publication in new window or tab >>Konditionering av virke vid olika fuktkvoter: studier i tomograf
2019 (Swedish)Report (Other academic)
Abstract [sv]

Fuktförändringar i virke under pågående konditionering har aldrig tidigare studerats i tomograf.

Resultat av denna labbstudie av diffusionsbaserad, icke-kondenserande jämviktskonditionering vid olika fuktkvotsnivåer sammanfattas enligt följande: (Notera att torkningsspänningar inte utvärde­rats i denna studie utan enbart fuktförändringar.)

  • Studien styrker industriella erfarenheter att konditionering ”tar bättre” på virke nedtorkat till lägre fuktkvot jämfört än om fuktkvoterna är högre.
  • Försöken ger en god fingervisning om hur länge konditionering bör pågå för en viss önskad medel­fuktkvotshöjning i ett industriellt vanligt förekommande klimat 70 °C och psykrometer­skillnad 2° vilket motsvarar en jämviktsfuktkvot på 16,8%. Vill man ex höja medelfuktkvoten från 10 – 12% visar resultaten att 4 timmars konditionering är tillräckligt för furuvirket. Att i samma klimat höja medel­fuktkvoten 2% vid högre startfuktkvoter (mellan 14–23%) har inte i något fall varit möjligt för vare sig gran eller furu under de 8 timmar som konditionering pågick. Det är också viktigt att påpeka att konditioneringsklimatet i dessa labbförsök har uppnått börvärden mycket snabbt (figur 3) vilket inte är fallet vid stora virkeslaster i industriskala där basningskapacitet och blåsdjup påverkar tid till uppnådda börvärden.
  • Vad gäller fuktkvotsskillnad nära ytorna ses generellt en utplaning av fuktförändringar i samtliga försök efter 3–4 timmar.
  • Fuktkvotsnivån spelar roll för den inledande fuktkvotsförändringen inom tvärsnittet: ju torrare virke desto snabbare förändring.
  • När konditioneringen startar är fuktvandringen i splintved effektivare än i kärnved vilket sannolikt förklaras av splintvedens högre diffusivitet.
  • Vad gäller eventuella skillnad mellan träslag är det inte möjligt att dra några slutsatser.
  • Metodstudien visar att upplösningen i tomografen är tillräcklig för att kunna utvärdera fuktkvotsförändringar nära virkesytorna i ca 3 mm tjocka skal.
Place, publisher, year, edition, pages
Skellefteå: , 2019. p. 28
Series
TräCentrumNorr
Keywords
trä, furu, gran, tomografi, torkning, konditionering
National Category
Engineering and Technology Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-72978 (URN)
Projects
”TiiN, TräInnovation i Norr”
Funder
Swedish Agency for Economic and Regional Growth
Note

Denna studie har utförts i projektet "Utveckling av industriell virkestorkning" inom ramen för projektet ”TiiN, TräInnovation i Norr”  

Available from: 2019-02-21 Created: 2019-02-21 Last updated: 2019-02-28Bibliographically approved
Couceiro, J., Lindgren, O., Hansson, L., Söderström, O. & Sandberg, D. (2019). Real-time wood moisture-content determination using dual-energy X-ray computed tomography scanning. Wood Material Science & Engineering, 14(6), 437-444
Open this publication in new window or tab >>Real-time wood moisture-content determination using dual-energy X-ray computed tomography scanning
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2019 (English)In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 14, no 6, p. 437-444Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
Taylor & Francis, 2019
Keywords
CT-scanning, dual-energy X-ray absorptiometry, wood drying, attenuation coefficient
National Category
Wood Science Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-75497 (URN)10.1080/17480272.2019.1650828 (DOI)000480865200001 ()
Note

Validerad;2019;Nivå 2;2019-10-24 (johcin)

Available from: 2019-08-13 Created: 2019-08-13 Last updated: 2019-10-24Bibliographically approved
Couceiro, J., Hansson, L., Ahec, A. & Sandberg, D. (2018). CT-scanning of the drying process of Eucalyptus nitens.. In: Cárcel JA, Polo GC, García-Pérez JV, Mulet A, Rosselló C., (Ed.), Proceedings of 21st International Drying Symposium.: . Paper presented at 21st International Drying Symposium, Valencia, Spain, Sep 11-14, 2018 (pp. 1269-1276). Valencia: Editorial Universitat Politècnica de València
Open this publication in new window or tab >>CT-scanning of the drying process of Eucalyptus nitens.
2018 (English)In: Proceedings of 21st International Drying Symposium. / [ed] Cárcel JA, Polo GC, García-Pérez JV, Mulet A, Rosselló C.,, Valencia: Editorial Universitat Politècnica de València , 2018, p. 1269-1276Conference paper, Published paper (Refereed)
Abstract [en]

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 .

Place, publisher, year, edition, pages
Valencia: Editorial Universitat Politècnica de València, 2018
Keywords
Cell collapse, computed tomography, surface checks, wood drying, internal checks
National Category
Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-71201 (URN)10.4995/ids2018.2018.7380 (DOI)000477977800160 ()978-84-9048-688-7 (ISBN)
Conference
21st International Drying Symposium, Valencia, Spain, Sep 11-14, 2018
Available from: 2018-10-13 Created: 2018-10-13 Last updated: 2019-09-13Bibliographically approved
Couceiro, J., Hansson, L., Sehlstedt-Persson, M. & Sandberg, D. (2018). CT-studies during the Conditioning phase of the Wood Drying Process. In: : . Paper presented at 21st International Drying Symposium (IDS), Valencia, Spain, Sep 11-14, 2018.
Open this publication in new window or tab >>CT-studies during the Conditioning phase of the Wood Drying Process
2018 (English)Conference paper, Poster (with or without abstract) (Other academic)
Abstract [en]

Computed tomography (CT) during drying of sawn timber is an excellent non-destructivetechnique to study the moisture flux as a function of drying time. In this study, a climatechamber combined with a medical CT- scanner has been used for non-destructive studies ofdensity changes in sawn timber during drying and conditioning.Green sawn timber contains large amounts of water and has to be dried before it can befurther processed and used in various building applications. The most common dryingmethod is convective air-circulation drying in large industrial kilns, where the relativehumidity (RH) of the hot circulating air is gradually reduced until the timber reaches thetarget moisture content (MC).Drying of sawn timber is driven by the existence of a difference in MC between the coreand the surface, so that moisture moves from the wet inner region towards the drier outerregion. During the early capillary stages of drying, the drying rate is high while, at the laterstages when all liquid water has evaporated, the drying rate is slow and diffusioncontrolled.At the end of the drying process, the timber surface is always drier than its core.In addition to this moisture gradient, internal stresses develop within the cross section withcompression stresses in the timber surface and tension in the inner regions. To avoidunwanted distortions, both these stresses and the moisture gradient, need to be eliminatedbefore the timber is further processed. This is achieved in a final conditioning stage withinthe drying process by moistening the circulating air through steaming or water spraying.The aim of the present work was to optimize the conditioning stage by developing amethod for studying of moisture gradients, deformations and internal and externaldimensional changes in sawn timber during the conditioning phase by using a CT-scannercombined with a drying unit for in-situ measurements of moisture flow.The results show that it is possible to detect the moisture gradient between the surface andcore of the timber with satisfactory reliability, but not the internal and external dimensionalchanges. However, this method creates a potential for increasing the knowledge andunderstanding of the conditioning phase and makes it possible to optimize and develop thisstep in the drying process to improve the yield and ensure a higher quality of the sawntimber.

National Category
Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-71117 (URN)
Conference
21st International Drying Symposium (IDS), Valencia, Spain, Sep 11-14, 2018
Available from: 2018-10-05 Created: 2018-10-05 Last updated: 2019-09-06Bibliographically approved
Hansson, L., Couceiro, J. & Fjellner, B.-A. (2017). Estimation of shrinkage coefficients in radial and tangential directions from CT images. Wood Material Science & Engineering, 12(4), 251-256
Open this publication in new window or tab >>Estimation of shrinkage coefficients in radial and tangential directions from CT images
2017 (English)In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 12, no 4, p. 251-256Article in journal (Refereed) Published
Abstract [en]

The aim of the present work was to use the displacement information generated from the spatial alignment in order to compute wood shrinkage in the radial and tangential directions in computed tomography (CT) images, and to compare the results with those obtained with computer-aided design software on the same images. To estimate the shrinkage coefficients from tomography images, wood specimens in the green state, equilibrium moisture content 15% and 8% state and oven dry condition were scanned. Specimens were taken from Norway spruce and Scots pine logs. The root-mean-square-error calculations showed acceptable small differences between the two measuring methods, which means that the algorithm is a useful tool for estimating the shrinkage coefficients in radial and tangential direction from CT images. This provides an image processing tool to monitor the dimensional changes during the drying and heat treatment process. 

Place, publisher, year, edition, pages
Taylor & Francis, 2017
National Category
Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-60142 (URN)10.1080/17480272.2016.1249405 (DOI)000402709800009 ()2-s2.0-84997272329 (Scopus ID)
Note

Validerad;2017;Nivå 2;2017-06-07(andbra)

Available from: 2016-11-03 Created: 2016-11-03 Last updated: 2019-05-07Bibliographically approved
Couceiro, J., Hansson, L. & Sandberg, D. (2016). In situ CT-scanning for detection of internal checking and cell collapse during drying of hardwood species. In: Teischinger A., Németh R., Rademacher P., Bak M. & Fodor F. (Eds.) (Ed.), The 7th European Conference on Hardwood, Eco-efficient resource wood with special focus on hardwoods: . Paper presented at 7th European Conference on Hardwood, Eco-efficient resource wood with special focus on hardwoods, Sopron, 8–9th September 2016 (pp. 58-59). Sopron: University of West Hungary
Open this publication in new window or tab >>In situ CT-scanning for detection of internal checking and cell collapse during drying of hardwood species
2016 (English)In: The 7th European Conference on Hardwood, Eco-efficient resource wood with special focus on hardwoods / [ed] Teischinger A., Németh R., Rademacher P., Bak M. & Fodor F. (Eds.), Sopron: University of West Hungary , 2016, p. 58-59Conference paper, Published paper (Refereed)
Abstract [en]

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.

Place, publisher, year, edition, pages
Sopron: University of West Hungary, 2016
Keywords
CT-scanning, Eucalyptus nitens, wood drying, image processing, cell collapse
National Category
Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-60264 (URN)978-963-334-291-6 (ISBN)
Conference
7th European Conference on Hardwood, Eco-efficient resource wood with special focus on hardwoods, Sopron, 8–9th September 2016
Available from: 2016-11-10 Created: 2016-11-10 Last updated: 2017-11-24Bibliographically approved
Couceiro, J., Vikberg, T., Hansson, L. & Morén, T. (2016). In Situ CT-Scanning of Checking and Collapse Behaviour of Eucalyptus nitens During Drying. In: Proceedings of the 59th International Convention of Society of Wood Science and Technology March 6-10, 2016 – Curitiba, Brazil: . Paper presented at 59th International Convention of Society of Wood Science and Technology, Curitiba, Brazil, March 6-10, 2016.
Open this publication in new window or tab >>In Situ CT-Scanning of Checking and Collapse Behaviour of Eucalyptus nitens During Drying
2016 (English)In: Proceedings of the 59th International Convention of Society of Wood Science and Technology March 6-10, 2016 – Curitiba, Brazil, 2016Conference paper, Published paper (Other academic)
Abstract [en]

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.

Keywords
CT-scanning, Eucalyptus nitens, wood drying, image processing, cell collapse
National Category
Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-61768 (URN)
Conference
59th International Convention of Society of Wood Science and Technology, Curitiba, Brazil, March 6-10, 2016
Available from: 2017-02-02 Created: 2017-02-01 Last updated: 2018-05-22Bibliographically approved
Couceiro, J., Hansson, L., Sehlstedt-Persson, M. & Sandberg, D. (2016). The use of X-ray computed tomography in timber construction research (ed.). In: (Ed.), New Horizons for the Forest Products Industry: 70th Forest Products Society International Convention, June 26-29, Portland, Oregon, USA. Paper presented at Forest Products Society International Convention : 26/06/2016 - 29/06/2016. Madison: Forest Products Society
Open this publication in new window or tab >>The use of X-ray computed tomography in timber construction research
2016 (English)In: New Horizons for the Forest Products Industry: 70th Forest Products Society International Convention, June 26-29, Portland, Oregon, USA, Madison: Forest Products Society, 2016Conference paper, Published paper (Other academic)
Abstract [en]

powerful tool for the non-destructive measurement of dynamic processes in wood. For more than 20 years, CT has been used in wood research at Luleå University of Technology. The uniqueness of the CT equipment means that processes such as drying, modification, water absorption, internal and external cracking and material deformation can be studied in temperature- and humidity-controlled environments. The data recorded by the CT during the process is converted into two- or three-dimensional images that for instance can show dynamic moisture behavior in wood drying.This paper gives an overview of the possibilities of using CT in timber construction research, and shows examples of applications and results which can be particularly difficult to achieve using other methods. A specific focus is on studies on wood products for construction, and how to deal with different material combinations such as wood and metal.The practical application of the result is that CT-scanning, combined with image processing, can be used for non-destructive and non-contact 3-D studies of exterior constructions elements during water sorption and desorption, to study swelling and shrinking behaviour, delamination phenomena, crack development, etc.

Place, publisher, year, edition, pages
Madison: Forest Products Society, 2016
Keywords
Forestry, agricultural sciences and landscape planning - Wood fibre and forest products, Skogs- och jordbruksvetenskap samt landskapsplanering - Träfiber- och virkeslära
National Category
Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-27860 (URN)16d03bdd-a509-4462-9ea7-bff1b8e82a8f (Local ID)16d03bdd-a509-4462-9ea7-bff1b8e82a8f (Archive number)16d03bdd-a509-4462-9ea7-bff1b8e82a8f (OAI)
Conference
Forest Products Society International Convention : 26/06/2016 - 29/06/2016
Note

Godkänd; 2016; 20160712 (dicsan)

Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2017-11-25Bibliographically approved
Ahmed, S. A., Hansson, L. & Morén, T. (2013). Distribution of preservatives in thermally modified Scots pine and Norway spruce sapwood (ed.). Wood Science and Technology, 47(3), 499-513
Open this publication in new window or tab >>Distribution of preservatives in thermally modified Scots pine and Norway spruce sapwood
2013 (English)In: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 47, no 3, p. 499-513Article in journal (Refereed) Published
Abstract [en]

Studying the impregnation and distribution of oil-based preservative in dried wood is complicated as wood is a nonhomogeneous, hygroscopic and porous material, and especially of anisotropic nature. However, this study is important since it has influence on the durability of wood. To enhance the durability of thermally modified wood, a new method for preservative impregnation is introduced, avoiding the need for external pressure or vacuum. This article presents a study on preservative distribution in thermally treated Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) sapwood using computed tomography scanning, light microscopy, and scanning electron microscopy. Secondary treatment of thermally modified wood was performed on a laboratory scale by impregnation with two types of preservatives, viz. Elit Träskydd (Beckers) and pine tar (tar), to evaluate their distribution in the wood cells. Preservative solutions were impregnated in the wood using a simple and effective method. Samples were preheated to 170°C in a drying oven and immediately submerged in preservative solutions for simultaneous impregnation and cooling. Tar penetration was found higher than Beckers, and their distribution decreased with increasing sample length. Owing to some anatomical properties, uptake of preservatives was low in spruce. Besides, dry-induced interstitial spaces, which are proven important flow paths for seasoned wood, were not observed in this species.

National Category
Bio Materials
Research subject
Wood Physics
Identifiers
urn:nbn:se:ltu:diva-10629 (URN)10.1007/s00226-012-0509-4 (DOI)000318292900005 ()2-s2.0-84877828892 (Scopus ID)9759fb33-caeb-4495-80d5-0bcb79063304 (Local ID)9759fb33-caeb-4495-80d5-0bcb79063304 (Archive number)9759fb33-caeb-4495-80d5-0bcb79063304 (OAI)
Note

Validerad; 2013; 20121009 (sheahm)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-12-14Bibliographically approved
Ahmed, S. A., Sehlstedt-Persson, M., Hansson, L. & Morén, T. (2013). Evaluation of preservative distribution in thermally modified European aspen and birch boards using computed tomography and scanning electron microscopy (ed.). Journal of Wood Science, 59(1), 57-66
Open this publication in new window or tab >>Evaluation of preservative distribution in thermally modified European aspen and birch boards using computed tomography and scanning electron microscopy
2013 (English)In: Journal of Wood Science, ISSN 1435-0211, E-ISSN 1611-4663, Vol. 59, no 1, p. 57-66Article in journal (Refereed) Published
Abstract [en]

The aim of this experiment was to impregnate thermally modified wood using an easy and cost-effective method. Industrially processed thermally modified European aspen (Populus tremula L.) and birch (Betula pubescens Ehrh.) were collected and secondarily treated at the laboratory scale with the preservatives tung oil, pine tar and Elit Träskydd (Beckers) using a simple and effective method. Preservative uptake and distribution in sample boards were evaluated using computed tomography (CT) and scanning electron microscopy (SEM) techniques. Preservative uptake and treatability in terms of void volume filled were found the highest in Beckers and the lowest in tung oil-treated samples. Thermally modified samples had lower treatability than their counterpart control samples. More structural changes after thermal modification, especially in birch, significantly reduced the preservative uptake and distribution. The differences of preservatives uptake near the end grain were high and then decreased near the mid position of the samples length as compared with similar type of wood sample. Non-destructive evaluation by CT scanning provided a very useful method to locate the preservative gradients throughout the sample length. SEM analysis enabled the visualization of the preservative deposits in wood cells at the microstructural level.

National Category
Bio Materials
Research subject
Wood Physics
Identifiers
urn:nbn:se:ltu:diva-7179 (URN)10.1007/s10086-012-1299-x (DOI)000315037000008 ()2-s2.0-84874105544 (Scopus ID)5807e96a-4097-4c82-9f68-31f9f6386aee (Local ID)5807e96a-4097-4c82-9f68-31f9f6386aee (Archive number)5807e96a-4097-4c82-9f68-31f9f6386aee (OAI)
Note

Validerad; 2013; 20121022 (sheahm)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-12-14Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-5869-2236

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