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Publications (10 of 89) Show all publications
Pahlberg, T., Thurley, M., Popovic, D. & Hagman, O. (2018). Crack detection in oak flooring lamellae using ultrasound-excited thermography. Infrared physics & technology, 88, 57-69
Open this publication in new window or tab >>Crack detection in oak flooring lamellae using ultrasound-excited thermography
2018 (English)In: Infrared physics & technology, ISSN 1350-4495, E-ISSN 1879-0275, Vol. 88, p. 57-69Article in journal (Refereed) Published
Abstract [en]

Today, a large number of people are manually grading and detecting defects in wooden lamellae in the parquet flooring industry. This paper investigates the possibility of using the ensemble methods random forests and boosting to automatically detect cracks using ultrasound-excited thermography and a variety of predictor variables. When friction occurs in thin cracks, they become warm and thus visible to a thermographic camera. Several image processing techniques have been used to suppress the noise and enhance probable cracks in the images. The most successful predictor variables captured the upper part of the heat distribution, such as the maximum temperature, kurtosis and percentile values 92–100 of the edge pixels. The texture in the images was captured by Completed Local Binary Pattern histograms and cracks were also segmented by background suppression and thresholding.

The classification accuracy was significantly improved from previous research through added image processing, introduction of more predictors, and by using automated machine learning. The best ensemble methods reach an average classification accuracy of 0.8, which is very close to the authors’ own manual attempt at separating the images (0.83).

Place, publisher, year, edition, pages
Elsevier, 2018
National Category
Computer Vision and Robotics (Autonomous Systems) Other Mechanical Engineering Signal Processing
Research subject
Wood Science and Engineering; Signal Processing
Identifiers
urn:nbn:se:ltu:diva-65698 (URN)10.1016/j.infrared.2017.11.007 (DOI)000423650700007 ()2-s2.0-85034628056 (Scopus ID)
Note

Validerad;2017;Nivå 2;2017-12-05 (andbra)

Available from: 2017-09-18 Created: 2017-09-18 Last updated: 2018-02-16Bibliographically approved
Vorobyev, A., Garnier, F., van Dijk, N. P., Hagman, O. & Gamstedt, K. (2018). Evaluation of displacements by means of 3D laser scanning in a mechanically loaded replica of a hull section of the Vasa ship. Digital Applications in Archaeology and Cultural Heritage, 11, Article ID e00085.
Open this publication in new window or tab >>Evaluation of displacements by means of 3D laser scanning in a mechanically loaded replica of a hull section of the Vasa ship
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2018 (English)In: Digital Applications in Archaeology and Cultural Heritage, ISSN 2212-0548, Vol. 11, article id e00085Article in journal (Refereed) Published
Abstract [en]

For a development of full-scale finite-element models of large objects in cultural heritage, it can be useful to mechanically test replicas of key parts to identify structural properties which would otherwise not be available. This paper presents full scale tests on a replica of a section of the hull of the 17th century warship Vasa in three load configurations. We focus on determining a displacement of the loaded replica from 3D laser measurements. Two measures were found useful: (i) 3D displacements at well-defined intersections of the wooden replica, and (ii) normal displacements of larger surfaces. Wood surfaces were preferred to steel parts of the rig since the latter showed more scatter in displacement values in their point clouds caused by their reflective properties. The measurements were verified with draw-wire sensors. Some of these sensors were attached to the steel rig supporting the replica and, therefore, measured relative displacements. The scanning data was also useful to quantify the absolute movement of the steel rig supporting the replica, which improved the precision of the measurements of replica deformation. Finally, it is discussed how the replica test results can be used in a model of the entire museum ship.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
3D laser scanning; Structural analysis; Vasa; Wood; Shear
National Category
Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-71806 (URN)10.1016/j.daach.2018.e00085 (DOI)2-s2.0-85057593098 (Scopus ID)
Funder
Swedish Research Council for Environment, Agricultural Sciences and Spatial PlanningSwedish Research Council FormasVINNOVA
Available from: 2018-11-29 Created: 2018-11-29 Last updated: 2019-02-01Bibliographically approved
Garzon, A. & Hagman, O. (2018). Future requirement for sustainable building envelope. In: : . Paper presented at 2018 World Conference on Timber Engineering, WCTE 2018; COEX Convention and Exhibition CenterSeoul; South Korea; 20-23 August 2018.
Open this publication in new window or tab >>Future requirement for sustainable building envelope
2018 (English)Conference paper (Refereed)
Identifiers
urn:nbn:se:ltu:diva-72854 (URN)
Conference
2018 World Conference on Timber Engineering, WCTE 2018; COEX Convention and Exhibition CenterSeoul; South Korea; 20-23 August 2018
Available from: 2019-02-12 Created: 2019-02-12 Last updated: 2019-02-12
Myronycheva, O., Karlsson, O., Sehlstedt-Persson, M., Hagman, O., Sidorova, E. & Sandberg, D. (2018). Hyperspectral Imaging Surface Analysis for Dried and Thermally Modified Wood: An Exploratory Study. Journal of Spectroscopy, Article ID 7423501.
Open this publication in new window or tab >>Hyperspectral Imaging Surface Analysis for Dried and Thermally Modified Wood: An Exploratory Study
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2018 (English)In: Journal of Spectroscopy, ISSN 2314-4920, E-ISSN 2314-4939, article id 7423501Article in journal (Refereed) Published
Abstract [en]

Naturally seasoned, kiln-dried, and thermally modified wood has been studied by hyperspectral near-infrared imaging between 980 and 2500 nm in order to obtain spatial chemical information. Evince software was used to explore, preprocess, and analyse spectral data from image pixels and link these data to chemical information via spectral wavelength assignment. A PCA model showed that regions with high absorbance were related to extractives with phenolic groups and aliphatic hydrocarbons. The sharp wavelength band at 2135 nm was found by multivariate analysis to be useful for multivariate calibration. This peak represents the largest variation that characterizes the knot area and can be related to areas in wood rich in hydrocarbons and phenol, and it can perhaps be used for future calibration of other wood surfaces. The discriminant analysis of thermally treated wood showed the strongest differentiation between the planed and rip-cut wood surfaces and a fairly clear discrimination between the two thermal processes. The wavelength band at 2100 nm showed the greatest difference and may correspond to stretching of C=O-O of polymeric acetyl groups, but this requires confirmation by chemical analysis.

Place, publisher, year, edition, pages
Hindawi Publishing Corporation, 2018
National Category
Wood Science
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-71584 (URN)10.1155/2018/7423501 (DOI)2-s2.0-85057402277 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-11-20 (svasva)

Available from: 2018-11-14 Created: 2018-11-14 Last updated: 2019-06-14Bibliographically approved
Buck, D. & Hagman, O. (2018). Mechanics of diagonally layered cross-laminated timber. In: : . Paper presented at 2018 World Conference on Timber Engineering, WCTE 2018; COEX Convention and Exhibition CenterSeoul; South Korea; 20-23 August 2018.
Open this publication in new window or tab >>Mechanics of diagonally layered cross-laminated timber
2018 (English)Conference paper (Refereed)
Identifiers
urn:nbn:se:ltu:diva-72853 (URN)2-s2.0-85058158349 (Scopus ID)
Conference
2018 World Conference on Timber Engineering, WCTE 2018; COEX Convention and Exhibition CenterSeoul; South Korea; 20-23 August 2018
Available from: 2019-02-12 Created: 2019-02-12 Last updated: 2019-02-12
Hagman, O., Porzilli, S., Seppänen, M. & Winsa, M. (2018). Meän sauna: Inventory of old smoke saunas in the Torne river valley using laser scanning and photogrammetry. In: : . Paper presented at XVII International Sauna Congress, Torneå Haparanda, 7-10 June 2018.
Open this publication in new window or tab >>Meän sauna: Inventory of old smoke saunas in the Torne river valley using laser scanning and photogrammetry
2018 (English)Conference paper, Oral presentation only (Refereed)
Abstract [en]

MEÄN SAUNA

- Inventory of old smoke saunas in the Swedish Torne river valley using laser scanning and photogrammetry.

 

The cultural heritage of the Swedish Torne river valley has been dominated by the Finns. A strong manifestation of this are the numerous smoke saunas on the area. Due to the Lapland war in 1944- 45 the building stock as well as saunas where largely destroyed in Northern Finland. The smoke saunas in the Swedish side were left untouched and are representing the historical type of Finnish sauna culture and sauna buildings in Torne river valley and Lapland.

 

Every time a smoke sauna is warmed up there is a risk of fire, especially with old saunas. In Torne river valley there is a strong risk of cultural heritage vanishing, since no inventory of these saunas has been done on Swedish side.

 

In Project MEÄN SAUNA selected old smoke saunas in Swedish Torne river valley will be inventoried by researching of history, laser scanning and photogrammetry.  3D models of sauna buildings will be created and saunas will be classified. The lecture will present at least two old smoke saunas of which one is from 1720. Presentation will contain a brief historical background of saunas as well as explanation and photographs of the site. The methods for laser-scanning and photogrammetry measuring method will be explained. The smoke saunas buildings will be presented by photography, laser-scanning and technical drawings. At the lecture live use of computers and program will be displayed, to make it possible to discover the saunas within the 3D models.

 

 

Olle Hagman, PhD, Professor Wood Products Engineering, Luleå University of Technology.

Sara Porzilli, Architect, PhD Europaeus, Post Doctoral Fellow at the University of Oulu.

Markku Seppänen, BSc(Arch), Building Information Modeling Specialist, Oulu.

Mats Winsa, Architect SAR / MSA, Tärendö / Luleå. 

National Category
Engineering and Technology Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-70434 (URN)
Conference
XVII International Sauna Congress, Torneå Haparanda, 7-10 June 2018
Available from: 2018-08-16 Created: 2018-08-16 Last updated: 2018-08-17Bibliographically approved
Buck, D. & Hagman, O. (2018). Production and In-Plane Compression Mechanics of Alternatively Angled Layered Cross-Laminated Timber. BioResources, 13(2), 4029-4045
Open this publication in new window or tab >>Production and In-Plane Compression Mechanics of Alternatively Angled Layered Cross-Laminated Timber
2018 (English)In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 13, no 2, p. 4029-4045Article in journal (Refereed) Published
Abstract [en]

Increasing awareness of sustainable building materials has led to interest in enhancing the structural performance of engineered wood products. This paper reports mechanical properties of cross-laminated timber (CLT) panels constructed with layers angled in an alternative configuration on a modified industrial CLT production line. Timber lamellae were adhesively bonded together in a single-step press procedure to form CLT panels. Transverse layers were laid at an angle of 45°, instead of the conventional 90° angle with respect to the longitudinal layers’ 0° angle. Tests were carried out on 20 five-layered CLT panels divided into two matched groups with either a 45° or a 90° configuration; an in-plane uniaxial compressive loading was applied in the principal orientation of the panels. These tests showed that the 45°-configured panels had a 30% higher compression stiffness and a 15% higher compression strength than the 90° configuration. The results also revealed that the 45°-configured CLT can be industrially produced without using more material than is required for conventional CLT 90° panels. In addition, the design possibility that the 45°-configured CLT can carry a given load while using less material also suggests that it is possible to use CLT in a wider range of structural applications.

Place, publisher, year, edition, pages
University of North Carolina Press, 2018
Keywords
CLT manufacturing, Crosslam, Cross-ply, Diagonal-laminated lumber, Impact of laminate orientation, In-plane rotation, Grain inclination angle, Mass timber engineering, Solid wood panel, X-lam
National Category
Building Technologies Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-68424 (URN)10.15376/biores.13.2.4029-4045 (DOI)000440518000021 ()
Note

Validerad;2018;Nivå 2;2018-04-26 (andbra)

Available from: 2018-04-20 Created: 2018-04-20 Last updated: 2019-01-15Bibliographically approved
Björngrim, N., Fjellström, P.-A. & Hagman, O. (2017). Factory Mounted and Retrofit Passive Resistance Sensors Adapted to Monitor Moisture Content in Timber Bridges. BioResources, 12(4), 7218-7227
Open this publication in new window or tab >>Factory Mounted and Retrofit Passive Resistance Sensors Adapted to Monitor Moisture Content in Timber Bridges
2017 (English)In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 12, no 4, p. 7218-7227Article in journal (Refereed) Published
Abstract [en]

The biggest threats to the longevity of a timber bridge are rot and decay. Wood protection by design, inspections, and monitoring of the bridge for elevated moisture content will ensure that the full service life of the structure can be achieved. Today's sensors for moisture content measurements are limited in their functionality and range. This paper presents a sensor that can be both factory installed and retrofitted, which can measure the moisture content through the cross-section of the member in a timber bridge. The sensor has been mounted on Sundbron bridge during manufacturing and retrofitted on Gislaved bridge. The ensuing measurements helped to adjust a design flaw on Gislaved bridge. Monitoring of Sundbron showed that the bridge deck dried up after the bridge had been exposed to sleet and snow during the on-site assembly of the stress laminated bridge deck

Place, publisher, year, edition, pages
North Carolina State University, 2017
National Category
Engineering and Technology Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-63538 (URN)10.15376/biores.12.4.7218-7227 (DOI)000422879900024 ()2-s2.0-85032702721 (Scopus ID)
Note

Validerad;2017;Nivå 2;2017-09-15 (andbra)

Available from: 2017-05-26 Created: 2017-05-26 Last updated: 2018-05-18Bibliographically approved
Scheepers, G., Olsson, J., Lycken, A., Grahn, T., Lundqvist, S.-O. & Hagman, O. (2017). Hållfasthetsbestämning av virke med en NIR-kamera.
Open this publication in new window or tab >>Hållfasthetsbestämning av virke med en NIR-kamera
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2017 (Swedish)Report (Other academic)
Publisher
p. 17
National Category
Other Materials Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-62012 (URN)
Available from: 2017-02-15 Created: 2017-02-15 Last updated: 2017-11-24Bibliographically approved
Björngrim, N., Fjellström, P.-A. & Hagman, O. (2017). Long Term Evaluation of Factory Installed And Retro Fitted Moisture Content Sensor adapted for Timber Bridges.
Open this publication in new window or tab >>Long Term Evaluation of Factory Installed And Retro Fitted Moisture Content Sensor adapted for Timber Bridges
2017 (English)In: Article in journal (Refereed) Submitted
National Category
Engineering and Technology Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-63539 (URN)
Available from: 2017-05-26 Created: 2017-05-26 Last updated: 2018-05-18
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-8404-7356

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