Ändra sökning
Avgränsa sökresultatet
12 1 - 50 av 70
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Träffar per sida
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
Markera
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 1.
    Ah Shenga, Pedro António
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Bomark, Peter
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    External Log Scanning for Optimizing Primary Breakdown of Tropical Hardwood Species2015Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    The sawing of tropical hardwood species is a big challenge for sawmills in developing countries. In order to investigate sawing strategies and volume recovery of tropical hardwood species, a log shape database was created using a portable 3D laser scanner. The data were collected in Mozambique, where twelve Jambirre (Millettia stuhlmannii Taub.) and five Umbila (Pterocarpus angolensis DC) logs were scanned. The logs were selected among the most commercialized species and the crook was the main selection parameter. In addition, straight logs were incorporated as reference. A saw simulation Matlab algorithm that combines skew and rotation was developed. The results show that point cloud data from the 3D scanner provide detailed models of the external log geometry and accurately describe the log shapes and volumes. Preliminary results from breakdown simulation revealed that the through-and-through sawing pattern yields more than the cant saw pattern and that the increase in yield was almost the same for both species.

    Ladda ner fulltext (pdf)
    fulltext
  • 2.
    Ah Shenga, Pedro António
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Bomark, Peter
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Simulated Breakdown of Two Tropical Hardwood Species2015Ingår i: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 11, nr 4, s. 450-456Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A simulation study has been performed on a small log database of tropical hardwoods consisting of 10 Jambirre (Millettia stuhlmannii Taub.) and 5 Umbila (Pterocarpus angolensis D.C.) logs. The outer log shape was acquired by a 3D laser scanner before sawing and the heartwood content was estimated by measurement on images of the centre slabs after through-and-through sawing. Yield and value recovery using different sawing techniques and different sawing patterns, together with rotational and skew positioning errors, are presented. The results show that through-and-through sawing in the best rotation and skew positions tested improves the yield of Umbila logs by an average of 4.5 percentage points and Jambirre logs by 3.6 percentage points compared to cant sawing. It can be concluded that positioning and sawing patterns have a great influence on the yield and value recovery of these species and that log grade and species have an impact on the sawing pattern that should be used.

    Ladda ner fulltext (pdf)
    fulltext
  • 3.
    Ah Shenga, Pedro
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Bomark, Peter
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Hagman, Olle
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    3D Phase-shift Laser Scanning of Log Shape2014Ingår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 9, nr 4, s. 7593-7605Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, a portable scanner to determine the 3D shape of logs was evaluated and compared with the measurement result of a computer tomography scanner. Focus was on the accuracy of the shape geometry representation. The objective is to find a feasible method to use for future data collection in Mozambique in order to build up a database of logs of tropical species for sawing simulations. The method chosen here was a 3D phase-shift laser scanner. Two logs, a birch log with bark and a Scots pine log without bark, were scanned, resulting in 450 cross sectional “images” of the pine log and 300 of the birch log. The areas of each point cloud cross section were calculated and compared to that of the corresponding computer tomography cross section. The average area difference between the two methods was 2.23% and 3.73%, with standard deviations of 1.54 and 0.91, for the Scots pine and birch logs, respectively. The differences in results between the two logs are discussed and had mainly to do with presence of bark and mantle surface evenness. Results show that the shape measurements derived from these methods were well correlated, which indicates the applicability of a 3D phase-shift laser scanning technology for gathering log data.

  • 4.
    Ah Shenga, Pedro
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Bomark, Peter
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Log sawing positioning optimization and log bucking of tropical hardwood species to increase the volume yield2017Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 12, nr 4, s. 257-262Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The sawmill industry is a very important link in the Mozambique forest products value chain, but the industry is characterized by undeveloped processing technology and high-volume export of almost unrefined logs. The low volume yield of sawn timber has been identified as a critical gap in the technological development of the industry. To improve the profitability of the industry, there is thus a need to develop methods and techniques that improve the yield. In this paper, different positioning of logs prior to sawing and the possibility of increasing the volume yield of crooked logs by bucking the logs before sawing have been studied. A computer simulation was used to study the cant-sawing and through-and-through sawing of the logs to determine the volume yield of sawn timber from the jambirre (Millettia stuhlmannii Taub.) and umbila (Pterocarpus angolensis DC.) species. The optimal position, i.e. the position of the log before sawing that gives the highest volume yield of sawn timber for a given sawing pattern when the positioning parameters, offset, skew and rotation, are considered gave a considerable higher volume yield than the horns-down position. By bucking very crooked logs and using the horns-down positioning before sawing, the volume yield can be of the same magnitude as that obtained by optimal positioning on full-length (un-bucked) logs. The bucking reduces the crook of the logs and hence increases the volume yield of sawn timber.

  • 5.
    Ah Shenga, Pedro
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Bomark, Peter
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Simulation of Tropical Hardwood Processing – Sawing Methods, Log Positioning, and Outer Shape2015Ingår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 10, nr 4, s. 7640-7652Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To increase understanding of breakdown strategies for Mozambican timber, simulations were carried out using different sawing patterns that can be alternatives to the low degree of refinement performed for export today. For the simulations, 3D models of 10 Jambirre and 5 Umbila logs were used. The log shape was described as a point cloud and was acquired by 3D-laser scanning of real logs. Three sawing patterns (cant-sawing, through-and-through sawing, and square-sawing) were studied in combination with the log positioning variables skew and rotation. The results showed that both positioning and choice of sawing pattern had a great influence on the volume yield. The results also showed that the log grade had an impact on the sawing pattern that should be used for a high volume yield. The volume yield could be increased by 3 percentage points by choosing alternative sawing patterns for fairly straight logs and by 6 percentage points for crooked logs, compared to the worst choice of sawing pattern.

  • 6.
    Ah Shenga, Pedro
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Bomark, Peter
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    The Effect of Log Position Accuracy on the Volume Yield in Sawmilling of Tropical Hardwood2016Ingår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 11, nr 4, s. 9560-9571Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study investigated the effect of the positioning of the log before sawing on the volume yield of sawn timber from tropical hardwood species. Three positioning parameters were studied, the offset, skew, and rotation, combined with two sawing patterns of cant-sawing and through-and-through sawing. A database consisting of two tropical hardwood species with very different outer shapes, jambirre (Millettia stuhllmannii Taub.) and umbila (Pterocarpus angolensis DC.), was used to simulate the sawing process. The result of the simulation revealed that, according to the combined effect of offset, skew, and rotation positioning, the positioning of the log before sawing is extremely important to achieve a high volume yield of sawn timber. The positioning parameter that has the highest effect on the volume yield is the rotation, and the variation in the volume yield associated with a deviation in the positioning can reduce the volume yield of sawn timber by between 7.7% and 12.5%.

    Ladda ner fulltext (pdf)
    fulltext
  • 7.
    Ah Shenga, Pedro
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Cristovao, Luis
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    A review of Mozambican wood exploitation: map of the processing chain2013Ingår i: Proceedings of the 21th International Wood Machining Semina: August 4th – 7th, Tsukuba International Congress Center, Japan, 2013, s. 293-301Konferensbidrag (Övrigt vetenskapligt)
  • 8.
    Berglund, Anders
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Grönlund, Anders
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Fredriksson, Magnus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Improved log rotation using information from a computed tomography scanner2013Ingår i: Computers and Electronics in Agriculture, ISSN 0168-1699, E-ISSN 1872-7107, Vol. 90, s. 152-158Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The development of an industrial computed tomography scanner for the sawmilling industry raises the question of how to find a production strategy that uses a computed tomography scanner in the sawmill production line to its full potential. This study was focused on a Scandinavian sawmill processing Scots pine (Pinus sylvestris) and Norway spruce (Picea abies). The potential value increase when allowing an alternative log rotation other than the horns down position was investigated using a log breakdown simulation. The resulting data was analysed with respect to the size of the log rotational step, an introduced rotational error of the sawing machine and different price differences between the quality grades. It was also of interest to define the outer log properties that characterise the logs sawn for the greatest profit return close to the horns down position compared to logs sawn for a greater profit return in a different log rotation. Such characteristics can be used to reduce the number of degrees of freedom in an optimisation and consider instead other parameters, such as positioning and sawing pattern. Other defects such as pitch pockets, splits and rot are also of interest. The results shows that there is a potential value increase when applying the log rotation that maximises the value for each log instead of processing all logs in the horns down position. However, the potential value increase depends on the rotational error of the used sawing machine and the price differences between the quality grades. The log properties that differ between logs sawn for the greatest profit return close to the horns down position compared to a different log rotation are the bow height and the log taper. Unfortunately, predictability of log rotation for greatest profit return based on the outer properties of logs is poor. It is not possible to differentiate logs which would be sawn for the greatest profit return close to the horns down position from those where a different log rotation results in the greatest profit return, based only on their outer properties.

  • 9.
    Berglund, Anders
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Oja, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Grönlund, Anders
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Customer adapted grading of Scots pine sawn timber using a multivariate method2015Ingår i: Scandinavian Journal of Forest Research, ISSN 0282-7581, E-ISSN 1651-1891, Vol. 30, nr 1, s. 87-97Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To define new grading rules, or to customize the ones in use in a rule-based automatic grading system of boards, is a time-consuming job for a sawmill engineer. This has the effect that changes are rarely made. The objective of this study was to continue the development of a method that replaces the calibration of grading rule settings by a holistic-subjective automatic grading, using multivariate models. The objective was also to investigate if this approach can improve sawmill profitability and at the same time have a satisfied customer. For the study, 323 Scots pine (Pinus sylvestris L.) boards were manually graded according to preferences of an important customer. That is, a customer that regularly purchases significant volumes of sawn timber. This manual grading was seen as reference grading in this work. The same boards were also scanned and graded by a rule-based automatic grading system, calibrated for the same customer. Multivariate models for prediction of board grade based on aggregated knot variables, obtained from the scanning, were calibrated using partial least squares regression. The results show that prediction of board grades by the multivariate models were more correct, with respect to the manual grading, than the grading by the rule-based automatic grading system. The prediction of board grades based on multivariate models resulted in 76-87% of the boards graded correctly, according to the manual grading, while the corresponding number was 63% for the rule-based automatic grading system.

  • 10. Berglund, Anders
    et al.
    Fredriksson, Magnus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Grönlund, Anders
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Project: CT-Pro2012Övrigt (Övrig (populärvetenskap, debatt, mm))
    Abstract [sv]

    Projektet är finansierat av WoodWisdom-Net, VINNOVA, Fachagentur Nachwachsende Rohstoffe e. V. och medverkande företag. Syftet med projektet är att visa att det är möjligt att extrahera ut viktig och detaljerad information från en timmerstock med hjälp av en speciellt utvecklad röntgenskanner och sedan utnyttja denna information i produktionsstategier för att öka värdet i den träindustiella värdekedjan.

  • 11.
    Breinig, Lorenz
    et al.
    Forest Research Institute of Baden-Württemberg, 79100, Freiburg, Germany.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Brüchert, Franka
    Forest Research Institute of Baden-Württemberg, 79100, Freiburg, Germany Freiburg.
    Becker, Gero
    Forest Research Institute of Baden-Württemberg, 79100, Freiburg, Germany.
    Optimization potential for perception-oriented appearance classification by simulated sawing of computed tomography-scanned logs of Norway spruce2015Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 10, nr 4, s. 319-334Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Wood, as a natural material, has favourable properties in both technical and aesthetic aspects. Due to its inherent variability,production of high-quality sawn timber demands adequate control of log conversion, which is feasible with computedtomography (CT) log scanning. Existing appearance grading rules for sawn timber might not fully reflect people’s visualperception of wood surfaces, and therefore, an alternative, more perception-oriented appearance classification could bebeneficial. An appearance classification of sawn timber based on partial least squares discriminant analysis (PLS-DA) ofknot-pattern variables was developed and tested. Knot-pattern variables derived from images of board faces were used intraining PLS-DA models against an initial classification of the board faces previously established by aid of cluster analysis.Virtual board faces obtained from simulated breakdown of 57 CT-scanned Norway spruce logs were graded according tothe developed classification. Visual assessment of the grading results indicated that the classification was largely consistentwith human perception of board appearance. An initial estimation of the potential to optimize log rotation, based on CTdata, for the established appearance grades was derived from the simulations. Considerable potential to increase the yield ofa desired appearance grade, compared to conventional log positioning, was observed.

    Ladda ner fulltext (pdf)
    fulltext
  • 12.
    Breinig, Lorenz
    et al.
    Forest Research Institute of Baden-Württemberg, 79100 Freiburg.
    Leonhart, Rainer
    Institute of Psychology, University of Freiburg.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Manuel, Andreas
    University of Freiburg, Institute of Forest Sciences, University of Freiburg.
    Brüchert, Franka
    Forest Research Institute of Baden-Württemberg, 79100 Freiburg.
    Becker, Gero
    Institute of Forest Sciences, University of Freiburg.
    Classification of wood surfaces according to visual appearance by multivariate analysis of wood feature data2015Ingår i: Journal of Wood Science, ISSN 1435-0211, E-ISSN 1611-4663, Vol. 61, nr 2, s. 89-112Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Its natural aesthetics make wood an attractivematerial for construction and design. However, there is nodetailed understanding of the relationships between humanperception of the appearance and measurable features ofwood surfaces that could be used for controlling sawntimber production. This study investigated whether woodsurfaces can be classified according to their visualappearance on the basis of wood feature measurements.Cluster analysis was used to discover a classification basedon a set of feature pattern variables in a sample of 300softwood floorboards. A finely graded visual appearancesorting provided a reference. Discriminant analysis wasapplied to identify the relevant variables from the tested setand to assess predictability of the classification. The resultsindicated that visual appearance sorting could be approximatedquite well by the variable-based classification afterpregrouping according to board position in the log.Ambivalent results were obtained for group predictionwithin the validation sample. While for boards from somegroups prediction was mostly or entirely correct, boardsfrom other groups were largely misclassified. An effect ofthe available sample was one of the surmised causes,making repetition of the analysis based on a larger sample adesirable focus of further research.

    Ladda ner fulltext (pdf)
    fulltext
  • 13.
    Broman, N. Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Visual impression of features in Scots pine wood surfaces: a qualitative study1995Ingår i: Forest products journal, ISSN 0015-7473, Vol. 45, nr 3, s. 61-66Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Wood has inherent aesthetic features which give the final product competitive advantage over other materials. The goal of this study was to describe and create understanding of people's feelings and attitudes toward wood in order to develop quantitative studies in the future. Ten persons with different backgrounds were interviewed regarding 27 wood surfaces made of Scots pine. Their impressions and feelings were documented and analyzed with a qualitative method. The result is a map describing what features people see in wood. Depending on the mixture of wood features the impression will differ. Interviews made clear that people prefer different blends of wood features. There are two qualitative differences that are of importance for people's impression and valuation of wood. First there is the overall blending of wood features and second, if there are divergent features that mismatch in the surface. The latter factor can be divided into two ; - Distinguishing natural defects. - Technical defects made by machine or the carpenter. It was found that divergent features are more important than the overall mixture of features. But if there are no defects that mismatch, the overall mixture will then be the key to a person's appreciation of a wood surface. Wood features can be seen as input data for interpretation and valuation by a person and the impression of sight should be seen as output data from the valuation process. Input data are quite objective and can be measured automatically by scanning techniques. Interviews have to be used to measure the subjective output data. The results of this investigation point toward useful queries or measurements to be made in future qualitative or quantitative studies.

  • 14.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Aesthetic properties in knotty wood surfaces and their connection with people's preferences2001Ingår i: Journal of Wood Science, ISSN 1435-0211, E-ISSN 1611-4663, Vol. 47, nr 3, s. 192-198Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    For wood products that contain visible wood surfaces it is important to be able to describe, measure, and communicate the aesthetic properties desired. The aims of this investigation were to shed light on how people's preferences toward different wood appearances containing knots can be described and to create a better understanding of how to measure those preferences. A total of 215 persons from Sweden with different backgrounds were interviewed as to their preferences for 10 Scots pine wood surfaces containing knots. Their impressions and preferences were documented by a questionnaire with 54 questions and analyzed by a principal component analysis. A thorough description of what people see and value in a wood surface with knots is given in the body of the text. People's preferences are affected by a balance between two main properties: the degree of harmony and activity, and the importance of avoiding a state of disharmony when composing wood surfaces. When investigating people's preferences toward a knotty wood appearance, 13 of 54 questions proved to be important. Three questions detect the final assessment, and four describe the reasons for the final assessment. Finally, six questions describe the blend of wood properties in a more objective way and are to only a minor extent connected with the final assessments.

  • 15.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Attitudes toward Scots Pine wood surfaces: a multivariate approach1995Ingår i: Mokuzai Gakkaishi, ISSN 0021-4795, E-ISSN 1880-7577, Vol. 41, nr 11, s. 994-1005Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Wood as a material has inherent aesthetic features which, rightly used, give the final product competitive advantage over other materials. The aim of this investigation was to find relevant questions to ask when measuring people's preferences for different looks of wood and to reveal the relationship between the mixture of features in a wood surface and people's attitudes. A total of 344 persons participated in the study judging the look of 16 wood surfaces made of Scots pine (Pinus sylvestris). Their impressions and feelings were analysed by three multivariate methods; correlation, principal component and partial least squares analysis. The study shows that it is possible to measure people's feelings for different looks of wood surfaces. The results show that there are differences in people's judgements for surfaces with knots and without knots. The results also show that there are about 15 questions needed to detect people's preferences for a wood surface.

  • 16.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Means to measure people's attitudes towards wood1995Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Wood is a material with many faces. It evokes feelings in us that no artificial material can do. Wood has inherent aesthetic features which, rightly used, give the final product competitive advantage over other materials.In this thesis people's feelings and preferences for Scots pine (Pinus sylvestris) wood surfaces have been examined. It comprises a qualitative study of what people see and evaluate in wood and two separate investigations aiming at quantifying people's preferences for wood. Those two investigations were analysed by multivariate techniques.The results show that people prefer different blends of wood features. There are two qualitative differences that are of importance for people's impression and valuation of wood: The overall blending of wood features and divergent features that mismatch in a surface. It was found that divergent features are more important than the overall mixture of features. But if there are no defects that mismatch, the overall mixture will then be the key to a person's appreciation of a wood surface. Other results from the qualitative study are a map of wood features that people see and a description of the phenomenon Attitudes Toward Wood divided into properties and aspects.The quantitative studies show that it is possible to measure people's attitudes toward wood by a questionnaire technique. The results also show that there are differences in people's judgements for surfaces with knots and without knots and that there are about 10 questions needed for detecting people's preferences for wood. A wood surface that people prefer should have at least one of the following characteristics:- Have a fresh look - Be restful- Be in harmony - Have an eventful look- Be interesting to look at - Not look like an imitation- Be elegant - Be imaginative- Be exciting to look at - Not be gaudyTwo interviewing methods were compared. The first method used wood surfaces and the second used computer images with the same wood surfaces applied to an example product, a kitchen cabinet. The result shows that the two methods are comparable and useful.

    Ladda ner fulltext (pdf)
    FULLTEXT01
  • 17.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Means to measure the aesthetic properties of wood2000Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Wood is a biological material with inherent aesthetic properties which can give the final product a competitive advantage over other materials. In this thesis, people’s feelings and preferences for Scots pine (Pinus sylvestris) wood surfaces have been examined. The main objectives of this thesis are to develop methods for measuring people’s preferences toward different looks of wood and to connect the subjective preference data with objective measurements of wood features. It comprises both qualitative and quantitative methods for collecting preference data. Two projection methods, PCA and PLS, were used to analyze the quantitative studies. Interviews made clear that people prefer different blends of wood features. There are two qualitative differences that are of importance for people's impressions and valuations of wood: The overall blend of wood features and divergent features that mismatch in a surface. It was found that divergent features are more important than the overall mixture of features. But if there are no defects that mismatch, the overall mixture will then be the key to a person's appreciation of a wood surface. Wood surfaces should stimulate people's interest and be fresh looking. A clear surface is naturally rather harmonious, elegant and easy to look at. On the other hand, a clear surface should be stimulating to look at, should be exciting and it should not look like an imitation. Knotty surfaces usually are less harmonious. Therefore, questions about harmony, easiness to look at and balance are of importance. Just as for clear surfaces, a knotty surface should also stimulate people's interest, have a fresh look, be exciting and stimulating to look at. The quantitative studies show that it is possible to measure people’s preferences toward wood by a questionnaire technique. The results also show that there are differences in people’s judgments for surfaces with knots and for those without knots. There are stronger connections between questions regarding the overall impression and the final assessment than there are for detailed questions regarding certain wood features. Thirteen questions were pointed out as relevant to use with interviews. Two interview methods were compared. The first method used wood surfaces and the second used computer images with the same wood surfaces applied to an example product, a kitchen cabinet. The results show that the two methods are comparable and useful. It was shown that it is possible to some extent to connect subjective preference data with objective wood feature measurements. Results show that a lot of wood feature measurements are needed and that it is a multivariate problem. Concerning the measurements, it seems easier to find features that negatively affect people’s liking than to find the opposite. Among the most important variables were those that detect different kinds of feature distribution over a wood surface, and especially those variables that detect a deviation in center of gravity. Increased knowledge about people’s preferences for the aesthetic properties of wood will lead to a better understanding of which wood features should be measured and controlled in the future.

    Ladda ner fulltext (pdf)
    FULLTEXT01
  • 18.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    The measurement of wood features in knotty Scots pine wood surfaces and the connection with people´s preferences2003Ingår i: Developments in image processing and scanning of wood: selected and edited papers from the 4th International Conference on Image Processing and Scanning of Wood, Mountain Lake, Virginia, USA, 21 - 23 August, 2000, 2003Konferensbidrag (Refereegranskat)
  • 19.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    The measurement of wood features in knotty Scots pine wood surfaces and the connections with people's preferences2000Ingår i: Developments in image processing and scanning of wood: selected and edited papers from the 4th International Conference on Image Processing and Scanning of Wood, Mountain Lake, Virginia, USA, 21 - 23 August, 2000 / [ed] Earl D. Kline, Virginia Tech , 2000Konferensbidrag (Refereegranskat)
    Abstract [en]

    For wood products that contain visible wood it is important to be able to describe the aesthetic properties desired, to measure and communicate them. The aim of this investigation was to shed light on the connections between people's preferences and the physical blend of wood features measured in digital images of Scots pine wood surfaces.  A total of 215 persons from Sweden with different backgrounds were interviewed regarding their preference for ten Scots pine wood surfaces containing knots. Their impressions and preferences were documented by a questionnaire. Many texture features (140 variables) were extracted from grayscale images of the wood surfaces and the connections with the preference data were modeled by partial least square analysis. Results from detail questions concerning what people thought about specific wood features were used as guidelines for the variable extraction. Prediction models for the preference questions were established and reported. For each prediction model, the 30 most robust wood feature variables were sorted out before the modeling. The results show that the wood feature variables varied in importance and all but one model was significant. The most important variables were those that detect different kinds of feature distribution over a wood surface and especially those variables that detect a deviation in center of gravity. The results illuminate the use of subjective preference data regarding the aesthetic properties of wood and give rise to some ideas of how to implement them in a production process.

  • 20.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Two methods for measuring people's preferences for Scots pine wood surfaces: a comparative multivariate approach1996Ingår i: Mokuzai Gakkaishi, ISSN 0021-4795, E-ISSN 1880-7577, Vol. 42, nr 2, s. 130-139Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The aim of this investigation was to compare two methods for measuring people's attitudes toward different appearances of Scots pine (Pinus sylvestris L.) and to determine relevant questions to ask them. Interviews were made at a fumiture exhibition in Sweden, and people were asked to evaluate different appearances of wood used in a kitchen cabinet. The first method used plain wood surfaces, and the second method used computer images of the same wood surfaces used in a kitchen cabinet.The results showed that it is possible to measure people's feelings and preferences for wood and that people's preferences for different appearances of wood are not affected if their judgements are based on computer images or if they are based on real wood surfaces. There are about ten questions needed to describe people's attitudes towards wood. A wood surface that people prefer should :-Have a fresh appearance -Be restful-Be in harmony -Have an eventful appearance-Be interesting to look at -Not look like an imitation-Be elegant -Be imaginative-Be exciting to look at -Not be gaudyThis study was the third part in a major project "price sensitivity for wood features".

  • 21.
    Broman, Olof
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Fredriksson, Magnus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Effect of Raw Material on Yield in a Furniture Production Process2015Ingår i: Proceedings of the 22nd International Wood Machining Seminar, June 14-17, 2015 Qebec City, Canada / [ed] Roger Hernández; Claudia Cáceres, Quebec City: Universite Laval , 2015, s. 311-322Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    In the process of wood manufacturing, each step affects the material utilization and the cost efficiency. Wood has got high diversity in its inherent features and the different manufacturing steps must be able to handle this. In most end products the proportion of the raw material cost is high. Thus, material utilization and cost efficient processes are of great importance. The overall aim of this project was to study the potential in a manufacturing production process in terms of material utilization efficiency. A production process of finger-jointed furniture components was chosen as a study case. Its chain of production units consists of: a sawmill, a finger-joint plant producing components and finally a furniture company that produce the end product. The aim of this article is to describe the impact of different raw material (log type and board quality) and what wood features affect the total yield of a manufactured product.In total 105 logs of three different types were tested: butt, intermediate and top logs. The logs were sawn with two different sawing patterns, 3X- and 2X-log. The quality of the wood material was measured by aid of 3D-scanning and X-ray (logs), manual grading (boards), and WoodEye (boards/components) and manual inspection of the final products. With a data collection with traceability the quality of the test material was followed through all steps in the manufacturing chain.The result show differences between log types in down-grade causes, reject volume and the final yield of accepted products. Different ways of improving the raw material efficiency of the studied chain of operations are also discussed.

    Ladda ner fulltext (pdf)
    fulltext
  • 22.
    Broman, Olof
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Fredriksson, Magnus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Wood material features and technical defects that affect the yield in a finger joint production process2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    A cost efficient process is the goal for every production process. In wood manufacturing, each step in the process may affect the material utilization and the cost efficiency. Wood as a material has got high diversity in its inherent features and the different manufacturing steps must be able to handle this. In most end products the proportion of the raw material cost is high. Thus, material utilization and cost efficient processes are of great importance. The overall aim of the project was to study the potential and problems in manufacturing production processes in terms of material utilization efficiency. A production process of finger jointed bed sides for IKEA was chosen as a study case and its chain of production units are; a sawmill for plank production, a finger joint company producing components and finally a furniture company that produce the end product. The aim of this article is to describe the impact of different raw material and what wood and technical defects that affect the total yield of a manufactured product. In total 177 logs of three different log types were tested; butt logs, intermediate logs and fresh knot logs. The quality of the wood material was detected and measured by aid of 3D-scanning and X-ray (logs), FinScan (planks), and WoodEye (planks/components) and manual inspection of the final products. With a full traceability data collection the quality of the test material was followed through all steps in the manufacturing chain. The result show differences between log types in down-grade causes, reject volume and the final yield of accepted products. Also, the test material showed high levels of reject with non-biological background which suggest the need of technical improvements in the finger joint and the furniture manufacturing process. The intermediate log group showed overall the best result.

    Ladda ner fulltext (pdf)
    fulltext
  • 23.
    Broman, Olof
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Fredriksson, Magnus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Wood material features and technical defects that affect yield in a finger joint production process2012Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 7, nr 4, s. 167-175Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A cost efficient process is the goal of all production, and each manufacturing step affects the material utilization and cost efficiency. There is high diversity in the inherent features of wood, and manufacturing steps must be able to handle this. The overall objective was to study the potential and problems in manufacturing production processes in terms of material utilization efficiency. The production of finger jointed bed sides was chosen as a study case, where the chain of production units are the sawmill, finger joint plant and furniture plant. This article describes the impact of raw material and wood defects that could affect the total yield. A total of 177 logs of three types were tested: butt, intermediate and fresh knot logs. The test material quality was detected and measured through all steps in the manufacturing chain. The results show differences between log types in down-grade causes, reject volume and final yield. Also, the test material showed high levels of defective components with process-related defects, which suggested the need for technical improvement in the manufacturing process. The intermediate log group showed the overall best result.

  • 24.
    Broman, Olof
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Grönlund, Anders
    The end-users´ requirements for the aesthetical features of scots pine wood1996Ingår i: Connection between silviculture and wood quality through modelling approaches and simulation softwares: Second Workshop, Berg-en-Kruger, Kruger National Park, South Africa, August 26-31, 1996 : proceedings / [ed] Gérard Nepveu, Nancy: INRA Editions, 1996, s. 343-352Konferensbidrag (Refereegranskat)
    Abstract [en]

    Wood has inherent aesthetic features which can give the final product competi­tive advantage over other materials. It is therefore important for the forest products industries to take advantage of those features of wood that have great influence on customers' choice of product. It is the final consumer's willingness to buy a product that is the motive power for the whole production process. Today, the forest products industry is not using any scientific method in order to utilize the aesthetic features of wood. Therefore methods to measure people's preferences for different wood features and also methods to measure these features in an objective way are needed.We have in an earlier study shown that it is possible to measure people's attitudes toward wood by a questionnaire technique. The results show that people prefer different blends of wood features. There are two qualitative differences that are of importance for people's impression and valuation of wood: The overall blending of wood features and divergent features that mismatch in a surface. It was found that divergent features are more important than the overall mixture of features. But if there are no defects that mismatch, the overall mixture will then be the key to a person's appreciation of a wood surface. In a new study, we have started to measure the different wood features in an objective way and developed statistical models of the relationship between the objective parameters and people's subjective preferences for different wood surfaces made of Scots pine (Pinus sylvestris). In this first attempt we have made very simple manual measurements of parameters such as knot size, knot type, knot shape and distribution of knots over the surface.The statistical analyses show that it is difficult to find any significant relation­ships between people's subjective preferences and the simple objective para­meters we have measured. It is evident that more sophisticated measure­ment tech­nique is needed. We must be able to measure parameters such as colour, grain pattern etc. Therefore we will use colour camera technique in future studies.

  • 25.
    Broman, Olof
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Grönlund, Anders
    Nordvik, Enar
    Lundahl, Carl Gustav
    Estetiska kvaliteter och skillnader i preferenser för limfog: en jämförelse mellan två intervjumetoder2008Rapport (Övrigt vetenskapligt)
    Abstract [sv]

    Den produktgrupp som här studerats är limfog för Gör-Det-Själv-marknaden. Limfog är en vanlig produkt som konsumenter köper styckevis och där träets estetiska blandning av träegenskaper kan vara av betydelse för ett aktivt val eller köp av kunden. Projektets övergripande mål var att studera vanliga konsumenters olika känslighet (smakprofiler) för olika utseenden på trä. Huvudmålet med studien var att jämföra två metoder för preferensmätning; dels användandet av riktiga träytor (limfog) och dels digitala bilder av desamma för rangordning av produktalternativ. För att validera användbarheten av de båda metoderna jämfördes deras rangordningsresultat. Ett delmål med studien var att studera skillnader mellan preferenser för limfog som producerats enligt alternativa produktionssätt med traditionellt producerad limfog. Femton personer intervjuades i två omgångar. I den första intervjun fick personerna rangordna 11 limfogsytor med hjälp av datorbilder och en webapplikation. I den andra intervjun två veckor senare fick samma personer rangordna samma limfogsytor fast nu med riktiga träytor. Resultaten från intervjuerna visar att de båda metoderna gav likvärdiga resultat. Det fungerade bra att använda digitala bilder och utföra preferensstudier via utvecklad web-applikation. För båda metoderna gällde att 11 stycken produktalternativ var på gränsen till för många att ta ställning till för de intervjuade personerna. Detta gällde båda intervjumetoderna. Bildernas kvalitet visade sig vara viktigt och de små skillnader i rangordningsresultat mellan de två intervjumetoderna kan till viss del förklaras av bristande återgivning av färgnyanser. Metoden att rangordna de verkliga limfogsskivorna fungerade mycket bra. Principen att välja ömsom bäst och sämst och kontinuerligt plocka bort valda produktalternativ fungerade bra. Följande estetiska kvalitetsskillnader visade sig vara viktiga för intervjupersonerna: En jämn fördelning av kvistar över ytan (limfogen) tillika blandning av kvistutseende är viktigt för helhetsintrycket. Märgstråk upplevdes starkt negativt då de ses som streck i ytan, en artefakt. Detta gäller också hög grad av randighet som upplevdes negativt. Detta kan orsakas av splint-/kärnvedsvariationer, speciellt när limfogen producerats med låg lamellbredd. Negativt var också tjurvedsstråk som orsakar randighet i en yta, vilket stör den visuella balansen och harmonin. Den limfog som producerats inom ramen för en ny högutbytesstrategi rankades högre än den traditionellt tillverkade limfogen som var inköpt. Detta kan förklaras främst av en hög grad av färska kvistar (ej svarta och eller döda kvistar), som kommer sig av valet av råvara. Råvaran utgjordes av klentimmer medan råvaran till den traditionellt tillverkade limfogen kom från plank med ursprung från osorterat timmer. Slutsatsen är att för limfog så har valet av råvara minst lika stor betydelse än produktionssätt (lamellbredd, koniska lameller etc) för det estetiska uttrycket och kundtillfredsställelse.

    Ladda ner fulltext (pdf)
    FULLTEXT01
  • 26.
    Broman, Olof
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Nordvik, Enar
    Fjellner, Bengt-Arne
    Means for measuring people's preferences for visual wood with aid of Internet2006Ingår i: Wood resources and panel properties :: Conference Proceedings ; Valencia, Spain, 12-13. Juni 2006 / [ed] Joris Van Acker;, AIDMA , 2006Konferensbidrag (Refereegranskat)
    Abstract [en]

    It is of interest to study and analyse the consumer market for visual wood so as to produce the right "look" of wood to the right product and the right group of customer. The choice of wood quality to a certain product is often decided at the production site without good information of people's sensitivity (taste profiles) for different blending of wood features. Today, regarding the issue of wood quality, there are no established techniques for detecting people's taste profiles.The aim of the work has been to develop a method for preference studies where visible wood is in focus. The aim was also to present interview results showing differences in acceptance among interviewed people just to persuade the readers about the usability of the methodology.In this investigation only wood floors of parquet type have been examined. Only one room type has been used. The interior was changed over time to study possible affect on parquet flooring preferences. About 50 persons participated in the study and they answered three times each during the development process.The interview concept is interactive and self instructive to measure preferences of different appearances of wood (in this study floor). The same room is shown but with different wood flooring and the floors is ranked with aid of paired comparison. When the ranking is completed, questions with both open and given answer alternatives are asked, just to get a description of the cause of preferences.Principal Component Analysis together with simple statistics was used to envisage the reader about the usability of the method. Perhaps the most important results of the research is that it is possible to measure what people prefer and to a certain extent why. Groups of peoples with different taste profiles can be found even if the number of interviewed people was small. The different wood species was described in words of the interviewed people, which of course from a wood producing company view, can be valuable in a market communication situation.

    Ladda ner fulltext (pdf)
    FULLTEXT01
  • 27.
    Broman, Olof
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Nordvik, Enar
    Fjellner, Bengt-Arne
    Metod för mätning av människors preferenser för synligt trä med hjälp av Internet2003Rapport (Övrigt vetenskapligt)
    Abstract [sv]

    Detta utvecklingsarbete är finansierat av Svenskt Trä och arbetet faller inom två prioriterade FoU områden, synligt trä och marknad. Det är av intresse att studera och analysera marknaden för synligt trä för att på så sätt producera rätt träutseende till rätt produkt och till rätt kund. Val av träkvalitet till en produkt bestäms alltför ofta i produktionsledet utan god information om känslighet för olika blandningar av träegenskaper (smakprofiler) bland sina tänkta slutkunder. Det finns idag ingen etablerad teknik för och kunskap om hur man kan mäta folks preferenser för olika träutseenden. Målet har varit att utveckla en metod för preferensstudier där synligt trä står i fokus och som ska kunna användas av företag och branschorganisationer. Målet är också att presentera de skillnader i tycke och smak som råder bland de intervjuade personerna, dels för att verifiera tidigare resultat och föreslagna metoder och dels för att visa på metodens möjligheter så att den kan utvecklas vidare till att bli ett användbart verktyg för marknadsstudier. I denna undersökning har enbart utseenden på trägolv av parkettyp studerats och endast ett visningsrum har använts dock med förändring av dess utseende och möblering under studiens gång. Ett 50-tal personer har deltagit och svarat tre gånger var under utvecklingsprocessen. Frågorna har förbättrats och rummets utseende har varierats. Förbättringsarbetet fortgår och det är snart dags att offentliggöra länken så att fler har möjlighet att delta. Fler exempelprodukter kommer att studeras. Ett konkret resultat av FoU arbetet hittills är den mötesplats på nätet http://trasmak.tt.luth.se/, som utvecklats för att mäta preferenser för olika utseenden på trä. Intervjukonceptet är självinstruerande och interaktivt där de intervjuade svarar på frågor som rör deras visuella intryck och trätexturernas utseende. Det kanske viktigaste resultatet av FoU arbetet är att det går att mäta vad folk föredrar och till viss del varför. Metoden bygger på att man rangordnar bilder av ett och samma rum men med olika trägolv med hjälp av parvis jämförelse. När rangordningen är gjord ställs frågor med både öppna och fasta svarsalternativ för att få en beskrivning av orsaken till personens val. Principal Component Analysis, PCA tillsammans med enkla tabellsammanställningar har använts med framgång för att beskriva resultaten av intervjutesterna. Grupper av olika smakriktningar kan ses även om testpersonerna var få. De olika träslagens utseende har beskrivits i ord av de intervjuade vilket kan vara värdefullt för en fullgången marknadskommunikation i träförädlingskedjan.

  • 28.
    Broman, Olof
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Nyström, Jan
    Oja, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Effektiv produktion av golvprodukter med krav på estetiska egenskaper2007Rapport (Övrigt vetenskapligt)
    Abstract [sv]

    Trä används i många tillämpningar där träet är synligt och där råvarans estetiska egenskaper därför är mycket. Exempel på sådana tillämpningar är produkter är golv och paneler. I detta projekt har produktionsprocessen för solida furugolv studerats, det vill säga hela kedjan från sortering av stockar till slutkonsumenters preferenser. Samarbetspartners i detta FoU- projekt har varit SCA -Bollsta sågverk, Norrlands Trä AB, SP Trätek och LTU - Träteknologi, Skellefteå. Syftet med projektet har varit att demonstrera hur man med hjälp av modern marknadsanalys, modern, industriellt implementerad mätteknik och avancerade sorteringsalgoritmer kan effektivisera produktionen av kundanpassade produkter med krav på estetiska egenskaper. Ett delmål var att undersöka alternativa utseendekvaliteter till dagens produktion av golvträ. Den genomgående metoden har varit att mäta och dokumentera råvarans egenskaper genom hela processen från stock till färdig produkt. En lättanvänd interaktiv databas har utvecklats inom ramen för projektet och använts för simulering av alternativa sorteringar av råvara avsedd för golvproduktion. Kopplat till databasen har även ett visualiseringsverktyg utvecklats. Detta gör det möjligt att direkt kunna se resultatet av simuleringarna i form av digitala golvytor. Utöver resultat i form av utvecklad databasgränssnitt, visualiseringsverktyg och verktyg för konsumentudersökningar så har projektet visat på intressanta resultat vad gäller både produktions och marknad. Resultatet av databassimuleringarna visar att man genom att förändra sorteringsstrategin och sortera stockarna baserat på information från en röntgenmätram helt kan undvika utsortering i råsorteringen, minska utsorteringen i justerverket med 25% (från tolv till nio procentenheter) och ändå producera en golvråvara med samma estetiska egenskaper som tidigare. Som ett alternativ till den ursprungliga golvråvaran har även en ny golvråvara definierats. Preferensstudier i både Sverige och Norge visade att konsumenternas tyckte bättre om den nya kvaliteten än den utsprungliga. Samtidigt gjorde denna nya golvråvara det möjligt att helt undvika utsortering i både råsortering och justerverk och samtidigt öka den tillgängliga golvråvaran med 27% (från 30 till 38 procentenheter).

    Ladda ner fulltext (pdf)
    FULLTEXT01
  • 29.
    Broman, Olof
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Nyström, Jan
    Oja, Johan
    Modelling the connection between industrially measured raw material properties and end user preferences: Part 2. Results from preference studies2008Ingår i: Connection between Forest Resources and Wood Quality: Modelling Approaches and Simulation Software. IUFRO Working Party 5.01.04 Wood Quality Modelling, June 8. - 14, Koli, Finland / [ed] H. Peltola, 2008Konferensbidrag (Övrigt vetenskapligt)
  • 30.
    Broman, Olof
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Wixe, David
    LTU Skellefteå, Träteknologi.
    Grönlund, Anders
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Oja, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Råvarustyrning för materialeffektiv produktion av limfog: En studie utförd vid Norrfog AB2011Rapport (Övrigt vetenskapligt)
    Abstract [sv]

    Norrfog AB i Malå tillverkar limfogskivor i olika kvaliteter, bland annat till gör-det-själv- (GDS)-limfog, möbelfog och IKEAs hyllkoncept Ivar. Då Norrfog planerar att öka sin producerade volym av limfog ökar behovet av en effektiv styrning av rätt råvara till rätt slutprodukt. Samtidigt stiger råvarupriserna och det blir allt viktigare att maximera volyms- och värdeutbytet. Vid tidpunkten för studien: Norrfog AB köper klena furustockar och försorterar stockarna i diameterklasser med hjälp av en 2D-mätram. Ingen sortering sker på stocktyp och därmed blandas rotstockar, svartkviststockar och friskkviststockar. Stockarna sågas med en 2ex postning till plankor som efter torkning kapas upp till komponentlängder som därefter klyvs till färdiga lameller för limfogsproduktion. Huvudsyftet med detta projekt var att undersöka möjligheterna att styra rätt kvalitet av timmer till rätt slutprodukt; Ivarhyllan, GDS-limfog och möbelfog samt för- och nackdelar med att införa ett alternativt sågsätt – genomsågning. Inom ramen för studien fanns följande forsknings- och utvecklingsfrågor: •Stocklängdens betydelse för volymutbytet av limfog? •Stocktypens betydelse för kvaliteten på producerad limfog? •Går det att hitta rätt typ av stockar till en specifik produkt redan vid timmerplanen med hjälp av befintlig 2D-mätram och förbättrar 3D eller röntgen-skanning denna klassificering av stockar? •Finns det ett motstånd till fingerskarv bland konsumenter och vad anses vara ett önskvärt utseende på en träyta av limfog? Studien visar att den stocktyp som gav den bästa kvaliteten var friskkviststockarna, men även de stockar som sorterades som svartkvistiga visade sig innehålla mestadels friska kvistar i de aktuella timmerdimensionerna. Ett tydligt resultat var att rotstockar innehöll den lägsta kvaliteten med för många och/eller för stora svarta kvistar och det visade sig vara lämpligt att om möjligt sortera bort dessa stockar för att såga dessa separat till produkter med lägre krav på kvalitet. Sorteringsalgoritmer för olika mättekniker för timmer speciellt anpassade för att maximera utbytet kvalitet 1 i den färdiga limfogen testades. Med befintlig 2D-mätram sorterades 81 % av rotstockarna bort och med röntgenmätning ökade andelen bortsorterade rotstockar till 98 %. Ett viktigt resultat var att genomsågning gav i snitt 13 % högre volymutbyte än 2ex-sågning och att korta stockar gav ökat volymutbyte jämfört med fullängdsstockar. En separat undersökning angående skivornas utseende visar att fingerskarvade limfogskivor är något konsumenten kan tänka sig, så länge färgskiftningarna mellan lamellerna är små. Stora färgskiftningar och små svarta kvistar var det som respondenterna rankade som minst tilltalande för alla skivor oavsett fingerskarv eller inte.

    Ladda ner fulltext (pdf)
    FULLTEXT01
  • 31.
    Cristovao, Luis
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Grönlund, Anders
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Ekevad, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Sitoe, Rui
    Eduardo Mondlane University.
    Main cutting force models for two species of tropical wood2011Ingår i: Proceedings of the 20th International Wood Machining Seminar, Skellefteå, 2011, s. 428-435Konferensbidrag (Refereegranskat)
  • 32.
    Cristóvão, Luís
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Grönlund, Anders
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Ekevad, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Sitoe, Rui
    Department of Mechanical Engineering , Eduardo Mondlane University, Maputo, Mozambique.
    Main cutting force models for two species of tropical wood2012Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 7, nr 3, s. 143-149Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The aim of the study was to evaluate the main cutting force for two species of tropical Mozambican wood and to develop predictive models. Cutting these hardwoods is difficult. Determination of cutting parameters is required to optimize cutting processes, machines and tools in the cutting operations. This determination would enable the forestry and wood sector to achieve higher financial results. Samples of a lesser-known wood species Pseudolachnostylis maprounaefolia (ntholo) and a well-known wood species Swartzia madagascariensis (ironwood) were machined in a test apparatus. A standard single saw tooth mounted on a piezoelectric load cell was used to evaluate the main cutting force. Data were captured using an A/D converter integrated with National Instruments LabVIEW software. The measured signals were recorded at a sampling frequency of 25 kHz. The experimental set-up used response surface methodology for developing predictive models. The experimental clearly determined the relationship between the main cutting force and edge radius, wood density, rake angle, chip thickness, moisture content (MC) and cutting direction (CD). Among the studied variables, chip thickness and CD had the highest effect on the main cutting force level while wood density, MC and rake angle had the lowest effect.

  • 33.
    Fredriksson, Magnus
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Berglund, Anders
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Validating a crosscutting simulation program based on computed tomography scanning of logs2015Ingår i: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 73, nr 2, s. 143-150Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Wood scanners and software for calculating crosscutting positions have been used in the wood industry for some years now. The scanners are used to detect biological and geometrical deviations on the sawn timber, which makes it possible to remove undesired defects using crosscut saws. Yield calculations for crosscutting have not been investigated to the same extent as sawing yield calculations for primary breakdown of logs, especially if the whole chain from log to end product is considered. The objective of this study was to validate the result of a computer program developed for simulating crosscutting of boards. The crosscut simulations were performed with respect to knot characteristics on Scots pine (Pinus sylvestris L.) board surfaces. Validating a crosscutting simulation program would mean that it can be used to investigate how raw material and customization of quality rules affect the yield in a wood production chain from log to crosscut end product. The validation showed that crosscutting yield for boards could be predicted with a root mean square error of 13 percentage points, and the technique can be used to identify unsuitable logs for a certain product at an early stage of production.

    Ladda ner fulltext (pdf)
    fulltext
  • 34.
    Fredriksson, Magnus
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Bomark, Peter
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Grönlund, Anders
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    A trapeze edging method for cross laminated timber panel production2015Ingår i: Proceedings of the 22nd International Wood Machining Seminar / [ed] Roger Hernández; Claudia Cáceres, Quebec city, Kanada: Universite Laval , 2015, s. 323-332Konferensbidrag (Refereegranskat)
    Ladda ner fulltext (pdf)
    fulltext
  • 35.
    Fredriksson, Magnus
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Bomark, Peter
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Grönlund, Anders
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Using Small Diameter Logs for Cross Laminated Timber Production2015Ingår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 10, nr 1, s. 1477-1486Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Sawing small diameter logs results in lower yield compared to sawing large diameter logs. This is due to geometry; fitting rectangular blocks inside an approximately cylindrical shape is more difficult for small than for large diameters. If small diameter logs were sawn in a way that follows the outer shape, yield would increase. The present study considers whether this can be done by sawing flitches into trapeze shapes. These can be glued together into rectangular products. Cross laminated timber (CLT) products are suitable for this. The study was based on 4,860 softwood logs that where scanned, and the scanning data was used for sawing simulation. The log top diameters ranged from 92 to 434 mm. The volume yield of CLT production using trapeze edging was compared to cant sawing of boards. The trapeze edging and CLT production process improved yield compared to cant sawing by 17.4 percent units, for logs of a top diameter smaller than 185 mm. For all logs, the yield decreased using the trapeze edging method. To conclude, a trapeze edging method shows promise in terms of increasing volume yield for small diameter logs, if boards can be properly taken care of in a CLT production process

  • 36.
    Fredriksson, Magnus
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Factors Affecting Volume Yield in a Forestry-Wood Value Chain: A Simulation Study Based on CT Scanning2017Ingår i: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 13, nr 4, s. 540-548Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The paper presents the results of a simulation study, where log models based on CT scanned logs of Scots pine (Pinus sylvestris L.) was used as input material to a computer simulation model of a generic value chain involving sawing, drying, crosscutting and finger jointing. The aim was to investigate which factors that affect the volume yield in the value chain, be it forestal, log-, process- or quality-related factors. The results show that factors related to growth conditions and log size have a large impact on the volume yield in the studied value chain, together with quality requirements on knots. Factors such as sawing positioning and log quality had a much smaller impact. It can be concluded that it is possible to model a forestry-wood value chain, while assessing which input variables affect the result in terms of volume yield, using CT scanning of logs and subsequent computer simulation of the production processes.

    Ladda ner fulltext (pdf)
    fulltext
  • 37.
    Fredriksson, Magnus
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Persson, Fredrik
    SP Trä.
    Axelsson, Ann
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Ah Shenga, Pedro
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Rotational Position of Curved Saw Logs and Warp of the Sawn Timber2014Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 9, nr 1, s. 31-39Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    With the development of scanning technology in sawmills, it is possible to optimise log rotational position when sawing. However, choosing a different rotational position than horns down might be detrimental for the board shape after drying, especially for curved logs. Thus, there is a need to investigate at what level of log curve it is possible to freely rotate logs without causing board warp. This study was carried out through a test sawing that was conducted at a sawmill situated in the middle of Sweden. The tests were made on 177 Norway spruce logs, with varying amount of curve. Half of the logs were sawn in the horns-down position, half were sawn rotated perpendicular to horns down. Log shape and warp of the dried boards were measured. The results indicated a relationship between board spring, log curve and choice of rotational position. Furthermore, board bow was related to log curve but not rotational position. It can be concluded that for straight logs, with a bow height of less than 15 mm, an unconventional rotational position does not cause excess spring in the boards. Bow and twist are not affected by the rotational position at all.

  • 38.
    Fredriksson, Magnus
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    The Use of CT-Scanning Technology in Wood Value-Chain Research and in Wood Industry: A State of The Art2017Ingår i: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 13, nr 4, s. 533-539Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    X-ray computed tomography (CT) is a powerful tool for the non-destructive  measurement  of  dynamic  processes in wood. After more than 25 years of research at Luleå University of Technology in the field of CT-scanning of wood material, the first industrial CT-scanners are now installed in sawmill production for the in-situ measurement of internal  log features to steer of the sawmill process with the help of this information.This  paper  provides  an  overview  of  the  potential  of  CT-scanning in wood-material  research  and  how  this data can be used for the modelling and simulation of the wood value chain. A database of CT-images of trees  is  used  to  create  a  log  model  including  the  outer  shape  of  the  logs  and  their  internal  knot  structure.  Simulation software is used to saw these virtual logs in different positions relative to the sawblade, and also for the crosscutting of the sawn timber to components. The output is dimensions and grades of sawn timber, volume yield as well as an economic result based on real economic conditions. A specially designed climate chamber  for  CT  studies  of  the  drying  of  sawn  timber  is  used  to  increase  the  knowledge  of  how  the  drying  affects the response from the sawn timber during seasoning.

    Ladda ner fulltext (pdf)
    fulltext
  • 39. Grönlund, Ulla
    et al.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Relations between wood properties and manual grading: an approach based on multivariate analysis1995Ingår i: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 53, nr 6, s. 413-420Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Pinus sylvestris ) boards from Sweden have been scanned on all four sides. The output variables together with additional variables describing e.g. geographic areas and manual classification class are analysed by using multivariate statistical methods. The purpose was to study if the manual grading procedure of boards/blanks are in conformity with automatically measured properties and if there is any single property that carries more information than others. The results show that most of the original variables are uncorrelated and therefore it is impossible to reduce and simplify the grading procedure by e.g. measuring only a few characteristics. The study also shows the weakness of the objective grading procedure describing only the amount of characteristics.

  • 40.
    Hagman, Olle
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Popovic, Djordje
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Optimizing the cross cutting operation using research design metod2014Konferensbidrag (Refereegranskat)
    Ladda ner fulltext (pdf)
    fulltext
  • 41.
    Huber, Johannes A. J.
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Ekevad, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Oja, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Hansson, Lars
    Department of Ocean Operations and Civil Engineering, Faculty of Engineering, Norwegian University of Science and Technology, 6025 Ålesund, Norway.
    A method for generating finite element models of wood boards from X-ray computed tomography scans2022Ingår i: Computers & structures, ISSN 0045-7949, E-ISSN 1879-2243, Vol. 260, artikel-id 106702Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A method is presented for reconstructing the geometry, the pith, the knots and the local fibre orientations in timber boards, based on X-ray computed tomography scans. The local fibre deviations around knots were found by a new algorithm, based on image analysis. The experimental data comprised tomography scans, eigenfrequency measurements and four-point bending tests of 20 Norway spruce boards. 3D and 1D finite element models of the pure bending zone of the bending tests were created, accounting for the exact board geometry and the reconstructed fibre deviations. A purely density based, a purely eigenfrequency based, and a mixed constitutive law were compared. Model estimations showed a high coefficient of determination (R2) for global modulus of elasticity (MoE) (R2⩽0.93), local MoE (R2⩽0.87), bending strength (R2⩽0.83), and the location of initial failure. Constitutive laws accounting for eigenfrequency showed the most accurate results. In the future, adapting the method for logs could enable analyses of boards before sawing.

    Ladda ner fulltext (pdf)
    fulltext
  • 42.
    Huber, Johannes Albert Josef
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Oja, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Ekevad, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Generating 3D Finite Element Models of Boards from Computed Tomography Images2020Ingår i: Proceedings of the 16th Annual Meeting of the Northern European Network for Wood Science and Engineering - WSE2020 / [ed] Marketta Sipi, Juha Rikala, Helsinki, Finland: University of Helsinki, 2020, s. 71-73Konferensbidrag (Refereegranskat)
    Ladda ner fulltext (pdf)
    fulltext
  • 43.
    Huber, Johannes Albert Josef
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Oja, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Hansson, Lars
    Department of Ocean Operations and Civil Engineering, Norwegian University of Science and Technology, Ålesund, Norway.
    Ekevad, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Nondestructive Testing of Timber Prior to Sawing Using Finite Element Models Based on X-ray Computed Tomography Data - A Preliminary Study2022Ingår i: Proceedings: 22nd International Nondestructive Testing and Evaluation of Wood Symposium / [ed] Wang, Xiping; Ross, Robert J., Madison, WI, USA: United States Department of Agriculture , 2022, s. 200-200Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    X-ray computed tomography (CT) of wood delivers internal density data of a scanned object, where, depending on the resolution, internal features like the pith, annual rings and knots can be identified. Some sawmills use CT scanners in front of the saw line to determine the optimal positioning of the log in the saw, to maximise the value yield of the sawn products. We envision that the gathered CT data also could be used for mechanical evaluations of the timber using numerical models of boards prior to sawing. In a recent study by the authors, a method was developed to create 3D and 1D finite element (FE) models based on CT scans of dried sawn timber, which could predict bending stiffness and strength in bending simulations with high accuracy. The objective of the present study is to explore how the method can be adapted to CT scans of logs before sawing. Our preliminary study was based on CT data of green Norway Spruce logs and the corresponding scans of dried sawn timber. The stiffness and strength were evaluated using four-point bending tests. Additionally, the resonance frequency of the logs was recorded. The corresponding volume of each piece of sawn timber was extracted from the log data and an FE model was created. The model accounted for the pith, the annual rings, the knots, and the local fibre deviations around knots. Various laws for local stiffness and different failure criteria were tested. The study showed how FE models of virtual pieces of sawn timber can be created from CT data and what obstacles need to be overcome for further development of the presented method. The results indicated that more detailed evaluations of the relationship between local stiffness and density may be required, in specific for knots and for wood in green state.

    Ladda ner fulltext (pdf)
    fulltext
  • 44.
    Huber, Johannes Albert Josef
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Ekevad, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Using Computed Tomography Data for Finite Element Models of Wood Boards2021Ingår i: 14th World Congress on Computational Mechanics (WCCM) ECCOMAS Congress 2020 / [ed] F. Chinesta, R. Abgrall, O. Allix, M. Kaliske, Computational Structural Mechanics Association , 2021Konferensbidrag (Refereegranskat)
    Abstract [en]

    A procedure is presented to generate 3D FE models of timber boards based on CT scans. Theboards were tested in four-point bending tests until failure and the local displacement in the pure bendingzone was recorded. The CT scans were treated as 3D images and image processing methods were usedto reconstruct the board,  the knots and the pith. A new procedure to reconstruct the fibre deviationsaround knots by accounting for image gradient information was used. A quadratic tetrahedral mesh wasgenerated for the region of the board which was under pure bending in the tests. The fibre directions andthe stiffness tensor, scaled by the local density, were transferred into each integration point of the meshand the bending test was replicated.  Preliminary results show that the procedure is able to realisticallypredict the observed local stiffness of the boards. Further development of the procedure is required toaccount for dead knots and to extend the procedure for indicating strength and predicting failure.

    Ladda ner fulltext (pdf)
    fulltext
  • 45.
    Huber, Johannes Albert Josef
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Oja, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik. Norra Timber.
    Ekevad, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    3D Quasi-Continuum and Finite Element Models Based on CT Scans of Timber Boards to Predict Stiffness and Strength2021Ingår i: ICCSE1 1st International Conference on Computations for Science and Engineering: Book of Abstracts / [ed] António J.M. Ferreira; Nicholas Fantuzzi; Michele Bacciocchi, 2021, artikel-id 159Konferensbidrag (Refereegranskat)
    Abstract [en]

    Engineered wood products of today's construction industry require predictable mechanical properties of the used structural timber. At sawmills, automated strength grading is used to assess the stiffness and strength of sawn and dried timber boards. This process can be based on various technologies, e.g. surface scanning, dynamic excitation, flat-wise bending, which are used to derive so-called indicating properties, i.e. simplified numerical values. Heuristically derived statistical models can then be used to predict the stiffness and strength based on indicating properties. However, statistical strength grading can only exploit a small fraction of the potential strength of a single board, since it assesses the properties of a board in relation to its population. 

    A growing number of sawmills in Sweden use computed tomography (CT) scanners to assess the incoming logs to optimise their positioning prior to sawing. CT scans provide high-quality data of the cross-sectional density distribution along the length of a log, which could also be used to derive continuum mechanical models of the yet unsawn boards and with that assess their mechanical properties. If the stiffness and strength of a virtual board can be predicted before it is sawn, then it could be pre-classified into a strength class or its specific use as a specific construction part could be predetermined already at the log stage, which would lead to a more efficient material usage. Additionally, the predictive power of the existing statistical strength grading processes could be improved for the final boards.

    The goals of this study were to i) derive 3D quasi-continuum and finite element (FE) models of CT scanned timber boards using different material laws for local stiffness based on measured density and ii) compare their capabilities for predicting stiffness and strength of the boards.

    The experimental material consisted of dried softwood boards (12% moisture content) of nominal cross-sectional dimensions 50x100mm with different lengths, scanned with a medical high-resolution CT scanner. The boards underwent an eigenfrequency measurement by dynamic excitation and were tested until failure in a four-point bending test, where both the local and global displacement were recorded.

    A previously developed algorithm was used to derive 3D quasi-continuum reconstructions from the CT scans and subsequently finite element (FE) models. The algorithm reconstructed the board geometry, pith, knots and local fibre directions (material coordinate system) on a volume grid of material points spaced 0.68mm apart. The stiffness tensor in each material point was made locally dependent on the measured density by different mathematical laws, e.g. constant, linear or power laws. Furthermore, material laws which scaled the stiffness tensor based on the ratio between the simulated and measured eigenfrequency were tested for comparison. The bending stiffness profile was calculated for each board along its length and different indicating properties for predicting stiffness and strength were derived and compared with respect to the experimental results. With the FE model, strain distributions in the cross-sections were studied and local stress states around the experimentally observed points of initial failure were investigated to determine whether similar dominant failure stress states existed among boards.

    The results showed high coefficients of determination between predicted stiffness and strength for material laws based on power laws and low values for linear laws. Nevertheless, the four-point bending tests only provided point-wise data (mid points) that could be used to validate the numerical model. It is therefore recommended to use field-based evaluations in the future, e.g. the surface strain obtained with DIC under four-point testing.

    Ladda ner fulltext (pdf)
    fulltext
  • 46.
    Hyll, Kari
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik. Skogforsk.
    Joevenller, Sheng
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Svennerstam, Henrik
    Skogforsk.
    Nordström, Maria
    Skogforsk.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Oja, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    CT-skanning som verktyg för detektering av törskateangrepp på tall2022Rapport (Refereegranskat)
    Abstract [sv]

    Törskateangrepp på tall förväntas bli ett allt större problem för både skogsägare och sågverk i Norden. Det finns samtidigt stora kunskapsluckor om törskate generellt och om hur man ska hantera angripet timmer för att minska de ekonomiska konsekvenserna av angreppen. Det finns exempelvis inget tillförlitligt sätt att detektera och bedöma skadegraden hos sågtimmer, vilket leder till ökat spill vid sågning då hela stockar oftast nedklassas där man eventuellt skulle kunna använda delar eller merparten av timret. Osäkerheten om de ekonomiska konsekvenserna är stor. Det saknas även kunskaper kring törskatesvampens biologi, samt trädets respons och försvar mot pågående infektion. 

    Syftet med denna förstudie var att (1) undersöka om röntgenbaserad datortomografi (CT-skanning) kan detektera törskateangrepp hos talltimmer, för att därmed kunna optimera sågningen och “rädda” det sågade virkets värde, (2) att jämföra CT-bildernas 3-dimensionella beskrivning av törskateangreppet med hur skadorna ser på utsidan, för att kunna ta fram rekommendationer för yttre bedömning av skadeangrepp till exempel vid avverkning, samt (3) att bedöma möjligheterna att beskriva skadeförloppet och trädets försvar mot svampangreppet. 

    Åtta törskateangripna och två icke angripna träd (tall) insamlades från ett gallringsbestånd och ett slutavverkningsbestånd utanför Bjurselet, Norsjö kommun i Västerbotten. Träden avverkades under januari månad 2022. Efter fällningen gjordes en okulär besiktning av trädstammarna, där de törskateskadade delarna märktes med färg på mantelytan. Stammarna apterades i lämpliga längder för transport, samtidigt som det undveks att utföra apteringen i de törskateskadade områdena. Virket transporterades till LTU Träteknik i Skellefteå för CT-skanning.

    CT-skanningen av provträden visade att törskate kan detekteras på ett sätt som möjliggör fortsatt utveckling av en industriell detektering av törskate och optimering av timrets sönderdelning. En svårighet som dock uppdagades var att törskateangripna områden i splintveden har snarlika bildanalystekniska egenskaper som icke angripen kärnved. Det kunde även konstateras att törskatens utbredning i stammens volym är större än vad som kan detekteras okulärt på stammens mantelyta, framför allt i stammens längdriktning. I de preliminära analyser som ligger till grund för denna rapport är det dock inte möjligt att urskilja svampens tidsmässiga utbredning från angrepp till tidpunkten då CT-skanningen genomfördes. Däremot kan det konstateras att årsringar går att urskilja både i skadad och oskadad ved vilket ger möjligheten att från år till år följa skadeutvecklingen. DNA-analys detekterade förekomst av törskatesvamp i veden, både i och utanför kådrika områden. Den högsta mängden av törskatespecifikt DNA uppmättes utanför det kådrika området i splintvedens yttre delar.

    Sammanfattningsvis visar studien att de tekniska förutsättningarna för att detektera de inre skadorna av törskate med CT-skanning är goda och att utveckling av algoritmer för bildbehandling är ett viktigt nästa steg för automatiserad detektion av törskate i tall.

    Ladda ner fulltext (pdf)
    fulltext
  • 47.
    Hyll, Kari
    et al.
    The Forestry Research Institute of Sweden (Skogforsk), Uppsala, Sweden.
    Joevenller, Sheng
    The Forestry Research Institute of Sweden (Skogforsk), Uppsala, Sweden.
    Svennerstam, Henrik
    The Forestry Research Institute of Sweden (Skogforsk), Uppsala, Sweden.
    Nordström, Maria
    The Forestry Research Institute of Sweden (Skogforsk), Uppsala, Sweden.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Oja, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    X-ray computed tomography for the detection of damage in Scots pine trunks caused by blister-rust fungus Cronartium pini (Willd.)2022Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 17, nr 6, s. 1022-1024Artikel i tidskrift (Refereegranskat)
  • 48.
    Johansson, Marie
    et al.
    RISE.
    Gustafsson, Anders
    RISE.
    Olsson, Jörgen
    RISE.
    Ylmén, Peter
    RISE.
    Nord, Tomas
    LIU.
    Dorn, Michael
    LNU .
    Frühwald Hansson, Eva
    LTH.
    Serrano, Erik
    LTH.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Jansson, Gustav
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriellt och hållbart byggande.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Brännström, Mattias
    Renewinn.
    Slutrapport: Framtidens biobaserade byggande och boende2019Rapport (Övrigt vetenskapligt)
    Abstract [en]

    The aim of the project “Biobased building and living for the future” was to create conditions for increased use of bio-based products and services in the construction sector in Sweden and Europe and to increase the competitiveness of the Swedish timber manufacturing industry. The project has shown ways to develop E-commerce, parts of the production where increased digitalization leads to increased capacity and quality, as well as solutions for development of floor systems, external walls and tall timber buildings. The project has shown development opportunities to increase the use of bio-based products that implemented will increase competitiveness.

    The project has been divided into eleven sub-projects to study the various aspects of external factors, market conditions and business models, process development and product development. Within each sub-project, several workshops have been carried out to jointly evaluate results and decide the next step in the sub-project. Through joint workshops, the partners have also been able to meet and share results across the subprojects and spread knowledge and create networks within the industry. The last part is perceived as very valuable by both the companies and the academy / institute.

    For the joinery value chain, a current situation analysis has been carried out and shown how the development of E-commerce platforms must be combined with process development in order to have a large effect. The results will be utilized in the companies' strategy work ahead. For the timber building value chain, demonstrators have shown development opportunities for both process and product development. The next step for the companies is to evaluate the various solutions linked to their own production conditions.

    Ladda ner fulltext (pdf)
    fulltext
  • 49.
    Larsson, Maria
    et al.
    The University of Tokyo, Japan.
    Ijiri, Takashi
    Shibaura Institute of Technology, Japan.
    Yoshida, Hironori
    Future University Hakodate, Japan.
    Huber, Johannes A. J.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Fredriksson, Magnus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Igarashi, Takeo
    The University of Tokyo, Japan.
    Procedural texturing of solid wood with knots2022Ingår i: ACM Transactions on Graphics, ISSN 0730-0301, E-ISSN 1557-7368, Vol. 41, nr 4, artikel-id 45Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present a procedural framework for modeling the annual ring pattern of solid wood with knots. Although wood texturing is a well-studied topic, there have been few previous attempts at modeling knots inside the wood texture. Our method takes the skeletal structure of a tree log as input and produces a three-dimensional scalar field representing the time of added growth, which defines the volumetric annual ring pattern. First, separate fields are computed around each strand of the skeleton, i.e., the stem and each knot. The strands are then merged into a single field using smooth minimums. We further suggest techniques for controlling the smooth minimum to adjust the balance of smoothness and reproduce the distortion effects observed around dead knots. Our method is implemented as a shader program running on a GPU with computation times of approximately 0.5 s per image and an input data size of 600 KB. We present rendered images of solid wood from pine and spruce as well as plywood and cross-laminated timber (CLT). Our results were evaluated by wood experts, who confirmed the plausibility of the rendered annual ring patterns.

    Ladda ner fulltext (pdf)
    fulltext
  • 50.
    Manuel, A.
    et al.
    Albert Ludwigs Univ Freiburg, Forstbenutzung, Freiburg, Germany.
    Leonhart, R.
    Albert Ludwigs Univ Freiburg, Inst Psychol, Freiburg, Germany.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Becker, G.
    Albert Ludwigs Univ Freiburg, Forstbenutzung, Freiburg, Germany.
    Visuelle Wahrnehmung und sprachliche Beurteilung von Holzoberflächen durch Endverbraucher - Relevante Begrifflichkeiten untersucht am Beispiel von Kiefernholz-Dielenböden: [Visual perception and verbal assessment of wood surfaces by consumers - Relevant expressions on floors of pine wood boards as an example]2017Ingår i: Allgemeine Forst und Jagdzeitung, ISSN 0002-5852, Vol. 188, nr 9-10, s. 186-196Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Interior design and flooring from wood are highly appreciated by consumers. Today's wood industries use mostly technical parameters to identify wood quality, whereas knowledge about consumer preferences is rarely taken into account. The exploration of terms consumers use in their day-to-day language characterising wood surfaces (Picture 1) can help to direct and focus the production and marketing of high valuable wood products according to consumers' appreciation and preferences. This study aims at (1) identifying relevant items which consumers use when assessing wood surfaces. (2) Relevant items are examined with regard to the construction of a practically feasible set of different Items and factors. The final number of items and factors should comprise the whole range of diverse aspects of the consumer's visual assessment of wood surfaces. A questionnaire in German language was used (1) to collect relevant terms and criteria in an open question. (2) A Set of 39 pre-set items, which have been found to be meaningful in earlier studies (in English language) was translated into German and offered to consumers (n = 102) to test their relevance in German language. This set of items was analysed in an exploratory factor analysis on the base of 96 answers. Two other questions requested terms (3) that were missing and (4) which were the most relevant. Out of the answers to the questions 1 and 4, objective and subjective Items (Table 1) were categorised. Based on the answers to question 2, the Kaiser-Gutttman criterion suggested a solution based on 12 factors, but further analysis revealed four factors the most appropriate solution (Table 2). Meaning and interpretation of the items and factors from this study need to be set in the context of the people's socio-demographic environment and so results cannot be generalised. The adjustment and validation of the items and factors identified in this study is recommended with regard to different panels of consumer groups and wood products, for which this study suggests adequate methods and tools for questionnaire design and data analysis. This may help to direct production and marketing of valuable wood products more effectively towards consumer's preferences with positive effects for a more efficient use of the raw material and added value.

12 1 - 50 av 70
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf