| 1. |
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| 2. |
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| 3. |
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| 4. |
- Oja, Johan, et al.
(författare)
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Automatic grading of sawlogs : a comparison between X-ray scanning, optical three-dimensional scanning and combinations of both methods
- 2004
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Ingår i: Scandinavian Journal of Forest Research. - : Informa UK Limited. - 0282-7581 .- 1651-1891. ; 191:1, s. 89-95
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Tidskriftsartikel (refereegranskat)abstract
- As sawmills become increasingly efficient, the importance of focusing on value recovery becomes obvious. To maximize value recovery, sawmills require the ability to sort logs according to quality. This study compares four different combinations of three-dimensional (3D) and X-ray scanning that can be used to grade logs automatically. The study was based on 135 Scots pine (Pinus sylvestris L.) logs that had been scanned with both a 3D scanner and an X-ray scanner with two X-ray sources. The percentage of boards with correct grade sawn from automatically graded logs varied from 57% when using only 3D scanning to 66% when using a combination of 3D scanning and X-ray scanning in two directions. The highest possible result, with ideal log grading, was 81%. The result also shows that the combination of a 3D scanner and one X-ray direction results in higher accuracy than a scanner based on two X-ray directions
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| 5. |
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| 6. |
- Olofsson, Linus, et al.
(författare)
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New possibilities with CT scanning in the forest value chain
- 2019
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Ingår i: Proceedings 21st International Nondestructive Testingand Evaluation of Wood Symposium. - : U.S. Department of Agriculture. ; , s. 569-576
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Industrial high-resolution X-ray computed tomography (CT) scanners have recently been installed at several sawmills worldwide for the description of roundwood interior features and external log shape. These CT scanners represent a technological advancement for sawmill businesses that open a way to higher volume and value yields and new production planning strategies. This paper will present an indicative study of innovative use of non-destructive CT log data in a Swedish softwood sawmill, linking high-quality information of the wood material along the wood-value chain. Sawn timber was observed throughout the sawmill process line, i.e. from the log yard through the sawmill process until grading after the timber was dried. Before sawing, the CT scanner scanned the logs and calculated knot measurements from the 3D CT log data of simulated value-optimized center yield. A corresponding set of knot measurements were later calculated from the camera-based grading of the dried timber. Only considering knots from the two sets of measurements, the sawn timber was automatically given a quality assessment based on CT data, by camera-based scanning data, and by manual visual grading for reference. Partial least squares regression was used to create prediction models by correlating the two sets of knot measurements with the automatically determined grade from the dry-sorting. The prediction models tested increased the grading consistency between the grading based on CT data of virtual planks and based on camera data of the same planks. Furthermore, a traceability algorithm was tested as a tool to generate large data sets for future studies.
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| 7. |
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| 8. |
- Skog, Johan, et al.
(författare)
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Combining x-ray and three-dimensional scanning of sawlogs : comparison between one and two x-ray directions
- 2009
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Ingår i: Proceedings of the 6th International Symposium on Image and Signal Processing and Analysis, 2009. - Piscataway, NJ : IEEE Communications Society. - 9781424456499 ; , s. 353-358
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Konferensbidrag (refereegranskat)abstract
- In many sawmills, presorting of sawlogs is based on data from optical three-dimensional (3D) scanners. The use of x-ray log scanners is also becoming increasingly common and most sawmills installing an x-ray scanner already have a 3D scanner present. It is in this paper demonstrated how data from oneand two-directional x-ray scanners can be combined with 3D scanner data using path length compensation. Examples show how the resulting images may be processed in order to predict quality parameters such as heartwood diameter and green heartwood density. Using the proposed method, it is possible to improve the accuracy of these important quality sorting parameters using existing equipment. This will improve the presorting at sawmills, thus reducing the production of off-grade products carrying unwanted combinations of dimension and grade.
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| 9. |
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| 10. |
- Skog, Johan, et al.
(författare)
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Density measurements in Pinus sylvestris sawlogs combining X-ray and three-dimensional scanning
- 2010
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Ingår i: Scandinavian Journal of Forest Research. - 0282-7581 .- 1651-1891. ; 25:5, s. 470-481
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Tidskriftsartikel (refereegranskat)abstract
- Wood density is an important quality variable, closely related to the mechanical properties of the wood. Precise wood density measurements in the log sorting would enable density sorting of logs for products such as strength-graded wood and finger-jointed wood. Density sorting of logs would also give more homogeneous drying properties and thus improve the quality of the final products. By compensating the radiographs from an X-ray log scanner for the varying path lengths using outer shape data from a three-dimensional (3D) scanner, it is possible to make precise estimates of both green and dry density. Measurements on simulated industrial data were compared with densities measured in computed tomographic (CT) images for 560 Scots pine (Pinus sylvestris L.) logs. It was found that green sapwood density could be measured with predictability R 2=0.65 and root mean square error (RMSE) of 25 kg m-3. Green and dry heartwood densities were measured with similar precision: R 2=0.79 and RMSE=32 kg m-3 for green density and R 2=0.83 and RMSE=32 kg m-3 for dry density.
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| 11. |
- Skog, Johan, et al.
(författare)
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Density measurements in Pinus sylvestris sawlogs combining X-rayand three-dimensional scanning
- 2010
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Ingår i: Scandinavian Journal of Forest Research. - : Informa UK Limited. - 0282-7581 .- 1651-1891. ; 25:5, s. 470-481
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Tidskriftsartikel (refereegranskat)abstract
- Wood density is an important quality variable, closely related to the mechanical properties of the wood. Precise wood density measurements in the log sorting would enable density sorting of logs for products such as strength-graded wood and fingerjointed wood. Density sorting of logs would also give more homogeneous drying properties and thus improve the quality of the final products. By compensating the radiographs from an X-ray log scanner for the varying path lengths using outer shape data from a three-dimensional (3D) scanner, it is possible to make precise estimates of both green and dry density. Measurements on simulated industrial data were compared with densities measured in computed tomographic (CT) images for 560 Scots pine (Pinus sylvestris L.) logs. It was found that green sapwood density could be measured with predictability R2 = 0.65 and root mean square error (RMSE) of 25 kg m-3. Green and dry heartwood densities were measured with similar precision: R2 = 0.79 and RMSE = 32 kg m-3 for green density and R2 = 0.83 and RMSE = 32 kg m-3 for dry density.
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| 12. |
- Skog, Johan, et al.
(författare)
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Detecting Top Rupture in Pinus sylvestris Sawlogs
- 2011
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Ingår i: Proceedings of the 20th international wood machining seminar. - Skellefteå : Luleå University of Technology. - 9789174392647 ; , s. 132-140
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Konferensbidrag (refereegranskat)
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| 13. |
- Skog, Johan, et al.
(författare)
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Heartwood diameter measurements in Pinus sylvestris sawlogs combining X-ray and three-dimensional scanning
- 2009
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Ingår i: Scandinavian Journal of Forest Research. - : Informa UK Limited. - 0282-7581 .- 1651-1891. ; 24:1, s. 182-188
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Tidskriftsartikel (refereegranskat)abstract
- Quality sorting of sawlogs based on three-dimensional (3D) or X-ray scanning or a multivariate combination of variables from both methods may be used to decrease the production of off-grade products carrying unwanted combinations of dimension and grade. There is, however, potential for further improving the sorting accuracy if 3D and X-ray raw data are combined at an early stage using path length compensation. From the measured 3D shape, a good estimate of the length of each X-ray path through the log can be made, enabling the calculation of a log density profile from the measured X-ray attenuation. The effect of this technique on heartwood diameter measurements of 423 Scots pine (Pinus sylvestris L.) logs was evaluated. By the addition of 3D data to the X-ray data it was possible to raise the predictability of the heartwood diameter from R 2=0.84 to 0.95 and to improve the root mean square error from 17 mm to 9.3 mm, primarily because of the enhanced contrast between heartwood and sapwood.
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| 14. |
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| 15. |
- Skog, Johan, et al.
(författare)
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Improved log sorting combining X-ray and 3D scanning : a preliminary study
- 2007
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Ingår i: Quality control for wood and wood products. - Warsaw : Warsaw University of Life Sciences. - 9788372449047 ; , s. 133-140
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Konferensbidrag (refereegranskat)abstract
- Quality sorting of sawlogs is becoming more and more common. This is the result of increasing production of customer specific products in combination with high raw material prices. Today, log quality sorting is being based on either 3D or X-ray scanning techniques. Previous research has shown that sorting accuracy is improved when using multivariate models to combine variables from both 3D and X-ray scanners. There is however a potential of further improving the sorting if 3D and X-ray data are combined at an earlier stage; from the measured 3D shape a better estimate of the X-ray path lengths through the log may be found, thus enabling the calculation of a log density profile from the measured X-ray attenuation. The development and evaluation of such a technique is the topic of current research at SP Trätek and Luleå University of Technology in Skellefteå. Preliminary results show that the method is good at calculating large scale properties such as heartwood content and heartwood and sapwood densities. When looking for smaller geometric objects, e. g., knot whorls, extra care must be taken so that observational errors from the 3D scanner do not compromise the X-ray data. Software simulating industrial X-ray scanner data from CT-scanned logs has also been developed. A very good agreement was found between simulated data and actual data from an industrial installation. This underlines that such a simulation tool is very valuable when developing algorithms for industrial X-ray scanners.
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| 16. |
- Skog, Johan, et al.
(författare)
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Sapwood moisture-content measurements in Pinus sylvestris sawlogs combining X-ray and three-dimensional scanning
- 2010
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Ingår i: Wood Material Science & Engineering. - : Informa UK Limited. - 1748-0272 .- 1748-0280. ; 5:2, s. 91-96
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Tidskriftsartikel (refereegranskat)abstract
- Because today's sawmill processes are not fully adapted to the variability of the raw material, it is crucial to sort sawlogs according to material properties in order to process the wood efficiently and to obtain high-quality end-products. One material property that could be used for sorting is the moisture content (MC) of the sapwood, an important parameter for both the processing and the end-products. Most sawmills use three-dimensional (3D) scanners to sort logs and some have also invested in X-ray scanners. Previous studies have shown that, by combining raw data from 3D and X-ray log scanners, green sapwood density and dry heartwood density in Scots pine sawlogs can be estimated. In this study, the method was used to estimate sapwood MC in green logs. It was found that the MC estimate could be used to separate the logs into groups with high and low MC, correctly classifying all logs with MC below 100% as low MC logs. Out of all logs, 70% were correctly classified. The MC estimate could also be compared to the dry density-dependent maximum MC and used to identify logs that have actually started to dry.
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| 17. |
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| 18. |
- Skog, Johan, et al.
(författare)
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Sapwood moisture content measurements in Scots Pine sawlogs combining X-ray and 3D scanning
- 2010
-
Ingår i: Proceedings, 11th International IUFRO Wood Drying Conference. - Luleå : Luleå tekniska universitet. ; , s. 357-362
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Konferensbidrag (refereegranskat)abstract
- Wood industry of today deals with large volumes in an almost automatic process, which is not fully adapted tothe variability of the raw material. Consequently, it is crucial to sort the wood according to material properties inorder to process the wood efficiently and to obtain high quality end products. One material property which could beused for sorting is the moisture content of the sapwood, an important parameter for both the processing and the endproducts.Most large Swedish sawmills are using 3D scanners for quality sorting of Scots pine (Pinus sylvestris L.)sawlogs based on outer shape. Recently, some sawmills have also invested in X-ray log scanners in order to sort thesawlogs based on inner properties. It has previously been shown that, by combining raw data from industrial 3D andX-ray log scanners using path length compensation, green sapwood density and dry heartwood density can beestimated.In this study, the dry heartwood density was used to find an estimate of the dry sapwood density, thus allowingthe calculation of the sapwood moisture content. The log scanner data used in this study was simulated from 560Scots pine sawlogs which had previously been scanned in a computed tomography (CT) scanner. The estimatedsapwood moisture contents were then compared to reference values calculated by drying samples to 9% moisturecontent.It was found that the moisture content estimate could be used to separate the logs into two groups with high andlow moisture content, correctly identifying all logs with very low moisture content as dry logs. Out of all logs, 70%were correctly classified. The moisture content estimate could also be compared to the dry density dependentmaximum moisture content and used to identify logs that have actually started to dry.
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| 19. |
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| 20. |
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| 21. |
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| 22. |
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| 23. |
- Berglund, Anders, et al.
(författare)
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Customer adapted grading of Scots pine sawn timber using a multivariate method
- 2015
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Ingår i: Scandinavian Journal of Forest Research. - : Informa UK Limited. - 0282-7581 .- 1651-1891. ; 30:1, s. 87-97
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 24. |
- Broman, Olof, et al.
(författare)
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Effektiv produktion av golvprodukter med krav på estetiska egenskaper
- 2007
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- 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).
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| 25. |
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| 26. |
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| 27. |
- Broman, Olof, et al.
(författare)
-
Råvarustyrning för materialeffektiv produktion av limfog : En studie utförd vid Norrfog AB
- 2011
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 28. |
- Brännström, Mattias, et al.
(författare)
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Predicting board strength by X-ray scanning of logs : the impact of different measurement concepts
- 2007
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Ingår i: Scandinavian Journal of Forest Research. - : Informa UK Limited. - 0282-7581 .- 1651-1891. ; 22:1, s. 60-70
-
Tidskriftsartikel (refereegranskat)abstract
- The objective of this study was to compare the individual board strength predictions from an X-ray log scanner by using either two or four X-ray directions. The benefit of applying traceability between log and board was also studied. In total, 119 Norway spruce [Picea abies (L.) Karst.] sawlogs were scanned by an X-ray log scanner at the log sorting station of a sawmill and sawn into two centre pieces per log. Individual board traceability was enabled by following the rotational position of the log in the scanner and at the succeeding sawing. All boards were graded by a commercial strength grading machine before destructive testing was done. The resulting data were used to derive variables for building multivariate partial least squares strength prediction models. In the modelling a hierarchical modelling approach was used, where annual ring width, dry density and elasticity were also modelled. For all concepts studied the models' fit was similar. Only minor benefits could be found when using four directions and traceability compared with two directions and no traceability. One conclusion is that the result for traceability, from four directions in particular, is more sensitive for the interior knot reconstruction result. The strength prediction was on the same R2 level as for the strength grading machine
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| 29. |
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| 30. |
- Brännström, Mattias, et al.
(författare)
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Predicting the strength of sawn wood by tracheid laser scattering
- 2008
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Ingår i: BioResources. - 1930-2126. ; 3:2, s. 437-451
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Tidskriftsartikel (refereegranskat)abstract
- An industrial laser light scattering scanner, designed to detect the spiral grain angle of logs by the light scattering along the grain, was used on two large samples of Norway spruce (Picea abies (var. Karst)) in various sawn dimensions (approximately 750 pieces). Additional measurements were made by other techniques, such as X-ray scanning, resonance frequency measurement, and various manual measurements. The strength properties of the boards were measured by destructive testing in four-point bending according to European standard. Multivariate methods (PLS) were used to model the relationship between the bending strength of the board (MOR) and the measurements. Based only on the output from the simple tracheid scattering equipment, a model for MOR achieved an R² exceeding 0.3. Combinations with average density or outer shape parameters from log scanning resulted in R² 0.4 and 0.3 respectively, although these parameters alone only accounted for R² 0.2. The results can be used to increase the understanding of strength in wood and in an improved industrial strength-grading process.
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| 31. |
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| 32. |
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| 33. |
- Flodin, Jens, et al.
(författare)
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Fingerprint traceability of logs using the outer shape and the tracheid effect
- 2008
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Ingår i: Forest Products Journal. - 0015-7473. ; 58:4, s. 21-27
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Tidskriftsartikel (refereegranskat)abstract
- Traceability in the sawmilling industry is a concept that, among other benefits, could be used to more effectively control and pinpoint errors in the production process. The fingerprint approach is a traceability concept that in earlier studies has shown good potential for tracing logs between the log sorting station and the saw intake. In these studies, bark has been identified as a large source of measurement inaccuracy. This study was set out to investigate whether the fingerprint recognition rate could be improved when compensating for bark with traditional bark functions or a new automatic bark assessment based on the tracheid effect. The results show that the fingerprint recognition rate can be improved by using more sophisticated bark compensation. Compared to no bark compensation, improvements can be made by using the existing bark functions, and even further improvements can be made by using automatic bark assessment based on the tracheid effect. The results further show that the butt-end reducer between the log sorting station and the saw intake has a very negative effect on the fingerprint recognition rate, but that significant improvements in the recognition rate can be achieved by excluding the section of the log's butt end that is affected by the butt-end reduction.
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| 34. |
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| 35. |
- Flodin, Jens, et al.
(författare)
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Fingerprint Traceability of Sawn Products Using Connected Sawn Timber
- 2009
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Ingår i: Proceedings of 16th International Symposium on Nondestructive Testing and Evaluation of Wood.. - : Beijing Forestry University. Beijing Forestry University & US Forest Service Forest Products Laboratory.
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Konferensbidrag (refereegranskat)
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| 36. |
- Flodin, Jens, et al.
(författare)
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Fingerprint traceability of sawn products using industrial measurement systems for x-ray log scanning and sawn timber surface scanning
- 2008
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Ingår i: Forest Products Journal. - 0015-7473. ; 58:11, s. 100-105
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Tidskriftsartikel (refereegranskat)abstract
- Traceability in the sawmilling industry is a concept that, for example, could be used to more effectively control the production process and the utilization of raw material. The fingerprint approach is a traceability concept that rests on the principle that every piece of wood is a unique individual with unique properties and therefore can be identified and separated if a sufficient number of these properties are measured accurately enough. This study was made with the aim of making the fingerprint connection between logs and the center yield sawn from those logs using length and knot information. The material used was Scots pine logs from six different diameter groups sawn with a two-ex sawing pattern into six different dimensions of center-yield planks. The data from the logs were collected at the log sorting station by an industrial one-directional x-ray log scanner in combination with a 3-D optical scanner. The data from the sawn center yield were collected by an industrial cross-fed surface scanning system situated in the sawmill's green sorting station. The results show that over 95 percent of all planks could be matched to the right log. This gives a high potential for further development and realization of fingerprint tracing between the log sorting and the green sorting station into a practical application for process control and process improvement.
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| 37. |
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| 38. |
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| 39. |
- Flodin, Jens, et al.
(författare)
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Fingerprint traceability of sawn products using x-ray logscanning and sawn timber surface scanning
- 2007
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Ingår i: Quality control for wood and wood products. - Warsaw : Warsaw University of Life Sciences. - 9788372449047 ; , s. 39-42
-
Konferensbidrag (refereegranskat)abstract
- Traceability in the sawmilling industry is a concept that could be used to more effectively control the production processand the utilization of the raw material. The fingerprint approach is a traceability concept that rests on the idea that everypiece of wood is a unique individual with unique properties and hence can be identified and separated if a sufficientnumber of these properties are measured accurately enough. This study was hosted by a sawmill in northern Sweden andwas aimed at making the fingerprint connection between logs and the center yield sawn from those logs using length andknot information. The 140 logs involved in the study were of Scots pine with top diameters spanning the range from 153 to213 millimeters. The center yield sawn from these logs was of two dimensions. The smaller logs (153-187 mm) were sawnwith a 2 ex pattern to 50 by 100 mm, and the larger logs (174-213 mm) were sawn to 50 by 125 mm with a 2 ex pattern.The data from the logs were collected at the log sorting station by an industrial one-directional x-ray log scanner incombination with a 3-D optical scanner. The data from the sawn center yield were collected by an industrial cross-fedsurface scanning system situated in the sawmill's green sorting station. Both systems are used in the sawmill's normalcontinuous production. The results show that over 90% of all planks could be matched to the right log, which bespeaksa great potential for further development and realization of fingerprint tracing as a tool for process control and processimprovement.
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| 40. |
- Grundberg, Stig, et al.
(författare)
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Detecting knots in logs using a simulated X-ray cone-beam scanner
- 2004
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Ingår i: Fourth workshop "Connection between forest resources and wood quality: modelling approaches and simulation software" : Harrison Hot Springs, British Columbia, Canada, September 8 - 15, 2002 ; proceedings. - : International Union of Forestry Research Organisations.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 41. |
- Grundberg, Stig, et al.
(författare)
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Log models reconstructed from X-ray LogScanner signal
- 1999
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Ingår i: Connection between silviculture and wood quality through modelling approaches and simulation softwares. - Nancy : INRA Editions.
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Konferensbidrag (refereegranskat)
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| 42. |
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| 43. |
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| 44. |
- Grönlund, Anders, et al.
(författare)
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Scanning techniques as tools for integration in the wood conversion chain : some industrial applications
- 2005
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Ingår i: Broad spectrum utilisation of wood. - Wien : Institutes für Holzforschung, Universität für Bodenkultur Wien.
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Konferensbidrag (refereegranskat)abstract
- The market makes lot of different demands on sawn wood products. There are requirements regarding strength, straightness, durability, aesthetic appearance, etc. Most of these demands can be fulfilled by the inherent properties of the trees in the forest. The challenge is to utilize the wood properties to fulfil the market demands in an efficient way. The raw material has to be selected so every customer gets the right piece of wood with the required properties. In order to achieve this, the raw material has to be characterized with different scanning techniques in several steps before and during the breakdown process. In this presentation some examples and experiences from industrially implemented scanning techniques will be described. We can today, after some years of R&D efforts, see how X-ray LogScanners are implemented in the industry. So far they are used for measurement of diameter under bark, internal knot structure, annual ring width, heartwood content and commodity grades. The full potential of this technique is, however, not being fully utilized yet. Equipment for measurement of spiral grain on logs and sawn wood has also been implemented industrially. It has been proven that with the aid of this equipment boards that will twist during drying can be sorted out and treated separately, thus enabling production of straighter timber. The third type of equipment that will be presented is a heartwood scanner. With this scanner, sawmills select Scots pine planks with high heartwood content that are suitable for applications where improved durability is required. These examples show that scanning technology is a key factor for a successful integration between market and forest.
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| 45. |
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| 46. |
- Huber, Johannes Albert Josef, 1989-, et al.
(författare)
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3D Quasi-Continuum and Finite Element Models Based on CT Scans of Timber Boards to Predict Stiffness and Strength
- 2021
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Ingår i: ICCSE1 1st International Conference on Computations for Science and Engineering.
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 47. |
- Huber, Johannes A. J., 1989-, et al.
(författare)
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A method for generating finite element models of wood boards from X-ray computed tomography scans
- 2022
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Ingår i: Computers & structures. - : Elsevier. - 0045-7949 .- 1879-2243. ; 260
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 48. |
- Huber, Johannes Albert Josef, 1989-, et al.
(författare)
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Evaluation of Models Of Fibre Orientation in Sawn Timber Using Synchronised Computed Tomography and Optical Scanning Data
- 2023
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Ingår i: World Conference on Timber Engineering (WCTE 2023). - : World Conference on Timber Engineering 2023 (WCTE 2023). ; , s. 421-427, s. 421-427
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Konferensbidrag (refereegranskat)abstract
- Optical scanning and X-ray computed tomography (CT) scanning of sawn timber provide a large number of data points, on which data-driven numerical models can be based for simulations. These models require information about the deviations of the fibre orientations in the vicinity of knots. Optical scanning can be used to measure the in-plane fibre orientation on wood surfaces. In CT scans of sawn timber, the fibre orientation around knots can be estimated using a new fibre reconstruction algorithm based on the density gradient. The goal of this paper is to compare and synchronise optical and CT scanning data of sawn timber and then use the combined data set to evaluate fibre orientations derived from both representations. The material comprised sawn timber of Norway spruce, in which alignment holes were drilled. The timber was scanned in an industrial CT scanner and subsequently in an industrial optical scanner where scanning was repeated after successive planing of the sawn timber surface. The results show that a projective mapping in combination with a spline interpolation are required for synchronisation, and that the in-plane fibre orientations calculated from the density gradients are qualitatively similar to the orientations derived from the optical data.
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| 49. |
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| 50. |
- Huber, Johannes Albert Josef, 1989-, et al.
(författare)
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Nondestructive Testing of Timber Prior to Sawing Using Finite Element Models Based on X-ray Computed Tomography Data - A Preliminary Study
- 2022
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Ingår i: Proceedings: 22nd International Nondestructive Testing and Evaluation of Wood Symposium. - Madison, WI, USA : United States Department of Agriculture. ; , s. 200-200
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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