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Publications (10 of 15) Show all publications
Ah Shenga, P., Bomark, P., Broman, O. & Sandberg, D. (2017). Log sawing positioning optimization and log bucking of tropical hardwood species to increase the volume yield. Wood Material Science & Engineering, 12(4), 257-262
Open this publication in new window or tab >>Log sawing positioning optimization and log bucking of tropical hardwood species to increase the volume yield
2017 (English)In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 12, no 4, p. 257-262Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Taylor & Francis, 2017
National Category
Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-61459 (URN)10.1080/17480272.2016.1275788 (DOI)000402709800010 ()2-s2.0-85008622401 (Scopus ID)
Note

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

Available from: 2017-01-16 Created: 2017-01-16 Last updated: 2020-01-28Bibliographically approved
Ah Shenga, P., Bomark, P., Broman, O. & Sandberg, D. (2016). The Effect of Log Position Accuracy on the Volume Yield in Sawmilling of Tropical Hardwood. BioResources, 11(4), 9560-9571
Open this publication in new window or tab >>The Effect of Log Position Accuracy on the Volume Yield in Sawmilling of Tropical Hardwood
2016 (English)In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 11, no 4, p. 9560-9571Article in journal (Refereed) Published
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%.

Keywords
Log positioning error, Tropical species, Skew, Offset, Rotation
National Category
Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-37010 (URN)10.15376/biores.11.4.9560-9571 (DOI)000391801300108 ()
Note

Validerad; 2016; Nivå 2; 2016-11-23 (andbra)

Available from: 2016-10-03 Created: 2016-10-03 Last updated: 2020-01-28Bibliographically approved
Fredriksson, M., Bomark, P., Broman, O. & Grönlund, A. (2015). A trapeze edging method for cross laminated timber panel production (ed.). In: (Ed.), Roger Hernández; Claudia Cáceres (Ed.), Proceedings of the 22nd International Wood Machining Seminar: . Paper presented at International Wood Machining Seminar : 14/06/2015 - 19/06/2015 (pp. 323-332). Quebec city, Kanada: Universite Laval
Open this publication in new window or tab >>A trapeze edging method for cross laminated timber panel production
2015 (English)In: Proceedings of the 22nd International Wood Machining Seminar / [ed] Roger Hernández; Claudia Cáceres, Quebec city, Kanada: Universite Laval , 2015, p. 323-332Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
Quebec city, Kanada: Universite Laval, 2015
National Category
Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-30380 (URN)42931d02-f2a2-44c4-985e-2f52f33f5357 (Local ID)978-0-9947964-0-0 (ISBN)42931d02-f2a2-44c4-985e-2f52f33f5357 (Archive number)42931d02-f2a2-44c4-985e-2f52f33f5357 (OAI)
Conference
International Wood Machining Seminar : 14/06/2015 - 19/06/2015
Note

Godkänd; 2015; 20140930 (magfre)

Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2017-11-25Bibliographically approved
Bomark, P., Hirche, J. & Hagman, O. (2015). Colour visualisation of real virtual timber using image quilting (ed.). European Journal of Wood and Wood Products, 73(6), 837-839
Open this publication in new window or tab >>Colour visualisation of real virtual timber using image quilting
2015 (English)In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 73, no 6, p. 837-839Article in journal (Refereed) Published
Abstract [en]

When presenting images of wood obtained through x-ray computed tomography to an audience inexperienced in interpreting radiological images, explaining the correspondence between mass attenuation and features of wood could be time consuming and confusing. Realistically colourised attenuation images might be a suitable option in order to facilitate understanding of the images. Mass attenuation and colour of wood does not have a simple correlation, so naive grey-scale to colour conversion does not work. This paper describes how image quilting can be used to transfer colour information from a image pair where both mass attenuation and colour is known to a target mass attenuation image. An example of this method applied on scots pine shows that it is capable of retaining the major structures of wood, such as year rings and knots. The method could allow for easier understanding of simulation studies where logs scanned using x-ray computed tomography are virtually sawn.

National Category
Other Mechanical Engineering Media and Communication Technology
Research subject
Mobile and Pervasive Computing; Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-4876 (URN)10.1007/s00107-015-0940-y (DOI)000363718300015 ()2-s2.0-84944931025 (Scopus ID)2e0febd0-4f4d-40a2-a195-f8f9aa139061 (Local ID)2e0febd0-4f4d-40a2-a195-f8f9aa139061 (Archive number)2e0febd0-4f4d-40a2-a195-f8f9aa139061 (OAI)
Note

Validerad; 2015; Nivå 2; 20141112 (petbom)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Ah Shenga, P. A., Bomark, P. & Broman, O. (2015). External Log Scanning for Optimizing Primary Breakdown of Tropical Hardwood Species (ed.). In: (Ed.), : . Paper presented at International Wood Machining Seminar : 14/06/2015 - 17/06/2015.
Open this publication in new window or tab >>External Log Scanning for Optimizing Primary Breakdown of Tropical Hardwood Species
2015 (English)Conference paper, Poster (with or without abstract) (Other academic)
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.

National Category
Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-39529 (URN)10.13140/RG.2.1.2918.3446 (DOI)e5513fe5-d6cc-4317-8883-90fb92571aab (Local ID)e5513fe5-d6cc-4317-8883-90fb92571aab (Archive number)e5513fe5-d6cc-4317-8883-90fb92571aab (OAI)
Conference
International Wood Machining Seminar : 14/06/2015 - 17/06/2015
Note

Godkänd; 2015; 20151112 (pedant)

Available from: 2016-10-03 Created: 2016-10-03 Last updated: 2017-11-25Bibliographically approved
Rebstock, F., Bomark, P. & Sandberg, D. (2015). Makerjoint, a new concept for joining members in timber engineering: Strength test and failure analyses (ed.). Pro Ligno, 11(4), 397-404
Open this publication in new window or tab >>Makerjoint, a new concept for joining members in timber engineering: Strength test and failure analyses
2015 (English)In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 11, no 4, p. 397-404Article in journal (Refereed) Published
Abstract [en]

The wood construction industries are becoming more focused on climate change and resourcedepletion, and individual and industrial consumption must reflect a greater degree of concern for theclimate and environmental wellbeing. This paper presents a new concept for timber engineering, thepurpose being to acquire information about the failure modes and the tensile and compressivestrengths of two types of joint, the Simple Gooseneck and Thick Gooseneck, that can be used in anew concept for joining members in timber structures. This Makerjoint concept uses laminated veneerlumber (LVL) as nodes in regions with a pronounced non-uniform stress distribution and sawn timberin regions with a more uniform stress distribution. No metal fasteners or adhesives are used in thejoint between timber and LVL. The concept is intended for joints using 3-axis CNC machinery and tobe a system for on-site- and pre-fabrication of e.g. small houses, emergency shelters and exhibitionstands. The joints have a higher compressive than tensile strength. The joints exhibited brittle failure intension (beam and/or node failure) and buckling occurred in compression around the thinnest crosssection of the beams. Suggestions are made for how the mechanical properties of the joints can beimproved.

Keywords
Forestry, agricultural sciences and landscape planning - Wood fibre and forest products, Skogs- och jordbruksvetenskap samt landskapsplanering - Träfiber- och virkeslära
National Category
Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-14005 (URN)d540d8ef-1a19-43c2-8493-cbd6e3873a87 (Local ID)d540d8ef-1a19-43c2-8493-cbd6e3873a87 (Archive number)d540d8ef-1a19-43c2-8493-cbd6e3873a87 (OAI)
Note

Validerad; 2016; Nivå 1; 20151225 (dicsan)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2020-01-28Bibliographically approved
Ah Shenga, P. A., Bomark, P. & Broman, O. (2015). Simulated Breakdown of Two Tropical Hardwood Species (ed.). Pro Ligno, 11(4), 450-456
Open this publication in new window or tab >>Simulated Breakdown of Two Tropical Hardwood Species
2015 (English)In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 11, no 4, p. 450-456Article in journal (Refereed) Published
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.

National Category
Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-16039 (URN)f9ed7528-65fa-486b-85b8-d429d2521c2a (Local ID)f9ed7528-65fa-486b-85b8-d429d2521c2a (Archive number)f9ed7528-65fa-486b-85b8-d429d2521c2a (OAI)
Note

Validerad; 2016; Nivå 1; 20151222 (andbra)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-11-24Bibliographically approved
Ah Shenga, P. A., Bomark, P., Broman, O. & Sandberg, D. (2015). Simulation of Tropical Hardwood Processing: Sawing Methods, Log Positioning, and Outer Shape (ed.). BioResources, 10(4), 7640-7652
Open this publication in new window or tab >>Simulation of Tropical Hardwood Processing: Sawing Methods, Log Positioning, and Outer Shape
2015 (English)In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 10, no 4, p. 7640-7652Article in journal (Refereed) Published
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.

Keywords
Simulation, Tropical hardwood processing, Sawing Methods, Log Positioning, Materials science - Other processing/assembly, Teknisk materialvetenskap - Övrig bearbetning/sammanfogning
National Category
Other Mechanical Engineering
Research subject
Wood Science and Engineering; Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-14760 (URN)10.15376/biores.10.4.7640-7652 (DOI)e2e93312-1e42-4e11-b23a-31002fb45f7e (Local ID)e2e93312-1e42-4e11-b23a-31002fb45f7e (Archive number)e2e93312-1e42-4e11-b23a-31002fb45f7e (OAI)
Note

Validerad; 2015; Nivå 2; 20150925 (pedant)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2020-03-06Bibliographically approved
Fredriksson, M., Bomark, P., Broman, O. & Grönlund, A. (2015). Using Small Diameter Logs for Cross Laminated Timber Production (ed.). BioResources, 10(1), 1477-1486
Open this publication in new window or tab >>Using Small Diameter Logs for Cross Laminated Timber Production
2015 (English)In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 10, no 1, p. 1477-1486Article in journal (Refereed) Published
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

National Category
Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-14792 (URN)e36814b4-8cf7-4fb9-9c77-1d0cd6528cba (Local ID)e36814b4-8cf7-4fb9-9c77-1d0cd6528cba (Archive number)e36814b4-8cf7-4fb9-9c77-1d0cd6528cba (OAI)
Note

Validerad; 2015; Nivå 2; 20141019 (magfre)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-11-24Bibliographically approved
Ah Shenga, P., Bomark, P., Broman, O. & Hagman, O. (2014). 3D Phase-shift Laser Scanning of Log Shape (ed.). BioResources, 9(4), 7593-7605
Open this publication in new window or tab >>3D Phase-shift Laser Scanning of Log Shape
2014 (English)In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 9, no 4, p. 7593-7605Article in journal (Refereed) Published
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.

Keywords
Outer shape, Log measurement, 3D scanner, CT scanner, Information technology - Other information technology, Informationsteknik - Övrig informationsteknik
National Category
Other Mechanical Engineering
Research subject
Wood Technology; Wood Products Engineering
Identifiers
urn:nbn:se:ltu:diva-5940 (URN)421b96bb-ab34-4037-9af4-7557868effb8 (Local ID)421b96bb-ab34-4037-9af4-7557868effb8 (Archive number)421b96bb-ab34-4037-9af4-7557868effb8 (OAI)
Note

Validerad; 2014; 20141031 (pedant)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-11-24Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-5329-8654

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