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Bengtsson, Charlotte
Publications (7 of 7) Show all publications
Hu, M., Johansson, M., Olsson, A., Bengtsson, C. & Brandt, A. (2011). Grading of sawn timber using the vibration technique: locating imperfections based on flexural mode shapes. In: Ference Divos (Ed.), 17th international nondestructive testing and evaluation of wood symposium: . Paper presented at 17th international nondestructive testing and evaluation of wood symposium (pp. 269-276). Sopron, Hungary: University of West Hungary
Open this publication in new window or tab >>Grading of sawn timber using the vibration technique: locating imperfections based on flexural mode shapes
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2011 (English)In: 17th international nondestructive testing and evaluation of wood symposium / [ed] Ference Divos, Sopron, Hungary: University of West Hungary , 2011, p. 269-276Conference paper, Published paper (Refereed)
Abstract [en]

The present study aims at investigating the potential of using mode shape or mode shape curvature (MSC) for detecting defects in wooden beams. It includes modal analysis, Finite Element (FE) modeling and visual scanning. An FE model was created to investigate the effect of defects of different size and location on the mode shape/MSC. The mode shape/MSC showed a good potential to be used for finding defects. An experimental study on 17 boards of Norway spruce, dimensions of 50×150×3900 mm, was conducted using experimental modal analysis. The findings reveal that: (1) the mode shape/MSC studied in the FE-model could be used to locate defects, (2) the method is very sensitive to measurement noise and it requires an accurately measured mode shape, (3) an error analysis shows that it is not possible to achieve the accuracy needed using accelerometers.

Place, publisher, year, edition, pages
Sopron, Hungary: University of West Hungary, 2011
Keywords
experimental modal analysis, finite element modeling, mode shape, mode shape curvature, resonance frequency, strength grading, visual scanning
National Category
Building Technologies
Research subject
Technology (byts ev till Engineering), Civil engineering; Technology (byts ev till Engineering), Forestry and Wood Technology
Identifiers
urn:nbn:se:lnu:diva-15747 (URN)978-963-9883-81-9 (ISBN)
Conference
17th international nondestructive testing and evaluation of wood symposium
Available from: 2011-11-15 Created: 2011-11-09 Last updated: 2019-10-17Bibliographically approved
Lycken, A., Ziethén, R. & Bengtsson, C. (2010). Development of a simulation-evaluation program for introducing and using output control in the sawmill industry. In: Proceedings of the Final Conference of COST Action E53 “The Future of Quality Control for Wood & Wood Products”, May 4-7 2010, Edinburgh, UK. Paper presented at The Future of Quality Control for Wood & Wood Products.
Open this publication in new window or tab >>Development of a simulation-evaluation program for introducing and using output control in the sawmill industry
2010 (English)In: Proceedings of the Final Conference of COST Action E53 “The Future of Quality Control for Wood & Wood Products”, May 4-7 2010, Edinburgh, UK, 2010Conference paper, Published paper (Refereed)
National Category
Building Technologies
Research subject
Technology (byts ev till Engineering), Civil engineering
Identifiers
urn:nbn:se:lnu:diva-6669 (URN)
Conference
The Future of Quality Control for Wood & Wood Products
Available from: 2010-07-02 Created: 2010-07-02 Last updated: 2011-04-05Bibliographically approved
Ziethén, R., Lycken, A. & Bengtsson, C. (2010). Machine strength grading – “output control” as a method for production control. In: Proceedings of the 11th World Conference on Timber Engineering, WCTE 2010, June 20-24, Riva del Garda, Italy. Paper presented at WCTE 2010.
Open this publication in new window or tab >>Machine strength grading – “output control” as a method for production control
2010 (English)In: Proceedings of the 11th World Conference on Timber Engineering, WCTE 2010, June 20-24, Riva del Garda, Italy, 2010Conference paper, Published paper (Refereed)
Abstract [en]

The paper describes the Output control method in EN 14081-3 as an alternative to the more common machine control method in EN 14081-2 for strength grading of timber. A newly developed program for analysing settings and varying input material is presented, as well as results from the analysis. If output control is used instead of machine control, it is possible to increase the yield, at the expense of making more proof-loading tests. The output control method can hardly catch a shift in input material quality, unless the shift stretches over several weeks. At present is the evaluation of the proof-loading results for MOR and MOE dependant of each other. If one of the properties goes out of control then both properties are evaluated according to the out-of-control procedure. This results in an inconsistent evaluation of the grading result. A pre-grading of logs gives a more reliable grading but results also in a lower yield.

Keywords
Cusum, EN14081, Machine strength grading, Output control, Standard
National Category
Building Technologies
Research subject
Technology (byts ev till Engineering), Civil engineering
Identifiers
urn:nbn:se:lnu:diva-6667 (URN)
Conference
WCTE 2010
Available from: 2010-07-02 Created: 2010-07-02 Last updated: 2011-03-21Bibliographically approved
Ziethén, R. & Bengtsson, C. (2010). Machine strength grading – prediction limits – evaluation of a new method for derivation of settings. In: Proceedings of the Final Conference of COST Action E53 “The Future of Quality Control for Wood & Wood Products”, May 4-7 2010, Edinburgh, UK. Paper presented at COST Action E53 “The Future of Quality Control for Wood & Wood Products”.
Open this publication in new window or tab >>Machine strength grading – prediction limits – evaluation of a new method for derivation of settings
2010 (English)In: Proceedings of the Final Conference of COST Action E53 “The Future of Quality Control for Wood & Wood Products”, May 4-7 2010, Edinburgh, UK, 2010Conference paper, Published paper (Refereed)
National Category
Building Technologies
Research subject
Technology (byts ev till Engineering), Civil engineering
Identifiers
urn:nbn:se:lnu:diva-6671 (URN)
Conference
COST Action E53 “The Future of Quality Control for Wood & Wood Products”
Available from: 2010-07-02 Created: 2010-07-02 Last updated: 2011-04-05Bibliographically approved
Ziethén, R. & Bengtsson, C. (2010). Machine strength grading - prediction limits - evaluation of a new method for derivation of settings. In: Proceedings of the 11th World conference of timber engineering. WCTE2010, June 20-24, Riva del Garda, Italy.. Paper presented at WCTE2010.
Open this publication in new window or tab >>Machine strength grading - prediction limits - evaluation of a new method for derivation of settings
2010 (English)In: Proceedings of the 11th World conference of timber engineering. WCTE2010, June 20-24, Riva del Garda, Italy., 2010Conference paper, Published paper (Refereed)
Abstract [en]

This paper presents and analyses a new method for derivation of setting values for strength grading machines. The method uses a model for the relationship between indicating property (measured by a grading machine, IP) and the grade determining property (GDP). This model is of course not perfect and by summarising the errors in the model a confidence interval for the model can be calculated. The confidence interval is used for creating a prediction interval. The lower limit of the prediction interval, the prediction limit, is used to predict the GDP. The prediction limit method is analysed and evaluated by well defined input data. It is shown that fewer perimental data than required by the method in EN 14081-2 today is needed to determine reliable settings but the producer is awarded with less conservative settings with an increased number of experimental data. A weak correlation between IP and GDP or a high coefficient of variation also results in conservative settings. The settings are not dependent on average strength of the raw material used for deriving the settings.

Keywords
machine strength grading, structural timber, linear regression, prediction limit
National Category
Building Technologies
Research subject
Technology (byts ev till Engineering), Civil engineering
Identifiers
urn:nbn:se:lnu:diva-6666 (URN)
Conference
WCTE2010
Available from: 2010-07-02 Created: 2010-07-02 Last updated: 2011-03-21Bibliographically approved
Ziethén, R. & Bengtsson, C. (2009). Machine strength grading – a new method for derivation of settings. In: Blass, H J (Ed.), CIB-W18 Timber Structures, Zürich, August 2009: Paper 42-5-1. Karlsruhe
Open this publication in new window or tab >>Machine strength grading – a new method for derivation of settings
2009 (English)In: CIB-W18 Timber Structures, Zürich, August 2009: Paper 42-5-1 / [ed] Blass, H J, Karlsruhe, 2009Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
Karlsruhe: , 2009
Keywords
machine strength grading, machine settings
National Category
Building Technologies
Research subject
Technology (byts ev till Engineering), Civil engineering
Identifiers
urn:nbn:se:vxu:diva-6902 (URN)
Available from: 2010-01-23 Created: 2010-01-23 Last updated: 2011-03-17Bibliographically approved
Bengtsson, C., Serrano, E., Fonselius, M. & Riipola, K. (2008). Conformity assessment for machine graded timber by using output control. SP Sveriges Tekniska Forskningsinstitut
Open this publication in new window or tab >>Conformity assessment for machine graded timber by using output control
2008 (English)Report (Other academic)
Abstract [en]

In the Nordic countries machine strength grading of structural timber is becoming increasingly important. A new standard, EN 14081, which allows CE-marking of strength graded structural timber was recently accepted. This standard allows both machine

control and output control as methods for controlling the graded timber. Machine control is most commonly used in Europe. The project reported here deals with output control. This method is commonly used in for example USA.

Theoretical studies carried out within this project show that applying output control gives higher yield, especially in high strength classes. A document describing the implementation of the output control procedure is written and given in Appendix 1 of this report.

Place, publisher, year, edition, pages
SP Sveriges Tekniska Forskningsinstitut, 2008. p. 35
Series
SP Report, ISSN 0284-5172 ; 2008:1
Keywords
outout control, stress grading
National Category
Building Technologies
Research subject
Technology (byts ev till Engineering), Civil engineering
Identifiers
urn:nbn:se:vxu:diva-3647 (URN)978-91-85829-15-6 (ISBN)
Available from: 2008-11-28 Created: 2008-11-28 Last updated: 2015-09-28Bibliographically approved
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