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  • 1.
    Bengtsson, Charlotte
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design. Byggteknik.
    Serrano, Erik
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Fonselius, Mikael
    Riipola, Kirsti
    Conformity assessment for machine graded timber by using output control2008Report (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.

  • 2.
    Hu, Min
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Johansson, Marie
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Olsson, Anders
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Bengtsson, Charlotte
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Brandt, Anders
    University of Southern Denmark, Denmark.
    Grading of sawn timber using the vibration technique: locating imperfections based on flexural mode shapes2011In: 17th international nondestructive testing and evaluation of wood symposium / [ed] Ference Divos, Sopron, Hungary: University of West Hungary , 2011, p. 269-276Conference 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.

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  • 3. Lycken, Anders
    et al.
    Ziethén, Rune
    Bengtsson, Charlotte
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Development of a simulation-evaluation program for introducing and using output control in the sawmill industry2010In: 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 (Refereed)
  • 4. Ziethén, Rune
    et al.
    Bengtsson, Charlotte
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Machine strength grading – a new method for derivation of settings2009In: CIB-W18 Timber Structures, Zürich, August 2009: Paper 42-5-1 / [ed] Blass, H J, Karlsruhe, 2009Conference paper (Refereed)
  • 5. Ziethén, Rune
    et al.
    Bengtsson, Charlotte
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Machine strength grading – prediction limits – evaluation of a new method for derivation of settings2010In: 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 (Refereed)
  • 6. Ziethén, Rune
    et al.
    Bengtsson, Charlotte
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Machine strength grading - prediction limits - evaluation of a new method for derivation of settings2010In: Proceedings of the 11th World conference of timber engineering. WCTE2010, June 20-24, Riva del Garda, Italy., 2010Conference 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.

  • 7. Ziethén, Rune
    et al.
    Lycken, Anders
    Bengtsson, Charlotte
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Machine strength grading – “output control” as a method for production control2010In: Proceedings of the 11th World Conference on Timber Engineering, WCTE 2010, June 20-24, Riva del Garda, Italy, 2010Conference 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.

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