Influence of slope of grain on the mechanical properties of hardwoods and the consequences for grading

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Abstract

The main parameter that influences the bending strength of timber from tropical hardwood is the slope of grain. Although in the grading rules a specific threshold value is given, in these hardwoods the global slope of grain is very difficult to quantify by a visual assessment. The slope of grain measured after testing gives a better indication, but still it can only poorly describe the Hankinson relations. By rewriting the Hankinson relations, the slope of grain can be determined from the bending strength test values and from the MOE test value, both in combination with the density values and constants derived by non-linear regression analysis. These two values correlate very well and the average value is designated as the theoretical slope of grain. With the theoretical slope of grain 5 test samples of tropical wood species were evaluated and slope of grain values of 0.3 were observed where 0.1 is the limit value. Because all pieces passed the normal visual grading method in practice, slope of grain values should be incorporated in the strength class assignment test program, when these qualities cannot be ruled out for coming on the market. The (dynamic) modulus of elasticity can be used to evaluate the occurrence of desired range of slope of grain values in the test samples.
Original languageEnglish
Title of host publicationISCHP 2019 - 7th International Scientific Conference on Hardwood Processing
EditorsJan-Willem van de Kuilen, Wolfgang Gard
Place of PublicationDelft
PublisherDelft University of Technology
Pages169-175
Number of pages7
Publication statusPublished - 2019
EventISCHP 2019: 7th International Scientific Conference on Hardwood Processing - Delft University of Technology, Delft, Netherlands
Duration: 27 Aug 201930 Aug 2019
https://www.aanmelder.nl/105829

Conference

ConferenceISCHP 2019: 7th International Scientific Conference on Hardwood Processing
Abbreviated titleISCHP 2019
CountryNetherlands
CityDelft
Period27/08/1930/08/19
Internet address

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