Batch measurements of wood density on intact or prepared drill cores using x-ray microdensitometry |
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Authors: | U Bergsten J Lindeberg A Rindby R Evans |
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Institution: | Swedish University of Agricultural Sciences, Dept. of Silviculture, 90183 Ume?, Sweden?e-mail: Urban.Bergsten@ssko.slu.se, SE Swedish University of Agricultural Sciences, Dept. of Silviculture, 90183 Ume?, Sweden?e-mail: Johan.Lindeberg@vfp.slu.se, SE Chalmers University of Technology, 41296 G?teborg, Sweden?e-mail: f3bar@fy.chalmers.se, SE CSIRO Forestry and Forest Products, Private Bag 10, Clayton South MDC, Victoria 3169, Australia?e-mail: Robert.Evans@ffp.csiro.au, AU
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Abstract: | The performance of a batch scanning x-ray densitometer for measuring wood density without sample preparation, i.e., on intact
drill cores, or on rectangular samples prepared from drill cores, was analysed. Effects of x-ray intensity, sample thickness
and fiber direction, as well as extractives content, were evaluated for young (mainly sapwood) and old (mainly heartwood)
wood from Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.). The x-ray power level used as standard (1.4 kW; 40 kV and 35 mA) seemed appropriate for the tested species
and specimen thickness. The density of intact drill cores could be determined with a mean standard deviation of 1.6% for each
sample, with a single machine run, if the cores were mounted with a fixed fiber direction and calibrations were made for each
wood type. The corresponding precision for rectangular samples was 1.0%. Further improvements are attainable by using standard
reference samples in each machine run and batch-wise analysis. For the chosen wood types and measurement technique, a sample
thickness of 5 mm should give the best precision. However, for species with very narrow rings, thinner samples would improve
the spatial resolution when ring boundaries are angled or curved. Extractives should be removed, especially for pine, but
possibly also for spruce, if high precision in density determination is required.
Received 19 January 2000 |
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