Use of SilviScan for the Rapid Estimation of Some Properties of Tonewoods——2019世界木材日研讨会
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University of Melbourne, Australia
Commonly measured properties of tonewoods include ring width uniformity, density (ρ), modulus of elasticity (E), acoustic velocity (c), acoustic radiation coefficient (c/ρ) and acoustic impedance (c.ρ). SilviScan is a suite of instruments developed for the rapid measurement of wood microstructure in small samples taken from standing trees, discs, boards or panels. This instrument is capable of estimating the above tonewood properties with certain limitations. Automated scanning image analysis, scanning x ray densitometry and scanning x ray diffractometry are the three main functions of this instrument and it has been used in a large variety of forestry and forest products programs for almost thirty years. The third generation system is currently operating in Australia (University of Melbourne), Sweden (RISE, Stockholm) and Canada (FP Innovations, Vancouver). SilviScan generates radial profiles of many wood properties by direct measurement and many others by modelling and by combining measured data. Radial property profiles are normally reported with a step size of 25 microns. Although other step sizes can be chosen, 25 microns usually allows sufficiently accurate measurement of ring width as well as within-ring density and cell geometry profiles. The diffractometric properties are measured with a 200 micron x ray beam (although narrower beams could be generated with finer focussing capillaries at the cost of much longer measurement time) and so the step size is normally 100 microns or more. Estimates of within-ring variation in diffractometric properties (such as microfibril angle and modulus of elasticity) are therefore only of acceptable accuracy when the ring width and latewood width are much greater than 200 microns. By combining the densitometric and diffractometric properties it is possible to estimate the velocity of sound and the longitudinal modulus of elasticity but their spatial resolution is limited by that of the diffractometer. Estimation of acoustic velocity and modulus of elasticity using SilviScan is, however, currently limited to the longitudinal direction. Advantages and limitations of the method as applied to tonewoods are discussed. Although cell cross-sectional dimensions are not normally considered when selecting tonewoods, SilviScan can also provide high resolution images of the polished transverse surface of the wood, which may provide further insight into the behaviour of differentspecies for this purpose.