Abstract
BackgroundMeasurement of microfibril angle (MFA) in the S2 layer of the cell walls of wood using speed of sound in wood has become a common way to estimate wood stiffness and stability. Measurements across the radius of a disc can be critical, but sonic testing needs to be validated against direct measurements of MFA.MethodsA robotic machine that uses two transducers to detect the speed of sound through discs of wood from tree stems was validated by comparing its measurements with wood MFA, air-dry density, and modulus of elasticity assessed by X-ray diffractometry through the “Silviscan” system.ResultsUltrasonic velocity (USV) was highly correlated with MFA but not with air-dry density. Variable moving averages were assessed in order to estimate the resolution of the USV measurements, and it appeared that the diameter of the swath detected by the transducers was between 23 and 30 mm.ConclusionsIt was concluded that MFA in wood samples can be assessed rapidly and cheaply using USV measurements but at lower resolution than assessments using X-ray diffractometry.
Highlights
Measurement of microfibril angle (MFA) in the S2 layer of the cell walls of wood using speed of sound in wood has become a common way to estimate wood stiffness and stability
Cave (1968) found that modulus of elasticity (MOE) of wood was strongly correlated with the angle from vertical of cellulose microfibrils, known as the “microfibril angle” (MFA), in the S2 layer of the cell wall of gymnosperms, and so finding ways to reduce MFA in the corewood zone is an important focus of wood quality research
Ultrasonic velocity (USV) measurements were most strongly correlated with Silviscan estimates of MFA and MOE and were not significantly correlated with air-dry density
Summary
Measurement of microfibril angle (MFA) in the S2 layer of the cell walls of wood using speed of sound in wood has become a common way to estimate wood stiffness and stability. The cores of conifer logs often contain wood with relatively low stiffness and instability during drying (Walker & Nakada, 1999), and so finding efficient ways to assess these properties can help researchers and forest managers to select genotypes, silvicultural operations, or growing sites that minimise this problem. Cave (1968) found that MOE of wood was strongly correlated with the angle from vertical of cellulose microfibrils, known as the “microfibril angle” (MFA), in the S2 layer of the cell wall of gymnosperms, and so finding ways to reduce MFA in the corewood zone is an important focus of wood quality research. The system, known as “Silviscan” is relatively expensive for clients, but it has been extensively used by researchers to compare wood quality samples
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