An Ultrasonic Technique for Predicting Tensile Strength of Southern Pine Lumber

Abstract

ABSTRACT. The goal of this research was to develop nondestructive evaluation (NDE) he strong demand for wood together with timber harvest restrictions and escalating raw material costs have accentuated the need for efficient T utilization of wood resources. In the case of lumber, efficiency dictates that it be accurately sorted into grades, each having an acceptable range of quality for the intended uses.Current methods for grading structural lumber include visual stress rating (VSR), machine stress rating (MSR), and machine evaluating lumber (MEL). Both visual and mechanical lumber grading methods inherently have some limitations. The VSR categorizes lumber strength by surface characteristics alone, resulting in relatively wide variabilities of mechanical properties within grades. The MSR and MEL use nondestructively measured properties of modulus of elasticity (MOE) and density, respectively, to predict lumber strength, followed by a visual check for certain defects in the lumber. Linear correlations between MOE or density and lumber strength typically range from 0.6 to 0.8. Since predictions of lumber strength are not 100% accurate, visual grading rules and machine grading thresholds are conservatively set to minimize the probability of assigning a piece of lumber a grade that is too high.Research is needed to develop innovative stress rating technology for more accurate grading of lumber, leading to better utilization of timber resources. Another incentive for developing new lumber grading technology is the cost of present grading machines, which is prohibitive for many of

Relationship Between Wood Density, Microfibril Angle and Stiffness in Thinned and Fertilized Pinus Radiata

“…There is increasing interest in the application of acoustic analysis as a means of predicting log and board strength (Schad et al 1995;Rajesjwar et al 1997;Marchal & Jacques 1999). Karsulovic et al (1987) showed that the speed of propagation of stress waves were an excellent predictor of MOE in radiata pine timber.…”

Automatic measurement of wood fiber orientation and knot detection using an optical system based on heating conduction

“…However, wood presents significant variability in terms of its mechanical properties, mainly due to factors such as wood species, tree growth rate, density, local singularities (knots, cracks, slope of grain), etc. Machines can be used to perform the mechanical grading of wood, in accordance with the relevant European standards [2][3][4][5].Wood grading machines are based on various principles, such as density measurement, vibrational measurement of the MOE [6][7][8] or singularity detection using optical means, X-rays, or scattering measurement techniques [9][10][11]. To predict bending strength, most of these grading techniques are extremely dependent on the correlation between the MOR and the density or the MOE, and thus only partially take into account local singularities.…”

Influence of Zirconium Doped Titanium Oxide towards Photocatalytic Activity of Paraquat

“…The average crystallite size was estimated using Scherrer's equation from the anatase TiO 2 peak (101) represented in the Table 1. The average crystal size decrease when the catalyst ratio was increased due to the suppresses of crystal growth affect replacement of Ti 4+ with zirconium [8].…”