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Stress-wave nondestructive evaluation (NDE) techniques are used widely in the forest products industry--from the grading of wood veneer to inspection of timber structures. Inspection professionals frequently use stress-wave NDE techniques to locate internal voids and decayed or deteriorated areas in large timbers. Although these techniques have proven useful, little information exists concerning the relationship between stress-wave parameters and deterioration observed as a consequence of marine borer attack. In this pilot test, we examined the relationship between stress-wave transmission time and the quality of wood in Sitka spruce and western hemlock logs that had varying degrees of deterioration as a consequence of attack from marine borers. Stress-wave transmission time, perpendicular to grain, was measured at several locations on each log. The logs were then sawn into lumber, which was then visually evaluated. A relationship was observed between stress-wave transmission time and deterioration of the logs and the yield of lumber from the logs.
Stress-wave nondestructive evaluation (NDE) techniques are used widely in the forest products industry--from the grading of wood veneer to inspection of timber structures. Inspection professionals frequently use stress-wave NDE techniques to locate internal voids and decayed or deteriorated areas in large timbers. Although these techniques have proven useful, little information exists concerning the relationship between stress-wave parameters and deterioration observed as a consequence of marine borer attack. In this pilot test, we examined the relationship between stress-wave transmission time and the quality of wood in Sitka spruce and western hemlock logs that had varying degrees of deterioration as a consequence of attack from marine borers. Stress-wave transmission time, perpendicular to grain, was measured at several locations on each log. The logs were then sawn into lumber, which was then visually evaluated. A relationship was observed between stress-wave transmission time and deterioration of the logs and the yield of lumber from the logs.
Wood degradation and defects, such as voids and knots, affect the quality and processing time of lumber. The ability to detect internal defects in the log can save mills time and processing costs. In this study, we investigated three nondestructive evaluation techniques for detecting internal wood defects. Sound wave transmission, x-ray computed tomography, and impulse radar were used to examine white spruce and balsam fir logs. Computed tomography resulted in the highest resolution for voids, knots, and high moisture content areas, but at a very high price. Both sound wave transmission and impulse radar were able to detect large voids and areas of degradation, and these techniques showed some sensitivity to very knotty logs. None of the methods was able to detect small pockets of decay. The use of radar requires an experienced operator because of the difficulty of interpreting the data.
Six chemical wood preservatives were selected for evaluation over long periods of exposure in extremely borer-active marine environments. Southern Yellow Pine and Douglas Fir were full-cell pressure-treated with these chemicals and exposed in tropical seas and tropical brackish water for periods up to 90 months. Subsequently, 16 of the natural tropical woods considered best for use with pressure preservatives were combined with whole creosote and exposed in the most borer active of the seawater sites for periods exceeding 4 years. All samples have been removed, sectioned, and rated separately for the three major groups of marine borers: teredo, pholad, and limnoria. The long-term results show that heavy treatments of whole creosote and chromated copper arsenate (CCA, type A) are very effective preservatives for Southern Pine exposed in seawater, while the CCA was the singularly most effective treatment against the brackish-water Psiloteredo. Some of the most promising results were obtained with combinations of a few relatively limnoria-resistant tropical woods with a teredo-effective creosote pressure treatment. (Author).