Warp requirements and yield efficiency in the visual grading of sawn radiata pine timber
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Three samples of sawn Radiata pine (Pinus radiata D. Don) timber, consisting of 150 pieces with dimensions of 80 mm x 120mm x 2400mm, 80 pieces with dimensions of 150mm x 200mm x 4500 mm, and 75 pieces with dimensions of 150mm x 250mm x 5600 mm, were visually graded according to the Spanish standard UNE 56544 (2011) to analyze the influence of visual grading requirements on both the grading yield and mechanical properties. The resulting percentages of the rejected pieces stood at 19 and 28% for 150 x 200mm and 150 x 250mm cross - section pieces, respectively. That percentage increased to 73% for 80 x 120 mm cross - section pieces. The grading yield and mechanical properties were then analyzed to determine the influence of warp defects. Three different criteria for limiting warp defects were considered, reducing the standard specifications. The modulus of elasticity, bending strength, and density were obtained. The results concluded that loosening specified requisites improves the visual grading output in the smallest cross-section, with no significant reduction in themechanical properties. A proposal for a less rigorous specification of twist defects in the Spanish visual grading standard has been introduced.
CitacióMonton, J. [et al.]. "Bioresources". Febrer 2015.