Comparison between static modulus of elasticity, non-destructive testing moduli of elasticity and stress-wave speed in white spruce and lodgepole pine wood

Abstract

Static bending tests to measure modulus of elasticity (MOE ST ) or wood stiffness provide an indicator of the structural performance of a finished product. These tests are however, slow and expensive. Tests to measure MOE using non-destructive testing (NDT) provide alternatives to MOE ST tests; however, relationships between the different modes of measurement need to be established. Nondestructive testing MOE measured by two methods (SilviScan [MOE SS ] and time of flight [MOE TOF ]) have been compared with MOE ST for lodgepole pine and white spruce. The relationships between stress wave speed (SWS) and MOE ST have also been evaluated. Simple linear regressions of MOE SS , MOE TOF , and SWS had greater explanatory power (higher coefficients of determination (R 2 )) than did multiple linear regressions including growth rate or other wood fibre attributes. Simple linear regression from MOE TOF and MOE SS on MOE ST had lower R 2 for lodgepole pine than for white spruce; however, the converse was true for SWS. SWS had the highest R 2 (89%) and MOE SS the lowest R 2 (47%) when regressed on MOE ST in lodgepole pine. The results were tool and species specific, suggesting that R 2 between MOE ST and non-destructive testing MOE values must be validated separately for each commercial tree species and for each measurement technique.

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