Assessment of Density in Timber Using X-Ray Equipment

Wood density has a strong relationship with several mechanical properties, such as strength and stiffness. An x-ray image calibration procedure, which enables the determination of density properties for the in situ assessment of timber structures, has been developed. This nondestructive method is useful for evaluating the internal condition for global assessments of the structure. For this study, 14 wood specimens with significant density differences were exposed to x-rays. The specimens were set up in a number of image configurations. The images were analyzed and evaluated using an image toolbox. A similar procedure was applied to six built-up blocks with different thicknesses in order to calibrate the thickness of the specimens. Finally, a calibration wedge was set up to verify the procedure. The density calibration procedure from x-ray images was verified on a timber beam specimen, resulting in good agreement and an average accuracy of 97%. The values obtained from the image calibration presented a very good linear correlation between the measured density and the grayscale from x-ray images with coefficients of determination (R-2) ranging from 0.90-0.98. The main advantages compared with conventional techniques are the detection and quantification of internal damage, defects, disturbances, and deterioration that may reduce the mechanical properties of the structure. This study shows good potential when it comes to the development of a viable tool for in situ assessments of timber structures. This technique could be used indirectly in analyses of structural behavior