Classification of structural woods by X-ray densimetry

In order to control the important variability of wood mechanical properties to use it in structure, this material is visually graded by a measurement oi knot dimensions. The control process is comparatively slow and above all liable to human errors. Furthermore the low level of correlation between k not dimensions and strength leads us to a reducted result of this grading t ype. In order to compensate this visual grading, the strength grading machi ne has been developped. For the last years, CTBA and CEA have developped a grading chain of lumber by means of a x-ray device. This machine allows US to measure the variation of volume. 1500 lumber were analysed with a x-ray device before being tested in bending until it breaks. The statistical anal ysis allowed us to notice relations between mechanical characteristics and variations of volume. This method also allowed us to increase the material ouput and the strength level of grading material. A technological transfer towards timber industries is actually studied.