Ultrasound and Wood Science at the Forestry Research Centre in Nancy, France, for a period of twenty years, between 1979 and 1999

The aim of this article is to describe the development of the ultrasonic non-destructive velocity method for applications in Wood Science and Forestry. A key question addressed was the mechanical characterisation of wood on an increment core of 5 mm diameter bored from a standing tree. Theoretical considerations were studied for the characterisation of wood as an orthotropic solid. Acoustic invariants were introduced to characterise wood anisotropy. Wave propagation phenomena were related to macroscopic and microscopic particularities of wood structure. The mechanical characteristics of wood species for violins have been thoroughly studied. The detection of wood degradation by biological agents producing decay (fungi, bacteria), using the ultrasonic velocity method combined with X ray densitometry was studied. The ultrasonic velocity method was also applied to quality assessment of some wood-based composites. For applications in Forestry, it was demonstrated that on increment cores of 5 mm diameter bored from standing trees, it was possible to determine three stiffnesses and three shear moduli of wood and to assess the mechanical wood quality of standing trees. Other factors (the slope of the grain, pruning) affecting the quality of wood of standing trees were detected with the velocity method. In Forestry, seeds are important products. The capacity of the germinability of acorns was detected with the ultrasonic velocity method.