Ultrasonic modification for improvement of wood-Surface properties

This study evaluated the effect of ultrasonic densification technology on the surface hardness of the following wood species: aspen (Populus tremula), Scots pine (Pinus sylvestris) linden (Tilia europaea), alder (Alnus glutinosa), and oak (Quercus robur). The machine realising the proposed technology consists of an ultrasonic module and an infeed system that allows the treatment of sawn timber. The densification was achieved by feeding sawn timber specimens once through a pair of opposing ultrasonic sonotrodes, with the gap between them being smaller than the specimen thickness. This and the direct contact between the sonotrodes and the specimens led to an increase in density in the surface region and an increase in surface hardness, measured by the Leeb method. The internal structure was not damaged by the ultrasonic treatment. The simplicity of the process and the processing speed of several meters per minute merit further investigations of the technology.