Improvement of Thermally Modified Oak Wood Surface Hardness by Ultrasonic Treatment

In this paper the possibilities of original ultrasonic technology for improving of surface hardness of thermally modified oak (Quercus robur) wood are investigated as decreasing of thermally modified wood mechanical properties and also wood hardness is one of the known disadvantages of this modification method. The machine realizing the proposed treatment technology consists of an ultrasonic module and an infeed system. Effect of two opposite located sonotrodes of ultrasonic module, directly contacting the surface of the lumber when passing through the machine, allows improving its mechanical properties in one pass without any additional operations. It is shown that by this technology surface hardness of thermally modified oak wood timber can be significantly increased up to 1.5 times, that corresponds to the initial values of wood hardness.