Investigation of the quality of the surface of wood lamellas using air – coupled ultrasonic technique

The investigation of roughness and presence of surface defects in wooden lamellas, which are used in manufacturing of glued wood panels, is an important industrial problem. Well prepared and defect free surfaces guarantee qualitative jointing of the panels. Air – coupled ultrasonic is a very attractive technique for investigation of surfaces of wooden products, because it allows to perform measurements without liquid or semi liquid coupling material. Experimental investigations of wooden lamellas were carried out using focussed dual element and planar air coupled ultrasonic transducers operating in a pitch – catch mode. Experimentally obtained signals are presented in terms of peak to peak amplitude and time of flight.