Variation of Mechanical Characteristics for Thin Wall Tubes Processed in Ultrasonic Field Journal title: Analele Universitatii "Dunarea de Jos" din Galati. Fascicula IX, Metalurgie si Stiinta Materialelor Authors: Mihai SUSAN, Dragoş Cristian ACHIŢEI, Roxana Gabriela ŞTEFANICĂ, Bogdan Lucian GAVRILĂ Subject(s):