Ultrasonic method of evaluation of diffused material damage based on back-scattered signal - R. І. Romanishin; Ja. L. Іvanitskij; V. V. Koshovij; S. T. Shtajura; І. M. Romanishin; O. M. Mokrij; P. M. Semak (Technical diagnostics and non-destructive testing, 2017)