Semi-analytical elastic wave-field modeling applied to arbitrarily oriented orthotropic media

Three-dimensional elastic wave-field calculation is addressed for the case of orthotropic materials with arbitrary spatial orientation. Based on a mat hematical formulation involving Green's dyadic displacement tensor function , appropriate evaluation yields a representation of the displacement vector of transducer wave fields in anisotropic media which is convenient for eff ective numerical computation. With respect to bulk wave propagation, the nu merical evaluation of Green's dyadic function is circumvented by applying a reciprocity-based approach, which is valid in the (point source) far field . The presented formulation involves characteristic quantities obtained fro m plane-wave theory and appears as a point-source superposition representat ion including the respective point-source directivities. Thus, it is in the same form as a corresponding formulation for scattered elastic wave fields presented previously [M. Spies, J. Acoust. Sec. Am. 107, 2755-2759 (2000)] . Focusing on orthotropic composite materials, numerical evaluation example s are presented for ultrasonic tranducer field patterns and time-dependent radio frequency (rf)-pulse propagation. (C) 2001 Acoustical Society of Amer ica.