H. Ledbetter C. M. Fortunko
Natl. Inst. of Standards and Technology, 325 Broadway, Boulder, CO 80303
Colorado State Univ., Fort Collins, CO 80523
Several authors used ultrasonic resonance spectroscopy to determine a material's elastic-stiffness constants, the Voigt C[sub ij]. Complementary to these are the out-of-phase C[sub ij][sup *], which give the complete elastic stiffness C[sub ij]=C[sub ij]+iC[sub ij][sup *]. Here, C[sub ij][sup *] measurements for both monocrystal and polycrystal copper are reported. For the monocrystal case, the C[sub ij][sup *] vary strongly with the vibrational mode. And, when interpreted against a vibrating-string dislocation model, the C[sub ij][sup *] present several surprises. For the polycrystal, the C[sub ij][sup *] are much lower and nearly independent of vibration mode.