No abstract

No abstract

Developed in the late 1980s, Nonlinear Resonant Ultrasound Spectroscopy (NRUS) has been widely employed in the field of material characterization. Most of the studies assume the measured amplitude to be proportional to the strain amplitude which drives nonlinear phenomena. In 1D resonant bar experiments, the configuration for which NRUS was initially developed, this assumption holds. However, it is not true for samples of general shape which exhibit several resonance mode shapes. This paper proposes a methodology based on linear resonant ultrasound spectroscopy, numerical simulations and nonlinear resonant ultrasound spectroscopy to provide quantitative values of nonlinear elastic moduli taking into account the 3D nature of the samples. In the context of license renewal in the field of nuclear energy, this study aims at providing some quantitative information related to the degree of micro-cracking of concrete and cement based materials in the presence of thermal damage. The resonance based method is validated as regard with concrete microstructure evolution during thermal exposure.

The elastic moduli of pure polycrystalline beta plutonium were measured over its full range of existence (417 K to 491 K) using resonant ultrasound spectroscopy. The Debye temperature (138 K), Poisson's ratio (0.28), Grüneisen parameter (2.3), and the zerotemperature atomic volume (21.2 Å 3 ) were computed from the measurements. Both bulk and shear moduli decrease smoothly on warming with expected discontinuities at the phase boundaries. The shear modulus is surprisingly nearly the same for beta and gamma Pu. The temperature dependence of bulk moduli for beta Pu is, like gamma Pu, unusually small. Poisson's ratio shows very strong differences among alpha, beta, and gamma Pu indicating they are entirely different metals. The zero-temperature elastic moduli were computed for the three phases as well as for gallium-stabilized delta Pu (also measured by us) and compared to calculations.PACS numbers: 62.20. de, 63.70.+h, 65.40.G-, 62.20.dj