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.

A new nonlinear ultrasonic technique for nondestructive evaluation of concrete components is developed and implemented to characterize the effects of carbonation on concrete. The physical principle of this method is the second harmonic generation (SHG) in propagating Rayleigh surface waves which are detected by a non-contact air-coupled transducer. The nonlinearity parameter, as an indicator of material properties, is experimentally obtained from measured Rayleigh wave signals and is used to quantitatively evaluate the progress of carbonation under accelerated conditions. The experimental results show that there is a significant decrease in the measured nonlinearity parameter, most likely originated from the deposit of the carbonation product, CaCO 3 , in pre-existing voids and microcracks. The sensitivity of the nonlinearity parameter is also verified by comparing with the measured Rayleigh wave velocity. The results in this paper demonstrate that the SHG technique using Rayleigh surface waves can be used to monitor carbonation in concrete.

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O comportamento reológico da polpa de cupuaçu integral foi determinado na faixa de temperatura de 10 a 60ºC. Os efeitos da temperatura e da taxa de deformação foram avaliados por meio de testes em cisalhamento estacionário. As análises reológicas foram conduzidas num reômetro Thermo Haake RheoStress 1. Os reogramas foram descritos pelos modelos reológicos de Ostwald-de-Waelle e o de Herschel-Bulkley. As curvas de escoamento mais bem ajustadas pelo modelo de Ostwald-de-Waelle. O produto apresentou comportamento pseudoplástico, e o índice de comportamento de fluxo (n) decresceu com o aumento da temperatura. O efeito da temperatura sobre a viscosidade aparente foi descrita por uma equação tipo Arrhenius e discutida em termos de energia de ativação. Essa energia aumentou com o aumento da taxa de deformação, sendo obtidos valores na faixa de 1 a 2 kcal/gmol.

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