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In this paper, a dislocatlon-based plasticity model is formulated in the framework of continuum mechanics and nonequllibrium thermodynamics for solids under high strain rates. Specifically, the formation of a dislocation network behind the shock front, associated plastic flow, resulting heating due to plastic work, and evolution of the morphology of the polycrystalline structure are modeled. T he associated changes of dynamic strength or yield stress with the increasing shock strength due to nucleation of dislocations at the shock front are modeled. The microstructural characteristics of the dislocation network are modeled by selected internal state variables. The irreversible nonequilibrium processes at high strain rates are modeled by selected nonequilibrium state variables and their evolution equations. The results clearly show the increased localized heating due to increased dynamic strength and the associated plastic flow.

Self-heating or dissipation of piezoelectric ceramic elements is observed to be severe under dynamic operations even in the linear range. A nonequilibrium thermodynamic model is developed to delineate the coupled irreversible mechanical, electric, and thermal processes, which jointly contributes to dissipation.

A method for scanning the laser Doppler vibrometer (LDV) velocity output signal in the frequency domain to obtain the deflection shape of a vibrating structure during modal testing is discussed. The method relies on the Fourier transform in modulating the LDV output signal into a Chebyshev series form. To test the validity of this approach, an LDV test was carried out on a rectangular bar subjected to a 25 hertz excitation frequency. It was foound that the incorporation of Chebyschev coefficients in the use of LDV improved the method's reliability.

A new physical parameter is presented and it is applied to damage detection to address the two main challenges in the field of vibration-based structural health monitoring: the sensitivity of detection and the requirement of data of the baseline state. The parameter is also shown to be not affected by noise in the detection ambience. Assuming the damaged structure to be a linear system, its response can be expressed as the summation of the responses due to the undamaged and the damaged part. If the part of the response due to the damage is isolated, it forms what can be regarded as the damage signature. In this paper, the occurrence of damage signature is investigated when the damaged structure is excited at one of its natural frequencies, and it is called partial-mode contribution. The existence of damage signature as partial-mode contribution is first verified using an analytical derivation. Thereupon, its existence is ascertained using finite element models and by doing experiments. The limits of size of the damage that can be determined using the method are also investigated. [ABSTRACT FROM AUTHOR]