The vibration responses of structures under controlled or ambient excitation can be used to detect structural damage by correlating changes in structural dynamic properties extracted from responses with damage. Typical dynamic properties refer to modal parameters: natural frequencies, mode shapes, and damping. Among these parameters, natural frequencies and mode shapes have been investigated ex...

The damping capacity and mechanical properties of Mg-6Al-1Zn alloy after heat treatment were investigated. The damping characteristics of un-heat-treated, solution treated, and aged Mg-6Al-1Zn specimens were determined by measuring the damping ratio and the logarithmic decrement of free vibrations of a bending beam clamped at one side. The microstructural evaluations confirmed that the β-Mg17Al...

The undamped naturalfrequency CO, and the damping ratio [ can be determined from a plot of the jiee motion of the system. If the damping is light, ( < 0.2, the lqqarithmic decrement can be used to determine the coeficients. Systems with moderate damping are those in the range 0.2 < ( -C 1.2. A methodfor determining vibration parameters for systems with moderate damping is presented here. The me...

Damping material is usually applied on the steel panel of a vehicle to reduce vibration level. On the other hand, the weight reduction is also required to improve fuel consumption. Therefore, modal loss factors induced by damping material on the steel panel of a vehicle body structure need to be maximized with a given volume. In this paper we propose a practical design method to maximize modal ...

For advanced aerospace propulsion systems, development of ceramic matrix composite integrally-bladed turbine disk technology is attractive for a number of reasons. The high strength-to-weight ratio of ceramic composites helps to reduce engine weight and the onepiece construction of a blisk will result in fewer parts count, which should translate into reduced operational costs. One shortcoming w...

We present the theory of damping of low-energy excitations of a trapped Bose condensate at finite temperatures, where the damping is provided by the interaction of these excitations with the thermal excitations. We emphasize the key role of stochastization in the behavior of the thermal excitations for damping in non-spherical traps. The damping rates of the lowest excita-tions, following from ...

We present results for step-strain experiments and the resulting damping functions of polyethylene blends of different structures, including solutions of linear, star and comb polymers. Remarkably, an entangled melt of combs exhibits a damping function close to that for entangled linear chains. Diluting the combs with fasterrelaxing material leads to a more nearly constant damping function. We ...

In this paper, a new viscoelastic size-depended model developed based on a modified couple stress theory and the for nonlinear viscoelastic material in order to vibration analysis of a viscoelastic nanoplate. The material of the nanoplate is assumed to obey the Leaderman nonlinear constitutive relation and the von Kármán plate theory is employed to model the system. The viscous parts of the clas...