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Hydraulic bushings are widely used in vehicle applications, such as suspension and sub-frame systems, for motion control and noise and vibration isolation. To study the dynamic properties of such devices, a controlled laboratory bushing prototype is designed and fabricated. This device has the capability of varying different combinations of long and short flow passages and flow restriction elements. Transient experiments with step-up and step-down excitations are conducted on the prototype, and the transmitted force responses are measured. The transient properties of several commonly seen hydraulic bushing designs are experimentally studied. Analytical models for bushings with different design features are developed based on the linear system theory. System parameters are then estimated for step responses based on theory and measurements. Finally, the linear models are utilized to analyze the step force measurements, from which some nonlinearities of the bushing system are identified.

A study has been conducted to determine the noise and vibration effect of inserting a cardboard liner into a thin, circular cross-sectioned, cylindrical shell. The relevance of such a study is to improve the understanding of the effects when a cardboard liner is used in a propeller shaft for noise and vibration control purposes. It is found from the study that the liner adds significant modal stiffness, while an increase in modal mass is also observed for a particular shell type of mode. Further, the study has shown that the additional modal damping provided by the liner is not appropriately modeled by Coulomb friction damping, a damping model often intuitively associated with cardboard materials. Rather, the damping is best modeled as proportional viscous damping.

In many vibration isolation problems, translational motion has been regarded as a major contributor to the energy transmitted from a source to a receiver. However, the rotational components of isolation paths must be incorporated as the frequency range of interest increases. This article focuses on the flexural motion of an elastomeric isolator but the longitudinal motion is also considered. In this study, the isolator is modeled using the Timoshenko beam theory (flexural motion) and the wave equation (longitudinal motion), and linear, time-invariant system assumption is made throughout this study. Two different frequency response characteristics of an elastomeric isolator are predicted by the Timoshenko beam theory and are compared with its subsets. A rigid body is employed for the source and the receiver is modeled using two alternate formulations: an infinite beam and then a finite beam. Power transmission efficiency concept is employed to quantify the isolation achieved.

Amongst various sources of noise and vibrations in gear meshing, transmission error and sliding friction between the teeth are two major constituents. As the operating conditions are altered, the magnitude of these two excitations is affected differently and either of them can become the dominant factor. In this article, an experimental investigation is presented for identifying the friction excitation and to study the influence of tribological parameters on the radiated sound. Since both friction and transmission error excitations occur at the same fundamental period of one meshing cycle, they result in similar spectral contents in the dynamic response. Hence specific methods like the variation of parameters are designed in order to distinguish between the individual vibration and noise sources. The two main tribological parameters that are varied are the lubricant and the surface finish characteristics of gear teeth.