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A general numerical method, the so-called Fourier Spectral Element Method (FSEM), is described for the dynamic analysis of complex systems such as car body structures. In this method, a complex dynamic system is viewed as an assembly of a number of fundamental structural components such as beams, plates, and shells. Over each structural component, the basic solution variables (typically, the displacements) are sought as a continuous function in the form of an improved Fourier series expansion which is mathematically guaranteed to converge absolutely and uniformly over the solution domain of interest. Accordingly, the Fourier coefficients are considered as the generalized coordinates and determined using the powerful Rayleigh-Ritz method. Since this method does not involve any assumption or an introduction of any artificial model parameters, it is broadly applicable to the whole frequency range which is usually divided into low, mid, and high frequency regions.

The cab vibration and ride comfort of off-highway vehicles were analyzed using a multi-body system dynamics model that consists of cab and four isolation mounts. The vibrational Power Spectral Density (PSD) data measured on four mounting brackets was used as excitation input to the model to represent real-world situations. As specified in the SAE and ISO recommendations, a weighted rms acceleration was used as a measure of ride comfort or human perception of vibration severity of vehicles. The analytically predicted results have shown excellent agreement to the measured data. Design optimization process or sensitivity analysis was demonstrated to investigate the effects on vehicle ride quality of isolation mount characteristics (axial and radial stiffness) and mounting configuration (mount location and orientation).

Tractor cab interior noise has been predicted by using a numerical method whereby cab structural and acoustic characteristics are described, respectively, by finite element and boundary element models. The spectral vibrational data measured below cab isolation mounts is used as mechanical excitations to cab-mount system. Responses on each grid point are calculated in structural analysis and subsequently converted to velocity boundary conditions in acoustic prediction of interior noise. The analytical results match reasonably well with the measured regarding cab vibration and the noise level at operator ear. Panel contribution analysis is also performed to examine the relative importance of concerned portions of cab structure or enclosure.

A rectangular thin-walled box is used as a test problem for comparing the results obtained from finite element analysis (FEA), boundary element analysis (BEA), statistical energy analysis (SEA), and experimental measurement. The box structure is mechanically excited by a random point force generated by a vibration exciter. The structural acoustic coupling has been taken into account because there is a significant acoustical pressure load acting on structural surfaces of the box. Both structural and acoustic responses are investigated and good agreement is observed between the numerical and experimental results.

Power flows from a vibratory machine to its mounting structure are of primary concern in passive or active isolation system designs. The total power flow is increasingly believed to be a more reasonable measure of the effectiveness of a vibration isolation system as compared with the traditional measure in terms of the force or displacement transmissibility. In order to calculate the power flows, one needs to know the reaction forces and the vibrations at the isolator locations on the mounting structure. In this paper, the process of determining the power flows through the vibration isolators is discussed for some commonly-used mounting structures which include platforms (reinforced plates), cylindrical shells and other complicated structures. The power flows through the rotational displacements or the bending stiffnesses of the isolators have been taken into account, which tends to become important at high frequencies.

A frame structure such as vehicle frames is usually the primary load-carrying member and typically plays a dominant role in transmitting vibratory and acoustic energies from excitation sources to a receiver that may be a human body or any other subject sensitive or vulnerable to vibration and noise. Determination of vibratory power flows between beam-like structures has been the subjects of many investigations. However, most of these studies have been confined to some simplified or specific boundary and/or junction conditions. In this investigation, a general analytical method is developed for predicting the vibratory power flows between two beams that are rigidly or non-rigidly coupled together at an arbitrary angle. The cross coupling between the flexural and longitudinal waves at the junction has been taken into account, which becomes necessary when two beams are joined together at an angle.