Search Results

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.

It is well known that sound radiation from a rectangular panel can be significantly affected by its boundary condition. However, most of the existing investigations are primarily focused on sound radiation from plates with simply supported boundary conditions. The objective of this paper is to study the effect on sound radiation of the boundary supporting conditions generally specified in the form of discrete and/or distributed restraining springs. This will have practical implications. For example, in automotive NVH design, it is of interest to understand how the sound radiation from a body panel can be affected by the number and distribution of spot-welds. It is demonstrated through numerical examples that the distribution of spot-welds can be tuned or optimized, like other conventional design parameters, to achieve maximum sound reduction.

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.