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At low frequencies, the finite element method reliably predicts the dynamic response of structures. At high frequencies where modal density is high, statistical energy analysis (SEA) is a useful tool to determine the global dynamic behavior of the structures. SEA gives only the space frequency band averaged energy for each subsystem. In the mid-frequency range where both short and long waves are present, neither low nor high frequency approximation to the dynamic response is valid. In this frequency range, there is a need to utilize another technique to capture the dynamic response of the structure. In this study, the energy finite element analysis (EFEA) method is evaluated as a possible technique to close the mid-frequency analysis gap related to NVH analyses. EFEA gives spatial variations of energy density and power in each subsystem, and models localized damping treatment and localized power input.

A finite element-based acoustic-structure interaction analysis tool has been developed to determine the noise transmission loss characteristics of door seal systems. This tool has been applied to determine the effects of the individual parameters, such as seal material density, seal constitutive model, separation distance between seal layers, external cavity shape, and seal prestress field, on noise transmission characteristics. Our findings indicate that the external and internal cavity shapes, seal material density, and deformed seal geometry are the key factors affecting the noise transmission through seal system. Increasing seal material density decreases the resonance frequencies and increases the overall sound transmission loss. Changing the separation distance between seal layers changes the sound transmission characteristics without changing the compression load deflection behavior of the seal system.

Door weather strip seals are designed with ventilation holes spaced at regular intervals along the seal system to expedite the flow of air from the seal system during the door closing process. The flow of air through the ventilation holes represents a nonlinear damping mechanism which, depending upon hole size and spacing, can significantly contribute to door closing effort. In this study we develop one- and two- dimensional versions of a nonlinear damping model for seal compression load deflection (CLD) behavior which incorporate the effects of seal damping response due to air flow through the ventilation holes. The air flow/damping models are developed from first physical principles by application of the mass and momentum balance equations to a control volume of entrapped air between consecutive air ventilation holes in the seal system.

Nonlinear finite element analysis has been applied to determine the conditions conducive to seal system aspiration. Aspiration noise occurs and propagates into the passenger compartment of a vehicle when there exists a gap between the seal and sealing surface due to pressure differential between the vehicle interior and exterior. This pressure differential is created by the vehicle movement which reduces the pressure acting on the exterior surface of the vehicle, and it is on the order of , where ρ and U∞ are the density of air and vehicle speed, respectively. The pressure difference is also created by turning on the climate control system which pressurizes the passenger cavity. Since aspiration increases door seal cavity noise level and creates a direct noise transmission path without any significant transmission loss, the presence of an aspiration noise source can dominate the vehicle interior noise level if it is close to the driver or passenger's ears.

A novel application of a nonparametric identification technique is described for reducing the complexity of models for structural/mechanical systems components to levels where they are acceptable for inclusion in computation intensive, large-scale vehicle simulations. The technique is based on an integral-series expansion of the functional relating component response to input. Solution of the identification and modeling problem requires the determination of “kernel” functions appearing in the integral-series expressions.

This paper identifies significant features of automotive composite structural response, discusses the computer implementation of analysis methods to solve the composite structural response problem, and evaluates a number of existing computer programs with respect to their abilities to model composite structures.

In structural modeling and optimum design considerations, three-dimensional stress analyses are becoming increasingly important. In this paper, a hybrid technique for the analysis of full three-dimensional stress problems is developed. Using this technique, the finite element and boundary integral stress analysis methods are combined. Solutions to several stress concentration problems are given. Comparisons are given of modeling effort, computer time and accuracy of stress concentration values for finite element, boundary integral and hybrid runs. Presentation of boundary integral models using the MOVIE.BYU graphics package is demonstrated.

A three degree-of-freedom mathematical model formulation for a double-wishbone front suspension is presented which treats the effects of the tire vertical stiffness, the fore-and-aft bushing compliance in the lower arm, the compliance in a steering linkage and the inertia of the suspension links. The model equations are derived retaining all non-linearities associated with large changes in the geometric configuration of the suspension system and are solved within a digital computer program which computes the suspension force and displacement response to prescribed ground terrain inputs at the tire patch. Results obtained with the computer model are presented and compared with test measurements.

An approximate theoretical treatment is presented for the large deformation of non-linear viscoelastic cylindrical blocks bonded between rigid end-plates. The measured compressive force relaxation of two blocks of different initial radius to height ratios is shown to be in good agreement with the theoretical predictions for a carbon-black filled vulcanizate. Measurements of dynamic stiffness k* (=k1+jk2) for various compressive pre-loads and a frequency range of .05 to 30 Hz were also conducted. The measured values for the storage stiffness, k1 are shown to be in good agreement with the theoretical predictions, but poor correlation between experiment and theory is obtained for the loss stiffness, k2. Discrepancies between experimental and analytical results are attributed to the approximations employed to make the analysis mathematics more tractable rather than to the basic theory involved.