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Turbosets used in power generation industry are frequently placed on flexible foundations, which significantly influence the overall dynamics. Establishment of structaral models that capture the rotor and foundation effects reliably using finite element modeling or modal analysis is difficult because of model complexity and/or costs involved. This paper presents a method to extract modal parameter information of a turboset using frequency response function data recorded during high speed balancing. The main advantage of the present method over the others is the low cost and small effort involved, so that it is of practical use in an industrial setting. A real life example dealing with parameter extraction for a large generator rotor is presented to demonstrate its implementation. [DOI: 10.1115/1.2938275]

This paper examines the influence of frame flexibility on the optimization of an engine mounting system for enhanced vibration isolation in motorcycles. A theoretical model is developed to represent the structural dynamics of an engine mount system in motorcycles. The model consists of the power-train assembly, modeled as a six-degree-of-freedom (DOF) rigid body; the swing arm assembly, connected to the power-train through a coupler shaft assembly; and the frame, connected to the power-train by elastomeric mounts and to the swing-arm through the rear suspension. Two models of the flexible frame are developed for analysis. The first model uses an equivalent stiffness matrix of the frame, derived from its finite element model, in terms of the nodes connecting the frame to the other subsystems. The second model is based on a dynamic model of the frame as well as the swing arm derived from their respective finite element models. The optimization procedure minimizes the load transmitted to the frame while constraining the engine displacement due to imposed loads within prescribed limits. The mount stiffnesses, locations and orientations are used as design variables. Examples are presented to demonstrate the influence of frame flexibility on the force transmitted to the frame. [DOI: 10.1115/1.2748468] Keywords: engine mounts, mount optimization, frame flexibility

In the drag racing environment, maximizing tractive effort is essential to competitive performance. Anti-squat is a transient vehicle suspension parameter which can dramatically affect tractive effort available at the motorcycle drive tire. This paper addresses the design of a four-link rear suspension for a drag racing motorcycle to provide anti-squat, which increases rear tire traction, thereby improving vehicle acceleration performance. Utilizing PC based CAD, finite element analysis and dynamic system analysis software, a motorcycle rear suspension system was designed, built and tested under actual racing conditions. Parametric studies using dynamic theoretical models were conducted for both unsuspended and four-link equipped versions of the same vehicle. Based on the results, it is shown that the four-link suspension, when applied to a drag racing motorcycle, does provide opportunity for improving tractive effort at the beginning of a race which will improve overall drag racing performance. [DOI: 10.1115/1.1431261]

Multiobjective optimization methods are employed to solve a constrained reliability and redundancy assignment problem involving series systems with time-dependent reliability. At issue is the balance required to achieve optimal component reliability with the minimum amount of components at every stage of the system. A gas turbine overspeed protection system is used as an example to derive a solution using fuzzy sets to model fuzzy objective and constraint functions.

The use of fuzzy optimization techniques for the design of mechanical and structural systems is discussed. The technique relies on linear membership functions to solve the fuzzy mathematical programming problems involved in a decision-making process. To evaluate its reliability, this optimization approach is employed in the solution two design problems regarding truss construction. Results reveal that the sign of the membership satiation coefficient strongly affects the optimum designs of both sample specimens.