A major constraint on the application of new gas turbine structural concepts is the control of engine system vibration and maneuver loads and deflections. Because many iterations are usually needed to arrive at a satisfactory design, and because batch oriented computer calculations require substantial turnaround time between runs, there is often a limitation on the number of analyses that can be made prior to a design decision. The VISA (Vibration Interactive System Analysis) computer program has been developed at General Electric Aircraft Engines (GEAE) to facilitate system vibration and maneuver loads analysis and to improve its quality. The VISA interactive program is based on a unique adaptation of the finite element method that provides an extremely user friendly and efficient general rotordynamics analysis capability, thereby resulting in a cost effective optimum design. The VISA interactive analysis utilizes a combined transfer matrix/finite–element formulation which combines the advantages of both of these methods. In the former case, the dimensionality of the analysis is reduced, and in the latter case, automatic analysis of multibranch, multilevel engine structures, and a generalized approach to modeling various types of boundary and constraint conditions is provided.

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