Accession Number : ADA309849

Title :   Minimization of the Vibration Energy of Thin-Plate Structures and the Application to the Reduction of Gearbox Vibration.

Descriptive Note : Technical memorandum,

Corporate Author : NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CEN TER

Personal Author(s) : Inoue, Katsumi ; Krantz, Timothy L.

PDF Url : ADA309849

Report Date : DEC 1995

Pagination or Media Count : 50

Abstract : While the vibration analysis of gear systems has been developed, a systematic approach to the reduction of gearbox vibration has been lacking. The technique of reducing vibration by shifting natural frequencies is proposed here for gearboxes and other thin-plate structures using the theories of finite elements, modal analysis, and optimization. A triangular shell element with 18 degrees of freedom is developed for structural and dynamic analysis. To optimize, the overall vibration energy is adopted as the objective function to be minimized at the excitation frequency by varying the design variable (element thickness) under the constraint of overall constant weight. Modal analysis is used to determine the sensitivity of the vibration energy as a function of the eigenvalues and eigen- vectors. The optimum design is found by the gradient projection method and a unidimensional search procedure. By applying the computer code to design problems for beams and plates, it was verified that the proposed method is effective in reducing vibration energy. The computer code is also applied to redesign the NASA Lewis gear noise rig test gearbox housing. As one example, only the shape of the top plate is varied, and the vibration energy levels of all the surfaces are reduced, yielding an overall reduction of 115 compared to the initial design. As a second example, the shapes of the top and two side plates are varied to yield an overall reduction in vibration energy of 1/30.

Descriptors :   *VIBRATION, *GEARS, *TRANSMISSIONS(MECHANICAL), COMPUTER PROGRAMS, FREQUENCY, THICKNESS, OPTIMIZATION, EXCITATION, FINITE ELEMENT ANALYSIS, STRUCTURAL ANALYSIS, THEORY, INTENSITY, EIGENVALUES, RESONANT FREQUENCY, HELICOPTERS, PLATES, SHIFTING, SEARCHING, WEIGHT, AIRCRAFT EQUIPMENT, SIDES, ENERGY LEVELS, GRADIENTS.

Subject Categories : Machinery and Tools
      Mechanics
      Aircraft

Distribution Statement : APPROVED FOR PUBLIC RELEASE