ANALYSIS OF GEOMETRICALLY NONLINEAR VIBRATIONS OF FUNCTIONALLY GRADED SHALLOW SHELLS OF A COMPLEX SHAPE

Abstract

GEOMETRICALLY NONLINEAR VIBRATIONS OF FUNCTIONALLY GRADED SHALLOW SHELLS OF COMPLEX PLANFORM ARE STUDIED. THE PAPER DEALS WITH A POWER-LAW DISTRIBUTION OF THE VOLUME FRACTION OF CERAMIC AND METAL THROUGH THE THICKNESS. THE ANALYSIS IS PERFORMED WITH THE USE OF THE R-FUNCTIONS THEORY AND VARIATIONAL RITZ METHOD. MORE-OVER, THE BUBNOV-GALERKIN AND THE RUNGE-KUTTA METHODS ARE EMPLOYED. A NOVEL APPROACH OF DISCRETIZATION OF THE EQUATION OF MOTION WITH RESPECT TO TIME IS PROPOSED. ACCORDING TO THE DEVEL-OPED APPROACH, THE EIGENFUNCTIONS OF THE LINEAR VIBRATION PROBLEM AND SOME AUXILIARY FUNCTIONS ARE APPROPRIATELY MATCHED TO FIT UNKNOWN FUNCTIONS OF THE INPUT NONLINEAR PROBLEM. APPLICATION OF THE R-FUNCTIONS THEORY ON EVERY STEP HAS ALLOWED THE EXTENSION OF THE PROPOSED APPROACH TO STUDY SHALLOW SHELLS WITH AN ARBITRARY SHAPE AND DIFFERENT KINDS OF BOUNDARY CONDITIONS. NUMERICAL REALI-ZATION OF THE PROPOSED METHOD IS PERFORMED ONLY FOR ONE-MODE APPROXIMATION WITH RESPECT TO TIME. SIMULTANEOUSLY, THE DEVELOPED METHOD IS VALIDATED BY INVESTIGATING TEST PROBLEMS FOR SHALLOW SHELLS WITH RECTANGULAR AND ELLIPTICAL PLANFORMS, AND THEN APPLIED TO NEW KINDS OF DYNAMIC PROBLEMS FOR SHALLOW SHELLS HAVING COM-PLEX PLANFORMS.