A TIME-DOMAIN FINITE ELEMENT MODEL REDUCTION METHOD FOR VISCOELASTIC LINEAR AND NONLINEAR SYSTEMS

Abstract

MANY AUTHORS HAVE SHOWN THAT THE EFFECTIVE DESIGN OF VISCOELASTIC SYSTEMS CAN BE CONVENIENTLY CARRIED OUT BY USING MODERN MATHEMATICAL MODELS TO REPRESENT THE FREQUENCY- AND TEMPERATURE-DEPENDENT BEHAVIOR OF VISCOELASTIC MATERIALS. HOWEVER, IN THE QUEST FOR DESIGN PROCEDURES OF REAL-WORD ENGINEERING STRUCTURES, THE LARGE NUMBER OF EXACT EVALUATIONS OF THE DYNAMIC RESPONSES DURING ITERATIVE PROCEDURES, COMBINED WITH THE TYPICALLY HIGH DIMENSIONS OF LARGE FINITE ELEMENT MODELS, MAKES THE NUMERICAL ANALYSIS VERY COSTLY, SOMETIMES UNFEASIBLE. IT IS ESPECIALLY TRUE WHEN THE VISCOELASTIC MATERIALS ARE USED TO REDUCE VIBRATIONS OF NONLINEAR SYSTEMS. AS A MATTER OF FACT, WHICH THE RESOLUTION OF THE RESULTING NONLINEAR EQUATIONS OF MOTION WITH FREQUENCY- AND TEMPERATURE-DEPENDENT VISCOELASTIC DAMPING FORCES IS AN INTERESTING, BUT HARD-TO-SOLVE PROBLEM. THOSE DIFFICULTIES MOTIVATE THE PRESENT STUDY, IN WHICH A TIME-DOMAIN CONDENSATION STRATEGY OF VISCOELASTIC SYSTEMS IS ADDRESSED, WHERE THE VISCOELASTIC BEHAVIOR IS MODELED BY USING A FOUR PARAMETER FRACTIONAL DERIVATIVE MODEL. AFTER THE DISCUSSION OF VARIOUS THEORETICAL ASPECTS, THE EXACT AND REDUCED TIME RESPONSES ARE CALCULATED FOR A THREE-LAYER SANDWICH PLATE BY CONSIDERING NONLINEAR BOUNDARY CONDITIONS.