GEOMETRICALLY NON-LINEAR ANALYSIS IN ELASTODYNAMICS USING THE EIGHT-NODE FINITE ELEMENT WITH ONE-POINT QUADRATURE AND THE GENERALIZED-ALPHA METHOD

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ALEXANDRE LUIS BRAUN
ARMANDO MIGUEL AWRUCH

Abstract


A FORMULATION FOR THE GEOMETRICALLY NON-LINEAR DYNAMIC ANALYSIS OF ELASTIC STRUCTURES USING THE EIGHT-NODE HEXAHEDRAL ELEMENT WITH ONE-POINT QUADRATURE AND THE GENERALIZED-METHOD IS PRESENTED IN THIS PAPER. IT IS WELL KNOWN THAT THE NEWMARKÂS METHOD, WHICH IS CONSIDERED THE MOST POPULAR TIME-STEPPING SCHEME FOR STRUCTURAL DYNAMICS, EXHIBITS UNCONDITIONAL STABILITY IN THE CASE OF LINEAR SYSTEMS. HOWEVER, THIS CHARACTERISTIC IS LOST IN THE NON-LINEAR REGIME OWING TO THE LACK OF AN ENERGY BALANCE WITHIN EACH TIME STEP OF THE INTEGRATION PROCESS. IN ORDER TO OBTAIN A NUMERICAL SCHEME WITH ENERGY-CONSERVING AND CONTROLLABLE NUMERICAL DISSIPATION PROPERTIES THE GENERALIZED- METHOD IS IMPLEMENTED, WHERE OPTIMIZED TIME INTEGRATION PARAMETERS ARE DETERMINED AS FUNCTIONS OF THE SPECTRAL RADIUS. THE FINITE ELEMENT METHOD (FEM) IS EMPLOYED IN THE PRESENT MODEL FOR SPATIAL DISCRETIZATIONS USING THE EIGHT-NODE HEXAHEDRAL ISOPARAMETRIC ELEMENT WITH UNIFORM REDUCED INTEGRATION. IN ORDER TO AVOID THE EXCITATION OF SPURIOUS MODES AN EFFICIENT HOURGLASS CONTROL TECHNIQUE IS USED SO THAT VOLUMETRIC LOCKING AND SHEAR LOCKING ARE NOT OBSERVED. SOME EXAMPLES ARE ANALYZED IN ORDER TO INVESTIGATE THE BEHAVIOUR OF THE ELEMENT FORMULATION WITH ONE-POINT INTEGRATION UNDER HIGHLY NON-LINEAR CONDITIONS.

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