A SIMPLE FEM FORMULATION APPLIED TO NONLINEAR PROBLEMS OF IMPACT WITH THERMOMECHANICAL COUPLING

Abstract

THE THERMAL EFFECTS OF PROBLEMS INVOLVING DEFORMABLE STRUCTURES ARE ESSENTIAL TO DESCRIBE THE BEHAVIOR OF MATERIALS IN FEASIBLE TERMS. VERIFYING THE TRANSFORMATION OF MECHANICAL ENERGY INTO HEAT IT IS POSSIBLE TO PREDICT THE MODIFICATIONS OF MECHANICAL PROPERTIES OF MATERIALS DUE TO ITS TEMPERATURE CHANGES. THE CURRENT PAPER PRESENTS THE NUMERICAL DEVELOPMENT OF A FINITE ELEMENT METHOD SUITABLE FOR NONLINEAR STRUCTURES COUPLED WITH THERMOMECHANICAL BEHAVIOR; INCLUDING IMPACT PROBLEMS. A SIMPLE AND EFFECTIVE ALTERNATIVE FORMULATION IS PRESENTED, CALLED FEM POSITIONAL, TO DEAL WITH THE DYNAMIC NONLINEAR SYSTEMS. THE DEVELOPED NUMERICAL IS BASED ON THE MINIMUM POTENTIAL ENERGY WRITTEN IN TERMS OF NODAL POSITIONS INSTEAD OF DISPLACEMENTS. THE EFFECTS OF GEOMETRICAL, MATERIAL AND THERMAL NONLINEARITIES ARE CONSIDERED. THE THERMODYNAMICALLY CONSISTENT FORMULATION IS BASED ON THE LAWS OF THERMODYNAMICS AND THE HELMHOLTZ FREE-ENERGY, USED TO DESCRIBE THE THERMOELASTIC AND THE THERMOPLASTIC BEHAVIORS. THE COUPLED THERMOMECHANICAL MODEL CAN RESULT IN SECONDARY EFFECTS THAT CAUSE REDISTRIBUTIONS OF INTERNAL EFFORTS, DEPENDING ON THE HISTORY OF DEFORMATION AND MATERIAL PROPERTIES. THE NUMERICAL RESULTS OF THE PROPOSED FORMULATION ARE COMPARED WITH EXAMPLES FOUND IN THE LITERATURE.