S24  Mecânica dos Sólidos    Titulo: PLASTIC EXTRUSION OF A SQUARE SHAPE FROM THE CIRCULAR TUBE   Resumo : ABSTRACT. A THEORETICAL ANALYSIS OF THE EXTRUSION OF A CIRCULAR TUBE INTO A SQUARE SHAPE IS DEVELOPED. A COMPUTATIONAL MODEL FOR THE SHELL IS PROPOSED IN ORDER TO DERIVE A CLOSED-FORM SOLUTION FOR THE AXIAL LOAD NECESSARY TO PERFORM THE EXTRUSION. THE MOST SIGNIFICANT DEFORMATION COMPONENTS ARE DISCUSSED. THE PLASTIC DEFORMATIONS OF THE TUBE ARE CAUSED BY THE CHANGE IN THE CURVATURE IN THE CIRCUMFERENTIAL DIRECTION. IN THE AXIAL DIRECTION, THE DEFORMATION IS ASSOCIATED TO NON LINEAR EFFECTS. THE SHEAR EFFECTS ARE PRESENT BUT THEY HAVE NOT BEEN TAKEN INTO ACCOUNT BECAUSE THEY REPRESENT A SMALL FRACTION OF THE TOTAL ENERGY INVOLVED IN THE PROCESS. A CLOSED-FORM SOLUTION IS DERIVED FOR THE FORCE NECESSARY TO EXTRUDE THE TUBE. THIS SOLUTION IS PRESENTED IN A DIMENSIONLESS FORM RELATING THE FORCE TO THE GEOMETRIC AND MECHANICAL PARAMETERS OF THE PROCESS. THE SOLUTION IS COMPARED TO THE RESULTS OF AN AXIS-SYMMETRIC CRUSHING OF A TUBE WHICH IS RELATED TO THE PRESENT PROBLEM. APPLICATION OF THE SOLUTION TO THE DESIGN OF ENERGY ABSORBING DEVICES IS DISCUSSED. KEY WORDS:PLASTICITY, EXTRUSION, SHELL, ENERGY ABSORBING DEVICE    Autores : de Aguiar, João Batista de Aguiar, José Manuel     Trabalho Completo :   COBEM99 | Comissão  Organizadora | Palestras | Sessões Técnicas | Autor | Simpósios e Sessões Especiais | Revisores |  Título  dos  Trabalhos | Local