Modeling and analysis of extrusion pressure and die life for complex aluminum profiles.

摘要

Extrusion is a very popular manufacturing technique, especially as it can produce a large variety of complicated shapes with no requirement for downstream machining or finishing. Aluminum extrusion finds extensive application in the construction, automobile and aerospace industries. The thermo-mechanical process is complex in nature. In cold extrusion, heat is generated due to friction and deformation. In hot extrusion, high temperatures are involved since billet, die and deformation chamber are preheated. Irregularities in metal flow add to this complexity, especially in multi-cavity production and in extrusion of complex solid and hollow profiles. High pressures, elevated temperatures, and intricate section geometries also lead to repeated mechanical and thermal stresses in the die and affiliated tooling. Moreover, process aberrations and tooling related problems directly contribute to extrusion defects and affect product quality. A comprehensive investigation of the entire operation can thus be divided into three distinct yet inter-related areas: deformation process, dies and tooling, and product defects.; The focus of the current work is on two major issues of aluminum extrusion: extrusion process and extrusion tooling. Some aspects of extrusion product defects have also been explored to complete the picture. Study-A (Extrusion Process) is an investigation into the variation of extrusion pressure and how it is affected by different process parameters (Chapter-2), relationship between extrusion pressure and profile complexity (Chapter-3), and interaction of various extrusion parameters in the deformation chamber (Chapter-4). In Study-B (Extrusion Tooling), modes and mechanisms of die failure are examined (Chapter-5), a probabilistic study of die life is undertaken (Chapter-6), a complexity-based die-life prediction scheme has been formulated (Chapter-7), fracture toughness evaluation of extrusion die materials has been carried out in order to develop an optimum heat treatment strategy (Chapter-8), and a simulation scheme has been worked out to forecast die failures due to fracture and wear (Chapter-9). Study-C (Product Defects) covers defect morphology, defect mechanisms and causes, and remedial measures for various defects encountered in aluminum extrusion (Chapter-10), along with a brief statistical analysis of product defects in a typical large-size aluminum extrusion plant (Chapter-11).