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Investigation of tensile plastic instability and necking for AL2024T3 aluminum and S235JR steel alloys

İli, Volkan
Tensile plastic instability phenomenon is defined as the mode of deformation so that large amounts of deformation is localized in a certain region of a component during product life or testing procedure. Several studies have been published to assess the methods proposed to predict tensile plastic instability and necking behavior of materials. Although research has been done by using various specimens, comparative results on different specimen materials and geometries as well as different test methods have not been covered in most of these studies. The purpose of this work is to investigate tensile plastic instability and necking prediction methods both experimentally and numerically. Two classical procedures have been selected: Uniaxial tensile test and deep drawing process, since they are still among the most common applications in the literature. To observe different material characteristics, Al2024T3 and S235JR specimens underwent several tensile tests. Both materials were used to manufacture cylindrical and sheet tensile test specimens. Furthermore, straight, tapered and notched forms of both cylindrical and sheet specimens have been tested and the results are compared. Further, Al2024T3 material specimens are used in cylindrical cup, round bottom cup and square cup deep drawing processes to review the applicability of the tensile test results. The efficiency, precision and effectivity of tensile plastic instability and necking prediction methods have been discussed based on the finite element analysis results. The generalization of the methods so that they can be applied in any plastic deformation analysis is another focus point of this thesis.