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Theories on Flow and Fracture in Metalworking Processes. Part I. A Theory of Metal Flow in Axisymmetric Piercing and Extrusion. Part II. A Theory on Ductile Fracture in Metalworking Processes.
Final rept. Mar 75-Mar 76,
CALIFORNIA UNIV BERKELEY DEPT OF MECHANICAL ENGINEERING
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The objective of this investigation was to establish theories on flow and fracture in order to apply workability theory to metalworking processes. It has been shown in the application to upsetting that the matrix method is a powerful tool for the analysis of metalworking deformation mechanics. In Part I the matrix method was refined by the use of a different linearization technique, and the area of its application was expanded through the introduction of a technique for effectively treating the nondeforming regions in the computation. The refined version of the method was then applied to a non-steady-state process of axisymmetric piercing and a steady-state process of axisymmetric extrusion. In part II the deformation mode of void growth was re-examined, using the model proposed previously but with formulations for large elastic-plastic deformation. The results show that the nonuniform mode due to void interaction could reduce the fracture strain by several times, compared to the results based on uniform void growth. The results also lead to a question as to the effect of the void-free surface interaction on the stress and strain fields and possible nonsymmetric bifurcation mode.
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