Digitized by Kansas Correctional Industries

Call number: LD2668 .T4 1963 V31 / Master of Science

Vita. / Digitized by Kansas Correctional Industries

This study presents a novel methodology to characterize material plastic behavior within a practical range of stresses, strains, strain rates, and temperatures encountered in the metal cutting process. The methodology is based on integrating a newly developed analytical model with quasi-static tests and orthogonal cutting experiments that incorporate a laser heating system. Friction and heat transfer models are developed to describe the tribological and thermal interactions at the tool-chip interface. These models are implemented in a FEM package in order to improve the accuracy of the simulation of the machining process. / The new analytical model, which is developed to predict the distributions of the stress, the strain, the strain rate, and the temperature in the primary shear zone, is based on conceptual considerations, as well as characterization of the plastic deformation process through comprehensive FEM simulations. / Orthogonal cutting experiments at room temperature and preheated conditions were carefully designed. While the cutting tests at room temperature provided the constitutive data encountered in the primary shear zone, the preheated cutting tests were designed to capture the material behavior at the high level of temperature and strain encountered in the secondary shear zone. In these preheated cutting tests, a laser beam was employed. Quasi-static tests were also utilized to identify some of the coefficients in the constitutive equations, in order to improve the convergence to a unique solution for the constitutive law. / Evaluation criteria were developed to assess the performance of constitutive equations. Based on the developed methodology and the evaluation criteria, a new constitutive equation for Inconel 718 has been proposed. This constitutive equation was further validated by Split Hopkinson Pressure Bar (SHPB) tests and cutting tests in conjunction with FEM simulations. The SHPB test data show an excellent agreement with the proposed material model. The cutting tests and the FEM simulation results also proved the validity of the proposed material constitutive law.

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