| The goal of this research was to obtain a better understanding of the metal cutting process. This dissertation consisted of three parts. In the first part, based on the observation of high speed videography, a new "stack of cards" model was developed to represent the actual chip formation process. Using a minimum energy principle, a new shear strain expression for machining was derived from the new "stack of card" model. Experimental results showed that predicted shear strains obtained from the new expression were much more accurate than those obtained from Merchant's shear strain expression. In the second part, the finite element method (FEM) was used to simulate the machining process. An FEM model for machining was developed using NIKE2D with ISLAND. An interactive solution strategy was developed to control and monitor the FEM analysis procedure so that different chip separation criteria can be used for the same FEM model. Then various chip separation criteria for machining simulations were evaluated. A new chip separation criterion, which combined a geometrical criterion and a physical criterion, was suggested. In the third part, a comprehensive FEM model for machining was developed using ABAQUS. The flow stress was modeled as a function of strain, strain-rate, and temperature. The tool/chip interface interaction was modeled as the sticking/sliding process. The effect of the work material model and tool/chip interface model on simulations was investigated. The effect of rake angles and the controlled contact tools on machining was studied. A new distribution of normal stress on the tool face was also suggested. |
