| This thesis presents the modification and application of a version of the finite-element code, DEFEL, for modeling segmented chip formation in high-speed machining processes (HSM). In HSM three different types of chips can be formed: continuous, segmented, and continuous with a built-up edge. In this research the mechanics of formation of segmented chips is simulated. A new slide-line algorithm and a fracture algorithm were developed which simulated the automatic generation of cracks and interaction of contacting surfaces. Three criteria for crack formation were implemented. The fracture criteria available are based on maximum principal stresses, maximum shearing stresses or maximum effective plastic strain respectively. DEFEL is capable of analyzing large changes in geometry and is effective in calculating the stress and deformation. The addition of the slide-line generation routine to the DEFEL code gives it the needed capability to simulate the segmented chip formation of material in high-speed machining processes. The modification of DEFEL and the implementation of the slide-line and fracture algorithms are the main contributions of this thesis. A plane strain simulation of orthogonal metal cutting process with elastic-perfectly plastic material and frictionless boundary conditions was performed in which a cutting speed well within the high speed range was used (1000. in/sec). DEFEL successfully simulated the formation of segmented chips at high speed. The results have been compared with existing experimental data, analytical solutions, and numerical results. It is concluded that his version of DEFEL is capable of modeling the process of machining. Addition of more accurate material models and friction simulation will further improve the results. |
