Abstract
The mathematical, physical and morphological characteristics of the chip formation process during cutting of Ti-6Al-4V will be analyzed and presented in this paper. In recent years titanium has received more attention due to their unique material properties, such as light weight by height strength, small deformation at high temperatures, low brittleness at low temperatures, and nearly no oxidation at high temperatures, but with the disadvantage that it is difficult to machine. A lot of investigations have been conducted to solve the complex process of machining. But the real complex phenomena at the cutting edge can’t be explained with the help of simplified models. This paper presents a new mathematical-physical model describing the process mechanics leveraging two kinds of friction to explain the metal behavior to strain and stress with self-hardening or softening effects, and the dynamic chip formation behavior due to strain rate discontinuity. All these influencing parameters have an interdependent relationship; thus, they cannot be analyzed separately. The resultant deformation process leads to a grid deformation pattern in the relevant region of the transversal section of a chip that can be used for comparing the theoretical solution with the experimental result. This deformation pattern is the only characteristic that will not disappear after machining. As long as the theoretical results are found to be in agreement with the experimental data of the produced segmented chip, we can be sure, that the models integrating the friction conditions, strain-stress, and metallurgical conditions are correctly developed. In approaching these problems, it is difficult to choose the relevant machining conditions, because a “quick-stop” test is difficult to produce. The reason might be the existing contact conditions at the tool-chip interface, which has an intensive connection due to the diffusion process. Therefore, two different cutting velocities were chosen with the hope that the diffusion is not too intensive; (one slow velocity with vc = 12.5 m/min and a higher velocity with vc = 100 m/min). In addition, a photomicrograph of a chip was taken for the validation process between theoretical and experimental results. Furthermore, the existing temperatures in the contacting zone as well as in the chip formation area could be developed and are discussed and presented in this paper.
Simulation of plastic deformation and destruction in the process of chip formation
