SOM based Methodology for Evaluating Shrinkage Parameter of the Chip Developed in Titanium Dry Turning Process

Abstract

In the most of machining processes, chip morphology and microstructure contain deep information about the cutting mechanisms, their evolution and, even, about both the process and the workpiece. However, usually, changes in the process are related only to changes in the tool morphology and in the surface integrity hiding relevant information. This is commonly due to the chip characterization is not an easy task. In effect, chip geometry and dimensional features are habitually hardly measurable and evaluable. In this work, a methodology for characterizing the chip developed in the dry turning processes of Titanium alloys (Ti6Al4V - UNS R56400) has been proposed. This characterization has been achieved by considering different geometrical and dimensional parameters. Thus, shrinkage parameter has been evaluated through the changes in length and compared with the corresponding values determined through variations measured in thickness and width. However, the partially discontinuous form of the Ti chips makes difficult the dimensional evaluation. Stereoscopic Optical Microscopy (SOM) techniques can help to evaluate the chip shrinkage parameter through the measurement of the shear angle. In parallel, SOM techniques can assist for measuring other geometrical parameters of the chip. In this context, the evolution of the shrinkage parameter with the length of machining and the changes of the chip geometry with the cutting parameters (cutting speed and feed) has been also analyzed.