Development of a Methodology for Strain Field Analysis during Orthogonal Cutting

Abstract

Functionality of all machined parts depends on their dimensional tolerance, surface condition and subsurface characteristics, which are often summarized as surface integrity. Key aspects of surface integrity are a change of the residual stress state and white layer formation. Reasons for any workpiece modification of the surface rim zone can be found in the occurring high thermo-mechanical loads during the cutting process. Over the last years, many researchers published simulation based approaches to determine both thermo-mechanical loads and changes in workpiece microstructure induced by machining. Nevertheless, the direct measurement of relevant state variables such as plastic strain and temperature fields at relevant cutting conditions is still a key challenge. Directly obtaining those state variable fields from the process will enable the development of fast computing analytical models to in-process estimate surface integrity features. As a basis for later modelling of dynamic recrystallization during cutting, a methodology to calculate the accumulated equivalent plastic strains alongside one particle movement path throughout the shear zone is developed in this paper. Therefore, an orthogonal cutting test bench has been used to obtain high resolution images when cutting AISI 4140 which were then analyzed using Digital Image Correlation (DIC).