A generalized approach for mechanics of chip formation in steady-state and dynamic orthogonal metal cutting using a new model of shear zone with parallel boundaries and its validation to cutting-forces prediction in self-piloting machining.

摘要

This study presents a novel approach to the mechanics of chip formation based on a shear zone model with parallel boundaries that has been developed by applying the continuum mechanics to the analysis of the chip formation process. Such a model is formulated without imposing the assumptions commonly made in the single shear or parallel-sided shear zone models.; A steady-state cutting force model has been derived and adapted to orthogonal cutting of a self-piloting drilling. In the formulated model, special attention has been devoted to the thermomechanical state which defines the effect of the temperature on the yield shear stress of the work piece material.; The proposed steady state cutting force model has been extended to formulate a cutting force model to analyze the dynamic behavior of the machining process in orthogonal cutting. The cutting system was modeled using a single degree-of freedom dynamic system where the variations of the cutting forces are represented by their total differentials.; Special attention in this study has been dedicated to experimental verification. The meaningful design, accuracy, precision, and the calibration of the experimental setups are considered in details and several new experimental methodologies are proposed and used.; This study shows the fluctuation of the cutting forces is a result of chip segmentation and not the cause. It also shows the effect of materials and cutting conditions on the cutting signatures that has never been considered as a factor in the known studies on cutting dynamics.; Special attention has been devoted to the chip morphology of the partially and fully deformed chips to verify the proposed model. A quick stop device has been designed to obtain samples of partially formed chip.; A new methodology has been proposed to align the machine such that the misalignment between the tool and the workpiece is near zero to make sure that the measured forces are not affected by any other sources. A low cost laser-camera based system has been built to achieve this goal.