On the inadequacy of the single-shear plane model of chip formation

Abstract

This paper argues that the single-shear plane model is inadequate to the real cutting process. The model has been developed in the late 19th century on the basis of simple observations of the cutting process. Although a number of other models are known to the specialists in this field, the single-shear plane model survived all of them and, moreover, is still the first choice for studies on metal cutting, computer simulations programs and students’ textbooks. Although it is usually mentioned that the model represents an idealized cutting process, no information about how far this idealization deviates from reality is provided. This paper lists and discusses the following principal drawbacks of the single-shear plane model: infinite strain rate; unrealistically high shear strain; unrealistic behavior of the work material; improper accounting for the resistance of the work material to cut; unrealistic representation of the tool-workpiece contact; inapplicability for cutting brittle work materials; incorrect velocity diagram; incorrect force diagram; inability to explain chip curling. The paper concludes that any progress in the prediction ability of the metal cutting theory cannot be achieved if the single-shear plane model is still in the very core of this theory.