Abstract
The cutting mechanisms of polycrystals of Al, Cu, Zn and Fe-3.5%Si are studied on the basis of those of single crystals of the same materials. For this purpose, the orthogonal cutting of Al-bicrystals (situated side by side in the cutting direction) were carried out and the effects of the grain boundary and the interaction of the adjacent grains on the cutting mechanism were investigated. The experimental results of polycrystals are compared with the results estimated from those of both single crystals and bicrystals.
The main results obtained are as follows:
(1) In cutting the bicrystals, the chip thickness changes drastically at the grain boundary. Then the chip is bent towards its thicker side. Consequently the chip thickness decreases gradually from the inside to the outside of the curvature.
(2) In cutting the bicrystals, the specific cutting resistance is obtained as the weighted average of each crystal with respect to its cutting width, but the side force (fs) varies from the weighted average.
(3) The interaction of the adjacent grains in a series position concerning the cutting direction has a greater influence than that in a parallel position on the cut surface.
(4) There is good agreement between the shear of polycrystals and the arithmetical mean value of the single crystals. The laryer the work-hardenability the smaller becomes the shear angle.
(5) The shear stress on the shear plane and the specific cutting resistance of polycrystals are larger than the arithmetical mean values of single crystals. Especially in Zn and Fe-3.5%Si, there are large differences between those values.
