岩石およびセメントモルタルの切削抵抗について (第1報)

抄録

In this paper the authors report some results of the cutting experiments in two dimesions, using a tuffaceous sandstone and a cement mortar as the test piece. The cutting mechanisms, the process of chip formation and the cutting force with some orthogonal cutting tools are obserbed.
When the wedge of tool is penetrated into the rock or similar brittle materials, a crushing zone is initiated in the vicinity of the top of wedge. After some growths of this crushing zone and some increases of cutting force, an arc shaped crack propagates to the free surface of test piece, and the cutting force decreases instantaneously. And then a phase of crushing out of some remainded buttocks follows. Again the crushing zone grows with the penetration of wedge, until the second crack would be able to propagate. These phenomena are repeated.
It is obserbed that the arc shaped crack starts from the vicinity of the upper end of the crushing zone, and the relations between the cutting force and the cutting dephth are represented by the following equations:
P=a₁+b₁t, Q=a₂+b₂t (1)
In these equations, ai is the parameter representing the crushing resistance to the penetration of the wedge, especially the blund land of the wedge, and bi is the parameter repesenting thee force for crack initiation.
The second terms of these equations are corespond to the analytical formula reported by the authors, that is:
_??_(2)
where_??_
These equations are fitted to the results of the cutting experiments, to calculate the angle of friction φ and the stress distribution factor n.
It is concluded that:
(1)φ increases with the increase of the rake angle α
(2) n decreases with the increase of the rake angle α
Finally it is suggested that the crushing zone at the top of wedge has an inportant effect on the cutting force of brittle materials.