岩石の切削抵抗におよぼす刃物すくい角の影響

Abstract

A series of rock cutting tests is conducted by drag bits of various geometries. In order to evaluate the effect of rake angle of bit as well as mechanical properties of sample rock on the cutting force, theequation of cutting force Pgiven in previous paper P=(a. t/B+b).t. B+cis applied to the test result, where t is the depth of cut, B is the blade width of bit, a, b and c areparameters as functions of th e rake angle ofbit and mechanical properties of rock. It is concluded that(a) Parametersa and b decrease with increase of the rake angle of bit.(b) When parameters a and b are assumed as proportional to the shear strength of rock. both of them depend upon the angle of internal friction of rock as well as the apparent angle of friction between bit and rock. The latter angle is noti ndependent of the rake angle of bit.(c) Parameter c is approximately proportional to the shear strength of rock, and independent of the rake angle of bit.Furthermore, on the basis of the test result, it is indicated that(d) The ratio of thrust to cutting force decreases with increase of the rake angle of bit.(e) When the cross-section of cut groove A is expressed asA=(d.t1B+1). t. B, the parameter d is independent of the rake angle of bit.