掘削機械の刃物速度に関連する2, 3の問題について
1971 年 87 巻 995 号 p. 65-73
詳細
1971 年 87 巻 995 号 p. 65-73
In this paper, the author discusses some problems on the tool velocity in the coal and rock cutting. A review on the present state of the tool velocity of various coal getting and rock tunnelling machines is firstly given. The test results by many authors about the effect of cutting speed on the cutting force are discussed. Most of them, with some exceptions, have shown that the cutting force does not depend upon the cutting speed.
Considering with the feed velocity of machines and the effect of depth of cut on the cutting force, the effect of cutting speed on the specific energy consumption is also discussed, to be suggested that a slower cutting speed is more desirable.
In order to reveal the reason of the independency of cutting force with the tool velocity, the propagation velocity of brittle crack in the rock sample is calculated. As a result of these culculations, it is shown that the crack velocity is more than several hundreds m/sec, and much higher than the practical range of tool velocity.
The effect of the rate of loading on the failure stress of rock is discussed to show that the rate of stress generated in the practical rock cutting could not affect the failure stress. This suggests that. the cutting force does not depend on the tool velocity.
Noticing the effect of tool life on the cost of rock cutting, the effect of tool velocity on the tool life or specific tool wear is discussed. It is concluded that most of the energy consumed in the rock cutting is converted into the thermal energy to generate a high temperature in the cutting tool.
Finally, using the dimensional analysis, the effect of tool velocity on the tool temperature is discussed, to show that the tool temperature is proportional to the tool velocity. Thus, the higher tool velocity would result in the higher tool wear and shorter tool life.
Remembering that the cutting capacity for most machines does not depend upon the tool velocity, it is concluded that the slower tool velocity is the better, concerning with the cutting force and the consumption of cutting tool.
