Abstract
A test mill of rotating disc type was devised to make clear the grinding mechanism in an attrition-and-friction mill. The friction force and the surface roughness of the friction surface were measured, and the production rate and the size distribution of fine particles with respect to load, sliding velocity, and sliding distance were investigated in relation with them. The inorganic matrials such as dolomite earthernware and chalk were used. The experimental variables and ranges were as follows: load; 1.04-23.2N, sliding velocity; 0.22-2.1m/sec.
The following experimental results are obtained:
1) The kinetic friction coefficient μk is increased in a small degree with the increase of applied load, but it is independent of the sliding velocity Furthermore, the fluctuation of friction force has a close relation with the production rate of fine Particles.
2) From the observation of scanning electron micrographs, the fracture surface of brittle fracture is confirmed in the friction surface.
3) The applied load has more significant influence on the average surface roughness of the friction surface than other factors such as sliding velocity and sliding distance.
4) The relationship between the production rate of fine particles Q and the value of PV can be formulated as follows:
Q=k1(PV)
where the constant k1 is considered to be an index for easiness of grinding of material, and its value is 0.31mg/J for dolomite earthenware and 0.9mg/J for chalk.
5) The median particle size measured with the electron microscope is about 0.7±0.1μm for dolomite earthenware, and the shape' of particles is an ellipsoid of which the ratio of major radius to minor radius is 1.9.
6) The grinding energy applied to unit volume of produced fine particles and specific fracture-suface energy for dolomite earthenware are estimated to be 2.19±0.39×103MJ/m3, 200J/m2, respectively.
