As an abrasive wheel for Taber abraser, the rubber wheel covered with sandpaper manufactured and standardized by Taber Instruments Company is now internationally specified to be used. However, the test results obtained from the sandpaper are noted for poor reproducibility. It is suspected that the glue applied for cementing abrasive grains changes its strength according to relative humidity of testing and storaging conditions. In this paper, the influence of relative humidity (R. H.) on abrasive quality was examined. The results are as follows:
(1) The friction between an abrasive wheel and a specimen consists of sliding and rolling. As regards sliding friction which contributes most to the wear of specimen, abrasive grains scratched the specimen very slowly in almost straight line during contact. The velocity was given not by 2πr, but by 2π
H mm/sec (Fig. 1).
(2) The expressions were derived to relate
pf,
Wsp,
Wgf,
Fp and R. H. each other, where
pf is the fracture probability of grains,
Wsp the weight loss of specimen,
Wgf the weight loss of grains by fracture and
Fp the peel strength of applied glue. The expressions agreed well with the experiments (Eq.9∼15).
(3)
k(=
dWsp/
dWgf) represents a factor of abrasive quality. It is desirable that
k takes a large value at the beginning of abrasion and keeps it as long as possible. Under high humidity conditions, the initial
k was very small but became larger rapidly. In this case the paper was exhausted easily.
(4) It was concluded that 65% R. H. specified in JIS Standard was too high to give reliable data, and 50% R. H. was preferable. When R. H. differs from this, the date must be corrected strictly. From this standpoint Taber Instruments Company also published the diagram for compensation, but some disagreements were recognized between the diagram and the results obtained in this experiment. More experiments are required for more accurate compensation.
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