The main purpose of this research is to seek experimentally the influences of shearing velocities on the shearing characters and to make clear the relations between the static shearing behaviers and the dynamic ones at the practical shearing velocity on the ordinary mechanical presses. In general, in order to know the shearing characters, we use universal testing machines, but the ratio of the practical shearing velocity to the one obtained by testing machine reaches over 10⁴ : 1, so it is very significant to do the dynamic shearing tests. To carry out the perfect shearing tests, we must record the shearing stroke, the shearing force and the time. The author performed the circular blanking tests (Fig. 8), and measured the shearing force i. e. the blanking force by the piezo-crystals (Fig. 5), and the blanking stroke in use of the photo-tubes, that transformed the punch stroke into the variation of the quantity of light brought into the photo-tubes, which was later changed into the photo-current (Fig. 1, 2 and 3). The produced piezo-electricity and the photo-current were so slight, that the author had to amplify them by the D. C. amylifiers (Fig. 9 and 10), and this outputs were directly led respectively to the horizontal and vertical deflecting plates of the cathode-ray tube. Thus the author obtained the shearing diagrams directly on the screen of the cathode-ray tube (Fig. 20), and the time was measured simultaneously by the intensity modulation of the cathode ray tube (Fig. 11).
The tested materials were usual rolled plates about 0.8mm thick of zinc, aluminium, copper, mild steel, 60 : 40 brass, German silver, and phosphor bronze (Table. 4). The tested clearances were six kinds between 0.048mm and 0.362mm (Table. 3). The numbers of stroke of press were changed between 28 s. p. m. and 190 s. p. m. (Table. 2). The tests were performed, of course, in the room temperature.
Thus, the author sought the influences of the shearing velocity x on the shearing resistance k_sm, the shearing work (i. e. energy) W, the sheared edges, etc. (the data will be found in the next report, Vol. 25, No. 9 ). By these investigations, it was made sure that for the above materials the relations k_sm∝(x)ⁿ and W∝(x)^n' were substantiated in the range of tested shearing velocities including the static shearing velocity (Fig. 2440). Here, n and n' are the constants concerning the sort of materials. Zinc is the most affected by the shearing velocity, and n=0.056, n'=0.044. For mild steel, n=0.016 and n'=0.011. For copper, n=0.015 and n'=0. 012. For aluminium, n=n'=0. 008. And for other materials, n and n'≤0.004, so it has been made sure that there are nearly no influences of the shearing velocities in the room temperature.
The influences of tensile strain rates on the tensile strength etc. has been particularly well studied by many foreign and domestic investigators, whose results coinside well with the author's shearing tests about the tendencies and the values of n. This fact shows that the tensile factors predominate in the later period of shearing.
From the above experimental results, for the materials popular to press-working except zinc, the dynamic shearing resistance and work at the practical working velocity are at most about 20% greater than the static ones (Table 6 and 7 in the next report), so we can utilize the results of static shearing tests.
On the other hand, the author measured the length of the punch-stroke till the point of the maximum blanking force (Fig. 45 and 46), the shape of sheared edge (Fig. 41, 42, 43 and 44), the dimension (Fig. 47, 48 and 49), and the deflection (Fig. 50 and 51) of sheared blanks, and the flowed grain structure near the sheared edge (Fig. 52),