岩石のシヤルピー試験

抄録

The Charpy impact test which is recognised as a fast, inexpensive and versatile method of obtaining meaningful data ond ynamic fracture of materials was carried out to propose the simple ways of obtaining the fracture energy, W, and the crackpropagation velocity.
The total absorbed energy, ΔE, in Charpy test contains, in addition to W, a considerable amount of loss energy, L, mainlyspent to accelerate the broken specimen and caused by friction between the specimen and its support. The test with a brokenspecimen slightly connected by cellophane tape, which may be called “Blank Test”, was performed to estimate L because theabsorbed energy in the blank test, ΔEblank, may be the summation of the kinetic energy of broken specimen and the friction alloss. Experimentally, it was verified that L can be equated with ΔEblank at the same counter angle of pendulum. Therefore, W can be calculated by (ΔE-ΔEblank).
In the second part of the paper, a new approach to crack velocity measurement was discussed. The very fine lines of conducting silver paint were applied to the side of the specimen, spaced at 3mm intervals. In the test, the subsequent failure of paint lines associated with crack propagation through the specimen was monitored as a series of small step voltage changein the recording circuit. The results showed that the crack velocity first accelarated and attained to the maximum near the centerline of the specimen, followed by the rapid decrease toward the end of the crack path. The maximum velocity measuredin this experiment was about 60% of the theoretical terminal velocity (=0.38 E/ρ).