Abstract
Instrumented Charpy impact test becomes more useful by connecting the digital memory and microcomputer, in which yield load(Py), maximum load(Pm), pre-maximum load energy(Ei)and post-maximum load one(Ep) are automatically and rapidly analyzed. In this analysis, cyclic oscillations in a load signal are corrected and smoothened by using a method of moving averages(the nonrecursive low pass digital filter).
Dynamic, JIC value(JId)of A533B steel can be measured a fatigue pre-cracked type Charpy specimen, provided that a true deflection of specimen and a true crack initiation point the load-deflection curve are known. For this purpose, elastic compliance values of the testing machine and the specimen are measured dynamically by the elastic low blow test to correct the apparent deflection. Crack iniitiation point, on the other hand, is detected by the plastic low blow test. It is shown that the crack initiation in the fatigue pre-cracked specimen of this material occurs prior to the maximum load, and that the relation between crack initiation energy(EΔa)and pre-maximum load energy(Ei)is EΔa/Ei≅0.8.
