Abstract
In contemporary standards of strength and durability analysis of components of nuclear equipment, their predicted service life is estimated only on the basis of data on crack growth from a certain fixed size to the critical size. Investigations of the influence of high-temperature reactor water on the precracking time under conditions of cyclic loading originated relatively recently. This is explained by difficulties connected with recording the time of crack initiation (CI) in an autoclave with a high-temperature aqueous medium under pressure. As a result of the tests, it was shown that media of this sort decrease significantly the number of cycles prior to CI, and cracks begin to nucleate after 10-100 cycles of low-cycle loading. It is necessary to study the influence of high-temperature aqueous media on the precracking time in structural steels. Determination of the precracking time in structural materials placed in a high-temperature aqueous medium involves the problem of recording the time of CI. Hence, the design features of a testing installation are determined by the method of detecting nucleating cracks. Since the time of CI cannot be recorded visually at a temperature of the aqueous medium of 573 K under equilibrium pressure, it is necessary to usemore » indirect methods. Measurements of specimen resistance based on the use of high-frequency currents and the polarization method distort the testing conditions because any external potential applied to a specimen affects the characteristics of electrochemical reactions proceeding on the metal surface in the course of destruction. The method used to measure specimen compliance in the process of crack growth is not sensitive enough to detect the time of CI. An analysis of these and other indirect methods shows that the time of crack initiation in specimens loaded in a high-temperature aqueous medium can be recorded most efficiently by the resonance method.« less
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