Time dependences of acoustic signal characteristics during fracture of metal samples

Abstract

Analysis of time dependences of the amount of acoustic emission signals during the fracture processes is important for both the diagnosis and forecast of breaking at various stages of the process and also for the investigation of the influence of different factors on the fracture process. It was shown in [1–3] that the time dependences of the acoustic emission signals observed at the final stage of the breaking of rock sam� ples are similar to the time dependences of the number of seismic events (aftershocks) during the develop� ment of processes in the Earth’s crust after the main event, an earthquake. They are described by the Omori–Ursu relation [4]: n(t) = K(t + c) p ,( 1 ) where n(t) is the rate of aftershocks; t is the time from the moment of the main event; K is the number of aftershocks; p is the exponent; and c is the time delay before the beginning of the realization of the power dependence of the aftershock rate. The similarity between the time dependences of the number of acoustic emission signals preceding the crack jump during fracture of metal samples and the number of seismic events before an earthquake (fore� shocks) was found in [5]. This allows us to suppose that a similarity between time dependences of acoustic sig� nals in metal samples and seismic signals might be found at the stage of the aftershock activity described by the Omori–Utsu law. If such a similarity exists, experiments with metal samples should give us the possibility to study the influence of stress on the parameters of this relation. With this in mind, we con� ducted the study reported here.