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| Titel |
Memory effects on mechanically stimulated electric signal; diversification of stimuli impact on material memory and comments on the observed features |
| VerfasserIn |
Panagiotis Kyriazis, Ilias Stavrakas, Cimon Anastasiadis, Dimos Triantis, John Stonham |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250043156
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| Zusammenfassung |
| Memory is defined as the ability of marble and generally of brittle geomaterials to retain
“imprints” from previous treatments and to reproduce information about these treatments
under certain conditions, by analogy to the memory of human beings. Memory effects have
been observed in the evolution of a variety of physical properties like the acoustic emissions
of brittle materials during fracture.
The existence of memory effects for the mechanically stimulated electric signal, either by
Pressure (PSC) or by Bending (BSC), is examined in this work, alongside with an attempt to
distinguish between the two different manifestations of ‘memory’ based on the electrification
mechanism that is triggered at different levels of externally applied load on samples.
Having identified two main mechanisms (i.e. the dynamic and the cracking) and
following the human memory model, we suggest the separation of memory of a
material specimen into two levels i.e. the short or temporary and long or permanent
memory.
For the observation and analysis of the short memory of brittle materials we have
conducted experiments using the PSC technique in marble specimens. The materials are
imposed to cyclic stepwise loading of the same level, scheme and direction (axial stress –
unchanged position of material) in order to comply with the conditions that are
proposed as suitable for memory effects study by other researchers. We have also
conducted experimental tests of cyclic high level stepwise loading on amphibolite
rock specimens in order to verify and study the existence of permanent memory
effects.
Modelling the signal recordings and studying the effects of memory on the signals, we
have identified certain trends manifestation for the two types of memory that are summarised
to the following points. (a) Both types of memory influence the PSC peaks evolution
(exponential decrease) in cyclic loadings of the same level. (b) Permanent memory
cannot be erased and affects PSC signal permanently and severely. (c) The short
memory has temporary influence on the PSC signal and the impacts on the signal are
milder.
The main properties of the PSC signal, which are affected by the existence of
memory, converge to an inertial attitude of the material to the same stimuli and
they are quite common with the properties of other fracture induced signals (i.e.
AE). Namely, they are the following: (a) The PSC peak evolution over loading
cycles is a changing signal property either in the case of permanent or of temporary
memory, with respect to the time interval between events, especially in the latter case.
(b) The decrease of the dissipated electric energy during cyclic loading tests. (c)
The PSC slower relaxation in each loading, quantified by the relaxation process
parameters evolution. (d) The PSC signal response delay in each loading cycle
increase
The existence of memory effects on the mechanically stimulated electric signal is an
indication that information about the deformation history (paleostresses) of the material
reside inside the material. Under certain conditions such information can be revealed
by analysis of the PSC signal response to specific external mechanical triggering. |
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