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001-es BibID:BIBFORM078785
035-os BibID:(cikkazonosító)20170393 (WoS)000451219600008 (Scopus)85057260752
Első szerző:Kun Ferenc (fizikus)
Cím:Effect of disorder on the spatial structure of damage in slowly compressed porous rocks / Ferenc Kun, Gergő Pál, Imre Varga, Ian G. Main
Dátum:2019
ISSN:1364-503X
Megjegyzések:Faults and damage zone properties control a range of important phenomena, from the hydraulic properties of underground reservoirs to the physics of earthquakes on a larger scale. Here, we investigate the effect of disorder of porous rocks on the spatial structure of damage emerging under compression. Model rock samples are numerically generated by sedimenting particles where the amount of disorder is controlled by the particle size distribution. To obtain damage bands with a sufficiently large length along axis, we performed simulations of ?Brazilian'-type compression tests of cylindrical samples. As failure is approached, damage localization leads to the formation of two conjugate shear bands. The orientation angle of bands to the loading direction increases with disorder, implying a decrease in the internal coefficient of friction. The width of the damage band scales as a power law of the degree of disorder. Inside the damage band, the sample is crushed into a large number of pieces with a power law mass distribution. The shape of fragments undergoes a crossover at a disorder-dependent size from the isotropy of small pieces to the anisotropic flattened form of the large ones. The results provide important constraints in understanding the role of disorder in geological fractures.
Tárgyszavak:Műszaki tudományok Informatikai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
folyóiratcikk
damage band
fault
compression
fragmentation
disorder
discrete element simulation
Megjelenés:Philosophical Transactions Of The Royal Society A-Mathematical Physical And Engineering Sciences. - 377 : 2136 (2019), p. 1-14. -
További szerzők:Pál Gergő (1987-) (fizikus) Varga Imre (1979-) (fizikus, informatikus) Main, Ian G.
Pályázati támogatás:EFOP-3.6.1-16-2016-00022
EFOP
NKFIH K-16 K 119967
egyéb
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2.

001-es BibID:BIBFORM069501
035-os BibID:(Scopus)84996865562 (WoS)000388278300006
Első szerző:Pál Gergő (fizikus)
Cím:Fragmentation and shear band formation by slow compression of brittle porous media / Gergő Pál, Zoltán Jánosi, Ferenc Kun, Ian G. Main
Dátum:2016
ISSN:2470-0045 2470-0053
Megjegyzések:Localized fragmentation is an important phenomenon associated with the formation of shear bands and faults ingranular media. It can be studied by empirical observation, by laboratory experiment, or by numerical simulation.Here we investigate the spatial structure and statistics of fragmentation using discrete element simulations of thestrain-controlled uniaxial compression of cylindrical samples of different finite size. As the system approachesfailure, damage localizes in a narrow shear band or synthetic fault "gouge" containing a large number of poorlysorted noncohesive fragments on a broad bandwidth of scales, with properties similar to those of natural andexperimental faults. We determine the position and orientation of the central fault plane, the width of the shearband, and the spatial and mass distribution of fragments. The relative width of the shear band decreases as apower law of the system size, and the probability distribution of the angle of the central fault plane converges toaround 30 degrees, representing an internal coefficient of friction of 0.7 or so. The mass of fragments is powerlaw distributed, with an exponent that does not depend on scale, and is near that inferred for experimental andnatural fault gouges. The fragments are in general angular, with a clear self-affine geometry. The consistencyof this model with experimental and field results confirms the critical roles of preexisting heterogeneity, elasticinteractions, and finite system size to grain size ratio on the development of shear bands and faults in porousmedia.
Tárgyszavak:Természettudományok Fizikai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
folyóiratcikk
shear band
porous material
discrete element model
quasi-static fragmentation
Megjelenés:Physical Review E. - 94 : 5 (2016), p. 053003-1 - 053003-8. -
További szerzők:Jánosi Zoltán Kun Ferenc (1966-) (fizikus) Main, Ian G.
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3.

001-es BibID:BIBFORM069498
035-os BibID:(Scopus)84963599543 (WoS)000373108700005
Első szerző:Pál Gergő (fizikus)
Cím:Record-breaking events during the compressive failure of porous materials / Gergő Pál, Frank Raischel, Sabine Lennartz-Sassinek, Ferenc Kun, Ian G. Main
Dátum:2016
ISSN:2470-0045 2470-0053
Megjegyzések:An accurate understanding of the interplay between random and deterministic processes in generating extremeevents is of critical importance in many fields, from forecasting extreme meteorological events to the catastrophicfailure of materials and in the Earth. Here we investigate the statistics of record-breaking events in the time seriesof crackling noise generated by local rupture events during the compressive failure of porous materials. Theevents are generated by computer simulations of the uniaxial compression of cylindrical samples in a discreteelement model of sedimentary rocks that closely resemble those of real experiments. The number of recordsgrows initially as a decelerating power law of the number of events, followed by an acceleration immediatelyprior to failure. The distribution of the size and lifetime of records are power laws with relatively low exponents.We demonstrate the existence of a characteristic record rank k ? , which separates the two regimes of the timeevolution. Up to this rank deceleration occurs due to the effect of random disorder. Record breaking thenaccelerates towards macroscopic failure, when physical interactions leading to spatial and temporal correlationsdominate the location and timing of local ruptures. The size distribution of records of different ranks has auniversal form independent of the record rank. Subsequences of events that occur between consecutive recordsare characterized by a power-law size distribution, with an exponent which decreases as failure is approached.High-rank records are preceded by smaller events of increasing size and waiting time between consecutive eventsand they are followed by a relaxation process. As a reference, surrogate time series are generated by reshufflingthe event times. The record statistics of the uncorrelated surrogates agrees very well with the correspondingpredictions of independent identically distributed random variables, which confirms that temporal and spatialcorrelation in the crackling noise is responsible for the observed unique behavior. In principle the results couldbe used to improve forecasting of catastrophic failure events, if they can be observed reliably in real time.
Tárgyszavak:Természettudományok Fizikai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
folyóiratcikk
shear band formation
earthquake
macroscopic failure
discrete element model
Megjelenés:Physical Review E. - 93 : 3 (2016), p. 033006-1 - 033006-10. -
További szerzők:Raischel, Frank Lennartz-Sassinek, Sabine Kun Ferenc (1966-) (fizikus) Main, Ian G.
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