97 research outputs found
Graded damage in quasi-brittle solids
A novel approach to damage modeling for quasi-brittle solids is presented relying upon a differential inclusion that is closely related to the one of implicit gradient models. The proposed formulation naturally fits in the so-called nonlocal standard approach, whereby the framework of generalized standard materials is extended to include gradients of internal variables to account for the physics of the fracture phenomenon in a regularized sense, that is, via extended constitutive equations in which a length scale parameter brings to the macro level information about material microstructure. This concept is fully embodied into the present approach to quasi-brittle fracture, whereby progressive damage occurs in layers of finite thickness where the gradient of damage is bounded and a fully damaged region is understood as a fracture with no ambiguity. Key to the effective implementation of the model are the choice of two constitutive functions and the implicit tracking of regions in a state of progressive damage via Lagrange multipliers acting on internal constraints. The ideas are developed for a general Cauchy continuum and representative numerical simulations are included that demonstrate the model capabilities
Evaluation of Conjugate Stresses to Sethâs Strain Tensors
An explicit expression providing the symmetric stress tensor T(m) conjugate to the Sethâs strain measure E(m) for each integer m unequal 0 is presented. The result is obtained by exploiting an original approach for the solution of a tensor equation in the unknown T(m) expressed as function of the powers of the right stretch tensor U. The proposed approach is based upon the spectral decomposition of U and exploits some peculiar features of the set of fourth-order tensors obtained as linear combination of dyadic and square tensor products of the eigenprojectors of U. On the basis of such properties it is shown that the unknown T(m) can be expressed in the given reference frame as linear combination of six fourth-order tensors scaled through coefficients which are rational functions of the eigenvalues of U
Image Correlation-Based Identification of Fracture Parameters for Structural Adhesives
We consider the identification problem of a cohesive model using kinematic full-field data obtained via digital image correlation during the fracture test of an adhesive joint. A criterion is presented for selecting measurements that exhibit optimal features for identification purposes. The proposed selection scheme is constructed using the sensitivity information and its performances are evaluated at varying noise-to-signal ratio
Critical Behavior of a Three-State Potts Model on a Voronoi Lattice
We use the single-histogram technique to study the critical behavior of the
three-state Potts model on a (random) Voronoi-Delaunay lattice with size
ranging from 250 to 8000 sites. We consider the effect of an exponential decay
of the interactions with the distance,, with , and
observe that this system seems to have critical exponents and
which are different from the respective exponents of the three-state Potts
model on a regular square lattice. However, the ratio remains
essentially the same. We find numerical evidences (although not conclusive, due
to the small range of system size) that the specific heat on this random system
behaves as a power-law for and as a logarithmic divergence for
and Comment: 3 pages, 5 figure
Nouvelles mĂ©thodes dâintĂ©gration pour traiter la plasticitĂ© en X-FEM
La mĂ©thode dâintĂ©gration utilisĂ©e classiquement en X-FEM fait dĂ©pendre la position des points dâintĂ©gration de la position de la fissure, ce qui convient difficilement Ă lâĂ©tude de la propagation dâune fissure dans un milieu plastifiĂ©. En effet, des Ă©tapes de projection de champs sont alors nĂ©cessaires. Afin de sâen affranchir, cette contribution propose deux approches alternatives. La premiĂšre sâappuie sur les schĂ©mas dâintĂ©gration standards tandis que la seconde propose de diffĂ©rencier les points dâintĂ©gration des points oĂč le comportement est Ă©valuĂ©. Les mĂ©thodes proposĂ©es se limitent aux cas des interfaces
The 2009 LâAquila (central Italy) MW6.3 earthquake: Main shock
A MW
6.3 earthquake struck on April 6, 2009 the
Abruzzi region (central Italy) producing vast damage in the
LâAquila town and surroundings. In this paper we present
the location and geometry of the fault system as obtained
by the analysis of main shock and aftershocks recorded
by permanent and temporary networks. The distribution of
aftershocks, 712 selected events with ML 2.3 and 20 with
ML 4.0, defines a complex, 40 km long, NW trending
extensional structure. The main shock fault segment extends
for 15â18 km and dips at 45 to theSW, between 10 and 2 km
depth. The extent of aftershocks coincides with the surface
trace of the Paganica fault, a poorly known normal fault
that, after the event, has been quoted to accommodate the
extension of the area.We observe a migration of seismicity to
the north on an echelon fault that can rupture in future large
earthquakes.PublishedL183083.1. Fisica dei terremotiJCR Journalreserve
A practical approach for the separation of interfacial toughness and structural plasticity in a delamination growth experiment
Rapid response to the earthquake emergency of May 2012 in the Po Plain, northern Italy
No abstrac
Emergenza âLâAquila2009â: la campagna di acquisizione dati della Rete Sismica Mobile stand-alone del Centro Nazionale Terremoti
Il 6 aprile 2009 (3.32 locali) un terremoto di Mw 6,3 ha colpito la regione Abruzzo (Italia centrale)
producendo un enorme danno alla cittĂ de L'Aquila e ai paesi limitrofi causando circa 300 morti e 60.000
senza fissa dimora.
A seguito di questo evento sismico, la struttura di Pronto Intervento dellâINGV (Istituto Nazionale di
Geofisica e Vulcanologia), si Ăš rapidamente attivata installando in area epicentrale due reti sismiche
temporanee (Re.Mo.Tel. in real-time e Re.Mo. in stand-alone) ed il Centro Operativo Emergenza Sismica.
In questo lavoro presentiamo come si eâ svolta la campagna sismica della Re.Mo., avente lâobiettivo di
acquisire dati di alta qualitĂ e dettaglio per studiare le sorgenti sismiche, lâevoluzione spazio temporale della
sequenza e caratterizzare attraverso la microsismicitaâ le strutture di faglia attivate ed le proprietaâ del mezzo
circostante. Saranno descritte nel dettaglio lâinstallazione compiuta a poche ore dal mainshock, il suo
sviluppo legato allâevoluzione della sequenza sismica, fino alla sua dismissione nel Marzo 2010.Istituto Nazionale di Geofisica e VulcanologiaPublished1.1. TTC - Monitoraggio sismico del territorio nazionaleope
Emergenza âLâAquila2009â: la campagna di acquisizione dati della Rete Sismica Mobile stand-alone del Centro Nazionale Terremoti
Il 6 aprile 2009 (3.32 locali) un terremoto di Mw 6,3 ha colpito la regione Abruzzo (Italia centrale)
producendo un enorme danno alla cittĂ de L'Aquila e ai paesi limitrofi causando circa 300 morti e 60.000
senza fissa dimora.
A seguito di questo evento sismico, la struttura di Pronto Intervento dellâINGV (Istituto Nazionale di
Geofisica e Vulcanologia), si Ăš rapidamente attivata installando in area epicentrale due reti sismiche
temporanee (Re.Mo.Tel. in real-time e Re.Mo. in stand-alone) ed il Centro Operativo Emergenza Sismica.
In questo lavoro presentiamo come si eâ svolta la campagna sismica della Re.Mo., avente lâobiettivo di
acquisire dati di alta qualitĂ e dettaglio per studiare le sorgenti sismiche, lâevoluzione spazio temporale della
sequenza e caratterizzare attraverso la microsismicitaâ le strutture di faglia attivate ed le proprietaâ del mezzo
circostante. Saranno descritte nel dettaglio lâinstallazione compiuta a poche ore dal mainshock, il suo
sviluppo legato allâevoluzione della sequenza sismica, fino alla sua dismissione nel Marzo 2010
- âŠ