Search results for " Boundary"

The late Carnian Rhaetian Succession at Pizzo Mondello (Sicani Mountains).

2010

Sedimentology and biostratigraphy of a peritidal succession across the Triassic/Jurassic boundary: Monte Sparagio, north western Sicily

2016

A 490 m thick section of shallowing upward peritidal cycles spanning the Triassic-Jurassic boundary is exposed along the northern slope of Mount Sparagio in the San Vito Lo Capo Peninsula (Western Sicily). A detailed microfacies analysis allowed defining the aspects of cyclic sedimentation of this section and especially the stratigraphic occurrence patterns of benthic foraminifera and algae across the T/J boundary. The lower part of cycles commonly shows medium to low energy subtidal facies, typical of the inner lagoon of the carbonate platform. Subtidal facies such as coral bafflestone in some cycles suggest more open lagoonal conditions (patch reefs), while some higher energy layers such …

Correlation between extinction pattern and δ13C fluctuations across the Triassic Jurassic boundary in shallow water settings: a proxy for the present…

2018

With the aim to assess the possible influence of the carbon variations on the benthic communities across the Triassic Jurassic boundary we have carried out sedimentological, biostratigraphic and stable isotope studies on an about 220 m thick peritidal section cropping out in Northwestern Sicily. The subtidal facies of the lower and middle part of this succession show the common occurrence of large and thick megalodontids and a benthic foraminiferal assemblage with Triasina hantkeni and Aulotuortids that supports a Rhaetian age. In the lower part of the succession, a significative biotic perturbation is evidenced by a sudden reduction of the size, shell thickness and abundance of the large m…

Paleokarstic overprint on the Panormide Carbonate Platform (Sicily)around the T/J boundary

2011

Modellazione lineare delle grandezze di contorno nell'analisi per sottostrutture delle piastre inflesse via SBEM

2009

On the transient response of actively repaired damaged structures by the boundary element method

2010

The transient fracture mechanics behavior of damaged structures repaired through active piezoelectric patches is presented in this paper. The analyses have been performed through a boundary element code implemented in the framework of piezoelectricity to take account of the coupling between the elastic and the electric fields, which represents the peculiar feature of piezoelectric media. The multi-domain technique has been also involved to assemble the host structures and the active patches and to model the cracks. Moreover, the patches have been considered elastically bonded to the damaged structure by means of a zero thickness adhesive layer. This has been achieved through the implementat…

Dual Boundary Element Method for fatigue crack growth: implementation of the Richard’s criterion

2013

A new criterion for fatigue crack growth, whose accuracy was previously tested in the literature with the Finite Element Method, is here adopted with a Dual Boundary Element formulation. The fatigue crack growth of an elliptical inclined crack, embedded in a three dimensional cylindrical bar, is analyzed. In this way in addition to the propagation angle estimated by the Sih’s criterion, it is possible to take into account a twist propagation angle. The two propagation criteria are compared in terms of shape of the propagated crack and in terms of SIFs along the crack front. The efficiency of the Dual Boundary Element Method in this study is highlighted.

Virtual Element based formulations for computational materials micro-mechanics and homogenization

2021

In this thesis, a computational framework for microstructural modelling of transverse behaviour of heterogeneous materials is presented. The context of this research is part of the broad and active field of Computational Micromechanics, which has emerged as an effective tool both to understand the influence of complex microstructure on the macro-mechanical response of engineering materials and to tailor-design innovative materials for specific applications through a proper modification of their microstructure. While the classical continuum approximation does not account for microstructural details within the material, computational micromechanics allows detailed modelling of a heterogeneous…

Effects of voids and flaws on the mechanical properties and on intergranular damage and fracture for polycrystalline materials

2013

It is widely recognized that the macroscopic material properties depend on the features of the microstructure. The understanding of the links between microscopic and macroscopic material properties, main topic of Micromechanics, is of relevant technological interest, as it may enable the deep understanding of the mechanisms governing materials degradation and failure. Polycrystalline materials are used in many engineering applications. Their microstructure is determined by distribution, size, morphology, anisotropy and orientation of the crystals. It worth noting that also the physical-chemical properties of the intergranular interfaces, as well as the presence of micro-imperfections within…

Computational modelling of brittle failure in polycrystalline materials using cohesive-frictional grain-boundary elements

2014

A 3D grain-level formulation for the study of brittle failure in polycrystalline microstructures is presented. The microstructure is represented as a Voronoi tessellation and the boundary element method is used to model each crystal of the aggregate. The continuity of the aggregate is enforced through suitable conditions at the intergranular interfaces. The grain-boundary model takes into account the onset and evolution of damage by means of an irreversible linear cohesive law, able to address mixed-mode failure conditions. Upon interface failure, a non-linear frictional contact analysis is introduced for addressing the contact between micro-crack surfaces. An incremental-iterative algorith…