1,721,354 research outputs found
Consistent derivation of the constitutive algorithm for plane stress isotropic plasticity. Part II: Computational issues
No full textThe implementation of the projected algorithm and of the consistent tangent tensor for general isotropic three-invariant elastoplastic models under plane stress conditions discussed in Part I of this paper [Valoroso, N., Rosati, L., 2008. Consistent derivation of the constitutive algorithm for plane stress isotropic plasticity. Part I: Theoretical formulation. International Journal of Solids and Structures, doi: 10.1016/j.ijsolstr.2008.08.012.] is addressed. The connections between the general three-dimensional case and the plane stress problem are analyzed in detail and an algorithmic treatment taking full advantage of the isotropic properties of the model is presented. In particular, intrinsic (matrix-free) expressions are provided for all steps of the stress computation scheme that allow one to carry out the numerical implementation in a way that is completely independent from the matrix representations. The numerical performances of the present solution scheme are evaluated through representative numerical examples
Phytosociological study of fringe communities of Sardinia (Italy)
No full textQuestion: This study represents the first contribution to the description and ecological characterization of fringe communities of Sardinia (Italy), and aimed: 1) to describe Sardinian fringe communities from a floristic vegetational point ; 2) to provide a syntaxonomic scheme, confirming or not the applicability of the most recent framework, proposed at the European scale, also in a Mediterranean insular context (Sardinia); 3) to verify if there is a correspondence among fringe communities and potential natural vegetation in the study area. Study area: Sardinia, the second largest island of the Mediterranean basin (Italy). Methods: 65 phytosociological plots realized using the Braun-Blanquet approach; for each of them, bioclimatic indices were derived from the available Bioclimatic map of Sardinia; Raunki??r life-forms were considered as species functional traits. Furthermore, by using Ellenberg Indicator Values (EIVs) we calculated for each relev?? an abundance-weighted mean indicator value. Main vegetation types were identified through a Hierarchical Cluster Analysis (HCA) and NMDS ordination. A permutational multivariate analysis of variance was used to test the overall significance in EIVs distribution differences among the clusters obtained from HCA. Results: we found a total amount of 139 vascular plant species. Hierarchical clustering detected the presence of seven interpretable clusters, well differentiated in terms of floristic composition, geographic distribution, bioclimatic characters and EIVs, and in terms of their inclusion in different vegetation series. Conclusions: we describe 5 new associations, four of them included in the new alliance Digitalido purpureae-Pteridion aquilini (Melampyro-Holcetalia mollis order, Trifolio-Geranietea sanguinei class), clearly differentiated with respect to other alliances described from both the eastern and the western side of the Tyrrhenian Sea. Another new association was referred to the Epilobietea angustifolii class (Galio-Alliarietalia order)
Per una didattica speciale di qualità: Dalla conoscenza del deficit all’intervento inclusivo
No full textEvaluation of conjugate stresses to Seth’s strain tensors
No full textAn explicit expression providing the symmetric stress tensor T(m) conjugate to the Seth’s strain measure
E(m) for each integer m 6= 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
Classification and modeling of uniaxial rate-independent hysteresis phenomena: some preliminary results
No full textRepetitive manual operations in the dairy sector: analyses and criteria for intervention
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Computational analysis of isotropic plasticity models
No full textThe implementation of plasticity models with general isotropic yield surfaces is discussed. The computation of the return map solution and the algorithm
linearization are carried out by suitably exploiting the isotropic character of the elastic constitution and of the yield function; the consistent tangent tensor is given an intrinsic explicit representation and the relevant coefficients are provided. It is also addressed the implementation of the constitutive algorithm in the subspace defined by the plane stress condition. This is obtained only by specializing the three-dimensional formulation to a two-dimensional ambient space, with the result that the structure of the return mapping scheme and the formal expression of the consistent tangent tensor are preserved. The effectiveness of the approach is demonstrated by means of representative numerical simulations
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