Search results for " BEM"
showing 10 items of 39 documents
Strain gradient elasticity within the SGBEM
2014
Frictionless contact-detachment analysis: iterative linear complementarity and quadratic programming approaches.
2012
The object of the paper concerns a consistent formulation of the classical Signorini’s theory regarding the frictionless contact problem between two elastic bodies in the hypothesis of small displacements and strains. The employment of the symmetric Galerkin boundary element method, based on boundary discrete quantities, makes it possible to distinguish two different boundary types, one in contact as the zone of potential detachment, called the real boundary, the other detached as the zone of potential contact, called the virtual boundary. The contact-detachment problem is decomposed into two sub-problems: one is purely elastic, the other regards the contact condition. Following this method…
An Improved Hierarchical ACA Technique for Sound Absorbent Materials
2011
This paper presents an improved adaptive cross approximation (ACA) approach developed in conjunction with the Hierarchical format matrix and the GMRES solver. A novel scheme to generate the cluster tree (based upon preliminary considerations of the prescribed boundary conditions) and an improved ACA algorithm (approximating the system matrix for mixed Robin conditions) are described. The asymptotic smoothness property of a kernel generated by a linear combination of two asymptotic smooth kernels is demonstrated. Numerical results show the new approach to be up to 50% faster than the conventional ACA approach.
A fast BEM for the analysis of plates with bonded piezoelectric patches
2010
In this paper a fast boundary element method for the elastodynamic analysis of 3D structures with bonded piezoelectric patches is presented. The elastodynamic analysis is performed in the Laplace domain and the time history of the relevant quantities is obtained by inverse Laplace transform. The bonded patches are modelled using a semi-analytical state-space variational approach. The computational features of the technique, in terms of required storage memory and solution time, are improved by a fast solver based on the use of hierarchical matrices. The presented numerical results show the potential of the technique in the study of structural health monitoring (SHM) systems.
A fast BEM model for 3D elastic structures with attached piezoelectric sensors
2009
A fast boundary element model for the analysis of three-dimensional solids with cracks and adhesively bonded piezoelectric patches, used as strain sensors, is presented. The piezoelectric sensors, as well as the adhesive layer, are modeled using a 3D state space finite element approach. The piezoelectric patch model is formulated taking into account the full electro-mechanical coupling and embodying the suitable boundary conditions and it is eventually expressed in terms of the interface variables, to allow a straightforward coupling with the underlying host structure, which is modeled through a 3D dual boundary element method, for accurate analysis of cracks. The technique is computational…
Multidomain SBEM analysis of two dimensional elastoplastic-contact problems
2012
The Symmetric Boundary Element Method based on the Galerkin hypotheses has found application in the nonlinear analysis of plasticity and contact-detachment problems, but dealt with separately. In this paper we wants to treat these complex phenomena together. This method works in structures by introducing a subdivision into sub-structures, distinguished into macroelements, where elastic behaviour is assumed, and bem-elements, where it is possible for plastic strains to occur. In all the sub-structures, elasticity equations are written and regularity conditions in weighted (weak) form and/or in nodal (strong) form between boundaries have to be introduced, to attain the solving equation system.
Fast Solution of 3D Elastodynamic Boundary Element Problems by Hierarchical Matrices
2009
In this paper a fast solver for three-dimensional elastodynamic BEM problems formulated in the Laplace transform domain is presented, implemented and tested. The technique is based on the use of hierarchical matrices for the representation of the collocation matrix for each value of the Laplace parameter of interest and uses a preconditioned GMRES for the solution of the algebraic system of equations. The preconditioner is built exploiting the hierarchical arithmetic and taking full advantage of the hierarchical format. An original strategy for speeding up the overall analysis is presented and tested. The reported numerical results demonstrate the effectiveness of the technique.
Effetti del raggio di raccordo al fondo foro nella analisi delle tensioni residue con il metodo della rosetta forata
2007
Il metodo della rosetta forata è una delle tecniche di analisi delle tensioni residue più utilizzati in campo industriale. Il metodo è abbastanza accurato per tensioni costanti, mentre nel caso di tensioni variabili nello spessore del componente esaminato diverse cause di incertezza devono essere attentamente esaminate. Poiché nella valutazione numerica dei coefficienti di influenza il foro è considerato perfettamente cilindrico e privo di raccordo, una sorgente di errore è costituita dal raggio di raccordo al fondo foro. In questa memoria viene studiato l’effetto che il raggio di raccordo ha sulle deformazioni misurate e sulle tensioni calcolate. E’ cosi mostrato come anche piccoli raggi d…
Tappe e testimonianze nella vicenda trentennale di ALEA. Cenni storici e opinioni su un'associazione fra Cafoscarini
2015
In considerazione dei trent’anni dalla fondazione di ALEA, il presente contributo vuole essere occasione per ricostruire l’evoluzione storica di questa realtà. Il breve contributo è incentrato soprattutto sulla ricostruzione delle vicende e delle motivazioni che hanno visto nascere e fiorire l'associazione dei laureati in economia aziendale, intesa come bordo di coltura per le più attuali esperienze di associazionismo fra Cafoscarini. Tale tentativo si riconnette metodologicamente al saggio della sezione terza del presente volume, poiché discende dal medesimo lavoro di ricerca, soffermandosi sulle fonti capaci di illuminare il percorso di ALEA. Nello specifico, affianco ai materiali prodott…
Computational aspects in 2D SBEM analysis with domain inelastic actions
2009
The Symmetric Boundary Element Method, applied to structures subjected to temperature and inelastic actions, shows singular domain integrals. In the present paper the strong singularity involved in the domain integrals of the stresses and tractions is removed, and by means of a limiting operation, this traction is evaluated on the boundary. First the weakly singular domain integral in the Somigliana Identity (S.I.) of the displacements is regularized and the singular integral is transformed into a boundary one using the Radial Integration Method; subsequently, using the differential operator applied to the displacement field, the S.I. of the tractions inside the body is obtained and through…