114 research outputs found
Boundary integral formulation for interfacial cracks in thermodiffusive bimaterials
An original boundary integral formulation is proposed for the problem of a
semi-infinite crack at the interface between two dissimilar elastic materials
in the presence of heat flows and mass diffusion. Symmetric and skew-symmetric
weight function matrices are used together with a generalized Betti's
reciprocity theorem in order to derive a system of integral equations that
relate the applied loading, the temperature and mass concentration fields, the
heat and mass fluxes on the fracture surfaces and the resulting crack opening.
The obtained integral identities can have many relevant applications, such as
for the modelling of crack and damage processes at the interface between
different components in electrochemical energy devices characterized by
multi-layered structures (solid oxide fuel cells and lithium ions batteries).Comment: 43 pages, 9 figure
Multiscale asymptotic homogenization analysis of thermo-diffusive composite materials
In this paper an asymptotic homogenization method for the analysis of
composite materials with periodic microstructure in presence of thermodiffusion
is described. Appropriate down-scaling relations correlating the microscopic
fields to the macroscopic displacements, temperature and mass concentration are
introduced. The effects of the material inhomogeneities are described by
perturbation functions derived from the solution of recursive cell problems.
Exact expressions for the overall elastic and thermodiffusive constants of the
equivalent first order thermodiffusive continuum are derived. The proposed
approach is applied to the case of a two-dimensional bi-phase orthotropic
layered material, where the effective elastic and thermodiffusive properties
can be determined analytically. Considering this illustrative example and
assuming periodic body forces, heat and mass sources acting on the medium, the
solution performed by the first order homogenization approach is compared with
the numerical results obtained by the heterogeneous model.Comment: 40 pages, 13 figure
Effective elastic properties of planar SOFCs: A non-local dynamic homogenization approach
The focus of the article is on the analysis of effective elastic properties
of planar Solid Oxide Fuell Cell (SOFC) devices. An ideal periodic
multi-layered composite (SOFC-like) reproducing the overall properties of
multi-layer SOFC devices is defined. Adopting a non-local dynamic
homogenization method, explicit expressions for overall elastic moduli and
inertial terms of this material are derived in terms of micro-fluctuation
functions. These micro-fluctuation function are then obtained solving the cell
problems by means of finite element techniques. The effects of the temperature
variation on overall elastic and inertial properties of the fuel cells are
studied. Dispersion relations for acoustic waves in SOFC-like multilayered
materials are derived as functions of the overall constants, and the results
obtained by the proposed computational homogenization approach are compared
with those provided by rigorous Floquet-Boch theory. Finally, the influence of
the temperature and of the elastic properties variation on the Bloch spectrum
is investigated
Integration algorithms of elastoplasticity for ceramic powder compaction
Inelastic deformation of ceramic powders (and of a broad class of rock-like
and granular materials), can be described with the yield function proposed by
Bigoni and Piccolroaz (2004, Yield criteria for quasibrittle and frictional
materials. Int. J. Solids and Structures, 41, 2855-2878). This yield function
is not defined outside the yield locus, so that 'gradient-based' integration
algorithms of elastoplasticity cannot be directly employed. Therefore, we
propose two ad hoc algorithms: (i.) an explicit integration scheme based on a
forward Euler technique with a 'centre-of-mass' return correction and (ii.) an
implicit integration scheme based on a 'cutoff-substepping' return algorithm.
Iso-error maps and comparisons of the results provided by the two algorithms
with two exact solutions (the compaction of a ceramic powder against a rigid
spherical cup and the expansion of a thick spherical shell made up of a green
body), show that both the proposed algorithms perform correctly and accurately.Comment: 21 pages. Journal of the European Ceramic Society, 201
- …