1,721,044 research outputs found
A fracture evolution procedure for cohesive materials
No full textThe present paper deals with the problem of the evaluation of the softening mechanical response of cohesive materials under tensile loading. A nonlinear fracture mechanics approach is adopted. A new numerical procedure is developed to study the evolution of the crack processes for 2D solids. The proposed algorithm is based on the derivation and use of the fracture resistance curve, i.e., the R-curve, and it takes into account the presence of the process zone at the crack tip. In fact, assuming a nonlinear constitutive law for the cohesive interface, the procedure is able to determine the R-curve, the process zone length and hence the mechanical response of any material and structure. Numerical applications are developed for studying the damage behavior of a infinite solid with a periodic crack distribution. Size effects are investigated and the ductile-brittle transition behavior for materials characterized by the same crack density is studied. The results obtained adopting the proposed procedure are in good accordance with the results recovered through nonlinear step by step finite element analyses. Moreover, the developed computations demonstrate that the procedure is simple and efficient
Micromechanical damage of FRC: Modeling and parametric analyses
No full textIn the present paper the nonlinear response of fiber reinforced concrete
(FRC) material is investigated in the framework of the micromechanics
of heterogeneous materials. In fact, FRC is regarded as
a composite with fibers embedded into a concrete matrix. A 2D
unit cell, with a single fiber, subjected to tensile strain in the fiber
direction is considered. To model the progressive FRC damage, i.e.
the fiber debonding and pull-out and the concrete cracking, fibermatrix
elastoplastic and matrix-matrix damaging interfaces are
introduced. Then, numerical analyses are performed to investigate
the interaction between the fiber debonding and the crack propagation,
and to derive the overall macroscopic response of the FRC
composite material. The numerical results obtained allow to verify
the accurancy of the model adopted for the computation and its
limits. Furthermore, several different analyses are performed in
order to investigate on the role played by the fundamental material
and geometric parameters
Multiscale analysis for layered composite SMA plates
No full textAim of the present work is to analyse of smart laminates, obtained as staking sequence of fiber-reinforced composite laminae and composite SMA layers developing a full multiscale approach. In particular, a nonlinear MITC4 laminate finite element, based on the first-order shear deformation theory, is developed. The SMA layer constitutive relationship is determined solving at each nonlinear iteration of each time step for each integration Gauss point a nonlinear homogenization problem
Computational Modeling of FRP Reinforced Cementitious Beams
No full textIn the present paper, a one-dimensional elastoplastic-damage
model for the analysis of the mechanical response of beams constituted by cementitious materials, i.e., concrete or masonry, strengthened by fiber reinforced polymers (FRP), is developed. The analysis is performed for a typical section, representing an elementary part of beam characterized by the finite length, defined as the distance between two fractures. A thermodynamically consistent model is
proposed; it takes into account the different behavior in tension and in compression of the cohesive materials.
The governing equations are derived and a numerical procedure is developed. It is based on thearc-length method, withinan implicit Euler algorithm for the time integration. An accurate choice of the control parameters is performed. The finite step nonlinear problem is solved adopting a Newton-Raphson scheme within a predictor-corrector procedure.
Some numerical examples are developed in order to analyze
the non trivial axial and bending behavior of reinforced concrete and masonry beams and to assess the efficiency of the proposed pmedure. Comparisons with analytical solutions are reported
A three phase thermo-mechanical constitutive model for shape memory alloys
No full textThe aim of the paper is to present a one-dimensional model for shape memory alloys (SMAs)
able to take into account the pseudo-elastic and shape memory effects, the martensite reorientation, the
different elastic properties of the SMA phases and the different behavior in tension and compression of the
material. Analytical solutions are presented to solve the axial problem of a SMA beam
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