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Abstract: In this methodological study, delamination phenomena of Carbon Fiber Reinforced Polymer (CFRP) strips from masonry pillars were investigated on the basis of single-lap shear tests. The masonry pillar considered in this case was constituted of three historical bricks, derived from a XVII century rural building. The bricks were bonded by a high strength mortar recently proposed for the restoration process. To follow the specimen response up to collapse, the test was controlled by a clip gauge located at the anchorage of the reinforcement strip. The conventional experimental information, concerning the overall reaction force and relative displacements provided by point sensors (LVDTs and clip gauge), were herein enriched with no-contact, kinematic full-field measurements provided by 2D Digital Image Correlation (2D DIC). Special care was devoted to improve the precision of the optical measurement, which included correction of the effects owing to the lens distortion and to lack of coplanarity between the camera sensor and the monitored flat surface. The overall accuracy was assessed through laboratory benchmarking tests. Moreover, an advanced three-dimensional mechanical model based on nonlinear finite elements was developed under the simplifying assumption of perfect adhesion. This model was adopted to describe bulk damage inside the heterogeneous specimen and to correlate it to the macroscopic response and surface measurements. Coherence between the above mentioned sources of information and the predictions provided by the advanced finite element model were critically discussed. [Copyright &y& Elsevier]

Abstract: A chemo-thermo-damage model is proposed to simulate the swelling and the deterioration of local stiffness and strength in concrete due to the alkali-aggregate reaction (AAR). Concrete affected by AAR is conceived as a two-phase heterogeneous material constituted by the expanding gel and by the homogenized concrete skeleton. The micro-cracking produced by the gel expansion is taken into account by means of an isotropic damage model based on the definition of two scalar damage variables, one for stress states of prevailing tension and the other for compression. The developed model is validated on the basis of multiaxial accelerated laboratory tests performed on small specimens of reactive concrete, and documented in the recent literature. The model has been implemented in the finite-element code Abaqus and has been used to simulate the response of two concrete gravity dams subjected to service loading and to chemo-physical deterioration. The obtained results show that the developed model can be used to predict the damage evolution within the dams and the consequent progressive reduction of their bearing capacity. [Copyright &y& Elsevier]

Abstract: A methodology is presented suitable to identify properties of single phases, locally at the microscale, within a heterogeneous periodic material, on the basis of measurements at the macroscale and homogenization techniques. Reference is made to periodically perforated steel sheets, regarded as a prototype of a ductile composite material with periodic microstructure. The proposed method might be applied to industrial situations where the fabrication process of a composite material alters the mechanical properties of individual phases or constituents. Experimental data are obtained through monotonic uniaxial tensile tests at the macroscale. An elastic–plastic hardening model is attributed to the matrix material. Weighted least-squares, Monte Carlo simulations and sequential non-linear Kalman filters are employed to solve the parameter identification problem in a stochastic context, and comparative assessments of diverse strategies of inverse analysis are presented, as to accuracy and computational effectiveness. [Copyright &y& Elsevier]

Abstract: The identification of the parameters contained in an elastic–plastic material model, apt to simulate steady-state ratchetting, is studied herein with reference to cyclic biaxial tests on cylindrical compact specimens. The material considered is steel employed for high-speed train wheels. In order to generate strain states close to those expected in severe service conditions due to wheel-rail rolling-sliding contact, out-of-phase tension–torsion unsymmetric cycles are applied in laboratory tests. The experiments are simulated by conventional finite elements and Chaboche model with nonlinear kinematic hardening. The material parameters are identified through a deterministic, batch (non-sequential) inverse analysis in two stages (genetic and first-order algorithms) in view of the peculiar constraints in the minimization problem. This study leads to the following conclusions of practical use: multiaxial ratchetting tests are desirable to characterize cyclic material behavior in the industrial context considered; compact (instead of thin-walled tubular) specimen tests, combined with parameter identification by inverse analysis, exhibit the advantages of cost effectiveness and of small size needed to assess material properties locally. [Copyright &y& Elsevier]

It is shown that partial incoherence, in the form of stochastic phase noise, of a Langmuir wave in an unmagnetized plasma gives rise to a Landau-type damping. Starting from the Zakharov equations, which describe the nonlinear interaction between Langmuir and ion-acoustic waves, a kinetic equation is derived for the plasmons by introducing the Wigner–Moyal transform of the complex Langmuir wave field. This equation is then used to analyze the stability properties of small perturbations on a stationary solution consisting of a constant amplitude wave with stochastic phase noise. The concomitant dispersion relation exhibits the phenomenon of Landau-like damping. However, this damping differs from the classical Landau damping in which a Langmuir wave, interacting with the plasma electrons, loses energy. In the present process, the damping is non-dissipative and is caused by the resonant interaction between an instantaneously-produced disturbance, due to the parametric interactions, and a partially incoherent Langmuir wave, which can be considered as a quasi-particle composed of an ensemble of partially incoherent plasmons. [Copyright &y& Elsevier]