Roberto Fedele

• Associate Prof., Habil Full prof. , Engineer, PhD
• Professor (Associate) at Politecnico di Milano

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 stren...

In this study, reference is made to a mixed numerical-experimental methodology proposed in Fedele et al. (J Mech Physics Solids 57(7):1003–1016, 2009 ), based on full-field kinematic measurements at the micro- scale provided by 2D Digital Image Correlation. The aim was to estimate mechanical properties of joints or interfaces in industrial manufact...

In this study, we analyzed the problem of a compact furnace, to be used for in situ experiments in a cone-beam X-ray microtomography commercial system. The design process was accomplished and outlined through its main steps, until the realization of a prototype. The furnace was conceived to carry out wettability experiments at temperatures up to 70...

In this study, some pioneering contributions, envisaged in theworks of Gabrio Piola, were developed through tools of the modern differential geometry and applied to the second gradient continua. Part I introduced the variational approach for the equilibrium problem according to the first gradient theory and exploited differential geometric perspect...

The clinical challenge of percutaneous coronary interventions (PCI) is highly dependent on the recognition of the coronary anatomy of each individual. The classic imaging modality used for PCI is angiography, but advanced imaging techniques that are routinely performed during PCI, like optical coherence tomography (OCT), may provide detailed knowle...

Background and Objectives: Periodontal therapy aims to arrest the progression of periodontal diseases and possibly to regenerate the periodontal apparatus. To shift healing from repair to regeneration, the blood clot that fills the periodontal defect and remains in contact with structures such as tooth root, mucosa and bone needs to be stable, whic...

The expression of the elastic energy, postulated for a given material, specifies through the principle of virtualwork which external loadings turn out to be admissible. For the elastic bodies, the energy of which dependson the gradients of the placement higher than (𝐻 + 1) (or, equivalently, on the derivatives of the deformationgradient higher than...

In this paper, an extension of the Timoshenko model for plane beams is outlined, with the aim of describing, under the assumption of small displacements and strains, a class of dissipative mechanisms observed in cementitious materials. In the spirit of micromorphic continua, the modified beam model includes a novel kinematic descriptor, conceived a...

Starting from the seminal works of Toupin, Mindlin and Germain, a wide class of generalized elastic models have been proposed via the principle of virtual work, by postulating expressions of the elastic energy enriched by additional kinematic descriptors or by higher gradients of the placement. More recently, such models have been adopted to descri...

In this communication some preliminary results are outlined, concerning the design of a small furnace for in situ testing by X-ray computed microtomography. The furnace was conceived to carry out wettability experiments for sessile droplets of molten metal alloys, with a few millimeters diameter, on a thin ceramic substrate, at temperatures close t...

In this study some results of a wide numerical campaign were discussed, concerning shear tests on masonry triplets strengthened by means of Fiber-Reinforced Polymer (FRP) strips. Two different configurations were considered for the samples, at varying the orientation of the brick units (as "soldier" or "sailor"), with the reinforcement strips glued...

Permeable pavement systems provide rainwater temporary storage promoting on-site stormwater management in areas that otherwise would generate runoff. The pavement surface manages runoff peak flow by infiltrating promptly rainwater and function as a filter, retaining particulate matter that accumulates on the surface. When acceptable for the site co...

In this paper Piola transformations are found that relate the Eulerian and Lagrangian external loads which third gradient continua can sustain. As shown by Gabrio Piola and Paul Germain, the most effective postulation scheme in mechanics is based on the principle of virtual work and therefore continuum mechanics must be mathematically founded based...

In this communication the problem of transforming the equilibrium equations from the Eulerian to the Lagrangian form is discussed with reference to materials governed by second-gradient energy densities. In particular, novel theoretical achievements are outlined, which represent intermediate steps to attain the purpose: the transformation of edge v...

Il presente volume, destinato agli allievi dei corsi in ingegneria, costituisce una guida per lo studio dei temi fondamentali di Scienza delle Costruzioni. Con un linguaggio che cerca di coniugare semplicità e rigore, il lettore viene accompagnato alla riscoperta degli strumenti algebrici e differenziali necessari per una corretta formulazione dei...

Numerical simulations of several planar failure modes of masonry structures are presented, based on the model and solving code from a recent hemivariational block-based model inspired from granular micromechanics (Tran et al. [33]). The numerical tests include a comparison with literature results for a constant shearing load, a parametric study of...

In this study, diverse typologies of external actions are outlined, which turn out to be admissible for the third-gradient modeling of elastic materials. It is shown how such loading, when prescribed over the boundary surface, along the border edges and at the wedges of a deformable body in the Eulerian configuration, can be transformed into the La...

This paper outlines the variational derivation of the Lagrangian equilibrium equations for the third-gradient materials, stemming from the minimization of the total potential energy functional, and the selection of suitable dual variables to represent the inner work in the Eulerian configuration. Volume, face, edge and wedge contributions were prov...

After the wide premise of Part I, where the equations for Cauchy's continuum were retrieved through the energy minimization and some differential geometric perspectives were specified, the present paper as Part II outlines the variational derivation of the equilibrium equations for second gradient materials and their transformation from the Euleria...

Systems of diffusion-reaction PDEs are widely applied in science and engineering to describe space and time evolution of individual entities whose cross interactions compete with their diffusion. In particular, such equations are utilized to model chem- ical species, increasing or decreasing their concentrations according to specific mutual interac...

In this communication reference was made to PolyLactic Acid products of 30 printing by Fused Filament Fabrication technique. To assess the fracture behavior of such manufactured parts, consistently with their transversal isotropy and brittle behavior, a modified Arcan fixture was proposed, allowing one to easily generate mixed mode loading conditio...

In this communication reference was made to the inverse problem of detecting displacement fields by optically monitoring through a single camera the in plane deformation process of a flat domain. A Bayesian, stochastic formulation was proposed for such Digital Image Correlation (2D DIC) problem, in the framework of a finite element discretization f...

Permeable asphalt (PA) is a composite material with an open graded mix design that provides a pore structure facilitating stormwater infiltration. PA is often constructed as a wearing course for permeable pavements and on impervious pavements to reduce aquaplaning and noise. The pore structure of PA functions as a filter promoting particulate matte...

In this paper, we represent second-gradient internal work functionals in Lagrangian (referential) and Eulerian (spatial) descriptions, and we deduce the corresponding expressions for the Piola transformations of stress and double-stress tensors and of external forces and double-forces. We also derive, in both the Eulerian and Lagrangian description...

Second-gradient continua are defined as those continua whose internal virtual work functionals depend on the first and second-gradient of the virtual displacement. These functionals can be represented either in Lagrangian (referential) or Eulerian (spatial) description thus defining respectively the Piola–Lagrange as well as the Cauchy–Euler stress...

Permeable asphalt (PA) is a composite material with an open graded mix design that provides a pore structure facilitating stormwater infiltration. PA is often used as a wearing course for permeable pavements and on roadways to reduce aquaplaning and noise pollution. The pore structure functions as a filter promoting particulate matter (PM) separati...

An advanced metal-ceramic brazing joint HfB2/NiB/HfB2, especially suitable for aerospace and energy applications, was subjected to instrumented nanoindentation at room temperature. A Berkovich pyramidal tip was utilized, with a prescribed maximum load equal to 200 mN, generating measured depths around one micrometer. By repeating the indentation ex...

A composite sample, constituted of a Silicon Carbide (SiC) ceramic matrix reinforced by SiC fibers, was analyzed by phase-contrast synchrotron X-ray computed microtomography at the SYRMEP beamline of the Elettra synchrotron laboratory in Trieste (Italy). Experiments were performed in filtered white beam mode, leading to tomographic images with enha...

In this communication a novel implementation was outlined to simulate surface tension and adhesion by weakly compressible Smoothed Particle Hydrodynamics (SPH). Physical effects in a liquid phase of surface tension and adhesion toward a solid surface were generated by including proper particle-particle interactions within the SPH scheme. The analyt...

Preface of MiniSymposium inside ICCMSE 2020

Nuclear spreading plays a crucial role in stem cell fate determination. In previous works, we reported evidence of multipotency maintenance for mesenchymal stromal cells cultured on three-dimensional engineered niche substrates, fabricated via two-photon laser polymerization. We correlated maintenance of multipotency to a more roundish morphology o...

A method for the reconstruction of a vessel centerline from angiographic images is outlined in this work. A typical coronary artery segment with bifurcations was emulated with a 3D printed static phantom and several angiograms were acquired at various angular positions on the C-Arm. The effectiveness of the reconstruction turned out to be largely i...

Scitation is the online home of leading journals and conference proceedings from AIP Publishing and AIP Member Societies

A fast and reliable non-linear heterogeneous FE approach specifically conceived for the analysis of FRP-reinforced masonry arches is presented. The approach proposed relies into the reduction of mortar joints to interfaces exhibiting a non-linear holonomic behavior, with a discretization of bricks by means of four-noded elastic elements. The FRP re...

A simple and reliable finite element model is presented, specifically conceived for the analysis of FRP-reinforced masonry arches. The approach proposed relies on the reduction of mortar joints to interfaces exhibiting a non-linear holonomic behaviour under mixed mode conditions, whilst bricks are discretized by means of four-noded elements remaini...

Nuclear spreading plays a crucial role in stem cell fate determination. In previous works, we reported evidence of multipotency maintenance of mesenchymal stromal cells cultured on three-dimensional engineered niche substrates fabricated via two-photon laser polymerization (2PP). We correlated multipotency maintenance to a more roundish nuclear mor...

Scitation is the online home of leading journals and conference proceedings from AIP Publishing and AIP Member Societies

In this contribution, original limit analysis numerical results are presented dealing with some reinforced masonry arches tested at the University of Minho-UMinho, PT. Twelve in-scale circular masonry arches were considered, reinforced in various ways at the intrados or at the extrados. GFRP reinforcements were applied either on undamaged or on pre...

In this paper, a comparison between results furnished by a 3D FE upper bound limit analysis and experimental results for some reinforced masonry arches tested at the University of Minho (Portugal) is provided. While the delamination from arches support can be modelled only in an approximate way within limit analysis, the aim of the paper is to accu...

In this methodological study, the ultimate response of masonry pillars strengthened by externally bonded Carbon Fiber Reinforced Polymer (CFRP) was investigated. Historical bricks were derived from a XVII century rural building, whilst a high strength mortar was utilized for the joints. The conventional experimental information, concerning the over...

In this study focus is posed on an innovative joint between a Carbon Fiber reinforced carbon-matrix Composite (CFC) and copper (Cu or its alloys), based on the modification of the CFC substrate and on a one-step brazing process with a non-active brazing alloy. To assess the mechanical response of the joint subjected to shear tests, a numerical-expe...

During the past decade, several approaches have been proposed to investigate the response of masonry structures strengthened by externally bonded Fiber Reinforced Polymer (FRP) reinforcements. Nowadays, regardless of the great efforts made, scarce information are available on the delamination behavior of reinforced curved substrates. An experiment...

In this review paper the synergistic combination of X-ray microtomography, in situ mechanical tests on material samples and full-field kinematic measurements by 3D-Volume Digital Image Correlation is discussed. First, basic features are outlined, concerning X-ray microtomography by either laboratory sources or synchrotron radiation. The main equati...

In this study the inverse problem of reconstructing the in-plane (2D) displacements of a monitored surface through a sequence of two-dimensional digital images, severely ill-posed in Hadamard’s sense, is deeply investigated. A novel variational formulation is presented for the continuum 2D Digital Image Correlation (2D DIC) problem, and critical is...

In this study a robust strategy for 3D-Volume Digital Image Correlation (DIC) is presented, apt to provide accurate kinematic measurements within a loaded sample on the basis of three-dimensional digital images by X-ray computed micro-tomography. As an alternative to conventional Rayleigh-Ritz approach, a novel variational formulation is presented...

Closed-cell cross-linked PVC foams display high specific strength and stiffness and are frequently used as core of light-weight sandwich structures, such as inner aircrafts panels. The compressive behavior of a commercially available foam was investigated under both quasi-static and dynamic conditions. In the first case effects of foam anisotropy a...

Delamination phenomena between fiber reinforced polymer (FRP) strips and concrete support are investigated on the basis of single lap shear tests. To capture a stable post-peak response of the FRP-concrete joint, the slip between the concrete support and the reinforcement strip using a clip gauge mounted at the end of the reinforcement was the cont...

In this study a robust strategy for 3D-Volume Digital Image Correlation (DIC) is presented, apt to provide accurate kinematic measurements within a loaded sample on the basis of three-dimensional digital images by X-ray computed micro-tomography. In the framework of a Galerkin, finite element discretization of the displacement field, the inverse pr...

This paper represents a further contribution to the study of identification procedures for material mechanics resting on kinematic measurements provided by 2D Digital Image Correlation (DIC) at the microscale. Reference is made to non-conventional experiments on adhesively bonded assemblies industrially manufactured for aerospace applications. For...

Under the simplifying assumption of perfect adhesion, motivated by the wide adoption of highly resistant glues, delamination of FRP-reinforced masonry pillars turns out to be governed exclusively by the non-linear behavior of the quasi-brittle, heterogeneous support. However, at the structural level, the macroscopic delamination response can be des...

We consider the identification problem of a cohesive model using kinematic full-field data obtained via digital image correlation during the fracture test of an adhesive joint. A criterion is presented for selecting measurements that exhibit optimal features for identification purposes. The proposed selection scheme is constructed using the sensiti...

In this study, delamination of a perfectly-adherent FRP reinforcement from a masonry pillar is investigated by means of a fully three-dimensional finite element model. It is shown that the width of the FRP reinforcement governs the propagation of damage through the brick bulk starting from the anchorage of the strip, and influences significantly th...

In this study a heterogeneous model at the meso-scale is presented, suitable to interpret delamination phenomena of FRP strips glued to masonry. Both mortar and bricks are modeled independently in tension and compression, through different isotropic damage variables and activation criteria. Reference is made to a masonry pillar, constituted by thre...

The identification of mode-I parameters of a cohesive-zone model for the analysis of adhesive joints is presented. It is based on an experimental–numerical methodology whereby the optimal parameters are obtained as the solution of a nonlinear programming problem. The data set for inverse analysis is provided either by local kinematic data, by globa...

An experimental–numerical methodology is introduced to identify the parameters of a cohesive law of an adhesive layer within a joined assembly on the basis of kinematic data provided by digital image correlation. Non-conventional experiments on joined samples were designed to generate within the assembly and the adhesive film complex strain and str...

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 produ...

RIASSUNTO. In questa comunicazione si presenta l'applicazione di una metodologia di analisi inversa ai modelli di zona coesiva utilizzando come dati misure cinematiche a tutto campo. L'analisi di sensitività e l'identificazione parametrica vengono condotte con riferimento a dati pseudo-sperimentali disturbati da rumore e consentono di apprezzare l'...

An experimental-numerical methodology is introduced to identify the parameters of a cohesive law of an adhesive layer within a joined assembly on the basis of kinematic data provided by digital image correlation. Non-conventional experiments on joined samples were designed to generate within the assembly and the adhesive film complex strain and str...

In this paper an experimental-numerical method, centred on flat-jack tests, is presented for the identification of local stress states and possibly deteriorated elastic properties of concrete in existing dams. It is shown herein that the synergistic combination of new pattern of flat-jack experiment, computer simulation of the test (by conventional...

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 period...

In several existing dams alcali–silica reaction (ASR) during several decades of service life, or diffused micro-cracking (due to concrete ageing and/or past extreme loads, such as earthquakes) give rise to deterioration of concrete stiffness and to correlated reduction of its strength. An inverse methodology is presented herein apt to identify dama...

In many existing concrete dams chemical-physical processes, such as the alkali-aggregate reaction (AAR) [1] and/or past extreme loadings, have given rise to reductions of local stiffness and strength during decades of service life. Moreover, concrete expansion due to AAR and possible geological motions in the foundation may have generated self-equi...

In this study a chemo-elasto-damage model is developed in order to simulate the swelling phenomena and the correlated deterioration of stiffness and strength in concrete due to the alkali-aggregate reaction.

In this paper an experimental – numerical methodology is proposed for the in situ assessment of possibly deteriorated elastic properties of dam concrete and for the estimation of the local stress state in a concrete dam. The methodology described herein consists of the following operative stages: excavation of two parallel small holes (instead of t...

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...

This chapter presents several applications of various parameter identification methods to practical engineering problems. The focus is here on novel industrial uses of inverse analyses as integration of experimental and computational mechanics and on the potential benefits which derive, or may reasonably be expected in the near future. The paramete...

In a number of technologies computational and experimental mechanics join for the solution of inverse problems. Concrete dams are referred to in this lecture, which is intended to outline and briefly discuss recent research results on representative inverse problems in structural engineering, namely: diagnostic overall analysis of a dam monitored b...

The Kalman filter (KF) methodology is apt to solve parameter identification (inverse) problems in a statistical context, through a sequence of estimations, which starts from an a priori estimation by an “expert” (Bayesian approach) and exploits a time-stepping flow of experimental data until convergence is empirically ascertained. Such methodology...

The Kalman filter (KF) methodology is apt to solve parameter identification (inverse) problems in a statistical context, through a sequence of estimations, which starts from an a priori estimation by an ‘‘expert’’ (Bayesian approach) and exploits a time-stepping flow of experimental data until convergence is empirically ascertained. Such methodolog...