bluuebunny/crossref_metadata_2025 huggingface dataset:
Fractional viscoelastic characterization of laminated glass
Authors: Viviani L.
Published: February 2023

Abstract. Glass façades are often required to withstand against explosive events due to premeditated or accidental causes. Laminates made by glass plies bonded by thin polymeric foils (laminated glass) need to be used to avoid catastrophic breakage. The paradigmatic case study considered is that of a rectangular three-layer laminate, made of two glass plies, modelled as Kirchhoff-Love plates, sandwiching a thin viscoelastic polymeric interlayer. Its time-dependent response under the action of a blast wave is described via fractional calculus operators, whose main advantage is that only two material constants are needed for an exhaustive characterization. The dynamic equations are treated à la Galёrkin and their integration in time relies on the Grünwald-Letnikov approach. The fractional characterization presents noteworthy advantages from a computational point of view. We find that the maximum stress peak is mildly affected by the viscosity of the interlayer, which instead dictates the subsequent rebounding oscillations.
A phase-field model for fracture in beams from asymptotic results in 2D elasticity
Authors: Corsi G.
Published: February 2023

Abstract. We propose a derivation of a damage model in slender structures, focusing on the particular case of a rod. The peculiarity of the model is that it takes into account the changes in rigidity of the body, distinguishing between bending, traction and the possible mixed interactions between the two. The approach is based on a matched asymptotic expansion, taking the recent work of Baldelli et al [1] as starting point. Choosing the slenderness of the rod as small parameter for the asymptotic expansion, we determine the first order at which a correction occurs with respect to the Saint-Venant solution of the elastic problem, due to the presence of a crack. The results highlight that the presence of a defect affects in different ways the bending and traction rigidities of the rod, and that a coupling between the two deformation modes might occur, depending on the geometry of the crack. Moreover, the derivation allows to explicitly calculate the coefficients of this correction, for any given depth of the crack, by means of a simple numerical procedure. Application to the classic three-point bending problem is considered in order to highlight the predictive capabilities of the model. These results suggest ways in which state of the art phase-field models (e.g. [2]) for damage could be refined. This work goes in the direction of developing phase-field models suitable for application to slender structures, where the use of reduced dimensional models has proved promising [3].
Static and free vibration analysis of anisotropic doubly-curved shells with general boundary conditions
Authors: Tornabene F.
Published: February 2023

Abstract. In the present work, a two-dimensional model based on a higher order Layer-Wise (LW) approach is presented for the static and dynamic analysis of doubly-curved anisotropic shell structures. The Equivalent Single Layer (ESL) methodology is also obtained as particular case of LW. Each lamina of the stacking sequence is modelled as an anisotropic continuum. The fundamental equations account for both surface and concentrated loads, as well as the effects of the Winkler-Pasternak foundation. Moreover, non-conventional boundary conditions are introduced, and the numerical solution is assessed from the Generalized Differential Quadrature (GDQ) method. The proposed formulation is validated with respect to refined three-dimensional simulations, pointing out its accuracy and computational efficiency.
Tensile behaviour of rayon cords in different conditions
Authors: Pires da Costa L.
Published: February 2023

Abstract. Different polymeric fibrous materials, such as polyester, nylon, aramid and rayon, can be employed as reinforcement in tyres or in other rubber composites. The present contribution focuses on the experimental characterization of rayon yarns and cords and makes some steps towards developing a constitutive model for cords, to be later integrated into a finite element procedure for the analysis of fibre-reinforced composites. Uniaxial tensile tests under monotonic and cyclic loading together with creep tests have been performed on rayon specimens in different conditions. A simple, preliminary viscoelastic-viscoplastic model is proposed which can describe the main experimental findings for untwisted yarns.
Lower bound limit analysis through discontinuous finite elements and semi-analytical procedures
Authors: Zona R.
Published: February 2023

Abstract. This work deals with the limit analysis of structures through the lower-bound theorem, using dislocations based finite elements and eigenstress modelling. The lower bound approach is based on the knowledge of the self-equilibrated stresses that constitutes the basis of the domain where the optimal solution should be searched. A twofold strategy can be used to get self-equilibrated stresses, i.e., eigenstresses. The first one pursues the calculation of the self-equilibrated stress through the numerical approximation of the differential equilibrium equation in homogeneous form through an a posteriori discretization that used polynomial representation of finite degree. The second one consists of Finite Element implementation of the self-equilibrated stress calculation by discontinuous finite elements based on Volterra's dislocations theory. Both the formulations are written in terms of the strain and precisely in terms of the strain nodal displacement parameters. Consequently, it is possible to formulate an iterative procedure starting from the knowledge of the dislocation at the incoming collapse, in Melan’s residual sense, and calculate the structural ductility requirement. Several numerical examples are presented to confirm the method's feasibility.
Experimental analysis of new moment resisting steel connections
Authors: Benfratello S.
Published: February 2023

Abstract. In the recent past, the authors proposed a new steel device devoted to representing an innovative moment resisting connection for steel frame elements called LRPD (Limited Resistance Plastic Device). It is a steel element characterized by symmetry with respect to three orthogonal barycentric planes and constituted by a sequence of three portions with abrupt cross section changes, each of one identifies a steel element of suitably designed geometry. LRPD possesses the following characterizing features: any elastic flexural stiffness variation with respect to the original selected member must be avoided; the bending moment resistance must be an appropriate reduced percentage of the original beam bending resistance; any local instability phenomenon must be avoided ensuring a full plastic deformation field. In previous papers the deep description of the geometrical and mechanical features of the device and the optimal design formulation are reported. In the present paper a first stage of experimental campaign on the mechanical behaviour of LRPD is presented. Specifically, the pure bending behaviour of LRPD is investigated by performing the four-point bending test. The test is performed monotonically until the selected ultimate plastic bending moment acts on the specimen. The mechanical response of LRPD, both in terms of deflections as well as of axial strains is evaluated by means of suitably positioned displacement and strain gauges. The experimental test is performed on LRPD designed for HEB240 cross section beams. The obtained results confirm the expected performance of LRPD constituting a fundamental step for the subsequent experimental steps mainly constituted by cyclic tests.
Stress and strain fields in non-prismatic inhomogeneous beams
Authors: Migliaccio G.
Published: February 2023

Abstract. Beamlike structures are commonly studied via 1D beam models, which are more efficient than 3D finite element methods, but do not permit accurate predictions of 3D stresses in non-prismatic cases. Despite the progress made in their modeling, either via direct 1D approaches or dimensional reductions from 3D formulations, the accurate analytical prediction of stresses and strains in beamlike yet 3D elements, with non-uniform properties both in terms of materials and cross-section shape, subject to large displacements, is an open problem. This work presents a model for such elements that is particularly suitable for efficient numerical implementations and that allows accurate analytical predictions of stresses and strains. A paradigmatic example shows the importance of non-trivial stress terms that are absent in prismatic homogeneous elements and the inadequacy of usual beam models and stepped-beam approaches when dealing with predictions of stresses and strains in non-prismatic inhomogeneous cases.
Dynamic performance of an aerostatic pad with internal pressure control
Authors: Colombo F.
Published: February 2023

Abstract. This paper presents a theoretical study on the dynamic performance of an aerostatic pad with an internal pressure control. The trend of the dynamic stiffness and damping over the frequency domain is analysed.
Braking torque estimation through machine learning algorithms
Authors: Bonini F.
Published: February 2023

Abstract. MotoGP class motorcycles rely on carbon braking system to cope with their incredible acceleration capability and high speed. Hence, assessing the torque generated by the front discs is a key to improve the vehicle performance. As direct measurement of the braking torque is not allowed during races, its value may be estimated through a physical model, using as inputs the brake fluid pressure (monitored on board), the braking system geometry and the friction coefficient (μ). However, the results obtained with this method are highly limited by the knowledge of the instantaneous friction coefficient between the disc rotor and the pads. Since the value of μ is a highly nonlinear function of many variables (namely temperature, pressure and angular velocity of the disc), an analytical model appears impractical to establish. This work aims to implement an innovative algorithm, based on machine learning, for determining μ from the signals regularly available in races, to enable accurate breaking torque computation. The proposed method consists of two main tools. An artificial neural network (ANN) is developed to approximate the unknown function that relates the input variables to μ, while a Kalman filter (KF) is implemented to estimate the real temperature distribution on the disc surface that constitutes one of the most important ANN inputs. The proposed algorithm has been successfully validated with real data collected from extensive tests in racetracks, with a special sensor setup.
A mixed finite-element formulation for the elasto-plastic analysis of shell structures
Authors: Liguori F.
Published: February 2023

Abstract. Mixed assumed stress finite elements for elastic-perfectly plastic materials require the solution of a Closest Point Projection (CPP) involving all the element stress parameters for the integration of the constitutive equation. Here, a dual decomposition strategy is adopted to split the CPP at the element level into a series of CPPs at the integration points level and in a nonlinear system of equations over the element. The strategy is tested with a four nodes mixed shell finite element, named MISS-4, characterised by an equilibrated stress interpolation and a displacement field assumed only along its boundaries. The recovered elasto-plastic solution preserves all the advantages of MISS-4, namely it is accurate for coarse meshes in recovering the equilibrium path and evaluating the limit load showing a quadratic rate of convergence.
Geometrically nonlinear thermoelastic analysis of shells: modelling, incremental-iterative solution and reduction technique
Authors: Liguori F.
Published: February 2023

Abstract. This work presents an accurate and efficient numerical tool for geometrically nonlinear thermoelastic analyses of thin-walled structures. The structure is discretized by an isogeometric solid-shell model avoiding the parameterization of finite rotations. An efficient modeling of thermal strains, temperature-dependent materials and general temperature profiles is proposed. Then, a generalized path-following method is developed for solving the discrete equations with the temperature amplifier as additional unknown. Finally, a reduction technique based on Koiter theory is derived for a quick estimate of the nonlinear thermal buckling.
Extended virtual element method for elliptic problems with singularities and discontinuities in mechanics
Authors: Chiozzi A.
Published: February 2023

Abstract. Drawing inspiration from the extended finite element method (X-FEM), we propose for two-dimensional elastic fracture problems, an extended virtual element method (X-VEM). In the X-VEM, we extend the standard virtual element space with the product of vector-valued virtual nodal shape functions and suitable enrichment fields, which reproduce the singularities of the exact solution. We define an extended projection operator that maps functions in the extended virtual element space onto a set spanned by the space of linear polynomials augmented with the enrichment fields. Several numerical examples are adopted to illustrate the convergence and accuracy of the proposed method, for both quadrilateral and general polygonal meshes.
A coupled thermo-mechanical and neutron diffusion numerical model for irradiated concrete
Authors: Zhang J.
Published: February 2023

Abstract: Neutron irradiation plays an important role in nuclear-induced degradation for concrete shielding materials, specifically in determining the radiation induced volume expansion (RIVE) phenomenon driving its failure. When analyzing at the structural level the effects of nuclear radiation on concrete, a non-uniformed distribution of neutron radiation must be considered. This can be done via particle transport calculations preventive to the thermo-mechanic study, or by solving numerically the coupled set of governing equations of the problem. In this work the second approach is pursued in the theoretical framework of the Finite Element Method (FEM). The proposed formulation not only considers an accurate neutron transport model based on the two-group theory, but also it includes the effects induced by thermal neutrons to the temperature field. The formulation lends itself to include RIVE and the other relevant radiation induced effects on the mechanical field. The governing equations are presented and discussed, and some results obtained by using the general 3D numerical formulation proposed herein are compared to results from literature obtained via analytical methods addressing simplified 1D problems.
An efficient plasticity-based model for reinforced concrete flat shells by a 4-nodes mixed finite element
Authors: Liguori F.
Published: February 2023

Abstract. A 4-nodes flat shell Finite Element (FE) is formulated on the basis of an assumed interpolation of the stress and displacement fields in order to perform the elastoplastic analysis of reinforced concrete structures. The nonlinear material behaviour of the concrete is described through a confinement-sensitive plasticity constitutive model not requiring the often difficult calibration of several parameters but it is expressed in terms of only the uniaxial compressive strength of the concrete. The presence of steel reinforcement bars is accounted by defining additional material layers with a uniaxial von Mises elastoplastic behaviour. These different material responses are assembled through the shell thickness by numerical integration. Computational efficiency and accuracy are assessed by comparing the proposed shell strategy and other shell FE models by performing the step-by-step nonlinear analyses on a numerical test.
An unconditionally stable time integration for the dynamics of elastic beams and shells in finite motions
Authors: Magisano D.
Published: February 2023

Abstract. This work presents a numerical framework for long dynamic simulations of structures made of multiple thin shells undergoing large deformations. The C1-continuity requirement of the Kirchhoff-Love theory is met in the interior of patches by cubic NURBS approximation functions with membrane locking avoided by patch-wise reduced integration. A simple penalty approach for coupling adjacent patches, applicable also to non-smooth interfaces and non-matching discretization is adopted to impose translational and rotational continuity. A time-stepping scheme is proposed to achieve energy conservation and unconditional stability for general nonlinear strain measures and penalty coupling terms, like the nonlinear rotational one for thin shells. The method is a modified mid-point rule with the internal forces evaluated using the average value of the stress at the step end-points and an integral mean of the strain-displacement tangent operator over the step computed by time integration points.
Numerical simulation of coronary arteries blood flow: effects of the aortic valve and boundary conditions
Authors: Mousavi S.M.
Published: February 2023

Abstract. Sudden cardiac death in athletes is often related to anomalies in coronary origin, which may affect how coronary arteries supply blood to the heart; this highlights the importance of understanding coronary perfusion. Studies for the simulation and predictions of coronary blood flow under normal or disease conditions are many. Numerical simulations can provide rich information about the coronary blood flow with reduced costs in relation to physical models. Correct numerical simulation of the coronary blood flow is still challenging due to the complex interactions with the upstream, e.g., the aortic root, and downstream, e.g., the ventricular contraction, parts of the coronary arteries. Among all, the intrinsic ability of coronary artery autoregulation, intramyocardial resistance, cardiac frequency, and aortic valve functioning could significantly affect the coronary artery perfusion. In the present study, we aim at investigating the effects of the aortic valve and boundary conditions on coronary perfusion. We numerically modeled, by means of the ANSYS-Fluent software, the blood flow inside the proximal parts of the left and right coronary arteries, aortic sinuses of Valsalva, and ascending aorta with and without the aortic valve; the geometry of the computational model represents the average healthy person. Physiological boundary values have been applied at the computational domain boundaries to achieve a stable solution of the Navier-Stokes equations, which govern the incompressible, laminar, Newtonian blood flow. Our numerical results give insight into a proper numerical setup to predict coronary blood flow.
A limit analysis approach for the prediction of the human proximal femur ultimate load
Authors: Pisano A.A.
Published: February 2023

Abstract. A limit analysis numerical procedure for the determination of a lower bound on the ultimate load of the human proximal femur is presented. The procedure, already applied by the authors in different contexts, is based on a simplified 3D geometrical model of the human femur and on the assumption of a few geometric and material data available in the relevant literature. The perfectly plastic behaviour of the human bone, due to phenomena starting at molecular scale, and the orthotropic behaviour of the main human femur tissues, trabecular and cortical, allows to assume a yield surface of Tsai-Wu-type for its constitutive description. The effectiveness of the promoted numerical approach is validated by comparison of the obtained results with experimental findings on in-vitro tests of human femurs.
The role of the interstitial fluid content in bone remodeling
Authors: Esposito L.
Published: February 2023

Abstract. Bone is an extraordinary biological material able to modify dynamically its outer shape and inner microstructure in response to chemo-mechanical stimuli coming from the environment adapting its hierarchical microstructure to respond to static and dynamic loads for offering optimal mechanical features, in terms of stiffness and toughness. To date, many theories and mathematical models have been proposed by several authors to describe the remodeling phenomenon, all approaches starting from the adaptive elasticity and the bone maintenance theories. Within this framework, one of the most classical strategies employed in the studies is the so-called Stanford’s law, which allows uploading the effect of the time-dependent load-induced stress stimulus into a biomechanical model to guess the bone structure evolution. In the present work, we generalize this approach by introducing the bone poroelasticity, thus incorporating in the model the role of the fluid content that, by driving nutrients and contributing to the removal of wastes of bone tissue cells, synergistically interacts with the classical stress fields, in this way affecting growth and remodeling of the bone tissue. Two paradigmatic example applications, i.e. a cylindrical slice with internal prescribed displacements idealizing a tract of femoral diaphysis pushed out by the pressure exerted by a femur prosthesis and a bone element in a form of a bent beam, and a real study case of a patient subject to total hip replacement, and CT scanned at 24 hours after surgery and at 1 year post-surgery have been considered. It has to note that the proposed model is capable to catch more realistically both the transition between spongy and cortical regions and the expected non-symmetrical evolution of bone tissue density in the medium-long term, unpredictable with the standard approach. Although limitations still characterize some hypotheses at the basis of the present approach, the proposed model overcomes the intrinsic - and unrealistic - independence of the bone remodeling from the stress sign and from the indirect effect of stress gradients driving nutrients through the flow of the fluid content in the tissue, allowing to predict important spatial asymmetries in bone mass density, so paving the way to more reliable mechanobiological strategies and engineering tools for the faithful prediction of bone remodeling, with implications in diagnosis of risk fracture, optimal design of scaffolds and bone prostheses.
Fracturing process in an anisotropic layered geomaterial: theoretical and computational predictions
Authors: Rinaldi M.
Published: February 2023

Abstract. The present work investigates the fracturing behavior of an anisotropic layered geomaterial, known as Opalinus Clay (OPA). The formation of this rock is mainly related to a sedimentation process, where bedding planes correspond to planes of isotropy. OPA is here studied because of its good properties, primarily, the low permeability and high adsorption capability, which make it a perfect candidate for the storage of radioactive waste. The characterization of this rock takes place experimentally in the Mont Terri Rock Laboratory, in the northern Switzerland, with an increased attention to theoretical and computational predictions. In this context, this work aims at simulating the nonlinear crack behavior of OPA by using the eXtended Finite Element Method (XFEM) and damage mechanics. The study is applied on a Semi-Circular specimen under a Bending load (SCB), whose fracturing response is investigated in terms of peak load and direction of the cracking propagation for different notch dimensions and geometries.
Gaussian process emulation for rapid in-plane mechanical homogenization of periodic masonry
Authors: da Silva L.C.M.
Published: February 2023

Abstract. Numerical homogenization strategies can provide average mechanical responses, either in stress or coupled-stress quantities, which include many phenomenological features. Nonetheless, a direct application of numerical homogenization in sensitivity analysis in which uncertainty is propagated becomes impractical, as hundreds or thousands of simulations are conventionally required. In this study, a reliable and rapid predictive surrogate model is developed aiming to characterize the homogenized response of masonry. The case of English-bond arrangement is addressed, and the following steps are considered: (1) creation of a synthetic database through numerical homogenization based on a Finite-Element method, generated by randomization of model parameters; (2) training of a nonlinear Gaussian process; and (3) approximation of homogenized stress-strain curves for a masonry wall and for both linear and nonlinear ranges. The performance of the proposed technique is evaluated using training-validation-test in terms of computational accuracy. Results indicate that computational time is lessened 1200% while relative errors remain below 5-10%.
Numerical strategies for modelling masonry arch bridges strengthened with PBO-FRCM composites
Authors: Compagnone E.
Published: February 2023

Abstract. The work reports some numerical tests concerning the use of the Embedded Truss elements implemented in the Midas FEA NX software in modeling a specific FRCM reinforcement system for masonry structures. The efficacy of the finite element is demonstrated through the comparison of the numerical results with experimental results obtained by other authors relating both to the mechanical characterization of the FRCM system materials and to the response of masonry arch models. The Embedded Truss element appears to be promising for application to real large structures, such as masonry arch bridges of large span or multi-span masonry bridges.
Numerical procedure for detecting the optimal stress state within the profile of a cracked arch
Authors: Galassi S.
Published: February 2023

Abstract. The method for identifying the line of thrust closest to the geometrical axis of an undamaged arch, developed by the authors in a publication in 2019 for the first time, is extended in this paper to the case of cracked arches. Cracks subdivide the arch into rigid portions linked in-between in correspondence to points at the extrados or the intrados, which can be interpreted as internal hinges. Under this assumption, the procedure is reformulated and extended to the cases of the one and two-hinged arch. In the paper, the procedure is presented in detail for the case of the one-hinged arch.
Vulnerability assessment of historical masonry buildings to excavation-induced settlements: palazzo assicurazioni generali
Authors: Addessi D.
Published: February 2023

Abstract. Historical masonry structures represent a conspicuous part of the European architectural heritage. However, these often are more vulnerable to damage risk than other constructions due to their peculiar mechanical properties. This justifies the lively interest in the development of efficient and reliable approaches for their structural capacity assessment. This work presents the vulnerability assessment of the historical masonry building, “Palazzo Assicurazioni Generali”, for the effects induced by the underlying tunnel excavation required for line C of the Rome underground. The structure is a 12-floor building, built in 1902-1906 in Piazza Venezia, one of the most prestigious areas of the city. A detailed macromechanical three-dimensional numerical model of the entire structure is developed and two kinds of static analyses are conducted, assuming linear elastic and nonlinear constitutive response for masonry.
Pure compressive solutions for masonry domes under gravity loads
Authors: Cutolo A.
Published: February 2023

Abstract. In recent years, efforts have been made to compare equilibrium solutions of masonry domes obtained through different methods. The research summarized in the present paper focuses on the evaluation of the equilibrium of masonry domes in the context of the classical membrane theory, in comparison with more sophisticated finite element models. In particular, we consider solutions, with vanishing tensile stresses, for domes under gravity loads. The equilibrium problem is traced back to the equilibrium of a thrust surface under the assumption of no-tension material in the sense of Heyman (i.e., no tensile strength, infinite resistance in compression, and no slide along fracture lines). A finite difference discretization of the equilibrium equation is proposed and the obtained solution is compared with results from a nonlinear finite element analysis. The good agreement of the results shows that both finite difference and finite element approaches represent reasonable and reliable alternative tools.
Classification and modeling of uniaxial rate-independent hysteresis phenomena: some preliminary results
Authors: Vaiana N.
Published: February 2023

Abstract. In this paper, we propose a preliminary classification of complex generalized force-displacement hysteresis loops, that is, asymmetric, pinched, S-shaped, flag-shaped hysteresis loops or those obtained as arbitrary combination of them, that generally characterize the nonlinear response of mechanical systems and materials. Subsequently, we present a preliminary formulation of a novel phenomenological model capable of reproducing such complex hysteresis phenomena and we illustrate the different types of hysteresis loop shapes that can be simulated. Finally, we perform an experimental verification of the proposed model by adopting some experimental hysteresis loops retrieved from the literature.
An inhomogeneous inelastic beam-like model for dynamic analyses of multistorey buildings
Authors: Fiore I.
Published: February 2023

Abstract. This study presents an original inelastic beam-like model for the simulation of the nonlinear dynamic behaviour of three-dimensional buildings subjected to earthquake loadings. The proposed model is defined as a step-wise shear only cantilever beam, whose segments have the same mechanical properties of the corresponding inter-storeys of the building. The inter-storey constitutive laws are calibrated by means of the results of a static nonlinear analysis performed on the 3D FEM model of the building. An inverse nonlinear static identification procedure allows obtaining an inelastic beam-like model equivalent to the more demanding 3D FEM model, related to a specific direction and under a precise distribution of horizontal loadings. Dynamic nonlinear analyses performed on this simplified model allow a drastic reduction of the required computational effort and time with respect to the more demanding 3D FEM model. The reliability of the proposed beam-like model is validated through numerical applications on an irregular multi-storey RC frame representative of residential buildings in Catania designed to resist only gravity loadings.
A reduced hysteretic model of stockbridge dampers
Authors: Bogani F.
Published: February 2023

Abstract. This paper presents a reduced model to describe the nonlinear dynamic behavior of Stockbridge dampers. The proposed model is based on the classic Bouc-Wen hysteretic law and requires the identification of a small number of model parameters. The proposed formulation is used within an extended version of the classic Energy Balance Method to assess the role of the damper nonlinearities in mitigating aeolian vibrations of a reference overhead transmission line.
Optimal design of single-degree-of-freedom vibro-impact system under harmonic base excitation
Authors: Perna G.
Published: February 2023

Abstract. Strong seismic excitations can induce considerable displacements in base-isolated structures. These may in turn cause damage to the isolation system or impacts against adjacent structures in the event of an insufficient seismic gap. A strategy of reducing displacements can be achieved through the interposition, between the isolated structure and adjacent structures, of deformable and dissipative devices, called bumpers. In this paper, the response of single-degree-of-freedom (SDOF) base-isolated systems subjected to sine excitations and whose displacements are limited by optimally designed bumpers are analyzed, the bumpers being designed according to an optimal design criterion.
Friction-induced parametric oscillations in automotive drivelines: experimental analysis and modelling
Authors: Tentarelli M.
Published: February 2023

Abstract. Clutch judder is a friction-induced self-excited vibration occurring in automotive drivelines, an NVH issue studied for more than forty years and attributed by the scientific community to three possible causes: stick-slip, negative gradient of the coefficient of friction and geometric disturbances. However, these explanations fail to describe the kind of judder studied in this contribution, arising in presence of an oscillating component (dither) in the clutch actuation pressure. The analysis of experimental data collected on a dual-clutch transmission mounted on a specific test bench suggested the presence of a parametric resonance, generated by the dither. A specific 4 degrees of freedom model was then developed, able to predict with good accuracy the unstable parametric region in which judder occurs and useful in the design stage.
Complex dynamics in non-Newtonian fluid-structure interaction
Authors: Pellicano F.
Published: February 2023

Abstract. This paper presents the results of an extensive experimental campaign focused on the analysis of the dynamic interactions between an elastic structure and a non-Newtonian fluid. The structure is a circular cylindrical shell clamped in one end to a shaking table and in the other end to a heavy rigid disk. The shell has been investigated both in presence and absence of fluid. The fluid is a mixture of water and corn starch flour, commonly called Oobleck. The experiments were carried out at low and high vibrating energy, in order to clarify the influence of the fluid in different conditions: changing of modal properties, onset of complex dynamics when the fluid-solid transitions take place in the fluid.
The minimum variance distortionless response beamformer for damage identification using modal curvatures
Authors: Pau A.
Published: February 2023

Abstract. This study presents a damage identification procedure in beams based on the use of beamforming algorithms, which are mostly utilized in inverse problems of source identification and image reconstruction. We choose the modal curvatures as observed quantities and compare the performance of the Bartlett beamformer, minimum variance distortionless response (MVDR) processor, and of a conventional objective function based on the modal curvatures. By means of a set of experiments, we show that the MVDR processor can overcome some of the difficulties encountered with other estimators, especially in cases of slight damage, or damage located between two sensors.
Experimental characterisation and numerical modelling of axially loaded wire rope isolators
Authors: Pellecchia D.
Published: February 2023

Abstract. We present the main outcomes of a recent experimental activity denoted to studying the dynamic behaviour of Wire Rope Isolators loaded along the axial direction. The experimental activity has been carried out at the laboratory of the Department of Structures for Engineering and Architecture of the University of Naples Federico II (Italy). Furthermore, a new hysteretic model derived from a recently developed class of asymmetric hysteretic models is illustrated. The main advantages of the proposed model with respect to the classical ones, typically having a differential nature, are: 1) the output variable is computed in closed-form, i.e. without numerically solving a differential equation; 2) the proposed model is based on two different sets of parameters that allows one to independently model the loading and unloading curves. Specifically, a close matching between the experimental asymmetric loop and the numerically one has been obtained.
Shake-table test assessment of a base-isolation device for the seismic protection of the Goddess of Morgantina statue
Authors: Alberti E.
Published: February 2023

Abstract. Monuments and museums contents in the Mediterranean area have revealed a poor dynamic behavior and suffered large damages during past severe seismic events. Their protection deserved great research efforts due to their inestimable values and high cultural significance. From an analytic point of view, art and museum objects, statues and displays are generally modelled as rigid blocks and have been extensively studied in the non-linear dynamic context. On the other hand, only limited experimental researches have been carried out. Base isolation devices have proven to be highly effective in control the dynamic behavior of for statue-like items. This work presents an analytical and experimental study for the dynamical characterization of a bidirectional base-isolation device. The ability of the device in reducing the dynamic response of statue-like objects has been investigated by means of full-scale shaking table tests carried out at L.E.D.A. Research Institute at the “Kore” University of Enna. Experimental results are then used to calibrate an analytical model of the device. The Goddess of Morgantina statue has been selected as case-study due to its significance and since it is equipped with a base-isolating device in its present placement.
Microcontroller design for active vibration control
Authors: Zippo A.
Published: February 2023

Abstract. Active Vibration Control (AVC) problem is successfully studied considering all the characteristics of a control problem. The controlled system consists of a honeycomb panel of carbon fiber. Expensive devices are in general used for setting up and designing AVC this due to limitations for practical implementation. In our work we point to a low cost and practical solution using a microcontroller that has been verified. The honeycomb plate has been forces with out of plane load using an electrodynamic shaker at resonances that has been identified by experimental modal analysis. Piezoceramic patches are used as sensor and actuator for the control. Multiple analog signal processing circuits were developed to scale and shift the signal at the input and output of the MCU. The Positive Position Feedback (PPF) control algorithm is proposed, and a campaign of tests are carried out with harmonic excitations at resonance frequencies. Experimental results show an amplitude velocity reduction from 50% to 77% less and Power Spectral Density (PSD) attenuation up to 12.8 dB. The size and structural properties of the MFC patches, the control unit and structure under control are suitable for automobile and aerospace applications.
Stability domain and optimal design of a metamaterial made-up of a beam lattice with diagonal cables
Authors: Trentadue F.
Published: February 2023

Abstract. The elastic stability of a plane metamaterial made up of a mesh of orthogonal rods coupled with diagonal cables is studied. The stability domain and the optimal values of the stiffness of the cables are determined.
Microgeometrical design of lightweight bioinspired nacre-like composite materials for wave attenuation tuning
Authors: Pranno A.
Published: February 2023

Abstract. Numerical simulations give the opportunity for designing periodic microstructured materials by tuning and manipulating their dynamic properties in terms of vibration control by varying their main micro-geometrical parameters. Specifically, the bandgap formation in 2D nacre-like composites characterized by a brick-and-mortar arrangement of stiff platelets and a soft matrix containing periodically arranged cavities was investigated through the Bloch-wave analysis. The numerical outcomes highlighted that, by varying the microstructural topology of the void inclusions and the stiff platelets, enhanced wave absorption capabilities can be obtained providing new opportunities to design periodic lightweight bioinspired composite metamaterials with elastic wave attenuation properties.
Design of architected materials composed by periodic surfaces
Authors: Cuomo M.
Published: February 2023

Abstract. Architected materials possess extraordinary mechanical properties, that cannot be met by natural materials, either in the static and in the dynamic range. For this reason, the study of metamaterials is a very active field of research. Although lattice architectures are commonly preferred, especially for the relative simplicity of manufacturing, geometries based on thin shells may present considerable advantages. Indeed it has been shown that shell metamaterials, still preserving lightness and versatility, can present excellent stiffness and strength properties, and ability to absorb strain energy by means of very large deformations, that make them useful for the design of shock absorbing elements. In the contribution will be examined a class of shell metamaterials, composed of triple periodic minimal surfaces TPMS, that having zero mean curvature can be in equilibrium with an isotropic state of stress. Two particular surfaces, the Schwarz P and the Schwarz G minimal surfaces, the first centro-symmetric, the second chiral, are examined.
Fractional differential equations under stochastic input processes handled by the improved pseudo-force approach
Authors: Sofi A.
Published: February 2023

Abstract. This paper presents a step-by-step procedure for the numerical integration of the fractional differential equation governing the response of a single-degree-of-freedom (SDOF) system with fractional derivative damping. The procedure is developed by extending the improved pseudo-force method proposed by the second author for the numerical integration of classical differential equations. To this aim, the Grünwald–Letnikov approximation of the fractional derivative is adopted. The proposed numerical procedure is exploited to compute response statistics of a SDOF system subjected to stochastic excitation by applying classical Monte Carlo Simulation.
One century of theoretical and applied mechanics of concrete and stone materials permeability. What have we learned?
Authors: Monaco M.
Published: February 2023

Abstract. Periodic and non-routine inspections on buildings, infrastructures, and sites of historical or architectural interest frequently involve a necessary deepening of the knowledge of natural or artificial stone materials of the built heritage. Insight into stone materials is of particular relevance when the problem is approached of fine-tuning best practices for assessment and maintenance within Life Cycle Assessment methodologies, in the light of an increased awareness that social, infrastructural and environmental issues and policies cannot be faced by single compartments but need comprehensive evaluation. Permeability has been early recognized as a basic property for the assessment of durability of concrete and stone materials. This contribution reports and discusses selected conclusions of studies which have scrutinized a large body of theoretical and technical scientific literature on permeability testing of concrete, as well as of regulatory literature, keeping a historical perspective and a focus in pinpointing fundamental open research issues of both theoretical and applied relevance in the mechanics of permeation of fluids through porous media. The fundamental experimental studies conducted in the first decades of last century are also the starting point for an assessment of the continuum mechanics and thermodynamics equations describing the flow of compressible fluids in porous media and for a critical review of the approach of current European standards to the determination of concrete watertightness.
Stochastic analysis of double-skin façades subjected to imprecise seismic excitation
Authors: Genovese F.
Published: February 2023

Abstract. Double-skin façades (DSFs), widely used in buildings to provide specific thermal efficiency, acoustic isolation, and weather resistance properties, have been recently used as passive control systems. The present study focuses on the stochastic analysis of a shear-type frame equipped with a DSF subjected to ground motion acceleration modelled as a zero-mean stationary Gaussian random process fully characterized by an imprecise power spectral density function i.e., with interval parameters. The influence of imprecision of the seismic excitation on the performance of the DSF is investigated by evaluating the bounds of the interval reliability function for a selected displacement process of the frame structure, in the framework of the classical first-passage problem.
Identification of tie-rod properties in monumental buildings under uncertainty
Authors: Pepi C.
Published: February 2023

Abstract. Tie-rods are simple structural elements that have been commonly used throughout the centuries to improve the stability of old masonry buildings. Measuring the dynamic vibrations of such elements can give important information on the structural performance variation with time if proper system models can be calibrated taking into account all the relevant sources of uncertainties. This paper poses and solves the inverse problem of quantifying the uncertainty in the mechanical properties, tensile axial force and boundary conditions of tie-rods from measurements of their experimental frequencies of vibrations. It is assumed that the probabilistic models of the random entries of the problem, i.e., the mass per unit length, the bending stiffness, the tensile force and the boundary conditions, are known up to some parameters which need to be estimated. Both the physical and probability spaces are discretized using finite dimensional (FD) models, i.e., deterministic functions of time and/or space and finite numbers of random variables. Monte Carlo simulation is finally used to completely characterize the uncertain features obtaining the best estimation of all the unknown features such as mass per unit length, stiffness, boundary conditions and tensile force that give the target free vibration modal parameters, i.e. natural frequencies.
A proposal of classification for machine-learning vibration-based damage identification methods
Authors: Marafini F.
Published: February 2023

Abstract. Recent advances in computing power and sensing technology led to a significant evolution of Structural Health Monitoring (SHM) techniques, transforming SHM into a “Big Data” problem. The use of data-driven approaches for damage identification purposes, specifically Machine Learning (ML) methods, has gained popularity. ML can help at various levels of the SHM process: to pre- and post-process input data, extract damage sensitive features, and operate pattern recognition in measured data and output valuable information for damage identification. In this paper, the role of ML in SHM applications is discussed together with a new scheme for classifying ML applications in SHM, especially focusing on vibration-based monitoring, given its consolidated theoretical base. Finally, the implications of the application of these methods to historic structures are discussed, with a brief account of existing case studies. The proposed classification is exemplified using the most recent studies available in the literature on cultural heritage structures.
Line element-less method (LEM) for arbitrarily shaped nonlocal nanoplates: exact and approximate analytical solutions
Authors: Di Matteo A.
Published: February 2023

Abstract. This paper presents an innovative procedure for the analysis of nonlocal plates with arbitrary shape and various boundary conditions. In this regard, the Eringen’s nonlocal model is used to capture small length scale effects. The proposed procedure, referred to as Line Element-Less Method (LEM), is a completely meshfree approach requiring the evaluations of simple line integrals along the plate boundary parametric equation. Further, the deflection function is represented by a series expansion is terms of harmonic polynomials whose coefficients are found by performing variations of appropriately introduced functionals, leading to a linear system of algebraic. Notably, the proposed procedure yields approximate analytical solutions for general shapes and boundary conditions, and even exact solutions for some plate geometries.