Archivio della ricerca dell'Università di Modena e Reggio Emiliahttps://iris.unimore.itIl sistema di repository digitale IRIS acquisisce, archivia, indicizza, conserva e rende accessibili prodotti digitali della ricerca.Wed, 08 Apr 2020 18:36:53 GMT2020-04-08T18:36:53Z10821Thin film bonded to elastic orthotropic substrate under thermal loadinghttp://hdl.handle.net/11380/1101715Titolo: Thin film bonded to elastic orthotropic substrate under thermal loading
Abstract: The problem of thin elastic films bonded on an elastic orthotropic substrate under thermal load is investigated in this work. Differently from past studies on the same topic, the effects induced by anisotropic behavior of the elastic substrate will be taken into account. Particular attention will also be paid to the determination of the displacement and stress fields induced by thermal loading. In particular, it is assumed that the thin films are deposed on the substrate at high temperature, and then the mismatch occurring during the cooling process, due to the difference between the thermal expansion coefficients of the two materials, is responsible for the permanent deformation assumed by the system. This phenomenon can be exploited for realizing a crystalline undulator. To this aim, the permanent deformation must be optimized in order to encourage the channeling phenomenon. By imposing equilibrium conditions and perfect adhesion between the film and the substrate, a singular integral equation is derived. A closed-form solution is achieved by expanding the interfacial shear stress fields in Chebyshev series. The unknown coefficients in the series expansion are then determined by transforming the integral equation into an infinite algebraic system.
Fri, 01 Jan 2016 00:00:00 GMThttp://hdl.handle.net/11380/11017152016-01-01T00:00:00ZStress and pressure fields around two wellbores in a poroelastic mediumhttp://hdl.handle.net/11380/1137511Titolo: Stress and pressure fields around two wellbores in a poroelastic medium
Abstract: The problem of two circular wellbores of different size in a poroelastic medium is considered in the present work. The constitutive behaviour of the poroelastic medium is assumed to comply with the classical Biot model for isotropic porous materials infiltrated by compressible fluid. The wellbores are assumed infinitely long and the fluid flow is taken stationary, thus making it possible to perform a plane strain analysis. Owing to the geometrical layout of the system, bipolar cylindrical coordinates have been adopted. Three different sets of BCs on the pressure field and on the fluid flux have been considered, founding the corresponding forms of the pressure field. Based on Helmholtz representation, a displacement potential has been introduced, and the corresponding stress field in the poroelastic medium has been assessed. However, such a solution does not satisfy the BCs at the edges of the wells. Then, an auxiliary stress function, which allows accomplishing the BCs, is introduced, leading to the complete solution of the problem. The cases of two coaxial wellbores (eccentric annulus), a single hole bored in a poroelastic half plane and two intersecting holes have been considered also. The proposed approach allows evaluating the pore pressure and the stress and strain fields in the system varying the amplitude of the wells and the physical parameters of the porous material. In particular, the evaluation of the peak values of the stress components around the circular boreholes plays a key role in a variety of engineering contexts, with particular reference to the stability analysis of wellbores and tunnels and failure of vascular vessels in biological tissues.
Mon, 01 Jan 2018 00:00:00 GMThttp://hdl.handle.net/11380/11375112018-01-01T00:00:00ZShaft-hub press fit subjected to bending couples: Analytical evaluation of the shaft-hub detachment couplehttp://hdl.handle.net/11380/1136858Titolo: Shaft-hub press fit subjected to bending couples: Analytical evaluation of the shaft-hub detachment couple
Abstract: A mathematical modelling of a shaft-hub press-fit subjected to bending couples applied to the shaft extremities is developed, and the value of the bending couple inducing an un- desired shaft-hub incipient detachment is analytically determined. The shaft-hub contact is modelled in terms of two elastic Timoshenko beams connected by a distributed elastic spring, whose stiffness is analytically evaluated. Two models of the distributed spring are considered. The first model expresses the combined deformability of both the shaft and the hub cross sections. The second model accounts for the stiffening effect exerted by the shaft portion protruding from the hub on the adjacent shaft part that is in contact with the hub, and, consequently, it assumes only a rigid body motion of the shaft cross section, thus neglecting its deformability. Based upon this beam-like model, the bending couple producing the incipient detach- ment between the shaft and the hub is theoretically determined in term of the shaft-hub geometry, of the initial shaft-hub interference, and of the elastic constants. Comparisons with selected Finite Element (FE) forecasts indicate that the first modelling produces an incipient detachment couple that appreciably overrates the FE forecasts, whereas the sec- ond modelling lowers the error down to technically acceptable predictions.
Sun, 01 Jan 2017 00:00:00 GMThttp://hdl.handle.net/11380/11368582017-01-01T00:00:00ZMISSION PROFILE FOR AGRICULTURAL TRACTORS: A FOCUS ON HYDRAULIC CIRCUIThttp://hdl.handle.net/11380/884091Titolo: MISSION PROFILE FOR AGRICULTURAL TRACTORS: A FOCUS ON HYDRAULIC CIRCUIT
Abstract: Mission profile for agricultural vehicles aims to define a picture of a typical working condition of the vehicle. The collection of these pictures gives information about the performance, the efficiency, and the eventual critical conditions with reference to the kind of operation and terrain. Unfortunately, to be at the same time quick, easy to be interpreted and effective, this analysis has to neglect the details and to take into consideration the whole situation. However, detailed considerations about the efficiency of the vehicle subsystems and of their components may derive only from a deeper analysis and it is from these information that designers and technicians can derive improvements of the system.
A promising way to solve this discrepancy is to integrate experimental analysis with simulation: from experimental test on field is possible to define several duty cycles representing different working conditions on the vehicle. These data can then be used as input in a simulation model representing the system, able to replicate its dynamic behaviour. Finally, possible modifications of the system architecture or components, aimed at the improvement of the performance or efficiency, may be more easily tested on the virtual model. In this paper this methodology is presented with reference to the hydraulic circuit of an agricultural tractor, in particular the portion related to the managing of the auxiliary utilities, showing the capability to represent in detail the behaviour of the system and to explore the critical performances.
Sun, 01 Jan 2012 00:00:00 GMThttp://hdl.handle.net/11380/8840912012-01-01T00:00:00ZA Wiener-Hopf System of Equations in the Steady-State Propagation of a Rectilinear Crack in an Infinite Elastic Platehttp://hdl.handle.net/11380/1145086Titolo: A Wiener-Hopf System of Equations in the Steady-State Propagation of a Rectilinear Crack in an Infinite Elastic Plate
Abstract: A Wiener-Hopf system of functional equations is shown to govern the steady-state propagation of a semi-infinite rectilinear crack in an infinite elastic Kirchhoff–Love plate. Solution is presented in terms of Fourier transforms via kernel factorization
Sun, 01 Jan 2017 00:00:00 GMThttp://hdl.handle.net/11380/11450862017-01-01T00:00:00ZExperimental investigation and monitoring of a polypropylene-based fiber reinforced concrete road pavementhttp://hdl.handle.net/11380/966896Titolo: Experimental investigation and monitoring of a polypropylene-based fiber reinforced concrete road pavement
Abstract: In this work, basic guidelines are provided for the design of a polypropylene-based fiber reinforced (PFRC) road pavement.
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/11380/9668962013-01-01T00:00:00ZEffect of cylindrical fibers, with cross-sections formed by two circular arcs, on the overall conductivity of a compositehttp://hdl.handle.net/11380/1150968Titolo: Effect of cylindrical fibers, with cross-sections formed by two circular arcs, on the overall conductivity of a composite
Abstract: An analytic solution for the steady-state temperature distribution in an infinite conductive medium, containing non-conductive fiber with the cross-section of irregular shape formed by two circles, and subjected to remotely applied uniform heat flux is obtained. The temperature flux on the surface of the inhomogeneity is then determined as a function of the geometrical parameters. This result is used to calculate resistivity contribution tensor for the fiber and to evaluate effective conductive properties of a material containing multiple inhomogeneities of this shape.
Mon, 01 Jan 2018 00:00:00 GMThttp://hdl.handle.net/11380/11509682018-01-01T00:00:00ZSafety Assessment of Historic Timber Structural Elementshttp://hdl.handle.net/11380/1159926Titolo: Safety Assessment of Historic Timber Structural Elements
Abstract: Dealing with the safety assessment of existing buildings engineers often have to face the diagnosis of old timber structures. The current standards framework does not provide clear prescriptions about the evaluation of these kinds of structures, so the principal aim of this work is to outline an alternative methodology that leaves the concept of "Knowledge Level" and "Condence Factor", usually applied for existing buildings. An experimental campaign carried out on old timber joists supplied a sample of homogeneous data that
were the support to the theoretical reasoning.
Mon, 01 Jan 2018 00:00:00 GMThttp://hdl.handle.net/11380/11599262018-01-01T00:00:00ZBuckling of a Timoshenko beam bonded to an elastic half-plane: Effects of sharp and smooth beam edgeshttp://hdl.handle.net/11380/1179985Titolo: Buckling of a Timoshenko beam bonded to an elastic half-plane: Effects of sharp and smooth beam edges
Wed, 01 Jan 2020 00:00:00 GMThttp://hdl.handle.net/11380/11799852020-01-01T00:00:00ZFull field solution for a rectilinear crack in an infinite Kirchhoff plate supported by a Pasternak elastic foundation.http://hdl.handle.net/11380/1025114Titolo: Full field solution for a rectilinear crack in an infinite Kirchhoff plate supported by a Pasternak elastic foundation.
Abstract: The failure of cracked ceramic components is governed by the stresses in the neighbouring of the crack tip, which is described by the stress intensity factor (SIF).
Despite the availability of several handbooks for SIFs, very few full-field solutions are available for cracked plates resting on an elastic foundation. This lack of results is problematic, since this situation often occur in practice (e.g. roadways, pavements, floorings, etc.).
Furthermore, when some results are available, they never involve the foundation's mechanical properties alone.
For instance, the problem of a finite crack in an infinite Kirchhoff plate supported by a Winkler foundation is considered in [1] and it is reduced to a singular integral equation. However, since two length scales exist in the problem (the crack length and the foundation relative Winkler modulus), the SIF may be related to some dimensionless ratio of them and not directly to the foundation's mechanical property. In actual facts, this outcome stems from the Winkler approximation to the foundation and not from the physical feature of the problem. The full-field solution for a semi-infinite rectilinear crack in an infinite Kirchhoff plate resting on a Winkler foundation is found in [2]. Since this is a self-similar problem, no characteristic length scale exists. Application of the above results to road and airport pavements is given in [3]. As a result, the influence of the pavement foundation on the SIF cannot be properly assessed.
Several papers address crack problems in plate theory and a literature review of the stress field at the crack tip in thin plates and shells is given in [4] along with comparison with the available experimental results.
The present work deals with the elastostatic problem of a semi-infinite rectilinear crack in an infinite Kirchhoff plate resting on a two-parameter elastic foundation under very general loading conditions. The foundation, also termed Pasternak-type, is weakly non-local, as it accommodates for coupling among the independent springs of a purely local model (i.e. the Winkler model).
The same model governs the problem of a Kirchhoff plate equi-biaxially loaded in its mid-plane. The Pasternak foundation accounts for two length scales such that the whole problem is governed by a parameter η expressing the soil to plate relative stiffness. The discussion was addressed in a previous paper [5] but therein limited to the range 0 < η < 1, where the limiting case as η → 0 recovers the non-local Winkler model. In the present work the analysis has been extended to the full range of values for the paremeter η. The problem is formulated in terms of a pair of dual integral equations solved through the Wiener–Hopf technique. Numerical results are given for the full field bending and shear stress field within the plate, the corresponding SIFs are obtained and some conclusions drawn.
Wed, 01 Jan 2014 00:00:00 GMThttp://hdl.handle.net/11380/10251142014-01-01T00:00:00Z