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.Fri, 29 May 2020 14:45:18 GMT2020-05-29T14:45:18Z101391A 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/11380/11450862017-01-01T00:00:00ZFlexural edge waves generated by steady-state propagation of a loaded rectilinear crack in an elastically supported thin platehttp://hdl.handle.net/11380/1144688Titolo: Flexural edge waves generated by steady-state propagation of a loaded rectilinear crack in an elastically supported thin plate
Abstract: The problem of a rectilinear crack propagating at constant speed in an elastically supported thin plate and acted upon by an equally moving load is considered. The full-field solution is obtained and the spotlight is set on flexural edge wave generation.
Below the critical speed for the appearance of travelling waves, a threshold speed is met which marks the transformation of decaying edge waves into edge waves propagating along the crack and dying away from it. Yet, besides these, and for any propagation speed, a pair of localized edge waves, which rapidly decay behind the crack tip, is also shown to exist. These waves are characterized by a novel dispersion relation and fade off from the crack line in an oscillatory manner, whence they play an important role in the far field behaviour. Dynamic stress intensity factors are obtained and, for speed close to the critical speed, they show a resonant behaviour which expresses the most efficient way to channel external work into the crack. Indeed, this
behaviour is justified through energy considerations regarding the work of the applied load and the energy release rate. Results might be useful in a wide array of applications, ranging from fracturing and machining to acoustic emission and defect detection.
Sun, 01 Jan 2017 00:00:00 GMThttp://hdl.handle.net/11380/11446882017-01-01T00:00:00ZEffect 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/11380/11509682018-01-01T00:00:00ZInterface fracture phenomena in quasicrystals.http://hdl.handle.net/11380/963727Titolo: Interface fracture phenomena in quasicrystals.
Abstract: The two-dimensional setting selected here allows the use of Stroh formalism, leading to a complex variable representation of generalized stress and displacement fields in terms of four complex potentials. We adapt it to the mechanics of QCs by following the path used to describe the steady-state crack propagation of straight cracks in bodies constituted by a single type of QCs. When applied directly to the mechanics of QCs, the procedure based on the standard Stroh formalism involves a degenerate eigenvalue problem, so appropriate modifications have to be considered. The bi-material nature of the body under scrutiny here is accounted for by generalizing the approach used for classical elastic bimaterial.
The results shows that macroscopic and substructural stresses display oscillatory behaviour or classical square root singularity at the crack tip, depending on the constitutive parameters of both QCs. Finally, the energy release rate is evaluated for subsonic sub-Rayleigh crack propagation.
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/11380/9637272013-01-01T00:00:00ZA steadily propagating crack in planar quasicristals with fivefold symmetryhttp://hdl.handle.net/11380/920291Titolo: A steadily propagating crack in planar quasicristals with fivefold symmetry
Abstract: A closed-form solution is provided for the stress, strain and velocity fields due to a planar crack steadily propagating in an elastic quasicrystal with fivefold symmetry at speed lower than the bulk wave-speeds. The case of a semi-infinite rectilinear crack loaded on its surfaces is considered. The dynamic theory of quasicrystal with inertia forces, but neglecting dissipative phonon activity, is assumed to govern the motion of the medium. Both phonon and phason stress fields display square-root singular at crack tip. The energy release rate is positive for subsonic and subRayleigh crack propagation. The limit case of a stationary crack is then recovered as the crack tip speed becomes vanishing small.
Tue, 01 Jan 2008 00:00:00 GMThttp://hdl.handle.net/11380/9202912008-01-01T00:00:00ZEffects of nano-silica treatment on the flexural post cracking behaviour of polypropylene macro-synthetic fibre reinforced concretehttp://hdl.handle.net/11380/1151181Titolo: Effects of nano-silica treatment on the flexural post cracking behaviour of polypropylene macro-synthetic fibre reinforced concrete
Abstract: The effects of a surface nano-silica treatment, carried out with the sol gel method, on the post-cracking behaviour of polypropylene macro-synthetic fibre reinforced concrete are experimentally investigated here for the first time. The present study extends previous experimental and analytical investigations on the corresponding improvement of the bonding properties of a single synthetic macro fibre, performed by means of pull-out test. Scanning electron microscopy is adopted here to explore the changes in the morphological characteristics of polypropylene macro synthetic fibres, before and after mixing in the concrete matrix. A comparative analysis, carried out with three-point bending tests on notched beam specimens, is used to evaluate the effects of the nano-silica treatment on the concrete post cracking behaviour. Increase in concrete toughness and residual post-cracking strength is recorded due to improved adhesion between fibres and the concrete matrix and to the consequent increase in the frictional shear stress generated during the fibre pull-out, especially for large crack opening. As shown by the SEM images, the nano-treatment favours the bonding of the concrete hydration products to the surface of the treated fibres, thus ensuring strengthening of the interface transition zone. In addition, the links between the nano-silica coating and the concrete hydration products improve the frictional shear stress and thus the overall energy absorption, as denoted by the increase of the residual strength during the post-cracking phase.
Mon, 01 Jan 2018 00:00:00 GMThttp://hdl.handle.net/11380/11511812018-01-01T00:00:00ZAnalytical solution for ductile and FRC plates on elastic ground loaded on a small circular areahttp://hdl.handle.net/11380/933290Titolo: Analytical solution for ductile and FRC plates on elastic ground loaded on a small circular area
Abstract: The problem of an infinite FRC slab resting on a Winkler-type elastic foundation and subject to a transversal load distributed over a small circular area is investigated in the present work. The mechanical behavior is described by the Kirchhoff theory of elastic-perfectly plastic plates obeying Johansen’s yield condition and associative flow rule. The governing equations within both the inner elastic-plastic circular region near to the loaded area and the outer elastic region are found in terms of the transversal displacement and solved in closed form. After the formation of radial positive yield lines, namely cracks at the bottom side of the slab, the onset of a circumferential crack at the top of the slab defines its load-carrying capacity. Two possible configurations are envisaged, depending on whether the circumferential crack occurs within the inner elastic-plastic region, where radial cracks take place on the bottom side, or the outer uncracked elastic region. The ratio between the subgrade modulus and flexural rigidity of the plate allows introducing a characteristic length. The influence of both material and geometrical parameters on the ultimate load is then investigated. Based on the analytical results, a simplified method for the calculation of the load-carrying capacity of FRC slabs on grade is also proposed and compared with previously developed models.
Wed, 01 Jan 2014 00:00:00 GMThttp://hdl.handle.net/11380/9332902014-01-01T00:00:00ZOn the edge-wave of a thin elastic plate supported by an elastic half-spacehttp://hdl.handle.net/11380/1150972Titolo: On the edge-wave of a thin elastic plate supported by an elastic half-space
Abstract: In this contribution, we consider edge-wave propagating in a thin elastic semiinfinite
plate which is bilaterally supported by a homogenenous isotropic elastic half-space. The
problem is formulated in terms of a eigenproblem constituted by a system of five linear PDEs
in the plate transverse displacement and in the scalar and vector elastic potentials subject
to mixed boundary conditions accounting for plate-fundation displacement continuity under
the plate and zero normal stress outside. Zero tangential stress is envisaged throughout. The
problem could be reduced to an inhomogenenous Wiener-Hopf functional equation in terms of
the half-space surface displacement and of the plate-to-fundation contact pressure only. The
kernel function is analyzed and the Rayleigh wave speed is obtained together with a novel
dispersion equation. Finally, kernel factorization is performed.
Sun, 01 Jan 2017 00:00:00 GMThttp://hdl.handle.net/11380/11509722017-01-01T00:00:00ZAnalytical bounds for the electromechanical buckling of a compressed nanocantileverhttp://hdl.handle.net/11380/1152717Titolo: Analytical bounds for the electromechanical buckling of a compressed nanocantilever
Abstract: An analytical approach is presented for the accurate definition of lower and upper bounds for the pull-in voltage and tip displacement of a micro- or nano¬cantilever beam subject to compressive axial load, electrostatic actuation and intermolecular surface forces. The problem is formulated as a nonlinear two-point boundary value problem that has been transformed into an equivalent nonlinear integral equation. Initially, new analytical estimates are found for the beam deflection, which are then employed for assessing accurate bounds from both sides for the pull-in parameters, taking into account for the effects of the compressive axial load. The analytical predictions are found to closely agree with the numerical results provided by the shooting method. The effects of surface elasticity and residual stresses, which are of significant importance when the physical dimensions of structures descend to nanosize, can also be included in the proposed approach.
Mon, 01 Jan 2018 00:00:00 GMThttp://hdl.handle.net/11380/11527172018-01-01T00:00:00ZMechanics of interfacial cracks between dissimilar quasicrystalshttp://hdl.handle.net/11380/645258Titolo: Mechanics of interfacial cracks between dissimilar quasicrystals
Abstract: We analize the steady propagation of a straight interfacial crack between two dissimilar quasicrystals in the infinitesimal deformation regime. A closed form solution to the balance equations is furnished. Inertia is attributed only to the macroscopic motion.The two-dimensional setting selected here allows the use of Stroh formalism, thus generalizing the method used to describe the propagation of straight cracks in bodies constituted by a single type of quasicrystals. Boundary conditions are prescribed at infinityand along the interface, including the crack.
Fri, 01 Jan 2010 00:00:00 GMThttp://hdl.handle.net/11380/6452582010-01-01T00:00:00Z