1,721,202 research outputs found
JP Journal of Solids and Structures
No full textThe JP Journal of Solids and Structures is a fully refereed international journal, which publishes original research papers and survey articles in all aspects of Mechanics of Solids and Structures as a field of physical and mathematical basis to materials engineering, Life Sciences, technological applications and methods of modern computational mechanics, both pure and Applied Science and Engineering research.
F. Ubertini is an associate editor
A posteriori error estimation in finite element analysis of plate structures
No full textA posteriori error estimation is an important tool in finite element software development, since it allows to verify and validate the finite element simulations. An efficient and practical way to derive a posteriori error estimators is offered by recovery procedures, which estimate the error by comparing the original finite element solution with the recovered one. The major steps forward in using recovery procedures were made with the Superconvergent Patch Recovery
(SPR) and the Recovery by Equilibrium in Patches (REP) procedures [1,2], both successfully applied to plate problems in [3]. Recently, a new superconvergent procedure called Recovery by Compatibility in Patches (RCP) has been proposed by one of the authors [4] and shown to provide an excellent basis for error estimation in 2D problems [5].
Within this context, the present paper aims at presenting an extension of the RCP-based error estimation to Reissner-Mindlin plates finite element analysis. The basic idea is to recover stress
resultants by enforcing compatibility over patches of elements. Displacements computed by the finite element analysis are prescribed on the boundary of the patch, and improved stress
resultants are computed by minimizing the complementary energy of such a sub-model. The resulting procedure is simple, efficient, numerically stable and does not need any knowledge of superconvergent points. Some numerical examples are given.
References:
1. O.C. Zienkiewicz, J.Z. Zhu, “The superconvergent patch recovery and a posteriori error estimates. Part I: The recovery technique”, International Journal for Numerical Methods in Engineering, v. 33, p. 1331-1364, 1992.
2. B. Boroomand, O.C. Zienkiewicz, “An improved REP recovery and the effectivity robustness test”, International Journal for Numerical Methods in Engineering, v. 40, p. 3247-3277, 1997.
3. B. Boroomand, M. Ghaffarian, O.C. Zienkiewicz, “On application of two superconvergent recovery procedures to plate problems”, International Journal for Numerical Methods in Engineering, v. 61, p. 1644-1673, 2004.
4. F. Ubertini, “Patch recovery based on complementary energy”, International Journal for Numerical Methods in Engineering, v. 59, p. 1501-1538, 2004.
5. A. Benedetti, S. de Miranda, F. Ubertini, “A posteriori error estimation based on the superconvergent Recovery by Compatibility in Patches”, International Journal for Numerical
Methods in Engineering, in press
Operational modal testing and analysis of a long span footbridge
No full textWithin the reception tests of a long span footbridge, over-passing the A13 highway near Bologna (Italy), dynamic tests were performed, with the excitation being mainly provided by the micro-tremors, wind and traffic in the neighbouring highway. Although no serviceability issues were observed, the vertical dynamic characteristics of the bridge turned out to be quite complex, with several couples of modes exhibiting closely spaced natural frequencies. The paper mainly focuses on the application to the data collected on the footbridge of different output-only identification techniques, ranging from the classic peak picking technique to the more recent frequency domain decomposition and stochastic subspace identification methods. Hence, the reliability of the different techniques, especially in the correct identification of the dynamic characteristics of the closely spaced modes, is investigated
Discontinuous Galerkin approach for mechanically driven mass diffusion in elastic solids
No full textMechanically driven mass diffusion is characterized by a two-way interaction between mechanical and diffusive quantities: changes in mass concentration induce volumetric strain in the solid (swelling effect) and, vice versa, volumetric strain induces mass fluxes
(piezo-diffusive effect). In the standard finite element setting, the presence of strain gradients in the piezo-diffusive coupling term demands C1 continuous displacement interpolation. Various techniques can be used to avoid C1 continuous shape functions. In
the literature, the most used strategies for the solution of the problem are: a mixed approach, where the volumetric strain is interpolated as an independent variable (early explored in [1]), and a staggered solution strategy in conjunction with a smoothing L2
projection in the entire domain [2].
In this paper, a new formulation, which requires standard C0 interpolation for both displacement and concentration, is presented, basing on a discontinuous Galerkin approach. Recently, these approaches have been successfully used for strain gradient
models [3]. The new formulation is discussed and compared with a mixed one and with a staggered solution strategy used employing a smoothing superconvergent patch-based recovery procedure, proposed in [4]. An error analysis is carried out to show the convergence rate. The discontinuous formulation exhibits convergence properties comparable to those of the mixed formulation, but allows to drastically reduce the computational cost with respect the other approaches. Some benchmarks are proposed to validate the formulation.
References:
1. S. P. Girrens, F. W. Smith, "Finite element analysis of coupled constituent diffusion in thermoelastic solids", Computer Methods in Applied Mechanics in Engineering, v. 62, p. 209-223, 1987.
2. K. Garikipati, L. Bassman, M. Deal, "A lattice-based micromechanical continuum formulation for stress-driven mass transport in polycrystalline solids", Journal of the Mechanics and Physics of Solids, v. 49, p. 1209-1237, 2001.
3. L. Molari, G. N. Wells, K. Garikipati, F. Ubertini, "A Discontinuous Galerkin method for a strain gradient-dependent damage: Study of interpolations, convergence", Computer Methods in Applied Mechanics in Engineering, v.195, p. 1480-1498, 2006.
4. F. Ubertini, "Patch recovery based on complementary energy", International Journal for Numerical Methods in Engineering, v. 59, p. 1501-1538, 2004
Modelling of Damaged Laminated and Sandwich Shell Structures by means of Higher-order Shear Deformation Theories
No full textThe main aim of the current research is the development of a mathematical formulation for the modelling of damage in laminated and sandwich composite shells. For this purpose, the damage of some areas of the structures can be seen as concentrated decays of the mechanical properties of the elastic constituents. In general, several kinds of damage can affect the mechanical behavior of a generic laminated structure, such as microcracking, debonding, fiber ruptures, and transverse matrix cracking, as specified in [1].
Without investigating the causes of the damage, the current approach suggests to introduce peculiar functions that multiply directly the mechanical properties of the elastic media, expressed in terms of engineering constants. To this aim, the Gaussian function and an ellipse shaped law are used to model a quick variation of the mechanical properties within the whole structural domain. By setting properly the parameters that characterize these distributions, it is possible to control the intensity of the deterioration and the width of the damaged areas, as well as the point of applications.
The present approach is employed to characterize the damage in some doubly-curved shells characterized by different radii of curvature. The difficulties related to the description of these curved surfaces are overcome by means of an analytical formulation based on differential geometry [2]. As far as the mechanical properties are concerned, several constituents are considered and combined.
The theoretical framework is based on a formulation that allows to develop easily different kinematic models and expansions in a unified manner. Thus, several Higher-order Shear Deformation Theories, which can include also the zig-zag effect, are employed. In fact, it has been proven that peculiar mechanical configurations require an enriched structural model, since lower-order theories could be inadequate to capture the effective mechanical behavior.
Finally, a numerical technique able to solve the strong form of the governing equations is used. For this purpose, the partial derivatives that appear in the fundamental system are directly approximated through the Generalized Differential Quadrature method due to its accuracy [3].
References
[1] Tornabene, F., Fantuzzi, N., Bacciocchi, M., “Linear Static Behavior of Damaged Laminated Composite Plates and Shells”, Materials, 10, 811, 1-52 (2017).
[2] Tornabene, F., Fantuzzi, N., Bacciocchi, M., and E. Viola, Laminated Composite Doubly-Curved Shell Structures. Differential Geometry. Higher-order Structural Theories, Esculapio, Bologna (2016).
[3] Tornabene, F., Fantuzzi, N., Ubertini, F., Viola, E., “Strong Formulation Finite Element Method Based on Differential Quadrature: A Survey”, Applied Mechanics Reviews, 67, 020801-1-55
Modelling of Damaged Laminated and Sandwich Shell Structures by means of Higher-order Shear Deformation Theories
No full textThe main aim of the current research is the development of a mathematical formulation for the modelling of damage in laminated and sandwich composite shells. For this purpose, the damage of some areas of the structures can be seen as concentrated decays of the mechanical properties of the elastic constituents. In general, several kinds of damage can affect the mechanical behavior of a generic laminated structure, such as microcracking, debonding, fiber ruptures, and transverse matrix cracking, as specified in [1].
Without investigating the causes of the damage, the current approach suggests to introduce peculiar functions that multiply directly the mechanical properties of the elastic media, expressed in terms of engineering constants. To this aim, the Gaussian function and an ellipse shaped law are used to model a quick variation of the mechanical properties within the whole structural domain. By setting properly the parameters that characterize these distributions, it is possible to control the intensity of the deterioration and the width of the damaged areas, as well as the point of applications.
The present approach is employed to characterize the damage in some doubly-curved shells characterized by different radii of curvature. The difficulties related to the description of these curved surfaces are overcome by means of an analytical formulation based on differential geometry [2]. As far as the mechanical properties are concerned, several constituents are considered and combined.
The theoretical framework is based on a formulation that allows to develop easily different kinematic models and expansions in a unified manner. Thus, several Higher-order Shear Deformation Theories, which can include also the zig-zag effect, are employed. In fact, it has been proven that peculiar mechanical configurations require an enriched structural model, since lower-order theories could be inadequate to capture the effective mechanical behavior.
Finally, a numerical technique able to solve the strong form of the governing equations is used. For this purpose, the partial derivatives that appear in the fundamental system are directly approximated through the Generalized Differential Quadrature method due to its accuracy [3].
References
[1] Tornabene, F., Fantuzzi, N., Bacciocchi, M., “Linear Static Behavior of Damaged Laminated Composite Plates and Shells”, Materials, 10, 811, 1-52 (2017).
[2] Tornabene, F., Fantuzzi, N., Bacciocchi, M., and E. Viola, Laminated Composite Doubly-Curved Shell Structures. Differential Geometry. Higher-order Structural Theories, Esculapio, Bologna (2016).
[3] Tornabene, F., Fantuzzi, N., Ubertini, F., Viola, E., “Strong Formulation Finite Element Method Based on Differential Quadrature: A Survey”, Applied Mechanics Reviews, 67, 020801-1-55
On the automatic identification of modal parameters by subspace methods
No full textThe paper presents an alternative approach for the automatic selection of modal parameter estimates obtained by subspace methods. The proposed methodology represents an improved version of existing approaches and it is based on a noise modes elimination procedure and on a clustering analysis. Two illustrative examples, with different levels of complexity, are pre-sented to show the enhanced performance of the method with respect to existing techniques
Some preliminary computational results on a refined shape memory alloy model taking into account multiple phase transformations and martensite reorientation
No full textThe employment of shape memory alloys (SMAs) in a large number of engineering applications has been the motivation for an increasing interest toward a correct and exhaustive modeling of SMA macroscopic behavior. The aim of this paper is the numerical investigation of the theoretical model recently proposed by Auricchio and Bonetti, performed through a more effective and efficient procedure, inspired to that presented for crystal plasticity and consisting in the replacement of the classical set of Kuhn-Tucker conditions by the so-called Fischer-Burmeister complementarity function. Numerical predictions associated with various thermo-mechanical paths are compared to experimental results and the analysis of a boundaryvalue problem is described. Numerical results assess the reliability of the new model and the procedure is verified to be appropriate for the model itself
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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