1,721,222 research outputs found
A thermal stress finite element analysis of isotropic and laminated beams via unified formulation
No full textIn this work the mechanical and thermal behaviour of three-dimensional isotropic and laminated beams is investigated. The beam-like three dimensional structure is modelled through refined 1D finite elements obtained via hierarchical expansion of the displacement field over the cross-section coordinates. The approximation order of the displacements is a free parameter that leads to the formulation of a family of several beam elements. Linear, quadratic and cubic one-dimensional finite elements are considered. The governing algebraic equations are obtained via the Principle of Virtual Displacements.The temperature field is obtained by exactly solving Fourier's heat conduction equation and it is treated as an external load within the mechanical analysis. Results in terms of displacements and stresses are validated towards three-dimensional FEM results as well as analytical solutions. Numerical investigations show that the proposed finite elements yield accurate yet computationally efficient solutions for the three-dimensional stress state generated by the thermal load
A thermal stress analysis of functionally graded beam structures by hierarchical finite elements
No full textIn this study, the thermoelastic behaviour of three-dimensional functionally graded beams is investigated. The temperature field is treated as an external load within the mechanical analysis and it is obtained by exactly solving Fourier's heat conduction equation. The three-dimensional beam is modelled through advanced one-dimensional finite elements derived via hierarchical expansion of the displacements over the cross-section. The approximation order of the displacement field is a free parameter that leads to the formulation of a family of several beam elements. The number of nodes per elements is also a free parameter. Linear, quadratic and cubic variations over the beam axis are considered. The governing algebraic equations are obtained via the Principle of Virtual Displacements. Displacements and stresses are evaluated and results are validated towards three-dimensional FEM results as well as analytical solutions. The temperature load results in a three-dimensional stress state that calls for accurate models. Numerical investigations show that the proposed finite elements yield accurate yet computationally efficient solutions
A hygro-thermal stress finite element analysis of laminated beam structures by hierarchical one-dimensional modelling
No full textA hygro-thermal stress finite element analysis of laminated beam structures by hierarchical one-dimensional modelling Composite structure operating under severe temperature conditions and/or wet environments are very common is several engineering fields such as aeronautics, space and transportation. Hygro-thermal solicitation of beam-like structures results in a three- dimensional response that classical one-dimensional models are not always capable of describe effectively. An accurate prediction calls, then, for refined higher-order theories making this subject of research relevant and up-to-date. In this work, laminated composite Several beam models are hierarchically derived by means of a unified formulation [1, 2] that allows for atheoretical derivation of the finite elements independent from the displacements polynomial approximation order over the cross-section as well as the number of nodes per element. Elements stiffness matrix are derived in a compact form ("fundamental nucleus") via the Principle of Virtual Displacements. As a result, a family of several one-dimensional finite elements accounting for transverse shear deformations and cross section in- and out-of-plane warping can be obtained. Temperature and humid-ity profiles are obtained by directly solving the corresponding diffusion equation(Fourier's heat conduction equation for temperature and Fick's law for moisture). These fields are, then, accounted as sources terms in the elastic analysis through Hooke's law. Simply supported and cantilever configurations are considered. Numerical results in terms of temperature, moisture, displacement and stress distributions are provided for different beam slenderness ratios. Three-dimensional finite element solutions developed within the commercial code Ansys are presented for validation. The numerical investigations show that the hygro-thermo-elastic problem presents a complex three-dimensional stress state that can be efficiently obtained by a suitable choice of approximation order over the cross section: the accuracy is comparable to the reference solutions whereas the computational costs can beconsiderably reduce
A multi-scale model of fibre reinforced beams using hierarchical one-dimensional finite elements
No full textA multi-scale model of fibre reinforced beams using hierarchical one-dimensional finite elements A multi-scale analysis of fibre reinforced composite beams was proposed by this presentation. At structural level, several higher-order refined beam theories can be easily implemented on the basis of Carrera's unified formulation (CUF) by deriving a fundamental nucleus that does not depend upon the approximation order nor the number of nodes per element (they are free parameters of the formulation). Under the framework of FE2 method, the effective properties of the fibre-reinforced composite material are found by numerical homogenization over representative volume elements, that is, the unknown constitutive relationship at the macro-scale is obtained by solving a local finite element problem at the micro-scale. Consequently, a coupled two-scale problem is obtained for linear cases. Results are validated in terms of accuracy and computational costs towards FEM solutions. Numerical investigations show that accurate results can be obtained with reduced computational costs
A Novel FE2 Method Based Fourier Macroscopic Model for Instability Phenomena of Long Fiber Reinforced Composites
No full textInvestigating behavioural synthesis into bespoke instruction set processors
No full textWe propose a new approach to the behavioural synthesis of digital systems for which a synthesis tool has been implemented.Traditionally, behavioural synthesis tools convert the behaviour of a system into a RTL description, modelling a data-path and a controller. Instead, in the proposed approach, a behavioural description is translated into a RTL description that models a set of Bespoke Instruction Set Processors (BISPs). A BISP is a stripped-down microprocessor, which is composed of the minimal computational resources necessary to implement the part in the behavioural description from which it is derived. We refer to a BISP as a nano-processor throughout the thesis. This thesis looks at previous research on behavioural synthesis, describes the new approach and outlines the results of its evaluation and comparison to an existing behavioural synthesis tool. Results show that the new approach is less efficient than the existing technique when applied to small systems. However, the inability to support some VHDL constructs was the main obstacle against a full evaluation of the new approach
Geometrically nonlinear hierarchical finite elements via a unified formulation
No full textThis paper presents the formulation of advanced one-dimensional finite elements for the geometrically non-linear static analysis of beams. The kinematic field is axiomatically assumed along the thickness direction via a Unified Formulation. The approximation order of the displacement field along the thickness is a free parameter that leads to the formulation of a family of several beam elements. The tangent stiffness matrix of the element is obtained via the Principle of Virtual Displacements. A total Lagrangian approach is used. Newton-Raphson method is employed in order to solve the non-linear governing equations. Numerical investigations in terms of displacements and stresses are validated towards two-dimensional FEM solutions in order to show the correctness and the advantages of the proposed modelling approach
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