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During the on-orbit service of an deployable antenna, the resonance of the antenna will affect the accuracy of direction. The nonlinear dynamics of a rigid-flexible space antenna is studied under the conditions of two-to-one or three-to-one internal resonance analytically and experimentally. The nonlinear dynamic equations for the planar vibration of the antenna structure with two degrees of freedom...
The electro-hydrostatic actuator (EHA) pump of aircraft is usually characterized as high speed for improved power density. High-speed condition leads to a considerable tilting inertia moment acting on the cylinder block, which has a significant effect on the cylinder block balance. Therefore, the cylinder block spline is required to be designed properly to achieve the cylinder block balance at high...
Supersonic flutter behaviors of functionally graded material (FGM) shallow conical panel with steady thermal stress are investigated. It is assumed that temperature dependent material properties are graded along the radial direction following power law form. The shallow conical panel is formulated with the aid of first-order shear deformation theory and von-Karman geometrical nonlinearity. The aerodynamic...
The image force on a screw dislocation at the distance $$\rho =\alpha a\,(\alpha >1)$$ ρ=αa(α>1) from the tip of an isotropic wedge of shear modulus G with a circular inhomogeneity of radius a and shear modulus $$G'$$ G′ at its end is determined by the method of image dislocations. If the wedge angle is $$\pi /n$$ π/n , for an integer $$n\ge 1$$ n≥1 , $$4n-1$$ 4n-1 image dislocations are...
In the present note, we suggest a single-line equation estimate for adhesion between elastic (hard) rough solids with Gaussian multiple scales of roughness. It starts from the new observation that the entire DMT solution for “hard” spheres (Tabor parameter tending to zero) with the Maugis law of attraction can be obtained using the Hertzian relationship load-indentation and estimating the area of...
The aim of this study is to define a new kinetostatic model of the knee, in order to analyze the joint behavior both in unloaded and loaded conditions. This model was obtained as an extension of an existing kinematic model. Anatomical surfaces and a comprehensive representation of the ligamentous structures were modeled. A second model was also defined by replacing the anatomical surfaces with spherical...
The focus of this paper is on the analysis of a semi-infinite crack lying along a perfect interface in a piezoelectric bimaterial with arbitrary loading on the crack faces. Making use of the extended Stroh formalism for piezoelectric materials combined with Riemann–Hilbert formulation, general expressions are obtained for both symmetric and skew-symmetric weight functions associate with plane crack...
In the formulation of mechanical theories, physicists usually neglect complementary energy, while rational mechanicians and engineers widely use it, especially in continuum physics and structural mechanics. Indeed, in many cases the solutions of elastic problems are found in a simpler way by resorting to complementary, rather than potential, energy. Moseley and Cotterill in England, Menabrea and Castigliano...
This paper describes the use of load-path optimisation for discrete, doubly curved, compression-only structures, represented by thrust networks. The load-path of a thrust network is defined as the sum of the internal forces in the edges multiplied by their lengths. The presented approach allows for the finding of the funicular solution for a network layout defined in plan, that has the lowest volume...
In this study, a numerical model is developed to simulate an air ejector pump that is proposed for the carpet industry. Simulations have been performed by solving the compressible, steady-state, two-dimensional Reynolds-averaged Navier–Stokes equations, and k–ε Realizable model is used to simulate a turbulent flow. A comparison of the computed results with the published experimental data is presented...
We present some results about the asymptotic behavior of a Kirchhoff plate with viscoelastic dissipative effects, making use of the concept of minimal state. This approach allows to obtain results in a larger class of solutions and data with respect to the classical one, based on the histories of the deformation gradient. Recently, a lot of attention has been paid to find unified approaches to study...
We provide numerical simulations of an incompressible pressure-thickening and shear-thinning lubricant flowing in a plane slider bearing. We study the influence of several parameters, namely the ratio of the characteristic lengths $$\varepsilon >0$$ ε>0 (with $$\varepsilon \searrow 0$$ ε↘0 representing the Reynolds lubrication approximation); the coefficient of the exponential pressure–viscosity...
We consider the inverse problem of reconstructing the axial stiffness of a damaged rod from the knowledge of a finite number of resonant frequencies of the free axial vibration under supported end conditions. The damage is described as a reduction of the axial stiffness, and the undamaged and damaged configurations of the rod are assumed to be symmetric. The method is based on repeated determination...
To try and enhance the performance of a tuned mass damper, nonlinear stiffness can be introduced to good use. In this paper, an investigation is performed on the characteristics of a nonlinear tuned mass damper when attached to a linear oscillator. The whole system is modelled as a two degree-of-freedom system with cubic stiffness nonlinearity, and the effect of the nonlinearity and mass ratio of...
This paper is devoted to analyze the phase-lag thermoelasticity problem. We study two different cases and we prove, for each one of them, that the solutions of the problem are determined by a quasi-contractive semigroup. As a consequence, existence, uniqueness and continuous dependence of the solutions are obtained.
Flow of Bingham plastics through straight, long tubes with non-circular cross-sections is studied by means of an analytical method that allows to model a wide spectrum of tube geometries. Shear stress normal to equal velocity lines, velocity field and plug zones are explored, in particular in a tube with equilateral triangular cross-section for small values of the Bingham number Bi, and they are compared...
For accurate measurements of moments of inertia, or gyradii, about a vertical axis the offset of the center of mass of the suspended body from the symmetry axis of the suspension is required. A number of simple methods of determining this offset from yaw period measurements are described and experimentally shown to provide results of precision equal or better than suspension line tension measurements...
A harmonic drive is a two gear epicyclic drive with a gear set of circular ring gear (RG), a flex rimmed external toothed gear (FG) and an oval cam. FG, with oval cam inside, takes non-circular gear shape encounters improper teeth mating with RG, having only two teeth difference. Consequently, interferences occur at several tooth pairs even at no load. These are inherent and obvious. Overcoming such...
In this work we present a novel method for the solution of gear contact problems in flexible multi-body. These problems are characterized by significant variation in the location and size of the contact area, typically requiring a high number of degrees of freedom to correctly capture deformation and stress fields. Therefore fully dynamic simulation is computationally prohibitive. To overcome these...
The dimensional synthesis of translational parallel manipulators (TPMs) of type PRRR-PRPU is addressed by using an overall novel method. Addressing this design step on such TPMs is interesting for the scientific community since, in a previous paper, one of the authors showed that it has the following promising features: a single-loop not-overconstrained architecture with all the actuators on or near...
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