Search results for "stiffne"
showing 10 items of 533 documents
Modeling and Analysis of Flexible Bodies Using Lumped Parameter Method
2020
The modeling, identification and analysis of a flexible beam is presented. The lumped parameter method is used to model a flexible beam. The use of camera measurements to identify lumped parameters, namely spring stiffness and damping coefficient, is described. The measurements of the tip oscillations using a high-speed camera and high-precision laser tracker are compared. The static and dynamic behavior of the flexible beam model is compared to the experimental results to show the validity of the model.
Effects of damage on the response of Euler-Bernoulli beams traversed by a moving mass
2003
The perturbation induced by damage in the dynamic response of Euler-Bernoulli beams traversed by a moving mass is investigated. The structure is discretized into segments of constant bending stiffness, connected together by elastic hinges representing damaged sections. The beam-moving mass interaction force is modelled in the most accurate way by taking into account the effective structural mass distribution and the convective acceleration terms, often omitted in similar studies. The analytical response is obtained through a series expansion of the unknown deflection in a basis of the beam eigenfunctions. The results of experimental tests, performed on a small-scale model of a prototype bri…
Application of Rotational Measurements in Stiffness Reconstruction of Beams and Frames
2009
A stiffness reconstruction method is tested when rotational degrees of freedom are added to the dynamic model of the structure. The inverse problem is formulated as a minimization problem in terms of harmonic vibrations of the structure and its finite element model. An example of frame structure is analyzed by numerical simulations. The results of these numerical analyses show that the damage detection appeared to be much more effective when the angular amplitudes of harmonic vibrations are acquired. This makes very good prospects for the future applications of angular sensors in damage detection of structures.
Stability analysis of an electromagnetically levitated sphere
2006
We present a combined numerical and analytical approach to analyze the static and dynamic stabilities of an electromagnetically levitated spherical body depending on the ac frequency and the configuration of a three-dimensional (3D) coil made of thin winding which is modeled by linear current filaments. First, we calculate numerically the magnetic vector potential in grid points on the surface of the sphere and then use Legendre and fast Fourier transforms to find the expansion of the magnetic field in terms of spherical harmonics. Second, we employ a previously developed gauge transformation to solve analytically the 3D electromagnetic problem in terms of the numerically obtained expansion…
On the beneficial effect of rotor suspension anisotropy on viscous-dry hysteretic instability
2012
The destabilizing influence of the internal friction on the supercritical rotor whirl can be efficiently counterbalanced by other external dissipative sources and/or anisotropic suspension systems. The theoretical approach may take the internal dissipation into consideration either by dry or viscous models. Nevertheless, several numerical results and a new perturbation technique of the averaging type prove that similar rotor motions and stability limits are achievable by both models, whence the linear viscous assumption appears preferable. Thus, the internal hysteretic force may be expressed by the product of an equivalent viscous coefficient and the rotor centre velocity relative to a refe…
Spin stiffness of vector spin glasses
2011
Abstract We study domain-wall excitations for O ( m ) vector spin glasses in the limit m → ∞ , where the energy landscape is simplified considerably compared to XY or Heisenberg models due to the complete disappearance of metastability. Using numerical ground-state calculations and appropriate pairs of complementary boundary conditions, domain-wall defects are inserted into the systems and their excitation energies are measured. This allows us to determine the stiffness exponents for lattices of a range of spatial dimensions d = 2 , … , 7 . Compiling these results, we can finally determine the lower critical dimension of the model. The outcome is compared to estimates resulting from field-t…
Non-local stiffness and damping models for shear-deformable beams
2013
This paper presents the dynamics of a non-local Timoshenko beam. The key assumption involves modeling non-local effects as long-range volume forces and moments mutually exerted by non-adjacent beam segments, that contribute to the equilibrium of any beam segment along with the classical local stress resultants. Elastic and viscous long-range volume forces/moments are endowed in the model. They are built as linearly depending on the product of the volumes of the interacting beam segments and on generalized measures of their relative motion, based on the pure deformation modes of the beam. Attenuation functions governing the space decay of the non-local effects are introduced. Numerical resul…
Metamodel-Based Analysis of Cross-Flow-Induced Vibrations
2018
This work presents the study of numerical modelling of the fluid flow and circular cylinder interaction to investigate the cross-flow induced vibrations in the rod bundle. It is assumed that failure due to flow-induced vibrations of the rod can be described by the reduction of the rod mass, the rod support stiffness or damping coefficient. The metamodel-based approach is applied to investigate the main trends of the system’s characteristic behaviour related to the variations of the chosen parameters. The two-dimensional Finite Volume models have been developed using open-source software to get a mapping of input and output variables for the metamodel. The impact of assumed failure parameter…
Longterm damped dynamics of the extensible suspension bridge
2010
This work is focused on the doubly nonlinear equation, whose solutions represent the bending motion of an extensible, elastic bridge suspended by continuously distributed cables which are flexible and elastic with stiffness k^2. When the ends are pinned, long-term dynamics is scrutinized for arbitrary values of axial load p and stiffness k^2. For a general external source f, we prove the existence of bounded absorbing sets.When f is timeindependent, the related semigroup of solutions is shown to possess the global attractor of optimal regularity and its characterization is given in terms of the steady states of the problem.
Crumpling of a stiff tethered membrane.
2003
first-principles numerical simulation model for crumpling of a stiff tethered membrane is introduced. In our model membranes, wrinkles, ridge formation, ridge collapse, as well as the initiation of stiffness divergence, are observed. The ratio of the amplitude and wave length of the wrinkles, and the scaling exponent of the stiffness divergence, are consistent with both theory and experiment. We observe that close to the stiffness divergence there appears a crossover beyond which the elastic behavior of a tethered membrane becomes similar to that of dry granular media. This suggests that ridge formation in membranes and force-chain network formation in granular packings are different manife…