Search results for "STIFFNESS"
showing 10 items of 524 documents
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…
The Rolf Method of Structural Integration on Fascial Tissue Stiffness, Elasticity, and Superficial Blood Perfusion in Healthy Individuals: The Prospe…
2020
Introduction: There are multiple theories surrounding the physiological impact of structural integration (SI) with little evidence or research corroborating any of these. The aim of the study was to assess the effectiveness of 10 sessions of SI on fascial tissue (FT) superficial blood perfusion, stiffness, and elasticity in 13 healthy women.Methods: This was a prospective, interventional study. The primary outcome measures were FTs’ superficial blood perfusion, stiffness, and elasticity of bilateral selected FT points on the body. Data were collected before and after 10 sessions of SI intervention. Statistical analysis was performed using the non-parametric Wilcoxon test (intragroup compari…
Effects of Different Long-Term Exercise Modalities on Tissue Stiffness
2022
AbstractStiffness is a fundamental property of living tissues, which may be modified by pathologies or traumatic events but also by nutritional, pharmacological and exercise interventions. This review aimed to understand if specific forms of exercise are able to determine specific forms of tissue stiffness adaptations. A literature search was performed on PubMed, Scopus and Web of Science databases to identify manuscripts addressing adaptations of tissue stiffness as a consequence of long-term exercise. Muscular, connective, peripheral nerve and arterial stiffness were considered for the purpose of this review. Resistance training, aerobic training, plyometric training and stretching were r…
Design and use of a Fatigue Test Machine in Plane Bending for Composite Specimens and Bonded Joints
2011
Polymeric and composites materials are increasingly used in industry as structural parts, so that specific information on their mechanical properties "at long term" (creep, relaxation, fatigue) are requested. The design and implementation of these components also requires that they are permanently connected together to perform certain functions. The use of adhesives in structural joints has increased over recent years thanks to the continuous development by companies which provide the market with adhesive having better and better mechanical properties. The main areas relate to the aerospace, aeronautical and automotive industries, where requirements are required for lightness and reliabilit…