Search results for "STIFFNESS"
showing 10 items of 524 documents
Crack bifurcations in a strained lattice
1996
Dynamic crack propagation in a strained, granular, and brittle material is investigated by modeling the material as a lattice network of elastic beams. By tuning the strain and the ratio of axial to bending stiffness of the beams, a crack propagates either straight, or it branches, or it bifurcates. The crack tip velocity is calculated approximately for cracks that propagate straight. In a bifurcated crack the number of broken beams follows a scaling law. The shape of the branches is found to be the same as in recent experiments.
Dynamic analysis for axially moving viscoelastic panels
2012
In this study, stability and dynamic behaviour of axially moving viscoelastic panels are investigated with the help of the classical modal analysis. We use the flat panel theory combined with the Kelvin–Voigt viscoelastic constitutive model, and we include the material derivative in the viscoelastic relations. Complex eigenvalues for the moving viscoelastic panel are studied with respect to the panel velocity, and the corresponding eigenfunctions are found using central finite differences. The governing equation for the transverse displacement of the panel is of fifth order in space, and thus five boundary conditions are set for the problem. The fifth condition is derived and set at the in-…
A symmetric nonlocal damage theory
2003
The paper presents a thermodynamically consistent formulation for nonlocal damage models. Nonlocal models have been recognized as a theoretically clean and computationally efficient approach to overcome the shortcomings arising in continuum media with softening. The main features of the presented formulation are: (i) relations derived by the free energy potential fully complying with nonlocal thermodynamic principles; (ii) nonlocal integral operator which is self-adjoint at every point of the solid, including zones near to the solid's boundary; (iii) capacity of regularizing the softening ill-posed continuum problem, restoring a meaningful nonlocal boundary value problem. In the present app…
Stochastic linearization critically re-examined
1997
Abstract The stochastic linearization technique, widely used for the analysis of nonlinear dynamic systems subjected to random excitations, is revisited. It is shown that the standard procedure universally adopted for determining the so-called effective stiffness of the equivalent linear system is erroneous in all previous publications. Two error-free stochastic linearization techniques are elucidated, namely those based on (1) the force linearization and (2) energy linearization.
Effects of confinement level, cross-section shape and corner radius on the cyclic behavior of CFRCM confined concrete columns
2014
Abstract The main results of an experimental research aiming to investigate the behavior of medium-size low-strength concrete columns wrapped with Carbon Fiber Reinforced Cementitious Matrix (CFRCM) under monotonic and cyclic compressive axial loads are presented. Thirty columns with circular, square and rectangular cross-sections were tested under monotonic and cyclic axial loads to investigate the effect of the confinement level, the cross-section shape and the corner radius on the stiffness, strength, and ductility of CFRCM confined concrete columns under cyclic loads. The results prove that CFRCM confining jackets provide substantial gain in compressive strength, deformability and absor…
Refined equivalent single layer formulations and finite elements for smart laminates free vibrations
2014
A family of 2D refined equivalent single layer models for multilayered and functionally graded smart magneto-electro-elastic plates is presented. They are based on variable kinematics and quasi-static behavior for the electromagnetic fields. First, the electromagnetic state of the plate is determined by solving the strong form of the electromagnetic governing equations coupled with the corresponding interface continuity conditions and external boundary conditions. The electromagnetic state is then condensed into the plate kinematics, whose governing equations can be written using the generalized principle of virtual displacements. The procedure identifies an effective elastic plate kinemati…
Variable kinematics models and finite elements for nonlinear analysis of multilayered smart plates
2015
Abstract A variable kinematics approach for moderately large deflection analysis of smart magneto-electro-elastic multilayered plates is presented. The approach is based on the condensation of the electro-magnetic state into the plate kinematics, whose nonlinear strain–displacement relationships are expressed in the von Karman sense. This leads to models resulting in an effective mechanical plate, which takes the multifield coupling effects into account by the plate stiffness, inertia and loading characteristics, consistently defined as combinations of the layers material properties. By a unified approach, both equivalent single layer and layerwise models are developed formulating the assoc…
An equivalent single-layer approach for free vibrations analysis of smart laminated thick composite plates
2012
An equivalent single-layer model for the free vibration analysis of smart laminated plates is presented. The electric and magnetic fields are assumed to be quasi-static and third-order in-plane kinematics is employed to adequately take the shear influence into account when the plate thickness increases. The model governing equations are the plate equations of motion written in terms of mechanical primary variables and effective stiffness coefficients, which take the multifield coupling effects into account. The model shows that the surfaces magneto-electric boundary conditions enter the definitions of the laminate forces and moments resultants. Moreover, it reveals that new stiffness terms,…
Integration of finite displacement interface element in reference and current configurations
2017
In the present paper the non-linear behaviour of a solid body with embedded cohesive interfaces is examined in a finite displacements context. The principal target is the formulation of a two dimensional interface finite element which is referred to a local reference frame, defined by normal and tangential unit vectors to the interface middle surface. All the geometric operators, such as the interface elongation and the reference frame, are computed as function of the actual nodal displacements. The constitutive cohesive law is defined in terms of Helmholtz free energy for unit undeformed interface surface and, in order to obtain the same nodal force vector and stiffness matrix by the two i…
Efficacy of 8 weeks elbasvir/grazoprevir regimen for naïve-genotype 1b, HCV infected patients with or without glucose abnormalities: Results of the E…
2022
Background and aim: Direct Acting Antivirals(DAAs) achieve the highest rate of sustained viral re- sponse(SVR) in patients with genotype-1b(G1b) Hepatitis C virus(HCV) infection. Reducing treatment du- ration can simplify the management and improve adherence of therapy. Patients and methods: The study evaluates the efficacy of 8 weeks of elbasvir/grazoprevir regimen in 75 treatment-naïve(TN), G1b patients with mild-moderate fibrosis(Liver Stiffness by Fibroscan®< 9.0 kPa). Viral load(VL) has been evaluated by Roche TaqMan RT-PCR(LLOQ < 15 IU/ml). Results: Mean age was 61.0 ±14.2 years, 44% were male, mean LS by Fibroscan®was 6.1 ±1.8 kPa. Twenty-eight patients(37.3%) had an HOMA > …