Layerwise Analyses of Compact and Thin-Walled Beams Made of Viscoelastic Materials

This paper evaluates the vibration characteristics of structures with viscoelastic materials. The mechanical properties of viscoelastic layers have been described with the complex modulus approach. The equations of motion are derived using the principle of virtual displacement (PVD), and they are solved through the finite element method (FEM). Higher-order beam elements have been derived with the Carrera Unified Formulation (CUF), which enables one to go beyond the assumptions of the classical one-dimensional (1D) theories. According to the layerwise approach, Lagrange-like polynomial expansions have been adopted to develop the kinematic assumptions. The complex nonlinear dynamic problem has been solved through an iterative technique in order to consider both constant and frequency-dependent material properties. The results have been reported in terms of frequencies and modal loss factors, and they have been compared with available results in the literature and numerical three-dimensional (3D) finite element (FE) solutions. The proposed beam elements have enabled bending, torsional, shell-like, and coupled mode shapes to be detected.

Dynamical analysis of vibratory feeder and feeding parts considering interactions by an improved increment harmonic balance method

Vibratory feeder is known as one of major machines in various industries. The feeding parts in a vibratory feeder are experiencing repeated discontinuous friction that can be considered as a typical strong nonlinear dynamic problem. It is very significant to obtain the motion of parts under different alternating loads for the design of vibratory feeder. An analytical model of parts’ motion in sliding regime was constructed and verified with a simplified model based on discrete element method. An improved increment harmonic balance method was proposed to obtain the dynamic behaviors of vibratory feeder and the motion of feeding parts. In contrast to previous researches, we considered the interactions between vibratory feeder and parts in detail, not only containing the effects of the dynamics of vibratory feeder on the motion of parts but also the motion of parts on vibratory feeder. Finally, studying the interactions for various parts’ masses in different frequencies, the motion of parts had a significant effect on the dynamics of vibratory feeder. In reverse, the alterations of the dynamics of vibratory feeder influenced the motion of parts and conveying speed. In the design of vibratory feeder, the interactions between vibratory feeder and parts should not be neglected.

Seismic Analysis of Concrete Gravity Dams: Nonlinear Fracture Mechanics Models and Size-Scale Effects

The phenomenon of interface crack propagation in concrete gravity dams underseismic loading is herein addressed. This problem is particularly important from the engineeringpoint of view. In fact, besides Mixed-Mode crack growth in concrete, dam failure is oftenthe result of crack propagation along the rock-concrete interface at the dam foundation. Toanalyze such a problem, the generalized interface constitutive law recently proposed by the¯rst author is used to proper modelling the phenomenon of crack closing and reopening at theinterface. A damage variable is also introduced in the cohesive zone formulation in order topredict crack propagation under repeated loadings. Special attention is given to the complexityresulting from the solution of the nonlinear dynamic problem and to the choice of the interfaceconstitutive parameters, taking into account the important size-scale e®ects observed in thesecyclopic structures. Numerical examples will show the capabilities of the proposed approachwhen applied to concrete gravity dams.

Stochastic Finite Element Method for Nonlinear Dynamic Problem with Random Parameters

Several algorithms were proposed relating to the development of a framework of the perturbation-based stochastic finite element method (PSFEM) for nonlinear dynamic problem with random parameters, for this purpose, based on the stochastic virtual work principle , some algorithms and a framework related to SFEM have been studied. An interpolation method was used to discretize the random fields, which is based on representing the random field in terms of an interpolation rule involving a set of deterministic shape functions. Direct integration Wilson- Method in conjunction with Newton-Raphson scheme was adopted to solve finite element equations. Numerical examples were compared with Monte-Carlo simulation method to show that the approaches proposed herein are accurate and effective for the nonlinear dynamic analysis of structures with random parameters

Dynamic Analysis of Frame Structure Using Nonlinear Stochastic Finite Element Method

The objective of this paper is to propose an algorithms and a frame work of perturbation-based stochastic finite element method for large variation nonlinear dynamic problem of ship frame structure. For this purpose, based on the principle of stochastic virtual work some algorithms and a framework related to stochastic finite element method have been studied. To prove the validity and practicality, a numerical example for nonlinear dynamic problem with large variation was calculated to compare with Monte-Carlo simulation method. The results showed that the approaches proposed herein are feasible and effective for the nonlinear dynamic analysis of structures with random parameters.