Shock and Vibration

https://www.hindawi.com/journals/sv/

List of Papers (Total 10,282)

Nonlinear Resonance Behavior in the Human Exposed to Whole-Body Vibration

The driving-point impedance technique was applied to identify nonlinear resonance behavior in the human exposed to sinusoidal vibration between 3 and 20 Hz at three acceleration levels. Up to four regions of resonance were observed. A significant decline in the first and fourth resonance frequency and the disappearance of the second resonance peak occurred with a fivefold...

Fully Coupled FE Analyses of Buried Structures

Current procedures for determining the response of buried structures to the effects of the detonation of buried high explosives recommend decoupling the free-field stress analysis from the structure response analysis. A fully coupled (explosive–soil structure) finite element analysis procedure was developed so that the accuracies of current decoupling procedures could be...

Structural Synthesis in the Frequency Domain: A General Formulation

A general formulation for frequency domain structural synthesis is presented. The formulation is based on a physical coordinate transformation of the presynthesis frequency response system model and addresses modification, general coupling, and constraint imposition. Notable features of the formulation includes the ability to directly synthesize response quantities such as...

Feedforward Control of Gear Mesh Vibration Using Piezoelectric Actuators

This article presents a novel means for suppressing gear mesh related vibrations. The key components in this approach are piezoelectric actuators and a high-frequency, analog feed forward controller. Test results are presented and show up to a 70% reduction in gear mesh acceleration and vibration control up to 4500 Hz. The principle of the approach is explained by an analysis of...

Spectral Analysis of Large Finite Element Problems by Optimization Methods

Recently an efficient method for the solution of the partial symmetric eigenproblem (DACG, deflated-accelerated conjugate gradient) was developed, based on the conjugate gradient (CG) minimization of successive Rayleigh quotients over deflated subspaces of decreasing size. In this article four different choices of the coefficient βk required at each DACG iteration for the...

Head Injury Reduction in Automobile Pedestrian Impact

This article presents and discusses automobile hood/fender rail design to reduce head injury of pedestrians struck by the front of the vehicle. Fender seam designs are presented that reduce the head injury criterion values by over 50%. The procedures and analysis are conducted using a nonlinear dynamic finite element program for an Oldsmobile Ciera hood and a Ford Taurus hood...

Coupled Dynamics of a Rotor-Journal Bearing System Equipped with Thrust Bearings

The rotordynamic coefficients of fixed-pad thrust bearing are introduced and calculated by using the out-domain method, and a general analysis method is developed to investigate the coupled dynamics of a rotor equipped with journal and thrust bearings simultaneously. Considerations include the effects of static tilt parameters of the rotor on rotordynamic coefficients of thrust...

Motions of a Powered Top with a Spherical Tip on a Curved Surface

The purpose of this article is to model the dynamics of a top with a finite radius tip on a curved basin in a gravitational field without (and with) energy addition and dissipation. This is an extension of a very general and classical problem and requires development of a method for treating the dynamical interactions between the two curved surfaces. The full nonlinear equations...

Performance Characteristics of Active Constrained Layer Damping

Theoretical and experimental performance characteristics of the new class of actively controlled constrained layer damping (ACLD) are presented. The ACLD consists of a viscoelastic damping layer sandwiched between two layers of piezoelectric sensor and actuator. The composite ACLD when bonded to a vibrating structure acts as a “smart” treatment whose shear deformation can be...

Periodic and Near-Periodic Structures

Extensive work has been done on the vibration characteristics of perfectly periodic structures. This article reviews the different methods of analysis from several fields of study, for example solid-state physics and civil, mechanical, and aerospace engineering, used to determine the effects of disorder in one-dimensional (1-D) and 2-D periodic structures. In the work examined...

Air Bag Momentum Force Including Aspiration

A gas-jet momentum force drives the air bag into position during a crash. The magnitude of this force can change as a result of aspiration. To determine the potential magnitude of the effect on the momentum force and mass flow rate in an aspirated system, a series of experiments and simulations of those experiments was conducted. The simulation consists of a two-dimensional...

Waves, Solids, and Nonlinearities

In this article nonlinearity is taken as a basic property of continua or any other wave-bearing system. The analysis includes the conventional wave propagation problems and also the wave phenomena that are not described by traditional hyperbolic mathematical models. The basic concepts of continuum mechanics and the possible sources of nonlinearities are briefly discussed. It is...

A Toeplitz Jacobian Matrix/Fast Fourier Transformation Method for Steady-State Analysis of Discontinuous Oscillators

A semianalytical algorithm is proposed for the solutions and their stability of a piecewise nonlinear system. The conventional harmonic balance method is modified by the introduction of Toeplitz Jacobian matrices (TJM) and by the alternative applications of fast Fourier transformation (FFT) and its inverse. The TJM/FFT method substantially reduces the amount of computation and...

Motions of a Constrained Spherical Pendulum in an Arbitrarily Moving Reference Frame: The Automobile Seatbelt Inertial Sensor

A common automatic seatbelt inertial sensor design, comprised of a constrained spherical pendulum, is modeled to study its motions and possible unintentional release during vehicle emergency maneuvers. The kinematics are derived for the system with the most general inputs: arbitrary pivot motions. The influence of forces due to gravity and constraint torque functions is developed...

Finite Element Analysis of Fluid-Conveying Timoshenko Pipes

A general finite element formulation using cubic Hermitian interpolation for dynamic analysis of pipes conveying fluid is presented. Both the effects of shearing deformations and rotary inertia are considered. The development retains the use of the classical four degrees-of-freedom for a two-node element. The effect of moving fluid is treated as external distributed forces on the...

Free Vibration of Partially Supported Cylindrical Shells

The effects of detached base length on the natural frequencies and modal shapes of cylindrical shell structures were investigated in this work. Some of the important applications for this type of problem can be found in the cracked fan and rotor blades that can be idealized as partially supported shells with varying unsupported lengths. A finite element model based on small...

An Algorithm for Higher Order Hopf Normal Forms

Normal form theory is important for studying the qualitative behavior of nonlinear oscillators. In some cases, higher order normal forms are required to understand the dynamic behavior near an equilibrium or a periodic orbit. However, the computation of high-order normal forms is usually quite complicated. This article provides an explicit formula for the normalization of...

Differential Quadrature Analysis of Free Vibration of Symmetric Cross-Ply Laminates with Shear Deformation and Rotatory Inertia

In the present work, laminates having two opposite edges simply supported are considered. The boundary conditions at the other two opposite edges may be general, and between these two edges, the thickness of the plate may be nonuniform. The theory used for the vibration analysis of such laminates includes shear deformation and rotatory inertia. The solution approach of the...

Numerical Analysis for Dynamic Instability of Electrodynamic Maglev Systems

Suspension instabilities in an electrodynamic maglev system with three- and five-degrees-of-freedom DOF vehicles traveling on a double L-shaped set of guideway conductors were investigated with various experimentally measured magnetic force data incorporated into theoretical models. Divergence and flutter were obtained from both analytical and numerical solutions for coupled...

Continuous Sliding Mode Control of Flow-Induced Vibrations

Vortex-induced vibrations of flexible circular cylinders and galloping oscillations of square prisms are controlled using a robust continuous sliding mode (CSM) controller. The ability of the CSM controller in rejecting the flow-induced disturbances and accommodating parameter uncertainties is numerically demonstrated. In the present study, emphasis is placed on the development...

Testing Procedures for High Output Fluid Viscous Dampers Used in Building and Bridge Structures to Dissipate Seismic Energy

Today's economic climate demands that conversion of military technology for commerical applications be a part of an aerospace and defense company's strategic planning. Toward this goal, a successful defense conversion has occurred recently with the application of high capacity fluid damping devices from the defense community for use as seismic energy dissipation elements in...

Experimental Investigation of Effects of Vibration upon Elastic and Cohesive Properties of Beds of Wet Sand

The transmission of sinusoidal vibrations through beds of cohesive particulate solids was measured. Results were interpreted in terms of a critical state model to predict the elastic swelling constant k, and the cohesive stress C. Factorial experimental design was used to identify significant parameters. Factors that affect k include percent moisture, bulk density, sample size...

Free Vibration of Thick Multilayer Cylinders

In this study of the free vibration of multilayer thick cylinders, the medium is modeled by laminated linear viscoelastic cylinders of an infinite extent. The analytical modeling is based on three-dimensional wave propagation utilizing constant complex elastic moduli. The solution is achieved by determining the displacements and stresses for each interface and by complying with...