Shock and Vibration

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List of Papers (Total 159)

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...

Bulging Modes of Circular Bottom Plates in Rigid Cylindrical Containers Filled with a Liquid

In this article the free vibrations of the bottom plate of an otherwise rigid circular cylindrical tank filled with liquid are studied, considering only the bulging modes (when the amplitude of the plate displacement is predominant with respect to that of the free surface). The tank axis is vertical, thus the free liquid surface is orthogonal to the tank axis. The liquid is...

Optical Measurement of Cable and String Vibration

This paper describes a non contacting measurement technique for the transverse vibration of small cables and strings using an analog position sensing detector. On the one hand, the sensor is used to monitor the cable vibrations of a small scale mock-up of a cable structure in order to validate the nonlinear cable dynamics model. On the other hand, the optical sensor is used to...

A Dynamic Branch-Switching Method for Parametrically Excited Systems

The branch-switching algorithm in static is applied to steady state dynamic problems. The governing ordinary differential equations are transformed to nonlinear algebraic equations by means of harmonic balance method using multiple frequency components. The frequency components of the (irrational) nonlinearity of oscillator are obtained by Fast Fourier Transform and Toeplitz...

Dispersion Analysis of the XM881APFSDS Projectile

This study compares the results of a dispersion test with mathematical modeling. A 10-round group of modified 25-mm XM881 Armor Piercing Fin Stabilized Discarding Sabot projectiles was fired from the M242 chain gun into a designated target. The mathematical modeling results come from BALANS, a product of Arrow Tech Associates. BALANS is a finite-element lumped parameter code that...

Fatigue Failure Results for Multi-Axial versus Uniaxial Stress Screen Vibration Testing

To date, the failure potential and prediction between simultaneous multi-axial versus sequentially applied uniaxial vibration stress screen testing has been the subject of great debate. In most applications, current vibration tests are done by sequentially applying uniaxial excitation to the test specimen along three orthogonal axes. The most common standards for testing military...

On the Investigation of State Space Reconstruction of Nonlinear Aeroelastic Response Time Series

Stall-induced aeroelastic motion may present severe non-linear behavior. Mathematical models for predicting such phenomena are still not available for practical applications and they are not enough reliable to capture physical effects. Experimental data can provide suitable information to help the understanding of typical non-linear aeroelastic phenomena. Dynamic systems...

Lessons Learned in Applying Accelerometers to Nuclear Effects Testing

Exoatmospheric nuclear effects, such as those that would be encounter by reentry bodies, provide instantaneous (near zero-duration), impulsive loading of structures. Endoatmospheric nuclear effects possess an impulse that is finite in duration, but whose rise time is still instantaneous. The commonality of these loadings is that they initiate waves propagating through structures...

Particle Damping with Granular Materials for Multi Degree of Freedom System

A particle damper consists of a bed of granular materials moving in cavities within a multi degree-of-freedom (MDOF) structure. This paper deals with the damping effects on forced vibrations of a MDOF structure provided with the vertical particle dampers. In the analysis, the particle bed is assumed to be a single mass, and the collisions between the granules and the cavities are...

Vibration Attenuation by a Combination of a Piezoelectric Stack and a Permanent Magnet

The present work proposes a non-contact vibration attenuator made up of a permanent magnet mounted on a piezoelectric stack. Two such actuators are made to work simultaneously in a 'twin-actuator

Damage Identification in Bars with a Wave Propagation Approach: Performance Comparison of Five Hybrid Optimization Methods

The formulation and solution of the inverse problem of damage identification based on an one-dimensional wave propagation approach are presented in this paper. Time history responses, obtained from pulse-echo synthetic experiments, are used to damage identification. The identification process is built on the minimization of the squared residue between the synthetic experimental...

Sensor Placement Strategies for the Seismic Monitoring of Complex Vaulted Structures of the Modern Architectural Heritage

Effective diagnostic and monitoring systems are highly needed in the building and infrastructure sector, to provide a comprehensive assessment of the structural health state and improve the maintenance and restoration planning. Vibration-based techniques, and especially ambient vibration testing, have proved to be particularly suitable for both periodic and continuous monitoring...

Dynamic Characteristics Analysis of Vehicle Incorporating Hydraulically Interconnected Suspension System with Dual Accumulators

A novel roll-resistant hydraulically interconnected suspension with dual accumulators on each fluid circuit (DHIS) is proposed and dynamic characteristics of vehicle incorporating DHIS subsystem are studied in this paper. A 10-degrees-of-freedom (DOFs) vehicle model coupled with DHIS subsystem is established and validated. Four physical parameters of DHIS subsystems which are...

Modeling Accuracy in FEA of Vibrations of a Drumhead

The study of the problem of predicting values of Rayleigh’s quotient for a square drumhead provides a basis for assessing the relation between grid size, accuracy of analysis results, and efficiency of data processing in finite element analysis. The analysis data indicate that unacceptable grid sampling can occur even for the fine grids, that strictly monotonic convergence is...

Specification of Modal Participation Factors in Acoustic Scattering Problems

Using the wet modes of a submerged structure as expansion functions, it is shown how the scattered far-field pressures induced by an incident harmonic wave may be modified in a prescribed manner. This is done by applying forces directly to the structural surface, which superposes a radiated pressure field on the scattered one. By appropriate choice of the applied nodal forces...

Evaluation of Eigenvalue Routines for Large Scale Applications

The NASA structural analysis (NASTRAN∗) program is one of the most extensively used engineering applications software in the world. It contains a wealth of matrix operations and numerical solution techniques, and they were used to construct efficient eigenvalue routines. The purpose of this article is to examine the current eigenvalue routines in NASTRAN and to make efficiency...

Vibration Isolation: A Review, I. Sinusoidal and Random Excitations

This article reviews the engineering theory and technology associated with the use of dicrete Isolators to protect Vibration-sensitive equipment or machinery against sinusoidal or random excitation. Special attention is given to protection against low frequency (<5 Hz) and high-frequency (>100 Hz) excitation. Both passive and active isolators systems are discussed.

Exact and Direct Modeling Technique for Rotor-Bearing Systems with Arbitrary Selected Degrees-of-Freedom

An exact and direct modeling technique is proposed for modeling of rotor-bearing systems with arbitrary selected degrees-of-freedom. This technique is based on the combination of the transfer and dynamic stiffness matrices. The technique differs from the usual combination methods in that the global dynamic stiffness matrix for the system or the subsystem is obtained directly by...

Influence of Flexible Foundation on Isolator Wave Effects

This article deals with the interaction between wave effects in mounts and resonances of foundations inflexible vibration isolation systems. A new model is proposed that is represented as a rigid mass supported by two linear unidirectional isolators on a flexible foundation beam, whose closed-form solutions for transmissibility and response ratio are then obtained, with which the...

Vibration Analysis of Structures with Rotation and Reflection Symmetry

The article applies group representation theory to the vibration analysis of structures with Cnv symmetry, and presents a new structural vibration analysis method. The eigenvalue problem of the whole structure is divided into much smaller subproblems by forming the mass and stiffness matrices of one substructure and than modifying them to form mass and stiffness matrices in each...

Vibration Isolation Review: II. Shock Excitation

This is the second part of a two part review of shock and vibration isolation. It covers three distinct categories of shock excitation—pulselike shock, velocity shock, and complex shock—and discusses the means that are available in each case to measure the effectiveness of shock mitigation by the imposition of flexible connections between the isolated system and its base.

Description of Muzzle Blast by Modified Ideal Scaling Models

Gun blast data from a large variety of weapons are scaled and presented for both the instantaneous energy release and the constant energy deposition rate models. For both ideal explosion models, similar amounts of data scatter occur for the peak overpressure but the instantaneous energy release model correlated the impulse data significantly better, particularly for the region in...

Nonlinear Response of Cantilever Beams to Combination and Subcombination Resonances

The nonlinear planar response of cantilever metallic beams to combination parametric and external subcombination resonances is investigated, taking into account the effects of cubic geometric and inertia nonlinearities. The beams considered here are assumed to have large length-to-width aspect ratios and thin rectangular cross sections. Hence, the effects of shear deformations...