Transient Finite Element Analysis of the Exterior Structural Acoustics Problem

1990 ◽  
Vol 112 (2) ◽  
pp. 245-256 ◽  
Author(s):  
P. M. Pinsky ◽  
N. N. Abboud
Keyword(s):  
Finite Element ◽  
Single Layer ◽  
Mirror Image ◽  
Time Dependent ◽  
Element Approximation ◽  
Element Formulation ◽  
Structural Acoustics ◽  
Element Analysis ◽  
Displacement Potential ◽  
Variational Formalism

Considerable progress has been made in the development of numerical methods for the time-harmonic exterior structural acoustics problem involving solution of the coupled Helmholtz equation. In contrast, numerical solution procedures for the transient case have not been studied so extensively. In this paper a finite element formulation is proposed for solution of the time-dependent coupled wave equation over an infinite fluid domain. The formulation is based on a finite computational fluid domain surrounding the structure and incorporates a sequence of boundary operators on the fluid truncation boundary. These operators are designed to minimize reflection of outgoing waves and are based on an asymptotic expansion of the exact solution for the time-dependent problem. In the fluid domain, a mixed two-field finite element approximation, based on a specialization of the Hu-Washizu principle for elasticity, is proposed and employs pressure and displacement potential as independent fields. Since radiation dissipation renders the coupled system nonconservative, a variational formalism based on the Morse and Feshbach concept of a “mirror-image” adjoint system is used. The variational formalism also accommodates viscoelastic dissipation in the structure (or its coatings) and this is considered in the paper. Very accurate results for model problems involving a single layer of fluid elements have been obtained and are discussed in detail.

Finite Element Solution and Dispersion Analysis for the Transient Structural Acoustics Problem

1990 ◽  
Vol 43 (5S) ◽  
pp. S381-S388 ◽  
Author(s):  
N. N. Abboud ◽  
P. M. Pinsky
Keyword(s):  
Finite Element ◽  
Wave Equation ◽  
Three Dimensional ◽  
Finite Element Approximation ◽  
Dispersion Analysis ◽  
Time Dependent ◽  
Element Approximation ◽  
Element Formulation ◽  
Structural Acoustics ◽  
Boundary Operators

In this paper a finite element formulation is proposed for solution of the time-dependent coupled wave equation over an infinite fluid domain. The formulation is based on a finite computational fluid domain surrounding the structure and incorporates a sequence of boundary operators on the fluid truncation boundary. These operators are designed to minimize reflection of outgoing waves and are based on an asymptotic expansion of the exact solution for the time-dependent problem. The variational statement of the governing equations is developed from a Hamiltonian approach that is modified for nonconservative systems. The dispersive properties of finite element semidiscretizations of the three dimensional wave equation are examined. This analysis throws light on the performance of the finite element approximation over the entire range of wavenumbers and the effects of the order of interpolation, mass lumping, and direction of wave propagation are considered.

Finite Element Analysis of Beams With Constrained Damping Treatment Modeled Via Fractional Derivatives

1997 ◽  
Vol 50 (11S) ◽  
pp. S216-S224 ◽  
Author(s):  
Luis E. Sua´rez ◽  
Arsalan Shokooh ◽  
Jose´ Arroyo
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Single Layer ◽  
Element Model ◽  
Beam Element ◽  
Element Formulation ◽  
Beam Model ◽  
Element Analysis ◽  
Damping Material ◽  
Derivatives Of

This paper presents a finite element formulation for the modeling of beams and frames with artificial damping provided by means of a constrained single layer of damping material. The behavior of the damping material is described using the fractional derivative model of viscoelasticity. In this model, the first order derivatives of the strains in the constitutive equations of the viscoelastic materials are replaced by derivatives of order α < 1. The finite element model developed is a one-dimensional beam element with three degrees of freedom per node. The dynamic response is calculated with a procedure involving a transformation of the original equations of motion to the state space and its decoupling with the eigenvectors of a special eigenvalue problem. The accuracy of the modal properties obtained with the beam model is compared with those calculated from a more elaborate plane stress finite element model. It was found that the proposed beam element provides very accurate results and with much lower computational costs than the 2-D model.

Design and Analysis of Viscoelastic Seismic Dampers

2002 ◽  
Author(s):  
N. Shimizu ◽  
H. Nasuno ◽  
T. Yazaki ◽  
K. Sunakoda
Keyword(s):  
Finite Element ◽  
Constitutive Relation ◽  
Time Domain ◽  
Dynamic Properties ◽  
Design Procedure ◽  
Fe Analysis ◽  
Damping Capacity ◽  
Element Formulation ◽  
Element Analysis ◽  
Equivalent Viscous Damping

This paper describes a methodology of design and analysis of viscoelastic seismic dampers by means of the time domain finite element analysis. The viscoelastic constitutive relation of material incorporating with the fractional calculus has been derived and the finite element formulation based on the constitutive relation has been developed to analyze the dynamic property of seismic damper. A time domain computer program was developed by using the formulation. Dynamic properties of hysteresis loop, damping capacity, equivalent viscous damping coefficient, and equivalent spring constant are calculated and compared with the experimental results. Remarkable correlation between the FE analysis and the experiment is gained, and consequently the design procedure with the help of the FE analysis has been established.

FINITE ELEMENT ANALYSIS OF PIEZOELECTRIC ELASTICITY WITH SINGULAR INPLANE ELECTROELASTIC FIELDS

2006 ◽  
Vol 03 (01) ◽  
pp. 115-135 ◽  
Author(s):  
MENG-CHENG CHEN ◽  
JIAN-JUN ZHU ◽  
K. Y. SZE
Keyword(s):  
Finite Element ◽  
Ad Hoc ◽  
Wedge Angle ◽  
Electric Displacement ◽  
Weak Form ◽  
Efficient Solutions ◽  
Element Formulation ◽  
Displacement Fields ◽  
Element Analysis ◽  
Electroelastic Fields

An ad hoc one-dimensional finite element formulation is developed for the eigenanalysis of inplane singular electroelastic fields at material and geometric discontinuities in piezoelectric elastic materials by using the eigenfunction expansion procedure and the weak form of the governing equations for prismatic sectorial domains composed of piezoelectrics, composites or air. The order of the electroelastic singularities and the angular variation of the stress and electric displacement fields are obtained with the formulation. The influence of wedge angle, polarization orientation, material types, and boundary and interface conditions on the singular electroelastic fields and the order of their singularity are also examined. The simplicity and accuracy of the formulation are demonstrated by comparison to several analytical solutions for piezoelectric and composite multi-material wedges. The nature and speed of convergence suggests that the present eigensolution could be used in developing hybrid elements for use along with standard elements to yield accurate and computationally efficient solutions to problems having complex global geometries leading to singular electroelastic states.

Failure Analysis of Bamboo Bolt Connection in Uniaxial Tension by FEM by Considering Fiber Direction

2021 ◽  
Vol 71 (1) ◽  
pp. 58-64
Author(s):  
Raviduth Ramful
Keyword(s):  
Finite Element ◽  
Uniaxial Tension ◽  
Failure Modes ◽  
Damage Mechanism ◽  
Field Analysis ◽  
Fiber Direction ◽  
Element Formulation ◽  
Element Analysis ◽  
Test Standards ◽  
Lack Of Information

Abstract Full-culm bamboo has been used for millennia in construction. Specific connections are normally required to suit its unique morphology and nonuniform structure. Presently, the use of full-culm bamboo is limited in the construction industry as a result of a lack of information and test standards about the use and evaluation of full-culm connections. This study aims to further explore this area by investigating the failure modes in bamboo bolt connections in uniaxial tension by considering fiber direction in finite element analysis. Three types of bolt configurations of varying permutations, namely, single, dual, and orthogonal, were investigated. An orthotropic material was used as a constitutive model in finite element formulation to capture the inhomogeneity prevailing in bamboo culm. From the strain-field analysis of a hollow-inhomogeneous model representing bamboo, shear-out failure was dominant, as a localized area equivalent to the bolt diameter was affected due to high material orthotropy with high axial strength but weak radial and tangential strength. Bearing failure is assumed to precede shear-out failure at the bolt–bamboo contact interface, as the embedding strength was affected by localized strain concentration. The strain distribution in various bolt arrangements was found to vary between bolted connections of inhomogeneous-hollow geometry of bamboo and the ones of inhomogeneous-solid geometry representing timber. The observation in this study highlights the need for alternative design criteria to specifically assess the damage mechanism in bamboo connections.

Energy Harvesting From Droplet Interface Bilayers

2015 ◽  
Author(s):  
Ashok K. Kancharala ◽  
Eric Freeman ◽  
Michael K. Philen
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Energy Harvesting ◽  
Nonlinear Finite Element ◽  
Time Dependent ◽  
External Excitation ◽  
Biologically Inspired ◽  
Element Analysis ◽  
Interfacial Membrane ◽  
Membrane Deflection

Biologically inspired droplet interface bilayers have found applications in the development of hair cell sensors and other mechanotransduction applications. In this research, the flexoelectric capability of the droplet bilayers under external excitation is explored for energy harvesting. Traditionally, membrane capacitance models are being used for inferring the magnitude of the membrane deflection which do not account for the relation between the applied force or deflection and the deflection of the interfacial membrane and time dependent variations. In this work, the dynamic behavior of the droplets under external excitation has been modeled using nonlinear finite element analysis. A flexoelectric model including mechanical, electrical, and chemical sensitivities has been developed and coupled with the calculated bilayer deformations to predict the mechanotransductive response of the droplets under excitation. Using the developed framework, the possibilities of energy harvesting for different droplet configurations have been investigated and reported.

The Finite Element Analysis of Dynamic Interaction of High-Speed Shinkansen, the Rail, and Bridge

1993 ◽  
Author(s):  
Makoto Tanabe ◽  
Hajime Wakui ◽  
Nobuyuki Matsumoto
Keyword(s):  
Finite Element ◽  
Dynamic Response ◽  
High Speed ◽  
Response Analysis ◽  
Element Formulation ◽  
Element Analysis ◽  
Finite Element Program ◽  
The Finite Element Analysis ◽  
Element Program ◽  
The Impact

Abstract A finite element formulation to solve the dynamic behavior of high-speed Shinkansen cars, rail, and bridge is given. A mechanical model to express the interaction between wheel and rail is described, in which the impact of the rail on the flange of wheel is also considered. The bridge is modeled by using various finite elements such as shell, beam, solid, spring, and mass. The equations of motions of bridge and Shinkansen cars are solved under the constitutive and constraint equations to express the interaction between rail and wheel. Numerical method based on a modal transformation to get the dynamic response effectively is discussed. A finite element program for the dynamic response analysis of Shinkansen cars, rail, and bridge at the high-speed running has been developed. Numerical examples are also demonstrated.

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