scholarly journals On sensitivity analysis of unsteady responses for FEM models of beams

2020 ◽  
Vol S-I (2) ◽  
pp. 103-109
Author(s):  
M. Mironov ◽  
Keyword(s):  
Cross Sections ◽  
Quality Criteria ◽  
Element Model ◽  
Optimality Criteria ◽  
Design Parameters ◽  
Fe Model ◽  
Vibration Frequencies ◽  
Various Boundary Conditions ◽  
Analytical Derivatives ◽  
Analytical Expressions

This paper discusses optimal design of structures in terms of various quality criteria with limitations for the parameters of dynamic stress-strain state (steady, unsteady, spectral). Efficiency of the methods based on the compliance with indirect optimality criteria, in particular, on the Kuhn-Tucker conditions, considerably depends on fast and accurate calculations of derivatives for the parameters of state in terms of design parameters, which is achieved by obtaining the analytical expressions. Introduction of these expressions to the optimization of FEM-based models is only possible if structural design parameters and the parameters of stiffness matrix and element masses are linked explicitly. The purpose of this work is to finalize and verify the methods for obtaining analytical derivatives of design parameters as functions of vibration frequencies, forced harmonic vibration frequencies and natural vibration frequencies of finite-element model with subsequent transition to completely analytical (not subtractive) differentiation of unsteady and spectral responses of design parameters. For an FE model of beam with a large number (one hundred) of finite elements, this study obtained and verified, for various boundary conditions and loading scenarios, the distributions of sensitivity coefficients for steady dynamic parameters in terms of design parameters, i.e. cross-sections of elements.

Nonlinear Vibrations of Beams, Strings, Plates, and Membranes Without Initial Tension

2004 ◽  
Vol 71 (4) ◽  
pp. 551-559 ◽  
Author(s):  
Zhongping Bao ◽  
Subrata Mukherjee ◽  
Max Roman ◽  
Nadine Aubry
Keyword(s):  
Boundary Conditions ◽  
Young’S Modulus ◽  
Cross Sections ◽  
Nonlinear Vibrations ◽  
Young's Modulus ◽  
Thin Plates ◽  
Radius Of Gyration ◽  
Initial Tension ◽  
Various Boundary Conditions ◽  
Analytical Expressions

The subject of this paper is nonlinear vibrations of beams, strings (defined as beams with very thin uniform cross sections), plates and membranes (defined as very thin plates) without initial tension. Such problems are of great current interest in minute structures with some dimensions in the range of nanometers (nm) to micrometers (μm). A general discussion of these problems is followed by finite element method (FEM) analyses of beams and square plates with different boundary conditions. It is shown that the common practice of neglecting the bending stiffness of strings and membranes, while permissible in the presence of significant initial tension, is not appropriate in the case of nonlinear vibrations of such objects, with no initial tension, and with moderately large amplitude (of the order of the diameter of a string or the thickness of a plate). Approximate, but accurate analytical expressions are presented in this paper for the ratio of the nonlinear to the linear natural fundamental frequency of beams and plates, as functions of the ratio of amplitude to radius of gyration for beams, or the ratio of amplitude to thickness for square plates, for various boundary conditions. These expressions are independent of system parameters—the Young’s modulus, density, length, and radius of gyration for beams; the Young’s modulus, density, length of side, and thickness for square plates. (The plate formula exhibits explicit dependence on the Poisson’s ratio.) It is expected that these results will prove to be useful for the design of macro as well as micro and nano structures.

scholarly journals DESIGN OPTIMIZATION OF A CIVIL STRUCTURE USING NUMERICAL SIMULATIONS

2020 ◽  
Vol 10 (2) ◽  
pp. 5-13
Author(s):  
Florian VLĂDULESCU
Keyword(s):  
Geometric Model ◽  
Input Parameter ◽  
Element Model ◽  
Design Parameters ◽  
Fe Model ◽  
Shell Elements ◽  
Optimization Study ◽  
Input Parameters ◽  
Parametric Relationships

This optimization study aims to determine the effect of each input parameter on the output parameters, how the input parameters can interact with each other and also it is emphasized the determination of the values for the input parameters that optimize the responses. In this study, the objective is to obtain an optimal configuration for a resistance structure specific to a telecommunications tower. For this purpose, a variable geometric model using design parameters is created, based on which a 3D finite element model (FEM) is obtained, which is used in the optimization study. The FE model is updated automatically for each version of geometric model and is made using beam and shell elements. Design of Experiments (DOE) methodology allows for using a mathematical model that predicts how input parameters interact to create output responses in an optimization process. Parameters’ correlation and monitoring allow for identifying important parameters and the correlation matrix and sensitivity graphs also help understanding the parametric relationships. Variation limits for design parameters are defined and these parameters can have integer or fractional values.

A Hybrid LP/FE Model for the Dynamic Analysis of External Gear Pumps

2007 ◽  
Author(s):  
Emiliano Mucchi ◽  
Valerio Venturi ◽  
Giorgio Dalpiaz
Keyword(s):  
Finite Element ◽  
Internal Surface ◽  
Element Model ◽  
Design Parameters ◽  
Fe Model ◽  
Gear Pump ◽  
Time Varying ◽  
Pump Operation ◽  
Lumped Parameter ◽  
Lp Model

In this work a hybrid lumped-parameter finite-element model of an external gear pump for automotive applications is presented and experimentally assessed; the finite element (FE) model regards the external parts of the pump (case and end plates) while the lumped-parameter (LP) model regards the interior parts (bushes and gears). The LP model is a non linear kineto-elastodynamic model and includes the most important phenomena involved in the pump operation as time-varying oil pressure distribution on gears, time-varying meshing stiffness and hydrodynamic journal bearing reactions. A forced vibration analysis has been carried out by means of the FE model for the evaluation of the acceleration levels on the external surfaces of the pump; for this analysis, the damping has been estimated using data coming from an experimental modal analysis (EMA) whereas the excitation forces, acting on the internal surface of the case due to bearing reactions and pressure forces, have been obtained from the LP model. In this sense the model is globally a hybrid LP/FE model. The model has been assessed using experiments: the experimental accelerations measured during run-up tests have been compared with the simulated accelerations coming from the FE/LP model. Finally the assessed model has been used in order to identify the effects of design parameters in terms of case vibrations.

A Simplified Design Model for Modular Steel Buildings Subject to Vapor Cloud Explosions (VCEs)

2020 ◽  
Vol 14 ◽  
Author(s):  
Osama Bedair
Keyword(s):  
Dynamic Response ◽  
Minimum Cost ◽  
Design Parameters ◽  
Front Wall ◽  
Steel Buildings ◽  
Element Analysis ◽  
Analysis And Design ◽  
Vapor Cloud ◽  
Building Components ◽  
Analytical Expressions

Background: Modular steel buildings (MSB) are extensively used in petrochemical plants and refineries. Limited guidelines are available in the industry for analysis and design of (MSB) subject to accidental vapor cloud explosions (VCEs). Objectives: The paper presents simplified engineering model for modular steel buildings (MSB) subject to accidental vapor cloud explosions (VCEs) that are extensively used in petrochemical plants and refineries. Method: A Single degree of freedom (SDOF) dynamic model is utilized to simulate the dynamic response of primary building components. Analytical expressions are then provided to compute the dynamic load factors (DLF) for critical building elements. Recommended foundation systems are also proposed to install the modular building with minimum cost. Results: Numerical results are presented to illustrate the dynamic response of (MSB) subject to blast loading. It is shown that (DLF)=1.6 is attained at (td/t)=0.4 for front wall (W1) with (td/T)=1.25. For side walls (DLF)=1.41 and is attained at (td/t)=0.6. Conclusions: The paper presented simplified tools for analysis and design of (MSB) subject accidental vapor cloud blast explosions (VCEs). The analytical expressions can be utilized by practitioners to compute the (MSB) response and identify the design parameters. They are simple to use compared to Finite Element Analysis.

scholarly journals Total cross sections of eγ → $$ eX\overline{X} $$ processes with X = μ, γ, e via multiloop methods

2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
Roman N. Lee ◽  
Alexey A. Lyubyakin ◽  
Vyacheslav A. Stotsky
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Elliptic Integral ◽  
High Energy ◽  
Calculation Methods ◽  
Complete Elliptic Integral ◽  
Total Cross Sections ◽  
Multiloop Calculation ◽  
The Cross ◽  
Analytical Expressions

Abstract Using modern multiloop calculation methods, we derive the analytical expressions for the total cross sections of the processes e−γ →$$ {e}^{-}X\overline{X} $$ e − X X ¯ with X = μ, γ or e at arbitrary energies. For the first two processes our results are expressed via classical polylogarithms. The cross section of e−γ → e−e−e+ is represented as a one-fold integral of complete elliptic integral K and logarithms. Using our results, we calculate the threshold and high-energy asymptotics and compare them with available results.

Finite Element Analysis of the Distributed Vibration Absorbers for Structural Noise Control

2005 ◽  
Author(s):  
Ashwini Gautam ◽  
Chris Fuller ◽  
James Carneal
Keyword(s):  
Finite Element ◽  
Numerical Model ◽  
Base Plate ◽  
Element Model ◽  
Fe Model ◽  
Vibration Absorbers ◽  
Element Analysis ◽  
Poroelastic Media ◽  
Hexahedral Elements ◽  
Component Models

This work presents an extensive analysis of the properties of distributed vibration absorbers (DVAs) and their effectiveness in controlling the sound radiation from the base structure. The DVA acts as a distributed mass absorber consisting of a thin metal sheet covering a layer of acoustic foam (porous media) that behaves like a distributed spring-mass-damper system. To assess the effectiveness of these DVAs in controlling the vibration of the base structures (plate) a detailed finite elements model has been developed for the DVA and base plate structure. The foam was modeled as a poroelastic media using 8 node hexahedral elements. The structural (plate) domain was modeled using 16 degree of freedom plate elements. Each of the finite element models have been validated by comparing the numerical results with the available analytical and experimental results. These component models were combined to model the DVA. Preliminary experiments conducted on the DVAs have shown an excellent agreement between the results obtained from the numerical model of the DVA and from the experiments. The component models and the DVA model were then combined into a larger FE model comprised of a base plate with the DVA treatment on its surface. The results from the simulation of this numerical model have shown that there has been a significant reduction in the vibration levels of the base plate due to DVA treatment on it. It has been shown from this work that the inclusion of the DVAs on the base plate reduces their vibration response and therefore the radiated noise. Moreover, the detailed development of the finite element model for the foam has provided us with the capability to analyze the physics behind the behavior of the distributed vibration absorbers (DVAs) and to develop more optimized designs for the same.

scholarly journals Numerical Modelling of Reinforced Concrete Slender Walls Subjected to Coupled Axial Tension–Flexure

2021 ◽  
Vol 15 (1) ◽  
Author(s):  
Xiaowei Cheng ◽  
Haoyou Zhang
Keyword(s):  
Reinforced Concrete ◽  
Plastic Hinge ◽  
Element Model ◽  
Lateral Loading ◽  
Design Parameters ◽  
Seismic Behaviour ◽  
High Rise ◽  
Ultimate Deformation ◽  
Axial Tension ◽  
Plastic Hinge Length

AbstractUnder strong earthquakes, reinforced concrete (RC) walls in high-rise buildings, particularly in wall piers that form part of a coupled or core wall system, may experience coupled axial tension–flexure loading. In this study, a detailed finite element model was developed in VecTor2 to provide an effective tool for the further investigation of the seismic behaviour of RC walls subjected to axial tension and cyclic lateral loading. The model was verified using experimental data from recent RC wall tests under axial tension and cyclic lateral loading, and results showed that the model can accurately capture the overall response of RC walls. Additional analyses were conducted using the developed model to investigate the effect of key design parameters on the peak strength, ultimate deformation capacity and plastic hinge length of RC walls under axial tension and cyclic lateral loading. On the basis of the analysis results, useful information were provided when designing or assessing the seismic behaviour of RC slender walls under coupled axial tension–flexure loading.

scholarly journals Bond Behaviour of Near-Surface Mounted Strips in RC Beams—Experimental Investigation and Numerical Simulations

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4362
Author(s):  
Renata Kotynia ◽  
Hussien Abdel Baky ◽  
Kenneth W. Neale
Keyword(s):  
Concrete Strength ◽  
Element Model ◽  
Steel Reinforcement ◽  
Reinforcement Ratio ◽  
Experimental Program ◽  
Fe Model ◽  
Bond Behaviour ◽  
Near Surface ◽  
Cfrp Laminates ◽  
Near Surface Mounted

This paper presents an investigation of the bond mechanism between carbon fibre reinforced polymer (CFRP) laminates, concrete and steel in the near-surface mounted (NSM) CFRP-strengthened reinforced concrete (RC) beam-bond tests. The experimental program consisting of thirty modified concrete beams flexurally strengthened with NSM CFRP strips was published in. The effects of five parameters and their interactions on the ultimate load carrying capacities and the associated bond mechanisms of the beams are investigated in this paper with consideration of the following investigated parameters: beam span, beam depth, longitudinal tensile steel reinforcement ratio, the bond length of the CFRP strips and compressive concrete strength. The longitudinal steel reinforcement was cut at the beam mid-span in four beams to investigate a better assessment of the influence of the steel reinforcement ratio on the bond behaviour of CFRP to concrete bond behaviour. The numerical analysis implemented in this paper is based on a nonlinear micromechanical finite element model (FEM) that was used for investigation of the flexural behaviour of NSM CFRP-strengthened members. The 3D model based on advanced CFRP to concrete bond responses was introduced to modelling of tested specimens. The FEM procedure presents the orthotropic behaviour of the CFRP strips and the bond response between the CFRP and concrete. Comparison of the experimental and numerical results revealed an excellent agreement that confirms the suitability of the proposed FE model.

Finite Element Model of Human Cochlea Considering of the Helicotrema Size

2013 ◽  
Vol 456 ◽  
pp. 576-581 ◽  
Author(s):  
Li Fu Xu ◽  
Na Ta ◽  
Zhu Shi Rao ◽  
Jia Bin Tian
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Basilar Membrane ◽  
Round Window ◽  
Element Model ◽  
Oval Window ◽  
Fe Model ◽  
Cochlear Duct ◽  
Human Cochlea ◽  
Set Up

A 2-D finite element model of human cochlea is established in this paper. This model includes the structure of oval window, round window, basilar membrane and cochlear duct which is filled with fluid. The basilar membrane responses are calculated with sound input on the oval window membrane. In order to study the effects of helicotrema on basilar membrane response, three different helicotrema dimensions are set up in the FE model. A two-way fluid-structure interaction numerical method is used to compute the responses in the cochlea. The influence of the helicotrema is acquired and the frequency selectivity of the basilar membrane motion along the cochlear duct is predicted. These results agree with the experiments and indicate much better results are obtained with appropriate helicotrema size.

SCATTERING AND DISSOCIATION OF DEUTERONS AND 3H-NUCLEI BY NUCLEI AT INTERMEDIATE ENERGIES

1995 ◽  
Vol 04 (03) ◽  
pp. 563-586 ◽  
Author(s):  
YU. A. BEREZHNOY ◽  
V. YU. KORDA
Keyword(s):  
Elastic Scattering ◽  
Closed Form ◽  
Cross Sections ◽  
Differential Cross ◽  
Particle System ◽  
Center Of Mass ◽  
Scattering Angle ◽  
Intermediate Energies ◽  
Oscillating Functions ◽  
Analytical Expressions

We present a closed-form description that enables us to obtain the analytical expressions for the elastic scattering and dissociation differential cross-sections of deuterons and 3H-nuclei by heavy target nuclei. The resulting expressions are used to analyze the data for the 110 MeV deuterons elastically scattered on 208Pb-nuclei. The dissociation cross-sections of deuterons and 3H-nuclei are the oscillating functions of the scattering angle of the released two- and three-nucleon-particle system center-of-mass.

Sign in / Sign up

Export Citation Format

Share Document