scholarly journals Dynamic Instability in Shallow Arches under Transversal Forces and Plane Frames with Semirigid Connections

2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
William Luiz Fernandes ◽  
Daniel Boy Vasconcellos ◽  
Marcelo Greco
Keyword(s):  
Structural Engineering ◽  
Dynamic Instability ◽  
Physical Nonlinearity ◽  
The Finite Element Method ◽  
Structural Element ◽  
Shallow Arches ◽  
Semirigid Connections ◽  
Overall Stability ◽  
Plane Frames ◽  
The Time Domain

Structural engineering demands increasingly lighter systems, which can cause instability problems and compromise performance. A high slenderness index of a structural element makes it susceptible to instability. It is important to understand the problem, the limits of stability, and its postcritical behavior. An example that can occur in collapsed arches under a cross load is the dynamic snap-through behavior, where the structure in a given equilibrium condition jumps to a new remote equilibrium setting, causing usually sudden curvature. The semirigid connections are a source of physical nonlinearity and can influence the overall stability of the structural system, in addition to the distribution of stresses in the same system. Conventional approaches make use of static considerations. However, instability problems are inherently evolutionary processes, so a transient analysis is necessary for a complete description of structural behavior. The present work evaluates the geometrically nonlinear dynamic behavior of collapsed arches subjected to transverse force and plane frames with semirigid connections. The time domain responses, via Newmark's Method and positional formulation of the Finite Element Method, were obtained in terms of displacements, velocities, acceleration, and phase diagrams.

scholarly journals Stability charts based on the finite element method for underground cavities in soft carbonate rocks: validation through case-study applications

2019 ◽  
Vol 19 (10) ◽  
pp. 2079-2095 ◽  
Author(s):  
Michele Perrotti ◽  
Piernicola Lollino ◽  
Nunzio Luciano Fazio ◽  
Mario Parise
Keyword(s):  
Finite Element ◽  
Safety Margin ◽  
Structural Elements ◽  
The Finite Element Method ◽  
Geometrical Features ◽  
Overall Stability ◽  
Underground Cavities ◽  
The Stability ◽  
Rock Mechanical Properties

Abstract. The stability of man-made underground cavities in soft rocks interacting with overlying structures and infrastructures represents a challenging problem to be faced. Based upon the results of a large number of parametric two-dimensional (2-D) finite-element analyses of ideal cases of underground cavities, accounting for the variability both cave geometrical features and rock mechanical properties, specific charts have been recently proposed in the literature to assess at a preliminary stage the stability of the cavities. The purpose of the present paper is to validate the efficacy of the stability charts through the application to several case studies of underground cavities, considering both quarries collapsed in the past and quarries still stable. The stability graphs proposed by Perrotti et al. (2018) can be useful to evaluate, in a preliminary way, a safety margin for cavities that have not reached failure and to detect indications of predisposition to local or general instability phenomena. Alternatively, for sinkholes that already occurred, the graphs may be useful in identifying the conditions that led to the collapse, highlighting the importance of some structural elements (as pillars and internal walls) on the overall stability of the quarry system.

scholarly journals Application of Multi-Branch Cauer Circuits in the Analysis of Electromagnetic Transducers Used in Wireless Transfer Power Systems

Sensors ◽  
2020 ◽  
Vol 20 (7) ◽  
pp. 2052
Author(s):  
Milena Kurzawa ◽  
Cezary Jędryczka ◽  
Rafał M. Wojciechowski
Keyword(s):  
Power Systems ◽  
Field Model ◽  
Wireless Power Transfer ◽  
Equivalent Model ◽  
Power Transfer ◽  
Wireless Power ◽  
The Finite Element Method ◽  
Harmonic Field ◽  
Time Harmonic ◽  
The Time Domain

In this paper, the feasibility of applying a multi-branch equivalent model employing first- and second-order Cauer circuits for the analysis of electromagnetic transducers used in systems of wireless power transfer is discussed. A method of formulating an equivalent model (EqM) is presented, and an example is shown for a wireless power transfer system (WPTS) consisting of an air transformer with field concentrators. A method is proposed to synthesize the EqM of the considered transducer based on the time-harmonic field model, an optimization algorithm employing the evolution strategy (ES) and the equivalent Cauer circuits. A comparative analysis of the performance of the considered WPTS under high-frequency voltage supply calculated using the proposed EqM and a 3D field model in the time domain using the finite element method (FEM) was carried out. The selected results of the conducted analysis are presented and discussed.

Structural similitudes of stiffened cylinders

2017 ◽  
Vol 24 (3) ◽  
pp. 527-541 ◽  
Author(s):  
G Petrone ◽  
M Manfredonia ◽  
S De Rosa ◽  
F Franco
Keyword(s):  
Numerical Simulation ◽  
Structural Engineering ◽  
Scaling Laws ◽  
Similarity Theory ◽  
Design Tool ◽  
Engineering Science ◽  
The Finite Element Method ◽  
Engineering Problems ◽  
Incomplete Similarity ◽  
Scaled Models

Similarity theory is a branch of engineering science that deals with establishing conditions of similarity among phenomena and is applied to various fields, such as structural engineering problems, vibration and impact. Tests and numerical simulation of scaled models are still a valuable design tool, whose purpose is to accurately predict the behaviour of large or small prototypes through scaling laws applied to the experimental and numerical results. The aim of this paper is to predict the behaviour of the complete and incomplete similarity of stiffened cylinders by applying distorted scaling laws of the models in similitude. The investigation is performed using models based on the finite element method within commercial software. Two classes of cylinders scaled, with different laws, and, hence, reproducing replicas (exact similitude) and avatars (distorted similitude) are investigated.

Experimental and analytical investigation on the in-plane dynamic instability of arches owing to parametric resonance

2017 ◽  
Vol 24 (19) ◽  
pp. 4419-4432 ◽  
Author(s):  
Airong Liu ◽  
Zhicheng Yang ◽  
Hanwen Lu ◽  
Jiyang Fu ◽  
Yong-Lin Pi
Keyword(s):  
Parametric Resonance ◽  
Dynamic Instability ◽  
Damping Ratio ◽  
Analytical Investigation ◽  
Engineering Practice ◽  
Test Results ◽  
Periodic Load ◽  
Shallow Arches ◽  
Excitation Frequencies ◽  
Critical Regions

When an arch is subjected to a periodic load, it may lose in-plane stability dynamically owing to parametric resonance. Previous investigations have been concentrated on in-plane dynamic buckling of pin-ended shallow arches. However, in engineering practice, fixed arches with different rise-to-span ratios are often encountered. Little research on in-plane dynamic instability of deep fixed arches has been reported in the literature. This paper is concerned with experimental and analytical investigations for in-plane dynamic instability of fixed circular arches with rise-to-span ratios 1/8–1/2 under a central periodic load owing to parametric resonance. Experiments are carried out to determine the in-plane frequency and damping ratio of arches, to investigate critical regions of frequencies and amplitudes of the periodic load for in-plane dynamic instability of arches, and to explore effects of the rise-to-span ratio and additional weights on dynamic instability. The analytical method for determining the region of excitation frequencies and amplitudes of the periodic load causing in-plane instability of the arch is established using the Hamilton’s principle by accounting for effects of additional concentrated weights. Comparisons of analytical solutions with test results show that they agree with each other quite well. These results show that the rise-to-span ratio significantly influences the bandwidth of regions of critical excitation frequencies for in-plane dynamic instability of arches. The critical frequencies of the periodic load and their bandwidth increase with a decrease of the rise–span ratio of the arch, whereas the corresponding amplitude of the periodic load decreases at the same time. It is also found that the central concentrated weight influences in-plane dynamic instability of arches significantly. As the weight increases, the critical frequencies of excitation and their bandwidth for in-plane dynamic instability of arches decreases, whereas the corresponding amplitude of excitation increases.

Static and Dynamic Crush Testing and Analysis of a Rail Vehicle Corner Structural Element

1999 ◽  
Author(s):  
Ronald A. Mayville ◽  
Randolph P. Hammond ◽  
Kent N. Johnson
Keyword(s):  
Structural Engineering ◽  
Current Strength ◽  
Test Element ◽  
Structural Element ◽  
Element Analysis ◽  
Explicit Finite Element ◽  
Rail Vehicle ◽  
Explicit Finite Element Analysis ◽  
Deformation And Fracture ◽  
Baseline State

Abstract This paper presents the results of an experimental study to establish the strength and energy absorption capability of cab car rail vehicle corner structures built to current strength requirements and for structures modified to carry higher loads and absorb more energy. We reviewed current structures and designed an end beam test element — the most common way of meeting current requirements — whose strength in the baseline state was at least 150,000 lbf. This design was then modified to provide a strength of over 400,000 lbf. The designs, which included consideration of the deformation and fracture response under impact loading, were carried out using conventional structural engineering methods and explicit finite element analysis.

Dynamic Instability of Delaminated Composite Plates under Parametric Excitation

2006 ◽  
Vol 326-328 ◽  
pp. 1765-1768 ◽  
Author(s):  
Meng Kao Yeh ◽  
Kuei Chang Tung
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Parametric Excitation ◽  
Composite Plate ◽  
Dynamic Instability ◽  
Composite Plates ◽  
Modal Parameters ◽  
The Finite Element Method ◽  
Electromagnetic Device ◽  
Instability Regions

The dynamic instability behavior of delaminated composite plates under transverse excitations was investigated experimentally and analytically. An electromagnetic device, acting like a spring with alternating stiffness, was used to parametrically excite the delaminated composite plates transversely. An analytical method, combined with the finite element method, was used to determine the instability regions of the delaminated composite plates based on the modal parameters of the composite plate and the position, the stiffness of the electromagnetic device. The delamination size and position of composite plates were varied to assess their effects on the excitation frequencies of simple and combination resonances in instability regions. The experimental results were found to agree with the analytical ones.

Transient Vibroacoustic Analysis of Functionally Graded Plates

2021 ◽  
pp. 1-36
Author(s):  
Avnish Mahendra Pandey ◽  
K. V. Nagendra Gopal
Keyword(s):  
Volume Fraction ◽  
Free Field ◽  
Shear Deformation Theory ◽  
Structural Response ◽  
Functionally Graded ◽  
Functionally Graded Plates ◽  
The Finite Element Method ◽  
Time Marching ◽  
The Time Domain ◽  
Vibroacoustic Response

Abstract This paper presents the vibroacoustic response of pure functionally graded plates under transient loading of mechanical nature. The functionally graded plate is modelled using the conventional first-order shear deformation theory to incorporate the effects of transverse shear and rotary inertia. The mid-surface variables are determined using the finite element method. Transient structural response is determined using Newmark Beta time marching scheme and the acoustic pressure in the free field is obtained using the time-domain Rayleigh integral. The effective material properties of the FG plate and the transient response of both the structural and acoustic fields have been computed in MATLAB. The influence of the volume fraction index, thickness ratio and boundary conditions of pure FG plate on its transient vibroacoustic response is investigated by a detailed parametric study.

Numerical Simulation of Ultrasonic Shear Wave Propagation Based on the Finite Element Method

2014 ◽  
Vol 488-489 ◽  
pp. 926-929 ◽  
Author(s):  
Jian Ma ◽  
Yang Zhao ◽  
Ji Hua Sun ◽  
Shuai Liu
Keyword(s):  
Numerical Simulation ◽  
Shear Wave ◽  
Present Method ◽  
Steel Plate ◽  
Mode Conversion ◽  
Simulation Method ◽  
The Finite Element Method ◽  
Propagation Process ◽  
The Time Domain ◽  
Ultrasonic Shear

The present paper provided a kind of numerical simulation method which was employed to guide the process of ultrasonic nondestructive testing and analyze the inspection results. The simulation concerning the propagation process of shear wave in the steel plate was carried out using the ANSYS, according to the mechanism of ultrasonic mode conversion. Then, the frequency, velocity and refraction angle were extracted from the time-domain date in order to verify the simulation. It is found that the result of simulation agrees well with the theoretical one, which shows that the present method is correct and reliable.

scholarly journals Vibration of a Laminated Beam with a Delamination Including Contact Effects

2004 ◽  
Vol 11 (3-4) ◽  
pp. 157-171 ◽  
Author(s):  
W. Ostachowicz ◽  
A. Żak
Keyword(s):  
Time Domain ◽  
Dynamic Contact ◽  
Equation Of Motion ◽  
Newmark Method ◽  
The Finite Element Method ◽  
Laminated Beam ◽  
Contact Algorithm ◽  
Vibration Responses ◽  
Newton Raphson ◽  
The Time Domain

Certain results are presented in this paper on damped vibration of a laminated cantilever beam with a single closing delamination. In order to investigate this task the finite element method has been applied in the current study. For modelling the beam higher order shear deformation beam finite elements have been used. The vibration of the beam is investigated in the time domain using a dynamic contact algorithm developed by the authors. The algorithm is based on the Newmark method and also incorporates a Newton-Raphson based procedure for resolving the equation of motion. The time series obtained from solving the equation of motion have been subsequently analysed in the frequency domain by using FFT (Fast Fourier Transform). The vibration responses of the beam due to various harmonic and impulse excitations, at different delamination locations, and for different delamination lengths, as well as changes in the dissipation of damping energy due to the delamination, have all been considered in the paper.

scholarly journals Features of compressed rods calculations with account of initial imperfections and creep effects

2020 ◽  
Vol 164 ◽  
pp. 02003
Author(s):  
Viacheslav Chepurnenko ◽  
Batyr Yazyev ◽  
Ludmila Dubovitskaya
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Software Package ◽  
Physical Nonlinearity ◽  
The Finite Element Method ◽  
Ansys Software ◽  
Modular Theory ◽  
Initial Imperfections ◽  
Creep Models ◽  
The Finite Difference Method

The article presents solutions to the problem of rod buckling, taking into account creep effects. Trigonometric series, the finite difference method in combination with the programming language MATLAB, as well as the finite element method in the ANSYS software package were used in the solutions. The behavior of the rods is researched for two types of relations between strain and stress during creep, with strains in an explicit and implicit form. When solving, the criterion of initial imperfections with their different values is used, as well as the tangential-modular theory. The results obtained for the two creep models are compared. The conclusion is made about the accuracy of the results of calculations in ANSYS with the presence of a combination of geometric and physical nonlinearity for various creep models.

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