Transient Dynamics of Harmonic Devices Under Thermal Loading

2018 ◽  
Author(s):  
Heshan Unamboowe ◽  
Amit Shukla
Keyword(s):  
Thermal Properties ◽  
Thermal Loading ◽  
Harmonic Excitation ◽  
Engineering Industry ◽  
Dynamic Responses ◽  
Transient Dynamics ◽  
Beam Model ◽  
Curved Beams ◽  
Varying Λ ◽  
The Time Domain

Curved beams are an essential structural form widely used in the engineering industry. When loaded past a critical point, they may buckle in a bifurcation or snap-through mode. Studies have shown that structural buckling problems are highly sensitive to slight changes in thermal properties. A shallow curved beam model subjected to a harmonic excitation is considered in this paper. A simplified, dimensionless one degree of freedom model is obtained following the works of [1]. Using this model, the transient dynamics of the system is analyzed for varying forcing parameters. The effect of the arch rise (λ) is also examined as the varying thermal properties effect the geometry of the beam system. Dynamic and transient dynamic responses of the system are obtained in the time domain for both constant and linearly varying λ. Wavelet analysis is utilized to analyze this data in the frequency domain and it provided an effective representation of the system responses that are localized in both time and frequency.

Dynamics of Beams under Coupled Thermo-Mechanical Loading

2016 ◽  
Vol 849 ◽  
pp. 57-64
Author(s):  
Emil Manoach ◽  
Anna Warminska ◽  
Jerzy Warminski
Keyword(s):  
Timoshenko Beam ◽  
Thermal Loading ◽  
Resonance Condition ◽  
Heat Pulse ◽  
Transient Dynamics ◽  
Beam Model ◽  
Large Deflections ◽  
Timoshenko Beam Model ◽  
Mechanical Problem ◽  
Different Response

An effect of thermal loading on vibrations of beams is investigated in the paper. A beam is considered as an extended Timoshenko beam model with nonlinear terms resulted from large deflections. Dynamics of the structure is analysed under thermal and mechanical loadings considering transient dynamics due to a heat pulse imposed to the beam. The numerical method for solving coupled thermo-mechanical problem is presented. On this basis the importance of the heat pulse intensity around the first resonance condition is demonstrated. The effect of the heat on the the complex transient dynamics of the beam and its qualitatively different response is shown as well.

Dynamic responses of clearance-type non-linear systems subjected to base harmonic excitation and their experimental verification

2021 ◽  
pp. 107754632110128
Author(s):  
K Renji
Keyword(s):  
Linear Systems ◽  
Experimental Verification ◽  
Harmonic Excitation ◽  
Dynamic Responses ◽  
Maximum Response ◽  
Base Excitation ◽  
Mathematical Expressions ◽  
Non Linear Systems ◽  
Propellant Tank ◽  
Different Levels

Realistic joints in a spacecraft structure have clearances at the interfacing parts. Many such systems can be considered to be having bilinear stiffness. A typical example is the propellant tank assembled with the structure of a spacecraft. However, it is seen that the responses of such systems subjected to base excitation are rarely reported. In this work, mathematical expressions for theoretically estimating the amplitude of its response, the frequency at which the response is the maximum and the maximum response when it is subjected to base sine excitation are derived. Several experiments are conducted on a typical such system subjecting it to different levels of base sine excitation. The frequency at which the response is the maximum reduces with the magnitude of excitation. The expressions derived in this work can be used in estimating the amplitudes of responses and their characteristics reasonably well.

Investigating the Effect of Prestress Force on Cross-Tensioned Concrete Pavement Vibration

2020 ◽  
Vol 2674 (8) ◽  
pp. 875-886
Author(s):  
Hongduo Zhao ◽  
Mengyuan Zeng ◽  
Hui Chen ◽  
Jianming Ling ◽  
Difei Wu
Keyword(s):  
Spectral Distribution ◽  
Field Testing ◽  
Dominant Frequency ◽  
Fe Analysis ◽  
Concrete Pavement ◽  
Vibration Characteristics ◽  
Dynamic Responses ◽  
Power Spectral ◽  
Force Monitoring ◽  
The Time Domain

Prestress force loss is crucial to the structural performance of cross-tensioned concrete pavement (CTCP). Severe loss in prestress force will reduce the constricting-cracking capacity of the CTCP, resulting in damage with load and temperature applied. Vibration-based methods are commonly used in prestress force monitoring, but few relative studies are reported into CTCP and the relationship between prestress force and CTCP vibration is still unclear. The purpose of this paper is to investigate the effect of prestress force on CTCP vibration. The vibration characteristics of CTCP subjected to different prestress forces were studied through field testing and finite element (FE) analysis. Impulse load was applied as excitation at the anchorage zone and dynamic responses were measured in the time domain. A signal processing method was employed to obtain short-time power spectral from original vibration signals, which was utilized to extract vibration characteristics in time and frequency. As shown in both the field testing and the FE analysis, the prestress force has a more significant effect on frequency spectral distribution, rather than the dominant frequency. Integrated frequency is proved to be a reliable index for describing frequency spectral distribution and has a good correlation with prestress force, which suggests it can be used to reflect the change in prestress force. Overall, these findings indicate that vibration testing has potential in prestress force monitoring in CTCP, though the practicality of this method requires further demonstration.

scholarly journals Dynamic Responses of an Overhead Crane’s Beam Subjected to a Moving Trolley with a Pendulum Payload

2019 ◽  
Vol 2019 ◽  
pp. 1-14 ◽  
Author(s):  
Huasen Liu ◽  
Wenming Cheng ◽  
Yinqi Li
Keyword(s):  
Integral Method ◽  
Lagrange Equation ◽  
Dynamic Responses ◽  
Underactuated System ◽  
Beam Model ◽  
Moving Mass ◽  
Overhead Crane ◽  
Precise Positioning ◽  
Pendulum Swing ◽  
Coupling System

An overhead crane with a flexible cable is an underactuated system; the vibration of the crane’s beam and the residual swinging of the payloads cause fatigue in the crane and affect the precise positioning of the payloads. In this paper, the coupling system of an overhead crane was simplified to that of a moving mass with pendulum swing passing beam model. The differential equation motion of a coupled overhead crane system was derived based on the Lagrange equation. Mathematical solution was carried out by using the Newmark-β integral method. The influences of the trolley’s acceleration and the parameters of the payloads on the vibration of the beam and the payloads’ swing were, respectively, analyzed. A numerical analysis of the results indicates that increasing the mass of the payloads leads to a larger deflection of the beam, whereas increasing the speed and acceleration of the trolley does not obviously influence the maximum deflection of the central beam.

Dynamic Response of 3D Surface/Embedded Rigid Foundations of Arbitrary Shapes on Multi-Layered Soils in Time Domain

2019 ◽  
Vol 19 (09) ◽  
pp. 1950106 ◽  
Author(s):  
Zejun Han ◽  
Mi Zhou ◽  
Xiaowen Zhou ◽  
Linqing Yang
Keyword(s):  
Dynamic Response ◽  
Frequency Domain ◽  
Time Domain ◽  
Dynamic Stiffness ◽  
Dynamic Responses ◽  
Rigid Foundation ◽  
Layered Soils ◽  
Stiffness Matrices ◽  
The Time Domain ◽  
Arbitrary Shapes

Significant differences between the predicted and measured dynamic response of 3D rigid foundations on multi-layered soils in the time domain were identified due to the existence of uncertainties, which makes the issue a complicated one. In this study, a numerical method was developed to determine the dynamic responses of 3D rigid surfaces and embedded foundations of arbitrary shapes that are bonded to a multi-layered soil in the time domain. First, the dynamic stiffness matrices of the rigid foundations in the frequency domain are calculated via integral domain transformation. Secondly, a dynamic stiffness equation for rigid foundations in the time domain is established via the mixed variables formulation, which is based on the discrete dynamic stiffness matrices in the frequency domain. The proposed method can be applied to the treatment of systems with multiple degrees of freedom without losing the true information that concerns the coupling characteristics. Numerical examples are presented to demonstrate the accuracy of the proposed method for predicting the horizontal, vertical, rocking, and torsional vibrations. Further, a parametric study was carried out to provide insight into the dynamic behavior of the soil–foundation interaction (SFI) while considering soil nonhomogeneity. The results indicate that the elastic modulus of the soil has a significant impact on the dynamic responses of the rigid foundation. Finally, a numerical example of a rigid foundation resting on a six-layered, semi-infinite soil demonstrates that the proposed method can be used to deal with multi-layered media in the time domain in a relatively easy way.

Investigating vibrations of viscoelastic fluid-conveying carbon nanotubes resting on viscoelastic foundation using a nonlocal fractional Timoshenko beam model

2020 ◽  
pp. 239779142093170
Author(s):  
M Faraji Oskouie ◽  
R Ansari ◽  
H Rouhi
Keyword(s):  
Carbon Nanotubes ◽  
Free Vibration ◽  
Boundary Conditions ◽  
Timoshenko Beam ◽  
Time Domain ◽  
Beam Model ◽  
Viscoelastic Foundation ◽  
Timoshenko Beam Model ◽  
Governing Equations ◽  
The Time Domain

On the basis of fractional viscoelasticity, the size-dependent free-vibration response of viscoelastic carbon nanotubes conveying fluid and resting on viscoelastic foundation is studied in this article. To this end, a nonlocal Timoshenko beam model is developed in the context of fractional calculus. Hamilton’s principle is applied in order to obtain the fractional governing equations including nanoscale effects. The Kelvin–Voigt viscoelastic model is also used for the constitutive equations. The free-vibration problem is solved using two methods. In the first method, which is limited to the simply supported boundary conditions, the Galerkin technique is employed for discretizing the spatial variables and reducing the governing equations to a set of ordinary differential equations on the time domain. Then, the Duffing-type time-dependent equations including fractional derivatives are solved via fractional integrator transfer functions. In the second method, which can be utilized for carbon nanotubes with different types of boundary conditions, the generalized differential quadrature technique is used for discretizing the governing equations on spatial grids, whereas the finite difference technique is used on the time domain. In the results, the influences of nonlocality, geometrical parameters, fractional derivative orders, viscoelastic foundation, and fluid flow velocity on the time responses of carbon nanotubes are analyzed.

scholarly journals Dynamic Analysis of Vehicle Track Coupling Based on Double Beam Track Model

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Yayun Qi ◽  
Huanyun Dai ◽  
Jianjin Yang ◽  
Kun Xu
Keyword(s):  
Frequency Band ◽  
High Frequency ◽  
Harmonic Excitation ◽  
Vertical Acceleration ◽  
Beam Model ◽  
Vertical Force ◽  
Nonlinear Method ◽  
Single Beam ◽  
Double Beam ◽  
Random Irregularity

The rail was considered as double Timoshenko beam in this paper, applied to the vehicle track coupling dynamics model; the Hertz nonlinear method is used to calculate the wheel rail contact force. Wheel rail vertical force and response of vehicle are calculated by using the model under random irregularity and single harmonic excitation; at the same time, wheel rail force and vertical acceleration response of 3-order, 10-order, and 19-order wheel polygon were calculated. The results show that, under the excitation of random irregularity, the wheel rail vertical force of two models was very close in the low frequency band, and the response of the double beam model in the high frequency band of 200–1000 Hz is larger than the single beam model, and the acceleration and displacement responses of the double beam model are relatively close. Under a single harmonic excitation, the double beam model has a shorter wheel rail force attenuation time than that of the single beam model. And wheel rail force peak value of double beam model is 9% larger than that of single beam model. Similarly, the vertical displacement of the double beam model increased by 2.6%. Under the 3-order and 10-order wheel polygon excitation, vertical wheel rail peak force of double beam is, respectively, 37.5% and 50% larger than single beam model; the vertical frame acceleration amplitude is 1 g and 1.7 g; under the 19-order polygon wheel excitation, the difference of the wheel rail force between two models is very small, and the amplitude of acceleration of bogie is 2.3 g. And double beam model has more advantage in analyzing high frequency problems such as wheel polygonization.

Strength of a Container Ship in Extreme Waves Obtained by Nonlinear Hydroelastoplasticity Dynamic Analysis and Finite Element Modeling

2016 ◽  
Vol 138 (3) ◽  
Author(s):  
Weiqin Liu ◽  
Xuemin Song ◽  
Weiguo Wu ◽  
Katsuyuki Suzuki
Keyword(s):  
Finite Element ◽  
Nonlinear Dynamic ◽  
Structural Response ◽  
Bending Moment ◽  
Dynamic Responses ◽  
Container Ship ◽  
Extreme Waves ◽  
Wave Models ◽  
The One ◽  
The Time Domain

Extreme waves have caused a lot of ship accidents and casualties. In this paper, a two-dimensional (2D) hydroelastoplasticity method is proposed to study the nonlinear dynamic responses of a container ship in extreme waves. On the one hand, the traditional ultimate strength evaluation is mainly performed using a quasi-static assumption without considering the dynamic wave effect. On the other hand, the dynamic response of a ship induced by a wave is studied based on hydroelasticity theory, which means the ship structural response to large waves is linear. Therefore, a 2D hydroelastoplasticity method that accounts for the coupling between the time-domain wave and ship beam for nonlinear vertical bending moment (VBM) is proposed. In addition, a nonlinear dynamic finite element method (FEM) is also applied for the nonlinear VBM of ship beam. The computational results of the FEM, including the nonlinear VBM and deformational angle, are compared with the results of the 2D hydroelastoplasticity and hydroelasticity. A number of numerical extreme wave models are selected for computations of hydroelasticity-plasticity, hydroelasticity, and FEM. A difference is observed between the nonlinear VBM calculated by FEM and linear VBM calculated by hydroelasticity, and conclusions are drawn.

Inflight Deicing of Self-Actuating Aircraft Wing Structures With Piezoelectric Actuators

2002 ◽  
Author(s):  
Y. J. Lin ◽  
Suresh V. Venna
Keyword(s):  
Finite Element ◽  
Natural Frequencies ◽  
Laminated Composite ◽  
Piezoelectric Actuators ◽  
Element Model ◽  
Harmonic Excitation ◽  
Dynamic Responses ◽  
Underlying Structure ◽  
Shear Stresses ◽  
Modeling And Analysis

Self-actuating aircraft wings for in-flight deicing with minimal power requirements are proposed. Lightweight piezoelectric actuators are utilized to excite the wing structure to its natural frequencies to induce shear stresses on the surface of the wing. The shears are generated in such a way that they are sufficient to break the weak bond between the ice layer and the wing surface. A laminated composite cantilever plate is used for the modeling and analysis. Analytical model is developed to predict the natural frequencies and shear stresses on the surface of the plate and finite element modal analysis is carried out to verify the results. In addition, finite element model involving the ice deposited on the underlying structure is built. The dynamic responses of the structure to harmonic excitation to its first five natural frequencies are investigated. It is observed that significant amount of ice de-bonding from the substrate occurs in the third mode, or the second symmetric mode. Moreover, the energy requirements of the piezoelectric actuators to actuate an adaptive composite structure with given weight are evaluated.

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