scholarly journals A Comparison between Elastic and Viscoelastic Asymmetric Dynamics of Elastically Supported AFG Beams

Vibration ◽  
2020 ◽  
Vol 3 (1) ◽  
pp. 3-17 ◽  
Author(s):  
Alireza Gholipour ◽  
Mergen H. Ghayesh ◽  
Yueqiang Zhang
Keyword(s):  
Energy Loss ◽  
Elastic Foundation ◽  
Functionally Graded ◽  
Transverse Motion ◽  
Elastic Model ◽  
Exponential Functions ◽  
Viscosity Effects ◽  
Simulation Results ◽  
Elastically Supported ◽  
Derivation Procedure

This investigation compares the dynamic simulation results of perfect, elastically-supported, axially-functionally-graded (AFG) beams between viscoelastic and elastic models. When modeling and simulating the dynamics of AFG beams, the elastic model is commonly assumed so as to simplify calculations. This investigation shows how the dynamics varies if viscosity is present. The nonlinear continuous/discretized, axial/transverse motion derivation procedure is explained briefly based on Hamilton’s principle for energy/energy-loss, Kelvin–Voigt viscosity, elastic foundation assumption, and exponential functions for material and geometric variations along the axial axis. A comparison between elastic and Kelvin–Voigt viscoelastic AFG beams on an elastic foundation shows that the viscosity influences the asymmetric dynamics of AFG beams; the viscosity effects become more dominant for larger motion amplitudes, for example.

Dynamic Stiffness Formulation for Out-of-Plane Natural Vibration of Elastically Supported Functionally Graded Plates

2021 ◽  
pp. 2150062
Author(s):  
Md. Imran Ali ◽  
Mohammad Sikandar Azam
Keyword(s):  
Elastic Foundation ◽  
Power Law ◽  
Natural Vibration ◽  
Plate Theory ◽  
Dynamic Stiffness ◽  
Functionally Graded ◽  
Rotary Inertia ◽  
Neutral Surface ◽  
Edge Conditions ◽  
Elastically Supported

In this paper, the natural vibration characteristics of elastically supported functionally graded material plate are investigated using the dynamic stiffness method (DSM). Power-law functionally graded (P-FG) plate, the material properties of which vary smoothly along the thickness direction following the power-law function, that has been used for the analysis. Classical plate theory and Hamilton’s principle are used for deriving the governing differential equation of motion and associated edge conditions for P-FG plate supported by elastic foundation. During the formulation of dynamic stiffness (DS) matrix, the concepts of rotary inertia and neutral surface are implemented. Wittrick–Williams (W-W) algorithm is used as a solving technique for the DS matrix to compute eigenvalues. The results thus obtained by DSM for the isotropic, P-FG plate, and the P-FG plate with elastic foundation compare well with published results that are based on different analytical and numerical methods. The comparisons indicate that this approach is very accurate. Furthermore, results are provided for elastically supported P-FG plate under four different considerations in order to see the differences in frequencies with the inclusion or exclusion of neutral surface and/or rotary inertia. It is noticed that the inclusion of rotary inertia and neutral surface influences the eigenvalues of P-FG plate, and that cannot be discounted. The study also examines the influence of plate geometry, material gradient index, edge conditions, and elastic foundation modulus on the natural frequency of P-FG plate.

Postbuckling analysis of functionally graded plates on an elastic foundation

2015 ◽  
Vol 132 ◽  
pp. 842-847 ◽  
Author(s):  
Maciej Taczała ◽  
Ryszard Buczkowski ◽  
Michal Kleiber
Keyword(s):  
Elastic Foundation ◽  
Functionally Graded ◽  
Functionally Graded Plates

scholarly journals On the Finite Element Model of Rotating Functionally Graded Graphene Beams Resting on Elastic Foundation

2021 ◽  
Vol 2021 ◽  
pp. 1-18
Author(s):  
Nguyen Van Dung ◽  
Nguyen Chi Tho ◽  
Nguyen Manh Ha ◽  
Vu Trong Hieu
Keyword(s):  
Finite Element ◽  
Free Vibration ◽  
Elastic Foundation ◽  
Mechanical Response ◽  
Shear Deformation Theory ◽  
Free Vibration Analysis ◽  
Element Model ◽  
Functionally Graded ◽  
Mode Shapes ◽  
Engineering Practice

Rotating structures can be easily encountered in engineering practice such as turbines, helicopter propellers, railroad tracks in turning positions, and so on. In such cases, it can be seen as a moving beam that rotates around a fixed axis. These structures commonly operate in hot weather; as a result, the arising temperature significantly changes their mechanical response, so studying the mechanical behavior of these structures in a temperature environment has great implications for design and use in practice. This work is the first exploration using the new shear deformation theory-type hyperbolic sine functions to carry out the free vibration analysis of the rotating functionally graded graphene beam resting on the elastic foundation taking into account the effects of both temperature and the initial geometrical imperfection. Equations for determining the fundamental frequencies as well as the vibration mode shapes of the beam are established, as mentioned, by the finite element method. The beam material is reinforced with graphene platelets (GPLs) with three types of GPL distribution ratios. The numerical results show numerous new points that have not been published before, especially the influence of the rotational speed, temperature, and material distribution on the free vibration response of the structure.

scholarly journals A Study of ZVS, ZCS and ZVZCS Techniques in Reducing the Energy Loss and Improving the Soft Switching Range

2020 ◽  
Author(s):  
Ratil H Ashique ◽  
Zainal Salam
Keyword(s):  
Energy Loss ◽  
Loss Factor ◽  
Recent Literature ◽  
Soft Switching ◽  
Low Loss ◽  
Turn On ◽  
Switching Losses ◽  
Extended Range ◽  
Simulation Results ◽  
Switch Voltage

This paper presents a comparative analysis of the ZVZCS soft switching technique with the ZVS and the ZCS counterpart. The generalization of the voltage-current crossover or the energy loss factor obtained from simulation of the prototype converter shows that the ZVZCS significantly reduces the loss and helps to improve the efficiency of the converter as compared to the ZVS or the ZCS. On the other hand, it is also found that the soft switching range of operation of the ZVS and the ZCS are largely affected by the maximum switch voltage and switch current respectively. In contrary, these factors have a negligible effect on the ZVZCS operation which results in an extended range of soft switching operation. Additionally, a detailed LTPICE simulation is performed for selected ZVS, ZCS and ZVSCS topologies from the recent literature and the switching losses in the main switches of the converters are measured. It is observed that the energy losses in the ZVZCS mode are reduced on average by approximately 26 % at turn on and 20 % at the turn off as compared to the ZVS and the ZCS. Besides, the low standard deviation in this mode confirms a stable low loss profile which renders extended soft switching range. An experimental test is also conducted by building the prototype converter to verify the simulation results. It is found that the switching losses are minimum while the converter is operated in the ZVZCS mode. Besides, the efficiency drop remains consistently low as compared to the ZVS and the ZCS in the whole operating range. Resultantly, the simulation and the experimental results are both found to be consistent.

scholarly journals Multi-moving Loads Induced Vibration of FG Sandwich Beams Resting on Pasternak Elastic Foundation

2021 ◽  
Vol 18 (9) ◽  
Author(s):  
Wachirawit SONGSUWAN ◽  
Monsak PIMSARN ◽  
Nuttawit WATTANASAKULPONG
Keyword(s):  
Dynamic Response ◽  
Elastic Foundation ◽  
Excitation Frequency ◽  
Beam Theory ◽  
Equation Of Motion ◽  
Functionally Graded ◽  
Sandwich Beams ◽  
Moving Loads ◽  
Layer Thickness Ratio ◽  
Pasternak Elastic Foundation

The dynamic behavior of functionally graded (FG) sandwich beams resting on the Pasternak elastic foundation under an arbitrary number of harmonic moving loads is presented by using Timoshenko beam theory, including the significant effects of shear deformation and rotary inertia. The equation of motion governing the dynamic response of the beams is derived from Lagrange’s equations. The Ritz and Newmark methods are implemented to solve the equation of motion for obtaining free and forced vibration results of the beams with different boundary conditions. The influences of several parametric studies such as layer thickness ratio, boundary condition, spring constants, length to height ratio, velocity, excitation frequency, phase angle, etc., on the dynamic response of the beams are examined and discussed in detail. According to the present investigation, it is revealed that with an increase of the velocity of the moving loads, the dynamic deflection initially increases with fluctuations and then drops considerably after reaching the peak value at the critical velocity. Moreover, the distance between the loads is also one of the important parameters that affect the beams’ deflection results under a number of moving loads.

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