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EN
In the present paper, trigonometric B-spline DQM is applied to get the approximated solution of coupled 2D non-linear Burgers’ equation. This technique, named modified cubic trigonometric B-spline DQM, has been used to obtain accurate and effective numerical approximations of the above-mentioned partial differential equation. For checking the compatibility of results, different types of test examples are discussed. A comparison is done between 2L and L∞ error norms with the previous, present results and with the exact solution. The resultant set of ODEs has been solved by employing the SSP RK 43 method. It is observed that the obtained results are improved compared to the previous numerical results in the literature.
EN
A novel shear and normal deformations theory is presented in this article to illustrate the wave propagation and free vibration of three-layer sandwich curved beams subjected to elevated temperature and moisture environments and resting on viscoelastic foundation. The upper and lower layers are made of metal matrix reinforced with functionally graded (FG) graphene platelets (GPLs). While, the core layer is made of auxetic honeycomb structures. For the layers to be more bonded, the matrix of the face layers and the auxetic layer are both made of aluminum material. The volume fraction of GPLs is varied through the thickness of the face layers according to a layer-wise rule. The modified Halpin–Tsai model is used to describe the effective material properties of the face layers. Four types of GPLs distribution are considered in the present analysis. The differential quadrature method (DQM) is employed to discretize the equations of motion and then converted to a system of algebraic equations. This system can be solved to obtain the natural frequencies of the sandwich curved beams. Whereas, the wave dispersion relations are determined by solving the motion equations analytically. Convergence and comparison examples are presented to adjust and validate the present solution. In addition, comprehensive parametric studies are performed to investigate the effects of the weight fraction of GPLs, temperature, moisture concentrations, core thickness, boundary conditions, and viscoelastic foundation stiffness on the natural frequency, wave frequency and phase velocity of the honeycomb sandwich curved beams.
EN
The present study deals with the primary damped natural frequency of dielectric composite beam reinforced with graphene platelet (GPL). The beam is subjected to pre-stress in the longitudinal direction and external electrical loading throughout the beam thickness direction for tuning the frequency characteristics. The material properties of the composites required for structural analysis are determined by effective medium theory (EMT) and rule of mixture. Using Timoshenko beam theory and Hamilton’s principle, the governing equations for damped nonlinear free vibration of the beam are derived and solved numerically by differential quadrature (DQ) and direct iterative methods. The effects of the attributes of the electrical loading and the GPL fillers on the damped free vibration characteristics are investigated. The analysis shows that when the GPL concentration is greater than the percolation threshold, the voltage of the electrical loading and GPL aspect ratio start to play a vital role in the damped vibration. The nonlinear damped frequency of the hinged-hinged (H–H) beam decreases by 83.8% when the voltage increases from 0 to 30 V. It is found that there exist two critical AC (alternating current) frequencies, i.e., approximate 10−3 Hz and 102 Hz, around which the primary damped natural frequency has a sudden jump as AC frequency either slightly increases or decreases. The vibration characteristics presented demonstrate the potential of developing smart composite structures whose vibration characteristics can be actively tuned by changing the attributes of the applied electrical loading.
EN
Axisymmetric bending analysis of graphene platelet (GPL) sandwich annular and circular nanoplates with FG porous core and integrated with sensor and actuator resting on an elastic substrate under various boundary conditions is presented in this article. The present nanocomposite model is subjected to mechanical load and an external voltage. The upper and lower sandwich layers are made of aluminum matrix with GPL reinforcement. The effective material properties of the sandwich face layers are estimated in the framework of Halpin–Tsai scheme. In accordance with a refined four-variable theory considering the transverse shear and normal strains, the motion equations are obtained from principle of the virtual work. The size effects are considered by employing the nonlocal strain gradient theory. The differential quadrature method is utilized here to solve the governing equations. First, the obtained results are validated by implementing some comparisons with previous work. Then a comprehensive illustration is executed to show the impacts of boundary conditions, GPLs weight fraction, geometrical dimensions, elastic foundation parameters and applied voltage on the bending of the sandwich nanoplates with FG-porous core and piezoelectric layers.
EN
We present a new nonlocal elasticity-based analysis method for free vibrations of functionally graded rectangular nanoplates. The introduced method allows taking into account spatial variation of the nonlocal parameter. Governing partial differential equations and associated boundary conditions are derived by employing the variational approach and applying Hamilton’s principle. Displacement field is expressed in a unified way to be able to produce numerical results pertaining to three different plate theories, namely Kirchhoff, Mindlin, and third-order shear deformation theories. The equations are solved numerically by means of the generalized differentia quadrature method. Numerical results are generated by considering simply-supported and cantilever nanoplates undergoing free vibrations. These findings demonstrate the influences of factors such as dimensionless plate length, plate theory, power-law index, and nonlocal parameter ratio upon vibration behavior.
EN
Thermal buckling analysis of functionally graded cylindrical panels subjected to various conditions is discussed in this paper. Buckling governing equations are solved using the differential quadrature method. It is assumed that the mechanical properties of the panel are graded through thickness according to a power function of the thickness variable. The panel is assumed to be under the action of three types of thermal loading including uniform temperature rise and variable temperature rise in the axial and radial direction. In the present study, the effects of power law index, panel angle, different thermal load conditions and geometric parameters on the buckling behavior of functionally graded curved panels are studied. The results obtained through the present method are compared to the finite element solutions and the reported results in the literature. A desirable compatibility is concluded.
EN
The stability and free vibration of axially-loaded tapered beams with elastic end restraints resting on two-parameter foundations are studied using the differential quadrature method (DQM). The governing differential equation is discretized at sampling points, and then the boundary conditions due to elastic end restraints are implemented and substituted into the governing differential equation yielding a system of homogeneous algebraic equations. The equivalent two-parameter eigenvalue problem is obtained and solved for critical loads in the static case and for natural frequencies in the dynamic case. The obtained solutions are found compatible with those obtained from other techniques. The influences of different parameters on the critical loads and natural frequencies are investigated.
EN
The paper deals with the methodology of the determination of the weighting coefficients for differential quadrature method based on spline interpolation. Appropriate formulas are derived and two practical approaches to determine mentioned coefficients are proposed, one – pure numeric, the other that uses symbolic-numeric programming. Both approaches are analyzed on account of efficiency, conditioning of the problem and easiness of the implementation.
PL
W artykule omówiono metodykę wyznaczania współczynników wagowych dla metody kwadratur różniczkowych bazującej na interpolacji funkcjami sklejanymi. Wyprowadzono związki na wspomniane współczynniki oraz zaproponowano dwa sposoby praktycznej realizacji tego zagadnienia, jeden – czysto numeryczny, drugi – wykorzystujący programowanie symboliczno- numeryczne. Oba sposoby przeanalizowano pod kątem efektywności obliczeń, uwarunkowania zagadnienia oraz łatwości implementacji.
EN
In the paper the method of the generation of the global difference formulas based on the arbitrary irregular node distribution is presented. The presented method uses approach that comes from DQ technique. As the base functions, radial functions are assumed, which are especially efficient in the approximation of a function given in a large number of scattered nodes. In order to show the accuracy of the formulas some derivatives of an exampled function are computed. The influence of the number of nodes as well as the shape parameter of the radial function on the accuracy and condition number of the system is investigated.
PL
W artykule przedstawiono metodę generacji globalnych wzorów różnicowych opartych na dowolnie nieregularnie rozmieszczonych węzłach. Przedstawiony sposób wykorzystuje podejścia stosowane w metodzie kwadratur różniczkowych. Jako funkcje bazowe przyjęto funkcje radialne, które są szczególnie skuteczne w aproksymacji funkcji zadanych w dużej liczbie nieregularnie rozmieszczonych punktów. Dla zilustrowania dokładności schematów różnicowych obliczono pochodne przykładowej funkcji oraz zbadano wpływ liczby węzłów i współczynnika kształtu funkcji radialnych na dokładność przybliżenia pochodnej i wskaźnik uwarunkowania układu równań.
10
Content available remote Comparison of SDQM and FDM in nonlinear free vibration analysis of beam
EN
In the paper the formulation of the differential quadrature method based on spline functions as well as the way of determination of the weighting coefficients are presented. The convergence and accuracy of the method in comparison to the finite difference method are studied on the example of the geometrically nonlinear free vibrations of a beam.
EN
The paper deals with the methods based on the differential quadrature and their application to the free vibration analysis of plates. The spline-based differential quadrature Method (SDQM) is presented as an alternative to known methods based on the interpolation polynomial (PDQM). The SDQM uses a polynomial piecewise function to approximate the wanted solution of a governing equation. The way of determining the spline functions as well as the way of computing weighting coefficients for the method are presented in the paper. Then the SDQM is applied to determine natural frequencies of plates. The influence of the spline degree, number of nodes and grid point distribution on the accuracy, convergence and stability is investigated in an example. All results are compared with values obtained by the conventional differential quadrature method (PDQM).
PL
Praca dotyczy metod opartych na kwadraturach różniczkowych i ich aplikacji do zagadnienia drgań własnych płyt. W pracy, jako alternatywę do znanych metod kwadratur różniczkowych, opartych na wielomianie interpolacyjnym (PDQM), przedstawiono metodę bazującą na funkcjach sklejanych (SDQM). W SDQM poszukiwane rozwiązanie przybliżane jest funkcją wielomianową, przedziałami zmienną. W pracy przedstawiono sposób wyznaczenia takiej funkcji interpolacyjnej, jak również sposób obliczenia współczynników wagowych, używanych w metodzie kwadratur różniczkowych. Następnie SDQM użyto do wyznaczenia częstości drgań własnych płyt, gdzie analizowano wpływ stopnia wielomianu, liczby węzłów i ich rozmieszczenia na zbieżność, dokładność i stabilność metody. Otrzymane rezultaty porównano z wynikami uzyskanymi przy pomocy konwencjonalnej metody kwadratur różniczkowych (PDQM).
EN
The paper deals with the application of the differential quadrature method based on a piecewise polynomial to the nonlinear vibration analysis of beams. The initial–boundary-value problem is solved to study the computational stability of the method. The results are compared with those, obtained by the conventional differential quadrature. The effects of the spline degree, the number of nodes and the distribution of sampling points on the convergence and stability is also presented. The nonlinear free vibration analysis is carried out to verify the accuracy of the method.
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