Accurate free vibration solutions of orthotropic rectangular thin plates by straightforward finite integral transform method

Orthotropic thin plates are essential in aerospace applications due to their high strength-to-weight ratio, which is critical for efficient structural performance. The mechanical properties of these structures are influenced by numerous factors, with free vibration characteristics being particularly significant. However, analytical solutions for free vibration are often limited to plates with simple boundary conditions (BCs). Few exact analytical solutions exist for plates with complex non-Lévy-type or rotationally restrained BCs. This study aims to analyze the free vibration behavior of orthotropic thin plates featuring three rotationally restrained edges and one free edge, employing the finite integral transform (FIT) method. A key advantage of this method is its simplicity and versatility, as it does not require the predefinition of a deflection function. By setting different values of the rotating fixed coefficient, the study offers analytical free vibration solutions for plates with various combinations of rotationally restrained, simply supported, clamped, and free BCs without additional derivations. The solutions derived using the FIT method are validated by comparison with numerical results obtained from ABAQUS software and available analytical solutions, confirming the method’s accuracy and reliability. Parameter analyses are conducted to examine the effects of aspect ratio, BCs, material properties, and rotating fixed coefficient on non-dimensional frequency parameters and corresponding vibration modes. The results reveal that these parameters significantly influence the frequency characteristics of orthotropic thin plates. The results can be used as a benchmark for validating other analytical and numerical methods.

Reliability, survivability, as well as the optimal operating mode of operation of the supercomputer will depend on the architecture and efficiency of the cooling system of the hot components of the supercomputer. That is why the number of problems, of great theoretical and practical interest, is the problem of studying the temperature fields arising in elements of arbitrary configuration, cooling a supercomputer. To solve this class of heat conduction problems, the method of finite integral transformations turned out to be the most convenient. This article is the first to construct a new finite integral transformation for the Laplace equation in an arbitrary domain bounded by several closed piecewise-smooth contours. An inverse transformation formula is given. Finding the core of the constructed new finite integral transformation by the finite element method in the Galerkin form for simplex first-order elements reduces to solving a system of algebraic equations. To test the operability of the new integral transformation, calculations were carried out of solutions of the boundary value problem for the Laplace equation obtained using the developed new integral transformation and the well-known analytical solution. The results of comparison the calculations of the solution of the Laplace equation are presented. In the case of a square with a side length equal to one and on one side of the square, the temperature is unity, and on the other, the temperature is zero, with a well-known analytical solution and a solution obtained using the new integral transformation. These results were obtained for 228 simplex first-order elements and 135 nodes. The maximum deviation modulo of these solutions is 0,096, the mathematical expectation of deviations is 0,009, and the variance of the type is 0,001. The developed integral transformation makes it possible to obtain a solution to complex boundary value problems of mathematical physics.

On the symplectic superposition method for new analytic free vibration solutions of side-cracked rectangular thin plates

Analytical solutions for elastoplastic buckling of plates play a crucial role in providing benchmark results and facilitating fast structural analyses for preliminary designs. However, the analytical solutions for elastoplastic buckling of plates remain incomplete due to the inherent mathematical difficulties associated with higher-order partial differential equations and material nonlinearity. Consequently, the existing analytical solutions for rectangular plates are only applicable to those with Lévy‐type boundary conditions. To address the limitation, this study extends a novel symplectic superposition method to obtain new analytical elastoplastic buckling solutions of non-Lévy‐type rectangular plates, where both the incremental theory (IT) and deformation theory (DT) are adopted. Comprehensive benchmark elastoplastic buckling loads are presented and validated by the modified differential quadrature method. The plastic buckling paradox is explicitly observed, which highlights a significant disparity between the IT and DT in predicting buckling loads for relatively thick plates. Furthermore, our analysis reveals that the DT provides an optimal load ratio for buckling resistance, while no such finding is observed with the IT. The stability criterion curves are plotted using the elastic theory and plastic theories (IT and DT) to further reveal the importance of incorporating the effect of plasticity as well as to provide a useful guideline for the relevant analyses and designs.

In this study, an exact analytical solution for the convective heat transfer equation from a semi-spherical fin was presented. To obtain a mathematical model, the system was assumed to be a lump in the vertical direction and the governing equation in the Cartesian coordinate was transferred to the Mathieu equation. The exact solution was compared with numerical results such as the finite difference method and midpoint method with Richardson extrapolation (Midrich). Not surprisingly, the exact solution prevailed over the numerical solutions in terms of accuracy and ease of use. Furthermore, the effect of Biot number on the heat transfer of the fin and the fine performance was investigated. The relative error of the results obtained from the analytical and numerical solutions at the base, center, and tip of the fin was 0, 7.72, and 40.25 percent, respectively. The results showed that the relative error between the analytical and numerical solutions depends on the Biot number and varies as a function of the fin length. The obtained analytical solution could be encouraging from different mathematical and industrial applications' points of view.

In this article, we have study a 2D Legendre and Chebyshev wavelets collocation scheme for solving a class of linear and nonlinear weakly singular Volterra partial integro-differential equations (PIDEs). The scheme is based on wavelets collocation for PIDEs with uniquely designed matrices over the Hilbert space defined on the domain $$\left( [0, 1]\times [0, 1]\right) $$ . Using piecewise approximation associated with 2D Legendre wavelet, 2D Chebyshev wavelet and its operational matrices, the considered PIDEs will be reduced into the corresponding system of linear and nonlinear algebraic equations. The corresponding linear and nonlinear system of equations solved by collocation scheme and well-known Newton–Raphson scheme at collocation points respectively. In addition, the convergence and error analysis of the numerical scheme is provided under several mild conditions. The numerical results are correlated with the exact solutions and the execution of the proposed scheme is determined by estimating the maximum absolute errors, $$l_{2}\hbox {-}norm$$ errors and $$l_{\infty }\hbox {-}norm$$ errors. The numerical result shows that the scheme is simply applicable, efficient, powerful and very precisely at small number of basis function. The main important applications of the proposed wavelets collocation scheme is that it can be applied on linear as well as nonlinear problems and can be applied on higher order partial differential equations too.

New analytic buckling solutions of rectangular thin plates with two free adjacent edges by the symplectic superposition method

In reality, the behavior and nature of nonlinear dynamical systems are ubiquitous in many practical engineering problems. The mathematical models of such problems are often governed by a set of coupled second-order differential equations to form multi-degree-of-freedom (MDOF) nonlinear dynamical systems. It is extremely difficult to find the exact and analytical solutions in general. In this paper, the homotopy analysis method is presented to derive the analytical approximation solutions for MDOF dynamical systems. Four illustrative examples are used to show the validity and accuracy of the homotopy analysis and modified homotopy analysis methods in solving MDOF dynamical systems. Comparisons are conducted between the analytical approximation and exact solutions. The results demonstrate that the HAM is an effective and robust technique for linear and nonlinear MDOF dynamical systems. The proof of convergence theorems for the present method is elucidated as well.

Free Vibration Analysis Of Two-Layered Shells Of Revolution

In this paper, authors propose a new integral transform “Rishi Transform” with application to determine the exact (analytic) solution of first kind Volterra integral equation (V.I.E.). For this purpose, authors first derived the Rishi transform of basic mathematical functions (algebraic and transcendential) and then the fundamental properties of Rishi transform is discussed, which can be used for solving ordinary differential equations (O.D.E), partial differential equations (P.D.E.), delay differential equations (D.D.E.), fractional differential equations (F.D.E.), difference equations (D.E.), integral equations (I.E.) and integro-differential equations (I.D.E.). After this, authors determined the exact (analytic) solution of general first kind V.I.E.. They have considered three numerical problems and solved them completely step by step for explaining the utility of Rishi transform. Results depict that the proposed new integral transform "Rishi Transform" provides the exact results for first kind V.I.E. without doing complicated calculation work.

This paper presents an exact analytical solution of one-dimensional transport of a contaminant undergoing advection, dispersion, sorption, and first-order decay, subject to unique boundary conditions, a first-order decaying contaminant concentration in time at the source with a constant concentration at infinity. This exact solution provides a method to study a new area of physical processes and to evaluate approximate methods and models that have been developed to analyze these problems. Recently two fields have developed interest in modeling physical processes that are best conceptualized using a decaying source boundary condition. These two fields are long-term modeling of recalcitrant non-aqueous phase liquid (NAPL) spills and radioactive waste disposal. Both of which can be approximated using a decaying source term. This paper briefly introduces some general field transport problems that can conceptually be described using a decaying source boundary condition. The paper then describes the governing equations, boundary and initial conditions, and the solution techniques used to develop the analytical solution. Next the analytic solution is provided and discussed along with some example cases. The results of the exact analytical solution are compared to another similar solution from the literature.

Granular materials are extensively used throughout many industries. In countries like Australia and South Africa, national economies are critically dependent on the agricultural and mining industries, and it is important to understand bulk material behaviour in order to handle these materials properly. There are many diverse approaches to modelling granular materials. In this thesis, the Coulomb-Mohr continuum mechanical theory of granular materials is utilised, and some exact analytical solutions are presented for both stress and velocity fields. These solutions are formally valid provided sin φ = 1, where φ is the angle of internal friction, and they provide limiting solutions for so called highly frictional granular materials, for which sin φ ≈ 1. The solutions so obtained are exploited for three real industrial granular problems, namely gravity flow from converging hoppers, the stress distribution in stockpiles and finally, the stress distribution within rat-holes. The flow of granular materials, in the presence of gravity, through a converging hopper is an important problem that occurs in many industrial processes. Here, for highly frictional granular materials for both wedge and conical hopper flows, exact analytical solutions are obtained to determine the stress and velocity fields within the neighborhood of the hopper outlet. For the same problem, these exact solutions are exploited as the leading order terms in a regular perturbation series, where the correction terms are of order 1− sin φ. In this way, approximate analytical solutions are obtained that can be used to describe the behaviour of more realistic granular materials. The practice of storing granular materials in stockpiles occurs throughout the ii world in many industrial situations. In this thesis, exact solutions for highly frictional granular materials are used for the determination of the stress distributions within two-dimensional and axially symmetric stockpiles. Stockpile profiles considered here include the standard wedge and cone, as well as two-dimensional parabolic and axially symmetric cubic curved shaped stockpiles. We emphasise that curved stockpiles have not previously been considered in the literature. Our model assumes that the stockpile is composed of two regions, namely an inner rigid region and an outer yield region. The exact solution applies in the outer yield region, which is then extended continuously into the inner rigid region. A rat-hole is the general term used to describe those stable cavities, which frequently occur in storage hoppers and stockpiles, whose formation prevents further material falling through the outlet. In this thesis, we present exact solutions for both two-dimensional and axially symmetric rat-holes, where it is assumed that the highly frictional granular material has flowed through a central outlet, until the point is reached when there is no further flow of material. The remaining material is assumed to be in limiting equilibrium, that is static but on the point of yield. In both two dimensions and axial symmetry, two types of rat-holes are studied. The first type has a sloping upper surface of infinite extent, where the material is resting on a sloping rigid base containing an infinitesimal central outlet. The second type has a curved upper surface, where the material is resting between vertical walls and a horizontal rigid plane containing an infinitesimal central outlet. Again, we emphasise that neither of these rat-hole problems have previously been investigated in the literature.

Coordinate mapping of analytical contaminant transport solutions to non-uniform flow fields

New and expressive analytical approximate solutions to resonance response of harmonically forced strongly odd nonlinear oscillators are proposed. This method combines Newton’s iteration with the harmonic balance method. Unlike the classical harmonic balance method, accurate and explicit analytical approximate solutions are established because linearization of the governing nonlinear differential equation is conducted prior to harmonic balancing. The approach yields simple linear algebraic equations instead of nonlinear algebraic equations which have no analytical solution. With carefully constructed corrective measures, only one single iteration is required to obtain very accurate analytical approximate solutions to resonance response. It is found that since determination of stability of the initial approximate solution that resulted from the single-term harmonic balance can lead to erroneous conclusions, correction to the solution is necessary. Three examples are presented to illustrate the applicability and effectiveness of the proposed technique. Specially, for oscillations in high-energy orbits of the bistable Duffing oscillator, the proposed method can also give excellent analytical approximate solutions.

Explicit analytical expressions for the temperature profile, fin efficiency, and heat flux in a longitudinal fin are derived. Here, thermal conductivity and heat transfer coefficient depend on the temperature. The differential transform method (DTM) is employed to construct the analytical (series) solutions. Thermal conductivity is considered to be given by the power law in one case and by the linear function of temperature in the other, whereas heat transfer coefficient is only given by the power law. The analytical solutions constructed by the DTM agree very well with the exact solutions even when both the thermal conductivity and the heat transfer coefficient are given by the power law. The analytical solutions are obtained for the problems which cannot be solved exactly. The effects of some physical parameters such as the thermogeometric fin parameter and thermal conductivity gradient on temperature distribution are illustrated and explained.