Journal of Applied and Computational Mechanics
Volume:4 Issue: 4, Autumn 2018

In this paper, the first-order shear deformation theory is used to derive theoretical formulations illustrating the nonlinear dynamic response of functionally graded porous plates under thermal and mechanical loadings supported by Pasternak’s model of the elastic foundation. Two types of porosity including evenly distributed porosities (Porosity-I) and unevenly distributed porosities (Porosity-II) are assumed as effective properties of FGM plates such as Young’s modulus, the coefficient of thermal expansion, and density. The strain-displacement formulations using Von Karman geometrical nonlinearity and general Hooke’s law are used to obtain constitutive relations. Airy stress functions with full motion equations which is employed to shorten the number of governing equations along with the boundary and initial conditions lead to a system of differential equations of the nonlinear dynamic response of porous FGM plates. Considering linear parts of these equations, natural frequencies of porous FGM plates are determined. By employing Runge-Kutta method, the numerical results illustrate the influence of geometrical configurations, volume faction index, porosity, elastic foundations, and mechanical as well as thermal loads on the nonlinear dynamic response of the plates. Good agreements are obtained in comparison with other results in the literature

In the present study, some perturbation methods are applied to Duffing equations having a displacement time-delayed variable to study the stability of such systems. Two approaches are considered to analyze Duffing oscillator having a strong delayed variable. The homotopy perturbation method is applied through the frequency analysis and nonlinear frequency is formulated as a function of all the problem’s parameters. Based on the multiple scales homotopy perturbation method, a uniform second-order periodic solution having a damping part is formulated. Comparing these two approaches reveals the accuracy of using the second approach and further allows studying the stability behavior. Numerical simulations are carried out to validate the analytical finding.

Cold drawing process is one of the most used metals forming processes in industries for forming seamless tubes. This process of plastic deformation of metals occurs below the recrystallization temperature and is generally performed at room temperature. When metal is cold worked, upon the release of forming force, the springback occurs. In this paper, the springback effect of the seamless tube that has undergone cold drawing is studied for three different reduction ratios viz.10-15 %,15-20 %, and 20-25 % having the aim to reduce it. Experiments are conducted under different reduction ratios with working conditions of die semi angles of 10 and 15 degrees, die land width of 5 mm and 10 mm as well as drawing speed of 4, 6, and 8 m/min for C-45 tube material. Optimum reduction ratio is finalized using Statistical Package for Social Science (SPSS) software of data analysis using statistical tests like Kruskal-Wallis, ANOVA, Post-hoc, etc. Metallurgical analysis through microstructural investigation, XRD and mechanical testing via cold draw load, and hardness testing for different reduction ratios are also studied for validation purposes. The results of this research show that 10-15 % reduction ratio yields the minimum springback. This can be used to help designing tools in the metal forming industry to minimize springback and improve the quality of the product.

In the present study, the effect of temperature-dependent heat sources on the fully developed free convection flow of an electrically conducting micropolar fluid between two parallel porous vertical plates in the presence of a strong cross magnetic field is analyzed. The micropolar fluid fills the space inside the porous plates when the rate of suction at one boundary is equal to the rate of injection at the other boundary. The coupled nonlinear governing differential equations are solved using the differential transform method (DTM). Moreover, the Runge-Kutta shooting method (RKSM), which is a numerical method, is used for the validity of DTM method and an excellent agreement is observed between the solutions of DTM and RKSM. Trusting this validity, the effects of Hartmann number, Reynolds number, micropolar parameter, and applied electric field load parameter are discussed on the velocity, microrotation velocity, and temperature. The skin friction, the couple stress, and Nusselt numbers at the plates are shown in graphs. It is observed that the Hartmann number and the micropolar parameter decreases the skin friction and the couple stress at both plates for suction and injection

In this paper, a transient thermal stress investigation on a simply supported thin elliptical plate during sectional heating with time-dependent temperature supply is considered. The solution of heat conduction equation with corresponding initial and boundary conditions is obtained by employing an integral transform approach. The governing equation solution for the small deflection theory is obtained and utilized to preserve the intensities of thermal bending moments, involving the Mathieu and modified functions and its derivatives. The deflection results show an approximately good agreement with the previously given results. It is also demonstrated that the temperature field in a circular solution could be resulted in a particular case of the present mathematical solution. The obtained numerical results utilizing computational implements are precise enough for practical purposes.

The impeller-clogging phenomenon in centrifugal pumps is such a kind of the fault that leads to increase the vibration and reduce the performance of pumps. In addition, impeller-clogging could make some problems in the production process of factories. This research assigns to the detection of clogged impeller in a centrifugal pump using the vibration and motor current analysis. In this research, a test rig is set up and one of the impeller’s passageways is clogged by the sealing tape. The clogging detection, based on the vibration analysis, is done using the Fast Fourier Transform (FFT). The obtained results show that the dominant frequency in the impeller-clogging phenomenon is the rotational frequency of impeller (1xRPM). The measuring vibration values in three directions (horizontal, vertical, and axial) show that the clogged impeller has more effects on the axial vibration responses. Furthermore, in this case, the electrical current consumption of electromotor is reduced

This paper analyzes the aerodynamic performance and flow separation characteristics of a rectangular wing for varying Reynolds numbers. The mechanism of separation and its effect on the rectangular wing were simulated in ANSYS FLUENT using K-ω SST turbulence model. A detailed analysis was performed to discuss aspects like the lift and drag force of the wing surface, surface pressure distribution around the wing surface, flow separation characteristics for different angles of attack, velocity profiles at different sections of the wing surface along the chord length, and the effect of wing tip vortices. The simulation results showed that by increasing the angles of attack, the separation point moves towards the leading edge and the onset of stalling is very much closer to the leading edge. Also, the experimental and numerical results indicated that NACA4415 airfoil had enhanced coefficient of lift to coefficient of drag ratio at the angles of attack (AoA) ranging between 4◦ and6◦,which are distinctively advantageous for the better performance of small-scale wind turbine rotors. The experimental and computational results were analyzed in the context of effective change in stalling characteristics at different Reynolds numbers.

This paper presents Best Theory Diagrams (BTDs) constructed from various non-polynomial theories for the static analysis of thick and thin symmetric and asymmetric cross-ply laminated plates. The BTD is a curve that provides the minimum number of unknown variables necessary for a fixed error or vice versa. The plate theories that belong to the BTD have been obtained by means of the Axiomatic/Asymptotic Method (AAM). The different plate theories reported are implemented by using the Carrera Unified Formulation (CUF). Navier-type solutions have been obtained for the case of simply- supported plates loaded by a bisinuisoidal transverse pressure with different length-to-thickness ratios. The BTDs built from non-polynomials functions are compared with BTDs using Maclaurin expansion. The results suggest that the plate models obtained from the BTD using non-polynomial terms can improve the accuracy obtained from Maclaurin expansions for a given number of unknown variables of the displacement field.

This study presents a computational investigation on heat and flow behaviors between non parallel plates with the influence of a transverse magnetic field when the medium is filled with solid nanoparticles. The nonlinear governing equations are treated analytically via Differential Transform Method (DTM). Thereafter, obtained DTM results are validate with the help of numerical fourth order Runge-Kutta (RK4) solution. The main aim of this research work is to analyze the influence of varying physical parameters, in particular Reynolds number, nanofluid volume fraction, and Hartmann number. It was found that the presence of solid nanoparticles in a water base liquid has a notable effect on the heat transfer improvement within convergent-divergent channels. The comparison of DTM results with numerical RK4 solution also shows the validity of the analytical DTM technique. In fact, results demonstrate that the DTM data match perfectly with numerical ones and those available in literature.

In this study, four optimization algorithms are applied to identify the damage in a multi-DOF dynamical system composed of masses, springs, and dampers. The damage is introduced artificially by choosing a lower value for the stiffness. The applied algorithms include Nelder-Mead Simplex, BFGS Quasi-Newton, interior point, and sequential quadratic programming - SQP. In addition, some different strategies to identify damage are applied. First, a deterministic analysis is performed to identify the damage; i.e, the values of the stiffnesses. Then, random forces are considered, and finally, the stiffness values are considered uncertain and the different strategies are compared.

A current study and discussion in detail about many solar energy collectors of various types, components, classifications and configurations, through the analysis of their performance, is our aim through this review paper. The effects of the geometrical parameters of the solar air collectors as well as the functioning parameters on heat transfer and fluid flow processes were also discussed in detail. The numerical, analytical, and experimental analyses on different models of flat plate solar air collectors with various thermal transfer enhancement strategies were shown in various stages, i.e., modelling, control, measurement, and visualization of airfield, determination of heat transfer, control of friction loss and pressure drop, and evaluation of the thermal performance by the measurement of the augmentation in the temperature of the working fluid at a given solar irradiance and under given flow rate. We concluded this review by identifying the various applications possible for the solar air collectors such as heating and cooling of houses, drying agricultural food materials, and water desalination process