JOURNAL OF MECHANICAL ENGINEERING AMIRKABIR (AMIRKABIR)
Year:2009 | Volume:41 | Issue:1|Papers Count:13

Analytical investigation of the vibration behavior of thin circular functionally graded (FG) plates integrated with two uniformly distributed piezoelectric actuator layers based on the classical plate theory (CPT) is presented. The material properties of the FG substrate plate are assumed to be graded in the thickness direction according to the power-law distribution. The differential equations of motion are solved, analytically for clamped edge boundary condition of the plate. The detailed mathematical derivations are presented and numerical investigations are performed while the emphasis is placed on investigating the effect of varying the gradient index of FG plate on the vibration characteristics of the structure.

This research presents a semi-analytical solution of finitely long, simply supported, orthotropic and radially polarized piezoelectric shell panel under? dynamic electro-mechanical loading. The highly coupled partial differential equations set are reduced to ordinary differential equation set with variable coefficients by the trigonometric function expansion of displacement and electric potential in circumferential and axial directions. The displacement components and electric potential are expanded in appropriate trigonometric Fourier series in circumferential and axial coordinate to satisfy the boundary conditions at the simply supported circumferential and axial edges. The resulting ordinary differential equations are solved by Galerkin finite element method. In this procedure, a quadratic shape function is used for each element. Numerical example is provided for dynamic response of a single layer piezoelectric cylindrical panel under dynamic external loading.

Atomic force microscope (AFM) is one of the powerful and useful tools in nanoscale science and technologies with applications from surface characterization in material science, to the study of living biological system in their natural environment. AFM operate in three mods of contact, non-contact and tapping mode. In this paper, by focusing on the development of a more comprehensive model of an AFM micro-cantilever beam, considering the effects of mass and rotary inertia of the tip using Euler-Bernoulli beam theory is considered. The comparison of the present results and the results of other investigators, which has been done in case studies, generally shows a very good agreement. The results show that the effect of mass and rotary inertia of the tip depending on its dimensions is important and should be considered. Finally, the effects of cantilever inclination and tip height on the resonance frequencies are also examind.

In this paper, a new algorithm for attitude estimation in maneuvering flight, utilizing a combination of inertial measuring unit (IMU) and altimeter information is presented. Attitude estimation using a single IMU is possible only for near cruise flights, however for non-cruise flights, very large errors are obtained. In this paper, attitude estimation error is stabilized using an integrated IMU and altimeter system. The altimeter output being affected by gravity and the specific forces projected into the vertical plane bears insufficient information regarding the attitude states. Being a function of the roll and pitch angle, the specific forces will be in error, due to errors estimation of the attitude angles. Subsequently the vehicle vertical acceleration, speed and attitude will be inaccurate. In addition, due to a weak observability between the altitude measurements and the attitude angles to be estimated. For this reason and having a better estimate of the attitudes, the nonlinear attitude equations are converted into linear space, which will be beneficial for the estimation algorithm. Finally, simulation results using linear and unscented Kalman filters are curried out. A Monte Carlo simulation reveals that the newly suggested linear filter has a better performance in comparison with the non-linear unscented Kalman filter.

This paper presents an optimal path planning ~for planar hyper redundant robot manipulators in presence of circular obstacles with a new analytical collision avoidance approach. To generate the robot's trajectory, a dual genetic algorithm for rapid achievement to the optimal solutions in complex space is offered. A polynomial based on cubic spline interpolation? is applied to approximate trajectories in joint space. The GA determines the parameters, which are the interior points to be interpolated to formulate the polynomial representing the trajectory, it is to minimize the fitness of the desired objective function. The effectiveness and capability of the proposed approach is demonstrated through simulation studies.

In this paper, a static analysis of functionally graded cylinders under axisymmetric mechanical and thermal loads is presented. It is assumed that the distribution of material properties through the thickness of the cylinder is continuous and graded according to a power low distribution. For solving equations, two-dimensional finite element method is employed. To this end, a functionally graded material element is defined for accurate finite element modeling of cylinder with continuous distribution of material properties and avoiding the limitation in the radius to thickness ratio. Numerical results are obtained for a clamped cylinder subjected to a uniform internal pressure and a simply supported cylinder subjected to a temperature distribution through the thickness. In addition, the numerical results for thick and thin cylinders are obtained. The results show that the stress and temperature distribution in functionally graded cylindrical shells are dependent on the material kind and distribution of material properties and this dependency can be utilized for controlling the stress level.

Deep drawing is one of the most important processes in manufacturing of CNG pressure vessel liner. Due to the high thickness of initial blank, liner manufactures can use different types of dies such as conical, tractrix and flat dies. In this paper, a sample of "type 3" aluminum liner has been selected and the deep drawing process has been simulated by using, finite-element method. Three types of dies behavior have been compared for parameters such as the required drawing force and cup wall thickness variations. Available experimental data was used to verify the numerical results. The results have shown that in a tractrix die, the required drawing force will decrease, and minimum wall thickness variations can be obtained.

Parametric geometric modeling of spur gears, precision forging die set modeling and upper bound analysis were studied in this paper. Module, teeth number, pressure angle, gear width and bore radius of the spur gear were input to a computer program, written with Visual Basic in Solid Works, and then solid model of that was constructed in Solid Works. Then billet and precision forging die set were designed and modeled. For upper bound analyze, half pitch of a tooth with involute curve has been divided into six deformation zones. A new kinematic ally admissible velocity field that includes bulging of the tooth has been proposed. Forging load obtained using the upper bound were compared with theoretical and experimental results carried out in literature and also using Super Forge of FVM simulation package.

Coordination is an important function in supply chain management (SCM) to provide better competitive capability of the chain. Coordination through vendor-buyer negotiation is an area which has received great research attention in particular in modem systems. In this study, a number of methods, including those based on price discount and cost minimization models have been suggested in the literature. Mathematical models developed to determine economic order/production lot size for a "single vendor single buyer" stochastic demand situation are proposed. These models consider both independent and joint decisions for chain member. Through considering price discounts it is suggested a vendor buyer coordination mechanism to reach the most appropriate decision. For this, a solution algorithm has been detailed in the paper. Numerical study is also provided to illustrate the effectiveness of the proposed method.

In this paper, by developing a mixed integer stochastic programming model, total cost of construction of new power generation capacity using various technologies and the cost of generating electricity during a planning horizon is minimized. The demand is considered uncertain in this model and is assumed to follow three possible scenarios. In this study, the country is divided to several regions and the investment decisions are taken for each region in an integrated model. Furthermore, a learning mechanism of technologies is considered in the model, so the cost of investment in technologies will decrease as installed capacity of each technology is increasing. Finally, in order to analyze the output of optimization model, by developing a system dynamic model, the impacts of the proposed plan on some power industry indicators such as cost and profit is shown with respect to each demand scenario. The resulting capacity expansion plan consists of various power generation technologies among which gas turbine power plant constitutes the biggest part of the expansion plan. Other technologies such as hydro, combined cycle, nuclear, geothermal and wind power plants exist in the expansion plan. 

The introduction of Rapid Prototyping and Rapid Tooling (RP&RT) Technologies in past two decades has caused great changes in manufacturing and production procedures. Investment casting as a process for production of complex metal parts from various alloys is one of the areas that application of RP and RT should be concerned. Gas turbine blade as an investment cast part with geometrical and dimensional complexity and close manufacturing tolerances has been investigated in this research,. As a result 3D-CAD model that has been evolved from reverse engineering of a blade, was used in Stereo lithography for manufacturing of the master models. Then, Epoxy and RTV rapid mould tooling used for wax production mould making. At last the results of application of these methods and application of metal die for wax model production has been assessed and compared based on parameters such as time, cost, surface roughness, and dimensional accuracy.