International Journal of Advanced Design and Manufacturing Technology
Volume:4 Issue: 2, 2011

At the beginning of this paper, design and manufacturing stages of the 3 degree of freedom test stand for a remotely piloted helicopter is described, in which the helicopter is able to rotate about its three primary accesses. In the next parts the dynamical model of the RPH in the yaw channel is presented and lateral transfer function of RPH (yaw channel) is extracted by performing several tests and gathering dynamical data. Least square method is used for system identification and finally results validation would be possible through comparison between simulated behavior of the RPH and experimental data of the test stand.

In this paper, a viscous flow simulation is presented using the Lattice Boltzmann Equation (LBE). A finite volume approach is adapted to discretize the LBE on a cell-centered, arbitrary shaped, rectangular tessellation. The formulation includes upwind scheme and high order descretization schemes for the flux term and collision operator respectively. A consistent open and solid boundary treatment according to cell-centered scheme also addressed, which resulted in a wider domain of stability and faster convergence. Validation of the results is conducted by symmetric sudden expansion. The results are compared with reliable analytical or experimental results, indicating the accuracy and robustnes's of the proposed method for analyzing different flows of the interest.

In this paper, controlling the gyros with linear plus cubic damping is considered. Hence, an adaptive control algorithm is proposed to overcome the uncertainties in model parameters and the chaotic behavior of gyroscopes. It is noted that for general applications dynamic model coefficient of gyros is not precisely determined, on the other hand, with respect to a particular coefficient gyroscopes demonstrate chaotic responses. The designed controller guarantees the tracking property and closed loop stability, despite the model uncertainties. The proposed algorithm is then modified to meet the control objectives without estimating the model parameters simplifying the implementation procedure. The stability analysis is presented based on the Lyapunov stability theorem. In order to show the effectiveness of the method, several simulations are also performed. With respect to the result, it is concluded that the performance of adaptive mechanism is verified the convergence of tracking error to zero is conformed; and the closed-loop stability is also verified.

In this paper, a nonlinear free vibration analysis of thin annular functionally graded (FG) plate integrated with two uniformly distributed actuator layers made of piezoelectric (PZT4) material on the top and bottom surfaces of the annular FG plate is presented based on Kirchhoff plate theory. The material properties of the FGM core plate are assumed to be graded in the thickness direction according to the power-law distribution in terms of the volume fractions of the constituents and the distribution of electric potential field along the thickness direction of piezoelectric layers is simulated by a sinusoidal function such that the Maxwell static electricity equation is satisfied. The differential equations of motion are solved analytically for various boundary conditions of the plate. The analytical solutions are derived and validated by comparing the obtained resonant frequencies of the piezoelectric coupled FG annular plate with those of an isotropic core plate. In numerical study, the emphasis is placed on investigating the effect of varying the gradient index of FG plate on free vibration characteristics of the structure. In addition, good agreement between the results of this paper and those of finite element (FE) analyses validated the present approach. The analytical solutions and findings contribute towards a simplified model for the parametric study and understanding of vibration of piezoelectric-coupled FGM annular plate.

This paper aims at investigating the effects of weld nugget size and expulsion on the mechanical properties of low carbon steel resistance spot welds using tensile-shear test. Mechanical performance of spot welds are described in terms of failure mode, peak load and failure energy obtained from the tensile-shear test. The effects of voids and porosity as well as electrode indentation associated with expulsion on the peak load and failure energy of spot weld are discussed. Results showed that although expulsion does not reduce load carrying capacity of spot welds, it decreases their energy absorption capability. This can be attributed to the change in the failure location of the base metal in expulsion free welds to fusion zone/heat affected zone boundary in expulsion-experienced welds.

Rails fracture by the growth of fatigue crack or critical crack is one of the prevalent defects in railway. The rail fracture, failure and stress analysis should be studied in order to prevention of rail fracture. In this paper, new formulation of contact stress for two rolling bodies is presented, where the results are closed to the hertz stress formulation. Moreover, stress analysis is done by FEM and compared with hertz stress and new stress formulation results. Then, the stress analysis, fracture, prediction of fracture and path of crack motion in rail and wheel is studied, statically which plays important role in this field. Next, the methods of analysis of stress theory fracture with numerical and FEM is compared and it is consequently proved that these approaches have acceptable results compared to other results. Therefore it is possible to rely on these methods and their results. Next, relation between maximum displacement and maximum stress is presented, and path of crack growth and fracture is predicted. For the purpose of analysis, exerted pressure on the rail and wheel assembly is considered on the quadrant of elliptical contact surface, rather than the whole assembly. With this assumption, acceptable results will be obtained. Moreover, in order to prevent crack growth and penetration the plastic method and building of negative discharge energy hole with closed loop path is presented to restrict crack motion. Finally correction coefficient is introduced for the results.

In this project creep feed grinding process of gas turbine blade root is investigated with the aim of consistant and controlable production. Inthispaper, effectiveness of creep feed grinding process prometers suchas wheel speed, workpiece speed, grind depth and dresser speed are investigated. This investigation include their interaction on thelob of gas torbine blade root, as amajor cause of a erosion of grinding dresser, using designof experiment (DOE). Before conducting the experiments, the creep feed grinding machine was checked in order to verify the repeatability and performance assurance of the machine, using Statistical Process Control (SPC). After conducting the experiments, a mathematic model for predicting torbine blade lobe was developed using experiment results and various analyses are analyzed by variance analysis and predicted mathematic model of lobe of turbine blade is obtained and by using thise model and amount of desirable lobe of blade, input parameters for optimum production are achieved. It is found that increasing of wheel speed, workpiece speed, grinding depth and slower dresser speed, have advantages for obtaining smaller lobe of blade within tolerance.

The effect of weak shear Thickening and shear thinning on the stability of the Taylor-Couette flow is explored for a Carreau-Bird fluid in the narrow-gap limit. The Galerkin projection method is used to derive a low-order dynamical system from the conservation of mass and momentum equations. In comparison with the Newtonian system, the present equations include additional nonlinear coupling in the velocity components through the viscosity. Similar to Newtonian fluids, there is an exchange of stability between the Couette and Taylor vortex flows. The results indicate that with increasing shear-thickening effect, the flow turns into unsteady state at higher Taylor numbers. In contrast, with increasing the shear-thinning effect the flow turns into unsteady state at lower Taylor numbers. Moreover, the results are in accordance to the other present research results.