Applied Mechanics and Materials Vols. 110-116

Abstract: The application of Timoshenko beam theory is presented, thereby the effects of airfoil camber can be investigated analytically and numerically by considering rotary inertia and shear deformation in addition to moment of inertia, aerodynamic loading and bending/torsion coupling. Regarding a tuned blisk, the analysis is simplified to a single blade with plunge and pitch DOF. Pressure distribution of the airfoil surfaces and the resulting aerodynamic forces are calculated with ‘ANSYS/FLOTRAN’ during one-cycle time marching at several reduced frequencies. A parametric relation is then achieved by Roger’s approximation including quasi-inertia, quasi-damping, quasi-elastic and lag terms. The final aeroelastic equations are established by bending-torsion and aerodynamics-structure coupling which is solved by state space approach. This procedure is repeated at several free stream velocities until the real component of an eigenvalue equals zero. The latest velocity is the flutter speed. Following this procedure, flutter characteristics of two similar aeroleastic cases are determined considering only one difference in blade configuration; one with cambered and the other with uncambered airfoil. Comparison of these two cases shows the considerable suppression effect of airfoil camber on flutter.

Abstract: This paper analyzes the hole and open hole wall without cracking load, crack distribution and the order of appearance. We use MSC.Macr software and two-dimensional four-node element and the constitutive relation proposed masonry. Masonry shear wall is failed criterion for the force and deformation of elastic-plastic finite element analysis, wall cracking load is ultimate shear capacity. The predicted values of cracking load, ultimate shear load-bearing capacity and maximum horizontal deformation of wall agree better with testing results.

Abstract: here, a time optimal control scheme for trajectory planning of kinematically manipulators subjects to actuator torque limits is proposed by using the phase plane analysis and linear programming technique. In addition, the limit on joint velocities is considered. In order to affect the constraint of joint velocities, this constraint is converted to constraint on joint acceleration and it is affected linear programming problem as an additional constraint. Also, an explicit algorithm for finding the switching points is presented. To this end, some simulations are given to demonstrate the efficiency of proposed trajectory planning algorithm.

Abstract: This work is aimed at optimizing the various parameters of the electro discharge machining process in order to Maximize material removal rate (MRR) and Minimize electrode wear rate (EWR) for machining silicon or resin bonded silicon carbide, which is widely used in various applications like high-temperature gas turbines, bearings, seals and linings of industrial furnaces. The five parameters being optimized are intensity supplied by the generator of the EDM machine, open voltage, pulse on time, duty cycle and pressure of flushing fluid. The polynomial models for MRR and EWR proposed by Luis, Puertas and Villa [1] in terms of the five input parameters was used for formation of the objective function. Optimization was carried out using the multi objective genetic algorithm, which is a heuristic search technique that mimics natural selection. A Pareto-optimal front was obtained using this technique, and the points lying on this front represent the set of optimal solutions for the optimization problem. The resultant Pareto– optimal front can be used to select the appropriate operating conditions depending on the specific MRR, EWR or combination requirements.

Abstract: Tool wear is a major issue in ultrasonic machining and it is more significant in case of micro-ultrasonic machining. Because of the size of the tool in micro domain; the strength is relatively poor and hence more tool wear results. Generally, in the off-line methods, tool wear is measured after machining and by the removal of the tool from the machine tool. However, it is difficult and untidy process to remove the tool for each measurement and reinstall it on the machine. In this paper a simple technique ‘Reference Point’ method has been proposed to assess the linear tool wear on the machine itself. A comparative study of tool wear in case of solid and hollow tool was made while drilling silicon wafer. Static load was considered as a process parameter. Surface topography and fracture mechanism are discussed with the help of scanning electron microscope (SEM) micrographs.

Abstract: A structured frame for the design optimization problem of satellite platform structure was established through the definition, flow and modification research of design parameters in the ANSYS/CATIA system. Problems with creating complex satellite structure FEA (Finite Element Analysis) models were discussed, including the idealization of real structure, as well as embedment of APDL (ANSYS Parametric Design Language) programme developed specially for the pre-processing and post-processing of FEA model. The optimization model was established under structural design requirements, and a graded optimization method was applied for calculation. Light-weight design schemes for two satellite platform structure were obtained through the subsequently optimization implemented using approaches put forward previously. The optimization design problems of two satellite platform structure were settled well, and work done in this paper provides certain reference value for optimization of other spacecraft structures.

Abstract: A comprehensive numerical investigation on the natural convection in an isotropic porous enclosure is presented. All the walls of the enclosure are adiabatic except the bottom wall which is partially heated and cooled by sinusoidal temperature profile. The governing equations were written under assumption of Brinkman-extended non-Darcy model, including material derivative, and then solved by numerically using spectral element method (SEM). The heat transfer and fluid flow mechanisms in isotropic case are governed by periodicity parameter (N) Rayleigh Number (Ra), Darcy number (Da), aspect ratio (A), Prandtl number (Pr) and media permeability (K). The main emphasize is given on effect of N on local heat transfer as well as mechanism of heat transfer and fluid flow in enclosure. The results shows that, as the periodicity is decreased on increasing N the absolute value of Nux at the bottom left corner point increases. For odd values of N, the local heat transfer profile is symmetric about the line x=0.5, which is consequence of symmetric boundary condition at the bottom wall of the enclosure. The entire flow is governed by two type convective cells: (i) rotating clockwise (ii) rotating anticlockwise. Furthermore for even values of N cells rotating anticlockwise are dominated and covered the entire domain. In particular the present analysis shows that, different periodicity of temperature boundary condition has the significant effect on the flow mechanism and consequently on the heat transfer rate.

Abstract: In order to enable a mini-UAV to perform target acquisition, localization and continuous surveillance in real world environment one must develop a technology which may be a combination of aircraft engineering, control systems, and wireless communication. The major limiting factors in developing the capabilities of small low cost UAVs are connectivity, computational processing power and lack of resource integration. To overcome these limitations in this research we have tried to assemble an experimental fixed wing prototype glider plane capable of being remotely controlled in the range of 20 meters. We started with a light and flexible fat-propylene twine flute material and developed the airframe, interfaced it with radio controlled remote and embedded on-board micro controller on the glider airframe. Our glider took stable flight with the assembled propeller for 20 minutes successfully. The brushless DC servomotors used for electronic speed control of the UAV worked efficiently and were able to control the rudder and elevator in both directions. The significance of this research is that all the devices used here are low cost and highly efficient. In this paper we have investigated the use of reconfigurable computing as a viable alternative to increase the amount of computational power whilst at the same time minimizing the amount of weight, size, and power consumption.

Abstract: Environment and green energy awareness are two main factors why this study has been carried out. This research is focused on aerodynamics study for airfoil structure modification based on NACA 0044 and NACA 0063 by using wind tunnel experiment. Aerodynamic characteristics such as lift coefficient, C_L, drag coefficient, C_D, lift to drag ratio and cell relative velocity has been investigated in this study. CFD simulation has been carried out at the early stage of the investigation (for NACA 0044 and NACA 0063), and a new airfoil profile had been created (0044-63) by modified the chord length and the location of maximum thickness of the airfoil by using the modified NACA Four-Digit Series. Wind tunnel experiment has been take place for three different wind speeds from 25m/s, 35m/s and 45m/s at various angles of attack from 0^o to 40^o with 5^o incremental for the respective airfoil. The results show that the modified 0044-63 produced the better lift coefficient and this airfoil has been fabricated and tested in the wind tunnel experiment in order to validate the CFD result. This paper reports the result of aerodynamics characteristics for respective new airfoil and it shows that at angle of attack between 5 ^o to 15 ^o, this airfoil produced good lift to drag ratio value. Also, by modified the location of maximum thickness 30% to the trailing edge give the increment of lift to drag ratio produced approximately 15% and at the same time, give insignificant changes to the drag coefficient value.

Abstract: In mechanical transmission, widely adopted involute spline link, it has self-centering, spline tooth bending strength, high bearing capacity is strong, force is more homogeneous, long service life, components small volume and other characteristics. For involute spline tooth shape through the analysis of the forming and working principle, combining the working practice, will involute spline from zero connected as center of cylindrical gears transmission internal meshing, according to the internal meshing of cylindrical gears deflection is deduced calculation formula of involute spline displacement inside and outside the geometry size calculation is feasible.