Applied Mechanics and Materials Vols. 813-814

Abstract: The workspace and load bearing involved in a given operation are the deciding criteria for choosing the size and type of the manipulator that has to be used. The hybrid manipulator, which is a serial manipulator mounted on top of a parallel manipulator, derives benefits from both, such as better rigidity from the parallel manipulator and better dexterity from the serial manipulator. In this paper, comparative study of workspace and effectiveness of a hybrid manipulator is done to bring out its advantages, in comparison to a parallel or a serial manipulator. The workspace is determined using geometrical techniques. The effect of having inclined links and its impact on the load bearing capacity of the manipulator is also studied. Serial manipulators on top of mobile robots are used in nuclear power plants to replace spent fuel rod. The serial manipulators have lesser load bearing capacity than hybrid manipulators. By, using a hybrid manipulator, the load bearing capacity is improved.

Abstract: Mechanical design engineers design products by selecting the best possible materials and geometries that satisfies the specific operational requirements of the design. It involves lot of creativity and aesthetics to make better designs. A gear design makes the designer to compromise many design variables so as to arrive the best performance of a gear set. The best possible way for multi variable, Multiobjective gear design is to try design optimization. For many complex engineering optimization problems multi objective design optimization methods are used to simplify the design problem. In this paper, multiobjective design of helical gear pair transmission with objective functions namely volume of the small and large helical gear and opposite number of overlap ratio is taken into account. The design variables considered are normal module, helix angle, gear width coefficient and teeth number of small helical gear. A recent meta-heuristic algorithm namely parameter adaptive harmony search algorithm is applied to solve this problem using the weighted sum approach. It is evident from the results that the proposed approach is performing better than other algorithms.

Abstract: Aim of this present work is to study the combined effect of distributed geometric global imperfection and a local dent on buckling strength of thin square plates subjected to uni-axial compression. Steady state non linear FE analysis including both material and geometrical non linearities is used to determine the ultimate strength of the dented plates. From the numerical result it is found that in case of low thickness plates global geometric imperfections effect is more dominant and in case of thick plate dent effect is found to be more dominant.

Abstract: Carbon fibers find their application in lightweight structures due to high strength to weight ratio. Passive damping is proving important for vibration control and dynamic stability in advanced engineering systems like aerospace, automobiles and in ship building industry. In the present investigation, Mechanical properties and free vibration characteristics of woven fabric carbon composites were studied by adding micro rubber alone as reinforcement and combination of micro rubber and nanosilica particles as other reinforcements in epoxy matrix. Carbon composites were prepared with two different epoxy matrices containing 9 wt. % micro rubber particle and 6wt. % nanosilica and 9 wt. % micro rubber particles as another combination. To study the influence of cross sectional shapes on vibration behavior of beams, most widely used structural shapes like I, Box and Channel section were chosen. Beams were fabricated with woven carbon fabric and epoxy resin by hand layup technique by maintaining 40 % fiber volume fraction and 60 % matrix volume fraction for all epoxy combinations. Mechanical behavior of modified carbon composites were studied by conducting tests as prescribed by ASTM standards. Vibration damping behavior was studied by subjecting fabricated beams to Impulse frequency response test under cantilever end boundary conditions. It was found that the hybrid carbon epoxy beams with 6% nanoSilica and 9% Micro Rubber by weight showed better damping performance for successive resonance frequencies. Modal responses of all beams like mode shapes and their corresponding natural frequencies were extracted using MEScopeVES^® software and discussed.

Abstract: Predicting shape and finding out exact area of the workspace of 3-DOF planar parallel manipulator having three rotary joints has been a research topic for long time. Optimal design based on such calculations provides a conclusive design methodology. In this work, geometrical method is used o get the exact shape of the workspace and expression of area for the shape obtained. The 3-DOF parallel manipulator is treated as a combination of three independent serial manipulators and its workspace as the common intersection area of these three serial manipulators. The three workspaces are then translated by length equal to radius of the end effecter and the common intersection area is obtained as the workspace of the parallel manipulator under study. The area is determined using the mathematical expression for the shape obtained. Based on direct search algorithm, a methodology is developed to optimize the area. Thus, following, this methodology, an user with specification of area of the workspace can be provided with an optimized parallel manipulator taking into account the inventory of link lengths and the cost of the links.

Abstract: In the current automated high-tech world the applications and use of robot has become the vital role in all areas in industries and in common social applications. The mechanical design process essentials to improve and also it is a way to capable of giving consistent and fast efficient products. One way of altering the process is through reducing the manual work by systematizing the repetitive tasks using static analysis ways in the computer software. With a view to meet the purpose of inspecting the outer surface weldments in steel storage canister used to store the High-level fuel waste at nuclear industry with the help of Non-destructive testing (NDT) equipment. In this research work the new mechanical configuration of the robot arm was designed, and this arm was utilized to carry the vision camera at the end effector to capture the weld surfaces. This paper focuses the mechanical modeling of the manipulator mechanism and finite element (FE) method and analysis of the designed arm with different positions and specific load condition. From this study the statically balanced design of the robot was determined with three different positional conditions. The largest value of displacement and stress produced in the arm also discussed with clear FEA simulation results. In this paper mechanism of seven degrees of freedom robot arm is discussed.

Abstract: Gearbox is the only medium which balances the power and torque relations for the appropriate operating conditions, at very high speeds it controls the power output of the drive unit. Its application is wide in the field of automotive and industries. Condition monitoring of gearbox access the operating condition of the gearbox components such as gears and, bearings to take necessary condition based maintenance to avoid the machine downtime and operation losses. This paper identifies the suitable accelerometer position to acquire vibration signals for identification of gear faults using machine learning techniques. The study includes 2 fault class, 2 gear speeds (1^st and 4^th gear), 3 loading conditions and, 3 operating speeds each for 2 sensor locations. Features were collected for each class in both sensor location points from accelerometer. Statistical features were extracted and the classification efficiencies were calculated from both SVM and J48 Decision tree algorithm.

Abstract: Innovative methods in the design of radial diffuser are necessary for reducing the energy losses associated with diffusion in order to design an efficient centrifugal compressor. Rotating vaneless diffusers is one such concept, in which a particular type, free rotating vaneless diffuser, the diffuser speed becomes a fraction of the rotating impeller speed and rotates independently. In this paper, an impeller with stationary vaneless diffuser alone of diffuser diameter ratio 1.40 and the same impeller with a freely rotating vaneless diffuser of diffuser diameter ratio 1.30 along with stationary vaneless diffuser at downstream for the remaining radius ratio are analyzed for flow diffusion and performance. Higher static pressure rise with reduced stagnation pressure losses and a marginally lesser efficiency by around 3.5% compared to SVD is achieved by the free rotating vaneless diffuser configuration (FRVD30SR0.5).

Abstract: The capacity of wind power generation has increased across India due to various activities encouraged by government. Moreover, onshore potential in India is in the order of 100GW. However, the plant load factor is often very low in wind power production. In most of the place, low-rated wind speed is available. Effective utilization of the wind to produce small power will reduces the grid load. There is in need to effectively utilize the available potential to meet the energy demand. The low cost vertical axis wind turbine designed for low rated wind regime has the hybrid of simple Savonius and helical Savonius. Various experimental parameters are measured to check the suitability of the vertical axis wind turbine in the low rated wind speed regions. Numerical simulation are carried out for three dimensional steady flow around the combined Savonius and helical Savonius vertical axis wind turbine blades using ANSYS Fluent^(C). Numerical investigation are conducted to study the effect of hybrid combination on performance of the rotor in terms of coefficient of torque, coefficient of power, etc. Self-starting behaviour of the vertical axis wind turbine is improved by using this hybrid vertical axis wind turbine.

Abstract: Pipes in power plants generally subjected to high pressures and temperatures. These are connected by elbow, T-joints to get the continuity between different stages. Due to excessive joints the outlet velocity and pressure will drops by considerable amount. Stresses will be produced due to high pressure and temperature of fluid flow, which in turn creates the failure of the pipes. The turbulence of the fluid passing through the pipes will also plays a vital role to decide the outlet pressure and velocity. In this present study pipes are connected by the elbow joint are considered and observed the effect of pipe thickness, turbulence intensity and length of elbow on outlet pressure, velocity, von mises stress and turbulence kinetic energy. It results that with increase in pipe thickness and length of elbow, the velocity, von mises stress and turbulence kinetic energy are decreases but with increase in turbulence intensity, the velocity and turbulence kinetic energy are increases.