Applied Mechanics and Materials Vol. 787

Abstract: This is Part-1 of the two-part paper in considering the effect of cambered airfoil blades on self-starting of vertical axis wind turbine. Part 1 reports the numerical studies on self-starting of vertical axis wind turbine with comparative studies involving NACA 0012 and cambered airfoil NACA 4415. Part 2 of the paper deals with numerical studies of NACA 0018 and cambered air foil NACA 63415. Darrieus type VAWT is attracting many researchers attention for its inherent advantages and its diversified applications. However, a disadvantage is when the rotor is stationary, no net rotational forces arises, even at high-wind speed. The principal advantage of the vertical axis format is their ability to accept wind from any direction without yawing mechanism. However, self-starting capability is the major drawbacks. Moreover, literatures based on computational analysis involving the cambered airfoil are few only. The objective of this present study is to select the suitable airfoil blades on self-starting of VAWT at low-Reynolds number. The numerical studies are carried out to identify self-starting capability of the airfoil using CFD analysis by studying the flow field over the vertical axis wind turbine blades. The commercial CFD code, ANSYS CFX 13.0^© was used for the present studies. Initially, the flow over NACA 0012 was simulated and analyzed for different angles of attacks and similarly carried out for NACA 4415. The contours of static pressure distribution and velocity as well as the force and torque were obtained. Even though the lift force for cambered airfoil NACA 4415 is higher, based on the torque values of the above blade profiles, asymmetrical airfoil NACA 0012 is found to be appropriate for self-starring of VAWT.

Abstract: This paper presents the dynamic modeling of 210MW Industrial Coal Fired Boiler which is used commonly in thermal power plants. The goal of developing the first principle model is to capture the key dynamical properties of the boiler over a wide operating range. The model describes the complicated dynamics of the various components of Industrial coal fired boiler such as furnace, boiler drum, primary superheater attemperator and secondary superheater. The model is developed based on the physical principles, and is characterized by a few physical parameters. The parameters are determined from the construction data, and a few of them from the field test data. A strong effort has been made to strike a balance between fidelity and simplicity. From the modeling point of view, the boiler is divided into five subsystems and for each subsystem, the first principle models are developed using the mass and energy balance equations. The subsystem models are then integrated to obtain the integrated boiler model. Simulation studies are carried out based on the nominal values of the system variables and the parameters collected from a power plant. The integrated boiler model obtained is tested for its dynamic and steady state characteristics and the results of which are described. The model is validated against the unique plant data and the results are presented. The model describes the behaviour of the system over a wide operating range. A good agreement is found between the simulation and actual parameters of the boiler.

Abstract: NiTi alloys are advance materials which possess superior properties such as pseudoelasticity, shape memory effect, high wear resistance, high corrosion resistance and high strength. NiTi alloys causes serious tool wear, hardening of the machined surface and poor surface finish. Electro discharge machining (EDM) is an unconventional machining process which demonstrates high capability to machine NiTi alloys. Present work emphasis on investigating the effect of EDM process parameters on the tool wear rate. Gap current, pulse on time and pulse off time were considered at three levels as input process parameters along with electrical conductivity of workpiece and tool electrode at two levels. Taguchi L₃₆ (2² x 3³) mixed orthogonal array was utilized to design the experimental plan. Based on the statistical analysis at 95% confidence level it was found that tool electrical conductivity, gap current and pulse on time are the most significant factors that influence the tool wear rate. At optimal setting of parameters the predicted value of tool wear rate obtained was 0.00811 mm³/min.

Abstract: This investigation was done to study machinability during drilling on sandwichlaminates. Vetiver and jute were used as natural fibers and glass was used as synthetic fibers in vinyl ester matrixin the form oflaminatesby varying the fiber content in each laminate.The laminateswere drilled during which spindle speed, spindle feed rate, tool point angle and sample laminate weremodified using D-optimal design technique. During drilling of each hole, thrust force impressed and torque developedwere noted as outputs.The outputswere optimized to observe best drilling conditions.A fuzzy model was created and its predictions for trialconditionswere noted. A comparison between trial values, regression values and fuzzy values was made. Confirmatory trialswere madefor optimumset of runs and outputswere again noted.The percentage of error between the model, confirmatory trials and fuzzy were found to be meagre and hence concluded that the optimization was satisfactory.

Abstract: This article emphasizes on finite element modeling and simulation of train car body structure in order to ensure a crashworthy structure. Crashworthiness is a principal parameter to be considered to be taken into account in case of design of train car body structure. The present paper deals with the development of virtual prototype with energy absorption capabilities. The train car body structure with trapezoidal core has been modeled using SOLIDWORKS^® software. The entire crash simulation in the present study was done by using LS-Dyna^® Explicit finite element software. The crash analysis of train car body over a rigid concrete wall was numerically simulated at three different speeds viz. 60 km/hr, 90 km/hr, 120 km/hr. In every crash analysis, the stress plot and history of deformation from the developed virtual prototype. The simulation of the rail vehicle collision presented in this article is based upon the standard specified in crashworthy section of Technical Standards of interoperability. The dynamic numerical simulation of two train car bodies with equal velocities has also performed using LS-Dyna^®.

Abstract: The objective of the present paper is to carry out the numerical studies on the buckling characteristics of unstiffened and anisogrid aluminium conical structures under axial static loading conditions. This study emphasizes the importance of lattice structures in space application wherein the minimization of weight of the principal part is given greater importance. Lattice structures are preferred in space applications due to their extremely low weight and high structural performance. Both unstiffened and anisogrid aluminium conical shell structures were modelled using Solidworks^®. The finite element computations were done using LS-Dyna^® under static loading conditions. The results of unstiffened and anisogrid shell structures are compared. Based on these studies, it has been asserted that there exists more energy absorption in case of anisogrid conical shell structures than the unstiffened counterpart. The results also reveal about 70% weight reduction in anisogrid conical shell structures.

Abstract: Concentrated solar thermal (CST) power has been used for years to help supply power to certain energy markets and has proven to be fairly successful. Unfortunately the high prices of these solar technologies have prohibited them from really making a large impact on the world's energy scene. This study analyses the structural, thermal, and CFD performance of a parabolic dish concept which could be the basis for large scale commercial concentrated solar thermal electricity. Simulation of the structural, thermal and CFDanalysis of the dish with varying metallic properties (Aluminium, Copper and StainlessSteel) under different windconditionswas compared. Computational Fluid Dynamics (CFD) was done to simulate the thermal performance of the dish at two different wind velocities.

Abstract: Fixture is a work-holding or supporting device used in the manufacturing industry to hold the workpiece. Fixtures are used to securely locate (position in a specific location or orientation) and support the work, ensuring that all parts produced using the fixture will maintain conformity and interchangeability. The location of fixture elements is called as fixture layout. The fixture layout plays major role in the work piece deformation during the machining operation. Hence optimization of fixture layout to minimize the work piece deformation is one of the critical aspects in the fixture design process. Minimization the workpiece deformation which is the objective function in the present work is calculated using Finite Element Method (FEM) and the fixture layout is optimized using Discrete fixture layout optimization method (DFLOM), Continuous fixture layout optimization method (CFLOM) and Integrated fixture layout optimization method (IFLOM).The workpiece deformation is minimum in Particle Swarm Optimization (PSO) based IFLOM is reported for the selected fixture. In this paper the PSO is used as an optimization tool to optimize the workpiece deformation.

Abstract: Recent research works indicate that magnesium alloy can be used for constructing light weight armor because of its density, which is 35% lower than aluminium and 77% lower than steel and also it exhibits superior vibration damping and better failure mechanisms than the contemporary ballistic materials. In this study, numerical simulations were carried out in a monolithic magnesium AZ31B plate using AUTODYN software to understand the effect of Impact velocity and plate thickness on the deformation of target plates. The projectiles are normally impacted on target plates of varying thickness plates at different velocities. Lagrangian solver was used for meshing, in which the grid developed by the solver distorts with the material helps in eliminating the inaccuracies caused by the cell growth due to the shear force of the bullet impact. The simulation results are verified with the experimental data available in the literature.

Abstract: Around 70% of the cost in piping industry is spent in the pipe manufacturing with optimum design of pipes without defects. Research on design of pipes has gained importance from the last decade. There are numerous methods being developed to improve the efficiency of piping units considering various parameters. The pipe tends to flatten when they are forced to bend, this geometrical changes has a significant role in the acceptability criteria of pipes. It is necessary to bend pipes in order to transmit liquid or gas from one place to other place. In this work special attention is given to pipe bends because of high stress concentration due to various loading conditions. From several kinds of piping systems, process piping systems are chosen for analysis since pipes used here transport important and hazardous materials. Damage to such piping system can cause serious loss to economy and human lives. The geometrical imperfection associated with bending of pipes is ovality. This degree of ovality determines the acceptance of pipes. Thickening and thinning effects cause additional problems like large plastic deformation and loss of flexibility respectively. Hence estimation of the best degree of ovality is required. In this work effect of ovality is estimated by taking the internal fluid pressure and In plane bending moment into account.