Applied Mechanics and Materials Vols. 110-116

Abstract: Recently, the demands for superfinishing machines have increased, but the development of superfinishing devices and superfinishing technology remain insufficient. And titanium, with its infinite potential, is widely known as a highly ideal material. It is therefore used in various industries that require precision-machined parts, such as the automobile, chemistry and aerospace industries, due to its outstanding specific strength and corrosion resistance compared to any other alloys. In this study, a series of experiments was performed to determine the mirror surface finishing conditions of titanium as well as efficient superfinishing conditions that can be utilized practically and economically at production sites. The applied conditions were the workpiece rotation speed, the oscillation speed, the contact pressure, the roller hardness and the type of abrasive film used when superfinishing was performed using an abrasive film for titanium-based materials such as pure titanium and titanium alloy. From the experiments, it was confirmed that efficient superfinishing conditions and mirror surface finishing conditions were determined for pure titanium and titanium alloy.

Abstract: Plasma Arc Machining is one of the most important non conventional machining method used in fabrication industries because of its high accuracy, ability to machine any hard material, ability to produce any intricate shape and better finish. In the present investigation, plasma arc cutting of stainless steel (316L) materials has been carried out using plasma arc cutting machine. The optimization of process has been carried out using Taguchi method of design of experiment.

Abstract: The aim of the research in progress is to enhance continuously cast billets images software analyzer (based on sulfur prints and template photos) data aquisition and preparation methods. Aquired sulfur prints images and templates photographs were evaluated according to statistical criteria. Raw data aquisition and preparation methods for continuously cast billets analysis software based on sulfur prints and templates photographs were developed in course of work. Conditions of aquiring templates sulfur prints and photographs were also evaluated

Abstract: This paper aims to investigate cutting conditions influence on main cutting force and surface roughness based on considered chip form types in cast nylon turning operation with single-point high speed steel cutting tool. The 75 experiments were performed by average of three levels of cutting speed, five levels of cutting depth and five levels of feed rate. The results reveal that main cutting forces were increased by an increasing of cutting speed and cutting depth for all obtained chip form types for all chip form types. The surface roughness is affected by increasing of feed rate and reduction of cutting speed for 2.3 Snarled and 4.3 Snarled chip form types. The statistical path-coefficient analysis results are shown that the main cutting force affected by cutting speed, depth of cut and feed rate with total causal effect value of 0.5537, 0.4785 and 0.1718, respectively. The surface roughness is influenced by feed rate, cutting speed and depth of cut with 0.8400, -0.2419 and-0.0711 of total causal effect value, respectively. These results are useful to perform varying cutting conditions for high quality of workpiece in cast nylon turning by control the chip form type.

Abstract: Direct metal deposition (DMD) using wire feedstock than powder feeding offers potential advantages such as high material usage efficiency and deposition rate and therefore employed in this work. The deposition process was conducted using metal inert gas (MIG) as the heat source. This study involves manipulating one variable that is deposition parameter to determine if changes in this variable cause changes in another variable that is microstructure and hardness variation. The deposited material was characterized by means of optical microscope and Rockwell microhardness testing machine. In addition, Design Expert Software that implemented Response Surface Methodology (RSM) technique was used in determining optimization of parameters. Results from the software were compared to the results obtained from the experimental works. This study shows that the deposition parameters such as current, arc voltage and travel speed significantly affect the microstructural development and microhardness variations of the stainless steel deposited structure. At the end of this study, directions for future work were suggested in order to further enhance the microstructural and microhardness properties of deposited material.)

Abstract: In Gas Metal Arc Welding (GMAW) process, one of the main goals is to reach high depth of penetration as a characteristic of quality. This requires high amount of input heat. On the other hand high amount of input heat causes the increase in dimensions of heat affected zone (HAZ) which is not desirable. In this paper, an objective function including both depth of penetration of weld bead and the width of heat affected zone namely F = (HAZ+t) / (P+t) has been considered where, HAZ, P, and t denote the width of heat affected zone, the depth of penetration, and thickness of test pieces respectively. A five level five factor rotatable central composite design was used to collect the data for depth of penetration and width of heat affected zone. After collecting the data, the regression equation of objective function was obtained as a function of wire feed rate, welding voltage, nozzle-to-plate distance, welding speed and gas flow rate using least squares method. Then the objective function (f) was minimized by using the Imperialist Competitive Algorithm. One can be sure that the width of HAZ will decrease and the depth of penetration will increase due to minimization of the objective function. The computational result demonstrates that the proposed optimization algorithm is quiet effective in minimizing the objective function. The result shows that in order to obtain higher depth of penetration and lower width of heat affected zone at the same time, wire feed rate, arc voltage and nozzle-to-plate distance must be at their lowest levels while welding speed and gas flow rate should be at their highest levels.

Abstract: The design of a nonlinear adaptive dynamic surface controller for the longitudinal model of a hypothetical supersonic flight vehicle is considered in this work. The uncertain nonlinear functions in the strict feedback flight vehicle model are approximated by using radial basis function neural networks. A detailed stability analysis of the designed angle-of-attack controller shows that all the signals of the closed loop system are uniformly ultimately bounded. The performance of the designed controller is verified through numerical simulations of the flight vehicle model.

Abstract: The combined energy storage and attitude control system (CEACS) combines both energy storage and attitude control modules via the flywheel technology. Previously only the conventional control methods were tested for CEACS. In this paper, H2 and H-infinity control methods are implemented in CEACS. The satellite attitude control performances show that both control options can be employed for a good attitude pointing accuracy. (Abstract)

Abstract: An analysis of linear and nonlinear dynamics of rotors is presented taking into account the shear effects. The nonlinearity arises due to the consideration of large deformations in bending. The rotor system studied is composed of a rigid disk and a circular shaft. In order to study the combined effect of rotary inertia and shear effects the shaft is modeled as a Timoshenko beam of circular cross section. A mathematical model is developed consisting of 4th order coupled nonlinear differential equations of motion. Method of multiple scales is used to solve these nonlinear equations. Linear and nonlinear dynamic behavior is studied numerically for different values of slenderness ratio r. Resonant curves are plotted for the nonlinear analysis. Due to nonlinearity these curves are of hard spring type. This spring hardening effect is more visible for lower values of r. Also the nonlinear response amplitude is higher when shear deformations are taken into account.

Abstract: Firstly, the superior performance and industrial application prospects of non-rotationally symmetric (NRS) optical surfaces are detailed. Secondly, those high precision machining processes to generate NRS optical surfaces are overviewed, it’s been stressed that fast tool servo (FTS) based diamond turning has been the most promising, cost-effective, and high precision machining process to generate NRS surfaces. Finally, the recent research progress in FTS based diamond turning of NRS optical surfaces is remarked, both the tool trajectory generation and the FTS actuation techniques are discussed, the limitations of the existing researches are disclosed, and then the academic and technological researches to be urgently carried out are suggested.