Applied Mechanics and Materials Vols. 110-116

Abstract: Milling is the most widely applied machining process for producing flat surfaces and prismatic shapes. To minimize the process time and maximize the quality of the workpiece, it is essential to monitor the condition of cutting tool in machining operation and to optimize the process parameters. In the present investigations, experiments were performed on EN31 steel with un-coated carbide inserts in face milling with tools having different approach angles in order to determine the performance of the tool. The effects of process parameters namely speed, depth of cut and feed on tool wear of work piece were investigated. The cutting forces and tool wear are measured in order to evaluate the performance of the cutter. Acoustic emission signal was used for the online tool monitoring. A statistical technique, Taguchi design of experiments was used to optimize the machining process parameters such as speed, feed, depth of cut and approach angle.

Abstract: Due to complexity of condensate-migration into a porous-bed, the analytically simplified studies using uniform-flow assumption need enhancement through performing experiments. This study is conducted by maintaining saturated vapor-air over porous-alumina-balls and glass-beads-bed in a nonperforated chamber. Walls of the chamber are controlled isothermally. By evaluating on subcooling-, diffusive-, and porous perturbation-parameter, it is known that condensate migrates in Darcian regime. In this regime, based on visualized evidence and proposed Lyapunov-exponent-base series, this migration study finds that there are periodic- and unperiodic-dominant subregimes, where a temporal chaotic-migration case is found in the unperiodic-dominant subregime.

Abstract: there are some parameters in friction stir welding (FSW) technique such as tool design, tool rotation speed and tool travel which can be controlled in a precise manner thus controlling the energy input into the system. In this study the effects of these parameters were investigated on microstructure and tensile strength of 5052 aluminum alloy. Roll sheets of this alloy were welded by FSW method at different rotation speeds (400, 800, 1600 and 2500 rpm), welding speeds (50 and 100 mm/min) and tools shoulder diameters (14 and 20 mm). The microstructure results showed that the stir zone (SZ) and thermo-mechanically affected zone (TMAZ) had dynamically recrystallized and recovered respectively. Also the tensile strength of samples welded at tool rotation speeds of 400 and 800 rpm, travel speed 50 mm/min and tools shoulder diameter of 20 mm is similar to that of base metal. The tool rotation speeds of 400 rpm have a good welding ability with higher travel speed and lower tools shoulder diameter.

Abstract: Gas metal arc welding is one of the most important arc welding processes used in manufacturing and repair. In this process selecting appropriate values for process variables is essential in order to decide upon metal transfer and subsequently control the heat input into the workpiece from which reliable predictions could be made about the metallurgical, mechanical properties and performance of the welded joints. In this paper, the welding dilution in gas metal arc welding of ST37 steel has been predicted by fuzzy logic. A five level five factor rotatable central composite design was used to collect the welding data and the weld dilution was modeled as a function of wire feed rate, welding voltage, nozzle-to-plate distance, welding speed and gas flow rate.

Abstract: This study aims to develop a leveling position control of an active PWM-controlled pneumatic isolation table system. A novel concept using parallel dual-on/off valves with PWM control signals is implemented to realize active control and to improve the conventional pneumatic isolation table that supported by four pneumatic cushion isolators. In this study, the cushion isolators are not only passive vibration isolation devices, but also pneumatic actuators in active position control. Four independent closed-loop position feedback control system are designed and implemented for the four axial isolators. In this study, on/off valves are used, and PWM is realized by software. Therefore, additional hardware circuit is not required to implement PWM and not only cost down but also reach control precision of demand. In the controller design, the Fourier series-based adaptive sliding-mode controller with H∞ tracking performance is used to deal with the uncertainty and time-varying problems of pneumatic system. Finally, the experiments on the pneumatic isolation table system for synchronous position and trajectory tracking control, including no-load and loading conditions, and synchronous position control with master-slave method, are implemented in order to verify that the controller for each cushion isolator can realize good position and trajectory tracking performance.

Abstract: This paper deals with the solutions of lateral heat loss equation by using collocation method with cubic B-splines finite elements. The stability analysis of this method is investigated by considering Fourier stability method. The comparison of the numerical solutions obtained by using this method with the analytic solutions is given by the tables and the figure.

Abstract: The high-strength low-alloy microalloyed steel was procured as a hot rolled plate with accelerated cooling. The Gleeble thermal simulated process involved heating the steel specimens to the peak temperature of 1400 °C, with constant cooling rates of 3.75 °C/s and 2 °C/s to room temperature. The four-wire tandem submerged arc welding process, with different heat input, was used to generate a welded microstructure. The martensite/austenite constituent appeared in the microstructure of the heat affected zone region for all the specimens along the prior-austenite grain boundaries and between bainitic ferrite laths. The blocky-like and stringer martensite/austenite morphology were observed in the heat affected zone regions. The martensite/austenite constituents were obtained by a combination of field emission scanning electron microscopes and image analysis software The Charpy absorbed energy of specimens was assessed using Charpy impact testing at-50 °C. Brittle particles, such as martensite/austenite constituent along the grain boundaries, can make an easy path for crack propagation. Similar crack initiation sites and growth mechanism were investigated for specimens welded with different heat input values.

Abstract: Selecting feature in slow-speed and heavy-load equipments has always been a difficult problem. A new feature selection method based on Laplacian Score is used to Acoustic Emission signal. The more capable of describing the sample clustering property, the more important the selected feature is. The method is a ‘filter’ and unsupervised feature selection method which is just dependent on the space distribution of the sample instead of classifier. Therefore, the method enjoys a simple algorithm and low complexity. The effectiveness of the method is verified by the AE datasets from the bearings of a blast furnace’s belt conveyor.

Abstract: In view of digitized heavy-duty mechanical driving technology of alternating current servo machine from the connection between innovative and high technology and conventional mechanical technology, we regard it as the main drive of mechanical press machine, which can improve greatly the performance and intelligent level of press machine. The thesis studies the control system of servo spiral coining machine. We design the hardware of control system based on the scheme about “PC+moving controller”, take GT 200-SV moving controller as upper control unit, alternating current servo driver and special alternating current servo electrical machinery as actuating element to constitute full-closed loop control system. On the basis of it, we choose Visual C++ 6.0 as development tool on the software, adopt modularized and object-oriented design procedures to design control system software.

Abstract: Wide amplitude, DC motor's speed and their facile control cause its great application in industries. Generally the DC motors gain speed by armature voltage control or field control. The suggestion method in this paper is using sliding mode fuzzy control for DC motors robust control. The result is showing by use of this method we can't see any oscillation in responses and the time for reaching the normal speed is very short.