Showing papers on "Rotational speed published in 2008"

Microstructure and tensile properties of friction stir welded AZ31B magnesium alloy

Abstract: The microstructural change in AZ31B-H24 magnesium (Mg) alloy after friction stir welding (FSW) was examined. The effects of tool rotational speed and welding speed on the microstructure and tensile properties were evaluated. The grain size was observed to increase after FSW, resulting in a drop of microhardness across the welded region from about 70 HV in the base metal to about 50 HV at the center of the stir zone. The obtained Hall–Petch type relationship showed a strong grain size dependence of the hardness. The aspect ratio and fractal dimension of the grains decreased towards the center of the stir zone. The welding speed had a significant effect on the microstructure, with larger grains at a lower welding speed. The yield strength and ultimate tensile strength increased with increasing welding speed due to a lower heat input. A lower rotational speed of 500 rpm led to higher yield strength than a higher rotational speed of 1000 rpm. The friction stir welded joints were observed to fail mostly at the boundary between the weld nugget and thermomechanically affected zone at the advancing side. Fracture surfaces showed a mixture of cleavage-like and dimple-like characteristics.

Effect of friction stir welding speed on the microstructure and mechanical properties of a duplex stainless steel

Abstract: The present study focuses on the effect of the welding speed on the microstructure and mechanical properties of the stir zone (SZ) in friction stir welding (FSW) of SAF 2205 duplex stainless steel. A single tool, made of a WC-base material, was used to weld 2 mm-thick plates at a constant rotational speed of 600 rpm. X-ray radiography revealed that sound welds were successfully obtained for the welding speeds in the range of 50–200 mm/min, whereas a groove-like defect was formed at the higher speed of 250 mm/min. Moreover, increasing the welding speed decreased the size of the α and γ grains in the SZ, and hence, improved the mean hardness value and the tensile strength of the SZ. These results are interpreted with respect to interplay between the welding speed and the peak temperature in FSW.

Analysis and experiment of capillary valves for microfluidics on a rotating disk

Abstract: This paper presents an analytical expression of the pressure barrier in a capillary-burst valve for flow regulation in centrifugal microfluidics. The analysis considers variations of the interfacial energies at the meniscus of three-dimensional (3D) configuration in a rectangular microchannel with a sudden expansion in cross-section. We derive a simple expression that predicts the critical burst pressure or rotational speed to overcome the capillary valve. Experiments were carried out for capillary valves that were integrated with microchannels on a rotating disk having various cross-sectional dimensions (300 and 400 μm in width and 80–600 μm in depth) and wedge angles (30°–100°) of sudden expansion. The flow visualization of the meniscus development across the capillary valve supports the assumptions made for the present analysis. The measurements of burst rotational speeds for the capillary valves are in good agreement with the predictions by the simple expression except that those with a larger channel width and wider wedge angles are nearly 10% lower than the predicted values.

Effect of Tool Pin Profile and Tool Rotational Speed on Mechanical Properties of Friction Stir Welded AA6061 Aluminium Alloy

Abstract: AA6061 aluminium alloy (Al-Mg-Si alloy) has gathered wide acceptance in the fabrication of light weight structures requiring a high strength-to-weight ratio and good corrosion resistance. Compared to many of the fusion welding processes that are routinely used for joining structural aluminium alloys, the Friction Stir Welding (FSW) process is an emerging solid state joining process in which the material that is being welded does not melt and recast. This process uses a nonconsumable tool to generate frictional heat in the abutting surfaces. The welding parameters such as tool rotational speed, welding speed, axial force, etc., and tool pin profile play a major role in deciding the joint properties. In this investigation, an attempt has been made to study the effect of rotational speed and tool pin profile on mechanical properties of AA6061 aluminium alloy. Five different tool pin profiles (straight cylindrical, tapered cylindrical, threaded cylindrical, triangular, and square) have been used to fabricate ...

Granular mixing and segregation in a horizontal rotating drum: A simulation study on the impact of rotational speed and fill level

Abstract: The rich phase behavior of granular beds of bidisperse hard spherical particles in a rotating horizontal drum is studied by Discrete Element Method (DEM) simulations. Several flow regimes and various forms of radial segregation, as well as mixing, are observed by systematically varying the operational parameters of the drum, i.e. fill level and angular velocity, over a wide range. Steady states after several dozen revolutions are summarized in two bed behavior diagrams, showing strong correlations between flow regime and segregation pattern. An entropy method quantifies the overall degree of mixing, while density and velocity plots are used to analyze the local properties of the granular bed. The percolation mechanism may provide a qualitative explanation for the distinct segregation processes, and for the transient mixing in nonradially segregated beds. Initially blockwise segregated beds are found to mix before radial segregation sets in. High fill fractions (>65%) show the most intense segregation.

Method for determining inertia effects for a hybrid powertrain system

Abstract: A method for controlling a hybrid powertrain system based upon determined inertial effects for a continuously variable operating range state includes monitoring an operator torque request and a rotational speed of the output member, determining an inertial effect on an input speed of the input member for a continuously variable operating range state, and controlling motor torque outputs from the electric machines to meet the operator torque request based upon the inertial effect on the input speed of the input member.

Wind turbine monitoring

Abstract: A method of monitoring the performance of a wind turbine (1) uses bending momentdata from strain sensors (4) in the turbine blades (2) to calculate rotational speed of the turbine (1), angular position of the turbine blades (2), drive torque and resultant load on the rotor (3). The method has the advantage that the inputs to the drive train of the wind turbine can be (5) measure directly.

The three-dimensional transition in the flow around a rotating cylinder

Abstract: The flow around a circular cylinder rotating with a constant angular velocity, placed in a uniform stream, is investigated by means of two- and three-dimensional direct numerical simulations. The successive changes in the flow pattern are studied as a function of the rotation rate. Suppression of vortex shedding occurs as the rotation rate increases (>2). A second kind of instabilty appears for higher rotation speed where a series of counter-clockwise vortices is shed in the upper shear layer. Three-dimensional computations are carried out to analyse the three-dimensional transition under the effect of rotation for low rotation rates. The rotation attenuates the secondary instability and increases the critical Reynolds number for the appearance of this instability. The linear and nonlinear parts of the three-dimensional transition have been quantified by means of the amplitude evolution versus time, using the Landau global oscillator model. Proper orthogonal decomposition of the three-dimensional fields allowed identification of the most energetic modes and three-dimensional flow reconstruction involving a reduced number of modes.

Control device for vehicle

Abstract: PROBLEM TO BE SOLVED: To provide a control device for a vehicle enabling generation of engine brake at lower vehicle speed on a descent than conventional case by cooperative control of engagement of a lock up clutch and fuel cut SOLUTION: This control device for a vehicle executes cooperative control of engagement of the lock up clutch and fuel cut, and enables generation of engine brake at lower vehicle speed than conventional cases by engaging the lock up clutch first and starting fuel cut with changing fuel cut start rotation speed raised to predetermined rotation speed after engagement of the lock up clutch to usual fuel cut rotation speed when rotation speed of an input shaft of a transmission exceeds a predetermined value during deceleration travel with fully closed throttle valve COPYRIGHT: (C)2008,JPO&INPIT

Ultraminiaturized High-Speed Permanent-Magnet Generators for Milliwatt-Level Power Generation

Abstract: This paper presents the design, fabrication, and characterization of millimeter-scale rotary electromagnetic generators. The axial-flux synchronous machines consist of a three-phase microfabricated surface-wound copper coil and a multipole permanent-magnet (PM) rotor measuring 2 mm in diameter. Several machines with various geometries and numbers of magnetic poles and turns per pole are designed and compared. Moreover, the use of different PM materials is investigated. Multipole magnetic rotors are modeled using finite element analysis to analyze magnetic field distributions. In operation, the rotor is spun above the microfabricated stator coils using an off-the-shelf air-driven turbine. As a result of design choices, the generators present different levels of operating frequency and electrical output power. The four-pole six-turn/pole NdFeB generator exhibits up to 6.6 mWrms of ac electrical power across a resistive load at a rotational speed of 392 000 r/min. This milliwatt-scale power generation indicates the feasibility of such ultrasmall machines for low-power applications. [2008-0078].

Power output apparatus, hybrid vehicle with the same, and control method of power output apparatus

Abstract: When a predetermined change speed state shift condition is satisfied while the transmission connects a carrier with a drive shaft, a hybrid vehicle performs a rotational speed adjustment process of conforming a rotational speed of a motor to a target rotational speed based on a gear ratio of the transmission and a rotational speed of the drive shaft, a connection a sun gear with the drive shaft by a gear train of the transmission corresponding to a target speed, a power transfer process of transferring power between the motors in a simultaneous engagement state to make the motors output power required in a post-change speed state corresponding to a target speed, and a disconnection the carrier from the drive shaft.

Power generation system

Abstract: A power generation system including an engine and an electrical generator driven to rotate at rotational speed by the engine. The generator is configured to supply an adjustable amount of required electrical power having a voltage and a current to at least one electrical load. The system also includes a controller configured to adjust at least one operating parameter of the engine in order to maximize efficiency of the system. The system efficiency is a measure of the combined operation of generator and engine and load for a given load condition. The controller is configured to maximize system efficiency based only upon the required electrical power being supplied by the generator. The controller is configured so that the controller does not independently consider any one of the rotational speed, the voltage or the current being supplied by the generator when adjusting the at least one operating parameter.

Design of a Hybrid Composite Flywheel Multi-rim Rotor System using Geometric Scaling Factors:

Abstract: The effects of geometric scaling on the static and dynamic behavior of a multi-rim hybrid press-fitted composite flywheel rotor are investigated and applied to its design procedure. It is verified that the stresses among the scaled multi-rim hybrid rotors remain the same as long as press-fit interferences are linearly scaled, curing temperature remains unchanged, and the rotational speed is inversely proportional. With the linearly scaled supporting stiffness of the scaled rotor and shaft, a relationship between inversely scaled critical speeds and rotational speeds remains unchanged. Double rim rotors of 5 kWh and 100 kWh energy storage are designed by scaling an optimized 0.5 kWh multi-rim rotor. Then, the rotors of 5 kWh were manufactured by wet-winding E-glass and T-700 fibers with a low-temperature cured epoxy system.

Basic characteristics of 150,000r/min switched reluctance motor drive

Abstract: Developments of high speed motor drive have been described. A switched reluctance motor has been designed for 2 kW output at a rotational speed of more than 100,000 r/min. A test machine has been constructed based on the design. The iron parts are fabricated by 6.5% silicon steel, i.e., low iron loss material. The rotational speed of 150,000 r/min is reported experimentally. Fast and accurate controller has been developed using field programmable gate array device.

Application of Differential Transform Method in Free Vibration Analysis of Rotating Non-Prismatic Beams

Abstract: Rotating beams are considerably used in different mechanical and aeronautical installations. In this paper, free vibration of non-prismatic rotating Euler-Bernoulli beams is studied. Dynamic stiffness matrix is evaluated by using differential transform method, a powerful numerical tool in solution of ordinary differential equations, for solving the governing equation of motion. The method is capable of modeling any beam whose cross-sectional area and moment of inertia vary along beam with any two arbitrary functions and any type of cross-section with just one or few elements so that it can be used in most of engineering applications. In order to verify the competency of the method, natural frequencies are obtained for two problems and the effects of rotational speed parameter and taper ratio on natural frequencies are investigated.

Engine control apparatus

Abstract: An engine control apparatus controls an engine rotational speed to a target rotational speed by using a detected input side transmission rotational speed of a manual transmission as the target rotational speed upon detecting a clutch pedal depression amount during shifting being equal to or larger than a first prescribed depression amount, which is equal to or larger than a depression amount corresponding to a clutch disconnect position. The engine rotational speed is controlled to the target rotational speed by using the smaller of a computed transmission rotational speed (based on vehicle speed and gear ratio using a shift position) and the detected input side transmission rotational speed, upon detecting the clutch pedal depression amount during shifting being smaller than the first prescribed depression amount and larger than a second prescribed depression amount, which is smaller than the depression amount corresponding to the clutch disconnect position.

Direct torque control method for permanent magnetic synchronous electric machine

Abstract: The invention relates to a direct torque control method for a permanent-magnet synchronous motor, which is characterized in that: based on a flux linkage and torque estimator, the estimated values of a stator flux linkage and the torque at the present moment are calculated. The error between the estimated value of the torque and a torque reference value is simply adjusted by PI to obtain the dynamic speed difference Delta Omega s of the stator flux linkage and a rotor flux linkage, and then the speed difference Delta Omega s is added with a steady-state rotational speed Omega to obtain total rotational speed of the stator rotational speed. After the total flux linkage rotational speed Omega s is obtained, a specified reference flux linkage vector Psi s in the next sampling period is obtained by referring to a flux linkage computational model. The reference flux linkage vector Psi s and an estimated flux linkage vector Psi s at the present moment are simply calculated to obtain an SVPWM Us which is exerted in the next sampling period. The SVPWM Us is modulated by a space vector modulating method to generate the switching signals of a voltage source inverter. The direct torque control method of the invention has the advantages that as the concept of the space vector is adopted to analyze the mathematical model of PMSM and control the physical quantity thereof, the problems become especially simple and clear.