Showing papers on "Rotational speed published in 2010"

Pneumatic hand tool rotational speed control method and portable apparatus

Abstract: The rotational speed of a pneumatic hand tool is adjusted in real time to maintain a selected speed level irrespective of exterior parameters affecting the performance of the tool. The apparatus is comprised of a rotational speed sensor installed directly on the tool, a digital microprocessor using control algorithms, and a valve to adjust the flow of air to the tool.

Rotational abrasive flow finishing (R-AFF) process and its effects on finished surface topography

Abstract: The present study focus on abrasive flow finishing (AFF), a process that finishes complex internal and external geometries with the help of viscoelastic abrasive medium, while keeping in mind its low finish and material removal rates (MRR). Researchers have often strived to improve finishing rate and MRR. As an attempt to overcome the said limitations, this paper discusses rotational abrasive flow finishing (R-AFF) process wherein complete tooling is externally rotated and the medium reciprocates with the help of hydraulic actuators. In this study, preliminary experiments are conducted on Al alloy and Al alloy/SiC metal matrix composites (MMCs) at different extrusion pressures, and medium compositions are employed for finding optimum conditions of the same for higher change in roughness (ΔRa). The same optimum conditions are used to study the effect of workpiece rotational speed on (ΔRa), material removal (MR), change in workpiece hardness and surface topology. It is noted that as the workpiece rotational speed increases from 2 to 10 RPM, the experimental helix angle decreases from 22° to 9° and the helical path length increases from 67 to 160 mm. Based on these findings the mechanism of material removal of matrix and reinforcement in MMC using R-AFF have been proposed. Here the matrix material is removed by micro-cutting and three methods of material removal mechanisms for reinforcement are also explained. The scientific logic behind finishing mechanism of matrix and reinforcement, cross hatch patterns, helical path directions, micro-scratch (μ-scratch) width and depth variation with size, orientation and support that active abrasive grain obtains from neighboring abrasives is derived from scanning electron microscopy micrographs. Finally this study establishes that R-AFF can produce 44% better ΔRa and 81.8% more MR compared to the AFF process. Accordingly, R-AFF generates micro cross hatch pattern on the finished surface that can improve lubricant holding capabilities.

An Investigation into Microstructures and Mechanical Properties of AA7075-T6 during Friction Stir Welding at Relatively High Rotational Speeds

Abstract: In this study, microstructural changes and mechanical properties during friction stir welding of AA7075-T6 have been investigated. Friction stir welding at relatively high rotational speeds ranging from 1000 to 1400 rpm and longitudinal speeds in the range of 40 to 80 mm/min have been performed and then microstructures and mechanical properties of the weldments have been studied. The results show that the rotational and longitudinal speeds have a significant effect on the microstructures as well as the mechanical behavior of the welded material while a fine grain structure is produced at higher ratio of rotational speed to longitudinal speed. On the other hand, for a given longitudinal speed, it is revealed that there is an optimum rotational speed which gives the highest tensile strength and elongation for the stirred zone.

Improving the Aerodynamic Performance of Micro-Air-Vehicle-Scale Cycloidal Rotor: An Experimental Approach

Abstract: Performance and flowfield measurements were conducted on a small-scale cyclorotor for application to a micro air vehicle. Detailed parametric studies were conducted to determine the effects of the number of blades, rotational speed, and blade pitching amplitude. The results showed that power loading and rotor efficiency increased when using more blades; this observation was found over a wide range of blade pitching amplitudes. The results also showed that operating the cyclorotor at higher pitching amplitudes resulted in improved performance, independently of the number of blades. A momentum balance performed using the flowfield measurements helped to quantify the vertical and sideward forces produced by the cyclorotor; these results correlated well with the force measurements made using load balance. Increasing the number of blades increased the inclination of the resultant thrust vector with respect to the vertical because of the increasing contribution of the sideward force. The profile drag coefficient of the blade sections computed using a momentum deficit approach correlated well with typical values at these low chord Reynolds numbers. Particle image velocimetry measurements made inside the cage of the cyclorotor showed that there are rotational flows that, when combined with the influence of the upper wake on the lower half of the rotor, explain the relatively low efficiency of the cyclorotor.

System for cranking internal combustion engine by engagement of pinion with ring gear

Abstract: In a system for driving a starter with a pinion so that the starter rotates a ring gear coupled to a crankshaft of an internal combustion engine to crank the internal combustion engine during a drop of a rotational speed of the crankshaft by automatic-stop control of the internal combustion engine, a predictor predicts a future trajectory of the drop of the rotational speed of the crankshaft based on information associated with the drop of the rotational speed of the crankshaft. A determiner determines a timing of the driving of the starter based on the future trajectory of the drop of the rotational speed of the internal combustion engine.

Peak temperatures during friction stir welding of Ti–6Al–4V

Abstract: Experimental measurements were made to determine the peak temperatures during friction stir welding of Ti–6Al–4V alloy as a function of the processing conditions such as tool rotation speed and feedrate It was found that the spindle speed has a dominant effect on peak temperatures, while feedrate controls exposure time Low spindle speed conditions lead to peak temperatures near, or below, the beta transus temperature of the material, 1000°C (1800°F), while high spindle speed welds result in peak temperatures above 1200°C (2100°F) Weld microstructures were also evaluated as a function of the weld parameters Higher spindle speeds and lower federate lead to increased grain size

A Miniature 500 000-r/min Electrically Driven Turbocompressor

Abstract: The trend in compressors for fuel cells, heat pumps, aerospace, and automotive heating, ventilation, and air-conditioning systems is toward ultracompact size and high efficiency. This can be achieved by using turbocompressors instead of scroll, lobe, or screw compressors, increasing the rotational speed and employing new electrical drive system technology and materials. This paper presents a miniature electrically driven two-stage turbocompressor system running at a rated speed of 500 000 r/min. The design includes the thermodynamic analysis, the electric motor, the inverter, the control, and the system integration with rotor dynamics and thermal considerations. Experimental measurements such as the compressor map are presented for air under laboratory conditions. The two-stage turbocompressor has been tested up to a speed of 600 000 r/min, where a maximal pressure ratio of 2.3 at a mass flow of 0.5 g/s has been reached. To the authors' knowledge, this is the highest rotational speed achieved with an electrically driven turbocompressor.

An experimental investigation on friction stir welding of AZ31B magnesium alloy

Abstract: The conventional fusion welding of magnesium alloys often produces porosity in the weld joint, which deteriorates its mechanical properties. To solve this problem, friction stir welding (FSW), a solid-state welding technique, can be applied for joining of magnesium alloys. In this investigation, an attempt was made to understand the effect of FSW process parameters such as tool rotational speed, welding speed, and axial force on tensile properties of AZ31B magnesium alloy. Fourteen joints were fabricated using different levels of tool rotational speed, welding speed, and axial force. Tensile properties of the welded joints were evaluated and correlated with the weld zone microstructure and hardness. From this investigation, it is found that the joints fabricated using a tool rotational speed of 1,600 rpm, a welding speed of 0.67 mm/s, and an axial force of 3 kN yielded superior tensile properties compared to other joints. Optimum level of heat generation, formation of finer grains, and higher hardness are the main reasons for the superior tensile properties of these joints. Fatigue properties of FSW joints were evaluated, and it was found that fatigue properties of FSW joints were slightly lower than the base metal.

Force transmission device in particular for power transmission between a drive engine and an output

Abstract: A force transmission device, in particular or power transmission between a drive engine and an output, comprising a damper assembly with at least two dampers, which can be connected in series, and a rotational speed adaptive absorber, wherein the rotational speed adaptive tuned mass damper is disposed between the dampers at least in one force flow direction through the force transmission device.

Rotary impact tool

Abstract: A rotary impact tool includes: a hammer rotating by receiving a rotational force of a motor; an anvil rotating by receiving a rotational force of the hammer; and an end tool attached to the anvil, the rotary impact tool being constructed such that when a torque of a value not less than a predetermined value is applied to the anvil from the outside, the hammer is disengaged from the anvil to rotate idle and applies an impact to the anvil in a rotational direction after rotating idle by a predetermined angle, the rotary impact tool including an impact detector configured to detect impacts and a speed switching device configured to switch the rotational speed of the motor, and when the impact detector detects an impact during rotation of the anvil in a tightening direction, the speed switching device switches the rotational speed of the motor from a normal speed to a low speed.

Cutting process of composite materials: An experimental study

Abstract: This paper focuses on experimental research of milling process of the epoxide-polymer matrix composite reinforced carbon fibers (EPMC—carbon composite). An influence of two control parameters, namely feed and rotational speed, on cutting forces is investigated. The experiment is conducted on a CNC machine with feed rate ranging from 200 to 720 mm/min and rotational speed from 2000 to 8000 rpm. The experimental time series are analysed by means of the delay coordinates method in order to find stable cutting regions and to recognize the kind of behaviour. Using this information, a new model for the cutting forces is proposed that can be used to build a new regenerative vibration model for EPMC milling.

Control apparatus for vehicle

Abstract: A control apparatus for a vehicle is provided for a vehicle that has a normal mode and a power mode as vehicle driving characteristics. The control apparatus includes a continuously variable transmission mechanism that steplessly changes a speed ratio when rotational driving force of an engine output shaft is transmitted to a rotating output shaft; and a control portion that controls the continuously variable transmission mechanism such that, when a rotation speed is increased to a target rotation speed and a required output of an internal combustion engine when the power mode is selected is the same as when the normal mode is selected, the rate of increase in the rotation speed is greater when the power mode is selected than when the normal mode is selected.

Optimisation of process parameters in friction stir welding based on residual stress analysis: a feasibility study

Abstract: The present paper considers the optimisation of process parameters in friction stir welding (FSW). More specifically, the choices of rotational speed and traverse welding speed have been investigated using genetic algorithms. The welding process is simulated in a transient, two-dimensional sequentially coupled thermomechanical model in ANSYS. This model is then used in an optimisation case where the two objectives are the minimisation of the peak residual stresses and the maximisation of the welding speed. The results indicate that the objectives for the considered case are conflicting, and this is presented as a Pareto optimal front. Moreover, a higher welding speed for a fixed rotational speed results, in general, in slightly higher stress levels in the tension zone, whereas a higher rotational speed for a fixed welding speed yields somewhat lower peak residual stress, however, a wider tension zone, leading to a substantially higher residual tensile force.

Rotational angle-measurement apparatus and rotational speed-measurement apparatus

Abstract: A rotational angle-measurement apparatus with high accuracy is provided through electric correction of the rotational angle-measurement apparatus by rotating the rotation shaft at a constant speed. The rotational angle-measurement apparatus includes an electric motor having a rotation shaft, a magnet mounted on one end of the rotation shaft, and a magnetic sensor with an output signal that changes in accordance with an orientation of a magnetic field surrounding the magnetic sensor. The magnetic sensor outputs an angle signal representing the rotational angle of the rotation shaft, and the correction procedure utilizes rotation of the electric motor shaft through more than one revolution at a rotational speed with a known rate of change.

Force transmission device with a rotational speed adaptive damper and method for improving the damping properties

Abstract: The invention relates to a force transmission device for power transmission between an input and an output, comprising at least an input and an output, and a vibration damping device disposed in a cavity that can be filled at least partially with an operating medium, in particular oil, the vibration damping device coupled with a rotational speed adaptive absorber, wherein the rotational speed adaptive absorber is tuned as a function of an oil influence to an effective order qeff, which is greater by an order shift value qF than an order q of an exciting vibration of a drive system.

A centrifugal separator

Abstract: The present invention relates to a centrifugal separator for separating solid particles from a liquid mixture, said centrifugal separator comprising a rotor body (1) which is rotatable around an axis of rotation(R), the rotor body (1) having a separation chamber(16)with an inlet (13, 15) for the liquid mixture, at least one liquid outlet (25, 26, 31, 32) for a separated liquid from the liquid mixture, a sludge outlet(34)for the separated solid particles,a screw conveyor (2) adapted to rotate in the rotor body (1) around the axis of rotation (R), at a speed differing from the rotational speed of the rotor body (1), for transporting the separated solid particles in the separation chamber(16)towards and out of the sludge outlet(34), a drive arrangement (3, 3a, 3b, 3c) adapted to rotate the rotor body (1) and the screw conveyor (2) at their respective speeds, and a control unit (44) which is adapted to control the drive arrangement (3, 3a, 3b, 3c) to rotate the rotor body (1)at a first speed during a separation phase and at a second speed, which is lower than the first speed, during a particle discharge phase.