Rotational speed

About: Rotational speed is a research topic. Over the lifetime, 23327 publications have been published within this topic receiving 151696 citations. The topic is also known as: speed of revolution & revolution rate.

Effects and defects of the polypropylene plate for different parameters in friction stir welding process

Abstract: Polypropylene is one of the thermoplastic materials used in the lot of engineering applications such as marine, aerospace, automotive, toys and etc. Friction Stir Welding (FSW) is a solid-state method of used for joining metals. FSW process was successfully extended to join thermoplastic materials. In this paper an attempt has been made to understand the mechanism of friction stir welding joints of polypropylene plates. In this study, the role of FSW tool pin profile, rotational speed and welding speed are analyzed with respective to the quality of the joints. This research outlines the method of welding and optimization of FSW process parameters for polypropylene material by Taguchi optimization methodology. Experiments were performed at rotational speed of 1500, 1750, 2000 and 2250 rpm, Welding speeds of 30, 40, 50 and 60 mm/min, and tool pin profiles of Triangular, square, Threaded and taper pin profiles. The experiments are conducted in CNC vertical machining centre with special fixture. Microstructural characteristics were evaluated by using optical microscopy and hardness are observed in weld joints. The micro structure and Rockwell hardness of the welded region was created by threaded pin profile with welding speed of 40 and 50 mm/min and rotational speed of 2250 and 1500 rpm act as right friction stir welding parameters to avoid defects in joining of polypropylene materials.

A stacked electromagnetic energy harvester with frequency up-conversion for swing motion

Abstract: This paper undertakes theoretical and experimental investigations of a stacked magnetic modulation harvester with frequency up-conversion for energy harvesting performance enhancement from swing motion. The harvester includes stacked rings including a coil ring, an energy harvesting magnetic ring, a ferromagnetic ring, and a frequency up-conversion magnetic ring with a proof mass, which are axially designed in the same rotating axis to increase the rotation speed of the magnetic field due to swing excitations from human motion. The magnetic flux density produced by frequency up-conversion mechanisms is calculated to derive the governing theoretical model for harvester performance prediction. The rotation speeds and inductive voltages of theoretical results show good agreement with the experimental results in a range of rotational speeds. A range of motion speed tests on a treadmill are performed to demonstrate the advantage of the stacked electromagnetic harvesters on harvested energy from human motion. The average output power improves from approximately 1.5 mW to 11.8 mW when motion speed increases from 4 km/h to 8 km/h. The maximum power density under human motion is 61.9 μW·g−1, with a total weight of 190.7 g.

Discrete Element Simulation of the Effect of Roller-Spreading Parameters on Powder-Bed Density in Additive Manufacturing.

Abstract: The powder-bed with uniform and high density that determined by the spreading process parameters is the key factor for fabricating high performance parts in Additive Manufacturing (AM) process. In this work, Discrete Element Method (DEM) was deployed in order to simulate Al2O3 ceramic powder roller-spreading. The effects of roller-spreading parameters include translational velocity Vs, roller's rotational speed ω, roller's diameter D, and powder layer thickness H on powder-bed density were analyzed. The results show that the increased translational velocity of roller leads to poor powder-bed density. However, the larger roller's diameter will improve powder-bed density. Moreover, the roller's rotational speed has little effect on powder-bed density. Layer thickness is the most significant influencing factor on powder-bed density. When layer thickness is 50 μm, most of particles are pushed out of the build platform forming a lot of voids. However, when the layer thickness is greater than 150 μm, the powder-bed becomes more uniform and denser. This work can provide a reliable basis for roller-spreading parameters optimization.

Analysis of Surface Pressure Pulsation Characteristics of Centrifugal Pump Magnetic Liquid Sealing Film

Abstract: In order to discuss the surface pressure pulsation characteristics of the magnetic-fluid sealing membrane of centrifugal pump, this paper studies the surface pressure pulsation characteristics of the shaft end sealing membrane under different flow operating conditions of centrifugal pump based on the combination of numerical calculation and experimental verification. The results show that the pressure value on the surface of the magnetic-fluid sealing film decreases with the increase of the flow rate of the centrifugal pump, and the pressure on the surface of the magnetic-fluid sealing film has periodic pulsation, and the period is the time required for a single blade to sweep the volute separating tongue. In one rotation cycle of the runner, the number of reciprocating movements of the magnetic-hydraulic sealing film is the same as the number of blades of the runner. The main reason for the pressure pulsation is that the impeller periodically sweeps the fixed surface of the centrifugal pump.

Dual input drive AGB for gas turbine engines

Abstract: A mechanical drive system of an aircraft gas turbine engine includes a tower shaft operatively connected to first and second shafts in an accessory drive gearbox. The first shaft rotates at a rotational speed lower than the rotational speed of the tower shaft and the second shaft rotates at a rotational speed equal to or higher than the rotational speed of the tower shaft.