Topic
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.
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Abstract: The 7020-T6 aluminum alloy plates of 4 mm thickness were friction stir welded at rotational speeds of 400, 600, 800, and 1000 rpm and constant traverse speed of 100 mm/min. The peak temperatures of the joints were recorded by precise thermocouples. Microstructure, hardness, tensile properties, and fracture surfaces of the joints were analyzed. The results showed that decreasing the tool rotational speed from 1000 to 400 rpm decreased the peak temperature from 311 to 209 °C, and hence caused a lower heat input. In addition, lower rotational speeds result in higher hardness and tensile strengths. The higher hardness and ultimate tensile strength were related to the grain boundary, precipitation, and substructure strengthening mechanisms. In addition, the fracture surfaces of the joints welded at higher heat input conditions showed more ductile mode in comparison with that of welded at lower heat input condition, which confirmed the lower tensile elongation of the joints welded at lower rotational speeds.
55 citations
TL;DR: In this paper, a digital recording device was used to capture images of the transverse plane of the material bed and analyses of the images were carried out to extract the bed behaviour as a function of rotational speed, drum fill level and particle size.
Abstract: Rotating drums are extensively used in the chemical and process industries as mixers, dryers, granulators and reactors for processing granular materials. As a result, granular behaviour in rotating drums has attracted numerous research efforts from both engineering and physics communities over the past few decades. Most of these studies have been focused on drums operated in or close to the rolling mode. However, there are many industrial cases where drums are operated in other modes, e.g. the cascading and cataracting modes, which forms the main motivation for this work. Comprehensive experiments have been carried out to investigate granular behaviour in a drum operated over a wide range of rotational speed with solids motion across the rolling, cascading and cataracting modes. A digital recording device was used to capture images of the transverse plane of the material bed. Analyses of the images were carried out to extract the bed behaviour as a function of rotational speed, drum fill level and particle size. This has led to three relationships between the surface shape expressed in terms of three characteristic lengths, operating conditions, as well as the friction properties of both particles and drum wall. These relations are found to apply approximately to the whole range of rotational speed used in this work. The generality of these relationships and possible application of them for drum scaling are discussed.
55 citations
TL;DR: In this article, the sensitivity analysis of hydraulic transient for two parallel pump-turbine units operating at runaway (unstable S-shaped zone of pump-turbine hill-chart) has been numerically investigated.
55 citations
TL;DR: Based on the average flow model proposed by Patir and Cheng and the Ng-Pan turbulence model, a generalized average Reynolds equation is derived in this paper, where turbulence remarkably increases friction coefficient, slightly increases the minimum nominal film thickness, and decreases the transition speed from mixed-lubrication regime to hydrodynamic lubrication regime.
55 citations
TL;DR: In this article, the authors describe aerodynamically excited supercritical disk vibration observed in experiments and show that at pre-flutter speeds, the fluid acts as a random excitation source, but at higher speeds the fluid and the disk are strongly coupled.
55 citations