Search results for "Friction."
showing 10 items of 350 documents
Incremental forming of friction stir welded taylored sheets
2006
In the last decade sheet metal forming market has undergone substantial mutations since the development of more efficient strategies in terms of flexibility and cost reduction is strictly due. Such requirements are not consistent with traditional metal stamping processes which are characterized by complex equipment, capital and tooling costs; thus the industrial application of such processes is economically convenient just for large scale productions. For this reason most of the research work developed in the last years has been focused on the development of new sheet forming processes able to achieve the above discussed goals. Contemporary, with particular reference to the automotive indus…
Control of hysteretic instability in rotating machinery by elastic suspension systems subject to dry and viscous friction
2010
Abstract Most of the undesired whirling motions of rotating machines can be efficiently reduced by supporting journal boxes elastically and controlling their movement by viscous dampers or by dry friction surfaces normal to the shaft axis, which rub against the frame. In the case of dry dampers, resonance ranges of the floating support configuration can be easily cut off by planning a motionless adhesive state of the friction surfaces. On the contrary, the dry friction contact must change automatically into sliding conditions when the fixed support resonances are to be feared. Moreover, the whirl amplitude can be restrained throughout the speed range by a proper choice of the suspension-to-…
Comments on “Measurement of dimensionless Chezy coefficient in step-pool reach (Case study of Dizin River in Iran)” by Torabizadeh A., Tahershamsi A.…
2018
This paper is a comment on a previous published paper.
Flow Resistance in Step-Pool Rills
2017
Rills evolve morphologically, and the adjustment of rill channel geometry to flow affects the relationships among velocity, discharge, and slope. The resistance to flow in step-pool rills is mainly due to form-induced mechanisms and, in comparison, grain resistance is of minor significance. Previous studies on rill flow resistance have been performed exclusively for grainresistance conditions and use a stream flow equation. In this study, a new flow resistance equation, deduced by applying dimensional analysis and self-similarity theory, was applied to rill flow in step-pool channels. First, the incomplete self-similarity hypothesis was used for establishing a power flow velocity profile wh…
Rill flow resistance law under sediment transport
2021
Abstract Purpose In this paper, a deduced flow resistance equation for open-channel flow was tested using measurements carried out in mobile bed rills with sediment-laden flows and fixed bed rills. The main aims were to (i) assess the effect of sediment transport on rill flow resistance, and (ii) test the slope-flow velocity relationship in fixed bed rills. Methods The following analysis was developed: (i) a relationship between the Γ function of the velocity profile, the rill slope and the Froude number was calibrated using measurements carried out on fixed bed rills; (ii) the component of Darcy-Weisbach friction factor due to sediment transport was deduced using the corresponding measurem…
Flow Resistance Law in Channels with Flexible Submerged Vegetation
2005
In this paper, experimental data collected in a straight flume having a bed covered by grasslike vegetation have been used to analyze flow resistance for flexible submerged elements. At first, the measurements are used to test the applicability of Kouwen’s method. Then, a calibration of two coefficients appearing in the semilogarithmic flow resistance equation is carried out. Finally, applying the P-theorem and the incomplete self-similarity condition, a flow resistance equation linking the friction factor with the shear Reynolds number, the depth-vegetation height ratio and the inflection degree is deduced.
Analysis of microsphere oblique impact with planar surfaces based on the independent friction-restitution approach
2020
The independent friction restitution closure (IFR) previously applied to describe planar oblique impact of a homogeneous sphere on an infinitely massive rough plane is applied here to microsphere collisions and is extended to describe horizontal launch experiments. The model provides analytical solutions of the motion equations based on a unique set of values of the coefficients of normal and tangential restitution and friction. Comparison with experimental data in literature for the impact of microspheres of diameter <100 mu m yields a satisfactory agreement between experimentation and theory.
Physics of agarose fluid gels: Rheological properties and microstructure
2021
Agarose, a strongly gelling polysaccharide, is a common ingredient used to optimize the viscoelastic properties of a multitude of food products. Through aggregation of double helices via hydrogen bonds while cooling under quiescent conditions it forms firm and brittle gels. However, this behavior can be altered by manipulating the processing conditions viz shear. For example, gelation under shear leads to microgel particles with large surface area, which in turn leads to completely different rheological properties and texture. Such fluid gels are shown to play an important role in texture modification of foods and beverages for dysphagia patients. In this study, different concentration of a…
Friction Stir Welding Of AA6082-T6 Sheets: Numerical Analysis And Experimental Tests
2004
3D numerical simulation of the Friction Stir Welding process is developed with the aim to highlight the process mechanics in terms of metal flux and temperature, strain and strain rate distributions. The numerical results have been validated though a set of experimental tests.
Hard-wall interactions in soft matter systems: Exact numerical treatment
2011
An algorithm for handling hard-wall interactions in simulations of driven diffusive particle motion is proposed. It exploits an exact expression for the one-dimensional transition probability in the presence of a hard (reflecting) wall and therefore is numerically exact in the sense that it does not introduce any additional approximation beyond the usual discretization procedures. Studying two standard situations from soft matter systems, its performance is compared to the heuristic approaches used in the literature.