The objective of this article is the description of advantages of a slanted die geometry, used for equal channel angular extrusion (ECAE) of materials. The prime novelty statement of the present ...research is an experimental flow pattern, obtained with circular gridlines and a numerical solution of a viscous flow 2D problem for the slanted die, derived with Navier–Stokes equations in curl transfer form. The geometry of the slanted die was chosen for the case of a rectangular die with channel intersection angle 2
θ =
90° and with parallel slants in the channel intersection zone, where the slant width is equal to the inlet and outlet channel widths. Computational material flow kinematics, macroscopic rotation patterns, material flow velocity fields, tangential stresses, and punching pressure fields during viscous materials ECAE have been derived with a numerical finite-difference solution of the curl transfer equation for 2D viscous flow of incompressible continuum during ECAE. Theoretical results have been verified with physical simulation experiments by the introduction of initial circular gridlines. Both theoretical and computational results confirm the suitability and technological advantages of dies with parallel slants over the known Segal and Iwahashi dies for ECAE, as slanted convergent dies enable the reduction of the dead zone size and provide the minimization of dangerous macroscopic rotation during ECAE processing of both metal and polymer materials.
The present article is focused on a 2D computational fluid mechanics study of local viscous flow dynamics and the formation character of rotary modes of deformation during Equal Channel Multiple ...Angular Extrusion (ECMAE) of a polymer workpiece fluid model through a U-shaped die with parallel slants in channel intersection zones. The present local flow problem was experimentally analyzed using physical simulation methods and theoretically studied with numerical fluid mechanics techniques. The computational approach has been grounded on the numerical finite difference solution of the boundary value problem for the Navier-Stokes equations in the curl transfer form for the local viscous flow of incompressible Newtonian fluid through a U-shaped rectangular die with parallel slants. The derived research results allow us to draw a conclusion that the implementation of a geometric design of parallel slants within a 2-turn U-shaped die results in localization of the maximum tangential stresses within the workpiece volume to the vicinity of these parallel slants during ECMAE.
Better student understanding of the dynamic trends in graduate employment requires the development of the author's description of this multidisciplinary social problem.
This educational paper is ...focused on an author-proposed engineering-friendly description of oscillatory dynamics in the employment market for university graduates.
This didactical paper widely uses computational methods of oscillations theory, theory of electrical and hydraulic circuits as well as concepts of physical analogies and similarity.
The generalized character of the employment-related oscillations in the studied social system of employees was didactically enhanced through the original introduction of two technical analogies with similar oscillations in the electrical system of an LC-field-effect transistor oscillator and the mechanical system of a hydraulic ram pump.
The author-proposed triple physics-and-engineering analogy for the periodic oscillations in the socio-economic problem in graduate employment provides a broadening of the cross-disciplinary ideas of engineering students about oscillatory dynamics in the social, electrical and hydraulics systems. It was found in the case of the Donbass State Engineering Academy (Kramatorsk, Ukraine), that this original author's approach provides simultaneous enhancement of the cross-disciplinary undergraduate engineering curriculum in the courses of economics, management, higher education pedagogy, physics, hydraulics and electrical engineering.
The present work is focused on a 2D fluid dynamics description of equal channel multiple angular extrusion (ECMAE) or equal channel multiple angular pressing (ECMAP), using a numerical mathematical ...simulation for viscous flows of physical polymeric materials models through a die with a movable inlet wall. A numerical finite-difference model for plane viscous Newtonian flow of an incompressible continuous medium in a multiple-angle region with a movable inlet die wall, based on the formulation and numerical solution of the boundary value problem for the Navier-Stokes equations in curl transfer form, is derived. A numerical estimation of the influence of the direction of movement of a movable entrance die wall on computational flow lines, stream and curl functions, and viscous flow velocity fields was carried out within the scope of the developed model for a movable inlet wall of the die. The proposed hydrodynamic approach extends the ideas concerning the dynamics of the macroscopic rotation formation within the volume of the viscous physical model of a polymeric material during ECMAE or ECMAP through a die with a movable inlet wall.
The present article addresses strain unevenness effects during equal channel angular extrusion (ECAE) of physical models of polymer workpieces with viscosity flow features through a Segal die with ...channel intersection angle of 2θ = 90°. Computational viscous flow lines, flow velocity fields, and material dead zone formation in the physical simulation of ECAE have been numerically derived for planar flow of viscous incompressible continua in an angular die with 2θ = 90°. This is accomplished through the introduction of Navier-Stokes equations with the following dimensionless physical variables: polymer model local flow velocities u, v and punching pressure p. Derived experimental results are grounded on the application of the following physical simulation techniques: marker method, based on harder disperse particles partially forcing into the front faces of soft workpieces; layered model production by assembling the workpiece soft model with different layers, and circular gridlines use with viscous flow of the polymer soft model. Good agreement has been found between the computational and observable physical simulation results. Based on the obtained results, recommendations are made for polymer ECAE technology enhancement and angular die design for polymer workpiece pressure forming.
It is a common practice in pressure forming to make an Equal Channel Angular Extrusion (ECAE) of a workpiece through a die with channel intersection angle 2θ = 90° using a standard punch of brick or ...cylindrical shape with 2θ0 = 90°. However Nejadseyfi et al (2015) have applied a beveled 2θ0-punch to the process of ECAE through a standard angular die of Segal geometry with 2θ = 90° and 2θ0 ≠ 2θ. The scope of the article is focused on an alternative numerical study of Nejadseyfi-ECAE-Scheme using techniques of Computational Fluid Dynamics (CFD). A finite-difference method was applied to the numerical solution of the boundary value problem for the Navier-Stokes equations in the form of a vorticity transfer equation. The complex of 2D plots for CFD-derived fields of flow lines and flow velocities and 3D plots for spatial distributions of flow velocities and tangential stresses were firstly derived for Nejadseyfi-ECAE-Scheme during viscous flow of polymer workpiece models through angular die with 2θ = 90° for the different punch inclination angles 30° ≤ 2θ0 ≤ 150°. It was found that Nejadseyfi-ECAE-Scheme provides enhancement of the rotary modes of intensive deformations during ECAE. Results provide visualization of velocity gradients and macroscopic rotation and the illustration of Nejadseyfi et al’s ideas from an alternative CFD-based viewpoint.
The present article is focused on a phenomenological description of a polymer workpiece Equal Channel Angular Extrusion (ECAE) through 2θ-dies of Segal and Iwahashi geometries with a channel ...intersection angle 2θ = 105° with fixed and movable external inlet and outlet die walls. The local flow dynamics, including the formation of macroscopic rotation and a dead zone appearance during the flow of plasticine, paraffin, and wax workpiece models through the subject die configuration was studied using physical simulation techniques. The present article utilizes a Computational Fluid Dynamics (CFD) numerical approach to a theoretical description of 2D viscous flow of incompressible Newtonian continuum through the stated die geometries. The boundary value problem for the Navier-Stokes equations in the curl transfer form for the local viscous flow was formulated and numerically solved with a finite-difference method. Theoretical CFD-derived plots with computational flow lines, dimensionless flow and curl functions, flow velocities, and tangential stresses for viscous material flow through the stated die geometries have been generated and described. As a first rheological approximation the derived computational results provide the theoretical description of physical simulation experiments and visualize the formation of ECAE-induced rotational modes of large deformations like macroscopic rotation and rotational inhomogeneity.
Equal channel angular extrusion of soft solids Perig, Alexander V.; Laptev, Alexander M.; Golodenko, Nikolai N. ...
Materials science & engineering. A, Structural materials : properties, microstructure and processing,
06/2010, Volume:
527, Issue:
16
Journal Article
Peer reviewed
The influence of rheological properties of processed materials on deformation heterogeneity has been studied for the viscous flow of plasticine during equal channel angular extrusion (ECAE) through a ...rectangular die 2
θ
=
90° without any external rounding
φ
=
0°. To perform the physical simulation of ECAE a hydraulic workbench and a plexiglass split die were fabricated. Application of an experimental circular grid technique for planar flow of plasticine billets allows us to investigate the formation of turbulence elements and a material dead zone. Theoretical material flow patterns, the characteristics of deformation non-uniformity, flow lines, the flow velocity fields, energy-power parameters and dead zone formation in the physical simulation of the ECAE in a rectangular die have been determined with a numerical finite-difference solution of the Navier–Stokes equation in the curl transfer form for the planar flow of viscous incompressible continua. Good agreement between theoretical and averaged experimental results was found. The legitimacy of an existing analogy between viscous liquid flow and polycrystalline plastic flow during ECAE has also been analyzed. This proposed technique may be useful when applied to the analysis of polymer flow with severe plastic deformation.
The continuing development of new deformation schemes for material pressure forming resulted in the appearance of new technological process of Expansion Equal Channel Angular Extrusion (Exp-ECAE), ...which was proposed by Sepahi-Boroujeni and Fereshteh-Saniee in 2015. The present original research is a novel approach to an alternative hydrodynamic study of the Exp-ECAE deformation scheme with wide use of the numerical techniques of computational fluid dynamics (CFD). Additional mechanical degrees of freedom (DOFs) for Exp-ECAE die tooling equipment were first introduced by accounting for the dynamic effects of independent translational motion of the external movable walls of an Exp-ECAE angular domain. The proposed novel paper provides the possibility for original engineering-friendly visualisation of dead zone formation in the process of Exp-ECAE pressure forming. Multiple results of CFD-based numerical modelling show new promising ways for engineering minimisation of dead zone areas through alternative triggering of different DOFs of Exp-ECAE die tooling resulting in independent transport motion of the external walls of an Exp-ECAE angular domain.
Abbreviation: SPD is Severe Plastic Deformation; ECAE is Equal Channel Angular Extrusion; Exp-ECAE is Expansion Equal Channel Angular Extrusion; CFD is computational fluid dynamics; DOF is degree of freedom.
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