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Abstract The objectives of this research are to characterize the effects of hydration on the elasticity and fracture properties of electrospun polyacrylonitrile (PAN) and PAN/halloysite meshes and to use the information for design analysis for water filtration application. Electron micrographs of these meshes revealed pore diameters ranging 1–7 μm. Direct measurement of the mesh stiffness and strength in water revealed that PAN/halloysite meshes were stiffer and stronger than PAN meshes. Solution diffusion model predicted that PAN/halloysite mesh can support a water flux of 2.4 times higher than PAN mesh without breaking during desalination. However, wet meshes were weaker and less stiff than dry meshes. This was attributed to a reduced effectiveness for stress transfer between fibres, caused by the presence of water in (and swelling of) the inter-fibre space, as reflected by a reduction in the volume fraction of the respective PAN and halloysite components. Highlights • Micromechanical tests showed wet meshes were weaker and less stiff than dry meshes. • PAN/HNT meshes were stiffer and stronger than PAN meshes. • Water in inter-fibre space reduced effectiveness for stress transfer between fibres. • Solution diffusion model predicted HNT reinforced mesh supports higher water flux. [ABSTRACT FROM AUTHOR]

Spread extrusion could be used for manufacturing of wide profiles in the extrusion industry. In this paper a new method of design and analysis has been presented for such a problem. Special dies were designed for profiled sections such as square, rectangular, elliptical and cross shapes. These dies force the material to flow sideways and spread so as to extrude sections with wider dimensions than the initial billet or the maximum container diameter. The geometry of the deforming zone in the die was formulated and based upon that, a kinematically admissible velocity field was derived. Using this velocity, we estimated the field upper bound on extrusion power. Profile sections with different aspect ratios were investigated and the influence of other process parameters such as friction and reduction of area on the extrusion pressure were studied. Optimum die lengths for each die were calculated so as to minimize the extrusion pressure. Finite element analysis for the numerical simulation of the process was also carried out. The finite element results were also used as an aid to the design process of the extrusion dies. Dies were manufactured for different sections such as square, rectangle, and ellipse and cross shapes. Experiments were carried out to obtain data to verify the theory. Comparison of the results showed good agreement between the theoretical, numerical and experimental data. It was concluded the present method could be used to design dies for the spread extrusion of different shaped dies. [ABSTRACT FROM AUTHOR]

Abstract: A new analysis for the three-dimensional solution for the extrusion of sections with larger dimensions than the initial billet or container is presented in this paper. A generalized kinematically admissible velocity field was formulated using the upper bound theorem. The problem tackled in this paper is a practical one encountered in the extrusion industry where for the production of sections whose dimensions are larger than the container or billet diameter there exist some difficulties and sometime it is impossible to produce such products. The solution to this problem was suggested in a new design for the extrusion die which was done using the upper bound analysis. In this design unlike flat-faced dies the material has to flow over two kinds of surfaces namely converging and diverging surfaces, the combination of which causes the material flow in a smooth manner and with the correct speed so that the required final shape would be achieved. For such geometries kinematically admissible velocity fields were obtained. Using this new formulation, extrusion of shapes such as square and rectangle were analyzed. Influence of the process parameters such as friction, extrusion ratio and aspect ratio on the extrusion load was investigated and the optimum die length was obtained. Finite element analysis for the same problem was also carried out and the comparison of the results showed good agreement. The finite element simulation was especially used to assist the theoretical analysis with regards to the material flow and filling of the die cavity. Based on the analytical results, extrusion dies for the rectangular sections were designed and manufactured and experiments were carried out. The results of the tests showed that the dies performed very well and complete filling of the die cavity and a successful extruded profile was observed. [Copyright &y& Elsevier]