The Experts below are selected from a list of 3588 Experts worldwide ranked by ideXlab platform
Jean-marc Lefebvre - One of the best experts on this subject based on the ideXlab platform.
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Deformation behaviour and mechanical properties of polypropylene processed by equal channel angular Extrusion: Effects of back-pressure and Extrusion Velocity
Polymer, 2009Co-Authors: R. Boulahia, Jean-michel Gloaguen, Fahmi Zaïri, Moussa Nait-abdelaziz, Roland Seguela, T. Boukharouba, Jean-marc LefebvreAbstract:Severe plastic deformation by equal channel angular Extrusion (ECAE) is an ingenious deformation process used to modify texture and microstructure without reducing sample cross-section. The application of single ECAE pass to polypropylene (PP) was meticulously investigated at room temperature using a 90° die-angle tooling. The ECAE-induced deformation behaviour was examined in relation to the load versus ram-displacement curves. Depending on Extrusion conditions, PP displayed various types of plastic flow. For ram velocities beyond 4.5 mm/min, severe shear bands consisting of successive translucent and opaque bands were observed, accompanied on the top surface by more or less pronounced periodic waves. Although the application of a back-pressure significantly reduced the wave and shear-banding phenomena, slightly inhomogeneous shear deformation was still observed. Shear bands were only suppressed by decreasing Extrusion Velocity. The strain-induced crystalline microstructure was investigated by X-ray scattering. Shear-banded samples exhibited a strong texturing of the (hk0) planes along the shear direction in the translucent bands whereas perfect crystalline isotropy appeared in the opaque bands. Application of back-pressure and/or reducing ram Velocity resulted in uniform texturing along the extruded sample. Yet, texturing changed from single shear to twin-like shear orientation about the shear direction. Mechanical properties changes of the extruded samples due to back-pressure and Extrusion Velocity effects were analyzed via uniaxial tensile tests. The tensile samples displayed multiple strain localizations in shear-banded materials whereas quite homogeneous deformation appeared for non-banded ones. These effects were connected with the crystalline texturing. The results also revealed significant increase in the strain hardening after ECAE. Digital image correlation technique suitable for large deformation was used for determining the full-field strain of the tensile samples in relation to tensile strain and ECAE conditions.
Tsuyoshi Furushima - One of the best experts on this subject based on the ideXlab platform.
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production process of biocompatible magnesium alloy tubes using Extrusion and dieless drawing processes
Journal of Materials Engineering and Performance, 2016Co-Authors: Piotr Kustra, Andrij Milenin, Bartlomiej Plonka, Tsuyoshi FurushimaAbstract:Development of technological production process of biocompatible magnesium tubes for medical applications is the subject of the present paper. The technology consists of two stages—Extrusion and dieless drawing process, respectively. Mg alloys for medical applications such as MgCa0.8 are characterized by low technological plasticity during deformation that is why optimization of production parameters is necessary to obtain good quality product. Thus, authors developed yield stress and ductility model for the investigated Mg alloy and then used the numerical simulations to evaluate proper manufacturing conditions. Grid Extrusion3d software developed by authors was used to determine optimum process parameters for Extrusion—billet temperature 400 °C and Extrusion Velocity 1 mm/s. Based on those parameters the tube with external diameter 5 mm without defects was manufactured. Then, commercial Abaqus software was used for modeling dieless drawing. It was shown that the reduction in the area of 60% can be realized for MgCa0.8 magnesium alloy. Tubes with the final diameter of 3 mm were selected as a case study, to present capabilities of proposed processes.
John Bridgwater - One of the best experts on this subject based on the ideXlab platform.
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surface fracture in axisymmetric paste Extrusion an experimental study
Chemical Engineering Research & Design, 2000Co-Authors: Annette T J Domanti, John BridgwaterAbstract:In the Extrusion of pastes, fractures can be found on the surface of product. Such fractures compromise strength and are often unacceptable aesthetically. Here, experiments show that increasing the length of the die has a beneficial effect on surface quality in all pastes examined. The materials were α-alumina pastes allied to those used for making catalyst that could additionally contain Bentonite clay and carbohydrates. Defects can be completely eliminated for a-alumina pastes with starch additives. Increasing Extrusion Velocity increases the depth of fracture in pastes with glucose additives. Reduced frequency and depth of fracturing is found when using tapered dies. All the materials show a decrease in the depth of fracture with increasing Extrusion ratio, i.e. the ratio of barrel to die diameter. For a sample paste, the product of the frequency of fracture and diameter of the Extrusion die yields a dimensionless quantity independent of Extrusion Velocity and Extrusion ratio, having a value of two.
Herbert Sixta - One of the best experts on this subject based on the ideXlab platform.
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Dry jet-wet spinning of strong cellulose filaments from ionic liquid solution
Cellulose, 2014Co-Authors: Lauri K. J. Hauru, Michael Hummel, Anne Michud, Herbert SixtaAbstract:Considerable growth is expected in the production of man-made cellulose textile fibers, which are commercially produced either via derivatization to form cellulose xanthate (viscose) or via direct dissolution in N -methylmorpholine N -oxide (Lyocell). In the study at hand, cellulosic fibers are spun from a solution in the ionic liquid [DBNH] [OAc] into water, resulting in properties equal or better than Lyocell (tensile strength 37 cN tex^−1 or 550 MPa). Spinning stability is explored, and the effects of Extrusion Velocity, draw ratio, spinneret aspect ratio and bath temperature on mechanical properties and orientation are discussed. With the given set-up, tenacities and moduli are improved with higher draw ratios, while elongation at break, the ratio of wet to dry strength, modulus of resilience and birefringence depend little on draw ratio or Extrusion Velocity, elastic limit not at all. We find the process robust and simple, with stretching to a draw ratio of 5 effecting most improvement, explained by the orientation of amorphous domains along the fiber axis.
R. Boulahia - One of the best experts on this subject based on the ideXlab platform.
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Deformation behaviour and mechanical properties of polypropylene processed by equal channel angular Extrusion: Effects of back-pressure and Extrusion Velocity
Polymer, 2009Co-Authors: R. Boulahia, Jean-michel Gloaguen, Fahmi Zaïri, Moussa Nait-abdelaziz, Roland Seguela, T. Boukharouba, Jean-marc LefebvreAbstract:Severe plastic deformation by equal channel angular Extrusion (ECAE) is an ingenious deformation process used to modify texture and microstructure without reducing sample cross-section. The application of single ECAE pass to polypropylene (PP) was meticulously investigated at room temperature using a 90° die-angle tooling. The ECAE-induced deformation behaviour was examined in relation to the load versus ram-displacement curves. Depending on Extrusion conditions, PP displayed various types of plastic flow. For ram velocities beyond 4.5 mm/min, severe shear bands consisting of successive translucent and opaque bands were observed, accompanied on the top surface by more or less pronounced periodic waves. Although the application of a back-pressure significantly reduced the wave and shear-banding phenomena, slightly inhomogeneous shear deformation was still observed. Shear bands were only suppressed by decreasing Extrusion Velocity. The strain-induced crystalline microstructure was investigated by X-ray scattering. Shear-banded samples exhibited a strong texturing of the (hk0) planes along the shear direction in the translucent bands whereas perfect crystalline isotropy appeared in the opaque bands. Application of back-pressure and/or reducing ram Velocity resulted in uniform texturing along the extruded sample. Yet, texturing changed from single shear to twin-like shear orientation about the shear direction. Mechanical properties changes of the extruded samples due to back-pressure and Extrusion Velocity effects were analyzed via uniaxial tensile tests. The tensile samples displayed multiple strain localizations in shear-banded materials whereas quite homogeneous deformation appeared for non-banded ones. These effects were connected with the crystalline texturing. The results also revealed significant increase in the strain hardening after ECAE. Digital image correlation technique suitable for large deformation was used for determining the full-field strain of the tensile samples in relation to tensile strain and ECAE conditions.
