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RISS 인기검색어
- 검색키워드
- 저자 : S. M. Alhosseini (검색결과 2 건)
- 무료
- 기관 내 무료
- 유료
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Hollow Twist Extrusion: Introduction, Strain Distribution, and Process Parameters Investigation
J. Joudaki,M. Safari,S. M. Alhosseini 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.6
Twist Extrusion is kind of severe plastic deformation process which enhances the strength of materials by applying a shearplastic strain and consequently grain refinement. The strain distribution is minimum at the center of the die and is maximumat outer surfaces. In this article, the plastic strain distribution will be studied within a hollow section. The billet is solid inprevious experimental and numerical studies in the literature, but by adding a new die (mandrel) for extruding the hollowbillet, it is possible to twist extrude hollow sections. A finite element model is developed in the ABAQUS finite elementsoftware and the effects of process parameters (slope line angle, thickness and friction coefficient) on equivalent plastic straindistribution are investigated. The numerical results show that the equivalent plastic strain will be increased by increasingthe slope line angle and decreasing the thickness and more homogeneity in the strain field will be obtained. In addition,increasing the friction coefficient higher than 0.2 can lead to an increase in induced plastic strain. The required force fortwist extrusion will be increased by increasing the friction coefficient.
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New Die Design Configuration for Grain Refinement by Hollow Twist Extrusion (HTE) Process
J. Joudaki,M. Safari,S. M. Alhosseini 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.4
The severe plastic deformation (SPD) processes used for applying an extensive shear plastic strain in the material andconsequently grain refinement and increase in the strength of materials. The strain distribution is very important and morehomogenous plastic strain is desired in SPD process modifications. In this article, four different die configurations will beinvestigated during the hollow twist extrusion (HTE) process and the plastic strain distribution will be compared within ahollow section. The die configurations are similar slope line angle of inner and outer dies (SD), opposite slope line anglebetween the inner and outer dies (OD), outer die with twist zone and flat inner die (FI) and inner die with twist zone and flatouter die (FO). The Von-Mises stress, plastic strain, and material deformation are studied by using a finite element modelwhich was developed in the ABAQUS finite element software. The results show that the FI and FO die configuration producehigher plastic strains than SD die configuration, but the strain homogeneity is not satisfactory. The plastic strain is higherand more homogenous for OD die configuration in comparison to the other die configurations. The required force for twistextrusion of the billet is almost equal for FI and FO die configuration (~ 216 kN) and increases to about 256 kN for SD dieconfiguration (16% increase). The required force for OD die configuration increased once more to 370 kN (44.5% increase). The element distortion along the two defined paths determined the material flow during the HTE process. The flat die retardsthe material flow for FI and FO die configurations. A significantly material flow will happen for OD die configuration. Theelement distortion leads to better material mixing in OD die configuration and consequently higher magnitude and morehomogenous plastic strain distribution and higher grain refinement will be obtained.
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