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RISS 인기검색어
- 검색키워드
- 저자 : Xuedao Shu (검색결과 2 건)
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Sutao Han,Xuedao Shu,Taizhu Chen,Ying Chang,Ji Chen,Xing Chen,Wei Xiang 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.12
The deforming process is complicated and both the end concave and the central defect can be easily formed in multi-step shafts shaped by the cross-wedge rolling technology. To realize the accurate forming of multi-step shafts without stub bar, this article breaks the bondage of traditional flat-end billet, and introduces into convex-end billet. Based on established mechanical models and the damage computation principles, the distribution and change features of stress fields, strain fields and microstructures in different segments of the multistep shaft during the progressive forming process are analyzed, and the location of the central defect is predicted. It is found that the concave depth of shaft ends decreases as the length of the convex-end of billet increases, the microcosmic grains are affected by the section shrinkage of the shaft segments and the larger the section shrinkage is, the smaller the size of the microcosmic grain will be. It records the longest duration of maximum stress, the largest fluctuation of lateral stress and the most frequent cycle of transverse strain in the multistep shaft end and therefore the central defect is most likely to occur. The research findings settle a dependable theoretical basis for enhancing the molding quality and realizing the accurate forming for multi-step shafts in cross wedge rolling.
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Shuhua Zheng,Xuedao Shu,Sutao Han,Penghui Yu 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.5
First, the rotation condition of a hollow shaft’s multi-wedge synchrostep cross-wedge rolling (MSCWR) is determined and the relevant influencing rule is illustrated based on a mechanical model of the hollow shaft and the theory of solid shaft’s rotation condition. The influence rule states that the increasing number of wedges increases the shrinkage rate of the hollow shaft and diminishes the rotation conditions, which can be improved by increasing μ on the forming surface of the hollow rolling mold, setting the stretching b , and forming α angles at approximately 4°-12° and 15°-35°, respectively. Second, a rigid-plastic finite element model is established for the hollow shaft with MSCWR by using the DEFORM-3D software, and the deformation mechanism of the hollow shaft is illustrated. The deformation degree of the rolling piece at the stretching stage decreases gradually from the surface to the interior of the hollow shaft, and radial compressive and transverse tensile strains interact with each other, thus resulting in an elliptic cross section of the hollow shaft. Stress field is mainly distributed in the exterior margin and then permeates into the inner part along the direction of the wall thickness, gradually transforming from compressive stress into tensile stress. Third, the influence of mechanical parameters on hollow shaft rolling is analyzed. The increased stretching angle increases the radial force, transverse force, and rolling torque and decreases the axial force. Moreover, the enlarged forming angle reduces the radial and transverse forces, while the decreased rolling torque increases the axial force. Finally, the 1:5 MSCWR experiment on the hollow shaft verifies the proposed finite element model’s accuracy. Results of the research provide a theoretical basis for the MSCWR of a precise hollow shaft.
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