The forming defects, including thinning, rupture, wrinkling and springback, usually arising in producing a side-door impact beam, were investigated by trial and numerical simulation. A temperature-related constitutive...The forming defects, including thinning, rupture, wrinkling and springback, usually arising in producing a side-door impact beam, were investigated by trial and numerical simulation. A temperature-related constitutive model specific to the temperature range from 350 °C to 500 °C was established and used for the numerical simulation. The trial and numerical simulation were conducted to clarify the quantitative characteristics of forming defects and to analyze the effects of process parameters on the forming defects. Results show that the rupture situation is ameliorated and the springback is eliminated in the aluminum alloy hot stamping. The wrinkling severity decreases with increasing blank holder force (BHF), but the BHF greater than 15 kN causes the rupture at the deepest drawing position of workpiece. The forming defects are avoided with lubricant in the feasible ranges of process parameters: the BHF of 3 to 5 kN and the stamping speed of 50 to 200 mm/s.展开更多
This paper presents a three-stage hypothesis on the development of creative industrial clusters, which includes stages of agglomeration, interfacing, and network development. In the first stage, micro-entities concent...This paper presents a three-stage hypothesis on the development of creative industrial clusters, which includes stages of agglomeration, interfacing, and network development. In the first stage, micro-entities concentrate geographically in a creative industrial cluster in search of resources. The second stage reflects the need for building identity. Finally, the third stage is the outcome of multi-dimensional expansion. As a creative industrial cluster develops, its focus moves from geographic concentration to division of labor and the creation of novel systems. Using this three-stage framework, this paper conducts an empirical study on Beijing＇s 798 District （＂798＂）. Our study finds that the ＂self-destruction ＂phenomenon （which appeared after 798 had reached the stage of network development in a low-level capacity） is essentially the product of a squeezing effect of commercial prosperity on art production. Our study further examines four models of art-commerce integration and explains the ways in which creative industrial clusters are different from conventional industrial clusters： a creative cluster is a platform of integration for culture, commerce, and technology. Its course of development is characterized by novelty, emergence of identity through interfacing, and network cooperation.展开更多
Based on the research of modem electronic packaging materials, thixo-forming technology was used to fabricate electronic packaging shell. The process of thixo-extrusion with SiCp/A356 composites was simulated by the f...Based on the research of modem electronic packaging materials, thixo-forming technology was used to fabricate electronic packaging shell. The process of thixo-extrusion with SiCp/A356 composites was simulated by the finite element software DEFORM-3D, then the flow velocity field, equivalent strain field and temperature field were analyzed. The electronic packaging shell was manufactured by extrusion according to the results from numerical simulation. The results show that thixo-forming technology can be used in producing electronic package shell with SiCp/A356 composites, and high volume fraction of SiCp with homogeneous distribution can be achieved, being in agreement with the requirements of electronic packaging materials.展开更多
基金Project(P2014-15)supported by the State Key Laboratory of Materials Processing and Die&Mould Technology,Huazhong University of Science and Technology,ChinaProject supported by the Beijing Laboratory of Metallic Materials and Processing for Modern Transportation,China
文摘The forming defects, including thinning, rupture, wrinkling and springback, usually arising in producing a side-door impact beam, were investigated by trial and numerical simulation. A temperature-related constitutive model specific to the temperature range from 350 °C to 500 °C was established and used for the numerical simulation. The trial and numerical simulation were conducted to clarify the quantitative characteristics of forming defects and to analyze the effects of process parameters on the forming defects. Results show that the rupture situation is ameliorated and the springback is eliminated in the aluminum alloy hot stamping. The wrinkling severity decreases with increasing blank holder force (BHF), but the BHF greater than 15 kN causes the rupture at the deepest drawing position of workpiece. The forming defects are avoided with lubricant in the feasible ranges of process parameters: the BHF of 3 to 5 kN and the stamping speed of 50 to 200 mm/s.
文摘This paper presents a three-stage hypothesis on the development of creative industrial clusters, which includes stages of agglomeration, interfacing, and network development. In the first stage, micro-entities concentrate geographically in a creative industrial cluster in search of resources. The second stage reflects the need for building identity. Finally, the third stage is the outcome of multi-dimensional expansion. As a creative industrial cluster develops, its focus moves from geographic concentration to division of labor and the creation of novel systems. Using this three-stage framework, this paper conducts an empirical study on Beijing＇s 798 District （＂798＂）. Our study finds that the ＂self-destruction ＂phenomenon （which appeared after 798 had reached the stage of network development in a low-level capacity） is essentially the product of a squeezing effect of commercial prosperity on art production. Our study further examines four models of art-commerce integration and explains the ways in which creative industrial clusters are different from conventional industrial clusters： a creative cluster is a platform of integration for culture, commerce, and technology. Its course of development is characterized by novelty, emergence of identity through interfacing, and network cooperation.
基金Project(2007AA03Z119) supported by the National High-tech Research and Development Program of ChinaProjects(2102029,2072012) supported by the Natural Science Foundation of Beijing,China
文摘Based on the research of modem electronic packaging materials, thixo-forming technology was used to fabricate electronic packaging shell. The process of thixo-extrusion with SiCp/A356 composites was simulated by the finite element software DEFORM-3D, then the flow velocity field, equivalent strain field and temperature field were analyzed. The electronic packaging shell was manufactured by extrusion according to the results from numerical simulation. The results show that thixo-forming technology can be used in producing electronic package shell with SiCp/A356 composites, and high volume fraction of SiCp with homogeneous distribution can be achieved, being in agreement with the requirements of electronic packaging materials.
