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
Dislocations are of great importance in revealing the underlying mechanisms of deformed solid crystals.With the development of computational facilities and technologies,the observations of dislocations at atomic level...Dislocations are of great importance in revealing the underlying mechanisms of deformed solid crystals.With the development of computational facilities and technologies,the observations of dislocations at atomic level through numerical simulations are permitted.Molecular dynamics(MD)simulation suggests itself as a powerful tool for understanding and visualizing the creation of dislocations as well as the evolution of crystal defects.However,the numerical results from the large-scale MD simulations are not very illuminating by themselves and there exist various techniques for analyzing dislocations and the deformed crystal structures.Thus,it is a big challenge for the beginners in this community to choose a proper method to start their investigations.In this review,we summarized and discussed up to twelve existing structure characterization methods in MD simulations of deformed crystal solids.A comprehensive comparison was made between the advantages and disadvantages of these typical techniques.We also examined some of the recent advances in the dynamics of dislocations related to the hydraulic fracturing.It was found that the dislocation emission has a significant effect on the propagation and bifurcation of the crack tip in the hydraulic fracturing.展开更多
针对电网设备状态检测技术推广应用过程中,面临的抗干扰技术研究、仪器性能检测与比对、技术培训、新技术研究等工作缺乏真型设备实验平台的问题,对状态检测特别是带电检测技术的研究应用现状及面临的问题进行了分析,提出了电网设备状...针对电网设备状态检测技术推广应用过程中,面临的抗干扰技术研究、仪器性能检测与比对、技术培训、新技术研究等工作缺乏真型设备实验平台的问题,对状态检测特别是带电检测技术的研究应用现状及面临的问题进行了分析,提出了电网设备状态检测实验平台的设计方案。利用110 k V GIS、变压器、电缆及10 k V开关柜、箱变等真型设备,在机械结构、绝缘性能、内置传感器优化布局、典型缺陷设置等方面进行了改造,研制了变压器、GIS内置特高频局放传感器、高压电缆内置电容型高频局放传感器,并建立了基于真型电网设备状态检测的实验平台。在该平台上对变压器、GIS、高压电缆、配电设备的典型局部放缺陷进行了同步模拟与检测实验。结果表明:该平台能够完成电网设备状态检测技术的研究开发、技能培训、仪器校验与比对等工作,能够真实模拟变电站运行工况、复杂电磁环境下各种输变配设备典型缺陷,对推动状态检测技术的研究与应用具有重要的实际意义。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.
基金supported by the National Natural Science Foundation of China(Grant Nos.11372313,11002011 and 11202213)the Key Research Program of the Chinese Academy of Sciences(Grant No.KJZD-EW-M01)+1 种基金the Instrument Developing Project of the Chinese Academy of Sciences(Grant No.Y2010031)the Fundamental Research Funds for the Central Universities and the Beijing Higher Education Young Elite Teacher Project
文摘Dislocations are of great importance in revealing the underlying mechanisms of deformed solid crystals.With the development of computational facilities and technologies,the observations of dislocations at atomic level through numerical simulations are permitted.Molecular dynamics(MD)simulation suggests itself as a powerful tool for understanding and visualizing the creation of dislocations as well as the evolution of crystal defects.However,the numerical results from the large-scale MD simulations are not very illuminating by themselves and there exist various techniques for analyzing dislocations and the deformed crystal structures.Thus,it is a big challenge for the beginners in this community to choose a proper method to start their investigations.In this review,we summarized and discussed up to twelve existing structure characterization methods in MD simulations of deformed crystal solids.A comprehensive comparison was made between the advantages and disadvantages of these typical techniques.We also examined some of the recent advances in the dynamics of dislocations related to the hydraulic fracturing.It was found that the dislocation emission has a significant effect on the propagation and bifurcation of the crack tip in the hydraulic fracturing.
文摘针对电网设备状态检测技术推广应用过程中,面临的抗干扰技术研究、仪器性能检测与比对、技术培训、新技术研究等工作缺乏真型设备实验平台的问题,对状态检测特别是带电检测技术的研究应用现状及面临的问题进行了分析,提出了电网设备状态检测实验平台的设计方案。利用110 k V GIS、变压器、电缆及10 k V开关柜、箱变等真型设备,在机械结构、绝缘性能、内置传感器优化布局、典型缺陷设置等方面进行了改造,研制了变压器、GIS内置特高频局放传感器、高压电缆内置电容型高频局放传感器,并建立了基于真型电网设备状态检测的实验平台。在该平台上对变压器、GIS、高压电缆、配电设备的典型局部放缺陷进行了同步模拟与检测实验。结果表明:该平台能够完成电网设备状态检测技术的研究开发、技能培训、仪器校验与比对等工作,能够真实模拟变电站运行工况、复杂电磁环境下各种输变配设备典型缺陷,对推动状态检测技术的研究与应用具有重要的实际意义。
