In this study,the interaction between deformation and precipitates during multiple equal channel angular pressing(ECAP)deformations and inter-pass aging combination and its effect on the mechanical properties of 7050 ...In this study,the interaction between deformation and precipitates during multiple equal channel angular pressing(ECAP)deformations and inter-pass aging combination and its effect on the mechanical properties of 7050 aluminum alloy are studied.The result show that ECAP induces numerous substructures and dislocations,effectively promoting the precipitation of theηʹphase exhibiting a bimodal structure during inter-pass aging.Following inter-pass aging and subsequent ECAP,the decrease in grain size(4.8μm)is together with the increase in dislocation density(1.24×10^(15) m^(−2))due to the pinning effect of the precipitated phase.Simultaneously,the dislocation motion causes the second phase particles to become even finer and more diffuse.The synergistic effects of precipitation strengthening,fine grain strengthening,and dislocation strengthening collectively enhance the high strength of aluminum alloys,with ultimate tensile strength and yield strength reaching approximately 610 and 565 MPa,respectively.Meanwhile,ductility remains largely unchanged,primarily due to coordinated grain boundary sliding and the uniform and fine dispersion of second phase particles.展开更多
基于农村代际流动背景,从理论角度分析农村子代人口流动对父辈土地流转影响的作用机理;借助2015年中国健康养老与追踪调查数据,采用两部分模型(Two Part Model):Probit模型探究子代人口流动能否推动父辈土地流转行为发生,Tobit模型分析...基于农村代际流动背景,从理论角度分析农村子代人口流动对父辈土地流转影响的作用机理;借助2015年中国健康养老与追踪调查数据,采用两部分模型(Two Part Model):Probit模型探究子代人口流动能否推动父辈土地流转行为发生,Tobit模型分析其对土地流转面积的影响。研究结果表明:农村子女受教育水平、非农户口、流入城市等级和收入水平显著正向影响其父辈土地流转;并通过分组回归发现,农村代际流动对父辈年龄差异群体、子女数量以及居住养老方式差异群体的土地流转行为,产生不同的影响效果。为此,应当根据农村地区差异和实际发展水平,加强教育建设,推动社会公平,阻断社会阶层固化与贫穷代际传递,增强代际流动性,进而推动土地流转。展开更多
运用大型有限元分析软件Abaqus,对船用钢板EH36平板CO2气体保护焊的温度场进行三维动态分析。以8 mm EH36平板为研究对象,考虑材料的热物理性能和对流、辐射散热的影响,建立Y型坡口对接两层两道焊模型,利用过渡网格技术划分网格,采用双...运用大型有限元分析软件Abaqus,对船用钢板EH36平板CO2气体保护焊的温度场进行三维动态分析。以8 mm EH36平板为研究对象,考虑材料的热物理性能和对流、辐射散热的影响,建立Y型坡口对接两层两道焊模型,利用过渡网格技术划分网格,采用双椭球热源模型和"单元生死"技术实现焊缝填充的动态过程。得到EH36温度场的分布规律,并研究层间冷却时间对焊接温度场的影响。展开更多
基金Project(52275350)supported by the National Natural Science Foundation of ChinaProject(0301006)supported by the International Cooperative Scientific Research Platform of SUES,China。
文摘In this study,the interaction between deformation and precipitates during multiple equal channel angular pressing(ECAP)deformations and inter-pass aging combination and its effect on the mechanical properties of 7050 aluminum alloy are studied.The result show that ECAP induces numerous substructures and dislocations,effectively promoting the precipitation of theηʹphase exhibiting a bimodal structure during inter-pass aging.Following inter-pass aging and subsequent ECAP,the decrease in grain size(4.8μm)is together with the increase in dislocation density(1.24×10^(15) m^(−2))due to the pinning effect of the precipitated phase.Simultaneously,the dislocation motion causes the second phase particles to become even finer and more diffuse.The synergistic effects of precipitation strengthening,fine grain strengthening,and dislocation strengthening collectively enhance the high strength of aluminum alloys,with ultimate tensile strength and yield strength reaching approximately 610 and 565 MPa,respectively.Meanwhile,ductility remains largely unchanged,primarily due to coordinated grain boundary sliding and the uniform and fine dispersion of second phase particles.
文摘基于农村代际流动背景,从理论角度分析农村子代人口流动对父辈土地流转影响的作用机理;借助2015年中国健康养老与追踪调查数据,采用两部分模型(Two Part Model):Probit模型探究子代人口流动能否推动父辈土地流转行为发生,Tobit模型分析其对土地流转面积的影响。研究结果表明:农村子女受教育水平、非农户口、流入城市等级和收入水平显著正向影响其父辈土地流转;并通过分组回归发现,农村代际流动对父辈年龄差异群体、子女数量以及居住养老方式差异群体的土地流转行为,产生不同的影响效果。为此,应当根据农村地区差异和实际发展水平,加强教育建设,推动社会公平,阻断社会阶层固化与贫穷代际传递,增强代际流动性,进而推动土地流转。
文摘运用大型有限元分析软件Abaqus,对船用钢板EH36平板CO2气体保护焊的温度场进行三维动态分析。以8 mm EH36平板为研究对象,考虑材料的热物理性能和对流、辐射散热的影响,建立Y型坡口对接两层两道焊模型,利用过渡网格技术划分网格,采用双椭球热源模型和"单元生死"技术实现焊缝填充的动态过程。得到EH36温度场的分布规律,并研究层间冷却时间对焊接温度场的影响。
