Effects of rare earth elements on the microstructureand properties of magnesium alloy AZ91D

The effects of rare earth elements on the microstructure and properties of magnesium alloy AZ91D alloy were studied. The different proportion of rare earth elements was added to the AZ91D and the tensile tests were carried out at different temperatures. The experimental results show that at room temperature or at 120℃ the AZ91D's strength decrease with the increasing amount of the rare earth elements. However, the ductility is improved. The influence of 0.14%Sb (mass fraction) on the AZ91D's strength is like that of rare earth elements (0.2%-0.4%) (mass fraction). Microstructure graphs demonstrate that appropriate amount of rare earth elements (0.1%-0.2%) can fine AZ91D's grain and improve its ductility.     

低应变速率下锰硫比对低碳钢高温塑性的影响

研究了在低应速率下锰硫比对低碳钢高温塑性的影响,实验结果表明,不同测试温度下锰硫比对钢的高温塑性的影响不同。按其影响规律,可分为４个温度区域即：（１）１３５０－１４００℃,锰硫比越高,塑性越差;（２）１０００－１３５０℃,锰硫比对塑性无影响;（３）８００－１０００℃,锰硫比越高,塑性越好;（４）６００－８００℃,锰硫比越高,塑性越差,同时还对锰硫比对高温塑性的影响机理进行了分析。     

CFRP加固RC矩形梁极限抗弯承载力与延性计算

根据碳纤维加固钢筋混凝土结构的受力特征,对碳纤维加固混凝土矩形梁的抗弯极限承载力、刚度和挠度进行了计算,得出不考虑二次受力和考虑二次受力的结构极限承载力的计算公式,以及加固后梁的刚度和挠度计算公式,并对加固后梁的延性进行分析,得出梁的截面曲率延性系数计算式,结合实验数据,验算了计算公式的精确性。     

表面温度波动对微合金钢连铸板坯热塑性的影响

由于铸坯表面与二冷辊列夹持辊发生的间断式接触传热,其表面温度存在一定程度的上下波动. 基于J55微合金钢,考虑温度波动的影响,研究了钢在不同热状态下的热塑性. 结果表明,高于850℃时温度波动制度下测得的断面收缩率低于常规恒温制度下的测量值,而等于或低于850℃时情况相反. 分析了两种不同温度制度下测试结果的差异,认为对于微合金钢,存在着略高于所测钢种Ae3温度的某一分界温度,高于该温度时恒温制度下测得的塑性值相比波动制度下塑性值偏高,而低于该温度时则偏低. 这一认识有助于更加合理地制定实际连铸过程的矫直温度.     

Toward the development of Mg alloys with simultaneously improved strength and ductility by refining grain size via the deformation process

Magnesium(Mg) alloys, as the lightest metal engineering materials, have broad application prospects.However, the strength and ductility of traditional Mg alloys are still relativity low and difficult to improve simultaneously.Refining grain size via the deformation process based on the grain boundary strengthening and the transition of deformation mechanisms is one of the feasible strategies to prepare Mg alloys with high strength and high ductility.In this review, the effects of grain size on the strength and ductility of Mg alloys are summarized, and fine-grained Mg alloys with high strength and high ductility developed by various severe plastic deformation technologies and improved traditional deformation technologies are introduced.Although some achievements have been made, the effects of grain size on various Mg alloys are rarely discussed systematically and some key mechanisms are unclear or lack direct microscopic evidence.This review can be used as a reference for further development of high-performance fine-grained Mg alloys.     

恒高温作用后圆钢管混凝土承载力的试验与分析

通过对20个圆形钢管混凝土短柱试件在恒高温作用后的轴压试验，研究了圆形钢管混凝土短柱的轴压力学性能．在分析试验数据的基础上，探讨了试验中对恒温温度(℃)和恒温时间(小时)的选择对研究结果的影响．     

可加工Ce-ZrO2/CePO4陶瓷的"塑性化"及其机理

针对工程陶瓷材料本征脆性问题，作者从应力-应变曲线、压痕及压痕尖端的裂纹扩展等方面探讨了可加工Ce-ZrO2／CePO4材料的“塑性化”，并从显微结构入手，研究了使这种材料产生“塑性化”的机理，即除CePO4本身具有一定的台阶和层片状断裂外，主要由于CePO4的引入出现了强弱界面共同存在的网络结构，弱界面可以产生和捕获微观缺陷，耗散主裂纹扩展能量，导致局部的剪切变形，从而赋予陶瓷“塑性”。     

无翼缘短肢墙结构低周反复荷载试验研究

通过三片无翼缘短肢剪力墙结构试件低周反复荷载试验,研究了肢厚比大小、连梁刚度等因素对无翼缘构件破坏形态和极限荷载的影响。分析了以上因素对无翼缘短肢墙结构耗能能力和延性的不同影响,并给出了一些工程设计建议。     

预制装配式框架结构梁柱节点力学性能试验研究

相比钢筋混凝土结构,钢骨混凝土结构因承载力较高和延性较好等诸多优点而应用广泛.以往的研究多数集中于整体式钢骨混凝土框架节点,有关采用钢板对焊拼接形式的预制装配式钢骨混凝土框架节点的研究相对较少.基于以上考虑,设计了两个预制装配式钢骨混凝土框架节点组合体和一个钢筋混凝土框架节点组合体,进行了柱向轴力恒定的拟静力加载试验.对节点组合体的破坏形态、延性、承载力退化、刚度退化和耗能能力作了详细论述.结果表明,轴压比对预制装配式钢骨混凝土框架节点的破坏形态无本质影响;相对钢筋混凝土框架节点,预制装配式钢骨混凝土框架节点具有较高的承载力和较好的延性;预制装配式钢骨混凝土框架节点的塑性变形能力强,具有较好的耗能能力;随轴压比的增大,预制装配式钢骨混凝土框架节点组合体的刚度退化和承载力退化速度提高,延性系数和耗能能力减小;梁连接区和节点核心区的应变随轴压比的增大而减小;框架梁连接区和节点核心区的钢骨和钢筋均未屈服,钢板对焊拼接的连接方式可行.     

钢梁贯穿式方钢管砼梁柱节点滞回性能分析

针对以往钢管混凝土梁柱节点受力性能及应用中的缺陷,提出钢梁贯穿节点.通过ANYSYS有限元软件分析其单调荷载作用下的内力传递机理,循环荷载作用下的滞回性能、延性及耗能性能.结果表明:穿心节点有效地降低了钢管壁所受应力,提高了节点刚度,能实现"强柱弱梁"和塑性铰形成于节点区外的抗震设计理念;滞回曲线均为饱满的梭形,强度和刚度退化不明显.