Nikhil KUMAR
,
R.JAYAGANTHAN
,
Heinz-GünterBROKMEIER
中国有色金属学报(英文版)
doi:10.1016/S1003-6326(17)60055-4
研究深冷轧制、室温轧制和后续退火对6082铝合金析出相、显微组织演变(回复,再结晶与晶粒生长)、力学性能和腐蚀行为的影响.采用差示扫描量热仪、透射电子显微镜和背散射电子衍射研究深冷轧制、室温轧制及后续热处理样品的析出动力学和显微组织形貌,以探讨其力学性能.经200°C退火后,深冷轧制样品的抗拉强度和硬度(345 MPa和HV 127)比室温轧制样品的抗拉强度和硬度(320 MPa和HV 115)更高.200°C退火后深冷轧制样品抗拉强度和硬度得到提高是因为铝基体中析出β'相,与室温轧制样品相比产生更大的Zener阻力.与室温轧制样品的腐蚀和点蚀电位(?1.335 V和?710 mV)相比,深冷轧制样品的腐蚀和点蚀电位(?1.321 V和?700 mV)也得到提高.深冷轧制样品具有较高的位错密度,Mg 4 Al 3 Si 4析出相溶解到基体中,通过形成钝化保护层和抑制原电池的形成,使样品的抗腐蚀性能得到提高.
关键词:
铝合金
,
深冷轧制
,
力学性能
,
腐蚀电位
,
析出相
Industrial & Engineering Chemistry Research
The densities, viscosities, and conductivities were measured for the ternary solution NaCl + urea + H(2)O, the quintuple solution NaC1 Na(2)SO(4) KCl K(2)SO(4) + H(2)O, and their binary subsystems at 298.15 K. The results together with the densities, viscosities, and conductivities of multicomponent solutions reported in the literature were used to study the predictability of the Young's rule for density and conductivity, the rule of Patwardhan and Kumar for density, Flu's equation for the viscosity of mixed electrolyte solutions based on the Eyring's absolute rate theory and the rule of Patwardhan and Kumar, and the semiideal solution theory for thermodynamic and transport properties. The results show that all the tested equations can provide comparable and accurate predictions for the densities of multicomponent electrolyte solutions. The semiideal solution theory is applicable to the aqueous solutions of electrolytes and nonelectrolytes, and its predictions for the densities of the examined solutions are in nice agreement with the experimental results. The simple equation based on Eyring's absolute rate theory and the rule of Patwardhan and Kumar and the semiideal solution theory can provide nice predictions for the viscosity of the tested electrolyte solutions. The predictions for the viscosity of the ternary solution NaCl + urea + H(2)O by the semiideal solution theory are also in accordance with the measured viscosities. The semiideal solution theory can provide better predictions for the conductivities of the tested electrolyte solutions than the extended Young's rule, and their predictions are both in good agreement with the experimental results. The advantages of the semiideal solution theory are briefly discussed and reviewed.
关键词:
mixed-electrolyte-solutions;linear isopiestic relation;absolute rate;theory;aqueous-solutions;298.15 k;activity-coefficients;sodium-chloride;potassium-chloride;ternary subsystems;unified;approach
LU Lu
,
WANG Fu-zhong
,
WANG Zhao-xu
,
ZHU Guang-ya4
,
ZHANG Xing-xiang5
钢铁研究学报(英文版)
Based on test data from the hot forge experiments on Gleeble 1500, a Kumar type constitutive equation for 33Mn2V steel is established. Applying this constitutive equation in commercial FEM software of MSC/SuperForm 2005, the piercing process of 33Mn2V steel in Mannesmann mill is then simulated. The modeling results visualized the dynamic evolution of equivalent stress, especially inside the workpiece. It is shown that the non-uniform distribution of stress on the internal and external surface of the workpiece is a distinct characteristic of processing tube piercing. The numerical model was verified by comparing the values of calculated force parameters of the piercing process with those measured in laboratory conditions. And it shows that the Kumar-type constitutive relationship meets the practical needs.
关键词:
33Mn2V
,
constitutive equation
,
tube piercing process
,
thermo-mechanical coupling simulation
,
FEM analysis
张辉
,
郑桂丽
,
田毅
,
张志东
液晶与显示
doi:10.3788/YJYXS20163108.0740
基于 Pramoda Kumar 等人文章中关于向列相液晶反转壁中＋1缺陷处挠曲电效应的实验现象，我们利用 Landau-de Gennes 理论给出相应的理论分析。当对弱锚定的平行排列向列相液晶盒施加垂直基板的直流电压，在反转壁中的±1缺陷会发生旋转。对于其中的＋1缺陷，我们给出了外加电场作用下液晶分子的自由能表达式并通过模拟描述指向矢的方位角和极角的变化情况给出相应的缺陷处电场驱动的结构变化。模拟结果给出的挠曲电效应引起的方位角的变化角度与 Pramoda Kumar 等人的实验得到的在＋1缺陷处消光刷的变化情况是一致的。
关键词:
液晶
,
挠曲电效应
,
+1 缺陷
,
Landau-de Gennes 理论
Journal of Physics-Condensed Matter
Nb(2)AsC showed superior mechanical properties to those of other layered ternary carbides (Kumar et al 2005 Appl. Phys. Lett. 86 111904). In the present density functional calculation, the underlying mechanism is interpreted by astonishing bonding features of Nb(2)AsC. The Nb d-As (p(x) + p(y)) and Nb d-As p(z) bonding states locate in the same energy range as those of Nb d-C p bonding, which indicates that the Nb-As bond has similar bonding strength as the Nb-C bond does; and thereafter, Nb(2)AsC has improved mechanical properties compared to the others. The present reported bonding features are interestingly different from those experienced by T(2)AlC (T=Ti, V, Cr, and Nb), wherein the weak T-Al coupling was separated from T-C bonding states in the higher energy level by a pseudogap. This work proposes an effective method to strengthen the relative weaker T-A (A is the A-group element) bonding in layered ternary carbides.
关键词:
ti3sic2;solids;gpa
袁清华
,
张文明
,
黄重国
,
任学平
稀有金属
doi:10.3969/j.issn.0258-7076.2009.04.005
采用普通工业TC4板料,在MTS高温拉伸试验系统上进行了不同变形条件的恒速拉伸试验,研究材料的高温变形行为.分析了5类通用高温本构关系对该材料真实应力应变曲线的拟合情况.最终,采用经典的Kumar模型建立了TC4的高温本构关系.利用MARC分析TC4机身盒形零件的气压成形过程,依据正交试验原理确定FEA仿真方案,并对成形模具进行了设计.以壁厚标准差为评价指标,采用极差分析法确定各因素对指标的影响程度和最佳工艺参数,并通过气压成形试验获得满足质量要求的零件.
关键词:
TC4(Ti-6Al-4V)
,
本构关系
,
气压成形
,
有限元分析
Weiyan LÜ
,
Lin LI
,
Li WANG
,
Yanlin HE
,
Shuigen HUANG
材料科学技术（英文）
Phase diagram information of the Fe-C, Fe-Al and Al-C systems are reviewed and the Fe-Al-C system is assessed. A FeAlC database is created by combining a set of thermodynamic parameters established by Kumar and SSOL database in Thermo-Calc software package. Ternary phase diagrams are calculated with FeAlC and the newly developed Thermo-Calc databases SSOL2 and SSOL4. The FeAlC database is the best one to describe the Fe-Al-C system. A1 and A3 values on the vertical section containing 1.5 wt pct Al are calculated with the FeAlC database in this work. To validate the thermodynamic calculation, critical temperatures Ac1 and Ac3 are determined by using dilatometer analysis. There exist some errors between the calculated values and the experimental results. So further optimization of the Fe-Al-C system regarding bcc and fcc phases is necessary. The experimental data in this work could be of some value in further optimization.
关键词:
Fe-Al-C
,
null
,
null
刘雨龙
,
王辅忠
中国冶金
使用MSC.Superform 2005有限元仿真软件,结合无锡西姆莱斯钢管有限公司提供的曼内斯曼穿管机结构,建立基于33Mn2V钢的三维有限元仿真模型.仿真设计采用静力隐式算法,结合Kumar本构模型对实心坯二辊斜轧穿孔过程进行热力耦合有限元模拟分析.模拟结果显示了穿管过程中出现的开裂等质量缺陷,而且缺陷位置处的塑性应变与试验计算值吻合.模拟结果表明:椭圆形孔腔以及管坯下压量是导致管口与导板摩擦过大并产生开裂的主要原因.为实际生产产品质量提高以及同行业进行相关仿真设计提供一定的参考.
关键词:
二辊斜轧
,
开裂
,
热力耦合
,
有限元仿真
朱磊
,
张麦仓
,
董建新
,
庞克昌
稀有金属材料与工程
通过在Gleeble 1500上试验机的热模拟压缩实验,分析了TC11合金的高温变形特性,进而,采用非线性回归方法建立了Kumar型的TC11合金的材料本构关系,并对该本构模型在热加工参数范围的延拓性进行了分析.结果表明,该模型具有较高的描述精度及良好的数值延拓性和稳定性.为了进一步验证该材料模型的工程实用性,将其应用于MARC/Autoforge3.1有限元商业软件,对TC11合金某型号涡轮盘的等温锻造工艺进行模拟式工艺设计.分析结果表明,该材料模型能够满足工程实用要求.
关键词:
TC11合金
,
本构关系
,
等温锻造
,
模拟式工艺设计
