Jiansong WAN
,
Zhufeng YUE
,
Xiaoliang GENG
,
Zhixian LU
材料科学技术（英文）
The influence of the grain boundary on the fatigue behavior was studied by two three-point-bending (TPB) specimens. One TPB specimen was named Bicrystal 1, whose pre-crack was along the grain boundary and the applied load paralleled to pre-crack direction, while the other TPB specimen was named Bicrystal 2, whose the pre-crack was perpendicular to the grain boundary and the applied load paralleled also to the pre-crack. It was found that the rate of the fatigue crack growth of Bicrystal 1 was about a tenfold higher than that of Bicrystal 2. The fatigue behavior of Bicrystal 2 specimens was dependent on the distance between the crack tip and grain boundary. The crack growth rate was highest when the crack tip was at a critical distance to the grain boundary, while the rate was the lowest when the crack tip reached grain boundary. After the crack was over the grain boundary, the crack growth rate increased. The crystallographic finite element method was applied to analyze the stress and strain structure ahead of the crack, in order to reveal the above characteristics of the fatigue behavior. It is the grain boundary-induced redistribution of stresses near the crack tip that induces the difference of fatigue behavior.
关键词:
Bicrystals
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null
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null
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null
Jiansong WAN
,
Zhufeng YUE
材料科学技术（英文）
The stress characteristics in the anisotropic bicrystal and tricrystal specimens were analyzed using the anisotropic elastic model, orthotropic Hill$'$s model and rate-dependent crystallographic model. The finite element analysis results show that non-uniform stresses are induced by the grain boundary. For bicrystal specimens in different crystallographic orientations, there exist stress concentrations and high stress gradients nearby the boundaries. The activation and slipping of the slip systems are dependent on the crystallographic orientations of the grains and also on the relative crystallographic orientations of the two adjoining grains. For the tricrystal specimens, there is not always any stress concentrations in the triple junction, and the concentration degree depends on the relative crystallographic orientations of the three grains. Different from the bicrystal specimens, there may be or no stress concentration in the vicinity of grain boundaries for the tricrystal specimens, which depends on the relative crystallographic orientations of the three grains. The stress concentration near to the grain boundaries and triple junction can be high enough for the local plastic deformation, damage and voiding or cracking even when the whole specimen is still under the elastic state. It can be further concluded that homogeneous assumption for polycrystalline materials is not suitable to study the detailed meso- or micro-mechanisms for damaging and fracturing.
关键词:
Crystallographic plasticity
,
null
,
null
Jiansong WAN
,
Zhenzhou LU
材料科学技术（英文）
Finite element (FE) analysis was employed to investigate the casting microcrack and micropore growth in nickel-base single-crystal superalloys DD3. Based on the finite deformation rate-dependent crystallographic constitutive equation, the simulations of casting microcrack and micropore growth in three-dimensional unit cell model were carried out in a range of parameters including stress triaxiality, Lode parameter and type of activated slip systems. The FE results show that the stress triaxiality has profound effects on growth behavior, and the Lode parameter is also important for the casting microcrack and micropore growth. The type of operative slip systems has remarkable effect on casting microcrack and micropore growth, so the life of single-crystal component is associated with the type of activated slip systems, which is related to Schmid factor and the number of activated slip systems. The growth comparison between microcrack and micropore reveals that when the material is subjected to large deformation, the growth rate of microcrack is faster than that of micropore, i.e. microcrack is more dangerous than micropore; the microcrack is easier to result in brittle fracture than micropore. The stress triaxiality and Lode parameter have strong influence on the growth of microcrack and micropore.
关键词:
Casting micropore
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null
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null
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null
孙国祥
,
殷瑞娟
色谱
doi:10.3724/SP.J.1123.2011.12085
建立了柏子养心丸(Baizi Yangxin Wan,BZYXW)毛细管区带电泳指纹图谱(CEFP).采用三棱柱优化法优化背景电解质(BGE),以色谱指纹图谱分离量指数(RF)为实验条件优化的目标函数,最终确定BGE为50mmoV/L硼砂-50 mmol/L磷酸氢二钠-200 mmol/L硼酸-150 mmol/L碳酸氢钠(体积比为7:7:1:1,含4％乙腈,pH 9.70).在其他优化的毛细管电泳条件为紫外检测波长228 nm,运行电压12 kV,重力进样25 s(高度14cm)条件下,采用未涂层石英毛细管(70cm(有效分离长度57 cm)× 75μm)分离,以阿魏酸峰为参照,确定了17个共有指纹峰.对样品聚类分析后用其中9批生成对照CEFP(RCEFP),以其为标准,用系统指纹定量法鉴别出12批BZYXW质量为:3批好.1批良好,3批中,1批一般,4批劣.三棱柱优化法为BGE选择提供了重要参考,建立的BZYXW-CEFP精密度好、重现性高,可用于BZYXW的质量控制.
关键词:
毛细管电泳指纹图谱
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三棱柱优化法
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系统指纹定量法
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色谱指纹图谱分离量指数
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柏子养心丸
孙国祥
,
豆小文
,
杨兰萍
,
刘中博
色谱
doi:10.3724/SP.J.1123.2012.12004
以样品指纹向量与对照指纹向量的多元化学组分间存在线性函数关系为基础,引入相关系数r、斜率a、截距6及线性定性相似度SL、线性定量相似度ML等概念,建立线性指纹定量法(linearly quantified fingerprint method,LQFM)模型以定性、定量控制中药质量.用高效液相色谱-二极管阵列检测法(HPLC-DAD)同时测定了10批人参归脾丸(Renshen Guipi Wan,RSGPW)分别在203、228和326 nm下的高效液相色谱指纹图谱,运用LQFM理论模型,鉴定RSGPW质量.LQFM能显著区别不同来源的产品,同一厂家产品质量控制一致.鉴定结果与已知的系统指纹定量法评价结果对比,LQFM对中药多元化学成分的复杂系统能实现客观的定性、定量评价.多波长指纹图谱能最大限度地兼顾中药各成分的紫外吸收特征,对中药质量控制具有更全面和可靠的特点.
关键词:
高效液相色谱
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线性指纹定量法
,
三波长指纹图谱
,
人参归脾丸
,
中成药
