纳米铜薄膜塑性变形中空位型缺陷形核与演化的分子动力学研究

本文采用分子动力学方法模拟了纳米单晶铜薄膜在单向拉伸载荷作用下的塑性变形过程, 重点分析了空位型缺陷的形核过程和演化机理. 在模拟过程中, 采用镶嵌原子势描述原子间的相互作用. 模拟结果表明纳米铜薄膜中塑性变形起源于位错的表面形核, 而空位型缺陷的形核及演化都与晶体内部的位错运动密切相关. 空位型缺陷通常从位错割阶及层错交截处开始形核, 以单空位、层错四面体和不规则空位团等形式存在. 关键词： 纳米薄膜 塑性变形 空位 层错四面体     

Electrical annealing of severely deformed copper: microstructure and hardness

Commercial pure copper sheets were severely deformed after primary annealing to a strain magnitude of 2.32 through constrained groove pressing. After induction of an electrical current, the sheets were heated for 0.5, 1, 2, or 3 s up to maximum temperatures of 150, 200, 250, or 300℃. To compare the annealing process in the current-carrying system with that in the current-free system, four other samples were heated to 300℃ at holding times of 60, 90, 120, or 150 s in a salt bath. The microstructural evolution and hardness values of the samples were then investigated. The results generally indicated that induction of an electrical current could accelerate the recrystallization process by decreasing the thermodynamic barriers for nucleation. In other words, the current effect, in addition to the thermal effect, enhanced the diffusion rate and dislocation climb velocity. During the primary stages of recrystallization, the grown nuclei of electrically annealed samples showed greater numbers and a more homogeneous distribution than those of the samples annealed in the salt bath. In the fully recrystallized condition, the grain size of electrically annealed samples was smaller than that of conventionally annealed samples. The hardness values and metallographic images obtained indicate that, unlike the conventional annealing process, which promotes restoration phenomena with increasing heating time, the electrical annealing process does not necessarily promote these phenomena. This difference is hypothesized to stem from conflicts between thermal and athermal effects during recrystallization.     

III型裂纹裂尖应力场的内聚力模型

摘要： 针对幂指数硬化材料,在小范围的屈服条件下,建立了III型裂纹的内聚力模型,获得了内聚区和塑性区中的应力 应变场及内聚区中的内聚力和张开位移的本构关系.结果表明：对于中等硬度的材料,如果内聚力的峰值小于2.5倍的屈服应力,那么内聚力对塑性区中的应力分布起决定性的作用,传统的弹塑性断裂力学方法和内聚力方法之间存在着差别;当牵引力的峰值变为无穷大时,无论有否内聚力,应力分布都会趋于收敛.     

基于Kriging近似模型的碳纤维增强复合

以平纹机织碳纤维增强树脂基(CFRP)复合材料为研究对象,通过力学试验测试材料的静态力学和疲劳力学性能,结合Kriging插值方法和Basquin疲劳方程建立预测任意载荷下疲劳应力 循环寿命(S N)曲线的恒幅寿命图模型,并以此作为复合材料结构优化设计的性能约束;同时,利用最优拉丁超立方试验设计方法和Kriging近似模型构建优化目标和约束响应的近似模型,采用遗传算法优化得到CFRP复合材料电动汽车电池箱壳体的厚度,并通过台架实验加以验证.结果表明,优化后,电池箱壳体结构的减重率达到34.39%.     

Study of the plastic zone near a crack in an anisotropic body

The plastic zone at a crack tip in a finite anisotropic body is studied. A boundary-value problem is formulated in terms of the components of the covariant displacement vector for small strains. Particular attention is given to the case of plain strain. In this case, a numerical solution is found for a long rectangular body with a central crack under tension. As a result, conditions for the occurrence and development of a plastic zone at the crack tip are established. A plastic zone on the lateral surface of the body is discovered. How both zones extend and coalesce is elucidated. The effect of anisotropy on the occurrence of a plastic zone is evaluated __________ Translated from Prikladnaya Mekhanika, Vol. 42, No. 7, pp. 29–44, July 2006.     

热交变压力下水泥环界面微间隙产生机理研究

目前中国四川地区页岩气开发均采用大排量分段压裂工艺技术,压裂改造过程中套管内温度以及压力的变化可能会导致油气井水泥环界面微间隙的产生。为此利用ABAQUS软件建立了热力耦合下的套管-水泥环-地层组合体有限元瞬态分析模型。基于前人实验的基础上,对温压耦合下的固井界面力学响应进行了模拟;同时分析了交变压力下微间隙的产生对组合体温度场分布的影响。研究结果表明:1微间隙的产生改变了组合体温度变化的连续性,后续施工过程中,套管温度基本接近注液温度;2井筒内的温度变化、套管内压作用下的水泥环塑性变形以及泄压后的井筒内压是导致微间隙产生的主要原因;3不同注液温度下,微间隙尺寸随着水泥环弹性模量的增大而增大。上述研究成果为压裂施工作业中油气井发生气窜以及环空带压的产生机理提供了理论依据。     

A plastic scintillating fiber position detector in vacuum for the test beam facility at BEPCⅡ-LINAC

Two plastic scintillating fiber position detectors for charged particles have been designed, built and installed inside the vacuum tube near two sides of the DM2 deflection magnet on the E3 beam line of the test beam facility at the BEPC-LINAC. A one-dimensional position resolution of sim 1 mm with a sensitive area of 60 mm×60 mm has been obtained for this detector.     

Eccentricity Effects on the Crushing History and Energy Absorption of Metal Tubes Collapsed in Concertina Mode

The classical problem of a round metal tube collapsing in concertina mode when subjected to axial compressive loading has been reexamined both theoretically and experimentally. The model including an eccentricity factor proposed by Wierzbicki et al. and modified by Singace et al. has been taken one step further to obtain the real load-displacement history and to investigate eccentricity effects. The influence of the eccentricity parameter m on the mean crushing load was discussed according to the present analysis.Experiments were carried out to verify the eccentricity effects. The results show that experimental and theoretical load-displacement curves match perfectly, especially in terms of half wavelength. Unlike previous researchs, the results suggest that m is not a fixed value and may affect energy absorption.     

塑料光栅生物传感器的传感特性分析

采用塑料矩形光栅作为生物传感器,将生物分子介质置于光栅凹槽内,通过测量光栅衍射效率进行传感测量.给出塑料光栅生物传感器的厚度法和折射率法传感特性公式,并通过建立测量实验装置进行葡萄糖溶液浓度的测量.结果表明:传感器具有很好的线性响应,且厚度法比折射率法具有更高的灵敏度,前者测量灵敏度优于100 μg·dL^-1.     

高效液相色谱-质谱法测定电子电气产品塑料部件中偶氮染料释放的致癌芳香胺

采用高效液相色谱-质谱(HPLC-MS)法对电子电气产品塑料部件中偶氮染料还原裂解产生的21种芳香族伯胺进行同时测定。塑料用有机溶剂溶解或溶胀,释放其中存在的偶氮染料,在连二亚硫酸钠的强还原性环境中,偶氮染料被还原为芳香胺。用甲基叔丁基醚提取芳香胺,提取液浓缩后用甲醇-水(1：1,v/v)定容,HPLC-MS检测。采用ZORBAX Eclipse XDB C₁₈色谱柱分离,乙腈和0.1%(v/v)甲酸溶液为流动相,流速0.6 mL/min,选择离子监测(SIM)采集数据,色谱峰保留时间和特征离子定性。21种芳香胺的线性关系良好,r >0.998,方法检出限为0.5 mg/kg。除个别物质外,在空白塑料基质中的加标回收率为60.1%~129.5%,相对标准偏差小于14.0%。本研究表明电子电气塑料部件中的禁用偶氮染料还原产生的芳香胺能够被定性定量测定,本方法的准确度高,精密度好。