Effect of Strain Rate on Formability in Sheet Metal Forming

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Restraint on the Effect of Friction by Localization Method

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Effect of Heat-treatment Temperature on HA-coated Titanium Materials

1Introduction Currently,Titaniumalloyiswidelyusedassubsti tutefordamagedteethandboneduetoitssuperiorme chanicalpropertiesandbiocompatibilitybutitisnotbio activeanditselasticmoduluscouldnotmatchtothatof naturalbone(theelasticmodulusoftitaniumis110GPa andth…     

The Effect of Surface Properties of Biomedical Materials on Their Blood Compatibility

The effect of surface properties of six types of biomedical materials on their blood compatibility was investigated in this study. The surface roughness of biomaterials was determined by confocal laser scanning microscopy （CLSM）. The contact angle was observed by contact angle measurement （CAM）. Then the surface free energy （SFE） and interfacial free energy （IFE） were calculated by the contact angle value based on the Owens- Wendt （OW） theoretical model and Young＇ s equation. Meanwhile, hemolytic assay was employed to evaluate the haemolysis. The experimental results showed that the greater roughness was, the greater contact angle would be ; the less proportion of polar component in surface free energy （SFE） was, the lower haemolysis would be.     

The Effect of Surface Properties of Biomedical Materials on Their Blood Compatibility

1Introduction Biomaterialsprovidethepossibilityofsavingpatient livesandimprovingthequalityofhumanlife.Blood com patibilityofbiomaterialsactsasakeyrolebecauseblood initiallycontactstheirsurface,laterthecellsadhereto andnewtissuegrowsinbiomaterials.Thereare…     

Strong Localization Effect of Oxygen Deficiency on Carriersin T1 Based Superconductors

Investigation on the effect of Fe-doped T1-1223 superconductors has been carried out by the simultaneousmeasurements of the spectra of positron annihilation lifetime and Doppler broadening of position annihilation,together with the measurement of Hall coefficient. The results of samples with different doping level show that theoccupation of Fe atoms on Cu sites results in a linear decrement of superconducting transition temperature. The electron concentration in Cu-O layer has been enhanced by Fe doping. The difference in valence between Fe3+ andCu+ induces extra oxygen into the lattice and forms the extra oxygen defects. This Fe dopant leads to a stronglocalization of the electrons in the Cu-O layer. So the decrement of the concentration of the itinerant electronsresults in a decline of the superconducting transition temperature.     

Constitutive Relation of Yunjialing Anthracite Under Medium Strain Rate

By means of the split Hopkinson pressure bar （SHPB） testing system, this paper presents a dynamic constitu- tive relation of anthracite at a strain rate of ε =5-85s^-1. Generally, the dynamic stress-strain curve for this kind of anthracite under uni-axial compression has the following four stages： a non-linear loading stage, a plastic yielding stage, a strain-strengthening stage and an unloading breakage stage. Correspondingly, the initial elastic modulus Eb, the yielding strength σs and the ultimate strength σb increase along with an increasing strain rate. The time-dependent elasticity was identified when we analyzed the mechanical properties of anthracite. Based on characteristics of measured dynamic stress-strain curves and an analysis of existing rock dynamic constitutive models, as well as a preparatory simulation, a new visco-elastic damage model has been introduced in this paper. A linear spring is put parallel to two Maxwell units with different relaxation times to express two distinct plastic flows. The damage D is equal to [Eb- E（εi）]/Eb, where Eb is the beginning modulus and the E（εi） is the slope of a connected line between the origin point and any other point on a tested stress-strain curve. In the new constitutive model, one Maxwell unit with low relaxation time φ is used to describe the response of anthracite to a low strain rate, while the other, with a high relaxation time φ describes the response of anthracite to a high strain rate. Simulated stress-strain curves from the new model are consistent with the measured curves.     

Effect of Tensile Deformation on Recovery Characteristics of a Ni-Ti-Nb Wide Hysteresis Shape Memory

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Influence of Predeformation on Shape Memory Effect in a Fe－Mn－Si－Ni Polycrstalline Alloy

ＩｎｆｌｕｅｎｃｅｏｆＰｒｅｄｅｆｏｒｍａｔｉｏｎｏｎＳｈａｐｅＭｅｍｏｒｙＥｆｆｅｃｔｉｎａＦｅ－Ｍｎ－Ｓｉ－ＮｉＰｏｌｙｃｒｓｔａｌｌｉｎｅＡｌｌｏｙＷＡＮＧＹｏｎｇｑｉａｎ；ＬＡＩＺｈｏｎｇｈｏｎｇ；ＹＡＮＧＪｉａｎｈｕａ；ＺＨＡＯＬｉａｎｃｈ...     

修正的多孔质材料屈服模型研究

文章在考虑材料内部塑性损伤的基础上,应用有限元方法对三维裂纹韧性断裂过程进行了数值模拟.通过研究多孔质材料屈服模型(G-T模型)中参数变化对初始起裂值J_i和J_R阻力曲线的影响,提出了参教q_2:的表达式,修正了G-T模型,使其能够更好地模拟三维韧性断裂过程,与实验结果相吻合.     

基体硬化对含微孔洞材料本构关系的影响

从细观力学角度出发分析了基体硬化对含微孔洞材料本构关系的影响，给出了一个简便的修正形式，并与有限元结果进行了对比。     

基于体绘制法的多孔材料三维重建

为了从根本上研究多孔材料的扩散、渗流等特性,首先需弄清其微观结构,而重现多孔材料的三维结构是一种直接有效的方法。采用体绘制法,并借助于Matlab工具箱实现了多孔材料的三维重建、剖面显示和骨架结构的提取,结果显示重建效果较好。三维重建的研究为揭示多孔材料微观结构提供了一种较好的方法,同时也为进一步研究多孔材料的特性奠定了良好的基础。     

确定岩石类材料SHPB试验中真实应变率效应的修正方法

建立了确定岩石类材料分离式霍普金森压杆(SHPB)试验中真实应变率效应的修正方法并提出了一套完整的修正程序。采用有限元动力软件分析岩石类材料的SHPB试验,对侧向围压效应和真实应变率效应进行解耦。确定了岩石类材料的真实应变率效应,基于由SHPB试验获得的实测数据验证提出的修正方法。结果表明,仅需几次迭代便可完成修正过程,岩石类材料的动态压缩强度增强中同时包含侧向围压和真实应变率效应的影响。     

新型高强复合胶凝材料的孔结构研究

本文借助于扫描电镜(SEM),x-射线衍射(XRD)和压汞仪等测试手段,比较详细地研究了高强复合胶凝材料的孔结构与强度性能的关系。并且研究了高强复合胶凝材料的孔结构随时间变化的规律。此外,还讨论了高强复合胶凝材料的组成与性能的关系。     

多孔吸声材料静流阻率的非线性估计

为得到多孔吸声材料的声学特征参数,提出采用非线性估计方法进行提取,并进行了相应的对比实验,通过对高孔隙率多孔金属纤维样本的声学测试,采用样本吸声系数的实测结果作为响应函数,估计的静流阻率参数与该参数的直接测试结果对比基本吻合,验证了所提方法的有效性.     

脆性材料SHPB试验中实现近似恒应变率加载必要性的研究

基于分离式霍普金森压杆（SHPB）试验的数值模拟,对脆性材料SHPB试验中是否需要实现近似恒应变率加载的必要性进行了研究。结果表明在脆性材料的SHPB试验中,即使整形入射应力波在反射应力波中产生了一个近似平台,脆性材料试样中仍旧存在显著的由惯性产生的径向围压,说明在SHPB试验中实现了由反射应力波中的近似平台所表征的近似恒应变率加载也不能表示SHPB试样中的应变率为近似恒定。因此,在脆性材料SHPB试验中应用波形整形技术并不能改变转折应变率表征SHPB试样中应力状态转变的特性。无论是否采用了波形整形技术,应用脆性材料SHPB试验结果时都应考虑惯性引起的径向围压的影响。     

Electrical Conductivity and pH Sensitivity of Ordered Porous Gel Acrylate Polymer Membrane with Nano-PANI Doping

纳米多孔聚苯胺复合膜的导电性和pH敏感性

赵 杰¹,李 宁²

（1.华南理工大学 机械与汽车工程学院;2.哈尔滨工业大学 化工与化学学院）

创新点说明：

（1）采用微乳液聚合的方法制备了高导电的纳米有序多孔聚苯胺复合膜;

（2）两种质子迁移隧道的存在使复合膜形成了三维的网状结构,大大缩短了材料的响应时间,提高了材料的响应可逆性。

研究目的：

制备结构有序的纳米聚苯胺复合膜,提高其导电性和敏感特性,实现其在超级电容器和pH传感器领域的有效应用。

研究方法：

采用微乳液聚合的方法,制备MMA/AA/PANI-DBSA/PVP/H2O的微乳液聚合体系。绘制三元相图,找出双连续相微乳液相区,并对双连续相微乳液聚合工艺进行优化,合成具有较高导电性、多孔性、均一透明、机械性能强的聚苯胺复合膜。讨论了聚合物材料的形态结构、导电性能以及pH敏感性。

使用的主要设备有：Park Systems公司的原子力显微镜,Gamry Inc公司的电化学工作站,以及JEOL的JSM6330F扫描隧道显微镜。

结果：

（1） 获得了有序的纳米多孔聚苯胺复合膜;

（2）复合膜中两种类型质子迁移隧道的存在提高了材料的响应特性和敏感可逆性;

（3）聚苯胺复合膜的导纳行为大大提高了其电导特性。

结论：

高导电纳米多孔聚苯胺复合材料的制备可以实现其在电催化材料与传感器方面的有效应用。

关键词：

纳米聚苯胺;多孔结构;迁移通道;感抗行为;pH敏感性

     

多孔调湿材料湿缓冲特性的实验研究

利用NORDTEST实验方法对中国长江中下游地区(以南京为例)多孔调湿材料的湿缓冲值(Moisture Buffer Value)进行测定,同时,研究湿缓冲值对建筑能耗及室内湿度的影响。实验结果显示,高湿度区间内材料的湿缓冲测定值较大,且不同材料的湿缓冲值存在较大差异。分析表明在长江中下游地区,使用具有吸放湿特性的建筑内表面材料可有效降低建筑能耗10%以上,同时,室内环境湿度也会得到一定程度的调节。