冲击速度对20Cr和40Cr钢应变速率、动态屈服强度作用的研究

研究了不同热处理状态的２０Ｃｒ和４０Ｃｒ钢在不同冲击速度（ｖ）下，应变速率（ε）和动态屈服强度（σα）的变化规律，研究表明：σα＝σ０ｅｘｐ（Ａｌｎε），ε＝ε０ｅｘｐ（Ｂｖ），σα＝σ０ｅｘｐ（Ｃｖ）．其中只有两个是独立的，并用粘塑性本构理论分析了微观作用机制。     

氧化铝陶瓷动态压缩强度的高压和高应变率效应

平面冲击压缩下材料由弹性到非弹性变形转变的临界值对应着材料的动态压缩强度,高压和高应变率强烈影响材料的强度。采用粘塑性比拟法建立了材料发生非弹性变形的动态屈服条件,并引入Drucker-Prager静态屈服准则,可以联合考虑动态压缩强度的高压和高应变率效应,据此提出了新的Hugoniot弹性极限表征形式。利用轻气炮进行了氧化铝陶瓷平板冲击实验,VISAR测试了样品的自由面速度历程,讨论了氧化铝陶瓷动态压缩强度的测定和存在的不确定性问题。     

热处理工艺对某低合金超高强度钢性能的影响

对某低合金超高强度钢采用四种不同温度淬火,而后进行低温回火,测定其静态力学性能,并采用动态压缩和强迫剪切方法对其动态压缩性能进行详细的研究,分析淬火温度对其性能的影响规律及机理。结果表明,在一定范围内淬火温度对此钢种的抗拉强度、屈服强度和硬度影响很小,而对其截面伸长率、断面收缩率、冲击功、动态压缩强度、应变率、最大剪切强度、产生绝热剪切带的时间和绝热剪切破坏程度影响很大。     

恒压驱动流下电流变液动力学可视化试验研究

针对动态场下电流变效应机理可视化试验研究工作较少的现状,设计并制造了一个可视化试验台。通过试验观察了电流变液在外电场和流动场耦合作用下的场致亚微观动态结构变化。试验结果表明,耦合场下的动力学过程中,电流变液的流变行为主要受极化力和液动力的影响;链结构的屈服断裂最先发生在极板附近,即表征出速度滑移的微流动特征,其屈服断裂也就是电流变液的屈服强度。试验还验证了俘获效应。     

冲击速度对20Cr和40Cr的钢应变速率,动态屈服强度作用的研究

研究了不同热处理状态的２０Ｃｒ和４０Ｃｒ钢在不同冲击速度（Ｖ）下，应变速率（ε）和动态屈服强度（σａ）的变化规律，研究表明：σａ＝σ０ｅｘｐ（Ａｌｉε）、ε＝ａｅｘｐ（Ｂｖ），σａ＝σ０ｅｘｐ（Ｃｖ）其中只两个是独立的，并用粘塑性本构理论分析了同作用机制。     

冲击强化对304奥氏体不锈钢拉伸性能的影响

选用304奥氏体不锈钢进行喷丸强化和表面机械研磨等硬球冲击强化。采用X射线衍射和透射电子显微分析技术测定304奥氏体不锈钢冲击强化形成的微观组织结构变化,并进行室温下的拉伸实验,研究冲击强化对微观组织与拉伸性能的影响。结果表明:冲击强化导致奥氏体转变为马氏体,而且表层晶粒明显细化,这提高了屈服强度和抗拉强度等拉伸性能。     

形变热处理工艺对2519A铝合金动态变形行为的影响

通过霍普金森压杆实验研究2519A铝合金T87,T8,T9和T9I64种形变热处理状态在1040~5900s^-1应变率范围的动态冲击变形行为,并利用金相、透射电镜等手段分析在动态变形中合金微观组织的演变规律,研究不同形变热处理工艺对2519A铝合金动态变形行为的影响。结果表明:与T87态合金相比,强冷变形的T8和T9态合金高速冲击的动态屈服强度大幅提升,但是合金的绝热剪切敏感性也显著增加,更容易发生绝热剪切开裂。断续时效T9I6工艺可以提高2519A合金强化析出相的密度,使θ'相(Al₂Cu)更细小弥散分布。这样降低了θ'析出相在高应变率下被位错切割分解的速率,提高合金在高速变形过程中的稳定性。2519A-T9I6铝合金在高应变率下拥有较高的动态屈服强度和较低的绝热剪切敏感性,在高速变形过程中表现最佳。     

聚氨酯蜂窝纸板动力学性能及其本构模型

将聚氨酯填充到蜂窝纸板的孔隙中制作了聚氨酯蜂窝纸板复合材料,进而对其进行落锤冲击实验。通过落锤实验得到聚氨酯蜂窝纸板复合材料的应力-应变曲线,对影响其动力学性能的复合材料孔径、厚度、横截面尺寸及冲击速率四个因素进行了分析。结果表明:复合材料的动态屈服强度和动态弹性极限随着蜂窝纸芯的孔径、复合材料厚度和横截面积的增大而减小,随着冲击速率的增大而提高。在实验数据的基础上拟合了复合材料的动态本构方程,并对本构方程与实验数据进行了比较,拟合效果较好。     

单轴动态加载下冻土的力学性能实验研究

为研究冻土单轴加载下的冲击动态力学性质,采用分离式霍普金森压杆(SHPB)在-28～-3℃不同负温下对人工冻土进行了应变率范围800～1500s-1的冲击实验.获得了人工冻土在不同温度与不同应变率下的应力应变关系,发现人工冻土具有显著的应变率效应和温度效应,即冻土动强度随应变率增大和温度的降低而增大.单轴高应变率加载下,冻土没有明显的屈服现象,加载后试样完全破坏.     

水下爆炸作用下金属材料动态失效判据

该文章对某金属材料制成的圆筒形试件进行水下近距爆炸试验,得到了水下近距爆炸条件下材料的动态断裂应变,结合能量方法,给出了水下近距爆炸时材料的动态屈服强度,并和静态拉伸试验及霍普金森拉杆试验（SHTB）结果对比,比较了屈服强度、极限拉伸应变和能量吸收率等参数,并探讨了SHTB试验所得失效判据在水下爆炸对某金属材料制成的圆筒形试件进行水下近距爆炸试验,得到水下近距爆炸条件下材料的动态断裂应变,结合能量方法,给出水下近距爆炸时材料的动态屈服强度,并和静态拉伸试验及霍普金森拉杆试验（SHTB）结果对比,比较屈服强度、极限拉伸应变和能量吸收率等参数,并探讨SHTB试验所得失效判据在水下爆炸条件下的适用性。对比材料失效判据常规研究方法和水下爆炸实际效果,对于船体及其模型的结构抗爆设计和评估具有参考价值。条件下的适用性。该文章创新的对比了材料失效判据常规研究方法和水下爆炸实际效果,对于船体及其模型的结构抗爆设计和评估具有参考价值。     

水分在粘接接头界面的扩散系数和动力学

为研究水分在粘接接头界面的扩散行为,采用X射线能谱（EDX）分析方法计算了水分在碳／碳复合材料粘接接头界面的扩散系数和扩散动力学,并比较了水分在不同表面处理方法处理的碳／碳复合材料粘接接头界面的扩散系数和扩散动力学．结果表明,经偶联剂处理的碳／碳复合材料耐久性能要好于化学氧化和砂纸打磨处理,这与剪切强度测试结果相一致．     

Nucleation of the diamond phase in aluminium-solid solutions

Precipitation was studied from f c c solid solutions with silicon, germanium, copper and magnesium. Of all these elements only silicon and germanium form diamond cubic (d c) precipitates in f c c Al. Nucleation of the d c structure is enhanced if both types of atom are dissolved in the f c c lattice. This is interpreted as due to atomic size effects in the pre-nucleation stage. There are two modes of interference of fourth elements with nucleation of the d c phase in Al + Si, Ge. The formation of the d c phase is hardly affected if the atoms (for example, copper) are rejected from the (Si, Ge)-rich clusters. If additional types of atom are attracted by silicon and/or germanium, d c nuclei are replaced by intermetallic compounds (for example Mg₂Si).     

Ellipsometric measurements on tantalum and tantalum oxide films and variation of the optical constants with structure

The optical constants n and k for films of tantalum and naturally grown tantalum oxide were determined at wavelengths of 4960 Å, 5487 Å and 6049 Å using an ellipsometer at two angles of incidence. The tantalum films were prepared at a pressure equal to or less than 2 × 10^-8 Torr during evaporation. Values are compared with those of other workers. Optical observations on films with mixed b.c.c. and f.c.c. structures (as determined from X-ray measurements) indicate the presence of a b.c.c. and f.c.c. mixture throughout; this is contrary to previous suggestions by other workers that the f.c.c. phase was present in very thin films only and was converted to b.c.c. in thick films.     

The electric and dielectric properties of a coal tar epoxy coating

The dielectric properties of a coal tar epoxy coating on a steel surface in a dry dielectric layer, metal/organic coating/metal (MOCM) structures, as well as in electrochemical systems, metal/organic coating/electrolyte (MOCE), have been investigated by means of impedance spectroscopy. The influence of temperature and chemically-different contacting electrolytes on the electrical properties of the organic coating are discussed on the basis of the frequency-dependent impedance modulus ωZ(ω)ω and the phase angle Θ(ω) which are both accessible through measurements. The results are presented in the form of Bode plots. It was possible to model the measured values of the modulus by the linear relation lnωZ(ω)ω = K−n ln ω and in terms of Kramers-Kronig (KK) relations. It was shown that the poles and residues of the KK integrand [lnωZ(ω)ω/(ω²−ω²_c)] suffice to establish Θ(ω) uniquely. This means that if the modulus in the Bode plot can be represented by a linear relation with a slope -n, the phase angle is frequency-independent. The experimental results for Θ(ω) are in good agreement with this prediction for a dry (MOCM) and an electrochemical system (MOCE).     

Effect of deformation mode on the strength of deformation processed Cu-20%Nb composites

It was previously concluded that all f.c.c.-b.c.c. deformation processed composites have larger Hall-Petch slopes than layered composites (1). The present results on rolled versus wire drawn Cu-20%Nb show that the Hall-Petch slopes in deformation processed f.c.c.-b.c.c. composites depend on the mode of deformation processing and presumably the resulting filament morphology. Layered composites appear to be a good approximation to rolled deformation processed composites because of the filaments being essentially planar in both types of composites. Layered composites appear to be a poor approximation to axisymmetrically deformation processed composites because of the convoluted ribbonlike morphology of the filaments in the latter composites as compared to their planar nature in the former composites.     

Surface Active Additives for Galvanic Coating of High Quality Obtainment

This article is devoted to research of surface active additive, acrylic reagent of the ＂Nakphlok＂ in the process of galvanic coating obtainment. It was proved that the copper coating obtained in the presence of electrolyte additives Nakphlok-C are of high quality.     

The influence of generation and transport processes in the constant photocurrent method

We investigate the differences observed in the absorption spectrum of a-Si : H measured by d.c. and a.c. constant-photocurrent methods (CPM). D.c. measurement gives a value for the absorption coefficient, α, at photon energies below the Urbach tail, of up to an order of magnitude greater than a.c. measurement. We examine the free-carrier generation processes occurring in a.c. CPM, and the influence of these processes on the photocurrent frequency response to modulated sub-gap illumination. A simple kinetic model is presented and used to explain quantitatively the differences in the photocurrent frequency response for sub- and super-gap excitation, and hence in the CPM α as determined by d.c. and a.c. techniques. The difference between d.c. and a.c. determined α is explained in terms of the relative contribution of phonon-assisted transitions in the generation process. A useful consequence of the analysis is that an a.c. measurement should provide a more accurate means for determining the density of occupied states in the material.     

Electrocrystallization of zinc on copper single crystal planes under the influence of an asymmetric alternating current

Zinc electrodeposited from a sulphate bath on to copper single crystal planes revealed a layer-type growth on copper (111) and (100) planes and ridge-type growth on the (110) plane at low d.c. densities. Dendritic growth appeared at higher d.c. densities on all the planes. Superimposition of a.c. on d.c. during electrocrystallization produced hexagonal pyramids on the copper (111) plane, which were transformed into hexagonal dendrites under suitable a.c. to d.c. ratios. The influence of a.c. on the degree of epitaxy of zinc on copper and the mechanism of the dendrite initiation are discussed.     

Removal of Arsenic from Waste Water by Using ZnO Nano-Materials

Zinc oxide has a unique position among semiconducting oxides due to its piezoelectric and transparent conducting properties. The catalyst-free synthesis of pure ZnO nanostructured material with 6-fold structural symmetry was synthesized by the chemical precipitation method. In this article, various nanostructures of ZnO which are grown by the chemical precipitation technique has been reported. Zinc oxide nanoparticles were synthesized by heating freshly prepared zinc hydroxide [Zn（OH）2] at 150℃ for two hours. The prepared compound was characterized by the X-Ray diffraction technique. Zinc oxide nanoparticles possess high removal capacity of As （III）, which can easily be separated and recycled during water treatment processes.     

Design,Prototype and Command for an Anthropomorphic Modular Reconfigurable Gripper with Three Fingers for Industrial Robots

This paper describes one anthropomorphic modular reconfigurable gripper for robots, including a prototype and one command solution. For the first time the stages of synthesis, analysis design and functional simulation are presented. The structural synthesis of the anthropomorphic grippers for robots can be made regarding the following main criteria： the number of fingers, the number of phalanxes, the relative dimensions of the phalanxes, the relative position of the fingers, the degree of freedom of the gripping mechanism and the characteristic constructive elements used. We have chosen a version with three identical fingers with three phalanxes on finger. The kinematic synthesis is used to obtain a correct closing of the finger and of the gripping mechanism. The static synthesis solves the problem to obtaining the necessary gripping force on each finger and the total gripping force. With the constructive dimensions a 3D model can be obtained using CATIA soft. Aspects regarding functional CAD and virtual simulations are shown too. For one variant of this type of gripper, the technical documentation is completed and the technical project has all the conditions for practical achievement and a prototype was made. There are two main constructive modules： the support, the palm and the finger. Main technical characteristics of the prototype are indicated. Some aspects regarding actuated and command schemes are shown.