Finite element simulation of the mechanics of flat contact pad fretting fatigue tests

An understanding into the macro kinetic and kinematic behaviour of fretted surfaces is provided. Making use of a modified version of a previously developed in‐house two‐dimensional elastic–plastic finite element analysis numerically simulates flat contact pad fretting fatigue tests. Basic macro mechanics concepts are adopted to idealise two bodies with rough contact surfaces and loaded at two different sites with arbitrary axial loading profiles. A time scale factor is devised to recognise the earliest candidate out of the events possibly accommodated at each loading increment. The present analysis utilises a relevant experimental set up developed in the Structural Integrity Research Institute of the University of Sheffield as an application. Computational results accurate to within 1.2% and corresponding to one contact pad span and six constant normal loads acting individually with four amplitudes of two sinusoidal axial load cycles are presented. The present computations include (1) the development of the global and local normal and tangential reactions and relative sliding displacement acting along the fretting surfaces and (2) contact pad deformation, generated stress fields and plasticity development within the neighbouring region of the fretted area.     

Contact interaction of double titanium and chromium diboride with Fe-Cr alloys

The kinetics of wetting double titanium and chromium diboride by iron-based alloys with different chromium content is studied. It is shown that contact angles are formed in such systems over the range 0–10°. The energy parameters of wetting are calculated. It is established that chromium as a surface-active element promotes Fe-Cr alloy spreading on the diboride surface. The microstructure of the interaction area is studied. It is shown that terminal solid solutions and eutectics are formed in the TiCrB₂-(Fe-Cr) system. The optimum compositions of the metallic binder are determined for TiCrB₂-based composite materials. __________ Translated from Poroshkovaya Metallurgiya, Vol. 46, No. 1–2(453), pp. 109–115, 2007     

矫直辊与板材的接触点位置对矫直过程影响的研究

介绍了辊式矫直过程中，板材与矫直辊的接触点位置对矫直过程的影响，以及接触点对矫直过程影响的一系列研究，最后对接触点在矫直过程中的分析方法及作用进行了预测。     

Ohmic contact and transport properties of II–VI Green/Blue laser diodes

The employment of the Zn(Se,Te) pseudo-graded contacting scheme to p-type ZnSe-based alloys contributes directly to the recent demonstration of room temperature continuous-wave operation of II– VI green-blue laser diodes. Contact ohmicity is maintained down to cryogenic temperatures which enabled the investigation of electrical transport properties associated with the p-type nitrogen-doped ZnSe, Zn(S,Se), and (Zn,Mg)(S,Se). The observation of both persistent photoconductivity and a metastable population of holes which are in thermodynamic equilibrium with hydrogenic acceptors having reduced activation energy suggests the presence of a DX-like behavior for holes in p-type (Zn,Mg)(S,Se).     

基于融合技术的新一代联络中心的研究与设计

随着通信和信息技术的跨越式发展,传统呼叫中心已经难以满足企业快速增长的需求,同时以客户为中心和以服务为导向的经营理念对新一代联络中心提出了更高的要求。在联络中心技术快速革新的背景下,文中以软交换、NGN和分布式技术为基础,深入研究了基于融合技术的新一代联络中心的系统架构和软交换平台的逻辑关系,构建了支持全媒体业务和标准化SIP的统一通信平台。文章以联络中心中实时和非实时业务为例,分析设计了适合联络中心典型的话务和多媒体业务的信令流程,提出了适应新一代联络中心的业务部署方式,利用模糊综合评价方法对不同部署方式的特点进行对比评估,为新一代联络中心在大型企业中推广和应用提供重要的理论和实践依据。     

Equations of state for hard-sphere fluids

Equations of state and contact values of hard-sphere radial distribution functions (rdf's) which are given by a linear combination of the Percus— Yevick and scaled-particle virial expressions are considered. In the one-component case the mixing coefficient() is, in general, a function of the volume fraction. In mixtures the coefficient( _i ,d _i ), in general, depends upon the volume fraction _i , and diameterd _i , of each species,i andj. For the contact valuesY _ij of the rdf's, the mixing coefficients _ij ( _k ) also depend on speciesi andj. Density expansions for the exact for the one-component hard-sphere fluid are obtained and compared with several approximations made in earlier works and in our own work, as well as with simulations. For a mixture, it turns out that one cannot obtain the exact fourth virial coefficient by using a linear combination of the Percus-Yevick and scaled-particle virial expressions forY _ij unless one allows _ij to depend on mole fractionsx _i even at the zeroth order of its density expansion. We also find that _ij must depend on particle speciesi andj in order to satisfy the exact limits obtained earlier by Sung and Stell. A new equation of state for the binary hard-sphere mixture which satisfies all the exact limits we have considered is suggested.Paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A.     

Study on diffusion welding SiCp/ZL101 with Cu interlayer

Through the vacuum diffusion welding SiCp/ZL101 aluminum with Cu interlayer,the effect of welding parame-ter and the thickness of Cu on the welded joint property was investigated,and the optimal welding parameters were putforward at the same time.The microstructure of joint was analyzed by means of optical-microscope,scanning electron mi-croscope in order to study the relationship between the macro-properties of joint and the microstructure.The results showthat diffusion welding with Cu interlayer could be used for welding aluminum matrix composites SiCp/ZL101 successfully.     

LF软吹时间对硅脱氧弹簧钢氧化物夹杂控制影响

 对于一些采用硅锰脱氧冶炼工艺的特殊钢,为保证钢水洁净度,常会选择较长时间的LF软吹处理,导致过程能耗增加。通过工业试验,借助FEI Explorer 4自动扫描电镜检测,研究不同LF精炼软吹时间对硅脱氧弹簧钢55SiCr铸坯氧化物夹杂成分、数量的影响;并采用夹杂物极值统计法,对比评价不同LF精炼软吹时间对应成品盘条横截面最大夹杂物尺寸控制情况。结果表明,在LF软吹10 min与软吹40 min 两种工艺条件下,铸坯中尺寸大于5 μm的氧化物夹杂成分接近,均在CaO-SiO₂-Al₂O₃相图中假硅灰石、钙长石和钙铝黄长石共晶低熔点区,其中软吹10 min工艺铸坯氧化物夹杂组成落入低熔点区的数量所占比例更大。LF软吹10 min与软吹40 min铸坯中尺寸大于5 μm的氧化物夹杂数量密度分别为11.70个/100 mm2和14.59个/100 mm2,尺寸大于15 μm 的氧化物夹杂数量密度分别为0.53个/100 mm2和1.65个/100 mm2,LF软吹10 min工艺铸坯大尺寸氧化物夹杂数量密度略低于LF软吹40 min工艺。当预测面积为30 000 mm2时,两种LF软吹时间对应成品盘条横截面最大夹杂物尺寸分别为27.1 μm和28.1 μm,盘条最大夹杂物尺寸控制无显著差别。结合硅锰脱氧钢中大尺寸低熔点CaO-SiO₂-Al₂O₃系夹杂物主要源自钢包渣乳化卷入,具有与钢水和氩气泡界面接触角很小、难以通过吹氩上浮去除的特点,建议硅锰脱氧钢LF软吹过程按短时间快节奏进行控制。     

Poly(butylene terephthalate)/organoclay nanocomposites prepared by in situ interlayer polymerization and its fiber (II)

Intercalated nanocomposites with poly(butylene terephthalate) (PBT) incorporated between the montmorillonite layers were synthesized from dimethyl terephthalate and 1,4-butane diol by using an in situ interlayer polymerization. The PBT nanocomposites were melt-spun at different organoclay contents to produce monofilaments. The samples were characterized by using wide angle X-ray diffraction, electron microscopy, thermal analysis, and tensile testing. The extent of the clay layer in the PBT was confirmed by using X-ray diffraction and electron microscopy, and the clay layer was found to be highly dispersed on a nanometer scale. The addition of only a small amount of organoclay was enough to improve the thermo-mechanical properties of the PBT hybrid fibers. The hybrids were extruded with various draw ratios (DRs) to examine the tensile mechanical property of the fibers. At DR=1, the ultimate tensile strength of the hybrid fibers increased with the addition of clay up to a critical content and then decreased. However, the initial modulus monotonically increased with increasing amount of organoclay in the PBT matrix. When the DR was increased from 1 to 6, for example, the strength and the initial modulus values of the hybrids containing 3 wt% organoclay decreased linearly.     

Design of a slave arm of a surgical robot system to estimate the contact force at the tip of the employed instruments

Acquisition of the contact force at the instrument tip can enable better performance, e.g. transparency of the haptic feedback in the surgical robot systems. It is, however, difficult to measure the contact force directly due to technical limitations in attaching sensors to the tip of the instruments. This paper proposes a method to estimate the forces by installing the sensors away from the instrument tip. The proposed method employs specially designed mechanical parts of the slave robot, i.e. a slider cover plate for the z-axis translational force along the insertion direction, and docking clamps for the rotational pivot torques around the fulcrum point. Strain gauges are attached to specially designed places with enhancing shapes. The simulation results of the force estimation are presented to confirm the strain concentration area. The proposed method is validated with quantitative experimental results. Calibrated weights are determined upon the comparison of the strain value with a calibrated 6-axis force/torque sensor. The percentage error in the force calibration is about 5~8% calculated by the root mean square error (RMSE) of force-sensing performance. In addition, it can be computed by considering only the bending phase of each sensor although the hysteresis is observed from the calibration graph.