脉冲镀Ni-Co合金镀层内应力及钴含量的研究

研究了脉冲镀Ni-Co合金的工艺,讨论了脉冲电镀中占空比及频率对镀层内应力及钴含量的影响.实验结果表明:镀层内应力随占空比的增加而降低,随脉冲峰值电流密度增加而升高,随温度的升高而降低.镀层中Co的质量分数则随温度的升高而升高.     

热处理对Ni-P镀层内应力及结合强度的影响

采用薄片弯曲法和压痕法分别研究了热处理温度对化学镀镍层的内应力以及镀层与基体的结合强度的影响规律。结果表明 :镀层的内应力为拉应力 ;当热处理温度为 2 0 0℃时 ,内应力减小 ,镀层经过 30 0、4 0 0或 6 0 0℃热处理 ,内应力逐步增大。随热处理温度升高 ,镀层与基体的结合力增大     

影响铝合金轮毂电镀层内应力的工艺研究

研究了铝合金材料多层电镀过程中的镀层内应力变化,结果表明半光亮镍镀层内应力增加最显著。而半光亮镍镀层内应力随镀液pH、阴极电流密度和氯离子质量浓度的增加而增大,随温度的升高而减小,由此提出了降低铝合金轮毂电镀层内应力的措施。     

Al-Mg-MMH/高岭土悬浮体流变性研究

研究了铝镁混合金属氢氧化物 (简称 Al-Mg-MMH) /高岭土悬浮体的流变性 ,主要考察了Al-Mg-MMH/高岭土含量比 R、p H、无机电解质 (Na Cl、Mg Cl2 、Al Cl3)和部分水解聚丙烯酰胺 (PHPA)对悬浮体切应力的影响。发现在所研究的范围内 ,随 R的增大 ,悬浮体切应力先增高后降低 ;R=0 .0 2 9的体系切应力随 p H的升高先升高后降低 ,而对于 R=0 .1 2 9的体系 ,切应力随 p H的升高而升高 ;无机电解质和PHPA均使体系的切应力降低。对影响机理进行了初步探讨     

沉积温度对射频磁控溅射TiN薄膜结构和表面形貌的影响

在不同沉积温度(25~400°C)下,利用射频磁控溅射技术在Si(100)基底上制备了TiN薄膜。采用X射线衍射仪和原子力显微镜研究了沉积温度对膜结构和表面形貌的影响,计算了晶面间距和晶格常数,分析了薄膜的应力性质。实验结果表明,不同沉积温度下制备的TiN薄膜主要含有(111)和(220)两种取向,以(220)为择优取向;随着温度的升高,薄膜晶化质量先提高然后趋于稳定。薄膜内应力为压应力,且随温度的升高而有所增大。随沉积温度升高,薄膜晶粒尺寸变小,表面结构更加均匀致密。     

氯化聚乙烯加工条件对门尼黏度的影响

本实验主要研究了氯化聚乙烯使用开炼机和密炼机在不同加工工艺条件下的门尼黏度。研究表明:在开炼机中加工氯化聚乙烯,加工温度相同时,较低温度(80~110℃)下,门尼黏度随时间的延长而增加,较高温度(120~130℃)下,门尼黏度随时间的延长先升高后降低;加工时间相同时,门尼黏度随加工温度的升高而升高。在密炼机中加工氯化聚乙烯,加工温度相同时,门尼黏度随时间变化不是很明显,较高温度(150℃)时,门尼黏度随时间的延长而升高;加工时间相同时,门尼黏度随温度的升高而降低。     

Ａl—Mg—ＭＭＨ／高岭土悬浮体系变性研究

研究了铝镁混合金属氢氧化物（简称Ａ１-Mg-MMH)/高岭土悬浮体的流变性,主要考察了Ａ１/Mg/MMH/高岭土含量比Ｒ,pH,无机电解质（ＮaCl,MgCl2,AlCl3) 和部分水解聚丙烯胺（ＰＨＰＡ）对悬浮体切应力的影响,发现在所研究的范围内,随Ｒ的增大,悬浮体切应力先增高后降低,Ｒ＝０．０２９的体系切应力随pH值的升高先升高后降低,而对于Ｒ＝０．１２９的体系,切应力随pH的升高而升高,无机电解质和ＰＨ－ＰＡ均使体系的切应力降低,对影响机理进行了初步探讨。     

原位弯曲阴极法测量不同基体上电沉积铜膜和镍膜的内应力

利用直流电沉积法,在碳素钢和铜基体上沉积Ni膜,以及在碳素钢基体上沉积Cu膜。用自行设计的原位弯曲阴极测量装置,测量了不同基体上不同薄膜的内应力。实验表明,原位弯曲阴极法比普通悬臂梁法更精确、简便。薄膜材料的内应力与基体材料有关。碳素钢基体和纯铜基体上沉积的Ni膜内应力随膜厚呈相反的变化趋势。碳素钢基体上电沉积Cu膜的内应力随膜厚的增加而降低;而碳素钢基体上电沉积Ni膜的内应力随膜厚的增加而增大,但当膜厚增大到一定程度时,内应力变化平缓。     

扫描温度对UHMWPP/UHMWPE冻胶体系动态流变行为的影响

应用ARE-RFS溶体/熔体旋转流变仪研究了UHMWPP/UHMWPE冻胶体系的动态流变行为。结果表明:UHMWPP/UHMWPE冻胶体系的储能模量、损耗模量和复数粘度随温度的升高而降低,随UHMWPE含量的增加而升高;耗散系数随温度的升高而增加,随UHMWWPE含量的增加而降低;当UHMWPE的添加量低于3%(w)时,能够有效地降低体系的粘流活化能。     

子午线轮胎接地问题的三维非线性有限元分析研究

根据9.00R20子午线轮胎的实际结构,考虑了轮胎的材料结构非线性、几何非线性、复合材料各向异性以及橡胶材料本身的弹性等特性,运用MARC有限元通用程序,建立轮胎模型,分析了9.00R20子午经轮胎静态下与地面的接触问题,考察了不同下沉量、内压及静摩擦因素等因素对轮胎静态接地面内应力应变场的影响。结果表明,在一定充气压力下,随下沉量的增大,接地区应力分布由内高外低变为内低外高,发生翘曲现象;静态接地时的摩擦力分布对称,但数值不大;随充气压力的升高,对应的下沉量下降,而在一定的下沉量下,接地面内的最大应力随充气压力的升高而增大。     

竖直套管内带热源的多孔介质中的自然对流

为研究内热源存在时多孔介质中流动和传热的特性,采用数值方法对上下底绝热、内外壁存在温差时,竖直套管中带均匀容积热源的多孔介质内的自然对流进行了分析。考查了内、外Rayleigh数之比Rai／Ra、高宽比A及半径比k对流场、温度场以及局部和平均Nusselt数的影响。研究结果表明,Rai／Ra和A较大时,内、外壁面附近分别形成两个逆向环流,温度场出现θ>1的高温区和θ<1的低温区,高温区的范围随Rai／Ra和A的增大而扩大。内壁面局部Nusselt数沿管长先增大后下降,分界点位置随k的减小和A的增大下移;外壁面局部Nusselt数在管上部区域迅速增大。内壁面平均Nusselt数Nui与Rai／Ra的增加呈现负的线性关系。     

水平微细管内CO2流动沸腾换热特性

对CO₂在水平微细管内流动沸腾换热进行了实验研究。实验工况：饱和温度-40～0℃,热通量5～35 kW·m^-2,质量流率200～1500 kg·m^-2·s^-1,管径1.5 mm。实验结果表明：热通量增加对于强化核态沸腾换热具有显著影响,同时加快干涸发展进程,降低干涸起始干度;质量流率对于传热系数的影响较小,随着质量流率的增加干涸起始干度降低,干涸后的传热系数有所增加;饱和温度对CO₂物性的影响是造成其不同工况时换热特性差异的主要原因,饱和温度升高干涸起始干度具有降低的趋势,且干涸后传热系数下降更为剧烈。通过与理论预测模型的对比研究：Cheng模型对干涸前具有较高的预测精度,在30%误差带内预测精度达到77.1%,绝对平均偏差为20.5%,干涸后对应预测精度比与绝对平均偏差仅为22.9%与57.8%。     

PP/MRP复合材料熔体挤出胀大行为的研究

采用熔体流动速率仪考察了温度、剪切应力、以及微胶囊红磷(MRP)含量对聚丙烯(PP)/MRP复合体系熔体挤出胀大比的影响。结果表明:PP/MRP复合体系熔体的挤出胀大比随着温度的升高而呈减小的趋势,随剪切应力的增加而显著增大,并且在185℃时,挤出胀大比与剪切应力之间基本符合线性关系;MRP含量增大,则PP/MRP复合体系熔体的挤出胀大比值呈减小的趋势。     

Dielectric Properties and Reliability of Zn0.95Mg0.05TiO3+0.25TiO2 MLCCs with Different Pd/Ag Ratios of Electrodes

In order to study the micromechanism of silver migration that influences the dielectric properties and reliability of Zn_0.95Mg_0.05TiO₃+0.25TiO₂ (ZMT") with 1 wt% 3ZnO–B₂O₃ multilayer ceramic capacitors (MLCCs), various silver (Ag)–palladium (Pd) ratios of conductors were used as inner electrodes. It was found that the electrical resistance of a MLCC sample with pure Ag as inner electrodes was degraded drastically to compared with the Ag/Pd inner electrodes at measuring temperatures ranging from 25°C to 175°C. It may be explained that the pure Ag migrates easily into the dielectric layer along the grain boundary during co-firing. The ZMT" MLCCs exhibited increasing dielectric constant and insulation resistance considerably with increasing sintering temperature. Moreover, the results also indicate that Ag diffusion changes the dielectric properties and decreases the breakdown voltage. A ZMT" MLCC with a high Ag content in the inner electrode exhibits poor reliability, and the effect of Ag⁺ migration is markedly enhanced when the activation energy of the ZMT" dielectric is considerably lowered due to the excessive formation of oxygen vacancies and the semiconducting Zn₂TiO₄ phase when Ag⁺ substitutes for Zn²⁺ during co-firing.     

斜削对折曲胶接接头的应力分布影响

采用弹塑性有限元法,研究了被粘物自由端外侧、内侧斜削角度对铝合金单搭接折曲接头中应力分布的影响。结果表明:被粘物自由端经外斜削处理后,胶层中间段的各应力分布无明显变化;外斜削角度越大,剥离应力峰值越高;被粘物自由端经内斜削处理后,内斜削角度越小,胶层端部的轴向应力峰值、剪切应力峰值越小,但剥离应力峰值越大。综合考虑胶层中部的应力分布情况,选择内斜削角度为5°时较适宜。     

Cation Deficiency in Bi2(Sr,Ca)3Cu2O8+d

X-ray lattice parameter measurements of the Bi_{2- x} (Sr,Ca)_{3- y} Cu_{2- z} O_{8+ d} system show that a continuously varying solid-solution cation nonstoichiometry exists within the overall composition ranges x < 0.32, -0.2 < y < 0.32, and z < 0.25. A modulated structure along the b axis remains present over these composition ranges. Defects introduced by cation deficiency have been clarified to be vacancies by density measurements. The oxygen content determined by titration decreases proportionately with increasing cation vacancy concentrations. In Bi-deficient compositions, the interstitial oxygen ion concentration decreased and the oxygen vacancy concentration increased with increasing concentration of Bi vacancies. The critical temperature, T _c , shows a maximum value at the stoichiometric cation composition and decreases to a slightly lower (5 to 10 K) constant value across the nonstoichiometric composition region with both increasing alkaline-earth and Cu deficiency.     

A crosslinking method of UHMWPE irradiated by electron beam using TMPTMA as radiosensitizer

Trimethylolpropane trimethylacrylate/Ultra high molecular weight polyethylene (TMPTMA/UHMWPE) composite and pure UHMWPE plates were made by compression molding and electron beam (EB) irradiation crosslinking methods. Fourier transform infrared spectroscopy (FTIR), Soxhlet extractor, electromechanical tester, and wear tester were used for the characterization of the structure, mechanical properties, and tribological performance of the crosslinked UHMWPE. FTIR analyses show that trans‐vinylene (965 cm^?1) absorption increases with the increasing dose and the trans‐vinylene intensity of TMPTMA/UHMWPE is higher than that of UHMWPE at the same dose, and Soxhlet experiments reveal that gel fraction increases with the increasing dose, both proving that crosslinking took place in all the irradiated samples. The results of the tensile tests indicate a significant decrease in elongation at break, but the stress of UHMWPE increases to 47 MPa at 10 kGy and then decreases with the increasing dose. The stress of TMPTMA/UHMWPE composites keeps at about 39 MPa before 50 kGy and then decreases with the increasing dose because of plasticization effect. The stress changes indicate that crosslinking and degradation occurred at the same time. Wear rate of 100 kGy 1% TMPTMA/UHMWPE is 1.76 × 10^?7mg/Nm, only 23.5% of wear rate of 0 kGy UHMWPE and 44.2% of wear rate of 100 kGy UHMWPE. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Wood Material Behavior During Drying: Moisture-Dependent Tensile Stiffness and Strength of Radiata Pine at 70–150°C

Improvements in kiln-drying efficiency and dried timber product quality are difficult to realize given the current lack of knowledge as to how in-kiln conditions impact wood basic properties such as strength and stiffness. In the last decade at Scion, significant effort has been invested in an initiative to evaluate the instantaneous stress-strain, time-dependent creep, and mechanosorptive behavior of radiata pine. The strength and stiffness of longitudinal specimens of radiata pine wood from the inner and outer portions of the stem have been evaluated across a range of low to high moisture contents at temperatures from 70 to 150°C. Results show expected decreases in both yield stress and MOE with increasing temperature and increasing moisture. Inner-wood is generally less rigid and strong than outer-wood. This article will review methodology and experimental results in addition to discussing trends in MOE and yield strength with temperature, moisture content, and sample type.     

Elastic stresses in an adhesively-bonded functionally-graded tubular single-lap joint in tension

In this study, the elastic stress analysis of an adhesively-bonded tubular lap joint with functionally-graded Ni-Al₂O₃ adherends in tension was carried out using a 3D 8-node isoparametric multilayered finite element with 3 degrees-of-freedom at each node. Stress concentrations were observed along the edges of both outer and inner tubes in the overlap region. Thus, the outer tube region near the free edge of the inner tube and the inner tube region near the free edge of the outer tube experienced considerable stress concentrations. Normal σ_zz and shear σ_rz stresses were dominant among the stress components. In addition, both edges of the adhesive layer experience stress concentrations, and the von Mises σ _eqv stress decreases uniformly across the adhesive thickness at the free edge of the outer tube, whereas it increases at the free edge of the inner tube. However, different compositional gradients had only a small effect on the through-the-thickness normal and shear stress profiles of both outer and inner tubes, and the peak von Mises σ _eqv stresses occurred inside the tube walls. As the ceramic phase in the material composition of the outer and inner tubes was increased, peak von Mises σ _eqv stress appeared in the ceramic layer. However, its magnitude was increased 1.75-fold in both tubes. In addition, the peak adhesive stresses appeared at the edge of the outer tube–adhesive interface near the free edge of the inner tube and at the edge of the inner tube–adhesive interface near the free edge of the outer tube. Increasing the ceramic phase in the material composition caused 1.22–1.67-times higher von Mises stresses along the free edges of the adhesivetube interfaces. In addition, with increasing number of layers across the inner and outer tubes the profiles of the normal σ_zz , shear σ_r and von Mises σ _eqv stresses across the tube walls and adhesive layer become similar. Increasing the ceramic phase in the material composition of the tubes causes also evident increases in the normal σ_zz and von Mises stresses while it does not affect their through-the-thickness profiles. However, it affects only shear σ_r and von Mises stresses across the adhesive layer. Finally, the layer number and the compositional gradient do not affect considerably through-the-thickness normal and shear stress profiles but levels in a functionally graded plate subjected to structural loads.     

Effects of shear thinning on forward roll coating

This paper described the forward mode roll coating process of generalised non-Newtonian fluids characterised by the Ellis model. The fluid in the coating bead and the free surface formation are described by the lubrication approximation and the stability is also considered using a perturbation analysis of the downstream meniscus. Results highlight the complex behaviour of this coating process and volume flow rate and film thickness results are obtained for a range of operating conditions. The stability of the downstream meniscus is observed to improve with increasing level of shear thinning when τ_1/2 (the shear stress at which the viscosity is half that of the zero shear stress viscosity) is small, however as τ_1/2 increases the meniscus stability decreases with increasing levels of shear thinning.