几种硫代磷酸酯在菜籽油中的摩擦学和抗乳化性能研究

在四球摩擦磨损试验机上对比考察了几种硫代磷酸酯和二烷基二硫代磷酸锌(ZDDP)作为菜籽油添加剂的摩擦学性能，并对比分析了两类添加剂的抗乳化能力．用X射线光电子能谱仪分析了磨损表面元素化学状态，并探讨了添加剂的减摩抗磨作用机理．结果表明：在几种磷酸酯分子中引入硫使得其极压抗磨性能得到不同程度的提高；在摩擦过程中，钢球表面发生了基础油的化学吸附以及添加剂的化学吸附和摩擦化学反应，生成由菜籽油和添加剂摩擦化学反应产物组成的边界润滑膜；磷酸酯的抗乳化性能随分子结构的不同存在很大差异．四硫代三正辛酯的摩擦学性能和抗乳化性能优于ZDDP，是一种潜在的环境友好多功能润滑油添加剂．     

氟代二酮的摩擦学特性及抗磨机理研究

采用Optimal SRV型微动摩擦磨损试验机评价了氟代二酮作为润滑油及其添加剂的摩擦学性能，并通过钢盘磨损表面的X射线光电子能谱和扫描电子显微镜分析探讨了氟代二酮的减摩抗磨作用机理．结果表明，氟代二酮的摩擦学性能受其化学结构和试验载荷的影响；烷基芳基二酮的抗磨效果最好；摩擦过程中氟代二酮在摩擦副表面发生了摩擦化学反应，形成了由化学反应膜和吸附膜构成的边界润滑膜，从而起到减摩抗磨作用．     

具有表面效应的球形纳米电极颗粒中的反应-扩散-力学全耦合分析

表面效应在纳米电极颗粒中占有主导地位,论文首先建立了锂离子电池充放电过程中考虑表面效应的反应-扩散-力学全耦合模型;然后对比了有无表面效应对锂离子浓度、径向应力和环向应力的影响;最后探讨了反应系数和尺寸效应对浓度和扩散诱导应力的影响.数值结果表明表面效应随着充电时间的增加逐渐减小直至充电结束趋于稳定;表面压效应对本模型的浓度无影响但抑制了扩散诱导应力的增加;较慢的化学反应和较小的纳米电极颗粒尺寸可抑制电极应力的增加.     

摩擦表面无机保护膜摩擦学研究进展

就化学热处理表面无机化合物改性层以及润滑油添加剂在摩擦表面形成的摩擦化学反应膜的摩擦学研究现状进行了总结；分析了润滑油添加剂同化学热处理表面相互作用研究的重要性及其对低摩擦、长寿命复合材料制备科学和技术研究的促进作用；指出通过化学热处理可以在材料表面形成由无机化合物组成的表面改性层，从而有效地提高材料的承载和抗磨能力；而润滑油添加剂通过摩擦化学作用亦可在摩擦表面形成主要由无机化合物构成的表面保护膜，从而大幅度地提高摩擦副的减摩抗磨性能，并延长其服役寿命．从摩擦学特别是摩擦学表面改性领域的发展趋势来看，摩擦表面无机保护膜制备技术研究将成为减轻机械设备摩擦磨损和提高其使用寿命的主流热点．     

双层球壳结构准静态线性化学弹性问题的位移势函数解

本文研究了各向同性固体的化学-力学耦合问题,在传统化学弹性理论描述的扩散-变形耦合关系基础上,进一步考虑了化学反应与固体变形的相互作用关系,发展了等温状态下固体-扩散-反应-变形耦合的线性化学弹性理论,拓展了化学弹性力学的应用范围．该理论能够同时描述固体内介质扩散和固体与介质之间化学反应两个不同时间尺度的化学过程,并给出由此引起的弹性范围内的应变和应力．为应用该模型求解具体化学弹性问题,本文通过构造扩散-反应位移势函数来获得位移特解形式,再与齐次Lamé方程通解叠加获得完整解;针对反应控制问题,引入化学弹性准静态假设,将反应-扩散-变形全耦合的瞬态过程分解为两个可解耦的相继过程,从而获得相应位移解．基于此解法,本文获得了反应控制的双层球壳结构化学弹性问题的解析解,并分析了化学反应、几何结构和弹性模量对应力分布的影响．     

流过泰氟龙烧蚀表面的化学非平衡边界层数值研究

对流过泰氟龙烧蚀表面的化学非平衡边界层进行了数值分析．研究了气体模型、化学反应速率常数和壁画催化对边界层特性的影响．研究表明，气体模型对烧蚀产物组元浓度大小的排序有很大影响，但不同气体模型造成的电子数密度差最大仅一个数量级；不同的氟碳反应速率常数，虽在非催化壁条件下，对组元浓度剖面有强烈影响，但对电子数密度剖面，不管壁面催化特性如何，几乎都没有影响；表面烧蚀可能引起边界层分离．     

含硫硼酸酯与磷酸三甲酚酯复合添加剂在菜籽油中的协同效应

合成了 3种含硫硼酸酯 ,利用四球摩擦磨损试验机考察了含硫硼酸酯、磷酸三甲酚酯及其复合添加剂对菜籽油摩擦学性能的影响以及添加剂结构、组成与其摩擦学性能的关系 ,用 X射线光电子能谱仪和扫描电子显微镜观察分析了磨损表面的形貌和元素化学状态 .结果表明 :合成的含硫硼酸酯在一定浓度范围可以改善菜籽油的抗磨性能 ;所考察的添加剂在适当的添加量下均可提高菜籽油的承载能力和抗磨性能 ,但减摩效果不显著 ;含上述添加剂的菜籽油在摩擦过程中发生摩擦化学反应 ,生成由菜籽油甘油酯和添加剂摩擦化学反应产物组成的边界润滑膜 ,从而改善菜籽油的摩擦学性能     

流过泰氟龙烧蚀表面的化学非平衡边界层数值研究

对流过泰氟龙烧蚀表面的化学非平衡边界层进行了数值分析．研究了气体模型、化学反应速率常数和壁画催化对边界层特性的影响．研究表明，气体模型对烧蚀产物组元浓度大小的排序有很大影响，但不同气体模型造成的电子数密度差最大仅一个数量级；不同的氟碳反应速率常数，虽在非催化壁条件下，对组元浓度剖面有强烈影响，但对电子数密度剖面，不管壁面催化特性如何，几乎都没有影响；表面烧蚀可能引起边界层分离．     

电子束处理的渗硼45^#钢在硫化异丁烯润滑下的摩擦学性能研究

对渗硼45^#钢进行电子束辐照改性处理，采用SRV摩擦磨损试验机考察了电子束辐照渗硼45^#钢在含硫化异丁烯的液体石蜡润滑下同GCrl5钢对摩时的摩擦磨损性能，用扫描电子显微镜观察分析了试样剖面形貌，用X射线光电子能谱仪分析了电子束辐照渗硼45^#钢及其磨损表面主要元素的化学状态．结果表明：渗硼45^#钢经电子束照射后硬度和抗磨性能显著提高；在边界润滑条件下，添加剂可以通过摩擦化学反应而在试样磨损表面形成由硫化物和硫酸盐等组成的润滑和防护薄膜，从而进一步改善试样的摩擦磨损性能．     

清水介质条件下天然橡胶磨损45#钢的机理研究

为了提高流体机械和石油机械中橡胶－金属摩擦副的使用寿命，针对目前人们大都只着眼于改善橡胶耐磨性的现状，对清水介质条件下天然橡胶磨损４５＃钢的机理进行了研究．用扫描电子显微镜和Ｘ射线光电子能谱仪，对天然橡胶和４５＃钢表面磨损前后的微观形貌、元素的组成和结合能进行了分析，用傅立叶表面红外分析仪分析了天然橡胶磨损前后表面官能团的变化．结果表明：在给定的试验条件下，天然橡胶磨损４５＃钢的物理过程主要是滞留在摩擦表面的铁屑和添加剂颗粒对钢的微切削作用；摩擦界面发生的力化学反应主要有橡胶表面的分子链力裂解和氧化降解，橡胶大分子自由基与Ｆｅ反应生成Ｆｅ－高分子化合物，橡胶大分子链中的羧基与Ｆｅ的反应，以及Ｆｅ的氧化反应．橡胶磨损４５＃钢的过程是Ｆｅ与橡胶及介质之间发生力化学反应在４５＃钢表面形成化学反应膜，反应膜在微切削作用下脱落造成钢的磨损．这种磨损机理主要属于摩擦界面材料的化学－力学自催化破坏机理     

Diffusion separation of chemical elements on a catalytic surface

An asymptotic expansion of the solution, for large Schmidt numbers, of the system of equations of a chemically nonequilibrium multicomponent boundary layer on the catalytic surface of a blunt body [1] is used to obtain expressions for the diffusion fluxes of the reaction products and chemical elements and the heat flux as functions of the gradients of the reaction product concentrations, chemical element concentrations and enthalpy across the boundary layer. It is shown that when the body is exposed to a supersonic air flow, the diffusion separation of the chemical element oxygen depends importantly on the atom concentration at the outer edge of the boundary layer and the nature of the homogeneous and heterogeneous catalytic reactions. If the surface promotes the rapid recombination of oxygen atoms and is chemically neutral with respect to nitrogen atoms, then an excess of the chemical element oxygen is formed on the body. Otherwise we get an enhanced concentration of the element nitrogen. As distinct from the case of an ideally catalytic wall [2–4], on a surface possessing the property of catalytic selectivity the diffusion separation of chemical elements takes place even when only atoms are present at the outer edge of the boundary layer. On a chemically neutral surface diffusion separation may be caused by homogeneous recombination reactions between oxygen and nitrogen atoms if their rate constants are essentially different.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 115–121, July–August, 1988.     

滚压强化的残余应力的数值仿真及工艺分析

表面滚压强化,由于在表层引起加工硬化和残余压应力,可以十分有效地提高构件、零件疲劳强度,而滚压强化的有限元数值仿真,将成为分析优化滚压强化工艺的重要手段.本文建立了连续多、圈滚压工艺的有限元数值仿真模型,获得了比较合理的滚压变形与残余应力结果.在此基础上对滚压工艺做了进一步分析.结果表明,滚压变形的进给量太大.滚压的转速太快都容易造成工件表层残余应力分布的不均匀甚至形成残余拉应力;在滚压与未滚压的过度区域,从表面到心部的近1mm范围内,均未出现人们通常所担心的残余拉应力.这将在工程生产实践中,为滚压工艺制订提供重要的依据.     

Performance evaluation of accelerometers used for penetration experiments

We present a Hopkinson bar technique to evaluate the performance of accelerometers that measure large amplitude pulses, such as those experienced during projectile penetration tests. An aluminum striker bar impacts a thin Plexiglas or copper disk placed on the impact surface of an aluminum incident bar. The Plexiglas or copper disk pulse shaper produces a nondispersive stress wave that propagates in the aluminum incident bar and eventually interacts with a tungsten disk at the end of the bar. A quartz stress gage is placed between the aluminum bar and tungsten disk, and an accelerometer is mounted to the free end of the tungsten disk. An analytical model shows that the rise time of the incident stress pulse in the aluminum bar is long enough and the tungsten disk length is short enough that the response of the tungsten disk can be accurately approximated as rigid-body motion. We measure stress at the aluminum bar-tungsten disk interface with the quartz gage and we calculate rigid-body acceleration of the tungsten disk from Newton's Second Law and the stress gage data. In addition, we measure strain-time at two locations on the aluminum incident bar to show that the incident strain pulse is nondispersive and we calculate rigid-body acceleration of the tungsten disk from a model that uses this strain-time data. Thus, we can compare accelerations measured with the accelerometer and accelerations calculated with models that use stress gage and strain gage measurements. We show that all three acceleration-time pulses are in very close agreement for acceleration amplitudes to about 20,000 G.     

应力平衡和接触状态在Hopkinson杆测试聚合物动态弹性模量中的影响研究

针对用Hopkinson杆试验能否准确测量聚合物动态弹性模量以及其中主要影响因素的问题,本文基于重构试样初始加载阶段的应力波反射透射过程,分别计算了6个特征时间内的前三次反射波和透射波,得到试样的应力平衡度和试样的应力应变曲线。对于所研究的聚合物材料,通过比较重构的应力应变曲线的弹性模量与输入的材料弹性模量,发现在4个特征时间后,误差仅在3%左右。因此试样变形过程中的应力平衡与否不是材料在Hopkinson杆试验中弹性模量测不准的原因。通过环氧树脂试样试验发现,根据Hopkinson杆理论计算的应变结果要大于试样上应变片实测的结果,误差在11%左右。相应的数值模拟研究发现:试样和杆子端面接触状态直接决定着试样弹性模量测量的精度。关于惯性效应和压痕效应的研究也证实它们的影响是可以忽略的。     

应力调整对石英玻璃珠低速冲击破碎行为的影响

结合高速摄影技术,应用SHPB加载装置,分别使用钢制、铝制和有机玻璃制3种透射杆,对直径约7.90、11.80、15.61 mm 3种尺寸的石英玻璃珠进行了低速冲击实验。根据不同透射杆条件下的玻璃珠破碎过程中的载荷-位移曲线,结合有限元软件计算玻璃珠在冲击作用下载荷的变化情况以及实验过程中玻璃珠的应变,探讨了应力调整对玻璃珠破碎过程的影响。结果表明:相同冲击条件作用下,改变透射杆的材料,会改变玻璃珠破碎过程中的载荷分布,即透射端边界波阻抗的改变会导致反射波发生改变,从而导致玻璃珠内部载荷发生变化;透射杆为铝材和有机玻璃材质时,玻璃珠在破碎过程中的载荷明显下降,在加载过程中伴随着垫块的变形,玻璃珠内部的应力调整时间变长;透射杆为钢杆时,玻璃珠的应变主要表现为两端最大,越靠近中间应变越小,对于透射杆为铝杆和有机玻璃杆的玻璃珠,透射端局部出现了卸载行为。采用有机玻璃透射杆之后,局部应力和变形降低的结果使得玻璃珠在经受较大的变形之后发生破碎,表明玻璃珠的破碎行为由局部变形和局部变形梯度共同控制。     

Damage characterization of SAE 1020 and 1045 steel under torsion and compression

A damage model is applied to characterize the ductile deformation of SAE 1020 and 1045 steel. Damage is evaluated for thin-walled cylindrical specimens in torsion and solid bar specimens in compression where stress triaxiality enhances crack initiation. Analyzed are the variations of the damage parameter with the average compressive axial strain at the different locations of the solid bar. Initially, stress triaxiality being largest at the center appeared to dominate damage. With increasing strain, pronounced damage tends to occur in the mid-plane at locations closer to the free surface. Change in the aspect ratio of the cylindrical bar specimens also had an effect on the stress triaxiality and hence the damage parameter. Less damage is prediated for slender bars at the same strain level although the difference is small for height to diameter ratio up to 1.86.     

Repeatability of the Contour Method for Residual Stress Measurement

This paper describes the results of a residual stress measurement repeatability study using the contour method. The test specimen is an aluminum bar (cut from plate), with cross sectional dimensions of 50.8 mm?×?76.2 mm (2 in?×?3 in) with a length of 609.6 mm (24 in). There are two bars, one bar with high residual stresses and one bar with low residual stresses. The high residual stress configuration (±150 MPa) is in a quenched and over-aged condition (Al 7050-T74) and the low residual stress configuration (±20 MPa) is stress relieved by stretching (Al 7050-T7451). Five contour measurements were performed on each aluminum bar at the mid-length of successively smaller pieces. Typical contour method procedures are employed with careful clamping of the specimen, wire electric discharge machining (EDM) for the cut, laser surface profiling of the cut faces, surface profile fitting, and linear elastic stress analysis. The measurement results provide repeatability data for the contour method, and the difference in repeatability when measuring high or low magnitude stresses. The results show similar repeatability standard deviation for both samples, being less than 10 MPa over most of the cross section and somewhat larger, around 20 MPa, near the cross section edges. A comparison with published repeatability data for other residual stress measurement techniques (x-ray diffraction, incremental hole drilling, and slitting) shows that the contour method has a level of repeatability that is similar to, or better than, other techniques.     

Pulse shaping techniques for testing brittle materials with a split hopkinson pressure bar

We present pulse shaping techniques to obtain compressive stress-strain data for brittle materials with the split Hopkinson pressure bar apparatus. The conventional split Hopkinson pressure bar apparatus is modified by shaping the incident pulse such that the samples are in dynamic stress equilibrium and have nearly constant strain rate over most of the test duration. A thin disk of annealed or hard C11000 copper is placed on the impact surface of the incident bar in order to shape the incident pulse. After impact by the striker bar, the copper disk deforms plastically and spreads the pulse in the incident bar. We present an analytical model and data that show a wide variety of incident strain pulses can be produced by varying the geometry of the copper disks and the length and striking velocity of the striker bar. Model predictions are in good agreement with measurements. In addition, we present data for a machineable glass ceramic material, Macor, that shows pulse shaping is required to obtain dynamic stress equilibrium and a nearly constant strain rate over most of the test duration.