考虑接触界面材料微观结构与势能参数的滑动摩擦计算研究

根据独立振子模型的能量耗散机理,提出了在无磨损界面摩擦中,利用通用界面粘附能量函数计算滑动时接触界面势能的变化从而计算摩擦力和摩擦系数的方法,建立摩擦力和摩擦系数与金属材料表面能与微观结构参数的关系,并利用已有的实验数据进行计算.结果表明,摩擦力与金属材料的表面能基本呈线性关系,与比例参数呈线性负相关关系,与晶格常数基本无关.计算结果与粘附理论公式以及超高真空原子力显微镜试验结果吻合较好.     

A quasistatic contact problem with slip‐dependent coefficient of friction

We consider a mathematical model which describes the bilateral quasistatic contact of a viscoelastic body with a rigid obstacle. The contact is modelled with a modified version of Coulomb's law of dry friction and, moreover, the coefficient of friction is assumed to depend either on the total slip or on the current slip. In the first case, the problem depends upon contact history. We present the classical formulations of the problems, the variational formulations and establish the existence and uniqueness of a weak solution to each of them, when the coefficient of friction is sufficiently small. The proofs are based on classical results for elliptic variational inequalities and fixed point arguments. We also study the dependence of the solutions on the perturbations of the friction coefficient and obtain a uniform convergence result. Copyright © 1999 John Wiley & Sons, Ltd.     

非连续变形计算力学模型的粘弹性分析方法Ⅱ:算例分析

应用作者提出的非连续变形计算力学模型粘弹性分析方法对具体的多体系统在动力外荷载作用下的响应进行了数值模拟，探讨了系统中物体的粘性阻尼对整个系统的变形、应力和接触应力等的影响。与通用软件ABAQUS的计算结果进行了比较研究，两种方法所得到的结果基本一致，但所发展的方法克服了ABAQUS中接触应力分段均匀分布的缺陷，因而所得到的接触应力较为合理，同时也说明了所提出的方法为由刚体、弹性体和粘弹性体所构成的复杂多体系统的数值分析提供了有力的工具。     

卷吸与滑动正交的热弹流润滑研究

在工程弹流润滑中两固体表面速度方向并不总是相同,当两表面速度大小相同而方向不同时,卷吸行为与滑动行为正交.针对该工作条件建立了热弹流润滑数学模型,得到完全数值解.数值模拟了固定卷吸速度条件下,当表面速度间夹角变化时油膜厚度和形状的改变.结果显示:随夹角增加中央膜厚增加,最小膜厚表现出先减小后增加的趋势.这种变化是几何楔与热黏度楔的共同作用的结果,也为近期Hoehn等膜厚随夹角不同的实验结果提供了另一种解释.     

Synthesis,hydrophilicity, and oxygen permeability of poly[(trimethylsilyl)propyne]-gr-poly(N,N-dimethylacrylamide)

N,N-dimethylacrylamide (DMAA) was graft copolymerized on poly[(trimethylsilyl)propyne] (PTMSP) by single electron reduction of PTMSP with potassium naphthalenide (K-Naph), followed by anion polymerization of DMAA from the carbanion formed in the reduction. A hard and practically non-water-swelling PTMSP-gr-poly(DMAA) was obtained under the conditions using controlled amount of K-Naph and DMAA. The graft copolymer was characterized with regard to structure, number-averaged molecular weight, and the amount of grafting poly(DMAA) determined by the relative absorbance of the IR absorption band assigned to the CO and SiC H functionalities (A_CO/A_{SiC H}). The oxygen permeability and water contact angle (θ) of the graft copolymer were evaluated while varying the amount of grafting poly(DMAA). The graft copolymer proved to be highly oxygen permeable (165 Barrers) and hydrophilic (θ = 27°). Its transparency was also elucidated with UV–vis spectra. This graft copolymer was proposed as a promising candidate for use as a hard contact lens material. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 603–610, 1998     

平面棱柱铰内考虑摩擦效应的接触分析

研究了多体系统中平面棱柱铰内的摩擦接触分析。在忽略铰内的碰撞效应的前提下,根据接触力系与约束反力的等效关系,以及各个角点接触力自身满足的互补关系,得到了接触力系关于摩擦力的线性互补方程。结合库仑摩擦定律,确定了铰内角点处的接触反力以及摩擦合力;另外,由接触力曲线可以得到铰内的接触形式,以及各个接触形式发生改变的时刻。通过ADAMS算例验证,这些接触形式转换的时刻就是铰内发生碰撞的时刻,为高效率地研究铰内碰撞提供了可能。     

Novel method to characterize the hydrolytic decomposition of biopolymer surfaces

Present pharmaceutical research is focused on the development, modification and characterisation of new drug delivery systems. Among the many different substances, biodegradable polymers and copolymers are of practical importance, especially if their degradation byproducts are non-toxic. The polymeric drug carriers are not easily wettable by water or aqueous solutions, i.e. they are hydrophobic. This surface hydrophobicity is unfavourable for keeping drug carriers circulating in the blood long enough to release the drug so that it reaches its target. Therefore, copolymers with components of different hydrophobicity were introduced, to make them less hydrophobic and hence more suitable for drug delivery in the human body. Exploratory experiments with one homopolymer, , -poly(lactic acid), , -PLA and two of its copolymers, , -poly(lactic/glycolic acid), and , -PLGA with 85/15 and 50/50 copolymer ratios were carried out. Films of these substances were prepared by dip coating onto hydrophobic and hydrophilic substrates. The changes in wettability of the polymer layers, caused by the direct contact with an aqueous environment (soaking the samples in distilled water), have been studied to model the hydrolytic decomposition of polymer surfaces and to follow the changes in their wettability by dynamic contact angle measurements in a non-destructive manner. It was found that each polymer film became less hydrophobic (dynamic contact angles decreased) and more heterogeneous as the decomposition progressed with time. Increasingly significant decreases in contact angles were observed for the copolymer films containing 15 and 50% glycolic acid, during the 50–80-day-long study. These findings were supported by gel chromatographic analysis of the soaking liquids. It was concluded that the homopolymer layer of , -PLA was the most resistant to hydrolysis and the stability of copolymer films decreased with increasing glycolic acid ratio in the copolymers. This is accordance with the fact that the less crystalline poly(glycolic acid) is more hydrophilic and hence less resistant to hydrolytic decomposition, than the poly(lactic acid). The effect of pH on the rate of hydrolysis of polymer films was also established; the influence of pH on the decomposition was best demonstrated, again, for the copolymer with 50/50 component ratio. The outcome of these experiments showed that the contact angle measuring method enables us to detect, follow and interpret the hydrolytic decomposition of biopolymer substances in a non-invasive manner.     

基于缩尺试验的联络通道机械法施工监测研究

机械法联络通道作为一种新兴的地下结构施工方法,开展监测技术研究对其安全施工具有重要的意义.针对目前工程中监测目标集成度不够、信息化程度不高的问题,以宁波地铁机械法联络通道项目为基础,提出了一套完整的联络通道施工安全在线智能监测系统.该系统分为应用层、传输层、感知层三个部分,并且具有采样、存储、传输、数据处理和预警功能.通过开展缩尺模型试验,测试了联络通道掘进过程中的变形及应力发展规律,并检验了监测系统的可靠性.试验结果表明该系统可实现实时监测、无线传输等目标,满足实际工程的监测需求,可进一步推广至实际工程.     

膦酸酯类离子液体作为钢/铜锡合金润滑剂的摩擦学性能及其机理研究

合成了三种膦酸酯类离子液体,在微动摩擦磨损试验机SRV-IV上评价其作为钢/铜锡合金润滑剂的摩擦学性能,并与全氟聚醚及传统离子液体1-甲基-3-丁基咪唑六氟磷酸盐对比.采用扫描电子显微镜(SEM)及X射线光电子能谱仪(XPS)对磨斑表面进行了分析.结果表明:所合成的膦酸酯类离子液体在常温及高温下均表现出优于全氟聚醚及1-甲基-3-丁基咪唑六氟磷酸盐离子液体的摩擦学性能.离子液体分子的极性使其形成有效的吸附润滑膜,并且膦酸酯类离子液体与金属基底发生了摩擦化学反应,形成了摩擦化学反应膜,从而使该离子液体表现出优异的摩擦学性能.     

工程力学中的互补问题:模型

对互补问题在非线性力学中的一些应用情况给出了较概括的介绍，重点放在了静态接触问题、弹塑性问题以及结构优化问题的互补模型上。将力学问题写成互补模型的好处主要有两点：一是使力学问题有更自然、更精确的数学描述；二是可以考虑用互补问题的有效和强健的数值算法来求解。