Tribological Properties between Taut Hair Fibers in Wet Conditions: A New Shampoo Formulation for Eliminating Stick-Slip Friction

The tribological properties between taut hair fibers in wet conditions were investigated to evaluate the tangling/detangling performance of shampoo formulations during washing (particularly rinsing). A new setup for friction measurements between taut hair fibers was established. Using the setup, tribological properties of hair fibers treated with two shampoo formulations, whose tangling performances were different, were investigated. The base formulation for the shampoos was the same; the only difference was the type of amino-modified silicones used as conditioning agents. Shampoo (Sp) A (poor detangling performance) incudes water-insoluble silicone, and Sp B (excellent detangling performance) includes water-soluble silicone. The tribological behaviors between taut hair fibers treated with the diluted solutions of the Sp were very different; the Sp A-treated hair exhibited stick-slip sliding, whereas the Sp B-treated hair exhibited smooth sliding. This difference presumably comes from the different coacervation behaviors in the diluted solutions and resulting structure of conditioning film formed on hair surfaces. The smooth sliding (ideal for detangling) of Sp B-treated hair comes from the two-layer structure of the conditioning film on hair; positively charged amino-modified silicone dissolved in water adsorbed immediately on negatively charged hair surface, followed by the physical adsorption of coacervates on the adsorbed silicone layer. The outer coacervate layer is easily removed during sliding, and smooth sliding comes from the low friction of the silicone layer. The relationship between the type of amino-modified silicones, conditioning film formation on the surface, and tribological properties was discussed, which gives insights into designing Sp formulations with excellent detangling performance.     

氧浓度振荡操作下的丙烯氨氧化反应动态动力学模型

针对Mo-Bi系催化剂作用下的丙烯氨氧化反应过程，采用氧浓度的强制周期振荡操作，根据理论推导和所定义的催化剂表面活性中心分率α，得到了丙烯转化率X及丙烯腈选择性SAN的动态动力学模型如下。进而结合在不同振荡操作周期，不同振幅条件下所采集到的实验数据，确定了模型参数，并进行优化计算得到最佳的振荡操作条件，丙烯腈周期平均收率达81．1％，比非振荡操作时提高了3．09个百分点。     

Probing the Physics of Slip-Stick Friction using a Bowed String

Slip-stick vibration driven by friction is important in many applications, and to model it well enough to make reliable predictions requires detailed information about the underlying physical mechanisms of friction. To characterize the frictional behavior of an interface in the stick-slip regime requires measurements that themselves operate in the stick-slip regime. A novel methodology for measurements of this kind is presented, based on the excitation of a stretched string “bowed” with a rod that is coated with the friction material to be investigated. Measurements of the motion of the string allow the friction force and the velocity waveform at the contact point to be determined by inverse calculation. These friction results can be correlated with microscopic analysis of the wear track left in the coated surface. Results are presented using rosin as a friction material. These show that “sticking” involves some temperature-dependent shear flow in the friction material, and that the exact definition of the states of “sticking” and “slipping” is by no means clear-cut. Friction force during slipping shows complex behavior, not well correlated with variations in sliding speed, so that other state variables such as temperature near the interface must play a crucial role. A new constitutive model for rosin friction, based on the repeated formation and healing of unstable shear bands, is suggested.     

Pd催化剂上CO氧化反应中波动现象的机理

归纳了发生在Pd催化剂上的氧化反应中波动现象的机理。介绍了三个相关的模型及其可能的反应机制。     

非等时空距灰色模型在摩擦因数预测中的应用

采用连续非等时空距GM（1，1）模型，对摩擦因数λ与雷诺准数Re的关系进行了研究，建立了可进行连续预测的数学模型，并与等时空距模型作了比较，所建立模型与实际情况吻合较好，精度检验为Ⅰ级，模型适宜于粗糙度（e/d )一定的管路系统摩擦因数λ的预测。     

CDQ焦炭运动粘性流模型壁面摩擦的研究

采用滑移边界条件,分析了颗粒群与壁面摩擦力的2个决定因素:摩擦系数和法向压力,提出了摩擦力计算表达式,并应用于模拟干熄炉内焦炭运动的粘性流模型。计算结果表明,滑移边界条件的处理能显著改善干熄炉渐扩段的模拟;干熄炉中下部,壁面摩擦力对近壁处焦炭下降影响显著;文中提出的摩擦力计算方法适用于模拟干熄炉内焦炭下降的粘性流模型。     

液体管道瞬变流摩阻模型综述

在液体有压管道瞬变流摩阻计算中,传统水击计算的局限性是不能预测水击发生后压力波的衰减和波形畸变过程。国内外学者通过对瞬变流摩阻机理进一步研究发现,瞬时摩阻可用拟稳态摩阻和附加摩阻项之和表征。对瞬时摩阻的模型的优缺点、适用范围及研究发展方向进行了详细的阐述和归纳总结,对于瞬变流的工程计算提供了便捷参考。     

混杂纤维对摩擦材料性能影响的研究

本文采用腰果壳油、三聚氰胺改性粉末酚醛树脂为基体,陶瓷纤维、钛酸钾晶须和kevlar纤维混杂制备制动摩擦材料,研究了不同混杂纤维含量对摩擦材料摩擦磨损性能影响。结果表明,增强纤维含量过低或者过高均会导致摩擦材料摩擦性能的降低。陶瓷纤维、钛酸钾晶须和kevlar三种增强纤维混杂使用能够提高并稳定制动摩擦材料的摩擦系数,对降低摩擦材料的磨损率有明显的作用。推荐在纤维混杂摩擦材料配方中采用25％的纤维含量和3％的Kevlar纤维含量。     

Investigation on the Friction Sensitivity of a Matchhead Composition Influenced by the Surface Roughness of Contact Materials

Fire and explosions in the processing of matchhead compositions are reported due to the friction sensitivity of materials used. This investigation is aimed at investigating the influence of different types of contact materials and their surface roughness on the friction sensitivity of a matchhead composition. The friction sensitivity of the matchhead composition was found to be dependent on the contact materials and their roughness. The results demonstrated that the contact materials and their surface roughness imparted variations to the sensitivity, ranging from 108 to 360 N. The sensitivity response of the energetic mixture was quicker in case of aluminum plate‐aluminum pin combinations than those when steel plate‐steel pin and brass plate‐brass pin combinations were used. For the first time, the experimental investigation identified a new value based on the material’s surface roughnesses called critical surface roughness, at which the matchhead composition ignited at a minimum frictional load. The matchhead composition was found to be highly hazardous at the critical surface roughness values of 1.09, 1.01, and 1.05 μm for aluminum, brass, and steel surfaces, respectively. Based on the experimental results this paper also discusses mechanism of ignition caused by the frictional load.     

计算摩擦系数的计算机模拟

本文针对摩擦系数计算的现状与存在的问题,提出了用计算机模拟计算摩擦系数的方法并编制了计算机程序,省时,省事,值得推广。     

不同种类酚醛树脂黏结剂对摩擦材料性能的影响

分别以未改性通用酚醛树脂、特殊改性刹车片专用酚醛树脂、腰果壳油改性酚醛树脂、丁腈橡胶改性酚醛树脂为黏结剂,玄武岩纤维、钢纤维为增强纤维制备四种酚醛树脂基摩擦材料。对试样进行物理性能、机械性能和摩擦磨损性能测试。结果表明,四种摩擦材料的密度相差不大,未改性通用酚醛树脂基摩擦材料的硬度符合刹车片使用要求,腰果壳油改性酚醛树脂基摩擦材料具有最佳的冲击强度和压缩强度;在摩擦过程中,腰果壳油改性树脂摩擦表面形成碳化膜,碳化膜的存在使摩擦材料的摩擦系数相对比较稳定,降低了磨耗量。研究表明,腰果壳油改性树脂基摩擦材料的综合性能最优。     

摩擦材料用改性酚醛树脂的研究进展

综述了摩擦材料用酚醛树脂改性的研究进展,重点讨论了酚醛树脂在耐热性、韧性、摩擦性等方面的改性,并对其发展前景做了展望。     

Grip to the Colon by Means of Macroscopic Adhesion-Controlled Friction

Manipulating friction without applying high normal forces is important for an intestine inspection and intervention device in order to eliminate the risk of tissue damage. One possible solution is to generate friction by means of adhesive forces. The adhesive forces should be high to offer sufficient grip without needing high normal forces. The generated friction is then called adhesion-controlled and depends on the size of the area in contact. Adhesion-controlled friction is well known to be dominant at microscopic and molecular levels. According to this paper, adhesion-controlled friction can be applicable on the macroscopic scale as well and, more specifically, within a range of forces in which friction is usually considered to be load-controlled. The intestine inspection and intervention device manipulates the friction with the colonic wall by means of mucoadhesive films. In this way, grip with high static friction is achieved without the need to apply high normal forces and friction is altered by changing the size of the area of the mucoadhesive film. Friction theories on different scales are revisited and considered in order to understand the dominant phenomena and the principles associated with this macroscopic adhesion-controlled friction.     

Grip to the Colon by Means of Macroscopic Adhesion-Controlled Friction

Manipulating friction without applying high normal forces is important for an intestine inspection and intervention device in order to eliminate the risk of tissue damage. One possible solution is to generate friction by means of adhesive forces. The adhesive forces should be high to offer sufficient grip without needing high normal forces. The generated friction is then called adhesion-controlled and depends on the size of the area in contact. Adhesion-controlled friction is well known to be dominant at microscopic and molecular levels. According to this paper, adhesion-controlled friction can be applicable on the macroscopic scale as well and, more specifically, within a range of forces in which friction is usually considered to be load-controlled. The intestine inspection and intervention device manipulates the friction with the colonic wall by means of mucoadhesive films. In this way, grip with high static friction is achieved without the need to apply high normal forces and friction is altered by changing the size of the area of the mucoadhesive film. Friction theories on different scales are revisited and considered in order to understand the dominant phenomena and the principles associated with this macroscopic adhesion-controlled friction.     

Explicit Determinations of the Colebrook Equation for the Flow Friction Factor by Statistical Analysis

The implicit Colebrook equation is considered as a fundamental equation for estimating the friction factor for turbulent flows in pipes. A large number of simple and accurate explicit approximations cover just a limited area of turbulent regime inside rough or smooth pipes. Here, three explicit approximations of the friction factor were determined. The friction factor data were fitted into polynomials using the response surface design of Minitab® software. To reduce the relative error of the first approximation compared with the implicit Colebrook equation, the domain was divided into two regions based on the Reynolds number (Re). To compare the accuracy and complexity of the approximations with existing relations, advanced comparison analysis based on the relative error was performed. The second set of approximations defined in two ranges of Re demonstrated high accuracy and a satisfying complexity index.     

Influence of Re-adhesion on the Wear and Friction of Glass Fibre-Reinforced Polyester Composites

Based on the well-known pin-on-disc test rig, a new test setup for online measuring of wear and friction behaviour of polymer matrix composites has been developed. In contrast to a traditional friction-and-wear test rig, a steel pin and composite disc are used for studying the influence of wear debris and fibre orientation. During sliding, a thin adhesive film is possibly formed on the wear track of a composite disc, consisting of wear debris that is squeezed under the steel pin and that finally smoothens onto the composite surface. By optical microscopy, it was observed that most of the debris particles originate from the edges of the wear track. The thin film deforms continuously, with large and dark wear particles observed at the edge of the wear track. A lower coefficient of friction is achieved when the particles are re-adhered to the mating surface. The film formation mechanism depends on the normal force, sliding velocity, and bulk composite structure: because pultruded composite profiles are presently used with a layered structure, a change in film properties is observed depending on the wear depth.     

汽车耐磨球座聚酯弹性体专用料的结构及性能

本文对用于制作汽车耐靡球座聚酯弹性体专用料进行了研制,并用红外光谱、X—光宽角衍射、GPC、DSC等分析手段对所合成专用料进行了结构表征,测定了专用料的耐磨性能和主要力学性能,确定了专用料的注射成型工艺条件     

酪氨酸-溴酸钾-硫酸铈-丙酮-硫酸振荡体系的量热研究

采用量热法研究了封闭体系中酪氨酸-溴酸钾-硫酸铈-丙酮在酸性介质中的振荡行为。考察了各反应物初始浓度和温度对振荡周期tp,诱导期tind,诱导期放热Qind的影响。基于可逆的Oregonator模型和溴水解控制（BHC）模型,提出了一个包含17个动力学步骤和10个中间变量的混合模型,数值模拟的结果与实验结果具有较好的一致性。     

Experimental Assessment of a Micro-Mechanical Model for the Static Strength of Hybrid Friction-Bonded Interfaces

Anaerobic adhesives are thermosetting acrylic polymers commonly used to improve the performance of most metal joints. Researches on the static strength of hybrid joints, available in the technical literature, show scanty and contradictory results that do not explain the effect of anaerobic adhesive on the hybrid joint behaviour. An early study by one of the authors of the present study formulates a micro-mechanical model describing the shear power of anaerobic adhesives as a function of the intimate properties of adherends and adhesive at the interface. According to the micro-mechanical model, the high local pressure acting on the thin film of adhesive trapped between the crests of the mating surfaces improves the film shear strength upon the adhesive's shear strength at zero pressure. The present work aims to assess this micro-mechanical model through a systematic experimental campaign. The tests are conducted on simple tubular specimens and consider three variables over two levels: adhesive-type (weak and strong anaerobic), pressure level during polymerization (0.5 and 134 MPa), and pressure level during failure test (0.5 and 134 MPa). The results confirm the proposed micro-mechanical model, and highlight that shear strength slightly differs by applying pressure before or after polymerization.