Hydrogen bonding induced enhancement for constructing anisotropic sugarcane composite hydrogels

Anisotropic hydrogels are appealing with their merits of similar biochemical and structural properties to the biological tissues. However, the mechanical properties of current anisotropic hydrogels need to be further improved. Herein, three kinds of novel anisotropic poly(2-hydroxyethyl methacrylate) (pHEMA), poly(acrylamide) (pAM), and poly(acrylamide-co-acrylic acid) (p[AM-co-AA]) sugarcane composite hydrogels were prepared successfully by filling the hydrogel monomer precursor into porous aligned sugarcane nanofibers network and then performing subsequent free radical polymerization. The hydrogel matrix and sugarcane nanofibers network were combined closely together through hydrogen bonding interaction. The anisotropic sugarcane composite hydrogels exhibit good flexibility and elastic recovery properties upon encountering mechanical crimping and twisting. In typical case, the as-prepared pHEMA sugarcane composite hydrogel can exhibit high anisotropic tensile strength of 2.37 and 0.54 MPa, while differential tear strength of 0.36 and 0.78 N/mm, along the parallel and vertical nanofibers directions. Finally, anisotropic lubrication behaviors were found and investigated systematically for those three kinds of sugarcane composite hydrogels when water was used as lubricant. Our current work proposes a simple and universal strategy for developing bioinspired anisotropic functional composite matters such as artificial skin, flexible sensor, and cartilage lubrication materials.     

Effect of nano fillers on the properties of polytetrafluoroethylene composites: Experimental and theoretical simulations

Polytetrafluoroethylene (PTFE) has excellent corrosion resistance and a low coefficient of friction; however, its high wear rate and low hardness severely limit its use. In the work, nano particles were used as fillers for PTFE. The composites were prepared by the homogeneous mixing of PTFE and other fillers and sintered at high temperatures. The work aimed to investigate the effect of various nano fillers (nanocarbon powders, graphene, fullerene, nano graphite powders, and nano copper powders) on the mechanical, thermal, and frictional properties of composites. The results of the experiments showed that the addition of graphene could improve the stress and strain values of the composites, and all the nano fillers could improve the thermal conductivity of the PTFE composites. The friction experiments showed that fullerenes could significantly improve the wear resistance of PTFE composites. In the theoretical simulation, the thermal conductivity of PTFE composites was predicted using ANSYS software, with the changes in the temperature and friction force in the friction process. The theoretical simulation results matched with the experimental values, which proved the accuracy of the theoretical simulations.     

MQL深孔钻削中关键因素的最适化研究

采用了微量润滑技术的钻削在长距或小孔径的条件下有必要对所供给的油雾和压缩空气进行最佳化分析.本文首先对切削变形与切削热分布的总能量进行了分析,并在把普通钻削过程中油雾假设为稳态可压缩绝热紊流状态的假设条件下,通过分析得到油膜厚度、气流速度、压缩空气温度和刀具平均温度等重要影响参数的相互关系.最后,给出微量润滑钻削条件下,切削过程中所需的油膜和压缩空气的最佳容量.     

纳米金刚石的应用

纳米金刚石不仅具有金刚石所固有优异特性，而且还具有纳米材料所拥有的奇异性能。正是这些综合技术特性，使得它在传统的和新的技术领域中得到应用，并初见成效，本文从超精抛光、润滑、复合镀、磁性录音系统和医疗等方面的应用做了扼要的叙述，指出，纳米金刚石颗粒具有球形和准球形的特点，使得摩擦表面形成滚珠轴承效应，而表现出良好的润滑性，从而避免于摩现象的发生，而对一些主要因接触疲劳或高温磨损而失效的工件，纳米金刚石金属的复合涂层，则具有明显的优越性。     

Effect of sintering parameters on warm compacted iron-based material

1　INTRODUCTIONItiswellknownthatincreasingdensityisthebestwaytoincreasetheperformanceofpowdermet allurgy(P/M ) parts.ConventionalP/Mprocessingcanproduceiron basedpartswithdensitylessthan 7.1g/cm3(arelativedensityof 90 %approximately) .Theirmechanicalpropertiesaresubstantiallylessthanthoseoftheirfulldensitycounterpart .TherearemanymethodsthatcanproduceP/M partswithrela tivelyhighdensitysuchaswarmcompaction ,hightemperaturesintering ,doublepress/doublesinteringandforging .Warmcompactioni…     

提高油气润滑使用效果的措施

介绍了油气润滑的组成、原理及优缺点，并着重阐述了油气润滑使用中存在的问题和对策。     

典型活动扇形段改造

从现有设备条件出发，对导向辊结构、润滑形式及框架结构等进行对比总结，通过对改造后的实际效果进行跟踪分析，验证了活动扇形段改造方案的正确性，为炼钢连铸区域相关设备改造提供依据。     

层状固体润滑薄膜的研究进展

层状物固体润滑薄膜是固体润滑薄膜中最常用的形式.本文针对4种有代表性的层状物固体润滑薄膜(硫化亚铁、二硫化钼、石墨及二硫化钨薄膜)的制备方法及摩擦学性能进行了详细论述,这些薄膜都具有优良的减摩、耐磨、抗擦伤性能,但不同的薄膜其摩擦学性能有差异,适用工况也不尽相同.     

Feasibility study of the minimum quantity lubrication in high-speed end milling of NAK80 hardened steel by coated carbide tool

High-speed milling of hardened steels generates high cutting temperature and leads to detrimental effects on tool life and workpiece surface finish. In this paper, feasibility study of the minimum quantity lubrication (MQL) in high-speed end milling of NAK80 hardened steel by coated carbide tool was undertaken. Flood cooling and dry cutting experiments were conducted also for comparison. It is found that cutting under flood cooling condition results in the shortest tool life due to severe thermal cracks while the use of MQL leads to the best performance. MQL is beneficial to tool life both in the lower speed cutting and the higher speed cutting conditions. A less viscous oil of MQL is essential in high cutting speed so that cooling effect can be effective. SEM micrograph of the insert shows that the use of MQL in high-speed cutting can delay welding of chips on the tool and hence prolongs tool life as compared with dry cutting condition. The application of MQL also improves machined surface finish in high-speed milling of die steels.     

反应等离子喷涂TiN/AlN涂层在润滑状态下摩擦磨损性能的研究

对用反应等离子喷涂法制备的TiN/AlN涂层在油润滑条件下的摩擦磨损特征进行了研究,并就轻、重载荷下的磨损机理进行了探讨。结果表明:油润滑条件下,涂层磨损体积显著降低。在轻载荷下,以疲劳磨损为主;在重载荷下,以脆性剥落和磨粒磨损为主。