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.     

Enhanced wear resistance of ultra-high molecular weight polyethylene fibers by modified-graphite oxide

A simple and feasible method to enhance the wear resistance of ultra-high molecular weight polyethylene (UHMWPE) fibers was reported. The graphite oxide (GO) prepared using improved Hummer's method was surface modified with hexadecylamine to improve its compatibility with UHMWPE. Combined with well-dispersion of modified-GO (m-GO) in dichloromethane and the fact that the viscosity of UHMWPE suspension can be decreased by dichloromethane, the well dispersed m-GO/dichloromethane was added into UHMWPE suspension to improve m-GO dispersion in UHMWPE fibers. Finally, UHMWPE fibers with different m-GO concentration were prepared using gel spinning technology. The effect of m-GO concentration on the structure and properties of modified UHMWPE fibers were investigated. The results indicated that the melting temperature and crystallinity of m-GO modified UHMWPE fibers increased with increasing of m-GO concentration, while the fiber's crystal sizes and orientation increased, thus the tensile strength of m-GO modified UHMWPE fibers remained almost undamaged. The introduction of m-GO is beneficial to the formation of smooth transfer film on fiber's surface, which enhanced the self-lubrication of UHMWPE fibers. Compared with pure UHMWPE fiber, the UHMWPE fiber containing 1.5 wt% m-GO had enhanced wear resistance by 55.4% and still maintained high tensile strength of 29.98 cN dtex⁻¹.     

Fatigue Delamination Characteristics of Plasma Sprayed Coatings under Fretting

FRETTING is referring to a reciprocating motion withthe small displacement between two components incontact[1].Fretting wear is superficial materialremoval during the fretting.It severely reduces theperformance,efficiency and service lifetime of thecomponents[2],Thermal spraying has been employedto enhance the fretting wear resistance of components,and the fretting wear behavior of the coatings has beenalso explored.However,the experimental results wereoften contradictive and confusing.On …     

基于加工尺寸检测数据的刀具磨损及寿命研究

在对机械加工尺寸跟踪检测和对检测数据进行建模分析的基础上，提出对刀具磨损状况及寿命进行估计和预测的新途径；将加工质量控制与刀具监控统一起来，为自动化机械加工设备的换刀决策提供了一种新方法。     

An experimental study of tool wear and cutting force variation in the end milling of Inconel 718 with coated carbide inserts

Inconel 718 is a difficult-to-cut nickel-based superalloy commonly used in aerospace industry. This paper presents an experimental study of the tool wear propagation and cutting force variations in the end milling of Inconel 718 with coated carbide inserts. The experimental results showed that significant flank wear was the predominant failure mode affecting the tool life. The tool flank wear propagation in the up milling operations was more rapid than that in the down milling operations. The cutting force variation along with the tool wear propagation was also analysed. While the thermal effects could be a significant cause for the peak force variation within a single cutting pass, the tool wear propagation was believed to be responsible for the gradual increase of the mean peak force in successive cutting passes.     

Ni-P-金刚石粉化学复合镀层的性能

本文用扫描电镜对Ni－P－金刚石粉化学复合镀层的表面状态及内部形貌进行了观察，并用图像处理仪定量计算了复合镀层中金刚石粉的体积百分数。结果表明，随镀液中金刚石粉添加量增加，镀层中金刚石粉含量也增加；金刚石粉在镀层中呈均匀分布。同时，测定了复合镀层的力学性能，结果指出，复合镀层中金刚石粉含量增加，硬度、耐磨性提高。     

热变形后低铬耐磨铸铁的组织与耐磨性的关系

研究了低铬耐磨铸铁经40％热变形及不同方式冷却后的组织与耐磨性的关系。结果表明：该铸铁经热变形后的组织与耐磨性有良好的对应关系，其耐磨性随硬度的增加而增大，同时也与组织中碳化物的形状、大小及分布有关。     

Tool wear mechanism in turning of novel wear-resisting aluminum bronze

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Structure/property relationships in sintered and thermally sprayed WC-Co

Thermally sprayed WC-Co is widely used as a wear-resistant coating for a variety of applications. Although it is well established that thermal spray processes significantly affect chemistry, microstructure, and the phase distribution of WC-Co coatings, little is known about how these changes influence wear resistance. In this study, the microstructure and wear behavior of sintered and thermally sprayed WC-Co materials are examined. Powders of WC-12 wt% Co and WC-17 wt% Co were pressed and sintered, as well as thermally sprayed by high-velocity oxy-fuel (HVOF), air plasma spray (APS), and vacuum plasma spray (VPS) techniques. Results indicated considerable differences in the resulting microstructures, mechanical properties, and wear resistance. The thermally sprayed coatings showed anisotropic fracture toughness, whereas the sintered materials did not. It was also shown that a combined mechanical property/microstructure parameter, based on considerations of indentation fracture mechanisms, can be used in most cases to describe abrasive and erosive wear resistance of thermally sprayed WC-Co materials as follows: Wear resistance a whereK _ic is the indentation fracture toughness,H is hardness, andV ^Co _f is the volume fraction of cobalt. This relationship provides a means for assessing wear resistance of WC-Co coatings intended for industrial applications requiring abrasion and/or erosion resistance.     

高铝锌基合金粉末冶金材料及其摩擦学特性初探

初步研究了高铝锌基合金的粉末冶金工艺及其材料的摩擦磨损性能。通过气喷气冷法制取合金粉末，用压制后真空烧结的方法制备高铝锌基合金粉末冶金材料。实验结果表明，高铝锌基合金的粉末冶金试样在干摩擦和油润滑条件下的磨损率及摩擦系数均小于同一合金的铸造试样，但其压溃强度有待提高。在实验的基础上还探讨了该材料的耐磨减摩机理