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1.
王均安 《上海大学学报(英文版)》2001,5(3):241-246
A review was made on the research progress of wear behavior of sintered steels in recent years.Wear is not an intrinsic property of sintered steels,which is strongly influenced by the wear test conditions.Howerver,many other factors that determine the mechanical properties of sintered steels also affect the wear behavior.Porosity has different effects on the wear of sintered steels depending on the application conditions.Under dry sliding condition ,higher porosity results in lower wear resistance.The influence of microstructures on wear resistance is in the order;Carbide,martensite,bainite and lamellar pearlite,The wear resistance increases with hardness,but this relationship changes with the porosity and microstructures of sintered steels. 相似文献
2.
AlSi12 samples were prepared by selective laser melting (SLM) under different processing conditions in order to obtain different top surface morphologies, where single tracks were produced using a fixed processing parameter to reveal the mechanism of the single track on different morphologies. The results show that the morphologies of single tracks changed with roughness of the top surface (Top Ra) of SLM parts, reflected in the variation of wetting angles on the surface processed previously as well as in dimensions of height, width, and depth at the cross-section of each single track. These changes were mainly caused by different wettability and flow behavior of the molten metal under various solidification environments of the single track during SLM. A poor solidification environment in which numerous balls existed limited an effective wetting behavior of molten metal on a previously processed surface of a SLM sample because of an increasing solid-liquid contact area, thus causing dramatical instability of the melt pool and attendant inferior processability of the single track. Meanwhile, under the action of surface tension, the molten metal had a high tendency to transfer into a pore near the single track to form an extending track or flow toward an upper region of melt to form a balling track, hence showing various morphologies of single tracks. This study proposes a theory of the solidification mechanism of single track on the non-ideal surface to provide a better understanding of the SLM processing of Al-Si alloy. 相似文献
3.
利用反应等离子熔覆技术、以Fe-Cr-C-W-Ni合金粉末为原料,在Q235钢表面制得了Cr7C3高铬铁基金属陶瓷增强耐磨复合涂层。利用SEM、EDS和X射线衍射分析了涂层的显微组织,在室温干滑动磨损试验条件下测试了涂层的耐磨性。结果表明:反应等离子熔覆Cr7C3高铬铁基金属陶瓷增强耐磨复合涂层硬度高、组织均匀、与基材之间为完全冶金结合;涂层在室温干滑动磨损试验条件下表现出优异的耐磨性,涂层磨损的质量损失随载荷增加十分缓慢,涂层具有优异的载荷特性。 相似文献
4.
Progress in selective laser melting equipment,related biomedical metallic materials and applications
Yu-chao Bai Fan Fu Ze-feng Xiao Ming-kang Zhang Di Wang Yong-qiang Yang Chang-hui Song 《浙江大学学报(A卷英文版)》2018,19(2):122-136
This paper introduces the latest achievements of the South China University of Technology in basic research on selective laser melting (SLM), applications of SLM manufacturing equipment, and biomedical metallic materials manufactured by SLM. First, we describe the use of DiMetal-100 equipment to study the process parameters, microstructure, and mechanical properties of three kinds of metal medical materials manufactured by SLM, including 316L stainless steel, CoCrMo, and Ti6Al4V. Second, we describe the application of 316L stainless steel manufactured by SLM to personalized lingual orthodontic brackets and surgical guide plates, the application of CoCrMo manufactured by SLM to knee prostheses and dental crowns and bridges, and the research results of Ti6Al4V manufactured by SLM in the treatment of pelvic fracture bone plates and personalized cranial prostheses. Finally, we introduce the development directions and research plans for SLM technology at the South China University of Technology, including the manufacture of a new porous structure by SLM directly, the manufacture by SLM of various material products simultaneously, SLM + material-reducing hybrid manufacturing, improving the negative feedback systems of SLM equipment, and developing SLM manufacturing processes using ceramics and new metals. 相似文献
5.
张扬龙 《福建工程学院学报》2014,(3):241-245
对某机床厂的龙门导轨磨床MMA52160A利用铁谱分析技术的油样进行定期检测,及时地掌握龙门导轨磨床的磨损状况。通过实验与分析发现,在检测时间段内导轨磨床内部存在着正常磨损、切削磨损、滚滑复合磨损磨粒以及铁的氧化物,在数量上以正常磨损居多,其它类型磨粒数量较少,可以判断导轨磨床仍处于正常运行状态。 实验表明,铁谱分析技术可以对机床的运行状态进行预报故障;同时,可合理地确定机床的换油周期,节省油料,做到科学润滑,以延长龙门导轨磨床的使用寿命。 相似文献
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7.
Because of the different ways in which contact materials work, the basic requirements for silver metal oxide contact materials are different. They are anti-welded and anti-erosion when closed, anti-erosion when broken, and arc easily moved and have smaller contact resistance. In this paper, La2O3 is used as a stable oxide in contact material to replace CdO. A new type of Ag/SnO2-La2O3-Bi2O3 contact material is first obtained through using powder metallurgical method. Then electrical contact material parameter tester is used to test the electrical contact performance of the contact material. Through experiments, the arcing voltage and current curves, arcing energy curves, fusion power curves while broken and contact resistance while closed were obtained. Analysis of the results showed that the addition of La2O3 makes the contact material have the following advantages: smaller electrical wear, smaller arc energy, smaller contact resistance and arc is more easily extinguished. 相似文献
8.
木材陶瓷的制备工艺现状及展望 总被引：1，自引：0，他引：1
陈璐 《毕节师范高等专科学校学报》2014,(8):90-94
木材陶瓷是近年来开始研究的一种新型环境材料,具有良好的力学性能和电、磁、耐磨和摩擦等方面的独特性能。在总结了木材陶瓷特点以及木材陶瓷的制备工艺,如熔融金属渗入法、有机聚合物前驱体法、生物模板法等的基础上,指出了现有木材陶瓷的不足,提出了木材陶瓷未来的发展方向。 相似文献
9.
利用自行研制的往复式摩擦磨损实验机对内燃机活塞环-缸套进行了摩擦磨损实验,主要测试载荷、转速以及润滑方式对摩擦副磨损的影响,应用称重法测量活塞环的磨损量,结果表明：在极限载荷下,活塞环的磨损量随着载荷的增大而加剧;若转速较低,难以形成润滑油膜,磨损加剧;必须使摩擦副处于一种弹性流体动力润滑状态,才能降低磨损量。 相似文献
10.
Elastohydrodynamic Lubrication Studies on Effects of Crowning Value in Roller Bearings 总被引：1，自引：0，他引：1
CHENXiao－yang SHENXue－jin 《上海大学学报(英文版)》2001,5(1):76-81
The purpose of this paper is to present a comparison of numerical calculations and experiment results of optical interferometry in finite line contact for the elastohydrodynamic lubrication(EHL)problem of Lundberg‘s profiled cylindrical roller under the conditions of flooded state,moderate load and material parameter.It shows clearly the effects of crowning value on the variations of oil film shape and thickness.The agreement between numerical analysis and experiment results is very good.The results indicate there must be an optimum crowning value that will induce the thickest and most even oil film in EHL state for a given working condition,and this value is larger than the design value in dry contact state for the same working coditiona. 相似文献
11.
由于高速搅拌机中的主要损耗零件耐磨片要经常更换,而充填站的高速搅拌机在工作位置箱盖是打不开的,必须把搅拌机挪开。为了减少工作量,一方面不移动搅拌机就能更换耐磨片,把原来的上下箱装拆结构改成壳体加端盖的左右装拆结构,并对壳体内的零件结构做了适当调整;另一方面,提高转子耐磨片的耐磨性,延长它的使用寿命。左右装拆结构使得搅拌的液体容易泄露,对密封性能要求提高,重新设计了合适的密封结构。 相似文献
12.
Dynamic behaviour of automotive dry clutches depends on the frictional characteristics of the contact between the friction lining material, the flywheel, and the pressure plate during the clutch engagement process. During engagement due to high interfacial slip and relatively high contact pressures, generated friction gives rise to contact heat, which affects the material behaviour and the associated frictional characteristics. In practice excess interfacial slipping and generated heat during torque transmission can result in wear of the lining, thermal distortion of the friction disc, and reduced useful life of the clutch. This paper provides measurement of friction lining characteristics for dry clutches for new and worn state under representative operating conditions pertaining to interfacial slipping during clutch engagement, applied contact pressures, and generated temperatures. An analytical thermal partitioning network model of the clutch assembly, incorporating the flywheel, friction lining, and the pressure plate is presented, based upon the principle of conservation of energy. The results of the analysis show a higher coefficient of friction for the new lining material which reduces the extent of interfacial slipping during clutch engagement, thus reducing the frictional power loss and generated interfacial heating. The generated heat is removed less efficiently from worn lining. This might be affected by different factors observed such as the reduced lining thickness and the reduction of density of the material but mainly because of poorer thermal conductivity due to the depletion of copper particles in its microstructure as the result of wear. The study integrates frictional characteristics, microstructural composition, mechanisms of heat generation, effect of lining wear, and heat transfer in a fundamental manner, an approach not hitherto reported in literature. 相似文献
13.
WANG Jing-qin WANG Hai-tao WEN Ming ZHU Yan-cai 《浙江大学学报(A卷英文版)》2007,8(3):459-463
Because of the different ways in which contact materials work, the basic requirements for silver metal oxide contact materials are different. They are anti-welded and anti-erosion when closed, anti-erosion when broken, and arc easily moved and have smaller contact resistance. In this paper, La2O3 is used as a stable oxide in contact material to replace CdO. A new type of Ag/SnO2-La2O3-Bi2O3 contact material is first obtained through using powder metallurgical method. Then electrical contact material parameter tester is used to test the electrical contact performance of the contact material. Through experiments, the arcing voltage and current curves, arcing energy curves, fusion power curves while broken and contact resistance while closed were obtained. Analysis of the results showed that the addition of La2O3 makes the contact material have the following advantages： smaller electrical wear, smaller arc energy, smaller contact resistance and arc is more easily extinguished. 相似文献
14.
胡登卫 《南阳师范学院学报》2010,9(6):49-55
聚对苯二甲酸丙二醇酯（PTT）是一种具有广泛应用前景的新型聚酯纤维,兼有聚对苯二甲酸乙二酯（PET）、聚对苯二甲酸丁二酯（PBT）、聚酰胺（PA）的优良性能,其蓬松性、回弹性、柔韧性、抗污性、耐磨性、抗潮性、染色性等使用性能和加工性能较好.合成PTT,以Ti及其化合物为催化剂,采用直接酯化法路线为佳,酯化时所需反应温度高于PET,缩聚温度低于PET,各阶段反应时间比PET短.根据我国国情,开发研究1,3-丙二醇（1,3-PD）、PTT具有极其重要的战略意义. 相似文献
15.
采用HL-5000型横流CO2激光加工机在TC4钛合金表面激光熔覆TiC+Ti和TiC+Ti+F102复合涂层。通过SEM、EDAX、XRD、HXD-1000TMC型显微硬度计,HT-600型高温摩擦磨损试验机,分析了熔覆层的显微组织、成分、物相,测试了激光熔覆层的显微硬度和滑动摩擦磨损性能。结果表明,激光熔覆制备的TiC复合涂层与基体呈冶金结合,在TiC+Ti激光熔覆层中,熔覆层的组织是在Ti基体上分布着TiC树枝晶;在TiC+Ti+F102激光熔覆层中,TiC颗粒发生了部分溶解,熔覆层的组织是在Ti基和γ-Ni基的基体上分布着细小的TiC颗粒和TiC树枝晶。TiC+Ti激光熔覆层的硬度约为700 HV0.1,TiC+Ti+F102激光熔覆层的硬度约为800 HV0.1,两种复合涂层耐磨性均比TC4钛合金显著提高。 相似文献
16.
为了分析非晶合金的力学特性,提出了一种可实时观测大块非晶合金摩擦磨损变形特性的实验方法.实验分两步进行,首先对Zr基大块非晶合金与铜、铁、塑料进行同速度的干摩擦实验,然后单独对Zr基大块非晶合金进行不同速度下的干摩擦实验,都提取摩擦过程中的摩擦力信号,并利用扫描电子显微镜观察磨损形貌.与其他材料对比,分析Zr基大块非晶合金材料的摩擦磨损变形特性,从而确定其摩擦磨损主要是塑性变形和脆性断裂综合作用结果.另外随着转速提高,磨粒磨损使多角度的摩擦力高频率出现. 相似文献
17.
Hypersonic vehicles subjected to strong aerodynamic forces and serious aerodynamic heating require more stringent design for an infrared window. In this paper, a finite element analysis is used to present the distributions of thermal and stress fields in the infrared window for hypersonic vehicles based on flowfield studies. A theoretical guidance is provided to evaluate the influence of aerodynamic heating and forces on infrared window materials. The aerodynamic heat flux from Mach 3 to Mach 6 flight at an altitude of 15 km in a standard atmosphere is obtained through flowfield analysis. The thermal and stress responses are then investigated under constant heat transfer coefficient boundary conditions for different Mach numbers. The numerical results show that the maximum stress is higher than the material strength at Mach 6, which means a failure of the material may occur. The maximum stress and temperatures are lower than the material strength and melting point under other conditions, so the material is safe. 相似文献
18.
Compacted graphite cast iron (CGI) has been the material for high-power diesel engines recently, but its increased strength causes poor machinability. In this study, coated and uncoated carbide tools were used in dry milling experiment and FEM simulation to study the machinability of CGI and wear behaviour of tools. The experimental and FEM simulation results show that coated tool has great advantage in dry milling of CGI. SEM and EDS analysis of tool wear indicate the wear morphology and wear mechanism. Adhesive wear is the main mechanism to cause un-coated tool wear, while abrasive wear and delamination wear are the main mechanism to cause coated tool wear. Stress and temperature distribution in FEM simulation help to understand the wear mechanism including the reason for coating peeled off. 相似文献
19.
本文通过回顾12条基于研究的教学设计原则,说明了如何设计计算机辅助多媒体教学材料来促进学习。首先介绍了多媒体原则(根据五个对照实验得到的中值效应量为d=1.67),其主张在计算机辅助教学中,语词和图像同时呈现的效果比只呈现语词的效果要好。无关认知加工做的是和教学目标无关的事情。为了减少无关认知加工,提出的教学原则有聚焦要义(d=0.70)、标记结构(d=0.46)、控制冗余(d=0.87)、空间邻近(d=0.79)和时间邻近(d=1.30)。基本认知加工的功能在于对基本材料进行心理表征。为了调节基本认知加工,提出的教学原则有分段呈现(d=0.70)、预先准备(d=0.46)和双重通道(d=0.72)。生成认知加工的功能是为了建构材料的意义。为了促进生成认知加工,提出的教学原则有个性化(d=0.79)、人声化(d=0.74)和具身化(d=0.36)。部分原则有边界条件,例如有的原则对新手学习者比对专家学习者更有效。 相似文献
20.
王党利 《邢台职业技术学院学报》2014,(3):84-88
本文针对切割丝不耐磨问题,通过分析钢丝磨损机理,研发加工工艺管理系统。综合改变压缩率、不同模具参数、不同黄铜丝生产工艺对切割钢丝表面硬度的影响等一系列的参数分析,从而得到提高钢丝寿命、不影响其它性能的工艺参数,进而改善钢丝耐磨性,改善硅片成材率。因此,本文研究的多丝切割加工工艺管理系统具有非常重要的实际应用价值。 相似文献