Optimum design of aramid-phenolic/glass-phenolic composite journal bearings

Composite journal bearings are increasingly employed in large journal bearings for marine applications because composite materials can eliminate the seizure problem between the journal and the bearing during the start and stop periods of journals. Recently, aramid/glass reinforced phenolic composite journal bearings have been employed rather than the asbestos-phenolic composite bearings due to the health hazard of asbestos. In this work, the mechanical properties of aramid/glass reinforced phenolic composite were measured in order to analyze the stress on the journal bearing using the finite element (FE) method. The failure modes of the aramid/glass reinforced phenolic composite journal bearings were observed. The modified dimensions of aramid/glass reinforced phenolic composite journal bearings and the optimum interference fit amount were suggested using the FE-analysis results.     

Characteristics of wood–polymer composite for journal bearing materials

Wood is widely used as a construction material, automotive parts, and equipment for leisure-time amusement; however, its application on the journal bearing was restricted, because of its low strength and poor tribological characteristics.In this work, paulownia wood which has low density and high porosity was impregnated with polyethylene glycol (PEG), lubricant oil (SAE 30), release agent and epoxy to improve the mechanical properties and tribological characteristics. The ultrasonic vibration was given to the wood immersed in the acetone tub to remove debris generated during the cutting process of wood and to dissolve the membrane of lignin in the wood. From the test results, it was found that the PEG was the promising material to improve the physical properties of wood for journal bearings.     

Investigation of tribological properties of boronized Fe-based SAE 1020 and TS-DDK 40 journal bearings at high loads

In practice, ferrous based materials are not used because they show similar properties to shaft material and are known to cause adhesive wear in journal bearings. With boronizing process, adhesive wear can significantly be decreased. In this study, boronizing has been applied to some ferrous based (SAE 1020, TS-DDK 40) journal bearings. Wear experiments were done on SAE 1050 steel shaft as counter abrader with 100 N loads, and 1500 rpm for 5 h by using a radial journal bearing test rig. Boronizing treatment increased wear resistance of SAE 1020, TS-DDK 40 about 10–25, and 5–7 times respectively.     

Effect of boronizing and shot peening in ferrous based FeCu–Graphite powder metallurgy material on wear,microstructure and mechanical properties

Ferrous based materials manufactured by powder metallurgy (P/M) method are widely used in industry. These materials are very important because they do not require machining, have self-lubricated properties as journal bearing material, find applications in medical industry. In this study, powder metal parts were manufactured from ferrous based FeCu–Graphite composites by P/M method. Wear and mechanical test samples were manufactured and boronizing and boronizing + shot peening was applied to samples. Wear properties of these parts were investigated by wearing at 17 N load and 50 rpm on pin-on-disc wear test rig under dry conditions. Moreover, mechanical properties of powder parts were investigated in detail.     

加载速率对点阵铝力学行为及吸能特性的影响

目的研究基体材料和加载速率对点阵铝力学性能和吸能特性的影响规律。方法针对工业纯铝、6063铝合金为基体的点阵铝在3种不同的加载速率下进行压缩力学试验。结果加载速率从2mm/min增加到250 mm/min时,点阵纯铝的屈服强度增加了2 MPa,点阵6063铝合金的屈服强度增加了7.6 MPa;加载速率从250 mm/min增加到500 mm/min时,点阵纯铝的屈服强度变化不大,而点阵6063铝合金的屈服强度增加了8.2 MPa;当加载速率一定时,点阵6063铝合金的屈服强度要大于点阵纯铝。结论点阵6063铝合金的力学性能和单位体积吸能随着加载速率的增大而增大,并且点阵6063铝合金的力学性能和吸能特性要大于点阵纯铝。     

Structure of surface layers of metal matrix composites

Macroheterogeneous composite materials are good prospects for applications as friction pairs. Macroheterogeneous casted composite materials (MCCM) were developed primary for use in severe working conditions such as heavy loads, elevated temperatures, dusty environment, etc., and to replace bronze and other antifriction plain bearing materials. Due to the production technology, secondary nonferrous alloys and even scrap can be used to produce MCCM. These materials are nearly suitable for all friction parts and are unaffected by dust, sand, and water. The structure of MCCM consists of a matrix with uniformly distributed reinforcing particles (e. g., iron based alloys). This feature allows for a reduction in the consumption of nonferrous alloys up to 70%. Depending on the working conditions (sliding velocities, specific pressure, etc.) different compositions of MCCM can be produced. The application of casting technology provides a cost reduction of plain bearings up to 40% depending on the size and design of parts compared to bronze ones. Moreover, in some cases an abnormally low friction coefficient can be achieved and as a result a wearless condition can be obtained. It is obvious that the service life and performance of bearing materials depend on the processes occurring in the contact area of the friction pairs. So, in order to develop new bearing materials and predict their performance one must have information about the materials' behavior in the contact area. This paper presents some results on the investigations of macroheterogeneous casted composite materials' behavior during dry sliding of plain bearings.     

Microstructure,mechanical and tribological properties of high velocity oxy fuel thermal spray coating: A review

Iron alloy based amorphous coating materials have enormous potential in wide range of applications such as petrochemical, aerospace, ocean, and electronic communications due to their better mechanical properties, chemical properties, magnetic properties and tribological properties. The industrial applications of coating are increasing rapidly due to many advancements in the material development and coating deposition techniques. The present paper reviewed the recent progresses in deposition technologies, development of new high order alloys and composite based coating materials. In this regard, change in microstructure, elemental composition, mechanical and tribological properties on performance of iron alloy based coating properties were presented. It can be concluded that the tribological properties of coating is dependent on pre-coating and post-coating factors. Pre-coating factors include coating deposition techniques, coating layer thickness and coating parameters such as spray distance, oxygen flow rate etc. Post-coating factors include microstructure, hardness, fracture toughness and adhesion strength. Therefore, multi-criteria decision making techniques can be the best approach to find the optimum formulation of coating materials to achieve desired set of objectives under the conflicting criteria.     

有机硅溶胶-凝胶防腐蚀涂层研究进展

有机硅溶胶-凝胶涂层是指以烷基烷氧基硅烷为前驱体通过溶胶-凝胶技术制备的涂层。有机硅是分子水平上的有机-无机杂化分子,因此有机硅溶胶-凝胶涂层兼具了有机材料和无机材料的性能,并且能通过合理的调控有机和无机成分来获得所需的性能。其热稳定、耐刮擦性与无机材料的结合性能明显高于普通的有机材料,柔韧性与有机材料的结合性能明显高于一般的无机涂层。近年来,这种新型的、具有特殊性能的涂层被广泛研究用来保护金属材料(如铝、铁、镁、铜基材料)。介绍了有机硅溶胶-凝胶涂层涉及的基本反应、硅烷在金属表面上的成键机理以及在不同金属上的应用等方面的研究进展,并展望了有机硅溶胶-凝胶涂层应用前景及未来的研究方向。     

Ultrasonic Torsion Welding of Sheet Metals to Cellular Metallic Materials

One of the most important requirements for finding new applications for cellular metals is to integrate them in complex technical structures. The metal foams have to be joined to each other, or to sheet materials, by suitable joining techniques. The main topics of this paper are the ultrasonic torsion welding of cellular metallic materials to sheet metals and the investigation of the mechanical properties of the joints. The basic materials of foams and sheet metals were different aluminum and iron alloys. Depending on the materials used, weldings with tensile shear strengths of up to 25 MPa were realized. Using aluminum foam sandwich (AFS) and sheet metals, successful weldings were performed before and after the foaming process. Furthermore, it was possible to perform a successful foaming process with the unfoamed AFS/sheet metal joints. Microscopic investigations showed that the ultrasonic welding technique allows the joining of the metal foams with sheet metals without significant deformation of the joining partners. The temperatures during the welding process in the interface were below the melting point of the foams and the sheet metals.     

Comparative study on mechanical behavior of low temperature application materials for ships and offshore structures: Part I—Experimental investigations

Austenitic stainless steels (ASSs), aluminum alloys, and nickel alloys are potential candidate materials for cryogenic applications owing to their superior mechanical properties under low temperatures. In the liquefied natural gas (LNG) industry, these materials are widely used in the construction of thermal barriers for the insulation systems of storage tanks and LNG equipment. Among the typical material nonlinearities of ASSs, phase transformation induced plasticity (TRIP)-related nonlinear hardening characteristics have been experimentally and numerically reported in a number of detailed studies [1] and [2]; however, to the best of our knowledge, quantitative studies on aluminum and nickel alloys are not available for reference. Moreover, although these materials are used under various temperatures and strain rates, their temperature- and strain rate-dependent properties have not been determined thus far.In this study, a series of tensile tests is carried out under various temperatures (110-293 K) and strain rate (0.00016-0.01 s⁻¹) ranges as a preliminary step in the overall process for understanding the material characteristics of ASSs, aluminum alloys, and nickel alloys. On the basis of the experimental results, the essential mechanical properties are summarized in a quantitative manner in terms of the temperature and strain rate. The strain-hardening rate and strain sensitivity, which can be used to describe cryogenic temperature dependent material nonlinearities, are also proposed for the selected materials.     

Structure, mechanical and tribological properties of diamond-like carbon films on aluminum alloy by arc ion plating

The low hardness and poor tribological performance of aluminum alloys restrict their engineering applications. However, protective hard films deposited on aluminum alloys are believed to be effective for overcoming their poor wear properties. In this paper, diamond-like carbon (DLC) films as hard protective film were deposited on 2024 aluminum alloy by arc ion plating. The dependence of the chemical state and microstructure of the films on substrate bias voltage was analyzed by X-ray photoelectron spectroscopy and Raman spectroscopy. The mechanical and tribological properties of the DLC films deposited on aluminum alloy were investigated by nanoindentation and ball-on-disk tribotester, respectively. The results show that the deposited DLC films were very well-adhered to the aluminum alloy substrate, with no cracks or delamination being observed. A maximum sp³ content of about 37% was obtained at −100 V substrate bias, resulting in a hardness of 30 GPa and elastic modulus of 280 GPa. Thus, the surface hardness and wear resistance of 2024 aluminum alloy can be significantly improved by applying a protective DLC film coating. The DLC-coated aluminum alloy showed a stable and relatively low friction coefficient, as well as narrower and shallower wear tracks in comparison with the uncoated aluminum alloy.     

Development of composite spherical bearing

Carbon–phenolic woven composite materials are employed in heavy-duty bearings due to their inherent self-lubricating properties and thermal stability. In this work, a composite spherical bearing (CSB) composed of carbon–phenolic composite race and steel ball is developed to solve the seizure of conventional metal–metal spherical bearings for the elevation driving mechanism (EDM) of a future battle tank. In order to eliminate machining and assembling processes of the composite race, the composite race was manufactured with precise compression molding on the ball surface directly. Several self-lubricating particles were embedded to improve the tribological properties of the inner surface of the composite race. Also the compressive strength of the carbon–phenolic composite with interior wrinkles which were induced during the compression molding was measured to verify the applicability of the carbon composite spherical bearing to the future battle tank.     

Material selection for microelectronic heat sinks: An application of the Ashby approach

This paper focuses on optimal materials selection for microelectronic heat sinks to maximize the thermal, mechanical and electronic response based on electro-thermal heat transfer analysis using the Ashby approach. In this work, material indices have been developed for a number of properties of heat sinks supported by materials selection tables/graphs. It is found that aluminum based alloys/metals perform better than other available materials for microelectronic heat sinks.     

Adhesive joining of composite journal bearings to back-up metals

Composite journal bearings are becoming popular for marine applications because they eliminate the possibility of seizure to steel journals, which is a drawback of white metal bearings. However, a reliable joining method for composite bearings to steel housings is required. In this work, hybrid composite journal bearings composed of carbon/phenolic and glass/epoxy laminated composites were manufactured with different stacking sequences and adhesively bonded to steel housings. The effect of deformations of the composite bearings due to thermal residual stresses on the adhesive joint performance was estimated with respect to stacking sequence by finite element method, and compared to the experimental results. From the measured and experimental results, it was found that the outward radial deformation of the composite bearings was beneficial to the adhesively bonded joint strength of the hybrid composite journal bearing.     

高熵合金摩擦磨损性能的研究进展EI北大核心CSCD

近年来,高熵合金成为金属材料领域的研究热点。高熵合金处于相图中心区域,具有广阔的合金成分空间和组织结构形成可能;成分和制备工艺的协同调控,能够获得更丰富的组织结构;非常规的化学结构有望突破传统抗磨、润滑合金的性能极限。本文讨论了耐磨高熵合金的分类,分析了化学活泼金属、软金属、难熔金属的添加对高熵合金抗磨、润滑性能的影响规律;总结了非金属元素和陶瓷相的添加对高熵合金基复合材料摩擦磨损性能的影响;综述了热处理和表面工程技术对高熵合金表面组织结构和摩擦磨损行为的作用;讨论了苛刻工况下抗磨润滑高熵合金的设计方法。对未来高熵合金在摩擦磨损领域的研究和应用进行了展望,高熵合金在解决传统合金的瓶颈问题上具有巨大潜力,如在极端工况下实现稳定润滑抗磨、保证特定功能作用下实现抗磨。     

Analysis of tribological behaviour of aluminum-titanium carbide-basalt metal matrix composite

In the recent years, particulate reinforced aluminum based matrix composites are playing an important role in automobile and aerospace applications due to their enhanced properties. In this work, an attempt has been made to optimize the tribological behaviour of aluminum 7075 matrix reinforced with titanium carbide (3 percent weight) and basalt particles (2 percent weight) using Taguchi based grey relational analysis. Composites are fabricated according to american society for testing materials standard using stir casting method dry sliding wear tests were carried out using pin on disc apparatus as per Taguchi's L9 orthogonal array. Grey relational analysis was used to obtain the optimum process parameters for multiple quality characteristics such as wear rate and coefficient of friction. Then significant contribution of wear parameters was determined by analysis of variance. A confirmatory test was carried out to validate the test result. Finally, the micro structural investigation on the worn surfaces was performed by scanning electron microscope.     

Characteristics of carbon fiber phenolic composite for journal bearing materials

Journal bearing materials are required to have special characteristics such as compatibility with rubbing interface materials, embeddability for particles and wear debris, conformability to accommodate misalignment, thermal and corrosion resistance. Although white metals or babbitt metals used in most journal bearing have almost the required characteristics, they have possibility of seizure between the bearing material and the journal when the oil film is broken.

In this study, a hybrid composite journal bearing composed of carbon fiber reinforced phenolic composite liner and metal backing was manufactured to solve the seizure problem of metallic journal bearing materials because the carbon fiber has self-lubricating ability and the phenolic resin has thermal resistance characteristics. To estimate the wear resistance of carbon fiber phenolic composite, wear tests were performed at several pressures and velocities. The oil absorption characteristics, coefficient of thermal expansion, strength and stiffness of the composite were also tested. Using the measured stiffness values, the thermal residual stresses in the composite were calculated to check the reliability of the composite journal bearing.     

银基钎料在制造业中的研究进展

钎料的性能很大程度上决定了钎焊接头的质量和钎料的应用范畴.银基钎料作为一类非常重要的硬钎焊材料,其填缝能力优异,强度与黄铜、低碳钢接近,可钎焊除铝、镁合金等轻金属之外的所有金属材料.因此,银基钎料广泛应用于航空航天、超硬工具等制造领域,并且受到国内外钎焊界学者们的高度关注.然而,银基钎料的发展及应用过程中仍存在以下问题:第一,钎料中贵金属银含量偏高(一般高于45%),导致钎料使用成本高;第二,银基钎料挤压、轧制、拉拔等加工过程中不可避免地存在夹杂物,影响钎料的使用性能和连接质量;第三,有益金属或合金调控钎料及其连接性能的机制较为复杂,尚未完全研究清楚;第四,传统制备银基钎料的方法产能低下;第五,银基钎料在制造业领域的应用研究尚未见系统报道.国内外对于银基钎料钎焊性能及工程应用方面的研究主要集中于:(1)开发多种节银降银钎料,主要是有益元素调控银基钎料连接性能方面的研究;(2)改进钎料的传统加工方法,提出新的制造方法,如粉末电磁压制成形、钎焊过程中原位合成、快速凝固、镀覆扩散组合等;(3)研究杂质元素(C、Ca、S、Al、Fe、Bi、Pb、O、N 等)的影响;(4)银基钎料形态创新研究,如三明治复合钎料(中间为铜合金、两边为银钎料)、箔带钎料、镀锡银钎料等;(5)工程应用研究,银基钎料在航空航天、汽车制造、电力能源等工业领域起着不可替代的作用,但目前国内外仍缺乏系统阐述该方面研究的报道.因此,本文对近20年国内外有关银基钎料的研究报道进行了评述,重点讨论了合金元素对银基钎料性能的影响.首先对银基钎料研究现状进行详述,总结了Cu、Zn、Sn、Ga、In、Ni、Mn、Cd、Li、Ce、La、P、Si、Pr在银基钎料中的优缺点,归纳了杂质元素C、S、O、N、Ca、Al、Fe、Pb、Bi的恶化作用.其次对银基钎料在航空航天、汽车制造、电力能源、超硬工具、家用电器、眼镜行业等制造业中的应用研究进行详细介绍.最后提出银基钎料研究和应用中的不足,为银基钎料的深入系统研究及相关技术发展提供理论指导.     

Einsatz von Hartstoffbeschichtungen bei Spindellagern

Application of hard surface coatings for spindle bearings The demands on modern Machine Tools ascends continuously with the requirements of the production for high quality and short‐time processings. Particularly the increase of the processing‐ and removal times of the last years dues to higher loads of the main spindle bearing. The bearing as a central machine component characterises the performance of the Machine Tool for the cutting process and defines the reliability of the main spindle. The majority of the applicated spindle bearings are ball bearings. A large amount of the spindle fall‐outs is caused by a non adequate or defecitive lubrication and is effected by the tribological properties of the bearing elements. For the reduction of friction and wear nowadays several materials, coatings and lubrication additives are applied. Actual researches focus on the development of hard surface coatings (a‐C:H:W) with a nano structure for the rolling contact of ball bearings to increase their reliability. In this article the test of nano structured hard surface coating systems for the reduction of friction, warming and wear are presented. Thus the coating systems are verificated for the application in spindle bearings by pretesting. According to the evaluation the inner and outer raceway of standard‐hybrid bearings are coated and the adhesion in reference to rotational speed, resistance and wear performance at high acceleration is analysed. Concluding the emergency running properties at dry‐running condition is evaluated to identify the field of application for the coatings.     

Fe3Si基合金的制备及应用研究进展

Ｆｅ３Ｓｉ基合金具有优异的软磁性能,不仅有希望硅钢片（在高频信息领域）,而且还广泛用作音几视频磁头材料和卡片阅读器用磁头材料。本文综述了Ｆｅ３Ｓｉ基合金的制备工艺及应用,并结合我们的研究工作,分析了其研究现状,简要论述了其发展前景。