Current Issue : July - September Volume : 2012 Issue Number : 3 Articles : 7 Articles
This paper discusses the application of noncontact methods to analyze the tire-surface contact interaction. This approach uses the\r\ntire test bench with the set of contact patch monitoring based on image processing procedures. The first part of this paper presents\r\nthe results of experimental estimation of the contact patch area depending on the normal wheel load and inflation pressure for\r\ndifferent car tires. The data were obtained for test bench conditions on the basis of the visual processing of tread footprint. Further,\r\nthe contact length in the cohesion area during wheel rolling for single points on the tire profile has been chosen as a benchmark\r\ncriterion. This paper has analyzed the influence of the wheel normal load and tire inflation pressure on the contact length with\r\nsmall rolling velocities. The results of the investigations are given for winter and racing tires with different grades of wear....
In this experimental study, the cutting performance of ball-end mills in high-speed dry-hard milling of powder metallurgical steels\r\nwas investigated. The cutting performance of the milling tools was mainly evaluated in terms of cutting length, tool wear, and\r\ncutting forces. Two different types of hardened steels were machined, the cold working steel HS 4-2-4 PM (K490 Microclean/66\r\nHRC) and the high speed steel HS 6-5-3 PM (S790 Microclean/64 HRC). The milling tests were performed at effective cutting\r\nspeeds of 225, 300, and 400 m/min with a four fluted solid carbide ball-end mill (D0 = 6, TiAlN coating). It was observed that\r\nby means of analytically optimised chipping parameters and increased cutting speed, the tool life can be drastically enhanced.\r\nFurther, in machining the harder material HS 4-2-4 PM, the tool life is up to three times in regard to the less harder material HS\r\n6-5-3 PM. Thus, it can be assumed that not only the hardness of the material to be machined plays a vital role for the high-speed\r\ndry-hard cutting performance, but also the microstructure and thermal characteristics of the investigated powder metallurgical\r\nsteels in their hardened state....
Electrical contacts are usually plated in order to prevent corrosion. Platings of detachable electrical contacts experience wear\r\nbecause of the motion between contacts. Once the protecting platings have been worn out, electrical contacts will fail rapidly due to\r\ncorrosion or fretting corrosion. Therefore the wear resistance of the platings is a very important parameter for the long lifetime of\r\nelectrical contacts.Many measures which improve the wear resistance can diminish the conductivity of the platings. Due to the fact\r\nthat platings of electrical contacts must have both a high wear resistance and a high electrical conductivity, the manufacturing of\r\nhigh performance platings of electrical contacts poses a great challenge. Our study shows firstly the correlation between the wear\r\nresistance of platings and lifetime of electrical contacts and then the measures, which improve the wear resistance without impairing\r\nthe electrical performance of the contacts....
The mixed and fluid film lubrication characteristics of plain journal bearings with shape changed by wear are numerically\r\nexamined. A mixed lubrication model that employs both of the asperity-contact mechanism proposed by Greenwood and\r\nWilliamson and the average flow model proposed by Patir and Cheng includes the effects of adsorbed film and elastic deformation\r\nis applied. Considering roughness interaction, the effects of the dent depth and operating conditions on the loci of the journal\r\ncenter, the asperity-contact and hydrodynamic fluid pressures, friction, and leakage are discussed. The following conclusions\r\nare drawn. In the mixed lubrication regime, the dent of the bearing noticeably influences the contact and fluid pressures. For\r\nsmaller dents, the contact pressure and frictional coefficient reduce. In mixed and fluid film lubrication regimes, the pressure\r\nand coefficient increase for larger dents. Furthermore, as the dent increases and the Sommerfeld number decreases, the flow rate\r\ncontinuously increases....
Recently, ââ?¬Å?tribocorrosion,ââ?¬Â a research area combining the science of tribology and corrosion, has drawn attention from scientists\r\nand engineers belonging to a wide spectrum of research domains. This is due to its practical impact on daily life and also\r\nthe accompanying economical burdens. It encompasses numerous applications including the offshore, space, and biomedical\r\nindustry, for instance, in the case of artificial joints (Total Hip Replacement, THR) in orthopedic surgery, where implant metals are\r\nconstantly exposed to tribological events (joint articulations) in the presence of corrosive solutions, that is, body fluids. Keeping\r\nthe importance of this upcoming area of research in biomedical applications in mind, it was thought to consolidate the work in this\r\narea with some fundamental aspects so that a comprehensive picture of the current state of knowledge can be depicted. Complexity\r\nof tribocorrosion processes has been highlighted, as it is influenced by several parameters (mechanical and corrosion) and also due\r\nto the lack of an integrated/efficient test system. Finally a review of the recent work in the area of biotribocorrosion is provided, by\r\nfocusing on orthopedic surgery and dentistry....
Tool wear and workpiece overcut have been studied in electrical discharge machining process with rotational external magnetic\r\nfield and rotational electrode. Experiments have been divided to three main regimes, namely, low-energy regime, middle-energy\r\nregime, and high-energy regime. The influence of process parameters were investigated on electrode wear rate and overcut. Results\r\nindicate that applying a magnetic field around the machining gap increases the electrode wear rate and overcut. Also, rotation of\r\nthe tool has negative effect on overcut....
Use of biodiesel produces engine oil dilution because of unburned biodiesel impinging on cold walls of the combustion chamber,\r\nbeing scrapped to the oil pan, and leading to changes of oil friction, wear and lubricity properties. In this paper, mixtures of SAE\r\n15W-40 oil, which were contaminated by known percentages of the biodiesels from canola oil, peanut oil, soybean oil, and chicken\r\nfat, were tested in a pin-on-disk tribometer. A contact was employed of AISI 1018 steel disk and AISI 316 stainless-steel ball for\r\npin material, and friction force and specific wear were measured. Wear on the disk surfaces showed that any degree of mineraloil\r\ndilution by the tested biodiesels reduces the wear protection of engine oil even at small mixture percentages. However, these\r\nreductions were not substantially different than those observed for same percentages of dilution of mineral oil by fossil diesel.\r\nThe tested mixture of oil contaminated with animal fat feedstock (e.g., chicken fat) biodiesel showed the best wear behavior as\r\ncompared to those for the other tested mixtures (of mineral oil with vegetable feedstock biodiesel dilutions). Obtained results are\r\ndiscussed as baseline for further studies in a renewable energy multidisciplinary approach on biofuels and biolubes....
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