Papers by Keyword: Roughness

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Authors: Diana Maria Vrânceanu, Mihai Tarcolea, Ana Iulia Gherghilescu, Florin Miculescu, Mihai Cosmin Cotrut
Abstract: Typical applications of metallic dental materials include metal-ceramic restorations, dental implants or orthodontic systems. Due to their contact with human tissues, corrosion resistance is one of the main requirements for dental materials. In the present paper, the corrosion behaviour in Fusayama Meyer artificial saliva solution (pH=5.2) on a selection of four different metallic dental materials (316 L steel, Au based alloy, cp-Ti, Ti6Al4V alloy) currently used in dentistry were investigated. The metallic dental materials have been investigated in terms of electrochemical analysis, chemical composition, morphology before and after corrosion, wettability and roughness. The results showed a hydrophilic behaviour in the case of Au based alloy, cp-Ti and Ti6Al4V alloy, and hydrophobic for 316L stainless steel. Considering the main electrochemical parameters, the cp-Ti alloy exhibited better corrosion resistance in artificial saliva with pH=5.2, followed by Au based alloy, Ti6Al4V alloy and 316L stainless steel. The main objective of the present paper was to evaluate the corrosion behaviour, as in important factor in the selection of metallic materials used in dentistry.
Authors: Xue Ping Zhang, C.H. Wang, Jia Cai Li, Yiu Wing Mai, Lin Ye
Authors: M.Madhu Vamsi, V. Pradeep Kumar, S.H. Shariff
Abstract: The use of aluminum castings in the automotive industry has increased dramatically over the past two decades. The Al-Si system forms the basis of many important casting alloys, LM 0, LM 2, LM 4, LM 5, LM 6, LM 12, LM 13, LM 24 and LM 26 are the major cast alloys used in aerospace casting (e.g., fuel pump connectors) and premium automotive castings (e.g., suspension arms). The driving force for this increased use is vehicle weight reduction for improved performance, particularly fuel efficiency. In many cases the mechanical properties of the cast aluminum parts are superior to those of the cast iron or wrought steel parts being replaced; however, in some applications, defects in the cast microstructure undermine performance characteristics.
Authors: Pramote Poonayom, Voraya Wattanajitsiri, Kittipong Kimapong
Abstract: The feasibility study of the face-milling performance of hard-facing weld metal on JIS-S50C carbon steel was investigated on microstructure, chip characteristics, wear properties, and surface roughness. Discontinuous chips were found in all machining conditions. No buffering weld metal (No buffering layer, NBL) produces longer and thicker chips than that of the buffering weld metal (Buffering layer, BL). The flank wear of the cutting tool edge increases with the cutting length of the test specimen. The maximum wear of 850 mm was found in a wet condition of the NBL weld metal which is about 4 times higher than that of the base metal. High hardness value of the NBL weld metal produces a higher flank wear of the cutting tool edge than that of the BL weld metal. After comparing the wear of the cutting tool edge in wet and dry conditions, it was found that the dry condition exhibits a smaller flank wear than that of the wet condition. In the wet condition, more amount of coolant oil droplets cannot penetrate into the chip-tool interface and then provides an insufficient amount of lubricant in order to decrease the cutting temperature. Therefore wet condition produces severe wear of the cutting.
Authors: Jun Feng Peng, Jun Hong, Yan Zhuang
Abstract: Thermal contact resistance plays an important role in many domains, such as microelectronics and nuclear reactors. This paper proposes a more comprehensive model for the prediction of constriction resistance of rough contact between nominally flat surfaces in vacuum. Firstly, a 3D geometrical asperity contact model is proposed based on the analysis of the profile of actual engineering surface. In this model, the contact is not simplified as a rough surface contacting with a perfectly smooth surface, but described as two rough surfaces. Oblique contact is considered and the effects of several parameters such as the shape of the asperity, the depth of interference, and the radial distance between the centerlines of the contacting asperities are investigated. Some mathematical derivations for constriction resistance are performed, and a series of numerical simulations are also carried out, covering a wide range of values of these parameters in practice applications. A comprehensive correlation for constriction resistance as a function of these parameters is finally obtained by nonlinear curve fitting, and it is validated through some comparisons and it can be used to predict more accurately the thermal contact resistance between rough surfaces.
Authors: Chao Hui Zhang, Jian Bin Luo, Qiu Ying Chang
Abstract: Chemical mechanical polishing (CMP) is a widely used technique to achieve high level of global and local planarity required in modern integrate circuit (IC) industries and hard disk manufacturing process, etc., which pleas for concentrate researches. The main purpose of the present research is in an attempt to express the counterintuitive experimental aftermath: the ‘negative’ pressure, i.e., a suction force occurred in conventional commercial CMP process. A preliminary two tiers wafer-scale flow model for CMP is presented considering the roughness as well as the elasticity of the bulk pad substrate. Numerical simulations were conducted to elucidate the contact pressure and flow pressure distributions. The results show that a divergence region appears near the leading edge, which contributes to the suction pressure. A stress-richened area near the edges will give rise to over polishing. The research aftermaths agree well with the experiments, that validate the proposed analysis to some extend. This will shed lights on the mechanism of CMP process, which for a long time is considered as a black art where empirical or semi-empirical data are dependent upon to optimize the CMP parameters.
Authors: Jorge Salguero, Julia Gerez, Moisés Batista, J. Enrique Garófano, Mariano Marcos Bárcena
Abstract: The UNS R56400 is a Titanium alloy commonly used in the aircraft industry. This alloy can be processed by machining depending on its final application. Drilling and turning are the most usual machining processes for working this alloy. Aerospace requirements involve high quality levels and, if possible, an on-line monitoring in order to preserve the workpiece design conditions. The machining process can be monitored by different methods. One of the most single methods involves the analysis of the finishing quality of the workpieces. This analysis is usually related to micro and macro geometrical considerations. In this paper a study of the finishing quality of dry turned UNS R56400 Ti alloy has been achieved. This study has been carried out based on the analysis of straightness and parallelism deviations as functions of cutting parameters, such as feed and cutting speed.
Authors: Armansyah Ginting, Mohammed Nouari, Nadhir Lebaal
Abstract: In this paper, the surface integrity is studied when machining the aeronautical titanium alloys. Surface roughness, lay, defects, microhardness and microstructure alterations are studied. The result of surface roughness judges that the CVD-coated carbide fails to produce better Ra value than the uncoated. Lay is characterized by cutting speed and feed speed directions. Feed mark, tearing surface, chip layer formation as built up layer (BUL), and deposited microchip are the defects. Microhardness is altered down to 350 microns beneath the machined surface. The first 50 microns is the soft sub-surface caused by thermal softening in ageing process. Microstructure alteration is observed in this sub-surface. Down to 200 microns is the hard sub-surface caused by the cyclic internal work hardening and then it is gradually decreasing to the bulk material hardness. It is concluded that dry machining titanium alloy is possible using uncoated carbide with cutting condition limited to finish or semi-finish for minimizing surface integrity alteration.
Authors: Shenq Yih Luo, Ching Win Shih, M.H. Chen
Abstract: The purpose of this paper is to investigate the performance of grinding alumina for the specific designed tools containing a controlled diamond protrusion and arrangement. The grinding forces, workpiece roughness and diamond wear at changing the depth of cut and feed under a fixed spindle speed were studied in the experiments. The experiment results showed that the grinding forces with the increase of feed slowly increased. However, the grinding forces with the increase of depth of cut showed a relatively larger rise. When the depth of cut reached to 0.09 mm that is about one fourth of diamond size, the axial grinding force obtained above about 20 N to cause some weaker or higher protrusive diamonds to produce a relatively larger fracture or pull-out. Furthermore, under a larger depth of cut and a larger feed rate the workpiece roughness obtained was the poorer. When diamond tool was employed for a longer time test under the depth of cut less than about one fourth of grit diameter, diamonds mainly displayed an attritious wear and the alumina roughness was about Ra 1.2-2.2 μm. This designed diamond tools are feasible for grinding alumina.
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