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摘要: In present study HVOF spraying process had been employed for depositing 93(WC-Cr3C2)-7Ni, 75Cr3C2-25NiCr, 83WC-17CO and 86WC-10CO-4Cr coatings on ASME SA213 T22. All the coatings were found dense and uniform having thickness between 200-250µm. All the coatings on ASME SA213 T22 used in present studies have provided resistance to corrosion in coal fired boiler environment in superheater zone when exposed for 10 cycles at 900°C. Each cycle consists of 100 hours heating followed by 1 hour cooling at ambient conditions. X-ray diffraction (XRD), Scanning Electron Microscopy/Energy Dispersive Spectroscopy (SEM/EDS) techniques were used to analyse corrosion products. The results showed that among coated specimens 93(WC-Cr3C2)-7Ni and 75Cr3C2-25NiCr coatings has shown maximum and minimum resistance to corrosion respectively. The better corrosion resistance of 93(WC-Cr3C2)-7Ni coated steel alloys may be attributed to the formation of thin band of oxides of nickel, chromium; and carbides of tungsten.
摘要: The low velocity impact is a common phenomenon which occurs in fiber reinforced polymer composite products like LPG cylinders, fighter aircraft fuel drop tanks, aircraft wing surfaces, sports goods etc. The consequences of low velocity impact will create a considerable damage and ultimately lead to a premature failure of the structure. Hence the polymer composites for engineering applications must be provided with a better design solution. From the literature survey it is observed that, the response of composite laminates subjected to quasi-static loading, exhibits similar results as that of low velocity impact. Polymer reinforced composites are poor in damage tolerance with better strength to weight ratio than conventional materials. However composite materials can be tailored to meet the design requirements by manipulating fiber orientations and laminae stacking sequence. In the present paper, principles of classical laminate theory are considered for analysis. FEM is implemented for thorough understanding of the failure mechanism of each laminate by layer wise. Simulated quasi-static loading tests and observed the layer wise distribution of transverse strain intensity. The experimental setup is designed and fabricated as per ASTM D 6264 standards. The E-glass/epoxy composite laminate is quasi-statically loaded at its center by a steel ball indenter of diameter 8.7mm and its response is measured by the degree of opacity or translucency in terms of interlaminar and intra-laminar damage area. The stacking sequence of composite laminates are chosen as [00/600]12, [00/750]12 and [00/900]12. The damage areas obtained from numerical analysis are in good agreement with experimental results.
摘要: Composite materials have increasingly being used on aerospace industry due to its low density and high mechanical strength as well as high fatigue endurance. Consequently, increase attention is being devoted to study the fatigue behavior of these materials under cyclic loads. This work presents results on fatigue under shear stress by using the Iosipescu method. For fatigue testing a cured neat epoxy resin and a carbon fiber/epoxy composite having orientations of 0/90o and ± 45o in relation to the loading axis were tested by using the Iosipescu coupon. Firstly, the specimens were submitted to static tests in order to obtain the ultimate shear strength (τ) and the in-plane shear modulus (G12). Further batches of specimens were tested under definite levels of stress ratio as a function of number of cycles. So, the S-N curves were obtained. The maximum number of cycles was set at 120,000 cycles, which corresponds approximately to two times the life of a structural element from a civilian airplane. The stress ratio used was R=0.1 and R=0.5. At the limit of 120,000 cycles the epoxy resin exhibited a shear strength of 18 MPa, for a stress ratio of R=0.5, and 10 MPa for a stress ratio of R=0.1. The carbon fiber/epoxy 0/90o composite, at the limit of 120,000 cycles, showed a shear strength of 84 MPa for a stress ratio of R=0.5, and 64 MPa for a stress ratio of R=0.1. For the carbon fiber/epoxy ±45o composite, at the limit of 120,000 cycles, a shear strength of 105 MPa and 90 MPa, where found for a stress ratio of R=0.5 and R=0.1, respectively.
摘要: Wire Electric Discharge Machining is one of the non-traditional machining process to develop and generate many complicated shapes with very much accuracy. Improper selection of cutting parameters may result in erroneous configuration and shapes. When cutting curve profile in WEDM process, it has been found out that the magnitude of corner inaccuracy in terms of uncut area at the corner of the die is much higher than the corner inaccuracy at the corner of the punch due to the excess material removal. In this study entropy based grey relation analysis has been used to identify the optimal cutting parameter for WEDM process. ANOVA has been adopted to distinguish the most consequential factors. Inconel 718 has been used as a work-piece material which is a new advance material and it has wide range of industrial application. The characteristics of the machined surfaces of Inconel 718 alloy have also been analyzed through scanning electron microscope (SEM).
摘要: WEDM process is newly emerged machining method in past decade which uses spark erosion method for the material removal while machining using high current. This method has shown high dimensional accuracy but gave rise to low machining rate. In current age of ultramodern technology a machine should satisfy more than one purpose. Therefore better Surface finish with dimensional accuracy for WEDM process has been very well presented in this paper with both the responses taken for study simultaneously. The paper deals with WEDM Process variables pulse ON/OFF time, peak current, servo voltage and wire feed rate. The paper also details about reduction of iterations for the desired output by using TLBO (Teaching-Learning Based Optimization) technique. The convergence graphs have been plotted in Minitab software to justify the reduction in iterations.
摘要: A new type of road material was made by modifying coal tar pitch with a kind of self-made compound modifier. According to technical standards “Standard Test Methods of Bitument and Bituminous Mixture for Highway Engineering” JTG E20-2011, the properties of modified coal-tar pitch (M-CTP) and its mixture were studied, the softening point, ductility and penetration of M-CTP were all up to standard. Moreover, the properties of M-CTP mixture were also investigated, the wheel tracking test showed the M-CTP mixture has a dynamic stability of 1511n/mm, which was higher than the requirement of ≥800n/mm. The beam bending test results indicated the low-temperature property of M-CTP mixture reach the standard of AH-70 mixture. The Freeze-thaw split test demonstated the water stability of M-CTP mixture meet the standard for using in asphalt pavement. In all, a new type of road material by modifying coal tar pitch was obtained and its properties meet the standard of AH-70. The additive amount of modifier was 15% and the optimum effect was attained. Moreover, the ultraviolet and visible spectrophotometer was used to test the content of benzopyrene (BaP) in CTP before and after modified by M. And the content decreased from 1.92% to 1.62%.
摘要: Geothermal systems have a big draw as a provider for free thermal energy for electrical generation. The resource based on fracture networks that permit fluid circulation, and allow geothermal heat to be extracted. Most geothermal resources occur in rocks that posses lack fracture permeability and fluid circulation. Hence, the fluid will be heated due to the Hot Dry Rock (HDR). The flow is circulated through the cracks, and extracts the heat to the ground. The emphasis of the simulators is on the HDR and on the development of methods that produce the hydraulic fractures. Linear elastic fracture mechanics approach (LEFM) was used to predict the crack propagation for initial crack. Finite element method (FEM) is used to predict the maximum stress areas, hence, determining the crack initiation.
摘要: On the basis of Krivoy Rog iron mining ore deposit companies (Ukraine) the complex field studies focused on the fast development of secondary landscapes in the surface of dumps after iron mining were carried out. In order to create the top layer of waste purification from household sewage was carried out sewage clearing facility silt. It is well known that breed dumps are dangerous for the environment, particularly for the surface and ground water. Overnormal concentrations of salt had been found in water samples, taken from the river Inhulets in a zone of influence breed (2.1 MPL), sulfates and carbonates (2.7 MPL), iron (2.1 MPL), chloride (1.7 MPL), magnesium (3.1 MPL). In the wells from nearest villages water is not suitable for drinking purposes and contains total sum of salts – 4.97 MPL, sulfates and carbonates – 5.16 MPL, cadmium – 3.7 MPL, lead – 1.53 MPL. Thus, the toxic heavy metals concentrations (Pb, Cd, Zn, Mn, Cu, Cr, Ni, Fe) in the fish and amphibians, as well as herbaceous plants in these areas did not exceed the permissible levels.Use of clearing facilities sludge aged from 1.5 years and more in the amount 15 kg/m2 did not lead to increased concentration of heavy metals in the top layer of dumps. Total pollution of the soil within six months after application of sludge correspond to the "permissible" level (Zc = 1.61).To assess the suitability of the silt dumps, we proposed list of indicators, which correspond to the chemical and epidemiological safety and classify as "suitable", "conditionally suitable" and "not suitable". We found that optimal conditions for formation of a new soil dumps with ratio of such indicators as "nitrogen: phosphorus: potassium" should be corresponded to the working dose 300 kg/ha by nitrogen amount. This is the maximum amount of mature silt 66.7-70 ton/ha.
摘要: In rural regions, mining is an activity that employs many people due to the fact that the barriers to entry are sometime trivial, with very low technology, capital fund and no specialized skills required. Many people including children into artisanal mining in Ivory Coast because they can earn higher incomes in mining than through other traditional activities such as agriculture, which is the main activity in the country. Artisanal mining contribute to reduce the abject poverty and it offers many others opportunities. However, this activity has many negative social impacts. Local people including miners are risking their life everyday due to the unsanitary conditions, prostitution, chemical contaminants, and alcoholism, and also the large degradation of lands. The main objective of this Paper is to understand how artisanal gold mining in the Ivory Coast affects local livelihoods and the environment. Some key recommendations for addressing artisanal mining activities in order to have a good option for sustainable management of mineral resources in the country are proposed.
摘要: This paper analyzes preventive maintenance scheduling of bottleneck equipment in a line concept of a wafer manufacturing line that has buffer in between equipment. After the start-up of the manufacturing, it has implemented time based maintenance and counter based maintenance without any fix sequence. The maintenance team will select in advance the date and time of the actual preventive maintenance to be perform and making sure all resources are planned. Then maintenance team implemented a Preventive Maintenance sequence which gives the lowest impact in production loss without sacrificing equipment’s quality and safety. This Preventive Maintenance Scheduling sequence is the best suitable method for manufacturing equipment that has buffer in between equipment which is arranged in a line concept. It has also been tested and proven in a wafer manufacturing industry.