摘要: In this study corrosion resistance of 316L stainless steel has been investigated in a solution containing different percentages of hypochloric solution. In order to examine the rate and mechanism of the occurrence of pitting corrosion in this steel, various corrosion tests have been used. In addition, the locale of the pitting corrosion has been examined by scanning electron microscope. Results show that the presence of chlorine ion with the increase of cathodic reaction rates cause to increase the likelihood of pitting corrosion in 316L steel.
摘要: This article showed that new mixed inhibitor type of cucurbit [n] urils based corrosion inhibitors with gossypol at the proportion of 50:50 is excellent efficiency for mild steel in in alkaline media containing chloride ions. The Polarization Resistance results suggest that this inhibitor decreased the rate of anodic mild steel dissolution and cathodic hydrogen evolution. Increased activation energy suggested that inhibitors adsorb physically during the first step of the adsorption process.
摘要: Polycarbonate bullet proof glass and acrylic heat resistant glass are used as the functional material in many application. In this research paper, Taguchi modal is utilized for the ultrasonic machining of these material. Surface roughness is significant output parameter, because it define accuracy of the process. Taguchi modal suggest that 40% concentration, mixture of Alumina, Silicon carbide and Boron carbide abrasive in 1:1:1, 600 abrasive grit size and 1.5% HF acid gives best results in polycarbonate bullet proof glass material and for acrylic heat resistant glass, mixture of Silicon carbide and Boron Carbide abrasive in 1:1, 600 abrasive grit size and 1% HF acid gives the best results. More significant parameters contribution in surface roughness are concentration of slurry, grit size of abrasive and HF acid. Optimum parameters improved the surface roughness by 23% and 24% in polycarbonate bullet proof glass and acrylic heat resistant glass respectively.
摘要: In order to develop a cost-effective carbon fiber reinforced polymer sensor for compressive strain monitoring, a study was carried out to assess electrical and piezoelectric properties of samples containing five different carbon fiber weight percentages. Testing focused on sensing ability throughout measurement of resistivity: (1) when submitted to uniaxial variable compressive strain; (2) to time prolonged relaxation at constant strain; (3) and influence of environment temperature on measurements. Results enabled the possibility of usage for live monitoring of samples by determining sensitivity values of each sample being tested. Electrical resistance measurements assessment test results, show real time resistivity change in respect to experienced strain. Further piezoelectric properties where determined. An exponential decay function was found in fractional resistance in respect to relaxation due to constant strain testing. The total amount of time needed for measurements to present an error less than 1% at the probes was determined and found to vary up to seven days. Strain reversibility of resistivity measurements varied according weight percentages of carbon fibers used in composite sample being tested. Samples were tested in situ for monitoring of displacement on foundations of a dwelling to be built, placed on foundation’s soil. The main objective here was to assess practical questions such as handling and how measurements could be made safely. Results demonstrated successful monitoring during construction phase with easy deployment on site, sensing each construction phase loading.
摘要: In this paper, we report a study on the possibility of fabricating porous silicon by exposing a multicrystalline silicon surface to gaseous etchants. The structural and optical properties of porous silicon (PS) layers prepared by vapour –etching (VE) are investigated. FTIR analysis confirms the existence of hydrogen incorporation bonding to the silicon atoms. Photoluminescence measurements reveal an efficient emission around 640 nm. The optical behaviour in the 350-1000 nm wavelength range was determined before and after PS formation, resulting in a notable reduction of reflectance and an enlargement of low reflectance region into short wavelengths and near IR region after PS formation. A significant increase of the quantum efficiency particularly in the short wavelength region is observed. The results make the use of such thin film very promising for multicrystalline silicon solar cell application.
摘要: Fiber-metal laminates (FMLs) are composites materials that are commonly used in areas such as aircraft industry. They are composed of ductile metal layers with high strength fiber reinforced polymer layers. So far, however, only uniaxial tests have been used to characterize the quasistatic mechanical properties, which cannot reflect the real loading situation of the FML applications. In this work biaxial tensile behavior of FMLs with glass and Kevlar fibers based on aluminum alloy is studied with finite element method simulation. The simulation is run to find the stress-strain relationship for FMLs at the off-axis angles of 0˚ and 45˚ for glass and Kevlar fibers. The “composites layups” are constructed for the 3D FML part. Two different elements C3D8R (8-node linear) and C3D20R (20-node quadratic) are used to carry out the simulation. The results show that C3D20R shows major advantages. Analytical solutions based on the classical laminate theory are obtained to compare with the finite element method (FEM) solutions. The results show good consistency.
摘要: Staircases in reinforced concrete (RC) frame structures have suffered severe damages in past earthquakes, despite being regarded as the main means of egress during emergencies. To make sure that staircases perform as safe passages in strong earthquakes, the performance of RC stair structures should be scrutinized under major earthquakes. In this research at first, staircases were simulated as shell elements in RC frames and analyzed under gravity loads in order to find the maximum forces and moments. In the second step, the influence of staircases on the structural behavior of RC frame structures under seismic loads was studied. The results showed that stairs act as a K-type bracing system. Furthermore, a parametric study was carried out and relations for calculating force and moment in stairs slabs that had been determined under gravity loads, were modified. In addition, affected areas of structure interacting with the stairs in an earthquake were distinguished.
摘要: Many patents have suggested that spinning aircraft wheels before landing could eliminate tyre smoke at touchdown. Most patents suggest using available wind power to rotate the wheel with wind turbines. In this paper, ANSYS CFX has been employed to simulate different wind turbines spinning a heavy aircraft wheel at approach. The aim of this research is to check the possibility of using wind power for this purpose and to optimize the wind turbine in a size acceptable in the field of aviation, in order to reach the target rotational speed.
摘要: Using of bearings and gearings is the most prevalent way to transform the momentum in mechanics, however their modular applications, namely – bearings as supports and gearings as transmissions have mutually exclusive weaknesses. This article analyze the jointing of rolling bearings and gearings as one unit, their types, difference and parameters variations, the profits of such constructions, the using of their assemblies and realizations ways.
摘要: In today’s world, every company is competing to enhance its time-based competitiveness. The time it takes to complete all activities of the order cycle is an important part of customer service. Accurate and fast order processing is a hallmark of high quality of service. This paper addresses the most time-consuming and costly factor of ordering process—order filling. According to the several researchers, order filling is composed of the physical activities for: acquiring products through stock retrieval, purchasing or manufacturing; packing products for consignments; scheduling the consignment for delivery; and preparing shipping documentation. Usually these series of activities in order-filling process need space of warehouses, making them a central part of company’s logistics system. This paper is based on a case study to identify how some simple approaches built in theory can be applied to firm’s current practice to enhance order-filling process. Specifically, a short plan consisting of ABC analysis and relocation of current positions of inventory is tested, and a long-term plan for redesigning the layout of warehouse is proposed.