Aerospace and Mechanical Engineering

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Authors: Ji Gang Li, Guo Ying Han, Xiu Min Li, Jiao Jiao Sun, Ke Jing Song, Ting Zhang
Abstract: Directional cloning is a prerequisite for the construction of expression vectors in molecular biology laboratories. Although TA cloning is widely used to clone unmodified PCR (polymerase chain reaction) products, a major disadvantage of this technique is that cloning is not directional. Here we reported a novel PCR products cloning vector with one deoxythymidine overhang and one deoxycytidine overhang at two 3'-ends respectively. With the choice of nucleotides of 5'-ends of PCR primers, PCR products can be cloned to this vector both directly and directionally. The feasibility and efficacy of this cloning method were confirmed by using a pET-17b derivative vector and a green fluorescent protein gene (EGFP) and a red fluorescent protein reporter (Ds-Red) gene. This cloning strategy may be useful in the high-throughput construction of expression vectors and could be viewed as an interesting improvement of existing TA cloning method.
Authors: Hai Jun Yang, Hui Zhen Wang, Li Zhong, Jun Qing Zhang, Yue Jia Liu
Abstract: In order to prevent silicone oils from suffering oxidative deterioration and prolong its service life at high-temperature, an effective way is adding an appropriate antioxidant package in the base oil. Antioxidants can not only inhibit oil oxidation that produces acidic substances but also prevent the viscosity of oil from increasing. In this work, 1,3-dioctyl-1,1,3,3-tetraphenyl-disiloxane (OPDS) was used as silicone base oil, and several commercially available antioxidants were screened. Data show that TNPP, phenyl sulfide, 2088, and KY01 were effective at 300 oC, which could be further used as candidates for the antioxidant formulations of silicone base oils used as high temperature lubricants or hydraulic oils.
Authors: Gergis W. William, Samir N. Shoukry, Jacky C. Prucz
Abstract: This paper presents two new 3D finite element Multi Fiber Models (MFM) that account for the effects of neighboring fibers on the stress distribution over fiber-matrix interface. One model assumes a hexagonal packing pattern of the neighboring fibers whereas the other assumes that the neighboring fibers are packed in a square pattern. Two scenarios regarding the contact surface between the fiber and the matrix are considered: the first one assumes no bond over the interface while in the other one the interface is perfectly bonded. The cooling process of the composite was simulated and then a transverse loading is applied to the composite. The results indicate that packing system and the characteristics of the fiber-matrix interface greatly influence the magnitude of the residual stresses developed in the matrix.
Authors: Qian Qian Wu, Li Guo Chen, Ming Qiang Pan, Lin Sen Chen
Abstract: Because of the complexity of bonding process, the mechanism of bonding has been unable to agree. Accoding to previous research, a new bond energy transfer model is established: bond energy equals to energy caused by temperature rising and the friction energy.Then do experiment on bonding time, bonding stress and ultrasonic energy.Experimental results show that as the increase of process parameters, the bonding strength first increases then decrease, which consistent with the hypothesis.
Authors: Elwaleed A. Khidir, N. Nikabdullah, M.J.M. Nor, M.F.Mat Tahir, M.Z. Nuawi
Abstract: Sound absorption of self-facing natural date palm fibershas been investigated.A single layer sample of the fibers was tested for its sound absorption properties. The sample was then faced with the originally date palm fiber netted structure. Experimental measurements were conducted on the impedance tube at the acoustic lab, Faculty of Engineering, UniversitiKebangsaan Malaysia, to determine the sound absorption coefficient.The single layer was also tested using an aluminum perforated plate, as facing, for comparison purposes.The results show a good improvement in the sound absorption for the self-facing panel for the whole frequency range. However, when using the aluminum perforated panel an improvement in the sound absorption was observed only above 2500 Hz. The effect of introducing air gap thickness was studied. The results show improvement for the sound absorption the low frequency.
Authors: Phatthaya Saohin, Julathep Kajornchaiyakul, Chaiyasit Banjongprasert
Abstract: The main objective of this study is to present the elementary path to develop applications of thermal analysis technique from the solidification in casting of hypoeutectic aluminum-silicon alloy. In order to successfully use the technique as a monitoring tool for an appropriate production of aluminum casting, all affecting process conditions must be taking into accounts when cooling curves are used as indicators. Although, the cooling curves can indicate the solidification characteristics, previous studies on casting trials designed by Taguchi method show that thermal analysis can be complex and sensitive. Also, there are many factors that influence the characteristics of cooling curves when grain refinement becomes more prominent. This study is to determine the effects of grain refiners and magnesium contents on the undercooling of nucleation of Alpha (α) aluminum phase. Different cooling rates and different magnesium contents were studied and the undercooling temperatures were measured. The cast samples were then subjected to the metallurgical analysis by macrostructure study to determine the average grain size. Under a controlled casting condition, it was found that grain refinement tended to decrease degrees of undercooling temperature. Also, higher magnesium content led to the suppression of the undercooling temperature.
Authors: Hadjadj Abdechafik, Kious Mecheri, Ameur Aissa
Abstract: The objective of this study is to develop a process of treatment of the vibratory signals generated during a horizontal high speed milling process without applying any coolant in order to establish a monitoring system able to improve the machining performance. Thus, many tests were carried out on the horizontal high speed centre (PCI Météor 10), in given cutting conditions, by using a milling cutter with only one insert and measured its frontal wear from its new state that is considered as a reference state until a worn state that is considered as unsuitable for the tool to be used. The results obtained show that the first harmonic follow well the evolution of frontal wear, on another hand a wavelet transform is used for signal processing and is found to be useful for observing the evolution of the wavelet approximations through the cutting tool life. The power and the root mean square (RMS) values of the wavelet transformed signal gave the best results and can be used for tool wear estimation. All this features can constitute the suitable indicators for an effective detection of tool wear and then used for the input parameters of an on-line monitoring system. Nevertheless we noted the remarkable influence of the machining cycle on the quality of measurements by the introduction of a bias on the signal; this phenomenon appears in particular in horizontal milling and in the majority of studies is ignored
Authors: Kious Mecheri, Benhorma Hadj Aissa, Ameur Aissa, Hadjadj Abdechafik
Abstract: The wear of cutting tool degrades the quality of the product in the manufacturing processes. The on line monitoring of the cutting tool wear level is very necessary to prevent the deterioration of the quality of machining. Unfortunately there is not a direct manner to measure the cutting tool wear on line. Consequently we must adopt an indirect method where wear will be estimated from the measurement of one or more physical parameters appearing during the machining process such as the cutting force, the vibrations, or the acoustic emission etc.... In this work, a neural network system is elaborated in order to estimate the flank wear from the cutting force measurement and the cutting conditions
Authors: S. Balaguru, K. Deenadayalan, Murali Vela, P. Chellapandi
Abstract: Colmonoy is a nickel based alloy hardfaced with SS-316 used in Prototype Fast Breeder Reactors (PFBR) to avoid self-welding and galling between nuclear reactor and grid plate. Colmonoy is coated on the base metal –SS 316 by Plasma transfer arc welding. Due to thermal cycling that exist in reactors de-bonding between colmonoy and base metal occurs which may lead to catastrophic failure of the Prototype fast breeder reactor. Hence, estimation of the fatigue life period of hardfaced colmonoy is mandatory. Before that, finding optimum parameters which influences fusion, weld strength, composition and dilution are mandatory. In order to evaluate the dilution characteristics with respect to welding speed, different specimens were prepared by holding other parameters constant. Prepared specimens were tested for hardness, microstructure and dilution to locate the difference between each specimen. Comparative studies were carried out on the specimen and their parameters like travelling speed, microscopic structure, Hardness and dilution percentage were tabulated. Based on the tabulated results, the best specimen is chosen with respect to its individual parameters.

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