JOURNAL OF MECHANICAL RESEARCH AND APPLICATION (JMRA)
Year:2012 | Volume:4 | Issue:3|Papers Count:7

In this study chemical method of dissolution-precipitation was applied to produce amorphous silica nanoparticles from rice straw ash (RSA), the waste material of rice cultivation. The morphology, particle size, structure and area of specific surface of synthesized amorphous silica nanoparticles were evaluated using transmission electron microscopy (TEM), X-ray diffraction analysis (XRD) and analysis technique for the measurement of the specific surface area of materials (BET). In addition, chemical composition of RSA, used and the synthesized silica nanoparticles was studied by X-ray fluorescence (XRF) spectroscopy. The effects of sodium hydroxide concentration, precipitation reaction temperature and precipitation reaction duration on the area of a specific surface were determined through Design of Experiments (DOE) Technique. Results depicted that silica nanoparticles with particle size of 10-15 nanometers were successfully synthesized. Average area of a specific surface and purity were 327 m2/g and 99.5% respectively. The interactive influence of temperature and duration having the highest effect on the average area of the specific surface.

Analyzing the nonlinear vibration of beams is one of the important issues in structural engineering. According to this, an impressive analytical method which is called modified iteration perturbation method (MIPM) is used to obtain the behavior and frequency of a cantilever beam with geometric nonlinear. This new method is combined by the Mickens and iteration methods. Moreover, this method does not require small parameter in the equation which is difficult to be found for nonlinear oscillation. The accuracy of the solution that is obtained by the use of MIPM has been shown graphically and compared with exact solution. Comparison shows that good adaptation is obtained and MIPM as a powerful method for solving the vibrational behavior of structures analytically.

In this paper, the methodology of aircraft air distribution system has been analyzed theoretically and experimentally. To achieve that, ducting pressure loss and air flow throw gaspers calculation has been done for cabin ducts according to the exact location of individual air distribution system in the cabin. The length of gasper air flow was compared with the distance between gasper outlet and passenger seats and the velocity of the gaspers has been measured with velocity gage on the mockup. Finally design results show a good agreement between air flow throw gaspers and gasper to passenger distance that makes comfortable air feeling conditions. Also the experimental analysis on the mockup validates the results of outlet velocity of gaspers and perforations calculation. Therefore, the validity and feasibility of the design methodology of installation gasper system to a cabin air distribution system for least modifications, suitable location and efficient air flow throw gaspers is confirmed.

This paper presents an analytical solution for two-dimensional conductive heat transfer in spherical composite pressure vessels. The vessels are in a spherical shape and fibers are winded in circumferential direction. The vessel is made of one-layer reinforced composite material. The analytical solution is obtained under the general boundary conditions which consist of convection, conduction and radiation inside/outside of vessel. The heat transfer equation for orthotropic conduction in spherical coordinates is derived and solved using separation of variables method based on the Legendre and Euler functions. Here, the effect of fiber's angle on heat conduction in orthotropic spherical pressure vessels is investigated in detail. These results can be used extensively for analyzing the thermal stress in this kind of vessels.

This paper deals with an inspection of defects including corrosion and leakage by Acoustic Emission (AE) in an oil tank floor. 5 AE sensors have been attached to an oil tank and the sensors were calibrated by pencil lead break test. The emissions have been recorded within an oil tank. The oil tank was not emptied and had an amount of oil for the test unlike other test methods like magnetic flux leakage, eddy current or ultrasonic. The test method and formulas of AE investigation and AE source location are presented in detail. The result of AE test in the studied oil tank verifies the presence of corrosion in some areas of the tank floor. After AE test, the tank was emptied and inspected using ultrasonic thickness meter. The result of thickness measurement reconciles in an acceptable manner with AE test.

The influence of surface roughness magnitude and direction on dry static friction coefficient between two similar steel samples has been studied through an experiment. A testing apparatus has been designed and fabricated to measure the friction coefficient for a few forms of surface asperity. The average, maximum and minimum values of static friction coefficients among steel samples have been measured and numerically proposed in terms of some discrete values of the surface roughness, base and counter body angles. Correction coefficient defined as the ratio of maximum to minimum friction coefficient has been found on the result basis. According to the results of the experiments, dry static friction coefficient between two similar steel samples is affected by both magnitude and direction of surface roughness. Under the condition of static equilibrium, the Colomb - Amonton formula has been used to determine friction coefficient between samples. The flexibility and mass of the string have been neglected, and the reservoir pendulum-like swinging and the water movement therein have been avoided within the experiments.

In this study, the application of gray relational analysis (GRA) and Taguchi method in multi-criteria process parameters selection of turning operation has been investigated. The process responses under study are material removal rate (MRR) and surface roughness (SR); in turn, the input parameters include cutting speed, feed rate, depth of cut and nose radius of the cutting tool. The proposed approach employs GRA to convert the values of process outputs, obtained from Taguchi method, into a single objective used to determine the best set of process parameters for turning operation of AISI 202 austenitic stainless steel. Analytical results reveal that the combination of higher levels of cutting speed, depth of cut, and nose radius and lower level of feed rate is essential to achieve simultaneous maximization of material removal rate and minimization of surface roughness. Using verification test, these settings would result in more than 14% improvement over those for initial settings. The analysis of variance (ANOVA) and F-tests showed that nose radius is the major factor affecting the gray relational grade (GRG) with 41% contribution.  In general, the proposed procedure is quite efficient in determining the effects of process parameters and finding the best set of process parameters.