Applied Mechanics and Materials Vol. 819

Abstract: Solar cell is the most cost effective and simple device to harvest solar energy as compared to other systems. Many types of single junction solar cell are available in market but their main problem is low efficiency. This paper focuses on the performance investigation of high efficiency multijunction solar cell using two axis solar tracker. High solar concentration is needed for multijunction solar cell with accurate solar tracking to get maximum energy output. Solar tracker is based upon the astronomical algorithm of solar tracking. Tracking System consists of GPS module, AVR microcontroller, stepper motors with drive modules and some other accessories. The tracking system takes geographical location data from GPS to calculate sun position for tracking.

Abstract: Energy consumption of buildings is increasing steadily and occupying approximately 30-40% of total energy use. It is important to predict heating and cooling loads of a building in the initial stage of design to find out optimal solutions among various design options, as well as in the operating stage after the building has been completed for energy efficient operation. In this paper, an artificial neural network model has been developed to predict heating and cooling loads of a building based on simulation data for building energy performance. The input variables include relative compactness, surface area, wall area, roof area, overall height, orientation, glazing area, and glazing area distribution of a building, and the output variables include heating load (HL) and cooling load (CL) of the building. The simulation data used for training are the data published in the literature for various 768 residential buildings. ANNs have a merit in estimating output values for given input values satisfactorily, but it has a limitation in acquiring the effects of input variables individually. In order to analyze the effects of the variables, we used a method for design of experiment and conducted ANOVA analysis. The sensitivities of individual variables have been investigated and the most energy efficient solution has been estimated under given conditions. Discussions are included in the paper regarding the variables affecting heating load and cooling load significantly and the effects on heating and cooling loads of residential buildings.

Abstract: The objective of this project is to design a center pivot irrigation system and determine the efficiency of the system by using experimental method by build a model of the system. For that, a literature study is carried out to understand the theories of center pivot irrigation system. Center pivot irrigation system is the system that can rotate 360 degree around the center pivot. Before model build, the theoretical calculation need to be done to calculate the specification of the model. The model of the experiment purpose build not included the rotation part because the rotation part not gives an effect to the water flow. The experiment procedure follows the standard of North Carolina State University that conducts this type of experiment. From the experiment, the uniformly efficiency of the irrigation system can be defined. Scaled model use in this experiment to determine the uniformly efficiency by using specification from the theoretical calculation. From the previous experiment the uniformly efficiency of the irrigation system is 50% - 60% and the uniformly efficiency of center pivot irrigation system is about 75% - 90%.

Abstract: An addition of cerium oxide to NiCrAiY coatings could boost the high temperature properties of the coatings in the actual service condition due to the purification of its microstructures. High temperature oxidation studies of D-Gun sprayed MCrAlY coatings with minor addition of CeO₂ is inadequate in the literature. Therefore, the present work was focused to study the effect of cerium oxide on the high temperature oxidation behavior coatings on superalloys. Cyclic oxidation tests were carried out for 100 cycles at 900 °C to study the oxidation kinetics of un-coated and bare superalloys. The corroded products obtained during cyclic oxidation of coatings were subjected to XRD, FE-SEM/EDAX and X-ray mapping analysis to reveal the high temperature oxidation mechanisms.

Abstract: This experimental work was carried out to examine the effect of road particle on squeal noise exerted at different load and sliding speed. The test was performed under dry sliding condition by utilizing brake test rig and commercial brake pad and discs. Squeal measurement was taken based on frequency, sound pressure level (SPL) value, vibration and brake torque measurement. The output signal from microphone and accelerometer was processed by Fast Fourier Transform analyzer to synchronize value SPL and vibration in the power spectrum graph. Simultaneous increase at the same value of frequency and SPL values showed the squeal occurrence for value above 70dBa and 1000Hz respectively. Result for test with road particle showed number of squeal tends to increase compared to test without road particle. SPL also showed high pitch of noise on squeal with road particle presence. Brake torque significantly increased with increasing brake line pressure and exaggerated with road particle. Higher brake torque resulted in higher coefficient of friction and showed high squeal generation.

Abstract: The oil and gas industry struggles to prevent formation of hydrates in pipeline by spending substantial amount of dollars. Hydrates are ice-like crystalline compounds that are composed of water and gas in which the gas molecules are trapped in water cavities. The hydrate formation is favorable at elevated pressure and reduced temperature and can be determined through experiment. However, the cost involved to determine early hydrate formation using experiment is driving researchers to seek for robust prediction methods using statistical and analytical methods. Main aim of the present study is to investigate applicability of radial basis function networks and support vector machines to hydrate formation conditions prediction. The data needed for modeling was taken from well-established literature. Performance of the models was assessed based on MSE, MAE, MAPE, MSPE, and Modified Pearson’s Correlation Coefficient. Data-based models enable the oil industry to predict the conditions leading to hydrate formation hence preventing clogging of the pipeline and high pressure buildup that could lead to sudden burst at the connections.

Abstract: Heat pipes are widely used in electronic cooling and other applications that require efficient transport or spreading of heat from local sources of high heat flux. One factor that most affect the performance of this device is the wetting properties of the wick material, whereby a hydrophilic wick material is required to transport the liquid from the evaporator to the condenser. The performance of heat pipe will decrease when the wick surface becomes hydrophobic as indicated by changes in its contact angle (CA). This study aims to determine the effect of ambient air exposure on the wettability of wick material. Wettability for a surface by a certain liquid can be shown by measuring the contact angle of liquid droplets on the surface. In this experiment, the contact angle was captured using a high speed video camera followed by image processing and then measured using Image J software. The surface of the sample/wick is a sintered copper powder which in this study through a process of forming or compaction by various parameters such as powder particle size, compacting pressure and sintering temperature. From the results of this study was found that the longer wicks were exposed in the ambient air, the contact angle of the liquid on the wick surface will be getting increased. After 7 days were contaminated on the ambient air, then all samples have been turned into hydrophobic, CA>90°.

Abstract: Polymers always show time-dependent mechanical properties. In order to use polymers in engineering applications, long-term mechanical propertes should be characterized. Free volume theroy is the mostly used theory to predict and model the mechanical properties of polymers. The effect of temperature is modelled thorugh William-Landel-Ferry (WLF) equation, whereas, the combined effect of temperature and pressure is modelled by Filler-Moonan-Tschoegl (FMT) equation. Both of the models are based on free volume theory. A set of expermentations were performed to investigate the validity of free volume concpet for one of the most important engineering polymer; i.e. Polyamide-6.

Abstract: A passive twist control is considered as an adaptive way to maximize the overall efficiency of a proprotor developed for convertible Micro Air Vehicles (MAV). In this paper, adaptation of the proprotor geometry in accordance to flight configurations is achieved by induced twist generated by the inherent structural coupling effect in anisotropic composite material and centrifugal force emanating from the tip load. Beam Finite Element Model based on Rotating Timoshenko Theory is used to predict structural loads, while Blade Element Momentum Theory is employed to predict the aerodynamic performance of adaptive proprotor as applied on Micro Air Vehicles (MAV). The iterative process of combination of aerodynamic model and structural model is used to compute the steady-state deformation of the flexible laminated proprotor blade due aerodynamic loads. Finally, the optimal design of lamina blade material is carried out to investigate the potential of flexible blade in the proprotorperformance enhancement.

Abstract: Major issues related to implant failure are wear debris and metal ions release where Titanium-Aluminium-Niobium alloys still face those problems despite of better biocompatibility. Surface modification is one of the alternatives in order to reduce those wear as well as ion release problems to the host tissue. In this study, experiments were carried out to investigate the element diffusion behaviour of Ti-6Al-7Nb alloy through thermal oxidation in order to obtain coating on the surfaces for diminishing those effects. Thermal oxidation was carried out at 650°C for three different durations 6, 12 and 24 hours. It is found that at prolong time, Niobium diffusion occurs where short duration Aluminium dominates. This suggests that longer heating time promotes heavy metal diffusion by restricting diffusion of light metal and hence, dominates the heavy metal oxide layer formation. The oxide layer formed on the substrate may lead to increase the lifespan of the implant and reduces the harmful effects caused by wear debris or toxic ion from metal alloys.