Applied Mechanics and Materials Vol. 704

Abstract: This work aims to enhance the power conversion efficiency of PEDOT:PSS/Si hybrid solar cells by reducing the resistance of PEDOT:PSS of hybrid solar cells using simple solvent treatment. A noticeable decrease in resistance of PEDOT:PSS layer was found after treating with DMSO and methanol using the dipping method or the mixing method. The combinations of these two methods allow us to greatly enhance the fill factor and power conversion efficiency of hybrid solar cells due to the significant reduction in R_s.

Abstract: Reburning technology has been developed to adopt various commercial combustion systems. Fuel lean reburning is an advanced reburning method to reduce NOx economically without using burnout air, however it is not easy to get high NOx reduction efficiency. In the fuel lean reburning system, the localized fuel rich eddies are used to establish partial fuel rich regions so that the NOx can react with hydrocarbon radical restrictively. In this paper, a new advanced reburning method which supplies reburn fuel with oscillatory motion is introduced to increase NOx reduction rate effectively. To clarify whether forced oscillating injection of reburn fuel can effectively reduce NOx emission, experimental tests were conducted in vertical combustion furnace. Experiments were performed in flames stabilized by a gas burner. The natural gas is used as both main and reburn fuel and total thermal input is about 40kW. The forced oscillating injection of reburn fuel is realized by electronic solenoid valve, so that fuel rich region and fuel lean region is established alternately. In the fuel rich region, NOx is converted to N₂ by reburning reaction, however unburned hydrocarbon and CO is oxidized in fuel lean zone and mixing zone at downstream where slightly fuel lean region is formed by mixing of two regions. The NOx reduction rate increases up to 41% by forced oscillating reburn motion. And this paper makes clear that in order to decrease NOx when oscillating reburn fuel injection system is adopted, the control of factors such as frequency and duty ratio is very important.

Abstract: This study presents statistical analysis of particle size distribution from a CFD simulation of polymer devolatilization in contactor, that uses superheated steam to isolate the polymers. This is accomplished by estimating marginal distributions of particle size and temperature using maximum Shannon Entropy theory and capturing their dependence structure by employing Copula thoery. The Copula-based conditional distribution of particles at different temperatures reveals the strong dependence of particle size to heat exchange and corresponding temperature.

Abstract: The microstructure evolution during the directional solidification of Al-Cu alloy is simulated using a phase field model. The transformation from liquid to solid phase is a non-equilibrium process with three regions (liquid, solid and interface) involved. Phase field model is defined for each of the three regions. The evolution of each phase is calculated by a set of phase field equations, whereas the solute in those regions is calculated by a concentration equation. In this work, the phase field model which is generally valid for most kinds of transitions between phases, it is applied to the directional solidification problem. Numerical results for the morphological evolution of columnar dendrite in Al-Cu alloy are in agreement with experimental observations found in the literature. The growth velocity of the dendrite tip and the concentration profile in the solid, interface and liquid region were calculated.

Abstract: Mechanical tests of alloyed TiNi compounds with shape memory effect were performed. Low-cycle tests of alloyed compounds showed that an increase in the number of cycles to failure doubled. Studies conducted using the indentation showed shape recovery of print on material of alloyed weld within 0.7-1.2%.

Abstract: In the aerospace industry, numerous large parts with complex curvatures and several thin wall/web pockets are required to ensure stiffness and low weight for aircraft structures. Costly processes and dedicated setups are usually required to machine such thin plate components. Therefore, investigating new machining methods involving flexible setups for such parts is an interesting avenue for cost savings, but a big challenge as well, due to a lack of support and part flexibility. In fact, a flexible setup is a tooling system with several adjustable positioning supports, which can easily adapt to different workpiece geometries. In this paper, an experimental investigation of the machining of pockets for thin components using flexible setup is presented. A design of experiments is proposed to verify the ability of pocket machining for thin plates of aluminum 2024-T3 in terms of quality. During the machining tests, the cutting forces were measured using a Kistler dynamometer table, while the displacement of the plates, for the flexible setup configuration, was measured using a Keyence displacement sensor. The force and displacement signals were analyzed and a fine correlation proposed between them and the resulting quality of the part, expressed in terms of profile and size errors.

Abstract: In the present investigation, microstructure and mechanical properties of nanocomposites fabricated via stir casting were evaluated. The composites were based on Al (99.7) reinforced with ilmenite nanoparticles. The characterization of the nanoparticles and nanocomposites was investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD) facilities. Microstructure of specimens show that reasonable distribution of FeTiO3 nanoparticles in the matrix, secondary phase FeAl3 observed in the microstructure. Ultimate tensile strength and compression tests were carried out in order to identify the mechanical properties. The hardness of the composites is enhanced with the addition of nanoparticles. The optimum value for ultimate tensile and compression strength are obtained with the addition of 3 % ilmenite nanoparticles. Ductile fracture in tensile fractured samples was observed by fractrography examination.

Abstract: Thermoplastic composite manufacturing is often difficult due to high viscosity of the matrix materials. Coupling a high level of mechanical properties with simple, low-cost processing technique is a difficult subject, but an important task for any state-of-the-art impregnation processes. In this paper, Thermoplastic Prepreg Fabrication Technology is utilized to prepare thermoplastic tapes and the technology's effect on strain energy absorption was investigated. The tape was prepared under three categories: first, with induced vibration and no fiber preheat (NV), second, without vibration and fiber preheat (HN) and last, with both fiber preheat and vibration (HV). For the purpose of comparison, all other variables such as pulling speed, fiber tension, fiber preheat and processing temperature were kept constant. The HV category showed improvement in the strain energy absorption by 10 and 23% when compared to HN and NV, respectively. In addition, HV had better wetting, fiber spread and dispersion. Fiber preheating is important as it worked well with vibration possibly due to good fiber spread on the HV category (widest tape). Also, HV had the least fiber volume fraction as it takes more matrix volume when exiting the die plate.

Abstract: Electrochemical Machining is one of established non-traditional machining process which is widely used in micro machining parts. Purpose of this research paper is to investigate effect of Electrochemical Machining under low voltage and relatively high current rating on concentrated or masked work piece of Copper and Carbon Steel EN9. Developing Machine set up with the help of PLC and SCADA device for Accurate Positioning and reliable data supervising which includes ECM, basic working principle of ECM, selection and development of components, implementation and to analyze the effect of change in the parameters of the process. Selection and development part will cover design of frame, fixture, pump, filter, tool, electrolyte, and work piece material as a mechanical part, selection of electric drive system and PLC. PLC programming and hardware circuit as electrical and programming part.