Advanced Materials Research Vol. 1016

Abstract: Helium diffusion is a very critical factor for designing a plasma facing components of fusion reactor. Because it not only reduce the thermal conductivity but also degrade the surface morphology of tungsten based materials. In this numerical study the specimens of tungsten, vanadium and tungsten vanadium alloys have been simulated under thermo-diffusion conditions. The finite element commercial software Abaqus was used for simulation to obtain helium diffusion profile at temperature of 800 K for concentration of10²⁴number of atoms in tungsten and vanadium metals. Due to its relatively low helium diffusion coefficient, vanadium has shown better resistance against helium penetration as compared to tungsten. Subsequently the analytical effect of helium diffusion in tungsten, vanadium and different grades of tungsten vanadium alloys has been investigated. To study the distribution of vanadium in tungsten, tungsten vanadium alloys were fabricated by spark plasma sintering technique and its morphology has been analyzed by scanning electron microscopy.

Abstract: In recent years, the Au-Ge-Sb system has been studied as a possible alternative alloy for soldering applications [1-4]. The alloy has various fbenefits such as (i) low melting temperature which allows the alloy system to be used as a drop-in solution for high performance lead-free solders, (ii) three distinct phases of different hardness values (100, 150 and 500 HV) which offer the ability to fine tune the composition and microstructure to a wide range of properties, and (iii) limited solute solubility which offers ease of control and fine-tuning of microstructure, mechanical properties and colors. Gold compositions centered around 75wt% gold were modeled and selected using the CALPHAD (CALculation of PHAse Diagram) method. Predictions were later confirmed by experimental results. The alloy solidifies in the range of 242.5-261.7 °C. The overall hardness values were measured and confirmed to be within the volume average value of all the phases combined.

Abstract: AISI 1020 steel bars cooling have been investigated aiming to obtain their cooling rate during heat treatment. Hot steel bars just taken out of the furnace are piled over other ones that were taken out of the furnace earlier. A mathematical model has been created and implemented using the software EES, Engineering Equation Solver. An experiment was conducted to validate the mathematical model. The experiment consists in three loads of three bars each with a time interval of 5 minutes between them. The initial temperature of each bar was 150^oC. The mathematical model can obtain the thermal profile of each bar and the average and maximum deviation when confronted with experimental data were about 8% and 20% respectively.

Abstract: Refueling aircraft has become a significant aspect of military strategy for air forces to work at further distances from safe shores. This paper will address the aerodynamics of the drogue refueling system and in particular its characteristics at low speeds, including head and tail winds. Data from wind tunnel experiments are used to show how the docking when refueling is affected by the lower speeds, position behind the supply aircraft and weather conditions. Possibilities of design improvements and implications are related to the task of refueling Unmanned Aerial Vehicles in-flight

Abstract: A 350-passenger BWB with a distributed propulsion system configuration is carried out and its aerodynamic performance in cruising and taking off are analyzed and discussed. It is shown from computation that the integrated configuration has a commendable aerodynamic performance in cruising and taking off. The cruise lift to drag ratio is reach to 24.0 in cruising. The ingestion effect of the propulsion system leads to a high lift at a low speed. The maximum lift coefficient C_Lmax is 1.62 when α=20° in taking off. In addition, the ingestion also delays the flow separation on the upper surface of center body, which contributes to a well stall performance of the configuration at large angle of attack.

Abstract: In this paper, aerodynamic properties of Blended Wing Body (BWB) civil aircraft are studied by two models: one calls complete model that is computed by numerical simulation coupling equations of motion with the Navier-Stokes equations, and the other doesn’t consider the equations of motion (without dynamic response). The results show that the model without dynamic response can also correctly predict the trend of the dynamic properties compared with complete model. Nevertheless, there are some quantitative differences existing between the complete model and the model without dynamic response.

Abstract: The present work describes an aircraft design methodology that uses the wingspan and its mean aerodynamic chord as main design parameters. In the implemented tool, low fidelity models have been developed for the aerodynamics, stability, propulsion, weight, balance and flight performance. A Fortran® routine that calculates the aircraft performance for the user defined mission and vehicle’s performance requirements has been developed. In order to demonstrate this methodology, the results for a case study using the design specifications of the Air Cargo Challenge 2013 are shown.

Abstract: A forward-facing cavity will be composed of the components of a scramjet from inlet to combustion chamber which has a uncovered inlet before the separation of the booster. Longitudinal oscillations are generated within the cavity under some certain flow conditions. Strong oscillations may damage the components of the scramjet, or induce bow-shock oscillations which may cause unsteady loads on the missile and affect the performance of the aerodynamical characteristics. An experimental study of missile model with a scramjet was conducted in a transonic wind tunnel. The characteristics of cavity flow were researched by both the dynamic force measurement and the fluctuation pressure measurement. In the experiments the oscillations within the cavity and the bow-shock in front of the inlet interacted. The oscillations of cavity flow and bow-shock affected the fluctuation pressure and the aerodynamical characteristics of missile remarkably. The amplitude of axial force was higher than the normal force's. The RMS of the fluctuation pressure of some measured place inside the scramjet reached a quarter of the total pressure, and the amplitude of the fluctuation reached half of the total pressure. Those might threaten the safety of the structure of the scramjet.

Abstract: In this study, an experimentally and numerically investigation was carried out to obtain characteristics (lift force, drag force ...) on 74.5 degree Delta wing. The experiment tests were conducted at Hanoi University of Science and Technology low-speed wind tunnel facility, whereas the numerical tests were performed using the commercial computational fluid dynamics software ANSYS/FLUENT. The apparition of the vortices upon the Delta wing caused the negative pressure distribution on the wing which reached a maximum absolute value at the vortex core. The characteristics of high swept-back Delta wing were investigated at air velocity of 10 m/s and attack angle of 20 degree in changing the rolling angle of the wing from 0 to 20 degree.

Abstract: This paper analyses a morphing leading edge device, activated by a Shape Memory Alloy (SMA) actuator. The objective is to achieve the Droop Nose effect for particular phases of the flight (e.g. take-off, landing), both obtaining an increased lift and preserving the laminar flow. The device is constituted of: a kinematic chain at the level of the wing section, transmitting motion to the skin, this way fitting the Droop Nose target shape; a span-wise architecture integrated with a SMA actuator, ensuring both a reduction of the actuation forces and the balancing of the aerodynamic external load. A dedicated logical framework was adopted for the design, taking into account the SMA material features and the device intrinsic non-linearity. The framework was integrated within an optimization genetic algorithm, to fit the target shape with an appropriate architecture topology. The optimized system proved to produce the desired morphing, also under the most severe aerodynamic loads.