Techno Press
Tp_Editing System.E (TES.E)
Login Search


You have a Free online access.
aas
 
CONTENTS
Volume 4, Number 1, January 2017
 

Abstract
Fatigue life prediction of a multi-row countersunk riveted lap joint was performed numerically. The stress and strain conditions in a highly stressed substructure of the joint were analysed using a global/local finite element (FE) model coupling approach. After validation of the FE models using experimental strain measurements, the stress/strain condition in the local three-dimensional (3D) FE model was simulated under a fatigue loading condition. This local model involved multiple load cases with nonlinearity in material properties, geometric deformation, and contact boundary conditions. The resulting stresses and strains were used in the Smith-Watson-Topper (SWT) strain life equation to assess the fatigue

Key Words
fatigue life; global/local FE model coupling; crack growth; riveted lap joint; the Smith- Watson-Topper (SWT) equation

Address
Gang Li, Guillaume Renaud and Min Liao: Aerospace, National Research Council, Canada
Takao Okada and Shigeru Machida: Aeronautical Technology Directorate, Japan Aerospace Exploration Agency, Japan

Abstract
Hydrogen peroxide is being considered as a monopropellant in micropropulsion systems for the next generation of miniaturized satellites („nanosats‟) due to its high energy density, modest specific impulse and green characteristics. Efforts at the University of Vermont have focused on the development of a MEMS-based microthruster that uses a novel slug flow monopropellant injection scheme to generate thrust and impulse-bits commensurate with the intended micropropulsion application. The present study is a computational effort to investigate the initial decomposition of the monopropellant as it enters the catalytic chamber, and to compare the impact of the monopropellant injection scheme on decomposition performance. Two-dimensional numerical studies of the monopropellant in microchannel geometries have been developed and used to characterize the performance of the monopropellant before vaporization occurs. The results of these studies show that monopropellant in the lamellar flow regime, which lacks a nondiffusive mixing mechanism, does not decompose at a rate that is suitable for the microthruster dimensions. In contrast, monopropellant in the slug flow regime decomposes 57% faster than lamellar flow for a given length, indicating that the monopropellant injection scheme has potential benefits for the performance of the microthruster.

Key Words
micropropulsion; heterogeneous catalysis; micro-reactor; hydrogen peroxide

Address
M. Ryan McDevitt and Darren L. Hitt: Department of Mechanical Engineering, University of Vermont, Burlington, Vermont, USA

Abstract
Gas turbines operating in dusty or sandy environment polluted with micron-sized solid particles are highly prone to blade surface erosion damage in compressor stages and molten sand attack in the hotsections of turbine stages. Commercial/Military fixed-wing aircraft engines and helicopter engines often have to operate over sandy terrains in the middle eastern countries or in volcanic zones; on the other hand gas turbines in marine applications are subjected to salt spray, while the coal-burning industrial power generation turbines are subjected to fly-ash. The presence of solid particles in the working fluid medium has an adverse effect on the durability of these engines as well as performance. Typical turbine blade damages include blade coating wear, sand glazing, Calcia-Magnesia-Alumina-Silicate (CMAS) attack, oxidation, plugged cooling holes, all of which can cause rapid performance deterioration including loss of aircraft. The focus of this research work is to simulate particle-surface kinetic interaction on typical turbomachinery material targets using non-linear dynamic impact analysis. The objective of this research is to understand the interfacial kinetic behaviors that can provide insights into the physics of particle interactions and to enable leap ahead technologies in material choices and to develop sand-phobic thermal barrier coatings for turbine blades. This paper outlines the research efforts at the U.S Army Research Laboratory to come up with novel turbine blade multifunctional protective coatings that are sand-phobic, sand impact wear resistant, as well as have very low thermal conductivity for improved performance of future gas turbine engines. The research scope includes development of protective coatings for both nickel-based super alloys and ceramic matrix composites.

Key Words
turbine blade coatings; thermal barrier coatings; sand particle glazing; gas turbine coating damage

Address
Muthuvel Murugan, Anindya Ghoshal, Michael J. Walock, Blake D. Barnett and Marc S. Pepi: U.S. Army Research Laboratory, Building 4603, Aberdeen Proving Ground, Maryland 21005, U.S.A.
Kevin A. Kerner: Aviation Development Directorate, U.S. Army Aviation and Missile Research, Development and Engineering Center, Building 401, Fort Eustis, Virginia 23604, U.S.A.

Abstract
Aerospace Launch Vehicles (ALV) are generally designed with high reliability to operate in complete security through fault avoidance practices. However, in spite of such precaution, fault occurring is inevitable. Hence, there is a requirement for on-board fault recovery without significant degradation in the ALV performance. The present study develops an advanced fault recovery strategy to improve the reliability of an Aerospace Launch Vehicle (ALV) navigation system. The proposed strategy contains fault detection features and can reconfigure the system against common faults in the ALV navigation system. For this purpose, fault recovery system is constructed to detect and reconfigure normal navigation faults based on the sliding mode observer (SMO) theory. In the face of pitch channel sensor failure, the original gyro faults are reconstructed using SMO theory and by correcting the faulty measurement, the pitch-rate gyroscope output is constructed to provide fault tolerant navigation solution. The novel aspect of the paper is employing SMO as an online tuning of analytical fault recovery solution against unforeseen variations due to its hardware/software property. In this regard, a nonlinear model of the ALV is simulated using specific navigation failures and the results verified the feasibility of the proposed system. Simulation results and sensitivity analysis show that the proposed techniques can produce more effective estimation results than those of the previous techniques, against sensor failures.

Key Words
sliding mode observer; fault detection and isolation; aerospace launch vehicle

Address
Mahdi Hasani, Jafar Roshanian and A. Majid Khoshnood: Department of Aerospace Engineering, K.N. Toosi university of Technology, Vafadar Blvd, Tehran, Iran

Abstract
Small aircrafts, Unmanned Aerial Vehicles (UAVs), are used especially for military purposes. Because landing fields are limited in rural and hilly places, take-off or landing distances are very important. In order to achieve a short landing or take-off distance many parameters have to be considered, for instance the design of aircrafts. Hence this paper represents a better design to enlarge the use of fixed wing aircrafts. The document is based on a live and simulated experiments. The various components of designed aircraft are enhanced to create short take-off distance, greater lift and airflow without the need for proper runway area. Therefore, created aerodynamics of the remotely piloted aircraft made it possible to use fixed wing aircrafts in rural areas.

Key Words
fixed wing; aircraft; take-off distance; design optimization

Address
Ugur C. Yayli, Cihan Kimet, Anday Duru, Ozgur Cetir, Ugur Torun and Ahmet C. Aydogan: Department of Mechanical Engineering, Karabuk University, Karabuk, 78050, Turkey
Ahmet H. Ertas: Department of Biomedical Engineering, Karabuk University, Karabuk, 78050, Turkey
Sanjeevikumar Padmanaban: Ohm Technologies, Research and Development, Chennai, India

Abstract
The performances of lifting surfaces are particularly critical in specific flight conditions like takeoff and landing. Different systems can be used to increase the lift and drag coefficients in such conditions like slat, flap or ailerons. Nevertheless they increase the losses and make difficult the mechanical design of wing structures. Morphing surfaces are a compromise between a right increase in lift and a reduction of parts movements involved in the actuation. Furthermore these systems are suitable for more than one flight condition with low inertia problems. So, flap and slats can be easily substituted by the corresponding morphing shapes. This paper deals with a genetic optimization of an airfoil with morphing flap with an already optimized nose. Indeed, two different codes are used to solve the equations, a finite volume code suitable for structured grids named ZEN and the EulerBoundary Layer Drela

Key Words
deflection; genetic algorithm; gap; Euler; morphing; overlap; RANS

Address
Antonio Carozza: Dipartimento di Meccanica dei Fluidi, Centro Italiano Ricerche Aerospaziali, CIRA, Capua, via Maiorise, 81043, Italy


Techno-Press: Publishers of international journals and conference proceedings.       Copyright © 2017 Techno-Press
P.O. Box 33, Yuseong, Daejeon 34186 Korea, Tel: +82-42-828-7996, Fax : +82-42-828-7997, Email: info@techno-press.com