Investigation of the heat and wear of aircraft landing gear tyres

In aircraft, the main landing gear wheels skid on the runway at the moment of touchdown because of high slip. A slipping tyre generates enough heat to melt its rubber. Melted rubber is easily eroded by the friction force between the tyre and runway; and part of eroded rubber stays on the runway, and other is burnt off as smoke. Since the early days of airplane use, a number of ideas have been patented to improve tyre safety and decrease the substantial wear and smoke during every landing by spinning the gear wheels before touchdown. In this thesis, there are three parts of research work. First part is to find the effectiveness of the technique of pre-spinning the wheel to reduce the tyre tread heat and wear, and then choosing the initial wheel rotation speed that prevent the tread rubber from melting temperature. For achieving this, a coupled structural – thermal transient analysis in ANSYS has been used to model a single wheel main landing gear as a mass-spring system. This model has been chosen to analyze the wheel’s dynamic behaviour and tyre tread temperature and wear during the short period from static to a matching free-rolling velocity in which the wheel is forced to accelerate by the friction between the tyre and ground. The tyre contact surface temperature and wear have been calculated for both the initially static and pre-spun wheels in order to compare the temperature and wear levels for different initial rotation speeds. In the second part, the required torque to spin the aircraft wheel to the required angular speed at approach speed has been calculated using ANSYS CFX, which is used to determine the wheel aerodynamic forces developed by simulation of fluid flows in a virtual environment. In the last part, several types of wind turbines have been simulate

Numerical modelling of additive manufacturing process for stainless steel tension testing samples

Nowadays additive manufacturing (AM) technologies including 3D printing grow rapidly and they are expected to replace conventional subtractive manufacturing technologies to some extents. During a selective laser melting (SLM) process as one of popular AM technologies for metals, large amount of heats is required to melt metal powders, and this leads to distortions and/or shrinkages of additively manufactured parts. It is useful to predict the 3D printed parts to control unwanted distortions and shrinkages before their 3D printing. This study develops a two-phase numerical modelling and simulation process of AM process for 17-4PH stainless steel and it considers the importance of post-processing and the need for calibration to achieve a high-quality printing at the end. By using this proposed AM modelling and simulation process, optimal process parameters, material properties, and topology can be obtained to ensure a part 3D printed successfully

The Validation and Application of CFD-generated Aircraft Carrier Airwakes for Flight Simulation

This thesis describes an extensive experimental and computational study of the air flow over the UK Royal Navy's Queen Elizabeth Class (QEC) aircraft carriers, including how the air flow will affect aircraft flying operations, particularly rotorcraft. Maritime fixed- and rotary-wing aircraft routinely perform launch and recovery manoeuvres to and from ships at sea, often in challenging environmental conditions. Pilots performing such manoeuvres must contend with ship motion, sea spray, and an unsteady airwake generated by the air flow shedding off the ship’s superstructure. The main aim of the research was to investigate the use of modelling and simulation to improve understanding of the flying environment over the flight deck of the QEC. The unsteady air flow over the QEC was created using Computational Fluid Dynamics (CFD) and incorporated into flight simulators at the University of Liverpool (UoL) and at BAE Systems, Warton. Experimental data to confirm the validity of the computed air flow was obtained from a small-scale experiment in which a 1.4 m long (1:200) scale model of the QEC was submerged in a water channel and Acoustic Doppler Velocimetry (ADV) was used to measure the unsteady flow around the ship. The results show generally very good agreement between the model-scale experiment and CFD. Piloted flight simulation trials were conducted using the UoL’s HELIFLIGHT-R full-motion flight simulator in which a test pilot conducted simulated deck landings of a representative Sikorsky SH-60B Seahawk helicopter to the flight deck of the QEC under a range of wind conditions. Results for aircraft performance and pilot workload are presented. These trials demonstrated how flight simulation could be used to support flight trials and helicopter clearance activities, but also notes that real-world trials data are needed to compare with the simulations before the techniques can be beneficially deployed. A non-piloted simulation technique was also deployed in which the unsteady forces and moments imposed by the air flow onto the helicopter fuselage were quantified; the results were correlated with the pilot workload ratings from the piloted simulation trials. The results have demonstrated how modelling and simulation can be effectively used to inform real-world flight trials. The simulations reaffirmed how important it is that helicopter flight models respond to the very different velocity components that are imposed on different parts of the aircraft by the highly unsteady three-dimensional air flow. Fixed-wing flight models, however, are not typically designed to capture the unsteady moments created during hover in a highly turbulent flow at low speeds. A new aerodynamic model of a fixed-wing aircraft has been developed which uses strip theory to create the overall forces and moments acting on the aircraft when hovering in a ship airwake. The results show the effect of the QEC airwakes on a hovering fixed-wing aircraft and provide recommendations for the number of strips required to accurately capture the effect of the flow

Integrated multi-functional morphing aircraft technologies

In the past years, the development of morphing wing technologies has received a great deal of interest from the scientific community. These technologies potentially enable an increase in aircraft efficiency by changing the wing shape, thus allowing the aircraft to fly near its optimal performance point at different flight conditions. This thesis explores the development, analysis, building and integration of two new functional Variable-Span Wing (VSW) concepts to be applied in Remotely Piloted Aircraft Systems (RPAS). Additional studies are performed to synthesize the mass of such morphing concepts and to develop mass prediction models. The VSW concept is composed of one fixed rectangular inboard part, inboard fixed wing (IFW), and a moving rectangular outboard part: outboard moving wing (OMW). An aerodynamic shape optimization code is used to solve a drag minimization problem to determine the optimal values of wingspan for various speeds of the vehicle’s flight envelope. It was concluded that, at low speeds, the original wing has slightly better performance than the VSW and for speeds higher than 25 m/s the opposite occurs, due to the reduction in wing area and consequently the total wing drag. A structural Finite Element Model (FEM) of the VSW is developed, where the interface between wing parts is modelled. Deflections and stresses resulting from static aerodynamic loading conditions showed that the wing is suitable for flight. Flutter critical speed is studied. FEM is used to compute the VSW mode shapes and frequencies of free vibration, considering a rigid or the real flexible interface, showing that the effect of rigidity loss in the interface between the IFW and the OMW, has a negative impact on the critical flutter speed. A full-scale prototype is built using composite materials and an electro-mechanical actuation system is developed using a rack and pinion driven by two servomotors. Bench tests, performed to evaluate the wing and its actuation mechanism under load, showed that the system can perform the required extension/retraction cycles and is suitable to be installed on a RPAS airframe, which has been modified and instrumented to serve as test bed for evaluating the prototype in-flight. Two sets of flight tests are performed: aerodynamic and energy characterization. The former aims at determining the lift-to-drag ratio for different airspeeds and the latter to measure the propulsive and manoeuvring energy when performing a prescribed mission. In the aerodynamic testing, in-flight evaluation of the RPAS fitted with the VSW demonstrates full flight capability and shows improvements produced by the VSW over a conventional fixed wing for speeds above 19 m/s. At low speeds, the original wing has slightly better lift-to-drag ratio than the VSW. Contrarily, at 30 m/s, the VSW in minimum span configuration is 35% better than the original fixed wing. In the other performed test, it is concluded that the VSW fitted RPAS has less overall energy consumption despite the increased vehicle weight. The energy reduction occurs only in the high speed condition but it is so marked that it offsets the increase in energy during takeoff, climb and loiter phases. Following the work on the first VSW prototype, a new telescopic wing that allows the integration of other morphing strategies is developed, within the CHANGE EU project. The wing adopted span change, leading and trailing edge camber changes. A modular design philosophy, based on a wing-box like structure, is implemented, such that the individual systems can be separately developed and then integrated. The structure is sized for strength and stiffness using FEM, based on flight loads derived from the mission requirements. A partial span, fullsized cross-section prototype is built to validate the structural performance and the actuation mechanism capability and durability. The wing is built using composite materials and an electromechanical actuation system with an oil filled nylon rack and pinion is developed to actuate it. The structural static testing shows similar trends when compared with numerical predictions. The actuation mechanism is characterized in terms of actuation speed and specific energy consumption and it was concluded that it functioned within its designed specifications. A full-scale prototype is later built by the consortium and the leading and trailing edge concepts from the different partners integrated in a single wing. Wind tunnel tests confirmed that the wing can withstand the aerodynamic loading. Flight tests are performed by TEKEVER, showing that the modular concept works reliably. From the previous works, it is inferred that morphing concepts are promising and feasible methodologies but present an undesired mass increase due to their inherent complexity. On the other hand, mass prediction methods to aid the design of morphing wings at the conceptual design phase are rare. Therefore, a mass model of a VSW with a trailing edge device is proposed. The structural mass prediction is based on a parametric study. A minimum mass optimization problem with stiffness and strength constraints is implemented and solved, being the design variables structural thicknesses and widths, using a parametric FEM of the wing. The study is done for a conventional fixed wing and the VSW, which are then combined to ascertain the VSW mass increment, i.e., the mass penalization of the adopted morphing concept. Polynomials are found to produce good approximations of the wing mass. Additionally, the effects of various VSW design parameters in the structural mass are discussed. On one hand, it was found that the span and chord have the highest impact in the wing mass. On the other hand, the VSW to fixed wing ratio proved that the influence of span variation ratio in the wing mass is not trivial. It is found that the mass increase does not grow proportionally with span variation ratio increase and that for each combination of span and chord, exists a span variation ratio that minimizes the mass penalty. Using the VSW to fixed wing ratio function, the mass model is derived. To ascertain its accuracy, a case study is performed, which demonstrated prediction errors below 10%. Although the mass model results are encouraging, more case studies are necessary to prove its applicability over a wide range of VSWs. The work performed successfully demonstrated that VSW concepts can achieve considerable geometry changes which, in turn, translate into considerable aerodynamic gains, despite the increased weight. They influence all aspects of the wing design, from the structural side to the actuation mechanisms. The parametric study summarizes the mass penalties of such concepts, being successful at demonstrating that the mass penalty is not straightforward and that a careful selection of span, chord and variable-span ratio can minimize the mass increase.Nos últimos anos, o desenvolvimento de asas adaptativas tem sido alvo de um grande interesse por parte da comunidade científica. Nesta tese explora-se o desenvolvimento, análise, construção e integração de dois novos conceitos de Asas de Envergadura Variável (VSWs) funcionais a serem aplicados em Sistemas de Aeronaves Pilotadas Remotamente (RPASs). Estudos adicionais são levados a cabo para sintetizar a massa desses conceitos e desenvolver modelos de previsão de massa. O conceito da VSW é constituído por uma parte interna retangular fixa, Asa Fixa Interna (IFW), e por uma parte externa retangular móvel, Asa Móvel Externa (OMW). Um código de otimização aerodinâmica é utilizado para minimizar a resistência ao avanço, determinando os valores ótimos de envergadura para várias velocidades de voo do veículo. Concluiu-se que, a baixas velocidades, a asa original apresenta um desempenho ligeiramente melhor que a VSW, enquanto que a velocidades superiores a 25 m/s, a VSW apresenta um desempenho melhor devido à redução da área das asas e, consequentemente, à redução da resistência total das asas. Para levar a cabo um estudo estrutural, foi desenvolvido um Modelo de Elementos Finitos (FEM) estrutural da VSW, no qual se modelou a interface entre a IFW/OMW. As deflexões e tensões resultantes dos carregamentos aerodinâmicos estáticos mostraram que a asa é capaz de suportar as cargas em voo. A velocidade de flutter é também investigada, sendo o FEM utilizado para calcular as formas dos modos de vibração da VSW e respetivas frequências de vibração livre. Considerou-se uma interface colada ou flexível, confirmando-se que o efeito da perda de rigidez na interface IFW/OMW, tem um impacto negativo sobre a velocidade de flutter. Um protótipo da VSW é construído, utilizando materiais compósitos, e um sistema de atuação eletromecânico é desenvolvido usando um sistema de pinhão e cremalheira movido por dois servomotores. Os testes de bancada, realizados para avaliar a asa e o mecanismo de atuação, mostraram que o sistema é capaz de realizar a extensão/retração da asa, sendo adequado para ser instalado num RPAS. Este RPAS foi modificado e instrumentado para servir de banco de ensaio para avaliação do protótipo em voo. São realizados dois conjuntos de testes de voo: caracterização aerodinâmica e energética. O primeiro incide na determinação da razão de planeio para diferentes velocidades e o segundo é levado a cabo para determinar a energia propulsiva e de manobra ao executar uma missão típica. Nos testes aerodinâmicos ficou comprovado que o RPAS equipado com a VSW é capaz de uma normal operação e ainda que mostra melhorias sobre uma asa fixa convencional para velocidades acima de 19 m/s. A velocidades mais reduzidas, a asa original tem um desempenho ligeiramente melhor do que a VSW. Por outro lado, a 30 m/s, a VSW na configuração de envergadura mínima é 35% melhor do que a asa fixa original. No outro ensaio realizado, conclui-se que o RPAS de envergadura variável tem menos consumo de energia global, apesar do aumento de peso do veículo. A redução de energia ocorre apenas na fase de cruzeiro de alta velocidade, mas foi tão acentuada que compensou o aumento da energia durante as fases de descolagem, subida e espera. Na sequência do trabalho anterior e no âmbito do projeto europeu CHANGE, é desenvolvida uma nova VSW que permite a integração de outras estratégias adaptativas. A nova asa adotou a mudança de envergadura, e a mudança de curvatura nos bordos de ataque e de fuga. Esta adotou uma filosofia de projeto modular, baseada numa caixa de torção, permitindo o desenvolvimento das diferentes tecnologias adaptativas separadamente. A estrutura é divmensionada para resistência e rigidez usando FEM, com base em cargas de voo derivadas dos requisitos da missão. Um primeiro protótipo é construído para validar o desempenho estrutural e a funcionalidade do mecanismo de atuação. A asa é construída usando materiais compósitos e utiliza um sistema de pinhão e cremalheira e um servomotor, para variar a envergadura. Testes estruturais estáticos mostram que as deflexões corroboram as previsões numéricas. O mecanismo de atuação é caracterizado em termos de velocidade de atuação e consumo de energia específica, concluindo-se que funciona dentro do previsto. O segundo protótipo é construído pelo consórcio e os conceitos de bordo de ataque e de fuga são integrados. Testes em túnel de vento confirmaram que a asa suporta o carregamento aerodinâmico. Os testes de voo, realizados pela TEKEVER, mostram que o conceito modular funciona de forma fiável. Baseado nos trabalhos anteriores, conclui-se que os conceitos adaptativos são promissores e viáveis, mas apresentam um aumento de massa indesejável devido à sua inerente complexidade. Por outro lado, os métodos de previsão de massa para auxiliar o projeto de asas adaptativas na fase de projeto conceitual são raros. Deste modo, um modelo de massa da VSW com um dispositivo de borda de fuga é proposto. A previsão de massa estrutural é baseada num estudo paramétrico. Um problema de minimização de massa com constrangimentos de rigidez e resistência é implementado e resolvido, sendo as variáveis de projeto espessuras e larguras estruturais. Para o levar a cabo, um FEM paramétrico da VSW é desenvolvido. O estudo é feito para uma asa fixa convencional e para a VSW, os quais são combinados para determinar o incremento de massa da VSW. Aproximações polinomiais das massas da asa são produzidas, mostrando serem capazes de produzir uma adequada representação. Adicionalmente, são discutidos os efeitos dos vários parâmetros de design da VSW na massa estrutural. Por um lado, verificou-se que a envergadura e a corda têm o maior impacto na massa da asa. Por outro lado, a razão de massas da VSW e da asa fixa provou que a influência da razão de variação de envergadura na massa das asas não é trivial. Verifica-se que o aumento de massa não cresce proporcionalmente com o aumento da razão de variação de envergadura e que para um dado conjunto de envergadura e corda existe uma razão de variação de envergadura que minimiza o aumento de massa. O modelo de massa é derivado usando a aproximação polinomial da razão da VSW com a asa fixa. Para verificar a precisão do modelo, é realizado um caso de estudo que demonstrou erros de previsão abaixo dos 10%. Embora os resultados do modelo de massa sejam encorajadores, mais casos de estudo são necessários para provar a sua aplicabilidade a uma ampla gama de VSW. O trabalho realizado demonstrou com sucesso que os conceitos de VSW podem alcançar consideráveis mudanças de geometria, que se traduzem em ganhos aerodinâmicos consideráveis, apesar do aumento de peso. Estes influenciam todos os aspetos do projeto da asa, desde a parte estrutural até aos mecanismos de atuação. O estudo paramétrico tentou resumir a penalização de massa de tais conceitos, sendo bem sucedido em demonstrar que esta penalização não é simples e que uma seleção cuidadosa de envergadura, corda e razão de variação de envergadura pode minimizar o aumento de peso.This thesis and the associated research was partially funded by the European Community’s Seventh Framework Programme (FP7) under the Grant Agreement 314139

NASA Tech Briefs, November 1994

Topics: Advanced Manufacturing; Electronic Components and Circuits; Electronic Systems; Physical Sciences; Materials; Computer Programs; Mechanics; Machinery/Automation; Manufacturing/Fabrication; Mathematics and Information Sciences; Life Sciences; Books and Reports

Hypersonic Vehicles

Some sixty years after the experimental flights of the North American X-15 hypersonic rocket-powered aircraft, sustained hypervelocity travel is still the next frontier in high-speed transportation. Today, there is much excitement and interest regarding hypersonic vehicles. In fact, many aerospace agencies, large industries, and several start-ups are involved in design activities and experimental campaigns both in wind tunnels and in-flight with full-scale experimental flying test beds and prototypes to make hypersonic travel almost as easy and convenient as airliner travel. Achieving this goal will radically revolutionize the future of civil transportation. This book contains valuable contributions that focus on various design issues related to hypersonic aircraft

Applications of Finite Element Modeling for Mechanical and Mechatronic Systems

Modern engineering practice requires advanced numerical modeling because, among other things, it reduces the costs associated with prototyping or predicting the occurrence of potentially dangerous situations during operation in certain defined conditions. Thus far, different methods have been used to implement the real structure into the numerical version. The most popular uses have been variations of the finite element method (FEM). The aim of this Special Issue has been to familiarize the reader with the latest applications of the FEM for the modeling and analysis of diverse mechanical problems. Authors are encouraged to provide a concise description of the specific application or a potential application of the Special Issue

ESSE 2017. Proceedings of the International Conference on Environmental Science and Sustainable Energy

Environmental science is an interdisciplinary academic field that integrates physical-, biological-, and information sciences to study and solve environmental problems. ESSE - The International Conference on Environmental Science and Sustainable Energy provides a platform for experts, professionals, and researchers to share updated information and stimulate the communication with each other. In 2017 it was held in Suzhou, China June 23-25, 2017

NASA Tech Briefs, March 1995

This issue contains articles with a special focus on Computer-Aided design and engineering amd a research report on the Ames Research Center. Other subjects in this issue are: Electronic Components and Circuits, Electronic Systems, Physical Sciences, Materials, Computer Programs, Mechanics, Machinery, Manufacturing/Fabrication, Mathematics and Information Sciences and Life Science